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 l3-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 [MCl2ACHTUNGTRENUNG(1H·OCH3)]. The molecular structure of [PdCl2- ACHTUNGTRENUNG(1H·OCH3)] 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 [PdCl2ACHTUNGTRENUNG(1H·OCH3)] with the chelating diphosphine DPEphos at room temperature in CH2Cl2 led quantitatively to [PdCl2ACHTUNGTRENUNG(DPEphos)] and phosphinine 1 by elimination of CH3OH and rearomatization of the phosphorus heterocycle.