摘要:

DALTON PERSPECTIVE J. Chem. Soc., Dalton Trans., 1999, 2249–2264 2249 Fluorine as a structure-directing element in organometallic fluorides: discrete molecules, supramolecular self-assembly and host–guest complexation † Herbert W. Roesky *a and Ionel Haiduc b a Institut für Anorganische Chemie der Universität Göttingen, D-37077 Göttingen, Tammannstrasse 4, Germany. E-mail: hroesky@gwdg.de b Facultatea de Chimie, Universitatea “Babes-Bolyai”, RO-3400 Cluj-Napoca, Str. Arany J. 11, Romania Received 4th March 1999, Accepted 13th May 1999 Although formally monovalent (in the classical sense) fluorine can behave as mono-, di-, tri- or tetra-connective and can be encrypted as a guest in host–guest complexes.The broad limits of valence bonds, spanning the range from below 908 to 1808 (linearity) and a strong tendency to form bi-, tri- and even tetra-metallic bridges, allows the formation of cyclic and cage compounds of very different compositions and structures.The emerging field of organometallic fluorides is a promising area of research. 1 Introduction Fluorine, the first member of the halogen family, is expected to be monocovalent or to form mono anions. Being the most electronegative element, fluorine forms very polar, strong chemical bonds with the non-metals and metalloids and/or ionic compounds with the electropositive metals. Its binary inorganic † Dedicated to Professor F. Albert Cotton. Herbert W. Roesky was born in 1935 in Laukischken.He studied chemistry at the University of Göttingen, Germany, where he obtained his Diploma in 1961 and doctoral degree in 1963. After one year of postdoctoral work at DuPont in Wilmington, DE, he made his habilitation at the University of Göttingen. In 1971 he became full professor in Frankfurt/Main, and since 1980 he has been a full professor and director of the Institute of Inorganic Chemistry at the University of Göttingen. He has been a visiting professor at Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Tokyo Institute of Technology, and Kyoto University and also frontiers lecturer at Texas A&M University at College Station, University of Texas at Austin and University of Iowa at Iowa City.He is a member of the Academy of Sciences at Göttingen, the New York Academy of Sciences, the Academy of Scientists ‘Leopoldina’ in Halle, and the Academia Europaea in London. He served as the vice-president of the German Chemical Society during 1995, and in the period from 1996 to 1998 he was the speaker of Wöhler Vereinigung für Anorganische Chemie.He has received many awards, e.g. the Dr.h.c.(honoris causa) of Bielefeld, Brünn, and Bucharest Universities, Alfred-Stock-Memorial Award, the French Alexander-von- Humboldt award. In 1998 he obtained the Grand Prix de la Maison de la Chimie and very recently (1999), the ACS award for creative work in fluorine chemistry. More than 750 publications, articles, patents, and books document his research activity in the areas of inorganic chemistry and materials science.Ionel Haiduc is professor at “Babes-Bolyai” University, in Cluj-Napoca, Romania. He obtained his PhD in Moscow with Professor K. A. Andrianov with a thesis on organosilicon chemistry, was a Fulbright Postdoctoral Fellow with Professor Henry Gilman at Iowa State University (1966–1968) and with Professor R. Bruce King at the University of Georgia, Athens, Georgia (1971–1972).He was visiting Professor at Instituto de Quimica, Universidad Nacional Autonoma de Mexico (1993–1994), University of Texas at El Paso (1997) and Universidad de Santiago de Compostela, Spain (1998). He received a Humboldt Fellowship for a research visit to Universität Magdeburg, Germany (1997) and the Gauss Professorship of the Akademie der Wissenschaften in Göttingen, Germany (1998). He also received visiting grants from the National Science Foundation (USA, 1992), European Community (Spain, 1993) and British Council (United Kingdom, 1995) and a NATO Cooperative Research Grant (United Kingdom, 1997).He has authored or co-authored several books (including The Chemistry of Inorganic Ring Systems, 1970, The Chemistry of Inorganic Homo- and Heterocycles, 1987, Basic Organometallic Chemistry, 1985, Organometallics in Cancer Chemotherapy, 1989, 1990 and Supramolecular Organometallic Chemistry, 1999 in press) and more than 250 research papers and several chapters in some multi-authored books.His interests cover inorganic ring systems, Main Group organometallic and coordination chemistry, organophosphorus and organoarsenic ligands and supramolecular organometallic chemistry. He participated in an extensive international collaboration with colleagues from the United Kingdom, Germany, Spain, Mexico, Belgium, United States of America, Brazil, Canada and France, which resulted in numerous joint publications.After the anticommunist revolution in Romania (December 1989) he was elected and served as Rector (President) of “Babes-Bolyai” University (1990–1993), and in 1998 was elected vicepresident of the Romanian Academy. Herbert W. Roesky Ionel Haiduc2250 J. Chem. Soc., Dalton Trans., 1999, 2249–2264 compounds are either molecular fluorides EFn or insoluble solids (in which F2 anions alternate with metal cations to form usually tridimensional networks). Between these two extremes, there are some associated compounds, such as tetrameric, cyclic transition metal pentafluorides, [MF5]4 (M = Nb, Ta, Mo) and polymeric antimony pentafluoride, [SbF5]n, in which the fluorine atoms form bridges,1 thus showing that in covalent bonds, the fluorine retains some Lewis base (donor) properties, resulting in an increase of its connectivity.We will use throughout this article the term connectivity to describe the number of links to other atoms, to avoid any implications about the nature of the bonds (covalent, coordinative, ionic or secondary interactions).Until relatively recently, organometallic chemists avoided fluorine for several reasons. One of them was probably the fact that alkyl and aryl fluorides, unlike other halides, do not react directly with active metals, such as magnesium to give Grignard reagents, or lithium, to give organolithium reagents, both extremely useful precursors in organometallic syntheses. The exchange of other halogens for fluorine was generally hampered by the lack of convenient reagents.With a few early exceptions, only in recent years have organometallic fluorides entered the stage and became an attractive field of research. Main group,2 d-block element 3 and f-element 4 organometallic fluorides are covered by some recent reviews. During recent years, not only have a large number of organometallic fluorides been synthesised, but numerous molecular and crystal structures have been determined by X-ray diVraction. An overview of the known structures of organometallic fluorides reveals the fact that fluorine plays an important role as a structure directing element, and its bonding patterns are much more diversified than one would expect from a monocovalent element.These patterns can be classified according to the connectivity of fluorine and its role in the molecular architecture of organometallic fluorides. Thus the following types can be distinguished (Scheme 1): (a) Monoconnective fluorine, forming ‘terminal’ polar covalent bonds.(b) Biconnective fluorine, forming symmetric or asymmetric bridges, which can be linear or bent. (c) Triconnective fluorine, in either a pyramidal or planar geometrical arrangement. (d) Tetraconnective fluorine, mostly tetrahedral. (e) Ionic fluorine encapsulated in cage-like hosts. All these sub-units may serve as building blocks for a broad diversity of chemical architectures.The similarity of bonding modes of fluorine with those known for a dicovalent element, oxygen, is striking. Oxygen forms similar building blocks. There is, however, a diVerence. Scheme 1 M M F M F M F M M M F M M F M M F M M F M M M M M F– M M M F– M M M M M M - encapsulated ionic: - tetraconnective: planar pyramidal - triconnective: asymmetric symmetric - bent: - linear: asymmetric symmetric - biconnective (bridging): - monoconnective (terminal): M F M Oxygen forms two covalent bonds, but in the case of fluorine, only one of the bonds can be described as covalent, the second and successive ones are coordinative bonds.Sometimes the coordinative bond character is maintained, leading to asymmetric bridges, but bond equalisation may occur and in the symmetric bridge the two bonds are the result of mixing covalent and coordinative bonds. The consequence will be an increase in the interatomic distance, in comparison with the terminal (monoconnective) M–F bonds.When fluorine becomes tri- or tetra-connective the contribution of coordinative bond character is still higher, and some further lengthening of the M–F bonds may be expected. The consequences of the diversity in connectivity patterns of fluorine will be discussed further. Monoconnective fluorine leads to the formation of discrete molecules, in which it is just another monovalent substituent. The formation of bridges between fluorine as donor and various atoms as acceptors, results in intermolecular self-assembly, with formation of cyclic and cage supermolecules or supramolecular arrays.Thus, the chemistry of organometallic fluorides steps into the field of supramolecular chemistry. Since reference was made to supramolecular chemistry, perhaps it is useful to remember some definitions and concepts which will be used throughout this article in the presentation of organometallic fluorides. Supramolecular chemistry is ‘the chemistry of molecular assemblies and of the intermolecular bond ’. It is ‘the chemistry beyond the molecule’ and deals with ‘organised entities of higher complexity that result from the association of two or more chemical species held together by intermolecular forces’.5,6 There are two types of subjects in supramolecular chemistry: (a) the supramolecular assemblies or systems, also called supramolecular arrays, i.e.‘polymolecular entities that result from the spontaneous association of a large undefined number of components’, and (b) supermolecules or supramolecular arrays i.e.‘well-defined discrete oligomolecular species that result from the intermolecular association of a few components’.7 Chemical bonds in fluorine chemistry are not limited to covalence. Very important are the coordinative bonds. In addition to normal covalent bonds, E–F, which are formed by pairing of the free p-electron of the fluorine atom, with an electron of the partner element, the monocovalent fluorine can participate in additional coordinative bonds, FÆE, formed by donation of an electron pair from fluorine to an acceptor atom, thus forming an M–FÆM bridge.There is a general tendency to assume that the two-electron bonds between a certain pair of atoms are identical, regardless of the origin of electrons (i.e. covalent and coordinative), but it has been pointed out that a distinction between the two types should be made.8,9 In practise, however, it is often impossible to diVerentiate between the two bonding modes.The normal covalent and coordinative bonds diVer in several major aspects: (a) the nature of the fragments formed when the bonds are broken; (b) the nature of the bond rupture process and (c) the magnitude of the bond cleavage enthalpy. The normal covalent bond ruptures homolytically and the neutral species formed are free radicals; the coordinative bond rupture proceeds in general heterolytically, with the formation of neutral diamagnetic molecules.When an electron pair donor and an acceptor site are present in the same molecule, and the molecular compound is coordinatively unsaturated, intermolecular association may occur with formation of cyclic (or polymeric) species. This frequently occurs in organometallic compounds,10 including fluorides. The process is called self-assembly. Self-assembly is defined as a spontaneous association of molecules under equilibrium conditions into stable aggregates held together by non-covalent forces.11 The resulting species is a supermolecule (see above).Numerous monomeric organometallic fluoride molecules are able to self-assemble into cyclic supermolecules or sometimesJ. Chem. Soc., Dalton Trans., 1999, 2249–2264 2251 into supramolecular polymeric arrays. However, most of the compounds characterized in the following sections are not under equilibrium conditions. 2 Discrete molecules 2.1 Monoconnective fluorine (terminal bonds) There are some organometallic compounds containing one or more fluorine atoms singly bonded to a central metal atom as single, covalent, terminal bonds in discrete, unassociated molecules.This monoconnective fluorine bonding is not particularly interesting, but the terminal covalent bonds are useful in estimating the standard M–F bond lengths. Table 1 contains a list of terminal M–F bond lengths measured in a number of organometallic compounds. They can serve for comparisons with M–F interatomic distances in bridging fluorine units. 2.2 Dinuclear compounds with bridging fluorine The simplest consequence of biconnective binding of fluorine is the formation of dinuclear compounds with fluorine bridging two identical or diVerent metal atoms. As shown above, there are four types of bridges, because both symmetric and asymmetric, linear and bent geometries are possible. When the two atoms bridged by fluorine are diVerent, asymmetry is most likely.A particular case of fluorine bridging results from the coordination of some fluoro anions, such as [BF4]2, [PF6]2, [AsF6]2 or [SbF6]2, which have the reputation of being weakly coordinating anions.59,60 However, they can be attached to metal atoms through M–F–E (E = B, P, As, Sb) bridges, showing that even in non-metal covalent compounds some terminal E–F bonds retain donor capacity. 2.2.1 Symmetric linear bridges. A linear symmetric bridge (Scheme 2) was first identified in dialuminium anions [R3Al–F– AlR3]2 1 (R = Me, Et) by X-ray diVraction analysis of a compound initially formulated as KF?2AlEt3,61 and later found also in K[Me3Al(m-F)AlMe3]?C6H6.62 The Al–F–Al bond angle is 1808 in both compounds, and the Al–F bond lengths are 1.820(3) Å in the ethyl derivative and 1.782(2) Å in the methyl derivative, significantly longer than terminal Al–F bonds (ca. 1.65 Å). The linear anion [Me3Al–F–AlMe3]2 is isoelectronic but not isostructural with the bent molecule of hexamethyldisiloxane, Me3Si–O–SiMe3 [Si–O–Si 148.8(1)8].63 Only hexaphenyldisiloxane, Ph3Si–O–SiPh3, is linear.64 A linear fluorine bridge is present in triphenyltin fluoride, which is a rod-like polymer [Ph3Sn(m-F)]x 2, with identical Sn–F interatomic distances of 2.1458(3) Å.65 Similar linear (rod-like) structures are those of [(PhCH2)3Sn(m-F)]x 66 and [(Me3SiCH2)3- Sn(m-F)]x (2.565 Å).67 In other triorganotin fluorides the Sn–F– Sn bridges are asymmetric and bent (see below). 2.2.2 Symmetric bent bridges. Symmetric bent bridges seem to be imposed by metal–metal bonds, leading to the formation of a three-membered ring (Scheme 3). Thus, in [Mn3- (CO)9(m-OEt)2(m-F)] 3 the fluorine bridge connecting two manganese atoms of a Mn3 cluster is symmetric (within experimental error) but bent [Mn–F 1.93(2) and 1.97(2) Å; Mn– F–Mn 93(1)8].68 Other examples of basically symmetric bridges are provided by the fluoride complex of o-bis(chlorodimethyl- Scheme 2 Sn F Sn Ph Ph Ph Ph Ph Ph F Al F Al R R R R R R 2 1 x – stannyl)benzene, [o-(ClMe2Sn)2C6H4?F)]2 4, [with Sn–F–Sn 119.56(13)8, Sn–F 2.139(3) and 2.213(3) Å],69 or of a complex m3-oxo-tris(dimethyltin)bis(salicyladoximate) [Sn–F 2.231(8) and 2.185(7) Å],70 and in the fluoride complexes of bis(halogenodiphenylstannyl)- methane 5 and -ethane 6, [{(CH2)n(SnPh2- X)2}F]2, [n = 1, X = F, bridging Sn–F 2.249(2) and 2.204(2) Å, terminal Sn–F 1.995(2) and 2.004(2) Å; n = 1, X = Br, bridging Sn–F 2.212(5) and 2.274(5) Å; n = 1, X = I, bridging Sn–F 2.231(4) and 2.248(4) Å; n = 2, X = Cl, bridging Sn–F 2.178(4) and 2.197(4) Å],71 and in the dimeric difluorodistannoxanes, [(FSnBut 2)2O]2 7.72 2.2.3 Asymmetric linear bridges.Several dinuclear compounds with asymmetric M–F ? ? ? M bridges are known and are illustrated in Scheme 4. In tricyclohexyltin fluoride 8, which is a polymeric supramolecular array in the solid state, [Cy3Sn(m- F)]x, the fluorine bridge is linear and asymmetric with Sn–F 2.051(10) and 2.303(10) Å.73 Another asymmetric linear bridge is observed in the antimony compound Ph2SbBr2(m-F)SbPh2Br3 9 [Sb–F 2.077(7) Å and Sb ? ? ? F 2.343(7) Å, Sb–F ? ? ? Sb 174.74(7)8].74 The asymmetry in this compound may result from the association of two sub-units with diVering substituents and coordination Scheme 3 Mn Mn F Mn O O OC OC OC CO CO CO OC CO CO Et Et Sn F Sn Cl Cl Me Me Me Me Sn Sn F X X Ph Ph Ph Ph Sn O Sn F O Sn Sn F R R F R R R R R Sn Ph Ph Sn Ph Ph Cl Cl F R F 6 – 7 5 4 3 R = But X =F, Br, I – – Scheme 4 Sn F Cy Cy Cy Sn F Cy Cy Cy Sb Br Br Ph Ph Br Sb Br Ph Br Ph F F Bi F C6F5 C6F5 Bi Bi C6F5 C6F5 C6F5 C6F5 C6F5 C6F5 C6F5 Yb Cp* Cp* F Yb Cp* Cp* Ti O O Ti O Ti O Ti F Cp* F F Cp* F Cp* Cp* AlMe3 Me3Al Me3Al AlMe3 12 11 10 9 8 x2252 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 Table 1 Interatomic distances in terminal M–F bonds M–F distance/Å Compound Ref. Al–F Ga–F Ge–F (5-coordinate Ge) Ge–F (6-coordinate Ge) Sn–F (4-coordinate Sn) Sn–F (4-coordinate Sn) Sn–F (4-coordinate Sn) Sn–F (5-coordinate Sn) Sn–F (6-coordinate Sn) Ti–F Zr–F V–F Nb–F Ta–F Mo–F W–F 1.653(2) 1.666(2) 1.838(3) 1.804(4) 1.815(4) 1.824(2) 1.833(2) 1.957(2) 1.956(6) 1.948(7) 1.975(6) 1.965(8) 1.965(2) 2.041(5) 2.049(5) 2.126(3) 2.121(5) 2.135(4) 1.823(1) 1.815(2) 1.832(2) 1.838(2) 1.838(3) 1.836(2) 1.845(5) 1.856(2) 1.807(4) 1.870(5) 1.845(4) 1.838(4) 1.98(1) 2.212(6) 2.012(3) 1.991(3) 2.182(2) 1.946(3) 1.944(3) 1.948(3) 1.960(3) 1.760(4) 1.755(4) 2.002(2) 1.920(8) 1.906(8) 1.910(2) 2.199(5) 1.960(2) 1.970(2) 1.931(2) 1.933(2) 1.924(4) 1.906(4) 1.925(12) 1.874(12) 2.059(13) 2.016(11) 2.059(13) 1.807(13) 1.906(4) 1.918(3) 1.924(4) 1.901(3) 1.910(3) 1.947(3) 1.981(4) 2.055(3) 1.925(1) 1.87(2) 1.90(2) 1.87(2) 1.91(2) 1.858(5) 1.855(5) 1.915(8) AlF2N(2,6-Pri 2C6H3)(SiPriMe2) [GaF(Mes)2(ButNH2)] [Me4N][GeF2(CF3)3] K2[GeF4(CF3)2-cis] SnF(Mes)3 SnF3{C[C6H3(OMe)2-2,6]3} SnFPh2C(SiMe3)3 SnFMe2C(SiMe2Ph)3 [Et4N][SnFMe2(OC6H4S-2)] [SnFBut 2(m-OH)]2 [NH4]2[SnF4Me2-trans] [TiF(C5Me4Et)(OSiBut 2O)]2 [TiF(C5H4Me)(OSiBut 2O)]2 TiF2{C5H3(SiMe3)2-1,3}2 TiF2{C5H4(SiMe3)}{C5H2(SiMe3)3-1,2,4} TiF(Cp)2{OC5(CF3)4} [TiF(C5Me4Et)(NSnMe3)]2 [TiF(m-O)(C5Me5)]4 TiF2(Cp*)[(Me3SiN)2CC6H4(OMe)-4] TiF2(Cp*)NPPh3 {TiF2(Cp*)NPPh2}2C2H2 TiIIIF(Cp*)2 ZrF2(Cp)2 ZrF2{C5H3(SiMe3)2}2 ZrF(Cl)(C5Me4Et)2 ZrF(Cl)(Cp*){N(SiMe3)C6H3Pri 2-2,6} ZrF2{N(SiMe3)C6H3Pri 2-2,6}2 VF2O(NPPh3) [FP(NEt2)3][VF(Mes)3] [NbF2(C5Me4Et)2][PF6] [NbF(C5H4Me)(CH2SiMe3)] [PF6] [NbF(C5H4SiMe3)(Ph2HCCNPh)][PF6] [Et3NH][TaF5(Cp*)] TaF4(Cp*) [TaF2(Cp*)2][BF4] TaF4(Cp*)?HNPPh3 TaF3(Cp*){OC(Ph)CHC(Ph)O} TaF3(Cp*){(Me3SiN)2CC6H4(OMe)-4} [MoF(PhCCH)(dppe)2][BF4] [NEt4][MoF(CO)2(S2CNEt2)] WF5(Cp*) WF5{NS(O)Me2} 12 13 14 15 16 17 18 18 19 20 21 22 22 23 23 24 25 26 27 27 27 28 29 30 31 32 33 25 34 35 36 37 38 39 39 40 41 42 43 44 45 46J.Chem. Soc., Dalton Trans., 1999, 2249–2264 2253 Table 1 (Contd.) M–F distance/Å Compound Ref. 1.880(5) WF4{NS(O)Me2}2 46 1.919(6) 1.857(6) 1.964(6) 2.044(3) WF(H)(C6H5Me)(dmpe) 47 Re–F 2.134(3) [ReF(CCH2CBut)(dppe)2][BF4] 48 1.97(1) [ReF(CO)(NO)(PPh3)3] 49 Ru–F 2.011(4) [RuF2(CO)2(PPh3)2] 50 Ir–F 1.998(3) 2.069(4) 2.089(4) 2.21(4) [IrF(CO)2(PEt3)2{C(O)F}][BF4] IrF(Ph)(PMe3)(C5Me4Et) IrF(Cl)(CO)(NSF2)(PPh3)2 [IrF(CO)(PPh3)2(NH]] NC6H3CF3-2)][BF4] 51 52 53 54 Pd–F 2.085(3) PdF(Ph)(PPh3)2 55 Pt–F 2.03(1) PtF(PPh3)2{CH(CF3)2} 56 Yb–F 2.015(4) 2.026(2) YbF(Cp*)2?Et2O YbF(Cp*)2?THF 57 57 U–F 2.106(12) UF(Cp)3 58 geometries: a square pyramidal Ph2SbBr3 molecule as acceptor and a trigonal bipyramidal Ph2SbBr2F molecule as donor.The bismuth compound (C6F5)3Bi(m-F)2?2Bi(C6F5)3 10 is formed by association of a trigonal bipyramidal (C6F5)3BiF2 sub-unit with two trigonal pyramidal (becoming distorted tetrahedral) Bi(C6F5)3 molecular sub-units, and the bridges are asymmetric [Bi–F 2.088(8) Å and Bi ? ? ? F 2.759(8) Å].75 The origin of asymmetry of the bridge in (C5Me5)2YbII- (m-F)YbIII(C5Me5)2 11 seems to be due to the diVerent oxidation states of the metal.In the linear Yb–F ? ? ? Yb bridge the interatomic distances are YbIII–F 2.084(2) Å and YbII ? ? ?F 2.317(2) Å.76 A peculiar case of a heterometallic bridge observed in [Cp*TiO(m-F)AlMe3]4 12 should be mentioned. In this compound, the terminal Ti–F bonds of the parent ring compound [Cp*Ti(O)F]4 connect AlMe3 molecules through strong F–Al bonds, forming basically symmetric linear bridges: Ti–F 1.9593(13), 1.9728(13), Al–F 1.8960(14), 1.8894(14) Å, Al–F– Ti 175.90(8)8 and 175.62(8)8.77 It seems that the asymmetry of the fluorine bridges can be caused by the steric demand of the groups attached to the metal (like in tricyclohexyltin fluoride) or by the non-equivalence of the molecular sub-units connected through the bridge.The non-equivalence may be due to diVerent substitution, diVerent oxidation states and/or diVerent coordination geometries of the metal centres.The fluorine atom is very flexible in terms of its bonding capabilities and adapts its bridging behaviour to each particular case. 2.2.4 Asymmetric bent bridges. Some asymmetric bent fluorine bridges are illustrated in Scheme 5. An early crystal structure determination of trimethyltin fluoride suggested a polymeric structure 13 with an asymmetric bent Sn–F ? ? ? Sn bridge (Sn–F 2.2 and 2.6 Å, Sn–F ? ? ? Sn not reported).78 The fluorine atoms are said to be disordered.In view of the importance of trimethyltin fluoride as a key compound in organometallic fluoride chemistry it would be useful to redetermine its crystal structure at low temperature. A clearly unsymmetric Sn–F ? ? ? Sn bridge was found in the compound N(CH2CH2CH2)3SnF?H2O 14, which is a tetramer held together by tin–fluorine bonds [intramolecular Sn–F 2.115(6), intermolecular Sn ? ? ? F 2.797(6) Å, Sn–F ? ? ? Sn angle 151.4(2)8], weak tin–oxygen bonds [Sn ? ? ? O 3.180(8) Å] and hydrogen bonds (O–H ? ? ? F).79 The rhenium carbonyl fluoride Re(CO)5F?ReF6 15 contains two independent molecules in the crystal, both with bent (but slightly diVerent) Re–F ? ? ?Re bridges: Re–F 1.98, Re ? ? ?F 2.13, terminal Re–F 1.78–1.93(3) Å, Re–F ? ? ?Re 142.0(1.4)8, and Re–F 1.95(2), Re ? ? ? F 2.20(2), terminal Re–F 1.84–1.88(3) Å, Re–F ? ? ?Re 138.8(1.2)8.80 When the metal atoms connected by a fluorine bridge are diVerent the asymmetry is not a surprise.It seems that the bending of the bridge is also to be expected. Thus, in [Cp*Zr(acac)2- (m-F)SnMe3Cl] 16 there is a normal, short Zr–F bond [2.030(2)] and a long Sn ? ? ? F bond [2.462(2) Å]. The bending angle of the Zr–F ? ? ? Sn bridge is 146.0(1)8.81 2.2.5 The case of weakly coordinating fluoro anions. The weakly coordinating anions, being good leaving groups, are important in synthesis and catalysis, since they are readily replaced by more powerful donor ligands or by reacting substrates. 60 Anions such as [BF4]2, [PF6]2, [AsF6]2 and [SbF6]2 fall into this category. They are present in numerous organometallic compounds as discrete anions, but in certain cases they can coordinate to coordinatively unsaturated metal centers,59 by forming asymmetric linear or bent M ? ? ? F–E bridges (M = metal, E = B, P, As, Sb). It is remarkable that the coordination of these anions may display various patterns.Thus, tetrafluoroborate can coordinate as monodentate monoconnective 17, monodentate triconnective 18, chelating 19 or bridging 20; a monodentate biconnective coordination 21 still awaits discovery (Scheme 6). Monodentate monoconnective type coordination is found in [Ph3PCH2SnBut 2F(FBF3)] 22, [Ph3PC(]] CH2)SnBut 2F(FBF3)] Scheme 5 Zr Cp* F Sn O R R O O R R O R R R Cl F Re Re F F F F F OC OC CO CO OC Sn Me MeMe Sn Me Me Me F Sn Me Me Me F F N Sn F N Sn F O H O H O H H H H H O H Sn F N Sn F N 16 15 14 13 R = Me2254 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 Table 2 Weakly coordinating anions with M ? ? ? F–E bridge Compound Bond M? ? ?F distance/Å ? ? ? F–E (bridging)/Å E–F (terminal)/Å M? ? ? F–E angle/8 Ref. Tetrafluoroborates F–B B–F 22 23 24 25 26 27 28 Sn ? ? ?F bridging terminal Sn ? ? ?F bridging terminal W? ? ?F W? ? ?F Ir ? ? ?F Pd ? ? ?F Re ? ? ?F 2.782(3) 2.027(3) 2.853(4) 1.972(2) 2.168(7) 2.15(2) 2.272(3) 2.355(5) 2.138(7) 2.146(7) 1.393(7) 1.394(4) 1.500(14) 1.45(5) 1.448(6) 1.336(7) 1.503(2) 1.347(7) 1.338(9) 1.324(7) 1.382(4) 1.344(5) 1.325(5) 1.316(18)–1.386(16) 1.28(5)–1.43(5) 1.329(9)–1.340(8) 1.315(8)–1.419(9) 1.395(16) 1.338(13) 141.9(3) n.a. 104.1(1) 141(2) 125.7(3) 141.9(4) 82 82 83 84 85 86 87 Hexafluorophosphates F–P P–F 29 30 W? ? ?F Ag ? ? ?F 2.187(10) 2.668(4) 1.733(11) 1.562(17) 1.550(13)–1.585(13) 1.505(18) 1.508(13) 142.4(6) n.a. 83 88 Hexafluoroarsenates F–As As–F 31 32 Ti ? ? ?F V? ? ?F 2.00(1) 2.03(1) 1.80(1) 1.78(1) 1.64(1)–1.66(1) 1.63(1)–1.67(1) 178.0(5) 173.2(5) 89 90 Hexafluoroantimonates F–Sb Sb–F 33a 33b W? ? ?F W? ? ?F 2.169(11) 2.186(3) 1.954(11) 1.979(3) 1.855(12)–1.878(12) 1.832(4)–1.68(4) 147.2(6) 138.9(2) 83 83 n.a.= not available 23,82 [W(NO)(CO)3(PMe3)(FBF3)] 24,83 [WH(CO)3(PCy3)- (FBF3)] 25,84 [IrH(PPh3)2(CO)(Cl)(FBF3)] 26,85 and [Pd{h2- C5Et5)C(Et)CH2C9H6N}(FBF3)] 27.86 The compounds are shown in Scheme 7. Bond distances and bond angles are collected in Table 2.The monodentate triconnective mode 18 is rare, and has been found only in the anion [Re3H2(CO)9(FBF3)]22 28 (tetraethylammonium salt) [Re–F 2.138(7), 2.146(7), bridging B–F 1.503(21), terminal B–F 1.395(16), 1.338(13) Å].87 The chelating mode 19 has been observed in [(Mes)2In][BF4], where in fact double chelating leads to the formation of a polymeric, supramolecular structure (see Section 3.3). The biconnective bridging mode 20, leading to cyclic or polymeric supramolecular assemblies, is also illustrated in Section 3.3.The hexafluorophosphate anion coordinates as monodentate monoconnective in [W(PMe3)(CO)3(NO)(FPF5)] 29,83 and the chelating mode in [{2,4,6-But 3C6H2NC}2Ag(F2PF4)] 30 (Scheme 8).88 Hexafluoroarsenate coordinates as monoconnective, forming a basically linear bridge in Cp2Ti(FAsF5)2 31 [Ti ? ? ? F–As 178.0(5)8],89 and in Cp2V(FAsF5)2 32 [V? ? ? F–As 173.2(5)8].90 The coordination of [SbF6]2 is also monoconnective in [W(PMe2Ph)(CO)3(NO)(FSbF5)] 33a and [W(PCy3)(CO)3(NO)- (FSbF5)] 33b.83 It is apparent that the weakly coordinating anions prefer soft metal centers in low oxidation states (with the simultaneous presence of p-acceptor ligands) 59 and the coordination is favoured when the coordination center is a bent metallocenium cation, with ample vacant space for the incoming anion.When the metal center is coordinatively saturated, the [EFn]2 anions do not coordinate and occur as discrete species, compensating the positive charge of a complex.Scheme 6 F B F F F M BF3 F M M M B F F F F M M F B F M F F BF3 F M M 21 20 19 18 17 3 Supramolecular self-assembly Fluorine bridging can be the source of a broad variety of complex structures which can be described as supramolecular. Molecules that contain simultaneously donor fluorine sites and acceptor (coordinatively or electronically) unsaturated metal sites, self-assemble into oligomeric supermolecules or polymeric supramolecular arrays.The simplest are the cyclic supermolecules followed by cages and host–guest architectures. In the latter, fluorine can be both the principal component of a Scheme 7 a Hydrogen atoms and charge are omitted. F Sn But But PPh3 F BF3 F F3B PPh3 CH2 Sn But F But W F CO CO Me3P OC NO BF3 BF3 F Re Re(CO)3 (CO)3Re W F H CO Cy3P OC CO BF3 Ir F PPh3 CO Ph3P Cl H BF3 N Pd R F BF3 R R R R R 27 25 26 28 a 24 23 22 (CO)3 R = EtJ. Chem. Soc., Dalton Trans., 1999, 2249–2264 2255 complex host molecule (acting as donor) or can be the host in a molecule of appropriate structure.The bending of the fluorine bridge allows cyclisation. The formation of four-, six- or eight-membered rings is the prerequisite for the fulfillment of specific geometric requirements, in terms of bond angles and steric crowding. Biconnective fluorine can display a wide range of bond angles, from small values required for the formation of four-membered rings, to wide angles allowed by non-planar eight-membered rings.Therefore, a broad variety of monocyclic structures are possible, depending to a great extent on the steric crowding of the metal site. Large, bulky organic substituents at the metal sites favour the formation of small, four-membered rings. With less crowded metal sites trimeric (six-membered) rings and tetrameric (eightmembered) rings can be formed. The four-, six- and eightmembered MnFn rings (n = 2, 3 and 4) will also be found as building blocks of polycyclic cages.Triconnective fluorine, with non-planar distribution of the three M–F bonds, provides the Gaussian curvature required for closing of spatial objects, and thus, polycyclic cages can be formed. There are a large number of such cages with triconnective oxygen and nitrogen atoms at the corners of various polycyclic cages, e.g. in metallasiloxanes, aluminium and gallium phosphonates, aluminium–nitrogen or tin–oxygen cages, to cite only a few examples. The development of a rather similar chemistry of cages containing triconnective fluorine is in full swing now, and many fascinating new structures can be expected. 