Polymerization of new 1-(trimethylsilyl)-1-propyne homologs containing two silicon atoms [CH3C?CSi(CH3)2CH2Si(CH3)3 and CH3C?CSi(CH3)2CH2CH2Si(CH3)3] was investigated by use of Ta and Nb catalysts. CH3C?CSi(CH3)2CH2Si(CH3)3 was polymerized quantitatively by TaCl5 alone to provide a polymer having molecular weight over 106. CH3C?CSi(CH3)2CH2CH2Si(CH3)3 was polymerized in good yield by an equimolar mixture of TaCl5 with an appropriate organometallic cocatalyst such as Ph4Sn to give a polymer with molecular weight of ca. 4 X 105. Nb catalysts were less active toward these monomers than the corresponding Ta catalysts. These two kinds of polymers had alternating double bonds along the main chain according to IR and 13C-NMR spectra. Both polymers were white solids completely soluble in low-polarity solvents like toluene, and solution casting afforded uniform, tough films. These polymers were thermally fairly stable, and their softening points were above 350°C. Films of these polymers showed smaller oxygen permeability coefficients [P = 4 × 10?9 – 8 × 10?9 cm3(STP) · cm/(cm2·sec·cmHg)] but larger separation factors [(P/P) = 3.4 – 3.6] than a poly[1-(trimethylsilyl)-1-propyne] film. 相似文献
Two series of neopentylbenzenes with one or two substituents on the benzyl group have been synthesized. In one series the substituents were H, F, Cl, Br, I, OCH3, OCOCH3, OSi(CH3)3 CH3 and CH2CH3, and in the other OH and R [R ? H, CH3, CH2CH3, (CH2)3CH3, CH(CH3)2 and C(CH3)3]. Barriers to internal C? C and C? C rotation have been estimated by 13C NMR band shape methods. Estimated barriers were found to increase as the size of the substituent increases. The results are discussed in terms of possible initial and transition states, based on summations of results from molecular mechanics (MM) calculations, using the Allinger MMP1 program. Barriers estimated experimentally are compared with results from other systems found in the literature. 相似文献
The reaction of sulfur with primary or secondary amines and formaldehyde has been studied. A simple one step process for the preparation of thioformamides (RR′NCHS; R ? H, R′ ? CH3, C2H5; R ? R′ ? CH3, C2H5; R+R′ ? ? (CH2), ? (CH2), ? C2H4OC2H) and the amine salts of N, N-dialkyl-dithiocarbamic acids (R2NCS2 · H2NR2, R ? CH3, C2H5, C4H9; R2 ? ? (CH2), ? (CH2), ? C2H4OC2H) is reported. In addition, the isolation of diethylamidosulfoxylic acid, (C2H5)2NSOH · 1/2 H2O, the first derivative of a new class of compounds, is described. The physical properties and the 1H-NMR. spectra of the above mentioned compounds are given. 相似文献
This contribution describes the reactivities of CO2, CO, O2, and ArNC with the pincer‐type complexes [(κP,κC,κP′‐POCOP)NiX] (POCOP=(R2POCH2)2CH; R=iPr; X=OSiMe3, NArH; Ar=2,6‐iPr2C6H3). Reaction of the amido derivative with CO2 and CO leads to a simple insertion into the Ni?N bond to give stable carbamate and carbamoyl derivatives, respectively, the pincer ligand backbone remaining intact in both cases. In contrast, the analogous reactions with the siloxide derivative produced kinetically labile insertion products that either revert to the starting material (in the case of CO2) or react further to give the mixed‐valent, dinickel species [(POCOP)NiII{μ,κO,κP,κP′‐OCOCH(CH2CH2OPR2)2}Ni0(CO)2]. The zero‐valent center in the latter compound is ligated by a new ligand arising from transformation of the POCOP ligand backbone. The carbonylation and carboxylation of the siloxido derivative also produced minor quantities of a side‐product identified as the trinickel species, [{(η3‐allyl)Ni(μO,κP‐R2PO)2}2Ni], arising from total dismantling of the POCOP ligand. Similar reactivities were observed with isonitrile, ArNC: reaction with the siloxido derivative resulted in a complex sequence of steps involving initial insertion, a 1,3‐hydrogen shift, and an Arbuzov rearrangement to give [Ni(CNAr)4] and a methacrylamide based on fragments of the POCOP ligand. Oxygenation of the amido and siloxido derivatives led to the phosphinate derivative, [(POCOP)Ni(OP(O)R2)], arising from oxidative transformation of the original ligand frame; the reaction with the Ni‐NHAr derivative also gave ArHNP(O)R2 through a complex N?P bond‐forming reaction. 相似文献
