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

Abstract

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)