Computational investigation of Au...H hydrogen bonds involving neutral AuI N-heterocyclic carbene complexes and amphiprotic binary hydrides

Groenewald, Ferdinand ; Raubenheimer, Helgard G. ; Dillen, Jan ; Esterhuysen, Catharine (2019-04-26)

CITATION: Groenewald, F. et al. 2019. Computational investigation of Au...H hydrogen bonds involving neutral AuI N-heterocyclic carbene complexes and amphiprotic binary hydrides. Journal of Molecular Modeling, 25: 135, doi:10.1007/s00894-019-4018-3.

The original publication is available at https://www.springer.com/journal/894

Article

In this computational study we investigate the ability of various neutral R-AuI-NHC (NHC = N-heterocyclic carbene) complexes [R = H, CH3, Cl, OH] to form hydrogen bonds with the amphiprotic binary hydrides NH3, H2O and HF. Optimised geometries of the adducts calculated at various levels of theory all exhibit Au···HX hydrogen bonds. In adducts of complexes containing NHC ligands with α -N–H units (NH)carbene···XH interactions also exist, yielding hydrogen-bonded rings with graph-set notation R22(6) that correspond to pseudo chelates with k²C,H coordination. AIM analysis at the MP2/aug-cc-pVTZ-pp level of theory indicates that the (NH)carbene···XH hydrogen bonds are generally stronger than the Au···HX interactions, except for those involving HF. The Au···HX interactions vary with the Lewis basicity of the Au(I) centre as a result of the nature of the R ligand, while the (NH)carbene···XH hydrogen bonds are unaffected by R. Energy Decomposition Analysis at the BP86/TZP level of theory identifies the origin of this difference as the greater component of polarisation involved in Au···HX interactions. Replacing the α(N)Hs with methyl groups prevents formation of a strong (NH)carbene···XH interaction, thus reducing the overall stabilisation of the adducts.

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