Cobalt(II) and cadmium(II) square grids supported with 4,4′-bipyrazole and accommodating 3-carboxyadamantane-1-carboxylate

Abstract

In poly[[bis(μ-4,4'-bi-1H-pyrazole-κ(2)N(2):N(2'))bis(3-carboxyadamantane-1-carboxylato-κO(1))cobalt(II)] dihydrate], {[Co(C12H15O4)2(C6H6N4)2]·2H2O}n, (I), the Co(2+) cation lies on an inversion centre and the 4,4'-bipyrazole (4,4'-bpz) ligands are also situated across centres of inversion. In its non-isomorphous cadmium analogue, {[Cd(C12H15O4)2(C6H6N4)2]·2H2O}n, (II), the Cd(2+) cation lies on a twofold axis. In both compounds, the metal cations adopt an octahedral coordination, with four pyrazole N atoms in the equatorial plane [Co-N = 2.156 (2) and 2.162 (2) Å; Cd-N = 2.298 (2) and 2.321 (2) Å] and two axial carboxylate O atoms [Co-O = 2.1547 (18) Å and Cd-O = 2.347 (2) Å]. In both structures, interligand hydrogen bonding [N...O = 2.682 (3)-2.819 (3) Å] is essential for stabilization of the MN4O2 environment with its unusually high (for bulky adamantanecarboxylates) number of coordinated N-donor co-ligands. The compounds adopt two-dimensional coordination connectivities and exist as square-grid [M(4,4'-bpz)2]n networks accommodating monodentate carboxylate ligands. The interlayer linkage is provided by hydrogen bonds from the carboxylic acid groups via the solvent water molecules [O...O = 2.565 (3) and 2.616 (3) Å] to the carboxylate groups in the next layer [O...O = 2.717 (3)-2.841 (3) Å], thereby extending the structures in the third dimension.

Cobalt(II) chloride complexes with 1,1′-dimethyl-4,4′-bipyrazole featuring first- and second-sphere coordination of the ligand

“…Considering bipyrazoles as simple bitopic coordination links between metal ions (Boldog et al, 2002;Tâ bâ -caru et al, 2012), the NH sites are also important. They commonly provide a peculiar hydrogen bonding with anionic co-ligands (Nazarenko et al, 2013;Ponomarova et al, 2013), thus appreciably contributing to the overall structure. Therefore, the substitution at the N 1 atom of the pyrazole ring could be of primary significance for fine-tuning the properties of the ligands in view of their ability to bridge metal ions and sustain secondary interactions.…”