Electrochemical and 95Mo NMR studies of triply-bridged dinuclear oxomolybdenum(V) complexes with various dithiocarbamates

Abstract

The electrochemical and 95Mo NMR behaviour of triply-bridged oxomolybdenum(V) dinuclear complexes with a series of dithiocarbamate ligands [Mo2O3(OC2H4S)(RR′dtc)2] (RR′dtc−=dithiocarbamate) has been investigated. [Mo2O3(OC2H4S)(RR′dtc)2] undergoes two successive one-electron reductions in dichloromethane, acetonitrile, dimethylsulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. The first reduction of [Mo2O3(OC2H4S)(RR′dtc)2] is a quasi-reversible one-electron reduction followed by a homogeneous chemical reaction. The formal potentials of the first reduction of these complexes correlate well with the values of σ* of the substituents on the dithiocarbamate ligands except for [Mo2O3(OC2H4S)(Ph2dtc)2] (σ* denotes Taft’s polar substituent constant) and become more positive with increase in acceptor number of the solvents. The chemical shifts of 95Mo NMR of the complexes varied from δ=329 (RR′=Me2) to δ=354 (RR′=i-Pr2) depending on the nature of the dithiocarbamate ligands. The linewidth of the NMR signal apparently increases with increase in steric bulkiness of the alkyl groups on the dithiocarbamate ligands. The X-ray crystal structure of [Mo2O3(OC2H4S)(i-Bu2dtc)2] is also reported.