A novel copper dimer structure
The reaction of bis(N-ethyl-2-hydroxybenzylideniminato)nickel(II), Ni(etsal)2, with copper(II) nitrate produced the title complex [Cu(etsal)NO3]2, in the form of crystals large enough for structure determination by x-ray diffraction. Crystal data: P21/c, Z = 2, a = 9.678 (6) Å, b = 9.82 (1) Å, c = 16.267 (7) Å, β = 134.69(4)°, V= 1100 Å3;, R = 3.8%, 1425 reflections. [Cu(etsal)NO3]2 is dimeric with adjacent metal atoms bridged by pairs of phenolic oxygens from the Schiff base ligands. The coppers are five-coordinated with four strong bonds (ranging from 1.93 to 1.99 Å) and a very weak fifth bond with a nitrato oxygen (Cu-O = 2.4 Å) to complete a rough square pyramid. Thus, an approximate comparison can be made with the analogous dimers with halide and alkoxy ligands. Within this approximation, the strength of antiferromagnetic interactions between the neighboring copper atoms (singlet-triplet separation, -2J ≈ 166 cm-1) fits into a series of four-coordinated copper dimers for which -2J decreases with increasing distortion toward tetrahedral geometry, if allowance is made for the perturbing effect of the weak fifth bond, which also weakens the superexchange.
E. Sinn, "Bis[nitrato(N-ethyl-2-hydroxybenzylideniminato-μ-O)copper(II)]," Inorganic Chemistry, American Chemical Society (ACS), Jan 1976.
The definitive version is available at http://dx.doi.org/10.1021/ic50156a025
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© 1976 American Chemical Society (ACS), All rights reserved.