Reaction Of Diethylzinc Research Articles

Zinc selenide films and heterojunctions

Polycrystalline films of zinc selenide (ZnSe) have been deposited on glass and ZnO:F/glass substrates at 400–500 °C by the reaction of diethylzinc (DEZn) and diethylselenium (DESe) in a hydrogen atmosphere. The DESe/DEZn molar ratio in the reaction mixture is an important factor affecting the deposition rate and dopant incorporation in deposited films. The deposited films have high lateral electrical resistivity and poor photoconductivity. The resistivity can be reduced and photoconductivity significantly improved by the incorporation of a group VI (Cl or Br) or a group III (Al) dopant, and the use of trimethylaluminum (TMAl) as a dopant is considerably more effective than the use of Cl or Br compounds. The structural, optical, and electrical properties of ZnSe films have been characterized. The use of ZnSe films as a heterojunction partner in II-VI thin-film solar cells has been explored. Zinc telluride and cadmium telluride films were deposited on ZnSe/ZnO:F/glass substrates, and the characteristics of ZnSe/ZnTe and ZnSe/CdTe junctions studied.

The surface reactions of ethyl groups on Si(100) formed via dissociation of adsorbed diethylzinc

The adsorption and reaction of diethylzinc on S(100)-2 × 1 surfaces has been studied using temperature programmed desorption and high resolution electron energy loss spectroscopy. Adsorbed diethylzinc dissociates on the S(100)-2 × 1 surface at temperatures below 400 K to form adsorbed zinc metal and ethyl groups. The zinc metal desorbs between 400 and 550 K leaving only adsorbed ethyl groups. These ethyl groups undergo β-hydride elimination at 550 K, producing both adsorbed and gaseous ethylene, as well as adsorbed hydrogen. The adsorbed ethylene, bound to the surface in a di-σ configuration, is stable up to 625 K, at which point it either desorbs directly or undergoes C-C bond scission to form surface CH 2 groups. For low coverages the adsorbed CH 2 species undergo complete dehydrogenation while for higher coverages a fraction recombine to form gaseous ethylene at 750 K.

Chiral catalysis in the alkylation of aldehydes with diethyl zinc

The reaction of diethyl zinc with benzaldehyde and ephedrine derived catalysts was investigated. It was found that O-alkylated ephedrine could act as a catalyst for the reaction, but that the reaction was no longer stereoselective to the same degree as for the ephedrine catalysed reaction.

Synthesis of novel monomeric zinc—oxygen compounds containing diethylzinc and pyrocatechol or saligenin moieties

Reactions of diethylzinc with dihydric phenols such as pyrocatechol and saligenin in a molar ratio of 1 1 yield zinc pyrocatecholate and ethylzinc 2-hydroxymethylphenoxide, whereas a molar ratio of 3 2 gives zinc bis(2-ethylzincoxyphenoxide) and zinc bis(2-ethylzincoxyphenylmethoxide), respectively. The latter ethylzinc-oxygen compounds, containing zinc diphenoxide — or zinc dimethoxide — units complexed internally by ethylzinc groups, form monomeric species in 1,4-dioxane.

Synthesis of Metal Sulfide Powders From Organometallics

ABSTRACTOrganometallic reagents have been examined for the low-temperature preparation of metal sulfide powders which are desired as precursors to optical ceramics. The general approach is typified by the reaction of diethylzinc with hydrogen sulfide in toluene solution at room temperature. Electron microscopy shows that the white ZnS product consists of aggregates of ≤ 0.1 μm particles. The product is further characterized as predominantly cubic zinc sulfide (X-ray diffraction) which contains some residual hydrocarbon. Various organozinc reagents and experimental procedures have been tried in order to optimize the reaction. The reaction has also been extended to organometallic complexes of Al and Mg, and also to a ternary system, ZnAl2 S4

