SYNTHFSIS OF ORGANOTUNGSTEN COMPOUNDS A Thesis submitted by A. I= GALYER, B.Sc., M.Sc., for the Degree of Doctor of Philosophy of the University of London. Royal College of Science, Imperial College of Science and Technology, London, SW7 2AY. July, 1976. 2 ABSTRACT Hexamethyltungsten has been synthesized by the reaction of tungsten hexachloride with trimethylaluminium in iso-pentane, This method replaces the earlier, unsatisfactory route, from tungsten hexachloride in diethylether. The salts, dilithium octamethyltungstate, are described as are the products of the reaction of hexamethyltungsten and trimethylsilylmethyllithium followed by treatment with acid. The improved synthesis has allowed multigram amounts of pure WMe6 to be prepared and a more detailed analysis of some of its physical properties has proved possible. Efforts to synthesize and then alkylate tungsten(IV) phosphine complexes and tungsten(VI) phenoxychlorides are also described. A computer programme for simulating mass spectral multiplets is presented. 3 ACKNOWLEDGEMENTS I would like to express gratitude to Professor G. Wilkinson, F.R.S., for his helpful advice and supervision during this work. Thanks also to the members of the department for all their help. I would also particularly like to thank Dr. D. R. Lloyd of Birmingham University for the photoelectron spectra and Dr. J.A. Connor of Manchester University for the thermochemical measurements. I acknowledge the donors of the Petroleum Research Fund of the American Chemical Society for support. CONTEES Page: ABSTRACT 2 ACKNOWLEDGEMENTS 3 CONTENTS 4 ABBREVIATIONS 6 INTRODUCTION (a) Transition Metal Methyls 7 (b) The Alkylation of Metal Salts with Alkylaluminium Compounds 12 RESULTS 15 (a) Reaction of Tungsten Hexachloride with Methylli thium 15 (b) Reaction of Tungsten Hexachloride with Trimethylaluminium 16 (c) Reaction of Trimethylaluminium with Other Transition Metal Compounds 19 (d) Reactions of Hexamethyltungsten 19 (e) Physical Properties of Hexamethyltungsten 22 (f) Reactions of the Lithium Salts of Octamethyl- and Mixed Methyltrimethylsilylmethyltangstate(VI) 25 (g) Tungsten(VI) phenol Compounds 26 (h) Tungsten(IV) phosphine Chloride Complexes 27 (1) Dimethylzinc and Pentamethyltantalum 28 EXPERIMENTAL 30 (a) Synthesis and Reactions of Hexamethyltungsten 32 (b) Reactions of Dilithiumoctarnethyltungstate 38 (c) Reaction of the Salt from Hexamethyltungsten and Trimethylsilylmethyllithium 39 (d) Reactions of Trialkylaluminium Compounds with Other Transition Metal Salts 41 (e) Preparation and Reactions of Some Tungsten(IV) Chloride Tertiary Phosphine Complexes 45 5 Page: (f) Synthesis and Reactions of cis-Dichloro- tetraphenoxytungsten 48 (g) MoC25 + PhOH 50 (h) WCA6 + 2-t-butylphenol 50 (i) WCA6 + PhSH 51 (j) WC/6 + Catechol 51 (k) WC2 6 + Hexachlorophene 51 (1) WCL6 + 2-isopropylphenol 52 (m) wae6 + 2,2'-biphenol 52 (n) WC26 + 2-allylphenol 52 (o) WCA6 + 2-naphthol 53 (p) Tungsten Hexaphenoxide 54 (q) Synthesis and Reactions of tris(2-methyl- phenoxy)tungsterrcrichloride 56 DISCUSSION 61 APPENDIX - Listing of and Input Information for Program PEAKS for Simulating Isotopic Multiplet Patterns 78 REFERENCES 85 6 ABBREVIATIONS THE - tetrahydrofuran DME - 1,2-dimethoxyethane Me - methyl Et20 - diethylether TMEDA - N,N,NI ,N1 -tetramethylethylenediamfme diphos - 1,2-bis(diphenylphosphino)ethane dipy - 2,21-dipyridyl en - ethylenediamine Et - ethyl Ph - phenyl By - butyl py - pyridine 7 INTRODUCTION (a) Transition Metal Methyls In recent years quite a large number of transition metal n,salts Li MMe or complexes MMe permethyls, as binary alkyls MMe m n n (donor ligand) have been reported: Ti V Cr Mn Fe Co Ni Cu Zr Nb Mo Tc Ru Rh Pd Ag Hf Ta W Re Os Ir Pt Au U The salts are stabilized by coordinated solvent e.g., Li4Mo2Me8.(THF)4 1 or some other donating ligand e.g., Li2UMe6(TMEDA)72 and some have been oiserved only in solution e.g., Li2PtMe6 3. In the complexes, cf the neutral permethyls, the donor ligand is usually a phosphine or aromatic heterocyclic amine. Of the donor-free binary alkyls MMen, only those of the metals Ti, Ta, W, Re and Cu are known and reasonably well characterized. These species vary widely in thermal stability (all ara extremely reactive to o 4 atmospheric oxygen) from TiMe4 which decomposes above - 70 to WMe6 which, when very pure, can be kept at room temperature for 5 and (MnMe2) 6 whilst being thermally short periods. (CuMe)n n more stable, explode when dry at room temperature. These two are polymers and it is unlikely that they have been prepared pure and purity would almost certainly enhance stability. The deep green solutions obtained on treating TiCL3 in THE or DME with ethereal LiMe at - 50° are thought to contain TiMe3 but these decompose above - 20° and isolation of an alkyl has not proved possible 6' 7. Pure TiMe4 (from TiCZ4 and LiMe) decomposes 8 o 0 6 above - 70 but the etherate distills unchanged at 0 . Some of the complexes TiMe4.Lni of which there are many, are stable at room 8 temperature e.g., TiMe4.py2 and TiMe4.Me2PC2H4PMe2 9. The salt LiTiMe5.