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 transiti on-metal compounds containing metal-metal bonds of various orders. It is shown that the structures of the dinuclear compounds can be accurat ely predicted by DFT methods. In particular, we show that accurate geo metry optimization can be performed efficiently by using small basis s ets in the calculations. Furthermore, an effective core potential appr oximation may be incorporated into the DFT calculations for computatio nal effectiveness without losing much accuracy. The molecules included in this study were M-2(O2CH)(4) (M = Nb, Mo, Tc), M-2(HNCHNH)(4) (M = Nb, Mo, Tc, Ru, Rh), M-2(HNNNH)(4) (M = Mo, Ru, Rh), and M2Cl4(PH3)(4 ) (M = Nb, Mo, Tc).