Coordination of a Pyrazole Functionalized Acetylacetone to the Coinage Metal Cations: An Unexpected Packing Similarity and a Trinuclear Cu^II/Au^I Complex

The heteroditopic molecule HacacMePz combines a Pearson hard acetylacetone donor site with a softer trimethylpyrazole and shows site selectivity towards the coinage metal cations. The coordination of the N donor function was achieved towards Ag^I and Au^I, leading to the salt [Ag(HacacMePz)₂]PF₆ (<b>1</b>) and the neutral complex [AuCl(HacacMePz)] (<b>2</b>). In either case, linear coordination about the coinage metal cation is observed. Interestingly, both complexes crystallize in space group <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mi>b</mi><mi>c</mi><mi>a</mi></mrow></semantics></math></inline-formula> with similar cell parameters. The two solids do not qualify as isostructural, albeit being closely related in real and reciprocal space. To probe the ligand’s ability for the envisaged synthesis of bimetallic coordination polymers, the mixed-metal Cu^II/Au^I complex [Cu(acacMePzAuCl)₂] (<b>3</b>) was obtained. In this mixed-metal oligomer, the central Cu^II cation adopts a square planar coordination environment with two O,O^′-coordinated acacMePz⁻ ligands, whose softer N donor sites are saturated with a AuCl moiety.