摘要:

Russian Chemical Reviews 70 (3) 177 ± 210 (2001) Nanoclusters and nanocluster systems. Assembling, interactions and properties I P Suzdalev, P I Suzdalev Contents I. Introduction II. Synthesis and classification of nanoclusters and nanocluster structures III. Properties of isolated nanoclusters IV. Cluster nanosystems and nanostructures V. Conclusion Abstract. nanoclusters of properties and structures the on Data Data on the structures and properties of nanoclusters and nanocluster systems are analysed. A classification of nano- and nanocluster systems are analysed. A classification of nano- clusters and nanosystems based on the method of their prepara- clusters and nanosystems based on the method of their prepara- tion is proposed. Methods for assembling nanoclusters to give tion is proposed.Methods for assembling nanoclusters to give nanostructures, the main principles of assembling and the types of nanostructures, the main principles of assembling and the types of nanosystems are described. The appearance of new properties nanosystems are described. The appearance of new properties upon combination of nanoclusters into a nanosystem is noted. upon combination of nanoclusters into a nanosystem is noted. The bibliography includes 274 references. The bibliography includes 274 references. I. Introduction The properties of a material are known to change significantly on passing from macrostructures to the microstructures the size of which lies in the nanometer range. Thus the crystal lattice parameters, the heat capacity, the melting point and the electrical conductivity of nanoclusters in the condensed state differ from those of the corresponding macrocrystals.In addition, they acquire new optical, magnetic, and electronic characteristics; their reactivity and catalytic properties also change.1± 10 The properties of nanostructures are determined by not only the cluster size but also the mode of their organisation or self- organisation into a nanocluster structure in which the clusters act as separate atoms. Nanostructures, in turn, can form supra- molecular structures. The ways of assembly of nanoclusters into nanostructures depend not only on the properties of separate nanoclusters and intercluster interactions but also on the methods used to prepare nanoclusters.Thus, several main trends can be distinguished in research on nanoclusters and cluster nanosystems � methods for the preparation and classification of nano- clusters; � properties of isolated nanoclusters; � ways of assembly (self-assembly) of cluster nanosystems; � properties of nanocluster systems. Great progress in studies of nanoclusters and nanostructures has been achieved in the last decade. An enormous number of publications have appeared, devoted both to fundamental research on nanoclusters and nanostructures and to the ways of I P Suzdalev, P I Suzdalev N N Semenov Institute of Chemichal Physics, Russian Academy of Sciences, ul. Kosygina 4, 117977 Moscow, Russian Federation. Fax (7-095) 137 83 18.Tel. (7-095) 939 71 01. E-mail: suzdalev@chph.ras.ru Received 9 October 2000 Uspekhi Khimii 70 (3) 203 ± 240 (2001); translated by Z P Bobkova #2001 Russian Academy of Sciences and Turpion Ltd DOI 10.1070/RC2001v070n03ABEH000627 177 177 179 185 206 using them in nanotechnologies (design of magnetic recording devices, nanodiodes, nanowires, and single-electron transfer devi- ces tuned by changing the size of the nanolaser; production of new nanomaterials with specific mechanical, thermal, electronic, opti- cal, and magnetic properties). In this review, we present data on nanoclusters and nano- structures obtained both by methods of inorganic, physical, and solid-state chemistry and by methods of condensed-state physics and the physics of gases, using diverse calculation procedures and experimental equipment.We have not intended to give an exhaustive review on the published data concerning all the properties of nanoclusters, but considered only those of them that are of fundamental importance in the formation of cluster systems. Some of the problems considered in the review related to the interpretation of experimental facts and, especially, classifica- tion of clusters and nanoparticles are debatable. In addition, not all the cluster effects are considered. Nevertheless, we hope that the information we present would be of interest for researchers engaged in the chemistry or nanotechnologies and in physics. II. Synthesis and classification of nanoclusters and nanocluster structures As noted above, many properties of nanoclusters and nano- systems depend on the method used to prepare them.Therefore, we attempted to classify the clusters in terms of the method of synthesis. With this empirical approach, the diversity of properties of clusters and cluster systems can be represented on the basis of their origin. In terms of the preparation method, clusters can be classified into six groups: molecular, gas-phase, colloid, solid- state, matrix and film clusters. Isolated nanoclusters can be prepared by chemical reactions (molecular clusters), laser vapor- isation (gas-phase clusters) or by matrix isolation (solid-state and colloid syntheses). Nanosystems are mainly formed in solid-state and colloid syntheses.1. Molecular ligand metal clusters Molecular metal clusters are multinuclear complex compounds the molecular structure of which is based on a core (cell) of metal atoms (their number should be greater than two) bound directly to one another and surrounded by ligands. The metal7metal distances in these clusters are usually shorter than those in the bulk metal.11 The metal core consists of chains of different lengths and different branching types, rings or polyhedra or combinations of these structural units. Both homo- and heterometallic clusters are known.178 Molecular ligand metal clusters are produced from metal complexes upon various chemical reactions. An enormous num- ber of publications have been devoted to the synthesis, structure and properties of molecular metal clusters (see, for example, a monograph 11 and references therein). 2.Gaseous ligand-free clusters Ligand-free clusters of metals or metal oxides can be prepared, for example, by laser vaporisation of metals from a substrate followed by separation according to size (or weight) in a time-of-flight mass-spectrometer. The clusters formed upon vaporisation are fixed in traps (or on substrates) and then their electronic, optical, and other properties are studied.12 The clusters obtained in this way contain from several dozens to several hundreds of atoms. The synthesis of big nanoclusters (5100 nm) is performed by heating and vaporisation of metals in a radio-frequency electro- magnetic field in vacuo or under an inert gas followed by deposition of clusters onto a substrate or a filter.13 The use of a substrate is necessary because nanoparticles are highly reactive and stick together upon collisions, while the substrate stabilises them.Yet another method for the preparation of gas-phase metal clusters is vaporisation of metals in an inert gas followed by the formation of metal clusters in a low-temperature matrix (cryo- chemical method).14 Gas-phase methods of synthesis are also used for the prepa- ration of carbon clusters (in particular, fullerenes). Thus C60 fullerene was prepared for the first time by laser vaporisation of graphite in 1985.15 Fullerenes with the compositions C36, C70 , C82, C84, C90 and C96 have also been synthesised.16 ± 19 Among other gas-phase ligand-free clusters, van der Waals clusters of noble gases and water should be mentioned.The evaporation ± condensation technique allows the prepa- ration of the purest metal particles; therefore, nowadays, this method is still finding application. However, when using this method, it is difficult to control the size of the resulting metal clusters. The clusters obtained in this way are characterised by broad size distributions. 3. Colloid clusters and nanosystems Colloid solutions containing metal nanoclusters and their com- pounds have long been known; however, in connection with the task of preparing assembled naures, it became necessary to synthesise monodisperse colloid systems with a controlled cluster size.Monodisperse colloid systems are usually synthesised using sol ± gel technology,20 which includes preparation of a sol and its transformation into a gel. Sols are prepared using dispersion and condensation (physical and chemical) methods. Thus hydrolysis of metal salts or metal alkoxides gives rise to sols of metal oxides or hydroxides characterised by high excess energy. Owing to the excess energy, aggregation of sols takes place in these systems, accompanied by the formation of a gel. This process affords nanostructures with a size of up to 100 nm. In recent years, the use of microemulsion systems (direct and reverse micelles) for the preparation of nanoclusters with a narrow size distributions of particles has started.{ Many metal clusters with particle size of 1 to 10 nm have been prepared in this way.21, 22 4.Solid-state clusters Solid-state clusters are formed as a result of diverse transforma- tions of the solid phase: chemical reactions in the solid phase, crystallisation of an amorphous phase, mechanochemical trans- formations, etc.23 Many chemical reactions in the solid state for example, thermal decomposition of metal salts and complexes are { Procedures for the synthesis of ultradisperse particles based on the sol ± gel method and microemulsion systems are described in the recent review by BDSumm,NI Ivanova Usp. Khim. 69 995 (2000). [Russ. Chem. Rev. 69 911 (2000)] I P Suzdalev, P I Suzdalev accompanied by the formation of metal or metal oxide nuclei, which then grow due to sintering.The size of nanoclusters thus formed varies over a very broad range�from one to hundreds of nanometers. Crystallisation is employed to prepare nanoclusters from amorphous alloys. The crystallisation conditions are maintained in such a way as to generate as many crystallisation centres as possible; the growth of nanoclusters should occur at a low rate. Solid-state nanoclusters can also be prepared via photochem- ical reactions, for example, those involving silver halides. These reactions, too, start with the formation of nuclei, which are then enlarged giving rise to nanoclusters with sizes ranging from tens to hundreds of nanometers.7 Apart from chemical reactions in solids, mechanochemical transformations can also be used to prepare solid-state clusters. Thus mechanical grinding of a bulk solid permits one to prepare nanoclusters the size of which does not exceed several nanometers.Due to the activation of the newly formed surface, new nano- cluster compounds differing from the initial ones can arise.6, 8 Yet another method for the preparation of solid-state nano- clusters consists in nanostructurisation of a material on exposure to pressure with shear.6 By increasing pressure to 5 GPa and shear to 1000 8C, one can prepare nanoclusters with a grain size reach- ing several nanometers the properties of which differ sharply from those of the initial material. Nanoclusters are also produced when other methods of plastic yield are employed.5. Matrix clusters Methods for the preparation of nanoclusters which make use of various inorganic and organic matrices and matrix isolation constitute a self-dependent group, although they can include some features of the gas-phase, solid-state and other methods. The point is that nanoclusters prepared using matrix methods differ from those formed, for example, in solid-state chemical reactions because they are isolated from one another by the matrix and, therefore, heating of the whole nanosystem does not result in an increase in the cluster size due to sintering. The originality of this approach is that it provides the possibility of restricting size dispersion of the nanoclusters and of changing the intercluster interactions in a required manner.Thus microencapsulation of nanoclusters in inert gases at low temperatures is used to prepare gas-phase metal clusters. Clusters and cluster systems are often prepared by chemical reactions in solution followed by precipitation of the resulting compounds in the pores of a solid. Nanoclusters and nanosystems can also be prepared by impregnating porous matrices with solutions and performing chemical reactions in the pore acting as a micro- or a nanoreactor. This procedure is used, for example, to prepare metal and metal oxide clusters in zeolites, the cluster size being determined by the size of zeolite cells (1 ± 2 nm). In this case, aluminosilicates promote the formation of assembled cluster structures.Broad opportunities for the variation of the size and composi- tion of clusters are provided by using inorganic and organic sorbents (for example, silica gels and aluminogels, ion exchange resins and polysorbs).3 In this case, the change in the cluster size and cluster organisation takes place due to both the change in the pore size and the variation of the surface hydrophilicity (or hydro- phobicity), the concentration of initial components, temper- ature, etc. 6. Nanofilms When nanoclusters are formed in nanofilms, the mechanism of nucleation and growth differs from those in the formation of solid-state clusters because the synthesis is related to the surface chemistry (the formation of two-dimensional structures). Epi- taxial nanofilms on an oriented crystalline surface are prepared using laser vaporisation and molecular beams.17 In recent years, the CVD method has started to be widely used to apply nanocluster nanofilms on the surface.24 According to thisNanoclusters and nanocluster systems.Assembling, interactions and properties method, the initial substances are first evaporated and then transferred through the gas phase and deposited in a required proportion onto a chosen substrate. To produce molecular layers with controlled composition and thickness, the method of molecular layering is used, the essence of which is to induce surface chemical reactions separated in space and time.25 ± 27 Nanofilms containing one to ten monolayers have been prepared in this way.The technology of synthesis of Langmuir ± Blodgett films, which has been developed in recent years, makes it possible to introduce metal ions and metal complexes into the surfactant film being formed on the surface of water and thus to prepare nano- clusters. The use of this approach results in the formation of Langmuir ± Blodgett films with an ordered monolayer of clusters, which can then be applied onto a solid substrate using a special technique. This procedure can be repeated thus forming multi- layer films and superstructures.28 III. Properties of isolated nanoclusters Clusters occupy an intermediate position between separate mole- cules and macro-solids. Therefore, the properties of a single isolated cluster can be compared both with the properties of separate atoms or molecules and with the properties of a bulk solid.The notion `isolated cluster' is rather abstract because it is virtually impossible to obtain a cluster not interacting with the environment. In addition, when investigating the properties of isolated clusters, one should take into account their interaction with the measuring instrument, which can change the properties of the cluster during the measurements. This is especially true for contact techniques of measurement (for example, tunnelling microscopy). However, these changes are relatively insignificant and we shall not consider this type of interaction in this review. Since molecular metal clusters, van der Waals noble gas and water clusters, gas-phase metal clusters, and fullerenes are subject only to weak intercluster interactions, they can conventionally be considered as isolated clusters.In this Section, we shall consider the structure, the atomic dynamics, and the electronic, optical, and magnetic properties of isolated clusters. 1. Molecular ligand clusters in solutions Molecular clusters are important objects of coordination, inor- ganic and structural chemistry. The unusual features of their structures and properties caused by the presence of a core of metal atoms have stimulated the development of a separate branch of science

ISSN:0036-021X    

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Russian Chemical Reviews 70 (3) 211 ± 230 (2001) Nitrosonium complexes of organic compounds. Structure and reactivity G I Borodkin, V G Shubin Contents I. Introduction II. Complexes of the nitrosonium ion with alkanes III. Complexes of the nitrosonium ion with alkenes IV. Nitrosonium complexes of aromatic compounds V. Complexes of the nitrosonium ion with nitrogen-containing organic compounds VI. Complexes of the nitrosonium ion with organic compounds containing Group VI elements VII. Complexes of the nitrosonium ion with halogen-containing organic compounds Abstract. nitrosonium of reactivities and structures the on Data Data on the structures and reactivities of nitrosonium complexes and systematised are compounds organic of complexes of organic compounds are systematised and general- general- ised.of structure electronic the of features characteristic The ised. The characteristic features of the electronic structure of the the NO of variety structural wide a for responsible are + cation cation are responsible for a wide structural variety of nitrosonium complexes. Reactions of nitrosonium complexes are nitrosonium complexes. Reactions of nitrosonium complexes are described. references 172 includes bibliography The described. The bibliography includes 172 references. I. Introduction Nitrosonium complexes of organic compounds have been exten- sively studied over many years. The continuing interest in these complexes stems from the fact that they are intermediates in a series of reactions, including nitrosation of aromatic compounds,1 nitrosohalogenation of alkenes,2±4 etc.5 Recently, interest in these complexes has increased due to the discovery of the unique role of the NO molecule in biochemical processes.6±15 It is assumed that the nitrosonium cation and some molecules generating the nitro- sonium ion are involved in processes of neurotoxic and neuro- protective actions of nitric oxide 16, 17 (cf.Refs 18 ± 20) { and participate in cross-linking of DNA.21, 22 Investigations of the structures and reactivities of nitrosonium complexes are essential to the understanding of the role of the NO+ cation in various chemical processes (from ionospheric 23, 24 to biochemical 9, 16 ± 19) giving rise to different classes of organic compounds. In the present review, the data on the structures and reactiv- ities of nitrosonium complexes published over the last 10 ± 15 years are analysed and systematised.The results of earlier studies are cited if they are necessary for an understanding of the problem and for elucidation of new trends in this area of exploration. { Hereinafter, the reader is referred to studies, which are either indirectly associated with the problem under consideration or even contradictory. G I Borodkin, V G Shubin N N Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Lavrent'eva 9, 630090 Novosibirsk, Russian Federation. Fax (7-383) 234 47 52. Tel. (7-383) 234 43 86. E-mail: gibor@nioch.nsc.ru (G I Borodkin).Tel. (7-383) 234 26 51. E-mail: vshubin@nioch.nsc.ru (V G Shubin) Received 10 November 2000 Uspekhi Khimii 70 (3) 241 ± 261 (2001); translated by T N Safonova #2001 Russian Academy of Sciences and Turpion Ltd DOI 10.1070/RC2001v070n03ABEH000634 211 211 212 214 223 225 228 II. Complexes of the nitrosonium ion with alkanes Electrophilic substitution in the aliphatic series of compounds lies at the basis of one of the procedures for the functionalisation of alkanes.25 ± 27 Weak electrophiles, in particular NO+, can be involved in electrophilic aliphatic substitution reactions along with strong electrophiles, such as H+ and Alk+. Nitrosonium salts react with adamantane in the presence of HF, oxygen or nitriles to form 1-fluoroadamantane,28 1-nitroadamantane 29 or N-(1-adamantyl)amides,30 respectively. Generally, it is assumed that the attack of the electrophile E+ in electrophilic aliphatic substitution reactions occurs at the C7H bond to give intermedi- ates of the type 1 characterised by the two-electron three-centre mode of bonding of the E, H and C atoms (3X-2e-intermedi- ates) 25 ± 27 (cf. Ref.31). E+ CR3E+H+ HCR3+E+ 3 H CR 1 According to high-level ab initio calculations for the reactions of the NO+ cation with methane and ethane,32, 33 the mechanism of the reactions of the nitrosonium cation with alkanes might differ from that described above. Thus, the NO+ cation attacks the methane molecule at the carbon atom to form complex 2 whose precursor is unstable complex 3 [DH0=715.5 kJ mol71, where DH0 is the relative energy of the complex taking into account the zero-point energy; the results of calculations by the MP4SDTQ/6-31+G(dp)/MP2/6-31+G(dp)+ZPVE//MP2/6-31 + G(dp) method]. An alternative path involving the attack of the NO+cation at theC7Hbond is less favourable (by 60.2 kJ mol71).+ 0.3106 nm + H O H H H O0.1041 nm 0.1161 nm C N C N 0.1471 nm H H H 0.2775 nm 2 H + 3 H H H 0.2344 nm C0.1519 nm C O 0.1109 nm H H H N 0.2348 nm 4212 Analogously, unstable complex 4 {DH0=716.7 kJ mol71; calculations by the CISD+Q/TZP+//MP2/6-31G(dp)+ ZPVE[MP2/6-31G(d)] method} is initially formed in the reaction with ethane. In the latter complex, theNO+ cation is bound to the ethane molecules via polarisation and Coulomb interactions.33 Subsequent conversions of this complex are shown in Scheme 1.Scheme 1 + b E CH3 H3C c or d H3C CH2 E+ H a E+ C2H6+E+ C2H6 H3C E H2 e +CH CH4 f H2C E+ (a) DH0=717.2 kJ mol71; (b) insertion of E+ at the C7C bond; DH0=7118.8 kJ mol71; (c) insertion of E+ at the C7H bond, DH0= ± 84.5 kJ mol71; (d ) elimination of H7, addition of EH, DH0= ± 84.5 kJ mol71; (e) elimination of H2 , DH0=119.2 kJ mol71; ( f ) elimination of CH4 , DH0=39.7 kJ mol71. Although the attack of the NO+ cation at the C7C bond is thermodynamically favourable (see Scheme 1), Schreiner et al.33 believed that the attack on the C (to form a complex of the type 2) andHatoms is kinetically more favourable.Elimination of theH2 molecule is also unlikely because this path is thermodynamically unfavourable (DH0=119.2 kJ mol71). Attempts to isolate the transition states in these reactions failed. The activation barriers to elimination of methane and the hydride ion giving rise to nirosomethane and nirosoethane, respectively, have similar values (140.2 and 130.1 kJ mol71, respectively). III. Complexes of the nitrosonium ion with alkenes In a series of investigations, alkene ±NO+ complexes were pro- posed as intermediates of reactions of alkenes with nitrosyl halides 2±4 and [NO]+X7 salts (see Refs 34 ± 37). These reactions are of importance in the synthesis of halonitroso- and haloni- troorganic,1 ± 4, 38 N,O-heterocyclic 34 ± 36, 39 and some other organic compounds.37, 40 ± 42 The energy profiles of fluoronitrosation of ethylenes were calculated by the MINDO/3 and UMINDO/3 quantum-chemical methods.43 The facts that the NO+ cation approaches the ethyl- ene molecule at an angle to the symmetry plane of the latter and attacks the carbon atom to form s-complex 5 are attributed to a strong ps ± ps interaction between the unoccupied e(p*)-MO of the NO+ cation and HOMO of ethylene.O O + O + N O H H N N N + + H H H H H H H H H H H H H H 6 5 50 7 According to the results of MINDO/3 calculations, the isomeric form 50 is less favourable than the structure 5 (DDHf=22.2 kJ mol71, where DHf is the enthalpy of complex formation).The open cation 5 is rearranged into isomeric cyclic structures 6 and 7, the activation energies (Ea) of these rearrange- ments being low (Ea=5.0 and 14.2 kJ mol71, respectively). Among the structures 5 ± 7, the p-complex 6 is the most stable. Ab initio calculations (the STO-3G basis set) predicted that the structure 7 should be the most stable.43 Higher-level ab initio G I Borodkin, V G Shubin Table 1. Relative energies (Erel /kJ mol71) of the structures 7 ± 10 obtained by ab initio quantum-chemical calculations.44 Erel a calculated by the method Struc- Basis set ture CCD+ST(4) MP3 MP4 MP2 HF 7 76.6 736.8 777.4 7 7 7 7 43.1 775.7 733.1 STO-3G 7335.6 6-31G 6-31G+D 775.3 716.3 77 8 17.6 31.0 779.5 789.1 7 7 7 75.0 760.7 711.7 713.8 STO-3G 7223.8 6-31G 6-31G+D 735.1 715.9 9 765.7 710.5 7 7 7 7 776.1 731.8 738.1 761.9 749.4 750.2 STO-3G 7132.6 6-31G 6-31G+D 730.1 741.4 10 STO-3G 7139.7 6-31G 6-31G+D 22.2 7.9 59.4 33.1 727.2 72.9 749.4 5.4 7 7 7 713.4 6.7 a The total energy of the C2H4 molecule and the NO+ cation was taken equal to zero.quantum-chemical calculations (MP4/6-31G+D) also provided evidence for higher stability of the structure 7 (Table 1).44 In addition to the p-complex 6 in which the NO group is located in proximity to the ethylene fragment [the distance from the N atom to the C7C bond (d ) is 0.1272 nm], more favourable (within the framework of the MP4 method) `loose' p-complex 9 was found.In the latter, the distance d is substantially larger (0.1978 nm) and the NO group is located at an angle to the plane passing through the C, C and N atoms (Fig. 1, see Table 1). The s-complex 10 is substantially less stable than the p-com- plexes 8 and 9 (see Table 1, Fig. 1). The C7N bond in the cation 10 is unusually long, which indicates that the C and N atoms are weakly bound together 44 (cf. Refs 37 and 43). The structural and energy characteristics of the nitrosonium complexes with cyclobutadiene were calculated by the MINDO/3 and ab initio methods (the STO-3G basis set).45 Qualitative analysis of orbital interactions revealed five structures with attractive interactions of the ps ± ps(ps ± ps) type between the NO+ cation and the ring.In the complexes 11 and 12, the nitroso group is located parallel to the plane of the carbon ring above its centre and above one of the double bonds, respectively. In the structures 13 ± 15, the NO group is perpendicular to the plane of the ring. Interactions between the orbitals of the nitroso group and the p orbitals of one of the double bonds occur in the isomers 13 and 15, whereas interactions between the orbitals of the nitroso group and all p orbitals of the ring take place in the pyramidal structure 14. The energy characteristics of the cations 11 ± 13, 15, 17 and 18 are given in Table 2. According to calculations by the MINDO/3 method, the azapyrylium cation 18 is the most stable one in the above-mentioned series. O O 0.1255 0.1176 N+ N+ 0.1194 O 0.1978 0.1487 104.88 H H H 58.88 + N 0.1737 H H H 0.1540 0.1434 0.1371 H H H H H H 8 (C2u) 10 (Cs) 9 (Cs) Figure 1.Geometric parameters of the p-complexes 8 and 9 and the s-complex 10 obtained by ab initio calculations (the STO-3G basis set).44 The bond lengths are expressed in nm; the symmetry is given in parentheses.Nitrosonium complexes of organic compounds. Structure and reactivity Table 2. Enthalpies of formation (DHf), total energies (Etot) and relative energies (Erel) of the structures 11 ± 13, 15, 17 and 18.45 11 Parameter MINDO/3 1036.0 DHf /kJ mol71 Etot /a.u. a 7 7279.1292 354.4 Erel /kJ mol71 a 1 a.u.=2625.5 kJ mol71.O+ N N O+ 11 (Cs) 12 (C1)O N + O+ 15 (Cs) 16 (Cs) Ab initio calculations (the STO-3G basis set) for the structures 11 ± 13 predicted the higher stability of the cation 12.In the case of the pyramidal structure 14, no minimum was found on the potential energy surface (PES).{ The conversion of this structure into the structure 13 is barrierless, the latter being the only Zn structure (n=1 ± 4) corresponding to a local minimum. There is also no minimum on the potential energy surface corresponding to the s-complex 16. Minkin et al. 45 believe that attempts to generate the nitrosocyclobutenyl cation in the gas phase or in a weakly solvating solvent will fail. Calculations by the MINDO/3 method for the structure 12 predicted that the nitroso group can either migrate parallel to the plane of the cyclobutadiene ring (Scheme 2, path a) or rotate about the C7O bond (Scheme 2, path b).45 a O+ N b O 12 For the Z2-isomer 13, the rotational-type rearrangement 13.130.1300 with the low energy barrier (Ea=46.9 kJ mol71) involving cation 16 as the transition state was revealed.45 O O + + N N 13 130 { Ab initio calculations taking into account the electron correlation (MP2/6-31G*+ZPE) also demonstrated that the structure 14 does not correspond to the minimum on the PES.46 12 STO-3G MINDO/3 STO-3G 1016.3 7 7 7279.1439 334.7 38.6 O O N+ +N13 (Cs) 14 (C4u) N + O N + N H O 18 (C1) 17 (C2u) Scheme 2 O+ O+ N N a + b N +O N O +N 1300 213 18 17 15 13 MINDO/3 STO-3G MINDO/3 681.6 931.4 885.8 1044.7 7 7 7 7 7 7 7279.0593 0 249.8 204.2 222.1 363.1 0 It should be noted that the above-considered topomerisation reactions of the structures 12 (see Scheme 2) and 13 are, appa- rently, of only theoretical interest because these complexes are kinetically unstable and are converted into the structures 18 and 17, respectively, with low energy barriers (Ea=14.2 and 16.7 kJ mol71, respectively).45 Until recently, experimental data on p-complexes of alkenes with the nitrosonium cation were lacking in the literature.Attempts to synthesise complexes of this type by reactions of [NO]+[BF4]7 with ethylene or 2,3-dimethylbut-2-ene failed. In the former case, the reaction did not proceed, whereas the latter reaction afforded exclusively polymeric products.47 Olah et al.47 believed that the reaction of [NO]+[BF4]7 with adamantylide- neadamantane gave rise to either a dynamical s-complex or a p-complex.However, the authors failed to choose between these complexes. The first reliable data on the synthesis of an alke- ne ±NO+ complex were obtained in a study by Borodkin and co- workers.48 According to the results of 1H, 13C and 27Al NMR spectroscopy using the isotope perturbation method, the complex of 1,2,3,3,4,5,6,6-octamethylcyclohexa-1,4-diene with the NO+ cation is a Z2-type p-complex (structure 19).48, 49 It appeared that this complex underwent degenerate p,p-rearrangement 19.19 0 (in the SO2±SO2ClF ±CD2Cl2 system), rapid within the NMR time scale even at low temperature (780 to 790 8C), the rate of intramolecular transfer of the NO+ group being higher than the rate of intermolecular transfer.+ON NO+ 19 19 0 +NO+ The rate of the intermolecular rearrangement increases on going from the SO2±SO2ClF ±CD2Cl2 system to the SO2 ± CD2Cl2 system.48, 49 The results of quantum-chemical calculations for the nitro- sonium complexes with cyclohexa-1,4-diene and 1,2,3,3,4,5,6,6- octamethylcyclohexa-1,4-diene by the MINDO/3 and MNDO/ PM3 methods indicate that Z2-type p-complexes (20 and 21) are more stable than the corresponding s-complexes (22 and 23) and Z4-type p-complexes (24 and 25) 48, 49 through which intramolec- ular transfer of the nitroso group apparently proceeds.O+ N R R NO R R R R R + R R R NO+ R RR R R R R R R R R R R R 24, 25 22, 23 20, 21 R = H (20, 22, 24), Me (21, 23, 25).214 As mentioned above, ab initio calculations provided evidence for the existence of two types of ethylene complexes with theNO+ cation (8 and 9).These complexes differ in geometry and, primarily, in the distance between the nitrogen atom and the C=C bond (d=0.1272 and 0.1978 nm, respectively).44 The structure of the nitrosonium complex with 2,3-dimethylbut-2-ene was analysed in detail by 1Hand 13C NMRspectroscopy using the isotope perturbation method and by ab initio quantum-chemical (6-31G* basis set) and IGLO calculations.50 As in the case of the ethylene ±NO+ isomers, the calculations predicted the existence of two types of complexes characterised by the symmetry C2u (26) and the approximate symmetry Cs (27).In these complexes, the distances from the N atom to the C=C bond are 0.1225 and 0.2183 nm, respectively. O O 0.1084 nm 0.1152 nm N+ N+ 0.2315 nm 0.2266 nm 0.1451 nm 35.18 64.88 Me Me 0.1381 nm 0.1555 nm Me Me Me Me Me Me 27 (*Cs) 26 (C2u) In the complexes 26 and 27, the energies of binding of the nitrosonium cation with 2,3-dimethylbut-2-ene are 93.7 and 117.6 kJ mol71, respectively, which is indicative of higher stabil- ity of the complex 27. The experimental chemical shifts of the C(2) and C(3) atoms (190.2 ppm) are substantially closer to those calculated by the IGLO(DZ) method for the complex 27 (dC 183.4 and 189.8, respectively) than to those for the complex 26 (dC 67.2).The equivalence of the C(2) and C(3) atoms and the equivalence of the carbon atoms of the methyl groups observed in the 13C NMR spectrum of the complex 27 were attributed either to the inversion of the nitrogen atom or to the rotation of the NO group about the axis passing through the nitrogen atom perpen- dicular to the C(2)7C(3) bond as well as to the high rate of migration of this group.50 Complexes of different alkenes with the [NO]+[BF4]7 and [NO]+[PF6]7 salts and with other sources of the nitrosonium cation (RONO±CF3CO2H, NOCl ±CF3CO2HandN2O4 ± SbF5) were investigated.51 At low temperature, the electronic spectra of 2,3-dimethylbut-2-ene, 2,3,4-trimethylpent-2-ene and adaman- tylideneadamantane have charge-transfer bands.The reactions of other alkenes, such as 2,5-dimethylhex-2-ene, 2,4,4-trimethyl- pent-2-ene, 1-methylcyclohexene, cyclohexene, 2,3,3-trimethyl- but-1-ene, norbornene, 3,3-dimethylbut-1-ene and hex-1-ene, with the above-mentioned salts either afforded slightly coloured solutions or did not give coloured solutions corresponding to the formation of charge-transfer complexes at all. These differences in the behaviour of alkenes containing the completely substituted C=C bond and those with the partially substituted C=C bond were attributed to the difference in the oxidation potentials (Eox) of these alkenes.51 Thus the oxidation potentials of 2,3-dimethyl- but-2-ene and 2,3,4-trimethylpent-2-ene (Eox=1.6 V) are sub- stantially smaller than those of 2-methylbut-2-ene and but-2-ene (Eox&2.0 and 2.4 V, respectively).The thermal and photochem- ical behaviour of the alkene ±NO+ complexes is explained by the formation of charge-transfer complexes. The photochemical activation of these complexes leads to generation of the corresponding radical cations. Thus irradiation of 2,3-dimethylbut-2-ene and N2O4 in a matrix at the frequency corresponding to the charge-transfer band (nCT) at 75K afforded a pair of the type 28. hnCT + , NO+ , NO 28 G I Borodkin, V G Shubin The subsequent reaction of the radical cation of 2,3-dimethyl- but-2-ene with nitric oxide gave rise to the 1-nitroso-2,3-di- methylbut-2-yl cation, which reacted with the NO¡3 anion to form nitrosonitrate.51, 52 The reaction of 1,2-bis(pentamethylphenyl)bicyclo[2.2.2]oct- 2-ene (29) with the nitrosonium cation in CH2Cl2 at 25 8C afforded p-complex 30.The characteristic feature of the latter complex is the fact that the NO group in this complex can interact with both the double bond and the aromatic rings (Scheme 3).53 Scheme 3 +NO+ O 29 N+ +. 