共查询到20条相似文献,搜索用时 609 毫秒
1.
Summary The kinetics of the reaction between nitrous acid and gold(III) in an HCl medium was studied. The reaction was first order with respect to [AuIII] and [HNO2]·H+ and Cl- ions inhibit the rate and alkali metal ions have specific effects on the rate. The reaction appears to involve different gold(III) species, viz. AuCl
inf4
sup–
, AuCl3(OH2) and AuCl3(OH)–, which undergo a two-equivalent reduction to gold(I) leading to the formation of NO
inf2
sup+
which under-goes rapid hydrolysis to give nitric acid. 相似文献
2.
Summary The kinetics of aqueous polymerization of acrylonitrile monomer (M) initiated by the MnIII-KNCS redox system have been studied under deaerated conditions in the temperature range 26–40 °C at constant ionic strength. The overall rates of polymerization and the disappearance of MnIII were determined. The polymerization was initiated by the free radicals arising from the MnIII-thiocyanate redox reaction. The rate of polymerization was investigated at various concentrations of monomer and initiator. The effects of varying [MnIII], [NCS–], pH, total [P2O
inf7
sup4–
], added [MnII], metal ions, ClO
inf4
sup–
, Cl– and SO
inf4
sup2–
were examined. Dependence of the rate of polymerization on temperature was studied and activation parameters were computed from an Arrhenius plot. A suitable kinetic scheme consistent with the observed results is proposed and discussed. 相似文献
3.
Hulin Li Boyan Zhang Lin Ma Liliu Wu James Q. Chambers 《Transition Metal Chemistry》1995,20(6):552-556
Summary The spectrochemical, electrochemical and electrocatalytic properties of Co[15]aneN4 ([15]aneN4 = 1,4,8,12-tetraazacyclopentadecane) have been investigated. The results show that, in aqueous solution, this compound mainly exists as three species whose axial coordination positions are occupied by water and/or hydroxy ligands; it is marginal whether other substrates such as Cl– and NO
inf3
sup–
interact with the central ion in acid-base solutions. The approximate Pourbaix diagram of CoIII/II[15]ane N4 was determined. There is an electrochemically-induced isomerization between two trans conformational isomers of the Co[15]aneN4 complexes in acid and netural solutions. The Co[15]aneN4 complex has electrocatalytic properties for reduction of nitrate and nitrite only in strong alkaline solution. 相似文献
4.
Summary The kinetics and mechanisms of the oxidation of Nb(CN)
inf8
sup5–
by the oxyanions S2O
inf8
sup2–
, BrO
inf3
sup–
, and IO
inf4
sup–
have been investigated in alkaline aqueous media (pH 12). The second-order rate constant for the electron transfer reaction between Nb(CN)
inf8
sup5–
and S2O
inf8
sup2–
at 25.0 °C, I = 0.36m (K+), is 11.1± 0.3 m
–1
s
–1 with H
= 30 ± 2kJmol–1 and S
= - 125 + 7JK–1 mol–1. The rate constant for the oxidation of Nb(CN)
inf8
sup5–
by BrO
inf3
sup–
at 25.0 °C, I = 0.20m (Na+), is 2.39 ± 0.08m
–1
s
–1 with H = 28 ± 2kJmol–1 and S
= -139 ± 7JK–1mol–1. The oxidation of Nb(CN)
inf8
sup5–
by IO
inf4
sup–
proceeds by two parallel pathways involving the monomeric IO
inf4
sup–
ion and the hydrated dimer H2I2O
inf10
sup4–
. The second-order rate constant for the oxidation of Nb(CN)
inf8
sup5–
by monomeric IO
inf4
sup–
at 5.0 °C, I = 0.050m (Na+), is (3.3 ± 0.6) × 103
m
–1
s
–1 with H
= 75 ± 6 kJ mol–1 and S
= 94 ± 15 J K–1 mol–1, while the rate constant for the oxidation by H2I2O
inf10
sup4–
is (1.8 ± 0.1) × 103
m
–1
s
–1 with H
= 97 ± 5 kJ mol–1 and S
= 166 ± 16 J K–1 mol–1 under the same reaction conditions. The rate constants for each of the oxidants employed display specific cation catalysis with the order of increasing rate constants: Li+ < Na+ < NH
inf4
sup+
< K+ < Rb+ < Cs+, in the same direction as the electronic polarizability of the cations. The results are discussed in terms of the outer-sphere electron-transfer processes and compared with the corresponding data and mechanisms reported for other metal-cyano reductants. 相似文献
5.
