Spectroscopic and Computational Evidence of Intramolecular Au I ⋅⋅⋅H + −N Hydrogen Bonding

Abstract

Despite substantial evidence of short Au⋅⋅⋅H−X contacts derived from a number of X‐ray structures of Au I compounds, the nature of Au I ⋅⋅⋅H bonding in these systems has not been clearly understood. Herein, we present the first spectroscopic evidence for an intramolecular Au I ⋅⋅⋅H + −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 Au I ⋅⋅⋅H + −N bond. Quantum chemical calculations reproduce the experimental IRPD spectra and allow to characterize the intramolecular Au⋅⋅⋅H + −N bonding with a short r Au⋅⋅⋅H distance of 2.17 Å and an interaction energy of approximately −10 kcal mol −1 . Various theoretical descriptors of chemical bonding calculated for the Au⋅⋅⋅H + −N interaction provide strong evidence for a hydrogen bond of moderate strength.