Transformation of Formazanate at Nickel(II) Centers to Give a Singly Reduced Nickel Complex with Azoiminate Radical Ligands and Its Reactivity toward Dioxygen

Oxidation mechanism of phenols by copper(II)-halide complexes

The mechanism of oxidation of phenols by tetrahedral copper(II)-halide complexes was investigated to demonstrate that phenols with an electron-withdrawing substituent are oxidized via a proton-transfer/electron-transfer (PTET) mechanism, whereas phenols with an electron-donating substituent involve a concerted proton/electron transfer (CPET) mechanism. The importance of the tetrahedral geometry of the metal centre as well as the effects of the halide ligands of the substrates were explored.

Trimetallic Iridium-Nickel-Iridium Bis(formazanate) Assemblies

Formazans have attracted a lot of attention in coordination chemistry since the early 1940s because of their unique properties engendered by the nitrogen-rich conjugated backbone. Although many studies have been done using formazanates to chelate transition metals, research using formazanates as building blocks for polynuclear compounds and supramolecular chemistry remains rare. In this paper, we describe a synthetic strategy that uses a pyridyl-substituted bis(formazanato)nickel complex as a metalloligand to further assemble with two [Ir(C^N)₂]⁺ centers (C^N is the cyclometalating ligand). The trimetallic complexes represent a new binding mode for flexidentate pyridyl-substituted formazanates and a new structural class of polynuclear formazanate complexes. This work expands the chemistry of polynuclear formazanate complexes, for the first time pairing 3d and 5d metals in the same assembly. The redox chemistry of these trimetallic complexes, evaluated via cyclic voltammetry, is described. The compounds described in this work are luminescent, and studies of bis-cyclometalated iridium model complexes lacking the formazanate bridge confirm that the phosphorescence arises from the iridium center.