HETERONUCLEAR TRINUCLEAR COMPLEX-IONS OF THE TYPES [CU(II)(CR(A)4(OH)2)2]4+ AND [CU(II)(CO(A)4(OH)2)2]4+

The syntheses and characterization of a series of trinuclear complex ions of the types [Cu(II){Cr(A)4(OH)2}2]4+ and [Cu(II){Co(A)4(OH)2}2]4+, where (A)4 represents the nitrogen donors from one tetradentate, two bidentate, or four monodentate ligands, are described. The complex [Cu{(OH)2Cr(bispictn)}2](ClO4)4-2H2O (1a), where bispictn is N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, C15H20N4, crystallizes in space group P2(1)/c of the monoclinic system with four trinuclear species in a cell of dimensions a = 14.650 (11) angstrom, b = 14.226 (8) angstrom, c = 22.754 (14) angstrom, and beta = 108.32 (6)-degrees. The structure has been refined to a final R-factor of 0.0534 based on 4825 observed independent reflections. The central copper(II) atom is bonded to the oxygen atoms of four bridging hydroxo groups and exhibits axial coordination to a perchlorate anion leading to approximate square pyramidal geometry. The hydroxo groups bridge, in pairs, to two chromium atoms. The complex [Cu{(OH)2Cr(cyclam)}2](ClO4)4.4H2O (7a), where cyclam is 1,4,8,11-tetraazacyclotetradecane, crystallizes in space group P2(1)/c of the monoclinic system with four trinuclear species in a cell of dimensions a = 8.770(1) angstrom, b = 20.791(3) angstrom, c = 11.833(2) angstrom, and beta = 99.47(1)-degrees. The structure has been refined to a final R-factor of 0.0593 based on 3415 observed independent reflections. The copper atom exhibits (4 + 2) axially elongated octahedral geometry, the in-plane ligands being the four oxygen atoms of the hydroxo bridges while the axial sites are occupied (at much longer distances) by the oxygen atoms of perchlorate anions. The hydroxo groups bridge, in pairs, to the two chromium atoms. Magnetic susceptibility data for both complexes indicate the presence of a ferromagnetic interaction between the central copper(II) ions and the chromium(III) centers, leading to an S = 7/2 ground state.