Showing papers on "Aquation published in 1973"
69 citations
42 citations
TL;DR: For the replacement of X− by H2O in Cr(NH3)5X2+, ΔVo* (the value of the volume of activation ΔV* at zero pressure) at 25.0° in 0.1
Abstract: For the replacement of X− by H2O in Cr(NH3)5X2+, ΔVo* (the value of the volume of activation ΔV* at zero pressure) at 25.0° in 0.1 m NH4ClO4 is −10.8, −10.2, and − 9.4 cm3 mol−1 respectively for X− = Cl−, Br−, and I−, while ΔV, the molar volume of reaction, is −8.4, −7.2 and −6.0 cm3 mol−1. The pressure-dependence of ΔV* can be expressed in terms of the number x of water-molecules which are electrostricted as the systems go from ground-state to transition-state; for X− = Cl−, Br−, and I−, x = 1.9, 2.0, and 1.7. These data, combined with ΔV* = −5.8 cm3 mol−1 for the aquo-exchange of Cr(NH3)5OH23+, indicate an associative mechanism for these reactions, as does the contrast with ΔV0* data for the formally analogous, but dissociatively-activated, reactions of Co(NH3)5X(3−n)+.
33 citations
24 citations
TL;DR: In this paper, the kinetics of the reactions of the tris[3-(2-pyridyl)-5,6-bis(4-Phenylsulphonato)-1,2,4-triazine]iron(II) in acid soloution, and with hydroxide, cynide, and peroxodisulphate ions, and hydrogen peroxide, have been investigated.
Abstract: The kinetics of the reactions of the complex tris[3-(2-pyridyl)-5,6-bis(4-Phenylsulphonato)-1,2,4-triazine]iron(II) in acid soloution, and with hydroxide, cynide, and peroxodisulphate ions, and hydrogen peroxide, have been investigated. The dependence of the observed rate constants on reagent concentration has been established for the reactions in acid, and with hydroxide and peroxodisulphate ions, at 35·0 ° C. For the reaction with cyanide ions, the rate law has been established and, from measured rate constants over a range of cyanide-ion concentrations and over the temperature range 25·3–44·1 °C, activation parameters both for cyanide-ion attack and for complex dissociation have been estimated. The variation of the rate of cyanide-ion attack with solvent composition has been determined for ethanol–water mixtures containg up to 30% ethanol. Patterns of reactivity for this complex are compared with those previously established for other low-spin iron(II) chelate complexes.
16 citations
15 citations
TL;DR: In this paper, a mechanism for aquation of the iron (III)-phenol complex is proposed in which a proton transfers intramolecularly from a co-ordinated water molecule to a phenolate ion, viz, Fe(OH2)5A2+→Fe(OH 2)4(OH)·AH2+ from the observed isotope effects.
Abstract: The complex formation between Fe(III) and 10 kinds of phenols was investigated using a stopped-flow apparatus It was confirmed that the reaction rate is acid-independent in the acid region 001–10 M A mechanism for the aquation of the iron (III)-phenol complex is proposed in which a proton transfers intramolecularly from a co-ordinated water molecule to a phenolate ion, viz, Fe(OH2)5A2+→Fe(OH2)4(OH)·AH2+ From the observed isotope effects it was concluded that the state of a proton of HA in Fe(OH2)4(OH)·AH2+ differs from that in a free phenol
13 citations
TL;DR: Pulse irradiation of octahedral complexes IrCl63 and IrCl62 indicates that the former may be oxidized or reduced and the latter reduced without structural change occurring within a few µs as mentioned in this paper.
Abstract: Pulse irradiation of octahedral complexes IrCl63– and IrCl62– indicates that the former may be oxidized or reduced and the latter reduced without structural change occurring within a few µs. The electron transfer reaction forms transient iridium(II) from iridium(III). Contrary to photochemical results irradiation does not promote aquation of the complexes in the early stages of reaction. The spectra, rate constants, and extinction coefficients of the discussed species have been determined.
