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1.
This paper overviews three living cationic polymerization systems (for styrene, p-methoxystyrene, and isobutyl vinyl ether) that are, in common, featured by: (i) specifically in nonpolar solvents, the use of the hydrogen halide/metal halide initiating systems (HX/MXn; X: I, Br, Cl; MXn: ZnX2, SnCl4), which generate a living growing carbocation stabilized by a nucleophilic counteranion (X…MXn); (ii) specifically in polar solvents, the use of externally added ammonium salts (nBu4N+Y; Y: I, Br, Cl), which permit the generation of living species from HX/MXn by providing nucleophilic halogen anions Y, either the same as or different from the halogen X in HX.  相似文献   

2.
New types of surface-active organocobaltocenium(I) complexes, η-CnH2n+1X-C5H4(ηC5H5)2Co+Y? and(η-CnH2n+1X-C5H4)Co+Y? (n = 6–16; X not present, NHCO or OCO; Y = Cl or PF6) were prepared and their surface character studied. (1) The critical micelle concentrations of the cobaltocenium chlorides were much lower than those of corresponding trimethylammonium-type cationic surfactants. (2) The surface-active character of the cobaltocenium chlorides in aqueous solution (and the redox potentials of the hexafluorophosphates in acetonitrile) were affected by the substituents (X) in the cyclopentadienyl groups. (3) The surface activities of the cobaltocenium salts were lost on reduction with NaBH4 to afford (alkyl-substituted cyclopentadiene) cyclopentadienylcobalt (0) complexes which were surface-inactive but could be re-oxidized to afford the surface-active cobaltoceium(I) salts. The cobalt complexes mentioned above may be the first examples of redoxresponsive surfactants.  相似文献   

3.
Neutron structure determinations have been made of Tutton's salts, X2[M(H2O)6] (YO4)2, where Y = Se, X = K+, M = Cu2+; Y = S, X = K+, M = Ni2+, Cu2+, Zn2+; X = Rb+, Cs+, M = Cu2+. This work has shown that there are extensive hydrogen networks with almost linear hydrogen bonds from [M(H2O)6]2+ to (YO4)2?. The (H … O) distance increases in the Cu2+ series for X = K+ to Cs+ but there is no difference for the potassium copper salts when Y = Se or S. Three different distorted [M(H2O)6]2+ octahedra were found in the series (orthorhombic, tetragonal with two long and four short, or four long and two short bonds). The interatomic distances from X+ to the neighboring O in a distorted XO8+ dodecahedron increases with increased cation size, implying that the X+ polyhedron is maintaining its shape.  相似文献   

4.
The low-temperature addition of tertiary phosphites to [(allyl)Fe (CO)4]+X? complexes proceeds regio- and stereospecifically and produces metal-coordinated β-olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO)3]+X? compounds give metal-coordinated (2,4-dien-1-yl)trialkoxyphosphonium salts or dialkyl (2,4-dien-1-yl)phosphonates. The mechanisms and their relationship to the classical Michaelis-Arbuzov reaction are discussed. The new compounds are characterized, if possible, by 1H-, 13C-, and 31P-NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig-Horner reactions, are difficult to obtain by conventional routes.  相似文献   

5.
Abstract

Tris(aminomethyl)phosphines and their oxides form triacidic salts that, unlike the free bases, are air-stable and non-hygroscopic. The salts of the unsubstituted compounds, (NH3 +CH2)3 P(O)n 3X?(3b: n = O, X = Br; 4a-c: n = 1, X = Cl, Br, or I), may be prepared directly from 1,3,5-triaza-7-phosphaadamantane (1) or its oxide (2) or from tris(N-carbomethoxylaminomethyl)phosphine oxide (9) by hydrolysis with the appropriate acid. The behaviour of the compounds towards acids and nucleophilic reagents is discussed.  相似文献   

6.
The oligomerization and/or polymerization of ethylene catalyzed by the cationic η3-benzylcomplexes [Ni(η3-CH2C6H4-p-CF3)(P-P)]+ BPh4 (P-P=iPr2P(CH2)nPiPr2, n=1-3) have been studied. The activity of these single component catalysts depends on the length of the (CH2)n bridge of the diphosphine ligand. Thus, the dippm derivative (n=1) displays higher activity than compounds of the dippe (n=2) or dippp (n=3) ligands. The molecular weight of the products is also a function of n, and varies in the order dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers.  相似文献   

