HALIDE-PROMOTED CARBONYLATION OF THE IMIDO LIGAND IN OS3(MU-3-NPH)(CO)10

The imido cluster Os3(mu-3-NPh)(CO)10 has been found to react with halides to give the isomeric clusters [PPN][Os3(mu(3)NPh)(mu(2)X)(CO)9] (7) and [PPN]Os3(mu(3)-NPh)(mu(2)-X)(CO)9] (7) and [PPN][Os3(mu(3)-NPh)(X)(CO)9] (8) which have bridging and terminal halide ligands, respectively, with the ratio of the isomers dependent upon the halide used. For chloride, the major isomer is 7, which has been crystallographically shown to have two Os-OS bonds and the chloride ligand bridging two nonbonded Os atoms. For iodide, the major isomer is 8, which has three Os-Os bonds and a terminal iodide ligand. Both isomers are present in nearly equal amounts when X = Br. The parent imido cluster Os3(mu-3-NPh)(CO)10 is inert to carbonylation, but when the isomeric halide-substituted clusters are placed under 1 atm of CO at 22-degrees-C, slow carbonylation occurs to form the two new clusters [Os3(eta(2)-mu(3)-PhNCO)(mu(2)-X)(CO)9]- (12) and [Os3(eta(2)-mu(2)-PhNCO)(mu(2)-X)(CO)10]- (13), which prossess bridging PhNCO ligands resulting from the insertion of CO into the Os-N bond. When left under CO, these clusters further carbonylate to release free PhN = C = O and form the known compounds [Os3(X)(CO)11]-. The oxygen atom of the eta(2)-mu(2)-PhNCO ligand in 13 can be protonated and alkylated with CF3CO2H and CF3SO3CH3, respectively, to give the clusters Os3(eta(2)-mu(2)-PhNCOR)(mu(2)-PhNCOR)(mu(2)-X)(CO)10 (R = H, Me; X = Cl, I), of which the R = Me, X = I derivative has been crystallographically characterized.