Showing papers on "Aquation published in 1982"
36 citations
TL;DR: In this paper, the synthesis of trans-solvento complexes trans-[Co(en)2(sol)N3](ClO4)2 (sol = Me2SO,Me2N·CHO (DMF)) are described.
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25 citations
TL;DR: In this paper, the authors described the preparation of the quinquedentate macrocyclic ligand, L, and the characterisation of three possible configurations as a result of the two chiral nitrogen centers; there are two N-meso diastereoisomers and one N-racemic diasterer.
Abstract: The preparation of the title quinquedentate macrocyclic ligand, L, is described. The complexes [NiL(OH2)][ClO4]2, [CuL][ClO4]2, and [CoLCl][ClO4]2 have been prepared and characterised. The complexes can have three possible configurations as a result of the two chiral nitrogen centres; there are two N-meso diastereoisomers and one N-racemic diastereoisomer. Carbon-l3 n.m.r. measurements establish that the CoIII complex is a mixture of the possible stereoisomers. The base hydrolysis of [COLCl]2+ is quite rapid with kOH= 2.45 × 104 dm3 mol–1 s–1 at 30 °C and I= 0.1 mol dm–3, which can be rationalised in terms of the mer-N3 donor set. Acid aquation with kaq= 1.66 × 104 s–1 at 50 °C is quite slow. The CuII and octahedral NiII complexes are labile in acidic solution, unlike the complexes of 1,4,8,11-tetra-azacyclotetradecane. The kinetics of the acid-catalysed dissociation have been studied in detail. For both complexes rate =kH[complex][H +]2, indicating the involvement of two protons in the transition state of the reaction. For [CuL]2+, kH= 4.9 × 10–2 dm6 mole–2 s–1 and for [NiL]2+, kH= 0.63 dm6 mol–2 s–1 at 25 °C and I= 0.98 mol dm –3. The acid-catalysed dissociation of the NiII complex of 1,4,7,10,13,16-hexa-azacyclo-octadecane has also been studied in order to define the mechanism of these reactions. In this case, rate =kH[complex][H+]3. Possible mechanisms are considered in detail.
21 citations
TL;DR: In this paper, pressure, temperature and pH dependencies of the rate of aquation of a range of trans-complexes with the general formula CoN4X+2 were studied.
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13 citations
TL;DR: In this article, the rate constants for the mercury-catalysed aquation of trichloro-transition metal complexes were investigated in water and methanol-, ethanol-, and acetonitrile-water solvent mixtures.
Abstract: Rate constants are reported for mercury(II)-catalysed aquation of thetrans-[Rh(en)2Cl2]+, [Cr(NH3)5Cl]2+, andcis-[Cr(NH3)4(OH2)Cl]2+ cations in water and in methanol-, ethanol-, and acetonitrile-water solvent mixtures. In the case oftrans-[Rh(en)2Cl2]+, the dependence of rate constants on mercury(II) concentration indicates reaction through a binuclear (Rh-Cl-Hg bridged) intermediate. The dependence of the equilibrium constant for the formation of this intermediate and of its rate constant for dissociation (loss of HgCl+) on solvent composition have been established. With the aid of measured solubilities, published ancillary thermodynamic data, and suitable extrathermodynamic assumptions, the observed reactivity trends for these mercury(II)-catalysed aquations are dissected into initial state and transition state components. The reactivity patterns for these three complexes are compared with those for mercury(II)-catalysed aquation of other chloro-transition metal complexes, particularlycis-[Rh(en)2Cl2]+, [Co(NH3)5Cl]2+, and [ReCl6]2−.
13 citations
TL;DR: The synthesis and characterisation of the new surfactant system dodecylpyrazinium chloride (DPC) and its effect on the rate of aquation of tris(1,10-phenanthroline)iron(II) perchlorate in aqueous perchloric acid solution are described.
