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1.
The equilibria AuCl4−+jOH−+kH2O⇌AuCl4−j−k
(OH)
j
(H2O)
k
k−1+(j+k)Cl−, β
jk
(0≤j,k≤4) have been studied spectrophotometrically at 20 °C in aqueous solution. For I=2 mol⋅dm−3(HClO4) the conventional constants, β
i
*, of the equilibria, Au*+iCl−
⇌AuCl
i
*, are equal to log 10
β
1*=(6.98±0.08); log 10
β
2*=(13.42±0.05); log 10
β
3*=(19.19±0.09); and log 10
β
4*=(24.49±0.07), where [AuCl
i
*]=∑[AuCl
i
(OH)
j
(H2O)4−i−j
] at i=const. The hydrolysis and other transformations of AuCl4− in aqueous solution are discussed. On the basis of new and known data, a full set of equilibrium constants, β
jk
, or their estimates has been obtained. 相似文献
2.
An O-bonded sulphito complex, Rh(OH2)5(OSO2H)2+, is reversibly formed in the stoppedflow time scale when Rh(OH2)
6
3+
and SO2/HSO
3
−
buffer (1 <pH< 3) are allowed to react. For Rh(OH2)5OH2++ SO2 □ Rh(OH2)5(OSO2H)2+ (k1/k-1), k1 = (2.2 ±0.2) × 103 dm3 mol−1 s−1, k−1 = 0.58 ±0.16 s−1 (25°C,I = 0.5 mol dm−3). The protonated O-sulphito complex is a moderate acid (K
d
= 3 × 10−4 mol dm−3, 25°C, I= 0.5 mol dm−3). This complex undergoes (O, O) chelation by the bound bisulphite withk= 1.4 × 10−3 s−1 (31°C) to Rh(OH2)4(O2SO)+ and the chelated sulphito complex takes up another HSO
3
−
in a fast equilibrium step to yield Rh(OH2)3(O2SO)(OSO2H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH2)3(O2SO)(OSO2)- → Rh(OH2)3(O2SO)(SO3)− (k
iso
= 3 × 10−4 s−1, 31°C). A dinuclear (μ-O, O) sulphite-bridged complex, Na4[Rh2(μ-OH)2(OH)2(μ-OS(O)O)(O2SO)(SO3) (OH2)]5H2O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water
and most organic solvents and very stable to acid-catalysed decomposition 相似文献
3.
Guru C. Pradhan 《Transition Metal Chemistry》1992,17(5):443-445
The kinetics of the base hydrolysis ofcis-[Co(en)2(RNH2)-(SalH)]2+ (R=Me or Et; SalH=HOC6H4CO
2
−
) were investigated in aqueous ClO
4
−
in the 0.004–0.450 mol dm−3 [OH−] range, I=0.50 mol dm−3 at 30–40°C. The phenoxide species is hydrolysed via [OH−]-independent and [OH−]-dependent paths, the latter being first order in [OH−]. The high rate of alkali-independent hydrolysis of the phenoxide species is associated with high ΔH≠ and ΔS≠ values, in keeping with the SNICB mechanism involving an amido conjugate base generated by the phenoxide-assisted NH-deprotonation
of the coordinated amine. The [OH−]-dependent path also involves the conventional SN1 CB mechanism. The rate constant, k1, for the SNICB path exhibits a steric acceleration with the increasing size of the non-labile alkylamine, whereas the rate
constant, k2, for the SN1CB path shows a reverse trend.
TMC 2578 相似文献
4.
The mechanism of the reactions of methane with the gold(III) complexes [AuClx(H2O)4− x
]3−x
(x = 2, 3, or 4) was studied by the DFT/PBE method with the SBK basis set. High activation barriers obtained for the reactions
of [AuCl4]− and [Au(H2O)Cl3] with methane suggest these reactions cannot proceed under mild conditions. The reaction of the [Au(H2O)2Cl2]+ complex with methane has a rather low energy barrier and proceeds through the formation of an intermediate complex.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 191–201, February, 2006. 相似文献
5.
