Ab-initio SCF molecular-orbital calculations on dinitrogen transition-metal complexes

Abstract

Ab-initio SCF molecular-orbital calculations have been made to test the value of such calculations by currently available procedures on the fragment [Ru(NH₃)₅]²⁺ and on the species [Ru(N₂)(NH₃)₅]²⁺, [Fe(N₂)(NH₃)₅]²⁺, [Ru(NH₃)₅(OH₂)]²⁺, [Ru(CO)(NH₃)₅]²⁺, [Mo(N₂)₂(NH₃)₄], [Mo(N₂)(NH₃)₅], and [Mo(N₂)₂(PH₃)₄]. In general where direct comparisons can be made, calculation and experiment are in reasonable agreement. It is predicted that the relative polarization of bound dinitrogen changes considerably from complex to complex, with the Mo and Ru complexes being in the senses Mo–[graphic omitted] and Ru–[graphic omitted]. The calculations suggest that the instability of [Fe(N₂)(NH₃)₅]²⁺ compared to [Ru(N₂)(NH₃)₅]²⁺ is due to the lability of the iron–ammonia system rather than to any weakness of the Fe–N₂ bond.