MONONUCLEAR AND BINUCLEAR QUINALDINATE COMPLEXES OF RHODIUM WITH (P-P) DONOR LIGANDS - CRYSTAL-STRUCTURE OF [RH2(QUIN)2(CO)2(MU-DPPM)] - OXIDATIVE ADDITION-REACTIONS .5.

Reactions of [Rh(quin)(CO)2] (quin = 2-quinaldinate, C9H6N-COO-) with diphosphine ligands [dppm (bis(diphenylphosphino)methane) or dppe ([1,2-bis(diphenylphosphino) ethane)] gave two types of compound, [Rh2(quin)2(CO)2(mu-P-P)] and [Rh(quin)(P-P)] (P-P = dppm, dppe) depending on the Rh: P-P molar ratio employed, 2:1 or 1:1, respectively. The binuclear [Rh2(quin)2(CO)2(mu-P-P)] species present a square-planar environment for each rhodium atom, which are bonded by a P-P bridging ligand. These results were also proved by the resolution of the crystal structure of [Rh2(quin)2 (CO)2(mu-dppm)]. The molecular structure shows the two CO groups occupying trans positions. This could prevent the formation of possible binuclear CO-free species. The Rh-Rh intramolecular distance was consistent with no formal Rh-Rh bond. The addition of I2 or CH3I to the above [Rh2(quin)2(CO)2(mu-P-P)] gave rise to the corresponding binuclear hexacoordinate rhodium(III) compounds [Rh2(I)2(X)2(quin)2(CO)2(mu-P-P)] (X = 1, CH3). Two isomers were detected in solution by H-1 and P-31 NMR spectroscopy for [Rh2(I)2(CH3)2(quin)2(CO)2(mu-P-P)].