The molecular structure of tris(dipivaloylmethanato) lanthanides, Ln(thd)3 (Ln = La–Lu): Peculiarities and regularities

The DFT calculations for tris-2,2,6,6-tetramethyl-heptane-3,5-dionato complexes of lanthanides, Ln(thd)3 (Ln = La–Lu) were performed. The most likely geometrical structures of D3, D3h and C2v symmetry have been examined. The D3 molecular structure with distorted antiprismatic LnO6 coordination polyhedron corresponds to the minimum of a potential energy hyper-surface (PES) for all complexes being studied. The D3h and C2v configurations correspond to the first-order saddle points on the PES. The analysis of the different ways of intramolecular rearrangements has been performed. The discrepancies between theoretical and available experimental structural data of Ln(thd)3 are explained. The regularities in molecular parameters and chemical bond nature are analyzed.