The oxidation of N,N-dimethylethanolamine (DMEA) by bis(hydrogenperiodato) argentate(III) ([Ag(HIO6)2]5−) was studied in aqueous alkaline medium. Formaldehyde and dimethylamine were identified as the major oxidation products after
the oxidation of DMEA. The oxidation kinetics was followed spectrophotometrically in the temperature range of 25.0 °C–40.0 °C.
It was found that the reaction was first order in [Ag(III)]; the oberved first-order rate constants k
obsd as functions of [DMEA], [OH−] and total concentration of periodate ([IO4-]tot[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}) were analyzed and were revealed to follow a rate expression: kobsd = (k1 +k2[OH-])K1K2[DMEA]/{f([OH-])[IO4-]tot+ K1 + K1K2[DMEA]}k_{\mathrm{obsd}} = (k_{1} +k_{2}[\mathrm{OH}^{-}])K_{1}K_{2}[\mathrm{DMEA}]/\{f([\mathrm{OH}^{-}])[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}+ K_{1} + K_{1}K_{2}[\mathrm{DMEA}]\}. Rate constants k
1 and k
2 and equilibrium constant K
2 were derived; activation parameters corresponding to k
1 and k
2 were computed. In the proposed reaction mechanism, a peridato-Ag(III)-DMEA ternary complex is formed indirectly through a
reactive intermediate species [Ag(HIO6)(OH)(H2O)]2−. In subsequent rate-determining steps as described by k
1 and k
2, the ternary complex decays to Ag(I) through two reaction pathways: one of which is spontaneous and the other is prompted
by an OH−. 相似文献
6.
Guru C. Pradhan 《Transition Metal Chemistry》1992,17(2):104-108
The formation and dissociation of the binuclear complexes of FeIII withcis-[Co(en)2(RNH2)SalH]2+ [R=Me, Et and SalH=C6H4(OH)CO
2
−
] were studied by a stopped-flow technique at 20–35°C, and I=1.0 mol dm−3 (ClO
4
−
). The formation of the binuclear species, N5CoSalFe4+, involves reactions of the phenol form of the CoIII substrates with Fe(OH2)
6
3+
and Fe(OH2)5OH2+. The mechanism of reaction of Fe(OH2)5OH2+ is essentially Id, while that of Fe(OH2)
6
3+
appears to be Ia. The formation rate constant, k1, for Fe(OH2)
6
3+
/N5CoSalH2+ reaction decreases as the amine chain length increases, whereas the same (k2) for the Fe(OH2)5OH2+/N5CoSalH2+ reaction does not show any such trend. The binuclear species, N5CoSalFe4+, dissociates to yield a CoIII substrate and FeIII speciesvia a predominantly spontaneous dissociation path and a minor acid catalysed path which are relatively insensitive to the variation
in size of the non-labile amine chain length. 相似文献
7.