3.1 Four-membered rings, M2F2 The number of known dimeric supermolecules based on fourmembered M2F2 rings is already quite impressive. A selection of such compounds is illustrated in Schemes 9 and 10 and molecular parameters (bond lengths and bond angles) are collected in Table 3. In all these compounds the basic skeleton is a four-membered rhomboidal ring with slightly unsymmetric bond lengths and acute bond angles at the metal site and bond angles slightly larger than 908 at fluorine.In certain cases, the M2F2 ring is spanned by a chelating bridge, e.g. acetate 43 and 44. Four-membered rings are formed both in very ionic compounds like caesium organofluorometalates, e.g. [Cs(m-F)Ga- (Mes3)(MeCN)2]2 34 (Mes = 1,3,5-trimethylbenzene), [Cs(m-F)- (MeCN)Ga(CH2Ph)3]2 35 or [Cs(m-F)In(Mes)3(MeCN)2]2 36 in which Cs2F2 rather than Ga2F2 or In2F2 rings are present 91 and in strongly covalent compounds like [(Mes)2Ga(m-F)]2? THF 37 which contains Ga2F2 rings.92 A large number of Scheme 8 W CO CO OC Me3P NO P F F F F F F Ag C C RN NR P F F F F F F Cp Ti Cp As F F F F F F As F F F F F F Cp V Cp As F F F F F F As F F F F F F Sb F F F F F W CO CO R3P ON CO F b PR3 = PCy3 a PR3 = PMe2Ph 33 32 31 30 29 compounds contain the Ti2F2 ring 38–45,93 but similar rings containing zirconium 47, 48,94,95 niobium 49,96 tantalum 50,97 molybdenum 51, 52,98 tungsten 53 99 and even mercury 54100 are known. 3.2 Six-membered rings, M3F3 Six-membered rings of varying conformations and with large M–F–M bond angles (in the range between 130 and 1538) and small F–M–F bond angles (in the range between 85 and 938) are known in some organometallic fluorides (Scheme 11). The sixmembered Al3F3 ring in [F2AlN(SiMe3)(C6H3Pri 2-2,6)]3 55, is planar,101 whereas in [F2AlC(SiMe3)3]3 56 the six-membered ring displays a flat-boat conformation.102 A distorted boat conformation is also displayed by the six-membered In3F3 ring in [(Mes)2InF]3 57,13 whereas in [Cp2ScF]3 58103 and in [(ButC5H4)2SmF]3 59 the rings are basically planar.104 It seems that the ring conformation is imposed by the steric requirements of the organic groups and the remarkable flexibility of the M–F–M bond angles can accommodate very diVerent organometallic building units for self-assembly into a cyclic, trimeric structure.Important molecular parameters are collected in Table 4. The structures of self-assembled organometallic fluoride trimers are reminiscent of the numerous six-membered metal–oxygen rings [e.g. cyclo-trititanoxanes 60105,106 and cyclotrizirconoxanes 61 107] (Scheme 12) which are also known to display a variety of conformations. The bond angles at oxygen are, however, not so wide open in the six-membered rings mentioned and they tend to stay closer to the ideal value of 1208.A bicyclic system, consisting of two fused six-membered Scheme 9 Cs F F Cs GaMes3 GaMes3 MeCN MeCN NCMe NCMe Cs F F Cs Ga(CH2Ph)3 Ga(CH2Ph)3 MeCN NCMe Ga F F Ga Mes Mes Mes Mes Ti F F Ti F F F F Cp* Cp* Ti F F Ti F F F F Cp# Cp# F Ti Ti F O O O O Cp* F F Cp* CF3 CF3 Cs F F Cs InMes3 InMes3 MeCN MeCN NCMe NCMe Ti Cp Ti F Cp F O O O Ti O F F Ti F Cp* F Cp* Et Et Ph Et Et Ph O Ti F Cp' F Ti Cp' F F F F F Ti Ti F O O O O Cp* F F Cp* C6F5 C6F5 36 35 34 37 40 39 38 44 43 42 41 = C5H4Pri Cp# = C5H4Me Cp'2256 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 Table 3 M–F bond lengths and bond angles in M2F2 four-membered rings Compound M–F bridging/Å M–F terminal/Å Endocyclic M–F–M/8 Angles F–M–F/8 Exocyclic M–F–M9/8 Ref. 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Cs–F Cs–F Cs–F Ga–F Ti–F Ti–F Ti–F Ti–F Ti–F Ti–F Ti–F Ti–F Ga–F Ti–F Zr–F Zr–F Nb–F Ta–F Mo–F Mo–F W–F Hg–F 2.880(5) 3.207(6) 2.838(2) 2.872(2) 2.852(2) 3.040(2) 1.947(2) 2.046(4) 2.047(4) 2.002(3) 2.021(3) 1.940(2) 2.170(3) 2.022(2) 2.030(2) 2.015(1) 2.028(1) 1.976(1) 2.083(1) 2.072(2) 1.985(2) 2.097(2) 1.974(2) 1.912(2) 2.106(2) 2.145(2) 2.142(7) 2.147(4) 2.145(4) 2.137(4) 2.040(3) 2.178(3) 2.044(5) 2.195(6) 2.206(5) 2.151(4) 2.095(6) 2.148(9) 2.156(8) 2.13(1) 2.15(1) 2.126(4) 2.146(3) 2.127(4) 2.077(3) 2.124(3) 2.126(3) 2.395(7) 2.418(7) 1.903(5) 1.864(2) 2.113(2) 1.822(3) 1.833(3) 1.829(2) 1.820(2) 1.821(2) 1.815(2) 1.822(1) 1.829(2) 1.967(3) 1.985(2) 1.964(3) 1.945(3) 1.906(3) 1.896(3) 1.900(5) 1.901(5) 1.909(8) 93.6(1) 95.15(7) 97.74(5) 101.1(2) 101.4(2) 101.5(2) 110.0(1) 109.9(1) 105.31(7) 104.28(7) 110.20(7) 107.59(6) 107.18(7) n.a.n.a. n.a. n.a. 108.2(2) 108.7(2) 110.5(1) 112.1(2) 111.8(2) 97.1(1) 97.1(2) 103.0(4) 102.1(4) 97.7(1) 99.8(2) 98.3(1) 97.6(2) 86.4(1) 84.5(6) 82.26(5) 78.9(1) 75.9(2) 75.9(2) 70.0(1) 70.1(1) 72.21(6) 69.80(7) 72.41(6) 72.82(7) 75.6(1) 78.4(1) (FGaF) 70.0(1) (FTiF) 88.6(1) 71.49(13) 71.64(13) 69.5(1) 68.2(2) 67.9(2) 70.1(2) 68.8(2) 69.8(4) 70.5(4) 68.6(1) 69.1(1) 68.1(1) 69.1(1) 69.9(1) 67.7(2) 82.4(2) 109.7 156.4 119.8 132.9 109.41(7) 152.75(9) 93.08(8) 151.36(6) 78.96(5) 151.36(8) 79.83(7) 91 91 91 92 93(a) 27 27 93(b) 93(c) 93(d) 93(d) 93(e) 93(e) 94 95 96 97 98(a) 98(b) 98(c) 99 rings, is present in the chromium compound [Cr4(Cp*)4(m-F)5- Cl2]PF6 62.Two views of the bicyclic cation are illustrated in Scheme 13.108 Alternatively, the bicylic system can be also described as an eight-membered Cr4F4 ring spanned by a transannular fluorine bridge.This structure is analogous to that of a borate anion [B4O5(OH)4]22 (borax) 63. A polymeric array 64 made up of Sn3F3 rings [terminal Sn–F 2.026(3), bridging Sn–F 2.147(1), 2.272(2) and 2.115(3) Å, F–Sn–F 85.7(2)–90.5(2) in the ring, and 175.7(1)–1808 between rings, Sn–F–Sn 150.1(2), 151.6(2)8 in the ring] is found in the compound {[NEt4][Me2Sn2F5]}x, which contains six-coordinate tin (Scheme 14).109 3.3 Eight-membered rings, M4F4 There are several eight-membered rings self-assembled through fluorine bridges (illustrated idealised in Scheme 15).Molecular parameters are listed in Table 5. The first eight-membered rings based upon fluorine bridging have been identified in some inorganic pentafluorides such as [MoF5]4 110 and [RuF5]4.111 Probably the first organometallic cyclic tetramer was the metal carbonyl compound [Ru(CO)3F(m-F)]4 65, containing a nonplanar eight-membered ring with non-linear Ru–F bridges (Ru–F–Ru 1458, compared with 1328 in [RuF5]4) and both bridging (Ru–F 2.04 Å) and terminal (Ru–F 1.99 Å) metal– fluorine bonds.112 In a mixed valence ytterbium(II,III) fluoride, (Cp*)6Yb4(m-F)4 66, the non-planar eight-membered ring contains two (Cp*)2- YbIII and two (Cp*)YbII building units, connected by nonlinear fluorine bridges (Yb–F–Yb 160.0 and 157.38).113 A rather unusual self-assembled ring containing tetrafluoroborate bridges is found in the (pentamethylcyclopentadienyl)- lead tetrafluoroborate, [(Cp*)Pb(BF4)]2 67, better formulated as [(Cp*)Pb(m-F)2BF2]2.It contains rather long Pb–F bonds [2.831(9) and 2.934(8) Å] which could be described as secondary bonds; the bridges are bent at fluorine [B–F–Pb 111.2(7)J. Chem. Soc., Dalton Trans., 1999, 2249–2264 2257 Table 4 Six-membered M3F3 rings Compound Ring M–F bond in ring/Å M–F–M/8 F–M–F/8 Ref. 55 56 57 58 59 62 Al3F3 planar a Al3F3 flat boat b In3F3 distorted boat Sc3F3 Sm3F3 almost planar two Cr3F3 fused rings (butterfly) 1.770(2)–1.788(2) 1.795(4)–1.815(4) 2.095(5)–2.140(5) 2.026(8)–2.063(8) 2.234(6)–2.259(2) 1.943(5)–1.972(5) 134.3(2) 144.61(13) 144.6(2) 145.2(2) 130.3(2) 141.6(3) 133.9(3) 134.5(3) 153.5(4) 153.9(5) 152.9(4) 157.2(3) 152.7(5) 136.1(3)–140.8(3) 91.93(11) 93.25(14) 91.40(17) 90.57(18) 91.96(18) 85.8(2) 86.0(2) 85.1(2) 86.6(2) 86.2(3) 86.7(3) 84.9(3) 82.8(3) 90.0(2)–93.2(2) 101 102 13 103 104 108 a Terminal Al–F 1.634(3)–1.642(2) Å (exocyclic). b Terminal Al–F 1.657–1.681 Å (exocyclic).and 163.1(8)8]. The B–F interatomic distances are short [1.370(16) and 1.380(16) Å] as expected for normal covalent bonds.114 The tetrameric structure of dimethylaluminium fluoride, [Me2Al(m-F)]4 68, has been established by electron diVraction in the vapor phase,115 confirming molecular weight determinations in solution.116 The Al4F4 ring is non-planar [Al–F–Al 148(2), F–Al–F 94(2)8] with Al–F 1.808(8) Å, longer than terminal Al–F bonds illustrated in Table 1, and shorter than the bridge in K[Et3Al–F–AlEt3] [1.820(3) Å].61 A non-planar eight-membered ring containing two diVerent Scheme 10 Ga F F F F F F Ti Ti Ti Ti F F F F F F Ti Ti Ti F Zr Zr O O O O CF3 CF3 F Zr F F Zr F DMSO F DMSO F F F F DMSO DMSO Cp* CF3COO Cp* OOCCF3 Nb F Cp* F F Ta F F Cp* F F F Nb F F F Cp* F Ta F F F F Cp* Mo F Mo F F L OC OC L L CO CO L Mo F Mo F F OC OC L L CO CO L L W F W F F L L OC OC L CO CO L F Hg Hg F CF3 CF3 CF3 CF3 48 47 50 49 53 52 51 54 46 45 2- = C5H4SiMe3 Cp# 2 Cp# 2 Cp# 2 Cp#2 Cp2 Cp2 Cp2 metals, connected through fluorine bridges was found in [(Cp)2Ti(m-F)2AlEt2]2 69 [Ti–F 2.0956(15) and 2.1063(15) Å; Al–F 1.7342(16) and 1.7364(16) Å] with large bent angles at fluorine [Al–F–Al 160.13(9), Al–F–Ti 169.08(10)8] and small bent angles at the metals [F–Al–F 100.18(8) and F–Ti–F 78.53(7)8].117 Diorganoaluminium fluorides [R2AlF]n [n = 3 70 and n = 4 71] are isoelectronic with diorganosiloxanes [R2SiO]n [e.g.R = Me, n = 3 72 and n = 4 73] 118 and the similarity of their cyclic structures (Scheme 16) is striking. Trimeric and tetrameric organometallic oxides, e.g. [(Cp)2Zr(m-O)]3, [(Cp*)TiMe- (m-O)]4 or [(Cp*)TiBr(m-O)]4 are also topologically similar to the cyclic fluorides.119 The mixed tetranuclear compound, cis-[{(Cp*)MeHf(m2-F)- AlMe2}(m2-F)2]2 74 contains an eight-membered ring contour, Scheme 11 F Al Al F Al F F F R¢RN NRR¢ F NRR¢ F Al F Al F Al R R F F F R In F In F In R R F R R R R F Sc Sc F Sc F F Sm Sm F Sm F R R R R R R 59 58 57 56 55 R = But R = C6H2Me3-2,4,6 R = C(SiMe3)3 R¢= C6H3Pri 2-2,6 R = SiMe3 Scheme 12 Ti O O Ti O Ti Cp* X X Cp* Cp* X Zr O O Cp* Cp* Zr Cp* Cp* Zr Cp* Cp* O 61 602258 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 Table 5 Eight-membered M4F4 rings Compound Ring Bond M–F bond in ring/Å M–F–M/8 F–M–F/8 Ref. 65 66 67 68 69 Ru4F4 Yb4F4 Pb2F4B2 Al4F4 Al2F4Ti2 Ru–F (bridge) Ru–F (exocyclic) Yb–F Pb–F B–F Al–F Al–F Ti–F 2.04(7) 1.99(7) 2.831(9) 2.901(9) 2.934(8) 1.370(16) 1.371(17) 1.380(16) 1.382(16) 1.808(4) 1.7342(16) 1.7364(16) 2.0956(15) 2.1063(15) 145 160.0(2) 157.3(2) B–F–Pb 111.2(7) 163.1(8) 148(2) Al–F–Al 160.13(9) Al–F–Ti 169.08(10) 91.9(1) 105.9(1) F–Pb–F 108.9(11) 108.7(10) F–B–F (in ring) 108.9(11) 108.7(10) 94(2) F–Al–F 100.18(8) F–Ti–F 78.53(7) 112 113 114 115 117 a Electron diVraction study.Al2Hf2F4, spanned by two transannular Hf–F–Hf bridges [Hf–F 2.100(7)–2.145(7), Al–F 1.776(8) Å, Hf–F–Hf 112.5(3) and Hf–F–Al 139.9(4) and F–Hf–F 96.1(4) and 152.2(3)8].120 Alternatively, the structure can be regarded as a tricyclic system, since two six-membered rings Hf2AlF3 can also be distinguished as building sub-units, and the Hf2(m2-F)2 group can be considered as a four-membered ring (Scheme 17). A similar zirconium compound 75 [Zr–F 2.111(3)–2.179(3), Al–F Scheme 13 a Cl atoms and PF6 2 are omitted.Cr F Cr F Cr Cr F F F –B O B O –B B O O O HO OH OH OH Cr F Cr F F F Cr Cr F 63 62 a Scheme 14 R Sn F F Sn F R R R R F F Sn F Sn F F R R Sn F R R F R R F F F F F Sn F F F F R R Sn R R F F Sn R F Sn F F 64 R = Me 1.776(4)–1.786(4) Å, Zr–F–Zr 111.67(12), Zr–F–Al 140.2(2), F–Zr–F 67.48(11)8] is also known.121 The tetrameric compound [(EtMe4C5)TiF3]4 76 contains an eight-membered ring Ti4F4 with two transannular Ti–F–Ti bridges that close a Ti2F2 four-membered ring.The terminal Ti–F bonds [1.832(3) Å] are shorter than the bridging Ti–F bonds [2.057(3) and 2.019(3) Å in the Ti2F2 ring]. The bond angles are Ti–F–Ti 108.7(1) and 110.9(1)8 and F–Ti–F 70.2(1)8 (in the Ti2F2 ring).27 The same type of self-assembled polycyclic structure, with weakly coordinating tetrafluoroborate, has been observed in the uranium complex [{Cp02U(m-F)(m-F2BF2)}2] [where Cp0 = C5H3(SiMe3)2 77].122 This type of architecture has oxygen-bridged counterparts, e.g.in organotin 78123 and organoantimony 79 124 chemistry. Eight-membered ring skeletons are also present in the tetranuclear compounds [Cp*ZrF3]4 80a, [Cp*ZrF2Br]4 80b, [Cp*- ZrF2Cl]4 80c, [Cp*ZrFCl2]4 80d and [{(Cp*)2Zr2(m-F)2(m-Cl)- Scheme 15 F Yb F Yb F Yb F Yb F Ru F Ru F Ru F Ru OC OC CO OC CO CO CO CO OC F F CO CO OC F F Al Et Et Ti Ti Al Et Et F F F F Al Me Me Al Me Me Al Me Me Al Me Me F F F F Pb Pb F B F F F F B F F F 69 68 67 66 65J.Chem. Soc., Dalton Trans., 1999, 2249–2264 2259 Cl2}(m-F)]2, and also in [Cp*HfF3]4 81. In these compounds two of the M–F–M bridges are tripled by two additional M–X–M bridges (X = F, Cl, Br) (Scheme 18).31,93b,125 3.4 Polycyclic cages The cyclic units, M2F2, M3F3 and M4F4 can be combined in space, in various ways as building units to form polycyclic cages. This allows self-assembly of organometallic fluoride molecules into more complex architectures.The formation of polycyclic cages requires triconnectivity of fluorine atoms, with M–F–M bond angles smaller than 1208, to ensure the convexity needed for the cage corners. Tetraconnective fluorine atoms can also occupy corners of a cage; in this case an external side group is attached to fluorine. 3.4.1 Cubane cages. Bond angles of 908 or values close to this aVord cubane cages, which can be regarded as the products of stacking two four-membered M2F2 rings (Scheme 19). Such a small value for the M–F–M bond angle is possible, as it seems more likely in highly polar or ionic M–F bonds. As a result, tetrameric caesium trialkylfluorometalates, [Cs{(R3M)F}]4 (M = Ga, In) 82 form heterocubane structures, based upon a Cs4F4 skeleton, rather than a M4F4 cubane or ring (as may have been expected).The MR3 fragments are side groups. Two isostructural compounds [Cs{(R3M)F}]4 with M = Ga, In and R = Pri, have been structurally characterised.126 The Cs–F–Cs bond angles, at the corners of the cube, are 99.43(5) in the gallium compound and 101.02(6)8 in the indium compound; the bonds to external side groups have Cs–F–Ga 118.25(9) and Cs– Scheme 16 F Al Al F Al F Al F Al F F Al F Al O Si Si O Si O Si O Si O O Si O Si 73 72 71 70 R2 R2 R2 (R2SiO)3 R2 R2 R2 R2 (R2SiO)4 R2 R2 R2 R2 R2 R2 R2 (R2AlF)3 (R2AlF)4 Scheme 17 Sb O O Sb O Sb O O Sb O R R R R R R R R F F F F Mo O O Sn O Sn O O Mo O O O O O R R R R Al F F M F M F F Al F Me Me Me Me Me Me Cp* Cp* B F F U F U F F B F F F F F Cp¢¢ Cp¢¢ Cp¢¢ Cp¢¢ Ti F F Ti F Ti F F Ti F F F Cp¢¢ Cp¢¢ F F Cp¢¢ Cp¢¢ F F 2- 79 78 77 76 Cp¢¢ = C5H4Et 74 M = Hf 75 M = Zr Cp¢¢ = C5H4SiMe3 H H R = Ph F–In 116.99(7)8, i.e.larger than tetrahedral values. The F–Cs–F bond angles are small, 79.70(6) in the gallium compound, and 77.77(5)8 in the indium compound. Thus, the cubes are rather distorted. The Cs–F distances in the two compounds diVer: 2.924(2) in the gallium compound and 2.889(2) Å in the indium compound, probably because of the increasing ionic character of the M–F bonds on going from gallium to indium, which leads to stronger ionic Cs–F interactions.Anyway, the Cs–F interatomic distances are shorter than in crystalline CsF (3.005 Å). It is remarkable that the two fluorine structures are similar to that of an oxygen compound, tetrameric [KOSiMe3]4 83.127 Other cubane clusters are present in [Mn4Fx(OH)4 2 x(CO)12] 84 [Mn–F–Mn 102.4(1), F–Mn–F 76.1(1)8, Mn–F 2.052(3) Å],128 [ReF(CO)3]4 85 [Re–F–Re 102.6(3), 102.9(4) and Scheme 18 Zr Zr Zr Zr F F F F X F X F Hf Hf Hf Hf F F F F F F F F 81 F F F 80 a X = X¢ = F b X = F, X¢ = Br c X = F, X¢ = Cl d X = X¢ = Cl X' X' X' X¢ F Scheme 19 Cs F Cs F Cs F Cs F R3M MR3 R3M MR3 K O K O K K O R3 M MR3 R3M MR3 Al R Al R Li L Li L Al Li L Li L Al R F F F F F F F F F F F F F (CO)3Mn F Mn(CO)3 F F (CO)3Mn Mn(CO)3 Re(CO)3 F (CO)3Re (CO)3Re F Re(CO)3 F F R 86 L = THF R = C(SiMe3)3 85 84 83 M =Si, R = Me b M = In, R = Pri 82 a M = Ga, R = Pri2260 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 105.8(4)8; F–Re–F 74.9(2), 74.7(2) and 73.0(2)8, Re–F av. 2.200(5) Å] 129 and [RhF(C2H4)(C2F4)]4 [rather distorted, with Rh–F 2.073(2)–2.334(2) Å, Rh–F–Rh 95.20(8)–111.92(9)8].130 Large cubane cages, with the fluorine bridges on the edges and metal atoms in the corners, can be formed by self-assembly of eight-membered rings. An example is [Li{F3AlC(SiMe3)3}? THF]4 86 which contains an Al4Li4F12 distorted cubane skeleton.131 3.4.2 Other cages.Various types of cages are illustrated in Scheme 20. An unprecedented cage, containing Al–Si bonds 87, formed in the reaction of [Cp*Al]4 with Ph2SiF2 contains only m-F bridges [Al–F 1.843(1) and 1.848(1) Å, Al–F–Al 149.0(1)8, F–Al–F 88.3(1)8], with two Al–Si–Al bridges.132 A gallium oxofluoride cage 88, made of Ga2OF fourmembered rings is the molecular skeleton of [(Mes)6Ga6F4O4]? THF and all fluorine atoms form triconnective bridges [Ga–F 1.973(3)–2.521(3) Å, Ga–F–Ga 84.5(1), 86.5(1), 88.0(1) and 90.3(1)8].92a Oxo analogues with the same topology are [(Mes)6Ga6(OH)4O4],92b and [But 6Al6(OH)4O4],92c suggesting that fluorine and oxygen (as OH groups in this case) can be mutually replaceable.An intriguing Na4 21 cluster 89 forms three Na–F bonds [2.284(3), 2.395(3) and 2.210(3) Å] to a tetraconnective fluorine atom attached to silicon, in the compound Na4[Pri 3Si–P– SiR2F]2. The Na–F–Na bond angles are 86.35(10) and 83.75(11)8.This intensely yellow compound was formed in a reaction between FR2SiPHSiPri 3 and NaN(SiMe3)2.133 A complex cage, containing Yb2F2, Yb3F3 and Yb4F4 rings and three diVerent bridging modes of fluorine, forms the skeleton of the compound [Cp*6Yb5(m4-F)(m3-F)2(m-F)6].134 3.5 Supramolecular polymeric arrays Some caesium fluorometalates, such as Cs[Me3GaF] 90, form ladder-like chain (ribbon) supramolecular polymeric arrays, containing tetraconnective fluorine.138 A similar ribbon structure with dangling R2GaF groups is found in [Cs{(PhCH2)2- GaF2}]x (Scheme 21).135 The structure of [Cs{(Mes)GaF3}]x contains a [CsF]x layer with the (Mes)Ga sub-units connected to caesium atoms through three Ga–F bonds in GaF2Cs rings [Ga–F 1.784(7) and 1.807(4) and Cs ? ? ? F 2.910(7)–3.229(5) Å], displaying a broad range of Cs–F–Cs and Cs–F–Ga bond angles.136 In the indium compound [(Pri 2InF)2(CsF?3MeCN)] the structure 91 is based on double chains containing triconnective fluorine [In–F 2.121(5)–2.607(5) Å, In–F–In 100.6(2)– 151.2(2)8].137 More complex supramolecular arrays are present in Cs[Me3AlF], based upon tetraconnective fluorine and Cs2F2 rings interconnected in puckered layers.138 As mentioned Scheme 20 Al F F F Al F Al Si Al Si Cp* Cp* Cp* Cp* R R R R Na F Na Na Na F P Si P Si SiPri 3 R R R R Pri 3Si Ga F Ga R O Ga R Ga R Ga R F Ga F O F O O R R 89 88 87 R = C6H2Pri 3-2,4,6 R = Mes above, tetrafluoroborate bridging leads to the formation of supramolecular polymeric arrays.Thus, double chelating in [In(Mes)2][BF4] produces a chain structure 92139 and simple bridging of the type in 20 (Scheme 6) leads to the formation of bent chain-like arrays in [InPri 2(THF)2][BF4] [In ? ? ? F–B 173.8(7) and 155.0(7), F ? ? ? In ? ? ? F 120.4(2)8].140 4 Host–guest complexation 4.1 Encapsulated fluorine ions The fluorine anion can be encrypted in various cage structures (Scheme 22).The simplest is an organotin macrobicyclic host in the anion [ClSn{(CH2)6}3SnCl?F]2 93. The tin–fluorine distances are 2.12(4) and 2.28(4) Å, and these values are in the range expected for coordinative tin–fluorine bonds.141 The inclusion of the fluorine anion changes the conformation of the host by changing the coordination geometry of the tin atoms from distorted tetrahedral [Cl–Sn–C 103(1), 103(1) and 99.1(1)8; C–Sn–C 106(1), 117(2) and 125(2)8 in the free cryptand] to trigonal bipyramidal [Cl–Sn–C 84(1), 100(1) and 83(1)8; C–Sn–C 120(2), 123(2) and 116(2)8; Cl–Sn–F 173(1)8 in the host–guest complex].The encapsulation of fluorine has an obvious templating eVect in the formation of vanadatophosphonates 94. Thus, under the directing eVect of fluorine the tetranuclear Scheme 21 Cs F In F In F In F In F In F In F L F L L R R R R R R R R R R L L L F Cs F Cs F GaMe3 GaMe3 Cs F Cs F GaMe3 GaMe3 Cs F Cs F GaMe3 GaMe3 B F F F F In R L L B F F F F In R L L B F F F F In R L L R R R 92 91 90 R = Pri L = MeCN R = Mes Scheme 22 O P V O P V O O O V O P O V P O O O O O R R R O R O O O O O Sn Cl (CH2)6 (CH2)6 Sn Cl F F F O Al Al Al Al F F Al THF F F NRR¢ F F F NRR¢ RR¢N Al F NRR¢ F F F THF F Ti Ti Ti Al F F Ti Cp¢ F F Cp¢ F F F Cp¢ Cp¢ Ti F Cp¢ F F F THF (CH2)6 F– Cp¢ =C5H4SiMe3 NRR¢ = N(C6H3Pri 2–2,6)(SiMe3) – 95 96 94 93 R = Ph, MeJ.Chem. Soc., Dalton Trans., 1999, 2249–2264 2261 host–guest complexes [NBun 4][V4O6(m4-F)(PhPO3)4] [V? ? ?F 2.412(4), 2.427(3), 2.477(4), 2.414(4) Å],142 [PEt4][V4O6(m4-F)- (PhPO3)4] [V? ? ? F 2.443(3), 2.412(3), 2.454(4) and 2.445(3) Å] and [PEt4][V4O6(m4-F)(MePO3)4] [V? ? ? F 2.486(4), 2.528(4), 2.403(3) 2.392(4) Å]143 are formed from appropriate precursors.The structure directing role of fluorine is underlined by the fact that in the presence of Cl2 anion as templating agent, octaphosphonato host–guest complexes, e.g. [V6O6(O3- POSiMe3)8Cl], [(V8O16){V4O4(H2O)12}(PhPO3)8Cl2]22,144 and [V6O6(PhPO3)8Cl]2,145 are formed.There is also evidence that the metal–fluorine polycyclic cages may act as hosts for various anions, which can be encapsulated into the cage, to form host–guest complexes. The host can be a fluorine anion F2, an oxygen anion O22, and possibly others. The future may provide some pleasant surprises in this respect. In some compounds fluorine displays a large coordination number, being six-coordinated and encapsulated in a polycyclic metal–fluorine cage 95.This is the case for [{(C5H4SiMe3)- TiF2}5AlF2(m6-F)(THF)]. The distances from the encapsulated fluorine to the surrounding metal atoms [Ti ? ? ? F av. 2.643(3), range 2.542(3)–2.670(3), Al ? ? ? F 1.850 Å] are significantly longer than the biconnective bonds in the m-bridges of the cage [Ti–F av. 2.024(3), range 1.985(3)–2.089(3) Å, and Al–F av. 1.785(3), range 1.780(3)–1.793(3) Å].146 The structure is similar to one with an oxygen ion encapsulated into a similar aluminium–oxygen–fluorine cage, in the compound [{(2,6- Pri 2C6H3)(SiMe3)AlF2}4{AlF2(THF)}2O] 96.12 The same type of cages with encapsulated O22 anions are characteristic for hexamolybdates and hexatungstates, [M6O19]22 (M = Mo, W) 147 and organometallic oxides, such as [CpTiMo5O18]32 (M = Mo, W), [Cp*Mo6O18]2, [Cp2W6O17] and other related compounds.148 4.2 Organometallic fluoride cages as guests for metal cations Organometallic fluorine cages are able to incorporate alkali metal and alkaline earth metal fluorides, formed in situ during the reduction of organometallic fluorides with the active metal. Such structures are illustrated in Scheme 23.A host–guest complex, [K(THF)2{(Me3Si)3CAlF2(m-F)F2AlC(SiMe3)3}]2 97 based on incorporation of potassium cations in a sandwich formed with two RF2Al(m-F)AlRF2 blocks, is relatively simple, since it contains only biconnective fluorine atoms in heterometallic asymmetric bridges.102 The Al–F distances in the Al–F–Al bridges are 1.821(2) and 1.817(2) Å, longer than the Al–F distances in the Al–F ? ? ? K bridges [1.672(2)–1.677(2) Å].The Al–F–Al angle is 126.2(1)8 and two sets of values are observed for the Al–F ? ? ? K angles [118.7(1), 107.6(1) and 144.8(1), 147.3(1)8]. Alkali metal host–guest complexes of organotitanium fluorides, M1[M9{(Cp*Ti)2F7}2]2 (M = Na, PPh4, M9 = Na, K) 98a 149 and a calcium complex [Ca{(C5Me4Et)2Ti2F7}2] 98b,150 are sandwiches in which the active metal cation is intercalated between two (Cp*Ti)2F7 moieties, in a manner which is reminiscent of crown ether complexation.The compound [(Cp*TiF2)12(TiF3)2(NaF)18?6THF] has a very complex supramolecular structure, incorporating the equivalent of 18 NaF molecules. In the calcium fluoride complex [Ca{(Cp*)3Ti3F7}2]?2THF 99, the metal cation is sandwiched between (Cp*Ti)3F7 cyclic subunits. Like in the solid CaF2, the calcium cation is eight-coordinate.151 A heterometallic cage compound [{(Mes)InF2}10MgF2] 100 is made up of two {(Mes)InF2}5 fragments held together by four m-F bridges and incorporates a guest ‘molecule’ of MgF2 in the cavity.The cage contains both biconnective m-F (In–F 2.08– 2.12 Å) and triconnective m3-F (In–F 2.22–2.24 Å) bridges.137 The magnesium atom is six-coordinate (distorted octahedron) and each indium atom displays tetragonal pyramidal geometry. Six-membered In3F3 and eight-membered In4F4 fused rings are readily identified as building sub-units of the cage.The compound [(Cp*TiF2)4(MgF2)2]?7THF 101 can be regarded as a magnesium fluoride host–guest complex, although the identity of the MgF2 ‘molecules’ is lost in the structure of the cage. It is easy to distinguish the six-membered rings TiMg2F3, Ti2MgF3 and TiF3 as structural elements of the cage. Incorporation of sodium fluoride, formed in situ, into organometallic fluoride cages, leads to the formation of a more intricate architecture, as found in [(Cp*TiF2)6(NaF)7?2.5THF].The formation of these species results in solubilisation of highly insoluble ionic solids in organic solvents, in a pseudomolecular form, protected by lipophilic organic groups.152 Similarly, compounds such as (Cp*ZrF3)6Li4O2 represent intercalation of a metal oxide into a fluorometalate cage.153 The incorporation of six caesium ions into an aluminophosphonate supramolecular structure (Scheme 24) also containing an Al2F2 cyclic sub-unit 102, occurs in a compound of composition [Cs3(THF)3(m4-F)(AlBui)3(O3PBut)4]2[(BuiAl)2Al2- (m-F)2(O3PBut)4], self-assembled from the very simple synthons Cs[FAlBui 3] and ButPO3H2 in THF.154 It illustrates the complexity of architectures which can be obtained by involving fluorine as the structure directing element.Scheme 23 97 99 98 a M = Na, K b M = Ca (Cp* and C5Me4Et) R = C(SiMe3)3 M Ti F Ti F F F F F Cp* Cp* F Ti F Ti F F F F F Cp* Cp* F F Ti F Ti F Ti F F Ca F F Cp* Cp* Cp* F Ti F Ti F Cp* Cp* Ti Cp* F F F F K K F F Al F R F Al F R F F Al R F F Al R F F Mg Ti F Mg F Ti F F Ti F F F F F F Ti F Cp* Cp* Mg F F F F F In In F F F In F R R R In In F F F In R R F R F In F In F R R F F In R F F F In F R 100 101 Cp* Cp* (THF omitted) (R = Mes) (THF omitted) Scheme 24 O Al P R Al R¢ P R Al F F O O O O Al O O Cs O Cs O O O O R P O Al O P O Al O O Al O P O O P O O O O Cs Cs Cs F R R¢ R R' R R¢ R Al O P P O Al O O P O Al O O P O O O O O Cs Cs Cs F R¢ R R¢ R R R R¢ 102 R =But R¢ = Bui2262 J.Chem. Soc., Dalton Trans., 1999, 2249–2264 5 Conclusions and outlook 1. Although monovalent (in the classical sense) fluorine can form more than one bond to other atoms (usually metals) and may appear as mono-, di-, tri- and tetra-connective in organometallic fluorides, the high degree of ionic character of most metal–fluorine bonds is probably the major factor which determines this behaviour. 2. In some cases fluoro anions such as [BF4]2, [PF6]2, [AsF6]2 and [SbF6]2, can behave as weakly coordinating ligands, although in most cases (not covered in this review) they tend to be discrete species that simply compensate the positive charge of a cationic complex. 3. The biconnective bridging mode of fluorine leads to supramolecular self-assembly into ring and chain polymeric structures. Four-, six- (planar and non-planar) and eightmembered rings are known and more can be expected. 4. The non-planar triconnective binding mode of fluorine allows it to occupy corners of self-assembled polycyclic cages. The smallest are the cubane structures (requiring M–F–M bond angles close to 908) and these are observed mainly in alkali metal organometallic fluorides. Larger M–F–M bond angles provide a convexity (or Gaussian curvature) leading to larger cages. The tri- and tetra-connective binding mode can also produce double-chain (ladder-like) supramolecular polymeric arrays. 5. Polycyclic cages of organometallic fluorides can encapsulate metal cations or even molecular fragments of solid state fluorides, leading to a particular type of inorganic–organometallic host–guest complex (‘molecular solids’). 6. The fluoride anion can be encapsulated as a guest in organometallic cryptands or in organometallic fluoride cages, acting as hosts, due to electrostatic interactions. In such cases the fluoride anion displays (in known examples) coordination numbers two, four or six. 7. There is a topological analogy between fluorine and oxygen, which suggests that many fluoro analogues of known organometallic oxo rings and cages, as well as mixed fluoro–oxo organometallic rings and cages can be envisaged. One can speculate that if RMIII and RMIV building blocks are considered as possible synthons for adamantane and cubane type Scheme 25 F Al Al O Al F O F Al R F R R R O Al Al F Al O F O Al R O R R R O Al Ti O Al O F O Al R O R R R O Al Ti O Ti O O O Al R O R R R Selected neutral adamantane cages: Selected cationic (2+) adamantane cage: Selected anionic (2–) adamantane cages: O Ti Al O Ti O F O Ti R O R R R F Ti Al F Ti O O O Ti R F R R R supermolecules, neutral, anionic and cationic species can be anticipated.A selection of such structures, imagined with RAl (R = alkyl, aryl) and RTi (R = substituted or unsubstituted h5- cyclopentadienyl) building units are illustrated in Schemes 25 and 26. Some can be realistic synthetic targets. 8. 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ISSN:1477-9226    