Enantiomerically pure triflones R1CH(R2)SO2CF3 have been synthesized starting from the corresponding chiral alcohols via thiols and trifluoromethylsulfanes. Key steps of the syntheses of the sulfanes are the photochemical trifluoromethylation of the thiols with CF3Hal (Hal=halide) or substitution of alkoxyphosphinediamines with CF3SSCF3. The deprotonation of RCH(Me)SO2CF3 (R=CH2Ph, iHex) with nBuLi with the formation of salts [RC(Me)? SO2CF3]Li and their electrophilic capture both occurred with high enantioselectivities. Displacement of the SO2CF3 group of (S)‐MeOCH2C(Me)(CH2Ph)SO2CF3 (95 % ee) by an ethyl group through the reaction with AlEt3 gave alkane MeOCH2C(Me)(CH2Ph)Et of 96 % ee. Racemization of salts [R1C(R2)SO2CF3]Li follows first‐order kinetics and is mainly an enthalpic process with small negative activation entropy as revealed by polarimetry and dynamic NMR (DNMR) spectroscopy. This is in accordance with a Cα? S bond rotation as the rate‐determining step. Lithium α‐(S)‐trifluoromethyl‐ and α‐(S)‐nonafluorobutylsulfonyl carbanion salts have a much higher racemization barrier than the corresponding α‐(S)‐tert‐butylsulfonyl carbanion salts. Whereas [PhCH2C(Me)SO2tBu]Li/DMPU (DMPU = dimethylpropylurea) has a half‐life of racemization at ?105 °C of 2.4 h, that of [PhCH2C(Me)SO2CF3]Li at ?78 °C is 30 d. DNMR spectroscopy of amides (PhCH2)2NSO2CF3 and (PhCH2)N(Ph)SO2CF3 gave N? S rotational barriers that seem to be distinctly higher than those of nonfluorinated sulfonamides. NMR spectroscopy of [PhCH2C(Ph)SO2R]M (M=Li, K, NBu4; R=CF3, tBu) shows for both salts a confinement of the negative charge mainly to the Cα atom and a significant benzylic stabilization that is weaker in the trifluoromethylsulfonyl carbanion. According to crystal structure analyses, the carbanions of salts {[PhCH2C(Ph)SO2CF3]Li? L }2 ( L =2 THF, tetramethylethylenediamine (TMEDA)) and [PhCH2C(Ph)SO2CF3]NBu4 have the typical chiral Cα? S conformation of α‐sulfonyl carbanions, planar Cα atoms, and short Cα? S bonds. Ab initio calculations of [MeC(Ph)SO2tBu]? and [MeC(Ph)SO2CF3]? showed for the fluorinated carbanion stronger nC→σ* and nO→σ* interactions and a weaker benzylic stabilization. According to natural bond orbital (NBO) calculations of [R1C(R2)SO2R]? (R=tBu, CF3) the nC→σ*S? R interaction is much stronger for R=CF3. Ab initio calculations gave for [MeC(Ph)SO2tBu]Li ? 2 Me2O an O,Li,Cα contact ion pair (CIP) and for [MeC(Ph)SO2CF3]Li ? 2 Me2O an O,Li,O CIP. According to cryoscopy, [PhCH2C(Ph)SO2CF3]Li, [iHexC(Me)SO2CF3]Li, and [PhCH2C(Ph)SO2CF3]NBu4 predominantly form monomers in tetrahydrofuran (THF) at ?108 °C. The NMR spectroscopic data of salts [R1(R2)SO2R3]Li (R3=tBu, CF3) indicate that the dominating monomeric CIPs are devoid of Cα? Li bonds. 相似文献
Two new polyoxometalate (POM)‐based hybrid monomers (Bu4N)5(H)[P2V3W15O59{(OCH2)3CNHCO(CH3)C?CH2}] ( 2 ) and (S(CH3)2C6H4OCOC(CH3)=CH2)6[PVMo10O40] ( 5 ) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells–Dawson and Keggin‐type clusters and were characterized by analytical and spectroscopic techniques including ESI‐MS and/or single‐crystal X‐ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by 1H, 31P NMR and IR spectroscopic techniques, gel‐permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E‐beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source. 相似文献
Novel fluorine-containing carbofunctional organosilicon monomers were synthesized: 3-pentafluorobenzylideneaminopropylethoxysilane
(EtO)3Si(CH2)3N=CH-C6F5, N-3-methoxydiethoxysilylpropyltrifluoroacetamide (EtO)2(MeO)Si(CH2)3NHC(O)CF3, and 1,1,5-trihydrooctafluoroamyl N-3-triethoxysilylpropylaminopropanoate (EtO)3Si(CH2)3NH(CH2)2C(O)OCH2(CF2)3CHF2. Compositions for the formation of transparent thermally stable films were prepared from these monomers. The films have low
absorbance intensity near 1550 nm, i.e., in the region of photosignal transmission of modern optical communication systems. The compositions can dissolve complexes