Summary The kinetics of formation and dissociation of the binuclear complex of CoII with histidinato(pentaammine)CoIII have been studied at 10.0°Ct°C25°C and I = 0.3 mol dm–3 (ClO
inf4
sup–
). The formation of the binuclear complex, [(NH3)5CoIIILCoII]4+ (L = histidinate), in the 5.7–6.8 pH range involves the reaction of Co(OH2)
inf6
sup2+
with the deprotonated, (NH3)5CoL2+, and monoprotonated, (NH3)5CoLH3+, forms of the complex. The rate and activation parameters for the formation are consistent with an I
d mechanism. The binuclear species undergoes dissociation to yield the parent CoIII substrate and Co(OH2)
inf6
sup2+
via spontaneous and acid-catalysed paths. Comparison of spontaneous dissociation rate of the binuclear complex with other related systems indicated the chelate nature of the binuclear species. 相似文献
6.
Mária Hvastijová Jozef Kožísek Jiří Kohout Lothar Jäger Hartmut Fuess 《Transition Metal Chemistry》1995,20(3):276-279
Summary Reaction of CoII with N(CN)
inf2
sup–
or C(CN)
inf3
sup–
in the presence of imidazole (iz) or its methyl derivatives (2-meiz and 4-meiz) gave eight compounds of CoII: ligand stoichiometry 12, including two isomeric pairs ( and ) for the complexes [Co{C(CN)3}2(2-meiz)2] and [Co{C(CN)3}2-(4-meiz)2]. The complexes were studied by electronic and i.r. spectroscopies. For -[Co{C(CN)3}2(2-meiz)2] singlecrystal X-ray analysis was performed; its crystal structure consists of one-dimensional chains, formed by C(CN)
inf3
sup–
anions bridging between the CoII atoms. The CoII atom is nearly octahedrally coordinated by two tertiary nitrogens of 2-meiz and four nitrogens of C(CN)
inf3
sup–
. The spectra of these compounds and of the complexes with iz, as well as that of -[Co{C(CN)3}2(4-meiz)2], indicate all these compounds to have basically the same bridging polymeric octahedral structure. However, the spectra indicate distorted tetrahedral structures for the remaining compounds. 相似文献
7.
Summary The heterobinuclear complex [FeIICuII(ttha)]2–
(1) (ttha6– = triethylenetetraminehexaacetate), exhibits the same two-nitrogen per metal coordination of the related homobinuclear [Cu
inf2
supII
(ttha)]2– complex, but(1) has a signature broad single derivative e.p.r. line atg = 2.11 with a peak-to-peak width of 182 G. Oxidation to the [FeIIICuII(ttha)]– complex by either O2 or H2O2 initiates a rapid cross-binuclear metal exchange forming homobinuclear [Fe
inf2
supIII
O(ttha)]2– and [Cu
inf2
sup–
(ttha)]2– products (t
1/2
ca 3.9 s). An isomeric form of [FeIIICuII(ttha)]–, which has three nitrogen donors bound to CuII and only the remaining iminodiacetate fragment bound to FeIII, rearranges much more slowly (t
1/2
ca 4.8 h). 相似文献
8.
Summary The kinetics of oxidation of aldoses, namely xylose, arabinose, galactose and glucose, by CeIV have been studied in HClO4 + H2SO4 medium and in the presence of PdII. The reactions exhibit a first order rate dependence with respect to oxidant. The rate is inversely dependent on the [HSO
inf4
sup–
][H+] ratio. The order of reaction with respect to aldose decreases at higher [aldose]. Due to the formation of a complex between CeIV and PdII, a retarding effect of [PdII] on the rate of disappearance of [CeIV] has been observed. A mechanism consistent with the observed kinetic data is proposed. 相似文献
9.
Summary The complex was prepared by reaction of cis-[Co(phen)2-Cl2] Cl·3H2O (phen = phenanthroline) with L-proline at pH 9, isolated by chromatography using an SP-Sephadex C-25 H+ form column, and characterized by elemental analysis, spectroscopy and thermogravimetry. The X-ray crystal structure has also been determined. There are 1.5 independent complex cations, 1.5 ClO
inf4
sup–
anions and two H2O molecules in each asymmetric unit, and two complex cations of similar structure in the crystal. There is a crystallographic C2 symmetry in the first of these. In the octahedral coordination sphere of the metal the oxygen and nitrogen chelating prolinato ligands are arranged in the trans-N,N form. 相似文献
10.
