Synthesis and Structures of Stable Pt(II) and (IV) Alkylidenes: Evidence for π-Bonding and Relativistic Stabilization

Isolable cationic Pt(II) and Pt(IV) alkylidenes, proposed intermediates in catalytic organic transformations, are reported. The bonding in these species was probed by experimental, structural, spectroscopic, electrochemical and computational methods, providing direct evidence for π-bonding, the oft-theorized relativistic stabilisation of these species, and the influence of oxidation state.