Abstract: The synthesis and characterisation of the new surfactant system dodecylpyrazinium chloride (DPC) and its effect on the rate of aquation of tris(1,10-phenanthroline)iron(II) perchlorate in aqueous perchloric acid solution are described. The aquation rate of the complex is accelerated by a factor of 10, from ca. 10–5 to ca. 10–4 s–1, in the presence of DPC. This increase is suggested to be due to an additional equilibrium pathway for removal of phenanthroline ligand resulting from favourable hydrophobic interactions between the surfactant aggregates and dissociated phenanthroline ligand and solubilisation of the ligand by DPC. Plots of observed pseudo-first-order rate constants against surfactant concentration show maxima, characteristic of many micellar catalyses. Shifts in the position of the maxima and the values of the aquation rates in the presence of other ions may be due to changes in the critical micelle concentration and the presence of submicellar aggregates. Additional rate enhancement is observed in the presence of sodium benzoate. In addition, complex kinetic behaviour is observed under these conditions. Additional pathways for complex and/or ligand binding may be responsible for these.
TL;DR: In this article, the steric course of spontaneous hydrolysis of trans [Co(en) 2 X 2 ] + in 0.1 M CF 3 SO 3 H at 25 °C is recorded: X = Cl, k s = (4.13 ± 0.07) 10 −4 s −1, 84.5 ± 1.
TL;DR: In this paper, the activation volume at normal pressure (ΔV\eweq) and the reaction volume ( ΔV) were obtained for five aquation reactions of the Co(III) complex ion, and they were interpreted as resulting from the counterbalance of the volume increase attributable to the leaving ligand and the volume decrease due to the partial incorporation of one water molecule in the activated complex.
Abstract: The activation volume at normal pressure (ΔV\eweq) and the reaction volume (ΔV) are obtained for five aquation reactions of the Co(III) complex ion. The results are [given as the complex ion, ΔV\eweq/cm3 mol−1 (t/°C), ΔV/cm3 mol−1 (t/°C)]: trans-[Co(en)2NO2Cl]+, 0.1 (15), −10.4(15); cis-[Co(en)2NO2Cl]+, 0.9 (30), −9.3 (25); cis-[Co(bpy)2NO2Cl]+, 2.9 (30), −9.1 (25); cis-[Co(bpy)2NO2Br]+, 11.3 (30), −6.7 (25); cis-[Co(phen)2NO2Br]+, 3.3 (35), −12.5 (30). These magnitudes of ΔV\eweq are interpreted as resulting from the counterbalance of the volume increase attributable to the dissociation of the leaving ligand and the volume decrease due to the partial incorporation of one water molecule in the activated complex.
TL;DR: In this article, the NH4[Co(tetrapeptidato) (NH3)2] complex was characterized by means of 1H NMR and circular dichroism (CD) spectral data.
Abstract: Complexes of the [Co(tripeptidato)(NH3)2] and NH4[Co(tetrapeptidato)(NH3)2] types (tripeptidato and tetrapeptidato denote the tri- and tetraanions of the coordinating peptides respectively) have been prepared and characterized by means of their electronic, 1H NMR, and circular dichroism (CD) spectral data. In the NH4[Co(tetrapeptidato) (NH3)2] complex, the pep tide coordinates to cobalt(III) as a quadridentate ligand through the nitrogens of an amino and three amide groups. The additivity of the vicinal CD spectra has been found to hold for the complexes of a series of tripeptides containing L-alanine and/or glycine residue. These tri- and tetrapeptidato complexes in water easily undergo aquation reaction, releasing the ammonia molecule.
TL;DR: In this article, the rate of Fe-N bond breakage in [Fe(CN)5L]n−(L = aromatic amine) ions has been determined for several neutral, anionic, and cationic amines.
Abstract: The rate of Fe–N bond breakage in [Fe(CN)5L]n–(L = aromatic amine) ions has been determined for several neutral, anionic, and cationic amines. The results, together with previously reported values for related systems, are used to discuss the mechanism of substitution on [Fe(CN)5L]n– systems. The contributions of inner (electronic and electrostatic) and solvent effects to the activation process are discussed.
