Reaction Of Diethylzinc Research Articles

N-alkyl-β-ketoiminate zinc complexes: Synthesis, structure, and reactivity in ring-opening polymerization of lactide

• Well characterized homoleptic bis(β-ketoiminate) monozinc complexes. • Bidentate N-alkyl-β-ketoiminate with tert-butyl substituents on the ligand backbone. • Metal catalysts to prepare biocompatible aliphatic polylactide. • Good catalytic activities towards the ROP of rac-lactide in the absence of alcohol. A series of N-alkyl-β-ketoiminate monozinc complexes [{tBuCN(R)CHC(O)CtBu} 2 Zn] (R = Me, 2a ; Et, 2b ; Pr, 2c ; iPr, 2d ; Cy, 2e ) were synthesized from the reaction of diethyl zinc with the corresponding β-ketimines. All these zinc complexes were characterized by NMR, elemental analysis and HRMS spectroscopy. The molecular structures of complexes 2 b -2 e were further confirmed by single-crystal X-ray diffraction. The structures exhibit that each zinc center is four-coordinate, and surrounded by two bidentate β-ketoiminate ligands, forming a distorted tetrahedral geometry. These homoleptic bis(β-ketoiminate) zinc complexes are active towards the ring-opening polymerization of rac-lactide in the absence of alcohol, yielding over 90% conversions within 1 h at 70 o C in toluene with the ratio of monomer to catalyst being 100.

Infiltration of Atomic Layer Deposition Precursors for Modification of Polymers and Covalent Organic Networks

Incorporation of transition metal oxides in polymers and covalent organic networks could add unique physical and chemical properties to the parent materials. Understanding the diffusion and reactions of atomic layer deposition (ALD) precursors in these organic substrates are key to the rational design and precise control for synthesizing the organic/inorganic hybrid materials. Current challenges of developing new vapor phase infiltration methods include difficulties in finding proper precursor-polymer pairs with moderate reactivity and enlarging the permeation depth of the ALD precursors in the substrates.In this talk, we will first discuss vapor phase infiltration of diethyl zinc (DEZ) in a variety of polymers. DEZ is known to possess lower reactivity but larger kinetic dimeter compared with trimethylaluminum (TMA). As a result, the mass uptake of DEZ in poly(methyl methacrylate) is negligible, while the DEZ loading in polybutylene terephthalate was found one order of magnitude lower than that in cellulose acetate and poly(1,3,5-trimethylcyclotrisiloxane). We investigated the effect of glass-transition temperature, free volume and functional groups of the polymers on the vapor phase infiltration of DEZ. We will also show how AlOx priming affects the subsequent diffusion and reactions of DEZ in the polymers. Furthermore, we will present our recent study on ALD ZnO in covalent organic frameworks (COFs). Mesoporous COFs with OH functional groups were synthesized in forms of powders and thin films. Using ALD, we were able to modify the pore dimension as well as internal functionalities. Additionally, we applied ALD as a pore engineering tool for gas separation membranes and achieved enhanced H2/CO2 selectivity while maintaining high permeance of H2.

Synthetic and Structural Studies of Ethyl Zinc β-Amidoenoates and β-Ketoiminates.

A set of heteroleptic ethyl zinc β-amidoenoates (1, 2) and β-ketoiminates (3) of the form [LZnEt]2 with varying steric bulk have been synthesised via the reaction of diethylzinc with β-aminoenoate ligands HL1 and HL2 and β-ketoimine HL3. These complexes have been characterised via 1H and 13C NMR, mass spectrometry and single-crystal X-ray diffraction, which unambiguously determined all three structures as dimeric species in the solid state. We observe the unusual dimerisation of 1 and 2 through coordination of the central zinc atom to the methine carbon of the second monomer, which gives these complexes high reactivity. The thermal properties of complex 3 are explored via thermal gravimetric analysis (TGA), to investigate their potential as single-source precursors to zinc oxide, which shows that 3 has a significantly lower decomposition temperature as compared to its bis-ligated counterpart [Zn(L3)2], which gives 3 promise as a single-source precursor to zinc oxide.

ZnO formation through decomposition of zinc bis(ethyl acetoacetate) by steaming treatment

Zn(etac)2 was prepared by the reaction of diethylzinc with ethyl acetoacetate. Zn(etac)2 was decomposed in hot water vapor. Zn(etac)2 was converted into wurtzite ZnO powder in water vapor at 60–70 °C.

