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151.
Siama Basharat Robert Palgrave Derek A. Tocher 《Journal of organometallic chemistry》2008,693(10):1787-1796
Structural studies by X-ray crystallography have been carried out for a range of diorganoalkoxogallanes incorporating donor-functionalized ligands. The compounds [Et2Ga(μ-OR)]2 (1, R = CH2CH2NMe2; 2, R = CH(CH3)CH2NMe2; 3, C(CH3)2CH2OMe; 4, R = CH(CH2NMe2)2) adopt dimeric structures with a planar Ga2O2 ring, and each gallium atom is coordinated in a distorted trigonal bipyramidal geometry. Low pressure chemical vapor deposition (CVD) of 2 and 4 resulted in the formation of oxygen deficient gallium oxide thin films on glass. However, the reaction of Et3Ga and ROH (R = CH2CH2NMe2, CH(CH3)CH2NMe2, C(CH3)2CH2OMe, CH(CH2NMe2)2) in toluene under aerosol assisted (AA)CVD conditions afforded stoichiometric Ga2O3 thin films on glass. This CVD technique offers a rapid, convenient route to Ga2O3, which involves the in situ formation of diethylalkoxogallanes, of the type [Et2Ga(μ-OR)]2, the structures of which are described in this paper. The gallium oxide films were deposited at 450 °C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. 相似文献
152.
Shohjiroh Tanase Kiyokazu Katayama Susumu Inasawa Fumio Okada Yukio Yamaguchi Takanori Sadashima Nobuhiro Yabunouchi Takehito Konakazawa Tadanori Junke Nobuhide Ishihara 《大分子反应工程》2008,2(3):233-239
In this study, novel carrier materials were synthesized by addition of metal dihalide compounds in the synthesis reaction of magnesium diethoxide using metallic magnesium, ethanol and iodine. Poly(propylene) polymerizations were then investigated with the MgCl2‐supported TiCl4 catalysts using these carrier materials. As results, magnesium diethoxide with extremely large particle sizes and spherical shapes were obtained and the angles of repose of PP particles obtained by using their catalysts as a flowability index showed high values. Furthermore, in order to confirm key points for excellent catalyst performance from detailed characterizations, SEM images, compositions and WAXS were measured.
153.
Marcin Florczak Jan Libiszowski Jaroslav Mosnacek Andrzej Duda Stanislaw Penczek 《Macromolecular rapid communications》2007,28(13):1385-1391
L,L ‐lactide (LA) and ε‐caprolactone (CL) block copolymers have been prepared by initiating the poly(ε‐caprolactone) (PCL) block growth with living poly(L,L ‐lactide) (PLA*). In the previous attempts to prepare block copolymers this way only random copolyesters were obtained because the PLA* + CL cross‐propagation rate was lower than that of the PLA–CL* + PLA transesterification. The present paper shows that application of Al‐alkoxide active centers that bear bulky diphenolate ligands results in efficient suppression of the transesterification. Thus, the corresponding well‐defined di‐ and triblock copolymers could be prepared.
154.
M. N. Bochkarev A. A. Fagin I. L. Fedushkin T. V. Petrovskaya W. J. Evans M. A. Greci J. W. Ziller 《Russian Chemical Bulletin》1999,48(9):1782-1785
The reactions of Tml2(DME)3 with phenol andtert-butyl alcohol afforded thulium(III)-alkoxyiodides ROTmI2(DME)2 (R=Ph and But, respectively). Their structures were determined by X-ray analysis. Monoiodides (RO)2 TmI(THF)2 were synthesized from TmI3 (THF)2 and ROH (taken in a ratio of 1∶2). Triphenoxides (RO)3Tm (R=Ph or 2,4,6-But
3C6H2) were prepared by the reactions of the naphthalene thulium complex [C10H8Tm(DME)]2C10H8, with an excess of the corresponding phenol. The iodide catechoxide complex 3,6-But
2C6H2O2TmI(DME)2 was prepared by the reaction of TmI2(DME)3 with 3,6-di-tert-butylbenzoquinone-1,2 or 3,6-di-tert-butylpyrocatechol.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1804–1807, September, 1999. 相似文献
155.
