▪ Abstract Proton-coupled electron transfer (PCET) is an important mechanism for charge transfer in a wide variety of systems including biology- and materials-oriented venues. We review several are...

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Proton-Coupled Electron Transfer

Mini-review: Ferrite nanoparticles in the catalysis

Magnetic nanoparticles have emerged recently as an alternative for the easy separation of nanosized catalysts from reaction mixtures by employing an external magnetic field. These magnetic nanoparticles have been used as supports for catalysts and/or as part of an active catalytic site. Herein, special attention is given to identify the main synthetic steps required to develop both precious‐ and nonprecious‐metal‐catalyzed CC and CX coupling reactions by using magnetically separable catalysts.

Recent Applications of Magnetically Recoverable Nanocatalysts in CC and CX Coupling Reactions

Reaction of [(dippe)Ni(μ-H)]2 with allyl cyanide at low temperature quantitatively generates the η2-olefin complex (dippe)Ni(CH2CHCH2CN) (1). At ambient temperature or above, the olefin complex is converted to a mixture of C−CN cleavage product (dippe)Ni(η3-allyl)(CN) (3) and the olefin-isomerization products (dippe)Ni(η2-crotonitrile) (cis- and trans-2), which form via C−H activation. The latter are the exclusive products at longer reaction times, indicating that C−CN cleavage is reversible and the crotononitrile complexes 2 are more thermodynamically stable than η3-allyl species 3. The kinetics of this reaction have been followed as a function of temperature, and rate constants have been extracted by modeling of the reaction. The rate constants for C−CN bond formation (the reverse of C−CN cleavage) show a stronger temperature dependence than those for C−CN and C−H activation, making the observed distribution of C−H versus C−CN cleavage products strongly temperature-dependent. The activation parameters f...

Kinetics, Thermodynamics, and Effect of BPh3 on Competitive C−C and C−H Bond Activation Reactions in the Interconversion of Allyl Cyanide by [Ni(dippe)]

Monovalent, trivalent and tetravalent nickel

High-spin octahedral (NiN 6 core;Dg≈ 1250cm -1 ) nickel(II) complexes of type Ni(HRRI) 2 X 2 (where HRRT is a tridentate ligand of class N.β-aminoethylisonitroso ketimine and X = CI0 4 . NO 3 ) are readily oxidized by concentrated nitric acid to yield the diamagnetic nicket(IV) species Ni(RRT).K.. Cyclic voltammcry (CV) of Ni(RRT) 2 (CIO 4 ) 2 has been thoroughly done in well-buffered aqueous media over a wide range of pH. Below pH 6.0. CV data show a single reversible two-electron, two-proton transfer process followed by an irreversible chemical decomposition of the nickel(II) species. The rate constant for this decomposition reaction has been determined to be 0.16s -1 (283 K) from CV data. In the pH range 7.0-9.0. two distinct reversible onc-elcctron processes are observed corresponding to Ni(IV)-Ni(III) and Ni(III- Ni(II) couples. The first of these has no proton involvement while the other involves one proton. The E°′ 298 values for the various couples have been accurately determined front CV data. Representative results are as follows: 
Ni(Me 2 T) 2 2+ -Ni(HMe 2 T) 2 2+ ,0.71 V; 
Ni(Me 2 T) 2 2+ -Ni(Me 2 T)2 + ,0.40 V; 
Ni(Me 2 T)2 + -Ni(HMe 2 T)(Me 2 T) + ,0.66 V;
Ni(Me 2 T)2 + -Ni(Me 2 T)2,0.07 V (estimated). The nickel(II) species involved in each of the above couples is what is expected from acid dissociation (oxime protons) data of Ni(Hme 2 T) 2 2+ (pK 1 =7.80;pK 2 =10.00).

Chemistry of tetravalent nickel and related species. 3. Characterization and cyclic voltammetry of new [NiN6] species based on tridentate ligands

Copper ferrite nano material as reusable heterogeneous initiator in the synthesis of β, γ-unsaturated ketones and allylation to acid chlorides are presented The reaction of allylichalides with various acid chlorides is achieved in the presence of copper ferrite nano powders at room temperature in tetrahydrofuran (THF) The present method is first of its kind in the synthesis of title compounds without any additive/ co-catalyst The nano catalyst is easily recovered and its reusability is recorded

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Nano copper ferrite: A reusable catalyst for the synthesis of β , γ -unsaturated ketones

Nano size nickel ferrite, copper ferrite, zinc ferrite, nickel copper ferrite, nickel zinc ferrite and nickel copper zinc ferrite powders have been prepared by citrate gel precursor method and calicinated at 800 o C temperature. The resulting powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The ferrite powders showed XRD line broadening and sizes of the crystals were calculated 20-65 nm at 800 o C temperature. Comparing the size of ferrites by addition of transition metal were discussed.

Synthesis and Characterization of Nano Ferrites by Citrate Gel Method

A thio carboxylic acid derivative: 2-aminocyclopent-1-ene-1-carbodithioic acid (ligand) was synthesized and characterized. It was used as a colorimetric chemo sensor (chads) for Ni. The absorption maximum of ligand and Ni shows a shift from 390 nm to 420 nm in absence of buffer solutions. The change in color is very easily observed by the naked eye, while other metal cations, such as Fe, Co, Hg, Zn, Cd, Cu, Fe, Ag, Pb, alkali metal and alkaline earth metal cations do not induce such a change with these chads. The response time upon exposure to Ni is instantaneous. The significant problem of nickel poisoning requires new methods of detection that are sensitive and selective. Here we report a simple system that takes advantage of the unique optical properties generated by ACDA-

Rajendra Singh

Papers

Chemistry of tetravalent nickel and related species. 3. Characterization and cyclic voltammetry of new [NiN6] species based on tridentate ligands

Nano copper ferrite: A reusable catalyst for the synthesis of β , γ -unsaturated ketones

Synthesis and Characterization of Nano Ferrites by Citrate Gel Method

A simple inexpensive detection method of nickel in water using optical sensor.

Chemistry of tetravalent nickel and related species. 3. Characterization and cyclic voltammetry of new [NiN6] species based on tridentate ligands