with organofluorine ligands and produce transparent homogeneous films doped with rare-earth metals. The concentrations of
the complexes in the matrices are 3.7–21.4 wt.% (metal concentrations are 0.6–3.7%). Fluorescence and fluorescence excitation
spectra of the matrices and electronic absorption spectra of the doped films were studied.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1131–1138, May, 2005. 相似文献
The mechanism of the photolysis of formaldehyde was studied in experiments at 3130 Å and in the pressure range of 1–12 torr at 25°C. The experiments were designed to establish the quantum yields of the primary decomposition steps (1) and (2), CH2O + hν → H + HCO (1): CH2O + hν → H2 + CO (2), through the effects of added isobutene, trimethylsilane, and nitric oxide on ΦCO and Φ. The ratio ΦCO/Φ was found to be 1.01 ± 0.09(2σ) and (Φ + ΦCO)/2 = 1.10 ± 0.08 over the range of pressures and a 12-fold change in incident light intensity. Isobutene and nitric oxide additions reduced Φ to about the same limiting value, 0.32 ± 0.03 and 0.34 ± 0.04, respectively, but these added gases differed in their effects on ΦCO. With isobutene addition ΦCO/Φ reached a limiting value of 2.3; with NO addition ΦCO exceeded unity. The addition of small amounts of Me3SiH reduced Φ to 1.02 ± 0.08 and lowered ΦCO to 0.7. These findings were rationalized in terms of a mechanism in which the “nonscavengeable,” molecular hydrogen is formed in reaction (2) with ?2 = 0.32 ± 0.03, while the “free radical” hydrogen is formed in reaction (1) with ?1 = 0.68 ± 0.03. In the pure formaldehyde system these reactions are followed by (3)–(5): H + CH2O → H2 + HCO (3); 2HCO → CH2O + CO (4); 2HCO → H2 + 2CO (5). The data suggest k4/k5 ? 5.8. Isobutene reduced Φ by the reaction H + iso-C4H8 → C4H9 (20), and the results give k20/k3 ? 43 ± 4, in good agreement with the ratio of the reported values of the individual constants k3 and k20. 相似文献
A kinetic study has been made of the 3130-Å photolysis of CH2O (8 torr) in O2-containing mixtures (0.02–8 torr) and in the presence of added CO2 (0–300 torr) at 25°C. Quantum yields of formation of H2, CO, and CO2 and the loss of O2 were measured. Φ and ΦCO were much above unity. In an explanation of these unexpected results, a new H-atom-forming chain mechanism was postulated involving HO2 and HO addition to CH2O: CH2O + hν → H + HCO (1) H + CH2O → H2 + HCO (3) H + O2 + M → HO2 + M (6) HCO + O2 → HO2 + CO (8) HO2 + CH2O → (HO2CH2O) → HO + HCO2H (15) HO + CH2O → H2O + HCO? (16); HCO? → H + CO (19) HO + CH2O → H2O + HCO (17) and HO + CH2O → HCO2H + H (18). When the results are rationalized in terms of this mechanism, the data suggest k16 ? k17 and k16/k18 ? 0.5. The data require that a reassessment of the relative rates of reactions (7) and (8) be made, since in the previous work HCO2H formation was used as a monitor of the rate of reaction (7) HCO + O2 + M → HCOO2 + M (7). The present data from experiments at P = 8 torr and P = 1–4 torr give k7[M]/(k7[M] + k8) ≥ 0.049 ± 0.017. These data coupled with the k8 estimates of Washida and coworkers give k7 ≥ (4.4 ± 1.6) × 1011 l2/mol2·sec for M = CH2O. The reaction sequence proposed here is consistent with the observed deterimental effect of O2 addition on the laser-induced isotope enrichment in HDCO. In additional studies of CH2O-O2-isobutene mixtures it was found that Φ was equal to ?2 as estimated in O2-free CH2O-isobutene mixtures. These results suggest that the increase in CO (ν = 1) product observed with O2 addition in CH2O photolysis does not result from perturbations in the fragmentation pattern of the excited CH2O, but it is likely that it originates in the occurrence of the exothermic reaction HCO + O2 → HO2 + CO (ν = 1). 相似文献
In this work, we have calculated the thermodynamic parameters of the polymerization of some derivatives of the species CH2X (X = CH2, NH, O), using ab initio methods of quantum chemistry and the usual formalism of statistical thermodynamics. It is shown that the Gibbs functions ΔG(l, c) corresponding to CH2NOCH3, CNCHNCN, CF2O and all the percyano derivatives are largely positive which indicates that the spontaneous (radical or ionic) chain polymerization of these monomers is thermodynamically prohibited. 相似文献