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine was subjected to stereospecific dihydroxylation with OsO4/NMO, resulting in the (1R,2R,3R,5R)-aminodiol diastereomer. The obtained primary aminodiol was transformed to a secondary analogue. The ring closure of the N-benzyl-substituted aminodiol with formaldehyde was investigated and regioselective formation of the spiro-oxazolidine ring was observed. Hydroboration or dihydroxylation of sabinol or its benzyl ether with OsO4/NMO resulted in the formation of sabinane-based diols and triols following a highly stereospecific reaction. Treatment of sabinol with m-CPBA afforded O-benzoyl triol as a diastereoisomer of the directly dihydroxylated product, instead of the expected epoxy alcohol. The resulting aminodiols, diol, and triols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde from moderate to good selectivity.

Binary Zinc Azides.

Pure, solvent-free Zn(N3 )2 was prepared by reaction of diethyl zinc and hydrazoic acid in aprotic solvents. The single-crystal structure determination, along with the comprehensive characterization of α-Zn(N3 )2 and two metastable polymorphs, could be achieved for the first time. Since these data disagree in large parts with the known, previously reported values, all previous syntheses of Zn(N3 )2 , and for comparison Zn(N3 )2 ⋅2.5 H2 O and Zn(OH)N3 were reinvestigated, indicating that some of the earlier work has to be revised.

ChemInform Abstract: Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by (R)‐1‐Phenylethylamine‐Derived 1,4‐Amino Alcohols.

Abstract A series of o-xylylene-type 1,4-amino alcohols, synthesized from (R)-1-phenylethylamine, were used as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. (S)-1-Phenyl-1-propanol was obtained with high enantioselectivity in all cases since the stereochemical outcome of the reaction was controlled by the chiral benzylic carbon bearing amino group. Highest catalytic activity was obtained by using (R)-1-{2-[1-(pyrrolidin-1-yl)ethyl]phenyl}cyclohexan-1-ol (1n) derived from (R)-1-(1-phenylethyl)pyrrolidine and cyclohexanone. Various chiral secondary alcohols were obtained by the reaction of diethylzinc and aldehydes in the presence of 1n within 2 h with good to high enantioselectivities.

Enantioselective addition of diethylzinc to aldehydes catalyzed by (R)-1-phenylethylamine-derived 1,4-amino alcohols

Abstract A series of o-xylylene-type 1,4-amino alcohols, synthesized from (R)-1-phenylethylamine, were used as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. (S)-1-Phenyl-1-propanol was obtained with high enantioselectivity in all cases since the stereochemical outcome of the reaction was controlled by the chiral benzylic carbon bearing amino group. Highest catalytic activity was obtained by using (R)-1-{2-[1-(pyrrolidin-1-yl)ethyl]phenyl}cyclohexan-1-ol (1n) derived from (R)-1-(1-phenylethyl)pyrrolidine and cyclohexanone. Various chiral secondary alcohols were obtained by the reaction of diethylzinc and aldehydes in the presence of 1n within 2 h with good to high enantioselectivities.

Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors

The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H2S as reactants. Depositions on SAMs with three different terminal groups, –CH3, –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH3 terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H2S with the Zn-surface adduct may be incomplete.

Effect of Diethylzinc on the Activity of Ethylene Polymerization by Metallocene Catalyst

Adding a suitable amount of diethylzinc as the third compound to a metallocene/MAO catalytic system for ethylene (co) polymerization gives rise to a sharp increase in activity. For ethylene homopolymerization, the activity is enhanced from 2.28 (Zn/Zr = 0) to 10.92 × 106 g/mol‐Zr/h (Zn/Zr = 100), and the activity for ethylene/1‐hexene copolymerization is enhanced from 7.68 (Zn/Zr = 0) to 16.20 × 106 g/mol‐Zr/h (Zn/Zr = 100). The activity decreases when the amount of diethylzinc is further increased. UV‐vis analysis shows that a mixed aluminoxane (MEAO) may be generated by the reaction of diethylzinc with MAO.

