Control of the photochemistry of Ru 3(CO) 12 and Os 3(CO) 12 by variation of the solvent

Abstract

The synthetic potential of the photosubstitution of CO by two-electron donor ligands in M 3(CO) 12 [M=Ru, Os] has been investigated. When used as photolysis media, diethyl ether, ethyl acetate and acetonitrile act as photofragmentation quenchers allowing for the synthesis of photosubstitution products in high yield. UV photolysis of M 3(CO) 12 with added triphenylphosphine in these photolysis media leads to M 3(CO) 12− n (PPh 3) n ( n=1, 2 or 3). Prolonged photolysis with added tricyclohexylphosphine generates the highly sterically crowded complex M 3(CO) 9(PCy 3) 3. Photolysis with thiols, RSH (R=Et, Ph), leads to the thiolato complexes HM 3( μ-SR)(CO) 10, prolonged photolysis of which generates the corresponding sulphido cluster M 3( μ 3-S)(CO) 10. Photolysis of M 3(CO) 12 in acetonitrile with no added ligand results in the generation of M 3(CO) 12− n (MeCN) n ( n=1 or 2). This offers a route to these complexes without the need for the use of oxidising agents such as trimethylamine- N-oxide. Photolysis of an ethene-saturated diethyl ether or ethyl acetate solution of M 3(CO) 12 leads to no net photoreaction in the case of ruthenium, whereas, for osmium, the olefin complex Os(CO) 4( η 2-C 2H 4) is formed. This highlights the difference in the photosubstitution mechanism for Ru 3(CO) 12 and Os 3(CO) 12.