Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VIII. Selectivity of the binary systems action

Selectivity of action of binary systems based on an organometallic compound and a transition metal compound in a direct synthesis of organometallic compounds via alkylation of metals with organic halides has been considered. Study of the side reactions in the course of zinc and cadmium powders alkylation (gaseous hydrocarbons evolution) taken as an example has demonstrated that the increase in activity of the binary system components is accompanied by decrease in its selectivity. The intensity of the side reactions is steeply increased above certain temperature determined by the nature of the reactants and components of the binary system. The surface of the alkylated metal containing adatoms and small clusters of the transition metal promotes the side processes.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VII. Additional details of the mechanism

Mechanism of metals alkylation with an organic halide in the presence of binary systems has been defined in more detail. It has been shown that the passivating film on the surface of zinc and cadmium is partially preserved in the course of the process, and the reaction in diethyl ether is decelerated due to the competitive adsorption of the organyl halide and diethyl ether on the surface of the reacting metal. The ratelimiting stages of the studied alkylation process have been elucidated basing on the experimental data on the effect of the reagents (organyl halide and alkylated metal) nature on the rate of the steady-state reaction and modeling of the suggested catalytic cycle.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: IX. Alkylation of aluminum and concluding remarks

Study of aluminum powder alkylation with ethyl bromide in the presence of ethylaluminum sesquibromide and copper(I) iodide has revealed that binary systems based on an organometallic compound and a transition metal compound are efficient promotors of direct synthesis of organoaluminum compounds as well. Major conclusions drawn in a series of studies on non-transition metals (Zn, Cd, and Al) alkylation with organic halides in the presence of the binary systems are summarized.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VI. Effect of various additives on the rate of the steady-state process

The effect of various additives such as transition and non-transition metal oxides, hydroxides, and salts on the rate of steady-state alkylation of commercial zinc powder with ethyl bromide in the presence of ethylzinc bromide–copper(I) iodide binary system has been studied. Most of the examined compounds either do not affect the reaction rate or reduce it. Only addition of zinc(II) bromide, zinc(II) hydroxide, and water appreciably accelerates the process. Mechanism of action of the additives is discussed.     

Promoting nontransition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: V. Effect of the nature of the transition metal compound in the binary system on the rate of a steady-state process

The example of alkylation of commercial zinc and cadmium powders with organic halides in the presence of binary systems comprising an organometallic and a transition metal compounds was used to show that the nature of the transition metal compound in the binary system strongly affects the rate of a steady-state process. Therewith, the significant factors are both the nature of the transition metal and the ligand composition. It was found that the activity of the binary systems correlates with the activity of the transition metal compound in the transmetalation reaction with the organometallic component of the binary system (reduction of the transition metal compound).     

Promoting alkylation of non-transition metals with organic halides in the presence of binary systems based on organometallic compound and transition metal compound: II. Comparative study of efficiency of various agents in the course of destruction of passivating film on the surface of alkylated metal

It has been demonstrated that alkylzinc halides efficiently destroy the passivating film on the zinc-copper pair in the course of its alkylation with ethyl bromide to give ethylzinc bromide. The alkylzinc halides efficiency is comparable to that of ethyl iodide and exceeds that of salts of transition or non-transition metals as well as of ultraviolet irradiation. Addition of alkylzinc halides or metal salts as well as ultraviolet irradiation have practically no effect on the developed reaction. The results have demonstrated that the organometallic component of the binary systems is polyfunctional; this permits a generalization of known features of a number of known methods promoting direct synthesis of organometallic compounds.     

Oligomerization of trimethylsilylacetylene in the presence of catalytic systems based on group III–VI transition metal halides

The features of the reaction of oligomerization of trimethylsilylacetylene in the presence of group III–VI transition metal compounds combined with triisobutylaluminum were investigated. The effect of the nature of the transition metal, cocatalyst, and conditions of conducting the oligomerization reaction on the yield and composition of the products of the reaction were studied. It was shown that it is possible to obtain either linear products of oligomerization or the cyclic trimer, or a mixture of both by varying the nature of the catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2823–2828, December, 1989.     

The reactions of transition metal chelates with organometallic compounds and their paramagnetic products. V—New possibilities in the generation of anion radicals by reactions of Grignard reagents and lithium alkyls in the presence of transition metal ions

In the reactions of Grignard reagents and n-butyllithium the presence of transition metals and complexing solvents facilitates the formation of anion radicals. High radical concentrations, observable for some days at laboratory temperature, and very well resolved e.s.r. spectra of the following structural types have been obtained using a relatively simple procedure: aromatic hydrocarbons, heteroaromatics, aldehydes, ketones, α-diketones, enolates of β-diketones, quinones, sulphones, sulphoxides, nitro-, nitroso- and azo-benzenes, cyano compounds and phosphine oxides. It is suggested that the transition metals, according to the type of reactants and the experimental conditions, mediate the transfer of one electron to the substrate in many reactions and stabilize the intermediate products as anion radicals. The variation of solvents and organometallic compounds modifies the reduction power of such systems and leads to the radical products in a different reduction state. The procedure described is advantageously employable in the generation of anion radicals, and the effect of transition metals which has been found may widen the scope of this phenomenon to many different applications.     