Guru C. Pradhan 《Transition Metal Chemistry》1993,18(4):431-434
Summary The kinetics of spontaneous, acid- and FeIII-catalysed aquation of cis-[Co(en)2(RNH2)(SalH)]2+ complexes (R = Me, Et; SalH = C6H4(OH)CO
inf2
sup-
) were studied in acid perchlorate medium, I = 1.5 mol dm–3 (NaClO4) at 70–80°C. The FeIII-catalysed aquation proceeds via formation of a binuclear species, the evidence of which follows from aquation, complexation and equilibrium studies. The spontaneous aquation rate shows steric acceleration with the increase of the nonlabile amine chain length, while that of acid- and FeIII-catalysed aquation shows the opposite trend. An attempt is made to explain the discrepancy in the rate on the basis of solvent cosphere effects. 相似文献
11.
Balaprasad G. Ankamwar Madukar D. Bhand Gavisiddappa S. Gokavi 《Transition Metal Chemistry》1993,18(4):361-363
The reaction between VV and TlI was studied in 4.0 mol dm–3 HCl at an ionic strength of 4.1 mol dm–3 at 25° C. The main active species under the reaction conditions were found to be VO
inf2
sup+
and TlCl
inf3
sup2–
for the oxidant and reductant, respectively. A probable mechanism in terms of these species is given, and follows the rate law:
相似文献
12.
Gianantonio Battistuzzi Marco Borsari Daniela Dallari Raffaele Battistuzzi 《Transition Metal Chemistry》1995,20(2):212-219
Summary
Tris-, bis- and mono-ligand complexes of NiII with 1-phenyl-4, 6-dimethylpyrimidine-2-thione (L) having the general formulae NiL3X2·2H2O (X = ClO
inf4
p–
, BF
inf4
p–
), NiL2X2 (X = Cl–, Br–, SCN– or NO
inf3
p–
), NiL2X2·EtOAc (X = Br– or I–), NiL2X2·H2O·EtOH (X = I– or NO
inf3
p–
) and NiLCl2·3H2O, were synthesized and their structures deduced from i.r. and electronic spectra, and magnetic properties. The combined evidence is consistent with an octahedral coordination for the NiII ion in all the complexes, with the ligand acting as a bidentate N,S-chelating agent. Spectral evidence, conductivity data and electro-chemical results in DMF solution show that the complexes undergo solvolysis readily. Polarographic and c.v. data for the [NiL3](ClO4)2·2H2O complex and for the [Ni-(DMF)6](ClO4)2-L systems, at increasing ligand concentrations, have shown that in DMF solution the [Ni(DMF)6]2+ cation prevails and that the thiopyrimidine-containing species, [NiL(DMF)5]2+ (L = N-monodentate ligand)
, can be formed only in the presence of a large excess of free ligand.Author to whom all correspondence should be directed. 相似文献
13.
Summary The kinetics of oxidation of d-glucose, d-galactose, d-fructose, d-ribose, d-arabinose, d-xylose and 2-deoxyd-glucose by diperiodatoargentate(III) (DPA) have been investigated in alkaline medium. The order of the reaction with respect to [DPA] is unity while the order with respect to [sugar] is < 1 over the concentration range studied. The rate increases with an increase in [OH –] and there is a marginal decrease in the rate with an increase in [IO
inf4
sup–
]. No significant dependence on ionic strength was found, but the rate increases with a decreasing dielectric constant. Formic acid and the corresponding aldonic acids were detected as the products of oxidation. The participation of the open chain form of the sugar and a mechanism involving the initial formation of a complex between the enediol of the sugar and AgIII are proposed. 相似文献
14.
Summary The stoichiometry, kinetics and mechanism of oxidation of N-(2-hydroxyethyl)ethylenediamine triacetate by K5CoIIIW12O40, Fe(phen)
inf3
sup3+
and Fe(bipy)
inf3
sup3+
have been studied. Each reaction is first order with respect to the oxidant and the reductant, but retarded by [H+] in the 0.20–1.60 mol dm –3 range. Simple electron exchanges are thought to occur, leading to the decarboxylation of the substrate. 相似文献
15.
