Synthesis, Spectroscopic and EPR Results and Crystal Structure of Copper(II) Formato Derivatives with Pyrazine and Dimethylpyrazines

Abstract

The complexes of copper formato with pyrazine and dimethylpyrazines: Cu(HCOO)2(pyrz) (1), Cu2(HCOO)4(pyrz) (2), Cu2(HCOO)4(2,3-Me2pyrz) (3), Cu2(HCOO)4(2,5-Me2pyrz) (4), and Cu2(HCOO)4(2,6-Me2pyrz)2 (5) have been synthesized and characterized by chemical analysis and IR and electronic spectro scopies. The three-dimensional structure of compound 1 consists of –Cu–pyrz–Cu–pyrz– chains joined by bridging formate groups coordinated, in configuration syn-anti, to two copper atoms. The coordination around the copper atom is orthorhombic with two Cu–O distances of 2.374(1) Å, two Cu–O of 1.952 Å and two Cu–N of 2.080 Å. Compound 5 is formed by molecular dimers with the [Cu2(μ-HCOO)4] unit, two copper atoms and four syn-syn fomate groups, and two ligands coordinated to the copper atoms in the axial positions. In compounds 2 and 3 chains of [Cu2(μ-HCOO)4] dimers with pyrz or 2,3-Me2pyrz as bridging ligands are formed. The EPR signal of 1 is orthorhombic (g = 2.23, 2.20 and 2.06). In the EPR spectra of 2 – 5 compounds the triplet (S = 1) signals are observed. The g⟂, g∥ and D values are been calculated.