PdII and PtII 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 PdII and PtII has been investigated. The molecular structures of the complexes [PdCl2(1)] and [PtCl2(1)] were determined by X-ray diffraction, representing the first crystallographically characterized ¿3-phosphinine–PdII and –PtII complexes. Both complexes reacted with methanol at the P=C double bond at an elevated temperature, leading to the corresponding products [MCl2(1HOCH3)]. The molecular structure of [PdCl2(1HOCH3)] 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 [PdCl2(1HOCH3)] with the chelating diphosphine DPEphos at room temperature in CH2Cl2 led quantitatively to [PdCl2(DPEphos)] and phosphinine 1 by elimination of CH3OH and rearomatization of the phosphorus heterocycle.