DOI:10.1039/a901728c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2265–2266 2265 New approach to dichloroindium amides Jörg Prust, Peter Müller, Carsten Rennekamp, Herbert W. Roesky * and Isabel Usón Institut für Anorganische Chemie der Georg August Universität Göttingen, Tammannstrasse 4, D-37077, Göttingen, Germany Received 22nd March 1999, Accepted 11th June 1999 Two different routes are presented for the synthesis of dichloroindium amides. On the one hand we prepared (THF)3Li(Ï-Cl)Cl2InN(SiMe3)(Dipp) (1) (Dipp 5 2,6- diisopropylphenyl) by the reaction of indium trichloride with the lithiated aniline, on the other hand Cl2InNEt2 (2) by trimethylsilyl chloride elimination.Compound 1 was characterized by X-ray structural analysis. Organoindium compounds were introduced by Rochow et al. in 1934.1 In recent years interest in the synthesis of organoindium amides, phosphides, selenides and arsenides has increased owing to their application in the fields of CVD (Chemical Vapour Deposition) and MOCVD (Metal Organic Chemical Vapour Deposition) for the production of thin layers.2–4 In this respect dimethylindium dimethylamide should be mentioned as a precursor for the synthesis of ceramics.5,6 Therefore new routes to indium compounds for use as single source precursors and their corresponding starting materials is an important target of current indium research.The syntheses of alkylindium dichlorides and dialkylindium amides have been thoroughly investigated.7 Two pathways for the syntheses of these compounds were found to work in high yields: on the one hand the commutation reaction of trialkylindium compounds with InCl3 for the preparation of alkylindium dichlorides, and on the other hand the reaction of trialkylindium derivatives with amines, with alkane elimination, for the synthesis of In–N compounds.8,9 The alternative route to these compounds via the reaction of InCl3 with lithiated alkyls or amides has been of no practical use until now.These reactions mostly lead to lower product yields due to metallic indium formation which is favoured in the presence of the lithiated amide or alkyl species.10 In contrast to these observations the reaction of a lithiated tris(trimethylsilyl)- methane with InCl3 yields an alkylindium dichloride–lithium chloride adduct in 87% yield, which has been characterized by X-ray structural analysis.11 To the best of our knowledge a successful synthesis of dichloroindium amides, or rather their derivatives, has not been reported yet. For the preparation of a dichloroindium amide we chose lithiated N-trimethylsilyl-2,6-diisopropylaniline for the reaction with InCl3, owing to its high sterical demand.In our previous work we established N-trimethylsilyl-2,6-diisopropylanilide as a bulky ligand for the production of stable silanetriol and silanetriamide systems.12 After the successful syntheses of gallium and aluminium amide systems using this ligand we are now interested in the corresponding indium compounds.A solution of 2.49 g (10 mmol) lithiated N-trimethylsilyl-2,6- diisopropylaniline in THF (20 ml) was added to a solution of 2.21 g (10 mmol) InCl3 in THF (50 ml) at 0 8C and stirred for an additional 1 h. The solution was allowed to reach room temperature, refluxed for 1 h and stirred at room temperature for another 6 h. THF was removed in vacuo and the remaining solid was dissolved in toluene.After filtration from the residue the solvent was removed in vacuo and 1 was isolated as a colourless solid in 83% yield (5.75 g). No reduction of In(III) was observed during the reaction (shown in Scheme 1). A sample of 1 was dissolved in n-hexane and kept for one week at room temperature. Single crystals suitable for X-ray crystallography were obtained from this solution. The single crystal X-ray structural analysis shows 1 to crystallize in the monoclinic space group P21/n with one molecule in the asymmetric unit. The core of the structure consists of an indium centre which is tetrahedrally coordinated by three chlorine atoms and one N-trimethylsilyl-2,6-diisopropylaniline ligand.One of the chlorine atoms bridges the indium to a lithium cation whose tetrahedral coordination sphere is completed by three THF molecules (Fig. 1). As expected the bridging In(1)–Cl(1) bond length of 2.4152 Å is longer than the terminal ones (2.3760 and 2.3614 Å).The bond lengths and angles are comparable to those in [Li(THF)3(m-Cl)InCl2- {C(SiMe3)3}].†11 The 1H NMR data are consistent with 1. The singlet (d 0.28) is assigned to the protons of the SiMe3 group. The expected doublets (d 1.13 and 1.19) and septets (d 2.86 and 3.65) for the isopropyl groups are found, whereas the aromatic protons give a multiplet (d 6.98 to 7.06). Signals for the THF groups are observed in the expected range (d 1.20 and 3.67). The consistency of the solid state structure also in solution of 1 can be proved by integration of the proton signals.In the 7Li NMR spectrum of 1 a singlet is found (d 20.21) assignable to Li coordinated to THF and the 29Si NMR data result in a singlet (d 4.07) for the SiMe3 group. The mass spectrum shows fragments of 1 assigned to DippNH2 (177; 30%), DippH (162; 100%), InCl (150; 48%) and In (115; 41%). The composition of 1 was confirmed by elemental analysis. We obtained dichloroindium Fig. 1 X-Ray structure of 1 with atomic numbering scheme.Hydrogen atoms have been omitted for clarity. Selected bond distances [Å] and angles [8]: In(1)–N(1) 2.054(2), In(1)–Cl(1) 2.4152(8), In(1)–Cl(2) 2.3760(5), In(1)–Cl(3) 2.3614(8), Li(1)–Cl(1) 2.392(4); Cl(1)–In(1)– Cl(2) 104.56(3), Cl(1)–In(1)–Cl(3) 106.30(4), Cl(2)–In(1)–Cl(3) 105.31(3), Cl(1)–In(1)–N(1) 110.41(6), Cl(2)–In(1)–N(1) 115.12(6), Cl(3)–In(1)–N(1) 114.32(5), Li(1)–Cl(1)–In(1) 116.3(1). Scheme 1 N TMS Li N In Cl (THF)3Li Cl Cl TMS InCl3 0 °C, THF + 12266 J.Chem. Soc., Dalton Trans., 1999, 2265–2266 amide as the LiCl adduct, which is in good agreement with the product proposed in Scheme 1. For the synthesis of dichloroindium diethylamide an alternative approach proved to be applicable. To avoid reduction by any lithiated amine a trimethylsilyl chloride elimination reaction of the trimethylsilyl derivative of diethylamine with InCl3 (Scheme 2) was carried out instead. A solution of 1.44 g (10 mmol) (SiMe3)NEt2 in toluene (20 ml) was added to a suspension of 2.21 g (10 mmol) InCl3 in toluene (50 ml) at 0 8C.The suspension was allowed to reach room temperature and refluxed for 8 h. Toluene was removed in vacuo and the remaining solid was treated with n-hexane. After filtration the solvent was removed in vacuo and 2 was isolated as a colourless solid in 78% yield (2.01 g). The 1H NMR data show the expected signals for 2. The triplet (d 1.28) and the quartet (d 3.11) are assigned to the protons of the ethyl group.The mass spectrum (EI) shows fragments of the monomer assigned to M (258 m/z; 53%) and InCl (150; 100%). The composition of 2 was confirmed by elemental analysis. The spectroscopic characterization established that the dimer of dichloroindium diethylamide was the product. This interpretation is supported by previous investigations of comparable alkylindium amides, as well as by infrared spectra, which reveal the nitrogen bridged dimeric system of 2.‡ With these two routes for the synthesis of compounds 1 and 2 we have opened up the field of dichloroindium amides.Further investigations in our laboratory will focus on exchange reactions of the halides in these systems to obtain new single source precursors for the CVD process. Acknowledgements This work was supported by the Deutsche Forschungsgemeinschaft. C. R. is grateful to the Fonds der Chemischen Industrie for a fellowship. Notes and references † Crystal structure analysis of 1: C27H50Cl3InLiNO3Si, Mr = 692.88, monoclinic, P21/n, unit cell dimensions: a = 9.472(2) Å, b = 24.866(5) Å, c = 14.625(3) Å, b = 91.58(3)8, V = 3444(1) Å3, Z = 4, rcalc.= 1.336 Mg m23, m = 0.980 mm21; total number of reflections measured 60120, Scheme 2 Et N Et TMS Et N Et In Cl Cl InCl3 + 8 h reflux toluene –TMSCl 2 unique 6753 (Rint = 0.0512). Final R indices: R1 = S|Fo 2 Fc|/S|Fo| = 0.0262, wR2 = [Sw(Fo 2 2 Fc 2)2/SwFo 4]1/2 = 0.0627 on data with I > 2s(I) and R1 = 0.0316, wR2 = 0.0681 on all data, goodness of fit S = [Sw(Fo 2 2 Fc 2)2/S(n 2 p)]1/2 = 1.161.The crystal was mounted on a glass fibre in a rapidly cooled perfluoropolyether.13 DiVraction data were collected on a Stoe-Siemens-Huber four-circle diVractometer coupled to a Siemens CCD area detector at 133(2) K, with graphitemonochromated Mo-Ka radiation (l = 0.71073 Å), performing f- and w-scans. The structure was solved by direct methods using SHELXS- 9714 and refined against F2 on all data by full-matrix least squares with SHELXL-97.15 All non-hydrogen atoms were refined anisotropically.All hydrogen atoms were included in the model at geometrically calculated positions and refined using a riding model. The disordered SiMe3 group in 1 was modelled with the help of similarity restraints for 1–2 and 1–3 distances and displacement parameters as well as rigid bond restraints for anisotropic displacement parameters.The occupancies for the disordered parts were refined and eventually set at the convergence value. CCDC reference number 186/1505. See http://www.rsc.org/suppdata/ dt/1999/2265/ for crystallographic files in .cif format. ‡ The infrared spectrum of 2 was recorded in CsI and shows the stretching of terminal In–Cl (279 and 259 cm21) and bending of In–m-N (447 cm21). Owing to the air and moisture sensitivity of 2 cryoscopic measurements for the molecular weight determination were not successful. 1 L. M. Dennis, R. W. Work and E. G. Rochow, J. Am. Chem. Soc., 1934, 56, 1047. 2 F. Runge, W. Zimmermann, H. PfeiVer and J. PfeiVer, Z. Anorg. Allg. Chem., 1951, 267, 39. 3 A. H. Cowley and R. A. Jones, Angew. Chem., 1989, 101, 1235; Angew. Chem., Int. Ed. Engl., 1989, 28, 1208. 4 J. H. C. Hogg, H. H. Sutherland and D. J. Williams, Chem. Commun., 1971, 1568. 5 K. A. Aitchison, J. Organomet. Chem., 1989, 366, 11. 6 A. H. Cowley, B. L. Benac, J. G. Ekerdt, R. A. Jones, K. B. Kidd, J. Y. Lee and J. E. Miller, J. Am. Chem. Soc., 1988, 110, 6248. 7 Gmelin Handbook of Inorganic and Organometallic Chemistry, vol. 37; 1, Springer Verlag, Berlin, 8th edn., 1991. 8 H. D. Hausen, K. Mertz, E. Veigel and J. Weidlein, Z. Anorg. Allg. Chem., 1974, 410, 156. 9 B. Neumüller, Chem. Ber., 1989, 122, 2283. 10 D. C. Bradley, D. M. Frigo, M. B. Hursthouse and B. Hussain, Organometallics, 1988, 7, 1112. 11 J. L. Atwood, S. G. Bott, P. B. Hitchcock, C. Eaborn, R. S. ShariVudin, J. D. Smith and A. C. Sullivan, J. Chem. Soc., Dalton Trans., 1987, 747. 12 K. Wraage, A. Künzel, M. Noltemeyer, H. G. Schmidt and H. W. Roesky, Angew. Chem., 1996, 107, 2954; Angew. Chem., Int. Ed. Engl., 1996, 34, 2645. 13 T. Kottke and D. Stalke, J. Appl. Crystallogr., 1993, 26, 615. 14 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467. 15 G. M. Sheldrick, SHELX 97, Universität Göttingen, 1997. Communication 9/04655K

ISSN:1477-9226    

DOI:10.1039/a904655k

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2267–2268 2267 Triazidogermyl complexes of tungsten: synthesis, crystal structure and hydrolysis to a metallocyclotrigermoxane Alexander C. Filippou,* Ragnar Steck and Gabriele Kociok-Köhn Fachinstitut für Anorganische und Allgemeine Chemie, Humboldt-Universität zu Berlin, Hessische Str. 1-2, D-10115 Berlin, Germany. E-mail: filippou@chemie.hu-berlin.de Received 9th June 1999, Accepted 10th June 1999 The synthesis and full characterization of the triazidogermyl complexes trans-(Á5-C5R5)W(CO)n(PMe3)3-nGe(N3)3 (2a: R 5 H, n 5 1; 2b: R 5 Me, n 5 1; 5b: R 5 Me, n 5 2) is reported; the crystal structures of 2a and of the metallocyclotrigermoxane [Cp*W(CO)2(PMe3)Ge(N3)(Ï2-O)]3? C6H6 (6b?C6H6), the product of partial hydrolysis of 5b, are described.Polyazidogermanes belong to a class of potentially explosive Ge(IV) compounds due to their propensity to decompose exothermally eliminating dinitrogen.1 Studies of these compounds are very rare, and include some synthetic and spectroscopic work on GeMen(N3)4 2 n (n = 0–3).2 An approach for the kinetic stabilisation of triazidogermanes is presented here involving the use of ‘electron-rich’ organometal fragments.This is demonstrated by the synthesis and full characterization of the tungsten triazidogermyl complexes trans-(h5-C5R5)W(CO)n- (PMe3)3 2 nGe(N3)3 (2a: R = H, n = 1; 2b: R = Me, n = 1; 5b: R = Me, n = 2). Treatment of 1a3 with an excess of NaN3 in THF at ambient temperature resulted in the formation of 2a.Similarly, prolonged heating of 1b 3 with NaN3 in refluxing THF aVorded 2b (eqn. (1)).† Monitoring of the reaction of 1b with NaN3 revealed the intermediate formation of the mixed azido- (chloro)germyl complexes trans-Cp*W(CO)(PMe3)2[GeCl3 2 m- (N3)m] (Cp* = C5Me5; 1b-1: m = 1; 1b-2: m = 2).‡ A byproduct was also formed in this reaction, which was easily separated from 2b by taking advantage of its high solubility in pentane; this byproduct was identified by IR and NMR spectroscopy to be the chloro complex trans-Cp*W(CO)(PMe3)2Cl (3b).3§ We suggest an associative mechanism for the nucleophilic substitution reactions in eqn.(1). In the first step, slow addition of the azide anion to the germanium atom of 1a and 1b occurs to give a five-coordinate metallogermanate intermediate. It is followed by a rapid displacement of chloride to aVord the substitution product trans-(h5-C5R5)W(CO)(PMe3)2[GeCl2(N3)], this sequence of steps being repeated consecutively to aVord 2a and 2b.Increased steric congestion at the germanium center of 1b is assumed to cause the five-coordinate germanate intermediates, formed after azide addition to 1b, 1b-1 and 1b-2, to follow a parallel decomposition pathway, which involves a-elimination of the chloro complex 3b.§ Complexes 2a and 2b were isolated as yellow, thermally robust solids, which begin to decompose upon slow heating at 150 and 177 8C.Both compounds are soluble in CH2Cl2 and in PMe3 W Me3P C GeCl3 PMe3 W Me3P C Ge(N3)3 R R R R R R R R R R (1) O + NaN3(ex.) –3 NaCl THF O 1a, 1b 2a, 2b a: R = H; b: R = Me THF but insoluble in pentane, and were fully characterized.† Thus, the IR spectra of 2a and 2b display two nasym(N3) absorptions, which appear at similar wavenumbers to those of germanium( IV) azides [Me3GeN3: nasym(N3) = 2103 cm21; Ph3GeN3: nasym(N3) = 2107 cm21] 4 and higher than those of germanium(II) azides [Tp9GeN3: nasym(N3) = 2043 cm21].5 The NMR spectroscopic data of 2a and 2b are similar to those of 1a and 1b and indicate the presence of only the trans stereoisomer in solution, which in the case of 2a was also confirmed by a single-crystal X-ray diVraction study (Fig. 1).¶ Single crystals were obtained upon diVusion of pentane into a THF solution of 2a at 230 8C. 2a has similar bonding parameters to 1a indicating the presence of an electron-rich metal center.3 The tetrahedral environment of the germanium atom is strongly distorted as shown by the mean N–Ge–N and W–Ge–N bond angles of 96.2(4)8 and 120.6(3)8, respectively.The W–Ge bond [2.5099 (9) Å] is short and the mean Ge–N bond length of 1.931(7) Å is larger than that of H3GeN3 (g) [1.845(6) Å] 6 and that calculated for a Ge–N single bond (1.84 Å).7 All these structural data can be rationalized using either the atom rehybridization model of Bent 8 or suggesting the presence of tungsten–triazidogermyl p back-bonding.3 As observed for other covalent azides of main-group elements,9 the azide groups in 2a adopt a slightly bent configuration with a mean N–N–N bond angle of 172.9(13)8 and two significantly diVerent N–N bond lengths [(Na–Nb)av.= 1.225(11) Å; (Nb–Ng)av. = 1.113(12) Å], which are close to the experimental values of a N–N double [1.20 Å] and a N–N triple bond [1.10 Å], respectively.10 Less electron-rich metal fragments can also be used for the kinetic stabilisation of triazidogermanes as shown by the high- Fig. 1 ZORTEP plot of the molecular structure of 2a with thermal ellipsoids drawn at 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (8): W–Ge 2.5099(9), W–P(1) 2.4818(18), W–P(2) 2.4796(19), W–C(6) 1.939(8), Ge–N(1) 1.942(7), Ge–N(4) 1.926(7), Ge–N(7) 1.925(7), N(1)–N(2) 1.221(11), N(2)–N(3), 1.110(11), N(4)–N(5) 1.207(11), N(5)–N(6) 1.104(13), N(7)–N(8) 1.247(11), N(8)–N(9) 1.124(12), W–Ge–N(1) 123.4(3), W–Ge–N(4) 111.4(3), W–Ge–N(7) 126.9(2), N(1)–Ge–N(4) 95.9(4), N(1)–Ge–N(7) 94.7(3), N(4)–Ge–N(7) 98.0(4), Ge–N(1)–N(2) 121.1(6), Ge–N(4)–N(5) 119.4(7), Ge–N(7)–N(8) 118.0(7), N(1)–N(2)–N(3) 171.6(16), N(4)–N(5)–N(6) 172.4(11), N(7)–N(8)–N(9) 174.6(11).2268 J.Chem. Soc., Dalton Trans., 1999, 2267–2268 yield synthesis of trans-Cp*W(CO)2(PMe3)Ge(N3)3 (5b) from trans-Cp*W(CO)2(PMe3)GeCl3 (4b) 11 and NaN3.† Single crystals of the metallocyclotrigermoxane 6b resulting from partial hydrolysis of 5b were obtained upon slow evaporation of a solution of 5b in benzene at 20 8C.Complex 6b crystallizes with one benzene molecule in the asymmetric unit. The crystal structure of 6b (Fig. 2), displays a non-planar six-membered Ge3O3 ring with similar Ge–O bond lengths [(Ge–O)av. = 1.774(8) Å] and Ge–O–Ge bond angles [(Ge–O–Ge)av. = 129.7(5)8] to those of (Ph2GeO)3 [(Ge–O)av. = 1.769(4) Å; (Ge–O–Ge)av.= 128.6(2)8] and (tBu2GeO)3 [Ge–O = 1.781(1) Å; (Ge–O–Ge) = 133.0(1)8].12 The cyclotrigermoxane ring in 6b adopts an unusual conformation, the O(20) atom residing outside the plane formed by the other ring atoms. Each germanium atom bears an azide group and a Cp*W(CO)2PMe3 fragment in a distorted tetrahedral environment. In order to minimize the steric repulsion between these substituents, the azide groups on Ge(1) and Ge(3) occupy the axial positions of the sixmembered ring, the transition-metal fragments the equatorial positions, and are trans arranged with respect to the corresponding substituents at the Ge(2) atom.Preliminary studies show that hydrolysis of the triazidogermyl complexes oVers a general route to ring structures. We thank the Humboldt Universität zu Berlin for financial support of this work. Notes and references † Spectroscopic data: For 2a: IR (THF, cm21): 2108 (vs), 2085 (s) [nasym(N3)], 1833 (s) [n(CO)]. IR (CH2Cl2, cm21): 2110 (vs), 2087 (s) [nasym(N3)], 1834 (s) [n(CO)]. 1H NMR (CD2Cl2, 300 MHz, 20 8C): d 1.78 (m, 2J(PH) 1 4J(PH) 8.7 Hz, 18H, PMe3), 5.18 (t, 3J(PH) 1.4 Hz, 5H, C5H5). 13C{1H} NMR (CD2Cl2, 75.5 MHz, 20 8C): d 23.6 (m, 1J(PC) 1 3J(PC) 34.9 Hz, PMe3), 85.4 (C5H5), 238.4 (t, 2J(PC) 24.7 Hz, CO). 31P{1H} NMR (CD2Cl2, 121.5 MHz, 20 8C): d 223.2 (1J(WP) 209.3 Hz). EI-MS (70 eV): m/z 629 [M]1, 587 [M 2 N3]1, 559 [M 2 N3 2 CO]1, 471 [M 2 GeN6]1, 429 [M 2 GeN9]1, 415 [M 2 GeN6 2 CO 2 N2]1, 401 [M 2 GeN9 2 CO]1, 277 [M 2 GeN9 2 2 PMe3]1.For 2b: IR (THF, cm21): 2110 (vs), 2084 (s) [nasym(N3)], 1822 (s) [n(CO)]. IR (CH2Cl2, cm21): 2112 (vs), 2087 (s) [nasym(N3)], 1822 (s) Fig. 2 ORTEP plot of a molecule of 6b in the crystal lattice of 6b?C6H6 with thermal ellipsoids drawn at the 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (8): W(1)–Ge(1) 2.5240(13), W(2)–Ge(2) 2.5365(12), W(3)–Ge(3) 2.5287(12), W(1)–P(1) 2.441(4), W(2)–P(2) 2.446(3), W(3)–P(3) 2.457(3), Ge(1)–N(1) 1.896(12), Ge(2)–N(4) 1.971(11), Ge(3)–N(7) 1.934(11), Ge(1)–O(10) 1.778(9), Ge(1)–O(20) 1.767(8), Ge(2)–O(10) 1.763(9), Ge(2)–O(30) 1.755(8), Ge(3)–O(20) 1.790(8), Ge(3)–O(30) 1.791(8), W(1)–Ge(1)–N(1) 113.0(5), W(2)–Ge(2)–N(4) 113.5(3), W(3)– Ge(3)–N(7) 112.4(4), O(10)–Ge(1)–O(20) 105.2(4), O(10)–Ge(2)–O(30) 107.9(4), O(20)–Ge(3)–O(30) 104.1(4), Ge(1)–O(10)–Ge(2) 130.8(5), Ge(1)–O(20)–Ge(3) 126.4(5), Ge(2)–O(30)–Ge(3) 131.8(4).[n(CO)]. 1H NMR (CD2Cl2, 300 MHz, 20 8C): d 1.66 (m, 2J(PH) 1 4J(PH) 8.9 Hz, 18H, PMe3), 2.00 (s, 15H, C5Me5). 13C{1H} NMR (CD2Cl2, 75.5 MHz, 20 8C): d 12.3 (C5Me5), 23.5 (m, 1J(PC) 1 3J(PC) 33.4 Hz, PMe3), 101.0 (C5Me5), 248.6 (t, 2J(PC) 28.7 Hz, CO). 31P{1H} NMR (CD2Cl2, 121.5 MHz, 20 8C): d 226.5 (1J(WP) 237.9 Hz). For 5b: IR (THF, cm21): 2114 (s), 2094 (s) [nasym(N3)], 1935 m, 1861 (vs) [n(CO)]. 1H NMR (C6D6, 300 MHz, 20 8C): d 1.09 (d, 2J(PH) 9.4 Hz, 9H, PMe3), 1.64 (s, 15H, C5Me5). 13C{1H} NMR (C6D6, 75.5 MHz, 20 8C): d 10.9 (C5Me5), 18.5 (d, 1J(PC) 37.8 Hz, PMe3), 103.0 (C5Me5). 31P{1H} NMR (C6D6, 121.5 MHz, 20 8C): d 221.3 (1J(WP) 235.4 Hz). EI-MS (70 eV): m/z 651 [M]1, 609 [M 2 N3]1, 437 [M 2 GeN6 2 CO 2 N2]1, 409 [M 2 GeN6 2 2 CO 2 N2]1. ‡ Several runs of the reactions of 1b with NaN3 were carried out and stopped at diVerent times leading, after separation of 3b, to mixtures of the germyl complexes 1b-1, 1b-2 and 2b in variable ratios. These were studied by NMR spectroscopy allowing an unequivocal assignment of the resonances of 1b-1 and 1b-2.Selected spectroscopic data: 1b-1: 1H NMR (CD2Cl2, 300 MHz, 20 8C): d 1.69 (m, 2J(PH) 1 4J(PH) 8.8 Hz, 18H, PMe3), 1.99 (s, 15H, C5Me5). 31P{1H} NMR (CD2Cl2, 121.5 MHz, 20 8C): d 228.6 (1J(WP) 242.5 Hz). 1b-2: 1H NMR (CD2Cl2, 300 MHz, 20 8C): d 1.67 (m, 2J(PH) 1 4J(PH) 8.9 Hz, 18H, PMe3), 1.98 (s, 15H, C5Me5). 13C{1H} NMR (CD2Cl2, 75.5 MHz, 20 8C): d 12.1 (C5Me5), 23.2 (m, 1J(PC) 1 3J(PC) 33.4 Hz, PMe3), 100.8 (C5Me5), 249.2 (t, 2J(PC) = 29.0 Hz, CO). 31P{1H} NMR (CD2Cl2, 121.5 MHz, 20 8C): d 227.5 (1J(WP) 236.8 Hz). In addition, IR monitoring of the reaction of 1b with NaN3 revealed the initial increase in intensity of an absorption at 2096 cm21, which is assigned to the nasym(N3) vibration of 1b-1. This absorption was gradually replaced by the two nasym(N3) absorptions of 1b-2 at 2106 and 2081 cm21, the latter overlapping with the absorptions of 2b at 2110 and 2084 cm21.In comparison, the n(CO) absorption was only slightly shifted with increasing reaction time from 1819 cm21 (1b) to 1822 cm21 (2b). § Formation of the azido complex trans-Cp*W(CO)(PMe3)2N3 was also observed to a much smaller extent and indicated in the IR spectra of the reaction solutions by a weak nasym(N3) absorption at 2160 cm21. Evidence for an associative mechanism is given by the fact, that reaction of 1b with NaN3 is considerably slower than those of 1a and 4b with NaN3, and takes weeks to achieve completion. ¶ Data for both structures were collected on a Stoe IPDS area detector. Crystal data: for 2a: C12H23GeN9OP2W, M = 627.79, orthorhombic, space group Pna21 (no. 33), a = 13.292(3), b = 17.976(5), c = 8.9106(17) Å, V = 2129.1(8) Å3, Z = 4, Dc = 1.959 g cm23, m(Mo-Ka) = 6.715 mm21, F(000) = 1208, T = 170 K. Data collection in the range 4.58 £ 2q £ 52.48. 17712 Total reflections, 4171 unique (R(int) = 0.0787) with I > 2s(I).Residual electron density, min./max. 20.907/0.932 e Å23. Refinement of the 235 parameters resulted in R1 = 0.0327, wR2(F2) = 0.0829, GOF = 1.065. For 6b: C51H78Ge3N9O9P3W3, M = 1823.51, tetragonal, space group P4� 21c (no. 114), a = b = 28.444(4), c = 15.907(3) Å, V = 12870(4) Å3, Z = 8, Dc = 1.882 g cm23, m(Mo- Ka) = 6.590 mm21, F(000) = 7055, T = 180 K. Data collection in the range 4.58 £ 2q £ 52.38. 111058 Total reflections, 12724 unique (R(int) = 0.0927) with I > 2s(I).Residual electron density, min./max. 21.165/1.525 e Å23. Refinement of the 704 parameters resulted in R1 = 0.0462, wR2(F2) = 0.1047, GOF = 1.059. CCDC reference number 186/1504. 1 G. Bertrand, J.-P. Majoral and A. Baceiredo, Acc. Chem. Res., 1986, 19, 17. 2 (a) I. Ruidisch and M. Schmidt, J. Organomet. Chem., 1964, 1, 493; (b) J. E. Drake and R. T. Hemmings, Can. J. Chem., 1973, 51, 302. 3 A. C. Filippou, J. G. Winter, G. Kociok-Köhn, C. Troll and I. Hinz, Organometallics, in press and references therein. 4 (a) J. S. Thayer and R. West, Inorg. Chem., 1964, 3, 889; (b) W. T. Reichle, Inorg. Chem., 1964, 3, 402. 5 A. C. Filippou, P. Portius and G. Kociok-Köhn, Chem. Commun., 1998, 2327. 6 J. D. Murdoch and D. W. H. Rankin, J. Chem. Soc., Chem. Commun., 1972, 748. 7 R. Blom and A. Haaland, J. Mol. Struct., 1985, 128, 21. 8 H. A. Bent, Chem. Rev., 1961, 61, 275. 9 (a) T. M. Klapötke and A. Schulz, Inorg. Chem., 1996, 35, 4995; (b) T. M. Klapötke, Chem. Ber., 1997, 130, 443. 10 Holleman-Wiberg, Lehrbuch der Anorganischen Chemie, Walter de Gruyter Verlag, Berlin, Germany, 1995. 11 A. C. Filippou, J. G. Winter, M. Feist, G. Kociok-Köhn and I. Hinz, Polyhedron, 1998, 17, 1103. 12 (a) L. Roß and M. Dräger, Chem. Ber., 1982, 115, 615; (b) H. PuV, S. Franken, W. Schuh and W. Schwab, J. Organomet. Chem., 1983, 254, 33. Communication 9/0462

