Nickel and Copper Complexes of Pyrrolecarboxamide Ligands – Stabilization of M³⁺ Species and Isolation of Ni³⁺ Complexes

Abstract

We report Ni II and Cu II complexes of a few pyrrolecarboxamide ligands containing -H, -Cl, and -CH 3 substituents on the phenylene ring. Solid-state X-ray diffraction and solution-based spectral studies substantiated a square-planar geometry around the metal ions in all six of the M II complexes. Electrochemical studies showed that the electronic substituents considerably influence the M 3+/2+ redox potentials. All [a]4957 of the complexes exhibit considerably low M 3+/2+ redox potentials owing to their tetraanionic coordination environments. Chemical and/or electrochemical oxidation has resulted in the isolation of Ni 3+ complexes and the generation of Cu 3+ species. The spectroscopic studies revealed squareplanar geometries around the metal ions in the resultant Ni 3+ and Cu 3+ complexes. 4958cations are involved in C-H···O interactions with O amide atoms to create a chain, whereas lattice N,N-dimethylformamide (DMF) molecules are held in place through C-H···π interactions from arene and pyrrole rings.

Manganese Complexes of Pyrrole‐ and ­Indolecarboxamide Ligands: Synthesis, Structure, Electrochemistry, and Applications in Oxidative and Lewis‐Acid‐­Assisted Catalysis

“…Further, the observed Mn-N amide bond lengths for complexes 3 and 5 are in good agreement with our earlier Ni II and Cu II complexes supported with similar ligands. [100,101] Furthermore, the M-N pyrrole and M-N indole distances are also comparable as noted before. [100,101] …”

“…[100,101] Furthermore, the M-N pyrrole and M-N indole distances are also comparable as noted before. [100,101] …”

“…[122,123] The ligands were synthesized according to our earlier report. [100,124] (Et 4 N) 2 Olefin Epoxidation: To a solution of substrate (1 mmol) in CH 3 CN (3 mL) was added PhIO (2 mmol) and the Mn III complex as the catalyst (0.01 mmol). The mixture was stirred at room temperature for 4 h. The progress of the reaction was monitored by TLC.…”

“…[100,101] We have delineated a few ligand architectural parameters, subtly altered by inserting electronic substituents, to affect the structure-redox relationship of the metal ion. Herein, we have used a set of pyrrolecarboxamide and indolecarboxamide ligands containing electron-donating and electron-withdrawing substituents for the synthesis of a few Mn III complexes.…”

Ethylene Polymerization Using Site‐Selective Pyridine‐Amide Based Iron Complexes

“…A variety of pyridine‐amide based transition metal complexes have been reported in the literature, such as cobalt(III), cobalt (II), iron(II),, iron(III),, manganese(II), nickel(II),, copper(II), rhodium(II), and ruthenium(III) ,. These studies indicated that designing of organic ligands and properly choosing metal ions are keys to create target transition metal‐based coordination complexes.…”