12 citations
TL;DR: In this paper, rate constants for spontaneous thermal aquation of the complexes [Cr(NH3)5Cl]2+, cis-[Cr(en)2Cl2]+(en = ethylenediamine), trans-[Cr[Cr(OH2)4Cl2]-+, and [Cr[NCS]6]3]3], in a range of solvents, including methanol, ethanol, acetone, dioxan, and t-butyl alcohol-water binary mixtures, are discussed in terms of the Grunwald-
Abstract: Rate constants are reported for spontaneous thermal aquation of the complexes [Cr(NH3)5Cl]2+, cis-[Cr(en)2Cl2]+(en = ethylenediamine), trans-[Cr(OH2)4Cl2]+, and [Cr(NCS)6]3– in a range of solvents, including methanol–, ethanol–, acetone–, dioxan–, and t-butyl alcohol–water binary mixtures. These results, and previously published results on similar chromium (III) complexes, are discussed in terms of the Grunwald–Winstein treatment of solvolyses in mixed aqueous solvents. Although this empirical approach can usefully be employed in discussing the aquation of chlorochromium(III) complexes, its extension to thiocyanatochromium(III) complexes does not seem profitable.
12 citations
TL;DR: In this article, the equilibrium of a metal acetate, M(OAc)2, with water was studied by cryoscopy, and the equilibrium was found to be 0·6 ± 0·3.
11 citations
TL;DR: In this paper, the aquation reaction of Co(NH3)5Br2+ was studied kinetically with Ag+, Hg2+ and Tl3+ as inducing cations.
Abstract: The aquation reaction of Co(NH3)5Br2+ was studied kinetically with Ag+, Hg2+ and Tl3+ as inducing cations. Addition of polyethylene sulphonate, polystyrene sulphonate and polyphosphate markedly enhanced the reaction. The acceleration factor, ranging from 10 to 104, was dependent on the inducing cations, polyelectrolytes, their concentrations and the concentrations of foreign salts. The enthalpy of activation (ΔH[graphic omitted]) and the entropy of activation (ΔS[graphic omitted]) were decreased by addition of polyelectrolytes in the case of Ag+ and Hg2+, as has been observed previously, whereas ΔH[graphic omitted] was not influenced and ΔS[graphic omitted] increased in the case of Tl3+. The behaviour of Tl3+ was ascribed to the strong hydration of this cation.
TL;DR: In this article, the spontaneous and acid-catalysed aquation of both sulfatopentamminemetal complexes appear to be essentially dissociative processes and both S N 1 CB and S N 2 CB mechanisms are consistent with the data although the entropy of activation is in favour of the second.
TL;DR: In this article, the Stern-Volmer relationship was obtained for quenching of the uranyl emission by the complex, with the quench constant of 38 M−1.
Abstract: A monochromatic 436 nm irradiation of Co(CN)63− in a degassed aqueous phosphoric acid solution in the presence of the uranyl ion led to photoaquation of the complex without chemical changes in the uranyl ion, with the apparent quantum yield of 0.1, whereas direct photoaquation in the absence of the sensitizer was negligible under similar conditions. No thermal reaction was found. Stern-Volmer relationship was obtained for the quenching of the uranyl emission by the complex, with the quenching constant of 38 M−1. Energy transfer from the lowest triplet state of the uranyl ion to the lowest ligand field triplet state of the complex was likely involved.
TL;DR: The first-order rate constants of spontaneous aquation of trans-chloronitro- and trans-dichlorobis(ethylenedi-amine)cobalt(III) ions were measured in a range of binary mixed solvents, including methanol, ethanol, dioxin, and acetone-water solutions extended to 10%(v/v) water content.
Abstract: The first-order rate constants of spontaneous aquation of trans-chloronitro- and trans-dichlorobis(ethylenedi-amine)cobalt(III) ions were measured in a range of binary mixed solvents, including methanol–, ethanol–, dioxin–, and acetone–water solutions extended to 10%(v/v) water content. Both complexes equated completely in water-rich mixtures and incompletely in solutions containing higher percentages of organic component.The logarithms of rate constants correlated linearly with Grunwald–Winstein solvent Y values, with slopes of m= 0·32 for the dichloro- and m= 0·09 for the chloronitro-complex. The lower susceptibility of the chloronitro-complex to solvent ionizing power indicates that the remaining bonding to the leaving chloride in the transition state is larger in the chloronitro- than in the dichloro-complex. Mechanistic implications are discussed.
TL;DR: In this article, it was shown that Nitrato-ligands in CrIIIammines strongly accelerate the aquation of NH3 ligands in the cis-positions.
