Nickel benzoate trihydrate (1) was prepared in singlecrystalline form by the reaction of nickel carbonate with benzoic acid in boiling aqueous solution. Its crystal structure comprises positively charged [Ni(Bz)(H2O)2]n n+ chains, benzoate anions and one independent water molecule of solvation. The hexacoordinated Ni(II) centres in the chains are triply bridged by one syn-syn carboxylato and two aqua bridges. Adjacent chains are linked by O-H•••O hydrogen bonds [O•••O distances in the range 2.647(3) -2.684 (3) Å] through solvate water molecules and benzoate anions. Thermal analysis revealed that 1 is stable up to 100 °C; further heating leads to full dehydration accompanied by an additional decomposition reaction, as characterized by IR spectra of the intermediates. Geometrical features about the Ni centers are compared to similar features at the active sites of urease. The effective magnetic moment per formula unit µeff has a value of 3.17 µB at room temperature and upon cooling reaches a maximum value of 12.39 µB at T = 4.6 K, indicating ferromagnetic coupling between the nearest Ni(II) atoms [3.0671(1) Å] within the chains; at lower temperature this is counteracted by zero-field splitting.
Reactions of Co(OH)2 with the Schiff base bis(2-hydroxy-3-methoxybenzylidene)ethylenediamine, denoted H2(o-van-en), under different conditions yielded the previously reported complex aqua[bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]cobalt(II), [Co(C18H18N2O4)(H2O)], 1, under anaerobic conditions and two polymorphs of [μ-bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]bis{[bis(3-methoxy-2-oxidobenzylidene)ethylenediamine]cobalt(III)} acetonitrile tetrasolvate, [Co2(C18H18N2O4)3]·4CH3CN, i.e. monoclinic 2 and triclinic 3, in the presence of air. Both novel polymorphs were chemically and spectroscopically characterized. Their crystal structures are built up of centrosymmetric dinuclear [Co2(o-van-en)3] complex molecules, in which each CoIII atom is coordinated by one tetradentate dianionic o-van-en ligand in an uncommon bent fashion. The pseudo-octahedral coordination of the CoIII atom is completed by one phenolate O and one amidic N atom of the same arm of the bridging o-van-en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvent molecules. The polymorphs differ in the packing orders of the dinuclear [Co2(o-van-en)3] complex molecules, i.e. alternating ABABAB in 2 and AAA in 3. In addition, differences in the conformations, the positions of the acetonitrile solvent molecules and the pattern of intermolecular interactions were observed. Hirshfeld surface analysis permits a qualitative inspection of the differences in the intermolecular space in the two polymorphs. A knowledge-based study employing Full Interaction Maps was used to elucidate possible reasons for the polymorphism.
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