ISSN:1477-9226    

DOI:10.1039/a904628c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2269–2271 2269 Systematic synthesis and photochemistry of tetraaryl porphyrins mono-substituted with a transition metal carbonyl: characterisation of a zinc porphyrin–rhenium carbonyl complex† Catherine J. Aspley, John R. Lindsay Smith and Robin N. Perutz* Department of Chemistry, University of York, Heslington, York, UK YO10 5DD. E-mail: rup1@york.ac.uk. Received 11th May 1999, Accepted 8th June 1999 A systematic synthesis designed to connect a metalloporphyrin to a metal carbonyl moiety is demonstrated through a zinc tetraphenyl porphyrin substituted with Re(CO)3(49-methyl-2,29-bipyridyl)Br via an amide bond; the emission and excited state absorption spectra are dominated by porphyrin transitions.Supramolecular systems containing porphyrins have been designed to mimic electron or energy transfer processes in photosynthesis.1 They include systems in which the porphyrin is coordinated to a peripheral transition metal complex.2–5 Our aim is to exploit the opportunities of combining a porphyrin and a single metal carbonyl into the same molecule and to investigate the intramolecular photochemical interaction between the two chromophores.Metal carbonyls have their own photochemistry and the benefit of structure-sensitive IR bands. The examples of porphyrins coordinated to a transition metal carbonyl described so far have the following transition metal carbonyl groups on the periphery of various porphyrins: Cr(CO)3, W(CO)5, RuCl2(DMSO)2CO, Re(CO)3Cl and (m-H)- Os3(CO)10.In most, the porphyrin is substituted by several metal carbonyl groups and only a few have been investigated photochemically.6–10 We report here a versatile synthesis capable of systematic variation which satisfies the following requirements: (i) it provides a simple route to monofunctionalised metalloporphyrin with established photochemistry suitable for coordination to a single metal carbonyl; (ii) it uses an adaptable linker between metalloporphyrin and metal carbonyl; (iii) it uses an accessible metal carbonyl with established photochemistry which can be linked by displacement of labile ligands.We have demonstrated these principles with the synthesis of a mono-substituted metalloporphyrin, 1, coordinated to a Re(CO)3Br moiety via an amido–bipyridyl linker unit. Tetraphenylporphyrin, H2tpp, was converted into 5-(4-aminophenyl)- 10,15,20-triphenylporphyrin 11 and metallated with zinc N N NH O N N Re Br OC C CO N N O Zn 1 † Supplementary data available: Characterisation data for complex 2.For direct electronic access see http://www.rsc.org/suppdata/dt/1999/ 2269/, otherwise available from BLDSC (No. SUP 57579, 2 pp.) or the RSC Library. See Instructions for Authors, 1999, Issue 1 (http:// www.rsc.org/dalton). acetate to give the zinc amino porphyrin. This was reacted with the acid chloride of 49-methyl-2,29-bipyridyl-4-carboxylic acid, prepared by selective oxidation of 4,49-dimethyl-2,29-bipyridine using SeO2 and AgNO3,12 to give zinc 5-[4-(49-methyl-2,29-bipyridyl- 4-carboxyamidyl)phenyl]-10,15,20-triphenylporphyrin, 2.Refluxing 2 with Re(CO)5Br in benzene gave the desired compound 1 in 12% overall yield.‡ NMR spectra were recorded in [2H5]pyridine,§ since 1 is insoluble in other, less strongly coordinating solvents. The resonances due to the bipyridyl protons are significantly shifted in the 1H NMR spectrum of 1 compared to those of 2, whereas the resonances due to the metalloporphyrin macrocyclic protons are barely aVected by peripheral coordination to rhenium (Fig. 1). This suggests that 1 has an extended conformation which was confirmed by models and NOESY experiments. The Re(CO)3 unit is detected in the 13C NMR spectrum recorded in [2H5]pyridine by the three carbonyl resonances observed at d 198.8, 198.4 and 190.5. The carbonyl region of the IR spectrum exhibits three peaks at 2020, 1920 and 1897 cm21 as expected for a fac-Re(CO)3X(diimine) complex (X = halide).13 Coordination of the Re(CO)3Br unit to the bipyridyl substi- Fig. 1 The 1H NMR spectra of zinc porphyrins 1 (top trace) and 2 (bottom trace) in [2H5]pyridine. S: pyridine resonances; j: resonances due to bipyridyl protons. N N NH O N N N N Zn 22270 J. Chem. Soc., Dalton Trans., 1999, 2269–2271 tuted metalloporphyrin (2) results in a colour change from purple to red and in a slight broadening of the Soret band.The UV–Vis spectrum of 1 is shown in Fig. 2(a). The Re to bipyridyl MLCT band anticipated at 350 to 420 nm 14 is masked by porphyrin bands.¶ The steady-state fluorescence spectra of 1 and 2 were recorded with excitation either at 355 nm, where both the metalloporphyrin and rhenium-based chromophores are expected to absorb, or at 556 nm, a metalloporphyrin Q-band absorption. The emission spectra (corrected for instrument response) are typical of a metalloporphyrin with peaks at 606 and 656 nm.The emission intensities of solutions of 1 in THF, using either 355 or 556 nm excitation, are ca. 50% lower than solutions of 2 which have an equal absorbance at the excitation wavelength (Fig. 3). The excitation spectrum of 1 [Fig. 2(b)] is in good agreement with the UV–Vis absorption spectrum [Fig. 2(a)]. Emission from the 3MLCT excited state of Re(CO)3- (bpy)Br (bpy = 2,29-bipyridine) was observed at 620 nm but no emission due to the 3MLCT excited state was detected in this region for 1. A preliminary time-resolved absorption and emission study of zinc porphyrin 1 has been carried out in THF solution using a YAG laser with a 10 ns pulse length and excitation at 355 nm.Zinc porphyrin 2 and Re(CO)3(bpy)Br were studied as controls. No significant diVerences between the transient spectra of the two zinc porphyrins were seen. The spectra are characteristic of Fig. 2 UV–Vis absorption (a) and excitation (b) spectra of metalloporphyrin 1 in THF.Fig. 3 The corrected emission spectra of 1 (dddd) and 2 (——) in THF. the porphyrin 3(pp*) excited states with intense absorption at 460 nm (Fig. 4), red-shifted from the Soret absorption of the ground state at 422 nm. Bleaching is seen in the Q-band region and weak, broad transient absorption extends into the near infra-red. There was no evidence of excited state absorption due to Re-to-bipyridylporphyrin MLCT transitions, presumably because these bands would be very weak in comparison with the very intense absorption of the zinc porphyrin transients. The decays of the 3(pp*) metalloporphyrin excited states of both zinc porphyrins fit bi-exponential functions.The 3(pp*) excited states of metalloporphyrins are known to decay by triplet–triplet quenching and unimolecular decay resulting in approximately bi-exponential kinetics.15 Both metalloporphyrins decay with essentially the same lifetimes: t1 = 3 × 1026 and t2 = 2 × 1025 s.Time-resolved emission from the 3MLCT excited state of the model, Re(CO)3Br(bpy), is detected between 580 and 670 nm with a lifetime of 63 ns. No emission could be detected in this region for zinc porphyrin 1 under these conditions. Either the rhenium-based emission has been quenched by the metalloporphyrin chromophore or the lifetime of the emission has become shorter than the instrumental limits. For comparison, Slone and Hupp reported that the Re(CO)3Cl units in their molecular squares with Re(CO)3Cl “corners” and 5,15-bis(4- pyridyl)porphyrin “sides” had only a structural rather than a direct photophysical role.9 The versatility of the synthesis of 1 opens the way to new complexes of the type porphyrin–linker–metal carbonyl with designed spatial arrangement of their components and tunable electronic and photophysical properties.Analogues of 2 with pyridyl groups in place of the bipyridyl have already been synthesised in a similar manner from the amino-porphyrin precursor.Work is currently underway to coordinate these porphyrins to peripheral W(CO)5 groups and to study the interaction of the excited states of the porphyrin chromophore and the pentacarbonyl group. Acknowledgements We thank Dr Davor Dukic for help with the laser experiments, Peter Howe for his contribution to the synthetic work, Dr Thomas Braun, Prof. Alistair J. Lees and Dr Paul H. Walton for helpful discussion, and the EPSRC for funding.Notes and references ‡ Synthesis of 1: Zinc porphyrin 2 (100 mg, 0.112 mmol) and Re(CO)5Br (46 mg, 0.112 mmol), were placed in a Schlenk tube equipped with a magnetic flea under Ar. Benzene (15 mL) was added and the solution heated to ª65 8C with stirring under Ar. After 4 h the solvent was removed under reduced pressure to give 1 in quantitative yield. UV–Vis lmax/nm (pyridine) 409 (sh, e/dm3 mol21 cm21 38 000), 429 (Soret, 465 000), 522 (Q3, 3200), 562 (Q2, 17 000) and 602 (Q1, 10 000).IR (THF) nmax/cm21 2020 (CO), 1920 (CO) and 1897 (CO). 1H NMR (500 MHz; solvent [2H5]pyridine; referenced to [2H5]pyridine at d 7.1) d 11.90 (1 H, s, amide NH), 9.41 (1 H, d, J 5.88 Hz, bpya), 9.22 (1 H, s, bpyb*), Fig. 4 The transient absorption spectrum of metalloporphyrin 1 recorded 0.8 ms after pulsed excitation at 355 nm with a YAG laser.J. Chem. Soc., Dalton Trans., 1999, 2269–2271 2271 9.16 (2 H, d, J 4.80 Hz, b-pyrrole), 9.10 (2 H, d, J 4.80 Hz, b-pyrrole), 9.07 (4 H, s, b-pyrrole), 8.97 (1 H, d, J 5.88 Hz, bpyc), 8.43 (2 H, d, J 8.43 Hz, bridging phenyld), 8.37 to 8.26 (m, two protons on phenyl bridge, six o-phenyl and two bpye*), 7.67 (9 H, m, m/p-phenyl), 7.18 (1 H, d, J 5.13 Hz, bpy f), 2.17 (3 H, s, bpy CH3). 13C NMR (126 MHz; solvent [2H5]pyridine; referenced to [2H5]pyridine at d 123.9) d 198.8 (ReCO), 198.4 (ReCO), 190.46 (ReCO), 164.1 (amide CO), 157.6 (C), 155.7 (C), 154.7 (CHa), 153.3 (CHc), 152.7 (C), 151.1, 146.8 (C), 144.3 (C), 140.8 (C), 139.1 (C), 136.2, 136.0, 135.5 (CHe), 132.8 (CH, b-pyrrole), 132.7 (CH, b-pyrrole), 129.0 (CH), 128.2 (CH f), 127.4 (CH, m/p-phenyl), 126.0 (CH), 125.8 (CH), 124.2, 123.1 (CHb), 121.8 (C), 121.2 (C), 119.7 (CHd), 21.5 (bpy CH3). 1H and 13C NMR resonances marked with a–f are correlated in the 2-D 1H–13C HETCOR spectrum. Resonances marked with * are concentration dependent. ES-MS m/z 1239 (100%, C59H37N7O4ZnBrRe), 887 [18, M 2 Re(CO)3Br].Further characterisation data (including elemental analysis) are supplied as supplementary data (SUP 57579). § The spectrum illustrated (Fig. 1) and listed was recorded at 2 × 1022 mol dm23. On dilution to 4 × 1023 mol dm23, some resonances shift indicating that there is intermolecular interaction between the porphyrin molecules in solution. Note also that in pyridine, the solvent is coordinated to the zinc atom in the porphyrin. ¶ Re(CO)3(diimine)X complexes have extinction coeYcients of 2–4 × 1023 dm3 mol21 cm21 for the MLCT bands.The porphyrin absorbance is ca. 2 × 104 dm3 mol21 cm21 in this region, even at wavelengths where the porphyrin absorbs least. 1 A. Harriman, Photosensitization by (Metallo)porphyrins: Formation and Photophysical Properties of Porphyrin Assemblies, in Photosensitization and Photocatalysis Using Inorganic and Organometallic Compounds, eds. K. Kalyanasundaram and M. Grätzel, Kluwer Academic Publishers, Dordrecht, 1993, ch. 9, pp. 273–306. 2 (a) B. Olenyuk, A. Fechtenkötter and P. J. Stang, J. Chem. Soc., Dalton Trans., 1998, 1707; (b) C. M. Drain, F. Nifiatis, A. Vasenko and J. D. Batteas, Angew. Chem., Int. Ed., 1998, 37, 2344. 3 (a) E. S. Schmidt, T. S. Calderwood and T. C. Bruice, Inorg. Chem., 1986, 25, 3718; (b) P. D. Beer, M. G. B. Drew and R. Jagessar, J. Chem. Soc., Dalton Trans., 1997, 881. 4 N. M. Rowley, S. S. Kurek, P. R. Ashton, T. A. Hamor, C. J. Jones, N. Spencer, J. A. McCleverty, G.S. Beddard, T. M. Feehan, N. T. H. White, E. J. L. McInnes, N. N. Payne and L. J. Yellowlees, Inorg. Chem., 1996, 35, 7526. 5 L. Flamigni, F. Barigletti, N. Armaroli, J.-P. Collin, J.-P. Sauvage and J. A. G. Williams, Chem. Eur. J., 1998, 4, 1744. 6 N. J. Gogan and Z. U. Siddiqui, Can. J. Chem., 1972, 50, 720. 7 G. Märkl, M. Reiss, P. Kreitmeier and H. Nöth, Angew. Chem., Int. Ed. Engl., 1995, 34, 2230. 8 (a) E. Alessio, M. Macchi, S. L. Heath and L. G. Marzilli, Inorg. Chem., 1997, 36, 5614; (b) F. Scandola, M. T. Indelli, A. Prodi and C. Kleverlaan, abstract 115a presented at the 33rd International Conference on Coordination Chemistry, Florence, 1998. 9 R. V. Slone and J. T. Hupp, Inorg. Chem., 1997, 36, 5422. 10 S. L. Darling, P. K. Y. Goh, N. Bampos, N. Feeder, M. Montalti, L. Prodi, B. F. G. Johnson and J. K. M. Sanders, Chem. Commun., 1998, 2031. 11 W. J. Kruper, Jr., T. A. Chamberlin and M. Kochanny, J. Org. Chem., 1989, 54, 2753. 12 D. G. McCaVerty, B. M. Bishop, C. G. Wall, S. G. Hughes, S. L. Mecklenberg, T. J. Meyer and B. W. Erickson, Tetrahedron, 1995, 51, 1093. 13 e.g. (a) M. Wrighton and D. L. Morse, J. Am. Chem. Soc., 1974, 96, 998; (b) I. P. Clark, M. W. George, F. P. A. Johnson and J. J. Turner, Chem. Commun., 1996, 1587. 14 W. Kaim, H. E. A. Kramer, C. Vogler and J. Rieker, J. Organomet. Chem., 1989, 367, 107. 15 K. Kalyanasundaram, Photochemistry of Polypyridine and Porphyrin Complexes, Academic Press, 1992, p. 414. Communication 9/03779I

ISSN:1477-9226    

DOI:10.1039/a903779i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2273–2274 2273 The first symmetrical tetrarheniumcyclodiyne type cluster containing phosphine ligands: Re4(Ï-O)4Cl4[P(C6H4OMe-p)3]4 Sophia S. Lau, Phillip E. Fanwick and Richard A. Walton * Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393, USA. E-mail: walton@chem.purdue.edu Received 28th April 1999, Accepted 27th May 1999 The reactions of methanol solutions of cis-Re2(Ï-O2- CCH3)2Cl4(H2O)2 with PAr3 (Ar = Ph, C6H4Me-p, C6H4Mem or C6H4Cl-p) afford the quadruply bonded dirhenium(IV,II) complexes Cl2(MeO)2ReReCl2(PAr3)2, whereas P(C6H4OMe-p)3 gives the complex Re4(Ï-O)4- Cl4[P(C6H4OMe-p)3]4, which X-ray crystallography has shown is the first symmetrical, neutral, tetrarheniumcyclodiyne type cluster containing phosphine ligands.The reactions of the dirhenium(III) carboxylate complex cis- Re2(m-O2CCH3)2Cl4(H2O)2 (1) with triphenylphosphine in primary alcohol solvents are unusual in that they aVord the unsymmetrical, quadruply bonded, alkoxide complexes Re2Cl4(OR)2(PAr3)2 (2), Ar = Ph [eqn.(1)], which are formally cis-Re2(O2CCH3)2Cl4(H2O)2 1 2PAr3 1 2ROH æÆ Re2Cl4(OR)2(PAr3)2 1 2CH3CO2H 1 2H2O (1) Re(IV)–Re(II) species that are derived from the Re(III)–Re(III) core by an intramolecular disproportionation.1 Subsequently, Chisholm and co-workers 2 discovered the remarkable compound Mo2(OPri)4(dmpe)2 (dmpe = Me2PCH2CH2PMe2) which is formally a Mo(IV)–Mo(0) complex, i.e.(PriO)4Mo- Mo(dmpe)2, and retains a metal–metal multiple bond.3,4 Our interest in probing the factors which favor the stability of unsymmetrical structures such as 2, coupled with attempts to design synthetic strategies to the symmetrical isomer 3,† have led us to study the reactions of the synthon cis-Re2(m-O2- CCH3)2Cl4(H2O)2 5 with triarylphosphines which vary in basicity and cone angle. We report in the present communication our findings concerning the reaction of 1 with P(C6H4OMe-p)3 in methanol which aVords a route to the prototype of a new class of neutral, symmetrical, tetrarheniumcyclodiyne type of cluster, viz., Re4(m-O)4Cl4[P(C6H4OMe-p)3]4 (4).Although methanol solutions of 1 react with PAr3 (Ar = Ph, C6H4Me-p, C6H4Me-m or C6H4Cl-p) to yield methoxide complexes of type 2, reactions with P(C6H4OMe-p)3 aVord the red complex 4 under these same conditions.‡ This compound could be isolated reproducibly in yields of ca. 35%.The use of refluxing ethanol as the reaction solvent produced only very small quantities of 4; the major product was the dirhenium(III,II) complex Re2(m-O2CCH3)Cl4[P(C6H4OMe-p)3]2,6§ along with small amounts of Re2Cl6[P(C6H4OMe-p)3]2 and Re2Cl4(OEt)2- O Re O Cl Cl PAr3 Re PAr3 Cl R R 2 Ar3P Re Cl Cl O Cl Re PAr3 O Cl 3 R R Cl Re Re O O Re Re OO Cl P Cl P Cl Cl P P 4 [P(C6H4OMe-p)3]2. The substitution of the pyridine analogue cis-Re2(m-O2CCH3)2Cl4(py)2 for 1 in the reaction with P(C6H4- OMe-p)3 in refluxing methanol aVorded 4 in low yield (<10%). While the reaction temperature may be important in the formation of 4, the origin of the oxygen in the {Re4(m-O)4} core of 4 is probably the alcohol solvent and not coordinated or adventitious water since the addition of varying amounts of water did not increase the yield of this product.The diamagnetic complex 4 was shown by X-ray crystallography to contain a rectangular cluster of metal atoms with two Re]] ] Re bonds and two Re–Re bonds.¶ Formally, this unit arises from the [2 1 2] cycloaddition of two Re]] ]] Re units (derived from two molecules of 1) by loss of their d components.An ORTEP representation of the structure of 4 is shown in Fig. 1. This centrosymmetric cluster possesses Re–Re Fig. 1 ORTEP13 representation of the structure of the tetranuclear cluster Re4(m-O)4Cl4[P(C6H4OMe-p)3]4 in crystals of 4?2MeOH. Thermal ellipsoids are drawn at the 50% probability level except for the phenyl group atoms of the P(C6H4OMe-p)3 ligands which are circles of arbitrary radius.Unlabeled atoms are related to the labeled atoms by an inversion center. Selected bond distances (Å) and bond angles (8): Re(1)–Re(2) 2.2726(5), Re(1)–Re(2)9 2.5388(5), Re(1)–Cl(1) 2.350(2), Re(2)–Cl(2) 2.359(2), Re(1)–P(1) 2.521(2), Re(2)–P(2) 2.524(2), Re(1)– O(1) 1.943(5), Re(1)–O(2) 1.995(5), Re(2)–O(1) 1.960(5), Re(2)–O(2) 1.988(5); Re(1)–Re(2)–Re(1)9 90.099(16), Re(2)9–Re(1)–Re(2) 89.901(16), Cl(1)–Re(1)–P(1) 84.16(7), Cl(2)–Re(2)–P(2) 84.41(7), O(1)–Re(1)–O(2) 96.0(2), O(1)–Re(2)–O(2) 95.7(2), Re(1)–O(1)–Re(2) 81.15(19), Re(2)–O(2)–Re(1) 79.19(19). The four Re atoms shown are those of the primary form of a disorder in which a secondary form (atoms Re(3) and Re(4)), appearing to share the same ligand atoms, is in a plane approximately orthogonal to the primary form.The distances Re(3)–Re(4) and Re(3)–Re(4)9 are 2.275(8) Å and 2.528(8) Å, respectively.2274 J.Chem. Soc., Dalton Trans., 1999, 2273–2274 bond distances of 2.273(1) Å and 2.539(1) Å, the longer distance being associated with the [Re(m-O)2Re] units. These Re]] ] Re and Re–Re bond distances are similar to those encountered in the [Bu4 nN]1 salts of the [Re4(m-O)2(m-OMe)2Cl8]22, [Re4(m-O)2(m- OMe)(m-Cl)Cl8]22 and [Re4(m-O)2(m-Cl)2Cl8]22 anions that have been structurally characterized by Cotton and co-workers.7,8 Unlike the latter species, compound 4 is neutral, contains phosphine ligands, and is the first tetrarheniumcyclodiyne type cluster with a [Re4(m-O)4]41 core.This compound represents one extreme in the chemistry of molecular rectangles (cyclic quartets) which range from those which contain four separate ligand-bridged metal centers 9 to those with pairs of ligandbridged multiply bonded dimetal units which may or may not be linked by metal–metal bonds within the rectangular cluster.10 While this type of dimerization of quadruply bonded dimetal complexes were first encountered by McCarley and co-workers many years ago,11 and has subsequently been developed quite extensively in Mo and W chemistry,12 it is rare in Re chemistry. 7,8 Our work expands this field and provides an interesting and potentially useful synthon for further reactivity studies. While 4 does not possess any readily accessible reversible redox chemistry, the P(C6H4OMe-p)3 ligands are substitutionally labile as shown by the conversion of 4 to Re4(m-O)4Cl4- (PMe2Ph)4 upon its reaction with PMe2Ph.Further studies are underway to develop the reaction chemistry of this new cluster and ones like it. Notes and references † Other isomers, based upon a (Ar3P)(RO)Cl2ReReCl2(OR)(PAr3) arrangement of ligands, are of course possible. ‡ Synthesis of 4: a sample of P(C6H4OMe-p)3 (184 mg, 0.522 mmol) was heated in methanol (20 mL) until it had completely dissolved, whereupon a quantity of 1 (113 mg, 0.169 mmol) was added via an addition sidearm. The resulting reaction mixture was then refluxed for 3 days, and the crop of red crystalline 4 was filtered oV, washed with methanol and diethyl ether; yield 67 mg (33%).Calc. for C86H92Cl4- O18P4Re4 (i.e. 4?2MeOH): C, 42.61; H, 3.83; Cl, 5.85. Found: C, 41.38; H, 3.63; Cl, 6.35%. A suitable single crystal of composition 4?2MeOH was selected from this batch for an X-ray structure analysis. Far IR spectrum (Nujol mull): n(Re–Cl) 326ms and 276m cm21. 1H NMR spectrum (CD2Cl2): d C6H4 of C6H4OMe-p 18.15m, 17.58m, 16.90m, 16.80m, 16.33m, 16.22m; OMe of C6H4OMe-p 13.87s, 13.84s; 13.58s; MeOH 13.42s. 31P-{1H} NMR spectrum (CD2Cl2): d 113.6s. Cyclic voltammogram (0.1 M Bu4 nNPF6 CH2Cl2, Pt-bead electrode, scan rate 200 mV s21, potential range 11.5 to 21.5 V, potentials vs. Ag– AgCl): Ep,a = 10.98 V. § This product has properties very similar to those of the structurally characterized complex Re2(m-O2CCH3)Cl4(PPh3)2.6 ¶ Crystal data: 4?2MeOH (C86H92Cl4O18P4Re4, M = 2424.19) at 296 K: space group P21/c with a = 13.9995(7), b = 23.5126(7), c = 14.3633(7) Å, b = 114.1998(16)8, U = 4312.4(6) Å3, Z = 2, Dc = 1.867 g cm23, m(Mo- Ka) = 5.937 mm21.Data collection performed on a Nonius Kappa- CCD and the structure solved by direct methods using SIR97 13 and refined through the use of SHELX-97:13 35082 reflections measured, 10854 unique (Rint = 0.101). Hydrogen atoms included but constrained to ride on the atom to which they are bonded.A cut-oV Fo 2 > 2s(Fo 2) used for R-factor calculations to give R(Fo) = 0.062, Rw(Fo 2) = 0.104, and GOF = 1.138. Disorder involving the four Re atoms of the rectangular cluster such that there are two incompletely occupied, approximately orthogonal sets, which to a first approximation share the same set of ligand atoms. The multiplicities of the primary and secondary forms are 0.949 and 0.051, respectively. CCDC reference number 186/1485.See http://www.rsc.org/suppdata/dt/1999/2273/ for crystallographic files in .cif format. 1 (a) A. R. Chakravarty, F. A. Cotton, A. R. Cutler, S. M. Tetrick and R. A. Walton, J. Am. Chem. Soc., 1985, 107, 4795; (b) A. R. Chakravarty, F. A. Cotton, A. R. Cutler and R. A. Walton, Inorg. Chem., 1986, 25, 3619. 2 M. H. Chisholm, J. C. HuVman and W. G. Van Der Sluys, J. Am. Chem. Soc., 1987, 109, 2514. 3 B. E. Bursten and W. F. Schneider, Inorg. Chem., 1989, 28, 3292. 4 R. Wiest, A.Strich and M. Bénard, New J. Chem., 1991, 15, 801. 5 R. A. Walton, J. Cluster Sci., 1994, 5, 173. 6 A. R. Cutler, P. E. Fanwick and R. A. Walton, Inorg. Chem., 1987, 26, 3811. 7 J. D. Chen and F. A. Cotton, J. Am. Chem. Soc, 1991, 113, 5857. 8 F. A. Cotton and E. V. Dikarev, J. Cluster Sci., 1995, 6, 411. 9 See for example: (a) J. A. Whiteford, C. V. Lu and P. J. Stang, J. Am. Chem. Soc., 1997, 119, 2524; (b) K. D. Benkstein, J. T. Hupp and C. L. Stern, J. Am. Chem. Soc., 1998, 120, 12982; (c) K. D. Benkstein, J. T. Hupp and C. L. Stern, Inorg. Chem., 1998, 37, 5404; (d ) S. M. Woessner, J. B. Helms, Y. Shen and B. P. Sullivan, Inorg. Chem., 1998, 37, 5406. 10 F. A. Cotton, L. M. Daniels, I. Guimet, R. W. Henning, G. T. Jordon, IV, C. Lin, C. A. Murillo and A. J. Schultz, J. Am. Chem. Soc., 1998, 120, 12531. 11 R. N. McGinnis, T. R. Ryan and R. E. McCarley, J. Am. Chem. Soc., 1978, 100, 7900. 12 F. A. Cotton and R. A. Walton, Multiple Bonds Between Metal Atoms, Oxford University Press, Oxford, 2nd edn., 1993, pp. 554–558. 13 A. Altomare, M. C. Burla, M. Camalli, G. Cascarano, C. Giacorazzo, A. Guagliardi, A. Moliterni, G. Polidori and R. Spagna, SIR97, J. Appl. Crystallogr., 1999, 32, 115; G. M. Sheldrick, SHELX-97, University of Göttingen, 1997; C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. Communication 9/03367J