30 +NO 31 6 Electrochemical oxidation of the alkene 29 gave rise to the corresponding radical cation 31 whose reaction with gaseous nitric oxide afforded the same p-complex 30 53 (cf. Ref. 54). X-Ray diffraction analysis of the p-complex 30 (with the SbCl¡ counterion) revealed the presence of noncovalent bonding of the NO+ cation with the aromatic rings (the average distance to the plane of the rings is *0.25 nm) and with the double bond, the positive charge being primarily localised at the aromatic and alkene carbon atoms, respectively.53 The C(1)=C(2) bond length in the complex 30 (0.137 nm) is larger than that in the precursor 29 (0.133 nm) and is virtually identical to the above-mentionedC=C bond lengths in the complexes 9 and 27 determined by ab initio calculations.The strong bond between the NO+ group and the unsaturated system in the complex 30 is consistent with its high formation constant (>36106 litre mol71).53 IV. Nitrosonium complexes of aromatic compounds Nitrosonium complexes of monocyclic aromatic compounds have been investigated in sufficient detail.44, 55 ± 90 These complexes attract the attention of organic chemists primarily because they are analogues of intermediates of such important reactions as diazotisation, C-nitrosation and nitration proceeding through nitrosation of aromatic compounds 1, 90 ± 95 (cf.Ref. 96). In addi- tion, it is known that the NO+ cation catalyses bromination of aniline derivatives 97 and proton exchange in the N,N-dimethyl- anilinium ion,98 which was assigned to the formation of the corresponding arene ±NO+ complexes. The nitrosation of benzene was investigated by quantum- chemical methods.70 Thus, the pathway of electrophilic replace- ment of the hydrogen atom in the benzene ring by theNO+ cation was calculated by the MINDO/3 method. Initially, the electron is transferred from the frontier orbital of the benzene molecule to the p* orbital of the nitrosonium cation to form p-complexes 32 and 33.The enthalpies of their formation are 1017.1 and 959.0 kJ mol71, respectively.Nitrosonium complexes of organic compounds. Structure and reactivity O O + N O+ N + N O N + H 35 (Cs) 33 (C1) 34 (C6u) 32 (C2u) According to the rule of electron counting for pyramidal structures,99 ± 101 the p-complex 34 with the symmetry C6u is unstable (DHf=1031.8 kJ mol71) and corresponds to a peak top on the potential energy surface. A shallow minimum on the PES (8.4 kJ mol71) corresponds to the structure of s-complex 35 (DHf=928.8 kJ mol71), which indicates that it is not detectable experimentally. Calculations for the p-complexes 32 and 33 provided evidence for the occurrence of a sixfold-degenerate rearrangement with a low energy barrier (Ea<12.6 kJ mol71) caused by `switching' of the C7N bond in the complex 32 and migration of the nitroso group over the plane of the ring in the structure 33: O O O N+ N+ N+ ...; ... 32 3200 320 + N N N O+ O O+ ... ... 33 3300 330 The DDHf value (relative to the C6H6±NO+system) found by higher-level quantum-chemical calculations (ab initio, MP2/6- 31G+D)44 for the centrosymmetrical structure 34 is 7189.1 kJ mol71, which is close to the experimental value for the gas phase (717221 kJ mol71).44, 64 The corresponding s-complex is substantially less stable (DDHf=723.4 kJ mol71). Table 3. 1H NMRspectral data for the p-complexes of benzene and its derivatives with the nitrosonium cation (the molar ratio ArH : [NO]+X7=1 : 1).Solvent Salt Compound Benzene Toluene SO2 SO2 H2SO4 see c SO2 SO2 SO2 SO2 see c SO2 SO2 p-Xylene NOAlCl4 NOGaCl4 NOHSO4 see b NOPF6 NOSbCl6 NOTiCl4 NOAlCl4 see b NOPF6 NOSbCl6 NOSbCl6 (see d) SO2 (NO)2SnCl4F2 NOTaCl6 NOAlCl4 NONbCl6 NONbF6 NOPF6 NOSbCl6 (NO)2SnCl4F2 NOTaCl6 NOTiCl6 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 Ab initio B3LYP/6-31G(d) calculations revealed stable p-com- plex 36 with the symmetry C1 . The energy of its formation from benzene and the NO+ cation is 7220.5 kJ mol71.89 In addition, the calculations gave local minima for the p-complexes 32 and 33 whose relative energies are 163 and 201 kJ mol71, respectively, smaller than that in the case of the p-complex 36.O 0.1115 nm N + 0.2436 nm 36 According to the results of quantum-chemical calculations, the p-complex of toluene with the NO+ cation (37) is more stable than the p-complex 36 (DErel=17.6 kJ mol71). The stretching vibration frequency of the NO group calculated for the complex 37 (2087 cm71) is smaller than that for the complex 36 (2110 cm71), which is indicative of a higher degree of electron density transfer from the aromatic ring to the NO group in the cation of the complex 37.89 The first experimental data on the formation of ArH ±NO+ p-complexes were obtained by electronic spectroscopy of nitro- sonium complexes of benzene and its derivatives.58, 59 Shortly thereafter, p-complexes of the NO+ cation with benzene deriva- tives were investigated by Allan et al.60, 61 More recently, NMR spectroscopy along with electronic and IR spectroscopy were employed for studying cationic p-complexes.The available spec- tral data for the nitrosonium p-complexes of benzene and its derivatives are summarised in Tables 3 ± 5. The formation of p-complexes leads to characteristic changes, in particular, to downfield shifts of the signals in the 1H and 13C NMR spectra (see Tables 3 and 4, respectively), to the appearance of charge- transfer bands in the electronic spectra and to a decrease in the stretching vibration frequency of the NO group in the complexes compared to those in [NO]+X7 salts (see Table 5).Apparently, all the above-mentioned changes are caused by the electron density transfer from the aromatic moiety of the complex to the nitroso group. Chemical shifts (dH) a CH3 2.67 (0.37) 2.52 (0.14) 2.42 (0.12) 2.78 (0.48) 2.47 (0.17) 2.56 (0.26) 2.57 2.63 (0.35) 2.57 2.45 2.55 (0.27) 2.58 (0.30) 2.67 (0.39) 2.44 2.38 (0.10) 215 O 0.1118 nm +N 0.2406 nm 37 Ref. Harom 8.03 (0.62) 7.75 (0.34) 7.89 7.49 (0.11) >7.34 7.81 7.60 (0.19) 7.92 (0.72) 7.57 (0.31) 7.38, 7.45 8.05 (0.85) 7.46 (0.26) 7.65, 7.74 7.70 ± 7.82 7.81 (0.70) 7.67 7.43 7.63 (0.52) 7.67 (0.56) 7.83 (0.72) 7.40 7.30 (0.19) 72 72 64 78 73 73 72 72 78 73 73 73 72 74 72 74 74 73 73 72 74 72216 Table 3 (continued).Compound Mesitylene Durene tert-Butylbenzene Pentamethylbenzene Hexamethylbenzene Chlorobenzene a The differences between the chemical shifts of the signals for the protons in the spectra of the p-complex and its precursor are given in parentheses. b Either NOBF4 or NOPF6 was used as the salt. c Either CD3CN or CD3NO2 was used as the solvent. d The ArH : [NO]+X7 molar ratio was 2 : 1. e The reaction temperature was 35 8C; in all other cases, the temperature was not reported. Table 4. 13C NMRspectral data for the p-complexes of benzene and its derivatives with the nitrosonium cation (the molar ratio ArH : [NO]+X7=1 : 1). Compound Benzene Solvent Salt NOAlCl4 see b NONbCl6 NONbF6 NOPF6 NOPF6 (NO)2SnCl6 (NO)2SnCl4F2 NOTaCl6 NOTaF6 see b NOPF6 NOPF6 NOSbÊ l6 see b NOPF6 SO2 see c SO2 SO2 SO2 CD3NO2 SO2 SO2 SO2 SO2 see c CD3NO2 (see e) CD3NO2 SO2 see c CD3NO2 (see e) NOPF6 (see d) CD3 NO2 (see e) NOPF6 NOAlCl4 NOAsF6 NOBF4 (NO)2GeCl2F4 (NO)2GeF6 NOMoCl6 NOMoF6 NOMo2O2F9 NONbCl6 NONbF6 NOPF6 NOPF6 NOPF6 NOSbCl6 NOSbF6 (NO)2SiF6 (NO)2SnCl6 (NO)2SnCl4F2 NOTaCl6 NOTaF6 (NO)2TiCl6 (NO)2TiF6 NOUF6 NOUF7 NOWCl7 NOW2O2F9 NOGaCl4 CD3NO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 CD3CN CD3CN SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 Solvent Salt Chemical shifts (dC) a CH3 SO2 see c SO2 SO2 SO2 SO2 NOAlCl4 see b NOGaCl4 NOPF6 NOTiCl4 NOSbCl6 Chemical shifts (dH) a CH3 2.58 (0.35) 2.52 (0.24) 2.52 2.41 2.52 (0.29) 2.51 2.42 (0.19) 2.60 (0.37) 2.58 2.51 2.48 (0.30) 2.37 (0.19) 2.43 1.47 (0.17) 2.44 (0.28), 2.46 (0.26) 2.38 (0.20), 2.44 (0.23) 2.27 (0.09), 2.31 (0.10) 2.44, 2.51 2.48 (0.33) 2.39 (0.24) 2.42 (0.27) 2.45 (0.30) 2.32 (0.17) 2.21 2.40 2.46 2.49 2.46 2.47 (0.32) 2.48 (0.30) 2.48 2.47 (0.32) 2.48 (0.33) 2.42 (0.27) 2.49 (0.34) 2.50 (0.35) 2.48 2.47 2.50 (0.35) 2.48 (0.33) 2.34 2.47 2.46 2.42 Carom 137.1 (7.9) 131.0 (1.2) 134.8 (5.6) >129.1 132.2 (3.0) 136.7 (7.5) G I Borodkin, V G Shubin Ref.Harom 7.58 (0.77) 7.49 (0.66) 7.44 7.18 7.45 (0.64) 7.50 7.21 (0.40) 7.57 (0.76) 7.57 7.40 7.67 (0.78) 7.42 (0.54) 7.56 7.89, 7.96, 8.05 7.66 (0.87) 7.52 (0.71) 7.1 (0.29) 7.66 72 78 74 74 73 76 72 72 74 74 78 62 76 73 78 62 62 76 72 73 72 72 72 74 74 74 74 74 73 78 76 73 73 72 72 72 74 74 72 72 74 74 74 74 72 7.38 Ref. 72 78 72 73 72 73Nitrosonium complexes of organic compounds. Structure and reactivity Table 4 (continued). Salt Compound Toluene see b NOPF6 p-Xylene Mesitylene Durene see c SO2 NOSbCl6 (see d) SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 see c SO2 SO2 SO2 SO2 SO2 CH2Cl2 (see g) see c see g, h SO2 see c (NO)2SnCl4F2 NOTaCl6 NOPF6 NONbF6 NOSbCl6 (NO)2SnCl4F2 NOTaF6 NOAlCl4 see b NOPF6 NONbF6 NOTaCl6 NOTaF6 (NO)2TiCl6 NOAlCl4 see b NOAlCl4 NOSbCl6 see b tert-Butylbenzene Pentamethylbenzene Hexamethylbenzene NOAlCl4 NOAlCl4 NOAlCl4 NOAsF6 (NO)2GeF6 NOMoCl6 NOMoF6 NOMo2O2F9 NONbF6 NOPF6 NOPF6 NOSbCl6 NOSbCl6 NOSbF6 (NO)2SiF6 (NO)2SnCl4F2 NOTaCl6 NOTaF6 (NO)2TiCl6 (NO)2TiF6 NOUF6 NOUF7 NOWCl7 NOW2O2F9 21.7 (0) 20.9 (0.1) 20.8 21.3 (0.5) 21.4 20.7 20.6 20.8 21.1 20.6 see f 21.6 (0.1) 20.9 20.7 21.2 20.9 20.9 19.8 19.7 (0.4) 20.1 30.5, 36.5 21.1 (0.3), 17.3 (0.9), 16.9 (0.8) 17.5 17.3 (1.6) 18.6 17.1 (1.4) 16.7 (1.0) 16.5 17.1 (1.4) 17.1 (1.4) 17.1 (1.4) 17.1 (1.4) 17.9 (0.9) 18.2 (2.5) 20.5 17.1 (1.4) 16.9 (1.2) 17.3 (1.6) 17.5 (1.8) 17.2 (1.5) 17.3 (1.6) 17.1 (1.4) 17.2 (1.5) 17.3 (1.6) 17.7 (2.0) 17.4 (1.7) a The differences between the chemical shifts of the signals for the carbon atoms in the spectra of the p-complex and its precursor are given in parentheses.b Either NOBF4 or NOPF6 was used as the salt. c Either CD3CN or CD3NO2 was used as the solvent. d The ArH : [NO]+X7 molar ratio was 2 : 1. e The chemical shift is given only for the CH fragment. f The chemical shift was not reported. g The reaction temperature was 20 8C; in all other cases, the temperature was not reported.h For the crystalline form. Table 5. Data from IR (nNO) and electronic absorption spectroscopy (lmax) of the p-complexes of benzene and its derivatives with the nitrosonium cation (the molar ratio ArH : [NO]+X7=1 : 1). Compound Benzene Solvent CH2Cl2 (see g) SO2 see g, h SO2 SO2 SO2 SO2 SO2 SO2 SO2 CD3NO2 SO2 see h SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 SO2 Reagent NOAlCl4 NOHSO4 NOBF4 NOGaCl4 217 Ref. Chemical shifts (dC) a Carom CH3 78 73 73 72 74 73 74 73 72 74 72 78 73 74 74 74 72 71 78 71 73 78 132.5 (4.8), 135.1 (5.1), 136.1 (5.7), 147.6 (8.0) 128.4, 131.3, 132.1, 142.0 129.8, 132.6, 133.2, 144.3 132.6, 135.1, 136.0 133.7, 136.1, 137.0, 149.3 137.6, 147.6 135.0 e 137.8, 148.0 139.9, 151.1 134.3, 142.5 139.1 e 137.8 (9.6), 151.8 (12.5) 137.1, 151.1 132.9, 145.5 138.9, 153.4 136.1, 149.8 135.2 (4.7) e 142.0, 150.3 142.9 (10.6), 151.3 (16.2), 148.3, 154.5 134.3, 134.8, 136.9, 163.5 141.5 (11.3), 151.0 (17.4), 151.5 (17.0), 152.8 (16.7) 147.7 149.9 (18.9) 142.1 149.1 (18.1) 142.1 (11.1) 131.7 147.9 (16.9) 148.6 (17.6) 148.1 (17.1) 149.8 (18.8) 150.8 (17.6) 150.2 (19.2) 151.9 150.1 (19.1) 144.6 (13.6) 150.2 (19.2) 150.3 (19.3) 149.8 (18.8) 150.2 (19.2) 148.8 (17.8) 143.7 (12.7) 149.5 (18.5) 150.5 (19.5) 146.9 (15.9) 71 72 71 73 72 74 74 74 74 73 78 73 78 73 72 72 74 74 72 72 74 74 74 74 Solvent Ref.nNO /cm71 lmax /nm (e) 72 64 76, 78 72 335 332 (18 000) 346 (780), 460 (60) 335 CH2Cl2 H2SO4 MeCN CH2Cl2 7777218 Table 5 (continued). Compound Benzene Toluene Toluene o-Xylene p-Xylene Mesitylene tert-Butylbenzene 1,3,5-Tri-tert-butylbenzene Durene Pentamethylbenzene Solvent Reagent MeNO2 2075 7 7 344 338 (11 000) 342 (400) 77 CH2Cl2 MeCN MeNO2 MeNO2 7 7 340 (10 600) 7 7 340 (5300) a MeCN MeNO2 CH2Cl2 MeCN CH2Cl2 CH2Cl2 MeNO2 see d see d CH2Cl2 CH2Cl2 CH2Cl2 MeCN MeCN MeNO2 CH2Cl2 CH2Cl2 see e NOPF6 NOSbCl6 NOAlCl4 NOBF4 NOPF6 NOSbCl6 NOSbCl6 NOSbCl6 NOBF4 NOPF6 NOAlCl4 NOBF4 NOBF4 N2O4 N2O4(SbCl6) CH2 Cl2 NOPF6 NONbF6 NOTaF6 NOTaF6 NOSbCl6 NOAlCl4 NOBF4 NOBF4 NOBF4 NOBF4 N2O4 N2O4(SbCl6) N2O4(SbCl6) CH2 Cl2 NONbF6 NOPF6 NOPF6 NOPF6 NOSbCl6 (NO)2SiF6 (NO)2SnCl4F2 NOTaF6 (NO)2TiCl6 CH2Cl2 CH2Cl2 MeNO2 see f MeNO2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 MeCN MeCN MeNO2 MeCN CH2Cl2 CH2Cl2 see e NOPF6 NOPF6 NOPF6 NOPF6 NOPF6 NOPF6 NOBF4 NOBF4 N2O4 MeCN7 7 339 (5000) 360 349 (1730) 349 (1700) 7336 (1100), 520 (40) 486 b 77489 b 7335,*500 77335 7337 (2400) 491 b 7490 b 340 77777 NOBF4 NOSbCl6 (NO)2SnÊ l6 NOBF4 NOBF4 NOPF6 NOBF4 NOBF4 N2O4 N2O4(SbCl6) N2O4(SbCl6) CH2 Cl2 MeNO2 CH2Cl2 MeCN MeNO2 MeCN or MeNO2 see f MeCN CH2Cl2 CH2Cl2 N2O4(SbCl6) CH2 Cl2 NOPF6 NOPF6 NOPF6 NOPF6 NOPF6 NOPF6 MeCN or MeNO2 CH2Cl2 MeCN MeNO2 MeNO2 see f G I Borodkin, V G Shubin Ref.lmax /nm (e) nNO /cm71 7 772037 2030 78 73 72 76, 78 78 78 73 73 78 78 72 78 83 83 83 78 74 74 74 73 72 76 78 62 83 83 83 83 74 76 78 76 78 72 72 74 72 338 (2200), 500 (180) 7340 336 (1300), 520 (81) 496 b 7506 b 777274, 446 340 (10 000) 343 345 (2080) 345 (2100) 7486 b 77493 b 386 335 777390 391 388 285 72000 7771964 c 71998 1810 1810 777772000 ± 1950 71948 c 1954 771967 1975 2016 1964 7777 340 (270), 460 (52) 7 78 73 72 76 78 78 78 83 83 83 83 62, 78 76 62 62 62 76 76, 78 83 83 83 62 76 62 62 78 76 7771964 771948 c 1880 71933 1929 1930 1930 71986 771896 c 771904 1900 1900 1907 1927219 Nitrosonium complexes of organic compounds.Structure and reactivity Table 5 (continued). Ref. Solvent Reagent Compound lmax /nm (e) nNO /cm71 Hexamethylbenzene see d CH2Cl2 7334 (10 000) MeCN MeCN CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 see d see d CH2Cl2 see e NOAlCl4 NOAlCl4 NOAsF6 NOBF4 NOBF4 NOBF4 (NO)2GeF6 NOFeCl4 NOMo2O2F9 NOMo2O2F9 NOMoF6 N2O4 N2O4(SbCl6) N2O4(SbCl6) CH2 Cl2 CH2Cl2 7777771870 1780 1862 c 1850 71880 MeNO2 see f see d CH2Cl2 see d 777330 7 MeNO2 see d CH2Cl2 77330 Hexaethylbenzene 1,3-Dineopentyl-2,4,5,6-tetramethylbenzene 1,4-Dineopentyl-2,3,5,6-tetramethylbenzene Anisole Chlorobenzene 2-Methylanisole 4-Methylanisole 71 72 73 76 78 72, 83 72 74 74 74 74 83 83 83 76 73 78 76 74 74 73 73 78 73 55 73 72 72 72 74 74 74 72 72 72 74 74 74 74 74 74 83 78 83 78 78 84 78 72 84 84 78 84 84 84 85 a The ArH : [NO]+X7 molar ratio was 2 : 1.b The lmax value is given only for the long-wavelength band (at 778 8C).c At 778 8C. d In KBr pellets. e Mineral oil mull. f Spectra of the crystalline form. g Shoulder. h At740 8C. 1853 7 7 7 334 (47 000) 337 (3000) 337 (3100) 325 (7300), 499 b 338 (7100) 325, 360 323 77495 b 7499 b 337,*500 7 7 275 g 1885 1899 1850 71849 7 7 334 (8100) 1885 1850 7 7 7 272 338 336 336 332 7334 310 340 326 7320 7325 358 7511 b 7516 b 77344 (1000), 480 (635) h 343 (110), 500 (6.4) 290 g 346, 477 h 346 (980), 506 (370) h 334 355, 488 h 353, 463 h 340 (470), 500 (100) h 366 c NOPF6 NOPF6 NOPF6 NOPF6 NONbF6 NONbF6 NOSbCl6 NOSbCl6 NOSbCl6 NOSbF6 NOSbF6 NOSbF6 (NO)2SiF6 (NO)2SnCl6 (NO)2SnCl4F2 NOTaCl6 NOTaF6 NOTaF6 NOTiCl6 (NO)2TiCl4F2 (NO)2TiF6 NOUF6 NOUF6 NOUF7 NOUF7 NOWCl7 NOW2O2F9 NOBF4 NOPF6 N2O4 NOPF6 NOPF6 NOBF4 NOBF4 NOGaCl4 NOBF4 NOBF4 NOBF4 NOBF4 NOBF4 NOBF4 NOBF4 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 see d CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 see d CH2Cl2 see d CH2Cl2 CH2Cl2 see d CH2Cl2 MeNO2 CH2Cl2 MeNO2 MeNO2 MeCN MeCN CH2Cl2 MeCN MeCN CH2Cl2 MeCN MeCN MeCN CH2Cl2 77771800 77771880 71870 771878 71900 71884 1884 7777777777 3,5-Dimethylanisole 2-Bromoanisole 4-Bromoanisole 1,4-Dimethoxybenzene The degree of electron density transfer can be estimated from 13C NMRspectral data.It is known that the chemical shifts of the positive p-charges (qáp ) and the ionisation potentials of the aromatic donor.78 Actually, a linear correlation between these characteristics takes place in the case of the nitrosonium p-com- plexes of benzene and alkylbenzenes 78 (Fig. 2) from which it can be seen that an increase in the donating ability of the aromatic substrate leads to an increase in the degree of charge transfer. sp2-hybridised carbon atoms in charged p-electron systems corre- late linearly with the p-charges on these atoms.102, 103 Assuming that the degree of electron density transfer to the nitroso group in the p-complex depends on the ionisation potential of the aromatic substrate (Ip), one would expect a relationship between the220 qáp1 0.6 2 3 4 0.4 5 0.2 6 0 Ip /eV 9.0 8.6 8.2 7.8 Figure 2.Correlation between the positive p-charges (qáp ) on the aro- matic fragments in the nitrosonium complexes with benzene and alkyl- benzenes and the ionisation potentials (Ip) of the aromatic donors:78 (1) hexamethylbenzene, (2) pentamethylbenzene, (3) durene, (4) mesityl- ene, (5) toluene, (6) benzene (r=70.998). The qáp values were calculated using the differences between the chemical shifts of the complexes and their precursors determined in the study;78 the value of 160 ppm was taken per unit p-charge. It was demonstrated 78 that the degree of charge transfer in p-complexes can be estimated by IR spectroscopy.Thus a linear correlation between the ionisation potentials of the aromatic substrate and the degree of charge transfer (Z) was found for benzene and its derivatives. The degree of charge transfer was determined from the following formula: Z = (n 2NOá 7n 2p) / (n 2NOá 7n 2NO), where n NOá , n p and n NO are stretching vibration frequencies of the NO group in the NO+ cation, the p-complex and nitric oxide, respectively (Fig. 3).78 X-Ray diffraction studies provide the most reliable informa- tion on the structures of cationic complexes. The first data on the structures of nitrosonium complexes of aromatic compounds obtained 68, 69 for the complex of hexamethylbenzene with the NO+ cation disclosed that the conventional view (cf.Refs 61 and 64) that p-complexes of aromatic compounds with electrophilic agents are highly symmetrical systems should be revised.104 According to the X-ray diffraction data,68, 71 the normal (which passes through the nitrogen atom of theNOgroup) to the plane of the core of this complex is displaced from the centre of the aromatic ring and the nitroso group is located at an angle of *50 8 (the structure 38), the nitrogen atom being rather far removed from the ring (by 0.21 nm). Z 11, 12 1.0 98 0.9 10 7 5 6 3 4 2 1 0.8 0.7 0.6 0.5 8.5 8.0 7.5 9.0 Ip /eV Figure 3. Correlation between the degree of electron transfer (Z) in nitrosonium complexes with benzene and alkylbenzenes and the ionisation potentials (Ip) of the aromatic donors: (1) benzene, (2) toluene, (3) 1,2- dimethylbenzene, (4) 1,4-dimethylbenzene, (5) 1,3,5-trimethylbenzene, (6) 1,3,5-tri(tert-butyl)benzene, (7) 1,2,4,5-tetramethylbenzene, (8) pen- tamethylbenzene, (9) hexamethylbenzene, (10) hexaethylbenzene, (11) 1,4- di(neopentyl)-2,4,5,6-tetramethylbenzene, (12) 1,3-di(neopentyl)-2,3,5,6- tetramethylbenzene (r=70.987).78 G I Borodkin, V G Shubin + O N 38 The nitrosonium complexes of toluene,73 mesitylene,78 durene,71 hexaethylbenzene,88 2,3-dimethyl-2,3-diphenyl- butane,81 1,2,3,4,5,6,7,8,9,10,11,12-dodecahydro-1,4;5,8;9,12- triethanotriphenylene 88 and octamethyl-9,10-dihydro-9,10-etha- noanthracene 105 have analogous structures.A comparison of the structures and geometric parameters of nitrosonium complexes of arenes and alkenes disclosed that these complexes are somewhat similar, viz., theNOgroup is located at an angle to the plane of the core and the distances from the nitrogen atom to this plane have close values.According to the results of CNDO/2 calculations with the use of the real geometry of the hexamethylbenzene complex with the nitrosonium cation, the positive charges on the aromatic carbon atoms of the same type differ substantially from those on the carbon atoms of the methyl groups.71 Nevertheless, two rather narrow singlets are observed in the 13C NMR spectra recorded both for solutions (in the HSO3F±SO2ClF mixture, 7130 8C) 75 and for the solid phase,71 which is attributable to the p,p- rearrangement, rapid within the NMR time scale.+ + + NO NO NO 38 3800 380 The mechanism of this rearrangement involves either the migration of the NO group over the plane of the ring or the rotation of this ring about its `normal' followed by `switching' of the Carom7N bonds, the latter situation being more probable for the complex in the crystalline state.71, 75 The results of studies of the isotope effects of deuterium manifested in the 13C NMR spectra of nitrosonium p-complexes with C6(CD3)m(CH3)67m compounds do not contradict the conclusion that these complexes undergo rapid p,p-rearrangement in solutions.80 The kinetic parameters of this rearrangement (Ea=42.72.5 kJ mol71, logA=13.90.3) for the crystalline complex were determined by relaxation NMR spectroscopy.75 According to the 1H and 13C NMR spectral data, analogous p,p-rearrangements occur, apparently, in the nitrosonium com- plexes of benzene,72, 73, 78 alkylbenzenes,62, 72 ± 74, 76, 78 chloro- benzene,72 anisole,87 2,3,5,6,8,9-hexahydro-1,2;3,4;5,6-tris- (cyclopenta)benzene,106 [2.2]paracyclophane 107 and tripty- cene.107 To reveal the contributions of the intermolecular and intra- molecular mechanisms of rearrangements of nitrosonium com- plexes, it is important to elucidate the influence of the structure of the aromatic substrate on the formation constants of these complexes (K): K ArH+NO+ ArH7NO+.The quantitative data on the constants K for the p-complexes of benzene and its derivatives were obtained 76, 78, 81, 84, 88 by processing electronic absorption spectra using the Benesi ± Hilde- brand method.A linear correlation between the logarithms of the formation constants of the p-complexes and the ionisation poten- tials of the corresponding aromatic hydrocarbons was found 76 (Fig. 4). The point corresponding to 1,3,5-tri(tert-butyl)benzene deviates from the dependence presented in Fig. 4 76 due, appa-Nitrosonium complexes of organic compounds. Structure and reactivity logK25 8C1 2 3 4 43210 5 71 8.0 7.5 9.0 Ip /eV 8.5 Figure 4. Dependence of the logarithms of the formation constants (logK) of the ArH ±NO+ complexes (BF¡4 as the anion) in MeCN at 25 8C on the ionisation potentials (Ip) of the aromatic donors: (1) hexa- methylbenzene (2) pentamethylbenzene (3) mesitylene (4) toluene (5) ben- zene (r=70.995).76 rently, to steric inhibition of the donor-acceptor interaction between the aromatic substrate and the nitrosonium cation (cf.Ref. 88). The high degree of charge transfer in the ground state of nitrosonium complexes of aromatic compounds containing donor substituents agrees well with the chemical behaviour of these complexes. The key stage of these reactions involves the transfer of one electron from the aromatic donor to the NO+ group giving rise to a radical cation, which undergoes further transformations: [ArH, NO+], ArH+NO+ [ArH+., NO.], [ArH, NO+] products. [ArH+., NO.] This general scheme can be exemplified by the conversions of aromatic compounds 39 ± 43 into products 44 ± 50 (Scheme 4). In these processes, ArH7NO+ p-complexes are, apparently, gen- erated at the initial stage (see Refs 78 and 81).All the above-considered calculated and experimental data provide evidence that the reactions of the nitrosonium cation with monocyclic aromatic compounds generally afford p-complexes rather than s-complexes. In this connection, it is of interest that investigation of the kinetics of nitrosodeiodination of 4-iodoani- sole by electronic absorption spectroscopy 63 provided evidence for the formation of the s-complex, viz., the 1-iodo-4-methoxy-1- nitrosobenzenonium ion (cf. Ref. 91). Recently, the nitrosonium s-complexes with benzene, mesitylene, hexamethylbenzene and other aromatic compounds have been detected by this method using the femtosecond laser technique at low temperature.90 However, it is known that information on the structures of cationic complexes of aromatic compounds obtained by electronic absorption spectroscopy is less reliable than that provided by NMR spectroscopy.103 The more reliable NMR spectral data demonstrated that the reactions of anisole 87 and hexamethylben- zene 80 with [NO]+[AlCl4]7 in the SO2±CD2Cl2 system at low temperature afforded p-complexes (cf. Refs 68 and 71 ± 76).The nitrosonium cation is a strong oxidising agent 108, 109 (cf. Refs 55 and 56). Generally, its reactions with bi- and polycyclic arenes possessing, as a rule, low ionisation potentials 110 give rise to the corresponding radical cations or their reaction prod- ucts.55, 78, 109 Thus, the reactions of naphthalene with nitrosonium salts in trifluoroacetic acid at *20 8C afforded initially a mono- meric radical cation, followed by the formation of a dimeric radical cation and, finally, of a mixture of hydrocarbons C10H7 ± (C10H6)m±C10H7.109, 111, 112 Most likely, the transfer of one electron from the aromatic substrate to the NO+ cation is preceded by the formation of the ArH7NO+ p-complex.In spite of the importance of the data on the structures and reactivities of nitrosonium complexes with polycyclic aromatic compounds, 221 Scheme 4 NHAc Me CH2 Me Me Me Me MeCN,*20 8C +[NO]+[BF4]7 H2O Me Me Me Me Me 44 Me 39 N MeCN, 25 8C +[NO]+[BF4]7 O Ph Ph H2O±NaHCO3 40 45 Me Me Me CH2Cl2, 25 8C + [NO]+[BF4]7 H2O MeO OMe OMe 41 46 Me Me MeMe MeNO2, 20 8C Ph +[NO]+[BF4]7 Ph Ph MeMe 42 Me47 MeO OMe MeCN, 25 8C Ph Ph + [NO]+[BF4]7 MeMe 43 Me X Me O +Ph2CO+ 49 Me Ph Ph Ph 50 Y48a,b 48a: X=OMe, Y=Me; 48b: X=Y=OMe.attempts to generate these complexes have long been unsuccess- ful.61, 76, 113 ± 117 The first data on the formation of nitrosonium p-complexes with fused arenes were obtained for derivatives of naphtha- lene,113, 114 fluorene 113 and acenaphthylene 114 (cf. Refs 55 and 76). The reactions of [NO]+[AlCl4]7 with methylnaphthalenes 51a ± i in SO2 at low temperatures (from770 to780 8C) afforded cationic p-complexes 52a ± i, respectively.115, 116 NO+ R1 R1 R2 R2 +NO+ R3 R3 R4 R5 R4 R5 52a ± i 51a ± i R5 Compounds 51, 52 R4 R3 R2 R1 H H H Me HHHMe HMe HH Me HHH Me Me Me MeH H H H H H H Me H H H HHMe H H H H Me Me H Me Me H H abcdefghi222 Table 6. Parameters of the 13C NMR spectra (dC ) of the complexes 57a,c ± f 117, 119 and the charges qáp on the C(3)7C(8b) atoms.System or solvent Complex Temperature /8C 57a HSO3F±SO2 770 740 795 780 780 750 57c 57d 57e 57f SO2±SO2ClF SO2 CD2Cl2 HSO3F±SO2ClF 0.21 0.22 7 70.26 0.06 0.11 a The chemical shifts are given relative toMe4Si;CD2Cl2 was used as the internal standard (d 52.9). b The difference between the total chemical shifts of the signals for the C(3) ± C(8b) atoms in the spectra of the p-complex and its precursor.c In calculations, the value of 160 ppm was taken per unit p-charge.102 The structures of these complexes were confirmed by the results of 1H, 13C and 15N NMR spectroscopy using the isotope perturbation method.116 The equivalence of the methyl groups in the p-complexes 52f ± i observed in the 1H NMR spectra was attributed 116 to the rapid (within the NMR time scale) intra- and(or) intermolecular migration of the NO group from one aromatic ring to another. Apparently, analogous rearrangements occur in the nitro- sonium complexes of fluorene (53),113 [2.2]paracyclophane (54),107 triptycene (55) 107 and corannulene (56) 118 (Scheme 5).Unlike the complexes of the nitrosonium ion 52 ± 56, the nitrosonium complexes with 1-R-2-methylacenaphthylene (R=Me, CH2D, CH2Cl or Br) 57a ± d do not exhibit dynamical properties.117 E+ R R 2 1 8a 2a E+ 8b 3 8 4 7 5a 6 5 57a ± f E R Compound 57 Me CH2D CH2Cl Br Me Me abcdef NO NO NO NO MeS PhS This is evidenced by the 1H, 13C and 15N NMR spectral data and by the results obtained by the isotope perturbation method.117 The fact that the signals for the C(1) and C(2) atoms in the p-complexes 57a ± d are shifted downfield compared to those of their analogues, viz., the episulfonium ions 57e,f 119 (Table 6), was taken 117 as convinicng evidence for the preferential localisation of the NO group at the C(1)7C(2) bond assuming that the C(1) and C(2) atoms have nearly sp2-hybridisation.p ) Substantial electron density transfer from the aromatic frag- ment to the NO+ group is observed in the complexes of acenaph- thylene and naphthalene derivatives (Table 7, see Table 6), as in nitrosonium complexes of monocyclic aromatic compounds con- taining donor substituents.78 The greater the number of methyl groups in the rings of the complexes 52a ± i, the higher the degree of transfer.116, 117 In addition, judging from the difference between the total chemical shifts of the signals for the C(1) ± C(4) and C(5) ± C(8) atoms in the 13C NMR spectra of the p-complex and its precursor, the positive charge is localised predominantly at the methylated aromatic ring.Interestingly, an approximate linear correlation between the total positive p-charges on the core (qá and the oxidation potentials of the precursors (E1/2) is observed for the nitrosonium complexes of naphthalene and its derivatives (Fig. 5, see Table 7). As expected, a decrease in the oxidation potential of the aromatic hydrocarbon leads to an increase in the positive p-charge on the aromatic fragment of the p-complex 52. dC(1) , dC(2) (see a) DPdC(3)7C(8b) (see b) 33.9 35.4 170.8 171.3 153.6, 168.0 150.6, 166.4 80.8 98.3 41.6 10.1 17.4 H H NO+ +ON 53 +ON NO+ 54 NO+ 55 550 +ON ... 56 560 As mentioned above, naphthalene is oxidised by the nitro- sonium cation at room temperature to form the corresponding Table 7. Parameters of the 13C NMR spectra of the complexes 52a ± i (SO2,770 8C) 116 and the oxidation potentials of their precursors 51a ± c, e ± i.Compounds DPdC(1) ±C(4) /DPdC(5) ± C(8) a qáp [C(1) ± C(8a)] b E1/2 51 and 52 /V c 25.2 / 25.2 44.9 / 16.2 40.6 / 18.6 60.9 / 19.7 56.2 / 16.9 60.8 / 15.6 36.2 / 36.2 d 32.7 / 32.7 e 47.2 / 16.8 abcdefghi 1.54 1.43 1.45 71.38 1.32 1.43 1.30 1.44 a The ratio of the differences between the total chemical shifts of the signals for the C(1) ± C(4) and C(5) ± C(8) atoms in the spectra of the complexes 52a ± i and their precursors. b In calculations, the value of 160 ppm was taken per unit p-charge.102 c The data were reported in Ref.120. d At 775 8C. e At780 8C. G I Borodkin, V G Shubin qáp (see c) Scheme 5 H H 530540 NO+ +ON 5500 NO+ ... NO+ 5600 0.34 0.40 0.39 0.54 0.47 0.49 0.49 0.42 0.42Nitrosonium complexes of organic compounds. Structure and reactivity qáp 0.48 1 2 0.44 4 0.40 3 5 0.36 6 0.32 E1/2 /V 1.3 1.5 1.4 p Figure 5. Correlation between the qá values for the p-complexes 52a ± c,e,f,i and the oxidation potentials (E1/2) of their precursors 51a ± c,e,f,i:120 (1) 1,4-dimethylnaphthalene, (2) 1,3-dimethylnaphthalene, (3) 1-methylnaphthalene, (4) 2,3-dimethylnaphthalene, (5) 2-methylnaph- thalene, (6) naphthalene (r=70.970). The data for the p-complexes 52g,h were not taken into consideration because the qáp values for the latter complexes were determined from 13C NMR spectra measured at different temperatures.radical cation.109, 111, 112 In the case of methylnaphthalenes, an analogous process takes place at low temperature. As the temper- ature increases from 760 or 770 8C to 730 or 750 8C, the signals in the 1H NMR spectra of the complexes 52a ± i become broader (up to their `disappearance'), which was explained 116 by the one-electron transfer between the aromatic core of the com- plex and the NO group. Dimerisation of the resulting radical cations is one of the possible conversions of these compounds.116 Actually, storage of solutions of the complexes 52b,d,e,h at720 to730 8C for 1 ± 2 h followed by their treatment with water afforded 4,40-dimethylbi- naphthyl, 3,30,4,40-tetramethylbinaphthyl, 2,20,4,40-tetramethyl- binaphthyl and 4,40,5,50-tetramethylbinaphthyl, respectively, in *20% yields.Analogous reactions proceeded with the participa- tion of 2-methyl-, 1-ethyl-, 2-ethyl-, 1,6-dimethyl-, 2,3-dimethyl-, 2,6-dimethyl-, 2,7-dimethyl-, 1-methoxy-, 2-methoxy-, 1-bromo- and 2-hydroxynaphthalenes (the yields of the dimeric products were 25%± 95%).121, 122 NO+ +.+NO. Men Men Mem Mem Mem Men Mem Men + H H + Men Mem Men Mem m=0, 1; n=0±2. V. Complexes of the nitrosonium ion with nitrogen- containing organic compounds In a number of studies it has been suggested that nitrosonium complexes of amines and N-heterocyclic compounds are inter- mediates in diazotisation,1 nitrosation of amides 1 and N-hetero- cyclic compounds,123, 124 the formation 1, 125 and denitrosation 126 of nitrosoamines and other reactions involving the nitrosonium cation.1, 127 ± 130 According to the results of quantum-chemical calcula- tions 131 ± 133 and experimental data for the gas phase,66, 134 N-bases possess high affinities for the NO+ cation.Thus accord- 223 Table 8. Energies of binding (Eb) of the NO+ cation with N-bases.134 Compound Eb /kJ mol71 Eb /kJ mol71 Compound 121.3 123.4 156.1 162.3 167.8 172.0 PhCN o-MeC6H4CN 3-FC5H4N 4-ClC5H4N C5H5N 3-MeC5H4N 82.0 110.5 115.5 117.2 118.8 121.3 CH2(CN)2 MeCN EtCN PrnCN PriCN ButCN ing to the results of ab initio calculations [HF/6-31+G(d)], the energy of binding of the NO+ cation with the methylamine molecule is 127.7 kJ mol71 (cf.Ref. 133). The data on the binding energies (Eb) of the NO+ cation with nitriles, pyridine and the derivatives of the latter 134 were obtained by ion-cyclotron reso- nance and in studies of the fragmentation of L1(NO+)L2 dimers by kinetic methods (Table 8). A linear correlation between the Eb values for alkylnitriles RCN and Taft's s*-constants of the substituents 135 was revealed (Fig. 6). Consequently, the inductive effect of the substituents R is the major factor responsible for the stability of the RCN7NO+ complexes (cf. Ref. 66). Eb /kJ mol71 1 3 120 4 2 5 100 6 80 0 1.0 0.5 70.5 sR Figure 6.Correlation between the energies of binding (Eb) of the NO+ cation with nitriles RCN134 and the s*-constants of the substituents R (sR), 135 where R=But (1), Pri (2), Prn (3), Et (4) or Me (5) and RCN=CH2(CN)2 (6) (r=70.995). A linear correlation between the Eb values 134 and the s-con- stants of the substituents X135 observed for pyridine and its derivatives XC5H4N (Fig. 7) indicates that both the inductive and resonance effects are of considerable importance. The reaction of the [NO]+[BF4]7 salt with pyridine in polar solvents (MeCN, MeNO2, SO2 or sulfolane) was examined by 1H NMR and IR spectroscopy.136 The results obtained in the Eb /kJ mol71 1 2 3 174 170 166 162 158 4 154 0.2 0.1 0.3 0 sX 70.1 Figure 7.Correlation between the energies of binding (Eb) of the NO+ cation with the XC5H4N compounds 134 and the s-constants of the substituents X (sX), 135 where X=3-Me (1), H (2), 4-Cl (3) or 3-F (4) (r=70.984).224 cited study provided evidence for the formation of the C5H5N7NO+ n-complex (cf. Refs 76, 82 and 137). It should be noted that the transfer of theNOgroup from the nitrogen atom to the carbon atom of the ring was not observed even under the conditions of thermal decomposition of the [C5H5N7NO]+[BF4]7 salt.136 The reactions of pyridine, its derivatives, quinoline and 1,10- phenanthroline with [NO]+[BF4]7 in (CD3)2SO at 20 8C or with [NO]+[AlCl4]7 in SO2 at 760 8C afforded complexes 58a ± d, 59 and 60 whose structures were confirmed by 1H and 13C NMR spectroscopy.138, 139 R3 R4 R2 + + + N N N R1 R5 N NO NO NO 58a ± d 60 59 R5 R4 R3 R2 R1 Compound 58 H H H H H H Me H H H HH HMe CHO Me HH HMe abcd The 1Hand 13C NMRspectra of the complex 60 are indicative of a degenerate rearrangement rapid within the NMR time scale, which proceeds through the intra- and(or) intermolecular transfer of the NO group.