Quantum chemical insight into C–H⋯F bonding interactions between noncovalently bonded ion-pairs in N-heterocyclic carbene complexes of gold(I) [(NHC*)2Au]+[PF6]−and gold(III) [(NHC*)2AuCl2]+[PF6]−

•New theoretical insights into ion-pairs interactions in ionic gold complexes.•Carbene ligand of gold cation fragments donates 0.20 electron to the [PF6]− anion.•Bonding between ion-pairs has covalent characters 14.5%–17.4% in ionic complexes.•Au–C(NHC*) bond distances are longer in catonic fragments than in ionic complexes.•BDE of Au–C(NHC*) bond in [(NHC*)2Au]+ is greater than in [(NHC*)2AuCl2]+.

New insights into ion-pairs interactions in N-heterocyclic carbene complexes of gold(I) [(NHC*)2Au]+[PF6]− and gold(III) [(NHC*)2AuCl2]+[PF6]− (NHC* = 1-methyl-2-pyridin-2-yl-2H-imidazo[1,5-a]pyridine-4-ylium hexafluorophosphate) have been investigated at DFT and DFT-D3(BJ) level of theory with density functionals BP86 and PBE with particular emphasis on the (i) bonding energy analysis between anion [PF6]− and cations [(NHC*)2Au]+, [(NHC*)2AuCl2]+ and (ii) effects of the non-covalent interactions between ion-pairs on the structures and the nature of Au–C(NHC*) bond in ionic complexes [(NHC*)2Au]+[PF6]−, [(NHC*)2AuCl2]+[PF6]− and as well as in cationic [(NHC*)2Au]+, [(NHC*)2AuCl2]+ complexes. The hydrogen-bonding interactions are stronger in Au(III) complex [(NHC*)2AuCl2]+ [PF6]− (II) than in Au(I) complex [(NHC*)2Au]+ [PF6]− (I). The carbene ligands donate about 0.20 electronic charge to the [PF6]− anion. The contributions of the electrostatic interaction ΔEelstat are significantly greater than the covalent bonding ΔEorb interaction. The bonding between ion-pairs has covalent character 17.4% in (I) and 14.5% in (II). The values of BDEs are depends on the choice of density functionals and follow the order BP86 < PBE < PBE-D3(BJ). The contribution of orbital interactions to the total attractive interactions for the Au–C(NHC*) bonds in cationic fragments [(NHC*)2Au]+ and [(NHC*)2AuCl2]+ varies from 27.8% to 36.7% and is higher for Au(III) complexes.

Graphical abstractNew insights into ion-pairs interactions through the C–H⋯F hydrogen bonding in N-hetereocyclic carbene complexes of gold(I), [(NHC*)2Au]+ [PF6]− and gold(III), [(NHC*)2AuCl2]+ [PF6]− have been investigated at DFT and DFT-D3(BJ) level of theory. The bonding between ion-pairs has covalent character 17.4% in I and 14.5% in II.Figure optionsDownload full-size imageDownload as PowerPoint slide