Magnetostructural correlations in μ-pyrazolato-μ-acetato dinickel(II) complexes: Subtle effects of acetate tilting

A series of dinickel acetato complexes [LNi2(OAc)(solvent)(x)](ClO4)(2) (1-3, 5) as well as related complexes [LNi2(OAc)(2)](OAc) (4) and [LNi2(OAc)( NO3)(2)] (6), all derived from three pyrazolate-based binucleating ligands, have been prepared and characterized by X-ray crystallography. The solid state structures reveal different acetate binding modes (mu(1,3)-bridging and bidentate chelating) plus severe twisting and tilting of the mu(1,3)-acetate bridges with respect to their bimetallic scaffolds, reflecting the great flexibility of carboxylate coordination. Magnetic properties of all six complexes have been investigated, and the strength of antiferromagnetic coupling is discussed in the light of the structural differences, suggesting a magneto-structural correlation for acetato-bridged complexes. (C) 2008 Elsevier B. V. All rights reserved.