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

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