共查询到20条相似文献,搜索用时 19 毫秒
1.
Gerd W. Rabe Sohrab Kheradmandan Louise M. Liable-Sands Ilia A. Guzei Arnold L. Rheingold 《Angewandte Chemie (International ed. in English)》1998,37(10):1404-1407
A coordination environment reminiscent of a paddle-wheel is exhibited by aryl groups about one of the two cesium ions in CsP(H)Dmp (Dmp=2,6-dimesitylphenyl; structure depicted on the right), which has now been synthesized and is found to exhibit Cs+{Cs2[P(H)Dmp]3}− contact ion pairs in the solid state. In contrast, the analogous rubidium compound displays a Rb4P4 cube as the central structural motif. 相似文献
2.
P. I. Dem'yanov D. P. Krut'ko M. V. Borzov E. V. Luk'yanov V. S. Petrosyan 《Russian Chemical Bulletin》1997,46(11):1939-1947
According to the spectrophotometric data, the lithium 1-(2-methoxyphenyl)-3,3-diphenylpropyne derivative in diethyl ether
exists as contact ion pairs, while in THF, according to the spectrophotometric and13C NMR data, solvent-separated ion pairs are predominantly formed. According to the13C NMR data, the carbanion in the solventseparated ion pairs has a structure close to the propargylic type. The regioselectivity
of reactions of the lithium derivative with ethyl halides in diethyl ether, THF, and hexamethyphosphoramide, with benzyl chloride
in the first two solvents, and with methanol in THF were studied. The protonation with methanol proceeds exclusively at the
allenylic center (C-1) while the ethylation and especially benzylation proceed predominantly at the propargylic center (C-3).
The selectivity of ethylation of the propargylic center of both solvent-separated ion pairs in THF and contact ion pairs in
diethyl ether increases as the hardness of the ethylating agent increases, and in the case of the same ethyl halide, the selectivity
increases from the solvent-separated ion pairs to the contact ion pairs. The spectral data obtained and the data on changes
in the regioselectivity do not allow one to believe that the contact ion pairs of the lithium derivative in ether exhibit
the intramolecular coordination of the lithium cation to the methoxy group, which might lead to the allenylic structure of
contact ion pairs of this derivative.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2043–2051, November, 1997. 相似文献
3.
Conductance measurements are reported for dilute aqueous solutions at 25°C of potassium hexacyanoferrate(III) and of sodium, potassium, rubidium, and cesium octacyanotungstate(V). The results are interpreted in terms of ion-pair formation, and association constants for the formation of these ion pairs are calculated. For the ion pairs MW(CN)
8
2–
, the results are: M=Na, 12±8; K, 23±7; Rb, 37±10; and Cs, 51±4M
–1, at 25°C and zero ionic strength. 相似文献
4.
Toshiyuki Uryu Toshiyuki Seki Tokiji Kawamura Akashi Funamoto Kei Matsuzaki 《Journal of polymer science. Part A, Polymer chemistry》1976,14(12):3035-3044
The stereoregularity of polystyrene prepared by anionic polymerization was determined by means of 13C-NMR spectroscopy. The stereoregularity changed with such polymerization conditions as catalyst, solvent, and temperature. Sodium naphthalene as catalyst gave a syndiotactic-rich polystyrene of 66–68% syndiotactic dyads independently of solvent and temperature, while potassium and cesium naphthalenes as catalyst produced polystyrenes with different stereoregularities ranging from syndiotactic-rich to isotactic-rich configurations, depending on solvent and temperature. The mechanism of anionic polymerization which caused the difference in stereoregularity was discussed from the viewpoint of growing ionic species. 相似文献
5.
Zheng Zhou Zheng Wei Yuki Tokimaru Shingo Ito Kyoko Nozaki Marina A. Petrukhina 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12235-12239
Mono‐ and dianions of 2‐tert‐butyl‐3a2‐azapentabenzo[bc,ef,hi,kl,no]corannulene ( 1 a ) were synthesized by chemical reduction with sodium and cesium metals, and crystallized as the corresponding salts in the presence of 18‐crown‐6 ether. X‐ray diffraction analysis of the sodium salt, [{Na+(18‐crown‐6)(THF)2}3{Na+(18‐crown‐6)(THF)}( 1 a 2?)2], revealed the presence of a naked dianion. In contrast, controlled reaction of 1 a with Cs allowed the isolation of singly and doubly reduced forms of 1 a , both forming π‐complexes with cesium ions in the solid state. In [{Cs+(18‐crown‐6)}( 1 a ?)]?THF, asymmetric binding of the Cs+ ion to the concave surface of 1 a ? is observed, whereas in [{Cs+(18‐crown‐6)}2( 1 a 2?)], two Cs+ ions bind to both the concave and convex surfaces of the dianion. The present study provides the first successful isolation and characterization of the reduced products of heteroatom‐containing buckybowl molecules. 相似文献
6.