ISSN:1477-9226    

DOI:10.1039/a903367j

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2275–2277 2275 Labile adducts of TiCl4 with thionyl chloride structurally characterized at low temperature: a comparison with the zirconium and hafnium analogues, [MCl4(SOCl2)]2 Fausto Calderazzo,a Michele D’Attoma,a Fabio Marchetti,b Guido Pampaloni *a and Sergei I. Troyanov *c a Universitá di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126, Pisa, Italy. E-mail: pampa@dcci.unipi.it b Università di Roma “La Sapienza”, Dipartimento di Ingegneria Chimica, dei Materiali e delle Materie Prime e Metallurgia, Via del Castro Laurenziano 7, Box 15 Roma 62, I-00185 Roma, Italy c Moscow State University, Department of Chemistry, Vorobjevy Gory, 119899 Moscow, Russia.E-mail: troyanov@thermo.chem.msu.su Received 25th May 1999, Accepted 9th June 1999 The thermally unstable (decomp. ca. 230 8C) titanium derivative [ TiCl4(SOCl2)]2, prepared from TiCl4 and SOCl2, forms three crystalline modifications (I–III) in the temperature range between 220 and 234 K; these modifications differ in the orientation of the SOCl2 ligand with respect to the titanium-containing fragment within the dinuclear molecule and in the packing modes due to intermolecular S ? ? ? Cl interactions at distances between 3.25 and 3.82 Å.Thionyl chloride, a reagent frequently used for the preparation of anhydrous metal chlorides,1 is a poor electron donor, as denoted by its low donor number (DN = 0.4).2 As far as metal chlorides of Group 4 are concerned, high solubility (HfCl4, mp 705 K), partial or complete miscibility (TiCl4, mp 284 K) with SOCl2 at room temperature were observed in our Laboratories.Moreover, in an early study on the TiCl4/SOCl2 system,3 a smooth maximum on the freezing point diagram was found at ca. 243 K, in the range of SOCl2 composition between about 40 and 70 mol%, which was attributed to the formation of a 1 : 1 adduct. This prompted us to investigate the molecular basis of these phenomena; further interest in this project came from the paucity of data concerning MCln/SOCl2 adducts.3a,4 We wish to report that while HfCl4 forms a binuclear complex with thionyl chloride of composition [HfCl4(SOCl2)]2 which is stable at room temperature, similar to that already reported in the literature for ZrCl4,5 the corresponding adduct with TiCl4 of the identical molecular composition [TiCl4(SOCl2)]2 and structure, is stable at low temperature only, according to both spectrophotometric and X-ray diVractometric experiments.† Titanium tetrachloride dissolves in SOCl2 to give a colorless solution which aVords large yellow crystals at dry ice temperature. At about 243 K, the solid converts into a liquid.The room temperature IR spectrum of TiCl4 dissolved in SOCl2 shows the absorption due to uncoordinated SOCl2 only at 1230 cm21. For comparison, solutions of MCl4 (M = Zr, Hf) in SOCl2, containing the thionyl chloride complex [MCl4- (SOCl2)]2, show a strong absorption at 1151 cm21 (M = Zr) or at 1145 cm21 (M = Hf) due to the S]] O stretching vibration of coordinated SOCl2.The X-ray crystallographic study of the materials obtained by cooling the TiCl4/SOCl2 solutions established the existence of three crystalline modifications of the 1 : 1 adduct. By repeated cycles of heating and cooling of the solutions, a single crystal of the dinuclear, chloride-bridged 1 : 1 adduct of TiCl4 with SOCl2, [TiCl4(SOCl2)]2, was obtained, hereinafter indicated as I, see Fig. 1, which is isotypic with the zirconium derivative 5 isolated by Collins and Drew at room temperature. The titanium atom of I, see Fig. 1, is hexacoordinated to five chlorine atoms and to the oxygen atom of the thionyl chloride ligand in an approximately octahedral coordination. The molecule is centrosymmetric. The mean Ti–Clt bond length is 2.221 Å, whereas the mean Ti–Clb (Clb, bridging chloride; Clt, terminal chloride) bond distance of 2.457 Å is appreciably longer.In [TiCl4(POCl3)]2,9 the mean Ti–Clt and Ti–Clb bond distances are 2.23 and 2.49 Å, respectively. The Ti–Cl(4) bond distance of 2.195 Å, trans to the Ti–O bond (2.196 Å), is the shortest of the three Ti–Clt bond distances. The O–Ti–Cl(4) bond angle is 171.08 and the mean values of the O–Ti–Clt (equatorial) and O–Ti–Clb bond angles are 87.7 and 80.48, respectively, both below 908. In the course of the freezing/melting cycles, single crystals of two additional crystalline modifications of [TiCl4(SOCl2)]2 were obtained.These crystalline modifications, hereinafter denoted as II and III, are stable over several hours below 220 K. Near their melting point (234 ± 2 K), they convert into I, whose melting point is 2–3 8C higher. Modifications I–III contain the same Ti2Cl8O2 frame, the only pronounced diVerence concerns the coordinated SOCl2 ligands. The Ti–O–S bond angle in I (154.78) decreases to 148.88 and 148.68 in II and III, respectively.Moreover, the three modifications of [TiCl4(SOCl2)]2 diVer in the dihedral angle f between the pseudosymmetry plane of the SOCl2 moiety (passing through the atoms S and O and bisecting the Cl–S–Cl angle) and the pseudosymmetry plane of the Ti2Cl8 moiety (passing through the titanium atoms and the two Cl(4) atoms). The f angle amounts, in fact, to 2.4, 57.4, and 50.48 in I, II, and III, respectively. The smaller angle f found in I reflects its Fig. 1 The centrosymmetric molecule of [TiCl4(SOCl2)]2 I. Main distances [Å]: Ti–Cl(1), 2.465(1); Ti–Cl(19), 2.450(1); Ti–Cl(2), 2.229(1); Ti–Cl(3), 2.210(1); Ti–Cl(4), 2.195(1); Ti–O, 2.196(3); S–O, 1.463(3); S–Cl(5), 2.043(1); S–Cl(6), 2.038(1).2276 J. Chem. Soc., Dalton Trans., 1999, 2275–2277 more symmetrical shape. This feature is associated with a closer packing of I, the V/Z ratio of 437.5Å3 being compared with 440.5 Å3 for II, both measured at 140 K.Phase III at 220 K shows a V/Z ratio of 451.6 Å3. Intermolecular S ? ? ? Cl interactions are important for both the crystal packing of I–III and for allowing the chalcogen atom to achieve hexacoordination, a situation frequently encountered in derivatives of sulfur(IV), such as (SCl3)(AlCl4),10 (SCl3)(Ti2Cl9),11 or SOCl2 itself.12 Although the S–O and S–Cl bond distances are similar within the three modifications, the sulfur environments and interaction distances are significantly diVerent.For example, in I, see Fig. 2, there are additional S ? ? ? Cl interactions with the chlorine atoms of two diVerent binuclear units, i.e., Cl(2ii) (S ? ? ? Cl = 3.464 Å), Cl(3iii) (3.392 Å), and Cl(4ii) (3.247 Å), where ii = x 2 1, y, z 2 1; iii = x, y, z 2 1. In II, see Fig. 2, the interactions involve the S-atom and the chlorine atoms of four diVerent binuclear units, i.e., Cl(2iv) (S ? ? ? Cl = 3.747 Å), Cl(3v) (3.420 Å), Cl(4vi) (3.791 Å), and Cl(5vii) (S ? ? ? Cl = 3.760 Å) where iv = x, y 2 1, z; v = x 1 1, y, z; vi = 2x, 2y, 2z; vii = x 1 1, y, z 1 1.As far as III is concerned, the interactions involve the sulfur and three chlorine atoms within the same adjacent binuclear unit at distances ranging from 3.486 to 3.820 Å, Thus, the tendency of sulfur(IV) to interact with atoms of the adjacent binuclear unit(s) substantially contributes to the stability of the observed three crystalline modifications of [TiCl4(SOCl2)]2.At variance with titanium and similar to zirconium,5 HfCl4 dissolves in SOCl2 to give a colorless adduct stable at room temperature. An X-ray diVractometric experiment † has shown the hafnium derivative to be isotypic with both the corresponding zirconium compound‡ and I, the metal–ligand bond distances changing according to the ionic radii of the hexacoordinated central metal atom: Ti (0.605 Å), Zr (0.72 Å), and Hf (0.71 Å).13 In the hafnium compound, the sulfur atoms also achieve hexacoordination by interaction with three chlorine Fig. 2 Crystal packing of [TiCl4(SOCl2)]2, I–III, along the x axis. atoms of two diVerent binuclear units, i.e., S ? ? ? Cl(2ii) (3.609 Å), S ? ? ? Cl(3iii) (3.443 Å), and S ? ? ? Cl(4ii) (3.316 Å): most of these distances are shorter than the sum of the van der Waals radii (3.55 Å).14 It is noteworthy that the 1 : 1 MCl4/SOCl2 adducts were isolated in the presence of a large excess of the ligand; in particular, crystals of [TiCl4(SOCl2)]2 were obtained even with SOCl2 to TiCl4 molar ratios as high as 8 : 1, thus suggesting that the 2 : 1 adducts, which are typical of MCl4 with more basic ligands containing oxygen or nitrogen donor atoms,15 are not stable under these experimental conditions.The low stability of the titanium derivative at room temperature is consistent with the observation that tetracoordination of the titanium atom is the preferred one for TiCl4,16 both in the liquid and in the solid state, while in ZrCl4 and HfCl4 the metal is octahedrally coordinated 17 to form polynuclear chloride-bridged aggregates. Apparently, the existence of [TiCl4(SOCl2)]2 is due to relatively weak Ti–O covalent bonds supported by additional S ? ? ? Cl interactions.The increase of the M–O bond enthalpy on descending the group Ti–Hf explains the higher stability of the zirconium and hafnium analogs up to at least room temperature. These results are complementary to those reported years ago by Floriani and co-workers,18 who isolated labile adducts of TiCl4 with benzene or 1,2,4,5-tetramethylbenzene and SO2 of formula [(TiCl4)2(SO2)2(C6H2R4)2], R = H, Me; in the case of the benzene derivative, S ? ? ? C weak interactions were suggested to be important in stabilizing the adduct.The less unfavourable entropic contribution in our case (SO2, bp 263 K; SOCl2, bp 349 K) also explains our successful isolation of the thionyl chloride adduct.In conclusion, we have shown that: i) the maximum at about 243 K in the freezing point diagram of the TiCl4/SOCl2 system corresponds to the formation of at least three diVerent 1 : 1 crystalline modifications; ii) non-isolable, presumably less stable, 1: 2 modifications may exist, at higher SOCl2 mol% compositions; iii) the formation of the Ti–O coordinated bond in the 1 : 1 adducts requires some further intermolecular interaction to stabilize the system, namely S ? ? ? Cl contacts.Acknowledgements The authors wish to thank the Ministero dell’ Università e della Ricerca Scientifica e Tecnologica (MURST, Roma) for financial support. Notes and references † [TiCl4(SOCl2)]2: A solution of TiCl4 (4.4 ml, 40.0 mmol) in SOCl2 (15 ml, 205.4 mmol) was cooled at dry-ice temperature. From the colorless solution, the light yellow adduct was collected by filtration at low temperature. Attempts to dry the substance in vacuo resulted in decomposition, the volatile components recombining in the cold trap (77 K).For X-ray diVractometry, single crystals of phases I, II and III of [TiCl4(SOCl2)]2 were obtained by repeated cooling and heating cycles of TiCl4/SOCl2 mixtures sealed in capillaries directly mounted on the diffractometer. The capillaries were firstly cooled (215–220 K) until the solution froze to a polycrystalline solid; they were then slowly heated until the major part of the solid melted. The temperature was then slowly lowered (0.5 8C min21) causing the growth of the crystal seeds.The melting–freezing procedure was repeated until single crystals of the appropriate quality were obtained. Modification I (mp 234 K) was obtained as a stable phase when the crystal growth occurred between 230 and 234 K. The first cycles of crystal growth gave modifications II and III from mixtures containing SOCl2 and TiCl4 in molar ratios ranging between 2.2 and 4.0. Crystal data: I, STADI-4(Stoe) diVractometer; M, 617.32; crystal size 0.4 × 0.3 × 0.3 mm; T = 140(2) K; monoclinic, P21/c; a = 6.442(1), b = 21.148(4), c = 7.065(1) Å; b = 114.63(3)8; V = 874.9 Å3; Z = 2; Dcalc = 2.343 g cm23, m = 2.968 mm21; reflections: 1911 (collected), 1911 (unique); ,R1 = 0.037.II, STADI-4 (Stoe) diVractometer; crystal size, 0.5 × 0.35 × 0.3 mm; T = 140(2) K; triclinic, P1� ; a = 6.179(1), b = 7.679(2), c = 10.715(2) Å; a = 107.74(3)8, b = 91.33(3)8 g = 112.81(3)8 V = 440.54 Å3; Z = 1; Dcalc = 2.327 g cm23; m = 2.948 mm21; reflections: 1827 (collected), 1827 (unique); R1 = 0.036.III, IPDS (Stoe) diVractometer; crystal size, 0.4 × 0.3 × 0.3 mm; T = 220(2) K; monoclinic, P21/c; a = 7.563(2), b = 10.074(3), c =J. Chem. Soc., Dalton Trans., 1999, 2275–2277 2277 12.235(4) Å; b = 103.36(3)8; V = 903.7 Å3; Z = 2; Dcalc = 2.269 g cm23; m = 2.874 mm21; reflections: 7852 (collected), 2032 (unique); R1 = 0.044. The structures were solved by using direct methods (SHELXS-866) and refined anisotropically using SHELXL-93.7 [HfCl4(SOCl2)]2?HfCl4 (1.964 g, 6.1 mmol) was treated with SOCl2 (15 ml, 205.4 mmol) at room temperature.Warming the colorless suspension at 343 K for 15 min aVorded a solution which was then cooled to 278 K giving colorless crystals of [HfCl4(SOCl2)]2 (64% yield, including a further crop from the mother liquor cooled at 243 K) with satisfactory analytical data (Hf, Cl), after drying in vacuo. IR (KBr, Nujol), cm21: 1122s, n(S]] O); 503 m, nas(S–Cl); 479m, nS(S–Cl).Crystal data: M, 878.5; P4 Siemens; crystal size, 0.3 × 0.3 × 0.09 mm; T = 293(2) K; monoclinic, P21/c; a = 6.6876(5), b = 21.581(4), c = 7.2813(4) Å; b = 114.654(5)8; V = 955.1(2) Å3; Z = 2; Dcalc 3.055 g cm23; m = 12.746 mm21; reflections: 3549 (collected), 2797 (unique); R1 = 0.043. The structure was solved by using direct methods and refined anisotropically by means of SHELXTL-Plus.8 CCDC reference number: 186/1503. See http// www.rsc.org/suppdata/dt/1999/2275 for crystallographic files in .cif format.‡ The crystal data 5 of [ZrCl4(SOCl2)]2 have been recalculated in the space group P21/c for a better comparison with the titanium and the hafnium analogs. 1 (a) H. Hecht, Z. Anorg. Allg. Chem., 1947, 254, 37; (b) A. R. Pray, Inorg. Synth., 1957, 5, 152; (c) J. H. Freeman and M. L. Smith, J. Inorg. Nucl. Chem., 1958, 7, 224; (d ) H. J. Seyfert, Z. Anorg. Allg. Chem., 1962, 317, 123; (e) V. Yu. Kukushkin, Russ.J. Inorg. Chem., 1990, 35, 1273; ( f ) F. Calderazzo, J. Organomet. Chem., 1990, 400, 303. 2 V. Gutmann, Chemtech, 1977, 255; V. Gutmann, The Donor- Acceptor Approach to Molecular Interactions, Plenum Press, New York/London, 1978. 3 (a) B. A. Voitovich, E. V. Zvagol’skaya and N. Kh. Tumanova, Izv. Akad. Nauk SSSR, Metally, 1965, 46; Chem. Abstr., 1966, 64, 15429h; (b) J. C. Sheldon and S. Y. Tyree, Jr., J. Am. Chem. Soc., 1959, 81, 2290. 4 I. Buscaglione, C. Stables and H. SutcliVe, Inorg.Chim. Acta, 1987, 128, 7. 5 R. K. Collins and M. G. B. Drew, J. Chem. Soc. (A), 1971, 3610. 6 G. M. Sheldrick, SHELXS-86, Program for Solution of Crystal Structures from DiVraction Data, Universität Göttingen, 1986. 7 G. M. Sheldrick, SHELXL-93, Program for Crystal Structure Refinement, Universität Göttingen, 1993. 8 G. M. Sheldrick, SHELXTL-Plus, Rel. 5.03, Siemens Analytical X-Ray Instruments Inc., Madison, Wisconsin, USA, 1995. 9 C. I. Branden, Acta Chem. Scand., 1962, 16, 1806. 10 S. I. Troyanov, L. Kolditz and A. Radde, Z. Chem., 1983, 23, 136. 11 S. I. Troyanov, V. B. Rybakov, N. I. Timoshchenko and Z. A. Fokina, Zhurn. Neorg. Khim., 1990, 35, 1683. 12 D. Mootz and A. Merschenz-Quack, Acta Crystallogr., Sect. C, 1988, 44, 926. 13 R. D. Shannon, Acta Crystallogr., Sect. A, 1976, 32, 751. 14 A. Bondi, J. Phys. Chem., 1964, 68, 441. 15 C. A. McAuliVe and D. S. Barratt, in Comprehensive Coordination Chemistry, eds. G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon, Oxford, 1987, vol. 3, p. 323; R. C. Fay, in Comprehensive Coordination Chemistry, eds. G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon, Oxford, 1987, vol. 3, p. 363. 16 (a) P. Brand and H. Sackmann, Z. Anorg. Allg. Chem., 1963, 321, 262; (b) S. I. Troyanov and E. M. Snigireva, Russ. J. Inorg. Chem., 1999, submitted. 17 ZrCl4:. Krebs, Z. Anorg. Allg. Chem., 1970, 278, 263; HfCl4: R. Niewa and H. Jacobs, Z. Kristallogr., 1995, 210, 687. 18 E. Solari, C. Floriani and K. Schenk, J. Chem. Soc., Chem. Commun., 1990, 963. Communication 9/04186I

ISSN:1477-9226    

DOI:10.1039/a904186i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 2277–2278 2277 Bis[dirhodium(II)] complexes with a Rh4(Ï-Cl)4 core: preparation and characterization ‡ Zhiyong Yang, Hiroki Oki, Masahiro Ebihara and Takashi Kawamura *,† Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan The reaction of [Rh2(O2CPrn)4] or [Rh2(mhp)4] (Hmhp = 2- hydroxy-6-methylpyridine) with a trialkylchlorosilane followed by crystallization from a nitrile unexpectedly gave [Rh4(O2- CPrn)4Cl4(CH3CN)4] 1 or an isomer of [Rh4(mhp)4Cl4(PhCN)2] both with a ‘twisted-cage’ Rh4(m-Cl)4 core, which were studied by X-ray crystallography, cyclic voltammetry and UV/VIS spectroscopy; 1 catalyzed the hydrogenation of acrylic acid in water.The chloro ligand is interesting because it is substitutionally labile, co-ordinates in both terminal and bridging fashion and has metal–ligand s- and p-type electronic interactions. When the ligand is bridging it may induce metal–metal indirect electronic interactions through its orbital(s).We have unexpectedly isolated bis[dirhodium(II)] complexes supported by four chloro bridges in low to moderate yields in trials aimed at substituting the bridging ligands of [Rh2(O2CPrn)4] or [Rh2(mhp)4] (Hmhp = 2-hydroxy-6-methylpyridine) with chloro ligands. Stimulated by the work of Cotton and co-workers in preparing [Rh2(O2CCH3)2Cl2(L]L)] and [Rh2Cl4(L]L)2] (L]L denotes a diphosphine) by the reaction of [Rh2(O2CCH3)4] with (CH3)3- SiCl in the presence of L]L we treated [Rh2(O2CPrn)4] or [Rh2(mhp)4] with trialkylchlorosilane.Since complexes with an M4(m-X)4 (X = halogen) skeleton similar to that found in [Rh4(O2CPrn 4)Cl4(CH3CN)4] and [Rh4(mhp)4Cl4(PhCN)2] have been known to us only in the chemistry of MoIII with a limited number of compounds,2 we report here the preparation, crystal structures and properties of the current Rh4(m-Cl)4 complexes as a preliminary communication.Axial-ligand free [Rh2(O2CPrn)4] 3 (2.22 g, 4.0 mmol) was heated with (C2H5)3SiCl (3.0 cm3, 18 mmol) in toluene (70 cm3) at reflux under Ar for 20 h to give a brown precipitate. After collection the precipitate was stirred with 40 mL of CH3CN to give a yellow-green powder of [Rh4(O2CPrn)4Cl4(CH3CN)4] 1 in 35% yield. The reaction of trans-(hh,tt)-[Rh2(mhp)4] (where hh,tt represents head-to-head, tail-to-tail) 4 with (CH3)3SiCl in toluene at reflux gave a brown precipitate, which was loaded onto a silica-gel column and eluted with a CH2Cl2–CH3CN mixture (4 : 1 v/v) to give (hh,hh)-[Rh4(mhp)4Cl4(CH3CN)2] [2; see Fig. 2 in the following paragraph for the arrangement of the mhp bridging ligands in the ‘(hh,hh)-isomer’] in 8% yield as the second band (yellow). Although we could obtain only poor-quality single crystals of 2, layering and solution of 2 in † E-Mail: kawamura@apchem.gifu-u.ac.jp ‡ Supplementary data available: UV/VIS absorption spectra of [Rh4(O2CPrn)4Cl4(CH3CN)4] in CH3CN, CH3CN–CH2Cl2 and CH2Cl2 and electronic spectra of [Rh4(O2CPrn)4Cl4L4] (L = CH3CN or H2O).For direct electronic access see http://www.rsc.org/suppdata/dt/1998/ 2277/, otherwise available from BLDSC (No. SUP 57 397, 3 pp.) or the RSC Library. See Instructions for Authors, 1998, Issue 1 (http:// www.rsc.org/dalton). CH2Cl2–PhCN with hexane resulted in axial ligand exchange and gave small brown single crystals of (hh,hh)-[Rh4(mhp)4Cl4- (PhCN)2] 3 which were of moderate quality for X-ray study.When [Rh2(O2CPrn)4] was refluxed with (CH3)3SiCl in CH3CN until complete consumption of the starting dirhodium complex had occurred (TLC), only a mononuclear rhodium(III) complex, mer-[Rh(CH3CN)3Cl3],5 was isolated. The crystal structures of 1 § and 3 ¶ are shown in Figs. 1 and 2, respectively. The two RhII–RhII units of these Rh4(m-Cl)4 complexes, each of which contains two bridging carboxylato or mhp ligands spanning a RhII]RhII bond, are linked together by four m-Cl ligands.The two RhII]RhII bonds are arranged perpendicularly when viewed along the centers of the Rh]Rh Fig. 1 An ORTEP7 view of the non-hydrogen atoms of [Rh4(O2- CPrn)4Cl4(CH3CN)4] 1. Thermal ellipsoids are drawn at the 50% level. The C(6) ellipsoid shows one of the two disordered methyl carbon atoms of the butyrato ligand. The geometry belongs to the S4 point group. Selected bond lengths (Å) and angles (8): Rh(1)]Rh(19) 2.5552(9), Rh(1)]Cl(1) 2.330(2), Rh(1)]Cl(10) 2.317(2), Rh(1)]O(1) 2.029(5), Rh(1)]O(29) 2.033(5), Rh(1)]N(1) 2.272(6); Rh(19)]Rh(1)] Cl(1) 99.72(4), Rh(19)]Rh(1)]Cl(10) 96.69(4), Rh(1)]Cl(1)]Rh(1*) 107.36(6), Cl(1)]Rh(1)]Cl(10) 87.81(3) § (Found: C, 26.80; H, 3.63; Cl, 13.29; N, 5.13.C24H40Cl4N4O8Rh4 requires C, 27.04; H, 3.78; Cl, 13.30; N, 5.26%). Crystal data for complex 1: M = 1066.04, tetragonal, space group I4� (no. 82), a = 10.512(2), c = 15.660(2) Å, U = 1730.4(6) Å3, Z = 2, m = 22.27 cm21, T = 280 8C.Solved by direct methods (SHELXS 866). R = 0.023, Rw = 0.031 and S = 1.25 for 962 unique reflections. ¶ Crystal data for complex 3: C38H34Cl4N6O4Rh4, M = 1192.16, monoclinic, space group C2/c (no. 15), a = 12.405(4), b = 24.119(4), c = 14.405(3) Å, b = 112.49(2)8, U = 3982(1) Å3, Z = 4, m = 19.42 cm21, T = 280 8C. Solved by direct methods (SHELXS 866). R = 0.069, Rw = 0.070 and S = 1.36 for 1157 unique reflections. Owing to weak diVraction due to the small size of the crystal, the deduced geometric parameters are not of high quality, but the chemical structure is reliable, CCDC reference number 186/1039.See http://www.rsc.org/suppdata/ dt/1998/2277/ for crystallographic files in .cif format.2278 J. Chem. Soc., Dalton Trans., 1998, Pages 2277–2278 bonds, thus the Rh4(m-Cl)4 skeleton looks like a twisted cage. The nitrile ligands occupy axial positions both in 1 and 3. In both of the two Rh2 41 units of 3 the mhp ligands are arranged in a head-to-head manner [‘(hh,hh)-isomer’] and the two axial PhCN ligands are bonded at the less hindered axial sites. The RhII]RhII bond lengths in 1 and 3 are longer than most Rh]Rh lengths in lantern-type dinuclear RhII complexes (2.35–2.45 Å),7 but are still acceptable for a RhII]RhII single bond.The distances between the rhodium atoms connected by a m-Cl bridge are 3.74 and 3.76 Å for 1 and 3, respectively. These separations are too long for direct Rh]Rh bonding interactions.The bond distances of Rh]N (nitrile) are similar to the corresponding lengths of dinuclear rhodium(II) complexes,8 while the Rh](m-Cl) bond lengths are slightly shorter than the Rh](m-Cl) distances in [Rh2(m-Cl)2(Cl)2(m-dppm)2] (average 2.460 Å).1 The dependence of the UV/VIS spectrum of 1 in CH2Cl2– CH3CN mixed solvents on their mixing ratios and on the concentrations of the complex showed equilibria of the extensive dissociation of the axial ligands when the complex concen- Fig. 2 An ORTEP view of the non-hydrogen atoms of (hh,hh)- [Rh4(mhp)4Cl4(PhCN)2] 3. Thermal ellipsoids are drawn at the 50% level.A crystallographic C2 axis passes through Cl(1) and Cl(3). Selected bond lengths (Å) and angles (8): Rh(1)]Rh(2) 2.537(3), Rh(1)]Cl(1) 2.356(6), Rh(1)]Cl(2) 2.343(7), Rh(1)]N(1) 2.04(2), Rh(1)]N(2) 2.06(2), Rh(2)]Cl(29) 2.329(7), Rh(2)]Cl(3) 2.328(7), Rh(2)]O(1) 2.02(2), Rh(2)]O(2) 2.02(2), Rh(2)]N(3) 2.13(2); Rh(2)]Rh(1)]Cl(1) 98.9(2), Rh(2)]Rh(1)]Cl(2) 99.2(2), Rh(2)]Rh(1)]N(1) 86.0(6), Rh(2)]Rh(1)]N(2) 86.8(6), Rh(1)]Rh(2)]N(3) 170.8(8), Rh(1)] Cl(1)]Rh(19) 105.9(3), Rh(1)]Cl(2)]Rh(29) 107.0(2) tration was around 1024 mol dm23 (see SUP 57397).The UV/ VIS spectrum of the CH3CN solution of 1 showed absorptions at lmax (log e/mol21 dm3 cm21) of 273 (4.36), 308 (4.18), 450 (sh) and 635 nm (2.36), which are similar to the wavelengths of peaks in the diVuse reflectance spectrum of crystalline 1 ground with MgO powder [lmax: 279, 310, 455 (sh) and 638 nm] showing that the solid-state structure of the complex is conserved in solution.Complex 1 is moderately soluble in water (ca. 3 × 10 mg cm23 at room temperature). The comparison of the electronic spectrum of 1 dissolved in war [lmax (log e/mol21 dm3 cm21) of 271 (4.38), 314 (4.25), 460 (sh) and 680 nm (2.34)] with that of its CH3CN solution implies that [Rh4(O2CPrn)4- Cl4(H2O)4] is formed by the substitution of the axial ligands with the conservation of the Rh4(m-Cl)4 skeletal arrangement. The cyclic voltammogram|| of 1 in CH3CN at a Pt button working electrode showed a chemically reversible one-electron oxidation response at 0.84 V vs. the ferrocenium–ferrocene couple.Trials to isolate cationic radical salts of 1 have not been successful. In a preliminary trial using 1 as a catalyst precursor in aqueous solution, acrylic acid was hydrogenated in water under 1 atm (101 325 Pa) of hydrogen at room temperature in the presence of 1 in 2 mol% of olefinic acid.Acknowledgements We thank the Ministry of Education, Science and Culture in Japan for financial support. References 1 F. A. Cotton, K. R. Dunbar and M. G. Verbruggen, J. Am. Chem. Soc., 1987, 109, 5498. 2 M. H. Chisholm, J. C. HuVman and R. L. Kelly, J. Am. Chem. Soc., 1979, 101, 7100; M. H. Chisholm, R. J. Errington, K. Folting and J. C. HuVman, J. Am. Chem. Soc., 1982, 104, 2025. 3 R. S. Drago, S. P. Tanner, R. M. Richman and J. R. Long, J. Am. Chem. Soc., 1979, 101, 2897. 4 M. Berry, C. D. Garner, I. H. Hillier, A. A. MacDowell and W. Clegg, J. Chem. Soc., Chem. Commun., 1980, 494. 5 B. D. Catsikis and M. L. Good, Inorg. Chem., 1969, 8, 1095. 6 G. M. Sheldrick, SHELX 86, Program for Crystal Structure Determinations, University of Göttingen, 1986. 7 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 8 F. A. Cotton and R. A. Walton, Multiple Bonds between Metal Atoms, Clarendon Press, Oxford, 2nd edn., 1993. Received 14th May 1998; Communication 8/03623C || The supporting electrolyte was 0.1 mol dm23 Bun 4NBF4, the counter electrode was Pt wire and the potential was measured relative to a BAS RE-5 Ag1–Ag–CH3CN reference electrode and converted to that relative to ferrocenium–ferrocene by measuring the oxidation potential of ferrocene.

