SOLUTION THERMOCHEMICAL AND STRUCTURAL STUDIES OF LIGAND SUBSTITUTIONOF 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-su bstituted monodentate tertiary phosphine ligands, leading to the forma tion of Cp'Ru(PR(3))(2)Cl (PR(3) = P(NC4H4)(3); P(NC4H4)(2)(C6H5), P(N C4H4)(C6H5)(2), P(NC4H8)(3)), have been measured by anaerobic solution calorimetry in THF at 30.0 degrees C. These reactions are rapid and q uantitative. Structural studies have been carried out on five complexe s in this series, and a discussion of bond length-bond strength relati onships is presented, The measured reaction enthalpies span a range of 5 kcal/mol. This series of ligands include some of the most weakly bo und phosphines calorimetrically investigated within these two related organometallic systems. Relative importance of phosphine steric vs ele ctronic ligand parameters is more closely examined in terms of the pre sented quantitative thermochemical and structural information. Compari sons with enthalpy data in related organometallic systems are also pre sented.