7.
Extensive DFT calculations provide deep mechanistic insights into the acylation reactions of tert-butyl dibenzo-7-phosphanobornadiene with PhCOX (X=Cl, Br, I, OTf) in CH2Cl2 solution. Such reactions are initialized by the nucleophilic P⋅⋅⋅C attack to the carbonyl group to form the acylphosphonium intermediate A+ together with X anion, followed either by nucleophilic X⋅⋅⋅P attack (X=Cl, Br, and I) toward A+ to eliminate anthracene or by slow rearrangement or decomposition of A+ (X=OTf). In contrast to the first case (X=Cl) that is rate-limited by the initial P⋅⋅⋅C attack, other reactions are rate-limited by the second X⋅⋅⋅P attack for X=Br and I and even thermodynamically prevented for X=OTf, leading to isolable phosphonium salts. The rearrangement of phosphonium A+ is initiated by a P-C bond cleavage, followed either by sequential proton-shifts to form anthracenyl acylphosphonium or by deprotonation with additional base Et3N to form neutral anthracenyl acylphosphine. Our DFT results strongly support the separated acylphosphonium A+ as the key reaction intermediate that may be useful for the transfer of acylphosphenium in general.  相似文献   

8.
The oxonium salts (Ph3PAu)3O+X- where X-  BF4-, CF3COO-, MnO4- have been prepared. These salts are formed from coordinatively unsaturated Ph3PAu+ cations in alkaline or acid media. An X-ray study of (Ph3PAu)3O+BF4- indicates that the oxonium ions are dimeric in the crystalline form. The fragment (Ph3PAu)3O has a pyramidal structure: the oxygen atom is outside the Au3 plane.  相似文献   

9.
Mono-, bis- and tris-(1,3,2,4-dithiadiazolium) salts [R-(CNSNS +)n]n+[AsF-6]n (R = aryl, n = 1, 2, 3) were found to initiate the cationic ring-opening polymerization of tetrahydrofuran (THF) at room temperature to give clear gels from which the pure polymer was precipitated. 1,3,2,4-Dithiadiazolium cations associated with the hard [AsF6]- anion thus constitute a new class of cationic polymerization initiators. The poly(THF) formed by initiation with 1,3,2,4-dithiadiazolium cation was characterized by gel permeation chromatography, infrared spectrophotometry, and 13C-NMR spectroscopy. Number-average molecular weights of 198 700 g mol-1 (polydispersity 1.96) and 190 000 g mol-1 (polydispersity 1.61) were obtained using [PhCNSNS ] [AsF6] and [C6H3-1,3,5-(CNSNS )3][AsF6]3, respectively, as initiators. The use of multifunctional dithiadiazolium salts as initiators suggests that they may be useful in the preparation of starburst and dendritic polymers. © 1992 John Wiley & Sons, Inc.  相似文献   

10.
The electronic structure of the C2nH2n+2 trans-polyenes, n = 3–7, is calculated by the Discrete Variational Xα method (DVM -Xα). The valence ionization potentials (IP ) calculated using the Clementi double zeta basis agree with the known experimental data within several tenths an electron volt. However, the DVM energies of the π → π* optical excitations are systematically underestimated by 0.8–1.0 eV. For polyenes with equal C—C bond lengths, the computed energies of the first optical transitions are smaller than those of polyenes with alternating C—C bond lengths. The charge distribution in polyenes is analyzed in the framework of a Mulliken scheme. The composition of the frontier molecular orbitals (MO ) is analyzed.  相似文献   

11.
曾志荣  杨清传  麦松威  谢作伟 《中国化学》2002,20(11):1241-1248
IntroductionItisuniversallyunderstoodthatwritingH+ isshort handforasolvatedproton ,[H(solvent) n]+ ,thevalueofnandthedetailsofthecoordinationenvironmentareoftenunspecified .Isolationandstructuralcharacterizationofvarioussaltscontainingrepresentative [H(solven…  相似文献   

12.
Quantum-chemical study of the electronic structure and the equilibrium geometry of the molecules X4−n M(OCH2CH2) n NH3−n and cations X3−n [M(OCH2CH2) n NH3−n ]+ (M = Si, Ge; X = F, H; n = 1–3) is performed by the B3LYP method using the cc-PVDZ basis set. It is shown that for X = F the strength of the coordination bond N→M increases with the number of the cycles (n), while for X = H, on the contrary, decreases, that is, the strength of the N→M bond increases with the total electronegativity of the substituents surrounding atom M. Effect of the number of the coordination cycles on the strength of the N→M bond in the cations is negligible. The obtained results agree with the experimental data on the structure and spectral properties of the studied compounds.  相似文献   

