Spectroscopic and Computational Evidence of Intramolecular AuIH+-N Hydrogen Bonding

Despite substantial evidence of short AuH-X contacts derived from a number of X-ray structures of Au-I compounds, the nature of (AuH)-H-I bonding in these systems has not been clearly understood. Herein, we present the first spectroscopic evidence for an intramolecular (AuH+)-H-I-N hydrogen bond in a [Cl-Au-L](+) complex, where L is a protonated N-heterocyclic carbene. The complex was isolated in the gas phase and characterized with helium-tagging infrared photodissociation (IRPD) spectra, in which H+-N-mode-derived bands evidence the intramolecular (AuH+)-H-I-N bond. Quantum chemical calculations reproduce the experimental IRPD spectra and allow to characterize the intramolecular AuH+-N bonding with a short r(AuH) distance of 2.17 angstrom and an interaction energy of approximately -10kcalmol(-1). Various theoretical descriptors of chemical bonding calculated for the AuH+-N interaction provide strong evidence for a hydrogen bond of moderate strength.