Crystal and Molecular Structure of (CH3)2SnSAB. (SAB = Dianion of 2-Hydroxy-N-(2-hydroxybenzylidene)-aniline) (CH3)2SnSAB, C15H15NO2Sn (SAB = tridentate dianion of 2-hydroxy-N-(2-hydroxybenzylidene)-aniline in SCHIFF base form) crystallizes in the space group Pben (D) with a = 19.271(5), b = 10.508(2), c = 13.379(1) Å and Z = 8. The structure has been solved using 1307 symmetrical independent reflections and applying the heavy atom method; the position of all atoms, except the H atoms, has been determined. As interatomic distances have been found: Sn? C: 2.117(14), Sn? O:2.112(9), Sn? N:2.229(11) N? C 10 (phenyl group II): 1.462(16), C9-N (SCHIFF base bridging group): 1.257(18), C 9? C8 (phenyl group I): 1.441(18) Å; mean C? C distances in the phenyl groups: 1.403(18) Å. Two molecules at a time have a centre of symmetry and weakly coordinate through two loose Sn? O bridges (intermolecular Sn? O distance: 2.881(8) Å). The individual molecules essentially form a distorted trigonal bipyramid with N and both methyl-C atoms in the equatorial plane; ? CSnC = 138.52(50)°; ? OSnO = 158.58(35)°. 相似文献
DFT (B3LYP, M06‐2X) and MP2 methods are applied to the design of a wide series of the potentially 10‐C‐5 neutral compounds based on 6‐azabicyclotetradecanes: XC1(YCH2CH2CH2)3N 1 – 3 , XC1(YC6H4CH2)3N 4 – 6 , XC1[Y(tBuC6H3)CH2]3N 7 – 9 and carbatranophanes 10 – 25 (X=Me, F, Cl; Y=O, NH, CH2, SiH2; Z=O, CH2, (CH2)2, (CH2)3). Carbatranophanes 10 – 25 are characterized by a sterical compression of their axial 3c–4e XC1←N fragment with respect to that in the parent molecules 4 – 6 . A magnitude of the revealed effect depends on a valence surrounding of the central carbon atom C1, the size and the nature of the side chains (Z) that link the “π‐electron cap” with a tetradecane backbone. This circumstance allowed us to obtain 10‐C‐5 structures with the configuration of the bonds around the C1 atom, which corresponds to practically an ideal trigonal bipyramid. In these compounds, the values of the covalence ratio χ of approximately 0.6 for the coordination C1←N contacts with a covalent contribution (atoms in molecules (AIM) and natural bond orbital (NBO)) are record in magnitude. These values lie close to a low limit of the interval of the χSi←D change (0.6–0.9) being characteristic of the dative and ionic‐covalent (by nature) Si←D bond (D=N, O) in the known 10‐Si‐5 silicon compounds. 相似文献
The unimolecular chemistry of the methyl carbamate radical cation, H2NCOOCH, 1, has been further investigated by a combination of mass spectrometry-based experiments (metastable ion (MI), collisional activation (CA), collision-induced dissociative ionization (CIDI), neutralization-reionization (NR) Spectrometry and 2H labelling) and ab initio molecular orbital calculations, executed at the MP3/6–31G*//4–31G level of theory and corrected for zero-point vibrational energies. Apart from the previously located maxima, i.e. H2NCOOCH3+·, 1, the distonic ion H2NC(OH)OCH3+·, 2, hydrogen-bridged ions [H2N? C?O…? H…?O?CH2]+·, 5, and [H2N? CH?O…?…?H…?O?C? H]+·, 7, there exist at least two other equilibrium structures, viz. the iminol ion H? N?C(OH)? OCH, la, and the hydrogen-bridged species [H2C?O…?H…?N(H)COH], 6a, which is closely related to ion 5. Although the iminol ion la lies only 30 kJ mol?1 above 1, our calculations indicate that the barriers for its formation either directly from ionized methyl carbamate 1 via a 1,3-hydrogen shift or indirectly via 1,4-hydrogen shifts from the distonic ion 2 are too high to allow the iminol ion to be involved in the unimolecular chemistry of ionized methyl carbamate. This explains the earlier observation that there are no H-D exchange reactions prior to decomposition of ionized labelled methyl carbamate, in contrast to the related ion methyl acetate. However, attempts to generate the iminol ion by loss of CH3CN from CH3CH?N? NHCOOCH3 produced