Intramolecular Metalloamination of N,N‐Dimethylhydrazinoalkenes: A Versatile Method to Access Functionalized Piperidines and Pyrrolidines

AbstractHighly diastereoselective metalloamination/cyclization reactions of zinc(II) hydrazides obtained through reaction of diethylzinc with N,N‐dimethylhydrazinoalkenes are described. The resulting organozinc intermediates undergo facile allylation and acylation, in situ, to provide the corresponding functionalized piperidines and pyrrolidines.

Intramolecular metalloamination of N,N-dimethylhydrazinoalkenes: a versatile method to access functionalized piperidines and pyrrolidines.

Highly diastereoselective metalloamination/cyclization reactions of zinc(II) hydrazides obtained through reaction of diethylzinc with N,N-dimethylhydrazinoalkenes are described. The resulting organozinc intermediates undergo facile allylation and acylation, in situ, to provide the corresponding functionalized piperidines and pyrrolidines.

A New Look at the Reactivity of TEMPO toward Diethylzinc

Reactions of diethylzinc with TEMPO were investigated. Dropwise addition of 1 equiv of TEMPO to Et2Zn at −10 °C leads to the nitroxide complex EtZn(TEMPO) in high yield, whereas upon addition of 2 equiv of TEMPO the corresponding homoleptic nitroxide compound Zn(TEMPO)2 is formed. Diffusion ordered NMR spectroscopy experiments revealed that both zinc nitroxide compounds exist in monomeric forms in solution, while single-crystal X-ray diffraction confirmed their dimeric structure in the solid state.

Stereoselective syntheses and transformations of chiral 1,3-aminoalcohols and 1,3-diols derived from nopinone

Abstract A library of 1,3-difunctionalized pinane derivatives were synthesized and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. 1,3-Aminoalcohol 6a was prepared from (−)-nopinone 2 via stereoselective Mannich condensation and reduction of the resulting β-amino ketone 4 . The key aminoalcohol 6a was transformed into primary, secondary and tertiary substituted aminoalcohols in order to study the effect of the substituent on catalytic activity. Starting from (−)-nopinone, cis - and trans -β-hydroxy esters 15 and 16 were prepared in a two-step stereoselective synthesis. Reduction of the hydroxy esters resulted in pinane-based 1,3-diols, while hydrolysis of the esters, followed by DCC-mediated amidation and subsequent reduction, led to cis - and trans - N -benzyl-1,3-aminoalcohols 8 and 23 . trans - N -Benzyl-1,3-aminoalcohol 8 was also prepared by selective mono-debenzylation of 6a via a continuous-flow process in an H-Cube® system. The resulting aminoalcohols and diols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde.

The ALD‐MLD Growth of a ZnO‐Zincone Heterostructure

A mixed inorganic/organic zinc oxide/zincone multilayer film, using a combination of atomic layer deposition (ALD) and molecular layer deposition (MLD), is grown. A molecular fragment is deposited in each half reaction in the MLD technique, thus making it similar to, and compatible with, the ALD method of deposition. Zinc oxide inorganic layers are grown at a substrate temperature of 150°C with alternate surface‐saturating reactions of diethylzinc and water. Under similar growth condition, diethylzinc and hydroquinone are used to deposit an organic zincone layer that follows the MLD reaction mechanism. Deposition rates are obtained from an in‐situ quartz crystal microbalance (QCM) and verified using X‐ray reflectivity (XRR) measurements and scanning electron microscopy (SEM). Chemical constituents of the hybrid layers are confirmed from secondary ion mass spectroscopy (SIMS) and Fourier transform infrared (FTIR) spectroscopy. Selective etching of the organic layers results in the formation of zinc oxide nanosheets stacked together by van der Waals attraction balanced by Coulombic repulsion.

Composition at the CuInSe2/ZnO interface: Copper depletion induced by diethyl-zinc

The interface formation between epitaxial CuInSe2(112) films and ZnO deposited by metal-organic MBE is investigated by photoelectron spectroscopy. Reaction of diethyl-zinc with CuInSe2 leads to the formation of an intrinsic ZnSe layer and copper depletion of the interface. This is associated with Zn doping of the chalcopyrite surface and a Fermi-level shift toward the conduction band. The implications on the band alignment are discussed.