13.
Three proton-transfer salts of diphenylphosphinic acid (DPPA) with 2-amino-5-(X)-pyridine (AMPY, X = Cl, CN or CH3), namely, 2-amino-5-chloropyridinium diphenylphosphinate, C5H6ClN2+·C12H10O2P ( 1 , X = Cl), 2-amino-5-cyanopyridinium diphenylphosphinate, C6H6N3+·C12H10O2P ( 2 , X = CN), and 2-amino-5-methylpyridinium diphenylphosphinate, C6H9N2+·C12H10O2P ( 3 , X = CH3), have been synthesized and characterized by FT–IR and 1H NMR spectroscopy, and X-ray crystallography. The crystal structures of compounds 1 – 3 were determined in the space group P for 1 and 2 , and C2/c for 3 . All three compounds contain N—H…O hydrogen-bonding interactions due to proton transfer from the O=P—OH group of DPPA as donor to the pyridine N atom of AMPY as acceptor. The proton transfer of compounds 1 – 3 was also verified by 1H NMR and FT–IR spectroscopy. The stoichiometry of all three proton-transfer salts was determined to be 1:1 and the Benesi–Hildebrand equation was applied to determine the formation constant (KCT) and the molar extinction coefficient (ϵCT) in each case. Theoretical density functional theory (DFT) calculations were performed to investigate the optimized geometries, the molecular electrostatic potentials (MEP) and the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of all three proton-transfer salts. The results showed good agreement between the experimental data and the DFT computational analysis.  相似文献   

14.
Complexes cis-[Ru(bpy)2(bipy)(X)] n + [bpy = 2,2'-bipyridyl, bipy = 4,4'-bipyridyl, X = Br-, ONO-, CN- (n = 1); MeCN, PPh3 (n = 2), and NO+ (n = 3)] were synthesized. Irradiation of acetonitrile solutions of the complexes with X = Cl-, Br-, ONO-, NO2-, CN-, NH3, MeCN, and PPh3 by visible light results in photosubstitution of 4,4'-bipyridyl by a solvent molecule. The electronic absorption spectra of the complexes were assigned on the basis of quantum-chemical calculations. A correlation was revealed between photolysis quantum yields and charges transferred from ligands X upon their coordination.  相似文献   

15.
With matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry, total abundance of product ions formed by dissociation inside (in-source decay, ISD) and outside (post-source decay, PSD) the source was measured for peptide ions [Y 5 X + H]+, [XY 5 + H]+, [Y 2 XY 3 + H]+, and [XY 4 X + H]+ (X = tyrosine (Y), histidine (H), lysine (K), and arginine (R) with H for the ionizing proton). α-Cyano-4-hydroxycinammic acid was used as matrix. Product abundance became smaller in the presence of basic residues (H, K, and R), in the order Y > HK > R. In particular, product abundances in ISD of peptide ions with R were smaller than those with H or K by an order of magnitude, which, in turn, were smaller than that for [Y 6 + H]+ by an order of magnitude. Product abundance was affected by the most basic residue when more than one basic residue was present. A kinetic explanation for the data was attempted under the assumption of quasi-thermal equilibrium for peptide ions in MALDI plume which undergoes expansion cooling. Dramatic disparity in product abundance was found to arise from small difference in critical energy and entropy. Results indicate similar transition structures regardless of basic residues present, where the ionizing proton keeps interacting with a basic site. Further implication of the results on the dissociation mechanism along b-y channels is discussed.  相似文献   

