Showing papers on "Aquation published in 1976"
TL;DR: In this article, the first and second aquation steps of c-Pt(NH 3 ) 2 Cl 2 have been determined by a titration technique, and the kinetics of isotopic exchange of chlorine were investigated in the ternary system.
48 citations
TL;DR: Gainsford and House as discussed by the authors measured the rates of aquaation of three isomers (a, d and h) of CoCl(tmd)(dien) 2+ and one isomer (i) (dpt) 2 + and determined the rate of base hydrolysis using pH-stat techniques at 273.7-313 K.
31 citations
TL;DR: Rate and equilibrium constants for the interaction of L-cysteine with vitamin B12a have been determined in aqueous solutions in the absence and in the presence of air as functions of pH, buffer concentration, and temperature.
Abstract: Rate and equilibrium constants for the interaction of L-cysteine with vitamin B12a have been determined in aqueous solutions in the absence and in the presence of air as functions of pH, buffer concentration, and temperature. Kinetic treatment of the data has afforded the pH-independent rate constants for the anation of aquo- and hydroxocobalamins by L-cysteine, for the aquation of the vitamin B12–L-cysteine complexes, and for the formation of vitamin B12r from the L-cysteine complex of vitamin B12a. The mechanism of these reactions is discussed.
28 citations
28 citations
21 citations
TL;DR: In this article, the authors performed kinetic and equilibrium studies on the aquation of TcX62− in ionic media which contained HX, LiX, NaX and/or KX (X = Cl, Br).
20 citations
20 citations
TL;DR: The acid-catalyzed aquation of the title compound has been studied over the range of 0.05 + ] + and 1.3 × 10 −3 M −1 sec −1 and the temperature variations describing this constant are ΔH*, 20.6 ± 0.4 kcal/mol and Δ* = -2.6±1.3 cal/deg mol.
18 citations
TL;DR: In this article, rate constants for tris(5-nitro-1,10-phenanthroline)iron(II) have been determined in a wide range of binary aqueous mixtures.
Abstract: Rate constants for the aquation of tris(5-nitro-1,10-phenanthroline)iron(II) have been determined in a wide range of binary aqueous mixtures. The results are presented and discussed in terms of correlation diagrams involving the excess molar Gibbs function of mixing for the binary mixtures. The behaviour of this iron(II) complex is compared and contrasted with that of t-butyl chloride. The possible advantages of this mode of treatment of kinetic results are outlined.
18 citations
14 citations
TL;DR: In this article, the rate and activation parameters for the k1 and k2 paths of the cobalt(III) complexes have been determined and the results indicate that the unbound carboxyl group does not exert a specific catalytic effect on the spontaneous and acid-catalysed paths of aquation of cobalt substrates derived from dicarboxylic acids.
TL;DR: Rates of racemization of the active hydroxo complexes cis-Co(en)2(A)(OH)2+ (A = NH3, CH3NH2, 3,5-lutidine, imidazole) were measured similarly at pH = 8 and pKa data calculated from the pH versus k plot are 5.50, 5.65, and 6.40, respectively.