ISSN:1477-9226    

DOI:10.1039/a803623c

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 2279–2280 2279 Structural distortions in Pd–MeO-Biphep and Pd–Binap aryl complexes. Anomalies induced via electronic eVects Daniela Drago,a Paul S. Pregosin,*a Matthias Tschoerner a and Alberto Albinati *b a Laboratory of Inorganic Chemistry, ETH Zentrum, 8092 Zürich, Switzerland b Chemical Pharmacy, University of Milan, I-20131 Milan, Italy Received 4th May 1999, Accepted 1st June 1999 The four-coordinate complexes [PdBr(p-NCC6H4)- (MeO-Biphep)], 1 [ MeO-Biphep = 6,69-dimethoxy-2,29-bis- (diphenylphosphino)-1,19-biphenyl], and [PdBr(p-NCC6H4)( p-tol-Binap)], 2 [p-tol-Binap = 2,29-bis(di-p-tolylphosphino)- 1,19-binaphthyl], both distort markedly, with the former no longer square-planar, and the latter, possessing the longest recorded Pd–P bond length.The atropisomeric chiral bidentates MeO-Biphep and Binap are recognised to be excellent auxiliaries in a number of enantioselective transformations,1–3 including C–C coupling.4 Pd–aryl complexes, which are intermediates in both cross-coupling and Heck chemistry,4 arise from the oxidative addition of aryl–X compounds, X = I, Br, OTs, to Pd(0) complexes.5–10 In connection with kinetic studies related to the enantioselective Heck reaction we recently noted 11 that aryl intermediates of the type [PdX(aryl)(MeO-Biphep)], with electron-donor groups on the aryl, are not very stable.We report here that the structures of the compounds [PdBr(p-NCC6H4)(MeO-Biphep)], 1, and [PdBr(p-NCC6H4)(p-tol-Binap)], 2, which are more stable, both distort markedly (but very diVerently) in order to accommodate the electronic pressure exerted by the aryl groups.† The molecular structures for 1 and 2 were determined via X-ray diVraction methods‡ and ORTEP views of these molecules are given in Figs. 1 and 2. Selected bond distances and bond angles are given in the captions. In compound 1 there is suYcient space for the aryl and bromide ligands; nevertheless both ligands deviate so strongly from the coordination plane defined by the two P-donors and the metal, 10.88 Å and 20.57 Å, respectively, that one can no longer speak of a square planar geometry.We envision the structure as arising via rotation of the P–Pd–P and Cl–Pd–Br, planes, relative to one another, and not due to a tetrahedral distortion (note that the P–Pd–P and C1L–Pd–Br angles are ca. 948 and 908, respectively). The Pd– C1L separation of 2.104(3) Å is relatively long [2.04–2.06 Å is normal for MeO-Biphep11 although, in general much shorter Pd–C(aryl) distances have been reported 12,13].The ring of the p-NCC6H4 ligand makes an angle of ca. 738 with the P–Pd–P plane, but seems to be somewhat bent, P2–Pd–C1L = 1638, see Fig. 1a. We find no evidence for strain due to packing eVects. For the Binap complex 2 the observed coordination geometry is slightly distorted square planar, see Fig. 2. Relative to 1 the Pd–C1L bond separation is now 0.078 Å shorter, 2.026(6) Å;14 however, a search of the Cambridge database reveals that the Fig. 1 ORTEP20 views of complex 1. (a) From above and (b) from behind (and slightly above) the p-cyanoaryl ligand. Selected bond lengths (Å) and bond angles (8) for 1: Pd–P1 2.2700(9), Pd–P2 2.3501(9), Pd–C1L 2.104(3), Pd–Br 2.4920(4), C7L–N1 1.126(5); P1–Pd–P2 94.06(3), P2–Pd–C1L 163.02(10), P1–Pd–C1L 92.22(9), P1–Pd–Br 158.96(3), P2–Pd–Br 89.69(2), C1L–Pd–Br 90.09(9).2280 J.Chem. Soc., Dalton Trans., 1999, 2279–2280 Pd–P2 bond, trans to the aryl, at 2.437(1) Å represents the longest Pd–P bond ever reported.§ For comparison, in the Binap b-pinene allyl complex [Pd(h3-C10H15){(R)-(1)-Binap}]- [CF3SO3], 3, the Pd–P distances are 2.312(3) Å and 2.347(5) Å.15 The observed Pd–P2 bond in 1, 2.3501(9) Å, is much shorter, but lies towards the upper end of the literature range (Pd–P separations of the order of ca. 2.20–2.36 Å are common16 –19).In both 1 and 2 the p-CN group appears to be a normal triple bond (see captions). Despite the superficial similarity of the ligands, i.e., biarylbased triaryl phosphine types, the structures for 1 and 2 are very diVerent. Whereas the extreme lengthening of the Pd–P2 bond in the Binap complex 2 arises due to good donor properties of the aryl group, the MeO-Biphep analog 1 avoids this electronic strain by strongly deviating from square planar geometry and thus weakening the Pd–C1L overlap.Given the rather novel structural results for these p-NCC6H4 aryl compounds, it is not surprising that we cannot readily isolate analogous complexes with aryl ligands which are even more electron donating, e.g. p-MeC6H4 and p-MeOC6H4. Acknowledgements P. S. P. thanks the Swiss National Science Foundation, and the ETH Zurich for financial support. A. A. thanks MURST and the Vigoni Foundation for support. We also thank Johnson Matthey for the loan of PdCl2 and F.HoVmann La Roche, Basel, for the MeO-Biphep ligand. Fig. 2 ORTEP view of complex 2 looking down on the p-cyanoaryl ligand and the coordination plane. Selected bond lengths (Å) and bond angles (8) for 2: Pd–P1 2.254(1), Pd–P2 2.437(1), Pd–C1L, 2.026(6), Pd– Br 2.4484(7), C7–N1 1.12(1); P1–Pd–P2 92.38(5), P2–Pd–C1L 175.6(2), P1–Pd–C1L 91.0(2), P1–Pd–Br 173.51(4), P2–Pd–Br 90.90(4), C1L– Pd–Br 85.4(2). Notes and references † The complexes were prepared as described in reference 11.‡ Crystal data for compound 1: C45H36BrNO2P2Pd, M = 871.00, orthorhombic, space group P212121 (no. 18), a = 11.4485(2), b = 17.3604(1), c = 19.0940(3) Å, U = 3794.94(9) Å3, Z = 4, m = 16.66 cm21, T = 200 K, R1 = 0.0267 (for 5794 unique reflections having I > 2s(I)), 0.0354 (for all 6492 independent reflections). Crystal data for compound 2?CH2Cl2: C56H46BrCl2NP2Pd, M = 1052.16, monoclinic, space group C2 (no. 5), a = 29.0943(4), b = 11.8671(2), c = 17.2953(2) Å, b = 116.790(3)8, U = 5330.51(13) Å3, Z = 4, m = 12.94 cm21, T = 293 K, R1 = 0.0419 (for 5550 unique reflections with I > 2s(I)), 0.0494 (for all 7049 independent reflections).CCDC reference number 186/1478. § Note added at proof: a Pd–P bond length of ca. 2.5 Å (trans to SiCl3) has been observed.21 1 R. Noyori, Chimia, 1988, 42, 215; R. Noyori, Asymmetric Catalysis in Organic Synthesis, John Wiley and Sons, New York, 1994. 2 Y. Crameri, J. Foricher, U. Hengartner, C. Jenny, F.Kienzle, H. Ramuz, M. Scalone, M. Schlageter, R. Schmid and S. Wang, Chimia, 1997, 51, 303; R. Schmid, M. Cereghetti, B. Heiser, P. Schönholzer and H. J. Hansen, Helv. Chim. Acta, 1988, 71, 897; R. Schmid, E. A. Broger, M. Cereghetti, Y. Crameri, J. Foricher, M. Lalonde, R. K. Mueller, M. Scalone, G. Schoettel and U. Zutter, Pure Appl. Chem., 1996, 68, 131; C. Bolm, D. Kaufmann, S. Gessler and K. Harms, J. Organomet. Chem., 1995, 502, 47. 3 G. Trabesinger, A. Albinati, N.Feiken, R. W. Kunz, P. S. Pregosin and M. Tschoerner, J. Am. Chem. Soc., 1997, 119, 6315. 4 L. E. Overman and J. T. Link, in Metal Catalyzed Cross-Coupling Reactions, ed. F. A. S. Diederich, P. J., Weinheim, 1998. 5 A. de Meijere and F. E. Meyer, Angew. Chem., 1994, 106, 2473; C. Amatore, E. Carré, A Jutand, M. A. M’Barki and G. Meyer, Organometallics, 1995, 14, 5605. 6 P. Garrou and R. F. Heck, J. Am. Chem. Soc., 1976, 98, 4115; R. F. Heck, Acc. Chem. Res., 1979, 12, 146; R.F. Heck, Comprehensive Organic Synthesis, ed. B. M. Trost and I. Flemming, Pergamon, Oxford, 1991. 7 O. Loiseleur, P. Meier and A. Pfaltz, Angew. Chem., 1996, 108, 218. 8 F. Ozawa, A. Kubo and T. Hayashi, J. Am. Chem. Soc., 1991, 113, 1417. 9 M. Tschoerner, G. Trabesinger, A. Albinati and P. S. Pregosin, Organometallics, 1997, 16, 3447. 10 J. F. Hartwig, Angew. Chem., Int. Ed., 1998, 37, 2090. 11 M. Tschoerner, P. S. Pregosin and A. Albinati, Organometallics, 1999, 18, 670. 12 A.G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Watson and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1; W. J. Marshall, D. L. Thorn and V. V. Grushin, Organometallics, 1998, 17, 5427. 13 J. M. Brown, J. Perez-Torrente, N. Alcock and H. J. Clase, Organometallics, 1995, 14, 207. The Pd–C distance in the aryl complex PdI- {[2-(CH2OCH]] CH2)C6H4](dppf)} is 2.055(7) Å. 14 J. M. Brown and J. J. P. Torrente, Organometallics, 1995, 14, 1195. Pt–C separations of 2.090(31) Å and 2.084(40) Å are reported for a biaryl-Binap complex. The Pt–P bond distances are 2.303(8) Å and 2.301(8) Å. 15 P. S. Pregosin, H. Rüegger, R. Salzmann, A. Albinati, F. Lianza and R. W. Kunz, Organometallics, 1994, 13, 83. 16 J. M. Wisner, T. J. Bartczak and J. A. Ibers, Organometallics, 1986, 5, 2044. 17 W. A. Herrmann, C. Brossmer, T. Priermeier and K. Oefele, J. Organomet. Chem., 1994, 481, 97. 18 G. Mann, D. Baranano, J. F. Hartwig, A. L. Rheingold and I. A. Guzei, J. Am. Chem. Soc., 1998, 120, 9205. 19 D. K. Wicht, M. A. Zhuravel, R. V. Gregush, D. S. Glueck, I. A. Guzei, L. M. Liable-Sands and A. L. Rheingold, Organometallics, 1998, 17, 1412. 20 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 21 A. Togni, personal communication. Communication 9/03509E

