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 (

摘要

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)(Me(2)bipy)]ClO4 (1), [Cu(acac)(Me(2)bipy)(NCS)] (2), [Cu(acac) (phen)(NCS)l (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)(Me(2)bipy)(mu-NCS)}(2)Hg(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)}(2)Hg(SCN)(2)] (6). The structure of 5 consists of a {Hg-2(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)}(2)Co(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)). (C) 2004 Elsevier B.V. All rights reserved.