Synthesis and characterization of trinuclear Schiff-base complexes containing sulphur dioxide or hydrogensulphite ions as bridging groups. Crystal structure of [Zn{(µ-CH3CO2)(salpd-µ-O,O′)Cu}2][salpd = propane-1,3-diylbis(salicylideneiminate)]
Abstract
Trinuclear complexes of general formulas [MCu2(CH3CO2)2(salpd)2](M = MgII, MnII, CoII, NiII, CuII, or ZnII) and [MNi2(CH3CO2)2(salpd)2](M = MgII, MnII, CoII, or NiII) were prepared, where H2salpd represents propene-1,3-diylbis(salicylideneimine). Further reactions of the complexes of the former series with sulphur dioxide yielded [MCu2(CH3CO2SO2)2(salpd)2](M = MgII, MnII, CoII, or NiII) and [Cu3(HSO3)2(salpd)2(H2O)2]. Cryomagnetic measurements (77.4–295 K) have shown that a weak or negligible antiferromagnetic spin coupling (J=–46 to 0 cm–1) is operating between the terminal and central metal ions in the complexes except for [Cu3(HSO3)(salpd)2(H2O)2] which showed a strong antiferromagnetic coupling (J=–186 cm–1) between neighbouring copper(II) ions. X-Ray crystal analysis was carried out for [Zn{(µ-CH3CO2)(salpd-µ-O,O′)Cu}2]. It crystallizes in the monoclinic space group P21/a with a= 16.228(5), b= 11.971 (2), c= 9.239(3)Å, β= 100.15(3)°Z= 2, and R=–0.0887. The complex consists of a linear CuII–ZnII–CuII trinuclear unit which has an inversion centre. The CuII and ZnII are bridged by the two phenolate oxygens of the salpd and the oxygens of the acetate ion.