Non-covalent interactions at bis(pyrazole)silver(i) or -gold(i) cations

Abstract

The reaction of AgBF₄ with two equivalents of pzH (pyrazole) or dmpzH (3,5-dimethylpyrazole) leads to [Ag(pzH)₂]BF₄ or [Ag(dmpzH)₂]BF₄. The reaction of [AuCl(tht)] with an equimolar amount of dmpzH in refluxing hexane leads to [Au(dmpzH)₂][AuCl₂]. Similar complexes [Au(dmpzH)₂]A (A = BF₄ or NO₃) are obtained from [AuCl(tht)], two equivalents of dmpzH, and AgBF₄ or AgNO₃. The complexes [Ag(dmpzH)₂]BF₄ and [Au(dmpzH)₂]A (A = [AuCl₂], BF₄ or NO₃) crystallize as ionic pairs where the NH groups of the pyrazoles are involved in short cation–anion interactions. The nitrate complex crystallizes as a dimer, where both molecules are supported by π-stacking interactions between the pyrazole rings. The crystal structure of [Ag(pzH)₂]BF₄ reveals a three dimensional array of cations and anions. In solution, [Ag(pzH)₂]BF₄ and [Ag(dmpzH)₂]BF₄ undergo intermolecular processes involving pyrazole decoordination, and behave as 1/1 electrolytes; whereas dimethylpyrazole gold complexes do not display any dynamic behavior, and show cation–anion association also in solution.