Abstract: Aquation rates forcis-CoCl(en)2(A)2+ (A = 3,5-lutidine, imidazole, N-methylimidazole, benzimidazole) have been determined by halide release titration in 1.0 M HNO3 at 50–80°C. Kinetic parameters are (in the above order of A) 107k298 (sec−1), 7.4, 5.7, 1.3, 9.7; Ea (kJ/mole), 103, 101, 130, 112; log PZ (sec−1), 11.89, 11.53, 16.04, 13.58; ΔS298‡ (J/°K· mole),−26, −32, +54,+7. Rates of racemization for active cis-Co(en)2(A)-(OH2)3+ were measured spectropolarimetrically in 0.1 M HClO4, 0.02 M Hg2+ for A = ammonia, cyclohexylamine, 3,5-lutidine, N-methylimidazole. Kinetic parameters are (units as above) 109k298 = 1.8, 38.0, 7.7, 1.7; Ea = 150, 135, 152, 157; log PZ = 17.49, 16.18, 18.56, 18.87; ΔS298‡ = +82, +57, +102,+108. Rates of racemization of the active hydroxo complexes cis-Co(en)2(A)(OH)2+ (A = NH3, CH3NH2, 3,5-lutidine, imidazole) were measured similarly at pH = 8 (π = 2.0, NaClO4). The racemization of the hydroxo is ca. (3–4) × 103 faster than for the corresponding aqua complex. Kinetic parameters are 106k298 = 2.55, 7.2, 30.1, 7.0; Ea = 138, 123, 122, 128; log PZ = 18.58, 16.39, 16.85, 17.18; ΔS298‡ = +102,+60, +69,+76. Racemization rates for aquahydroxo mixtures (A = CH3NH2, 3,5-lutidine, imidazole) were also determined in the pH range of 4–8 (θ = 2.0, NaClO4) at 50.6°C, and pKa data calculated from the pH versus k plot are 5.50, 5.65, and 6.40, respectively, for A.
TL;DR: The photochemistry of cis-[Rh(cyclam)X2]- and cis[Rh(en)2Cl2]- has been studied in this article, showing that the photosensitivity was greater for charge transfer excitation than ligand field excitation.
Abstract: The photochemistry of cis-[Rh(cyclam)X2]+ (where X = Cl, Br, or I) and cis-[Rh(en)2Cl2]+ have been studied. Whilst only halide aquation is observed for the cyclam complexes, amine aquation is the principal reaction mode for the ethylenediamine complex. In each case, the photosensitivity was greater for charge transfer excitation than ligand field excitation. Although this wavelength dependence was also exhibited for the corresponding trans complexes, the dependence on the leaving group which was for the trans complexes is completely reversed for cis-[Rh(cyclam)X2]+ where for ligand field excitation.The behaviour of cis-[Rh(en)2Cl2]+ and cis-[Rh(cyclam)I2]+ is seen to be consistent with the preferential amine activation predicted by the photochemical model proposed by Zink. The change in photospecificity observed with cis-[Rh(cyclam)Cl2]+ and cis-[Rh(cyclam)Br2]+ is interpreted as the result of distortion from effective tetragonal symmetry which causes the repulsive energy to become progressively more loca...
TL;DR: In this paper, conductivity results for aqueous solutions of seven salts of trans- and cis-[Co(en)2(NO2)2]+ were analyzed in terms of the full Pitts equation.
Abstract: Precise conductivity results are reported for aqueous solutions of seven salts of trans- and cis-[Co(en)2(NO2)2]+. They are analysed in terms of the full Pitts equation and the association constants for the salts, although small, are found to increase with increasing radii of the ions, being particularly large for cis-[Co(en)2(NO2)2]I. Contrary to popular belief, trans-[Co(en)2(NO2)2]ClO4 is also appreciably associated in dilute aqueous solution. Rate constants for the very slow aquation of these cations are also reported.
TL;DR: In this article, high-spin and low-spin [Fe(pmen)Cl2]Cl 2 complexes have been characterized by spectroscopic and magnetic measurements, showing that they have a cis-type geometry both in the solid state and in aqueous solution.
Abstract: High-spin [Fe(pmen)Cl2]Cl and low-spin [Fe(pmen)(OH2)(OH)][ClO4]2 complexes (pmen is the title ligand) have been prepared and characterized by spectroscopic and magnetic measurements. Electronic and e.p.r. spectra suggest that the complexes have a cis-type geometry both in the solid state and in aqueous solution. Peculiar features observed in solution are aquation of the cation of the chloride salt which effects electron pairing, whilst a change from low to high spin, accompanied by a structural rearrangement, occurs when the interaction of the complexes in aqueous solution with an optically active polyelectrolyte (Which does not absorb over the wave-length region explored), make possible an assignment of cis-α geometry to the high-spin form and cis-β geometry to the low-spin species, in agreement with predictions from qualitative steric considerations. Implications of stereochemical demands of the complexes on variation of the spin configuration of the iron are also discussed.
