MOLECULAR MECHANICS (MM2) PARAMETERS FOR THE (ETA-3-ALLYL)PALLADIUM MOIETY

Molecular mechanics parameters have been developed that allow calculat ion of (eta3-allyl)palladium complexes with the MM2 force field. Virtu al (dummy) atoms have been used to simulate the bond between palladium and the ligands. The parameterization was based upon selected X-ray s tructures together with ab initio calculations for different geometrie s of unsubstituted (eta3-allyl)palladium. For comparison, a few comple xes with auxiliary ligands were also calculated. All ab initio calcula tions were performed with electron correlation of all valence electron s. The parameter set is used to calculate syn-anti equilibrium data fo r substituted (eta3-crotyl)palladium complexes with 2,9-disubstituted phenanthrolines as ligands. The equilibrium calculations are correlate d with experimental data. The problems of adding parameters for atoms bound to more than four ligands to the MM2 force field are discussed.