Copper(II)-mediated oxime-nitrile coupling in non-aqueous solutions: Synthetic, structural and magnetic studies of the copper(II)-salicylaldehyde oxime reaction system

The reactions of salicylaldehyde oxime (H₂salox) with Cu^II precursors yielded the known complexes Cu(Hsalox)₂] (1) and Cu(Hsalox)₂]_n (2), as well as complexes Cu₃(salox)(L₁)(L₂)]·MeCN (3·MeCN), CuCl(L₁)] (4) and Cu₂Na(O₂CMe)₅(HO₂CMe)]_n (5), where L₁⁻ = o-O-C₆H₄-CHNO-C(CH₃)NH and L₂³⁻ = o-O-C₆H₄-CHNO-C(o-O-C₆H₄)N. L₁⁻ was formed in situ via the nucleophilic addition of the oximato O-atom of salox²⁻ to the unsaturated nitrile group of the MeCN reaction solvent. L₂³⁻ is also formed in situ probably through the nucleophilic attack of the oximato O-atom to the unsaturated nitrile group of salicylnitrile; the latter, although not directly added to the reaction mixture, can be produced via the dehydration of salox²⁻. Compounds 1 and 2 contain Hsalox⁻ bound to the metal center in two different coordination modes; they both contain the same mononuclear unit, however a 2D network is generated in 2 due to a relatively long Cu-O_oximato bond. Compound 3 contains three different ligands, i.e. salox²⁻, L₁⁻ and L₂³⁻, which act as μ₃-κ²O:κO′:κN, κO:κN:κN′ and μ₃-κ²O:κ²N:κO′:κN′, respectively, whereas 4 consists of a square planar Cu^II atom bound to a κO:κN:κN′ L₁⁻ and a chloride ion. Compound 5 consists of dinuclear Cu₂(O₂CMe)₅(HO₂CMe)]⁻ units and Na⁺ ions assembled into an overall 3D network structure. Magnetic susceptibility measurements from polycrystalline samples of 2 and 5 gave best-fit parameters J = +0.36 cm⁻¹ (H = −J?_i?_j) and J = −360 cm⁻¹, zj = +20 cm⁻¹ (H = −J?_i?_j − zJ〈S_z〉?_z), respectively.