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- R pz) 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- R pz) 12 ] 2- complexes, including extended three-dimensional metal-organic frameworks. In all three structures, the Ni 8 units are lined up in columns.