Surface organometallic chemistry: Reductive carbonylation of silica-supported MCl3·3H2O (M=Rh, Ir)

The reductive carbonylation of silica-supported MCl3·3H2O (M=Rh, Ir) was studied at atmospheric pressure under CO and under a mixture of CO and H2O. It was observed that these salts may be converted respectively into [Ir(CO)3 Cl]n and [Rh(CO)2Cl]2 under CO. At 70 °C, in the presence of CO and H2O, Ir4(CO)12 is selectively obtained. Under the same experimental conditions [Rh(CO)2Cl]2 sublimes, while at 25 °C the liberated HCl inhibits further reduction to rhodium carbonyl clusters. However, Rh6(CO)16 might easily be obtained, working at 25 °C with CO and H2O, using [Rh(CO)2Cl]2 as the starting material instead of RhCl3. The inhibiting effect on the nucleation process of HCl and the role of water are discussed in the comparison with the reductive carbonylation of a chlorine-free rhodium salt, [Rh(O2CCH3)2]2.