INVESTIGATION OF GEOMETRICAL AND CONFORMATIONAL ISOMERS OF COBALT(II) BIS(DIPHENYLACETATO)-BIS(G -PICOLINATE) BY DYNAMIC NMR SPECTROSCOPY AND MOLECULAR MECHANICS

Abstract

Cobalt(II) bis(diphenylacetato)-bis(γ-picolinate) is synthesized and its geometrical and conformational isomers are investigated using dynamic NMR and molecular mechanics methods. The complex in the solution is shown to exist as cis and trans isomers, which are detected at 263 K in the course of a slow intermolecular ligand exchange. At T < 223 K, the intramolecular rotation of the phenyl radicals about the -O2C-CH(Ph)2 and -O2CCH(Ph)-Ph bonds slows, which results in the formation of different conformers. The energies of the retarded intermolecular exchange and of the retarded rotation of the phenyl radicals were calculated from 1H NMR and molecular mechanics data.