7 The Halogens and Noble Gases By D.A. ARMITAGE Department of Chemistry King's College London Strand London WC2R ZLS UK 1 Introduction This chapter covers the 1992 literature and roughly follows last year's format. 2 Fluorine The syntheses of ClF, KrF, Xe, and XeF are reported in Inorganic Syntheses.' Calculations support short N . * . halogen interaction distances in the ammonia complexes with F, Cl, and CIF with that for ClF being the shortest (230pm). The increased demand for electrophilic fluorinating agents has led to the synthesis of a series of N-fluoro quaternary salts of quinuclidine 1,4-diazabicyclo[2.2.2)octane and the latter's monoquaternary salt. The fluoroammonium salts are stable high melting solids which readily fluorinate the enol diacetates of testosterone and androsterone 1-morpholinocyclohex-1 -ene acetanilide PhC(Na)(Et), and PhMgBr in very good yield.3 Monofluorination of RLi and RMgX (R = Bun Bus Ph) can be readily achieved at -60 "C in di-n-butyl ether using F, giving RF.Ru'MgCl is ~nreactive.~ A quantitative scale for oxidative fluorination based on the relative F+ detachment energies has been obtained from local density functional calculations based on KrFt as zero.' The data for 36 XF' agents closely supports qualitative data and considers the number of fluorine atoms oxidation state and electronegativity of the central atom together with the number of lone pairs and the geometry of the central atom. Calculations reveal a number of unexpected results and suggest a decrease in the oxidative strength with a decrease in the number of lone pairs making XeF a better oxidizing agent than XeF perhaps surprisingly.BuiP'HF and Bu",+H,F; are both useful reagents in the nucleophilic fluorina- tion of chloro and bromo substituted nitrobenzenes while BLI",+H,F with NBS fluorinates methyldithiocarbamates Ar(PhCH,)NC(S)SMe in very good yields to give the trifluoromethylamines Ar( PhCH,)NCF3.6 Just as crown ethers act as alkali metal cation traps so do coordinated fluorides. Reacting [Cp*TiF3] with NaF in MeCN in 'Inorganic Syntheses'. ed. R. N. Grimes Wiley-Interscience New York 1992 Vol. 29. 1. Roeggen and T. Dahl J. Am. Chem. Soc.. 1992. 114 511. R. E. Banks S. N. Mohialdin-Khaffaf G. S. IA I. Sharif and R. G. Syvret J. Chem. Soc.. Chem.Commun. 1992 595. J. DeYoung H. Kawa and R. J. Lagow J. Chem. Soc.. Chem. Comrnun.. 1992. 81 1. K.O. Christe and D.A. Dixon J. Am. Chein. Soc.. 1992 114 2978. ' Y. Uchibori. M. Umeno H. Seto. Z. Qian and H. Yoshioka Synletr 1992 345; M. Kuroboshi and T. Hiyama Tetrahedron Left.. 1992. 33. 4177. 85 D. A. Armitaye the presence of Ph,P+CI- gives the complex (Ph,P)+[(Cp*,Ti,F,),Na+] -in which Na' is sandwiched between two layers of fluorine atoms in an eight coordinate environment with Na .*. F contacts from 238-253 pm.' 3 Polyhalogen Cations and Anions The Raman spectra of CliSbF; supports a bent C,, structure for the cation while analysis of the structure of Brl supports a skew configuration of the terminal bromine atoms on an almost linear Br central unit.This is some 5-6 kJ mol- 'more stable than the planar trans C,,form found in crystals of Brl MF (M =As,Sb).* The structure of S,I,(MF,) shows the S21i+cation to have an open-book structure with an S unit as the spine and two I units lying parallel to this. The S-S and 1-1 bond lengths are about 180 and 260 pm respectively and support multiple bonding within these units. The diatomic units are held together through four-centre interactions of their n* orbitals. The S-I bonds are about 300 pm indicating a bond order of only 0.1 comparable in length to those in charge transfer complexe~.