+ + N N N N NO 60 NO 600 Nitrosonium complexes of pyrimidine derivatives (61 and 62) undergo analogous rearrangements persisting even at770 8C.140 R2 R2 + NO N N N R1 R3 R1 R3 N + NO 61, 62 61: R1=Me, R2=R3=Ph; 62: R1=PhO, R2=R3=Me. According to the experimental data for the gas phase, pyridine derivatives and alkylbenzenes possess similar affinities for the NO+ cation.134 The formation constant of the 2,6-dimethylpyr- idine complex with the nitrosonium cation in MeCN was deter- mined by the competitive method.82 On gradual addition of 2,6- dimethylpyridine to a solution of the durene complex with [NO]+[BF4]7 in acetonitrile, the intensity of the charge-transfer band for the durene ±NO+ complex decreases monotonically, while the intensity of the corresponding band for the nitrosonium complex with 2,6-dimethylpyridine increases due to the following reactions: K1 +NO+ NO+, K2 +NO+ .N +N 63 NO The equilibrium constant, K2, of the reaction of NO+ with 2,6-dimethylpyridine [K2=(32)6103 litre mol71] was deter- mined 82 from the equilibrium constant of the reaction of durene with theNO+cation (K1=450 litre mol71) estimated previously.A somewhat different value was obtained for electrochemical reduction of complex 63, (K2&500 litre mol71). This difference in the constant determined by different methods is due partially to salt effects.82 Intensely coloured solutions of complexes of aromatic com- pounds with C5H5N+7NO (PyNO+) in acetonitrile are decol- ourised in the presence of alkyl derivatives of benzene or naphthalene at room temperature in the dark, the rate of this process being decreased in the series 1,4-dimethylnaphthalene> hexamethylbenzene>durene 44 p-xylene>toluene.82 The chemical conversions responsible for decolouration of the com- plexes under the action of 1,4-dimethylnaphthalene, durene and hexamethylbenzene are shown in Scheme 6.82 MeCN, 25 8C +2 [PyNO]+[SbCl6]7 7NO Py+[SbCl6]¡2 Py+ 64 MeCN, 25 8C +2 PyNO+ 7NO +Py Py+ 66 MeCN, 25 8C +2 PyNO+ 7NO +Py Py+ 67 The structures of complexes 64 ± 67 were established by 1H NMR spectroscopy.The structure of the complex 65 (with the SbCl¡6 anion) was additionally confirmed by X-ray diffraction analysis. Interestingly, the reaction of durene with the [PyNO]+[SbCl6]7 salt afforded exclusively the trans-adduct 65, while the reaction with the [PyNO]+[BF4]7 salt gave rise to an equimolar mixture of the trans- and cis-adducts.82 N-Nitrosation reactions of secondary amines with complexes synthesised by the reactions of N2O4 with pyridine or triethyl- amine have been examined.137 R1R2NH CH2Cl2, ±60 8C +N2O4 N N + NO¡ NO CH2Cl2, ±60 8C Et3N NO+NO¡ Et3N+N2O4 Analogous N-nitrosation reactions of amino acids containing secondary amine groups under the action of a mixture of nitro- G I Borodkin, V G Shubin Scheme 6 Py+7PyH+ 65 Py+ 7PyH+ R1N NO 3 R2 R1 R1R2NH N NO 3 R2Nitrosonium complexes of organic compounds.Structure and reactivity sonium tetrafluoroborate and pyridine have been described 141 (cf. Ref. 127). Apparently, the [PyNO]+[BF4]7 complex served as an active nitrosating agent in these reactions.141 VI. Complexes of the nitrosonium ion with organic compounds containing Group VI elements Complexes of the nitrosonium ion with compounds of the R1ER2 andR1R2C=Etypes (E is the Group VI element) were considered as intermediates in many liquid-phase reactions of O-bases (alcohols,1, 142, 143 ketones,144 ± 146 etc.1, 92 ± 94) and S-bases (desul- fofluorination of thioesters,147 conversions of thioketones and thioamides giving rise to ketones and amides of acids, respec- tively,148 etc.149 ± 151).According to the results of quantum-chemical calcula- tions 133, 152 ± 154 and experimental data for the gas phase obtained by the ion-cyclotron resonance 66, 134 and kinetic methods,134 O- bases possess rather high affinities for the NO+ cation. Calculations based on thermochemical data demonstrated that the energy of the nitrosonium complex with ethylene oxide (68) is 112.5 kJ mol71 lower than those of the initial reagents.152 0.1062 nm O O 0.1125 nm N N 0.2063 nm 0.1969 nm O+ O+ 0.1475 nm 0.1468 nm H 0.1495 nm H H H 0.1459 nm 0.1472 nm H H H H 69 68 Ab initio calculations (SCF/MP2) demonstrated that the planar analogue of this complex (69) is somewhat energetically less favourable (DErel=15.1 kJ mol71), the latter being a transi- tional structure between two equivalent forms 68.According to the results of ab initio calculations (MP2/6-31+G*), the energy of the nitrosonium complex with acetaldehyde (70), which is iso- meric with structure 68, is 115.5 kJ mol71 lower than those of the initial reagents, whereas the nitrosonium complex with the enol form of acetaldehyde (71) is energetically less favourable than the complex 70 (DErel=105.0 kJ mol71).152O O 0.1124 nm 0.1111 nm H + N 0.2148 nm N 0.2001 nm O O + 0.1250 nm 0.1412 nmH H C C H0.1331 nm H0.1477 nm H 71 H H 70 Analogously, ab initio calculations [HF/6-31+G(d) 133 and G2 154] gave rather high affinities of the NO+ cation for methanol (97.3 and 105.9 kJ mol71, respectively).The ab initio energies of binding of the NO+ cation with acetaldehyde and methanol are very close to the experimental values determined for the gas phase (Table 9).134 The energies of binding of the NO+ cation with O-bases were analysed within the framework of Taft's equation.66 Linear correlations were revealed for each class of compounds (MeCOR, where R=H, Me or Et; ROAc or RCHO, where R=Me, Et or Pri; and ROH, where R=Me, Et or Pri).Analogous relationships are true for the compounds of the RONO2 and RNO2 types (Fig. 8). As mentioned above, nitrosonium complexes with O-bases were postulated for many liquid-phase reactions. However, the data on generation of these complexes in solutions are scarce.77, 155 ± 159 225 Table 9. Energies of binding (Eb) of the NO+ cation with O-bases.134 Compound Eb /kJ mol71 Eb /kJ mol71 Compound MeCHO Me2CO MeCO2Et MeCOEt Et2CO PriCOMe ButCOMe But2CO Pri2CO 115.5 130.1 131.4 134.3 136.8 138.1 140.2 141.0 142.3 146.9 152.7 160.2 165.3 PhCOMe (C3H5)2CO Ph2CO (PhCH2)2CO H2O 77.4 MeOH 97.5 CH2O 112.5 MeONO2 86.6 EtONO2 95.0 PriONO2 101.7 MeNO2 104.2 EtNO2 112.5 PrnNO2 115.9 PriNO2 118.0 BunNO2 116.7 ButNO2 123.4 MeCOC(OMe)2Me 154.8 MeCO2But 141.0 Eb /kJ mol71 3 1 120 4 2 5 110 6 7 100 8 90 9 sR 70.10 70.20 70.30 Figure 8.Correlation between the energies of binding (Eb) of the NO+ cation with the RNO2 (1 ± 6) and RONO2 compounds 134 (7 ± 9) and the s*-constants of the substituents R (sR),135 where R=But (1), Pri (2, 7), Bun (3), Prn (4), Et (5, 8) or Me (6, 9) (r=70.955 and 70.999, respectively). Thus, the reactions of the [NO]+[BF4]7 and [NO]+[PF6]7 salts with 18-crown-6, 15-crown-5 and 12-crown-4 in dichloro- methane, acetonitrile and nitromethane were studied by 1H NMR and IR spectroscopy and conductometry.155 The reactions of 18-crown-6 and 12-crown-4 with [NO]+X7 afforded the 1 : 1 and 2 : 1 complexes, respectively.In the case of 15-crown-5, the 1 : 1 stoichiometry was observed if the reaction was performed in MeCN orMeNO2, whereas the 2 : 1 stoichiometry was achieved in CH2Cl2. The addition of the [NO]+X7 salt to a solution of a complex always leads to a downfield shift of the signal of the crown ether in the 1H NMR spectrum, one narrow singlet being observed due to the rapid (within the NMR time scale) exchange between the free crown molecule and the molecule involved in the complex. New absorption bands at 1850 ± 1852 and 1876 cm71 appeared in the IR spectra of solutions of 18-crown-6, 15-crown-5 and 12-crown-4 in CH2Cl2 and MeCN, respectively, upon the addition of the [NO]+X7 salts, which indicates that the NO+ cation is covalently bonded to the crown molecule.155 It should be noted that the positions of the bands in the IR spectra are virtually independent of the nature of the counterion.155 The reaction of 18-crown-6 with the NO+ cation (BF¡4 as the counterion) was examined by 1H and 13C NMR, IR and Raman spectroscopy.156 The 1H and 13C NMR spectra of the 1 : 1 com- plex have singlets at d 3.67 and 70.327, respectively.The 13C chemical shift changes only slightly (by 0.428 ppm) on going from free 18-crown-6 to the ether involved in the complex. The IR spectrum of the [18-crown-6 ± NO]+[BF4]7 salt (in hexachloro- butadiene) has an absorption band of theNOgroup at 2274 cm71 the position of which differs substantially from those observed in the spectra of this complex in CH2Cl2 or MeCN (see above).226 3 ]2 Analogous results were obtained in another study.157 It was suggested that the band at 2250 cm71 in the IR spectrum of a solution of the [18-crown-6 ± NO]+[BF4]7 complex in CH2Cl2 and the charge-transfer band of this complex (lmax=300 nm) be used for the detection of an impurity of the [NO]+[BF4]7 salt in the [NO2]+[BF4]7 specimen.77 A polycrystalline specimen pre- pared by the reaction of N2O4 with 18-crown-6 was studied by Raman spectroscopy.158 The Raman spectrum of the salt [18-crown-6 ± NO]+H+[NO¡ has an intense band at 2270 cm71 belonging to the stretching vibration of the NO+ group bound to the crown ether.No explanation was provided for the above-mentioned differences in the stretching vibration fre- quency of the NO group.156 ± 158 Apparently, these differences are associated with a change in the mode of bonding of the NO+ cation with 18-crown-6. The complex of 18-crown-6 with [NO]+[BF4]7 in MeCN was examined by cyclic voltammetry.77 The complexation constant (K>104 litre mol71) was estimated based on the oxidation and reduction potentials. Reduction of the complex 72 gave rise to the compound 73. On oxidation of the latter, NOmolecules were only partially converted into NO+ cations and its complex with the crown ether. O O O O O O +e NO NO+ 7e O O O O O O 73 72 The reversible reduction potential of the complex 72 in MeCN (Ered&0.9 B) is smaller than the Ered values determined for the hexamethylbenzene complex with the NO+ cation (Ered= 1.02 V) and for NO+ (Ered=1.28 V).77 The reactivity of the nitrosonium cation changes substantially on the involvement of the [NO]+[BF4]7 salt in the complex with 18-crown-6.156 Thus the [18-crown-6 ± NO]+[BF4]7 complex did not react with benzamide in MeCN at low temperature, whereas the amide was rapidly converted into acid under the action of [NO]+[BF4]7 in the absence of the crown ether.156 The nitrosonium cation vigorously reacts with ketones in the gas phase 66, 134 to give the [R1R2C=ONO]+ complexes (see Table 9).Analogous complexes were obtained in the reactions of the NO+ cation with compounds of the ArN=O and R2S=O types in the liquid phase.93, 94, 159 Kinetic studies of the mechanism of nitrosation of aromatic compounds provided evidence for the formation of [ArNO ± NO]+ complexes in which the nitrosonium cation is bound to the oxygen atom of the NO group in the ArNO molecule.92 ± 94 The formation constants of the complex of the NO+ cation with 4-nitrosotoluene and 1,3-dimethyl-4-nitroso- benzene in trifluoroacetic acid are 58 000 and 38 000 litre mol71, respectively.93 Studies by 1H, 13C and 15N NMR spectroscopy showed 159 that the reaction of [NO]+[PF6]7 with dimethyl sulfoxide in SO2 or the reaction of [NO2]+[PF6]7 with dimethyl sulfide in SO2 at low temperature gave rise to nitrosonium complex 75 (existing in equilibrium with complex 74).Me + [NO2]+[PF6]7 S NO2 Me2S PF¡6SO2 Me 74 NO Me + [NO]+[PF6]7 S O Me2SO SO2 Me PF¡675 Analogously, the reaction of [NO2]+[PF6]7 with dimethyl selenide in SO2 at778 8Cafforded nitrosonium complex 77 along with complex 76.159 [NO2]+[PF6]7 Me2Se SO2 [NO]+[PF6]7 Me2SeO SO2 However, all attempts to generate the complex 77 by the reaction of [NO]+[PF6]7 with dimethyl selenoxide failed because the latter readily underwent Pummerer fragmentation.159 The ambident reactivity of theNOá2 cation (the competitive O- or N-reactions) is manifested in its reactions with triphenylphos- phine. In this case, as in the case of the S- and Se-analogues, the equilibrium 78.79 is shifted toward the nitritophosphonium complex 79.159 + Ph3P O NO Ph3P NO2 78 Investigations of the interaction of the NO+ cation with O- and S-anions using perturbation theory demonstrated that the nitrosonium cation acts as a soft acid 160 (cf.Ref. 161). According to the Pearson concept,162 the complexes of the NO+ cation with S-bases should be more stable than those with O-bases. This statement can be exemplified by the fact that the reaction of thioanisole with [NO]+[AlCl4]7 in the SO2±CD2Cl2 system at 770 8C afforded an n-complex (80), whereas the reaction of anisole under these conditions gave rise to p-complex 81, the oxygen atom of the anisole remaining unbound.87 Me +S NO 80 The structures of these complexes were confirmed by 1H, 13C and 15N NMRspectroscopy.In particular, the fact that the cation 80 belongs to an n-complex is witnessed by the close values of the corresponding chemical shifts in the 15N NMR spectra of this complex and Me2S+±NO (82) [HSO3F±SO2, d(770 8C) 291.6 and 258.6, respectively].87 The results of quantum-chemical cal- culations by the MINDO/3 method confirmed that of the n-, p- and s-complexes, the n-complex of thioanisole and the p-complex of ansiole are more stable.87 O N O Me DHf=643.9 kJ mol71 O N S Me DHf=832.6 kJ mol71 O N S Me DHf=788.3 kJ mol71 G I Borodkin, V G Shubin Me + Se NO2PF¡6Me 76 NO Me + Se O PF¡6Me 77 + 79 +NO NO Me + S O Me Me 81 82 O N O Me DHf=761.5 kJ mol71 O Me N O H DHf=663.6 kJ mol71 Me O N S H DHf =854.0 kJ mol71Nitrosonium complexes of organic compounds.Structure and reactivity The preferential binding of the NO+ cation at the sulfur atom rather than at the oxygen atom in the PhEMe compounds (E=O or S) was attributed 87 to the lower electronegativity of the S atom and a greater p,p-conjugation of the aromatic fragment with the MeO group compared to that with the MeS group. It was suggested 163 that binding of the nitrosonium cation in the case of thioanisole, occurs preferentially at the S atom due to the fact that the HOMO of thioanisole has the highest coefficient at the sulfur atom. Ab initio (the 4-31G basis set), CNDO and INDO quantum- chemical calculations were performed with the aim of studying the reaction of 2-(methylthio)ethylamine with the NO+ cation.164 The structures of the complexes 83a,b and 84 optimised by the CNDO and INDO methods are shown in Fig.9. Analysis within the framework of perturbation theory demonstrated that the NO+ cation acts as a soft acid, i.e., it is bound primarily to the sulfur atom rather than to the nitrogen atom, the energy of the N-complex 84 being 50 kJ mol71 higher than the energy of the stable syn-complex 83a.164 H H H H N N 0.145 0.143 O 0.118 N N 0.136 HH 0.142 HH H H C HH O 0.141 0.116 N C 0.180 H O 0.115N H C 0.147C0.178 H C0.146 C1.82 H 0.177 H H 0.181S S S0.179 0.178 0.179 C C C H H H HH HH HH 84 83b 83a Figure 9.Geometric parameters of the n-complexes 83a,b and 84 calcu- lated by the CNDO and INDO methods.164 The bond lengths are given in nm. The reaction of 1,3-dimethylthiobenzene with [NO]+[AlCl4]7 in the SO2±CD2Cl2 system at 770 8C produced n-complex 85, which underwent degenerate rearrangement, rapid within the NMR time scale (Scheme 7).165 Scheme 7 + Me Me Me ON S ON +SS NO+ 7NO+ NO NO +S +SS Me Me Me 86 85 850 The structure of the complex 85 was confirmed by 1H, 13C and 15N NMR spectroscopy. As expected, the 15N chemical shift for the complex 85 (dN 267.1 relative toMeNO2,770 8C) is similar to that observed in the spectrum of the nitrosonium complex with thioanisole (dN 291.6 relative to MeNO2, 770 8C).87 The signals for the protons of the aromatic ring and methyl groups and the signals for the C(2), C(4), C(5) and C(6) atoms are shifted down- field as the 1,3-dimethylthiobenzene : [NO]+[AlCl4]7 ratio changes from 1 : 1 to 1 : 2 due, apparently, to the shift of the equilibrium 85 0 86 (see Scheme 7) to the dication 86.A further increase in the amount of the salt (to 1 : 5) has no effect on the positions of the above-mentioned signals. The complexes of dialkyl, alkylaryl and diaryl sulfides with [NO]+[BF4]7 or N2O4 in CH2Cl2 were studied by electronic spectroscopy.86 At low temperature, the spectra have charge- transfer bands whose positions depend only slightly on the nature of the counterion (NO¡3 or BF¡4 ) (Table 10). It was demonstrated 227 Table 10.Parameters of electronic absorption spectra (lCT /nm) of the nitrosonium complexes with the R1R2E compounds (E=S or Se) in CH2Cl2 at778 8C.86, 166 R2 R1 lCT (E=Se) lCT (E=S) A B A B 426 Me Bun PhCH2 But 494 500 390 400 406 396 387 7502 500 494 510 514 542 514 393 400 406 400 386 408 500 500 494 512 514 542 517 7 7 452 5087 7 Me Bun Me Me(CH2)4 But Me Et Pri Me Me Me Me PhCH2 Ph Ph 7 7 7 7424 7 7 7 7 7 7498 7 7496 7 7 7 7 7 7 7 7444 506 Me(CH2)17 Ph Ph Ph p-ClC6H4 p-MeC6H4 p-MeOC6H4 p-ButC6H4 PhCH2 PhCH2 Ph 506 558 7563 Note.A and B are the complexes with the [NO]+[BF4]7 salt and N2O4, respectively. that low-temperature irradiation of the [R1R2SNO]+[NO3]7 complexes at the frequency corresponding to the charge-transfer band afforded sulfoxides. The complexation constants for dialkyl and alkylaryl sulfides (K1 and K2, respectively) were estimated by the competitive method. K1 [R2S, NO]+[BF4]7 R2S+[NO]+[BF4]7 K2 [R2S, NO]+[BF4]7 +ArH R2S+[ArH, NO]+[BF4]7 The complexation constant (K1) for Bun2 S in CH2 Cl2 at 778 8C is similar to that for hexamethylbenzene (K1& 36104 litre mol71), whereas ethylphenyl sulfide possesses a some- what lower affinity for theNO+ cation (K1436103 litre mol71). Analogously, the reactions of dialkyl and alkylaryl selenides with [NO]+[BF4]7 or N2O4 in CH2Cl2 at778 8C gave rise to the nitrosonium complexes R1R2SeNO+ (see Table 10).166 As can be seen from Table 10, the positions of charge-transfer bands in the spectra of the nitrosonium complexes R1R2S and R1R2Se are rather close.Low-temperature irradiation of the complex [PhMeSeNO]+[NO3]7 at the frequency nCT gave rise to the corresponding selenoxide PhSe(O)Me.166 The reactions of nitrosonium salts with diaryl tellurides, unlike those with S- and Se-containing aromatic compounds, did not produce nitrosonium complexes.167 Thus treatment of bis(4-methylphenyl) telluride (87) with the [NO]+[BF4]7 salt in the CH2Cl2 ±MeCN system at 740 8C under an atmosphere of argon afforded dication 88. Te +2 [NO]+[BF4]7 87 +Te 2 BF¡4 OTe +88 It was found that the oxygen atom in the dication 88 was derived from the nitrosonium salt.167228 VII.Complexes of the nitrosonium ion with halogen-containing organic compounds The reactions of the nitrosonium cation with organic halogen derivatives RX in the gas phase generate chemically active species, which can dissociate to form carbocations, nitrosyl halides and nitrosonium complexes of alkenes.168 H O O X N+ N+ NO+ H X H X X H +NO+ 7HXNO+ 7XNO 7HXNO+ H + X=F, Cl. PriX.NO++C3H6 The latter react with alkyl halides yielding halonitrosonium complexes. Thus the reactions involving PriCl or PriF proceeded as follows:168 (MeCH CH2) .NO++PriX X=F, Cl. It is assumed that analogous ion-molecular reactions take place upon interaction of the vibrationally excited NO+ cation with different alkyl halides (see Ref.169 and references cited therein). The data on the energies of binding of the NO+ cation with alkyl chlorides RCl (R=Me, Et or Pri; Eb=77.4, 82.0 and 89.5 kJ mol71, respectively) were determined by the ion-cyclo- tron resonance and kinetic methods.134 The following correlation between the Eb values for aryl chlorides and Taft's s*-constants was deduced: 135 Eb = (76.81.3)7(63.410.7) s*, r = 70.986, s = 1.4. To our knowledge, the data on generation of long-lived nitrosonium complexes of halogen-containing organic com- pounds in solutions are lacking. However, such complexes can be generated in different reactions of alkyl and aryl halides with salts of the nitrosonium cation.170, 171 Thus, a new procedure was developed 170 for the preparation of amides by the reactions of alkyl or aryl halides with nitriles in the presence of the [NO]+X7 salts.The assumed mechanism involves the formation of a nitro- sonium n-complex via the lone electron pairs of the halogen atom followed by nucleophilic substitution (of the SN1 or SN2 type) of nitrile for the XNO+ group.170 + NOPF6 [R1XNO] R1X O + R2CN H2O R1NH C R1N CR2 PF¡¦6 R2 7NOX (SN2) + R2CN (R3)+] [(R1)+ R3N CR2 PF¡¦6 H2O O 7NOX (SN1) R3NH C R2 R1=Alk, ArCR2R3; R2=Me, Et, Pr, Ph, PhCH2; (R3)+Disomer (R1)+; X=F, Cl, Br. Analogous results were obtained in another study.172 * * * To summarise, abundant data on the structures and reactiv- ities of different classes of nitrosonium organic complexes have G I Borodkin, V G Shubin been accumulated due to the extensive use of modern physical and quantum-chemical methods. In the present review, we generalise the results of recent studies in this area. The necessity of summa- rising these data stems from the fact that investigations aimed at refining the theoretical notion of the processes, which involve nitrosonium complexes and include both classical organic and biochemical reactions, are progressing rapidly. This review has been written with the financial support of the Russian Foundation for Basic Research (Project No. 99 ¡À 03 ¡À 32878).References 1. D L H Williams Nitrosation (Cambridge: Cambridge University Press, 1988) 2. P P Kadzyauskas, N S Zefirov Usp. Khim. 37 1243 (1968) [Russ. Chem. Rev. 37 543 (1968)] 3. P B D de la Mare, R Bolton Electrophilic Additions to Unsaturated Systems (Amsterdam: Elsevier, 1982) p. 247 4. L F Fieser, M Fieser Reagents for Organic Synthesis (New York: Wiley, 1968) 5. G A Olah, K K Laali, Q Wang, G K S Prakash, in Onium Ions (New York: Wiley, 1998) p. 40 6. E Culotta, D E Koshland Science 258 1862 (1992) 7. A R Butler, D L H Williams Chem. Soc. Rev. 22 233 (1993) 8. M Fontecave, J-L Pierre Bull. Soc. Chim. Fr. 131 620 (1994) 9. V P Reutov, in Uspekhi Biologicheskoi Khimii (Advances in Biological Chemistry) (Ed. B F Poglazov) (Pushchino: Izd.ONTI PNTs RAN, 1995) Vol. 35, p. 189 10. A R Butler Chem. Ind. 828 (1995) 11. J S Stamler,M Feelisch, in Methods in Nitric Oxide Research (EdsM Feelisch, J S Stamler) (Chichester: Wiley, 1996) p. 19 12. F Murad Angew. Chem., Int. Ed. Engl. 38 1856 (1999) 13. R F Furchgott Angew. Chem., Int. Ed. Engl., 38 1870 (1999) 14. L J Ignarro Angew. Chem., Int. Ed. Engl. 38 1882 (1999) 15. R P Patel, J McAndrew, H Sellak, C R White, H Jo, B A Freeman, V M Darley-Usmar Biochim. Biophys. Acta 1411 385 (1999) 16. S A Lipton, Y-B Choi, Z-H Pan, S Z Lei, H-S V Chen, N J Sucher, J Loscalzo, D J Singel, J S Stamler Nature (London) 364 626 (1993) 17. J S Stamler, D J Singel, J Loscalzo Science 258 1898 (1992) 18. A R Butler, F W Flitney,D L H Williams Trends Pharmacol. Sci.16 18 (1995) 19. M A de Groote, T Testerman, Y Xu, G Stauffer, F C Fang Science 272 414 (1996) 20. M N Hughes Biochim. Biophys. Acta 1411 263 (1999) 21. J J Kirchner, S T Sigurdsson, P B Hopkins J. Am. Chem. Soc. 114 4021 (1992) 22. A H Elcock, P D Lyne, A J Mulholland, A Nandra,W G Richards J. Am. Chem. Soc. 117 4706 (1995) 23. P Mack, J M Dyke, T G Wright Chem. Phys., 218 243 (1997) 24. L Angel, A J Stace J. Phys. Chem., A 102 3037 (1998) 25. G A Olah, O Farooq, G K S Prakash, in Activation and Functional- ization of Alkanes (Ed. C L Hill) (New York: Wiley, 1989) p. 27 26. G A Olah, G K S Prakash, R E Williams, L D Field, K Wade Hypercarbon Chemistry (New York: Wiley-Interscience, 1987) 27. G A Olah, G K S Prakash, J Sommer Superacids (New York: Wiley-Interscience, 1985) 28.G A Olah, JG Shih, B P Singh, B G B Gupta J. Org. Chem. 48 3356 (1983) 29. G A Olah, P Ramaiah, C B Rao, G Sandford, R Golam, N O Trivedi, J A Olah J. Am. Chem. Soc. 115 7246 (1993) 30. G A Olah, B G B Gupta J. Org. Chem. 45 3532 (1980) 31. A A Fokin, P A Gunchenko, S A Peleshanko, P von R Schleyer, P R Schreiner Eur. J. Org. Chem. 855 (1999) 32. P R Schreiner, P vonR Schleyer,H F Schaefer III J. Am. Chem. Soc. 115 9659 (1993) 33. P R Schreiner, P vonR Schleyer,H F Schaefer III J. Am. Chem. Soc. 117 453 (1995) 34. M L Scheinbaum, M B Dines Tetrahedron Lett. 2205 (1971) 35. G H Lee, J M Lee,W B Jeong, K Kim Tetrahedron Lett. 29 4437 (1988) 36. R L Danheiser, D A Becker Heterocycles 25 277 (1987)Nitrosonium complexes of organic compounds.Structure and reactivity 37. H O Bertrand, J L Burgot Phosphorus Sulfur Silicon Relat. Elem. 97 103 (1994) 38. A V Pankratov Khimiya Ftoridov Azota (The Chemistry of Nitrogen Fluorides) (Moscow: Khimiya, 1973) 39. Q B Broxterman, H Hogeveen, R F Kingma, F van Bolhuis J. Am. Chem. Soc. 107 5722 (1985) 40. G A Olah, G Salem, J S Staral, T-L Ho J. Org. Chem. 43 173 (1978) 41. V S Savostin, I I Krylov, A P Kutepov, A I Rapkin, A V Fokin Izv. Akad. Nauk SSSR, Ser. Khim. 1851 (1990) a 42. R Chang, K Kim Bull. Korean Chem. Soc. 16 475 (1995) 43. R M Minyaev, M E Kletskii, V I Minkin Zh. Org. Khim. 23 2508 (1987) b 44. K Raghavachari, W D Reents, Jr, R C Haddon J.Comput. Chem. 7 265 (1986) 45. V I Minkin, I A Yudilevich, R M Minyaev Zh. Org. Khim. 23 717 (1987) b 46. M N Glukhovtsev, P von R Schleyer, N J R von E Hommes, V I Minkin Chem. Phys. Lett. 205 529 (1993) 47. G A Olah, P Schilling, P W Westerman, H C Lin J. Am. Chem. Soc. 96 3581 (1974) 48. G I Borodkin, I R Elanov, V A Podryvanov, M M Shakirov, V G Shubin J. Am. Chem. Soc. 117 12863 (1995) 49. G I Borodkin, I R Elanov, M M Shakirov, V G Shubin Zh. Org. Khim. 33 363 (1997) b 50. G I Borodkin, I R Elanov, A M Genaev,M M Shakirov, V G Shubin Mendeleev Commun. 83 (1999) 51. E Bosch, J K Kochi Res. Chem. Intermed. 22 209 (1996) 52. F Blatter, H Frei J. Phys. Chem. 97 1178 (1993) 53. R Rathore, S V Lindeman, J K Kochi Angew. Chem., Int.Ed. Engl. 37 1585 (1998) 54. S Sankararaman,W Lau, J K Kochi J. Chem. Soc., Chem. Commun. 396 (1991) 55. J K Kochi Acta Chem. Scand. 44 409 (1990) 56. J K Kochi Acc. Chem. Res. 25 39 (1992) 57. G I Borodkin, V G Shubin Zh. Org. Khim. 36 479 (2000) b 58. D Dimitrov, F Fratev Compt. Rend. Acad. Bulg. Sci. 16 729 (1963) 59. D Dimitrov, F Fratev Compt. Rend. Acad. Bulg. Sci. 16 825 (1963) 60. Z J Allan, J Podstata, D SÏ nobl, J JarkovskyÆ Tetrahedron Lett. 3565 (1965) 61. Z J Allan, J Podstata, D SÆ nobl, J JarkovskyÆ Collect. Czech. Chem. Commun. 32 1449 (1967) 62. E Hunziker, J R Penton, H Zollinger Helv. Chim. Acta 54 2043 (1971) 63. A R Butler, A P Sanderson J. Chem. Soc., Perkin Trans. 2 1671 (1974) 64. W D Reents Jr, B S Freiser J.Am. Chem. Soc. 102 271 (1980) 65. R WolfschuÈ tz, H Schwarz. Int. J. Mass Spectrom. Ion Phys. 33 291 (1980) 66. W D Reents Jr, B S Freiser J. Am. Chem. Soc. 103 2791 (1981) 67. J A Stone, D E Splinter, S Y Kong Can. J. Chem. 60 910 (1982) 68. V I Mamatyuk, A N Detsina, ShMNagi, Yu V Gatilov, G I Borodkin, I L Mudrakovskii, in III Vsesoyuz. Soveshch. `Spek- troskopiya Koordinatsionnykh Soedinenii' (Tez. Dokl.), Krasnodar, 1984 [The IIIth All-Union Meeting `Spectroscopy of Coordination Compounds' (Abstracts of Reports), Krasnodar, 1984] p. 55 69. S Brownstein, E Gabe, F Lee, L Tan J. Chem. Soc., Chem. Commun. 1566 (1984) 70. V I Minkin, R M Minyaev, I A Yudilevich, M E Kletskii Zh. Org. Khim. 21 926 (1985) b 71. G I Borodkin, Sh M Nagi, Yu V Gatilov, V I Mamatyuk, I L Mudrakovskii, V G Shubin Dokl.Akad. Nauk SSSR 288 1364 (1986) c 72. S Brownstein, A Morrison, L K Tan Can. J. Chem. 64 265 (1986) 73. S Brownstein, E Gabe, F Lee, A Piotrowski Can. J. Chem. 64 1661 (1986) 74. S Brownstein, E Gabe, B Irish, F Lee, B Louie, A Piotrowski Can. J. Chem. 65 445 (1987) 75. A E Mefed, ShMNagi, G I Borodkin, V I Mamatyuk, V G Shubin Dokl. Akad. Nauk SSSR 297 133 (1987) c 76. E K Kim, J K Kochi J. Org. Chem. 54 1692 (1989) 77. K Y Lee, D J Kuchynka, J K Kochi Inorg. Chem. 29 4196 (1990) 78. E K Kim, J K Kochi J. Am. Chem. Soc. 113 4962 (1991) 79. T M Bockman, Z J Karpinski, S Sankararaman, J K Kochi J. Am. Chem. Soc. 114 1970 (1992) 229 80. G I Borodkin, I R Elanov,M M Shakirov, V G Shubin Izv.Akad. Nauk, Ser. Khim. 2104 (1992) a 81. E K Kim, J K Kochi J. Org. Chem. 58 786 (1993) 82. K Y Lee, J K Kochi J. Chem. Soc., Perkin Trans. 2 237 (1994) 83. E Bosch, J K Kochi J. Org. Chem. 59 3314 (1994) 84. E Bosch, J K Kochi J. Org. Chem. 59 5573 (1994) 85. R Rathore, E Bosch, J K Kochi Tetrahedron 50 6727 (1994) 86. E Bosch, J K Kochi J. Org. Chem. 60 3172 (1995) 87. G I Borodkin, V A Podryvanov,M M Shakirov, V G Shubin J. Chem. Soc., Perkin Trans. 2 1029 (1995) 88. R Rathore, S V Lindeman, J K Kochi J. Am. Chem. Soc. 119 9393 (1997) 89. S Skokov, R A Wheeler J. Phys. Chem. A, 103 4261 (1999) 90. S M Hubig, J K Kochi J. Am. Chem. Soc. 122 8279 (2000) 91. A R Butler, A P Sanderson J. Chem. Soc., Perkin Trans. 2 989 (1972) 92.V L Lobachev, O B Savsunenko, E S Rudakov Kinet. Katal. 32 17 (1991) d 93. J H Atherton, R B Moodie, D R Noble J. Chem. Soc., Perkin Trans. 2 699 (1999) 94. J H Atherton, R B Moodie, D R Noble J. Chem. Soc., Perkin Trans. 2 229 (2000) 95. M V Gorelik, V I Lomzakova, E A Khamidova, V Ya Shteiman, M G Kuznetsova Zh. Org. Khim. 31 408 (1995) b 96. L R Dix, R B Moodie J. Chem. Soc., Perkin Trans. 2 1097 (1986) 97. M V Gorelik, V I Lomzakova, E A Khamidova, V Ya Shteiman, M G Kuznetsova, A M Andrievskii Zh. Org. Khim. 31 553 (1995) b 98. D J Mills, J H Ridd J. Chem. Soc., Perkin Trans. 2 637 (1980) 99. V I Minkin, R M Minyaev Zh. Org. Khim. 15 1569 (1979) b 100. R M Minyaev Zh. Org. Khim. 20 897 (1984) b 101. V I Minkin, R M Minyaev Neklassicheskie Struktury Organi- cheskikh Soedinenii (Non-classical Structures of Organic Compounds) (Rostov-on-Don: Rostov State University, 1985) 102.J B Stothers Carbon-13 NMR Spectroscopy (New York: Academic Press, 1972) 103. V A Koptyug Arenonievye Iony. Stroenie i Reaktsionnaya Sposobnost' (Arenonium Ions. Structure and Reactivity) (Novosibirsk: Nauka, 1983) 104. V I Minkin, B Ya Simkin, R M Minyaev Kvantovaya Khimiya Organicheskikh Soedinenii. Mekhanizmy Reaktsii (Quantum Chemistry of Organic Compounds. Mechanisms of Reactions) (Moscow: Khimiya, 1986) 105. R Rathore, J K Kochi J. Org. Chem. 63 8630 (1998) 106. V F Loktev, V G Shubin Izv. Akad. Nauk SSSR, Ser. Khim. 2276 (1987) a 107. G I Borodkin, I R Elanov, V G Shubin, in Book of Abstracts of the 13th IUPAC Conference on Physical Organic Chemistry, Inchon, 1996 p.243 108. L Eberson, F Radner Acc. Chem. Res. 20 53 (1987) 109. A S Morkovnik Usp. Khim. 57 254 (1988) [Russ. Chem. Rev. 57 144 (1988)] 110. V N Kondrat'ev (Ed.) Energii Razryva Khimicheskikh Svyazei. Potentsialy Ionizatsii i Srodstvo k Elektronu (Energies of Rupture of Chemical Bonds. Ionisation Potentials and Electron Affinities) (Moscow: Nauka, 1974) 111. A S Morkovnik, O Yu Okhlobystin Zh. Obshch. Khim. 55 692 (1985) e 112. A S Morkovnik, N M Dobaeva, O Yu Okhlobystin Zh. Obshch. Khim. 59 921 (1989) e 113. G I Borodkin, I R Elanov, V G Shubin, in Sovremennye Problemy Organicheskogo Sinteza (Tez. Dokl. Vsesoyuz. Konf.Molodykh Uchenykh), Irkutsk, 1988 [Topical Problems of Organic Synthesis (Abstracts of Reports of The All-Union Conference of Young Scientists), Irkutsk, 1988] p. 141 114. G I Borodkin, I R Elanov, M M Shakirov, V G Shubin, in Tez. Dokl. Chetvertoi Vsesoyuz. Konf. po Khimii Nizkikh Temperatur, Moskva, 1988 (Abstracts of Reports of the Fourth All-Union Conference on the Chemistry of Low Temperatures, Moscow, 1988) p. 119 115. G I Borodkin, I R Elanov,M M Shakirov, V G Shubin Izv. Akad. Nauk SSSR, Ser. Khim. 206 (1989) a 116. G I Borodkin, I R Elanov, M M Shakirov, V G Shubin J. Phys. Org. Chem. 6 153 (1993)230 117. G I Borodkin, I R Elanov, M M Shakirov, V G Shubin Zh. Org. Khim. 27 889 (1991) b 118. G I Borodkin, I R Elanov, P-C Cheng, L T Scott, V G Shubin, in Book of Abstracts of the Sixth European Symposium on Organic Reactivity, Louvain-la-Neuve, 1997 p.98 119. G I Borodkin, E I Chernyak,M M Shakirov, V G Shubin Zh. Org. Khim. 26 785 (1990) b 120. N V Vasil'eva, V F Starichenko, V A Koptyug Zh. Org. Khim. 23 1020 (1987) b 121. F Radner J. Org. Chem. 53 702 (1988) 122. M Tanaka, H Nakashima, M Fujiwara, H Ando, Y Souma J. Org. Chem. 61 788 (1996) 123. A Castro, E Iglesias, J R Leis,M E PenÄ a, J V Tato, D L H Williams J. Chem. Soc., Perkin Trans. 2 1165 (1986) 124. R N Loeppky,W Cui Tetrahedron Lett. 39 1845 (1998) 125. R N Loeppky, Y T Bao, J Bae, L Yu, G Shevlin, in Nitrosamines and Related N-Nitroso Compounds. Chemistry and Biochemistry (Eds R N Loeppky, C J Michejda) (Washington, DC: American Chemical Society, 1994) p.52 126. D L H Williams, in Nitrosamines and Related N-Nitroso Compounds. Chemistry and Biochemistry (Eds R N Loeppky, C J Michejda) (Washington, DC: American Chemical Society, 1994) p. 66 127. M A Freitas, R A J O'Hair, J A R Schmidt, S E Tichy, B E Plashko, T D Williams J. Mass Spectrom. 31 1086 (1996) 128. A S Morkovnik, L N Divaeva, O Yu Okhlobystin Zh. Obshch. Khim. 58 2174 (1988) e 129. C York, G K S Prakash, Q Wang, G A Olah Synlett 425 (1994) 130. H Cai, J C Fishbein J. Am. Chem. Soc. 121 1826 (1999) 131. S A Kulkarni, S S Pundlik Chem. Phys. Lett. 245 143 (1995) 132. M Aschi, F Grandinetti Chem. Phys. Lett. 267 98 (1997) 133. L L Torday,M B Santilla'n, G M Ciuffo, E A Ja'uregui, 134. F Cacace, G de Petris, F Pepi Proc. Natl. Acad. Sci. USA 94 3507 J Pataricza, J G Papp, I G Csizmadia J. Mol. Struct. (Theochem) 465 69 (1999) (1997) 135. Yu A Zhdanov, V I Minkin Korrelyatsionnyi Analiz v Organi- cheskoi Khimii (Correlation Analysis in Organic Chemistry) (Rostov-on-Don: Rostov State University, 1966) 136. G A Olah, J A Olah, N A Overchuk J. Org. Chem. 30 3373 (1965) 137. N N Makhova, G A Karpov, A N Mikhailyuk, A E Bova, L I Khmel'nitskii, S S Novikov Izv. Akad. Nauk SSSR, Ser. Khim. 226 (1978) a 138. G I Borodkin, V G Shubin, R V Andreev, in Book of Abstracts of the International Conference on Reactive Intermediates and Reaction Mechanisms, Ascona, 1998 p. 38 139. R V Andreev, G I Borodkin, V G Shubin, in Molodezhnaya Nauchnaya Shkola po Organicheskoi Khimii (Tez. Dokl.), Ekaterinburg, 1999 [Young Researchers' School on Organic Chemistry (Abstracts of Reports), Ekaterinburg, 1999] p. 65 140. G I Borodkin, R V Andreev, I R Elanov, V G Shubin, in Book of Abstracts of the 7th European Symposium on Organic Reactivity, Ulm, 1999 p. 136 141. H T Nagasawa, P S Fraser, D L Yuzon J. Med. Chem. 16 583 (1973) 142. MJ Crookes, D L H Williams J. Chem. Soc., Chem. Commun. 571 (1988) 143. G A Olah, P Ramaiah J. Org. Chem. 58 4639 (1993) 144. J R Leis, M E PenÄ a, D L H Williams J. Chem. Soc., Chem. Commun. 45 (1987) 145. J R Leis,M E PenÄ a,D L H Williams, S D Mawson J. Chem. Soc., Perkin Trans. 2 157 (1988) 146. A Castro, M Gonza'lez, F Meijide,M Mosquera J. Chem. Soc., Perkin Trans. 2 2021 (1988) 147. C York, G K S Prakash, G A Olah Tetrahedron 52 9 (1996) 148. G A Olah, M Arvanaghi, L Onannesian, G K S Prakash Synthesis 785 (1984) 149. Y L Chow, K Iwai J. Chem. Soc., Perkin Trans. 2 931 (1980) 150. F Meijide, G Stedman J. Chem. Soc., Perkin Trans. 2 1087 (1988) 151. A Coello, F Meijide, J V Tato J. Chem. Soc., Perkin Trans. 2 1677 (1989) 152. F Cacace, G de Petris, F Pepi, I Rossi, A Venturini J. Am. Chem. Soc. 118 12 719 (1996) G I Borodkin, V G Shubin 153. F Bernardi,M A Robb, I Rossi, A Venturini J. Org. Chem. 58 7074 (1993) 154. M Aschi, F Grandinetti Chem. Phys. Lett. 258 123 (1996) 155. G S Heo, P E Hillman, R A Bartsch J. Heterocycl. Chem. 19 1099 (1982) 156. R Savoie,M Pigeon-Gosselin, A Rodrigue, R Cheà nevert Can. J. Chem. 61 1248 (1983) 157. R L Elsenbaumer J. Org. Chem. 53 437 (1988) 158. S Ricard, P Audet, R Savoie J. Mol. Struct., 178 135 (1988) 159. G A Olah, B G B Gupta, S C Narang J. Am. Chem. Soc. 101 5317 (1979) 160. K A Jùrgensen, M T MEl-Wassimy, S-O Lawesson Acta Chem. Scand., Ser. B 37 785 (1983) 161. K A Jùrgensen, S-O Lawesson J. Chem. Soc., Perkin Trans. 2 231 (1985) 162. R G Pearson Symmetry Rules for Chemical Reactions. Orbital Topology and Elementary Processes (New York: Wiley, 1976) 163. O Dolgounitcheva, V G Zakrzewski, J V Ortiz, G V Ratovski Int. J. Quantum Chem. 70 1037 (1998) 164. K A Jùrgensen J. Org. Chem. 50 4758 (1985) 165. G I Borodkin, E B Belikova, M M Shakirov, V G Shubin Zh. Org. Khim. 34 1868 (1998) b 166. E Bosch, J K Kochi J. Chem. Soc., Perkin Trans. 1 2731 (1996) 167. K Kobayashi, N Deguchi, E Horn, N Furukawa Angew. Chem., Int. Ed. Engl. 37 984 (1998) 168. A D Williamson, J L Beauchamp J. Am. Chem. Soc. 97 5714 (1975) 169. T Wyttenbach,M T Bowers J. Phys. Chem. 96 8920 (1992) 170. G A Olah, B G B Gupta, S C Narang Synthesis 274 (1979) 171. C Matt, A Wagner, C Mioskowski J. Org. Chem. 62 234 (1997) 172. R D Bach, T H Taaffee, S J Rajan J. Org. Chem. 45 165 (1980) a�Russ. Chem. Bull. (Engl. Transl.) b�Russ. J. Org. Chem. (Engl. Transl.) c�Dokl. Chem. Technol., Dokl. Chem. (Engl. Transl.) d�Kinet. Catal. (Engl. Transl.) e�Russ. J. Gen. Chem. (Engl

