Studies and Photoreactions of Os3(CO)12 with Chlorocarbons and with Triphenylphosphine in Solution

Article abstract of DOI:10.1021/ja00529a025

Irradiation (254, 313, 366, 405 nm) of Os3(CO)12 in CCl4, CHCl3, or CH2Cl2 solution at room temperature produces Os(CO)4Cl2 in low quantum yield (0.002 in CCl4 at 313 nm).A reasonable pathway for the photoreaction involves Os3(CO)12Cl2 as an intermediate, as irradiation of the complex at 313 nm in CCl4 gives Os(CO)4Cl2 with a quantum yield of 0.31.Irradiation of Os3(CO)12 under 6 atm CO in acetonitrile solution at room temperature gives no reaction; however, in the absence of carbon monoxide, Os3(CO)12 and PPh3 photoreact to give Os3(CO)11PPh3, and Os3(CO)10(PPh3)2 and Os3(CO)9(PPh3)3 are secondary and tertiary products.Prolonged irradiation of the trisubstituted complex in the presence of PPh3 yields Os(CO)3(PPh3)2 (Φ = 0.005 at 366 nm).The fact that fragmentation of the cluster is a principal photochemical pathway for Ru3(CO)12 but not for Os3(CO)12 is probably due to differences in M-M bond strengths (Os-Os > Ru-Ru) and also to the different character of the lowest energy electronic excited states of the two complexes (? -> ?^*, Ru3(CO)12; ?^*' -> ?^*, Os3(CO)12).