Tadahiro Wakui Johannes Smid 《Journal of inclusion phenomena and macrocyclic chemistry》1985,3(2):197-208
The binding constants,K
N, of sodium and potassium 8-anilinonaphthalene-1-sulfonate (ANS) and of sodium 5-dimethylamino-1-naphthalenesulfonate (DNS) to benzo-18-crown-6 bound to a 2% cross-linked polystyrene network (RN18C6) were measured spectrophotometrically in dioxane and the results compared with those obtained for picrate salts. The network RN18C6 was then used to measure in dioxane and toluene by a competition method the equilibrium constant,K, of the reaction A–M+N+CrA–M+Cr+N.A–M+N denotes the ionic solute (ANS, DNS, methyl orange or picrate salt) bound to the network RN18C6 (N) and A–M+Cr is the solute bound to a soluble ligand Cr, where Cr represents a series of 18-crown-6 and 15-crown-5 compounds. Combining theK
N andK values the formation constants,K
L, of the crown ether complexes of the respective salts were obtained in dioxane. The data show a reversal in the complexation strength of the 18-crown-6 compounds in dioxane when sodium picrate is replaced by sodium ANS. The results were rationalized in terms of a synergistic effect exerted by dioxane, with dioxane forming a 1:1 dioxanate with the crown ion pair complex. This effect is especially strong with ANS and with a rigid planar crown ether like dibenzo-18-crown-6. The binding constants,K
N, of NaANS and NaDNS to RN18C6 in dioxane are nearly three times larger than for sodium picrate, and the same holds for the potassium salts. Differences in anion interactions with the network appear to be a plausible cause for the anion dependence ofK
N. 相似文献
7.
CH. B. Tsvetanov D. T. Dotcheva 《Journal of polymer science. Part A, Polymer chemistry》1986,24(9):2253-2259
The electro-chemical characteristics of isobutyronitrile lithium (P1Li) and 2-lithio-4-cyano-2,4-dimethylpentanenitrile (P2Li) are studied. The dissociation constants K of P1Li and P2Li are of the order of 10?11M and show that in THF mainly contact ion pairs exist. The lower value of K for P2Li is an indication for intramolecular complexation between the counterion and the cyano group, next to the active center. Both compounds tend to form ion triples. The results obtained show that in THF the nitrile group of the second monomer unit participates both in intra- and intermolecular interactions with the counterion. 相似文献
8.
Chenting Yan Prof. Zhifang Li Dr. Xu‐Qiong Xiao Ningka Wei Qiong Lu Prof. Mitsuo Kira 《Angewandte Chemie (International ed. in English)》2016,55(47):14784-14787
A fluorostannylenoid ( Cs+[R2SnF]? ( 9 ), R2=(TMS)2CCH2CH2C(TMS)2) was prepared by reacting a stable dialkylstannylene (R2Sn ( 8 ), R2=(TMS)2CCH2CH2C(TMS)2) with cesium fluoride at room temperature in THF. While 9 is stable in THF and DME, removal of the solvent leads to the regeneration of stannylene 8 . No reaction occurred when 8 was treated with CsF in a hydrocarbon solvent. Addition of dibenzo‐21‐crown‐7 ether to the THF solution of stannylenoid 9 followed by usual workup affords the corresponding crystalline stannylenoid crown ether complex, the X‐ray structural analysis of which revealed a fluorine‐bridged contact ion‐pair structure. The reaction of 9 with excess phenylacetylene gives the corresponding di(phenylethynyl)stannane. 相似文献
9.
Samson Alev Andr Collet Michel Viguier Franois Schu 《Journal of polymer science. Part A, Polymer chemistry》1980,18(4):1163-1169
With the aid of DCHE and [222], solutions of sodium, potassium, rubidium, and cesium have been prepared in tetrahydrofuran (THF) and in benzene. All these new species initiate the polymerization of butadiene and isoprene avoiding the inconvenience of heterogeneous reactions. The presence of free ions and/or complexed ion pairs allows the increase of vinyl structures even in benzene. 相似文献
10.
