Chemistry at the apical position of square-pyramidal copper(II) complexes: synthesis, crystal structures, and magnetic properties of mononuclear Cu(II), and heteronuclear Cu(II)–Hg(II) and Cu(II)–Co(II) complexes containing [Cu(AA)(BB)]+ moieties (AA=acet

New families of mononuclear and heteropolynuclear complexes have been obtained by using [Cu(AA)(BB)]+ building-blocks (AA=acetylacetonate or salicylaldehydate; BB=1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine). The following mononuclear complexes have been structurally characterized: [Cu(acac)(Me2bipy)]ClO4 (1), [Cu(acac)(Me2bipy)(NCS)] (2), [Cu(acac)(phen)(NCS)] (3). In compound 1 the copper(II) exhibits a square planar geometry, while the stereochemistry of compounds 2 and 3 is square pyramidal, with the isothiocyanato ligand coordinated in the apical position. The reaction between 2 and HgCl2 affords a trinuclear complex, [{Cu(acac)(Me2bipy)(μ-NCS)}2Hg(SCN)2] (4). The reaction between 3 and HgCl2 leads to tetranuclear Cu2Hg2 compound, [{Cu(acac)(phen)(NCS)}2{(ClHg)2(NCS)2}] (5), with a unique structure, and to a trinuclear complex, [{Cu(acac)(phen)(NCS)}2Hg(SCN)2] (6). The structure of 5 consists of a {Hg2(NCS)2} ring on which two [Cu(acac)(phen)(NCS)] moieties are attached. In compounds 4, 5 and 6 the mercury atoms are tetracoordinated. By reacting [Cu(sal)(phen)(OClO3)] with (NEt4)2[Co(NCS)4], a heterohexanuclear compound is obtained: [{Cu(sal)(phen)(SCN)}2Co(NCS)2]2 (7), with the following topology of the metallic centers: Cu–Co–Cu–Cu–Co–Cu. The cobalt(II) ions in 7 are tetracoordinated by nitrogen atoms arising from two bridging and two terminal thiocyanato ligands. The central copper(II) ions are bridged by the phenoxo oxygen atom arising from the sal− ligand. The cryomagnetic properties of compounds 2–5 and 7 have been investigated and discussed. The magnetic behavior of compounds 2–5 has been ascribed to intermolecular exchange interactions mediated by the stacking interactions. The magnetic interaction between Cu(II) and Co(II) in 7 was found ferromagnetic (J=+0.6 cm−1), as theoretically predicted. The exchange interactions between the central copper(II) ions is antiferromagnetic (J=−5.8 cm−1).