Theoretical investigations on the H-2-AuX (X = F-I) series have been performed at the CCSD(T) theoretical level with extended basis sets and the T-shaped stable structures were found. Mechanisms of Au-X and Au center dot center dot center dot H-2 interactions were explored by NBO analysis, natural resonance theory, electron density deformation analyses, delocalization index and visualized by reduced density gradient analyses. Periodic trends are found in the bond length, stability and covalent nature of the Au-X interactions. For Au center dot center dot center dot H-2 interactions, the delocalization index values and the electron density difference analysis show the "charge-shift covalent" type of interaction. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.