Group Six Hexacarbonyls as Ligands for the Silver Cation: Syntheses, Characterization and Analysis of the Bonding compared to the isoelectronic Group 5 Hexacarbonylates.

The syntheses of the two novel complexes [Ag{Mo/W(CO)6}2]+[F-{Al(ORF)3}2]- (RF = 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 elec-tronic singlet state give equilibrium structures with C2 symmetry with two bridging carbonyl groups of 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+ ligands.