Reactivity of keteylidenetriphenylphosphorane (Ph3PC=C=O) with Pt(II) complexes. Evidences of formation of an up to now unknown bis-η1-ketenyl derivative

Ketenylidenetriphenylphosphorane, Ph3PC=C=O, 1, has been used to synthesize some Pt(II) η1-ketenyl derivatives, through reactions with dimeric and tetrameric chlorine-bridged compounds. Particularly it has been possible to isolate and characterize [Pt(η3-C3H5)Cl{η1-C(PPh 3)CO}], 2, and [PtCl2{η1-C(PPh3)CO}(PPh3)], 3. Moreover, the reaction of 2 with a further equivalent of 1, in the presence of AgBF4, lead to the formation of [Pt(η3-C3H5){η1-C(PPh 3)CO}2], 4, the first bis-η1-ketenyl derivative. Compound 4 is stable in solution only at low temperatures and its formation has been inferred unequivocally by IR, 1H and 31P-NMR measurements carried out at -50°C.