The redox reactions of thiosulfate with four iron(III) complexes having phenolate-amide-amine coordination, FeIII(L){L = 1,2-bis(2-hydroxybenzamido)ethane, L1; 1,3-bis(2-hydroxybenzamido)propane, L2; 1,5-bis(2-hydroxybenzamido)3-azapentane, L3; and 1,8-bis(2-hydroxybenzamido)3,6-diazaoctane, L4} have been investigated in 10% v/v MeOH + H2O and I = 0.3 mol dm−3. At constant pH (~ 4.8) and under pseudo-first order conditions of [S2O
3
2−
] the reaction obeyed the rate law : − d[FeIII(L)]/dt = k
obs [FeIII(L)] + k
obs
′
where k
obs
′
denotes the observed rate constant of thiosulfate decomposition; k
obs = a[S2O
3
2−
] + b[S2O
3
2−
]
T
2
is valid for all the complexes, particularly at pH < 6, while k
obs
′
= [H+][S2O
3
2−
]
T
2
is consistent with the rate law for thiosulfate decomposition proposed earlier. The rate data (k
obs) were analysed on the basis of the reactivities of various species of FeIII(L) generated by the equilibrium protonation of the sec-NH of dien and trien spacer units resulting in the ring opening (for [FeIII(L3/L4)]), and acid base equilibrium of the aqua ligand bound to the iron(III) centre
([FeIII(L)(OH2)
n
]). The redox activities, both for second and third order paths, show the ligand dependencies : L4<L3<L1<L2 conforming to the fact that the complexes tend to be less susceptible to electron transfer from S2O
3
2−
with (i) the increase of the number of chelate rings, (ii) the decrease of overall charge, and (iii) the decrease of ring
size offered by the amine moiety (from six membered to five membered one as for [FeIII(L1/L2)(OH2)2]+. There was no evidence for the formation of inner sphere thiosulfato complex, the possibility of the formation of the outer
sphere ion-pairs, [Fe(L/HL)(OH2)n
+/2+, S2O
3
2−
] with low equilibrium constant value may not be excluded. In view of this, the outer sphere electron transfer (ET) mechanism
is the most likely possibility. 相似文献
8.
Two solid complexes, fac–[Cr(gly)3] and [Cr(gly)2(OH)]2, (where gly is glycinato ligand) were prepared and their acid-catalysed aquation products were identified. The structure
of [Cr(gly)3] was solved by X-ray diffraction, revealing a cationic 3D sublattice with perchlorate anions inside its cavities. Acid-catalysed
aquation of [Cr(gly)3] and [Cr(gly)2(OH)]2 leads to the same inert product, [Cr(gly)2(H2O)2]+, in a two-stages process. At the first stage, intermediate complexes, [Cr(gly)2(O–glyH)(H2O)]+ and [Cr(gly)2(H2O)–OH–Cr(gly)2(H2O)]+, are formed respectively. Kinetics of the first aquation stage of [Cr(gly)3] were studied in HClO4 solutions. The dependencies of the pseudo first-order rate constants on [H+] are as follows: k
obs1H = k
0 + k
1
K
p1[H+], where k
0 and k
1 are rate constants for the chelate-ring opening via spontaneous and acid-catalysed reaction paths, respectively, and K
p1 is the protonation constant. The proposed mechanism assumes formation of the reactive intermediate as a result of proton
addition to the coordinated carboxylate group of the didentate ligand. Some kinetic studies on the second reaction stage,
the one-end bonded glycine liberation, were also done. The obtained results were analogous to those for stage I. In this case,
the proposed reactive species are intermediates, protonated at the carboxylate group of the monodentate glycine. Base hydrolysis
of two complexes, [Cr(gly)2(O–gly)(OH)]− and [Cr(gly)2(OH)2]−, was studied in 0.2–1.0 M NaOH. The pseudo first-order rate constants, k
obsOH, were [OH−] independent in the case of [Cr(gly)2(O–gly)(OH)]−, whereas those for [Cr(gly)2(OH)2]− linearly depended on [OH−]. The reaction mechanisms were proposed, where the OH− -catalysed reaction path was rationalized in terms of formation of the reactive conjugate base, [Cr(gly)2(OH)(O)]2−, as a result of OH− ligand deprotonation. Activation parameters were determined and discussed. 相似文献
9.
The kinetics of oxidation of phenyldiethanolamine (PEA) by a silver(III) complex anion, [Ag(HIO6)2]5−, has been studied in an aqueous alkaline medium by conventional spectrophotometry. The main oxidation product of PEA has
been identified as formaldehyde. In the temperature range 20.0–40.0 °C , through analyzing influences of [OH−] and [IO
4
−
]tot on the reaction, it is pseudo-first-order in Ag(III) disappearance with a rate expression: k
obsd = (k
1 + k
2[OH−]) K
1
K
2[PEA]/{f([OH−])[IO
4
−
]tot + K
1 + K
1
K
2 [PEA]}, where k
1 = (0.61 ± 0.02) × 10−2 s−1, k2 = (0.049 ± 0.002) M−1 s−1 at 25.0 °C and ionic strength of 0.30 M. Activation parameters associated with k
1 and k
2 have also been derived. A reaction mechanism is proposed involving two pre-equilibria, leading to formation of an Ag(III)-periodato-PEA
ternary complex. The ternary complex undergoes a two-electron transfer from the coordination PEA to the metal center via two
parallel pathways: one pathway is spontaneous and the other is assisted by a hydroxide ion. 相似文献
10.
