共查询到20条相似文献,搜索用时 15 毫秒
1.
The rate constants for the SH2 reactions of tri-n-butyltin radicals with several dialkyl selenides and tellurides have been measured by EPR spectroscopy. 相似文献
2.
聚集导致的荧光增强与双分子膜上能量转移吴立新,郑惠(吉林大学理论化学研究所,长春,130023)(吉林粮油食品专科学校)梁映秋(南京大学化学系)关键词聚集,双分子膜,荧光增强,能量转移在模拟生物膜功能研究中,以表面活性剂聚集体系为模拟剂研究其自组织行... 相似文献
3.
Santanu Bhattacharya Basudeb Saha Amitava Dutta Pradyot Banerjee 《Coordination chemistry reviews》1998,170(1):47-74
This review narrates the electron transfer reactions of various nickel(III) and nickel(IV) complexes reported during the period 1981 until today. The reactions have been categorized mainly with respect to the type of nickel complexes. The reactivity of nickel(III) complexes of macrocycles, 2,2′-bipyridyl and 1,10-phenanthroline, peptides and oxime–imine, and of nickel(IV) complexes derived from oxime–imine, oxime and miscellaneous ligands with various organic and inorganic electron donors have been included. Kinetic and mechanistic features associated with such interactions have been duly analyzed. The relevance of Marcus cross-relation equations in the delineation of the electron transfer paths has also been critically discussed. 相似文献
4.
Milica Kosović Željko Jaćimović Živadin D Bugarčić 《Journal of Coordination Chemistry》2015,68(17-18):3003-3012
Substitution reactions of five monofunctional Pd(II) complexes, [Pd(terpy)Cl]+ (terpy = 2,2′;6′,2″-terpyridine), [Pd(bpma)Cl]+ (bpma = bis(2-pyridylmethyl)amine), [Pd(dien)Cl]+ (dien = diethylenetriamine or 1,5-diamino-3-azapentane), [Pd(Me4dien)Cl]+ (Me4dien = 1,1,7,7-tetramethyldiethylenetriamine), and [Pd(Et4dien)Cl]+ (Et4dien = 1,1,7,7-tetraethyldiethylenetriamine), with unsaturated N-heterocycles such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazole, pyrazine, and imidazole were investigated in aqueous 0.10 M NaClO4 in the presence of 10 mM NaCl using variable-temperature stopped-flow spectrophotometry. The second-order rate constants k2 indicate that the reactivity of the Pd(II) complexes decrease in the order [Pd(terpy)Cl]+ > [Pd(bpma)Cl]+ > [Pd(dien)Cl]+ > [Pd(Me4dien)Cl]+ > [Pd(Et4dien)Cl]+. The most reactive nucleophile of the heterocycles is pyrazine, while the slowest reactivity is with pyrazole. Activation parameters were determined for all reactions and negative entropies of activation, ΔS≠, supporting an associative mode of substitution. The reactions between [Pd(bpma)Cl]+ and 1,2,4-triazole, pzI, and pzBr were also investigated by 1H NMR to define the manner of coordination. These results could be useful for better explanation of structure-reactivity relationships of Pd(II) complexes as well as for the prediction of potential targets of Pd(II) complexes toward common N-heterocycles, constituents of biomolecules and different N-bonding pharmaceutical agents. 相似文献
5.
The reactions of RCo(BDM1,3pn)(H2O) with light, heat, acids, electrophiles and nucleophiles were studied. (HBDM1,3pn is a mononegative, tetradentate dioxime-diimine ligand formed by condensing 2,3-butanedionemonoxime with 1,3-propanediamine in a 2/1 molar ratio; R = CH3, C2H5, n-C3H7, n-C4H9, and C6H3CH2-) Pyrolysis and photolysis of the alkyl complexes result in a cobalt(II) complex (anaerobic conditions) along with alkenes and alkanes. The major organic products from solid state pyrolysis at 200°C or photolysis in water are CH4 (R = CH3), C2H4 (R = C2H5), C3H6 (R = n-C3H7), C4H8 (R = n-C4H9) and (C6H5CH2)2 (R = C6H5CH2). No alkyl—cobalt bond cleavage occurs with acids or bases in most cases. Two exceptions are the reactions with 3 M HNO3 at 25°C and with 1 M NaOH at 52°C. Electrophiles like I2 cleave the alkyl—cobalt bond forming RI and CoIII (BDM1,3pn)I2. Nucleophilic reagents (N-) displace the H2O trans to the alkyl group to form RCo(BDM1,3pn)(N), but do not dealkylate the alkyl complex under the reaction conditions studied. 相似文献
6.
