Reactions of confacial bioctahedral ditungsten(III) species: Product distribution in reactions of the μ-hydrido-(bis-μ-dimethylsulfide)bis (trichlorotungstate(III)) ion, and trichlorotungsten(III)(μ-hydrido)bis((μ-dimethylsulfide)(dimethylsulfide)-dichlorotungsten(III) with benzyl bromide and bromide ion

Abstract

Reactions of compound Cl3W(μ-H)(μ-Me2S)2WCl2(Me2S), 1, and salts of derived chloro anion [Cl3W(μ-H)(μ-Me2S)2WCl3]−, 2, with bromide ion and with benzyl bromide are described. 1 was previously shown (1) to exist as a mixture of meso (C2v) and DL-pair (C1) of isomers, with the C2v isomer being the more stable. Displacement of the terminal dimethyl sulfide ligand of 1 by bromide ion results in the formation of the analogous isomers of ion [Cl3W(μ-H)(μ-Me2S)2WCl2Br]−, with retention of stereochemistry. The 1H NMR spectra of compounds in this series are uniquely informative as to the isomers present since the two environments of the methyl groups in the bridging dimethyl sulfide ligands (axial and equatorial) provide a probe for the ion stereochemistry. This is used to show that in reactions of 2 with benzyl bromide, after replacement of μ-H by Br, Br exchanges with terminal chlorides to give a mixture of isomers. Reactions of 1 with benzyl bromide are further complicated by the fact that both terminal dimethyl sulfide and μ-H are replaced by bromides which then redistribute over all possible terminal sites. Keywords: hydride, confacial bioctahedral complexes, tungsten, bromocarbons.