Amidine Production by the Addition of NH₃ to Nitrile(s) Bound to and Activated by the Lewis Acidic [Re₆(μ₃‑Se)₈]²⁺ Cluster Core

Acetonitrile bound to and activated by the Lewis acidic [Re₆(μ₃-Se)₈]²⁺ cluster core was transformed into acetamidine in quantitative yield using NH₃ as the nucleophile at room temperature. The amidine ligand was removed by treating the cluster–acetamidine complexes with trifluoroacetic acid in CH₃CN, affording amidinium trifluoroacetate and the starting acetonitrile complexes

Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes

The new binuclear chromium Pacman complex [Cr₂(L)] of the Schiff base pyrrole macrocycle H₄L has been synthesized and structurally characterized. Addition of isocyanide, CNR (R = xylyl, ^tBu), or triphenylphosphine oxide donors to [Cr₂(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr₂(μ-CNR)­(L)], in which the isocyanides bridge the two Cr­(II) centers, and [Cr₂(OPPh₃)₂(L)], a Cr­(II) phosphine oxide adduct with the ligands exogenous to the cleft

Cyclic Voltammetric Studies of Chlorine-Substituted Diiron Benzenedithiolato Hexacarbonyl Electrocatalysts Inspired by the [FeFe]-Hydrogenase Active Site

Chlorine-substituted benzenedithiols have been coordinated to iron carbonyl to yield a series of hydrogen-producing electrocatalysts: [Fe₂(μ-S₂C₆H_4–<i>x</i>Cl_<i>x</i>)­(CO)₆], where <i>x</i> = 0, 2–4, and [Fe₂(μ-S₂C₆H₃Me)­(CO)₆]. Among this series the novel compounds [Fe₂(μ-S₂C₆Cl₃H)­(CO)₆] (<b>4</b>) and [Fe₂(μ-S₂C₆Cl₄)­(CO)₆] (<b>5</b>) have been characterized by X-ray crystallography. IR spectroscopy and electrochemical analysis were used to evaluate the electronic structure of these proton-reducing molecular electrocatalysts. The increase in the number of electron-withdrawing groups upon the electrocatalyst leads to an anodic shift in reduction potential and a concomitant lowering of the overpotential of hydrogen evolution. An overpotential of just 0.39 V is observed for <b>5</b> with acetic acid (p<i>K</i>_a = 22.3 in acetonitrile)

Cyclic Voltammetric Studies of Chlorine-Substituted Diiron Benzenedithiolato Hexacarbonyl Electrocatalysts Inspired by the [FeFe]-Hydrogenase Active Site

Chlorine-substituted benzenedithiols have been coordinated to iron carbonyl to yield a series of hydrogen-producing electrocatalysts: [Fe₂(μ-S₂C₆H_4–<i>x</i>Cl_<i>x</i>)­(CO)₆], where <i>x</i> = 0, 2–4, and [Fe₂(μ-S₂C₆H₃Me)­(CO)₆]. Among this series the novel compounds [Fe₂(μ-S₂C₆Cl₃H)­(CO)₆] (<b>4</b>) and [Fe₂(μ-S₂C₆Cl₄)­(CO)₆] (<b>5</b>) have been characterized by X-ray crystallography. IR spectroscopy and electrochemical analysis were used to evaluate the electronic structure of these proton-reducing molecular electrocatalysts. The increase in the number of electron-withdrawing groups upon the electrocatalyst leads to an anodic shift in reduction potential and a concomitant lowering of the overpotential of hydrogen evolution. An overpotential of just 0.39 V is observed for <b>5</b> with acetic acid (p<i>K</i>_a = 22.3 in acetonitrile)

Cyclic Voltammetric Studies of Chlorine-Substituted Diiron Benzenedithiolato Hexacarbonyl Electrocatalysts Inspired by the [FeFe]-Hydrogenase Active Site