Square planar mixed ligand complexes of the type [CuLL′] where L = 5-chlorosalicylaldehyde and L′ = acetoacetanilide, have
been synthesized on treatment with ammonia. Amine exchange of the above Schiff base complexes has been carried out on treatment
with different amines. The reaction with ethanol amine is quite interesting compared to other amines. It reacts with 5-chlorosalicylaldehyde
to form a Schiff base, while the β-diketone part is removed in the complex formation. All the complexes were characterized
by elemental analysis, spectral studies, magnetic measurement, TLC, and conductane. 相似文献
7.
Reactions which proceed through energized adducts, including radical recombinations, insertions, and addition to unsaturates, frequently exhibit unusual kinetic behavior. The branching ratios among various product channels are often complex functions of both temperature and pressure. Four such reactions involving methyl radicals are analyzed by combining chemical activation distribution functions with QRRK methods to predict rate constants for each channel. These include three oxidation paths, CH3 + O, CH3 + O2, CH3 + OH, and the addition reaction CH3 + C2H2. These predictions are compared to experiments wherever possible; generally, the agreement is quite satisfactory. Analysis of the energetics of the various reaction channels, using parameters which are readily available, provides a convenient framework for prediction. Suggested rate constants for the various channels for the four reactions are given at three pressures, 20, 760, and 7600 Torr, for the temperature range 300–2500 K. The approach used here can easily be applied to other reactions. 相似文献
8.
Merlin Rosales Jesús A. Durn ngel Gonzlez Ins Pacheco Roberto A. Snchez-Delgado 《Journal of molecular catalysis. A, Chemical》2007,270(1-2):250-256
Cationic rhodium and iridium complexes of the type [M(COD)(PPh3)2]PF6 (M = Rh, 1a; Ir, 1b) are efficient precatalysts for the hydroformylation of 1-hexene to its corresponding aldehydes (heptanal and 2-methylhexanal), under mild pressures (2–5 bar) and temperatures (60 °C for Rh and 100 °C for Ir) in toluene solution; the linear to branched ratio (l/b) of the aldehydes in the hydroformylation reaction varies slightly (between 3.0 and 3.7 for Rh and close to 2 for Ir). Kinetic and mechanistic studies have been carried out using these cationic complexes as catalyst precursors. For both complexes, the reaction proceeds according to the rate law ri = K1K2K3k4[M][olef][H2][CO]/([CO]2 + K1[H2][CO] + K1K2K3[olef][H2]). Both complexes react rapidly with CO to produce the corresponding tricarbonyl species [M(CO)3(PPh3)2]PF6, M = Rh, 2a; Ir, 2b, and with syn-gas to yield [MH2(CO)2(PPh3)2]PF6, M = Rh, 3a; Ir, 3b, which originate by CO dissociation the species [MH2(CO)(PPh3)2]PF6 entering the corresponding catalytic cycle. All the experimental data are consistent with a general mechanism in which the transfer of the hydride to a coordinated olefin promoted by an entering CO molecule is the rate-determining step of the catalytic cycle. 相似文献
9.
Liliya P. Tikhonova Sergey V. Rosokha Edward A. Bakay 《Reaction Kinetics and Catalysis Letters》1998,63(1):129-136
The investigation of Briggs-Rauscher reactions (BRR) with nickel complexes have shown that the range of the standard redox
potentials of BRR catalysts is at least 0.7–1.7 V. An inner-sphere interaction of metal ions with hydrogen peroxide is a prerequisite
of the oscillatory behavior. The unique catalytic properties of the nickel compounds are probably due to their lower redox
potential. 相似文献
10.
Stability constants are reported for the coordination of pyridine and substituted pyridines to the alkylcobalt(III) complexes of octaethylporphyrin (OEP), t-octaethylchlorin (OEC), and ttt-octaethylisobacteriochlorin (OEiBC) in toluene solution. The stability constants correlate with the base strength of the nitrogenous ligand. A cis-influence of the macrocycle saturation level on the stability constants is observed. Stability constants for coordination of a given pyridine ligand to an alkylcobalt(III) complex are roughly 10 times smaller than the stability constants for the corresponding cobalt(II) complex. Analysis of a thermodynamic cycle demonstrates that this leads to decreased stability of the complex with respect to Co-C bond homolysis upon ligand coordination, a "base-on" effect. Alkyl exchange occurs between cobalt complexes of different tetrapyrroles. Equilibrium data establish that the exchange is nonstatistical and that the Co-C bond is stabilized by increasing the saturation of the tetrapyrrole macrocycle. 相似文献
11.
