Transition metal complexes with pyrazole based ligands. Part 27. Structural and thermal characterization of cobalt(II) halide and pseudohalide complexes with 4-acetyl-3-amino-5-methylpyrazole

Abstract

The crystal and molecular structures of four tetrahedral structurally similar [Co(aamp)2X2] complexes (aamp = 4-acetyl-3-amino-5-methylpyrazole, X = Cl, Br, I and NCS) were determined by X-ray diffraction analysis and are discussed in detail. It was found that the different capacity of the ligand X (NCS vs. Cl, Br, I) for the formation of non-bonding cntacts influence the mode of molecular association in the solid state. The complexes were characterized by UV–Vis spectroscopy. The first step of the thermal decomposition of the compounds was checked and is discussed in the view of the IR spectrum of the intermediate isolated from [Co(aamp)2Br2] by the quasi-isothermal technique.

Keywords

• Cobalt(II) complexes
• 4-acetyl-3-amino-5-methylpyrazole
• crystal structure
• electronic spectra
• quasi-isothermal TA