ISSN:1477-9226    

DOI:10.1039/a903509e

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 2281–2292 2281 In situ syntheses of trans-spanned octahedral ruthenium complexes. Crystal structures of trans-[Ru(Cl)(trpy){Ph2PC6H4CH2O(CO)- (CH2)4(CO)OCH2C6H4PPh2}][PF6]?0.25C6H5Me?0.5CH2Cl2 and trans-[Ru(Cl)(trpy)(PPh3)2][BF4]?CH2Cl2 † Willie J. Perez,a Charles H. Lake,a Ronald F. See,a Laurence M. Toomey,a Melvyn Rowen Churchill,a Kenneth J. Takeuchi,*a Christopher P. Radano,b Walter J. Boyko b and Carol A. Bessel *b a Department of Chemistry, Natural Sciences Complex, State University of New York at BuValo, BuValo, NY 14260, USA b Department of Chemistry, Villanova University, 800 Lancaster Ave., Villanova, PA 19085, USA Received 29th September 1998, Accepted 21st May 1999 The formation of stable, undistorted octahedral transition metal complexes which contain a trans-spanning bidentate ligand remains a synthetic challenge.The reported complexes are of the type trans-[Ru(Cl)(trpy){Ph2PC6H4CH2O- (CO)Y(CO)OCH2C6H4PPh2}][PF6] [where trpy = 2,29:69,20-terpyridine and Y = (CH2)3 = C3SPAN, 6; (CH2)4 = C4SPAN, 7; or isophthalate = ISPAN, 8] and represent the first examples of trans-spanned transition metal complexes which display little bond angle distortion from octahedral geometry and also contain a bridging linkage which is stable towards oxidation, reduction and hydrolysis.These complexes were characterized by elemental analyses, cyclic voltammetry, conductivity and UV-VIS spectroscopy.COSY, HETCOR and variable temperature (1H and 13C) NMR spectra of the complexes are consistent with a flexible spanning linkage that does not demonstrate restricted rotation about either the P–Cipso or the Ru–P bonds while the X-ray crystal structure analysis of 7 showed that the spanning linkage is positioned to one side of the meridional chloride. The formation of stable, undistorted octahedral transition metal complexes which contain a trans-spanning bidentate ligand presents a synthetic challenge in several respects.1,2 To date, trans-spanning bidentate ligands have been prepared by two distinct methods: the synthesis of a bidentate ligand and its subsequent coordination to the transition metal center (preformed ligand strategy), and the bonding of two monodentate ligands to the metal center followed by the joining of the ligands with a trans-spanning linkage (in situ ligand strategy).The preformed ligand strategy has been used eVectively by Shaw and coworkers as they prepared several series of large ring complexes of the general formula trans-[M(Cl)2{Bu2P- (CH2)nPBu2}] (M = Pd or Pt; n = 5–10),3–5 or trans-[{M(Cl)2- [Bu2P(CH2)nPBu2]}x] (M = Pd or Pt, n = 8, 9, 10 or 12; x = 1–3) 6–9 where each complex contained a flexible diphosphine ligand. Initially, Shaw and coworkers proposed that the presence of the bulky tert-butyl groups attached to the phosphorus donor atoms resulted in repulsive interactions between the substituents favoring a trans-geometry.Alcock10–12 and McAuliVe 13–17 later prepared a number of trans-spanning Rh, Ni, Pt and Pd complexes with bis(diphenylphosphino)ethers, bis(diphenylphosphino)alkanes and bis(dimethylarsino)alkanes suggesting that the length of the spanning ligand was a large contributor to obtaining the trans-geometry. This argument was in agreement with those of McAuliVe 17 and others 18 who prepared ligands with both methyl, ethyl or phenyl substituents on the pnictogen or chalcogen donor atoms. In addition to preformed bidentate ligands with flexible chains, Venanzi and coworkers 19–26 and others 27 demonstrated the use of bis(dialkyl † Supplementary data available: NMR spectra.Available from BLDSC (No. SUP 57568, 19 pp.). See Instructions for Authors, 1999, Issue 1 (http://www.rsc.org/dalton). or diaryl phosphinomethyl)benzophenanthrene ligands as rigid trans-spanning “spacers.” These rigid ligands have been used to span distorted trigonal, pseudo-tetrahedral, square planar, square pyramidal and octahedral metal centers.While the preformed ligand strategy has been successful, it is not without limitations. First, the successful trans-positioning of preformed spanning ligands with flexible backbones can be crucially dependent on the choice of starting material. For example, in the preparation of PtCl2[Ph2As(CH2)nAsPh2] (n = 6–12, 16), the use of the starting material K2PtCl4 leads to the formation of the cis isomer, the use of K[PtCl3(H2C]] CH2)] leads to the formation of the trans isomer, and the use of Pt(C6H5- CN)2Cl2 leads to the formation of a cis–trans mixture.17c This marked dependency on the starting material makes the rational and systematic design of trans-spanned complexes diYcult.Second, the use of preformed ligands can result in dimerization when the preformed ligands can bridge between two metal centers.16,17d,18,23,28 This behavior was observed for [Pt{Ph2As- (CH2)nAsPh2}Cl2] (n = 6–12, 16) where both trans monomers and cis dimers were formed,17d as well as for [PtCl2{Ph2P(CH2)n- PPh2}] complexes where both cis and trans monomers and cis and trans dimers were formed.16 A third limitation is that preformed ligands with flexible backbones can form cyclometallated complexes 28–37 such as [IrH(Cl)(Bu2PCH2CH2CHCHRCH2PBu2)], where the C forms an iridium–carbon bond.29 Such cyclometallation products are often observed with square planar or trigonal bipyramidal geometries.A fourth limitation is that the preformed rigid spanning ligands can cause strain which produces transition metal complex geometries distorted from octahedral geometry. The strain caused by the bis- (diphenylphosphinomethyl)benzo[c]phenanthrene ligand (SL1) is evident in complexes of the type [M(SL1)]X or [M(SL1)X] where Venanzi reported that the P–M–P angle ranges from 1328 for Cu to 1418 for Ag, to 1768 for Au.202282 J.Chem. Soc., Dalton Trans., 1999, 2281–2292 The second method for formation of complexes with a transspanning bidentate ligand is the in situ ligand strategy. Using this strategy, Takeuchi and coworkers synthesized transspanning octahedral complexes of the form [Ru(Cl)(trpy)- (SL2)]1 [trpy = 2,29:69,20-terpyridine and SL2 = Ph2PC6H4- CH2N(Me)(CH2)nN(Me)CH2C6H4PPh2 or Ph2PC6H4CH2N- (Me)2(CH2)nN(Me)2CH2C6H4PPh2; n = 5 or 6] by linking two coordinated trans-positioned tertiary phosphine ligands with a diamine.38 These complexes were the first reported cases of in situ generated, trans-spanning ligands on an octahedral metal center where the spanning ligand bridged over the cis coordinated meridional chloride ligand.Like the preformed ligand strategy, the in situ ligand strategy oVered flexibility in terms of both backbone length and composition. In addition, with the in situ ligand strategy the major reaction product was the transspanned complex and no cyclometallated complex was found.Disadvantages in the in situ strategy resulted from the use of the amine linkages. In the trans-spanned complex, the tertiary amine linkages were readily oxidized and evidence for dealkylation of the quaternary amine linkages was observed. To overcome these disadvantages, we developed a new ligand system that retained the benefits of the in situ ligand strategy while producing a ligand that is stable to oxidation and reduction.In this work we report the formation of [Ru(Cl)(trpy)(L)]1 [where L = Ph2PC6H4CH2O(CO)Y(CO)OC6H4PPh2 and Y = (CH2)3 = C3SPAN, 6; (CH2)4 = C4SPAN, 7; and isophthalate = ISPAN, 8]. The use of the in situ strategy with an ester linkage retains the span versatility in both length and structure, while making the span stable against degradation by oxidation and reduction. Additionally, decomposition due to hydrolysis is not observed on exposure of the complexes to either mildly acidic or basic solutions (pH = 2 to 10).Finally, the new transspanning complexes display good solubility in organic solvents, which facilitated the collection of variable temperature NMR spectra and the formation of single crystals suitable for X-ray diVraction studies. Experimental Materials RuCl3?nH2O was obtained on loan or purchased from Johnson Matthey/Alfa/Aesar. 2,29:69,20-Terpyridine was purchased from G. F. Smith Chemical Company or was synthesized by literature methods.39 Triphenylphosphine was purchased from Aldrich Chemical Company or Strem Chemical. Methylene chloride (J.T. Baker) was dried over activated 5 Å molecular sieves and distilled under N2.40 All other solvents and materials were of reagent quality and were used as received. Reactions were conducted under a nitrogen atmosphere unless otherwise noted. Measurements Elemental analyses were performed by Atlantic Microlabs, Norcross, GA. UV-VIS spectra were recorded using a Bausch and Lomb Spectronic 2000, a Milton Roy Spectronic 3000 Diode Array Spectrophotometer, or a Cary 1G UV-VIS Spectrophotometer.Conductivity measurements were performed in acetonitrile using a YSI Model 31 conductivity bridge. Electrochemical measurements were made versus a saturated sodium chloride calomel reference electrode (SSCE) using either an IBM EC/225 voltammetric analyzer, a PAR Model 173 Potentiostat/Galvanostat equipped with a PAR Model 175 Universal Programmer or a BAS CV-50W Voltammetric Analyzer.A platinum disc working electrode was used along with a platinum wire common electrode. Electrochemical measurements used 0.1 M tetrabutylammonium tetrafluoroborate (TBAB) as the electrolyte and were conducted with ferrocene (E1/2 = 10.40 V vs. SSCE in CH3CN, E1/2 = 10.50 V vs. SSCE in CH2Cl2) as the internal standard. All NMR spectra were obtained on a Varian XL-300 spectrometer in CD2Cl2. 1H spectra were obtained at 299.9 MHz and referenced to tetramethylsilane. 13C spectra were obtained at 75.4 MHz and referenced to CD2Cl2 (d 53.8). Proton–proton COSY and carbon–hydrogen HETCOR were run with standard Varian-supplied pulse sequences. The one-bond HETCOR direct detection sequence utilized BIRD pulses 41 to suppress proton–proton couplings in the f1 domain of the 2D maps. Quaternary carbon resonances in trpy were assigned using the Varian-supplied direct detection HETCOR sequence (no BIRD pulse) optimizing defocussing/refocussing delays for the appropriate nJC–H constants.Several sets of delays were used near each desired J-value in order to avoid loss of the appropriate correlation signals due to one-bond modulation of the longrange response intensity.42 Crystallography Data collection. Crystals were aligned on a Siemensupgraded Syntex P21/R3 diVractometer equipped with a highlyoriented graphite crystal monochromator. The determination of the Laue symmetry, crystal class, unit-cell parameters and the crystal orientation matrix were carried out by previously described techniques.43 Room-temperature data were collected with Mo-Ka radiation (l = 0.71073 Å), using the q–2q scan technique for 7, and the w scan technique for 5 where peak overlap was a possible problem.Details of the data collection are in Table 1. All reflections in each data set were corrected for Lorentz and polarization eVects and for absorption (semiempirical). Solution and refinement of the structures. All crystallographic calculations were carried out on a VAX3100 workstation with the use of the Siemens SHELXTL PLUS44 program set.The analytical scattering factors for neutral atoms were corrected for both the Df 9 and the iDf 0 components of anomalous dispersion. The structures were solved by a combination of direct methods and Fourier-diVerence techniques. All non-hydrogen atoms were refined anisotropically, and hydrogen atoms were included in calculated positions with d(C–H) = 0.96 Å.45 Details of each structure solution and its refinement may be found in Table 1.A diagram of one structure was generated using ORTEP II.46 CCDC reference number 186/1479. Preparations The complexes RuCl3(trpy),47 trans-[Ru(Cl)2(trpy){Ph2PC6H4- (CH2OC5H9O)-p}], 1,38 cis-[Ru(Cl)2(trpy){Ph2PC6H4(CH2OC5H9O)- p}], 2,38 trans-[Ru(Cl)(trpy){Ph2PC6H4(CH2OC5H9O)- p}2][PF6], 3,38 trans-[Ru(Cl)(trpy){Ph2PC6H4(CH2OH)-p}2]- [PF6], 4,38 and trans-[Ru(Cl)(trpy)(PPh3)2]1, 5,47 were synthesized following published procedures. trans-[Ru(Cl)(trpy)(C3SPAN)][PF6], 6.A 0.174 g (0.158 mmol) sample of 4 was dissolved in 17 mL of CH2Cl2 and the solution was outgassed with N2 for 5 min. Glutaryl dichloride (0.027 mL, 0.21 mmol) was added and the reaction mixture was heated to reflux for 24 h. After cooling, the volume of the solution was reduced to dryness on a rotary evaporator. The residue was redissolved in CH2Cl2 and purified by passing through an alumina column using 100 : 1 (v/v) CH2Cl2–MeOH as the eluent.The first tan-orange band was collected and the solution was reduced to dryness with a rotary evaporator. The product was redissolved in a minimal amount of CH2Cl2 and precipitated by dropwise addition to Et2O (ca. 100 mL). The solid was collected by vacuum filtration, washed with a minimum amount of Et2O and air dried. A 0.111 g (0.093 mmol, 59% yield) sample of yellow-brown product was obtained (Calc.for C58H49ClF6N3O4P3Ru?2H2O: C, 56.57; H, 4.02. Found: C, 56.58; H, 4.13%).J. Chem. Soc., Dalton Trans., 1999, 2281–2292 2283 Table 1 Details of X-ray diVraction studies of trans-[Ru(Cl)(trpy)(PPh3)2][BF4]?CH2Cl2 5 and trans-[Ru(Cl)(trpy)(C4SPAN)][PF6]?0.25C6H5Me? CH2Cl2 7 5 7 Formula M Crystal system Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z Dc/Mg m23 m(Mo-Ka)/mm21 Independent reflections Reflections > 6s(F ) Final R indices (all data): R, wR Final R indices (6s data): R, wR C51H41ClN3P2BF4Ru?CH2Cl2 1066.1 Monoclinic P21/c 17.8306(38) 12.7954(26) 21.7707(40) 90.00 104.195(15) 90.00 4815.4(1.7) 4 1.470 0.606 6329 3118 0.063, 0.038 0.049, 0.035 C59H51ClO4N3P3F6Ru?0.25C6H5Me?0.5CH2Cl2 1275 Triclinic P1� 10.9656(18) 13.9782(22) 19.8449(26) 89.212(12) 85.938(12) 68.071(12) 2814.4(7) 2 1.505 0.529 7391 4070 0.092, 0.076 0.044, 0.046 trans-[Ru(Cl)(trpy)(C4SPAN)][PF6], 7.A 0.101 g (0.0916 mmol) sample of 4 was dissolved in 7.2 mL of CH2Cl2. Adipoyl dichloride (0.020 mL; 0.14 mmol) was added and the reaction mixture was heated to reflux for 4 h.The reaction mixture was reduced to dryness with a rotary evaporator. The residue was passed through an alumina column using a 150: 1 (v/v) CH2Cl2–MeOH solution as the eluent. The first tan-orange band was collected and reduced to dryness with a rotary evaporator. This residue was redissolved in a minimum amount of CH2Cl2 and precipitated by dropwise addition to toluene. The yellow-brown product was collected by vacuum filtration, washed with Et2O and air dried; yield 0.067 g (0.055 mmol); 59% (Calc.for C59H51ClF6N3O4P3Ru?C6H5Me: C, 60.90; H, 4.56. Found: C, 60.57; H, 4.62%). trans-[Ru(Cl)(trpy)(ISPAN)][BF4], 8. A 0.100 g (0.0907 mmol) sample of 4 was dissolved in 7.0 mL of CH2Cl2. Isophthaloyl dichloride (0.022 g; 0.11 mmol) was added and the reaction mixture was heated to reflux for 4 h and then reduced to dryness with a rotary evaporator. The residue was passed through an alumina column using a 100: 1 (v/v) CH2Cl2– MeOH solution as the eluent.The first red-brown band was collected and reduced to dryness with a rotary evaporator, redissolved in a minimum amount of CH2Cl2, and precipitated by dropwise additon to Et2O. The red-brown product was collected by vacuum filtration, washed with Et2O and air dried; yield 0.051 g (0.039 mmol); 43% (Calc. for C61H47ClF4N3O4P2- BRu?0.5H2O: C, 59.16; H, 3.91. Found: C, 59.13; H, 4.05%).Results and discussion Fig. 1 shows the general scheme for the synthesis of the transspanning ruthenium complex, trans-[Ru(Cl)(trpy)(C3SPAN)]1, 6. The synthesis is initiated by combining RuCl3(trpy) with one protected phosphine ligand and a reducing agent to form the trans-[Ru(Cl)2(trpy){Ph2PC6H4(CH2OC5H9O)-p}], 1. Irradiation of the reaction mixture with light 47 converts 1 to cis- [Ru(Cl)2(trpy){Ph2PC6H4(CH2OC5H9O)-p}], 2. The combination of excess phosphine with 2 produces trans-[Ru(Cl)(trpy)- {Ph2PC6H4(CH2OC5H9O)-p}2][PF6], 3.Prior to the transspanning reaction, the phosphine groups are deprotected in an acid catalyzed step resulting in the formation of trans- [Ru(Cl)(trpy){Ph2PC6H4(CH2OH)-p}2][PF6], 4. trans-Spanning is achieved by reacting 4 with an organic dioxychlide to give 6, 7 or 8 in a double esterification reaction. The product is purified by column chromatography to isolate the monomeric species with yields of 40–60%. The use of a large volume of solvent during the spanning procedure prevents dimerization and/or oligimerization and increases the yields of the spanned complexes to values similar to those of the model reactions (i.e.the formation of dibenzyl adipate and dibenzyl glutarate).48 Through the use of three diVerent spans, –(CH2)3–, –(CH2)4– and –isophthalate–, we demonstrate that the trans-spanning linkage can be modified in terms of chain length and structure. Electronic spectroscopy and cyclic voltammetric data The UV-VIS spectroscopic and cyclic voltammetry data for the complexes are summarized in Table 2.Transitions at ca. 700, 550 and 400 nm in the trans-[Ru(Cl)2(trpy)(PR3)] complexes are assigned to Ru(dp)Æp*(trpy) metal-to-ligand charge transfer bands (MLCT) as observed for other trans-ruthenium complexes.47,49–52 The transitions observed at 380, 330, 320, 286 and 275 nm are assigned to pÆp* ligand (trpy, triphenylphosphine)- localized transitions.47,53,54 These trans-(dichloro)- ruthenium complexes display one reversible couple assigned to the ruthenium(III/II) potential at approximately 0.50 V vs.SSCE in CH2Cl2. The cis-[Ru(Cl)2(trpy)(PR3)] complexes are characterized by two MLCT transitions at ca. 530 and 490 nm. These wavelengths have shifted to shorter wavelengths relative to the trans- [Ru(Cl)2(trpy)(PR3)] complexes, however the absorbances maintain similar molar absorptivity values. The four ligand localized pÆp* transitions occur at ca. 360, 320, 285 and 275 nm. These cis-(dichloro)ruthenium complexes display one reversible couple assigned to the ruthenium(III/II) potential at approximately 0.60 V vs. SSCE in CH2Cl2. The shifts to shorter wavelengths which accompany the increases in E1/2 values are observed for other polypyridyl ruthenium complexes.47,49–52,55,56 Both 1 and 2 have E1/2 values which are 50 mV higher than the corresponding PPh3 complexes. This increase in E1/2 is consistent with the electron withdrawing nature of the protected group on the phosphine.The addition of a second phosphine ligand to 2 and the consequent change from a neutral to a positively charged molecule result in a shift of the absorption maxima to higher energies. These absorbances are again assigned to MLCT bands from Ru (dp)Æligand (p*) transitions. The absorption maxima of the complexes at 330, 310, 270, 230, and 210 nm are assigned to ligand localized pÆp* transitions. Interestingly, the reversible ruthenium(III/II) redox couples for complexes 3–8 demonstrate a small range in E1/2 values from 10.88 to 10.93 V vs.SSCE in CH3CN and a linear relationship between the peak current (ip,c) and the square root of the scan rate (n1/2). This linear relationship indicates that the electron transfer is diVusion controlled2284 J. Chem. Soc., Dalton Trans., 1999, 2281–2292 Table 2 UV-VIS spectroscopic and cyclic voltammetry data for selected ruthenium complexes Complex a E2� 1 /V vs.SSCE lmax/nm (1023e/cm21 M21) trans-[Ru(Cl)2(trpy)(PPh3)] 10.46 e 705 (sh), 549(4.66), 403(4.71), 375 (sh), 331(17.9), 320 (sh), 286 (sh), 275(16.5) trans-[Ru(Cl)2(trpy)(Ph2PR)], 1 b 10.51 701 (sh), 552(4.84), 403(4.86), 381 (sh), 331(20.5), 320 (sh), 286 (sh), 275(21.0) cis-[Ru(Cl)2(trpy)(PPh3)] 10.58 e 531(4.79), 488 (sh), 363 (sh), 319(20.8), 286 (sh), 275(16.3) cis-[Ru(Cl)2(trpy)(Ph2PR)], 2 b 10.63 533(5.35), 488 (sh), 362 (sh), 319(22.9), 285 (sh), 276(17.9) trans-[Ru(Cl)(trpy)(Ph2PR)2][PF6], 3 c 10.88 474(3.83), 431 (sh), 334 (sh), 310(29.8), 270(78.6), 236(62.0), 209(96.6) trans-[Ru(Cl)(trpy)(Ph2PR9)2][PF6], 4 c,d 10.88 473(3.35), 431 (sh), 332 (sh), 311(22.2), 270(45.8), 231 (sh), 208(98.6) trans-[Ru(Cl)(trpy)(PPh3)2][PF6], 5 c 10.90 473(3.62), 431 (sh), 330 (sh), 312(23.2), 268(43.2) trans-[Ru(Cl)(trpy)(C3SPAN)][PF6], 6 c 10.92 473(3.50), 432 (sh), 334 (sh), 311(21.7), 271(38.5), 232(52.1) trans-[Ru(Cl)(trpy)(C4SPAN)][PF6], 7 c 10.91 473(3.84), 432 (sh), 334 (sh), 311(21.4), 271(39.9), 231(51.0) trans-[Ru(Cl)(trpy)(ISPAN)][PF6], 8 c 10.93 471(4.10), 432 (sh), 333 (sh), 311(25.0), 271(42.0), 233(75.6) a Measured in methylene chloride unless otherwise stated.b R = C6H4(CH2OC5H9O)-p. c Measured in acetonitrile. d R9 = C6H4(CH2OH)-p. e From ref. 47. Fig. 1 The reaction scheme for the preparation of trans-[Ru(Cl)(trpy)(C3SPAN)]1, 6. and is not influenced by the steric bulk of the spanning linkage (for complexes 6–8).Finally, peak current ratios [cathodic peak current (ip,c)/anodic peak current (ip,a)], determined using the Nicholson Method,57 ranged from 0.90–1.0 : 1 for all of the complexes used in this study. These data imply that electron transfer at the ruthenium metal center is reversible and that the ester linkages found in complexes 6–8 are stable to oxidation and reduction under standard electrochemical conditions. Thus, the ester linkage overcomes the disadvantages observed with the Takeuchi SL2 ligand (see above).While changes in the electron donating or electron withdrawing nature of ligand substituents can result in variation of electronic properties at the metal center previous observations have also shown that the redox potential of a metal complex can change with steric ligand eVects.58–60 An advantage of the in situ ligand synthesis procedure is the ability to compare the span precursors to the spanned complexes.This comparison has enabled us to separate the electronic contributions from the steric contributions of the spanning linkage. This is most notable in light of studies involving the Venanzi preformed ligand SL1 complexes (see above),19–26 where isolating the electronic eVects of the spanning ligand from the steric eVects caused by the strained geometries proved diYcult.21,24 The consistency of the spectroscopic and electrochemical data for the protected (3), deprotected (4), unsubstituted (5) and spanned (6–8) complexes indicates that changes in the periphery of theJ.Chem. Soc., Dalton Trans., 1999, 2281–2292 2285 ligand structure leave the electronic environment about the metal center relatively unchanged and implies that the geometry about the metal center is relatively undistorted from an ideal octahedral arrangement (this was later proven by X-ray crystallography, see below). Conductivity analysis Conductivity measurements were performed on 6 and 7 using the method of Feltham and Hayter.61 The charge and nuclearity of the complexes were determined by measuring the equivalent conductivity (Le) over a range of concentrations (expressed in terms of equivalent concentration, c).The data are obtained as Lo, the conductance at infinite dilution and B, the slope of the plot of (Lo 2 Le) versus the square root of c. The use of equivalent concentrations in this technique eliminates the uncertainty in concentrations of complexes with unknown nuclearity and it allows for the diVerentiation of complexes having the same empirical formula but diVerent molecular weight.The B values were 297 and 373 for 6 and 7 respectively, and are consistent with the values proposed by Davies for monomeric complexes with a 1 : 1 electrolyte in acetonitrile,62 and by Leising for monomeric trans-diphosphine ruthenium(II) complexes and for ruthenium(II) complexes containing the Takeuchi SL2 spanning linkages.38,50 Table 3 Selected interatomic distances (Å) and angles (8) for trans- [Ru(Cl)(trpy)(PPh3)2][BF4]?CH2Cl2, 5 (A) Ruthenium–ligand distances Ru(1)–P(1) Ru(1)–P(2) Ru(1)–Cl(1) 2.398(2) 2.415(2) 2.457(2) Ru(1)–N(1) Ru(1)–N(2) Ru(1)–N(3) 2.098(6) 1.964(7) 2.072(6) (B) Phosphorus–carbon distances P(1)–C(11) P(1)–C(21) P(1)–C(31) 1.841(8) 1.831(8) 1.847(8) P(2)–C(41) P(2)–C(51) P(2)–C(61) 1.831(7) 1.813(9) 1.824(9) (C) Distances within terpyridyl systems N(1)–C(71) C(71)–C(72) C(72)–C(73) C(73)–C(74) C(74)–C(75) C(75)–N(1) C(75)–C(81) N(2)–C(81)(81)–C(82) C(82)–C(83) 1.363(12) 1.376(13) 1.351(18) 1.380(16) 1.377(13) 1.380(12) 1.473(13) 1.351(12) 1.386(14) 1.365(16) N(3)–C(91) C(91)–C(92) C(92)–C(93) C(93)–C(94) C(94)–C(95) C(95)–N(3) C(85)–C(95) C(83)–C(84) C(84)–C(85) C(85)–N(2) 1.350(10) 1.377(12) 1.397(15) 1.356(14) 1.383(13) 1.357(11) 1.476(12) 1.390(16) 1.376(12) 1.357(11) (D) Angles around the ruthenium atom P(1)–Ru(1)–P(2) P(2)–Ru(1)–Cl(1) P(2)–Ru(1)–N(1) P(1)–Ru(1)–N(2) Cl(1)–Ru(1)–N(2) P(1)–Ru(1)–N(3) Cl(1)–Ru(1)–N(3) N(2)–Ru(1)–N(3) 178.1(1) 90.7(1) 90.4(2) 90.3(2) 174.9(2) 90.1(2) 95.9(2) 79.5(3) P(1)–Ru(1)–Cl(1) P(1)–Ru(1)–N(1) Cl(1)–Ru(1)–N(1) P(2)–Ru(1)–N(2) N(1)–Ru(1)–N(2) P(2)–Ru(1)–N(3) N(1)–Ru(1)–N(3) 87.5(1) 90.8(2) 106.2(2) 91.4(2) 78.5(3) 89.4(2) 157.9(3) (E) Angles around phosphorus atoms Ru(1)–P(1)–C(11) Ru(1)–P(1)–C(21) Ru(1)–P(1)–C(31) Ru(1)–P(2)–C(41) Ru(1)–P(2)–C(51) Ru(1)–P(2)–C(61) 114.0(2) 121.1(3) 111.8(2) 118.2(2) 108.9(2) 119.6(3) C(11)–P(1)–C(21) C(11)–P(1)–C(31) C(21)–P(1)–C(31) C(41)–P(2)–C(51) C(41)–P(2)–C(61) C(51)–P(2)–C(61) 101.0(4) 108.4(4) 98.9(4) 105.9(4) 99.0(4) 103.6(4) (F) Angles at Cipso in PPh3 ligands C(16)–C(11)–C(12) C(26)–C(21)–C(22) C(36)–C(31)–C(32) 117.4(8) 117.8(7) 117.2(8) C(46)–C(41)–C(42) C(56)–C(51)–C(52) C(66)–C(61)–C(62) 118.5(7) 118.3(8) 117.7(8) Crystal structure analysis Crystals of 5 were grown using the double vial diVusion technique in a CH2Cl2–toluene solution and crystallize with CH2Cl2 molecules in the lattice.Crystallographic-grade crystals of 7 were grown, after purification by column chromatography, from a solution of 12 mg complex–0.5 ml chloroform at approximately 18 8C. Selected bond distances and bond angles for 5 and 7 are listed in Tables 3 and 4 respectively. Crystals of 7 contain a disordered array of C6H5Me and CH2Cl2 molecules of crystallization about the inversion center at 1/2 1/2 0.Fig. 2 and 3 give perspective views and numbering schemes for 5 and 7 respectively. The crystal structures of 5 and 7 are compared to determine whether distortions are brought about by the presence of the trans-spanning linkage. The crystal structures of 5 and 7 consist of arrays of ordered ruthenium cations and anions (BF4 2 for 5 and PF6 2 for 7) in a 1 : 1 stoichiometry along with solvent of crystallization. Results of the structural analyses indicate that 5 adopts a C2v geometry, while 7 adopts a C1 geometry due to the position of the spanning ligand.One of the most significant aspects of the crystal structure of 7 is that the complex is monomeric, confirming the conductivity studies. Both complexes show small distortions from an ideal octahedral geometry. First, the N(trpy terminal pyridine)–Ru– N(trpy terminal pyridine) bond angle for 5 is 157.9(3)8 and for 7 is 157.7(2)8. These deviations are attributed to the geometrical constraints of the trpy backbone.63 These angles diVer greatly from those of the free trpy ligand at 1288,64 however, they are within the range [156.9(5)–158.3(3)8] observed for other ruthenium( II) complexes.50–52,65,66 The Ru–N(central trpy) bond length is 1.964(7) and 1.955(5) Å for 5 and 7 respectively; both structures show some dissymmetry in the Ru–N(trpy terminal pyridines) bond distances.Comparisons between complexes containing two triphenylphosphine ligands and other trans-spanning ligands have been made in the literature.For example, the crystal structures of Fig. 2 ORTEP diagram of the trans-[Ru(Cl)(trpy)(PPh3)2]1 cation, 5.2286 J. Chem. Soc., Dalton Trans., 1999, 2281–2292 Au(SL1)Cl 20,67 and Au(PPh3)2Cl 68 have significantly diVerent P–Au–P bond angles [140.7(1)8 and 132.1(1)8 respectively]; as do CuCl(SL1)67 and CuBr(PPh3)2 69 [at 131.98 and 126.0(1)8, respectively]. These data imply that the rigid spacer ligand, SL1, may be better at enforcing linear trans-geometries than two monodentate PPh3 ligands.However, the latter diVerences must be interpreted with caution, especially in light of the significant changes in P–Ag–P bond angle that occur with change in anion.20,24 The P–Ru–P angles in both 5 and 7 deviate slightly from linearity (1808). Complex 5 has a P–Ru–P bond angle of 178.1(1)8 while 7 has a P–Ru–P bond angle of 175.0(1)8. Although the P–Ru–P bond angle in 7 is smaller than in 5, and could indicate strain on the octahedral geometry due to the spanning ligand, an investigation of trans-diphosphine- (terpyridyl)ruthenium(II) complexes which contain PMe3,50 PEt3,51 PPr3 66 or PPh3 65 ligands shows that P–Ru–P bond angles normally range between 175.1(1) and 178.2(2)8.Thus, the P–Ru–P bond angle observed in 7 is probably not caused by the spanning linkage. The P–Ru–P bond axis for both 5 and 7 appears to bend in the direction of the chloride ligand, implying that this region has less steric crowding than the region around the trpy ligand. The diagrams of 5 and 7 show that the phosphine ligands align in a similar fashion over and under the trpy ligand.That is, for both structures one phenyl ring of the phosphine is parallel to the central pyridine ring of trpy; a second phenyl ring is orthogonal to the plane of the trpy ligand; and a third phenyl group of the phosphine is tilted from the terminal pyridine of the trpy ligand. The Ru–P bond distances in both complexes fall within the expected range found for other phosphine ruthenium complexes, which is 2.26–2.41 Å.50–52,64–66 Such bond lengths are also similar to those observed with other metals and Table 4 Interatomic distances (Å) and angles (8) for trans-[Ru(Cl)(trpy)(C4SPAN)][PF6]?0.25C6H5Me?0.5CH2Cl2 7 (A) Ruthenium–ligand distances Ru(1)–P(1) Ru(1)–P(2) Ru(1)–Cl(1) 2.397(2) 2.397(2) 2.481(2) Ru(1)–N(71) Ru(1)–N(81) Ru(1)–N(91) 2.073(5) 1.955(5) 2.126(6) (B) Phosphorus–carbon distances P(1)–C(11) P(1)–C(21) P(1)–C(31) 1.836(8) 1.831(7) 1.825(6) P(2)–C(41) P(2)–C(51) P(2)–C(61) 1.852(6) 1.839(6) 1.817(9) (C) Distances within PPh2(C6H4) moieties C(11)–C(12) C(12)–C(13) C(14)–C(15) C(21)–C(22) C(22)–C(23) C(24)–C(25) C(31)–C(32) C(32)–C(33) C(34)–C(35) C(41)–C(42) C(42)–C(43) C(44)–C(45) C(51)–C(52) C(52)–C(53) C(54)–C(55) C(61)–C(62) C(62)–C(63) C(64)–C(65) 1.380(11) 1.385(12) 1.371(12) 1.392(8) 1.379(12) 1.381(11) 1.379(9) 1.386(10) 1.390(11) 1.371(9) 1.387(10) 1.373(10) 1.364(9) 1.364(10) 1.368(11) 1.387(9) 1.398(13) 1.371(12) C(11)–C(16) C(13)–C(14) C(15)–C(16) C(21)–C(26) C(23)–C(24) C(25)–C(26) C(31)–C(36) C(33)–C(34) C(35)–C(36) C(41)–C(46) C(43)–C(44) C(45)–C(46) C(51)–C(56) C(53)–C(54) C(55)–C(56) C(61)–C(66) C(63)–C(64) C(65)–C(66) 1.395(9) 1.375(9) 1.384(14) 1.387(10) 1.356(12) 1.388(13) 1.392(11) 1.361(13) 1.376(10) 1.397(12) 1.375(12) 1.384(9) 1.373(10) 1.362(13) 1.385(10) 1.420(11) 1.372(14) 1.379(16) (D) Distances within the trans-spanning bridge C(1)–O(2) O(2)–C(3) C(4)–C(5) C(6)–C(7) C(8)–O(9) C(10)–C(44) 1.451(9) 1.324(10) 1.524(12) 1.511(12) 1.325(10) 1.501(10) C(1)–C(14) C(3)–C(4) C(5)–C(6) C(7)–C(8) O(9)–C(10) 1.507(12) 1.512(10) 1.481(14) 1.512(14) 1.436(11) spanning linkages, for example [Ir(Cl)(CO)(SL1)] 22 has an Ir–P bond length of 2.310(4) Å and [Ir(Cl)3(CO)(SL1)] 22 has an average Ir–P bond length of 2.411 Å.The Cl–Ru–N(central pyridine) bond angles are also less than the ideal 1808 for both complexes: 174.9(2)8 for 5 and 174.7(2)8 for 7.The phenyl groups of the phosphines that are oriented orthogonal to the trpy plane appear to push the chloride ligand in the opposite direction and expand the Cl–Ru– N(trpy terminal pyridine) bond angle to 106.2(2)8 in 5 and 106.8(2)8 for 7. These angles are 10.38 and 11.38 greater than the second Cl–Ru–N(trpy terminal pyridine), i.e. where the phenyl group of the phosphine is approximately parallel to the terminal pyridine ring.This variation in bond angle is significant in light of other ligand (nitro or aqua)–Ru–N(trpy terminal pyridine) angles which vary between 99.6 and 102.58.50,51,65,66 The Ru–N(trpy terminal pyridine) bonds are diVerent by 0.026 Å in 5 and by 0.053 Å for 7. Also, the Ru–Cl bond distance in 7 is 0.024 Å longer than the Ru–Cl bond distance in 5. NMR spectroscopy 1H and 13C NMR spectroscopies were used to confirm the structures of the low spin, d6, ruthenium(II) complexes and to investigate the eVects of the trans-spanning linkages.The chemical shifts and coupling constants for all of the compounds are given in Table 5 (1H NMR) and Table 6 (13C NMR). Analysis of the free trpy spectra. In 1971, Carlson et al. assigned the 1H NMR spectrum of free trpy by drawing an analogy between trpy and 2,29-bipyridine (bpy).70 Assignments for bpy had previously been made by Castellano et al.71 Our analysis of the 1H NMR spectrum of the free trpy ligand diVers from that reported by Carlson et al.70 in our assignment of the (E) Distances within carbonyl groups C(3)–O(3) 1.204(9) C(8)–O(8) 1.188(9) (F) Angles around the ruthenium atom P(1)–Ru(1)–P(2) P(2)–Ru(1)–Cl(1) P(2)–Ru(1)–N(71) P(1)–Ru(1)–N(81) Cl(1)–Ru(1)–N(81) P(1)–Ru(1)–N(91) Cl(1)–Ru(1)–N(91) N(81)–Ru(1)–N(91) 175.0(1) 87.9(1) 91.2(2) 93.6(2) 174.7(2) 92.7(2) 106.8(2) 78.4(2) P(1)–Ru(1)–Cl(1) P(1)–Ru(1)–N(71) Cl(1)–Ru(1)–N(71) P(2)–Ru(1)–N(81) N(71)–Ru(1)–N(81) P(2)–Ru(1)–N(91) N(71)–Ru(1)–N(91) 87.1(1) 88.5(2) 95.5(2) 91.3(2) 79.3(2) 89.5(2) 157.7(2) (G) Angles around phosphorus atoms Ru(1)–P(1)–C(11) Ru(1)–P(1)–C(21) Ru(1)–P(1)–C(31) Ru(1)–P(2)–C(41) Ru(1)–P(2)–C(51) Ru(1)–P(2)–C(61) 114.4(2) 110.6(3) 119.7(2) 112.9(2) 120.7(2) 111.5(2) C(11)–P(1)–C(21) C(11)–P(1)–C(31) C(21)–P(1)–C(31) C(41)–P(2)–C(51) C(41)–P(2)–C(61) C(51)–P(2)–C(61) 108.0(3) 101.4(3) 101.5(3) 99.7(3) 107.9(3) 102.7(3) (H) Angles at Cipso in PPh3 ligands C(16)–C(11)–C(12) C(26)–C(21)–C(22) C(36)–C(31)–C(32) 116.6(7) 117.9(7) 117.5(6) C(46)–C(41)–C(42) C(56)–C(51)–C(52) C(66)–C(61)–C(62) 118.7(6) 118.2(6) 117.8(8) (I) Angles within trans-spanning bridge O(2)–C(1)–C(14) C(1)–O(2)–C(3) O(2)–C(3)–C(4) C(3)–C(4)–C(5) C(5)–C(6)–C(7) 110.7(8) 116.8(6) 110.0(6) 115.6(6) 114.3(8) O(9)–C(10)–C(44) C(7)–C(8)–O(9) C(8)–O(9)–C(10) C(4)–C(5)–C(6) C(6)–C(7)–C(8) 106.6(6) 111.6(7) 117.0(6) 115.3(8) 116.5(8) (J) Angles about carbonyl groups O(2)–C(3)–O(3) C(7)–C(8)–O(8) 125.8(7) 125.3(8) O(3)–C(3)–C(4) O(8)–C(8)–C(9) 124.2(8) 123.1(8)J.Chem. Soc., Dalton Trans., 1999, 2281–2292 2287 Table 5 1H NMR spectroscopy for ruthenium complexes Complex a d (ppm) (integration, multiplicity,b coupling/Hz, assignment c) trpy 7.35 (2 H, ddd, Jba = 4.8, Jbc = 7.5, Jbd = 1.2, b), 7.88 (2 H, ddd, Jcd = 8.0, Jcb = 7.5, Jca = 1.8, c), 7.96 (1 H, t, Jhg = 8.0, h), 8.47 (2 H, d, Jgh = 8.0, g), 8.63 (2 H, dt, Jdc = 8.0, d ), 8.69 (2 H, ddd, Jab = 4.8, Jdb = 1.2, Jda = 1.0, a) trans-[Ru(Cl)(trpy)(PPh3)2][PF6], 5 7.08 (12 H, cm, k), 7.11 d (2 H, —e, Jba = 5.4, Jbc = 7.4, Jbd e, b), 7.14 d (12 H, cm, j), 7.24 (6 H, cm, l ), 7.47 (3 H, s, Jgh e, g and h), 7.69 (2 H, td, Jca = 1.3, Jcb = 7.4, Jcd = 8.2, c), 7.75 (2 H, dd, Jdc = 8.2, Jdb = 1.6, Jda e, d ), 9.01 (2 H, d, Jab = 5.4, Jac = 1.3, Jad e, a) trans-[Ru(Cl)(trpy)(C3SPAN)][PF6], 6 2.09 (2 H, p, t), 2.71 (4 H, t, s), 4.90 (4 H, s, q), 6.17 (4 H, bs, n), 6.77 (4 H, bd, Jon = 7.7, o), 7.10 (2 H, bt, Jba = 5.8, Jbc = 7.6, Jbd e, b), 7.22 (8 H, cm, k), 7.29 f (2 H,e, Jgh = 8.0, g), 7.30 (4 H, cm, l ), 7.49 (1 H, t, Jhg = 8.0, h), 7.58 (2 H, d, Jda e, Jdb e, Jdc = 8.1, d), 7.67 (10 H, td, Jca = 1.2, Jcb = 7.6, Jcd = 8.1, c and j), 8.99 (2 H, bs, Jab = 5.8, Jac = 1.2, Jad e, a) trans-[Ru(Cl)(trpy)(C4SPAN)][PF6], 7 1.81 (4 H, cm, t), 2.56 (4 H, cm, s), 4.88 (4 H, s, q), 6.24 (4 H, cm, n), 6.80 (4 H, bd, o), 7.11 (2 H, ddd, Jba = 5.6, Jbc = 7.3, Jbd = 1.7, b), 7.21 (8 H, cm, k), 7.30 (4 H, cm, l), 7.35 (2 H, d, Jgh = 7.3, g), 7.44 (1 H, cm, Jhg = 7.3, h), 7.60 (2 H, d, Jda e, Jdb = 1.7, Jdc = 8.2, d), 7.60 (8 H, cm, j), 7.67 (2 H, td, Jca = 1.3, Jcb = 7.3, Jcd = 8.2, c), 9.00 (2 H, bd, Jab = 5.6, Jac = 1.3, Jad e, a) trans-[Ru(Cl)(trpy)(ISPAN)][PF6], 8 4.99 (4 H, s, q), 5.83 (4 H, p, n), 6.66 (4 H, bd, o), 7.10 (2 H, ddd, Jba = 5.3, Jbc = 6.7, Jbd = 2.2, b), 7.22 d (8 H, cm, k), 7.23 d (4 H, cm, l), 7.49 (2 H, dd, Jda = 1.7, Jdb = 2.2, Jdc = 8.5, d), 7.44 (3 H, bs, g and h), 7.54 (2 H, cm, Jca = 1.2, Jcb = 6.7, Jcd = 8.5, c), 7.66 (1 H, t, Jut = 7.9, u), 7.92 (8 H, cm, j), 8.37 (2 H, dd, Jtu = 7.9, Jtv = 1.6, t), 8.50 (1 H, bt, Jvt = 1.6, v), 9.20 (2 H, bd, Jab = 5.3, Jac = 1.2, Jad = 1.7, a).a NMR spectra were measured in CD2Cl2 and referenced against CDHCl2. b Abbreviations: s = singlet, d = doublet, t = triplet, p = pentuplet, bs = broad singlet, bd = broad doublet, bt = broad triplet, dd = doublet of doublets, dt = doublet of triplets, td = triplet of doublets, ddd = doublet of doublet of doublets, cm = complex multiplet. c Letters used in assignments correlate to trpy Fig. 4; 5 Fig. 5; 6 Fig. 6; 7 Fig. 7; 8 Fig. 8. d Shift determined from corrected HETCOR data. e Could not determine due to overlap or broad linewidth. f Shift determined by COSY. chemical shifts for the Hd and Hg protons (see Fig. 4). The terminal pyridine rings in trpy are magnetically equivalent and have the first order sub-spectrum of a 2-substituted pyridine while the middle ring has the first order sub-spectrum of a 2,6- disubstituted pyridine.Free trpy demonstrates a trans,transconfiguration both in solution 63 and in the solid state 64 due to the repulsion of the non-bonding electrons on the nitrogen atoms. This has consequences for the proton chemical shifts. Protons Ha, Hb, Hc and Hh in free trpy have shifts similar to the equivalent positions in pyridine.However, Hd and Hg are shifted over 1 ppm downfield from their position in pyridine due to their interaction with the non-bonding electron pairs on the adjacent pyridine rings. The two-dimensional COSY spectrum (see SUP 57568, Fig. 9) of free trpy is consistent with our current assignments. Notably, Jab is about half the size of Jcd for both free trpy and for trpy contained in complexes 5–8. When this information is used in conjunction with the carbon shifts determined by HETCOR spectroscopy, confirmation of the proton assignments in the ruthenium complexes is possible. The proton decoupled 13C NMR resonances for free trpy are assigned (Fig. 4) based on one-bond HETCOR experiments (SUP 57568, Fig. 10) except in the case of Ce and Cf which are Fig. 3 Molecular geometry of the trans-[Ru(Cl)(C4SPAN)(trpy)]1 cation, 7. Hydrogen atoms are omitted for clarity. assigned based on N-bond HETCOR experiments. The 13C NMR resonances for free trpy are within 0.3 to 2.5 ppm of the literature values for the resonances of free pyridine (Cortho to N d 149.8, Cmeta to N d 123.6 and Cpara to N d 135.7) 72 except for Ce and Cf which are shifted by 6.7 and 5.9 ppm downfield, respectively, due to substituent eVects.Analysis of triphenylphosphine spectra. The 1H NMR spectum of free triphenylphosphine (PPh3) shows one broad singlet in the aromatic region, d 7.28 in CDCl3.73 The 13C NMR spectrum of free PPh3 shows seven peaks at d 137.27, 137.12, 133.79, 133.53, 128.60, 128.44 and 128.35 in CDCl3.73 NMR studies have been successful in characterizing the dynamic processes of PPh3 ligands in many transition metal complexes.74–77 Coordinated PPh3 is capable of rotating about the three P–Cipso bonds as well as as the metal–P bond.For steric reasons, the three phenyl groups generally adopt a chiral propeller-like conformation with either a clockwise or anticlockwise screw configuration.77 Interconversion of the two enantiomeric configurations or full rotation about any P–Cipso bond requires cooperative motion within PPh3.78 In a conformational study of free triphenylphosphine, Brock and Ibers 78 estimated both of these barriers to rotation to be less than 2 kcal mol21.For [Fe(h5-C5H5)(CO)(PPh3)(COMe)], Davies determined that the P–Fe rotational activation energy barrier (DG‡) was 10.3 kcal mol21 and that the phenyl ring rotation about the P–Cipso was rapid on the NMR time scale down to 290 8C.77 In order to determine if the steric eVects of the trans-spanning linkage resulted in restricted rotation of the phosphine ligand we employed (see below) variable temperature NMR studies on ruthenium complexes which contain phosphine ligands.Analysis of the ruthenium complex spectra. The literature contains little information on the NMR behavior of trans-spanning complexes due at times to the diYculties associated with the separation of isomers (cis and trans, monomers and dimers) and also the insolubility of many of the complexes in common NMR solvents.21 In contrast, the trans-spanning complexes 6–8 are monomeric, trans-isomers and are soluble in a variety of common NMR solvents.The 1H and 13C spectra of 6, 7 and 8 are shown in Fig. 6–8 [HETCOR and COSY data are given in SUP 57568, Fig. 15, 16 (complex 6), 19, 20 (7), and 23, 24 (8); variable temperature data are also given in SUP 57568, Figs.2288 J.Chem. Soc., Dalton Trans., 1999, 2281–2292 Table 6 13C NMR spectroscopy for ruthenium complexes Complex a d (ppm) b (coupling/Hz, assignment c) trpy 121.10 c (b), 121.20 c ( g), 121.24 c (d ), 137.1 c (c), 138.2 c (h), 149.5 c (a), 155.7 d ( f ), 156.5 d (e) trans-[Ru(Cl)(trpy)(PPh3)2][PF6], 5 122.66 ( g), 122.83 (d ), 126.84 (b), 128.57 (|3JPCk 1 5JP9Ck| = 9.1, k), 130.10 (|4JPCl 1 6JPCl| = 1.6, l), 130.13 (|1JPCi 1 3JP9Ci | = 39.2, i), 132.52 (s, h), 133.23 (|2JPCj 1 4JP9Cj | = 10.3, j), 136.87 (c), 155.79 (a), 157.66 ( f ), 158.18 (e) trans-[Ru(Cl)(trpy)(C3SPAN)][PF6], 6 20.72 (t), 33.07 (s), 66.40 (q), 122.74 ( g), 122.76 (d ), 127.17 (b), 128.75 (|3JPCk 1 5JP9Ck| = 9.6, k), 129.74 (|1JPCm 1 3JP9Cm| = 36.9, m), 129.85 (|3JPCo 1 5JP9Co| = 7.7, o), 130.64 (|4JPCl 1 6JP9Cl | = 1.9, l), 130.96 (2 C, |2JPCn 1 4JP9Cn| = 8.6, n; |1 PCi 1 3JP9Cl | = 41.0, i), 132.45 (h), 134.15 (|2JPCj 1 4JP9Cj | = 10.8, j), 136.75 (c), 137.21 (|4JPCp 1 6JP9Cp| = 1.9, p), 155.45 (a), 157.37 ( f ), 157.97 (e), 172.91 (r) trans-[Ru(Cl)(trpy)(C4SPAN)][PF6], 7 24.67 (t), 34.17 (s), 66.00 (q), 122.55 (d ), 122.64 ( g), 127.08 (b), 128.67 (|3JPCk 1 5JP9Ck| = 9.8, k), 128.73 (|3JPCo 1 5J)P9Co| = 7.2, o), 128.94 (|1JPCm 1 3JP9Cm| = 36.4, m), 130.51 (|4JPCl 1 6JP9Cl | = 0.0, l), 130.82 (|1JPCi 1 3JP9Ci | = 41.4, i), 131.13 (|2JPCn 1 4JP9Cn| = 10.3, n), 132.32 (h), 134.07 (|2JPCj 1 4JP9Cj | = 11.0, j), 136.73 (c), 137.94 (|4JPCp 1 6JP9Cp| = 0.0, p), 155.54 (a), 157.43 ( f ), 157.87 (e), 173.26 (r) trans-[Ru(Cl)(trpy)(ISPAN)][PF6], 8 68.38 (q), 122.91 (d), 123.31 ( g), 126.96 (b), 127.28 (v), 128.80 (|3JPCk 1 5JP9Ck| = 9.7, k), 129.40 (|1JPCm 1 3JP9Cm| = 36.0, m), 130.08 (u), 130.78 (|4JPCl 1 6JP9Cl | = 0.0, l), 130.84 (|1JPCi 1 3JP9Ci | = 40.9, i), 130.89 (|2JPCn 1 4JP9Cn| = 8.7, n), 130.90 (s), 131.03 (|3JPCo 1 5JP9Co| = 7.4, o), 132.40 (h), 134.24 (|2JPCj 1 4JP9Cj | = 11.0, j), 135.59 (t), 135.70 (|4JPCp 1 6JP9Cp| = 0.0, p), 136.82 (c), 155.78 (a), 156.82 ( f ), 158.22 (e), 165.65 (r) a NMR spectra were measured in CD2Cl2 and referenced against CDHCl2.b Letters used in assignments correlate to trpy Fig. 4; 5 Fig. 5; 6 Fig. 6; 7 Fig. 7; 8 Fig. 8. c Determined by one-bond HETCOR. d Determined by N-bond HETCOR. 17, 18 (complex 6), and 21, 22 (complex 7)]. Room temperature spectra will be the subject of discussion below unless otherwise noted. I. Analysis of coordinated trpy spectra. The coordination of the trpy ligand to a ruthenium(II) cation can result in a down- field shift of the bonded trpy proton resonances relative to free trpy;50,70 however, while Ha moves downfield 0.30–0.51 ppm in 5–8 as expected, the chemical shifts of the other trpy protons in 5–8 move 0.19–1.18 ppm upfield relative to the free trpy ligand.A possible reason for the downfield shift of Ha is given below. The 13C NMR chemical shifts of bonded trpy in 5 (Fig. 5) vary little when compared with the free trpy resonances with the following exceptions: Ca is 6.3 ppm and Cb is 5.7 ppm downfield of the free trpy positions, while the chemical shift of Ch in 5 is 5.7 ppm upfield of that in free trpy. Similar changes in chemical shifts are observed for 6–8.II. Analysis of the coordinated phosphine ligand spectrum for 5. The proton chemical shifts of the triphenylphosphine ligands of 5 are assigned as complex multiplets: meta (Hk, d 7.08), ortho (Hj, d 7.14) and para (Hl, d 7.24).When compared to the free triphenylphosphine ligand, the chemical shifts of 5 are Fig. 4 1H and 13C NMR spectra (300 MHz) of 2,29:69,60-terpyridine (trpy) in methylene chloride-d2. 0.04–0.21 ppm upfield of their expected position. Thus, there seems to be a mutual anisotropic deshielding between the phenyl rings and the trpy ligand. These results can be explained for 5 if the possible motions of the triphenylphosphine groups are considered. As only three proton resonances are observed for the PPh3 moieties of 5, free rotation about all three P–Cipso bonds as well as the Ru–P bond is indicated.The ORTEP diagram of 5 (Fig. 2) shows that (a) each phenyl group of triphenylphosphine has a diVerent orientation depending on its position relative to the trpy ligand and (b) both PPh3 ligands are similarly arranged. Two phenyl rings are located over and under the central pyridine ring of trpy in an essentially parallel arrangement. The other two pairs of phenyl rings are positioned on each side of the trpy ligand and are nearly perpendicular to the plane of the terminal trpy pyridines.Thus, from the crystal structure it may be postulated that as each triphenylphosphine rotates along the Ru–P bond each phenyl ring will adjust its orientation along the P–Cipso axis. That is, as each phenyl ring moves around the Ru–P bond, it may travel a monotonic or slightly oscillatory path over the trpy ring, but, as it clears the plane above (or Fig. 5 1H and 13C NMR spectra (300 MHz) of trans-[Ru(Cl)(trpy)- (PPh3)2]1, 5 in methylene chloride-d2.J. Chem. Soc., Dalton Trans., 1999, 2281–2292 2289 Fig. 6 1H and 13C NMR spectra (300 MHz) of trans-[Ru(Cl)(trpy)(C3SPAN)]1, 6 in methylene chloride-d2. below) the trpy ligand, it may rotate about the P–Cipso bond to become perpendicular to the trpy ring thereby time averaging the ortho and meta proton resonances and resulting in only three unique proton resonances.If this model is correct, the chemical shifts of the PPh3 ligands are expected to be upfield relative to the free PPh3, since the PPh3 ligands of 5 spend more time in the shielding areas over the trpy compared to the two pockets between the chlorine and each of the terminal pyridines of trpy. Likewise the trpy protons of 5 (except for Ha) should experience shielding by the phenyl rings of the PPh3 ligands and should also be found upfield when compared to the free trpy ligand.As these general upfield shifts are indeed observed in both the PPh3 and trpy ligands, anisotropic deshielding may be the cause. Notably, the Ha protons are expected to be unique since the phenyl rings of the PPh3 may freely rotate once they clear the plane of the trpy ligand. The 0.3 ppm downfield shift for Ha of 5 may be due to anisotropic deshielding from the phenyls in the pockets. The triphenylphosphine ligands in the 13C NMR spectrum of 5 show a set of four triplets, although that from the para position, Cl, looks like a singlet at low resolution.The signals are triplets due to virtual coupling to the second phosphorus. Since the two-bond P–Ru–P9 coupling is much larger than the P–C couplings, the high order pattern is a triplet rather than a doublet-of-doublets or a pentuplet. One can then measure only the algebraic sum of the two P–C couplings across the outer line of the triplet. For 5 the values are ipso (|1JP–Ci 1 3JP–Ci | = 39.2 Hz), ortho (|2JP–Cj 1 4JP–Cj | = 10.3 Hz), meta (|3JP–Ck 1 5JP–Ck| = 9.1 Hz) and para (|4JP–Cl 1 6JP–Cl | = 1.6 Hz).The peak assignments for 5 have been corroborated through HETCOR and COSY experiments. III. Analysis of the coordinated phosphine ligand spectra for 6–8. Proton shifts for the phenyl groups of PPh3 show some changes on going from 5 to the span complexes, 6–8. First, complexes 6–8 show a sub-spectrum for a para-disubstituted phenyl ring in the aromatic region as part of the spanning linkage and 8 shows an additional 1,3-disubstituted phenyl pattern for the isophthalate linkage.For any given phenyl ring on the phosphine ligand, the two ortho positions are equivalent to each other as are the two meta positions. These results indicate that the phenyl rings are undergoing rapid rotation about the P–Cipso bond at room temperature. Second, meta and para protons maintain similar chemical shift values for 5–8 but there are significant diVerences between the complexes in the positions of the ortho protons of the phenyl rings, Hj.The Hj chemical shifts of 6 and 7 are approx. 0.5 ppm downfield relative to 5; while the chemical shift of Hj in 8 is 0.78 ppm downfield relative to 5. These downfield shifts will be discussed below in terms of motional averaging in the span complexes. Finally, the 0.3 ppm downfield shift for Ha of 6–8 may also be attributed to the anisotropic deshielding from the phenyls in the pockets.There is little diVerence in the 13C shifts between the spanned complexes, 6–8, and that containing the triphenylphosphine ligand, 5. IV. Analysis of the variable temperature spectra for 5. Restricted rotation about the P–Cipso bonds or Ru–P bond should be observed if the phosphine ligands are sterically con- fined; variable temperature studies were conducted to detect such restricted rotations. If the rotation about each P–Cipso becomes slow on cooling, it is expected that the ortho and meta peaks of the triphenylphosphine moiety will split into two distinct resonances while the ipso (13C only) and para resonances should remain singular.If rotation about the Ru–P bond becomes slow on the NMR time scale, the peaks observed from the ipso, ortho, meta and para carbons should split into three, one for each of the rotating phenyl groups. Variable temperature 1H and 13C NMR spectra for 5 (see SUP 57568, Fig. 13 and 14) show no line broadenings until 290 8C where Hj, Ci and Cj show significant broadening and Cl shows slight broadening.Since the ipso carbon, Ci and the para carbon, Cj, should not show broadening for slowed rotation about the P–Cipso bond, it is possible but not conclusive that rotation about the P–Ru bond is becoming slow at low temperatures. Interestingly, [Fe(h5-C5H5)(CO)(PPh3)(COMe)] shows a similar pattern of low temperature behavior in the 13C spectrum.77 For the iron complex, the ipso, ortho and para carbons show broadening at2290 J.Chem. Soc., Dalton Trans., 1999, 2281–2292 Fig. 7 1H and 13C NMR spectra (300 MHz) of trans-[Ru(Cl)(trpy)(C4SPAN)]1, 7 in methylene chloride-d2. Fig. 8 1H and 13C NMR spectra (300 MHz) of trans-[Ru(Cl)(trpy)(ISPAN)]1, 8 in methylene chloride-d2. 260 8C with complete freezing out of the spectrum at 290 8C. The meta carbons are only starting to broaden at 290 8C and there is no sign of broadening for the acetyl methyl group or the cyclopentadienyl ring.For [Fe(h5-C5H5)(CO)(PPh3)(COMe)], Davies determined an experimental DG = 10 kcal mol21 for the Fe–P rotation at 62.90 MHz. As 5 requires a lower temperature for the start of broadening, even at a higher frequency (75 MHz), the Ru–P rotation in 5 is faster. V. Analysis of the variable temperature spectra for 6–8. The variable temperature NMR spectra of 6 and 7 are qualitativelyJ. Chem. Soc., Dalton Trans., 1999, 2281–2292 2291 similar to that of 5 except that even though there is no sign of broadening for the trpy resonances of 5 at 290 8C, the Ha, Hj and Hn resonances of 6 and 7 are already broad at room temperature.Maximum line broadenings for Ha, Hj, Hn and Ho are found between 5 8C and 240 8C. Below 240 8C these resonances sharpen though they do not split into separate resonances as described above for slowed rotations about the Ru–P or P–Cipso bonds. At 260 8C, these resonances are sharp indicating that the motions about the Ru–P and P–Cipso bonds are still fast on the NMR time scale.At 290 8C, Ha, Hj and Hn start to broaden but again, there is no indication of which motion is slowing. The methylene proton signals for the span also broaden but it is not possible to tell if this is an independent conformational process in the spanning linkage or if this is related to rotation about the P–Ru bond. Complex 7 follows the same behavior as 6 but maximum coalescence starts about 40 8C lower.Complex 7 is expected to be more accommodating than 6 for rotation about either the trpy or chloride moieties. The diVerence in the coalescence temperatures may be related to subtle changes in span rotation about the P–Ru bond. Finally, two types of motion appear to be available in the spanned complexes. The first involves a complete 3608 rotation of the span about the P–Ru–P axis, where the span passes over both the chloride and the meridional trpy ligand. The second involves a restricted “fan-like” motion of the spanning linkage limited by the two terminal pyridines of the trpy ligands, where the span passes over only the chloride ligand and not the trpy ligand.Both mechanisms would time average the trpy resonances. At this time, it is not possible to distinguish which of these motional mechanisms is operating. Conclusions The in situ strategy for the preparation of trans-spanning ligands with ester linkages resulted in spanning linkages which are stable to oxidation and reduction, hydrolysis and cyclometallation while maintaining the benefits of span variability and the formation of ruthenium complexes which display bond angles close to ideal octahedral geometry.The NMR spectral analyses yielded several observations: (1) the original assignment of the 1H NMR spectrum of trpy by Carlson is inconsistent with our COSY and HETCOR analyses, (2) the NMR spectra of 6–8 are consistent with a flexible spanning linkage that does not demonstrate restricted rotation about either the P–Cipso or the Ru–P bonds even at low temperatures, and (3) maximal coalescence increased with temperature with shorter alkyl chain lengths in the trans-spanning linkage.Finally, the X-ray crystal structure analysis of 7 showed that the spanning linkage is positioned in one of the two pockets defined by the chloride ligand and the terminal pyridine groups of trpy. Acknowledgements This work was supported in part by the National Science Foundation (CHE 9120602) and the ARCO Chemical Company.Purchase of the Siemens R3m/v diVractometer was made possible by Grant 89-13733 from the Chemical Instrumentation Program of the National Science Foundation. The authors also gratefully acknowledge Johnson Matthey/Alfa/ Aesar for the loan of the RuCl3?nH2O used in these experiments. The authors acknowledge the assistance of Mr Simit D. Shah, Mr Sejal C. Patel and Mr Brian M. Scull of Villanova University in preparation, purification and characterization of the complexes. References 1 J.C. Bailar, Jr., Coord. Chem. Rev., 1990, 100, 1. 2 D. M. A. Minahan, W. E. Hill and C. A. McAuliVe, Coord. Chem. Rev., 1984, 55, 31. 3 A. Pryde, B. L. Shaw and B. Weeks, J. Chem. Soc., Dalton Trans., 1976, 322. 4 N. A. Al-Salem, H. D. Empsall, R. Markham, B. L. Shaw and B. Weeks, J. Chem. Soc., Dalton Trans., 1979, 1972. 5 C. Crocker, R. J. Errington, R. Markham, C. J. 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Clerc, Tables of Spectral Data for Structure Determination of Organic Compounds, Springer- Verlag, New York, 1983. 73 C. J. Pouchert and J. Behnke, Aldrich Library of 13C and 1H FT NMR Spectra, Aldrich Chemical Company, Inc., Milwaukee, WI, 1st edn., 1993, vol. 2, p. 1653. 74 J. W. Faller and B. V. Johnson, J. Organomet. Chem., 1975, 96, 99. 75 J. Vicente, M.-T. Chicote, M.-C. Lagunas, P. G. Jones and B. Ahrens, Inorg. Chem., 1997, 36, 4938. 76 E. E. Wille, D. S. Stephenson, P. Capriel and G. Binsch, J. Am. Chem. Soc., 1982, 104, 405. 77 S. G. Davies, A. E. Derome and J. P. McNally, J. Am. Chem. Soc., 1991, 113, 2854 and refs. therein. 78 C. P. Brock and J. A. Ibers, Acta Crystallogr., Sect. B, 1973, 29, 2426. Paper 8/07574C

