First Evidence of Au-CH3 Bonding in Superatomic Au13 Clusters

Abstract

Chemical reduction of a dinuclear [(di-NHC)Au₂Cl₂(di-NHC)] complex (NHC=imidazol-2-ylidene), using excess NaBH₄ as reducing agent in presence of dichloromethane (DCM) as solvent, provides a molecular cluster with formula [Au₁₃(di-NHC)₅(CH₃)₂]Cl₃, exhibiting covalent bonds between gold atoms of the cluster core and methyl groups. The presence of Au-CH₃ bonds, which is unprecedented in gold cluster chemistry, is confirmed by high resolution mass spectrometry (HRMS), NMR and the reactivity of the reported cluster in solid state. The cluster has been further characterized with single crystal X-ray diffractometry, UV-Vis and emission spectroscopies. The cluster displays remarkable stability in solution, which is indicative of the possible role played by Au-CH₃ bond formation in the conventional preparation of molecular gold nanoclusters by reduction with excess borohydride in DCM.