Lithium Salts of 2, 4, 6‐Triaryl‐λ4‐phosphinine Anions – A Comparison Study1. Issue 10 (3rd December 2013) - Bruce, Marlene
Abstract: The λ 3 ‐phosphinine derivatives 2, 6‐diphenyl‐4‐( p ‐tolyl)phosphinine and 2‐(2′‐pyridyl)‐4, 6‐diphenylphosphinine were quantitatively converted into the corresponding λ 4 ‐phosphinine anions by reaction with phenyllithium. Systematic hydrolysis experiments with H2 O and MeOH show that a subtle interplay between the p K a values of the generated 1, 2‐dihydrophosphinine derivatives and the p K b value of the formed bases, LiOH and LiOCH3, respectively, leads either to the kinetic or thermodynamic product. The coordination chemistry of the λ 4 ‐phosphinine anions towards Rh I was further investigated, and the anions based on 2, 6‐diphenyl‐4‐( p ‐tolyl)‐phosphinine and 2‐(2′‐pyridyl)‐4, 6‐diphenylphosphinine demonstrate different coordination modes. Whereas the former coordinates in an η 5 fashion towards the Rh I atom, the latter acts as a bidentate chelating ligand with an η 1 coordination to the metal center through the phosphorus lone pair. Abstract : The λ 4 ‐phosphinine anions of 2, 6‐diphenyl‐4‐( p ‐tolyl)phosphinine and the structurally related 2‐(2′‐pyridyl)‐4, 6‐diphenylphosphinine show a remarkable difference in selectivity towards hydrolysis with water and methanol. Moreover, the presence or absence of an additional nitrogen atom within the ligand framework influences the coordination chemistry of the phosphinine derivatives towards Rh I .