Abstract: Nitrato-ligands in CrIIIammines strongly accelerate the aquation of NH3 ligands in the cis-positions.
TL;DR: The second-order rate constants for the thallium(III)-induced aquation of cis-Co(en)2(RNH2)Cl]2+ cations, where R is H, Me, Et, Prn, and Pri, have been measured in aqueous solution over a range of temperatures, and the activation parameters calculated as discussed by the authors.
Abstract: The second-order rate constants for the thallium(III)-induced aquation of cis-[Co(en)2(RNH2)Cl]2+ cations, where R is H, Me, Et, Prn, and Pri, have been measured in aqueous solution over a range of temperatures, and the activation parameters calculated. The kinetic results are discussed in terms of a rapid pre-equilibrium formation of an activated complex Co-Cl-Tl, followed by a simple rate-determining aquation in which TlCl2+ acts as the leaving group, although the alternative possibility of a rate-determining attack by Tl3+ cannot be excluded. In the case of R = H, the investigations have been extended to the corresponding bromo cation which reacts some 50 times faster than its chloro analogue.
TL;DR: The kinetics of aquation and anation reaction have been studied with pentaamineruthenium(III) complexes containing halogenoacetates (fiuoro-, monochloro-, dichloro, trichloro*, bromo-, and iodoace).
Abstract: The kinetics of aquation and anation reaction have been studied with pentaamineruthenium(III) complexes containing halogenoacetates (fiuoro-, monochloro-, dichloro-, trichloro-, bromo-, and iodoace...
TL;DR: In this article, the acid and base hydrolysis of nitratopentaamminerhodium (III) and iridium(III) cations have been studied kinetically and the observed rate constants were found to follow the equation k obs = k aq + k OH [OH − ].
TL;DR: In this article, it was shown that 2 mol of base are consumed per mol of complex and the final product of the reaction is the penta-aminohydroxo-complex which has been identified by visible spectra and potentiometric titration.
Abstract: Base hydrolysis of the complex cis-[Co(en)2X(NH2CH2CH2OCOMe)]2+(en = ethylenediamine; X = Cl or Br) has been studied by pH-stat and spectrophotometry at 25 °C and I= 0·1M. Two consecutive reactions occur in basic media. Following loss of halide ion (kOHCl= 1·38 × 103, kOHBr= 8·7 × 103|mol–1 min–1), slower base hydrolysis of the ester function occurs (kOHester= 1·44 × 102|mol–1 min–1). Initial base hydrolysis of halide ion is consistent with the observations that (a) rate constants for the slow hydrolysis steps in the bromo- and chloro-complexes are identical, within experimental error, and (b) a single rate process is observed spectrophotometrically with kOH= 1·42 × 102|mol–1 min–1. In the pH-stat measurements 2 mol of base are consumed per mol of complex and the final product of the reaction is the penta-aminohydroxo-complex which has been identified by visible spectra and potentiometric titration. The pKap value for ionisation (i) is 6·1 at 25 °C and I= 0·1M. [Co(en)2OH2(NH2CH2CH2OH)]3+⇌[Co(en)2OH(NH2CH2CH2OH)]2++ H+(i) Hydrolysis of the complex cis-[Co(en)2Cl(NH2CH2CH2OCOMe)]2+ in ca. 6M-hydrochloric acid gives the corresponding penta-aminechloro-complex of 2-aminoethanol. Base hydrolysis of the penta-aminechloro-complex. containing N-co-ordinated 2-aminoethanol requires 1 mol of base for complete hydrolysis (kOH= 1·23 × 103|mol–1 min–1 by pH-stat and spectrophotometry at 25 °C and I= 0·1M). It is estimated that base hydrolysis of 2-aminoethyl acetate in the dipositive cobalt(III) complex is some 18 times faster than that for the free ligand and some 2 times faster than that for the protonated ligand. Mercury(II)-catalysed aquations of the complex cis-[Co(en)2Cl(NH2CH2CH2OCOMe)]2+ and the corresponding 2-aminoethanol derivative have also been studied. The reactions follow a rate law, rate =k[HgII][Complex] in 0·57M-HClO4. There is evidence for neighbouring-group participation (NGP–5OH) in aquation of the 2-aminoethanol derivative.
