Studies of confacial bioctahedral tungsten complexes containing metal-to-metal bonds: synthesis, reactions, and nuclear magnetic resonance studies of W2Cl4(μ-SR)2(μ-S)L2 (R = alkyl; L = monodentate ligand)

Abstract

A series of new binuclear tungsten(IV) complexes, W2Cl4(μ-SR)2(μ-S)L2 (R = Me, Et, iBu, CH2Ph; L = Me2S or THT), is readily synthesized from the metathetical reaction of WCl4L2 with 1 mol-equiv. of alkylthiotrimethylsilane (Me3Si(SR)). These complexes react with stronger nucleophiles (Ph3P, MeCN, C5H5N, Cl−) under ambient conditions to yield simple disubstituted products. Reaction of W2Cl4(μ-SEt)2(μ-S)(SMe2)2 with PhCH2X (X = Cl, Br) yields [Me2SCH2Ph]2[W2Cl4(μ-SEt)2(μ-S)X2], whilst with stronger alkylating agents, MeSO3F or Et3OBF4, intractable residues result.The series of homologous complexes has been studied by 1H and 13C nmr spectroscopy. When R = Me, two stable configurational isomers are present in solution, whilst only a single isomer exists for more bulky R groups. Trends in the 1H nmr chemical shifts of the methylene and methyl protons of the SEt groups in the complexes W2Cl4(μ-SEt)2(μ-S)L2 allow absolute assignment of the resonances to two magnetically inequivalent thiolato groups.