Ruthenium cluster chemistry: Monodentate bis(diphenylphosphino)acetylene-ligated cluster modules in chain and dendrimer formation

Reaction of Ru3(μ-dppm)(CO)10 [dppm = bis(diphenylphosphino)methane] with one equivalent of dppa [dppa = bis(diphenylphosphino)acetylene] afforded Ru3(μ-dppm)(CO)9(η1-dppa) which possesses a monodentate dppa ligand,an X-ray structural study revealing that all phosphorus donor atoms are arranged in equatorial coordination sites with respect to the triruthenium cluster plane.Reaction of Ru3(CO)9(NCMe)3 with excess dppa afforded fair yields of Ru3(CO)9(η1-dppa)3,which possesses three monodentate dppa ligands.Reaction of three equivalents of Ru3(μ-dppm)(CO)9(η1-dppa) with Ru3(CO)9(NCMe)3 or reaction of Ru3(CO)9(η1-dppa)3 with excess Ru3(μ-dppm)(CO)10 afforded low yields of the dodecanuclear first-generation dendrimer Ru3(CO)9{PPh2C2PPh2Ru3(μ-dppm)(CO)9}3.Reaction of WIr3(μ-CO)3(CO)8(η-C5Me5) with excess Ru3(μ-dppm)(CO)9(η1-dppa) afforded fair yields of the decanuclear dppa-bridged tri-cluster WIr3(CO)9{PPh2C2PPh2Ru3(μ-dppm)(CO)9}2(η-C5Me5).