环糊精与烷基钴配合物分子识别作用的DFT研究 总被引:2,自引:2,他引:0
用密度泛函理论(DFT)的B3LYP方法对Costa型烷基钴配合物[n-C6H13Co(C11H19N4O2)·H2O]+(A)和烷基钴肟配合物n-C6H13Co(C8H14N4O4)·H2O(B)进行计算研究,探讨了环糊精对它们的分子识别作用与其电荷分布之间的关系.结果表明,由于A和B的轴向烷基都是中性的,而且它们的烷基均插入环糊精腔内,而使A或B与环糊精形成包结物,因此,在环糊精边上修饰负离子不能加强其对+1价的Costa型配合物的识别作用,平面配体的类型及电荷对分子识别影响也不大. 相似文献
12.
Ferrocenecarboxaldehyde hydrazones were converted into palladium complexes on treatment with sodium tetrachloropalladate. The substitution pattern of the ferrocenylhydrazones was found to have a marked influence on the mode the palladium was attached to the organic moiety. The catalytic activity of the new palladium complexes in cross-coupling reactions was examined in detail, and it was compared with conventional catalyst systems. 相似文献
13.
运用光度法研究了RCo(Salen)L配合物在甲醇中热分解反应动力学;测定了Co—C键断裂的速率常数及活化能,得到表观速率常数顺序为i-C3H7>i-C4H9>n-C4H9>n-C3H7>C2H5,活化能顺序为i-C3H7相似文献
14.
An improved synthetic method of palladium(II) dinuclear macrocyclic complexes have been described. Each of the two isomers of the complexes [Pd2LBr2] has a macrocyclic ligand L in which two 2,6-bis(diaminomethyl)phenyl units coordinate to the Pd(II) centers with N, C, N donor atoms. Substitution of the bromo ligands of one of the isomer of the complexes with acetonitrile ligands affords a new dinuclear complex. Catalytic activities of these complexes were studied for the Mizoroki-Heck type reactions of iodobenzene and styrene. High turnover number up to 30,000 was achieved using one of the isomer of the complexes. 相似文献
15.
Snežana Jovanović Jovana Bogojeski Marijana Petković 《Journal of Coordination Chemistry》2015,68(17-18):3148-3163
Substitution reactions of the dinuclear Pt(II) complexes, [{Pt(en)Cl}2(μ-pz)]2+ (1), [{Pt(dach)Cl}2(μ-pz)]2+ (2) and [{Pt(dach)Cl}2(μ-4,4?-bipy)]2+ (3), and corresponding aqua analogs with selected biologically important ligands, viz. 1,2,4-triazole, L-histidine (L-His) and guanosine-5?-monophosphate (5?-GMP) were studied under pseudo-first-order conditions as a function of concentration and temperature using UV–vis spectrophotometry. The reactions of the chloride complexes were followed in aqueous 25 mmol L?1 Hepes buffer in the presence of 40 mmol L?1 NaCl at pH 7.2, whereas the reactions of the aqua complexes were studied at pH 2.5. Two consecutive reaction steps, which both depend on the nucleophile concentration, were observed in all cases. The second-order rate constants for both reaction steps indicate a decrease in the order 1 > 2 > 3 for all complexes. Also, the pKa values of all three aqua complexes were determined. The order of the reactivity of the studied ligands is 1,2,4-triazole > L-His > 5?-GMP. 1H NMR spectroscopy and HPLC were used to follow the substitution of chloride in the dichloride 1, 2, and 3 complexes by guanosine-5?-monophosphate (5?-GMP). This study shows that the inert and bridging ligands have an important influence on the reactivity of the studied complexes. 相似文献
16.
The dealkylation of a variety of RCo(BDMBg)+ complexes by Hg2+ is discussed. (The ligand BDMBg- is formed by the condensation of two moles of 2,3-butanedionemonoxime with one mole of 1,3-propanediamine or 1,2-ethanediamine.) The products of the dealkylation reaction are CoIII(BDMBg)(H2O)2+2 and RHg+. All reactions are first order in the [Hg2+]. The second order rate constants (k2) vary from 5.9 M-1 sec-1 (R = CH3) to 5.7 x 10-3M-1 sec-1 (R = n-C3H7). The relative rates for R are: CH3 ? C2H5 τ C6H5CH2 τ n-C4H9 ? n-C3H7. This order and other evidence are indicative of an SE2 mechanism with an attack by Hg2+ on the carbon bonded to the cobalt. 相似文献
17.