ISSN:0036-021X    

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Russian Chemical Reviews 70 (3) 231 ± 264 (2001) Chemistry of xenon derivatives. Synthesis and chemical properties V K Brel, N Sh Pirkuliev, N S Zefirov Contents I. Introduction II. Synthesis and properties of xenon difluoride-based reagents III. Reactions of xenon difluoride and its derivatives with unsaturated compounds IV. Reactions of xenon derivatives with aromatic and polyfluoroaromatic compounds V. Reactions of xenon difluoride with organic acids and their derivatives VI. Organic xenon(II) compounds containing the C7Xe bond VII. Reactions of xenon difluoride with nitrogen-containing compounds VIII. Oxidative fluorination of organoelement compounds by xenon difluoride and its derivatives IX. Miscellaneous reactions Abstract. chemical and synthesis the on data published The The published data on the synthesis and chemical transformations and generalised are derivatives xenon of transformations of xenon derivatives are generalised and ana- ana- lysed.references 489 includes bibliography The lysed. The bibliography includes 489 references. I. Introduction Xenon derivatives were obtained for the first time in 1962 by Bartlett 1 who used elementary xenon and PtF6 as the oxidant to synthesise a xenon-containing salt. XePtF6 Xe+PtF6 Further studies showed that xenon compounds can be syn- thesised from elementary xenon and other oxidants. For example, the oxidation of elementary xenon by AgF2 in anhydrous HF in the presence of BF3 (see Ref. 2) results in XeF2, whereas in the presence of AsF5 the cation Xe2Fá3 is formed (see Refs 2 ± 5).HF(liq) 2AgBF4+XeF2 2AgF2+2BF3+Xe HF(liq) 4AgF2+5AsF5+2Xe 4AgAsF6+Xe2Fá3 AsF¡6 Mass-spectrometric studies of the reaction of xenon with SiF4 in the gas phase revealed the presence of the cation F3SiXe+ (see Ref. 6), whereas the formation of the cations C2H4Xe+ and C2H4XeF+ was established in reactions where the cations Xe2F+ or XeFá2 were generated in the presence of ethene (see Ref. 7). These reactions present substantial theoretical interest, since they illustrate the high synthetic potential of xenon. At present xenon chemistry rests predominantly on fluori- nated derivatives of xenon, such as xenon tetrafluoride and V K Brel, N Sh Pirkuliev Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax (7-095) 913 21 13. Tel. (7-095) 913 21 13. E-mail: brel@ipac.ac.ru (V K Brel). Tel. (7-095) 939 51 55 (N Sh Pirkuliev) N S Zefirov Department of Chemistry, MV Lomonosov Moscow State University, Leninskie Gory, 119899 Moscow, Russian Federation. Fax (7-095) 932 88 46. Tel. (7-095) 939 16 20, (7-095) 524 50 62 Received 5 September 2000 Uspekhi Khimii 70 (3) 262 ± 298 (2001); translated by R L Birnova #2001 Russian Academy of Sciences and Turpion Ltd DOI 10.1070/RC2001v070n03ABEH000626 231 231 233 236 239 242 245 248 258 particularly xenon difluoride, the latter being produced by differ- ent manufacturers. The methods for the direct synthesis of XeF2 and XeF4 from fluorine and xenon at elevated temperatures were published in the early 1960's independently by several groups of investigators.8, 9 Further studies 10 were mostly directed at the elaboration of more convenient and simpler procedures for the preparation of xenon derivatives. A variety of inorganic xenon derivatives, both unstable and sufficiently stable in a broad temperature interval, were synthesised within a relatively short period of time.The first xenon derivatives containing Xe7N (see Ref. 11), Xe7B (see Ref. 12) and Xe7C bonds (see Ref. 13) were also prepared. The interest in xenon chemistry stimulated the appearance of numerous reviews. Some of those 14 ± 35 dealt with the discovery of noble gases, the chemistry of inorganic xenon derivatives and their applications in the fluorination of unsaturated and aromatic compounds.The physical and chemical properties of noble gas derivatives have been documented.22 ± 24 In some publications (see, e.g., Refs 26, 27 and 32), xenon chemistry is considered in only a little detail and mostly in connection with other fields of chemistry, e.g., the synthesis of organofluorine compounds, etc. All of these reviews generalised the literature data published before the early 1990's. The aim of this review is to systematise, analyse and generalise the literature data concerning the synthesis and chemical proper- ties of xenon derivatives with special emphasis on the chemistry of xenon difluoride and its derivatives.II. Synthesis and properties of xenon difluoride- based reagents At present, xenon difluoride is the only commercially available xenon derivative. A characteristic feature of this reagent is that it behaves as a radical fluorinating agent in the gas phase or under irradiation and as an electrophilic agent under other conditions. It is of note that the reactivity of XeF2 increases dramatically in the presence of Lewis acids, apparently due to ionization of the XeF2 molecule resulting in the formation of XeF+MF¡n or Xe2Fá3 MF¡nsalts which are both strong oxidants.35, 36 Some properties of xenon difluoride, e.g., melting point, enthalpy of formation, critical parameters, solubility, maximum permissible concentrations, etc., have been documented in earlier publications.3, 20 ± 24, 29, 30, 36 ± 39V K Brel, N Sh Pirkuliev, N S Zefirov 232 NO+XeOF¡ XeOF4+ONF 5 Perxenonates pertaining to octavalent xenon derivatives can be obtained by the following scheme:81 NaOH HOPOF2 XeF6 Na4XeO6+Xe.XeO3 Perxenonates are the starting compounds in the preparation of perxenates 82, 83 and hydroxenates.84 Perxenates of virtually all alkali metals,85 alkaline-earth metals and actinide elements have presently been synthesised.35 All of them are potent oxidants.86 Xenon fluorides react with various oxo acids to give com- pounds rather stable at low temperatures.87 ± 95 These reactions have been especially well studied for XeF2 which forms mono- (5a ± j) or diesters (6a ± j) depending on the reagent ratio (Scheme 1).Scheme 1 HOR CH2Cl2 FXeOR+HF 5a ± j XeF2 ±78 8C 2 HOR Xe(OR)2+2HF 6a ± j The methods used for the synthesis of inorganic xenon derivatives can arbitrarily be divided into two main groups, viz., reactions of elementary xenon with various oxidising systems and synthesis of fluorinated xenon derivatives directly from xenon and fluorine. Xenon difluoride, -tetrafluoride and -hexafluoride were obtained in good yields by varying xenon and fluorine ratios as well as by selecting appropriate reaction conditions (pressure, temperature).40 ± 43 A photochemical method was developed in addition to the thermal procedure. Thus UV irradiation of a xenon ± fluorine mixture results in xenon fluorides in satisfactory yields.44 ± 48 By virtue of their simplicity, thermal and photo- chemical methods are especially popular.These methods allow the synthesis of xenon difluoride with 99% purity. Other fluori- nating reagents (with the exception of elementary fluorine) can also be used for the fluorination of elementary xenon. Thus the more readily available and safe ClF3 was successfully used in the synthesis of large amounts of xenon difluoride,49 whereas O2F2 was used in the synthesis of xenon tetrafluoride and -hexafluor- ide.50 Other examples of xenon fluoride synthesis by oxidation of elementary xenon 13 ± 23, e.g., irradiation of crystalline xenon by a flux of fluorine atoms, thermocatalytic synthesis,51, 52 g-irradia- tion of a fluorine ± xenon mixture 53 and electrochemical fluorina- tion, have also been described.54 Compounds 5 and 6 R Ref.Other xenon halides, e.g., xenon chlorides 55, 56 and -bro- mides,57 are also known, but these compounds are difficult to access due to their low stabilities and are therefore virtually noninvestigated. abcdefghij 87, 88 89 89 89 ± 91 92 93, 94 87 ± 89 95, 96 90, 97 ± 99 88 OSO2F OSO2CF3 OSO2Me OCOCF3 OPOF2 OIOF4 OClO3 OSeF5 OTeF5 ONO2 Some xenon compounds are synthesised by substitution of ligands for fluorine in the corresponding fluorides. For example, the reaction of xenon fluorides with oxygen-containing substrates yields compounds containing covalent Xe7O or Xe=O bonds.58 The formation of the Xe=O bond usually occurs upon hydrolysis of xenon fluorides.The hydrolysis of xenon difluoride which gives xenon and hydrogen peroxide has been studied in detail. The Appelman hypothesis 59 about the formation of the oxidising species Xe=O in the first step of hydrolysis was corroborated by other authors.60 ± 64 The Xe7O bond can also be formed through insertion of XeF2 into the E=O bond. This approach was used in the reaction of XeF2 with SO3 100 and resulted in mono- (5a) or difluorosulfate (6a) depending on the reagent ratio. Aqueous solutions of XeF2 oxidise both inorganic 58 ± 60 and SO3 FXeOSO2F 5a XeF2 organic compounds.61 ± 64 The reactions of xenon difluoride with alcohols give reactive alkoxyxenonium fluorides ROXeF which manifest pronounced electrophilic properties (see Section III).2 SO3 Xe(OSO2F)2 6a XeF2 or the monoesters 5a,f react with iodine trifluorodioxide analogously.94 SO2ClF XeF2 + IO2F3 Hydrolysis of xenon hexafluoride by two equivalents of water results in xenon oxytetrafluoride XeOF4 (1);65 the highly explosive xenon trioxide XeO3 is formed in the presence of excess water, apparently, via xenon dioxydifluoride (2). Compound 2 reacts with AsF5 to yield the cation [XeO2F]+ (compound 3) or the bridged cationoid structure 4.66, 67 BrF5 or CFCl3 FXeOIOF4 5f XeF6+2H2O SO2ClF HF BrF5 or CFCl3 RXeOIOF4 6f,k FXeR +IO2F3 5a,f 6 XeOF4+2HF 1 [XeO2F]+AsF¡ 3 XeO2F2+AsF5 2 R=OSO2F (5a, 6k), OIOF4 (5f, 6f).HF 6 [FO2XeFXeO2F]+AsF¡ 4 2XeO2F2+AsF5 2 Exchange of ligands (other than fluorine) at the xenon atom is also possible, although this reaction has not been well studied yet.94 CFCl3 Xe(OIOF4)2+2HOTeF5 6f Xe(OTeF5)2+2 HOIOF4 6i Xenon oxytetrafluoride XeOF4 (1) is formed upon reactions of xenon hexafluoride with SeO2F2,68 NaNO3 69 ± 71 and TcO3F.72 However, these methods have some limitations connected with the use of toxic reagents and the possibility of formation of the explosive xenon trioxide as a by-product. These problems can be overcome by carrying out the reaction with phosphorus oxy- fluoride. This reaction proceeds with a nearly quantitative yield; XeO3 is not formed.73 In some cases, synthesis of bivalent xenon derivatives is accompanied by the formation of undesirable side products directly from acids and XeF2.Hydrogen fluoride liberated can be bound by (Me3Si)2NH or its formation can be prevented by boric anhydrides of the type B(OR)3 (R=SO2CF3, C(O)CF3).101 XeF6+POF3 XeOF4+PF5 1 B(OSO2CF3)3 XeF2 2/3B(OC(O)CF3)3 FXeOSO2CF3 5b Xe(OCOCF3)2+BF3 6d Xenon oxytetrafluoride (1) can form complexes with alkali metal fluorides 74, 75 which are attractive as regards their structural parameters and salts of the [XeOF5]Y type, e.g., where Y=NO+ (see Refs 76 ± 80).Chemistry of xenon derivatives. Synthesis and chemical properties The ligands OTeF5 and OSeF5 manifesting pronounced electron-withdrawing properties and maximum stabilising effect in comparison with other known oxygen ligands are the most suitable for the synthesis of tetra- and hexavalent xenon deriva- tives containing covalent Xe7O bonds.102, 103 The Xe(IV) 7 104 ± 108 and Xe(VI) 8 and 9 106 ± 109 derivatives were obtained using OTeF5 as the ligand.XeF4 >70 8C 6i 7F5TeOOTeF5 7BF3 Xe(OTeF5)4 7 720 8C 7+O2(TeF5)5 XeF6 20 8C 6i+2O2(TeF5)2 B(OTeF5)3 7BF3 Xe(OTeF5)6 9 hn Xe+O2(TeF5)2 790 8C OXeF4 6i 7BF3 O Xe(OTeF5)4 8 7F5TeOOTeF5 , 71/2O2 The synthesis of bis(pentafluorotellurium) xenonate (10) and tetrakis(pentafluorotellurium) xenonate (8) made use of the corresponding boric anhydride.110 3XeO2F2+2B(OTeF5)3 2 3(F5TeO)2XeO2+2BF3 10 3XeOF4+4B(OTeF5)3 3OXe(OTeF5)4+4BF3 8 The reaction of xenon with O2BF4 results in the evolution of O2 and F2 and the formation of white crystals with the composi- tion FXeBF2 (see Ref.11). This is the only currently known compound containing a Xe7B bond. At 243 K, it decomposes to yield an equimolar mixture of Xe and BF3. FXeBF2+O2+F2 Xe+O2BF4 III. Reactions of xenon difluoride and its derivatives with unsaturated compounds Reactions of XeF2 with alkenes, alkynes and dienes have been described in detail in reviews.20, 30 ± 33 In the general case, XeF2 reacts with ethylene and terminal alkenes to afford mixtures of the addition products to the double bond and of the substitution products of fluorine for an alkene hydrogen atom.111 ± 113 This reaction occurs more selectively in the presence of HF, viz., the addition products to the double bond are formed in up to 95% yields.114 ± 119 In addition to fluorine derivatives, the reaction of alkenes with XeF2 in CF3CO2H also gives the corresponding trifluoroacetates.120 1-Phenyl-substituted cycloalkenes react with XeF2 in the presence of HF to give a mixture of cis- and trans- difluorides (in up to 90% yields); the isomer ratio depends on the ring size.121, 122 Fluorohalogenation of the substrate occurs in the presence of a chlorine or a bromine source.122 The reaction of XeF2 with acenaphthylene, indene, 1,2- and 1,4-dihydronaphtha- lenes,123, 124 norbornene 125 ± 130 and norbornadiene 125, 130, 131 results in the corresponding difluorides.The reaction of aliphatic 1,3-dienes with XeF2 in the presence of BF3 .Et2O gives 1,2- addition products (75% ± 100%).132 The reaction of enols with XeF2 results in a-fluorocarbonyl compounds.133 ± 140 The reaction of diphenylacetylene with XeF2 catalysed by trace amounts of HF gives 1,2-diphenyltetrafluoroethane in 50% yield.141 The fluorination of acetyl derivatives of D-fucal, D-glucal and D-galactal by XeF2 has been described.142 ± 144 Thus tri-O-acetyl-D-glucal reacts with XeF2 in the presence of BF3 . OEt2 to give a mixture of 2-fluoroglycosyl fluorides.142 233 OAc O XeF2, BF3 . OEt, PhH, Et2O OAc 25 8C, 30 min AcO OAc OAc OAcF F O O O OAc F OAc OAc F AcO AcO AcO F F (61%) (5%) (12%) OAc OAc AcO AcO AcO HCl The fluorination of tri-O-acetyl-D-galactal by XeF2 in CFCl3 and subsequent hydrolysis of the reaction product with hydro- chloric acid affords 2-deoxy-2-fluoro-D-galactose.144 OAc O O O XeF2 OAc OAc OAc OH F (63%) F F A versatile procedure for chemical doping of p-conjugated polymers, e.g., polyacetylene and poly(p-phenylene), has been developed which allows introduction of various anions (A7) into the polymer. The polymer is treated with xenon difluoride used as the oxidant and the corresponding acid, e.g., HA (XeF2 :HA=1 : 2) in liquid HF or CH2Cl2.145 Such a modifica- tion of polymers is not accompanied by incidental formation of degradation or fluorination products.P n+(A7)n+1/2n Xe+1/nH P+1/2n XeF2 +1/nHA where P is the elementary unit of the polymer (CH or C6H4), n is the degree of doping, A=BF4, AsF6, SbF6, OSO2F, OSO2Me or OCOCF3.The degree of doping of the polymers under study by the XeF2 ±2HA system increases with increase in the reaction time and the reagent : polymer molar ratio. The doping ability of anions decreases in the following order: SbF¡6 >AsF¡6 5BF¡4 5 OSO2F7>OSO2Me7>OCOCF¡3 , which correlates with the order of the relative withdrawing capacity of the corresponding acids in reactions with XeF2.22 The maximum degree of doping of poly(p-phenylene) (0.97) is achieved with the anion SbF¡6 . This is probably due to the generation of the active species XeF+ [its electron affinity is 10.4 eV (see Ref. 3)] as a result of complete ionisation of the XeF2 ±2HA complex and the formation of XeF+SbF¡6 (see Ref.146). It should be noted that the oxidising system XeF2 ± 2HA allows variations of the anion A in a broad range, which makes this system superior to oxidants of the AsF5 and I2 type.145 Reactions of alkenes of different structures with other xenon derivatives including fluoroxenon triflate (5b), fluorosulfate (5a) and nitrate (5j), have been studied.147 ± 150 These reagents appeared to be more reactive than XeF2. Xenon bis(fluorosulfate) (6a) reacts explosively with ordinary unsaturated hydrocarbons even at low temperatures. On the other hand, electron-deficient alkenes (11) yield covalent bis(fluorosulfonates) 12.149 Freon 113,710 8C 7Xe 11 Cl(R)C C(R)Cl+Xe(OSO2F)2 6a (FSO2O)Cl(R)CC(R)Cl(OSO2F) 12 R=H, Cl, F.A one-step procedure for the preparation of fluorohaloge- noalkenes using the reagent 5b has recently been proposed.151 Thus mixing of equimolar amounts of XeF2 and CF3CO2H in anhydrous CH2Cl2 and subsequent addition of 1,1-dichloroal- kene results in fluorodichloroalkenes 13a ± c, viz., the products of formal substitution of fluorine for the vinylic hydrogen atom.151 This approach is an alternative to the Swarts fluorination.152234 RHC CCl2 CH2Cl2 TfOH+XeF2 7HF FXeOTf 5b 7TfOH RFC CCl2 13a ± c [RCHFCCl2OTf] 14 Tf=CF3SO2; R =H(13a, 65%),Me (13b, 66%), Et (13c, 63%). The addition of the reagent 5b follows the Markownikoff rule and yields the adducts 14.Spontaneous elimination of trifluoro- methanesulfonic acid from the adducts 14 can be attributed to the fact that the easily leaving triflate group and two electronegative chlorine atoms are localised at the same carbon atom. cis-b-Fluorocyclohexyl fluorosulfate (15) was obtained as the main product in 50% yield in the reaction of xenon fluorosulfo- nate fluoride (5a) with cyclohexene; the reaction with tetrachloro- ethylene gave the adduct 16, which was unstable at room temperature and could be identified as ethyl dichlorofluoroacetate (17).150 FOSO2F 15 FXeOSO2F 5a Cl2C CCl2 EtOH Cl2C CCl2 Cl2FCCO2Et 17 F OSO2F 16 The reactions of compounds 5a,b,j with hex-1-ene result in b-fluoroalkyl sulfonates or nitrates 18 and 19 with the predom- inance of the Markownikoff regioisomers 18a,b,j.148, 149 CH2Cl2 CH2 BunCH CH2+BunCH 778 to 0 8C BunCH CH2+FXeOZ 5a,b,j OZ F OZ F 18a,b,j 19a,b,j Yield (%) Z Reagent 19 18 5a 5b 5j SO2F 34 17 48 18 159 Tf NO2 Analogous reactions with cyclohexene yield predominantly cis-adducts.Thus cis-2-fluorocyclohexyl triflate 20b is exclusively formed in 75% yield when the reagent 5b is used. The reagent 5a reacts with cyclohexene to give a mixture of the cis- and trans- isomers 20a and 21a in a 3 : 1 ratio (the total yield is 64%). The reaction of cyclohexene with the reagent 5j gives a mixture of the isomers 20j and 21j in a total yield of 25%.148, 150 F F CH2Cl2 + 778 to 0 8C +FXeOZ 5a,b,j OZ OZ 21a,b,j 20a,b,j Z=OSO2F (a), OTf (h), ONO2 ( j).Earlier, it was assumed 20, 30 ± 34 that the addition of the reagents 5a,b,j to alkenes occurs by a carbocationic mechanism involving the `electrophilic' fluorine. However, the selective for- mation of cis-adducts in the reaction with cyclohexene cannot be rationalised within the framework of this mechanism. Based on the fact that the addition of triflates and perchlorates of trivalent iodine to alkenes also results in cis-adducts 153 ± 162 and taking into account the isoelectronic nature of I(III) and Xe(II) derivatives, a reaction mechanism was proposed 148 which includes electrophilic addition of the reagents 5 to the double bond and the formation of the intermediate 22. V K Brel, N Sh Pirkuliev, N S Zefirov Xe+ XeF R R R H H H SN2 AdE 7Xe0 H +FXeOZ 5 H H H H H F7 OZ 22 OZ 23 R H H H F OZ This reaction occurs in a trans-selective manner as in the case of trivalent iodine compounds.153 ± 162 Its second step includes stereospecific nucleophilic substitution of fluorine for xenon by the SN2 mechanism, which is accompanied by an inversion of configuration and the formation of the cis-product.163 Additional evidence in favour of the intermediate formation of the organo- xenon compounds 22 and 23 containing the C7Xe bond in these reactions will be given in Section VI.The reaction of XeF2 with alkenes in the presence of aliphatic alcohols has been studied.164 ± 169 It was shown that methanolysis of XeF2 yields an unstable electrophilic intermediate with hypo- thetical composition MeOXeF, which generates a potential elec- trophilic fluorine donor 24 in the presence of HX.MeOXeF reacts with boron trifluoride to give the positive oxygen electrophile 25. The reaction of the intermediates 24 or 25 with alkenes results in carbocations containing F or OR in the a-position.164 MeOXeF XeF2+MeOH 7HF H X7 F Nu7 HX + + products MeO Xe F 24 OMe d+ Nu7 BF3 + products d7 MeO....Xe....F....BF3 25 It was found 164 that the reaction of XeF2 with alkenes in methanol involves MeOXeF rather than MeOF170 the formation of which requires a stronger oxidant than XeF2 (e.g., F2). In the absence of alkenes, MeOXeF disproportionates quantitatively with the formation of HF, Xe and CH2O.The presence of an acid catalyst strongly affects the regioselectivity of the reaction. In the presence of hydrogen fluoride, MeOXeF reacts with cis- and trans-1-phenylpropenes 26 to give the final Markownikoff prod- ucts 27 and 28, whereas in the presence of BF3 (in Et2O or MeOH) the anti-Markownikoff products 29 predominate in the reaction mixture.164, 165 MeOXeF (24) PhCH CHMe 26 HF PhCH(OMe)CH(F)Me+PhCH(F)CH(F)Me 28 27 BF3 . Et2O Yield of 29 (%) Yield of 27 (%) Catalyst PhCH(F)CH(OMe)Me+27+28 29 Yield of 28 (%) threo threo erythro erythro threo erythro cis-26 as the substrate 0 0 43 0 27 73 26 23 251 0 HF BF3 . Et2O 0 trans-26 as the substrate HF BF3 .Et2O 1 0 47 0 20 96 29 23 20 1H and 13C NMR spectroscopy and mass spectrometry were used to study the regio- and stereochemistry of reactions of indeneChemistry of xenon derivatives. Synthesis and chemical properties with the unstable intermediates 30a ± j formed upon the reaction of XeF2 with the corresponding alcohols.164 ± 166, 169 XeF2+R1R2R3COH R1R2R3COXeF 30a ± j F OCR1R2R3 F OCR1R2R3 F+ F+ 31 33a ± j 32a ± j R1=R2=R3=H(a); R1=R2=Me, R3=H(b); R1=R2=R3= Me (c); R1=ClCH2, R2=R3=H(d); R1=FCH2, R2=R3=H(e); R1=CF3, R2=R3=H(f); R1=R2=R3=CF3 (g); R1=CF(NO2)2, R2=R3=H(h); R1=C(NO2)3, R2=R3=H(i); R1=MeC(NO2)2, R2=R3=H(j). The reaction with xenon methoxyfluoride (30a) in the pres- ence of HF (MeOH, 0 ± 12 8C) gives predominantly a mixture of cis- and trans-isomers of the methoxy fluoride 32a (52% and 46%, respectively); the yield of yet another reaction product, viz., the difluoride cis-31, is 2%. The anti-Markownikoff adducts 33 (26% of the cis-isomer and 52% of the trans-isomer) are the main products of the reaction carried out in the presence of BF3 .Et2O (MeOH, 0 8C).164, 165 Alkoxyfluorides 32b,c (cis- and trans isomers) are the main reaction products formed in the presence of protic catalysts (HF generated in situ) in PriOH or ButOH. Alkoxy fluorides 33b,c (cis- and trans-isomers) are formed first in the presence of BF3 . OEt2. In both cases, cis- and trans-difluoroindanes 31 are formed as admixtures. Compounds 33b,c rearrange under the reaction conditions into the thermodynamically more stable adducts 32b,c.In the absence of BF3 . Et2O, the rearrangement occurs more slowly, viz., within several days. Reactions with alcohols containing electron-withdrawing substituents occur faster due to their higher acidities. The product yields in CF3CO2H decrease owing to the polymerisation of indene.166, 169 The nortricyclane derivatives 38 and 39 were also identified in reactions with norbornene along with the isomeric difluorides 34 and the methoxy fluorides 35, 36 and 37.164, 165 F 24, HF OMe+ + MeOH, 0 ± 12 8C F F 35 34F F OMe F + + + OMe 37 36 38 24, BF3 .MeOH OMe 34+35+38+ MeOH, 0 8C 39 The reaction of 1,3-dimethylbuta-1,3-diene with XeF2 in methanol in the presence of a catalyst (HF or BF3 .MeOH) affords a mixture of various 1,2- and 1,4-adducts, viz., difluorides and methoxy fluorides.The addition occurs both according to the Markownikoff rule and against it.165 In the absence of a catalyst, dihydropyrane (40) reacts with XeF2 and MeOH to give cis- and trans-isomers of the adduct 41.165 235 F F XeF2 + MeOH OMe O OMe O O40 trans-41 (67%) cis-41 (33%) It is of note that hex-1-ene, buta-1,3-diene and methyl crotonate do not react with MeOXeF; in this case, the latter rapidly disproportionates to afford formaldehyde quantita- tively.165 Shellhamer et al.166 studied the mechanism of the reaction of alkenes with XeF2 in the presence of alcohols using indene as an example.a b XeF2+R1R2R3COH R1R2R3COXeF_Cat 42a ± c Xe+R3F + R1R2CO # Cat 42a ± c+ F F 7R1R2R3COH Xe 7Xe, 7Cat A + F7 R1R2R3COH 31a ± c + 32a ± c F 44 + BF¡4c D 32a ± c 33a ± c OCR1R2R3 7BF3 7Xe 43a ± c 42a ± c + F7 R1R2R3COH d 32a ± c F 7Xe 44 (a) Cat, slow step; (b) fast step; (c) BF3, fast step; (d) HF, fast step. In the absence of alkenes or in the case of their low reactivities, alcohols undergo oxidation into aldehydes or ketones with the concomitant formation of alkyl fluorides and evolution of ele- mentary xenon (routes a and b). It is believed that the complexes 42a ± c of xenon alkoxy fluorides 30a ± c with the catalyst are the intermediate products of this reaction. The intermediates 42a ± c are trapped by highly reactive alkenes (e.g., indene) to give complexes A; further conversions depend on the nature of the alcohol and the catalyst.In the presence of BF3, xenon alkoxy fluorides 30a ± c react with indene as positive oxygen electrophiles to give, after elimination of xenon, 2-alkoxyindan-1-ylium tetra- fluoroborates (43a ± c). Their stabilisation is accompanied by the liberation of BF3 and the formation of compounds 33a ± c (route c). The latter rearrange into more stable isomers 32a ± c. The intermediates 42a ± c act as electrophilic fluorine donors in the reaction with protic catalysts (HF); after the intermediate 2-fluo- roindan-1-ylium fluoride 44 has been formed, they give com- pounds 32a ± c (route d).166 The dependence of the direction of the reaction on the nature of the alcohols used (e.g., their acidity) is explained in the following way.In the presence of alkoxy substituents containing electron-withdrawing groups (CF3CH2, CF3) in the intermediates 42, they react as open ions (route d), whereas in the presence of electron-donor groups in alkoxy substituents they react with indene to afford the soft bridged intermediates 45a ± c. The reaction of these intermediates with the tetrafluoroborate anion results in the predominant formation of the trans-adducts 33a ± c which are transformed into compounds 32a ± c under the reaction conditions.166 + OR BF¡4 45a ± c R=Me (a), Pri (b), But (c).236 The reaction of 2-methylpent-1-ene with XeF2 in CF3CH2OH at 0 ± 25 8C yields the alkoxy fluorides 46 (route c) and 47 (route d) in a total yield of 76% and in a ca.1 : 1 ratio (these compounds were isolated by preparative GLC). Only the difluor- ides 48 and 49 could be prepared from hex-1-ene under analogous conditions, which corresponds to direct fluorination (route d). F OCH2CF3 CF3CH2OH CPr CPr FCH2 CH2 + CF3CH2OCH2CPr XeF2 Me Me 46 Me 47 CF3CH2OH CHFBu FCH2 CHBu CH2 XeF2 CHFBu +CF3CH2OCH2 49 48 tert-Butyl hypochlorite and XeF2 react with cyclohexene in CCl4 to give a complex mixture of compounds with trans-1- chloro-2-fluorocyclohexane (50) as the main product.171 Cl XeF2, ButOCl +other products CCl4 F 50 (49%) + Cl FXe CMe H2C O FXe+ClO7+HF+ Me H Me F7 CH2 Me 51 + Cl FXe O MeOCl+ClF+Xe0+Me2CO Me OCl7 Me Me 51 In this case, the lack of selectivity is attributed 171 to the formation of an intermediate complex of xenon fluoride with ButOCl (51), which generates various reactive species upon decomposition.It should be noted that tert-butyl hypochlorite and XeF2 do not react with cyclohexene when used separately.171 This reaction was extended to other hypohalites (MeOX, ButOX, where X=Cl, Br).171, 172 It is assumed that the reaction of hypohalites with XeF2 gives the corresponding interhalides HalX (Hal=Br, Cl), which are weaker electrophilic reagents than Cl2 or BrCl. Therefore, they react more selectively with electron- enriched unsaturated and aromatic compounds to give the corre- sponding difluorides in high yields.Cyclohexene, methylene- cyclohexane, hex-1-ene, hept-1-ene, hex-3-yne, 3,4-dihydro-2H- pyran, anisole, etc., were used as substrates.171, 172 The fluorination of the phenyl-substituted alkenes 52a ± e with XeF2 in the presence of 0.1 ± 0.2 equiv. of anhydrous HF results in the difluorides 53a ± e.173 F F R3 Ph XeF2, CH2Cl2 R3 Ph HF, 25 8C, 0.5 h R1 R1 R2 53a ± e R2 52a ± e R1=R2=R3=H(a); R1=Me, R2=R3=H(b); R2=Me, R1= R3=H(c); R1=Ph, R2=R3=H(d); R1=Ph, R2=Me, R3=H(e). The reaction of XeF2 with 3-phenyl-1H-indene (54a) affords 3-phenyl-2-fluoro-1H-indene (55a) as a result of addition ± elimi- nation. The fluorination of 4-phenyl-1,2-dihydronaphthalene (54b) and 9-phenyl-6,7-dihydro-5H-benzocycloheptene (54c) by XeF2 yields diastereomeric pairs of the vicinal difluorides 56a,b and 57a,b.They are unstable on heating and eliminate HF at 200 8C, being converted into 3-fluoro-4-phenyl-1,2-dihydronaph- thalene (55b) and 8-fluoro-9-phenyl-6,7-dihydro-5H-benzocyclo- heptene (55c).173 n=1 Ph XeF2 CH2Cl2 (CH2)n 54a ± c n=2, 3 n=1 (a), 2 (b), 3 (c). The reaction of enol trimethylsilyl ethers with XeF2 has recently been studied.174 Thus 1-trimethylsilyloxycyclohexene (58) reacts with XeF2 to give a-fluorocyclohexanone (59) in a quantitative yield. In the case of XeF+, this reaction gives a mixture of three products (59 ± 61); their formation is interpreted in terms of a single-electron transfer mechanism.174 O XeF2 OSiMe3 59 58 XeF+ 59 + IV.Reactions of xenon derivatives with aromatic and polyfluoroaromatic compounds Xenon difluoride is a convenient fluorinating agent for the preparation of fluorine-containing mono- and polycyclic aro- matic compounds. The reaction of aromatic and polyfluoroar- omatic hydrocarbons with XeF2 has been described in detail in reviews,20, 30 ± 33 therefore, in Table 1 we shall cite only the most common reactions. Special attention will be given only to those papers which have not been surveyed in the literature. Several papers are devoted to the reactions of functional derivatives of aromatic hydrocarbons with XeF2. Thus the reac- tion of XeF2 with anisole and 1,2-dimethoxybenzene gives 4-fluo- roanisole and 4-fluoro-1,2-dimethoxybenzene (yields 72% and 37%, respectively).198 The reaction of phenol with XeF2 in CH2Cl2 yields a mixture or isomeric fluorophenols (47%);198 in water, phenol is oxidised into p-benzoquinone.63, 199, 200 Hydro- quinone and 4-tert-butylcatechol are oxidised by XeF2 into benzoquinone derivatives,201 whereas catechol affords 4-fluoro- catechol in 38% yield.198 The initially proposed structure of the reaction product of pentafluorophenol with XeF2 (C6F5OOC6F5) 202 was later refuted;203 it was shown that this reaction yielded perfluoro-4-phenoxycyclohexa-2,5-dienone and perfluorocyclohexa-2,5-dienone.The reaction of (perfluoroaryl)- trimethylsilanes (ArF=C6F5, 4-CF3C6H4, 4-C5F4N) with XeF2 results in desilylation and formation of perfluorobiaryls.204, 205 The fluorination of the aromatic nucleus of L-3-methoxy-4- hydroxyphenylalanine 206, 207 used in the synthesis of L-6-fluoro- dihydroxyphenylalanine-[18F] occurs smoothly.207 V K Brel, N Sh Pirkuliev, N S Zefirov Ph F 55a (40%) Ph Ph F F H F + F H (CH2)n (CH2)n 57b (29%) 57c (31%) 56b (41%) 56c (38%) D Ph F (CH2)n 55b (65%) 55c (61%) FO O O + 61 60Chemistry of xenon derivatives.Synthesis and chemical properties Table 1. The reaction products of aromatic compounds with xenon difluoride. Starting compound PhH PhMe PhCl PhF PhCF3 PhOMe PhNO2 1,4-F2C6H4 1,2-F2C6H4 1,2,3-C6H3Me3 C6Me6 Indan 5-Fluoroindan Tetralin 9,10-Dihydro- anthracene Acenaphthene Trypticene Naphthalene Anthracene Phenanthrene Pyrene Benzo[a]pyrene Perylene C6F6 1-XC6F5 (X=F, H, Cl, Br, C6F5) C6F5Cl C6F5Br Decafluorobiphenyl C6F5H 25 CH2 Cl2 BF3 25 20 20 Octafluoro- naphthalene 2-Methoxyhepta- fluoronaphthalene 2-Ethoxyheptafluoro- 25 naphthalene a At 1076 mm Hg; b at 1075 mm Hg.Aromatic aldehydes react with XeF2 inCH2Cl2 in the presence of HF to give the ethers 62 in 67%± 86% yields, the maximum yields being achieved with 4 ± 5 equiv. of HF.208, 209 Solvent T/8C CCl4 CCl4 CCl4 CCl4 CCl4 CCl4 165 145 25 25 25 25 25 20 120 167 100 100 25 25 25 25 25 25 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 25 CH2Cl2 25 CH2Cl2 25 CH2Cl2 CH2Cl2 778 ± 20 a CH2Cl2 CH2Cl2 712 ± 12 a CH2Cl2 CH2Cl2 778 ± 20 b 25 7125 to778 b CH2Cl2 CH2Cl2 C6F12 778 to745 25 20 CH2Cl2 25 25 25 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 25 CH2Cl2 CH2Cl2 Reaction products Catalyst HF HF HF HF HF HF HF HF HF HF HF HF HF HF HF mixture of mono-, di and trifluorobenzenes the same C6H5F C6H4FMe (mixture of o-, m- and p-isomers) C6H4FCl (mixture of o-, m- and p-isomers) C6H4F2 (mixture of o-, m- and p-isomers) C6H4FCF3 (mixture of o-, m- and p-isomers) C6H4(OMe)F (mixture of o-, m- and p-isomers) mixture of o-, m- and p-nitrofluorobenzenes the same 1,2,4-C6H3F3 : 1,2,4,5-C6H2F4=8 : 1 1,2,4-C6H3F3 : 1,2,4,5-C6H2F4=42 : 1 1,4-F2-3,4,5-C6HMe3 : 1-F-2,3,4-C6H2Me3=1 : 2 C6Me5CH2F CF3CO2H C6Me5CH2OCOCF3 5-fluoroindan 5,6-difluorindan 5-fluorotetralin, 6-fluorotetralin 1-fluoro-9,10-dihydroanthracene, 3-fluoro-9,10-dihydroanthracene 3-fluoroacenaphthene, 5-fluoroacenaphthene 1-fluorotrypticene, 2-fluorotrypticene 1-fluoronaphthalene, 2-fluoronaphthalene mixture of 1-fluoro, 2-fluoro- and 1,4-difluoronaphthalenes 9-fluoroanthracene, 1-fluoroanthracene, 2-fluoroanthracene 9-fluorophenanthrene mixture of mono-, di-, tri- and tetrafluoro- phenanthrenes mixture of monofluoropyrenes 6-fluorobenzo[a]pyrene difluoroperylene, 3-fluoroperylene 1-X-heptafluorocyclohexa-1,4-dienes BF3 BF3 BF3 BF3 BF3 HF HF 1-chloroheptafluorocyclohexa-1,4-diene 1-bromoheptafluorocyclohexa-1,4-diene 1-(pentafluorophenyl)heptafluorocyclohexa-1,4-diene 1,2,3,3,4,6,6-heptafluorocyclohexa-1,4-diene octafluorocyclohexa-1,4-diene the same perfluoro-1,4-dihydronaphthalene, perfluoro-1,2-dihydronaphthalene 2-methoxynonafluoro-1,4-dihydronaphthalene BF3 2-ethoxynonafluoro-1,4-dihydronaphthalene BF3 XeF2, CH2Cl2, HF CHO X X=H, 4-Me, 4-Cl, 4-OMe, 4-OC5H11, 4-CO2H, 4-CO2Me, 2-NO2 , 3-NO2, 4-NO2, Ts.237 Yield Ref. (%) 68 32 65 47 75 65 81 175 175 176 ± 178 177, 179, 180 177, 179, 180 177, 179, 180 177, 179, 180 177, 179, 180 175 177, 179, 180 175 175 181 182 182 183 183 183 184 184 184 185 38 72 68 60 62 30 709 21 50 20 12 23 50 11 75 186 185 26 459 33 ± 40 79 185, 187 188 189 190 191 52 26 10 30 >80 192 193 193 193 193 193 194 194 ± 196 83 81 73 75 74 40 424 35 197 197 40 OCF2H X 62238 The difluoromethoxylation of aromatic aldehydes carrying electron-donor substituents, such as acetamido- and methoxy groups, is accompanied by fluorination of the aromatic ring.208 The difluoromethyl ethers 62 are formed as a result of rearrangement which probably occurs via the intermediates 63 in the reaction of the fluorohydrins 64 with XeF2.208 FXeO HO H H CHO HF F F XeF2 7Xe0 63 64 X X X O + O H H F7 H O F F + F F 62 X X X The aryl ketones 65 and 66a ± c react with XeF2 in a similar way to give the fluorinated phenol ethers 67 and 68a ± c in low yields with considerable recovery of the starting com- pounds.141, 210, 2111 equiv.XeF2, HF, CH2Cl2 ArCOCH2X 24 h, 25 8C ArOCF2CH2X 67 65 Ar=Ph, C6F5, 2-NO2C6H4; X=H, F. 1 equiv. XeF2, HF, CH2Cl2Ar1OCF2Ar2 24 h, 25 8C 68a ± c Ar1COAr2 66a ± c Ar1=Ar2=Ph (a); Ar1=Ph, Ar2=4-NO2C6H4 (b); Ar1=Ar2=C6F5 (c). 