Group 6 Hexacarbonyls as Ligands for the Silver Cation: Syntheses, Characterization, and Analysis of the Bonding Compared with the Isoelectronic Group 5 Hexacarbonylates

The syntheses of the two novel complexes [Ag{Mo/W(CO)₆}₂]⁺[F-{Al(OR^F)₃}₂]⁻ (R^F=C(CF₃)₃) are reported along with their structural and spectroscopic characterization. The X-ray structure shows that three carbonyl ligands from each M(CO)₆ fragment bend towards the silver atom within binding Ag−C distance range. DFT calculations of the free cations [Ag{M(CO)₆}₂]⁺ (M=Cr, Mo, W) in the electronic singlet state give equilibrium structures with C₂ symmetry with two bridging carbonyl groups from each hexacarbonyl ligand. Similar structures with C₂ symmetry (M=Nb) and D₂ symmetry (M=V, Ta) are calculated for the isoelectronic group 5 anions [Ag{M(CO)₆}₂]⁻ (M=V, Nb, Ta). The electronic structure of the cations is analyzed with the QTAIM and EDA-NOCV methods, which provide detailed information about the nature of the chemical bonds between Ag⁺ and the {M(CO)₆}₂^q (q = −2, M = V, Nb, Ta; q = 0, M = Cr, Mo, W) ligands.