PUB - Publikationen an der Universität Bielefeld

Structure-related DFT calculations for IIIA metal tripivalates [M(piv)(3)] (M = Al, Ga, In, Tl) were performed. On the potential energy hypersurface (PES) for the Al, Ga, In, and Tl complexes, only a molecular structure of C (3) symmetry based on a distortion of an antiprismatic MO6 coordination polyhedron is found as a minimum. The geometry of C (3v) symmetry corresponds to the first-order saddle points on the PES. The analysis of internal rotation of the tert-butyl groups and plane chelate ring in pivalate molecules was performed also. The structural flexibility within the coordination polyhedron MO6 was found to increase along the series Al -> Ga -> In -> Tl. According to the analyses of the electron density distribution (NBO and QTAIM), the central atom M has no appreciable effect on the geometry of the peripheral tert-butyl groups, so that the most significant differences occur in the coordination polyhedron MO6. The lengthening of the M-O bond and decreasing of the binding energy are correlated with the ionic radius of the metal atom M. This fact proves the ionic binding nature of the title molecules. Appropriate assignment of vibrational modes was carried out by usage of the potential energy distribution analysis among internal coordinates.