Organoruthenium thermochemistry. Enthalpies of reaction of Cp'Ru(COD)Cl (Cp'=eta(5)-C5H5 and eta(5)-C(5)Me(5)) with tertiary phosphite ligands

The enthalpies of reaction of Cp'Ru(COD)Cl (Cp' = eta(5)-C5H5 (Cp), eta(5)-C(5)Me(5) (Cp*); COD = cyclooctadiene) with a series of monodentate phosphite ligands, leading to the formation of Cp'Ru(P(OR)(3))(2)Cl, have been measured by anaerobic solution calorimetry in THF at 30 degrees C. The overall relative order of stability established for the preceding complexes is as follows: for the CpRu(P(OR)(3))(2)Cl series, P(O-o-MeC(6)H(4))(3) < P(OC6H5)(3) < P((OPr)-Pr-i)(3) < P(OCH2)(3)CEt < P(OMe)(3); for the Cp*Ru(P(OR)(3))(2)Cl series, P(O-o-MeC(6)H(4))(3) < P(OC6H5)(3) < P(OCH2)(3)CEt < P((OPr)-Pr-i)(3) < P(OMe)(3). Single-crystal diffraction studies were carried out on two members of the Cp*Ru(P(OR)(3))(2)Cl series, P(OR)(3) = P(OMe)(3) and P(OR)(3) = P(OCH2)(3)CEt (TMPP). Comparisons with other organometallic systems and insight into factors influencing the Ru-P(OR)(3) bond disruption enthalpies are discussed.