Organoruthenium Thermochemistry. Enthalpies of Reaction of Cp‘Ru(COD)Cl (Cp‘ = η⁵-C₅H₅ and η⁵-C₅Me₅) with Tertiary Phosphite Ligands

The enthalpies of reaction of Cp‘Ru(COD)Cl (Cp‘ = η 5 -C 5 H 5 (Cp), η 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 °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(OC 6 H 5 ) 3 < P(O i Pr) 3 < P(OCH 2 ) 3 CEt < P(OMe) 3; for the Cp*Ru(P(OR) 3 ) 2 Cl series, P(O-o-MeC 6 H 4 ) 3 < P(OC 6 H 5 ) 3 < P(OCH 2 ) 3 CEt < P(O i Pr) 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(OCH 2 ) 3 CEt (TMPP). Comparisons with other organometallic systems and insight into factors influencing the Ru−P(OR) 3 bond disruption enthalpies are discussed.