Showing papers on "Aquation published in 1992"
TL;DR: Synthesis and reactivity of ruthenium complexes with phosphites and phosphines, triphenylstibines and triphenlyarsines are discussed in this article.
33 citations
TL;DR: In the presence of air the 365 nm irradiation of mildly acidic aqueous solutions of Cr(bpy)33+ and phenol yields 1,4-benzoquinone (BQ) as the only organic product.
Abstract: In the presence of air the 365 nm irradiation of mildly acidic aqueous solutions of Cr(bpy)33+ and phenol yields 1,4-benzoquinone (BQ) as the only organic product; the aquation photoproduct Cr(bpy)2(OH2)23+ is also produced. Although *Cr(bpy)33+ is quenched by phenol (kq = 8.0 × 106 M−1 s−1), there is no evidence of redox products. The results suggest that singlet oxygen, generated in the quenching of *Cr(bpy)33+ by O2, is the mediator of the formation of BQ.
24 citations
TL;DR: In this article, the kinetics of substitution of aqua ligands from cis-[Ru(bipy)2(H2O)2]2+ ion by salicylhydroxamic acid (L) in aqueous medium has been studied spectrophotometrically at different temperatures (50 − 65°C).
Abstract: The kinetics of substitution of aqua ligands fromcis-[Ru(bipy)2(H2O)2]2+ ion by salicylhydroxamic acid (L) in aqueous medium has been studied spectrophotometrically at different temperatures (50–65°C). The following rate law has been established in the pH range 4.0 to 5.8;
$$k_{obs} = \frac{{k_1 (k_2 + k'_2 K/[H^ + ])[L]}}{{(k_2 + k'_2 K/[H^ + ])[L] + k_{ - 1} (1 + K/[H^ + ])}}$$
where k1 is the water dissociation rate constant of the reactant complex, k−1 is the aquation rate constant, k2 is the ligand (in neutral form i.e., SHAH) capturing rate constant and k′2 is the ligand (in anionic form i.e. SHA−) capturing rate constant of the penta coordinated intermediate, [Ru(bipy)2(H2O)]2+. Activation parameters have been calculated and compared with other substitution reactions of this complex. The rate increases with the increase in pH. The k1 values decrease with the decrease of the dielectric constant of the medium. The experimental results are consistent with a dissociative mechanism.
12 citations
TL;DR: In this article, the kinetics of aquation and anation of [RuCl 4 (H 2 O) 2 ] − ( 1), [RuCL 3 (H2 O) 3 ] ( 2 ), RuCl 2 (H 1 O) 4 ] + ( 3 ) and [Rucl(H 2O) 5 ] 2+ ( 4 ) species were studied spectrophotometrically at 288, 298, 308 and 318 K and the activation parameters corresponding to these reactions determined.
11 citations
TL;DR: In this paper, the results of the analysis of solvent effect are discussed in terms of D and Id mechanisms. And the values of transfer functions corresponding to the transfer of reactant and activated complex from H2O to the solvent mixtures were calculated from kinetic measurements and from solubilities of the complex salt.
Abstract: Kinetics of aquation ofcis- andtrans-[Co(en)2NO2Cl]+ were investigated in aqueous mixtures of MeOH, EtOH,i-PrOH andt-BuOH at 298.1 K. The values of transfer functions corresponding to the transfer of reactant and activated complex from H2O to the solvent mixtures were calculated from kinetic measurements and from solubilities of the complex salt. The results of the analysis of solvent effect are discussed in terms of D and Id mechanisms.
8 citations
TL;DR: In this paper, the kinetics of aqua ligand substitution from cis-[Ru-(tap)2(H2O)2]2+ (tap = 2-[m-tolylazo]pyridine) by 8-hydroxyquinoline (oxine) have been studied spectro-photometrically in various water-ethanol mixtures at different temperatures (30-45° C).
Abstract: The kinetics of aqua ligand substitution from cis-[Ru-(tap)2(H2O)2]2+ (tap = 2-[m-tolylazo]pyridine) by 8-hydroxyquinoline (oxine) have been studied spectro-photometrically in various water-ethanol mixtures at different temperatures (30–45° C). The following rate law has been established in the pH range 4.5 to 6.5; $$ {⤪ d[(2)]/dt=k_{1}k_{2}[(1)][L]/(k_{-1}+k_{2}[L])} $$ where (1), (2) and L represent ds-[Ru(tap)2(H2O)2]2+, [Ru(tap)2(oxine)]2+ and oxine respectively. k1 is the water dissociation rate constant of (1); k−1 is the aquation rate constant and k2 is the oxine capturing rate of the pentacoordinate intermediate, [Ru(tap)2(H2O)]2+. Ionic strength has very little effect on the rate constants. The rate increases with the increase in pH. The experimental results are consistent with a dissociative mechanism.
