Preparation, First Structure Analysis, and Magnetism of the Long‐Known Nickel Benzoate Trihydrate – A Linear Ni···Ni···Ni Polymer and Its Parallels with the Active Site of Urease

Abstract

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.

Exceptionally slow magnetic relaxation in cobalt(ii) benzoate trihydrate

“…1 left). The same type of crystal structure was reported for the isostructural Ni(II) analogue 13 and for the similar Cu(II) complex which, however, crystallizes in a different space group. 14 We note that the chain-like arrangements of Co(II) atoms were reported in both polymorphs of anhydrous Co(II) benzoate, where the chains are neutral, unlike the present case; in the monoclinic polymorph the zig-zag chains are formed by alternating octahedra and bicapped tetrahedra (the additional two Co-O bonds have a common length of 2.540(2) Å (2x)) linked by common edges, 9 while in the orthorhombic form the double zig-zag chains consist of alternating octahedra and tetrahedra linked via common vertices.…”

“…The most characteristic absorption bands are those originating from asymmetric and symmetric ν(COO) vibrations; these were found at 1539 and 1495 cm −1 (asymmetric ones), and at 1420 and 1383 cm −1 for the symmetric ones. In the spectrum of the isostructural Ni(II) complex the corresponding bands were observed at 1547, 1484 and 1424, 1384 cm −1 , respectively, 13 while for anhydrous cobalt benzoate somewhat different values were reported: 1541 (ν as (COO)) and 1433 cm −1 (ν s (COO)) 8 or 1522 cm −1 (ν as (COO)), and 1411 and 1380 cm −1 (ν s (COO)). 9…”

“…Due to the triple bridging, neighbouring Co(II) atoms are relatively close to each other, with a Co⋯Co distance of 3.1159(2) Å; this value is longer than the corresponding Ni⋯Ni separation of 3.0671(1) Å in the isostructural nickel complex. 13 Somewhat longer Co⋯Co distances were found in the monoclinic (3.145(1) Å) and orthorhombic (3.1657(4) and 3.1957(4) Å) forms of anhydrous cobalt(II) benzoate. 9,10a Alternatively, the chains in 1 can be viewed as formed of {CoO 6 } octahedra with common edges; neighbouring octahedra are canted (Fig.…”

“…10c Recently, the isostructural nickel(II) benzoate trihydrate was reported. 13 [Cu(Bz)(H 2 O) 2 ]Bz•H 2 O has an analogous chain-like arrangement of Cu(II) atoms bridged by benzoato and aqua ligands with marked differences in Cu-O bond distances due to the Jahn-Teller effect. 14 Even small changes in the chemical composition, such as the presence or absence of solvent molecules in the crystal lattice, can induce significant differences in the dynamics of the slow magnetic relaxation.…”

Synthesis, crystal structure, infrared spectrum, and thermal properties of [Ni(1,10-phenanthroline)3](fumarate)·9H2O complex with hydrogen bonded supramolecular layers involving fumarate anions

“…Surprisingly, to our knowledge, only two complexes from these systems have been structurally characterized up to now, namely [Ni 2 (phen) 4 (fum)(H 2 O) 2 ](fum)•16H 2 O containing a dinuclear complex cation (Ma et al, 2003) and ionic [Ni(phen) 3 ](fum)•2H 2 fum•4H 2 O with solvate molecules of fumaric acid (Lin and Zheng, 2004). Within a deeper study of low-dimensional Ni(II) complexes (Černák et al, 2009;Čerák et al, 2015;Vráblová et al, 2016), system Ni(II)-phen-fum was added to our research. As the result of our experiments, the title complex 1 was isolated in single crystal form in case of full occupancy of the coordination sites around the Ni(II) central atom by blocking ligand (3x phen) and its synthesis, IR spectroscopic characterization and crystal structure as well as its thermal properties are reported here.…”