The nature of M–Ga in metal(I) gallyl complexes of copper, silver and gold: A theoretical study

Density Functional Theory calculations have been performed for the gallyl complexes [(NHC)M{Ga(N(Ph)C(H))2}] (NHC = :C(N(Ph)C(H))2; I M = Cu, II M = Ag, III M = Au) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometries of the studied complexes are in good agreement with structurally characterized gallyl complexes of copper, silver and gold. The M–Ga bond distances as well as Pauling and Mayer bond orders of the M–Ga bonds suggest that the M–Ga bonds in these complexes are nearly M–Ga single bond. The π–bonding component of the total orbital contribution is significantly smaller than that of σ–bonding. Thus, in these complexes the Ga(N(Ph)C(H))2 ligand behaves predominantly as an σ–donor. The contributions of the electrostatic interaction terms ΔEelstat are significantly larger in all gallyl complexes than the covalent bonding ΔEorb term. The absolute values of the ΔEint and ΔE(De) contributions to the M–Ga bonds display a V-like trend, with a minimum at the silver complex.