TL;DR: In this article, a new synthesis of the complexes [Co(DH)2(NH3)Br] and Co(DH2(I)I] is given, where NH3 is substituted with Dimethylglyoxim.
Abstract: Eine neue Synthese der Komplexverbindungen [Co(DH)2(NH3)Br] und [Co(DH)2(NH3)J] wird angegeben (DH2 = Dimethylglyoxim). IR-Spektren und Struktur dieser Nichtelektrolyte werden diskutiert. In stark sauren Losungen findet nur der langsame Austausch der Halogenionen gegen Wasser statt. In neutralen und schwach sauren Losungen geht die Aquotisierung schneller vor sich, und es werden auch die Ammoniakmolekeln ausgetauscht. Geschwindigkeitskonstanten, Aktivierungsenthalpie- und -entropie-Werte werden mit den kinetischen Parametern der Aquotisierung anderer Komplexe des Typs [Co(DH)2XY] mit X = Cl, Br, J, Y = Cl, Br, J, H2O, NH3 verglichen. Die Ergebnisse werden auf Grund der moglichen protolytischen Gleichgewichte und der entsprechenden Elektroneneffekte diskutiert.
Kinetics and Mechanism of the Substitution Reactions of Complexes. XLII. Nonelectrolytes of the Type [Co(DH)2(NH3)X] and their Aquation Kinetics
A new synthesis of the complexes [Co(DH)2(NH3)Br] and [Co(DH)2(NH3)I] is given. IR spectra and structure of these nonelectrolytes are discussed. Aquation kinetics of these compounds is studied in acid solutions. In solutions of high acidity only the slow exchange of the halogen for water molecules occurs. In less acid and in neutral solutions aquation becomes much faster and also ammonia is substituted. Rate constants, activation enthalpy, and entropy values are compared to kinetic parameters of the aquation of other [Co(DH)2XY] type complexes, where X stands for Cl, Br, I, and Y for Cl, Br, I, H2O, and NH3. Results are discussed in therms of protolytic equilibria and of the corresponding electronic effects.
TL;DR: The dependence of rate 0constants for aquation of the complexes [FeL3]2+[L = 1,10-phenanthroline (phen), 5-nitro-1, 10-phenanol (5-NO2phen), 4,7-dimethyl-1.7-me2phen, and 3-sulphonato-1., 10-SO3phen] on solvent composition and the nature and concentration of the acid added is described for water-dioxan solvent mixtures with compositions in the range 0-60
Abstract: The dependence of rate 0constants for aquation of the complexes [FeL3]2+[L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (5-NO2phen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me2phen), and 3-sulphonato-1,10-phenanthroline (3-SO3phen)] on solvent composition and the nature and concentration of the acid added is described for water–dioxan solvent mixtures with compositions in the range 0–60%(by volume)dioxan.
TL;DR: In this paper, the mechanism of acid-catalyzed hydrolysis of (NH3)5RuO2CR2+ (R=H, CH3, C2H5, (CH3)2CH, CH2OH, and/or CH2NH2) has been established by trapezoidal simulation analyses with a computer.
Abstract: The mechanism of the acid-catalyzed hydrolysis of (NH3)5RuO2CR2+ (R=H, CH3, C2H5, (CH3)2CH, CH2OH, and/or CH2NH2) has been established by the trapezoidal simulation analyses with a computer. The proposed reaction sequences of SN1 combined with SN2 mechanisms involving a quasi-stable intermediate (NH3)5Ru3+ have proved to be plausible, and the kinetic parameters (rate constants, ΔH\eweq, ΔS\eweq, etc.) have been given for all of the elementary reactions. The aquation rate has been determined by the solvent-assisted, heterolytic dissociation of (NH3)5RuO2CR2+ and follows this order: formato>acetato>propionato>isobutyrato>glycolato>glycinato.
TL;DR: In this article, the kinetics of aquation of hexabromorhenate(IV) ion in aqueous solution and aquequeous organic media, and those of hexachlororhenates(IV), in the presence of mercury(II) ions, are reported.
Abstract: The kinetics of aquation of the hexabromorhenate(IV) ion in aqueous solution and aqueous organic media, and those of the hexachlororhenate(IV) ion in aqueous solution in the presence of mercury(II) ions, are reported. Activation parameters for the aquation of the hexabromorhenate(IV) ion in aqueous solution are ΔH‡= 26·0 kcal mol–1 and ΔS‡=–6 cal K–1 mol–1.
