Cationic Au(i) complexes (2, 5 and 8) supported by N-heterocyclic carbene, silylene and germylene ligands were prepared and their potential as catalysts in glycosidation chemistry has been evaluated. Insights into the mechanism are provided using DFT studies. Practical application of them as catalysts was achieved by the synthesis of the branched pentamannan core of the HIV-gp120 envelope under mild conditions.