~ 1,3-Diiodobicyclo[ 1.1.llpentane reacts with pyridine to give the ionic derivative [C5H5NC5H,13C,H4NC5H,]+I; (1 ) with linear cations and anions and the shortest 'non-bonded' C-C interactions (180pm) recorded to date for any organic com- pound." A resonance structure involving such a bond is invoked.The 1 ion (2) isolated as its Ph4P+ salt is polymeric with interconnected 1 units of appropriate C, symmetry with 1-1 distances in the two ranges of 305-329 pm and 273-281 pm and the I anion unit interacting with two I units at both ends." 4 Fluorosulfonium Derivatives XeF+(MF;) (M =As,Sb) will fluorinate (C,F,),S in HF to give deep violet crystals of (C,F,),SF+SbF; which slowly decompose after 24 h at room temperature. A structure determination shows the S-F bond to be short.' Perfluoro sulfur(1v) compounds also result from XeF'MF; with fluorination by F+ occurring for (CF,),SF,- to give (CF,),SF:-,.(CF,)FS=O behaves similarly to give (CF,)- S(O)FT whereas (CF,),SO forms13 the Xe complex (CF,),SOXeF+. 'H. W. Roesky M. Sotoodeh and M. Noltemeyer Angew. Chem. Inr. Ed. Engl.. 1992 31. 864. R. Minkwitz. J. Nowicki H. Hartner. and W. Sawodny Specrrochimicu Acta .4 1991 47. 1673 K.O. Christe D.A. Dixon and R. Minkwitz. Z. Anory. Ally. Chem. 1992 612 51. M. P. Murchie J. P. Johnson. J. Passmore G. W. Sutherland M. Tajik T. K.Whidden P. S. White and F. Grein Inorg. Chem. 1992. 31 273. J.L. Adcock A.A. Gakh J. L. Pollitte and C. Woods J. Am. Chem. Soc,.. 1992 114 3980. " R. Poli J.C. Gordon. R. K. Khanna and P.E. Fanwick Inorg. Chem. 1992 31. 3165. R. Minkwitz G. Nowicki and H. Preut. Z. Anory. Allg. Chem.. 1992 611. 23. l3 R. Minkwitz and W. Molsbeck Z.Anory. AIIg. Chem. 1992. 612 35. The Halogens atid Noble Gases 87 5 Rare Gas Compounds The high sensitivity of the chemical shift of 129Xe NMR to the local electronic environment has been used to show that if Xe is co-adsorbed with CCl in NaY zeolite at 144K then the CCI absorbed with xenon in the formed supercage suppresses the gas-liquid transition of Xe. Also the gas-liquid transition of Xe in super cages without CCl influences distribution of CC1 in the ze01ite.I~ Interest in the isolation of alkynyl iodonium salts (section 7) has led to the synthesis of analogous isoelectronic Xe(I1) derivatives that have been characterized at low temperature by reacting Bu'C=CI,i or RCGCSiMe with XeF,/BF to give the tetrafluoroborate salts (equation 1).They react with Ph,P to give phosphonium salts and release of Xe.' R-CZEC-SiMe + BF;OEt + XeF + R-CECXe'BF; + Me,SiF (1 1 XeF will cleave the B-0 bonds of B(OR) to give FXeOR (R = SO,CF and SO,C,F,) and Xe(OR) (R = COCF and COC,F,) while 1-chloro-2-fluorocyclo-hexanes result" from cyclohexene with alkyl hypochlorites and XeF,. Krypton difluoride fluorinates OsO to give cis-OsF,O, and not OsF,O as previously reported." The mean amplitude of vibrations of planar XeF; confirms that lone pairs exert repulsion thus forcing bond lengthening.' 