EXTENSION OF MOLECULAR MECHANICS TO HIGH-COORDINATE METAL-COMPLEXES - CALCULATION OF THE STRUCTURES OF AQUA AND NITRATO COMPLEXES OF LANTHANIDE(III) METAL-IONS

Molecular mechanics methods have been used to calculate the diverse geometries found in 58 known structures of 8- to 12-coordinate aqua- and nitratolanthanide(III) complexes. A simple model based on the replacement of L-M-L bending interactions with nonbonded interactions between the ligand donor atoms and the use of harmonic M-L stretching potentials is shown to yield very reasonable geometric results. A method of structure specification for coordination compounds is presented that allows these calculations to be carried out by using the MM2 program without requiring any software modification.