The synthetic potential of the photosubstitution of CO by two-electron dono
r ligands in M-3(CO)(12) [M = Ru, Os] has been investigated. When used as p
hotolysis media, diethyl ether, ethyl acetate and acetonitrile act as photo
fragmentation quenchers allowing for the synthesis of photosubstitution pro
ducts in high yield. UV photolysis of M-3(CO)(12) with added triphenylphosp
hine in these photolysis media leads to M-3(CO)(12-n)(PPh3)(n) (n = 1, 2 or
3). Prolonged photolysis with added tricyclohexylphosphine generates the h
ighly sterically crowded complex M-3(CO)(9)(PCy3)(3). Photolysis with thiol
s, RSH (R = Et, Ph), leads to the thiolato complexes HM3(mu-SR)(CO)(10), pr
olonged photolysis of which generates the corresponding sulphido cluster M-
3(mu(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). T
his offers a route to these complexes without the need for the use of oxidi
sing agents such as trimethylamine-N-oxide. Photolysis of an ethene-saturat
ed diethyl ether or ethyl acetate solution of M-3(CO)(12) leads to no net p
hotoreaction in the case of ruthenium, whereas, for osmium, the olefin comp
lex Os(CO)(4)(eta(2)-C2H4) is formed. This highlights the difference in the
photosubstitution mechanism for Ru-3(CO)(12) and Os-3(CO)(12). (C) 1999 El
sevier Science S.A. All rights reserved.