the more stable distonic ion 2 instead, but it proved very difficult to assign its structure unequivocally because 2 can rapidly interconvert with 1 and so virtually identical dissociation characteristics ensue. Only by integration of results obtained from many experiments and from ab initio calculations could structure 2 be assigned. The distonic ion 2 can undergo two transformations: after stretching of the C? OCH2 bond the incipient formaldehyde can migrate within the electrostatic field of ionized hydroxyaminocarbene to the OH end to generate 5, but it can also migrate to the NH end to generate 6a. This explains the previous puzzling observation that H2NCOOCD forms both CD2OD·and CD2OH· in CA and NR experiments. The calculations and experiments indicate that, although the ion is exceedingly difficult to characterize, the distonic ion 2 is the key intermediate for all the observed dissociations of methyl carbamate. 相似文献
The mechanism of copper‐mediated Sonogashira couplings (so‐called Stephens–Castro and Miura couplings) is not well understood and lacks clear comprehension. In this work, the reactivity of a well‐defined aryl‐CuIII species ( 1 ) with p‐R‐phenylacetylenes (R=NO2, CF3, H) is reported and it is found that facile reductive elimination from a putative aryl‐CuIII‐acetylide species occurs at room temperature to afford the Caryl?Csp coupling species ( IR ), which in turn undergo an intramolecular reorganisation to afford final heterocyclic products containing 2H‐isoindole ( P , P , PHa ) or 1,2‐dihydroisoquinoline ( PHb ) substructures. Density Functional Theory (DFT) studies support the postulated reductive elimination pathway that leads to the formation of C?Csp bonds and provide the clue to understand the divergent intramolecular reorganisation when p‐H‐phenylacetylene is used. Mechanistic insights and the very mild experimental conditions to effect Caryl?Csp coupling in these model systems provide important insights for developing milder copper‐catalysed Caryl?Csp coupling reactions with standard substrates in the future. 相似文献
The thermal, unimolecular elimination of HF from CH3CF3 was studied by three different groups over the temperature range 1000° to 1800°K. While the reported kinetic parameters varied greatly, it is shown here that these data may be satisfactorily correlated in terms of a four-center transition state. This correlation results in ΔE = 69.2 kcal/mol, and log (k/s?1) = 14.6 – 72.6/θ. These results may then be combined with the kinetics of the chemically activated elimination of HF from CH3CF3 formed by the recombination of methyl and trifluoromethyl radicals. The data from three different laboratories are shown to be in excellent agreement. These data, combined with extant thermal data, yield as a best value DH(CH3? CF3) = 99.6 ± 1.1 kcal/mol. This gives the unexpectedly high value of DH298°(CH3? CF3) = 101.2 ± 1.1 kcal/mol. It is suggested that dipoledipole interactions, primarily in CH3CF3, account for this surprisingly strong C? C bond dissociation energy. These results also yield δH(CH3CF3; g, 298) = ?178.6 ± 1.5 kcal/mol. 相似文献
The kinetics of the gas-phase thermal reaction between CF2(OF)2 and CO has been studied in a static system at temperatures ranging between 110 and 140°C. The only reaction products were CF2O and CO2, giving the following stoichiometry: The reaction is homogeneous. The rate is strictly second order in CF2(OF)2 and CO, and is not affected by the total pressure or by the presence of reaction products. Oxygen promotes a sensitized oxidation of CO and inhibits the formation of CF2O. The experimental results in the absence of oxygen can be explained by a chain mechanism similar to that proposed for the reaction between F2O and CO with an overall rate constant of From the experimental data obtained on the oxygen-inhibited reaction, the rate constant for the primary process can be calculated: The chain length v = 2.5 is independent of the temperature. Taking for collision diameters σ = 6 Å and σCO = 3.74 Å, a value α = 5.3 × 10?3 for the steric factor is obtained. 相似文献