16.
Abstract— The induction transient of delayed light of chlorophyll a, excited by repetitive flashes (0.5 ms in duration) and emitted 0.1 - 1.2 ms after the flashes, was measured in system II particles derived from spinach chloroplasts. An uncoupler, gramicidin S, was always added to the particles in order to eliminate the influence of the phosphorylation system on the delayed light and to isolate a direct relationship between the delayed light emission and the primary photochemical reaction, except for the experiments described in the next paragraph. The yield of delayed light emission from the system II particles was found to be about three–times higher than that of chloroplasts on a chlorophyll content basis. System I particles, on the other hand, emitted much weaker delayed light than chloroplasts. Upon intermittent illumination, induction of delayed light in system II particles showed a decrease from the initial rise level to the steady-state level. The initial rise level was the maximum. The fluorescence induction, on the other hand, exhibited an increase from the initial rise level to the maximum steady-state level. The induction of both delayed light emission and fluorescence arrived at their final steady-state levels after the same period of illumination. Induction of delayed light emission was measured under various conditions that changed the oxidation-reduction state of the primary electron acceptor, X, of photoreaction II: by adding an electron acceptor and an inhibitor of electron transport, and by changing the light intensity. The state of A'was monitored by measuring the fluorescence yield. The yield of delayed light emission excited by each flash was found to depend on the amount of oxidized form of X present before the flash. To examine the role of the primary electron donor Y of photoreaction II in delayed light emission, effects of electron donors of photoreaction II such as Mn2+, hydroquinone and p-phenylenediamine were investigated. These agents were found to markedly decrease the yield of delayed light emission without altering the pattern of its induction. They had little effect on the induction of fluorescence. These findings are interpreted by a mechanism in which transformation of the reaction center from the form (X-Y+) into (X Y) produces a singlet excitation of chlorophyll a that is the source of millisecond delayed light emission. This reaction is probably non–physiological and must be very slow if compared to the transformation of (X-Y+) into (X-Y). Since the form (X-Y+) is produced when the excitation is transferred to the reaction center in the form (XY), it is expected in this scheme that the yield of delayed light emission should depend on the amount of the form (X Y) present before the excitation flashes. Electron donors stimulate transformation of the reaction center from (X-Y+) into (X-Y). Since this reaction competes with the process of delayed light emission, electron donors are expected to suppress delayed light emission.  相似文献   

17.
The complexes [Pt(tBu3tpy){C?C(C6H4C?C)n?1R}]+ (n=1: R=alkyl and aryl (Ar); n=1–3: R=phenyl (Ph) or Ph‐N(CH3)2‐4; n=1 and 2, R=Ph‐NH2‐4; tBu3tpy=4,4’,4’’‐tri‐tert‐butyl‐2,2’:6’,2’’‐terpyridine) and [Pt(Cl3tpy)(C?CR)]+ (R=tert‐butyl (tBu), Ph, 9,9’‐dibutylfluorene, 9,9’‐dibutyl‐7‐dimethyl‐amine‐fluorene; Cl3tpy=4,4’,4’’‐trichloro‐2,2’:6’,2’’‐terpyridine) were prepared. The effects of substituent(s) on the terpyridine (tpy) and acetylide ligands and chain length of arylacetylide ligands on the absorption and emission spectra were examined. Resonance Raman (RR) spectra of [Pt(tBu3tpy)(C?CR)]+ (R=n‐butyl, Ph, and C6H4‐OCH3‐4) obtained in acetonitrile at 298 K reveal that the structural distortion of the C?C bond in the electronic excited state obtained by 502.9 nm excitation is substantially larger than that obtained by 416 nm excitation. Density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations on [Pt(H3tpy)(C?CR)]+ (R= n‐propyl (nPr), 2‐pyridyl (Py)), [Pt(H3tpy){C?C(C6H4C?C)n?1Ph}]+ (n=1–3), and [Pt(H3tpy){C?C(C6H4C?C)n?1C6H4‐N(CH3)2‐4}]+/+H+ (n=1–3; H3tpy=nonsubstituted terpyridine) at two different conformations were performed, namely, with the phenyl rings of the arylacetylide ligands coplanar (“cop”) with and perpendicular (“per”) to the H3tpy ligand. Combining the experimental data and calculated results, the two lowest energy absorption peak maxima, λ1 and λ2, of [Pt(Y3tpy)(C?CR)]+ (Y=tBu or Cl, R=aryl) are attributed to 1[π(C?CR)→π*(Y3tpy)] in the “cop” conformation and mixed 1[dπ(Pt)→π*(Y3tpy)]/1[π(C?CR)→π*(Y3tpy)] transitions in the “per” conformation. The lowest energy absorption peak λ1 for [Pt(tBu3tpy){C?C(C6H4C?C)n?1C6H4‐H‐4}]+ (n=1–3) shows a redshift with increasing chain length. However, for [Pt(tBu3tpy){C?C(C6H4C?C)n?1C6H4‐N(CH3)2‐4}]+ (n=1–3), λ1 shows a blueshift with increasing chain length n, but shows a redshift after the addition of acid. The emissions of [Pt(Y3tpy)(C?CR)]+ (Y=tBu or Cl) at 524–642 nm measured in dichloromethane at 298 K are assigned to the 3[π(C?CAr)→π*(Y3tpy)] excited states and mixed 3[dπ(Pt)→π*(Y3tpy)]/3[π(C?C)→π*(Y3tpy)] excited states for R=aryl and alkyl groups, respectively. [Pt(tBu3tpy){C?C(C6H4C?C)n?1C6H4‐N(CH3)2‐4}]+ (n=1 and 2) are nonemissive, and this is attributed to the small energy gap between the singlet ground state (S0) and the lowest triplet excited state (T1).  相似文献   

