Reactions of the dirhodium cation Rh24+, with triphenylphosphine and alkali metal carboxylates, dithiocarbamates and other anions

Abstract

Rhodium(I) carboxylates of stoicheiometry Rh(OCOR)(PPh₃)₃, (where R = alkyl, aryl, or substituted alkyl), have been obtained by the interaction of the dirhodium(II) cation, Rh₂⁴⁺, with a stoicheiometric amount of triphenyl-phosphine and an excess of the lithium salt of the appropriate carboxylic acid. The chemical properties of these carboxylates are described, and include reactions with hydrogen, oxygen, carbon monoxide and aldehydes. In benzene solution the Rh^I carboxylates catalyse the homogeneous hydrogenation of alkenes and alkynes; the rates are compared with those using chlorotris(triphenylphosphine)rhodium(I). The interaction of Rh₂⁴⁺ with triphenylphosphine in presence of sodium diethyldithiocarbamate, mercaptobenzthiazole, pyridine-2-thiol, toluene-3-thiol, diphenylphosphorodithioic acid, diethoxyphosphorodithioic acid and lithium thiocyanate have been studied, and also the interaction of chlorotris(triphenylphosphine)rhodium(I) with tin(II) chloride.