Chlorine-substituted benzenedithiols have been coordinated to iron carbonyl to yield a series of hydrogen-producing electrocatalysts: [Fe₂(μ-S₂C₆H_4–<i>x</i>Cl_<i>x</i>)­(CO)₆], where <i>x</i> = 0, 2–4, and [Fe₂(μ-S₂C₆H₃Me)­(CO)₆]. Among this series the novel compounds [Fe₂(μ-S₂C₆Cl₃H)­(CO)₆] (<b>4</b>) and [Fe₂(μ-S₂C₆Cl₄)­(CO)₆] (<b>5</b>) have been characterized by X-ray crystallography. IR spectroscopy and electrochemical analysis were used to evaluate the electronic structure of these proton-reducing molecular electrocatalysts. The increase in the number of electron-withdrawing groups upon the electrocatalyst leads to an anodic shift in reduction potential and a concomitant lowering of the overpotential of hydrogen evolution. An overpotential of just 0.39 V is observed for <b>5</b> with acetic acid (p<i>K</i>_a = 22.3 in acetonitrile)

Hybrids by Cluster Complex-Initiated Polymerization

Hybrids by Cluster Complex-Initiated Polymerizatio

Single Component Iron Catalysts for Atom Transfer and Organometallic Mediated Radical Polymerizations: Mechanistic Studies and Reaction Scope

Tetradentate amine–bis­(phenolate)­iron­(III) halide complexes containing chloro substituents on the aromatic ring are extremely efficient catalysts for controlled radical polymerization. Molecular weights are in good agreement with theoretical values, and dispersities are as low as 1.07 for substituted styrenes and methyl methacrylate polymerizations. Kinetic data reveal activity for styrene polymerization among the fastest reported to date, with the excellent control shown to be electronic rather than steric in origin. Mechanistic studies implicate a multimechanism system with cooperation between atom transfer radical polymerization (ATRP) and organometallic mediated radical polymerization (OMRP). The <i>in situ</i> reduction of the Fe­(III) complex with ascorbic acid or tin octanoate allows polymerizations to be initiated by both 1-phenylethyl chloride (1-PECl, ATRP regime) and azobis­(isobutyronitrile) (AIBN, OMRP regime) to isolate the mechanism of control and offer unique initiation pathways

Single Component Iron Catalysts for Atom Transfer and Organometallic Mediated Radical Polymerizations: Mechanistic Studies and Reaction Scope

Tetradentate amine–bis­(phenolate)­iron­(III) halide complexes containing chloro substituents on the aromatic ring are extremely efficient catalysts for controlled radical polymerization. Molecular weights are in good agreement with theoretical values, and dispersities are as low as 1.07 for substituted styrenes and methyl methacrylate polymerizations. Kinetic data reveal activity for styrene polymerization among the fastest reported to date, with the excellent control shown to be electronic rather than steric in origin. Mechanistic studies implicate a multimechanism system with cooperation between atom transfer radical polymerization (ATRP) and organometallic mediated radical polymerization (OMRP). The <i>in situ</i> reduction of the Fe­(III) complex with ascorbic acid or tin octanoate allows polymerizations to be initiated by both 1-phenylethyl chloride (1-PECl, ATRP regime) and azobis­(isobutyronitrile) (AIBN, OMRP regime) to isolate the mechanism of control and offer unique initiation pathways

Insertion and Substitution Chemistry at the Boron Fourth Position in Charge-Neutral Zwitterionic Tripodal Tris(methimazolyl)borate Ligands

A number of new charge-neutral zwitterionic tris­(methimazolyl)­borate ligands have been synthesized, either by substitution of the dimethylamine group in the adduct (dimethylamine)­tris­(methimazolyl)­borane (<b>1</b>) or by insertion into its B–N­(dimethylamine) bond by an unsaturated Lewis base. Two new anionic ligands, (thiocyanato)­tris­(methimazolyl)­borate and (cyano)­tris­(methimazolyl)­borate, have also been accessed by this method

Insertion and Substitution Chemistry at the Boron Fourth Position in Charge-Neutral Zwitterionic Tripodal Tris(methimazolyl)borate Ligands

A number of new charge-neutral zwitterionic tris­(methimazolyl)­borate ligands have been synthesized, either by substitution of the dimethylamine group in the adduct (dimethylamine)­tris­(methimazolyl)­borane (<b>1</b>) or by insertion into its B–N­(dimethylamine) bond by an unsaturated Lewis base. Two new anionic ligands, (thiocyanato)­tris­(methimazolyl)­borate and (cyano)­tris­(methimazolyl)­borate, have also been accessed by this method