1,1-Digoldallylium Complexes: Diaurated Allylic Carbocations Indicate New Prospects of the Coordination Chemistry of Carbon

Reacting (NHC)­(cyclopropenyl)­gold­(I) complexes with cationic gold complexes [(IPr)­AuX] afforded extremely reactive allylium-1,1-diido-bridged digold intermediates. We prove the existence and constitution of this structure with FT-ICR-MS/MS, NMR, and UV–vis–NIR experiments and isolated the nucleophilic addition product [(Me)­(Ph)­(CCHC)­{Au­(IPr)}2­(SOMe2)]­NTf2 with DMSO. Our computational investigation unveiled that the bonding situation of this μ-allylium-1,1-diido digold domain was best described as a three-center–four-electron bond with a π-backbond. The valence orbitals showed extreme delocalization and strong π-interactions between the three centers Au1–C1–Au2. The bridging carbon atom C1 was best described as trigonal planar sp-hybridized carbon in this structure. Excitation succeeded in UV–vis–NIR measurements with energies as low as near-IR radiation.