Aerosol Assisted Chemical Vapor Deposition of Transparent Conductive Zinc Oxide Films

Highly conductive and transparent ZnO films were synthesized by the reaction of diethyl zinc (in toluene) with methanol by dual source aerosol assisted chemical vapor deposition. These films displayed a stable sheet resistance of 7.2 Ω/□ and high transmission across the visible region comparable to commercial transparent conducting oxides (TCOs) based on oxides of tin or indium. Doping the zinc oxide structure with fluorine (trifluorotoluene) resulted in dense compact films with improved electrical properties than ZnO films with a sheet resistance of 4.5 Ω/□. These films also displayed idealized surface texturing for photovoltaic applications. Fluorine concentration was 2 at.% determined by wavelength dispersive X-ray analysis (WDX). Aluminum doped zinc oxide films were also synthesized by introducing dopant amounts of trimethylaluminium solution (in toluene) into the system. These films exhibited low sheet resistances of 14 Ω/□. The aluminum concentration in the films was 4 at.% determined by WDX.

Characterization of Spin Coated Nondoped and In-Doped ZnO Films Using Novel Precursor Solution

A novel precursor for ZnO film deposition with Zn-O structure was synthesized by the reaction of diethylzinc and water in some ether solvents. The novel precursor was characterized by 1H-NMR spectroscopy and differential scanning calorimetry (DSC). Nondoped and In-doped ZnO films on a glass substrate have been successfully grown by conventional spin coating using nondoped and In added novel precursor solution. The samples have an optical transmittance of more than 85%, and a smooth surface determined from optical transmittance and scanning electron microscopy, respectively. The sheet resistivity of In-doped ZnO films is lower than that of nondoped ZnO film.

Synthesis and characterization of zinc complexes and reactivity with primary phosphines

Zinc complexes of chelating monoanionic N-donors and neutral diphosphine ligands were synthesized by reaction of diethylzinc with 1,3-diketimine, diazabutadiene, and diphosphine ligand precursors. These complexes were reacted with primary phosphines in an attempt to solicit phosphine dehydrocoupling reactivity. In most cases, insoluble zinc-containing precipitates were formed and ligands were liberated. For the most sterically encumbered complex, (DippL)ZnEt (3, DippL = [(2,6-iPrC6H3)NC(CH3)]2CH−), a product assigned as the zinc-phosphide (DippL)ZnPHPh (6) was observed but could not be isolated as a pure compound. A new, less bulky β-diketiminate complex (TolL)ZnEt (2, TolL = [(p-CH3C6H4)NC(CH3)]2CH−) was reacted with primary phosphines to give a precipitate and the bis(β-diketiminate)zinc complex (TolL)2Zn (5), an apparent product of comproportionation. (MesAI)ZnEt (1, MesAI = MesNC(Me)(Et)C(Me) = NMes) and 2 were structurally characterized.

Ar‐BINMOLs with Axial and sp3Central Chirality – Characterization, Chiroptical Properties, and Application in Asymmetric Catalysis

Abstract2′‐Hydroxy‐1,1′‐binaphthalene‐2‐(arylmethanol) (Ar‐BINMOLs), a family of new 1,1′‐binaphthalene‐2,2′‐diol derivatives, prepared by a [1,2]‐Wittig rearrangement, are introduced as new chiral molecules for the study of the modes of supramolecular aggregation on the basis of ESI‐MS, NMR spectroscopy, differential scanning calorimetry (DSC), and X‐ray diffractometry. Characterization showed that Ar‐BINMOLs exhibit different characteristics to BINOL and act as supramolecules due to hydrogen bonding and aromatic π–π/C–H···π interactions. In particular, CD measurements of chiral and racemic Ar‐BINMOL2ain solution and the solid state show a strong Cotton effect, which revealed that amplification of chirality was observed because of the formation of a chiral supramolecular oligomer derived from the racemic monomer. To this end, the Ar‐BINMOLs were used as supramolecular auxiliaries to mediate the Michael reaction of anthrone to (E)‐β‐nitrostyrene and could give the Michael adduct with comparable enantioselectivities. In addition, the Ar‐BINMOLs act as ligands to promote asymmetric 1,2‐addition of diethylzinc to aldehydes, which resulted in excellent yields and enantioselectivities (up to >99.9 %ee) in the reactions of diethylzinc with a broad range of aromatic aldehdyes.