TL;DR: In this paper, the reactions of cis- and trans-diaquabis(methylmalonato)chromate(III) anions in 0·2-1·0 F HClO4 (μ = 1·0, NaClO 4) were studied at 25-40°.
TL;DR: In this paper, the losses of optical activity calculated using the known rates of these individual steps agree reasonably with the measured losses of activity, which is consistent with the proposal that each chloroaqua → diaqua reaction occurs with complete retention of configuration in the range 1 < [H+] < 10-3M.
Abstract: Studies of the aquation reactions of the α and β [Co(trien)ClOH2]2+ isomers are complicated by subsequent isomerization and racemization of the respective diaqua products, especially in the α system. Assuming the consecutive reactions involved are Λ-α-chloroaqua → Λ-α-diaqua → racemic-β-diaqua and Λ-β1-chloroaqua → Λ-β-diaqua → racemic-β-diaqua the losses of optical activity calculated using the known rates of these individual steps agree reasonably with the measured losses of activity. The chloroaqua-diaqua equilibria lie substantially (c. 93 %) toward the diaqua products under all the reaction conditions studied. This is consistent with the proposal that each chloroaqua → diaqua reaction occurs with complete retention of configuration in the range 1 < [H+] < 10-3M.
TL;DR: In this article, the aquation kinetics of the Co(en)2Cl(m-toluidine)](NO3)2 has been studied at 4 temperatures in the presence of various amounts of perchloric acid.
Abstract: The complex salt [Co(en)2Cl(m-toluidine)](NO3)2 has been synthesized and itscis configuration has been proved on the basis of i.r. spectra. The aquation kinetics of the complex ion has been studied at 4 temperatures in the presence of various amounts of perchloric acid. Experimental data are explained by assuming the following reaction scheme: the amino complex (I) is in equilibrium with its conjugated base, i.e. with the amido-complex (II). The equilibrium constant seems to be of the order of magnitude of 10−3. Both forms of the complex ion participate to aquation reactions. For the amino-form an activation energy of ΔH=25.6 kcal/mole and for the amido-form ΔH=20.4 kcal/mole have been found. These data are compared to the kinetic parameters of the aquation reaction of analogous complexes, and they are discussed, by presuming a dissociation mechanism.
TL;DR: In this paper, the isotopic ligand exchange reactions of cis-dibromotetraammineruthenium(III) were studied in aqueous and methanol-water solutions in order to distinguish them from those in the case of the monobromocomplex and to ascertain the role of water molecule with respect to the reaction mechanism.
Abstract: The isotopic ligand-exchange reactions of cis-dibromotetraammineruthenium(III) were studied in aqueous and methanol-water solutions in order to distinguish them from those in the case of the monobromocomplex and in order to ascertain the role of the water molecule with respect to the reaction mechanism. In an aqueous solution, the reaction proceeds through the rate-determining aquation step with the SN2 mechanism: Ru(NH3)4Br2++H2O→Ru(NH3)4(H2O)Br2++Br−, Ru(NH3)4(H2O)Br2++*Br−→Ru(NH3)4Br*Br++H2O. This result is similar to that for the monobromocomplex. In the methanol solution (H2O∼1.5%), the exchange reaction proceeds through the SN1 mechanism: Ru(NH3)4Br2+→Ru(NH3)4Br2++Br−, Ru(NH3)4Br2++*Br−→Ru(NH3)4Br*Br+. When the concentration of water becomes very low, the number of solvated water molecules decreases; therefore, the coordinated bromide ion may easily be liberated. When the concentration of water is higher than 10%, the rate constant increases with the increase in the water concentration. Since the el...
TL;DR: In this paper, the 520 nm d-d absorption band of Co(NH3)5N32+ has been found to result in relatively high yields of ammonia aquation with no other primary photoprocess detectable; this contrasts to what is commonly considered to be the general pattern of cobalt(III) photochemistry.
Abstract: Irradiation of the 520 nm d-d absorption band of Co(NH3)5N32+ has been found to result in relatively high (ϕ≃ 0·2) yields of ammonia aquation with no other primary photoprocess detectable; this contrasts to what is commonly considered to be the general pattern of cobalt(III) photochemistry.