Copper(II)-mediated oxime–nitrile coupling in non-aqueous solutions: Synthetic, structural and magnetic studies of the copper(II)–salicylaldehyde oxime reaction system
摘要:
The reactions of salicylaldehyde oxime (H(2)salox) with Cu-II precursors yielded the known complexes [Cu(Hsalox)(2)] (1) and [Cu(Hsalox)(2)](n) (2), as well as complexes [Cu-3(salox)(L-1)(L-2)]center dot MeCN (3 center dot MeCN), [CuCl(L-1)] (4) and [Cu2Na(O2CMe)(5)(HO2CMe)](n) (5), where L-1 = o-O-C6H4-CH=NO-C(CH3)=NH and L-2(3) = o-O-C6H4-CH=NO-C(o-O-C6H4)=N. L-1 was formed in situ via the nucleophilic addition of the oximato O-atom of salox(2) to the unsaturated nitrile group of the MeCN reaction solvent. L-2(3) 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 salox(2). 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. salox(2) , L-1 and L-2(3) , which act as mu(3)-kappa O-2:kappa O':kappa N, kappa O:kappa N:kappa N' and mu(3)-kappa O-2:kappa N-2:kappa O':kappa N', respectively, whereas 4 consists of a square planar Cu-II atom bound to a kappa O:kappa N:kappa N' L-1 and a chloride ion. Compound 5 consists of dinuclear [Cu-2(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 (S) over cap (i)(S) over cap (j)) and J = -360 cm (1), zj = +20 cm (1) (H = -J (S) over cap (i)(S) over cap (j) - zJ < S-z > i (S) over cap (z)), respectively. (C) 2011 Elsevier B.V. All rights reserved.