Polynuclear Nickel(II) Complexes:  Preparation, Characterization, Magnetic Properties, and Quantum-Chemical Study of [Ni₅(OH)(Rbta)₅(acac)₄(H₂O)₄] (RbtaH = Benzotriazole and 5,6-Dimethylbenzotriazole)

Abstract

The preparation and properties are described of two related NiII 5 clusters. The reactions of [Ni(acac)2(H2O)2] (acacH = acetylacetone) with benzotriazole (btaH) and 5,6-dimethylbenzotriazole (5,6diMebtaH) in refluxing Me2CO in the presence of H2O leads to the isolation of [Ni5(OH)(bta)5(acac)4(H2O)4] (1) and [Ni5(OH)(5,6diMebta)5(acac)4(H2O)4] (2) in 70−75 and 40−50% yields, respectively. Complex 1·4Me2CO·0.5C6H14 crystallizes in the triclinic space group P1̄ with (at 25 °C) a = 13.885(1) Å, b = 12.013(1) Å, c = 25.611(2) Å, α = 89.02(1)°, β = 104.76(2)°, γ = 111.78(1)°, and Z = 2. Complex 2·4Me2CO crystallizes in the monoclinic space group C2/c with (at 25 °C) a = 19.085(3) Å, b = 20.142(3) Å, c = 22.574(4) Å, β = 103.30(1)°, and Z = 4. The NiII assemblies of 1 and 2 are composed of a tetrahedral arrangement of four six-coordinate metal ions centered on the fifth. Each of the five η1:η1:η1:μ3 benzotriazolate ligands spans an edge of the Ni4 tetrahedron. The OH- ion bridges three NiII ions and spans the sixth edge of the tetrahedron. A chelating acac- ion and a terminal H2O molecule complete the coordination sphere of each peripheral metal. Variable-temperature magnetic susceptibility data (5.0−295 K), obtained for 1 and 2, show antiferromagnetic interactions for both of them. The data are interpreted using a five-J model, which is based upon the hierarchy of algebras approach. Least-squares fitting of the data gives exchange parameters J for the interactions between the benzotriazolate-bridged peripheral NiII ions in the range from −3.9 to −10.7 cm-1, and for those between the central ion and the peripheral ones in the range from −3.1 to −6.1 cm-1; the J value for the interaction between the O-bridged peripheral nickels is −39.6 cm-1 for 1 and −43.2 cm-1 for 2. Magnetization data are in line with an intermediate spin ground state [S = 0, S = 1] for both clusters. An orbital interpretation of the coupling is proposed.

The “periodic table” of benzotriazoles: Uranium(VI) complexes

“…Crystallographic data for 1, 2, 3 and 4 · diMebtaH · MeCN have been deposited with the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax + 44 1223 336 033; e-mail: Table S2, thin cyan lines), extended parallel to the [1][2][3][4][5][6][7][8][9][10] crystallographic direction in the crystal structure of complex 2. b) The U2-containing molecules form chains through intermolecular π-π (dark green lines) and "non-classical" H-bonding interactions (C13-H13⋯O6, Table S2, thin cyan lines), extended parallel to the b axis. These chains cross each other at points above and below the 6MebtaH ligands creating the 3D structure shown in c and resulting in stacks of ligands presented in d. Light green, yellow and dark green thick lines indicate the three different types of π-π overlaps in the structure of the complex, shown in e, f and g, respectively, with the corresponding distances and angles between the planes being 3.50 Å and 0°(e), 3.37 Å and 5.5°(f), and 3.44 Å and 0°(g).…”

“…Over the last 30 years or so, we [1][2][3][4][5][6][7][8] and other groups [8][9][10][11][12][13][14][15][16][17] have been exploring the coordination chemistry of benzotriazoles. Research in this area ranges from efforts to model the corrosion inhibition of some metals (particularly Cu and its alloys) by benzotriazoles [18], to the synthesis of benzotriazolato coordination clusters [2,[4][5][6][7]9,11,13,15] and polymers [1,3,12,14,16,17] with esthetically pleasing structures and exciting physical properties. Although the use of this family of ligands has been investigated widely in 3d- [1-11, 13-15,17] and 4f-metal [12,16] chemistry, their employment in the chemistry of 5f-metal ions has completely been ignored.…”

“…1) that are present in 1-3 and 4 · diMebtaH · MeCN present similarities and characteristic differences. Complex 2 contains two structurally similar, crystallographically independent [UO 2 (NO 3 ) 2 (6MebtaH) 2 The differences of the four complexes concern the relative orientations of the benzotriazole ligands. In compounds 1, 2 and 3, the benzene rings of the ligands are at opposite sides of the molecules (Fig.…”

“…S9-S11) of the uranyl complexes 1, 2 and 4 · diMebtaH · MeCN in d 6 -DMSO reveal that these compounds decompose in solution to release the benzotriazole ligand; the spectra of the complexes are identical with those of the corresponding free ligands Mebta, 5MebtaH and diMebtaH, respectively. For example, the spectrum of 1 shows a sharp singlet at δ 4.30, a triplet at δ 7.39, a triplet at δ 7.55, a doublet at δ 7.83 and a doublet at δ 8.01 ppm, with relative [1,2,3]triazole or simply benzotriazole (btaH; R_R΄_R΄΄_H). R, R΄ and R΄΄ can be non-donor (Me, Cl, NO 2 ,…) or donor (OH, COOH, CH 2 OH, CH 2 COOH,…) groups.…”

The Designed Assembly of Augmented Diamond Networks From Predetermined Pentanuclear Tetrahedral Units

“…It should be mentioned that similar pentanuclear tetrahedral structures have been reported for the copper complexes [Cu 5 (btz) 6 L 4 ] (L = tfpbd, trop, acac, ph/Me-pd, ph/ph-pd, C 4 H 3 S/CF 3 -pd) (tfpbdH = 4,4,4-trifluoro-1-phenyl-1,3-butanedione; tropH = tropolone; acacH = acetylacetone; ph/Me-pdH = 1phenyl-1,3-butanedione; ph/ph-pdH = 1,3-diphenyl-1,3-propanedione; C 4 H 3 S/CF 3 -pdH = 4,4,4-trifluoro-1-(2-thienyl-1,3-butanedione) [9] and the nickel complex [Ni 5 (OH)(Rbtz) 5 -(acac) 4 (H 2 O) 4 ]. [10] In view of the structural feature of the pentanuclear tetrahedron as well as the four apical M 2+ coordination sites, the nitrate groups and water molecules bonded to these apical sites might be replaceable by organic linkers that possess specific functionalities to give network structures with a desired shape, geometry, and rigidity. The pentanuclear clusters 1 and 2 also have the advantage of being readily soluble in common organic solvents such as methanol, ethanol, acetonitrile, and acetone.…”