The reaction of [{Rh(µ-Cl)(CO)2}2] with PPh2H in benzene affords the mononuclear complex [RhCl(CO)(PPh2H)2] for a molar ratio of 1 : 4 and the trinuclear derivative [Rh3(µ-PPh2)3(µ-Cl)2(µ-CO)(CO)3], for a molar ratio of 1 : 2. The structure of the trinuclear derivative has been determined by X-ray crystallography. It crystallises in the monoclinic space group P21/n, with a= 12.461(5), b= 32.867(5), c= 11.149(5)A, β= 99.29(1)°, Z= 4, and R= 0.085. The metal atoms adopt a triangular configuration with each edge of the triangle being bridged by a diphenylphosphido-group as well as by either a chloro or a carbonyl group. In spite of this compound being a 50-electron system, all of the Rh–Rh distances correspond with those normally associated with a formal rhodium–rhodium bond. The chloro-groups in this compound can be extracted as radicals by the addition of NEt2H, affording, in the presence of CO, [Rh3(µ-PPh2)3(CO)5], or displaced as chloride ions by treatment of the complex with AgSbF6; the former reaction is a reversible process with dissolution of [Rh3(µ-PPh2)3(CO)5] in CCl4 resulting in the regeneration of the title complex. [Rh3(µ-PPh2)3(µ-Cl)2(µ-CO)(CO)3] is only moderately stable in solution and converts slowly to an insoluble species formulated as [{Rh(µ-PPh2)(µ-Cl)(CO)}n].