Tungsten(VI) and Molybdenum(VI) Complexes with Soft Thioether Ligand Coordination - Synthesis, Spectroscopic and Structural Studies

Reaction of WX6 (X = Cl or Br) with O(SiMe3)2 in CH2Cl2, followed by addition of MeCN and a further equivalent of O(SiMe3)2 in CH2Cl2 gives [WO2X2(MeCN)2] in situ, which subsequently react with the dithioethers MeS(CH2)2SMe, iPrS(CH2)2SiPr or 1,4‐dithiane to afford the first series of WVI thioether complexes, [WO2X2(dithioether)]. The very moisture‐sensitive yellow complexes have been characterised by microanalysis, IR, 1H and 13C{1H} NMR spectroscopy, which indicate cis‐dioxido and trans‐dihalide arrangements in the monomers with two thioether donor atoms completing the very distorted octahedral geometry (confirmed by a crystal structure of [WO2Cl2{iPrS(CH2)2SiPr}]). The strongly polymerised WO2X2 compounds themselves are not useful synthons for the preparation of the WVI thioether complexes and substitution of the dimethoxyethane ligand in [WO2Cl2{MeO(CH2)2OMe}] by dithioethers is also incomplete. Molybdenum(VI) dioxidodichloride thioether complexes of the form [MoO2Cl2(L)] (L = iPrS(CH2)2SiPr, 1,4‐dithiane, κ2‐[15]aneS2O3, κ2‐[14]aneS4 and κ2‐[12]aneS4) ([15]aneS2O3 = 1,4‐dithia‐7,10,13‐trioxacyclopentadecane, [14]aneS4 = 1,4,8,11‐tetrathiacyclotetradecane, [12]aneS4 = 1,4,7,10‐tetrathiacyclododecane) and the unusual dinuclear [Mo2O4Cl4{o‐C6H4(CH2SMe)2}2] are obtained by direct treatment of MoO2Cl2 with the appropriate ligand. The [Mo2O4Cl4{o‐C6H4(CH2SMe)2}2] adopts an unexpected metallocyclic structure with cis‐MoCl2 units and bridging bidentate dithioether (confirmed crystallographically). The structure of a new polymorph of [WO2Cl2{MeO(CH2)2OMe}] is also described.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)