Molecular structure and intramolecular rearrangements in tris-2,2,6,6-tetramethyl-heptane-3,5-dione complexes, M(thd)3 (M = B, Al, Ga, In, Tl) by DFT calculations

The DFT calculations for tris-2,2,6,6-tetramethyl-heptane-3,5-dionato complexes of trivalent group 13 ions, M(thd)3 (M = B, Al, Ga, In, Tl) were performed. The most likely geometrical structures of D3, D3h and C2v symmetry were examined. The D3 molecular structure with distorted antiprismatic MO6 coordination polyhedron corresponds to the minimum of potential energy hyper-surface (PES) for Al, Ga, In and Tl complexes. Calculated structures of MO6 coordination polyhedron of studied complexes are in good agreement with the literature experimental results. The D3h and C2v configurations correspond to the first-order saddle points on the PES. The analysis of the different ways of intramolecular rearrangements was performed. Structure with D3 symmetry was found to be a second-order saddle point on PES for B(thd)3 complex. The configuration with one bidentate ligand and two monodentate bonded ligands and almost tetrahedron BO4 is energetically most preferred for B(thd)3.