Do Aurophilic Interactions Compete against Hydrogen Bonds? Experimental Evidence and Rationalization based on Ab Initio Calculations.

[M(C6F5){N(H)=CPh2}] (M = Ag (1) and Au (2)) complexes have been synthesized and characterized by X-ray diffraction analysis. Complex 1 shows a ladder-type structure in which two [Ag-(C6F5){N(H)=CPh2}] units are linked by a Ag(I)-Ag(I) interaction in an antiparallel disposition. The dimeric units are associated through hydrogen bonds of the type N-H···Fortho. On the other hand, gold(I) complex 2 displays discrete dimers also in an antiparallel conformation in which both Au(I)-Au(I) interactions and N-H···Foho hydrogen bonds appear within the dimeric units. The features of these coexisting interactions have been theoretically studied by ab initio calculations based on four different model systems in order to analyze them separately. The interactions have been analyzed at HF and MP2 levels of theory showing that, in this case, even at larger distances. The Au(I)-Au(I) (I) interaction is stronger than Ag(I)-Ag(I) and that N-H···F hydrogen bonding and Au(I)-Au(I) contacts have a similar strength in the same molecule, which permits a competition between these two structural motifs giving rise to different structural arrangements