Syntheses and Properties of Dinuclear Group 6 Metal Complexes with the Zwitterionic Sulfur Donor Ligand Bis(N,N-diethylamino)carbeniumdithiocarboxylate

Abstract

A class of dinuclear group 6 metal complexes [{M0(CO)5}2(μ-S,S′-EtL)] (M = Cr, Mo, W) with the asymmetrically bridged zwitterionic sulfur donor bis(N,N-diethylamino)carbeniumdithiocarboxylate (EtL) was prepared by photoreaction of [M0(CO)6] with EtL in hexane–CH2Cl2 for Cr and Mo or THF for W. The same structure in a syn–anti coordination mode was revealed by X-ray analyses for chromium(0) and tungsten(0) complexes, 1 and 3, respectively, and speculated from various analytical data for the molybdenum(0) complex 2. The pertinent criteria for the coordination mode are found to be the wavenumber of the asymmetric stretching vibration of the −CS2 moiety in the solid state and the ligand-based reduction potential in solution. Complexes 1 and 3 showed quasi-reversible reduction waves, which are assigned to a two-step, one-electron reduction process derived from the bridging EtL. In a series of [Cr(CO)5L] complexes (L = monodentate ligand), the 13C NMR chemical shifts of the trans-to-L carbonyl group showed the ...