A Molecular Orbital Rationalization of Ligand Effects in N2 Activation

Molecular orbital theory has been used to study a series of [(μ-N 2)-{ML3}2] complexes as models for dinitrogen activation, with M = Mo, Ta, W, Re and L = NH2, PH2, AsH2, SbH2 and N(BH2)2. The main aims of this study have been to provide a thorough electronic analysis of the complexes and to extend previous work involving molecular orbital analyses. Molecular orbitaldiagrams have been used to rationalize why for L = NH 2 ligand rotation is important for the singlet state but not the triplet, to confirm the effect of ligand itdonation, and to rationalize the importance of the metal d-electron configuration. The outcomes of this study will assist with a more in-depth understanding of the electronic basis for N2 activation and allow clearer predictions to be made about the structure and multiplicity of systems involved in transition-metal catalysis. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.