Chromium(III)-lutidinato complexes of general formula [Cr(lutH)
n
(H2O)6−2n
]3−n (where lutH− is N,O-bonded lutidinic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(lutH)3]0 leads to only one ligand dissociation, whereas base hydrolysis produces chromates(III) as a result of subsequent ligand liberation
steps. The kinetics of the first ligand dissociation were studied spectrophotometrically, within the 0.1–1.0 M HClO4 and 0.4–1.0 M NaOH range. In acidic media, two reaction stages, the chelate-ring opening and the ligand dissociation, were
characterized. The dependencies of pseudo-first-order rate constants on [H+] are as follows: k
obs1 = k
1 + k
−1/K
1[H+] and k
obs2 = k
2
K
2[H+]/(1 + K
2[H+]), where k
1 and k
2 are the rate constants for the chelate-ring opening and the ligand dissociation, respectively, k
−1 is the rate constant for the chelate-ring closure, and K
1 and K
2 are the protonation constants of the pyridine nitrogen atom and coordinated 2-carboxylate group in the one-end bonded intermediate,
respectively. In alkaline media, the rate constant for the first ligand dissociation depends on [OH−]: k
obs1 = k
OH(1) + k
O[OH−], where k
OH(1) and k
O are rate constants of the first ligand liberation from the hydroxo- and oxo-forms of the intermediate, respectively, and
K
2 is an equilibrium constant between these two protolytic forms. Kinetic parameters were determined and a mechanism for the
first ligand dissociation is proposed. The kinetics of the ligand liberation from [Cr(lut)(OH)4]3− were also studied and the values of the pseudo-first-order rate constants are [OH−] independent. 相似文献
11.
Małgorzata Pazderska-Szabłowicz Agnieszka Białkowska Ewa Kita 《Transition Metal Chemistry》2006,31(3):413-420
New chromium(III) complexes, [Cr(C2O4)2(2-hnic)]2− and [Cr(C2O4)2(3-hpic)]2− (where 2-hnic = O,O′-bonded 2-hydroxynicotinic acid and 3-hpic = N,O-bonded 3-hydroxypicolinic acid), were obtained and characterized
in solution. The acid-catalyzed aquation of the both complexes leads to liberation of the appropriate pyridinecarboxylic acid
and formation of cis-[Cr(C2O4)2(H2O)2]−. Kinetics of these reactions were studied spectrophotometrically in the 0.1–1.0 M HClO4 range, at I = 1.0 M. In the case of [Cr(C2O4)2(2-hnic)]2−, a slow chelate-ring opening at the Cr–O (phenolate) bond is followed by a fast Cr–O (carboxylate) bond breaking. The rate
law: kobs = kHQH[H+] was established, where kH is the acid-catalyzed rate constant and QH is the protonation constant of the coordinated phenolate oxygen atom. In the case of [Cr(C2O4)2(3-hpic)]2−, the reversible chelate-ring opening at Cr–N bond is followed by the rate determining step – the one-end bonded ligand liberation.
The rate law for the first step was determined: kobs = k1+k−1/Q1[H+], where k1 and k−1 are the rate constants of the chelate-ring opening and closure and Q1 is the protonation constant of the pyridine nitrogen atom. The aquation mechanisms are proposed and the effect of ligand
coordination mode on complex reactivity is discussed. 相似文献
12.
