Ruthenium Complexes of CP3: A New Carbon-Centered Polydentate Podand Ligand

A new tripodal, tetradentate, carbon-centered podand ligand based on HC(CH2CH2PPh2)(3) ((CP3)-C-H) has been prepared. In the presence of [RuCl2(PPh3)(3)], (CP3)-C-H dehydrogenates on heating to yield [Ru(C(CH2CH2PPh2)(2)(=CHCH2PPh2))Cl-2], where three phosphorus donors and a constrained alkene bind the metal. The metal carbon bond is then formed by reduction with hydride in the presence of an ancillary ligand, to give [Ru(C(CH2CH2PPh2)(3))LX] (L = ancillary ligand; X = H, CO, where the metal has the full CP3 donor set. The complex [Ru(CP3)(CO)H] displays moderate catalytic activity for the transfer hydrogenation of acetophenone.