Ylidyl‐substituted Phosphonio‐benzophospholides as Chelating Ligands

Phosphonio‐benzoc]phospholides with an additional phosphonium ylide substituent in 3‐position were synthesized by deprotonation of appropriately substituted 1, 3‐bis‐phosphonio benzophospholide cations and characterized by spectroscopic and analytical data. The ability of these molecules to act as bidentate P, C‐chelating ligands to transition metal atoms was demonstrated in the reactions with W(CO)₄(norbornadiene)] and MCl₂(cyclooctadiene)] (M = Pd, Pt). The Pd^II and Pt^II complexes are distinguished by a strong inclination towards addition of H₂O to the 10π‐electron system of the ligand. The molecular structures of a W⁰ complex with a P, C‐chelating ylidyl‐phosphonio‐benzophospholide ligand and of the product resulting from H₂O‐addition to a corresponding Pt^II complex were determined. The structural parameters of the W⁰ complex provide evidence for the presence of substantial steric strain around the metal atom.