Gold(I) Hydrides as Proton Acceptors in Dihydrogen Bond Formation.

Wavefunction and DFT calculations indicate that anionic dihydride complexes of Au form strong to moderate directed Au-H⋅⋅⋅H bonds with one or two HF, H O and NH prototype proton donor molecules. The largely electrostatic interaction is influenced by relativistic effects which, however, do not increase the binding energy. Very weak Au⋅⋅⋅H associations-exhibiting a corresponding bond path-occur between neutral AuH and HF units, although ultimately F becomes the preferred donor atom in the most stable structure. Increasing the hydridicity of AuH by attachment of an electron donating NHC ligand effects Au-H⋅⋅⋅H bonding of moderate strength only with HF, whereas competing Au⋅⋅⋅H interactions dominate for H O and NH . Rare η coordinated and HX (X=F or OH) associated H complexes are produced during interaction with a single ion of stronger acidity, H F or H O . Theoretically, reaction of excess [AuH ] as proton acceptor with H O or NH in 3:1 or 4:1 ionic ratios, respectively, affords H⋅⋅⋅H bonded analogues of Eigen-type adducts. Outstanding analytical relationships between selected bonding parameters support the integrity of the results.