Synthesis, Characterization, and Isomerization of trans- and cis- + and Related Complexes

Article abstract of DOI:10.1246/bcsj.60.575

A number of new diphosphine complexes of cobalt(III), trans- and cis-⁺, trans- and cis-⁺, trans- and cis-²⁺, trans-⁺, and ⁺ have been prepared and characterized, where dmpe, dmpp, dbpe, and dpee denote 1,2-bis(dimethylphosphino)ethane, 1,3-bis(dimethylphosphino)propane, 1,2-bis(dibutylphosphino)ethane, and cis-1,2-bis(diphenylphosphino)ethylene, respectively.The trans isomers of the dihalogeno complexes are stable to aquation, while the cis isomers release one of the halide ions in water fairly rapidly to yield cis-⁺ which isomerizes to the trans isomer on exposure of ultraviolet light.The cis-⁺ complexes in methanol or ethanol solution isomerize to the trans isomer, and the rates were followed spectrophotometrically in the temperature range of 39.0-65.0 deg C.The rates have a first-order dependence on the complex concentration.Both the ΔH^<*> and ΔS^<*> values for the isomerization increase in the order diphosphine=dmpe