Dr. Frank J. Owens 《Theoretical chemistry accounts》1975,40(2):87-92
The crystal field splitting of the ground2g state and the equilibrium orientation of the N
inf2
sup–
radical in the monoclinic barium azide are calculated employing a point ion representation of the lattice potential and assuming three different plausible trapping sites for the radical. When the N
inf2
–
is assumed to replace an azide ion which is parallel to thec axis of the unit cell, the previously suggested trapping site, the calculated crystal field splitting is in order of magnitude agreement with the value deduced from theg shift in the ESR spectrum. The calculated orientational angle of the molecular axis with thec axis of the unit cell is 9.0 degrees which compares favorably with the experimentally determined angle of 5.0 ± 1.5 degrees. Possible reasons why the N
inf2
–
can not be trapped at the site of an azide ion which is perpendicular to the c axis are suggested from the calculation. 相似文献
16.
The kinetics of oxidation of cis-[CrIII(ox)2(H2O)2]– (ox = C2O4
2–) by IO4
– showed a first-order dependence on the initial CrIII complex concentration in the presence of a vast excess of [IO4
–]. The dependence of the pseudo-first-order rate constant on [IO4
–] is complex and is consistent with the formation of a precursor complex. It is proposed that this complex is formed through the coordination of the two carbonyl oxygens of the ox ligand with the IO4
– ion, forming a cyclic intermediate. The kinetics are consistent with the hydroxo form of the CrIII complex being the reactive species, whereas the aqua species forms an unreactive complex. 相似文献
17.
Michail Bogdanov Ryszard Gryboś Alina Samotus Konstantin Bogolitsyn 《Transition Metal Chemistry》1993,18(6):599-603
Summary The kinetics of the reduction of octacyanometallates(IV) in alkaline aqueous medium have been studied spectrophotometrically. The experimental results are in agreement with following rate law:-d[M(CN)
inf8
sup3–
]/dt = k
obs[M(CN)
inf8
sup3–
]2[OH–][Na+] where k
obs = 4.1 × 10–2M–3s–1 (Mo) and 4.0 × 10–4 M–3 s–1 (W). The rate data were used to calculate the thermodynamic activation parameters H
and S
. A mechanism of the reaction is discussed.On leave from Faculty of Chemistry, Forest Engineering Institute, Archangelsk, Russia. 相似文献
18.
Summary The oxidation of formate ion by alkaline osmium tetroxide, such that [HCO
inf2
p–
] [OsVII], exhibits first-order dependence in [OsVII], an order less than unity in [HCO
inf2
p–
], and zero-order in [OH–]. HCO2– reacts as an ion-pair formed with an alkali metal ion and [OsO4(OH)2]2– is the reactive species of OsVII. The formation of an intermediate OsVII-HCO2M complex is substantiated by the rapid-scan spectra of the reaction mixture. Anions (Cl–, ClO
inf4
p–
) have no effect on the rate. The close agreement between the observed k
H/k
D = 7.1 and the theoretically calculated value (7.0), based on the stretching frequencies of C-H and C-D bonds in the free molecule, indicates an outer-sphere mechanism.Author to whom all correspondence should be directed. 相似文献
19.
Chimatadar Shivamurti A. Koujalagi Sangappa B. Nandibewoor Sharanappa T. 《Transition Metal Chemistry》2001,26(1-2):241-245
The oxidation of HgI by CeIV has been studied in aqueous H2SO4. A minute amount (10–6 mol dm–3) of OsVIII is sufficient to catalyse the reaction. The active catalyst, substrate and oxidant species are H2OsO5, [Hg2(SO4)HSO4]– and H3Ce(SO4)–
4, respectively. Possible mechanisms are proposed and the reaction constants involved have been determined. 相似文献
20.
Izak M. Potgieter Stephen S. Basson Andreas Roodt Johann G. Leipoldt 《Transition Metal Chemistry》1988,13(3):209-211
Summary The kinetics of the reaction between [MoO2(CN)4]4– and F– have been studied in the pH range 8 to 11. The results indicated that the diprotonated form, [MoO(OH2)(CN)4]2–, is the only reactive species and that the aqua-ligand is substituted by the F– ion according to the following reaction. The k1 and k–1 values are 8.8(2) M–1 s–1 and 0.6(1)s–1, respectively, at 15°C. A dissociative substitution process is proposed. 相似文献
|