Ordering transition and demixing of a binary mixture of thick and thin rodlike molecules in the presence of an external field

The effect of an external field (electric/magnetic) on the phase behavior of the binary mixture of very long thick and thin rodlike particles is studied. Both the thick and thin particles possess positive but different susceptibility anisotropics (Delta alpha). The difference in the extent of interaction between the external field and the two species is varied by means of a coupling parameter (l = Delta alpha(thick)/Delta alpha(thin)). Isotropic-nematic phase transition and demixing phase transitions taking place both in the isotropic and nematic phases are examined as a function of field strength on the level of the second virial theory of Onsager in the range of 0 < l <1. The approximate sixth order Legendre polynomial expansion method is used to represent the excluded volume interaction between the rodlike particles. It is found that the isotropic phase becomes weakly nematic (paranematic) in the presence of external field and the field orients both components in the direction of the field even if the field does not have direct interaction with the thick component (l = 0). Analytical expressions are derived for the external field induced order parameters and birefringence. The increasing field destabilizes both types of demixing transitions (isotropic-isotropic and nematic-nematic) and the paranematic-nematic phase transition. Moreover it induces closed loop immiscibility, and upper and lower critical points terminating the paranematic-nematic phase coexistence may occur for low values of the coupling parameter. It is interesting that while the phase boundaries of the paranematic-paranematic demixing and the paranematic-nematic transitions are very sensitive to the value of the coupling parameter at low pressures, the paranematic-nematic and nematic-nematic phase boundaries are practically independent of the coupling parameter at high pressures.     

Solvation of bivalent transition metal cations. I. Heats of transfer of the metal perchlorates between water,acetonitrile, and dimethylsulfoxide

Heats of solution of Mn(ClO₄)₂·6AN, Fe(ClO₄)₂·6AN, Co(ClO₄)₂·6AN, as well as Ni(ClO₄)₂·6AN, Cu(ClO₄)₂·4AN, and Zn(ClO₄)₂·6AN (AN=acetonitrile) have been determined in water, acetonitrile, and dimethylsulfoxide (DMSO). Coupled with the heats of solution of AN in the respective solvents they give the heats of transfer of the metal perchlorates. Heats of transfer of the cations as well as their heats of solvation are calculated using literature data for the heat of transfer of the perchlorate anion and the heats of hydration of the cations, respectively. The results are discussed in terms of the different contributions to the overall heat effects.     

Factors affecting the general shape of the phase diagram and compound formation in the binary copper(I) halide–alkali-metal halide systems

A set of phase diagrams for the systems CuX–AlkX (where Alk=Li, Na, K, Rb or Cs and X=Cl, Br or I) is given, basing on authors investigation and selected literature data. Sizes and valences of ions involved in Coulombic and polarization interactions were considered as main factors affecting phase equilibria. An increasing tendency for compound formation was noted in series Na→K→Rb→Cs, Na→Li and I→Br→Cl. The most strongly represented are compounds of the formulas AlkCu₂X₃ and Alk₂CuX₃.     

Fluorescence enhancement of a signaling system in the simultaneous presence of transition and alkali metal ions: a potential AND logic gate

Attachment of a laterally non-symmetric cryptand and a macrocycle at the 9- and 10-positions of anthracene leads to a fluorescent signaling system L1 which gives fluorescence enhancement in the simultaneous presence of alkali and transition metal ions.     

New systems for classical nitrosohalogenation of alkenes 1. Reactions of alkenes with ethyl nitrite in the presence of phosphorus halides and thionyl chloride

Studies of nitrosation of norbornene and norbornadiene derivatives and dimethyl tricyclo[4.2.2.0^2,5]deca-3,7-diene-9,10-cis-endo-dicarboxylate demonstrated that nitrosation of alkenes with EtONO-PHal₃, EtONO-POHal₃ (Hal = Cl or Br), and EtONO-SOCl₂ systems can afford nitroso halides in high yields without the formation of by-products (ketones and oximes). The reactions with 5-substituted norbornenes are nonregioselective. The trans dimer of endo-5-trifluoromethyl-cis-exo-2-chloro-3-nitrosobicyclo[2.2.1]heptane was studied by X-ray diffraction. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2070–2080, September, 2005.