Chang‐Ming Dong Kun‐Yuan Qiu Zhong‐Wei Gu Xin‐De Feng 《Journal of polymer science. Part A, Polymer chemistry》2001,39(3):357-367
D,L ‐3‐Methylglycolide (MG) was successfully polymerized with bimetallic (Al/Zn) μ‐oxo alkoxide as an initiator in toluene at 90 °C. The effect of the initiator concentration and monomer conversion on the molecular weight was studied. It is shown that the polymerization of MG follows a living process. A kinetic study indicated that the polymerization approximates the first order in the monomer, and no induction period was observed. 1H NMR spectroscopy showed that the ring‐opening polymerization proceeds through a coordination–insertion mechanism with selective cleavage of the acyl–oxygen bond of the monomer. On the basis of 1H NMR and 13C NMR analyses, the selective cleavage of the acyl–oxygen bond of the monomer mainly occurs at the least hindered carbonyl groups (P1 = 0.84, P2 = 0.16). Therefore, the main chain of poly(D,L ‐lactic acid‐co‐glycolic acid) (50/50 molar ratio) obtained from the homopolymerization of MG was primarily composed of alternating lactyl and glycolyl units. The diblock copolymers poly(ϵ‐caprolactone)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) and poly(L ‐lactide)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) were successfully synthesized by the sequential living polymerization of related lactones (ϵ‐caprolactone or L ‐lactide). 13C NMR spectra of diblock copolymers clearly show their pure diblock structures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 357–367, 2001 相似文献
156.
The potential of diorganotin compounds, in particular alkoxides and phenoxides, to function as neutral and non‐corrosive catalysts in the methanolysis of tripalmitin (the main triglyceride in palm oil) to methyl palmitate has been investigated. The compounds reveal a strong dependence of catalytic activity on the nature of the organic moiety on tin, the ring‐borne substituent on the phenoxyl group and the chain length of the alkoxyl fragment, as well as the ring size in cyclic alkoxides derived from bifunctional ligands such as diethanolamine. Kinetic studies, based on detailed compositional analysis of the reaction mixture by gas chromatography, were performed typically at 70.0 ± 0.1 °C in mixed methanol–tetrahydrofuran (3:2, v/v) medium and at 1.0 mol% catalyst concentration with respect to tripalmitin. The catalysts used for the kinetic studies were dibutyl bis( p‐chlorophenoxyl)tin 1, dibutyl bis(phenoxyl)tin 2, 1,1‐dibutyl‐5‐aza‐2,8‐dioxo‐1‐stannacyclo‐octane 3, 2,2‐dibutyl‐2‐stanna‐1,3‐benzdioxane 4 and dioctyltin oxide 5. The methanolysis was shown to proceed by a consecutive reaction pathway. Numerical analysis of the rate data yielded values of the three rate constants k1, k2 and k3 corresponding to the respective conversions, tripalmitin → dipalmitin → monopalmitin → glycerol. Based on t values ranging from 7.2 to 22.3 h−1, the following order of catalytic activity was established: 1 > 2 > 3 ≫ 5 ≫ 4; for catalyst 4 the t value was close to that of the uncatalysed reaction. A six‐fold increase in rate was observed when the catalyst concentration was raised from 1.0 to 3.0 mol% for 3. 119Sn NMR analysis of the chloroform extracts of the pot residue following solvent removal at the end of 24 h of the transesterification reaction revealed that the catalysts 1 and 3 essentially retained their chemical integrity. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
157.
The tetrameric titanium alkoxide (MeC(CH2‐μ3‐O)(CH2‐μ‐O)2)2Ti4(O‐i‐Pr)10 ( 1 ) catalyzes the ring‐opening polymerization (ROP) of lactide (LA) in toluene solution at various polymerization temperatures, and its bulk ROP at 130°C. Compound 1 facilitated reasonably controlled polymerization characteristics via a coordination/insertion mechanism in solution, whereas the bulk polymerization products displayed broad molecular‐weight distributions. The stereochemical microstructure of PLA was determined from homonuclear decoupled 1H NMR spectroscopic studies. 相似文献