Organometallic chemistry of Ph3PC=C=O.: Synthesis, characterization, X-ray structure determination, and density functional study of the first stable bis-η1-ketenyl complex, trans-[PtCL2{η1-C(PPh3)CO}2]

Mono- and bis-eta(1)-ketenyl Pt(II) complexes have been synthesized by reacting Zeise's salt or the related dimeric compound, [{PtCl2(C2H4)}(2)], with the oxocumulenic ylide ketenyliden-etriphenylphosphorane, Ph3PC=C=O, 1, in suitable ratios. In particular, the yl-ketenyl derivative, trans-[PtCl2(C2H4){eta(1)-C(PPh3)CO}], 2, has been isolated and characterized. The reaction of 2 with one more equivalent of 1 displaces the coordinated ethylene giving the first stable bis-eta(1)-ketenyl derivative, trans-[PtCl2{eta(1)-C(PPh3)CO}(2)], 6. The X-ray crystal structure of 6 shows a trans centrosymmetric geometry around Pt, with the PCCO moiety and the metal lying in a plane that forms an angle of similar to 65 degrees with the Pt(II) coordination plane. Density functional calculations indicate that steric effects play a leading role in determining such an arrangement. Data on the reactivity of 2 and 6 are also reported.