2-Fluoroindan-1-one (69) reacts with 1 equiv. of XeF2 in HF± Py to give 2,2,3-trifluoro-3,4-dihydro-2H-benzo[b]pyran (70) and 2,2,3,6-tetrafluoro-3,4-dihydro-2H-benzo[b]pyran (71) as the main products.210 2,2-Difluoroindanedione 72 yields tetra- fluorobenzopyrone 73 with XeF2 in the presence of HF. O 1 equiv. XeF2 F HF± PyH, 2 h, 25 8C 69 F F O O F F + F F F 71 (16%) 70 (24%) O F O F XeF2, HF FF F F O 72 O 73 (26.5%) The reactions of the benzyl alcohols 74 with XeF2 afforded the aryl fluoromethyl ethers 75 in high yields.212 The yield of the main product increases in the presence of electron-withdrawing sub- stituents, e.g., for R=3-NO2, it reaches 85%.Fluorinated ethers are not formed if benzyl alcohols contain hydroxy-, alkoxy- or alkylamino groups.212 CH2OH OCH2F 1 equiv. XeF2 CH2Cl2, 30±35 8C R 75 74 R R=H, 2-NO2, 3-NO2, 4-NO2, 4-Me, 3-F. Presumably, this reaction occurs via the intermediate 76 and according to the same mechanism as does the synthesis of the V K Brel, N Sh Pirkuliev, N S Zefirov difluoromethyl ethers 62 from aldehydes.The reaction is probably catalysed by HF; therefore, on the whole, it represents an autocatalytic process.212 CH2OH CH2OXeF XeF2 7Xe0 76 O F7 OCH2F + The reaction of indan-1-one with XeF2 is accompanied by ring expansion resulting in the difluoro-substituted dihydrobenzo- pyran 77. The a-fluoroketones 79 and 80a ± c are formed in the reaction of indan-2-one and the enol acetates 78a ± c with XeF2. The fluorination products of the aromatic ring have not been found in either case.211 O F O XeF2 F 77 F XeF2 O O 79 O OAc XeF2 F (CH2)n 80a ± c (CH2)n 78a ± c n = 1 (a), 2 (b), 3 (c). The [2.2]metaparacyclophane system contains two types of aromatic rings, viz., para- and meta-substituted ones.Reutov et al.213 proposed a method for selective introduction of functional groups into this compound based on the use of XeF2. It was shown that two cyclophane derivatives (82 and 83) containing a fluorine atom in the para- and meta-substituted benzene rings are formed from non-substituted [2.2]paracyclophane (81) after addition of an equimolar amount of XeF2. Mixing of the reaction compo- nents in a Teflon vessel with CH2Cl2 did not result in any reaction between them, at least within one hour. The reaction could be initiated only after addition of an equimolar amount of CF3CO2H. ortho-attack XeF2 F 82 (3%) F+(F ) 81 ipso-attack F 83 (9%) As mentioned above, the reaction of phenol with XeF2 is non- selective.198 4-Fluorophenol was obtained from 2,6-di-tert-butyl- phenol in high yield using a two-step synthesis, viz., fluorination by XeF2 at low temperatures and subsequent treatment of the monofluoride 84 with AlCl3 resulting in the elimination ofChemistry of xenon derivatives.Synthesis and chemical properties isobutylene and the formation of p-fluorophenol.214 It is of note that fluorination of phenols can also be achieved through the use of N-fluoropyridinium triflate.215, 216 OH But But XeF2, CH2Cl2 760 to 0 8C, 16 h OH OH But But AlCl3, PhMe 40 ± 50 8C, 4 h F (85%) F 84 (49%) It is known 217 that XeO3 and XeF2 decompose in the presence of water to form a vast array of products, e.g., HO. radicals, hydrogen peroxide, molecular oxygen, XeO and the superoxide ion.It can be assumed that these products will effectively hydroxylate arenes. Indeed, heating or irradiation of a XeO3 solution with a high-pressure mercury lamp at 20 8C in aqueous acetonitrile in the presence of benzene results in hydroxylation of the latter. The induction period of this reaction can be signifi- cantly reduced by addition of a catalytic amount of CrO3.218, 219 Xenon difluoride in aqueous acetonitrile is a more efficient hydroxylating reagent. In this case, the induction period is small, the initial rate of the reaction and the yield of phenol being strongly dependent on the concentration of water in the solution. HOXeF is a likely intermediate.219 Ethylbenzene is slowly oxidised by XeO3 to acetophenone in the presence of the tetraphenylporphyrin manganese complex (TPP)MnOAc (TPP is tetraphenylporphyrin) in aqueous acetone.In this case, XeO3 acts as an oxygen donor and is transferred by the metal-porphyrin catalyst to the substrate containing C7H bonds.218 A method for iodination of aromatic compounds by a mixture of XeF2 with iodine or N-iodosuccinimide has recently been described.172, 220 It is noteworthy that the same mixture was used for iodofluorination of alkenes. The IF generated from xenon difluoride is less reactive than that synthesised from I2 and F2. Presumably, in this case we deal with the reaction of an IF ± XeF2 complex with alkenes and aromatic compounds.206 The reaction of fluorene (85a) or dibenzofuran (85b) with XeF2 in the presence of BF3 .OEt2 gives a mixture of the mono- fluorides 86a,b ± 88a,b.221 Y Y XeF2, BF3 . OEt2 + CH2Cl2, 20 8C 85a,b 86a,b F F Y Y + F 88a,b 87a,b Y=CH2 (a), O (b). The reaction of XeF2 with 1-R-2,3,4,5-tetrafluorobenzene (R=H, F, Br, NO2) or 1-R-2,3,4,6-tetrafluorobenzene (R=H, CF3) inHF or CH2Cl2±BF3 . OEt2 results in the substitution of F for the hydrogen atom in the aromatic ring.222 Only the addition reaction occurs in 1-R-2,3,5,6- (R=H, Br, CF3) or 1-bromo- 2,3,4,6-tetrafluorobenzenes under these conditions. The role of radical cations as intermediate compounds has been discussed.222 239 V. Reactions of xenon difluoride with organic acids and their derivatives Earlier, it was shown (see Section II) that the reaction of XeF2 with protic oxygen-containing acids gives unstable compounds of the FXeOR and Xe(OR)2 types, which manifest strong electro- philic properties with respect to unsaturated and aromatic com- pounds.The reaction of benzoic acid with XeF2 in an excess of benzene which gives phenyl benzoate in up to 70% yield is an example.223, 224 PhCO2H+PhH+XeF2 PhCO2Ph+2HF+Xe Biphenyl (1% ± 5%) is formed along with phenyl benzoate. Kinetic studies have shown that this reaction occurs via the formation of PhCO2XeF or (PhCO2)2Xe with their subsequent reactions with benzene.224 For different benzoic acid derivatives, the yields of phenyl esters depend essentially on the structure of the original acid.225 In the case of p-fluorobenzoic acid, the yield of the corresponding phenyl ester reached 68%, whereas for o-toluic acid it was as small as 3%, which can be due to steric hindrances preventing the formation of the intermediate compound.RC6H4CO2XeF+HF RC6H4CO2H+XeF2 RC6H4CO2Ph+HF+Xe RC6H4CO2XeF+PhH R=H, 2-NO2, 3-NO2, 4-NO2, 2-Me, 3-Me, 4-Me, 4-Br, 4-F, 4-Cl. The possibility of incorporation of benzoyloxy groups into toluene, fluoro-, chloro-, bromo- and nitrobenzene using the XeF2 ± PhCO2H system has been studied.226 The kinetic data and the isomeric composition of the reaction products suggest that the benzoyloxy group is introduced into o- and p-positions of toluene, chloro- and bromobenzene. The nitro group deactivates the nucleus so that no esters are formed.The relative rates of acyloxylation of benzene derivatives in the presence of XeF2 decrease in the following order: MeC6H5>ClC6H5> BrC6H5>NO2C6H5. The experimental data suggest the electro- philic type of this reaction. The electrophilic reagent PhCOOXeF is deficient of electrons on the xenon atom and therefore attacks the positions with increased electron density in substituted ben- zenes.226 Kinetic studies of the reaction of benzene with Ph[14C]OOH revealed that benzoic acid is involved in the for- mation of phenyl benzoate and is not decarboxylated with the liberation of radiolabelled carbon dioxide.227 Aromatic dicarboxylic acids can be dehydrated by XeF2 or undergo more profound conversions. The reaction of phthalic acid with XeF2 (1 : 2) results in phthalic anhydride in 26% yield.Under the same conditions, 2,20-diphenic acid (89) generates 3,4- benzocoumarin (90) in 30% yield along with a small amount of the anhydride.228 The formation of compound 90 is due to partial decarboxylation of the intermediate with subsequent intramolec- ular acyloxylation. XeF2 MeCN O CO2H HO2C O 89 90 The reaction of fluoroxenon trifluoroacetate (5d) with aro- matic derivatives has also been studied. It was shown in particular that hexamethylbenzene reacts with the in situ generated com- pound 5d to give pentamethylbenzyl trifluoroacetate (91) in good yield, while the reaction with XeF2 in the presence of HF in CH2Cl2 gives pentamethylbenzyl fluoride (92) in 72% yield.182240 CH2OC(O)CF3 Me Me XeF2 CF3CO2H, CH2Cl2 Me Me Me Me Me Me 91 CH2F Me Me Me Me Me XeF2 HF, CH2Cl2 Me Me Me 92 Acids react with one equivalent of XeF2 in dichloromethane or chloroform to give alkyl fluorides in 20% to 95% yields.229, 230 This reaction, like other reactions occurring in the presence of XeF2, is catalysed by HF and thus represents an autocatalytic process.This conversion is a method for carbon chain shortening by one atom as a result of the halodecarboxylation reaction. 25 8C, 8 ± 16 h RF+Xe+HF+CO2 RCO2H+XeF2 R=PhCH2 (76%), Ph(CH2)2 (76%), Ph(CH2)3 (60%), Me(CH2)8 (54%), Ph2CHCH2 (63%), Me(CH2)14 (62%), MeC(O)CH2CH2 (82%), 2-norbornyl (74%), 1-adamantyl (82%), PhOCH2 (64%), 2,4-Cl2C6H3OCH2 (84%), Ph3C (65%), PhC(OMe)CF3 (95%), PhCH2 (76%), PhCH(CH2CO2H)CH2 (60%), PhCH2CHCO2H (68%), Ph (20%), Br(CH2)3 (91%).Alkanoic and arylalkanoic acids containing primary radicals, aryloxyacetic and dicarboxylic acids are highly susceptible to fluorodecarboxylation. Carboxylic acids containing secondary radicals form fluoro derivatives in low yields, whereas carboxylic acids with tertiary radicals react as smoothly as the acids with primary radicals. Those acids which contain other protic func- tional groups, e.g., amino acids, cholic acid, etc., as well as cinnamic acid do not enter into this reaction. Benzoic acid yields benzoyl fluoride in a low yield. The proposed mechanism 230 of fluorodecarboxylation entails the intermediate formation of xenon carboxylates.91, 116, 182, 226 a RF+Xe+HF+CO2 F7 XeF2 [RCO2XeF] RCO2H 7HF b RCO2 +Xe + F XeF F7 RF R+ R RCO2 7Xe,7F7 7CO2 According to Patrick et al.,230 the reaction follows both ionic (route a) and radical mechanisms (route b).Acids containing primary and secondary radicals react by route a, whereas acids containing tertiary radicals and arylalkanoic acids react by route b. Route a is realised when the reaction is carried out in the presence of [Bun4 N]+[18F]7. This made it possible to obtain 2-phenyl-1-[18F]fluoroethane and 3-bromo-1-[18F] fluoropropane in high radiochemical yields 230, 231 and opened a possibility of replacing the carboxy group by substituents other than the fluorine atom.230 PhCH2CH2[18F] (40%) PhCH2CH2CO2H+XeF2 + [18F]7 Br(CH2)3[18F] (78%) Br(CH2)3CO2H+XeF2 + [18F]7 The reaction with 3-phenylpropionic acid affords no elimina- tion side products or those involving the aromatic ring.4-Phenyl- butyric acid also reacts smoothly with XeF2 and undergoes no intramolecular rearrangements characteristic of radical proc- V K Brel, N Sh Pirkuliev, N S Zefirov esses,230 which makes it different from the reaction with Pb(OAc)4, which results in cyclisation.232 It could be expected that 1,2-diphenylethane would be the main reaction product of XeF2 with 3,3-diphenylpropionic acid, since such rearrangement is well known for phenylethyl radi- cals.233 However, 2,2-diphenyl-1-fluoroethane is formed instead.Presumably, this reaction is in some respect analogous to the Borodin ± Hunsdiecker reaction 234, 235 where the rearrangement products are not detected either, which makes it different from the Kochi reaction.236, 237 Racemic 1-methoxy-1-phenyl-1,2,2,2-trifluoroethane (94) was obtained in 95% yield by fluorodecarboxylation of the optically active (+)-a-methoxy-a-trifluoromethylphenylacetic acid (93). In the presence of [Bun4 N]+[18F]7, this reaction gave compound 94-[18F] in 65% radiochemical yield.230 F CO2H Ph C OMe Ph C OMe+XeF2 CF3 93 CF3 94 Pyridylacetic acid reacts with XeF2 in the presence of HF in dichloromethane to give products the compositions of which are typical of a radical reaction.238 PyCH2COOH XeF2, HF CH2Cl2 PyCH2CH2Py+PyMe+PyCH2F+PyCHCl2+PyCH2Cl (58%) (<1%) (11%) (17%) (10%) The reaction of hept-6-enoic acid (95) with XeF2 gives 6-fluorohex-1-ene (96) and fluoromethylcyclopentane (97).238, 239 Fluorocyclohexane was not detected.In this case, the feasibility of a radical mechanism was unambiguously confirmed by direct EPR identification of the alkyl radicals 98 and 99 (trapped by a-phenyl-N-tert-butylnitrone). Additional experiments demon- strated the impossibility of interconversion of the fluorides 96 and 97. The rate constant for the second-order reaction (k=1.16106 litre mol71 s71) was determined at 25 8C.239 XeF2 F 96 (75%) XeF2 CHCl3 CH2F CO2H XeF2 98 95 99 97 (25%) endo-Norbornane 2-carboxylic acid (100) does not afford fluoro derivatives in the reaction with XeF2, but rather gives 2-exo-norbornyl endo-norbornane-2-carboxylate (101) in 72% yield.The exo-position of the alcoholic function is explained by the generation of the 2-norbornyl cation, which reacts with nucleophiles to give exclusively products with an exo-configura- tion of the substituents.238 XeF2, CHCl3 O CO2H O 100 101 The reaction of the L-tartaric acid derivatives 102 with XeF2 is non-stereospecific. The meso-difluoro derivative 103 (yield 36%) was isolated as the main product.238Chemistry of xenon derivatives. Synthesis and chemical properties XeF2, CH2Cl2 H 5 8C, 5 min 4-MeOC6H4CO2 CO2H C O2CC6H4OMe-4 C H CO2H 102 H H + H 4-MeOC6H4CO2 FC O2CC6H4OMe-4 C H F FC O2CC6H4OMe-4 C O2CC6H4OMe-4 F (4%) 103 (36%) Patrick et al.230 suggested that the reaction of 3-phenylbi- cyclo[1.1.1]pentane-1-carboxylic acid (104a) with XeF2 generates a dimer; however, later it was shown 238 that this reaction yields the hydrocarbon 105a. 3-Methoxycarbonylbicyclo[1.1.1]pentane- 1-carboxylic acid (104b) and (7)-camphanic acid 106 are also decarboxylated by XeF2 to give compounds 105b and 107 in 80% and 85% yields, respectively.239 XeF2, CHCl3 R R H CO2H 104a,b 105a,b R=Ph (a), CO2Me (b).Me Me MeMe MeMe O O XeF2, CHCl3 O OH HO2C 107 106 The reaction of XeF2 with the carboxylic acids 108a,b containing a thiol group gives the disulfides 109a,b in a quantita- tive yield,238 which is consistent with the data described in Section VIII.2.XeF2, CH2Cl2 (SX)2 25 8C, 5 min 109a,b (100%) HSX 108a,b X=CH2CO2H (a), CH2CH2CO2H (b). Fluorodecarboxylation with 1.5 equiv. of XeF2 in dichloro- methane was successfully employed for the synthesis of bridged cage fluorides.238, 240 CO2Me CO2Me XeF2 (CH2)n (CH2)n CH2Cl2, 20 8C H HO2C104b, 110 105b, 111 n = 0 (104b, 105b); 1 (110, 111). CO2Me CO2Me CO2Me CO2Me XeF2 + + CH2Cl2, 20 8C 112 (15%) H Cl HO2C (4%) F (51%) CO2Me CO2Me CO2Me CO2Me XeF2 + + CH2Cl2, 20 8C 113 (4%) H (7%) Cl F HO2C (65%) CO2Me CO2Me CO2Me XeF2 + CH2Cl2, 20 8C 114 H (77%) F HO2C (12%) The yields and the compositions of the reaction products depend on the cage compound used.For example, 3-methoxycar- bonylbicyclo[1.1.1]pentane-1-carboxylic (104b) and 3-methoxy- carbonylbicyclo[2.1.1]hexane-1-carboxylic (110) acids yield exclusively the reduced decarboxylation products 105b and 111, whereas the monoester of a dicarboxylic acid of the cubane series (112) and 4-methoxycarbonylbicyclo[2.2.1]heptane-1-carboxylic acid (113) afford a mixture of fluorides, chlorides and reduction products. 4-Methoxycarbonylbicyclo[2.2.2]octane-1-carboxylic acid 114 forms no chlorination products under these condi- tions.240 Decarboxylation of some carboxylic acids by XeF2 is accom- panied by the formation of free radicals and can be used for their generation. Halogenocarboxylic acids, particularly trifluoroacetic acid, are especially prone to such reactions.The reaction of trifluoroacetic acid with the corresponding substrate in the presence of XeF2 was used by Tanabe et al.241 for the incorpo- ration of the trifluoromethyl radical into aromatic and hetero- cyclic compounds. The reaction with benzene gives trifluoromethylbenzene in 33% ±38% yield. An analogous reac- tion takes place in the case of other perfluorocarboxylic acids.241 ArH+RFCO2H+XeF2 Ar=Ph, 1,4-Cl2C6H4, 4-ClC6H4CO2Me, 4-ClC6H4NHAc, 3,5-Cl2C6H3NHAc, 2,5-F2C6H3NHAc. RFCO2H, XeF2 CO2Me O F3C RFCO2H, XeF2 O NH RF=CF3, C2F5, C3F7 . O NHO N AcO O OAc RF=CF3, C2F5. If a heterocyclic compound contains a thiol group, perfluoro- alkylation occurs exclusively at the sulfur atom.242 In this case, disulfides are formed as side products in the same manner as in the case of acids containing a thiol group.238 The trifluoromethylation 243 was extended to trimethylsilyl derivatives of arenes.241 Thus the reaction of compounds 115a,b with trimethylsilyl trifluoroacetate yields a mixture of the regioisomers 116a,b and 117a,b.The products of ipso-substitution of the trimethylsilyl group were not detected.241 SiMe3 OSiMe3 + O CF3 X 115a,b X Compound 115a 115b Cl NHAc 241 ArRF+CO2+Xe + 2HF CO2Me RF O RF F3C O NH O RF NHO N AcO RFCO2H, XeF2 O OAc SiMe3 SiMe3 CF3 1.5 equiv. XeF2 + CF3 20 8C, 10 h CH2Cl2 X X 117a,b 116a,b Yield (%) 117 116 34 29 98242 Perfluorodicarboxylic acids can generate biradicals in the reaction with XeF2.Thus the reaction of perfluoroglutaric acid (118) with XeF2 in benzene results in 1,3-diphenylhexafluoropro- pane (119a) (yield 47%). 1,3-Bis(p-tolyl)- (119b) and 1,3-bis- (4-fluorophenyl)hexafluoropropane (119c) are formed in toluene or fluorobenzene in 62% and 65% yields, respectively.244 The reaction of the dicarboxylic acid 118 with XeF2 in the presence of elementary chlorine or bromine was used to prepare 1,3-dichloro- or 1,3-dibromohexafluoropropanes. HO2C(CF2)3CO2H+XeF2 118 ArH 15 ± 20 8C Ar(CF2)3Ar+HF+CO2+Xe 119a ± c Ar=Ph (a), MeC6H4 (b), FC6H4 (c) Cl2 or Br2 X(CF2)3X+HF+CO2+Xe 0 ±5 8C X=Cl (54%), Br (71%) The reaction of XeF2 with the corresponding aromatic sub- strate in the presence of carboxylic acids containing different functional groups allows the introduction of polyfunctional sub- stituents into the molecule of an aromatic compound.The high value of this reaction was demonstrated using chlorofluoro- or difluoronitroacetic acid as examples.245 O2NCF(R1)CO2H+1/2 XeF2+PhR2 120 R1=Cl O2NCFClC6H4R2 121a ± c R1=F 122d ± f O2NCF2C6H4R2+O2NCF2CO2C6H4R2 121d ± f R1=Cl: R2 = H (a), Me (b), F (c); R1=F: R2=Me (d), F (e), H (f). It was found that the structures of the reaction products depend on the substituent R1 in the original acid 120. Thus for R1=Cl, the reaction gives the alkylation products 121a ± c, whereas forR1=F, aryl difluoronitroacetates 122d ± f are formed in addition to compounds 121d ± f, which is probably due to the higher stability of the intermediate difluoronitroacyl radical.245 In contrast with non-substituted carboxylic acid, the reactions of the halogeno nitro carboxylic acids 123a,b with XeF2 yield halogenodinitromethanes.246 XeF2 O2NCFXCO2H 123a,b X=F CF2(NO2)2+CF4+CO2+Xe+HF X=Cl CFCl(NO2)2+CFCl2NO2+CF4+CO2+Xe+HF X = F (a), Cl (b).If this reaction is carried out in the presence of chlorine, bromine or nitrogen oxides, the carboxy group in fluorochloro- (123a) or difluoronitroacetic acids (123b) can be replaced by the corresponding functional groups; compounds 124 are formed in satisfactory yields.247 If the reaction is carried out in aromatic solvents, they undergo alkylation.245, 248 Y2 O2NCF(X)CO2H+XeF2 O2NCFXY+CO2+Xe+HF 123a,b 124a ± f Y2=Cl2, Br2, N2O4; X=F, Y=Br (a); X=Cl, Y=Br (b); X=F, Y=NO2 (c); X=Cl, Y=NO2 (d); X=F, Y=Cl (e); X=Y=Cl (f).Xenon difluoride reacts with carboxylic acid imides. Thus the reaction of perfluorosuccinimide (125a) and -glutarimide (125b) with XeF2 gives N-fluoroimides (126a,b).249 V K Brel, N Sh Pirkuliev, N S Zefirov (CF2)n (CF2)n O O O O +XeF2 7HF, 7Xe NF NH126a,b 125a,b n = 2 (a), 3 (b). The reactions of phthalimide (127) and saccharin (128) or their potassium salts with XeF2 in dry benzene result in the N-phenyl derivatives of the corresponding imides 129 and 130 in 14% ± 22% yields. In addition toN-phenyl derivatives, biphenyl is formed as a side product; its yield is lower in the reactions of potassium salts.250 O O XeF2, PhH NPh NH O 129 O 127 O O XeF2, PhH NPh NH S S O O 130 O 128 O The reaction of trimethylsilyl arenecarboxylates 131 with XeF2 in dichloromethane or hexaflurobenzene results in the aryloxycarbonyl fluorides 132.Arenes or aryl fluorides generated from the corresponding aryl radicals are the main reaction products in acetonitrile.251 C6F6 or CH2Cl2 XeF2 FCO2Ar+Xe+Me3SiF 132 MeCN ArCO2SiMe3 131 ArF+Xe+Me3SiF+CO2 Ar=4-ButC6H4, 4-MeC6H4, 3-ClC6H4, 4-MeOC6H4, 4-CF3C6H4. The transformation of compounds 131 into compounds 132 is the first example of the R1CO2R2? R2CO2R1 rearrangement. A mechanism for this reaction has been proposed, which includes one-electron oxidation and the formation of a radical cation and a radical anion.251 (ArCO2SiMe3)+ +(XeF2)7 ArCO2 + XeF 7Me3SiF F7 O C Ar FCO2Ar 7Me3SiF 132 O Xe F Using this approach, the electron-enriched centre, i.e., the oxygen atom of the carbonyl group, can be converted into an electron-deficient centre using a temporary group.This is an example of so-called Umpolung.251 VI. Organic xenon(II) compounds containing the C7Xe bond The chemistry of organoxenon compounds has been developing intensively in the past two decades. This trend was initiated by the appearance of a report 13 on the synthesis of Xe(CF3)2 (133). This compound is sublimed in vacuo, is stable at low temperatures and can be stored for two weeks at liquid nitrogen temperature.Upon decomposition, it gives XeF2 and a mixture of fluorocarbons. XeF2 D 2CF3 C2F6 7F2 Xe(CF3)2 133Chemistry of xenon derivatives. Synthesis and chemical properties This experiment and the results of ion cyclotron resonance studies of the reaction mixture containing H2, Xe and MeF253, 254 which were aimed at the determination 252 of the strength of the Xe7C bond (438 kcal mol71) gave impetus to further inves- tigations into the synthesis of new compounds containing Xe7C bonds. Thus the formation of the methylxenon(II) cation was established in an equilibrium reaction which included a transfer of methyl cation fromMe2F+to Xe. The physicochemical character- istics of the equilibrium (K=0.160.05, DG8=1.10.2 kcal mol71, DS8=9.61.0 kcal mol71 K71, S8(MeXe+)= 60.5 cal mol71 K71, DH8=4.00.5 kcal mol71) confirmed 255 the earlier obtained 252 data on the strength of the Xe7C bond in MeXe+ (55.22.5 kcal mol71).Compound 133 had long been the only genuine organic xenon derivative. Further developments in the chemistry of organo- xenon compounds confronted the task of creating stable xenon derivatives by a correct choice of ligands linked to xenon atoms. For xenon compounds, as for any other hypervalent com- pounds,153, 154, 256 fluorine-containing ligands are the most suit- able ones. However, despite the presence of fluorine-containing ligands in compound 133, its stability was insufficient even for conducting routine spectral analyses.257 ± 259 It was sug- gested 260 ± 262 that perfluorinated compounds containing a Xe7C bond have been formed as intermediates.These conclu- sions were inferred from the structures of the reaction products assuming that they might be formed exclusively as a result of incorporation of xenon into the C7E bond (E is an element). These investigations provided a basis for the development of a methodology of synthesis of stable organic xenon derivatives. This approach was realised almost simultaneously by Naumann and Tyrra,263 and Frohn and Jacobs and coworkers.257, 264, 265 A procedure for the preparation of stable organic compounds with a covalent Xe7C bond, e.g., of the [Xe(C6F5)]+X7 type, was proposed based on the cleavage of the C7B bond.Thus the low-temperature reaction of tris(pentaflu- orophenyl)boron with XeF2 in CH2Cl2 gives the pentafluoro- phenylxenon salt 134a (yields 40%257 and 92%266) which separates from the reaction mixture as a colourless precipitate and could be recrystallised from acetonitrile. This compound is stable in the crystalline state for a long time at 760 8C; its solutions in acetonitrile are unstable at room temperature. A similar reaction in acetonitrile gives the pentafluorophenylxenon salt 134b.263 CH2Cl2 [C6F5Xe]+[C6F5BF3]7 B(C6F5)3+XeF2 730 8C 134a MeCN [C6F5Xe]+[(C6F5)3BF]7 B(C6F5)3+XeF2 0 8C 134b Presumably, the boron compounds B(C6F5)3, [B(C6F5)3F]7, BF3 .MeCN and BF¡4 identified by 11B NMR spectroscopy could be formed by dismutation of a putative intermediate 135.263 (37x) B(C6F5)3+x BF3 B(C6F5)37x+XeF2 135 x=1, 2.It should be noted that the dismutation results also in the formation of a weak BF3 ± XeF2 complex 267 which readily reacts with pentafluorobenzene derivatives to give 1-R-heptafluoro- cyclohexa-1,4-dienes (R=H, F, Cl, Br, C6F5).193 Hepta- fluorocyclohexa-1,4-diene and octafluorocyclohexa-1,4-diene were identified as the side products 263 using 19F NMR. The structures of compounds 134a,b were established from NMR268 ± 270 and X-ray diffraction data.263, 271 Some chemical properties of compounds 134 have been studied. Thus the reaction of the salts 134a,b with water or D2O is accompanied by the formation of C6F5H or C6F5D.257, 263 The salt 134a reacts with halide ions in acetonitrile with the liberation 243 of xenon and the formation of halopentafluorobenzene;257, 263 the salts 134a,b form the corresponding adducts 136 ± 139 with halopentafluorobenzenes,257, 263 tellurium- 263 or phosphorus- containing compounds.257KF C6F6+Xe+K[(C6F5)3BF] Te(C6F5)2 [C6F5Xe]+[(C6F5)3BF]7 [(C6F5)3Te]+[(C6F5)3BF]7+Xe 136 134b C6F5I [(C6F5)2I]+[(C6F5)3BF]7+Xe 137 [C6F5Xe]+[C6F5BF3]7 134a [R4N]+Hal7 C6F5Hal+Xe+R4N+[C6F5BF3]7 Hal=I, Br (4-CF3C6H4)3P [C6F5(p-CF3C6H4)3P]+[C6F5BF3]7+Xe 138 C6F5Hal [(C6F5)2Hal]+[C6F5BF3]7+Xe 139 The pentafluorophenylxenon cation in compound 134a reacts with benzylcyanide and triphenylmethane containing activated C7Hbonds to give the nitriles 140 and 141 in the former case and tetraarylmethane 142 and the biphenyl derivative 143 in the latter case.264, 265 PhCH2CN 7Xe,7HF Ph(C6F5)CHCN+Ph(C6F5)2CCN +(C6F5)2BF 141 140 134a Ph3CH 7Xe,7HF Ph3CC6F5+C6F5C6H4(Ph2)CC6F5 + (C6F5)2BF 143 142 The reaction of compound 134a with bis(pentafluorophenyl)- cadmium results in perfluorobiphenyl (144) and pentafluoroben- zene (145).The same products are formed in the reaction of XeF2 with one equivalent of Cd(C6F5)2.266 Both reactions seem to occur via the intermediate 146, which eliminates xenon to generate the radical .C6F5. [C6F5Xe]+[(C6F5)2BF2]7+Cd(C6F5)2 134a 7CdA2 7Xe [C6F5XeC6F5] 146 XeF2+Cd(C6F5)2 C6F5C6F5 144 C6F5 SolvH 7Solv C6F5H 145 A=F or [(C6F5)2BF2]7; SolvH is solvent.The anion in compound 134b can be replaced by using AsF5.258, 272 MeCN C6F5Xe+AsF¡6 +B(C6F5)3 C6F5Xe+[(C6F5)3BF]7+AsF5 720 8C 134c 134b The salt 134c formed is stable at temperatures up to 125 8C. Its chemical properties have been investigated.272, 273 The reaction with halide anions in acetonitrile yields different products depend- ing on the nature of the anion. Thus the reaction with the fluoride anion which is a hard nucleophile yields a C6F5H±C6F5C6F5 mixture, whereas the reactions with I7, Br7 and Cl7 anions give C6F5X (X=I, Br, Cl). The reactions with compounds containing the HF¡2 anion gives a mixture of C6F6, C6F5X and C6F5C6F5.273 The salt 134c was further used for the synthesis of the organo- xenon compound 147 by anionic exchange with an aqueous solution of cesium pentafluorobenzoate. Compound 147 is ther- mally stable up to 853 8C (T1/2&3 h at 35 8C).272, 274, 275244 D2O C6F5XeOCOC6F5 C6F5Xe+AsF¡6 +C6F5CO2Cs 147 134c The structure of compound 147 was established by X-ray diffraction analysis.275 The length of the C7Xe bond (2.122 A) is larger than that in the cation [MeCN .. . XeC6F5]+ (2.092 A), whereas the Xe7O bond (2.367 A) is much longer than those in other known xenon derivatives (2.12 ± 2.21 A).87, 89, 276 ± 279 It should be noted that the Xe7O bond in compound 147 cannot be regarded as a purely ionic bond because of the essential differences in the lengths of the C7O bonds (1.171 and 1.220 A) in the C6F5COO group,275 which is inconsistent with an ionic carboxylate (1.26 A).280 The reaction of XeF2 with arylboranes gave the arylxenonium salts 134d,e.257, 263, 271, 281 ± 284 (3-CF3C6H4)2BF +XeF2 (4-FC6H4)3B+XeF2 [3-CF3C6H4Xe]+[3-CF3C6H4BF3]7 134d [4-FC6H4Xe]+[(4-FC6H4)2BF2]7 134e The synthesis of organoxenon compounds from arylboranes can be carried out in the presence of boron trifluor- ide.257, 266, 271, 281, 285, 286 The resulting salts 134f,g are obtained in good yields.3 ArXe+BF¡ BAr3+3 XeF2+2BF3 4 134f,g Ar=C6F5 (f), 2,4,6-F3C6H2 (g). The structure of compound 134g was established by 129Xe, 19F, 13C and 1H NMR spectroscopy. The absolute value of 1J(129Xe713C), equal to 103.6 Hz (see Ref. 271), is much smaller than that in the cation C6F5Xe+ [1J(129Xe713C)= 119 Hz],257, 263 which suggests the existence of short and, as a consequence, strong bonds and the relative stability of compound 134g.Some reactions of compounds 134f,g have been studied.271 Te(C6F5)2 [Te(C6F5)2Ar]+BF¡4 +Xe 20 8C KCl ArCl+Xe+KBF4 134f,g IC6F5 Xe+[C6F5IAr]+BF¡460 8C Compounds 134f,g are inert with respect to atmospheric oxygen and water and can be stored in dry air for 21 days without any visible alterations, while their hydrolysis in aqueous acetoni- trile is completed within 7 days. Cyclic voltammograms of compounds of the X+Y7 type, where X=C6F5Xe, C6F5N2, C6F5Br, C6F5I and (C6F5)4P, were obtained in 0.1 M solution of Bu4NBF4 in MeCN.287 The mini- mum and maximum values of electroreduction potentials were obtained for C6F5Xe+ and (C6F5)4P+ cations, respectively.The attachment of the first electron to the cations C6F5Xe+ and C6F5Ná2 is accompanied by the evolution of Xe or N2 and the generation of the .C6F5 radical, which either undergoes dimerisa- tion or abstracts hydrogen from MeCN. The first step in the electroreduction of other cations is followed by the liberation of pentafluorophenyl derivatives, e.g., C6F5Br, C6F5I or (C6F5)3P, which undergo further reduction.287 XeF2 was used in the synthesis of new organoxenon com- pounds.288, 289 The reaction of stoichiometric amounts of XeF2 and trifluoroacetic acid in CCl3F at 720 8C gives xenon bis(tri- fluoroacetate) 6d,89 ± 91 which further reacts with trifluorometha- nesulfonic acid at 740 8C.This can be accompanied by the formation of the intermediate 148; indirect evidence can be derived from the appearance of a singlet in the 129Xe NMR spectrum at d=400 and the generation of signals at d=769.1 V K Brel, N Sh Pirkuliev, N S Zefirov (OCOCF3) and 775.6 (OSO2CF3) in the 19F NMR spectrum. Compound 148 reacts with fluorine-containing arenes to give the arylxenon triflates 134h ± k.288 TfOH CCl3F XeF2+2CF3CO2H 740 8C Xe(OCOCF3)2 6d ArH ArXeOTf [Xe(OCOCF3)OTf] 134h ± k 148 Ar=2,4,6-F3C6H2 (h), 3,5-(CF3)2C6H3 (i), 1-F-3-(CF3)C6H3 (j), 2-F-5-NO2C6H3 (k). It is noteworthy that this reaction does not occur if FXeOTf (5b) is used as a starting material, while the reaction of 1,3-F2C6H4 with the intermediate 148 gives a mixture of Xe(2,4-F2C6H3)(OTf) and Xe(3,5-F2C6H3)(OTf) (10 : 1) (129Xe NMR data) and several side products.The reaction of 1-F-3-(CF3)C6H4 with the inter- mediate 148 gives compound 134j and some non-identified products, whereas 1,3,5-(CF3)3C6H3 does not react at all. The addition of arenes devoid of a fluorine, chlorine or trifluoromethyl substituent to the reaction mixture results in immediate decom- position.288 A method for the synthesis of cycloalkenylxenon(II) salts by the reaction of (pentafluorophenyl)xenon(II) hexafluoroarsenate 134c with XeF2 in HF has been developed.273, 274, 290 ± 295 Thus the reaction of the salt 134c with XeF2 results in the addition of two or four fluorine atoms to the aromatic ring to afford the salts 149 or 150.290 F F F F F XeF2, HF XeF2, HF F Xe+ F Xe+AsF¡67Xe0 7Xe0 AsF¡6 F F F F F 149 134c F F F FF Xe+ AsF¡6F F F F 150 Compounds 149 and 150 are white crystalline substances stable at room temperature and soluble in MeCN.Their structures were established on the basis of 19F, 13C and 129Xe NMR spectral data and chemical transformations. The salts 149 and 150 react with the bromide anion or benzene in acetonitrile to give products with composition 1-R-1,4-C6F7 or 1-R-C6F9 (R=Br, Ph), respectively.296, 297 The reaction of the salt 149 with sodium fluoride in acetonitrile results in a ring contraction and the formation of perfluoro-3-methylenecyclopen- tene (151).F F F FF F F 7 NaF, MeCN F F Xe+ Xe+ 7Xe 7Na+ F F F F F 152 F149 F F F F FF F F F CF2 F F F F 153 F 151 The diene 151 was the main product in the reaction mixture and was unambiguously identified on the basis of 19F NMR spectra (see Ref. 291). Its formation can be interpreted in terms of the HSAB concept. Being a hard base, the nucleophilic fluorideChemistry of xenon derivatives. Synthesis and chemical properties anion predominantly attacks the hard electrophilic centre of C(2) rather than the soft electrophilic centre of xenon(II). Elimination of xenon from the intermediate 152 results apparently in the carbene 153, which is further transformed into the reaction product 151.291 The relative reactivities of alkenyl- and arylxenon(II) deriva- tives were studied in a competitive reaction with tetramethylam- monium chloride in acetonitrile.The conversion of the salt 149 was 67% and that of the salt 134c was 19%. These results and the compositions of the reaction products demonstrate the high electrophilicity of the xenon atom linked to the perfluorocyclo- hexen-1-yl group.295 MeCN + +Me4N+Cl7 F F 20 8C Xe+ AsF¡ Xe+ AsF¡ 6 6 134c 149 + Xe+Me4NáAsF¡6 + + F F F Cl H Cl A method for the synthesis of trifluorovinylxenon(II) tetra- fluoroborate (152) by the reaction of trifluorovinylboron difluor- ide with XeF2 in CH2Cl2 at740 8C has been developed recently. The salt 152 is a white solid, which decomposes at temperatures above 0 8C.Its solution in anhydrous HF is stable at 20 8C for several hours but rapidly decomposes in MeCN.298 F F F F CH2Cl2 F2C CFBF2+XeF2 740 8C F Xe+BF¡ I F 4 NaI EtCN, 730 8C 152 The reaction of the salt 152 with an excess of sodium iodide in EtCN at 730 8C results in trifluoroiodoethylene, which is an indirect proof of the structure of compound 152.298 The alkynylxenon fluoroborate 153 was synthesised using a similar approach.299 The borofluoride complex 154 generated from lithium tert-butylacetylide and BF3 reacts with XeF2 in CH2Cl2 at740 8C to give the salt 153 the structure of which was established by NMR and IR spectroscopy. Compound 153 is relatively stable in chloroform at730 8C, but slowly decomposes at room temperature.299 BF3 XeF2 CLi ButC CBF3) 740 8C Li(ButC154 CH2Cl2, 7100 8C PPh3 4 4 778 8C ButC CP+Ph3 BF¡ 155 ButC CXe+BF¡ 153 The salt 153 reacts with nucleophiles, e.g., triphenylphos- phine, at 778 8C to give the stable phosphonium salt 155,299 which confirms its structure.The attempts to prepare xenon-containing salts from other alkynes were unsuccessful. However, some organoxenon tetra- fluoroborates could be detected by 129Xe NMR (see Ref. 299). VII. Reactions of xenon difluoride with nitrogen- containing compounds Considerable experience has been gained in the study of reactions of xenon derivatives with nitrogen-containing compounds. Earlier it was shown 300 that aniline and benzylamine are fluorinated with XeF2 in the absence of a catalyst without involving the NH-bonds.Unlike benzene derivatives, pyridine easily reacts with XeF2 in the absence of a catalyst to give 2-fluoro- (35%), 3-fluoro (20%) and 2,6-difluoropyridines (11%).300 8-Hydroxyquinoline is converted into 5-fluoro-8-hydroxyquino- line (35%) under the action of XeF2.300 On the other hand, imidazo[1,2-b]pyridazine is not fluorinated by XeF2.301 The reaction of XeF2 with tetrabutylammonium salts of arenesulf- 245 amides 156a ± c in benzene yielded N-sulfoazepines 157a ± c pre- sumably formed as a result of generation and subsequent incorporation of nitrene into the benzene ring.302, 303 The yields of the azepines 157a ± c increase as the temperature increases. PhH RSO2NH7Bu4N++XeF2 NSO2R 80 8C 156a ± c 157a ± c Yield (%) R Compound 157 abc 47 41 42 Ph Me 4-MeC6H4 The reaction of uracil with XeF2 in hydrofluoric acid or anhydrous hydrogen fluoride results in 5-fluorouracil (158) in small yield.304 O O NH HN HF NH HN +XeF2 O O F 158 (10%) The reaction of the substituted pyrrole 159 with XeF2 in acetonitrile at 20 8C results in the fluoride 160 and the imide 161.305 If the reaction was carried out in dichloromethane, 3-methoxycarbonylmethyl-4-methoxycarbonylethyl-2-formyl-5- chloropyrrole was isolated in 24% yield; its formation is explained by the involvement of the solvent in the reaction.