Preparation and some properties of (CoIIorIII{RhIII (aet or L-cys-N,S)3}2)-type S-bridged trinuclear complexes.

The reactions of fac-[Rh(aet)3] (aet=2-aminoethanethiolate) or ΔLLL-fac-[Rh(L-cys-N,S)3]3− (L-cys=L-cysteinate) with [CoCl(NH3)5]2+ produced [CoIII{RhIII(aet or L-cys-N,S)3}2]3+or3−, while the reactions with Co2+ formed [CoII{RhIII(aet or L-cys-N,S)3}2]2+or4− which were oxidized to give [CoIII{RhIII (aet or L-cys-N,S)3}2]3+or3−. These complexes were optically resolved or separated by fractional crystallization or column chromatography, and characterized from their absorption, CD and 13C NMR spectra. The reactions of fac-ΔLLL-[Rh(L-cys-N,S)3]3− with [CoCl(NH3)5]2+ or Co2+ at room temperature proceeded with retention of the starting ΔLLL configuration to give the ΔLLLΔLLL isomer, while the reaction with Co2+ at high temperature (ca. 95 °C) was accompanied by inversion to form the ΔLLLΛLLL, ΛLLLΛLLL, and ΔLLLΔLLL isomers. Cyclic voltammetric measurements of [CoIII {RhIII(aet or L-cys-N,S)3}2]3+or3− in water showed a quasi-reversible redox couple corresponding to the central Co(III)/(II) at ca. −0.3 V vs. Ag/...