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

The electrochemical and Mo-95 NMR behaviour of triply-bridged oxomolybdenum (V) dinuclear complexes with a series of dithiocarbamate ligands [Mo2O3(OC2 H4S)(RR'dtc)(2)] (RR'dtc(-) = dithiocarbamate) has been investigated. [Mo2O 3(OC2H4S)(RR'dtc)(2)] undergoes two successive one-electron reductions in d ichloromethane, acetonitrile, dimethylsulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. The first reduction of [Mo2O3(OC2H4S)(RR'dtc)(2)] i s a quasi-reversible one-electron reduction followed by a homogeneous chemi cal reaction. The formal potentials of the first reduction of these complex es correlate well with the Values of sigma* of the substituents on the dith iocarbamate ligands except for [Mo2O3(OC2H4S)(Ph(2)dtc)(2)] (sigma* denotes Taft's polar substituent constant) and become more positive with increase in acceptor number of the solvents. The chemical shifts of Mo-95 NMR of the complexes varied from delta = 329 (RR' = Me-2) to delta = 354 (RR' = i-Pr- 2) depending on the nature of the dithiocarbamate ligands. The linewidth of the NMR signal apparently increases with increase in steric bulkiness of t he alkyl groups on the dithiocarbamate ligands. The X-ray crystal structure of [Mo2O3(OC2H4S)(i-Bu(2)dtc)(2)] is also reported. (C) 1999 Elsevier Scie nce S.A. All rights reserved.