Density Functional Theory Study of Transition-Metal Compounds Containing Metal−Metal Bonds. 1. Molecular Structures of Dinuclear Compounds by Complete Geometry Optimization

Complete geometry optimizations were carried out by methods of density functional theory to study molecular structures of dinuclear transition-metal compounds containing metal−metal bonds of various orders. It is shown that the structures of the dinuclear compounds can be accurately predicted by DFT methods. In particular, we show that accurate geometry optimization can be performed efficiently by using small basis sets in the calculations. Furthermore, an effective core potential approximation may be incorporated into the DFT calculations for computational effectiveness without losing much accuracy. The molecules included in this study were M 2 (O 2 CH) 4 (M = Nb, Mo, Tc), M 2 (HNCHNH) 4 (M = Nb, Mo, Tc, Ru, Rh), M 2 (HNNNH) 4 (M = Mo, Ru, Rh), and M 2 Cl 4 (PH 3 ) 4 (M = Nb, Mo, Tc).