Two Tetrachlorothiotantalates: [Na‐15‐crown‐5][TaSCl4 · dioxane] and [Na‐15‐crown‐5]2[(TaSCl4)2dioxane] · S8 During the reaction of Na2S4, TaCl5 and 15‐crown‐5 in dichloromethane the crown ether partly suffers degradation to 1,4‐dioxane. Aside from sulfur, [Na‐15‐crown‐5][TaSCl4 · dioxane] was the first product obtained. It crystallizes in the monoclinic space group P21/n with a = 1066.1, b = 1781.3, c = 1258.3 pm, β = 97.14°, Z = 4. In the [TaSCl4 · dioxane]– ion a dioxane molecule is loosely bonded to a square‐pyramidal TaSCl4– unit; two chlorine atoms are in contact with an Na+ ion. Upon standing with the mother liquor [Na‐15‐crown‐5]2[(TaSCl4)2dioxane] · S8 was formed. It crystallizes in the monoclinic space group C2/m; a = 1768.5, b = 1084.0, c = 1517.3 pm, β = 118.46°, Z = 4. In this case a dioxane molecule is coordinated with two TaSCl4– units. The [(TaSCl4)2 · dioxane]2– ions and S8 molecules alternate in the stacking direction b. 相似文献
11.
Kam-Han Wong Keiichi Kimura Johannes Smid 《Journal of polymer science. Part A, Polymer chemistry》1983,21(2):579-588
Binding of the cationic dye auramine O (AuO) to the polysoap-type polymers poly(vinylbenzo-18-crown-6) (P18C6) and polyvinylbenzoglyme (PVBG) in water were studied by fluorimetry and dialysis. The quantum yield of P18C6-bound AuO was found to be 0.028, the value being 0.018 for AuO bound to PVBG. The intrinsic binding constants were found to be 2.2 × 104M?1 (P18C6) and 1.2 × 104M?1 (PVBG), the respective first binding constants being 317 and 63M?1. Addition of crown-ether-complexable cations such as K+, Tl+, or Cs+ converts the neutral poly(crown ether) into a polycation, causing repulsion of the cationic dye and a strong decrease in the AuO fluorescence. AuO fluorescence was also studied in the absence of polymer in ether solvents, giving θ values of 0.011 and 0.018 in THF and dioxane. Traces of water rapidly form a nonfluorescent species. Solutions of AuO in water without polymer present exhibit very strong fluorescence on addition of BPh4 anions owing to formation of AuO+, BPh4? ion pairs and higher aggregates. 相似文献
12.
The chlorine substitution reaction of trimeric dichlorocyclophosphazene with sodium hydrosulfide has been examined. The reaction proceeded easily in dioxane and THF solutions. The reaction product, which had the chemical composition P3N3S6H6, was examined by 31P-NMR and IR spectroscopy. Further, it is suggested that the product was polymerized by heating with hydrogen sulfide, and the polymer (PNS) was formed. 相似文献
13.
Serge Raynal Gilberte Ndebeka Paul Caubere Satira Suparno Joseph Sledz Francois Schue 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):667-674
The stereoregularity of polystyrenes obtained with complex bases and salt complex bases in various solvents was determined by 13C-NMR spectroscopy. Polystyrenes produced by complex bases are mostly syndiotactic and obey Bernoullian statistics. 相似文献
14.
Robert Salle Alain Essel Jean Gole Quang-Tho Pham 《Journal of polymer science. Part A, Polymer chemistry》1975,13(8):1855-1867
The present work is concerned with the influence of the polymerization temperature on the propagation mechanisms of polyisoprenyl- and polybutadienyl-alkali metals. The thermodynamic parameters of the contact ion pairs and free ions propagations have been calculated. With Li+ in dioxane solvent, the vinyl propagation is stereospecific (for isoprene, the propagation is mainly 4–3). In comparison with benzene, the vinyl propagation of the polydienyl-Li contact ions pairs should be due to complexation of Li+ by dioxane, an electron donor having a weak dielectric constant. In general, the stereospecificity of the propagation of contact ion pairs decreases with increasing counterion size; little difference has been observed with K+ and Cs+ ion pairs in dioxane and benzene media. For isoprene, the methyl substituant should have chiefly a steric effect in the propagation of free ions, whereas it should confer a polar character to the isoprene molecule in the presence of ions pairs. 相似文献
15.
G.P. Schiemenz 《Journal of organometallic chemistry》1973,52(2):349-354
Arsonium and stibonium cations form contact ion pairs even with very large counterions in chlorohydrocarbons. In the tetraphenyloborates of these cations, the aromatic ring current of the anion phenyl rings causes the NMR signals of protons in α-position of As and Sb t move upfield 1 to 3 ppm. The ion pairs are short-lived so that the B(C6H5)?4 ion has the characteristic properties of an NMR shift reagent. 相似文献
16.
