Investigation of phosphine donor properties to vanadium(V) nitrides

Catalyst optimization has been greatly aided over the years by methods of characterizing donor and steric properties of ligands. Here, we investigated a vanadium model system, NV(NH2)(2)L, to determine if the enthalpic barriers associated with amide rotation are in a range that would make this a synthetic target for determining the donor ability of L experimentally, e.g., by spin saturation transfer of the amide protons in the H-1 NMR. In addition to determining that the barriers to rotation should be amenable to this method, we investigated how various phosphine donor properties affected amide rotation for the d(0) metal and contrasted this with a late transition metal system. The calculations suggest that some PX3 ligand features, such as lone pairs on the X substituent, may lead to increases in the high oxidation state system where they are electron withdrawing in the low oxidation state systems. The cause of this electronic difference was investigated using Natural Resonance Theory.