Pd II and Pt II Complexes of 2‐(2′‐Pyridyl)‐4,6‐diphenylphosphinine: Synthesis, Structure, and Reactivity

The coordination chemistry of the bidentate P,N hybrid ligand 2‐(2′‐pyridyl)‐4,6‐diphenylphosphinine ( 1 ) towards Pd II and Pt II has been investigated. The molecular structures of the complexes [PdCl 2 ( 1 )] and [PtCl 2 ( 1 )] were determined by X‐ray diffraction, representing the first crystallographically characterized λ 3 ‐phosphinine–Pd II and –Pt II complexes. Both complexes reacted with methanol at the P=C double bond at an elevated temperature, leading to the corresponding products [MCl 2 ( 1 H⋅OCH 3 )]. The molecular structure of [PdCl 2 ( 1 H⋅OCH 3 )] was determined crystallographically and revealed that the reaction with methanol proceeds selectively by syn addition and exclusively to one of the P=C double bonds. Strikingly, the reaction of [PdCl 2 ( 1 H⋅OCH 3 )] with the chelating diphosphine DPEphos at room temperature in CH 2 Cl 2 led quantitatively to [PdCl 2 (DPEphos)] and phosphinine 1 by elimination of CH 3 OH and rearomatization of the phosphorus heterocycle.