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.