Trinuclear, Tetranuclear, and Polymeric CuII Complexes from the First Use of 2-Pyridylcyanoxime in Transition Metal Chemistry: Synthetic, Structural, and Magnetic Studies

The first use of 2-pyridylcyarioxime, (py)C(CN)NOH, in transition metal chemistry is described. Depending on the nature of the metal starting material and the reaction conditions employed, the Cu-II/(py)C(CN)NOH system has provided access to complexes [Cu3O{(py)C(CN)NO)(3)(NO3)(H2O)(2)(MeOH)] (1), [Cu4O{(py)C(CN)NO}(4)(O2CMe)(2)] (2), [Cu-4(OH)(2){(py)C(CN)NO}(2)(O2CPh)(4)](2n)center dot n[Cu-4(OH)(2){(py)C(CN)NO}(2)(O2CPh)(4)] (3), and [Cu{(py)C(CN)NO}(2)](n) (4). The molecule of 1 consists of three Cu-II atoms in a strictly equilateral arrangement bridged by a central mu(3)-oxide group. The molecule of 2 consists of a tetrahedron of Cu-II atoms held together by a central mu(4)-oxide ion, four eta(1):eta(1):eta(1):mu-(py)C(CN)NO- ligands and two eta(1):eta(1):mu-MeCO2- groups. The crystal structure of 3 consists of [Cu-4(OH)(2){(py)C(CN)NO}(2)(O2CPh)(4)](2n) double chains and discrete cluster [Cu-4(OH)(2){(py)C(CN)NO}(2)(O2CPh)(4)] molecules. The crystal structure of 4 consists of neutral polymeric chains based on centrosymmetric mononuclear [Cu{(py)C(CN)NO}(2)] units. The Cull atoms are doubly bridged by the oximate groups of two eta(1):eta(1):eta(1):mu-(py)C(CN)NO- ligands. Variable-temperature, solid-state direct current (dc) magnetic sulceptibility studies were carried out for 1-4. The data indicate very strong antiferromagnetic exchange interactions for 1-3. The obtained J values are discussed in depth on the basis of the structural parameters of the complexes, literature reports, and existing magnetostructural correlations.