Solution Thermochemical and Structural Studies of Ligand Substitution of N-Pyrrolyl Phosphine Ligands in the (p-cymene)RuCl2(PR3) System

The enthalpies of reaction of [( p -cymene)RuCl 2 ] 2 ( p -cymene = (CH 3 ) 2 CHC 6 H 4 CH 3 ) with a series of N-substituted tertiary phosphine ligands, leading to the formation of ( p -cymene)RuCl 2 (PR 3 ) complexes (PR 3 = tertiary phosphine) have been measured by solution calorimetry in CH 2 Cl 2 at 30 °C. The overall relative order of stability, within this series, is as follows: P(NC 4 H 4 ) 3 < P(NC 4 H 4 ) 2 (C 6 H 5 ) < P(NC 4 H 4 )(C 6 H 5 ) 2 < P(NC 4 H 8 ) 3 . Structural studies have been performed on three complexes in the ( p -cymene)RuCl 2 (PR 3 ) system, PR 3 = P(NC 4 H 4 ) 3, P(NC 4 H 4 ) 2 (C 6 H 5 ), and PBz 3 . Thermochemical and structural data are compared to provide an understanding of the bonding involving these N -pyrrolyl-substituted phosphine ligands.