SYNTHESIS AND CHARACTERIZATION OF DINUCLEAR RHODIUM COMPLEXES CONTAINING (BENZYLTHIOMETHYL)DIPHENYLPHOSPHINE AS THE BRIDGING LIGAND - STRUCTURE OF THE NOVEL RHODIUM(II) COMPLEX [RH2CL4(CO)2(MU-PHCH2SCH2PPH2)2]

Treatment of [{RhCl(CO)2}2] with 5 equivalents of PhCH2SCH2PPh2 (btmp) gave the mononnuclear 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(mu-btmp)2] but the chloro-bridged complex [Rh2(mu-Cl)(CO)2(mu-btmp)2][RhCl2(CO)2]. The tetraphenylborate salt analogue [Rh2(mu-Cl)(CO)2(mu-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 [NBu(n)4][RhCl2(CO)2] with 1 equivalent of btmp afforded the carbonyl-bridged dinuclear complex [Rh2Cl2(mu-CO)(mu-btmp)2], while the above reaction performed in the presence of hydrochloric acid gave the novel dinuclear rhodium(II) complex [Rh2Cl4(CO)2(mu-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) angstrom, beta = 116.67(2)-degrees, 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) angstrom] and the two mu-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.