(dioxane)2 is stable at 0° and is a 1: 1 electrolyte in 10 THE . In ether TiMe4 decomposes to a species (n = 1.7-3.1) TiMe4-n and methane. This lower alkyl decomposes at 200° to titanium 11 carbide . A red etherate of ZrMe4 is obtained from ether-toluene mixtures of ZrCL4 and LiMe. This liquid product distills at - 30° but decomposes above - 15° and nothing is known about its chemistry. A bright yellow salt, Li2ZrMe6, is formed with excess LiMe and is o 12 stable at 0 for several hours . An ethereal solution of NbMe5 (from Me2NbC/3 and three equivalents of LiMe) decomposes at - 50° but addition of Me2PC2H4PMe2 precipitates NbMe5.L which is stable at room temperature. With excess LiMe a solution probably containing Li2NbMe7, is obtained, and is stable at 0° for a few hours. Analogous reactions with Me3TaCL2 produce much more stable species and it is possible to isolate pure volatile solid TaMe5 which also forms a more stable Me2PC2H4PMe2 adduct. The solution obtained from excess LiMe and Me3TaC/2 is o o 13 stable to at least 35 whereas TaMe5 decomposes rapidly above 0 Reaction of CrC22 with 4 molar equivalents of LiMe in ether yields the chromium(II) salt [Li2CrMe4.(Et20)2 ]2 which decomposes at 128-135° under argon 14. The crystal structure of the Try' 15 analogue: [Li2CrMe4.(THF)2 I has been published . There is a brief report on the reaction of CrMe3 with diphenylacetylene to give 1,2,3,4-tetraphenylcyclopentadiene but no details of the synthesis 16 or other properties of this alkyl are given . Similarly brief notes reporting the syntheses of CrMe3 and CrMe2 from LiMe in THE 6 and CrCL3 and CrC/2 respectively have never been substantiated . An 9 orange Cr(III) salt; Li3CrMe6, is formed from CrC/3 and 6 molar equivalents of LiMe in ether, addition of dioxane precipitates a blood-red dioxanate 14. The Cr(IV) binary alkyl is prepared by 17 reaction of LiMe and (t-Bu0)4 Cr in petrol and the maroon volatile oily product decomposes at - 600 18 • MoC/3.3THF or Mo2(000CH3)4 react with excess LiMe in THE or ether respectively to give the extremely reactive pyrophoric salts 1, 19 of Mo(II),Li4[M02Mes](solvent)4 . The deep red compound is stable to 25° (etherate) or 100° (tetrahydrofuranate) and the 1 crystal structure of the latter has been determined . The synthesis and some reactions of WMe6 (from WC/6 and LiMe) have been 20 published . (MnMe2)n is a bright yellow explosive polymer prepared from MnI2 and LiMe in ether. The products always contain ca. 10% I which is apparently impossible to remove. The salt LiMnMe3 is prepared o 6 21 from MnMe2 and LiMe and is stable to ca. 100 and not explosive ' The red salt Li2MnMe4.(TMEDA)2 is prepared from MnCi2 and LiMe in ether followed by TMEDA 2, the compound decomposes at 150°. Reaction of Re0C/3.(PP113)2 with LiMe in ether produces volatile magneta Re0Me4 22. This very stable alkyl reacts with A/Me3 to give ReMe6, a volatile green crystalline solid which is stable at 25° for short periods, and with NO to produce yellow crystalline cis-Re02Me3, a Re(VII) alkyl `-. Ei2FeMe4, prepared from FeC/3 and LiMe in ether, forms a dark-red etherate and a light-yellow dioxanate, both of which o decompose above 0 and are of uncertain composition 24. Me2Fe(PPh3)3 is prepared from Fe(acac)3 , PPh3 and Me 3A/ 25 and Me2Fe(diphos)2 similarly except that Me2A2OEt is used 26. The latter compound forms orange crystals that are stable to 130° and on 10 thermal decomposition CH4, C2116 and C2M4 are formed (mole ratio 75 : 20 : 5) and a carbenoid intermediate in this process is 26 postulated . Brief notes on the synthesis of Me2Ru(PPh3)4 , from the corresponding dichloride and Me3AL, have been published 27. Co(acac)3 reacts with R2A/0Et (R = Me, Et), in the presence of a donor ligand, to yield Et20o(dipy)2 28 or MeCo(PPh3)3 29, the former decomposing at 50° to give ethane and ethylene (2: 1). Li2CoMe4.(TMEDA)2 is prepared from CoC/2 and LiMe as a blue solid unstable at room temperature 2. MeRh(Pa3)3 is prepared from the 31 corresponding chloride 30 or bromide and methyl-Grignard reagent in ether. The complex melts at 120° with decomposition. A note reporting the synthesis of this alkyl from the chloride and Me3k/ has appeared 27 MeIr(PPh3)3 , from the chloride and LiMe, forms red crystals, stable in ethereal solution at 0° for a few hours, but in the solid state ortho-metallating very rapidly at much lower temperatures 32. Trimethylaluminium and nickel(II) salts form reaction mixtures which decompose above - 100° depositing metallic nickel 33.