Oxidative additions of coordinated ligands at unsaturated molybdenum and tungsten diphosphine-bridged carbonyl dimers .3. Decarbonylation reactions of [MoW(eta(5)-C5H5)(2)(CO)(4)(mu-Ph(2)PCH(2)PPh(2))]

Decarbonylation of the heterometallic title complex [MoWCp(2)(CO)(4)(mu-dppm)] (Cp = eta(5)-C5H5; dppm = Ph(2)PCH(2)PPh(2)) in refluxing tetrahydrofuran leads to the phosphido complex [MoWCp(2)(mu-CH(2)PPh(2))(mu-PPh(2))(CO)(2)], presumably via the tricarbonylic species [MoWCp(2)(mu-CH(2)PPh(2))(mu-PPh(2))(mu-CO)(CO)(2)]. The latter is an unstable compound which can be generated upon reaction of the former with CO and also contains the phosphinomethyl ligand C-bonded to the tungsten atom. In contrast, photolytic decarbonylation of the title complex at -10 degrees C leads reversibly to the hydride compound [MoW(mu-eta(1):eta(5)-C5H4)Cp(mu-H)(CO)(3)(mu-dppm)], in which the cyclopentadienylidene ligand is specifically eta(5)-bonded to tungsten and eta(1)-bonded to molybdenum. Further photolysis of this complex at 10 degrees C leads to the triply bonded dimer [MoWCp(2)(CO)(2)(mu-dppm)] with concomitant regeneration of a H-C (cyclopentadienyl) bond. The latter species reacts with (t)BuCN to give [MoWCp(2)(mu-eta(1):eta(2)-CN(t)Bu)(CO)(2)(mu-dppm)], in which the isocyanide ligand is specifically eta(1)-bonded to tungsten and eta(2)-bonded to molybdenum. In order to account;for the metal selectivity observed in the above species, two different intermediates, having either mu-eta(1)-CO or mu-eta(1):eta(2)-CO ligands, are thought to be involved in the decarbonylation reactions of the title compound.