6 Organofluorine Compounds Interest in the use of tertiary perfluoroalkyl amines as blood substitutes has led to structural studies; the electronegative perfluoroalkyl group results in an increase in C-C and C-N bond lengths and a widening of the angles at nitrogen.Fluorination of Me,N widens the CNC angle from 110.9 to 117.9' and in (C,F,),N to 119.3 ". Despite an increase in the C-N bond length from 142.6 to 148.2 pm contacts between non-geminal fluorine atoms are up to 36 pm less than the van der Waal's interaction distance. While complexes containing the I~-C,X ligand (X = C1,BrJ) have been known for some time the pentafluorocyclopentadienyl complex has only recently been de- scribed.20 Reacting [Cp*Ru(MeCN),] +CI with C,F,OTI gives the q5-oxopenta- Auorocyclohexadienyl complex which decarbonylates on flash vacuum pyrolysis at 750 "C to give the pentafluorocyclopentadienyl derivative in 20% yield. The I9FNMR absorption is only four ppm upfield from C,F; while the mass spectrum shows a prominent peak for RuC,Fl.The vibrational spectra of the trihalocyclopropenium ions C,Xi (X = Cl,Br,I) show symmetric C-X stretching vibrations2' at 458,269 and 180 cm- and ring breathing modes at 1790 1732 and 1650 cm ~ Elimination of Me,C from [(BU; P),CH,]PtH(CH,Bu') at room temperature gives l4 T.T. P. Cheung J. Phys. Cheni. 1992 96 5505. If V. V. Zhdankin P. J. Stang and N. S. Zefirov. J. Chem. Soc.. Chem. Commun.. 1992 578. 16 B. Cremer-Lober H. Butler D. Naumann and W. Tyrra Z. Anorg. Allg. Chem.. 1992 607 34; D.F. Shellhamer M. J. Horney A. L. Toth. and V. L. Heasley Tetrahedron Lert.. 1992. 33 6903. '' K.O. Christe and R. Bougon J. Chem. Soc. Chem. Commun. 1992 1056. '* E. J. Baran J. Mol. Struct.1992 271 327. 19 M. Gaensslen U. Gross H. Oberhammer and S. Rudiger Angew. Chem.. Int. Ed. EnqI. 1992 31 1467. 0. J. Curnow and R. P. Hughes. J. Am. Chem. Soc. 1992. 114 5895. M. J. Taylor P. N. Gates and P. M. Smith. Spectrochini. Acta A 1992. 48. 205. 88 D. A. Arrnituge the 14-electron Pto fragment that readily” inserts into the C-E’ bond of C6F6 while successive photolytic displacement of C2H4 from qS-R,C51r(C,H,) (R = Me,H) by C6F6 gives both q2-and q4-C6F complexes,23 with the fluorine atoms of the q2-complex bent away from the metal. The pentafluorophenyl group will stabilize the acetylide bridged complexes dppePt(pC-CPh),Pt(C,F,) and (Ph3PMe+)2(C6F,),Pt(p-C=CPh)2Pt(C,F,);- and the neutral gold cluster (C6Fs)4Au,o(PPh,)6.24 (Trifluoroethy1idyne)sulfurtrifluoride F,CC-SF occurs as two solid phases with CCS angles of 171.4 “ and 162.9 @.The small bending force constant is explained in terms of a low-lying excited carbene state. Rapid dimerization to the truns-alkene occurs and further carbene insertion into one C -S bond occurs more slowly to give the trimer (3) (equation 2).,’ (31 Odourless trifluoromethyl alkyl tellurides CF,TeR (R = Bu’ or CH,Ph) result from (CF,),Te and R,Te and provide for vapour phase deposition of tellurium alloys.26 (CF,),Te is formed from (CF,),TeCl and (CF,),Cd. It adds fluoride and is thought to be oxidized by XeF to (CF,),TeF,. The oligomers (R,),Te (R = C2F5 C3F7 and C,F,) are more stable and result,’ from TeCl and (R,),Cd. 7 Iodoniurn Derivatives The synthesis and use of alkynyl(pheny1)iodonium salts in organic synthesis has been reviewed.28 The diyne triflates PhIC-C(p-C6H4),C~CIPh.20Tf and PhIC-C(CH2),C=C1Ph.2OTf result from the stannyl diyne and PhICN+OTf- and react with Ph,P to give the bisphosphonium salts.29 Phenyl(2,2-dimethyl-4-(diethyl-phosphono)-2,5-dihydro-3-furyl)iodonium salts result from the allene (4) and PhIO/BF (equation 3).The perchlorate crystallizes as a dimer3* with a P=O -+ I interaction of 283.4pm and an angle at I of 99.2”. c=c=c/ PhIOF3B.OEt2 <OMe \ NaX (31 (Et0)2P+ ..IPh X-0’ (4) ” P. Hofmann and G. Unfried Chem. Ber.. 1992. 125 659. 23 T.W. Bell M. Helliwell M.G. Partridge and R.N. Perutz Oryanometallics 1992 11. 1911. 