Joanna Wiśniewska 《Transition Metal Chemistry》2007,32(6):811-815
The kinetics of the electron-transfer reactions between promazine (ptz) and [Co(en)2(H2O)2]3+ in CF3SO3H solution ([CoIII] = (2–6) × 10−3
m, [ptz] = 2.5 × 10−4
m, [H+] = 0.02 − 0.05 m, I = 0.1 m (H+, K+, CF3SO
3
−
), T = 288–308 K) and [Co(edta)]− in aqueous HCl ([CoIII] = (1 − 4) × 10−3
m, [ptz] = 1 × 10−4
m, [H+] = 0.1 − 0.5 m, I = 1.0 m (H+, Na+, Cl−), T = 313 − 333 K) were studied under the condition of excess CoIII using u.v.–vis. spectroscopy. The reactions produce a CoII species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (k
obs) on [CoIII] with a non-zero intercept was established for both redox processes. The rate of reaction with the [Co(en)2(H2O)2]3+ ion was found to be independent of [H+]. In the case of the [Co(edta)]− ion, the k
obs dependence on [H+] was linear and the increasing [H+] accelerates the rate of the outer-sphere electron-transfer reaction. The activation parameters were calculated as follows:
ΔH
≠ = 105 ± 4 kJ mol−1, ΔS
≠ = 93 ± 11 J K−1mol−1 for [Co(en)2(H2O)2]3+; ΔH
≠ = 67 ± 9 kJ mol−1, ΔS
≠ = − 54 ± 28 J K−1mol−1 for [Co(edta)]−. 相似文献
13.
E. A. Abu-Gharib R. M. El-Khatib L. A. E. Nassr A. M. Abu-Dief 《Kinetics and Catalysis》2012,53(2):182-187
Kinetics of the base hydrolysis of 6-nitro-2H-chromen-2-one (NC) and 6-nitro-2H-chromen-2-one-3-carboxylic acid (NCC) in water-methanol
and water-acetone mixtures was studied at temperature range from 283 to 313 K. The activation parameters of the reactions
were evaluated and discussed. The change in the activation barrier of the investigated compounds from water to water-methanol
and water-acetone mixtures were estimated from the kinetic data. The base hydrolysis of NC and NCC in the water-methanol and
water-acetone mixtures follows a rate law with k
obs = k
2[OH−] and k
obs = k
1 + k
2[OH−], respectively. The decrease in the rate constants of NC and NCC hydrolysis, as the proportion of methanol and acetone increases,
is accounted for by the destabilization of the OH− ion. The activation and thermodynamic parameters were determined. 相似文献
14.
The effect of bromide salts, MBr [M=Na, (CH3)4N, (C2H5)4N, (C4H9)4N, C8H17N(CH3)3], on the first-order rate constant, k
1, of basic hydrolysis of 2,4-dinitrochlorobenzene in micelle solutions of cetyltrimethylammonium bromide has been studied.
The main results are as follows. The molar ratio concentrations of OH−, m
S
OH, on the micelle surface in the presence of different concentrations of Br− ions, were calculated on the basis of the pseudophase ion-exchange model, and there is a linear relation between k
1 and m
S
OH. The relation between k
1 and the concentrations of various bromides could be presented with a single curve, and the cations of the bromides have little
effect on k
1. Under the experimental conditions, there is a linear relation between 1/k
1 and the concentrations of Br−; thereby a new method calculating the competition binding constant between OH− and Br− from dynamic data is proposed. The hydrodynamic radii of the micelles increase with the addition of bromide salts.
Received: 1 August 2000 Accepted: 31 January 2001 相似文献
15.
