A nickel(II) di-μ2-phenolato bridged dinuclear complex:: Weak antiferromagnetic interactions in nickel(II) dimers

[Ni(dpmap)(H2O)](2)(ClO4)(2) center dot 3(CH3)(2)CO, a dinuclear nickel(II) complex of 2-{[[Di(2-pyridyl)methyl](methyl)amino]methyl} phenol, dpmapH has been synthesized. X-ray diffraction analysis indicates that each nickel(II) center is coordinated by two dpmap ligands and two water molecules. The two nicke(II) centers are bridged by mu(2)-phenolate oxygen donors. The two nickel(II) centers each have distorted octahedral symmetry, comprised of cis-coordinated pyridyl nitrogen, a tert-amino nitrogen and a bridging phenolate oxygen. Hexacoordination is completed by an oxygen atom of a water molecule. The water molecules at each nickel center are trans- to each other across the Ni2O2 basal plane. The two Ni atoms are separated by 3.170 angstrom. Variable temperature and field magnetic measurements reveal weak antiferromagnetic coupling (J = -0.85 cm(-1)) between the nickel(II) centers. The T-chi m versus T data were fit using a model, derived from Kambe's method and include zero-field splitting (D = -1.6 cm(-1)). Broken-symmetry density functional theory (BS-DFT) indicates that the weak antiferromagnetism is due to electron density delocalization onto the ligand framework and the inability of the out-of plane phenolato-bridges to mediate superexchange. (C) 2006 Elsevier B.V. All rights reserved.