24 A. Laguna M.Laguna M. C. Gimeno and P. G. Jones Organometallics 1992. 11.2759; J. Fornies. M. A. Gomez-Saso E. Lalinde F. Martinez and M.T. Moreno. ihid. 1992 11. 2873. 25 J. Buschmann R. Damerius R. Gerhardt D. Lentz. P. Luger. R. Marschall. D. Preugschat K. Seppelt. and A. Simon J. Am. Chem. Soc. 1992 114 9465. 2h D. C. Gordon R. U. Kirss and D. W. Brown Organometallics. 1992 11 2947. ” D. Naumann. H. Butler J. Fischer J. Hanke J. Mogias and B. Wilkes,Z. Anory. Ally. Chem.. 1992,608.69. ’’ P.J. Stang Anyew. Chem. Int. Ed. Engl. 1992 31 274. 29 P. J. Stang R. Tykwinski. and V.V. Zhdankin J. Ory. Chem. 1992 57. 1861. 30 N.S. Zefirov A. S. Koz’min T. Kazumov. K. A. Potekhin V. D. Sorokin V. K. Brel E.V. Abramkin Yu.T. Struchkov V. V. Zhdankin and P. J. Stang J.Org. Chrm. 1992. 57. 2433. The Halogens and Noble Gases Bicycloalkenyldiiodonium salts result from cyclopentadiene and PhICKCIPh' + and react with nucleophiles to give a range of substitution products (Equation 4) while with Ph,P the diiodide result^.^' +IPh x PhIO and triflic acid react with arenes to give mixed diaryliodonium triflates of use in organic synthesis., The salts Ar,I+I-and Ar,I+Cl- (Ar = 4-halophenyl) react with PhTeNa or Na,Te to give the appropriate diary1 telluride.33 Electronic factors determine the regioselectivity of radical reactions of Ar21 and aryl(rn-carboranyl- + 9-y1)iodonium cations and proceed via [C,B ,H -I-Ar]. radical intermediates. However steric factors provide the major influence in the polar reactions and readily explain the ~rtho-effect.~~ Although difluoroiodo compounds have been used as synthetic intermediates none has been isolated to date.However treating 4-iodotricyclene with excess XeF in CCl gives the difluoroiodo derivative RIF (equation 5) as a pale yellow waxy solid that is stable in air for a few hours and indefinitely in solution under an inert atmosphere. No spectroscopic evidence was found to support the presence of any tetrafl~oride.,~ The first known binary nitrogen-iodine cation 12N3+(isolated as its SbF salt) results from iodoazide and iodine in SbF, or from fresh silver azide and I SbF,. This azidoiodoiodine cation is explosive even below -20 "C and the Raman spectrum supports an 1-1 bond slightly weaker than that in I, and an N-I bond slightly stronger than in IN,.The suggested structure involves a non-linear chain with approximate tetrahedral angles at the N-I bond. Slow decomp~sition~~ gives I;+(SbF;) and N,. 8 Oxygen Derivatives Dehydrating HIO or H510 with first conc. H,PO at above 300 "C,then with conc. H,SO at room temperature gives (IO,),HSO, which contains37 iodine in mixed oxidation states in the cation (5) two-thirds is iodine (111) as square planar 10 units and one-third is trigonal pyramidal iodine (v). A range of transition metal periodates 31 P.J. Stang. A. Schwarz T. Blume and V.V. Zhdankin. Tetrahedron Lett. 1992 33 6759. " T. Kitamura J.4. Matsuyuki K. Nagata. R. Furuki and H. Taniguchi. Synrhesis. 1992. 945. 33 J. You and Z. Chen Synthesis 1992 633; Synth.Commun. 1992 22 1441. 34 V. V. Grushin I. I. Demkina and T. P. Tolstaya J. Chem. Soc. Perkin Trans. 2 1992 505. 35 G. W. Bradley J. H. Holloway H. J. Koh. D.G. Morris. and P.G. Watson J. Chem. Soc. Perkin Trans. I 1992 3001. 36 I. C. Tornieporth-Oetting P. Buzek P. von Rague Schleyer and T. M. Klapotke Angew. Chem.. Int. Ed. Engl. 1992 31 1338. '' A. Rehr and M. Jansen. Z. Anorg. AIIg. Chem. 1992 608. 