2-(2-pyridyl)-4,6-diphenylphosphinine versus 2-(2-pyridyl)-4,6- diphenylpyridine: Synthesis, characterization, and reactivity of cationic RhIII and IrIII complexes based on aromatic phosphorus heterocycles

摘要

The bidentate P,N hybrid ligand 1 allows access for the first time to novel cationic phosphinine-based Rh~(III) and Ir~(III) complexes, broadening significantly the scope of low-coordinate aromatic phosphorus heterocycles for potential applications. The coordination chemistry of 1 towards RhIII and IrIII was investigated and compared with the analogous 2,2-bipyridine derivative, 2-(2-pyridyl)-4,6-diphenylpyridine (2), which showed significant differences. The molecular structures of [RhCl(Cp)(1)]Cl and [IrCl(Cp)(1)]Cl (Cp=pentamethylcyclopentadienyl) were determined by means of X-ray diffraction and confirm the mononuclear nature of the λ~3-phosphinine-Rh~(III) and Ir~(III)complexes. In contrast, a different reactivity and coordination behavior was found for the nitrogen analogue 2, especially towards Rh~(III) as a bimetallic ion pair [RhCl(Cp)(2)]~+[RhCl_3(Cp)]~- is formed rather than a mononuclear coordination compound. [RhCl(Cp)(1)]Cl and [IrCl(Cp)(1)]Cl react with water regio- and diastereoselectively at the external P?￡C double bond, leading exclusively to the anti-addition products [MCl(Cp)(1H×OH)]Cl as confirmed by X-ray crystal-structure determination.