Intramolecular Redox-Active Ligand-to-Substrate Single-Electron Transfer: Radical Reactivity with a Palladium(II) Complex
摘要:
Coordination of the redox-active tridentate NNO ligand L-H2 to Pd-II yields the paramagnetic iminobenzosemiquinonato complex 3. Single-electron reduction of 3 yields diamagnetic amidophenolato complex 4, capable of activating aliphatic azide 5. Experimental and computational studies suggest a redox-noninnocent pathway wherein the redox-active ligand facilitates intramolecular ligand-to-substrate single-electron transfer to generate an open-shell singlet "nitrene-substrate radical, ligand radical", enabling subsequent radical-type C-H amination reactivity with Pd-II.
series of five- and six-membered-ring Al complexes bearing Schiffbases was synthesized and their application to the ring-opening polymerization of ε-caprolactone (CL) was studied. The five-membered-ring Al complexes have been shown to have a significantly higher polymerization rate than six-membered-ring Al complexes (2–3 fold for CL polymerization). The X-ray data revealed that the Al center of a five-membered-ring
A chloro bridged Cu(II)–Cu(II) complex of a new aminophenol ligand: Magnetostructural, radical decay kinetic studies, highly efficient and aerial alcohol oxidation
A new tripodal aminophenol-based ligand containing a pyridine unit was synthesized and characterized by IR and H-1 NMR spectroscopic techniques. A dimeric copper(II) complex of this ligand was prepared and characterized by X-ray crystallography, DFT calculations, spectroscopic techniques and magnetic susceptibility measurements. X-ray analysis revealed a complex in which one phenolate, and amine and imine nitrogens of the ligand are arranged in a distorted square pyramidal geometry (SP) around the copper ions. Two chloride bridges hold both copper atoms together to form the binuclear [(LCuCl)-Cu-Aph](2) complex. This complex exhibits nearly no superexchange coupling between the copper centers. The phenolate moieties of the copper complex were electrochemically oxidized to phenoxyl radical cations [(LCuCl)-Cu-Aph](2)(center dot+). The decay kinetics of the mentioned radical were investigated using a simulation of the voltammogram data. In addition, highly efficient and eco-friendly oxidation of alcohols to aldehydes was achieved with molecular oxygen or air as the oxidant and the [(LCuCl)-Cu-Aph](2)-Cs2CO3 system as a catalyst. (c) 2012 Elsevier Ltd. All rights reserved.