Formation and Characterization of BeFe(CO) Anion with Beryllium-Iron Bonding.

Heteronuclear BeFe(CO) anion complex is generated in the gas phase, which is detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The complex is characterized to have a Be-Fe bonded Be-Fe(CO) structure with C symmetry and all of the four carbonyl ligands bonded on the iron center. Quantum chemical studies indicate that the complex has a quite short Be-Fe bond. Besides one electron-sharing σ bond, there are two additional, albeit weak, Be ← Fe(CO) dative π bonding interactions. The findings imply that metal-metal bonding between s-block and transition metals is viable under suitable coordination environment.