01 Oct 1982
TL;DR: In this article, spontaneous and Hg2+-induced aquation reactions of Co(NH3)5SO4+ were studied in the presence of sodium polyethylenesulfonate and sodium polystyrenesulfonates under high pressure.
Abstract: Spontaneous and Hg2+-induced aquation reactions of Co(NH3)5SO4+ are studied in the presence of sodium polyethylenesulfonate and sodium polystyrenesulfonate under high pressure. The spontaneous aquation rates are in the order of Co(NH3)5SO4+, Co(NH3)5Br2+ and Cr(NH3)5Br2+ and is accounted for in terms of the Bronsted-Bjerrum theory. The volume of activation (ΔV#) of both spontaneous and Hg2+-induced aquations of Co(NH3)5SO4+ greatly increased by addition of the macroions, which is attributed to stronger desolvation of the activated complex than the reactant in the strong electrostatic field of the macroions.
TL;DR: In this article, a model for mutarotation is proposed which involves a specifically oriented aquation sheath about the charged ion which then acts as an enhanced electrophile in the rate-determining step to form the aldehyde intermediate.
Abstract: The rate of mutarotation of α-D(+)-glucose is markedly affected by the addition of electrolytes. At 293 K the rate constants for reaction with H2O, HClO4, NaClO4 and CU(ClO4)2 are 4.6 × 10-6, 5.9 × 10-3,1.2 × 10-4 and 4.6 × 10-3 dm3 mol-1 s-1 respectively. In the pH range 3.5 - 4.4 the rate of mutarotation increases sharply in solutions of Cu(ClO4)2 because of the presence of small concentrations of Cu((OH)2CU)2+ for reaction with which the second-order rate constant is 4.0 dm3 mol-1 s-1. A model for mutarotation is proposed which involves a specifically oriented aquation sheath about the charged ion which then acts as an enhanced electrophile in the rate-determining step to form the aldehyde intermediate. In the presence of mixed cationic catalysts, additivity rather than competition is observed between the effect of two catalysts. This result and the observed increase in the entropy of activation in the presence of aquated copper(II) support this model.
TL;DR: In this article, the quantum yields for aquation of the title ion with loss of chloride or ammonia decrease monotonically across the envelope of the first spin allowed ligand field electronic band indicating competition of intersystem crossing or reactive processes with vibrational relaxation; since the curves for chloride loss and ammonia loss intersect, three potential surfaces are invoked in the interpretation.
Abstract: The quantum yields for the aquation of the title ion with loss of chloride or ammonia decrease monotonically across the envelope of the first spin allowed ligand field electronic band indicating competition of intersystem crossing or reactive processes with vibrational relaxation; since the curves for chloride loss and ammonia loss intersect, three potential surfaces are invoked in the interpretation.
TL;DR: In this article, a detailed analysis of the kinetic data reveals that the reactions proceed in two consecutive stages, the initial step being the faster one, and evidence has been presented that the initial faster step involves aquation releasing one NO 2 − ligand and forming an aquodinitro complex, which subsequently undergoes a slower intramolecular redox decomposition into Co2+.
Abstract: In aqueous acid media the title complexes undergo decomposition ultimately forming cobalt(II). Detailed analysis of the kinetic data reveals that the reactions proceed in two consecutive stages, the initial step being the faster one. Evidence has been presented that the initial faster step involves aquation releasing one NO 2 − ligand and forming an aquodinitro complex, which subsequently undergoes a slower intramolecular redox decomposition into Co2+. Each step, on the other hand, has been found to consist of two concurrent paths,viz. spontaneous and acid catalysed, respectively. Activation parameters corresponding to all these specific rate constants have been evaluated and a plausible mechanism for the overall reaction has been proposed.
TL;DR: A binding mechanism is postulated for the inhibition of the dehydrogenases by direct displacement of a halide ligand, probably by two groups on the enzyme, at least one of which may be a sulfur containing acid.
TL;DR: In this article, it was shown that the ligand field excitation of trans-(Ru(en)2l2]+(en = ethylenediamine) leads to iodide aquation with extensive stereochemical change (>85%), whereas ligand-to-metal charge transfer (l.m.t.) excitation leads to complete retention of configuration.
