Copper(II) nitrato and chloro complexes with sterically hindered tridentate ligands: Influence of ligand framework and charge on their structure and physicochemical properties

Abstract

Copper(II) coordination complexes of the neutral ligand, tris(3- tert-butyl-5-methyl-1-pyrazolyl)methane (L2′), i.e. the copper(II) nitrato complexes [Cu(L2′)(NO 3)][Cu(NO 3) 4] 1/2 ( 1) and [Cu(L2′)(NO 3)](ClO 4) ( 2) and the copper(II) chloro complex [Cu(L2′)(Cl)](ClO 4) ( 3), and its anionic borate analogue, hydrotris(3- tert-butyl-5-methyl-1-pyrazolyl)borate (L2 −), i.e. the copper(II) nitrato complex [Cu(L2)(NO 3)] ( 4) and the copper(II) chloro complex [Cu(L2)(Cl)] ( 5), were synthesized in order to investigate the influence of ligand framework and charge on their structure and physicochemical properties. While X-ray crystallography did not show any definitive trends in terms of copper(II) atom geometry in four-coordinate copper(II) chloro complexes 3 and 5, different structural trends were observed in five-coordinate copper(II) nitrato complexes 1, 2, and 4. These complexes were also characterized by spectroscopic techniques, namely, UV–Vis, ESR, IR/far-IR, and X-ray absorption spectroscopy.