The kinetics of methoxy-NNO-azoxymethane (I) hydrolysis in concentrated solutions of strong acids (HBr, HCl, HClO4, and H2SO4) has been investigated by a manometric method. The gas evolution rate is described by the equation corresponding to two consecutive
first-order reactions, with the rate constant of the second reaction considerably exceeding the rate constant of the first
reaction, i.e., k
2 {ie17-1} k
1. The temperature dependences of k
1 (s−1) in 47.59% HBr in the temperature range from 60 to 90°C and in 64.16% H2SO4 between 80 and 130°C are described by Arrhenius equations with IogA= 12.7 ± 1.5 and 13.6 ± 1.4 and E
a = 115 ± 10 and 137 ± 10 kJ/mol, respectively. The parameters of the Arrhenius equation for the rate constant k
2 for the reaction in 64.16% H2SO4 between 80 and 130°C are IogA= 9.1 ± 2.5 and E
a = 91 ± 18 kJ/mol. An analysis of the UV spectra of compound I in concentrated H2SO4 shows that I is a weak base $
(pK_{BH^ + } \approx - 6)
$
(pK_{BH^ + } \approx - 6)
. The rate-determining step of the hydrolysis of I is the attack of the nucleophile on the carbon atom of the MeO group of the protonated molecule of I. The resulting methyldiazene dioxide decomposes via a complicated mechanism to evolve N2, NO, and N2O. The pseudo-first-order rate constant k
1 of the reaction at 80°C depends strongly on the acid concentration and on the type of nucleophile (Br−, Cl−, or H2O). The relationship between k
1 and the rate constant k of the bimolecular nucleophilic substitution reaction (SN2) is given by the linear equation log$
[k_1 /(C_H + C_{Nu} )] = m^ \ne m*X_0 + \log (k/K_{BH^ + } )
$
[k_1 /(C_H + C_{Nu} )] = m^ \ne m*X_0 + \log (k/K_{BH^ + } )
, where $
C_{H^ + }
$
C_{H^ + }
and C
Nu are the concentrations of H+ and nucleophile, respectively; X
0 is the excess acidity; and m
≠ and m* are coefficients. The Swain-Scott equation log$
(k_{Nu} /k_{H_2 O} ) = ns
$
(k_{Nu} /k_{H_2 O} ) = ns
, where n is the nucleophilicity factor and s is the substrate constant (s = 0.72), is applicable to the rate constants k of the SN2 reactions of the protonated molecule of I with Br−, Cl−, and H2O. 相似文献
16.
The behaviour of 1-(2-bromoethyl) 4-nitrobenzene (1), N,N,N-triethyl-2-(4-nitrophenyl)ethanaminium bromide (2) and N,N-diethyl-N-[2-(4-nitrophenyl)ethyl]octan-1-aminium bromide (3) in the OH−-induced elimination reactions with formation of 1-nitro-4-vinylbenzene in mixtures of DMSO/H2O or CH3CN/H2O has been investigated. With all three substrates an increase in dipolar aprotic solvent content implies a limited increase
of the second-order rate constant k
OH up to ≅605, and then an exponential increase is observed. The variation of activation parameters ΔH
# and dGS
#, measured in DMSO/H2O mixtures, is parallel for 1 and 2. This similar behaviour of 1 and 2 with respect to variation in solvent composition is evidence that it is not possible to use this technique of solvent effect
for the mechanistic diagnosis of elimination reactions. 相似文献
17.
Emese Szabó Jérémy Tarmoul Alexandre Tomas Christa Fittschen Sándor Dóbé Patrice Coddeville 《Reaction Kinetics and Catalysis Letters》2009,96(2):299-309
Kinetics of the •OH-initiated reactions of acetic acid and its deuterated isomers have been investigated performing simulation chamber experiments
at T = 300 ± 2 K. The following rate constant values have been obtained (± 1σ, in cm3 molecule−1 s−1): k
1(CH3C(O)OH + •OH) = (6.3 ± 0.9) × 10−13, k
2(CH3C(O)OD + •OH) = (1.5 ± 0.3) × 10−13, k
3(CD3C(O)OH + •OH) = (6.3 ± 0.9) × 10−13, and k
4(CD3C(O)OD + •OH) = (0.90 ± 0.1) × 10−13. This study presents the first data on k
2(CH3C(O)OD + •OH). Glyoxylic acid has been detected among the products confirming the fate of the •CH2C(O)OH radical as suggested by recent theoretical studies. 相似文献
18.