(CH2)2CO2Me MeO2CCH2 XeF2 HOC HN 159 (CH2)2CO2Me MeO2CCH2 (CH2)2CO2Me MeO2CCH2 + O F O HOC HN HN 161 (20%) 160 (32%) It should be noted that XeF2 was found to be a most suitable reagent for the fluorination of pyrroles containing electron-with- drawing groups.305 The nitrone 162 reacts with XeF2 to generate a stable nitroxyl radical 163,306 which can be converted into an ammonium salt by a reaction with ammonia.O. O7 F Ph N N + Me Me Ph XeF2 Me Me Me Me N N Me NO 163 (70%) Me NO 162 The reaction of aliphatic nitro compounds with xenon difluor- ide has been studied in detail.307 ± 313 Thus it was shown that the potassium salt of 1,1-dinitroethane (164) reacts with XeF2 in CH2Cl2 to give a mixture of compounds.307 CH2Cl2 MeCO2H+MeC(NO2)2F+ 165 K+[C(NO2)2Me]7+XeF2 164 +MeC(NO2)2Cl+MeC(NO2)3+MeCH(NO2)2 168 167 166 When this reaction was carried out in dry dichloromethane, 1,1-dinitro-1-fluoroethane (165) was the main product, whereas the chlorodinitro derivative 166 was predominantly formed in246 CH2Cl2 saturated with water.The addition of nitrogen oxides to the reaction mixture increases the yield of 1,1,1-trinitroethane (167) to 22%. When this reaction is carried out in dry CH2Cl2, the addition of KCl and Na2CO3 does not influence the ratios of the reaction products. However, the yield of compound 166 in aqueous CH2Cl2 increases after addition of KCl, whereas 1,1-di- nitroethane (168) is not formed in the presence of sodium carbonate. Compound 168 does not react with XeF2 in CH2Cl2 at room temperature.As the reaction mixture contains simulta- neously 1,1-dinitroethane and its salt, one can anticipate the formation of a self-condensation product of compound 168, viz., 2,5,5-trinitro-3-aza-4-oxa-hex-2-ene, which was in due course detected. The data obtained suggest 307 that this reaction occurs by a radical or a radical-ion mechanism. The reaction of dinitromethane, trinitromethane and phenyl- dinitromethane salts with XeF2 in different solvents (CH2Cl2, MeCN, CCl4) have also been studied.308, 309 In this case, the formation of fluorination products, e.g., fluorodinitromethyl compounds, was accompanied by the formation of reaction products involving solvent molecules, viz., dinitromethyl com- pounds in CH2Cl2 (CH-form) and chlorodinitromethyl com- pounds (in CH2Cl2 and CCl4) Acetonitrile was found to be resistant to XeF2 and intermediate radical species.The fluorina- tion of 1,1-dinitroethane and phenyldinitromethane in acetoni- trile occurs with high selectivity.308 The reaction of the potassium salt of nitroform with XeF2 in acetonitrile containing 50 vol.% of benzene or THF is accompa- nied by the formation of a complex mixture of products.309 PhH FC(NO2)3+HC(NO2)3+PhNO2+ 7C(NO2)3+XeF2 MeCN +PhC(NO2)3+PhF+PhPh+FCH(NO2)2+PhC(NO2)2F THF FC(NO2)3+HC(NO2)3+FCH(NO2)2+ 7C(NO2)3+XeF2 MeCN+ + CF(NO2)2 C(NO2)3 O O It is of note that the side fluorination products of anions of dinitromethyl compounds with XeF2 in various solvents are similar to the reaction products of dinitromethyl radicals, gen- erated by electrochemical oxidation of polynitroalkane anions, with solvents.This similarity can be explained by the identity of the intermediate species.309 Xenon difluoride can play the role of a single-electron oxidant with respect to both 1,1-dinitrocarbanions and the difficultly oxidisable nitroazole anions.310 Thus the reaction of the potas- sium salt of 3-nitro-1,2,4-triazole (169) with XeF2 in acetonitrile results in the non-ionised 3-nitro-1,2,4-triazole (170) (yield 70%¡À 80%). A 3 : 2 mixture of 3-nitro- (170) and 1-phenyl-3- nitro-1,2,4-triazoles (171) is formed in the MeCN¡À PhH system. NO2 N XeF2 N MeCN NO2 NH 170 N NO2 NO2 N N N a N 7 +H+ N N 169 N XeF2 NPh 171 H MeCN¡À PhH b 170+171 172 NO2 N (a) XeF2,7XeF¡¦2 ; (b) .N N V K Brel, N Sh Pirkuliev, N S Zefirov Presumably, compound 171 is formed as a result of generation of the radical 172. The latter can be rearomatised by two equally probable routes, viz., by single-electron oxidation and deprotona- tion (route a) and by abstraction of the hydrogen atom by the 3-nitro-1,2,4-triazole radical (route b).310 However, the latter route is less probable, since benzene has a much higher oxidation potential (E1/2=2.02 V314) than the triazole anion [E1/2=1.77 V (see Ref. 315)]. The reactions of potassium salts of 1,1-dinitrobut-2-enonitrile (173a) and the respective amide (173b) with XeF2 were studied in order to compare the reactivities of the dinitromethyl group and the double bond.These reactions give the fluorination products 174a,b in high yields.311 MeCN [RCH CHC(NO2)2]7K++XeF2 173a,b RCH CHCF(NO2)2+KF+Xe 174a,b R=CN (a), CONH2 (b). Selective fluorination of the dinitromethyl anion without affecting the double bond can be explained by the absence of a catalyst (HF), since the reaction was carried out in a vessel made of ordinary silicate glass which is known to be an effective chemical acceptor of HF. According to 1H NMR and GLC data, this reaction gives <5% admixtures. When the fluorination was performed in a reactor made of a fluoropolymer resistant to HF, this resulted in a mixture of products, which can be assigned to the occurrence of HF-catalysed side reactions, e.g., the fluorination of the double bond.311 The kinetics of fluorination of salts of dinitromethyl com- pounds by XeF2 has been studied.312, 313 The kinetics is described by second-order equations, first-order with respect to each reagent.The nature of the cation in the salt does not influence the value of the fluorination rate constant in the concentration range from 1073 to 1075 mol litre71. The thermodynamic acti- vation parameters (DH6��298=30 ¡À 60 kJ mol71, DS6��298=760 to 7130 J mol71 K71) lie in the range characteristic of an SN2 reaction. A mechanism of the reaction of dinitro compounds with XeF2 has been proposed.307, 309, 310, 313 Its first step probably includes single-electron oxidation of the dinitro compound anion by XeF2.The reaction products result from the reaction of the solvent molecules with the radical species formed in the first step. The CH2Cl2 molecules serve as the source of chlorine and hydrogen atoms, whereas the radical of the original dinitro compound serves as the source of NO2. XeF2 (XeF) RC(NO2)2F RC(NO2)2+F7 [RC(NO2)2F]7 XeF2 (XeF) RC(NO2)3 [RC(NO2)3]7 [RC(NO2)2]7+NO2 The rates of the reaction of XeF2 with salts of ortho-, meta- and para-substituted aryldinitromethanes in MeCN were meas- ured by spectrophotometric methods.313 The relationship between the structures of the substrates and their reactivities with respect to XeF2 is described by linear free energy equations using inductive, resonance and steric constants of the substituents. For the over- whelming majority of dinitromethyl compounds, it was found that the rate of fluorination of the corresponding dinitrocarbanion decreases with the increase in the CH-acidity.Xenon difluoride acting as a single-electron oxidant converts the nitroxyl radicals 175 into the oxoammonium fluorides 176, nitroso compounds 177 and 178 and the products of more profound oxidation.316Chemistry of xenon derivatives. Synthesis and chemical properties XeF2 + + + N N N N O O O F7 O 175 176 178 177 The general stoichiometric equation for the oxidation was derived from the kinetic data.316 + 2 N O +n XeF2 n Xe+N O+2n F7 + (2n71) H++ +x RN O + (17x)P P are reaction products. A convenient procedure for the synthesis of fluorocarbonyl- substituted hydrazines 179 and 180 in the reaction of XeF2 with isocyanates has been developed.317 The reaction of XeF2 with perfluoroazapropene yields tetrakis(trifluoromethyl)hydrazine 181.317 CF3 F3C XeF2 N N CF3NCO 7Xe COF FOC 179 XeF2 (FOC)2N N(COF)2 CF3CONCO 7Xe,7CF4 180 XeF2 (F3C)2N N(CF3)2 NCF2 F3C 7Xe 181 Acompound containing the Xe7Nbond was first synthesised by the reaction of XeF2 with di(fluorosulfuryl)imide (181).318 ± 320 70775 8C [N(SO2F)2]2 184 AsF5 [(FO2S)2NXe]+AsF¡ XeF2+HN(SO2F)27HF FXeN(SO2F)2 182 181 6 185 74± 0 8C 184 7HF XeF2+2HN(SO2F)2 181 Xe[N(SO2F)2]2 183 Mono- (182) or bis[N,N-di(fluorosulfuryl)imido]xenon fluo- rides 183 can be obtained depending on the reagent ratio.The structures of compounds 182 and 183 were confirmed by X-ray diffraction analysis.321 ± 323 The magnitude of the angle C7Xe7N (174.5 8) corresponds to the structure of a distorted trigonal bipyramid with the substituents in the axial positions. The length of the Xe7C bond (2.092 A) is comparable with that of the C7I bond.153 The coordinate bond Xe7N (2.681 A) in com- pounds 134a,b is much longer than the covalent bond Xe7N.323, 324 The decomposition of compounds 182 and 183 is accompanied by the formation of the dimere intermediate radical .N(SO2F)2 was detected by EPR. The reaction of com- pound 182 with AsF5 gives the salt 185.319, 322, 324 N-Trimethylsilyl(trifluoromethylsulfonyl)amine (186) was used as the starting material for the preparation of bis[bis(tri- fluoromethylsulfonyl)imido]xenon (187), which is a stable com- pound and decomposes only at 72 8C to generate the radical .N(SO2CF3)2.325 XeF2+2Me3SiNTf2 72Me3SiF 186 Xe(NTf2)2 187 The attempt to prepare compounds containing a Xe7C bond by the reaction ofHCNwith XeF2 was unsuccessful.However, the fact that xenon-containing cations manifest the properties of Lewis acids 326 made it possible to synthesise xenon derivatives containing the Xe7Nbond from HCN.327 ± 330 The first adiabatic ionisation potential of HCN (13.80 eV) was determined from photoionisation data.331 The electron affinity of the XeF+ cation 247 6 is 10.9 eV. It may therefore be assumed thatHCN will be resistant to the oxidative attack of XeF+, and HC:NXeF+ should manifest satisfactory thermal stability. Indeed, compounds 188a ± g containing covalent Xe7N bonds were synthesised by the reaction of XeF+AsF¡ or Xe2Fá3 AsF¡6 with HCN or nitriles.327 ± 330 XeF+AsF¡6RC 6 N RC Xe2Fá3 AsF¡6 NXeF+AsF¡ 188a ± g 188a ± g 7XeF2 R = H (a), Me (b), CH2F (c), Et (d), C2F5 (e), C3F7 (f), C6F5 (g).Compounds 188a ± g were characterised by spectral meth- ods.328 The reaction product with hydrogen cyanide (188a) is a white crystalline substance stable below 760 8C. The derivatives 188e ± g containing perfluoroalkyl radicals are even less stable; they were characterised by spectral methods without being iso- lated from the reaction mixtures.The nature of the bond in the cation HC:NXeF+ has been discussed.328 It is of note that the corresponding fluorokrypton salts were synthesised by an ana- logous scheme in the reaction of the cation KrF+ with nitriles (the electron affinity of the cation KrF+ is 13.2 eV).330, 332 Equimolar amounts of XeF+AsF¡6 and perfluoropyridine (Ip=10.08 eV) react in anhydrous HF at 720 to 730 8C to give the salts 189a,b containing the Xe7N bond. Removal of the solvent (HF) at 750 8C leads to the formation of a white solid substance which represents a mixture of XeF2 with the salts 190a,b and 191a,b containing no xenon (data from the Raman spectra). BrF5 appeared to be a more suitable solvent than HF in the formation of the salts 189a,b.329 XeF+AsF¡64-RC5F4N + (n+1) HF 2 )n XeF2, nHF 4-RC5F4NH+(HF¡ 190a,b XeF2 6 6 HF 4-RC5F4NXeF+AsF¡ 189a,b 4-RC5F4NH+AsF¡ 191a,b R=F (a), CF3 (b).The reaction of trifluoro-s-triazine (Ip=11.50 eV) with XeF+AsF¡6 (1 : 1) for 4 h at room temperature gives the crystalline compound 192 which is stable at room temperature; this com- pound was characterised by spectral methods.330F F N N + XeF F N F N+XeF+AsF¡6 N N AsF¡6F F 192 The reaction of the salt 193, prepared by the reaction of trifluoroacetamide (Ip=10.77 eV) with AsF5, with xenon difluoride resulted in the organoxenon compound 194.333 The salt 193 was isolated in the crystalline state. At 0 8C, it rapidly decomposes to give gaseous products.+ XeF2, BrF5 HF CF3C(O)NH2+AsF5 6 750 8C 762 to755 8C CF3C(OH)NH2 AsF¡ 193 + 6 CF3C(OXeF)NH2 AsF¡ 194 6 Rapid removal of HF from a solution containing XeF+AsF¡ and CF3C(O)NH2 at 750 8C affords a white precipitate of composition identical to that of compound 195; the salt 194 was not detected.333 HF, 750 8C CF3C(O)NH2+XeF+AsF¡67XeF2 . xHF + XeF2 . x HF, 750 8C CF3C(OH)NH 7HF 2AsF¡6 . x HF 193248 + CF3C(OH)NH2AsF¡6 . XeF2 . x HF 195 A detailed study of the reaction of xenon difluoride withHN3, NaN3 and NaOCN in H2O, anhydrous HF and SO2ClF has been published.334 An analysis of reaction products made it possible to suggest the formation of FXeN3 (196) and FXeNCO (197) as intermediates, which react according to the following schemes: H2O [HON] [HON3] 7N2 7N2 7HF, 7Xe [FXeN3] 196 N2O, HON NOH 7H2O 2H2O H2O [HONCO] HONH2+H2O+CO2 .7HF, 7Xe [FXeNCO] 197 Ab initio quantum-chemical calculations of the structural parameters of both intermediates have been made.334 The data obtained suggest that the Xe7F bond in the intermediates 196 and 197 (2.051 and 2.024 A, respectively) is longer than that in bis[(difluorosulfuryl)imido]fluoroxenon 182 (1.97 A) and in XeF2 (1.977 A).318, 320, 322 ± 325, 328 The calculated length of the Xe7N bond (2.21 A) in compound 197 is comparable with the exper- imentally determined value (the length of the corresponding bond in compound 182 is 2.20 A). The Xe7N distance (2.32 A) in compound 196 is much longer (2.318 A).328 The thermodynamic possibility of formation of the intermediates 196 and 197 was demonstrated using an energy cycle for gas-phase reactions.The enthalpies of the reactions were calculated on the basis of the literature data.334 XeF2 (gas)+NH3 (gas) FXeN3 (gas)+HF (gas) (DH8<712.1 kcal mol71). XeF2 (gas)+HNCO (gas) FXeNCO (gas)+HF (gas) (DH8<712.1 kcal mol71). of NFá The synthesis of NO+XeF¡5 and NMeá4 XeF¡5 in the reaction of XeF4 with NOF or Me4N+F7 (see Ref. 335) and the synthesis 4 XeF¡7 from XeF6 and NFá4 HF¡2 were documented.336 VIII. Oxidative fluorination of organoelement compounds by xenon difluoride and its derivatives Oxidative fluorination of organoelement compounds by xenon difluoride and its derivatives presents theoretical and practical interest. The first reports on the feasibility of oxidative fluorina- tion of iodine to IF5 (see Ref.29) and of SO2 to SO2F2 (see Refs. 29 and 337) appeared in the late 1960's to early 1970's. Later, the reactions of other elements, their oxides, halides and carbonyls with XeF2 were also studied, which demonstrated convincingly the high potentials of the oxidative fluorination.338 The transformations of organoelement compounds under the action of XeF2 are extremely diverse and depend on the structures of the radicals linked to the heteroatom, the degree of oxidation of the heteroatom, the reaction conditions, the nature of the solvent, etc. The examples of the application of XeF2 for fluorination of the majority of classes of organoelement compounds are now available.1. Reactions of XeF2 with Group VII organoelement compounds a. Reactions of organoiodine compounds with XeF2 Organoiodine compounds are among the first to have been subjected to oxidative fluorination by XeF2. These studies were aimed at a search for convenient methods for the preparation of difluoro-l3-iodanylalkenes (arenes) used for fluorination of unsa- turated compounds.339 ± 342 The first report on the oxidative V K Brel, N Sh Pirkuliev, N S Zefirov fluorination of methyl iodide by XeF2 was published in the early 1970's. The difluoro-l3-iodanylalkene synthesised (198a) 339 was rather unstable and could only be characterised by spectral methods.However, despite its low stability this compound was used for iodofluorination of alkenes.343 ± 346 Later, this method of the synthesis of difluoro-l3-iodanylal- kanes (arenes) was extended to a vast variety of alkyl- and aryl iodides. Iodobenzene,347 substituted aryl iodides 348 as well as perfluoroalkyl- and perfluoroaryl iodides 349 are easily fluorinated by XeF2. In the case of 1-iodo-3,5-dichlorobenzene and iodopen- tafluorobenzene, the excess of XeF2 converts difluoro-l3-iodanyl- arenes into tetrafluoro-l5-iodanylarenes in quantitative yields,349 while the reaction of difluoro-l3-iodanylbenzene (198b) with XeF2 results in the fluorination of the aromatic nucleus and the formation of tetrafluoro-l5-iodanylbenzene.349, 350 20 8C RI+XeF2 RIF2+Xe 198a ± k R=Me (a), Ph (b), CF3CH2 (c), C6F5 (d), 3,5-Cl2C6H3 (e), 2-CF3C6H4 (f), 3-MeOC6H4 (g), 4-MeOC6H4 (h), 3-ClC6H4 (i), 4-ClC6H4 (j), 3-NO2C6H4 (k).Difluoro-l5-iodanylbenzene (198l) immobilised on a poly- meric support was synthesised using XeF2 as a soft fluorinating reagent.351, 352 The polymeric reagent was used for the fluorina- tion of alkenes.353, 354 F F XeF2 I P C C P I CH2Cl2 F F 198l P is polymeric support. In the majority of cases, (difluoro-l3-iodanyl)alkanes are unstable.339 However, treatment of a solution of 4-iodotricyclene in tetrachloromethane with a sixfold excess of XeF2 and subse- quent removal of the solvent and the excess of XeF2 yield a light- yellow solid stable product 198m.355 XeF2 CCl4 I F2I 198m In some cases, the reaction of iodoalkanes with XeF2 results in the substitution of fluorine for iodine instead of oxidation.This takes place in the reaction of XeF2 with polycyclic bridged iodides. Fluorinated bicycloalkanes and polycycloalkanes are formed in high yields.240, 356XeF2 F I (85%)F I XeF2 (80%) C(O)OMe C(O)OMe XeF2 F I (87%) It is assumed that this reaction occurs by a carbocationic mechanism. Initially, the difluoro-l3-iodanylalkanes generated undergo heterolytic cleavage of the C7I bond to give IF¡2 and the carbocations containing a cationic centre at the head of the bridge.343 The carbocation can further react either with the fluoride anion to give a fluoride or with CH2Cl2 to give a chloride.Chemistry of xenon derivatives.Synthesis and chemical properties Stable cations usually generate fluorides, whereas highly reactive cations, such as cubyl or norbornyl cations, react nonselectively to give chlorides. Their content in the reaction mixture correlates with the calculated values of the carbocation energies.356 Xe0 IF+F7 R+ + IF¡ RIF2 RI+XeF2 2 F7 RF R+ CH2Cl2 RCl Recently, divalent xenon derivatives other than XeF2, e.g., xenon bis(trifluoroacetate) (6d),89 ± 91 xenon fluoro(triflate) (5b) 89 and xenon fluoro(mesylate) (5c),89 came into use. Thus the reagent (6d) obtained in situ from XeF2 and trifluoroacetic acid in the presence of trifluoroacetanhydride reacts with aryl iodides to give bis(trifluoroacetoxy)-l3-iodanylarenes 199 ± 201.357 In the absence of trifluoroacetanhydride, this reaction affords m-oxobis- [trifluoroacetato(aryl)] iodides (202) the structure of which was established by X-ray diffraction analysis.357, 358 CF3C(O)O I I O CO2H O 199 RFI (CF3CO)2O ArI (CF3COO)2Xe 6d RFI[O(O)CCF3]2 200 ArI[O(O)CCF3]2 201 Ar O Ar ArI I I CF3C(O)O OC(O)CF3 202 Ar=Ph, 4-MeC6H4, 2-MeC6H4, 4-PhC6H4, 4-[MeC(O)O]C6H4, 4-NO2C6H4, 3-NO2C6H4, 2-Me-4-NO2C6H3; RF=C3F7, C4F9.A one-step procedure for the generation of iodanylarenes directly from aryl iodides 359 ± 367 is based on their oxidation by xenon fluorosulfonate which gives salts of the type 203. HOZ or Z2O or TMSOZ ArI+XeF2 7Xe ArIF2 198 ArI ArI+F ZO7 203 XeF2+HOZ 7HF FXeOZ 5b,c Z=Tf (b), Ms=SO2Me (c); TMS=Me3Si.The interest in the sulfonates 203 is due to the fact that they can react with aromatic compounds and terminal alkynes to give the corresponding diaryliodonium (204, 205) and alkenyl(aryl)- iodonium salts 206.359, 363, 365 CH2Cl2 778 to 20 8C Ar1I+F ZO7 203 Ar2H Ar1Ar2I+ ZO7+HF 204 Ph2CH2 ZO7 Ar1I+C6H4CH2C6H4I+Ar1 ZO7+HF 205 I+Ar1 R RC CH +Ar1IF2 ZO7 H ZO 206 Z=Tf, Ms; Ar1, Ar2=Ph, 4-MeC6H4, 2-MeC6H4, 4-NO2C6H4; R=H, Prn, Bun, n-C8H17, CH2OH, CH2OMe, CH2Cl, (CH2)2OH. 249 It is noteworthy that in earlier studies the alkenyl(aryl)iodo- nium sulfonates 206 were obtained by electrophilic addition of [PhIO7HOTf] to alkynes.368 ± 373 The use of xenon derivatives 5b,c for the synthesis of the salts 203 allows one-pot synthesis of b-functionalised vinyliodonium salts from iodobenzene and ter- minal acetylenes.The reagent 5b oxidises 1,4-diiodobenzene resulting in the bistriflate 207 which reacts with terminal alkynes to yield (p-phe- nylene)alkenyliodonium salts 208.364, 365 7OTf 7OTf RC CH 5b I+ +I I I 72Xe F F 207 7OTf 7OTf +I I+ R ROTf H H TfO 208 R=H, Me, Et, Ph, Prn, n-C8H17, CH2Cl. The oxidation of iodoarenes by bis(nitrodifluoroacetoxy)xe- non (6k) yields the iodonium salts 209 in 65% ±80% yields.374, 375 O(O)CCF2NO2 XC6H4I XC6H4I (O2NCF2CO2)2Xe 6k O(O)CCF2NO2 209 X=H, 4-Me, 4-F, 4-MeO, 3-CF3 , 4-NO2, 4-Cl. The reaction of XeF+AsF¡6 with HI in solution has been studied.376 Xe +HF+I4(AsF6)2 XeF+AsF¡6 +HI According to ab initio calculations, the enthalpy of the reaction of XeF2 with HI is equal to 763.4 kcal mol71 (see Ref.376). XeF++HI XeI++HF b. Reactions of organobromine compounds with XeF2 Nesmeyanov et al.377 have demonstrated that bromine can in principle be oxidised in mononuclear bromoarenes. However, this is possible only with XeF2. The difluorides 210 formed react with different arenes in the presence of boron trifluoride etherate to give the diarylbromonium salts 211, their structures were con- firmed by independent syntheses, viz., by decomposition of arenediazonium tetrafluoroborates in the presence of the corre- sponding bromoarenes. In some cases, the formation of bromo- nium salts could be detected using 19F NMRspectra.The yields of the salts 211 do not exceed 5%. Fluorination and oxidation of aromatic nuclei is the main route of this reaction even at770 8C. Ar2H XeF2,770 8C Ar1Br 4 SO3 or CH2Cl2 BF3 . Et2O Ar1Ar2Br+BF¡ 211 [Ar1BrF2] 210 Ar2Br 211 Ar1Ná2 BF¡4 Ar1=4-FC6H4, 4-ClC6H4, 4-MeC6H4, 2-MeO2CC6H4; Ar2=Ph, 4-FC6H4, 4-ClC6H4, 4-MeC6H4. 2. Reactions with Group VI organoelement compounds a. Reactions of organosulfur compounds with XeF2 Owing to the high oxidation potential of XeF2, its reaction with sulfur-containing compounds occurs vigorously at low temper- atures. Oxidative fluorination of sulfur-containing compounds, viz., methyl phenyl sulfide, tetrahydrothiopyrones and thiochro- manone, by XeF2 was carried out for the first time in 1976 by Zupan.378 The reaction of XeF2 with diaryl or alkyl aryl sulfides results in the formation of sulfur(IV) and sulfur(VI) compounds;250 the structures of the original sulfides influence the direction of the reaction.The nature of substituents at the a-carbon atom is the most important factor. The sulfides containing no a-hydrogen atoms are smoothly converted into difluorosulfuranes.379 The presence of Me, CH2 and CH fragments vicinal to the sulfur atom results in the formation of a-fluoro sulfides. For example, methyl phenyl sulfide is oxidised to fluoromethyl- (212) or difluoromethyl phenyl sulfide (213) depending on the amount of XeF2 used.378, 379 HF, CH2Cl2 XeF2 .HF, CH2Cl2 PhSMe+XeF2 PhSCHF2 PhSCH2F 25 8C 25 8C 213 (58%) 212 (67%) Sometimes, the reaction of alkyl aryl sulfides with XeF2 gives unsaturated sulfides. This is due to the low stability of a-fluo- roalkyl sulfides and their proneness to eliminate HF. Thus the reaction of isopropyl phenyl sulfide with XeF2 at710 8C gave the fluorination product 214, whereas isopropenyl phenyl sulfide (215) was obtained at 0 8C.379 MeCN 710 8C, 30 min PhSCFMe2 214 (>90%) XeF2 PhSCHMe2 MeCN 0 8C, 2 min PhSC(Me) CH2 215 (>90%) The reaction of XeF2 with diphenyl sulfide and subsequent hydrolysis of the reaction products afford diphenyl sulfoxide or sulfone. Presumably, diphenyldifluoro- (216), diphenyldifluoro- oxo-l4-sulfanes (217) and diphenyltetrafluoro-l4-sulfane (218) are formed as the intermediate products.380 OH7 XeF2 OH7Ph2SO2 Ph2SO HF XeF2 Ph2S(O)F2 217 Ph2S HF [Ph2SF2] 216 XeF2 OH7Ph2SO2 HF Ph2SF4 218 The fluorination of thiochroman-4-one (219a) or its 3-bromo derivative (219b) results in thiochromen-4-ones (220a,b), whereas the reaction of 3,3-dibromothiochroman-4-one (219c) gives 3,3- dibromo-2-fluorothiochroman-4-one (220c).378, 380 S 72HF, 7Xe R2 S XeF2 O 220a,b R1 F S R2 R1 O 219a ± c 7HF,7Xe R2 O 220c R1, R2= H (a); R1=H, R2=Br (b); R1=R2=Br (c). The reaction of thio-4-pyrone with XeF2 gives dihydro-2,6- diphenylthio-4-pyrone (221) which is dehydrogenated by XeF2.378 O O O XeF2 XeF2 Ph Ph Ph Ph Ph Ph S S S 221 The reaction of dimethyl sulfide with XeF2 has been studied in detail.In the absence of a solvent, this reaction is explosive. Dilution of the reaction mixture with trichlorofluoromethane results in FCH2SMe which further reacts with the excess of dimethyl sulfide to give the salt 222.381 It is of note that the reaction of dimethyl sulfide with XeF2 in the presence of BF3 or V K Brel, N Sh Pirkuliev, N S Zefirov AsF5 is not accompanied by fluorination of the methyl group but the salts 223 are formed instead. XeF2 Me2S Me2S MeSCH2F HF [Me2SCH2SMe]+[F(HF)n]7 222 Me2S XeF2 [Me2SF]+[AF]7 A 223 A=BF3 , AsF3 . The intermediate formation of the salts 223 in this reaction was confirmed by 19F NMR spectral data and independent syn- thesis.The cation [Me2SCH2SMe]+ is generated only in the presence of a protic acid. It is suggested 381 that R2S+X7 or R2S+XeFX7 are formed as intermediates. The latter are used 382 for the fluorination of carbanions. The reactions of sodium derivatives of diethyl malonate or of substituted malonates with XeF2 in CH2Cl2 result in the dimers 224. The fluorination products 225 were isolated in the presence of BF3 . Et2O. The methylthio derivatives of the malonates 226 are formed along with the fluorination products 225 after addition of dimethyl sulfide to the reaction mixture.382 It is interesting to note that the reaction of diethyl nitromalonate with XeF2 gives only a dimer of the type 224.(EtO2C)2C XeF2 CH2Cl2 R 2 224 RC7(CO2Et)2Na+ CH2Cl2, BF3 . Et2O RC(CO2Et)2 XeF2 F 225 XeF2, CH2Cl2, 225+ RC(CO2Et)2 BF3 . Et2O, Me2S SMe 226 R=H, Me, Et, C5H11, Bn, NO2. The highest yields of the reaction products are obtained for equimolar ratios of the reagents and at low temperatures (778 8C).382 The reaction of XeF2 with fluorinated sulfides generated easily hydrolysable aryl trifluoromethyl difluorosulfuranes 227.383 HF 4-RC6H4SCF3+XeF2 4-RC6H4SF2CF3+Xe 227 R=H, Cl, NO2. Thus, the reaction of sulfides with XeF2 affords three main types of reaction products, viz., a-fluoroalkyl sulfides, dehydro- fluorination products and sulfoxides or sulfones. A mechanism of this reaction has been proposed.384 The reaction of Ph2SO with XeF2 in the presence of *1% solution of Et4NCl inCH2Cl2 at 20 8C results in the difluoride 217 in quantitative yield.385 Et4NCl Ph2S(O)F2+Xe Ph2SO+XeF2 CH2Cl2 217 In the absence of Cl7, the reaction is sluggish (2 ± 6 days).Apparently, the chloride anion promotes the generation of the fluoride anion, which behaves as a strong base in CH2Cl2 in the absence of HF.386, 387 The reaction mechanism proposed by Ou and Janzen 385 which includes the formation of the anion 228 and its oxidation to the radicals 229 ± 231 is corroborated experimen- tally by the identification of the radical XeF. (spectroscopic data).388 2F7+Cl2+Xe 2Cl7+XeF2 e7 F7 XeF2 Ph2SO Ph2S(O)F 229 Ph2S(O)F7 228Chemistry of xenon derivatives.Synthesis and chemical properties O Xe F F S F Ph2S(O)F2+FXe Ph Ph 230 O 7Xe Xe S F 229 Ph Ph2SO+FXe Ph 231 Compounds 232a ± c (cis- and trans-isomers) were synthesised in the reaction of XeF2 with ArSSAr or ArSF3 in the presence of a chloride anion source, viz., Et4NCl.389 Individual isomers can be obtained by varying the reaction conditions and the ratios of the reagents. The maximum yield of the trans-232a (89%) is achieved for the Ph2S2 : Et4NCl : XeF2 ratio of 1 : 2 : 8, that of the cis-232c (83%), for the (4-O2NC6H4)2S2 : Et4NCl : XeF2 ratio of 1 : 2 : 6. In each case, the formation of side products (ArSF5 and ArSOF3) and fluorination of the solvent took place. CD2Cl2 Ar Ar ArSSAr+2 Cl7+5 XeF2 F F F F or CD3CN S S CD2Cl2 + F F F Cl ArSF3+Cl7+XeF2 F Cl cis-232a ± c trans-232a ± c Ar=Ph (a), 4-MeC6H4 (b), 4-O2NC6H4 (c).A scheme with the nomenclature N-X-L (where X is the central atom, N is the number of valent electrons and L is the number of ligands) 390 illustrates the mechanism of this reaction which includes the formation of the anion 233, its oxidation to the radical 234 391 and subsequent recombination.389 With a decrease in the content of the radical Cl., the concentration of ArSF5 should increase, which was confirmed experimentally.389 2F7+Cl2+Xe 2Cl7+XeF2 Cl Ar Ar F trans-232 (12-S-6) F F F F F F7 S S S F F e7 F F F Ar ArSF5 (12-S-6) F 10-S-4 234 (11-S-5) 233 (12-S-5) Ar F F F F F Cl cis-232 (12-S-6) S S F Cl Ar (11-S-5) F 10-S-4 The highly selective oxidative fluorination of sulfides by XeF2 was used for incorporating one or two fluorine atoms into the carbon chains of biologically active substances.For example, the fluorination of the methionine derivatives 235a ± d by XeF2 (720 to 20 8C) occurs regiospecifically and involves the MeS group.392, 393 MeS(CH2)2CHCOR1 XeF2,MeCN FCH2S(CH2)2CHCOR1 NHCOR2 720 to 20 8C NHCOR2 235a ± d R1=OMe, R2=CF3 (a); R1=OC6H4NO2-4, R2=OBut (b); R1=OC6H4NO2-4, R2=CF3 (c); R1=NHCH2C(O)OEt, R2=OCH2Ph (d). The reaction of XeF2 with methyl ester of b-biotin (236) results in the diastereomers of 6-fluorobiotin methyl ester 237a,b.394 251 O NH HN XeF2 H HH 7HF, 7Xe MeO2C(CH2)4 H H S 236O O NH HN NH HN + H H HF MeO2C(CH2)4 HF MeO2C(CH2)4 H H H H S237a S 237b The reaction of 20,30-di-O-acetyl-50-S-(4-methoxyphenyl)-50- thiouridine (237) with XeF2 yields a mixture of diastereomeric 20,30-di-O-acetyl-50-fluoro-50-S-(4-methoxyphenyl)-50-thiouridin- es (238).395 O NH 4-MeOC6H4S O N O XeF2 ,MeCN 720 8C OAc OAc 237 O NH F 4-MeOC6H4S O N O OAc OAc 238 Xenon difluoride was also used for the fluorination of 30,50-di- O-acetyl-20-S-alkyl(aryl)-20-thiouridines.Thus the reaction of compound 239 with XeF2 affords a mixture of diastereoisomeric 30,50-di-O-acetyl-20-S-alkyl(aryl)-20-fluoro-20-thiouridines 240 in 22% yield.396 This reaction is accompanied by partial oxidation of the sulfur atom in the initial sulfides 239 and the formation of the sulfoxides 241.O NH AcO O N O XeF2,MeCN 720 8C 239 OAc SR O O NH NH AcO AcO O N O N O + OF 240 OAc SR OAc SR O 241 R=Me, 4-MeOC6H4. A convenient method for the synthesis of 50-(fluoromethyl- thio)adenosine derivatives (242) (yield 70%) by regioselective fluorination of 5-methylthioadenosine derivatives 243 by XeF2 has been proposed.397 In this case, as in the fluorination of theV K Brel, N Sh Pirkuliev, N S Zefirov 252 Table 2. Perfluoroalkylation of pyridinethiols. Ref. R RF 50-arylthioadenosine,398 methionine 392 and biotin derivatives,394 the reaction occurs at the least substituted carbon atom. MeS Yield (%) Reagent (method of generation) Ad Compo- und 248 O XeF2, MeCN 760 8C OR OR 243 FH2CS MeS Ad Ad O O Cl Cl CCl3 CN Cl Cl 6d (A) 6d (B) 6d (A) 6d (A) 6l (B) 6m (B) 242 242, 399 242 242 242, 399 404 66 36.5 45 50 85 85 CF3 CF3 CF3 CF3 C3F7 C2F5 aabcde + O OR OR (*5%) OR OR 242 (*95%) R=Bz, Ac; Ad is 9-adenine.Thermolysis is carried out either using the preformed reagents 6d,l,m (method A) or with the simultaneous in situ generation of the xenonates 6d,l,m (method B). This reaction yields the polychloroperfluoroalkylthio- pyridines 248; their yields depend on the mode of generation of the xenonates 6d,l,m (Table 2). It was found that the reactivity of the thiol group decreases with an enhancement of the acceptor properties of the substituent R.242, 399 ± 404 In contrast to sulfides, thiols and thiophenols are not fluori- nated by XeF2, but are usually oxidised to disulfides in quantita- tive yields.The structure of the radical at the sulfur atom and the thiol : XeF2 ratio do not influence the direction of this reaction.379 RSSR +2HF+Xe SH SRF 2RSH+XeF2 Cl Cl Cl Cl R=Me, Pri, But, Ph. D +Xe(OCORF)2 6d,l,m R N Cl R N Cl 248 RF=CF3 (d), C2F5 (l), C3F7 (m). Under drastic conditions, disulfides also react with XeF2. Thus, fusion of bis(pentafluorophenyl) disulfide with XeF2 at 85 8C in a sealed tube for 3 h yields a mixture of C6F5SF3 and C6F5SOF which are identified by their 19F NMR spectra (see Ref. 20). H2O C6F5S(O)F C6F5SF3 C6F5SSC6F5+XeF2 7Xe This method allows direct perfluoroalkylation of thiols including those containing substitution-sensitive groups.405 4-Trifluoromethyl-2,3,5,6-tetrafluorothiopyridine (249) is formed upon the in situ generation of the xenonate 6d in the presence of di(1,3,5,6-tetrafluoro-4-pyridyl) disulfide with simul- taneous thermolysis at 50 ± 60 8C (yield 41%).242, 406 SCF3 F F F F F F S S N N +(CF3COO)2Xe 6d F F F F F F The use of XeF2 in reactions with polychloropyridinethiols allowed one to develop new methods for perfluoroalkylation and oxyfluorination of thiol groups as well as for the oxidation of polychloropyridines to N-oxides.Thus the reaction of 2,3,5,6- tetrachloropyridine-4-thiol with XeF2 in HF gave 4-fluorosul- fonyl-2,3,5,6-tetrachloropyridine (244) and 4-fluorosulfonyl- 2,3,5,6-tetrachloropyridine N-oxide (245).399, 400 This reaction is accompanied by oxidation of the original thiol into bis(2,3,5,6- tetrachloro-4-pyridyl) disulfide.N 249 SH SF3 Cl Cl Cl Cl H2O XeF2, HF 0 ±5 8C, 1 h Cl Cl Cl Cl N Xenon difluoride selectively oxidises the sulfur atom in com- pounds containing the S7N bond and the S7N bond is retained. Thus the S(IV) derivatives 252 and 253 containing the imidosul- fenyl group are formed from compounds 250 and 251 in the absence of a catalyst, whereas compound 252 is further oxidised into S(VI) compound 254, when BF3 is used as a catalyst.407 N 246 SO2F SOF SO2F XeF2 Cl Cl Cl Cl Cl Cl S NC(F)(CF3)2 (CF3)2C(F)N [XeO] [XeO] 252 7Xe Cl Cl Cl Cl N Cl N XeF2 [(CF3)2C N]2S 250 N 247 Cl 244 (25%) BF3 O 245 (8%) (CF3)2C(F)N S N(F)C(CF3)2 F F 254 XeF2 (CF3)2CFN SFCF3 (CF3)2C N SCF3 251 253 A reaction scheme which allows one to get insight into the mechanism of formation of the fluorosulfonyl fragment has been suggested.400 Initially, the thiol group is fluorinated by XeF2 in the presence of HF to the derivative 246 which is easily hydrolysed to the sulfoxide 247 and the sulfonylfluoride 244.The latter can be converted into compound 245 by oxidation with [XeO] species formed in the hydrolysis of XeF2 (the bonding energy of Xe7O is 7 kcal mol71 which corresponds to the weakly bound atomic oxygen).62 ± 64 (CF3)2C(F)N S(F)N C O + Anew method for perfluorination of polychloropyridinethiols The pseudo-triene system of the isocyanate 255 undergoes 1,3- and 1,5-difluorination by XeF2 in the absence of a catalyst resulting in compounds 256 and 257.The N1-(heptafluoroiso- propyl)-N2-(fluorocarbonyl)-S,S-difluorosulfodiimide (258) is formed in the presence of BF3.408 (CF3)2C NSN C O 255 256 + (CF3)2C(F)N S NC(O)F 257 which is based on the thermolysis of the xenon bisperfluoro- carboxylates 6d,l,m in the presence of thiols has been described.242, 399 ± 404Chemistry of xenon derivatives. Synthesis and chemical properties F XeF2 255 (CF3)2C(F)N S NC(O)F BF3 F 258 The oligomeric di-l4-thiatriazine 259 is easily fluorinated by XeF2 with the preservation of the ring and the formation of the cis-difluoride 260.409, 410 F S N S N XeF2 N N F3C F3C 7Xe N S N S n 259 F 260 N-Sulfinylperfluoroalkylamines 261 are converted intoN-per- fluoroalkyl-S,S-difluorosulfoximides 262 by XeF2 in perfluoro- decalin.411 20 8C 7Xe RFNSOF2 262 RFNSO+XeF2 261 RF=CF3 (54%), C2F5 (50%).The synthesis of sulfonyl fluorides from sulfonyl chlorides is effected by direct substitution of fluorine for chlorine. For example, the reaction of XeF2 with methane-, benzene-, p-toluene- and pentafluorobenzenesulfonyl chlorides affords the corre- sponding sulfonyl fluorides as the main products upon heating for 4 ± 10 h (yields 20%± 80%). This reaction is carried out in acetonitrile or without the solvent.In some cases, fluorination of the aromatic nucleus takes place.412 XeF2 RSO2F RSO2Cl R=Me, Ph, C6F5, p-MeC6H4. 