Can Silver(I) Act as a Hydrogen-Bond Acceptor? Spectroscopic and Computational Exploration of the Ag···H+ Bonds in the Gas Phase and in Solvent.

Recent experiments highlighted the significance of Au(I)···H interactions in the structures of Au(I)-containing materials as well as in catalysis. However, they also raised the important question of whether similar interactions could be observed for Ag(I) and Cu(I) analogues of Au(I). Herein, we present experimental and computational evidence for the formation of hydrogen bonds between the Ag(I) center and the dimethylammonium group of protonated bis(1-adamantyl)(2-(dimethylamino)phenyl)phosphine ligand (1). We support this in the gas phase by employing infrared (IR) photodissociation spectroscopy correlated with quantum chemical (QC) computations. For the Ag(I) complex (1AgCl2H) in solution, we show by correlating the nuclear magnetic resonance data and QC calculations that the formation of the Ag(I)···H bond competes with the formation of the Cl···H bond depending on the polarity of the environment. We evaluated interaction energies between the dimethylammonium group and the central metal across the coinage metal series (Au/Ag/Cu) using the relativistic CCSD(T) method. Furthermore, employing wave function analysis, we gained qualitative insight into Au/Ag/Cu···H bonding at the electronic level. The definition of Ag(I)···H interactions thus extends horizons in silver(I) chemistry.