K. P. Butin

Structure and solvent effects in organomercuric electrochemistry. Polarographical scale of CH bond acidities

Abstract A number of organomercuric compounds, R2Hg and RHgClO4, with different R groups have been studied by the polarographic method. Both the half-wave potential, E 1 2 , and the transfer coefficient, α, are shown to be necessary for judging the CHg bond strength from the polarographic data. These data for R2Hg were used for the construction of a polarographic scale of CH bond acidities.

Acidities of some fluorine substituted CH acids

Abstract Acidities of some fluorinated hydrocarbons, R F H, have been estimated by polarographic method. Polarographic data on electrochemical reduction of (R F ) 2 Hg have been correlated with rate constants of hydrogen isotopic exchange in R F H in methanol.

Exchange of organomercury compounds with mercury metal : II. Dismutation of organomercury radicals on the surface of mercury☆

The galvanostatic method has been applied to the study of the dismutation of organomercury radicals formed by the electrochemical reduction of organomercury salts on the mercury surface. The relative stabilities of organomercury radicals have been found to follow the series AlkHg· >ArHg·, CH2CHHg· ? PhCH2Hg·. The lifetimes on the mercury surface have been determined as 10−2 to 5 x 10−2 sec for AlkHg·, 1 x 10−4 to 2 x 10−4 for ArHg· and CH2CHHg.·, and < 10(su−4) sec for PhCH(in2)- Hg·. The CHg bond in radicals on the mercury surface is more stable than that in radicals generated under homogeneous conditions. This has been attributed to the stabilising effect of the metal.

Redox properties of dihalogermylenes, dihalostannylenes and their complexes with Lewis bases☆

Abstract Reduction and oxidation potentials of GeI2, GeBr2 · B (B = dioxane, PPh3), GeCl2 · (B = dioxane, PPh3, AsPh3, Py, dip), SnCl2 · dioxane, SnX2 (X = F, Cl Br, I) were measured in MeCN at 20 °C. The data obtained indicate that in many cases the EX2 and EX2 · B (E = Ge, Sn) can act not only as a good reducing agents, but also as strong oxidants. Examples of redox reactions in which EX2 and EX2 · B react as oxidizing agents were found. The variation of the redox potentials of the dihalogermylenes and dihalostannylenes with complexation and with the nature of the halogen substituent and the Lewis base is discussed. In some cases (GeI2, GeX2 · B; X = Cl, Br, B = dioxane, PPh3), the reduction or oxidation was found to be quasi-reversible, indicating the presence of relatively stable ion radicals. AM1 calculations on GeCl2 · dioxane and GeCl2 · PH3 complexes show that the complexation destabilizes both the highest occupied and the lowest unoccupied MOs of the carbene analogues. The complexation reduces the IP and lowers the oxidation potential; its influence on the electron affinity is not straightforward. Calculations of the ion radicals of GeCl2 and GeCl2 · B (B = dioxane, PH3) show that in the ground state an unpaired electron occupies σ-MO in the cation and π-MO in anion radicals.

Electrocatalytic CO2 reduction in methanol catalyzed by mono-, di-, and electropolymerized phthalocyanine complexes

The electroreduction of CO2 was studied in methanol in the presence of mono- and diphthalocyanine complexes and phthalocyanine films prepared by electrochemical anodic polymerization. Methyl formate is the main reaction product of the reaction catalyzed by the mono- and diphthalocyanine complexes of rare-earth metals. Copper 2,9,16,23-tetra-tert-butylphthalocyanine allows the transformation of CO2 into methane in ∼30% yield. In the presence of both electropolymerized and graphite electrode-supported copper 2,9,16,23-tetraaminophthalocyanine, CO and methyl formate are the main reaction products.

A new heterobimetallic palladium–[60]fullerene complex with bidentate bis-1,1′-[P]2-ferrocene ligand

Abstract A new heterobimetallic palladium–[60]fullerene complex with ferrocene bis-phosphine ligand was prepared using alternative paths: either via addition reaction of Pd 2 (dba) 3 ·C 6 H 6 (dba=dibenzylidenacetone) in the presence of 1,1′-bis(diphenylphosphino)ferrocene ( dppf ) to C 60 , or via electrochemical activation of C 60 to generate C 60 2− anions, which then react with PdCl 2 and dppf to yield the target complex. The obtained (η 2 -C 60 )Pd( dppf ) complex was characterized by 1 H- and 31 P-{ 1 H}-NMR and electronic spectroscopy as well as electrochemically.

Exchange of organomercury compounds with mercury metal : I. Diethylmercury and mercury metal. The application of the galvanostatic technique to radical reactions on the metal surface

Abstract By means of a galvanostatic method it has been shown that diethylmercury reacts with mercury metal to form organomercury radicals, a conclusion based on the similarity between the charging curves obtained for solutions of diethylmercury and ethylmercury bromide. RHg· radicals have been suggested as the intermediates in the exchange of organomercury compounds with mercury metal.

Lutetium monophthalocyanine and diphthalocyanine complexes and lithium naphthalocyanine as catalysts for electrochemical CO2 reduction

Phthalocyanine and naphthalocyanine complexes with redox-inactive metals adsorbed on activated carbon supports were shown to be effective catalysts for CO 2 electroreduction in the form of gas diffusion electrodes, yielding carbon monoxide with current efficiencies up to ca. 75%. A mechanism for CO 2 electroreduction catalyzed by these complexes has been proposed in which the key step is the coordination of a CO 2 molecule to the external N-atom of the phthalocyanine or naphthalocyanine ring.

Prospects of electroanalytical investigations of supramolecular complexes of a bis-crown stilbene with viologen-like compounds bearing two ammonioalkyl groups

Abstract Complexation of the bis-(18-crown-6) stilbene with viologen-like compounds, 1,2-bis{4-[ N -(3-ammoniopropyl)pyridylium]}ethylene, 1,2-bis{4-[ N -(2-ammonioethyl)pyridylium]}ethylene, 1,2-bis{4-[ N -(3-ammoniopropyl)pyridylium]}ethane, and 1,2-bis{3-[ N -(3-ammoniopropyl)pyridylium]}ethylene, bearing two ammonioalkyl groups has been studied in MeCN solutions using cyclic voltammetry and UV–vis spectroscopy. The bis-crown stilbene was found to form strong 1:1 charge-transfer complexes, with the viologen-like diammonium compounds via two-site H-bonding. The complexation results in a considerable positive shift of the first oxidation potential of the electron donor bis-(18-crown-6) stilbene molecule ranging from 160 to 240 mV depending on the nature of the diammonium viologen-like compounds. The magnitude of this shift was used as a measure of the thermodynamic stability of bimolecular complexes between bis-crown stilbene and these viologen-like compounds. The relative contributions of H-bonding and charge-transfer interactions on the complex stability are discussed.

Equilibria of redistribution reactions in group IVB organometallic compounds

Abstract A method of predicting the position of equilibria of redistribution reactions of Group IVb organometallic compounds is presented. Equations are proposed in which the equilibrium constant is related to the difference in the p K a values of the acids corresponding to the exchanging anions, and to the difference in affinity of the organometallic cations for the respective anions. For a large number of compounds the calculated positions of the equilibria are compared with experimental data available from the literature, good agreement being found in most cases. The proposed approach may be applied to equilibria in which organometallic compounds of other Groups in the Periodic Table participate.