Koji Ohta Yoshio Okamoto Koichi Hatada Heimei Yuki 《Journal of polymer science. Part A, Polymer chemistry》1979,17(9):2917-2928
The monomer reactivity ratios were determined in the anionic copolymerization of (S)- or (RS)-α-methylbenzyl methacrylate (MBMA) and trityl methacrylate (TrMA) with butyllithium at ?78°C, and the stereoregularity of the yielded copolymer was investigated. In the copolymerization of (S)-MBMA (M1) and TrMA (M2) in toluene the monomer reactivity ratios were r1 = 8.55 and r2 = 0.005. On the other hand, those in the copolymerization of (RS)-MBMA with TrMA were r1 = 4.30 and r2 = 0.03. The copolymer of (S)-MBMA and TrMA prepared in toluene was a mixture of two types of copolymer: one consisted mainly of the (S)-MBMA unit and was highly isotactic and the other contained both monomers copiously. The same monomer reactivity ratios, r1 = 0.39 and r2 = 0.33, were obtained in the copolymerizations of the (S)-MBMA–TrMA and (RS)-MBMA–TrMA systems in tetrahydrofuran (THF). The microstructures of poly[(S)-MBMA-co-TrMA] and poly-[(RS)-MBMA-co-TrMA] produced in THF were similar where the isotacticity increased with an increase in the content of the TrMA unit. 相似文献
17.
An ab initio calculation has been carried out for hydrated lithium, sodium, potassium, and rubidium toluenesulfonates, modeling the structure of sulfo cation exchangers in the form of alkali metal ions. In the optimized structure, water molecules are incorporated between the fixed ion and the counterions. This leads to dissociation of the ionogen groups, which increases the diffusion mobility of the counterions. Analysis of an elementary ion exchange process has revealed that cleavage of hydrogen bonds between the hydration water molecules of the fixed ion and the counterions plays a critical role in the ion exchange mechanism. 相似文献
18.
S. I. Kargov L. A. Shelkovnikova V. A. Ivanov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(5):860-866
The structure of aqua complexes of alkali metal ions Me+(H2O)
n
, n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH3)2PhO− selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me+(H2O)
n
, n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies
of binding of alkali metal hydrated cations with (CH3)2PhO− depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and
rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH3)2PhO− decreased in the series Li+ > Na+ > K+ > Rb+ > Cs+ as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with
respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution
to the phenol phase compared with the stage of binding with ion exchange groups. 相似文献
19.
Mana Ito Takashi Ishizone 《Journal of polymer science. Part A, Polymer chemistry》2006,44(16):4832-4845
Anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide ( 1 ) was carried out with 1,1‐diphenyl‐3‐methylpentyllithium and diphenylmethyllithium, ‐potassium, and ‐cesium in THF at ?78 °C for 2 h in the presence of Et2Zn. The poly( 1 )s were quantitatively obtained and possessed the predicted molecular weights based on the feed molar ratios between monomer to initiators and narrow molecular weight distributions (Mw/Mn = 1.1). The living character of propagating carbanion of poly( 1 ) either at 0 or ?78 °C was confirmed by the quantitative efficiency of the sequential block copolymerization using N,N‐diethylacrylamide as a second monomer. The methoxymethyl group of the resulting poly( 1 ) was completely removed to give a well‐defined poly(N‐isopropylacrylamide), poly(NIPAM), via the acidic hydrolysis. The racemo diad contents in the poly(NIPAM)s could be widely changed from 15 to 83% by choosing the initiator systems for 1 . The poly(NIPAM)s obtained with Li+/Et2Zn initiator system possessed syndiotactic‐rich configurations (r = 75–83%), while either atactic (r = 50%) or isotactic poly(NIPAM) (r = 15–22%) was generated with K+/Et2Zn or Li+/LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 < r < 83%) were water‐soluble, whereas isotactic‐rich one (r < 31%) was insoluble in water. The cloud points of the aqueous solution of poly(NIPAM)s increased from 32 to 37 °C with the r‐contents. These indicated the significant effect of stereoregularity of the poly(NIPAM) on the water‐solubility and the cloud point in water © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4832–4845, 2006 相似文献
20.
Avakyan V. G. Gromov S. P. Vedernikov A. I. Dmitrieva S. N. Alfimov M. V. 《Russian Chemical Bulletin》2004,53(1):24-32
The complexation constants of several azacrown ethers with Ca(ClO4)2 were determined and turned out to be the higher, the large the macrocycle. The structures of free ligands and their complexes and the complexation energies were calculated by the DFT method. In the aza-12(15)-crown-4(5) ether complexes with Ca(ClO4)2, the metal cations lie outside the averaged plane of heteroatoms of the macrocycle, and the coordination of both counterions is V-like. In the complexes of aza-18-crown-6 ethers, the counterions are in the axial position relatively to the macrocycle in the center of which the Ca2+ ion is localized. The complexation energies increase with an increase in the size of the azacrown ether macrocycle. The involvement of the nitrogen atom in binding with the Ca2+ ion decreases with the expansion of the macrocycle. Two methods for quantitative estimation of the degree of pre-organization of ligands to complexation were considered: geometric and energetic methods. Benzoaza-15-crown-5 ether is a ligand which is more pre-organized to complexation than N-phenylaza-15-crown-5 ether. 相似文献