V. A. Milyukov A. V. Kataev E. Hey-Hawkins O. G. Sinyashin 《Russian Chemical Bulletin》2007,56(2):304-306
Reactions of trisodium heptaphosphide with half-sandwich cyclopropenyl complexes of nickel gave sodium 1,2-diphosphacyclopentadienide.
The influence of the ligand environment of the nickel atom on the formation of sodium 1,2-diphosphacyclopentadienide was studied.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 294–296, February, 2007. 相似文献
18.
S. Masoud Nabavizadeh 《Journal of organometallic chemistry》2011,696(22):3564-3571
Substitution reaction of the labile SMe2 ligand in the cyclometalated platinum(II) complexes of general formula [PtAr(ppy)(SMe2)], 1, in which ppy = deprotonated 2-phenylpyridyl and Ar = p-MeC6H4 or p-MeOC6H4, by several N or P donor reagents were studied; the N-donors, N, are pyridine (Py) and substituted pyridines, N = 4-MePy, Py, Py-d5, 2-MePy, 3-PhPy, 3,4-Me2Py, 4-tBuPy or 3-C(O)OMePy, and the P-donors, L, are phosphines or phosphites, L = P(OPh)3, P(O-iPr)3, PPh3, PPh2Me and L2 = Ph2PCH2PPh2, bis(diphenylphosphino)methane (dppm). The products were identified by multinuclear NMR studies as [PtAr(ppy)(N)], 2, or [PtAr(ppy)(L)], 3, respectively. Complexes 1 have a MLCT band in the visible region which was used to easily follow the kinetics of the ligand substitution reactions by UV-vis spectroscopy. Although the complexes 1 contain two cis Pt-C bonds, the substitution reactions followed a normal associative mechanism. The rates of reactions were depended on the concentration and the nature of the entering group. The ΔH‡/ΔS‡ compensation plot gave a straight line suggesting the operation of the same mechanism for all entering nucleophiles. 相似文献
19.
A combined solid and solution phase methodology for the synthesis of a series of mononuclear and polynuclear zinc benzoate complexes is described. The substituent on the aromatic ring and the effect of solvent on deciding the composition of the complexes is presented. From the 4-substituted benzoic acids 4-methylbenzoic acid (ptolH), 4-nitrobenzoic acid (pnitrobenH) and 4-chlorobenzoic acid (pchlorbenH), the mononuclear complexes [Zn(ptol)2(H2O)2], [Zn(pnitroben)2(H2O)(DMSO)2] and [Zn(pchlorben)2py)2] (where DMSO = dimethylsulfoxide, py = pyridine) have been synthesized and structurally characterised. Zinc complexes from the reaction of zinc sulfate heptahydrate with 3-methylbenzoic acid (mtolH) and 2-methylbenzoic acid (otolH), the dinuclear complexes [Zn2(μ2-mtol)4(py)2], [Zn2(μ2-otol)4(py)2], pentanuclear complex [Zn5(μ2-mtol)6(mtol)2(μ3-OH)2 (py)2] and tetranuclear complex [Zn4(μ2-otol)6(μ4-O) (DMSO)2], have been prepared by varying the reaction conditions and the complexes have been structurally characterized. 相似文献
20.
Summary Three Cr(III) species (dichlorotetraaquachromium (III), [CrCl2(H2O)4]+; monochloropentaaquachromium(III), [CrCl(H2O)5]2+; and hexaaquachromium(III), [Cr(H2O)6]3+) have been separated and determined by capillary electrophoresis. The first two complexes could be detected in direct mode
in phosphate buffer, but because the absorption of complex [Cr(H2O)6]3+ is poor in the UV range, indirect UV detection had to be used. For indirect detection 5 mM imidazole was added to the buffer
solution. The formation and decomposition of the different Cr(III) complexes were monitored in time after the preparation
of solutions of CrCl3.6H2O. The slowest process was the decomposition of [CrCl(H2O)5]2+; 300 h after preparation of a solution of CrCl3.6H2O of pH 1 the solution contained only [Cr(H2O)6]3+. The effects of pH and the content of some matrix ions on the rates of conversion of the complexes were studied. The kinetic
characteristics of this complex system could be investigated adequately by means of capillary electrophoresis.
Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献