ISSN:1477-9226    

DOI:10.1039/a807574c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 2285–2287 2285 Synthesis and characterization of new titanium hexanuclear oxo carboxylato alkoxides. Molecular structure of [Ti6(Ï3-O)6- (Ï-O2CC6H4OPh)6(OEt)6] Renée Papiernik,a Liliane G. Hubert-Pfalzgraf,*,†,a Jacqueline Vaissermannb and Maria C. Henriques Baptista Goncalves c a Laboratoire de Chimie Moléculaire, URA CNRS, Parc Valrose, 06 108 Nice Cédex, France b Laboratoire de Chimie des Métaux de Transition, URA CNRS, 4 Place Jussieu, 75252 Paris Cédex, France c Departemento De Engenharia De Materias, Instituto Superior Tecnico, Av.Rovisco Pais, 1096 Lisboa-codex, Portugal The reaction between Ti(OR)4 (R = Et or Pri) and 2- phenoxybenzoic acid in refluxing toluene led to [Ti6(m3-O)6(m- O2CC6H4OPh)6(OR)6]; its structure corresponds to an assembly of two staggered triangular units sharing six edges (actually the m3-O ligands) and connected via the carboxylate ligands. Substitution of alkoxide ligands by carboxylate ligands was first investigated as a means of stabilizing metal alkoxides such as Ti(OR)4 (R = Et, Pri or Bu) in sol–gel processing; acetic acid was commonly used.1 These reactions were extended to functionalized acids having polymerizable groups such as methacrylic acid for hybrid materials applications 2 or to oleic acid for colloid stabilisation in non-aqueous media.3 The reactions were carried out at room temperature mostly without any solvent and in the stoichiometry Ti(OR)4–R9CO2H = 1: 2.Hexanuclear titanium oxo carboxylato alkoxides were generally isolated and characterized by X-ray diVraction. They display two types of formulations, namely [Ti6O4(R9CO2)4(OR)12] [R9 = Me, R = Pri;4 R9=Np (neopentyl), R = Pri or H;5 R9 = Co3C(CO)9, R = Et or Pri 6] or [Ti6O4(R9CO2)8(OR)8] (R9 = Me7 or CMeCH2,2a R = Et; R9 = Me, R = Bu8). Recently, tetranuclear clusters with a greater number of oxo groups per metal atom of formulation [Ti4O4(R9CO2)4(OR)4] [R9 = Co3C- (CO)9, R = Pri, Et or Ph;6 R9 = Pri, R = Bu5] were obtained. The generation of the oxo ligands was attributed to hydrolysis reactions as a result of esterification between excess acid and the alcohol generated by the substitution reaction.8 The diVerence in the formulation of the three types of clusters was attributed to the nature of the OR and R9CO2 ligands.6 No mention was made of temperature eVects which regulate the kinetics of substitution, esterification, hydrolysis and condensation reactions.This factor allowed us to obtain and characterize the new hexanuclear titanium oxo carboxylato alkoxide cluster [Ti6- (m3-O)6(m-O2CC6H4OPh)6(OEt)6] and analogs [Ti6(m3-O)6(m- O2CR9)6(OR)6] with R = Pri, R9 = C6H4OPh or Me and R = Et, R9 = Me. The reaction between titanium tetraethoxide and 2- phenoxybenzoic acid (1 : 2 stoichiometry) in refluxing CH2Cl2 for 3 h shows unreacted acid detected by IR spectroscopy [n(CO2) 1690 cm21].After refluxing for 15 h in toluene free acid is no longer detected. The FT-IR spectrum of the raw product indicates ester formation [n(CO) 1728 cm21]. The 1H NMR spectra show signals characteristic of a heteroleptic titanium species with a OR–R9CO2 integration ratio of 1 : 1 and additional signals due to ester [integration ratio OR(Ti complex)– (ester) = 1:1]. This latter value is incompatible with the form- † E-Mail: hubert@unice.fr ation of the known hexanuclear complexes [Ti6O4(OR)12(O2- CR9)4] or [Ti6O4(OR)8(O2CR9)8] which would lead to a ratio OR(complex)–OR(ester) of 3 : 1 or 2 : 1 respectively. It is however consistent with a [Ti4O4(OR)4(O2CR9)4] tetranuclear species. Crystallisation in CH2Cl2 aVords a pure titanium species 1 in 64% yield.‡ In the absence of informative 1H NMR data (one type of ethoxide ligand only), its structure was investigated by single crystal X-ray diVraction.§ Compound 1 corresponds to a hexanuclear cluster of formula [Ti6(m3-O)6(OEt)6(m-O2CC6H4OPh)6] (Fig. 1). Each titanium center is surrounded by three m3-O, two mcarboxylate and one alkoxide ligand in a distorted octahedron [O]Ti]O angles 77.3(2)–179.0(2)8]. The structure is symmetric and compact. It can be viewed as an assembly of two staggered triangular units built by sharing vertices of the octahedra [average Ti ? ? ? Ti distances of 3.111(2) Å] which are joined by six common edges (Fig. 2). All m3-oxo ligands are trigonal (average S = 333.88) and belong to the shared edges, the alkoxide ligands are in apical positions and the six carboxylate ligands are connecting the two triangular units.This arrangement makes enough room for the aromatic rings which are oriented toward the outside like an equatorial crown. The Ti]O bond lengths are in the range 1.751(5)–2.154(4) Å. The Ti]m3-O distances within the triangular units [1.878(4)–1.912(4) Å] are significantly shorter than those of the interunits [2.150(5)– 2.154(4) Å] and the Ti]m-O (carboxylate) distances [2.026(5)–2.081(5) Å] are longer than the Ti]OR [1.751(5)– 1.770(5) Å].The Ti]O]C angles related to the alkoxide ligands are quite large [149.0(8)–167.9(11)8] as commonly observed for early transition metals. These values are in agreement with those reported in the literature.8,9 The alkoxide ligands and carboxylate ligands are both equivalent on the NMR timescale, the 1H NMR spectrum shows only one signal per ligand type indicating that the solid-state structure is retained upon ‡ All manipulations were routinely performed under nitrogen using Schlenk and vacuum-line techniques. 2-Phenoxybenzoic and acetic acid (Aldrich) were used as received, Ti(OEt)4 and Ti(OPri)4 (Aldrich) were distilled before use.A solution of 2-phenoxybenzoic acid (2.789 g, 13.08 mmol) in toluene (50 ml) was added to Ti(OEt)4 (1.49 g, 6.54 mmol) in toluene (20 ml). After refluxing for 15 h, the solvent was removed under vacuum and cluster 1 was obtained at 0 8C from a CH2Cl2 solution (1.35 g, 64%) (Found C, 54.87; H, 4.06.Calc. for C90H84O30Ti6: C, 55.92; H, 4.35%). Similar synthetic procedures were applied for [Ti6O6(OPri)6- (O2CC6H4OPh)6] 2, [Ti6O6(OR)6(OAc)6] (R = Pri 3 and R = Et 4). § Crystal data for 1: C90H84O30Ti6?4C6H5CH3, M = 2301.6, triclinic, space group P1� , a = 13.162(6), b = 14.977(6), c = 17.110(2) Å, a = 102.97(2), b = 103.48(3), g = 112.15(3)8, U = 2849(2) Å3, Z = 1, m(Mo-Ka) = 4.68 cm21, 10 493 data of which 10 018 were unique were collected at room temperature, R = 0.0617, R9 = 0.0735 for 626 parameters.CCDC reference number 186/1036. See http://www.rsc.org/ suppdata/dt/1998/2285/ for crystallographic files in .cif format.2286 J. Chem. Soc., Dalton Trans., 1998, Pages 2285–2287 Table 1 Characterization of the diVerent titanium oxo carboxylato alkoxides 1 2 3 4 5 IR/cm21 n(CO2) n(M]O]M) n(M]OR), n(M]O2CR9) 1604s, 1584s, 1538s 734s 659s, 623m, 503m, 480m 1608s, 1591s, 1538s 733s 660s, 627m, 502m, 480m 1603s, 1548s 726s 659s, 629m, 605m, 487m 1594s, 1543s 738s 659s, 631m, 610m, 477m 1595s, 1571s, 1555s 785s–772s 689m–655s, 625s, 590m–543m, 510m–456m 1H NMR (CDCl3, ppm) OR R9CO2 OR–O2CR9 ratio 1.10 (t, 8 Hz, Me), 4.35 (q, CH2) 7.97 (d, 7 Hz, aromatic C]H a to CO2) 1:1 1.22 (d, 7 Hz, Me), 4.92 (sept, CH) 8.05 (d, 7 Hz, aromatic C]H a to CO2) 1:1 1.35 (d, 7 Hz, Me), 5.15 (q, CH) 2.04 (s, Me) 1:1 1.39 (t, 7 Hz, Me), 4.82 (q, CH2) 2.10 (s, Me) 1:1 1.25 (t, 7 Hz, Me), 4.35, 4.55, 4.90 (m, 3:4:1, CH2) 2.20 (s, Me) 1:1 dissolution.Cluster 1 represents the first hexanuclear titanium oxo carboxylato alkoxide having the formula [Ti6O6(OR)6- (O2CR9)6]. Refluxing Ti(OPri)4 and 2-phenoxybenzoic acid in toluene leads to analogous crystalline material (yield 30%) identified by FT-IR and 1H NMR spectroscopy as [Ti6O6(OPri)6(O2CC6H4OPh) 6] 2 (Table 1). Application of the same procedure to Ti(OR)4 and acetic acid aVorded [Ti6O6(OR)6(OAc)6] (R = Pri 3 or Et 4) in 60 and 33% yields respectively indicating that the formation of compounds of type 1 does not depend on the nature of R [equation (1)]. 6Ti(OR)4 1 12R9CO2H heat,toluene [Ti6O6(OR)6(R92)6] 1 6R9CO2R 1 12ROH (1) R = Et or Pri R9 = PhOC6H4 or Me Fig. 1 Ball and stick drawing of the [Ti6(m3-O)6(OEt)6(m- O2CC6H4OPh)6] cluster showing the atom numbering scheme. Selected average bond lengths (Å): Ti]m3-O 1.980, Ti]OR 1.761, Ti]m-O2CR9 2.056 The formation of 3 is quite easy to explain since temperature favors higher incorporation of carboxylato or oxo ligands into the metal co-ordination sphere.A similar oxocluster, [Sn6O6- (OBut)6(OAc)6], was obtained by non-hydrolytic condensation between Sn(OAc)4 and Sn(OBut)4 in refluxing toluene.10 Such a reaction was envisioned as a means to convert [Ti6O4(OR)8- (O2CR9)8] into a complex with a greater number of oxo groups. The cluster [Ti6O4(OEt)8(OAc)8] 5 was thus prepared according to the literature.7 Cluster 4 was obtained in 40% yield after refluxing 5 in toluene for 15 h and crystallisation from CH2Cl2 solution.Its formation can only be explained by elimination of the ester during heating. Cluster 4 can thus be obtained by two routes: substitution reactions between metal alkoxides and carboxylic acids [equation (1)] or by elimination of the ester from [Ti6O4(OR)8(O2CR9)8] [equation (2)]. Condensation with [Ti6O6(OR)8(R9CO2)8] heat,toluene [Ti6O6(OR)6(R9CO2)6] 1 2R9CO2R (2) R = Et or Pri R9 = Me elimination of ester promoted by heating was observed for systems involving the metal alkoxides (Pb–Ti or Pb–Nb systems) and carboxylates.9 Table 1 shows the diVerences between 5 and 4.These new hexanuclear clusters can be distinguished from each other using FT-IR and 1H NMR spectroscopy. Cluster 4 Fig. 2 The assembly of the co-ordination polyhedra in [Ti6(m-O)6- (OEt)6(m-O2CR)6]J. Chem. Soc., Dalton Trans., 1998, Pages 2285–2287 2287 Scheme 1 Reactions between titanium alkoxides and various carboxylic acids (bold = present work) [Ti6O4(OR)12(O2CR¢)4] [Ti6O4(OR)8(O2CR¢)8] [Ti6O6(OR)6(O2CR¢)6] [Ti3O4(OR)8(O2CR¢)2] [Ti4O2(OR)10(O2CR¢)2] [Ti4O4(OR)4(O2CR¢)4] [Ti9O8(OR)4(O2CR¢)16] Ti(OR)4 Pri, Me7 Et, CH2CH2 Bun, Me8 R, R¢ = Pri, Me5 R, R¢ = R, R¢ = Np, Me5 Pri, Me4 Pri, Np5 Pri, H5 Et, Co3C(CO)9 6 R, R¢ = Et, PhOC6H4 Pri, PhOC6H4 Et, Me Pri, Me R, R¢ = Pri, Co3C(CO)9 5 Ph, Co3C(CO)9 6 But, Pri 9 R, R¢ = Et, Me R, R¢ = Toluene, heat Pri, CMeCH2 11 R, R¢ = has a strong n(Ti]O) absorption band around 740 cm21 in its FT-IR spectrum, whereas more complex spectra are observed for compounds of type 5.Only one sharp 1H NMR signal is observed for the OR ligands in 4 in contrast to three signals for the magnetically non-equivalent alkoxides of [Ti6(m-O)2- (m3-O)2(m-OR)2(OR)6(m-O2CR9)8] clusters of type 5. Scheme 1 summarises the various titanium oxo carboxylato alkoxides known.The temperature plays an important role and is a factor which must be taken into account in the build-up of an already rich series of titanium oxo carboxylato alkoxide species. The recent report of the formation of the [Ti9(m-O)6- (m3-O)2(OPri)4(O2CCMeCH2)16] species obtained by reacting Ti(OPri)4 and excess methacrylic acid illustrates the structural diversity.11 References 1 S. DoeuV, M. Henry, C. Sanchez and J. Livage, J. Non-Cryst. Solids, 1987, 89, 206; L.G. Hubert-Pfalzgraf, New J. Chem., 1987, 11, 663. 2 (a) U. Schubert, E. Arpac, W. Glaubitt, A. Helmerich and C. Chau, Chem. Mater, 1992, 4, 291; (b) L. G. Hubert-Pfalzgraf, A. Abada, J. Vaissermann and J. Roziere, Polyhedron, 1996, 16, 1. 3 M. Green, T. Kramer, M. Parish, J. Fox, R. Lalananham, W. Rhine, S. Barclay, P. Calvert and H. K. Bowen, Adv. Ceram., 1987, 21, 449; R. R. Landham, M. V. Parish, H. K. Bowen and P. D. Calvert, J. Mater. Sci., 1987, 22, 1677. 4 S. DoeuV, Y. Dromzee and C. Sanchez, C.R. Acad. Sci. Ser. II, 1989, 308, 1409. 5 T. J. Boyle, personal communication. 6 X. Lei, M. Shang and T. P. Fehlner, Organometallics, 1996, 15, 3779; Organometallics, 1997, 16, 5289. 7 L. Gautier-Luneau, A. Mosset and J. Galy, Z. Kristallogr., 1987, 180, 83. 8 S. DoeuV, Y. Dromzee, F. Taulelle and C. Sanchez, Inorg. Chem., 1989, 28, 4439. 9 L. G. Hubert-Pfalzgraf, S. Daniele, R. Papiernik, M. C. Massiani, B. Septe, J. Vaissermann and J. C.Daran, J. Mater. Chem., 1997, 7, 753; S. Boulmaaz, R. Papiernik, L. G. Hubert-Pfalzgraf, B. Septe and J. Vaissermann, J. Mater. Chem., 1997, 7, 2053. 10 J. Caruso and M. J. Hampden-Smith, J. Sol-Gel Sci. Technol., 1997, 8, 35; J. Caruso, M. J. Hampden-Smith, A. L. Rheingold and G. Yap, J. Chem. Soc., Chem. Commun., 1995, 157. 11 G. Kickelbick and V. Schubert, Eur. J. Inorg. Chem., 1998, 159. Received 30th April 1998; Communication 8/03266AJ. Chem. Soc., Dalton Trans., 1998, Pages 2285–2287 2287 Scheme 1 Reactions between titanium alkoxides and various carboxylic acids (bold = present work) [Ti6O4(OR)12(O2CR¢)4] [Ti6O4(OR)8(O2CR¢)8] [Ti6O6(OR)6(O2CR¢)6] [Ti3O4(OR)8(O2CR¢)2] [Ti4O2(OR)10(O2CR¢)2] [Ti4O4(OR)4(O2CR¢)4] [Ti9O8(OR)4(O2CR¢)16] Ti(OR)4 Pri, Me7 Et, CH2CH2 Bun, Me8 R, R¢ = Pri, Me5 R, R¢ = R, R¢ = Np, Me5 Pri, Me4 Pri, Np5 Pri, H5 Et, Co3C(CO)9 6 R, R¢ = Et, PhOC6H4 Pri, PhOC6H4 Et, Me Pri, Me R, R¢ = Pri, Co3C(CO)9 5 Ph, Co3C(CO)9 6 But, Pri 9 R, R¢ = Et, Me R, R¢ = Toluene, heat Pri, CMeCH2 11 R, R¢ = has a strong n(Ti]O) absorption band around 740 cm21 in its FT-IR spectrum, whereas more complex spectra are observed for compounds of type 5.Only one sharp 1H NMR signal is observed for the OR ligands in 4 in contrast to three signals for the magnetically non-equivalent alkoxides of [Ti6(m-O)2- (m3-O)2(m-OR)2(OR)6(m-O2CR9)8] clusters of type 5. Scheme 1 summarises the various titanium oxo carboxylato alkoxides known.The temperature plays an important role and is a factor which must be taken into account in the build-up of an already rich series of titanium oxo carboxylato alkoxide species. The recent report of the formation of the [Ti9(m-O)6- (m3-O)2(OPri)4(O2CCMeCH2)16] species obtained by reacting Ti(OPri)4 and excess methacrylic acid illustrates the structural diversity.11 References 1 S. DoeuV, M. Henry, C. Sanchez and J. Livage, J. Non-Cryst. Solids, 1987, 89, 206; L.G. Hubert-Pfalzgraf, New J. Chem., 1987, 11, 663. 2 (a) U. Schubert, E. Arpac, W. Glaubitt, A. Helmerich and C. Chau, Chem. Mater, 1992, 4, 291; (b) L. G. Hubert-Pfalzgraf, A. Abada, J. Vaissermann and J. Roziere, Polyhedron, 1996, 16, 1. 3 M. Green, T. Kramer, M. Parish, J. Fox, R. Lalananham, W. Rhine, S. Barclay, P. Calvert and H. K. Bowen, Adv. Ceram., 1987, 21, 449; R. R. Landham, M. V. Parish, H. K. Bowen and P. D. Calvert, J. Mater. Sci., 1987, 22, 1677. 4 S. DoeuV, Y. Dromzee and C. Sanchez, C.R. Acad. Sci. Ser. II, 1989, 308, 1409. 5 T. J. Boyle, personal communication. 6 X. Lei, M. Shang and T. P. Fehlner, Organometallics, 1996, 15, 3779; Organometallics, 1997, 16, 5289. 7 L. Gautier-Luneau, A. Mosset and J. Galy, Z. Kristallogr., 1987, 180, 83. 8 S. DoeuV, Y. Dromzee, F. Taulelle and C. Sanchez, Inorg. Chem., 1989, 28, 4439. 9 L. G. Hubert-Pfalzgraf, S. Daniele, R. Papiernik, M. C. Massiani, B. Septe, J. Vaissermann and J. C. Daran, J. Mater. Chem., 1997, 7, 753; S. Boulmaaz, R. Papiernik, L. G. Hubert-Pfalzgraf, B. Septe and J. Vaissermann, J. Mater. Chem., 1997, 7, 2053. 10 J. Caruso and M. J. Hampden-Smith, J. Sol-Gel Sci. Technol., 1997, 8, 35; J. Caruso, M. J. Hampden-Smith, A. L. Rheingold and G. Yap, J. Chem. Soc., Chem. Commun., 1995, 157. 11 G. Kickelbick and V. Schubert, Eur. J. Inorg. Chem., 1998, 159. Received 30th April 1998; Communication 8/03266A

ISSN:1477-9226    

DOI:10.1039/a803266a

出版商:RSC    

年代:1998

数据来源: RSC