Ethylzinc hydroxide as an intermediate in the reaction of diethylzinc with water

The diethylzinc/water ( 1 1 mol) reaction in 1,4-dioxane as solvent has been studied by applying the cryoscopic method for molecular weight determinations to the products formed in the reaction solution. An ethylzinc hydroxide dimer was found to be formed as an intermediate in the reaction system during fast ethane elimination. Monomeric ethylzinc[tri(oxyzinc)] hydroxide was found to be the main product of the subsequent reaction of this intermediate, with further ethane elimination. A mechanism for the latter reaction, involving the formation of a transient ethylzinc hydroxide tetrameric species, is proposed. The reaction pathway in the diethylzinc/water ( 2 1 mol) system is also discussed. The formation of ethylzinc[tri(oxyzinc)] hydroxide, as in the 1 1 system, followed by the subsequent reaction of this compound with diethylzinc gave further ethane elimination and lead to ethylzinc[tri(oxyzinc)] ethylzinc oxide as the main product, is the proposed route in this case. In contrast to diethylzinc, which is too weak a Lewis acid to react with the ethylzinc hydroxide dimer, trimethylaluminium was found to undergo reaction with it in 1,4-dioxane solution, with fast methane and ethane elimination.

Enantioselective addition of diethylzinc to benzaldehyde catalyzed by a small amount of chiral 2-amino-1-alcohols

The reaction of diethylzinc with benzaldehyde catalyzed by a small amount of chiral 2-amino-1-alcohols in toluene at room temperature gave optically active 1-phenylpropan-1-ol almost quantitatively in ∼, 50% ee.

Regioselective ethyl transfer reactions between Diethylzinc and 1,4-Dialkyl-1,4-diaza-1,3-butadienes: Synthesis of EtZn[R(et)NCHCHNR

The l/l reaction of diethylzinc with 1,4dialkyl-1,4-diaza-1,3-butadienes (R-DAB = R-N=C(R’)-C(R’)=N-R) below -50°C results in formation of the l/l complex Et*Zn(R-DAB) (R = alkyl), containing o,a-N,N’ chelate bonded R-DAB. Above -50°C these complexes are unstable and undergo selective transfer of an ethyl group from Zn to the adjacent N atom, thus producing the novel species Et%[R(Et)NCR’=CR’NR] in quantitative yield. The proposed monomeric structure consists of a three-coordinate zinc atom bound to a 1-amino-2amidoethylene mono-anionic ligand via the N atoms. Reaction of these zinc complexes with t-BuOH(D) affords an equilibrium mixture of the ene-diamine and the 1-amino-2-iminoethane tautomers, which upon reaction with diethylzinc re-forms the EtZn[R(Et)NCR’=CR’NR] compound_ The tautomer equilibrium is dependent on the nature of R and R’. Branching at Co in R shifts the equilibrium towards the 1-amino-2-iminoethane tautomer, while introduction of an Me(R’) group stabilizes the ene-diamine tautomer.

Growth of Epitaxial ZnO Thin Films by Organometallic Chemical Vapor Deposition

Organometallic chemical vapor deposition of on sapphire, using the reaction of diethylzinc with , , and oxidizing gas systems, has been studied. Epitaxial films have been achieved at temperatures of 400° and 730°C, respectively, in the first two systems. The films have been characterized using scanning electron microscopy (SEM), reflection electron diffraction (RED), and surface acoustic wave techniques.

Stereoelective polymerization of racemic propylene oxide using a diethylzinc-chiral-1,2-diol system as initiator

The polymerization of racemic propylene oxide was performed using a chiral initiator obtained from the reaction of diethylzinc with (−) 3,3-dimethyl-1,2-butanediol. With this initiator R(+) enantiomer is preferentially incorporated into the polymer with a stereoelectivity ratio r equal to 1.8, the r value remaining constant during the polymerization. The polymer was fractionated into a crystalline isotactic part and an amorphous heterotactic part, both optically active. Partial stereoelectivities were determined for both fractions and found to be equal to 2.6 and 1.6 respectively for polymerization at 80°C. Two types of sites, stereospecific and non-stereospecific, formed in the first reaction between monomer and initiator are both active for the stereoelective polymerization. The stereospecificity of the monomer-initiator system increased at low temperatures, but the overall stereoelectivity remained constant and seemed to be an intrinsic property of the system.

Investigations on the catalytic systems diethylzinc/Di‐ and trihydroxybenzenes in the copolymerization of carbon dioxide with propylene oxide

AbstractInvestigations on the reactions of diethylzinc (1) with resorcinol (2) and phloroglucinol (8) were carried out for different mole ratios of the reactants. It was found that the reaction of 1 with 2 at a mole ratio of 1:1 is a two step process. In the first step 1 reacts very rapidly with half of applied 2 yielding di(ethylzinc) resorcinolate (6), which then reacts slowly with the remaining amount of 2. It was found that zinc 3‐ethylzincoxyphenolate resorcinolate (5) formed in the second step is an active catalyst of the copolymerization reaction of carbon dioxide with propylene oxide. The reaction of 1 with 8 shows a similar course.