159. D.A. Armitage have proved useful oxidants for alcohols aldehydes and benzyl halides including the gold derivative Na,KAu[IO,(OH)],~KOH~l 5H20 which shows square planar Au with two IO,(OH),-ligands bidentate.38 (5) 0= Iodine 0=Oxygen (Reproduced by permission from Z. Anory. Ally. Chern. 1992 608 159) PhI(OTf) and PhI(OCOCF,) will couple alkyllithium reagents RLi to give R-R (R = Bun BuSec Bu').PhI(OTf) undergoes electrophilic addition to alkynes to give (E)-~-[trifluoromethanesulfonyloxy)vinyl]iodonium triflates in good yield.39 Imperfect mixing on bistability in the BrOS -Celt'-Br -continuous-flow stirred tank reactor results in a broadening of the bistable region particularly at higher flow rates. This is thought to be due to effective initial segregation of the entering bromide from the bulk of the reacting mixture in packets dispersed uniformly throughout the reactor.40 The 1 1 and 7 :5 reactions of bromate with thiocyanate are indicated (equations 6 and 7). BrO + SCN-+ H,O -* HSO + HCN + Br-(61 7Br0 + SSCN-+ 2H+ +SBrCN + Br + 5SO:-+ H,O (7) The reaction of bromate with thiocyanate gives HSO, HCN and Br- with thiocyanate in excess but Br' Br, and SO:-with bromate in excess.41 The reaction occurs in three stages with the first involving consumption of thiocyanate the second consumption of cyanide and the third bromine accumulation.The kinetics of the reaction of iodine and triiodide with thiosulfate suggests the intermediacy of the I,S,Oi- adduct which though thermodynamically stable is kinetically reactive and dissociates to give IS,O;. The structures suggested involve I-S and not 1-0 bonding., 3R A. C. Dengel A.M. El-Hendawy. W. P. Griffith. S. I. Mostafa and D. J. Williams J. Chem. Soc. Dalton Truns.. 1992 3489. D. H. R. Barton J. Cs. Jaszberenyi K. Lessmann and T. Timar Terrahedron. 1992.48,8881:T.Kitamura R. Furuki H. Taniguchi and P. J. Stang ibid. 1992 48 7149. 4" L. Gyorgyi and R. J. Field J. Fhys. Chem. 1992 96 1220. 4' Y.-X. Zhang and R. J. Field J. Phps. Chem. 1992 96 1224. 42 W. M. Scheper and D. W. Margerum. Inorq. Chem. 1992 31. 5466. The Halogens and Noble Gases 9 Halide Traps Condensing HgBr with sodium cyclohexanethiolate followed by recrystallization from pyridine gives the complex Hg,(SC6Hl l)12Br in which six Hg atoms surround one bromide in a distorted ~ctahedron.~~ The carbollide mercury halide trap (HgC2B,oHlo)4 shows fluxional behaviour in solution but adds two iodide ions stepwise with consequent 199Hg NMR resonance ~harpening.~~ The structure of the Ph4As+ derivative shows the four mercury atoms in a plane with the two iodine atoms one above and one below both equidistant from one pair of Hg atoms (330.4and 330.6pm) but not the other pair (327.7and 389 10 Weak Interactions The crystal structure of cyanuric chloride (NCCl) shows .n-stacked layers with in-plane intermolecular interactions being short and approximately linear with six close contacts for each ring at 310.0and 31 1.3 pm.N . . . C1 contacts are not observed so extensively in other rings (for example 2,4,6-trichlor0-1,3,5-tricyanobenzene).~~ The structure of the aniline/dicyclohexylgallium bromide complex shows intramolecular hydrogen bonding with bromine (H . . . Br 248pm). This hydrogen bonding distorts the tetrahedral coordination at gallium and provides the first example of such in main group corn pound^.^^ 43 T.Alsina W. Clegg K.A. Fraser and J. Sola J. Chem. Soc.. Cheni. Comniun. 1992 1010. 44 X. Yang S. E. Johnson S. I. Khan. and M. F. Hawthorne Angew. Chem. Int. Ed. Engl.. 1992 31. 893. 4s X. Yang C. B. Knobler and M. F. Hawthorne J. Am. Cheni. Soc.. 1992. 114. 380.