An octa-nuclear nickel(II) pyrazolate cluster with a cubic Ni(8) core and its methyl- and n-octyl-functionalized derivatives.

The mol-ecular and crystal structure of a discrete [Ni(8)(μ(4)-OH)(6)(μ-4-Rpz)(12)](2-) (R = H; pz = pyrazolate anion, C(3)H(3)N(2) (-)) cluster with an unprecedented, perfectly cubic arrangement of its eight Ni centers is reported, along with its lower-symmetry alkyl-functionalized (R = methyl and n-oct-yl) derivatives. Crystals of the latter two were obtained with two identical counter-ions (Bu(4)N(+)), whereas the crystal of the complex with the parent pyrazole ligand has one Me(4)N(+) and one Bu(4)N(+) counter-ion. The methyl derivative incorporates 1,2-di-chloro-ethane solvent mol-ecules in its crystal structure, whereas the other two are solvent-free. The compounds are tetra-butyl-aza-nium tetra-methyl-aza-nium hexa-μ(4)-hydroxido-dodeca-μ(2)-pyrazolato-hexa-hedro-octa-nickel, (C(16)H(36)N)(C(4)H(12)N)[Ni(8)(C(3)H(3)N(2))(12)(OH)(6)] or (Bu(4)N)(Me(4)N)[Ni(8)(μ(4)-OH)(6)(μ-pz)(12)] (1), bis-(tetra-butyl-aza-nium) hexa-μ(4)-hydroxido-dodeca-μ(2)-(4-methyl-pyrazolato)-hexa-hedro-octa-nickel 1,2-di-chloro-ethane 7.196-solvate, (C(16)H(36)N)(2)[Ni(8)(C(4)H(5)N(2))(12)(OH)(6)]·7.196C(2)H(4)Cl(2) or (Bu(4)N)(2)[Ni(8)(μ(4)-OH)(6)(μ-4-Mepz)(12)]·7.196(ClCH(2)CH(2)Cl) (2), and bis-(tetra-butyl-aza-nium) hexa-μ(4)-hydroxido-dodeca-μ(2)-(4-octylpyrazolato)-hexa-hedro-octa-nickel, (C(16)H(36)N)(2)[Ni(8)(C(11)H(19)N(2))(12)(OH)(6)] or (Bu(4)N)(2)[Ni(8)(μ(4)-OH)(6)(μ-4-(n)Octpz)(12)] (3). All counter-ions are disordered (with the exception of one Bu(4)N(+) in 3). Some of the octyl chains of 3 (the crystal is twinned by non-merohedry) are also disordered. Various structural features are discussed and contrasted with those of other known [Ni(8)(μ(4)-OH)(6)(μ-4-Rpz)(12)](2-) complexes, including extended three-dimensional metal-organic frameworks. In all three structures, the Ni(8) units are lined up in columns.