6533b851fe1ef96bd12a99c7

RESEARCH PRODUCT

Computational Analysis of n→π* Back-Bonding in Metallylene–Isocyanide Complexes R2MCNR′ (M = Si, Ge, Sn; R = tBu, Ph; R′ = Me, tBu, Ph)

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A detailed computational investigation of orbital interactions in metal–carbon bonds of metallylene–isocyanide adducts of the type R2MCNR′ (M = Si, Ge, Sn; R, R′ = alkyl, aryl) was performed using density functional theory and different methods based on energy decomposition analysis. Similar analyses have not been carried out before for metal complexes of isocyanides, even though the related carbonyl complexes have been under intense investigations throughout the years. The results of our work reveal that the relative importance of π-type back-bonding interactions in these systems increases in the sequence Sn < Ge ≪ Si, and in contrast to some earlier assumptions, the π-component cannot be neglected for any of the systems investigated. While the fundamental ligand properties of isocyanides are very similar to those of carbonyl, there are significant variations in the magnitudes of different effects observed. Most notably, on coordination to metals, both ligands can display positive or negative shifts in t...