Tri- (M = Cu-II) and hexanuclear (M = Ni-II, Co-II) heterometallic coordination compounds with ferrocene monocarboxylate ligands: Solid-state structures and thermogravimetric, electrochemical and magnetic properties

The synthesis and characterization of the hexanuclear [M-2(kappa O-O(2)CFc)(2)(mu-O(2)CFc)(2)(mu-H2O)(kappa N-2,N'-tmeda)(2)] (M-II = Ni, 5; Co, 6; Fc = ferrocenyl, (eta(5)-C5H4)(eta(5)-C5H5)Fe; tmeda = N,N,N',N'-tetramethylethylendiamine) and the trinuclear [Cu(kappa N-2,N'-tmeda)(kappa O-2,O'-O(2)CFc)(2) (2)] (7) coordination compounds are described. Compounds 5-7 were prepared by the consecutive reaction of ferrocene carboxylic acid (FcCO(2)H; 1) with [(Bu4N)-Bu-n]OH followed by treatment of in situ formed [(Bu4N)-Bu-n][FcCO(2)] with the metal salts [M(tmeda)(NO3)(2)] (M = Ni, 2; Co, 3; Cu, 4). The structures of 5-7 in the solid state were determined by single crystal X-ray diffraction analysis. Isostructural 5 and 6 crystallise in the triclinic P (1) over bar (5) and in the monoclinic space group P2(1)/n (6). The two M-II(tmeda) entities of 5 and 6 with M-II = Ni, Co, respectively, are syn, syn-bridged by two FcCO(2)(-) functionalities and one mu-bridging water molecule. Additionally, two FcCO(2)(-) ligands are kappa O-coordinated to each M-II ion to form octahedral MN2O4 coordination setups. A related MN2O4 coordination setup is observed for 7 as well, whereby the Cu-II ion is coordinated by two O(2)CFc and one tmeda ligand. Electrochemical investigations reveal that all individual Fc units of 5-7 are oxidized separately. Thermogravimetric analysis showed that 5 and 6 start to decompose at 110 and 125 degrees C and thus at significantly lower temperatures compared to 7 (200 degrees C). The mass residues obtained after decomposition are composed of Fe2O3, FeNi3 and Fe0.64Ni = Ni-0.36 (5), Fe and Co3O4 (6) and Cu2O and CuFeO2 (7), as determined by powder X-ray diffraction analysis (PXRD). Thermal susceptibility measurements of 5 and 6 determined a weak antiferromagnetic coupling in 5 and 6 with J = 1.1 K and J = 1.9 K, respectively. (C) 2017 Elsevier Ltd. All rights reserved.