Reactions of organozinc coordination compounds : III. Reactivity towards acidic hydrocarbons

The reaction of diethylzinc and of the diethylzinc/ N, N, N′, N′-tetramethylethylene-1,2-diamine complex with cyclopentadiene, indene and fluorene is very slow. The diethylzinc/bipyridine complex shows a slightly enhanced reactivity towards cyclopentadiene. In view of the high reactivity of nitrogen acids such as pyrrole towards the above complexes, π-coordination of the acidic hydrocarbons and the nitrogen acids to the organozinc complex is not thought to play much part in the reaction.

Reactions of organozinc coordination compounds II. Reactivity with secondary amines

The reactivity of diethylzinc is much the same towards di-n-propylamine, diphenylamine, pyrrole, indole and carbazole, in spite of the differences in the acidities of the amines. N, N, N′, N−-Tetramethylethylenediamine has an accelerating effect on the reaction of diethylzinc with pyrrole and derivatives, and 2,2′-bipyridine a similar but much larger effect on this reaction. These facts indicate the importance of the coordination of the amine to the organozinc complex in the reaction.

Polymerization of Propylene Oxide by Diethylzinc-α,β-Unsaturated Ketone Systems

Abstract Propylene oxide was polymerized by a catalyst consisting of diethylzinc and α,β -unsaturated ketones. Ten α,β -unsaturated ketones and some other related compounds were examined. All methyl ketones were effective. α,β -Unsaturated phenyl ketones were effective except for a α,β-disubstituted derivative. α,β-Unsaturated carbonyl compounds other than ketones were practically ineffective. The initial step of the catalyst formation is considered to be the reaction of diethylzinc and α,β-unsaturated ketone which is either the conjugate addition to the α,β-unsaturated group or the hydrogen abstraction from the methyl group next to the carbonyl group. The conjugate addition gives the catalyst having larger activity and better stability at high temperature.

Asymmetric‐selection polymerization of DL‐propylene oxide by the (+) (2‐methylbutyl)zinc/water system

AbstractDL‐Propylene oxide was asymmetric‐selectively polymerized by the catalyst prepared by the reaction of (+)bis(2‐methylbutyl)zinc with water. This polymerization was carried out in order to confirm the previous concept that ethyl‐zinc bonds act as cocatalysts together with ZnO bonds in the catalytic system derived from the reaction of diethylzinc and water. The asymmetric catalyst thus prepared was found to yield optically active poly(propylene oxide) leaving the antipode monomer. The asymmetric catalyst is deactivated by the addition of water. After the further addition of diethylzinc, the catalyst activity is restored but not the asymmetric nature. On the contrary, the addition of (+)bis(2‐methylbutyl)zinc restores both catalyst activity and asymmetric action. Consequently, it is concluded that optically active alkyl groups are linked to zinc in the catalyst which participate in the asymmetric polymerization.

MECHANISMS OF THE REACTIONS OF DIETHYLZINC WITH ISOPROPANOL AND WATER

Reactions of diethylzinc with isopropanol and water were studied by means of infrared absorption and gas evolution. The former method was found to be more reliable. Ethylzinc isopropoxide, formed from diethylzinc and isopropanol, was shown to be stable in the presence of excess isopropanol. The reaction of diethylzinc with water was found to proceed in a two-step manner, the product of the first being ethylzinc hydroxide. The decomposition of ethylzinc hydroxide was found to be first order with respect to itself and independent of diethylzinc.

Infrared studies on organometallic compounds as polymerization catalysts. I. Diethylzinc‐alcohol system for epoxide polymerization

AbstractInfrared spectra of Et2Zn‐alcohol system were measured in a liquid cell with KBr or NaCl windows. The reaction of diethylzinc with alcohol proceeds according to the equations: magnified imageReaction 1 takes place rapidly, whereas reaction 2 proceeds very slowly. The active species in the polymerization of propylene oxide was confirmed to be zinc dialkoxide in situ. The nature of alcohol and the reaction temperature are important factors in the catalyst activity.

The Reaction of Diethylzinc on Acetoxime

The Reaction of Diethylzinc on Acetoxime