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

The complexes of copper formato with pyrazine and dimethylpyrazines: Cu(HCOO) 2 (pyrz) ( 1 ), Cu 2 (HCOO) 4 (pyrz) ( 2 ), Cu 2 (HCOO) 4 (2,3‐Me 2 pyrz) ( 3 ), Cu 2 (HCOO) 4 (2,5‐Me 2 pyrz) ( 4 ), and Cu 2 (HCOO) 4 (2,6‐Me 2 pyrz) 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 [Cu 2 (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 [Cu 2 (μ‐HCOO) 4 ] dimers with pyrz or 2,3‐Me 2 pyrz 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.