6 6 Recent reports suggest the use of XeF+MF¡6 salts (M=As, Sb) as the oxidants. It was shown in particular that XeF+MF¡ reacts with the sulfides R1SR2 (R1=R2=C6F5;413 R1=CF3, R2=Me;414, 415 R1=R2=Me 381, 414, 415) and thiols RSH [R=Me, CF3 (see Ref. 416)] to give the fluorosulfonium cations of the type R1R2S+(F)MF¡ and with disulfides R1SSR2 [R1=R2=CF3; R1=Me, R2=CF3; R1=R2=Me;417 R1=R2=Cl (see Ref. 418)] to give the sulfonium salts [R1SS(F)R2]+MF¡6 . The reaction of the l4-sulfanes 263 with XeF+MF¡6 (M=As, Sb) gives the corresponding fluorosulfo- nium salts 264 and XeF2 418 which cannot convert S(IV) into S(VI) due to its lower oxidation capacity in comparison with the cation XeF+ (see Ref.326). 6 RnS+F37nMF¡6 +XeF2 RnSF47n+XeF+MF¡ 263 264 R=CF3; n=0, 1, 2;M=As, Sb. It should be noted that in the case of the l4-sulfanes 263, XeF+MF¡6 salts behave as Lewis acids rather than oxidants. Their oxidative properties are manifested in the reaction with trifluoro- methane sulfinyl fluoride. The S7F bond in CF3S(O)F is rela- tively strong as can be judged from its length (1.591 A).419 Depending on the nature of the element, this reaction affords either (trifluoromethyl)difluorosulfinyl hexafluoroantimonate (265) or the adduct 266.419 The reaction with dimethyl sulfoxide gives similar adducts.419 M=Sb 2]+SbF¡6 CF3S(O)F M=As XeF+MF¡6 Me2SO Xe+[CF3S(O)F 265 CF3S(O)F .AsF5+XeF2 266 Me2S(O)F .MF5+XeF2 M=As, Sb. The reaction of bis(trifluoromethyl) sulfoxide with XeF+SbF¡6 yields the salt 267 which was identified by spectral methods.419, 420 It is assumed that its first step involves a cationic attack of the sulfoxide oxygen atom by XeF+, whereas the second step consists in the intramolecular migration of the fluoride anion to the sulfur atom. The second step seems to be hindered by steric shielding of the reaction centre by two CF3 groups.327 (CF3)2SO+XeF+SbF¡6 [(CF3)2SOXeF]+SbF¡ 267 The reaction of thionyl chloride with XeF+MF¡6 is accom- panied by the elimination of Xe and the formation of the salt 268.419 2OSCl2+3XeF+MF¡ 2[OSClF2]+MF¡6 +Cl2+MF5+3Xe 6 268 M=As, Sb.The reaction of bis(2,20-biphenylyl)-l4-sulfane 269 with 1 equiv. of XeF2 in the presence of BF3 . OEt2 gives the bis(tetra- fluoroborate) 270 which reacts with excess water or a dilute solution of an alkali to give cyclic sulfoxide 271 in a quantitative yield.421 2+ S S 2BF¡4 XeF2 , BF3 . OEt2 MeCN, 740 8C 270 269 S O 271 272 The formation of the sulfoxide 271 is associated with theC7C ligand coupling in the oxide 272.422 The first compound containing the Xe7S bond, viz., HXeSH, was studied by spectral methods.423, 424 It was generated by photolysis of H2S in a xenon matrix at 7.5 K and represents a particular case of a compound with the general formula HXY, where X=Xe, Kr, and Y is the fragment with a higher electron affinity (H, Cl, Br, I, CN, NC).425 ± 428 b.Reactions of organoselenium compounds with XeF2 For selenium, the transition into a four-coordinated state occurs much easier than for sulfur. Aryl trifluoromethyl selenides form more stable fluorides with XeF2 than the corresponding sulfides. Thus compounds 273 react with XeF2 in the presence of HF to give aryl trifluoromethyl difluoro-l4-selanes 274 in quantitative yields.429 Bis(pentafluorophenyl) diselenide forms the penta- fluorophenyl trifluoro-l4-selane (275) with XeF2. XeF2 4-RC6H4SeF2CF3 HF 274 XeF2 4-RC6H4SeCF3 273 R=H, Cl, NO2 . C6F5SeSeC6F5 C6F5SeF3 HF 275 An efficient procedure for vicinal fluoroselenenation of alkynes by addition of synthetic equivalents of the selanyl fluoride 253 6 H2O MeCN, 20 8C S O254 RSeF generated in situ from XeF2, diaryl, dibenzyl or dialkyl diselenides has been developed.430 The direction of this reaction depends on the structures of the alkyne and the diselenide.Thus symmetric dialkylacetylenes react smoothly with XeF2 and diphenyl diselenide to give the vicinal (fluoroalkenyl)phenyl selenides 276 in high yields.430 R F PhSeSePh a, b, c R SePh 276 (72% ± 87%) R=Me, Et, Pr, Bu; (a) XeF2, CH2Cl2,720 8C, 15 min; (b)RC CR,720 8C, 0.5 h, (c) 20 8C, 1 h. Terminal alkynes do not react with PhSeBr and AgF (soni- cation);431 phenylacetylene forms the adduct 277a with XeF2 and diphenyl diselenide in 27% yield. Under these conditions, hex-1- yne affords a mixture of E-isomers of the adducts 277b and 278b in a 3 : 1 ratio (total yield 31%).430 H PhSe H F 1) XeF2, CH2Cl2,720 8C PhSeSePh + 2) RC CH R SePh R F 277a,b 278b R=Ph (a), Bu (b).The reaction of asymmetrical inner alkynes with XeF2 and (PhSe)2 also results in the vicinal fluoroselenenation products 279a ± e and 280a ± e (total yield 26%± 83%).430 PhSe F R2 R2 a, b, c PhSeSePh + R1 R1 F 280a ± e SePh 279a ± e R1=Ph, R2=Me (a); R1=Bu, R2=Me (b); R1=Bu, R2=Et (c); R1=Bu, R2=Pri (d); R1=Bu, R2=But (e); (a) XeF2, CH2Cl2,720 8C, 15 min; (b)R1C CR2,720 8C, 0.5 ± 2 h; (c) 20 8C, 1 ± 2.5 h. Compounds 279 or a mixture of the selenides 279 and 280 are exclusively formed depending on the nature of the substituent in the alkyne.Thus 1-phenylpropyne and the sterically hindered 2,2- dimethyloct-3-yne react with XeF2 and (PhSe)2 to give exclusively the isomers 279a,e, while hept-2-yne and oct-3-yne give a mixture of the isomeric selenides 279b,c and 280b,c in a ca. 1 : 1 ratio. The proportion of the isomer 279d increases significantly in the case of 2-methyloct-3-yne.430 It can be expected that cycloalkynes will behave similarly in reactions with XeF2 and (PhSe)2. However, it was found that only cycloundecyne and cyclododecyne react selectively to give the adducts 281a,b (yields 68% and 80%, respectively), whereas cyclooctyne and cyclodecyne yield a mixture of non-identified products.430 SePh a, b, c PhSeSePh F (H2C)n 281a,b n = 1 (a), 2 (b); (a) XeF2, CH2Cl2,720 8C, 15 min; (b) , (CH2)n 720 8C, 1 h; (c) 20 8C, 1 h.The reactions of other diselenides with XeF2 and alkynes including functionally substituted ones have been studied.432 These reactions resulted in the adducts 282.430, 432 R2 F 1) XeF2, CH2Cl2,720 8C R12 Se2 2) R2C CR2 R2 SeR1 282 (46% ± 83%) R1=Me, Et, Pri, Bn, But, 2-NO2C6H4, CH2CH(OMe)2, (CH2)3CO2Et, (CH2)3CO2H, (CH2)2NMe2 , CH2SiMe3; R2=Me, Et, Pr, Bu. V K Brel, N Sh Pirkuliev, N S Zefirov Trimethylphenylselanylsilane and tert-butyldimethylphenyl- selanylsilane react with oct-4-yne under analogous conditions to give the adducts 283 (yields 73% and 82%, respectively). Contrary to expectations, alkynes do not react with the PhSeNCO ± XeF2 system.430 Pr F 1) XeF2, CH2Cl2,720 8C PhSeSiMe2R +RMe2SiF 2) PrC CPr SePh Pr 283 R=Me, But.The fluorophenylselenenation of various phosphaalkynes resulting in the adducts 284 has been studied.433 CH2Cl2,720 8C R C P 2PhSeF PhSeSePh+XeF2 7Xe R P SePh PhSe 284 R=But, adamantyl. R2 R2 XeF2, PhSeSePh Alkenes also react with XeF2 and (PhSe)2 in CH2Cl2 to give readily hydrolysable vicinal phenylselanylfluoroalkanes. The yields of the products depend on the reaction conditions and decrease dramatically with an increase in temperature.434 PhSe H H CH2Cl2 R1 F R1 R1=H, Me, Bu, CH2CN; R2=H, CH2CN, CO2Me, SO2Ph. SePh XeF2, PhSeSePh CH2Cl2 F F O O XeF2, PhSeSePh S S CH2Cl2 O O PhSe The in situ generated PhSeF is more reactive than PhSeCl or PhSeBr; it reacts even with electron-deficient alkenes and 2,5- dihydrothiophene 1,1-dioxide.Since the Se7F bond is more polar than the Se7Cl and Se7Br bonds, the PhSe fragment in PhSeF bears a higher positive charge than that in PhSeBr and PhSeCl and is therefore more electrophilic. Indirect evidence in favour of this assumption was obtained from spectral data.434 Bis(2,20-biphenylene)-l4-selane (285) reacts with XeF2 in acetonitrile at 740 8C to give the bis(2,20-biphenylene)difluoro- l6-selane (286) in 54% yield.435 F XeF2 Se Se MeCN,740 to 20 8C F 286 285 c. Reactions of organotellurium compounds with XeF2 Organotellurium compounds react smoothly with XeF2 to give derivatives of Te(IV) and Te(VI).XeF2 was successfully used for the synthesis of a vast variety of aryltellurium(VI) fluorides from diaryl tellurides or Te(IV) derivatives.389, 436Chemistry of xenon derivatives. Synthesis and chemical properties PhTeTePh XeF2 PhTeF5 PhTeF3 Ph2Te XeF2 Ph2TeF4 Ph2TeF2 XeF2 Ph3TeF Ph3TeF3 X=F, Cl, Br. XeF2 Ph4TeF2 Ph4Te Bis(trifluoromethyl)tellurium difluoride 287 was synthesised by fluorination of bis(trifluoromethyl) telluride by XeF2 in an acetonitrile ± Freon-11 mixture.437 Bis(pentafluorophenyl) ditel- luride reacts with XeF2 to give the pentafluorophenyltellurium trifluoride (288) with the cleavage of the Te7Te bond and the oxidation of Te(II) to Te(IV).429 XeF2 (CF3)2Te (CF3)2TeF2 287 XeF2 (C6F5)2Te2 C6F5TeF3 288 The oxidative fluorination of 2,5-dihydrotellurophene by xenon difluoride results in 2,5-dihydrotellurophene 1,1-difluoride (289).438 XeF2, CH2Cl2 778 8C Te Te F F 289 Special mention should be made of an unsuccessful attempt at the fluorotellurination of oct-4-yne by the Ph2Te2 ± XeF2 or PhTeSiMe3 ± XeF2 systems.430 3.Reactions of XeF2 with Group V organoelement compounds a. Reactions of organophosphorus compounds with XeF2 Xenon difluoride smoothly oxidises phosphorus(III) to phosphor- us(V) in various phosphorus derivatives. Under these conditions, other functional groups present in the molecule are not involved as a rule. Thus the oxidation of (1-hydroxyhexafluoroisopropyl)di- phenylphosphine (290) yields the pentavalent phosphorus deriva- tive 291.439OH F OH XeF2, CFCl3,MeCN Ph2P C(CF3)2 Ph2P C(CF3)2 or (CF3)2CO F 291 290XeF2 RPH2 HH XeF2 R2PH RR High selectivity is also observed in the oxidation of com- pounds containing a P7H bond.Thus the reaction of primary and secondary phosphines with XeF2 gives the corresponding difluorides 292 and 293 in high yields.347, 440 FP R F 292 (>90%) FP H F 293 R=Ph, CH2CH2CN. Oxidative fluorination also takes place in reactions with arylchlorophosphines 294 where it occurs simultaneously with the substitution of fluorine for chlorine. Triphenylphosphine 255 (294d) is quantitatively converted into triphenyldifluorophos- phorane 295d,347 whereas the chlorine-containing phosphines 294a ± c react with XeF2 to give the fluoro-substituted phosphor- anes 295a ± c in quantitative yields.No intermediate formation of chlorofluorophosphoranes was detected.353 710 to 0 8C PhnPF57n 295a ± d PhnPCl37n+XeF2 294a ± d n = 0 (a), 1 (b), 2 (c), 3 (d). The fluorination of four-coordinated phosphorus derivatives containing P7H bonds results in fluorides.441 Ph2P(O)H XeF2 Ph2P(O)F (RO)2P(O)H XeF2 (RO)2P(O)F The oxidation of organic derivatives of phosphorus(III) con- taining P7N, P7S or P7O bonds is complicated due to easy elimination of PF5 which is accompanied by the formation of compounds containing a P=X fragment (X=N, O, S). For example, the fluorination of bis(difluorophosphino)methylamine (296) by XeF2 gives difluorophosphino(tetrafluorophosphora- nyl)methylamine (297), which undergoes dimerisation to give compound 298.442 XeF2 XeF2 F2PN(Me)PF4 7Xe 7Xe MeN(PF2)2 296 297 [F4PN(Me)PF4] 7PF5 (MeNPF3)2 298 Silyl esters and silyl-substituted amides of trivalent phospho- rus acids are oxidised by XeF2 to dialkylphosphofluoridates or dialkyl fluorophosphazenes, respectively.441 XeF2 (MeO)2POSiMe3 10 ± 15 8C (MeO)2FP O XeF2 (MeO)2PN(SiMe3)2 10 ± 15 8C (MeO)2FP NSiMe3 An unusual reaction takes place on the interaction of isobutyl phosphodifluoridite with catalytic amounts of XeF2.In this case, the tert-butylphosphonic difluoride was isolated as the main product in 50% yield.441, 443 ButP(O)F2 BuiOPF2+XeF2 Presumably,441 this reaction occurs through the formation of alkoxytetraphenylphosphorane, which disproportionates with the formation of the isobutyl cation.443 The latter undergoes isomer- isation and reacts with the original phosphite to afford the final product.b. Reactions of organoarsenic derivatives with XeF2 The reactions of XeF2 with organoarsenic derivatives were studied in the single example.351 MeCN MePh2AsF2+Xe MePh2As+XeF2 720 8C It is quite probable that in other cases the behaviour of As(III) compounds in the reaction with XeF2 will also not be different from that of P(III) derivatives. c. Reactions of organoantimony compounds with XeF2 To date, reactions of XeF2 with antimony derivatives have been studied relatively little.Xenon difluoride fluorinates aromatic derivatives of trivalent respectively.444 antimony in quantitative yields under mild conditions. Trifluoro- diphenylantimony and difluorotriphenylantimony were prepared from fluorodiphenylstibine (or trifluorodiphenylacetoxystibine) and triphenylstibine, Tris(pentafluoro-256 phenyl)stibine yields difluoro tris(pentafluorophenyl)antimony in its reaction with XeF2.262 XeF2 Sb(C6F5)3F2+Xe Sb(C6F5)3 d. Reactions of organobismuth compounds with XeF2 Oxidative fluorination of triphenylbismuth with XeF2 is the most convenient and available method for the preparation of trisub- stituted bismuth difluoride 445 which is interesting as a fluorinat- ing reagent.446, 447 Ar3BiF2+Xe Ar3Bi+XeF2 Ar=Ph, C6F5.However, tris(trifluoromethyl)bismuth yields the bismuth trifluoride, CF4 and Xe even at 760 8C. Their formation is attributed either to the trifluoromethylation of the XeF+ inter- mediate or the degradation of the pentavalent bismuth deriva- tive.445 BiF3+3CF4+3Xe Bi(CF3)3+3 XeF2 The reactions of XeF2 or XeF+MF¡6 (M=As, Sb, Ta) with tris(pentafluorophenyl)bismuth have been studied.448 In both cases, (C6F5)3BiF2 was isolated from the reaction mixture with trace amounts of pentafluorobenzene which provides indirect support for the formation of xenon compounds, such as C6F5XeF or C6F5Xe+MF¡6 .262 4. Reactions of XeF2 with Group IV organoelement compounds a. Reactions of organosilicon compounds with XeF2 Reactions of organosilicon compounds with XeF2 were studied for compounds containing Si7Cl, Si7H, Si7C, Si7O, Si7S and Si7N bonds.The reactions of XeF2 with chlorosilanes are completed within several minutes. However, the yields of fluorosilanes depend on the number of chlorine atoms to be substituted in the original molecule. Mono- and dichlorosilanes are easily fluorinated to give fluoro- and difluorosilanes.440 MeCN 2R3SiF+Xe+Cl2 2R3SiCl+XeF2 MeCN Me2SiF2+Xe +Cl2 Me2SiCl2+XeF2 R=Me, Et, Ph. If the molecule contains a hydrogen atom, difluorosilanes are formed in satisfactory yields. A stepwise mechanism of this reaction which includes initial fluorination of the Si7H bond has been proposed.440 Cl2 XeF2 R2SiClF XeF2 R2SiF2 R2SiHF R2SiHCl R=Ph, Me.Triarylchlorosilanes yield products of more profound con- versions.440 The reaction of allylchlorodimethylsilane with XeF2 is accom- panied by the cleavage of the Si7C bond to afford difluorodime- thylsilane in a quantitative yield.440 Compounds containing alkoxy groups at the silicon atom react with XeF2 at a very slow rate (within 4 ± 5 days).399 On the other hand, the reaction of XeF2 with tert-butylthiotrimethylsi- lane in acetonitrile occurs easily and affords di-tert-butyl disulfide and flurotrimethylsilane in high yields.347 MeCN ButSSBut+Me3SiF+Xe Me3SiSBut+XeF2 ButSSSBut and ButSH are formed as side products. In the absence of a solvent, this reaction yields a mixture of products.347 The reaction of XeF2 with nitrogen-containing silanes is accompanied by the cleavage of Si7N bonds resulting in the formation of fluorotrimethylsilane in >90% yield.Presumably, V K Brel, N Sh Pirkuliev, N S Zefirov this reaction occurs by a radical mechanism. The formation of FXeNR2 (see Ref. 423) and FXeSR (see Refs. 318 ± 321) as intermediate products was proposed. MeCN Me3SiF+Xe+R2N Me3SiNR2+XeF2 R=Me polymer MeN CH2 R2N MeCN R2NH The ability of XeF2 to cleave smoothly the Si7N bonds in polyfunctional compounds was used in the synthesis of the hexamethyltriamido-N-fluorophosphazene (299) from hexa- methyltriamido-N-trimethylsilylphosphazene (300).449 MeCN (Me2N)3P NSiMe3+XeF2 300 715 8C (Me2N)3P NF+Me3SiF+Xe 299 An attempt to synthesise a compound containing the Xe7N bond by the reaction of XeF2 with Me3SiN=C(CF3)2 was unsuccessful.This reaction gave Xe, Me3SiF and (CF3)2C=NH.347 It was found that trimethylpentafluorophenylsilane (301a) does not react with XeF2 in acetonitrile at 20 8C. However, the addition of a catalytic amount of anhydrous CsF to the reaction mixture results in the formation of pentafluorobenzene and decafluorobiphenyl in 58% and 11% yields, respectively. In acetonitrile, this reaction is completed within 15 ± 20 min, but in CFCl3 or SO2FCl trimethylpentafluorophenylsilane (301a) does not react with XeF2 even in the presence of CsF, apparently due to the low solubility of the latter.450 ± 452 CsF, MeCN ArH+ArAr+Xe +Me3SiF 10 ± 20 8C ArSiMe3+XeF2 301a ± d Ar=C6F5 (a), 4-CF3C6F4 (b), 4-C5F4N (c), 4-CF3C6H4 (d).Arylsilanes 301a,b react similarly with XeF2 in the presence of anhydrous KF and RbF.450 Trimethyl-4-tetrafluoropyridylsilane (301c) reacts with XeF2 very slowly in the absence of a catalyst and within several minutes in the presence of CsF.450 In contrast to fluorinated arylsilanes, their hydrocarbon analogues (phenyl-, 4-tolyltrimethylsilane, tetraphenylsilane) do not enter into the reaction with XeF2 and CsF even on heating at 40 ± 60 8C for several hours.451 The presence of the electron- withdrawing CF3 group in (4-trifluoromethylphenyl)trimethyl- silane (301d) increases its reactivity in comparison with trimethyl- phenylsilane. It reacts with XeF2 to give benzotrifluoride and 4,40-bis(trifluoromethyl)biphenyl, although the conversion is low.450 19F CIDNP was used to establish a radical mechanism of the Si7C bond cleavage.450 This reaction seems to be convenient for generating polyfluoroaryl and polyfluorohetaryl radicals under mild conditions.Chemical reactions occurring in the arylsilane ± XeF2 ± CsF system and the CIDNP data offer the most probable mechanism for this reaction. F7 XeF2 7 C6F5SiFMe3 C6F5SiMe3 7XeF, 7F [C6F5] C6F5SiFMe3 C6F5H+C12F10 7Me3SiF A radical mechanism has also been proposed for the reaction of aryltrimethylsilanes 302a ± d.453 It was shown that compounds 302a ± d react with two equivalents of XeF2 to give the para-fluoro derivatives 303. Moreover, this reaction gives the isomeric mono- fluoroarylsilanes 304, the difluorides 305 and 1,4-difluorobenzene (306) as is the case with the reaction involving acetyl hypofluorite, the well-known radical fluorinating agent.453Chemistry of xenon derivatives.Synthesis and chemical properties F F F SiMe3 SiMe3 F F XeF2 + + + +Me3SiF+Xe C6F6 F R R R R 306 302a ± d 303a ± d 304a ± d 305a ± d Yield (%) Compounds R 302 303 306 305 304 But OMe Cl 86 61 82 000 8 39 12 abcd 606 If a molecule contains a functional group which can react with the radical, cascade reactions may be triggered. Thus the reaction of 2-trimethylstannyl(but-3-enyl)benzene (311) with XeF2 in the H 65 0 0 35 presence of a Pd complex results in 1-methylindan (312) in a satisfactory yield.In this case, no homocoupling reaction occurs.455 SnMe3 This reaction occurs through the formation of the cationoid intermediate 307, which is stabilised not only due to the b-effect of the silyl substituent but also due to the interaction of the cationic centre with the non-bonding molecular orbital of the hypervalent xenon.453 XeF Me3Si SiMe3 SiMe3 XeF XeF F7 XeF2 + 7Me3SiF + R R R 308 R 307 F XeF2 or F R R 303 The subsequent reaction with the fluoride anion results in the intermediate 308 (see Section VI) which further yields the aryl fluorides 303a ± d. Xenon difluoride is a convenient reagent for converting vinyl silanes into vinyl halides.This reaction was used in particular in the synthesis of 5-(2-halovinyl) derivatives of the pyrimidine nucleosides 309.454 H O O SiMe3 X HN HN H N N AcO AcO a, b OOAcO OOAcO 309 OAc OAc X=SiMe3, I, Br, Cl; , AcOEt; (b) XeF2, (a) Pd/CaCO3, N MX (MX=LiCl, LiBr, NaI), PhH. b. Reactions of organotin compounds with XeF2 Aryltrimethylstannanes react with XeF2 with cleavage of the C7Sn bond and can be used for the generation of aryl radicals. Thus trimethyl(phenyl)stannane reacts with XeF2 rather slowly, viz., the conversion of the original compound reaches 80% after 12 h. In the presence of BF3 . Et2O as the catalyst, this reaction is strongly accelerated but yields a complex mixture of products.455 XeF2 reacts with aryltrimethylstannanes more selectively in the presence of catalytic amounts of a palladium benzonitrile complex.Thus biaryls are formed in good yields from the 257 aryltrimethylstannanes 310; the yields of side products (benzene, chlorobenzene) do not exceed 1%± 2%.455 (PhCN)2PdCl2 (1 mol.%) ArAr+Me3SnF+Xe Me3SnAr+XeF2 CH2Cl2 or MeCN, 0 8C 310 (75% ± 85%) Ar=Ph, 1-naphthyl. (PhCN)2PdCl2 (1 mol.%) +XeF2 MeCN, 0 8C 311 +Me3SnF+Xe Me 312 Organotin compounds can be used for the synthesis of organofluorine derivatives.456 ± 462 Thus the reaction of the vinyl- stannanes 313 and 314 with XeF2 in the presence of silver triflate (*1 : 1.5) and a catalytic amount of 2,6-di-tert-butyl-4-methyl- pyridine in dichloromethane results in the vinyl fluorides 315 and 316.F SnMe3 XeF2, AgOTf B, 20 8C, CH2Cl2 Ph Ph 314 316 (84%) Me . B= But N But It should be noted that in contrast to compound 311, the stannane 314 does not undergo cyclisation.463 Diverse functional groups in the vinylstannane molecule do not inferfere with this reaction. Thus this approach was used for the synthesis of the vinyl fluorides 317 ± 320.460 ± 462 F O OH F CH(OMe)2 F F O Ph C5H11 317 (20%) 320 (52%) 319 (70%) 318 (53%) 5. Reactions of XeF2 with organoaluminium compounds The oxidation of organoaluminium compounds (OAC) by XeF2 is an exothermic reaction. Any contact of even small amounts of the reagents in the absence of a solvent brings about an explosion. Oxidation in solutions (toluene appeared to be the most suitable one) is associated with chemiluminescence,261 which is similar to that observed on oxidation of OAC by oxygen.464 It was found that this reaction involves exclusively the C7Al or the H7Al bond.The reactions of Et3Al, (EtO)2AlEt, Et2AlCl and Bui2AlH with XeF2 gave Et2AlF, (EtO)2AlF, EtAlClF and Bui2AlF (yields 95%, 97%, 80% and 79%, respectively). In addition to the above- mentioned products, Xe and C2H6 are formed as the main products, while C2H4 and C4H10 are formed as admixtures. The AOC: XeF2 ratio of 2 : 1 ensures the reaction of XeF2 with the258 most reactive substituent (H, Alk, Cl) bound to Al. The reactiv- ities of the substituents decrease in the following order: H>Alk>Cl.465 The mechanism of the reaction of OAC with XeF2 in toluene was studied in the example of a model compound (EtO)2AlEt containing only one non-oxidised Al7C bond.465, 466 The redox reaction begins with the formation of the intermediate complex 321 in which the electron is transferred from the OAC to the electrophilic XeF2.467 The reactive intermediates, viz., .C2H5 radicals, are converted through three main routes, viz., they react with each other to give ethane, ethylene and butane; they attack toluene at the side chain to give bibenzyl or at the aromatic ring to give ethyl-, diethyltoluenes and bitolyls.Chemiluminescence is evoked as a result of excitation and generation of the .XeF radicals formed in the reaction of polarised ethyl radicals with XeF2.466, 467 Al C2H5 .XeF2 Al C2H5+XeF2 321 Al F+XeF+C2H5 Al C2Há5 XeF¡2 The effects of luminescence activators, viz., 9,10-dibromo- anthracene, pyrene, p-terphenyl and the [Ru(bipy)3Cl2 . (OAC)n] complex (bipy is 2,20-bipyridyl) on the chemiluminescence of the reaction of (EtO)2AlEt with XeF2 in solution have been studied.468 It was shown that enhanced luminescence is a result of involvement of the activator in the oxidation ± reduction process.468 6. Reactions of XeF2 with Group II organoelement compounds a. Reactions of organomagnesium compounds with XeF2 The direction of the reactions of the Grignard reagents 322a ± c with XeF2 in diethyl ether at 20 8C depends on the structure of the substrate.Thus decylmagnesium bromide reacts with XeF2 to give 2-ethoxydecane (323a), decane (324a) and eicosane (325a) in a total yield 98%. In the case of benzylmagnesium bromide, the total yield of the three main reaction products 323b ± 325b is 80%; benzyl bromide was detected among side products. The composi- tion of the reaction mixture is even more complicated in the reaction of phenylmagnesium bromide with XeF2. In this case, the main products 323c ± 325c are formed in a total yield 70% (the side products include bromobenzene, bromophenyl, mono- and dibro- moacetophenone, etc.).469 Et2O RCHOEt + RH + RR RMgBr+XeF2 324a ± c 325a ± c 322a ± c Me 323a ± c R=n-C10H21 (a), Bn (b), Ph (c). A method for incorporating a trifluoromethyl group into the molecules of aromatic compounds has been proposed 470, 471 which includes the conversion of aryl halides (more preferably, bromides) into the corresponding Grignard reagents and their subsequent reaction with carbon disulfide and XeF2.1) Mg, Et2O ArX ArCF3 2) CS2 3) XeF2 ; X=Cl, Br. Ar=Ph, 4-MeC6H4, 4-MeOC6H4, 3-CF3C6H4, b. Reactions of organomercury compounds with XeF2 The C7Hg bond in the reaction of XeF2 with the mercury derivatives R2Hg is cleaved to yield a mixture of products, such as RHgF (or RHgF+HgF2), RF, RR, etc.260, 472 V K Brel, N Sh Pirkuliev, N S Zefirov RHgF (HgF2) +RR+RF+Xe R2Hg+XeF2 R=4-MeOC6H4, 4-Me2NC6H4, Bn, 4-EtO2CC6H4, PhC C. This reaction is carried out in an argon atmosphere to avoid the formation of oxygen-containing products.In the case of di(phenylethynyl)mercury, PhC:CF is unstable and could not therefore be detected in the reaction mixture. However, indirect evidence for the formation of this compound was obtained upon treatment of the reaction mixture with tetraethylammonium bromide after complete liberation of xenon eventually resulting in PhC:CBr in 43% yield.472 The efficiency of this reaction is judged by the temperature at which the liberation of xenon occurs. The reactivities of R2Hg were found to decrease in the following order depending on R: PhCH2>p-Me2NC6H4>PhC:C>p-MeOC6H4>p-EtO2C± C6H4. Hence, XeF2 acts as an electron acceptor, while R2Hg acts as an electron donor. Presumably, this reaction is a radical process involving an initial transfer of an electron from R2Hg to XeF2. The absence of R2Hg fluorination products in the reaction mixture suggests that the C7Hg bond is cleaved by XeF2 more easily than the C7H or C7C bond.260, 472R2Hg+ XeF¡ R2Hg+XeF2 R2Hg .XeF2 2 RHgF+R +X+F 2R RR R +F RF It should be noted that XeF2 also reacts readily with mercury dihalides to give mercury difluoride in a quantitative yield. This reaction occurs especially easily with HgI2.472 7. Reactions of other organometallic compounds with XeF2 Many metals, e.g., iridium, react with XeF2 to yield metal fluorides.473 The high oxidation potential of XeF2 allows the oxidation of carbonyl complexes of some metals. Thus the cationic complex tricarbonylbis(triethylphosphine)iridium(I) 326 reacts with XeF2 to give the complex 327.474 + + PEt3 PEt3CO XeF2 CO F OC Ir Ir 7Xe CO OCF PEt3 C PEt3 O 327 326 This approach can be used for preparing fluorinecarbonyl complexes of other metals.The reactions of [M2(CO)10] (M=Mn, Re) with Xe(OTeF5)2 at 778 8C in CH2 Cl2,475 and the reactions of [Os3(CO)12],476 [Ir4(CO)12] 421, 477, 478 and [Ru3(CO)12] 479 with XeF2 in the pres- ence of HF have been studied. IX. Miscellaneous reactions It was shown that the fluorination of polyethylene with XeF2 in liquid media follows a radical mechanism.480 The oxidation of methane by XeF2 in aqueous media at 10 ± 25 8C gives a mixture of MeOH (8%), MeF (2%) and CO2 (50%).481 The reaction of CF3COOXeF and (CF3COO)2Xe with adamantane and its 1-halogeno (Cl, Br) derivatives results in a mixture of isomeric trifluoroacetoxyadamantanes.482 The use of a new reagent, viz., I2 ± XeF2, has been documented recently.483 Its application allows one to convert terminal alkenes into geminal difluorides.484 ± 486 The hypothetical mechanism of this reaction is discussed.486 A new line of research in the chemistry of fullerenes associated with their fluorination has evolved and is developing actively.487 It was found that noble gas fluorides, particularly xenon difluoride, can be successfully used for the fluorination of fullerenes.487 ± 489Chemistry of xenon derivatives.Synthesis and chemical properties * * * The data discussed in the review provide convincing evidence that xenon chemistry is developing successfully and XeF2 is applicable to miscellaneous synthetic tasks.The reagents based on the xenon derivatives considered in the review surpass well-known classical reagents and can often replace them. References 1. N Bartlett Proc. Chem. Soc. 218 (1962) 2. V Zemva, R Hagiwara,W J Casteel, K Lutar, A Jesih, N Bartlett J. Am. Chem. Soc. 112 4846 (1990) 3. D SchroÈ der, J N Harvey,M Arschi, H Schwarz J. Phys. Chem. 108 8446 (1998) 4. D R Brown, M J Clegg, A J Downs, R C Fowler, A R Minihan, J R Norris, L Stein Inorg. Chem. 31 5041 (1992) 5. L Stein, W W Henderson J. Am. Chem. Soc. 102 2856 (1980) 6. R Cipollini, F Grandinetti J. Chem. Soc., Chem. Commun. 773 (1995) 7.M Attina, F Bernardi, F Cacace, I Rossi Chem. Eur. J. 5 1186 (1999) 8. R Hoppe,W DaÈ hne, H Mattauch, K-M RoÈ dder Angew. Chem., Int. Ed. Engl. 1 599 (1962) 9. H H Claassen, H Selig, J G Malm, J. Am. Chem. Soc. 84 3593 (1962) 10. K Lutar, A Smalc, B Zemva, S A Kinkead Inorg. Synth. 29 4 (1992) 11. R D LeBlond, D D DesMarteau J. Chem. Soc., Chem. Commun. 555 (1974) 12. C T Goetschel, K R Loos J. Am. Chem. Soc. 94 3018 (1972) 13. L J Turbini, R E Aikman, R J Lagow J. Am. Chem. Soc. 101 5833 (1979) 14. A V Eletskii, S N Spirin, E V Stepanov, B B Chaivanov Eksperimental'noe i Teoreticheskoe Issledovanie Protsessov Vzaimo- deistviya Atomarnogo Ftora s Kristallicheskim Ksenonom (Experimental and Theoretical Investigations of Processes of Interaction of Atomic Fluorine with Crystalline Xenon) Preprint of Institute of Nuclear Energy, No.3836/13, Moscow, 1983 15. J H Holloway J. Fluorine Chem. 33 149 (1986) 16. J H Holloway Chem. Br. 23 658 (1987) 17. N Bartlett The Chemistry of the Noble Gases (Amsterdam: Elsevier, 1971) 18. D T Hawkins, W E Falconer, N Bartlett Noble Gas Compounds. A Bibliography: 1962 ± 1976 (New York: Plenum, 1978) 19. P Laszlo, G J Schrobilgen Angew. Chem. 100 495 (1988) 20. V V Bardin, Yu L Yagupol'skii, in Ftoriruyushchie Reagenty v Organicheskom Sinteze (Fluorinating Agents in Organic Synthesis) (Ed L S German, S M Zemskov) (Novosibirsk: Nauka, 1987) p. 63 21. J H Holloway Noble Gas Chemistry (London: Methuen, 1968) 22. A B Neiding, V B Sokolov Usp.Khim. 43 2146 (1974) [Russ. Chem. Rev. 43 1043 (1974)] 23. R E banks (Ed.) Fluorine Chemistry at the Millennium: Fascinated by Fluorine (Amsterdam: Elsevier, 2000) 24. O Bostrup Dan. Kemi 76 35 (1995) 25. M R C Gerstenberger, A Haas Angew. Chem., Int. Ed. Engl. 20 647 (1981) 26. G Resnati Tetrahedron 49 9385 (1993) 27. G A Olah, R D Chambers, G K Surya Prakash (Eds) Synthetic Fluorine Chemistry (New York: Wiley, 1992) 28. M Hudlicky, A E Pavlath (Eds) Chemistry of Organic Fluorine Compounds (ACS Monograph. Ser.) Vol. 187 (Washington, DC: American Chemical Society, 1995) 29. V A Legasov, V N Prusakov, B B Chaivanov Reaktsii Okislitel'nogo Ftorirovaniya Diftorida Ksenona (Reactions of Oxidative Fluorina- tion of Xenon Difluoride) Preprint of Institute of Nuclear Energy, No.2185, Moscow, 1972 30. R Filler Isr. J. Chem. 17 71 (1978) 31. M Zupan, in The Chemistry of Functional Groups, Supplement D: The Chemistry of Halides, Pseudo-Halides, and Azides Parts 1, 2 (Eds S Patai, Z Rappoport) (Chichester: Wiley, 1983) p. 657 32. J A Wilkinson Chem. Rev. 92 505 (1992) 33. M A Tius Tetrahedron 51 6605 (1995) 34. V V Zhdankin Izv. Akad. Nauk, Ser. Khim. 1849 (1993) a 35. V K Brel, N S Zefirov, in Chemistry of Hypervalent Compounds (Ed. Kin-ya Akiba) (New York: Wiley-VCH, 1999) p. 389 36. F Sladky Allg. Prakt. Chem. 22 213 (1971) 259 37. T Cleveland, C R Landis J. Am. Chem. Soc. 118 6020 (1996) 38. V A Legasov, A S Marinin Zh. Neorg. Khim. 27 2408 (1972) b 39. W W Dukat, J H Holloway, E G Hope, P J Townson, R L Powell.J. Fluorine Chem. 62 293 (1993) 40. C L Chernick, J G Malm Inorg. Synth. 8 258 (1966) 41. W E Falconer, W A Sunder J. Inorg. Nucl. Chem. 29 1380 (1967) 42. J G Malm, E H Appelman At. Energy Rev. 7 3 (1969) 43. F Schreiner, G N McDonald, C L Chernick J. Phys. Chem. 72 1162 (1968) 44. J L Weeks, C L Chernick,M S Matheson J. Am. Chem. Soc. 84 4612 (1962) 45. L V Streng, A G Streng Inorg. Chem. 4 1370 (1965) 46. S M Williamson Inorg. Synth. 11 147 (1968) 47. J H Holloway J. Chem. Sos., Chem. Commun. 22 (1966) 48. M-Sh Liao, Q-E Zhang J. Phys. Chem. A 102 10 647 (1998) 49. V N Mit'kin, S V Zemskov Izv. Akad. Nauk SSSR, Ser. Neorg. Mater. 17 1897 (1981) c 50. J B Nielsen, S A Kinkead, J D Purson, P G Eller Inorg.Chem. 29 1779 (1990) 51. H Dang, L Huag, Q Xu, R Yang, B Zhang, D Wang, Z Lu Wuji Huaxue Xuebao 12 18 (1996); Chem. Abstr. 125 24 976 (1996) 52. A V Eletskii, V A Legasov, S N Spirin, E V Stepanov, B B Chaivanov Dokl. Akad. Nauk SSSR 280 909 (1985) d 53. D R MacKenzie, R H Wiswall, in Noble Gas Compounds (Chicago; London: University of Chicago Press, 1963) p. 81. 