Abstract
Reaction of WX~6~ (X = Cl or Br) with O(SiMe~3~)~2~ in CH~2~Cl~2~, followed by addition of MeCN and a further equivalent of O(SiMe~3~)~2~ in CH~2~Cl~2~ gives [WO~2~X~2~(MeCN)~2~] in situ, which subsequently react with the dithioethers MeS(CH~2~)~2~SMe, __i__PrS(CH~2~)~2~S__i__Pr or 1,4‐dithiane to afford the first series of W^VI^ thioether complexes, [WO~2~X~2~(dithioether)]. The very moisture‐sensitive yellow complexes have been characterised by microanalysis, IR, ^1^H and ^13^C{^1^H} 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 [WO~2~Cl~2~{__i__PrS(CH~2~)~2~S__i__Pr}]). The strongly polymerised WO~2~X~2~ compounds themselves are not useful synthons for the preparation of the W^VI^ thioether complexes and substitution of the dimethoxyethane ligand in [WO~2~Cl~2~{MeO(CH~2~)~2~OMe}] by dithioethers is also incomplete. Molybdenum(VI) dioxidodichloride thioether complexes of the form [MoO~2~Cl~2~(L)] (L = __i__PrS(CH~2~)~2~S__i__Pr, 1,4‐dithiane, κ^2^‐[15]aneS~2~O~3~, κ^2^‐[14]aneS~4~ and κ^2^‐[12]aneS~4~) ([15]aneS~2~O~3~ = 1,4‐dithia‐7,10,13‐trioxacyclopentadecane, [14]aneS~4~ = 1,4,8,11‐tetrathiacyclotetradecane, [12]aneS~4~ = 1,4,7,10‐tetrathiacyclododecane) and the unusual dinuclear [Mo~2~O~4~Cl~4~{o‐C~6~H~4~(CH~2~SMe)~2~}~2~] are obtained by direct treatment of MoO~2~Cl~2~ with the appropriate ligand. The [Mo~2~O~4~Cl~4~{o‐C~6~H~4~(CH~2~SMe)~2~}~2~] adopts an unexpected metallocyclic structure with cis‐MoCl~2~ units and bridging bidentate dithioether (confirmed crystallographically). The structure of a new polymorph of [WO~2~Cl~2~{MeO(CH~2~)~2~OMe}] is also described.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)