18.
Due to hydrogen bonding, bis(18-crown-6) stilbene forms 1 : 1, 1 : 2, and 2 : 2 complexes with H3N+(CH2) n NH3 + 2ClO4 salts (n = 2—10, 12). The length of the polymethylene chain in the diammonium ions affects the phototransformation direction of stilbene and the composition of the products. In the 2: 2 bispseudosandwich complexes with relatively short alkanediammonium ions (n = 2—4), the stereoselective reaction of [2+2] photocycloaddition proceeds to form mainly the rctt-isomer of the cyclobutane derivative. The structure of rctt-cyclobutane derivative as a complex with H3N+(CH2)4NH3 +2ClO4 - was confirmed by X-ray diffraction analysis.  相似文献   

19.
The electron impact fragmentations of some cyclotetraphosphazenes are reported and discussed. The major fragmentation path involves loss of two amine radicals and one chlorine radical in the series P4N4Cl8-n(NMe2)n when n=2, and subsequent stages involve a ring contraction process with elimination of a P = N fragment, when n = 5 loss of amine radicals predominates on statistical grounds with little evidence of ring contraction. In the series P4N4F8-n(NMe2)n fragmentation is dominated by loss of amino radicals when n = 4 and loss of fluorine radicals predominates on statistical grounds when n = 2. In the series P4N4F8-nXn (n = 2 or 4, X = Cl or Br), when n = 2 and X = Br the major fragmentation path is the loss of two bromine radicals, whereas when X = Cl the more favoured path is the loss of two chlorine radicals. In both, subsequent stages involve ring contraction reactions with elimination of a PN fragment. When n = 4 and X = Br or Cl on bond energy grounds the more favoured fragmentation pattern is the loss of bromine or chlorine radicals, respectively.  相似文献   

20.
Gold phosphides show unique optical or semiconductor properties and there are extensive high technology applications, e.g. in laser diodes, etc. In spite of the various AuP structures known, the search for new materials is wide. Laser ablation synthesis is a promising screening and synthetic method. Generation of gold phosphides via laser ablation of red phosphorus and nanogold mixtures was studied using laser desorption ionisation time‐of‐flight mass spectrometry (LDI TOFMS). Gold clusters Aum+ (m = 1 to ~35) were observed with a difference of one gold atom and their intensities were in decreasing order with respect to m. For Pn+ (n = 2 to ~111) clusters, the intensities of odd‐numbered phosphorus clusters are much higher than those for even‐numbered phosphorus clusters. During ablation of P‐nanogold mixtures, clusters Aum+ (m = 1‐12), Pn+ (n = 2‐7, 9, 11, 13–33, 35–95 (odd numbers)), AuPn+ (n = 1, 2–88 (even numbers)), Au2Pn+ (n = 1‐7, 14–16, 21–51 (odd numbers)), Au3Pn+ (n = 1‐6, 8, 9, 14), Au4Pn+ (n = 1‐9, 14–16), Au5Pn+ (n = 1‐6, 14, 16), Au6Pn+ (n = 1‐6), Au7Pn+ (n = 1‐7), Au8Pn+ (n = 1‐6, 8), Au9Pn+ (n = 1‐10), Au10Pn+ (n = 1‐8, 15), Au11Pn+ (n = 1‐6), and Au12Pn+ (n = 1, 2, 4) were detected in positive ion mode. In negative ion mode, Aum (m = 1–5), Pn (n = 2, 3, 5–11, 13–19, 21–35, 39, 41, 47, 49, 55 (odd numbers)), AuPn (n = 4–6, 8–26, 30–36 (even numbers), 48), Au2Pn (n = 2–5, 8, 11, 13, 15, 17), Au3Pn (n = 6–11, 32), Au4Pn (n = 1, 2, 4, 6, 10), Au6P5, and Au7P8 clusters were observed. In both modes, phosphorus‐rich AumPn clusters prevailed. The first experimental evidence for formation of AuP60 and gold‐covered phosphorus Au12Pn (n = 1, 2, 4) clusters is given. The new gold phosphides generated might inspire synthesis of new Au‐P materials with specific properties. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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