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)(m u-dppm)] (Cp = eta(5)-C5H5; dppm = Ph(2)PCH(2)PPh(2)) in refluxing tet rahydrofuran leads to the phosphido complex [MoWCp(2)(mu-CH(2)PPh(2))( mu-PPh(2))(CO)(2)], presumably via the tricarbonylic species oWCp(2)(m u-CH(2)PPh(2))(mu-PPh(2))(mu-CO)(CO)(2)]. The latter is an unstable co mpound 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 W(mu-eta(1):eta(5)- C5H4)Cp(mu-H)(CO)(3)(mu-dppm)], in which the cyclopentadienylidene lig and is specifically eta(5)-bonded to tungsten and eta(1)-bonded to mol ybdenum. Further photolysis of this complex at 10 degrees C leads to t he triply bonded dimer [MoWCp(2)(CO)(2)(mu-dppm)] with concomitant reg eneration of a H-C (cyclopentadienyl) bond. The latter species reacts with (t)BuCN to give WCp(2)(mu-eta(1):eta(2)-CN(t)Bu)(CO)(2)(mu-dppm)] , in which the isocyanide ligand is specifically eta(1)-bonded to tung sten and eta(2)-bonded to molybdenum. In order to account;for the meta l selectivity observed in the above species, two different intermediat es, having either mu-eta(1)-CO or mu-eta(1):eta(2)-CO ligands, are tho ught to be involved in the decarbonylation reactions of the title comp ound.