The gold(III) 1,3-diaminopropane complex [Au(1,3-pn)(1,3-pn-H)]Cl2 has been synthesized. Its dissociation constant has been determined: Au(1,3-pn)23+ = Au(1,3-pn-H)2+ + H+, logK
a1 = −7.03 ± 0.05 (I = 0.1 mol/L NaClO4). Considerable spectral changes are observed for strong alkali solutions (pH 11–14) containing the monoamido forms of the
gold(III) ethylenediamine, 1,3-diaminopropane, and diethylenetriamine complexes (Au(en)(en-H)2+, Au(1,3-pn)(1,3-pn-H)2+, Au(dien-H)OH+). These changes are attributed to the formation of the diamido species Au(en-H)2+, Au(1,3-pn-H)2+, and Au(dien-2H)OH0. The dissociation constants of the monoamido complexes have been determined: Au(en)(en-H)2+ (logK
a2 = −10.9 ± 0.1 at I = 0.001–0.01 mol/L NaCl); Au(1,3-pn)(1,3-pn-H)2+ (logK
a2 = −11.3 ± 0.1 at I = 0.1 mol/L NaCl); Au(dien-H)OH+ (logK
a2 = −12.4 ± 0.1 at I = 0.1 mol/L NaCl). 相似文献
19.
Masao Masamura 《Theoretical chemistry accounts》2001,106(4):301-313
For the intermolecular interaction energies of ion-water clusters [OH−(H2O)
n
(n=1,2), F−(H2O), Cl−(H2O), H3O+(H2O)
n
(n=1,2), and NH4
+(H2O)
n
(n=1,2)] calculated with correlation-consistent basis sets at MP2, MP4, QCISD(T), and CCSD(T) levels, the basis set superposition
error is nearly zero in the complete basis set (CBS) limit. That is, the counterpoise-uncorrected intermolecular interaction
energies are nearly equal to the counterpoise-corrected intermolecular interaction energies in the CBS limit. When the basis
set is smaller, the counterpoise-uncorrected intermolecular interaction energies are more reliable than the counterpoise-corrected
intermolecular interaction energies. The counterpoise-uncorrected intermolecular interaction energies evaluated using the
MP2/aug-cc-pVDZ level is reliable.
Received: 14 March 2001 / Accepted: 25 April 2001 / Published online: 9 August 2001 相似文献
20.
The kinetics of the process AuCl3(nu) + Cl−→ AuCl
4
−
+ nu (nu = one of a number of five-membered N-donor heterocycles covering a wide range of basicity, namely: oxazole, 2,4,5-trimethyloxazole,
thiazole, 5-methylthiazole, 4-methylthiazole, 4,5-dimethylthiazole, 2,4-dimethylthiazole, 2,4,5-trimethylthiazole, imidazole
and 2-methylimidazole) have been studied in methanol at 25 °C. The reactions follow the usual two-term rate law, rate = (k
1 + k
2[Cl−])[complex], observed in a square-planar substitution associative-mechanism. The second-order rate constants, k
2, indicate that the discriminating ability of Au(III) in these complexes is good and markedly influenced by the nature of the leaving group. A linear-free-energy relationship,
logk
2 = 0.53pK
a
+ constant, is observed between the rate constant and the basicity of the leaving group for its replacement by chloride.
The results are compared with data from the literature regarding a series of complexes of the type AuCl3(py) (py = one of a number of pyridines) reacting with the Cl− anion under the same experimental conditions. The reactivity depends not only upon ligand basicity but also upon the nature
of the ligand in the order: pyridines> five-membered heterocycles. Steric factor due to the presence of a single methyl group
ortho to the sp2 nitrogen atom in the ring has no influence on the rate of substitution while, surprisingly, when there are two ortho methyl groups a remarkable steric retardation effect is observable. The results are discussed in terms of reaction-profile
in the associative-substitution reaction and bonding interactions in the ground and transition states. 相似文献