TL;DR: In this paper, the rate of loss of H2PO4− ligand from bis-dihydrogenphosphato oxovanadium(IV) was determined from analysis of broadening of the 31P magnetic resonance line of LOM NaH2P4 solutions in the presence of vanadyl ion at pH 2.0.
TL;DR: In this paper, a pseudo-isokinetic plot of ΔH2-ΔH1- ΔS2-DeltaS1 was obtained for the trans-[Rh(en)2(OH)X]-complexes, showing that the reactions that lead to extensive streochemical rearrangement occur by an SN1 CB mechanism.
Abstract: Base hydrolysis of the complexes trans-[Rh(en)2X2]+(X = Cl, Br, and I) obeys the rate equation kobs=K1+k2[OH–] at an ionic strenth of 1·0 mol dm–3 where k2/k1≈ 1 dm3 mol–1. Activation parameters for the[OH–]-indepedent path are essentially the same as those for aquation. The [OH–]-dependent path leads to virtually complete trans→cis isomerisation when X = Cl or Br. and to ca. 50% when X = 1. The values of ΔH2‡ and ΔS2‡ lie at the upper end of an isokinetic plot that includes data for the trans-[Rh(en)2(OH)X]+ complexes. An excellent ‘pseudo-isokinetic’ plot of ΔH2‡–ΔH1‡ against ΔS2‡– DeltaS1‡ has also been obtained. The isokinetic plot lies above the corresponding plot for complexes with co-ordinated NH groups trans to the leaving group, the respective isokinetic temperatures being ca. 100 and 190 °C. It seems probable that the reactions that lead to extensive streochemical rearrangement occur by an SN1 CB mechanism but that reactions of complexes further down the isokinetic plot may well have a mechanism closer to the SN1 IP end of an SN1 CB–SN1 IP mechanistic spectrum.
TL;DR: In this article, the previously unknown cis-Cr(NH3)4X2+ (X = Cl, Br) cations were synthesized in high yield from reaction between cis-[CrClO4 and dry gaseous HX in 2-methoxyethanol.
TL;DR: In this article, a study of the kinetics of hydrolysis for several nitroamminecobalt(III) complexes in strongly alkaline solutions at a constant ionic strength is reported.
TL;DR: In this article, the authors reported the kinetic parameters for catalysis of the aquation of hexachlororhenate(IV) anion by thallium(III) in aqueous solution and the correlation of these kinetic results with stability constants for halogeno-complexes of the respective metal cations is discussed.
Abstract: Kinetic parameters are reported for catalysis of the aquation of the hexachlororhenate(IV) anion by mercury(II), thallium(III), cadmium(II), and indium(III), and of the hexabromorhenate(IV) anion by thallium(III), in aqueous solution. Correlation of these kinetic results with stability constants for halogeno-complexes of the respective metal cations is discussed.
TL;DR: The first-order rate constants for aquation of Co(NH3)5(DMF)3+ were determined in aqueous perchlorate media as discussed by the authors, and it was concluded that aquation occurred by an Id mechanism.
Abstract: The first-order rate constants for aquation of Co(NH3)5(DMF)3+ were determined in aqueous perchlorate media. The rate constants were independent of hydrogen ion concentration and ionic strength, but decreased with increasing perchlorate ion concentration. Proton magnetic resonance studies showed that dimethylformamide was not hydrolyzed to formic acid and dimethylamine in the aquation step. Mass-spectrometer studies showed that cobalt–oxygen bond breaking occurred in 98 percent, or more, of the aquation acts. Enthalpies and entropies of activation were determined. It was concluded that aquation occurred by an Id mechanism.
TL;DR: In this paper, the formation and aquation of acidopenta-amminechromium(III) complexes were investigated and shown to have a dissociative mechanism, which is similar to the one proposed in this paper.
Abstract: Kinetic and thermodynamic data for the formation and aquation of acidopenta-amminechromium(III) complexes provide strong evidence for a dissociative mechanism.