Decentralized Metal–Metal Bonding in the AuNi(CO)₄^– Anion Described Equally Well with Dative Bonding as with Electron-Sharing Bonding

The heterodinuclear AuNi(CO)₄^– complex is scrutinized in the gas phase by using mass-selected anionic photoelectron velocity-map imaging spectroscopy in conjunction with theoretical computations. The ground state of AuNi(CO)₄^– is characterized to have an Au–Ni bonded structure, consisting of an AuCO fragment attached to the Ni center of the Ni(CO)₃ fragment. Comprehensive quantum chemical studies reveal that the AuNi(CO)₄^– complex at equilibrium structure features a decentralized bonding scenario, where the exotic metal–metal σ bonding may be equally well described with dative bonding as with electron-sharing bonding between two fragments.