54. A D Kirshenbaum, L V Streng, A G Sreng, A V Grosse J. Am. Chem. Soc. 85 360 (1963) 55. J H Holloway Educ. Chem. 10 140 (1973) 56. C R Bieler, K C Janda J. Am. Chem. Soc. 112 2033 (1990) 57. K Seppelt Angew. Chem. 91 199 (1979) 58. A Filippi, A Troiani,M Speranza J. Phys. Chem. A 101 9344 (1997) 59. E H Appelman J. Am. Chem. Soc. 90 1900 (1968) 60. A Schneer-Ergey, K Kozmutza Magy.Kem. Foly. 78 486 (1972) 61. I Feher,M Semptey Magy. Kem. Foly. 76 141 (1970) 62. A A Goncharov, Yu N Kozlov, A P Purmal' Zh. Fiz. Khim. 52 2870 (1978) e 63. A A Goncharov, Yu N Kozlov Zh. Fiz. Khim. 52 945 (1978) e 64. A A Goncharov, Yu N Kozlov, A P Purmal' Zh. Fiz. Khim. 55 1633 (1981) e 65. D F Smith Science 140 899 (1963) 66. K O Christe,W W Wilson Inorg. Chem. 27 2714 (1988) 67. C L Chernick, H H Claassen, J G Malm, P L Plurien, in Noble Gas Compounds (Chicago; London: University of Chicago Press, 1963) p. 287 68. K Seppelt, H H Rupp Z. Anorg. Allg. Chem. 409 331 (1974) 69. W W Wilson, K O Christe Inorg. Chem. 26 916 (1987) 70. K O Christe,W W Wilson Inorg. Chem. 27 1296 (1988) 71. K O Christe,W W Wilson Inorg.Chem. 27 3763 (1988) 72. H P A Mercier, G J Schrobilgen Inorg. Chem. 32 145 (1993) 73. J B Nielsen, S A Kinkead, P G Eller Inorg. Chem. 29 3621 (1990) 74. H Selig Inorg. Chem. 5 183 (1966) 75. G J Moody, H Selig Inorg. Nucl. Chem. Lett. 2 319 (1966) 76. G J Schrobilgen, D Martin-Rovet, P Charpin, M Lance J. Chem. Soc., Chem. Commun. 894 (1980) 77. J H Holloway, V KaucÆ icÆ , D Martin-Rovet, D R Russell, G J Schrobilgen, H Selig Inorg. Chem. 24 678 (1985) 78. K O Christe, D A Dixon, J C P Sanders, G J Schrobilgen, S Tsai, W W Wilson Inorg. Chem. 34 1868 (1995) 79. K O Christe, E C Curtis, D A Dixon, H P Mercier, J C P Sanders, G J Schrobilgen J. Am. Chem. Soc. 113 3351 (1991) 80. A Ellern, K Seppelt Angew. Chem., Int. Ed. Engl. 34 1586 (1995) 81.J Foropoulos Jr, D D DesMarteau Inorg. Chem. 21 2503 (1982) 82. L D Shustov, N S Tolmacheva, Sh Sh Nabiev, E K Il'in, V D Klimov, V P Ushakov Zh. Neorg. Khim. 34 1673 (1989) b 83. V K Isupov, A V Oleinik, N N Aleinikov Zh. Neorg. Khim. 34 2080 (1989) b 84. N N Aleinikov, S A Kashtanov, I A Pomytkin, A M Sipyagin Izv. Akad. Nauk, Ser. Khim. 184 (1995) a 85. YuMKiselev, N E Fadeeva, A I Popov,MV Korobov, V V Nikulin, V I Spitsyn Dokl. Akad. Nauk SSSR 295 378 (1987) d 86. V A Legasov Vestn. Akad. Nauk SSSR (12) 3 (1976) f 87. N Bartlett, M Wechsberg, F O Sladky, P A Bulliner, G R Jones, R D Burbank J. Chem. Soc., Chem. Commun. 703 (1969) 88. MEisenberg, D D DesMarteau Inorg. Nucl. Chem. Lett. 6 29 (1970)260 89. M Wechsberg, P A Bulliner, F O Sladky, R Mews, N Bartlett Inorg.Chem. 11 3063 (1972) 90. F O Sladky Monatsh. Chem. 101 1571 (1970) 91. J I Musher J. Am. Chem. Soc. 90 7371 (1968) 92. M Eisenberg, D D DesMarteau Inorg. Chem. 11 1901 (1972) 93. R G Syvret, G J Schrobilgen J. Chem. Soc., Chem. Commun. 1529 (1985) 94. R G Syvret, G J Schrobilgen Inorg. Chem. 28 1564 (1989) 95. K Seppelt Angew. Chem., Int. Ed. Engl. 11 723 (1972) 96. K Seppelt, D Lentz, G Kloeter Inorg. Synth. 24 27 (1986) 97. F O Sladky Monatsh. Chem. 101 1559 (1970) 98. H P A Mercier, J C P Sanders, G J Schrobilgen J. Am. Chem. Soc. 116 2921 (1994) 99. F O Sladky Inorg. Synth. 24 33 (1986) 100. V K Brel, A S Koz'min, V I Uvarov, N S Zefirov, V V Zhdankin, P J Stang Tetrahedron Lett.5225 (1990) 101. B Cremer-Lober, H Butler, D Naumann,W Tyrra Z. Anorg. Allg. Chem. 607 34 (1992) 102. K Seppelt, D Lentz, in Progress in Inorganic Chemistry Vol. 29 (New York: Wiley, 1982) p. 167 103. T Birchall, R D Myers, H DeWaard, G J Schrobilgen Inorg. Chem. 21 1068 (1982) 104. L Turowsky, K Seppelt Inorg. Chem. 29 3226 (1990) 105. R G Syvret, K M Mitchell, J C P Sanders, G J Schrobilgen Inorg. Chem. 31 3381 (1992) 106. D Lentz, K Seppelt Angew. Chem., Int. Ed. Engl. 17 356 (1978) 107. E Jacob,D Lentz, K Seppelt, A Simon Z. Anorg. Allg. Chem. 472 7 (1981) 108. L Turowsky, K Seppelt Z. Anorg. Allg. Chem. 609 153 (1992) 109. D Lentz, K Seppelt Angew. Chem., Int. Ed. Engl. 18 66 (1979) 110. G A Schumacher, G J Schrobilgen Inorg.Chem. 23 2923 (1984) 111. T-C Shieh, N C Yang, C L Chernick J. Am. Chem. Soc. 86 5021 (1964) 112. T C Shieh, E D Feit, C L Chernick, N C Yang J. Org. Chem. 35 4020 (1970) 113. S A Shakelford, R R McGuire, J L Pflug Tetrahedron Lett. 363 (1977) 114. M Zupan, A Pollak J. Chem. Soc., Chem. Commun. 845 (1973) 115. M Zupan, A Pollak Tetrahedron 33 1017 (1977) 116. A GregorcÏ icÏ , M Zupan J. Org. Chem. 44 4120 (1979) 117. A GregorcÏ icÏ , M Zupan J. Org. Chem. 44 1255 (1979) 118. M Zupan, A Pollak J. Org. Chem. 41 4002 (1976) 119. S Stavber, M Zupan J. Fluorine Chem. 10 271 (1977) 120. D F Shellhamer, M L Ragains, B T Gipe, V L Heasley, G E Heasley J. Fluorine Chem. 20 13 (1980) 121. M Zupan, B SÏ ket J. Org. Chem. 43 696 (1978) 122.A GregorcÏ icÏ , M Zupan J. Org. Chem. 49 333 (1984) 123. M Zupan, A Pollak J. Org. Chem. 42 1559 (1977) 124. B SÏ ket,M Zupan J. Chem. Soc. Perkin Trans. 1 2169 (1977) 125. M Zupan, A GregorcÏ icÏ , A Pollak J. Org. Chem. 42 1562 (1977) 126. S A Shakelford Tetrahedron Lett. 4265 (1977) 127. S A Shakelford J. Org. Chem. 44 3485 (1979) 128. A GregorcÏ icÏ , M Zupan Bull. Chem. Soc. Jpn. 53 1085 (1980) 129. A GregorcÏ icÏ , M Zupan J. Fluorine Chem. 24 291 (1984) 130. R A Hildreth, M L Druelinger, S A Shakelford Tetrahedron Lett. 23 1059 (1982) 131. A GregorcÏ icÏ , M Zupan Tetrahedron 33 3243 (1977) 132. D F Shellhamer, R J Conner, R E Richardson, V L Heasley, G E Heasley J. Org. Chem. 49 5015 (1984) 133. S Rozen, R Filler Tetrahedron 41 1111 (1985) 134.T B Patrick, R Mortezania J. Org. Chem. 53 5153 (1988) 135. G S Garrett, T J Emge, S C Lee, E M Fischer, K Dyehouse, J M McIver J. Org. Chem. 56 4823 (1991) 136. B Zajc, M Zupan J. Chem. Soc., Chem. Commun. 759 (1980) 137. G L Cantrell, R Filler J. Fluorine Chem. 27 35 (1985) 138. B Zajc, M Zupan J. Org. Chem. 47 573 (1982) 139. T Tsushima, K Kawada, T Tsuji Tetrahedron Lett. 23 1165 (1982) 140. E Differding, G M Ruegg Tetrahedron Lett. 32 3815 (1991) 141. M Zupan, A Pollak J. Org. Chem. 39 2646 (1974) 142. W Korytnyk, S Valentekovic-Horvath, C R Petrie III Tetrahedron 38 2547 (1982) 143. W Korytnyk, S Valentekovic-Horvath Tetrahedron Lett. 21 1493 (1980) V K Brel, N Sh Pirkuliev, N S Zefirov 144. C C Geilen, N Loch, W Reutter, K Seppelt, F Oberdorfer Tetrahedron Lett.33 2435 (1992) 145. N N Aleinikov, I A Pomytkin, S A Kashtanov, O N Efimov, A F Zueva Izv. Akad. Nauk SSSR, Ser. Khim. 2850 (1988) a 146. F O Sladky, P A Bulliner, N Bartlett J. Chem. Soc., A 2179 (1969) 147. N S Zefirov, V V Zhdankin, A A Gakh, P J Stang Izv. Akad. Nauk SSSR, Ser. Khim. 1196 (1990) a 148. N S Zefirov, A A Gakh, V V Zhdankin, P J Stang J. Org. Chem. 56 1416 (1991) 149. V K Brel, V I Uvarov, N S Zefirov J. Fluorine Chem. 54 34 (1991) 150. V K Brel, A A Gakh, V V Zhdankin, N S Zefirov, A S Koz'min, A A Korkin, T G Kutateladze, R Caple, S A Lermontov, I G Plokhikh, S O Safronov, P J Stang, N G Chovnikova Dokl. Akad. Nauk SSSR 313 1131 (1990) d 151. V I Uvarov, V K Brel Izv.Akad. Nauk, Ser. Khim. 764 (1994) a 152. A L Henne, E C Ladd J. Am. Chem. Soc. 58 402 (1936) 153. A Varvoglis Hypervalent Iodine in Organic Synthesis (London: Academic Press, 1997) 154. P J Stang, V V Zhdankin Chem. Rev. 96 1123 (1996) 155. N Sh Pirkuliev, V K Brel, N S Zefirov Usp. Khim. 69 118 (2000) [Russ. Chem. Rev. 69 105 (2000)] 156. V V Zhdankin, R Tykwinski, B Berglund,M Mullikin, R Caple, N S Zefirov, A S Koz'min J. Org. Chem. 54 2609 (1989) 157. V V Zhdankin, M Mullikin, R Tykwinski, B Berglund, R Caple, N S Zefirov, A S Koz'min J. Org. Chem. 54 2605 (1989) 158. N S Zefirov, T M Kasumov, A S Koz'min, V D Sorokin, V R Polishchuk Zh. Org. Khim. 30 321 (1994) g 159. N S Zefirov, V V Zhdankin, Yu V Dan'kov, V D Sorokin, V N Semerikov, A S Koz'min, R Caple, B A Berglund Tetrahedron Lett.27 3971 (1986) 160. N S Zefirov, N Sh Samsoniya, T G Kutateladze, V V Zhdankin Zh. Org. Khim. 27 220 (1991) g 161. N S Zefirov, V V Zhdankin, Yu V Dan'kov, V V Samoshin, A S Koz'min Zh. Org. Khim. 20 444 (1984) g 162. V V Zhdankin, P J Stang Tetrahedron 54 10927 (1998) 163. N S Zefirov, V V Zhdankin, A S Koz'min Tetrahedron Lett. 27 1845 (1986) 164. D F Shellhamer, C M Curtis, D R Hollingsworth, M L Ragains, R E Richardson, V L Heasley, G E Heasley Tetrahedron Lett. 23 2157 (1982) 165. D F Shellhamer, C M Curtis, R H Dunham, D R Hollingsworth, M L Ragains, R E Richardson, V L Heasley, S A Shackelford, G E Heasley J. Org. Chem. 50 2751 (1985) 166. D F Shellhamer, S L Carter, R H Dunham, S N Graham, M P Spitsbergen, V L Heasley, R D Chapman,M L Druelinger J.Chem. Soc., Perkin Trans. 2 159 (1989) 167. D F Shellhamer, S L Carter,MC Chiaco, T E Harris, R D Henderson,WS C Low, B TMetcalf,MCWillis, V L Heasley, R D Chapman J. Chem. Soc. Perkin Trans. 2 401 (1991) 168. ML Druelinger, D F Shellhamer, R D Chapman, S A Shackelford, M E Riner, S L Carter, R P Callahan, C R Youngstrom J. Chem. Soc. Perkin Trans. 2 787 (1997) 169. M Zupan, M Metelko, S Stavber J. Chem. Soc. Perkin Trans. 1 2851 (1993) 170. S Rozen, E Mishani, M Kol J. Am. Chem. Soc. 114 7643 (1992) 171. D F Shellhamer, M J Horney, A L Toth, V L Heasley Tetrahedron Lett. 33 6903 (1992) 172. D F Shellhamer, M J Horney, B J Pettus, T L Pettus, J M Stringer, V L Heasley J.Org. Chem. 64 1094 (1999) 173. S Stavber, T Sotler, M Zupan, R G Syvret, J M Dobrolsky Jr, A PopovicÆ J. Org. Chem. 59 5891 (1994) 174. Ch A Ramsden, R G Smith J. Am. Chem. Soc. 120 6842 (1998) 175. D R MacKenzie, J Fajer J. Am. Chem. Soc. 92 4994 (1970) 176. M J Shaw,H H Hyman, R Filler J. Am. Chem. Soc. 91 1563 (1969) 177. M J Shaw,H H Hyman, R Filler J. Am. Chem. Soc. 92 6498 (1970) 178. M Ya Turkina, I P Gragerov Zh. Org. Khim. 11 340 (1975) g 179. US P. 3 833 581; Ref. Zh. Khim. 12N136P (1975) 180. M J Shaw, H H Hyman, R Filler J. Org. Chem. 36 2917 (1971) 181. S Stavber, M Zupan J. Org. Chem. 48 2223 (1983) 182. M Zupan Chimia 30 305 (1976) 183. B SÏ ket,M Zupan J. Org. Chem. 43 835 (1978) 184. B SÏ ket,M Zupan Bull.Chem. Soc. Jpn. 54 279 (1981) 185. S P Anand, L A Quarterman, P A Christian, H H Hyman, R Filler J. Org. Chem. 40 3796 (1975)Chemistry of xenon derivatives. Synthesis and chemical properties 186. M Rabinovitz, I Agranat, H Selig, C-H Lin J. Fluorine Chem. 10 159 (1977) 187. I Agranat,M Rabinovitz, H Selig, C-H Lin Chem. Lett. 32 1271 (1975) 188. M Zupan, A Pollak J. Org. Chem. 40 3794 (1975) 189. E D Bergmann, H Selig, C-H Lin, M Rabinovitz, I Agranat J. Org. Chem. 40 3793 (1975) 190. I Agranat,M Rabinovitz, H Selig, C-H Lin Experientia 32 417 (1976) 191. M T Stephenson, H J Shine J. Org. Chem. 46 3139 (1981) 192. S Stavber, M Zupan J. Chem. Soc., Chem. Commun. 969 (1978) 193. S Stavber, M Zupan J. Org. Chem.46 300 (1981) 194. V V Bardin, G G Furin, G G Jakobson Zh. Org. Khim. 18 604 (1982) g 195. V V Bardin, G G Furin, G G Jakobson, in Tez. Dokl. Vsesoyuz. Konf. Pamyati A E Favorskogo, Leningrad, 1980 (Abstracts of Reports of the All-Union Conference on A E Favorskii Memory, Leningrad, 1980) p. 110 196. G G Jakobson, V V Bardin, G G Furin, in The IIIrd Regular Meeting of Soviet-Japanese Fluorine Chemists, Tokyo, 1983 p. 14.1 197. B Zajc, M Zupan Bull. Chem. Soc. Jpn. 55 1617 (1982) 198. S P Anand, L A Quarterman, H H Hyman, K G Migliorese, R Filler J. Org. Chem. 40 807 (1975) 199. A A Goncharov, Yu N Kozlov, A P Purmal' Zh. Fiz. Khim. 51 2839 (1977) e 200. HKoudstaal, C Olieman Recl. Trav. Chim. Pays-Bas 100 246 (1981) 201. M Zupan, A Pollak J.Fluorine Chem. 7 443 (1976) 202. L N Nikolenko, T I Yurasova, A A Man'ko Zh. Obshch. Khim. 40 938 (1970) h 203. A A Avramenko, V V Bardin, A I Karelin, V A Krasil'nikov, P P Tushin, G G Furin, G G Jakobson Zh. Org. Khim. 21 822 (1985) g 204. V V Bardin, I V Stennikova, G G Furin, G G Jakobson, in Stroenie i Reaktsionnaya Sposobnost' Kremniiorganicheskikh Soedinenii (Tez. Dokl. 3-go Vsesoyuz. Simpoziuma), Irkutsk, 1985 [Structure and Reactivity of Organosilicon Compounds (Abstracts of Reports of the 3rd All-Union Symposium), Irkutsk, 1985] p. 133 205. V V Bardin, I V Stennikova, G G Furin, G G Jakobson Zh. Org. Khim. 21 458 (1985) g 206. G Firnau, R Chirakal, S Sood, S Garnett Can. J. Chem. 58 1449 (1980) 207. G Firnau, R Chirakal, S Sood, S Garnett J.Labelled Compd. Radiopharm. 18 7 (1981) 208. Z Planinsek, S Stavber, M Zupan J. Fluorine Chem. 45 141 (1989) 209. S Stavber, Z Koren, M Zupan Synlett 265 (1994) 210. B Zajc, M Zupan J. Org. Chem. 55 1099 (1990) 211. S Stavber, B SÆ ket, B Zajc, M Zupan Tetrahedron 45 6003 (1989) 212. S Stavber, M Zupan Tetrahedron Lett. 34 4355 (1993) 213. V A Nikanorov, V I Rozenberg, V G Kharitonov, D Yu Antonov, V A Mikul'shina,M V Galakhov, D P Krut'ko, N S Kopelev, V N Guryshev, V P Yur'ev, O A Reutov Dokl. Akad. Nauk SSSR 315 1388 (1990) d 214. I Takemoto, K Yamasaki Biosci. Biotechnol. Biochem. 58 594 (1994) 215. T Umemoto, S Fukami, G Tomizawa, K Harasawa, K Kawada, K Tomita J. Am. Chem. Soc. 112 8563 (1990) 216.G G Furin,A A Fainzilberg Usp. Khim. 68 725 (1999) [Russ. Chem. Rev. 68 653 (1999)] 217. S A Kashtanov, N N Aleinikov, F I Dubovitskii Izv. Akad. Nauk SSSR, Ser. Khim. 2678 (1987) a 218. G B Shul'pin, M M Kats, Yu N Kozlov Izv. Akad. Nauk SSSR, Ser. Khim. 2654 (1988) a 219. M M Kats, Yu N Kozlov, G B Shul'pin Zh. Obshch. Khim. 61 1835 (1991) h 220. D F Shellhamer, B C Jones, B J Pettus, T L Pettus, J M Stringer, V L Heasley J. Fluorine Chem. 88 37 (1998) 221. M Zupan, J Iskra, S Stavber J. Org. Chem. 63 878 (1998) 222. V V Bardin, L N Shchegoleva,H J Frohn J. Fluorine Chem. 77 153 (1996) 223. L N Nikolenko, L D Shustov, T N Bocharova, T N Yurasova, V A Legasov Dokl. Akad. Nauk SSSR 204 1369 (1972) d 224. L D Shustov, T N Bocharova, T I Yurasova, N G Marchenkova, V A Legasov, L N Nikolenko Zh.Obshch. Khim. 43 841 (1973) h 261 225. T N Bocharova, N G Marchenkova, L D Shustov, T Yu Prokof'eva, L N Nikolenko Zh. Obshch. Khim. 43 1325 (1973) h 226. L D Shustov, T D Tel'kovskaya, L N Nikolenko Zh. Org. Khim. 11 2137 (1975) g 227. L D Shustov, T D Tel'kovskaya, L N Nikolenko Zh. Obshch. Khim. 44 2564 (1974) h 228. L D Shustov, M N Semenova, L N Nikolenko Zh. Obshch. Khim. 48 1903 (1978) h 229. T B Patrick, K K Johri, D H White J. Org. Chem. 48 4158 (1983) 230. T B Patrick, K K Johri, D H White, W S Bertrand, R Mokhtar, M R Kilbourn, M J Welch Can. J. Chem. 64 138 (1986) 231. G J Schrobilgen, G Firnau, R Chirakal J. Chem. Soc., Chem. Commun. 198 (1981) 232. D I Davies, C Waring J.Chem. Soc., C 1865 (1968) 233. J W Wilt, in Free Radicals Vol. 1 (Ed. J K Kochi) (New York: Wiley, 1973) p. 333 234. C V Wilson Org. React. 9 332 (1957) 235. L Kaplan, in Free Radicals Vol. 2 (Ed. J K Kochi) (New York: Wiley, 1973) p. 372 236. J K Kochi J. Am. Chem. Soc. 87 2500 (1965) 237. R A Sheldon, J K Kochi Org. React. 19 179 (1972) 238. T B Patrick, S Khazaeli, S Nadji, K Hering-Smith, D Reif J. Org. Chem. 58 705 (1993) 239. D P Curran, E Bosch, J Kaplan, M Newcomb J. Org. Chem. 54 1826 (1989) 240. E W Della, N J Head J. Org. Chem. 57 2850 (1992) 241. Y Tanabe, N Matsuo, N Ohno J. Org. Chem. 53 4582 (1988) 242. A M Sipyagin, I A Pomytkin, S V Pal'tsun, N N Aleinikov, V G Kartsev Dokl. Akad. Nauk SSSR 311 1137 (1990) d 243.G G Furin Usp. Khim. 69 538 (2000) [Russ. Chem. Rev. 69 491 (2000)] 244. V K Brel, V I Uvarov, N S Zefirov, P J Stang, R Caple J. Org. Chem. 58 6922 (1993) 245. V I Uvarov, V K Brel, I V Martynov, N N Aleinikov, S A Kashtanov Izv. Akad. Nauk SSSR, Ser. Khim. 2650 (1988) a 246. I V Martynov, V K Brel, V I Uvarov, I A Pomytkin, N N Aleinikov, S A Kashtanov Izv. Akad. Nauk SSSR, Ser. Khim. 466 (1988) a 247. I V Martynov, V K Brel, V I Uvarov, N N Aleinikov, S A Kashtanov Izv. Akad. Nauk SSSR, Ser. Khim. 2639 (1988) a 248. V K Brel, A S Koz'min, I V Martynov, V I Uvarov, N S Zefirov, V V Zhdankin, P J Stang Tetrahedron Lett. 31 4799 (1990) 249. Yu L Yagupol'skii, T I Savina Zh. Org. Khim. 17 1330 (1981) g 250. L D Shustov, L N Nikolenko Zh.Obshch. Khim. 53 2408 (1983) h 251. P Nongkunsarn, Ch A Ramsden J. Chem. Soc., Perkin Trans. 1 121 (1996) 252. D Holtz, J L Beauchamp Science 173 1237 (1971) 253. H S Johnston, R Woolfolk J. Chem. Phys. 41 269 (1964) 254. J Berkowitz, W A Chupka, P M Guyon, J H Holloway, R Spohr J. Phys. Chem. 75 1461 (1971) 255. J K Hovey, T B McMahon J. Am. Chem. Soc. 108 528 (1986) 256. T Umemoto Chem. Rev. 96 1757 (1996) 257. H J Frohn, S Jacobs J. Chem. Soc., Chem. Commun. 625 (1989) 258. H J Frohn, S Jacobs, G Henkel Angew. Chem., Int. Ed. Engl. 28 1506 (1989) 259. R J Lagow, L J Turbini, R E Aikman,M M Brezinski J. Fluorine Chem. 45 12 (1989) 260. K P Butin, Ya M Kiselev, T V Magdesieva, O A Reutov Izv. Akad. Nauk SSSR, Ser.Khim. 716 (1982) a 261. R G Bulgakov, G Ya Mastrenko, G A Tolstikov, B N Yakovlev, V P Kazakov Izv. Akad. Nauk SSSR, Ser. Khim. 2644 (1984) a 262. W Tyrra, D Naumann Can. J. Chem. 67 1949 (1989) 263. D Naumann, W Tyrra J. Chem. Soc., Chem. Commun. 47 (1989) 264. W Breuer, H J Frohn,M Giesen, S Jacobs, in Chemiedozenten ± Tagung 1989 (Abstracts of Reports), Bielefeld, 1989 p. 108 265. W Breuer, H J Frohn,M Giesen, S Jacobs, in The 12th International Symposium on Fluorine Chemistry, 1988 p. 213 266. H J Frohn, S Jakobs, C Rossbach Eur. J. Solid State Inorg. Chem. 29 729 (1992) 267. H Meinert, S Rudiger Z. Chem. 9 35 (1969) 268. C J Jameson, in Multinuclear NMR (Ed. J Mason) (New York; London: Plenum, 1987)262 269. S Tanaka,M Sugimoto, H Takashima,M Hada, H Nakatsuji Bull.Chem. Soc. Jpn. 69 953 (1996) 270. C I Ratcliffe Annu. Rep. NMR Spectrosc. 36 123 (1998) 271. H Butler,D Naumann,W Tyrra Eur. J. Solid State Inorg. Chem. 29 739 (1992) 272. H J Frohn, A Klose, G Henkel GIT Fachz. Lab. 37 752 (1993) 273. H J Frohn, A Klose, V V Bardin, A J Kruppa, T V Leshina J. Fluorine Chem. 70 147 (1995) 274. H J Frohn, A Klose, V V Bardin J. Fluorine Chem. 64 201 (1993) 275. H J Frohn, A Klose, G Henkel Angew. Chem., Int. Ed. Engl. 32 99 (1993) 276. V M McRae, R D Peacock, D R Russell J. Chem. Soc., Chem. Commun. 62 (1969) 277. N Bartlett, M Wechsberg, G R Jones, R D Burbank Inorg. Chem. 11 1124 (1972) 278. L K Templeton, D H Templeton, K Seppelt, N Bartlett Inorg. Chem. 15 2718 (1976) 279.R J Gillepsie, G J Schrobilgen, D R Slim J. Chem. Soc., Dalton Trans. 1003 (1977) 280. A F Wells Structural Inorganic Chemistry (Oxford: Clarendon Press, 1984) p. 920 281. H J Frohn, C Rossbach Z. Anorg. Allg. Chem. 619 1672 (1993) 282. H J Frohn, S Jakobs, C Rossbach, in The 13th International Symposium on Fluorine Chemistry, Bochum, 1991 A 8 283. H J Frohn, S Jakobs, C Rossbach J. Fluorine Chem. 54 8 (1991) 284. V V Bardin, H J Frohn J. Fluorine Chem. 60 141 (1993) 285. D Naumann, H Butler, R Gnann,W Tyrra Inorg. Chem. 32 861 (1993) 286. D Naumann, H Butler, R Gnann Z. Anorg. Allg. Chem. 618 74 (1992) 287. S Datsenko, N Ignat'ev, P Barthen, H J Frohn, T Scholten, T Schroer, D Welting Z. Anorg. Allg. Chem. 624 1669 (1998) 288.D Naumann, W Tyrra, R Gnann, D Pfolk J. Chem. Soc., Chem. Commun. 2651 (1994) 289. D Naumann, W Tyrra, R Gnann, D Pfolk, T Gilles, K F Teble Z. Anorg. Allg. Chem. 623 1821 (1997) 290. H J Frohn, V V Bardin J. Chem. Soc., Chem. Commun. 1072 (1993) 291. H J Frohn, V V Bardin Mendeleev Commun. 114 (1995) 292. H J Frohn, V V Bardin Z. Naturforsch., B Chem. Sci. 51 1011 (1996) 293. H J Frohn, V V Bardin Z. Naturforsch., B Chem. Sci. 53 562 (1998) 294. H J Frohn, A Klose, T Schroer, G Henkel, V Buss, D Opitz, R Vahrenhorst Inorg. Chem. 37 4884 (1998) 295. H J Frohn, V V Bardin Z. Anorg. Allg. Chem. 622 2031 (1996) 296. V V Bardin J. Fluorine Chem. 89 195 (1998) 297. A A Avramenko, V V Bardin, G G Furin, A I Karelin, V A Krasil'nikov, P P Tushin Zh.Org. Khim. 24 1443 (1988) g 298. H J Frohn, V V Bardin J. Chem. Soc., Chem. Commun. 919 (1999) 299. V V Zhdankin, P J Stang, N S Zefirov J. Chem. Soc., Chem. Commun. 578 (1992) 300. S P Anand, R Filler J. Fluorine Chem. 7 179 (1976) 301. M Zupan, A Pollak J. Fluorine Chem. 8 275 (1976) 302. S V Kovalenko, V K Brel, N S Zefirov Izv. Akad. Nauk, Ser. Khim. 1841 (1994) a 303. S V Kovalenko, V K Brel, N S Zefirov, P J Stang Mendeleev Commun. 68 (1998) 304. T I Yurasova Zh. Obshch. Khim. 44 956 (1974) h 305. J Wang, A I Scott Tetrahedron 50 6181 (1994) 306. I A Grigor'ev, L B Volodarsky, V F Strichenko, I A Kirilyuk Tetrahedron Lett. 30 751 (1989) 307. I V Tselinskii, A A Mel'nikov, L G Varyagina, A E Trubitsin Zh.Org. Khim. 21 2490 (1985) g 308. I V Tselinskii, A A Mel'nikov, A E Trubitsin Zh. Org. Khim. 23 1657 (1987) g 309. I V Tselinskii, A A Mel'nikov, A E Trubitsin Zh. Org. Khim. 24 688 (1988) g 310. A E Trubitsin, A A Mel'nikov,M S Pevzner, I V Tselinskii, M E Niyazymbetov, V A Petrosyan Izv. Akad. Nauk SSSR, Ser. Khim. 736 (1989) a 311. I V Tselinskii, A A Mel'nikov, A E Trubitsin, G M Frolova Zh. Org. Khim. 26 69 (1990) g 312. I V Tselinskii, A A Mel'nikov, A E Trubitsin Zh. Org. Khim. 26 272 (1990) g V K Brel, N Sh Pirkuliev, N S Zefirov 313. A E Trubitsin, A A Mel'nikov, I V Tselinskii, A M Popov Zh. Org. Khim. 26 2007 (1990) g 314. V A Petrosyan,M E Niyazymbetov Izv. Akad. Nauk SSSR, Ser. Khim. 368 (1988) a 315. M E Niyazymbetov, V A Petrosyan, A A Gakh, A A Fainzil'berg Izv.Akad. Nauk SSSR, Ser. Khim. 2390 (1987) a 316. V A Golubev, N N Salmina, B L Korsunskii, N N Aleinikov, F N Dubovitskii Izv. Akad. Nauk, Ser. Khim. 778 (1978) a 317. W Sundermeyer, M Witz J. Fluorine Chem. 34 251 (1986) 318. G J Schrobilgen, J H Holloway, P Granger, C Brevard Inorg. Chem. 17 980 (1978) 319. D D DesMarteau J. Am. Chem. Soc. 100 6270 (1978) 320. D D DesMarteau, R D LeBlond, S F Hossain, D Nothe J. Am. Chem. Soc. 103 7734 (1981) 321. J F Sawyer, G J Schrobilgen, S J Sutherland J. Chem. Soc., Chem. Commun. 210 (1982) 322. R Faggiani, D K Kennepohl, C J L Lock, G J Schrobilgen Inorg. Chem. 25 563 (1986) 323. J F Sawyer, G J Schrobilgen, S J Sutherland Inorg. Chem. 21 4064 (1982) 324.G A Schumacher, G J Schrobilgen Inorg. Chem. 22 2178 (1983) 325. J Foropoulos Jr, D D DesMarteau J. Am. Chem. Soc. 104 4260 (1982) 326. H Selig, J H Holloway Top. Curr. Chem., Inorg. Chem. 124 33 (1984) 327. A A A Emara, G J Schrobilgen J. Chem. Soc., Chem. Commun. 1644 (1987) 328. A A A Emara, G J Schrobilgen Inorg. Chem. 31 1323 (1992) 329. A A A Emara, G J Schrobilgen J. Chem. Soc., Chem. Commun. 257 (1988) 330. G J Schrobilgen J. Chem. Soc., Chem. Commun. 1506 (1988) 331. V H Dibeler, S K Liston J. Chem. Phys. 48 4765 (1968) 332. G J Schrobilgen J. Chem. Soc., Chem. Commun. 863 (1988) 333. G J Schrobilgen, J M Whalen Inorg. Chem. 33 5207 (1994) 334. A Schulz, T M KlapoÈ tke Inorg. Chem. 36 1929 (1997) 335. K O Christe, E C Curtis, D A Dixon, H P Mercier, J C P Sanders, G J Schrobilgen J.Am. Chem. Soc. 113 3351 (1991) 336. K O Christe,W W Wilson Inorg. Chem. 21 4113 (1982) 337. N Bartlett, F O Sladky J. Chem. Soc., D 1046 (1968) 338. Yu M Kiselev Koord. Khim. 23 83 (1997) i 339. J A Gibson, A F Janzen J. Chem. Soc., Chem. Commun. 739 (1973) 340. J Bornstein, M R Borden, F Nunes, H I Tarlin J. Am. Chem. Soc. 85 1609 (1963) 341. W Carpenter J. Org. Chem. 31 2688 (1966) 342. J J Edmans, W B Motherwell J. Chem. Soc., Chem. Commun. 881 (1989) 343. M Zupan, A Pollak J. Org. Chem. 41 2179 (1976) 344. S Stavber, M Zupan J. Fluorine Chem. 12 307 (1978) 345. M Zupan Synthesis 473 (1976) 346. M Zupan, A Pollak J. Chem. Soc., Perkin Trans. 1 1745 (1976) 347.J A Gibson, R K Marat, A F Janzen Can. J. Chem. 53 3044 (1975) 348. M Zupan, A Pollak J. Fluorine. Chem. 7 445 (1976) 349. I I Maletina, V V Orda, N N Aleinikov, B L Korsunskii, L M Yagupol'skii Zh. Org. Khim. 12 1371 (1976) g 350. H J Frohn, V V Bardin Z. Naturforsch., B Chem. Sci. 51 1015 (1996) 351. M Zupan, A Pollak J. Chem. Soc., Chem. Commun. 715 (1975) 352. M Zupan Collect. Czech. Chem. Commun. 42 266 (1977) 353. K Alam, A F Janzen J. Fluorine Chem. 36 179 (1987) 354. A GregorcÏ icÏ , M Zupan Bull. Chem. Soc. Jpn. 50 517 (1976) 355. G W Bradley, J H Holloway, H J Koh, D G Morris, P G Watson J. Chem. Soc., Perkin Trans. 1 3001 (1992) 356. E W Della, N J Head, W K Janowski, C H Schiesser J. Org. Chem. 58 7876 (1993) 357. A N Chekhlov, T M Kasumov, V K Brel, N S Zefirov Zh.Strukt. Khim. 37 940 (1996) j 358. T M Kasumov, V K Brel, Yu K Grishin, N S Zefirov, P J Stang Tetrahedron 53 1145 (1997) 359. TMKasumov, N Sh Pirguliyev, V K Brel, Yu K Grishin, N S Zefirov, P J Stang Tetrahedron 53 13139 (1997) 360. T M Kasumov, V K Brel, K A Potekhin, E V Balashova, N S Zefirov Dokl. Akad. Nauk 351 644 (1996) d 361. T M Kasumov, V K Brel, K A Potekhin, A S Koz'min, E V Balashova, Yu S Struchkov, N S Zefirov Dokl. Akad. Nauk 349 634 (1996) dChemistry of xenon derivatives. Synthesis and chemical properties 362. T M Kasumov, V K Brel, K A Potekhin, E V Balashova, N S Zefirov, P J Stang Dokl. Akad. Nauk 353 770 (1997) d 363. N Sh Pirkuliev, V K Brel, T M Kasumov, N G Akhmedov, N S Zefirov Zh.Org. Khim. 35 1633 (1999) g 364. N Sh Pirguliyev, V K Brel, T M Kasumov,N S Zefirov, P J Stang Synthesis 1297 (1999) 365. N Sh Pirkuliev, Candidate Thesis in Chemical Sciences, Moscow State University, Moscow, 1999 366. TMKasumov, V K Brel, A S Koz'min, N S Zefirov, K A Potekhin, P J Stang New J. Chem. 21 1347 (1997) 367. N Sh Pirguliyev, V K Brel, N S Zefirov, P J Stang Mendeleev Commun. 189 (1999) 368. T Kitamura, R Furuki, K Nagata, H Taniguchi, P J Stang J. Org. Chem. 57 6810 (1992) 369. T Kitamura, R Furuki, H Taniguchi, P J Stang Tetrahedron Lett. 31 703 (1990) 370. T Kitamura, R Furuki, H Taniguchi, P J Stang Tetrahedron 48 7149 (1992) 371. P J Stang, V V Zhdankin, N S Zefirov Mendeleev Commun. 159 (1992) 372.T Kitamura, R Furuki, H Taniguchi, P J Stang Mendeleev Commun. 148 (1991) 373. T Kitamura, R Furuki, K Nagata, L Zheng, H Taniguchi Synlett 193 (1993) 374. V I Uvarov, V K Brel Izv. Akad. Nauk, Ser. Khim. 1629 (1994) a 375. V I Uvarov, V K Brel Zh. Obshch. Khim. 64 2060 (1994) h 376. T M KlapoÈ tke Heteroatom. Chem. 8 473 (1997) 377. A N Nesmeyanov, I N Lisichkina, A S Kulikov, A N Vanchikov, T P Tolstaya, V A Chertkov Dokl. Akad. Nauk SSSR 243 1463 (1978) d 378. M Zupan J. Fluorine Chem. 8 305 (1976) 379. R K Marat, A F Janzen Can. J. Chem. 55 3031 (1977) 380. M Zupan, B Zajc J. Chem. Soc., Perkin Trans. 1 9 965 (1978) 381. A M Forster, A J Downs J. Chem. Soc., Dalton Trans. 2827 (1984) 382. T B Patrick, S Nadji J. Fluorine Chem.39 415 (1988) 383. Yu L Yagupol'skii, T I Savina Zh. Org. Khim. 15 438 (1979) g 384. A GregorcÏ icÏ , B Zajc, M Zupan Phosphorus Sulfur 6 107 (1979) 385. X Ou, A F Janzen Can. J. Chem. 74 2002 (1996) 386. K O Christe,W W Wilson J. Fluorine Chem. 47 117 (1990) 387. J E Gordon The Organic Chemistry of Electrolyte Solutions (New York: Wiley, 1975) 388. G Zerza, G Sliwinski, N Schwentner, G J Hoffman, D G Imre, V A Apkarian J. Chem. Phys. 99 8414 (1993) 389. X Ou, G M Bernard, A F Janzen Can. J. Chem. 75 1878 (1997) 390. C W Perkins, J C Martin, A J Arduengo,WLau, A Alegria, J K Kochi J. Am. Chem. Soc. 102 7753 (1980) 391. X Ou, A F Janzen Inorg. Chem. 36 392 (1997) 392. A F Janzen, P M C Wang, A E Lemire J. Fluorine Chem. 22 557 (1983) 393. K Hatano Chem.Pharm. Bull. 46 1337 (1998) 394. X Huang, B J Blackburn, A F Janzen J. Fluorine Chem. 47 145 (1990) 395. M J Robins, S F Wnuk, K B Mullah, N K Dalley J. Org. Chem. 56 6878 (1991) 396. M J Robins, K B Mullah, S F Wnuk, N K Dalley J. Org. Chem. 57 2357 (1992) 397. G Guillerm, M Gatel J. Chem. Soc., Perkin Trans. 1 153 (1994) 398. M J Robins, S F Wnuk, K B Mullah, N K Dalley, C-S Yuan, Y Lee, R T Borchardt J. Org. Chem. 59 544 (1994) 399. A M Sipyagin, I A Pomytkin, N N Aleinikov, S V Pal'tsun, V G Kartsev, in Tez. Dokl. VI Vsesoyuz. Konf. po Khimii Ftororga- nicheskikh Soedinenii, Novosibirsk, 1990 (Abstracts of Reports of the VIth All-Union Conference on the Chemistry of Organofluorine Compounds, Novosibirsk, 1990) 400. A M Sipyagin, I A Pomytkin, S V Pal'tsun, N N Aleinikov Khim.Geterotsikl. Soedin. 58 (1994) k 401. A M Sipyagin, I V Efremov, I A Pomytkin, S A Kashtanov, N N Aleinikov Khim. Geterotsikl. Soedin. 1291 (1994) k 402. A M Sipyagin, Z G Aliev Khim. Geterotsikl. Soedin. 1278 (1994) k 403. A M Sipyagin, Z G Aliev Khim. Geterotsikl. Soedin. 1495 (1993) k 404. A M Sipyagin, I A Pomytkin, S V Pal'tsun, N N Aleinikov Chem. Heterocycl. Compd. 30 52 (1994) 405. V N Boiko, G M Shchupak, N V Ignat'ev, L M Yagupol'skii Zh. Org. Khim. 15 1245 (1979) g 263 406. V S Ershov, S A Kashtanov, I V Efremov, I A Pomytkin, A M Sipyagin, N N Aleinikov Khim. Geterotsikl. Soedin. 1703 (1995) k 407. J Varwing, R Mews J. Chem. Res. (S) 245 (1977) 408. H Steinbeisser, R Mews J.Fluorine Chem. 17 505 (1981) 409. R Maggiulli, R Mews, H Oberhammer, W-D Stohrer J. Fluorine Chem. 45 77 (1989) 410. E Jaudas-Presel, R Maggiulli, R Mews, H Oberhammer, T Paust, W-D Stohrer Chem. Ber. 123 2123 (1990) 411. W Leidinger, W Sundermeyer Chem. Ber. 115 2892 (1982) 412. S A Volkova, Z M Sinyutina, L N Nikolenko Zh. Obshch. Khim. 44 2592 (1974) h 413. R Minkwitz, G Nowicki, H Preut Z. Anorg. Allg. Chem. 573 185 (1989) 414. R Minkwitz, A Werner Z. Naturforsch.,B Chem. Sci. 43 403 (1988) 415. R Minkwitz, G Nowicki Z. Naturforsch., B Chem. Sci. 44 1343 (1989) 416. R Minkwitz, G Nowicki Inorg. Chem. 31 225 (1992) 417. R Minkwitz, G Nowicki Inorg. Chem. 30 4426 (1991) 418. R Minkwitz,W Molsbeck Z. Anorg. Allg. Chem. 612 35 (1992) 419. A J Downs, G S McGrady, E A Barnfield, D W H Rankin, H E Robertson, J E Boggs, K D Dobbs Inorg. Chem. 28 3286 (1989) 420. R Minkwitz, U Lohmann, H Bormann Z. Anorg. Allg. Chem. 622 889 (1996) 421. S Sato, H Ameta, E Horn, O Takahashi, N Furukawa J. Am. Chem. Soc. 119 12374 (1997) 422. T Kawashima, F Ohno, R Okazaki, H Ikeda, S Inagaki J. Am. Chem. Soc. 118 12455 (1996) 423. M Pettersson, J Lundell, L Khriachtchev, E Isoniemi, M RaÈ saÈ nen J. Am. Chem. Soc. 120 7979 (1998) 424. M Yamanishi, K Hirao, K Yamashita J. Chem. Phys. 108 1514 (1998) 425. M Pettersson, J Lundell,M RaÈ saÈ nen J. Chem. Phys. 102 6423 (1995) 426. M Pettersson, J Lundell,M RaÈ saÈ nen J. Chem. Phys. 103 205 (1995) 427. M Pettersson, J Nieminen, L Khriachtchev, M RaÈ saÈ nen J. Chem. Phys. 107 8423 (1997) 428. M Pettersson, J Lundell, L Khriachtchev, M RaÈ saÈ nen J. Chem. Phys. 109 618 (1998) 429. R Kasemann, D Naumann J. Fluorine Chem. 41 321 (1988) 430. H Poleschner, M Heydenreich, K Spindler, G Haufe Synthesis 1043 (1994) 431. Y Usuki, M Iwaoka, S Tomoda Chem. Lett. 1507 (1992) 432. H Poleschner,M Heydenreich, U Schilde Liebigs Ann. Chem. 1187 (1996) 433. K K Laali,W Fiedler, M Regitz J. Chem. Soc., Chem. Commun. 1641 (1997) 434. K Uneyama, M Kanai Tetrahedron Lett. 31 3583 (1990) 435. S Sato, H Arakawa, E Horn, N Furukawa Chem. Lett. 213 (1998) 436. K Alam, A F Janzen J. Fluorine Chem. 27 467 (1985) 437. D Naumann, S Herberg J. Fluorine Chem. 19 205 (1982) 438. J Bergman, L Engman J. Am. Chem. Soc. 103 2715 (1981) 439. A F Janzen, O C Vaidya Can. J. Chem. 51 1136 (1973) 440. J A Gibson, A F Janzen Can. J. Chem. 49 2168 (1971) 441. S A Lermontov, A V Popov, S I Zavorin, I I Sukhojenko, N V Kuryleva, I V Martynov, N S Zefirov, P J Stang J. Fluorine Chem. 66 233 (1994) 442. A H Cowley, R C-Y Lee Inorg. Chem. 18 60 (1979) 443. S A Lermontov, A V Popov, V O Zavel'skii, I I Sukhozhenko, N V Kirilova, I V Martynov. Izv. Akad. Nauk SSSR, Ser. Khim. 682 (1990) a 444. LMYagupol'skii, V I Popov, N V Kondratenko, B L Korsunskii, N N Aleinikov Zh. Org. Khim. 11 459 (1975) g 445. D Naumann, W Tyrra J. Organomet. Chem. 334 323 (1987) 446. I G Rakov, Candidate Thesis in Chemical Sciences, Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, 1997 447. S A Lermontov, D M Rakov, N S Zefirov, P J Stang Phosphorus Sulfur Silicon Relat. Elem. 92 225 (1994) 448. R Minkwitz, B Baeck ACS Symp. Ser. 555 90 (1994) 449. I V Martynov, R G Gafurov, A K Ustinov, N N Aleinikov, S A Kashtanov. Izv. Akad. Nauk SSSR, Ser. Khim. 1437 (1987) a 450. V V Bardin, I V Stennikova, G G Furin, T V Leshina, G G Jakobson Zh. Obshch. Khim. 58 2580 (1988) hV K Brel, N Sh Pirkuliev, N S Zefirov 264 a�Russ. Chem. Bull. (Engl. Transl.) b�Russ. J. Inorg. Chem. (Engl. Transl.) c�Inorg. Mater. (Engl. Transl.) d�Dokl. Chem. Technol., Dokl. Chem. (Engl. Transl.) e�Russ. J. Phys. Chem. (Engl. Transl.) f�Herald Russ. Acad. Sci. (Engl. Transl.) g�Russ. J. Org. Chem. (Engl. Transl.) h�Russ. J. Gen. Chem. (Engl. Transl.) i�Russ. J. Coord. Chem. (Engl. Transl.) j�J. Struct. Chem. (Engl. Transl.) k�Chem. Heterocycl. Compd. (Engl. Transl.) l�Organomet. Chem. (Engl. Transl.) m�High Energy Chem. (Engl. Transl.) n�Russ. J. Appl. Chem. (Engl. Transl.) o�Kinet. Catal. (Engl. Transl.) 451. V V Bardin, H J Frohn J. Fluorine Chem. 90 93 (1998) 452. A P Lothian, C A Ramsden Synlett 753 (1993) 453. G W M Visser, R E Herder, F J J de Kanter, J D M Herscheid J. Chem. Soc., Perkin Trans. 1 1203 (1988) 454. M J Robins, S Manfredini Tetrahedron Lett. 31 5633 (1990) 455. S A Klyuchinskii, M-A M Abid-Albaki, V S Zavgorodnii Zh. Obshch. Khim. 64 161 (1994) h 456. M A Tius, J K Kawakami Synth. Commun. 22 1461 (1992) 457. M A Tius, J K Kawakami Synlett 207 (1993) 458. D P Matthews, S C Miller, E T Jarvi, J S Sarbol, J R McCarthy Tetrahedron Lett. 34 3057 (1993) 459. H F Hodson, D J Madge, D A Widdowson Synlett 831 (1992) 460. M A Tius, J K Kawakami Tetrahedron 51 3997 (1995) 461. M A Tius, G S K Kannangara Tetrahedron 48 9173 (1992) 462. M A Tius, G S K Kannangara,M A Kerr, K J S Grace Tetrahedron 49 3291 (1993) 463. A L J Beckwith, D M O'Shea Tetrahedron Lett. 27 4525 (1986) 464. G A Tolstikov, S K Minsker, Z G Bulgakov, G Ya Maistrenko, A V Kuchin, U M Dzhemilev, V P Kazakov Izv. Akad. Nauk SSSR, Ser. Khim. 2631 (1979) a 465. R G Bulgakov, V N Yakovlev, G Ya Maistrenko, G A Tolstikov, V P Kazakov Izv. Akad. Nauk SSSR, Ser. Khim. 490 (1986) a 466. R G Bulgakov, V N Yakovlev, R A Sadykov, G Ya Maistrenko, V P Kazakov, G A Tolstikov Metalloorg. Khim. 2 339 (1989) l 467. G A Tolstikov, R G Bulgakov, S K Minsker, G Ya Maistrenko, A V Kuchin, U M Dzhemilev, V P Kazakov Khim. Vys. Energ. 15 248 (1981) m 468. V P Kazakov, V N Yakovlev, G Ya Maistrenko Khim. Vys. Energ. 31 133 (1997) m 469. Z Bregar, S Stavber, M Zupan J. Fluorine Chem. 44 187 (1989) 470. Z Bregar,M Zupan, in The 8th International Conference on Organic Synthesis (IUPAC), Helsinski, 1990 p. 123 471. M Zupan, Z Bregar Tetrahedron Lett. 31 3357 (1990) 472. K P Butin, Yu M Kiselev, T V Magdesieva, O A Reutov J. Organomet. Chem. 235 127 (1982) 473. R C Burns, I D MacLeod, T A O'Donnell, T E Peel, K A Phillips, A W Waugh J. Inorg. Nucl. Chem. 39 1737 (1977) 474. A J Blake, R W Cockman, E A V Ebsworth, J H Holloway J. Chem. Soc., Chem. Commun. 529 (1988) 475. M C Crossman, E G Hope, L J Wootton J. Chem. Soc., Dalton Trans. 1813 (1998) 476. S A Brewer, J H Holloway, E G Hope J. Chem. Soc., Dalton Trans. 1067 (1994) 477. S A Brewer, A K Brisdon, J H Holloway, E G Hope, L A Reck, P G Watson J. Chem. Soc., Dalton Trans. 2945 (1995) 478. S A Brewer, J H Holloway, E G Hope, P G Watson J. Chem. Soc. Dalton Trans. 1577 (1992) 479. K S Coleman, J H Holloway, E G Hope J. Chem. Soc., Dalton Trans. 11713 (1997) 480. V P Zubov, S D Stavrova, I P Chikhacheva, O A Prudnikova, G A Fedorova, G B Barsamyan, V B Sokolov Zh. Prikl. Khim. 71 848 (1998) n 481. Yu N Kozlov, A P Moravskii, A M Uskov, A E Shilov Kinet. Katal. 31 251 (1990) o 482. A I Yurtanov, V A Piven', S K Baidildaeva, A V Sliz'kii, V K Brel Zh. Org. Khim. 32 848 (1996) g 483. D L Shellhamer, B C Jones, B J Pettus, T L Pettus, J M Stringer, V L Heasley J. Fluorine Chem. 88 37 (1998) 484. T B Patrick, L Zhang Tetrahedron Lett. 38 8925 (1997) 485. T B Patrick, L Zhang, Q Li J. Fluorine Chem. 102 11 (2000) 486. T B Patrick, S Qian Org. Lett. 2 3359 (2000) 487. R Taylor Izv. Akad. Nauk, Ser. Khim. 852 (1998) a 488. O V Boltalina, A K Abdul-Sada, R Taylor J. Chem. Soc., Perkin Trans. 2 981 (1995) 489. L G Bulusheva, A V Okotrub

ISSN:0036-021X    

出版商:RSC    

年代:2001

数据来源: RSC