Theoretical investigation of C–HM interactions in organometallic complexes: A natural bond orbital (NBO) study

The nature of C–HM agostic interactions in model metal complexes [M²⁺(CH₂CH₃)(PH₃)_nCl] (where M = Sc, Ti, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn; n = 1, 2, 3, 4) was studied with the natural bond orbital analysis (NBO) approach using density functional theory (DFT) optimized geometries at the B3LYP/6-31G(d,p) level of theory. The effect of nature of metal, coordination number, oxidation state and ligand field effects on the agostic interaction is examined. A set of 20 crystal structures of organometallic complexes taken from the Cambridge Structural Database (CSD) was studied computationally employing AIM theory and NBO analysis, and the applicability of these methods was critically accessed in demarcating the two types of interaction.