Umwandlungen zwischen Vinyliden- und Alkylidin-verbrückten Dreikernclustern

Clusters, Vinylidene Ligands. Alkylidyne Ligands Based on the observation that the alkylidyne bridged cluster HFeCo2(CO)4(/<3-C —CH 3) spon­ taneously loses H ; to form the vinylidene bridged cluster FeCo2(CO)y(«3-C—CH :). the intercon­ versions between these types of ligands on mixed trinuclear clusters were investigated. It was found that in all cases clusters of the type HM3(/<3-C -C H 2R) could be transformed into clusters of the type M3(a3-C =C H R ); for M3 = FeCo2, FeCoMo, RuCoMo, RuCoW, OsCoMo. OsCoW; for R = H and in one case CH3; for dehydrogenation by thermolysis and in one case H +/H elimina­ tion. Conversely, hydrogenation of the vinylidene bridged clusters to the alkylidyne bridged clusters was only possible for the FeCoMo. RuCoMo. and RuCoW systems, for the unsubstituted C = C H 2 ligand, and for elemental hydrogen as the reagent. Together with previous observations this leads to the conclusion that among the interconvertible alkyne, vinylidene. and alkylidyne ligands the vinylidene unit represents the most stable entity on trinuclear clusters.