Synthesis and characterization of dinuclear rhodium complexes containing (benzylthiomethyl)diphenylphosphine as the bridging ligand. Structure of the novel rhodium(II) complex [Rh2Cl4(CO)2(µ-PhCH2SCH2PPh2)2

Abstract

Treatment of [{RhCl(CO)2}2] with 5 equivalents of PhCH2SCH2PPh2(btmp) gave the mononuclear Vaska-type complex trans-[RhCl(CO)(btmp-P)2], whereas the reaction with 2 equivalents of btmp afforded not the expected face-to-face complex [Rh2Cl2(CO)2(µ-btmp)2] but the chloro-bridged complex [Rh2(µ-Cl)(CO)2(µ-btmp)2][RhCl2(CO)2]. The tetraphenylborate salt analogue [Rh2(µ-Cl)(CO)2(µ-btmp)2]BPh4 was obtained from the reaction of an ethanolic solution of [RhCl2(CO)2]– with 1 equivalent of btmp and NaBPh4. Treatment of [NBun4][RhCl2(CO)2] with 1 equivalent of btmp afforded the carbonyl-bridged dinuclear complex [Rh2Cl2(µ-CO)(µ-btmp)2], while the above reaction performed in the presence of hydrochloric acid gave the novel dinuclear rhodium(II) complex [Rh2Cl4(CO)2(µ-btmp)2](5). Complex (5) was also obtained from the reaction of an ethanolic solution of [RhCl2(CO)2]–and 1 equivalent of btmp. Crystals of (5) are monoclinic, space group C2/c, with a= 14.064(3), b= 19.364(4), c= 16.930(5)A, β= 116.67(2)°, and Z= 4; final R= 0.036 for 3 529 observed reflections. The structure shows that there is a metal–metal bond [Rh–Rh 2.733(3)A] and the two µ-btmp ligands are co-ordinated to rhodium atoms cis to each other with a head-to-tail arrangement. The relationships among the synthesized complexes are discussed.