Imidazolidine Ring Cleavage upon Complexation with First‐Row Transition Metals

Abstract

The reaction of a cyclic diaminal ligand, obtained from the reaction of N,N′‐bis(2‐pyridylmethyl)ethane‐1,2‐diamine, as a secondary diamine, and isophthalaldehyde, with different first‐row transition‐metal ions, such as FeIII, ZnII, CuII, and CuI, was explored using UV/Vis kinetic studies, and cyclic voltammetry. The 3D structures of the resulting metal complexes were determined by single‐crystal X‐ray diffraction analysis. We demonstrate that the ring‐cleavage reaction of the imidazolidine ligand upon complexation with various metal ions depends on the Lewis acidity of the metal ions, as well as on the coordinative requirements of the metal centers. With a soft acid such as CuI, the diaminal ligand was unmodified and stabilized tricoordinate planar cuprous ions. In contrast, in the presence of harder acids, such as FeIII, ZnII, and CuII, the diaminal ligand undergoes hydrolysis/cleavage to yield complexes of the tetradentate N,N′‐bis(2‐pyridylmethyl)ethane‐1,2‐diamine ligand. Interestingly, it was also observed that the ring‐cleavage reaction in the presence of FeIII led to the formation of FeII complexes. However, we demonstrate that these two events are independent from each other.

Synthesis of Cu(II) complexes by N,O‐donor ligand transformation and their catalytic role in visible‐light‐driven alcohol oxidation

“…[ 1–6 ] It has been also noticed that in a sterically demanding situation or for the sake of less strainer chelating environment, certain ligands can decyclise or ring‐opening of the ligands can happen. [ 7–15 ] In point of view of the catalytic properties, in‐built flexibility of the associated ligands in terms of denticity, ability to engage in different noncovalent interactions with substrate, and providing an efficient and robust platform remain very crucial as per earlier reports. [ 16–21 ] Among various catalytic activities, aerobic oxidation of primary alcohol is an important subclass of catalytic reaction in terms of biological as well as industrial viewpoint.…”