Solution thermochemical and structural studies of ligand substitution of N-pyrrolyl-substituted phosphine ligands in the Cp'Ru(PR(3))(2)Cl (Cp'=eta(5)-C5H5 and eta(5)-C(5)Me(5)) systems

The enthalpies of reaction of Cp'Ru(COD)Cl (1) (Cp' = eta(5)-C5H5 and eta(5)-C(5)Me(5); COD = cyclooctadiene) with a series of N-pyrrolyl-substituted monodentate tertiary phosphine ligands, leading to the formation of Cp'Ru(PR(3))(2)Cl (PR(3) = P(NC4H4)(3); P(NC4H4)(2)(C6H5), P(NC4H4)(C6H5)(2), P(NC4H8)(3)), have been measured by anaerobic solution calorimetry in THF at 30.0 degrees C. These reactions are rapid and quantitative. Structural studies have been carried out on five complexes in this series, and a discussion of bond length-bond strength relationships is presented, The measured reaction enthalpies span a range of 5 kcal/mol. This series of ligands include some of the most weakly bound phosphines calorimetrically investigated within these two related organometallic systems. Relative importance of phosphine steric vs electronic ligand parameters is more closely examined in terms of the presented quantitative thermochemical and structural information. Comparisons with enthalpy data in related organometallic systems are also presented.