“…Triangular structures corresponding to nine-membered rings (three metal atoms and six atoms of the ligands) are well-known and they were reported in the literature (Figure 1, left hand side), for instance, imidazolates with coinage metals [56], phenylenes (most examples correspond to o-tetrafluorophenylene) with mercury [57,58] and 1,2-dicarba-closo-dodecaboranes with gold(I) [59,60]. Pyrazolate ligands (Py) with coinage metals, forming regium bonds, are also common, in any oxidation state: Cu(I)/Cu(II), Ag(I) and Au(I)/Au(III) [56,[61][62][63][64][65][66]. Particularly, cyclic [Py-M(I)] 3 systems with M = Cu, Ag and Au were studied [67] and the experimental evidences of the (Py-Cu) 3 systems with simultaneous interactions of the three copper atoms with one hydroxyl group were recently reviewed [68].…”