Equilibrium, solid state behavior and reactions of four and five co-ordinate carbonyl stibine complexes of rhodium. Crystal Structures of trans-[Rh(Cl)(CO)(SbPh 3) 2], trans-[Rh(Cl)(CO)(SbPh 3) 3] and trans-[Rh(I) 2(CH 3)(CO)(SbPh 3) 2

Abstract

The crystal structures of the four-coordinate trans-[Rh(Cl)(CO)(SbPh 3) 2] ( 1) and the five-coordinate trans-[Rh(Cl)(CO)(SbPh 3) 3] ( 2) are reported, as well as the unexpected oxidative addition product, trans-[Rh(I) 2(CH 3)(CO)(SbPh 3) 2] ( 3), obtained from the reaction of 2 with CH 3I. The formation constants of the five-coordinate complex were determined in dichloromethane, benzene, diethyl ether, acetone and ethyl acetate as 163±8, 363±10, 744±34, 1043±95 and 1261±96 M −1, respectively. While coordinating solvents facilitate the formation of the five-coordinate complex, the four-coordinate complex could be obtained from diethyl ether due to the favorable low crystallization energy. The tendency of stibine ligands to form five-coordinate rhodium(I) complexes is attributed mainly to electron deficient metal centers in these systems, with smaller contributions by the steric effects. The average effective cone angle for the SbPh 3 ligand in the three crystallographic studies was determined as 139° with individual values ranging from 133 to 145°.