V. E. Titov

Redox-Active Porous Coordination Polymers Prepared by Trinuclear Heterometallic Pivalate Linking with the Redox-Active Nickel(II) Complex: Synthesis, Structure, Magnetic and Redox Properties, and Electrocatalytic Activity in Organic Compound Dehalogenation in Heterogeneous Medium

Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv(-) = pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (SBET = 50 m(2) g(-1), VDR = 0.017 cm(3) g(-1) estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm(3) g(-1)) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of χMT of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin-orbit coupling of Co(II), and in the second model the spin-orbit coupling of Co(II) was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product.

Electrochemical carboxylation of benzoyl bromide as effective phenylglyoxylic acid synthesis route

Abstract Electrochemically activated insertion of carbon dioxide into benzoyl bromide (BB) is shown to result in phenylglyoxylic acid in yield of 88%. The influence of the nature of the cathode material and the background electrolyte on the electrochemical reduction of benzoyl bromide (the key step of its electrochemical carboxylation) and on the phenylglyoxylic acid yield in the presence of CO 2 is studied. Using benzoyl bromide instead of benzoyl chloride (BC) in the electrochemical carboxylation process enables the phenylglyoxylic acid yield to be raised from 39% to 88%.

A convenient electrochemical synthesis of α-oxoacids

Abstract The possibility of obtaining aliphatic and aromatic α-oxoacids via the direct electrochemical carboxylation of acetyl and benzoyl chlorides has been shown for the first time.

Electrochemical and Electrocatalytic Characteristics of Coordination Polymers Based on Trinuclear Pivalates and Heterocyclic Bridging Ligands

It was shown by cyclic voltammetry that the coordination polymers [Fe2NiO(Piv)6(L)x]n, where L is a ligand containing a 1,2,4,5-tetrazine or thiazolothiazole fragment, Piv– is pivalate, and x = 1 or 1.5, possess redox activity in the solid form when deposited on an inert electrode, and the redox potentials of the transitions correlate with the corresponding redox potentials of the ligands in solutions. The coordination polymer containing bis(4-pyridyl)thiazolothiazole catalyzes the electrochemical dehalogenation of CF3CHClBr with the formation of CF2=CHCl and CF3CH2Cl.

Electrochemical carboxylation of acyl chlorides, freons, and halogen-containing polymers

Processes of the carbon dioxide fixation are studied. The fixation is done by an electrochemical carboxylation of chlorides of aliphatic and aromatic carboxylic acids (acetyl chloride, benzoyl chloride and its derivatives), halogen-containing polymers (polyvinyl chloride, polyvinyl bromide), polybutadiene, and polyfluoroalkyl halides (CF3Br, CF3I, C3F7I). Major effects of some factors (reagent electronic structure, electrode materials, supporting electrolyte) on the occurrence of such processes and the yield of target products are studied.

Electrochemical functionalization of organic compounds by “small” molecules

The authors results and published data on the electrochemical insertion of “small” molecules (CO2, SO2, CS2, NO) into organic substrates are reviewed. Special attention is paid to the cathodic carboxylation of halogen-containing aliphatic and aromatic compounds, polymers, and olefins, the sulfonylation and dithiocarboxylation of Freons, and anodic nitrosation of amines. The probable mechanisms of such processes and the effects of the nature of the reagents and the electrolysis conditions on the composition and yields of the final reaction products are examined.

Effect of various factors on the electro-chemically activated insertion of carbon dioxide into acyl chlorides

The effect of the electronic structure of the reagents, the nature of the supporting electrolyte, the electrode material, the electrolysis conditions, and other factors on the electrochemical carboxylation of acyl chlorides (CH3COCl, p-X-C6H4COCl, where X=CH3, H, NO2) and on the yields of the respective α-oxocarboxylic acids were studied. It was shown that factors that accelerate the cathodic reduction of the acid chlorides and stabilize the intermediates and products of the electrosynthesis lead to an increase in the yield of the oxo acids.

Structure, magnetic, and electrochemical properties of complexes of 3d-metals as redox-active units for assembling coordination polymers and porous coordination polymer on their basis

Mononuclear complexes ML2 (MII = Fe, Co, Cu, Zn) and porous coordination polymer [{Fe2NiO(Piv)6}{CoL2}1.5]n (LH is the Schiff base of pyridine-4-carboxylic acid hydrazide and pyridine-2-carbaldehyde, and Piv– is pivalate) were synthesized and characterized. The structures of the compounds were determined by X-ray diffraction analyses. Each ML2 molecule contains two 4-pyridine fragments capable of coordinating metal ions. Polymer [{Fe2NiO(Piv)6}{CoL2}1.5]n was formed by cross-linking of trinuclear units with the CoL2 bridge. The temperature dependences of the magnetic susceptibility of CoL2, FeL2, and [{Fe2NiO(Piv)6}{CoL2}1.5]n were studied. The magnetic properties of [{Fe2NiO(Piv)6}{CoL2}1.5]n were described as a superposition of the susceptibilites of the trinuclear and mononuclear units, and their interaction was taken into account in the framework of the molecular field model. The magnetic properties of CoL2 in the individual state and in the framework of [{Fe2NiO(Piv)6}{CoL2}1.5]n were interpreted using a model taking into account the spin—orbit coupling in the Co2+ ion and the splitting of its levels by crystal field. For FeL2, a model taking into account the zero-field splitting of the ground state of the Fe2+ ion was used. Several redox processes were found for ML2 in a solution and for [{Fe2NiO(Piv)6}{CoL2}1.5]n in a suspension by cyclic voltammetry. The CoL2 and FeL2 complexes can catalyze the electrochemical dehalogenation of freon CF2ClCFCl2 but exhibit no activity in the dehalogenation of CHCl3; ZnL2 did not show catalytic activity in the dehalogenation of both substrates.

Electrochemically Activated Reaction of Benzoyl Halides with Carbon Dioxide

The electrochemical activation and carboxylation of benzoyl halides (benzoyl bromide, chloride, and fluoride) were studied. It was found that the yield of phenylglyoxylic acid increases from zero to 88% in the transition from benzoyl fluoride to the chloride and bromide. The effect of the nature of the halogen atom in the benzoyl halide and also the nature of the supporting electrolyte and the electrode material on the electrochemical reduction and carboxylation of benzoyl halides was studied.

Introduction of electrochemically activated carbon dioxide in halogen-containing polymers

The possibility of electrochemical carboxylation of halogen-containing polymers by using carbon dioxide has been shown on the example of polyvinyl chloride and polyvinyl bromide. The process proceeds via the substitution of halogen atoms by carboxylic groups; this leads to the formation of the corresponding polyacrylic acid copolymers. The influence of various factors (the nature of the medium and of the electrode materials, the electrolysis mode, etc.) on the degree of carboxylation of the polymers has been studied.