Aurophilicity-triggered assembly of novel cyclic penta- and hexanuclear gold(I) complexes with rigid anionic NHC-type ligands.

The products of the reaction between N,N'-diphosphanylimidazol-2-ylidene (P-C-P) and gold(I) precursors depend on the nature of the anions associated with the latter. In contrast to the reported reaction with [Au(tht)2(OTf)], the use of [AuCl(tht)] led to the new hexanuclear complex 1, which features a Au6(μ3-P-C,κC,κN,κP)3 skeleton. The reaction of lithium imidazolide (P-C-Li) and [AuCl(tht)] also afforded 1, together with an unusual salt of the general formula [Au5Cl(μ3-P-C-κP,κC,κN)3]2[AuCl2]2 (2), which contains Au5(μ3-P-C-κP,κC,κN) subunits. In the solid state, one of these Au5 cations is associated with an AuCl2 anion, while two other cations interact through their unique dicoordinated N-Au-N center with a AuCl2 anion, with the charge of the resulting monocation being compensated for by another AuCl2 anion to give a Au12 salt. Remarkably, the latter displays seven different bonding types at Au(I): C-Au-C, N-Au-N, P-Au-P, Cl-Au-Cl, C-Au-N, P-Au-Cl, and Au···Au.