Structural Snapshots in Reversible Phosphinidene Transfer: Synthetic, Structural, and Reaction Chemistry of a Sn═P Double Bond

The reaction of amido-substituted stannylenes with phospha-Wittig reagents (Me 3 PPR) results in release of hexamethyldisilazane and tethering of the resulting -CH 2 PMe 2 PR fragment to the tin center to give P-donor stabilized stannylenes featuring four-membered Sn , C , P , P heterocycles. Through systematic increases in steric loading, the structures of these systems in the solid state can be tuned, leading to successive P-P bond lengthening and Sn-P contraction and, in the most encumbered case, to complete P-to-Sn transfer of the phosphinidene fragment. The resulting stannaphosphene features a polar Sn═P double bond as determined by structural and computational studies. The reversibility of phosphinidene transfer can be established by solution phase measurements and reactivity studies.