Abstract: It has been demonstrated that the ligand-field (l.f.) excitation of trans-[Ru(en)2l2]+(en = ethylenediamine) leads to iodide aquation with extensive stereochemical change (>85%), whereas ligand-to-metal charge-transfer (l.m.c.t.) excitation leads to iodide aquation with complete retention of configuration. For trans-[Ru(en)2X2]+(X = Cl or Br), where l.f. and l.m.c.t. bands accidentally overlap with each other, the observed photochemical behaviour of halide aquation with extensive stereochemical change is taken to occur from the I.f. excited states, whether these states are populated by direct absorption into the l.f. bands or by internal conversion from the l.m.c.t. states. The gradual decrease in the isomerization quantum yields from X = Cl through Br to I (6.2 × 10–3, 3.2 × 10–3, and 2.3 × 10–3 respectively) is discussed.
TL;DR: Investigations on the aquation of tris-(substituted)malonatochromate(III)ion, between 25°–40° in the presence of acid, show that the mono- and dimethyl substituted complexes aquate by a two term rate law, only one of which is acid dependent.
Abstract: Investigations on the aquation of tris-(substituted)malonatochromate(III)ion, between 25°–40° in the presence of acid (I=1.0M) show that the mono- and dimethyl substituted complexes aquate by a two term rate law, only one of which is acid dependent. All other complexes aquate by a one term rate law which is first-order with respect to acid concentration; the unsubstituted malonato complex behaves in this way. Aquation of the first two complexes is dissociative, while for others appreciable associative character has been observed.
TL;DR: The presence of multivalent anions, such as sulfate, oxalate, and malonate ions, accelerated the aluminium ion-assisted aquation of CoF(NH3)52+ and gave the anionopentaamminecobalt(III) along with the aqua complex.
Abstract: The presence of multivalent anions, such as sulfate, oxalate, and malonate ions, accelerated the aluminium ion-assisted aquation of CoF(NH3)52+ and gave the anionopentaamminecobalt(III), along with the aqua complex. The competition reaction for the sulfate ion showed a saturation of the product percentage (33% CoSO4(NH3)5+) at nearly [SO42−]total=0.1 mol dm−3, while the saturation of the reaction rate was observed at a higher sulfate concentration. This difference can be explained by a scheme in which the reaction proceeds through two intermediates, CoF(NH3)52+·SO42−·Al3+ and SO42−·CoF(NH3)52+·SO42−·Al3+. The reaction for the oxalate and malonate ions gave extremely large yields (more than 90%) of CoA(NH3)5+ (A2−=oxalate ion or malonate ion) when [A2−]total/[Al3+]total>2, and the reaction rates showed a maximum at approximately [A2−]total/[Al3+]total=2. These specific effects can be attributed both to the strong affinities of the dicarboxylate ions for the aluminium ion and to the residual capacity of the...
TL;DR: In this paper, the rates of the release of first and second nitro groups were derived by a graphical method for both the steps of aquation, the presence of electron accepting "nitro" group, favours "bond formation" by the incoming ligand in the transition stage and it occurs before the 'bond rupture' is complete.
Abstract: Aquation of cis-dinitrobisbiguaniderhodium (III) nitrate was investigated conductometrically. Rates of the release of first and the second nitro groups were derived by a graphical method. For both the steps of aquation, the presence of electron accepting ‘nitro’ group, favours ‘bond formation’ by the incoming ligand in the transition stage and it occurs before the ‘bond rupture’ is complete. The loss of the second ‘nitro’ group most probably takes place along with a hydrogen ion from the ‘aquo’ ligand introduced in the first step of aquation with the resultant formation of the hydroxoaquobisbiguanide complex. Activation parameters were evaluated and are as follows: ΔH‡ are 18±1.2 and 18.6±1.1 k cals mole−1 and ΔS‡ are −15±2.7 and −19±2.3 e. u. respectively for the first and the second steps of aquation.