New metal oxamates as precursors of low-dimensional heterobimetallics

The goal of this work was to synthesize new molecular bricks which could be used as precursors of heterobimetallic low-dimensional compounds. Along this line, four compounds have been synthesized and structurally characterized, namely (NBu(4))(2)[Ni(Cl(2)opba)] (1), (NBu(4))(2)[Cu(Cl(2)opba)] (2), (NBu(4))(5)[Mn(Cl(2)opba)(DMSO)(2)](4) (3), and Cu(en)(2)[Mn(Cl(2)opba)(H2O)(2)](2) . 2DMSO (4), with Cl(2)opba = (4,5-dichloro-o-phenylene)bis(oxamato), NBu(4) = tetra-n-butylammonium, en = ethylenediamine, and DMSO = dimethyl sulfoxide. Compounds 1 and 2 are isostructural; they crystallize in the monoclinic system, space group C2/c, Z = 4, with a = 18.708(2) Angstrom, b = 17.525(2) Angstrom, c = 14.763(9) Angstrom, and beta = 92.03(4)degrees for 1 and a = 18.928(2) Angstrom, b = 17.634(2) Angstrom, c = 14.704(9) Angstrom, and beta = 92.38(3)degrees for 2. 3 crystallizes in the tetragonal system, space group P(4) over bar2$(1)c, Z = 2, with a = 26.295(10) Angstrom and c = 12.342(7) Angstrom. The structure shows a random occupation of the metal site by Mn(III) and Mn(II) ions in 3/4 and 1/4 ratios, respectively. 4 crystallizes in the triclinic system, space group <P(1)over bar>, Z = 1, with a = 7.066(7) Angstrom, b = 11.844(1) Angstrom, c = 14.292(5) Angstrom, alpha = 105.64(2)degrees, beta = 97.67(5)degrees, and gamma = 102.13(3)degrees. The structure consists of (MnCuMnIII)-Cu-III-Mn-II trinuclear species, with Cu-O-Mn bridges involving oxygen atoms of the oxamato groups already linked to the metal atom. The magnetic properties of compounds 1-4 have been investigated and quantitatively interpreted. For 3, this magnetic investigation has been performed on a single crystal, which allows us to determine unambiguously the sign of the axial zero-field splitting parameter for the Mn(III) ion. The potentialities of these new molecular bricks have been discussed.