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-pyridylcyanoxime, (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 CuII/(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), [Cu4(OH)2{(py)C(CN)NO}2(O2CPh)4]2n·n[Cu4(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 CuII atoms in a strictly equilateral arrangement bridged by a central μ3-oxide group. The molecule of 2 consists of a tetrahedron of CuII atoms held together by a central μ4-oxide ion, four η1:η1:η1:μ-(py)C(CN)NO− ligands and two η1:η1:μ-MeCO2− groups. The crystal structure of 3 consists of [Cu4(OH)2{(py)C(CN)NO}2(O2CPh)4]2n double chains and discrete cluster [Cu4(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 CuII atoms are doubly bridged by the oximate groups of two η1:η1:η1:μ-(py)C(CN)NO− ligands. Variable-temperature, solid-state direct current (dc) magnetic susceptibility 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.