7 citations
TL;DR: In this article, the authors attributed the formation of adducts between the complex ion and the polymer, in which some ligands are hydrogen-bound to protonated N atoms of the PEI and thus are prevented from definitely leaving the first coordination sphere of the metal ion.
Abstract: Addition of open-chain branched poly(ethyleneimines) (PEIs) to aqueous solutions of Co(CN) 6 3- causes a decrease of the quantum yield for the photoaquation reaction of the complex. This quenching effect is analogous to that caused by cyclic poly(ethyleneimines), and it is attributed to the formation of adducts between the complex ion and the polymer, in which some CN - ligands are hydrogen-bound to protonated N atoms of the PEI and thus are prevented from definitely leaving the first coordination sphere of the metal ion
5 citations
TL;DR: In this paper, the trans-[Cr(tn) 2 (CN) 2 ]ClO 4, where tn=1,3-diaminopropane, has been prepared and characterized.
Abstract: The compound trans-[Cr(tn) 2 (CN) 2 ]ClO 4 , where tn=1,3-diaminopropane, has been prepared and characterized. It undergoes an acid-catalyzed thermal aquation of the cyanide ligand to yield trans-Cr(tn) 2 (H 2 O)(CN) 2+ with a pseudo-first-order rate ccmstant of 8×10 -6 s -1 at 5×10 -4 H + and 15 o C
5 citations
TL;DR: In this paper, the trans-[Cr(NH3)4(CN)X]+ ions, where X = NCS, F and Cl, have been prepared by reaction in methanol suspension of either trans [Cr[Cr[NH3]4(H2O)(CN)]2+ with NCS− and F−, or trans [cr[Cr][Cr]-4(Me2SO)Cl] 2+ with CN−.
4 citations
TL;DR: A series of octahedral cis -diacetonitriletetraminecobalt(III) perchlorate complexes of the general formula [Co(N 4 )(CH 3 CN) 2 ](ClO 4 ) 3, where N 4 = (NH 3 ) 4, (en) 2, (tn) 2 and tren, were prepared and characterized by elemental analyses and UV-vis spectra.
3 citations
TL;DR: In this article, the effects of pH, temperature, acetyl acetone (acacH) concentration and substrate complex concentration on the rate of aqua ligand substitution in the title complex in aqueous medium have been studied.
Abstract: The effects of pH, temperature, acetyl acetone (acacH) concentration and substrate complex concentration on the rate of aqua ligand substitution in the title complex in aqueous medium have been studied. The following rate expression is proposed for the 5.0–6.5 pH range.
$$\begin{gathered} d[Ru(bipy)_2 (acac)^ + ]/dt \hfill \\ = \frac{{k_1 k_2 [Ru(bipy)_2 (H_2 O)_2^{2 + } ][(acacH]}}{{k_{ - 1} + k_2 [(acacH]}} \hfill \\ \end{gathered} $$
where k1 is the water dissociation rate constant of the substrate complex, k−1 is the aquation rate constant and k2 is the ligand capture rate constant of the reaction intermediate. Activation parameters were obtained from Eyring plots and are compared with other systems. The reaction rates increase with an increase in pH and temperature, whereas the ionic strength has little effect. A mechanism involving unimolecular activation is proposed.
TL;DR: The title reaction has been studied spectrophotometrically and a rate-law established within the pH range 5.0 to 6.5 and a mechanism involving dissociative interchange is proposed.
Abstract: The title reaction has been studied spectrophotometrically and a rate-law established within the pH range 5.0 to 6.5, $$ {⤪ [Ru(bipy)_{2}(cys)_{2}]/dt={k_{1}k_{2}[Ru(bipy)_{2}(H_{2}O)_{2}^{2+}][cysH]⩈er k_{-1}+k_{2}[cysH]}} $$ (where k1 is the water dissociation rate constant of the substrate complex, k−1 is the aquation and k2 is the ligand capturing rate constant of the penta co-ordinate intermediate [Ru(bipy)2(H2O)]2+). The reaction rate was found to be pH-dependent. Activation parameters have been calculated and compared with other anionic ligands such as $ {⤪ N}_{3}^{−} $, SCN− and neutral ligands e.g. o-phen-anthroline, 2,2′-bipyridine etc. A mechanism involving dissociative interchange is proposed.
TL;DR: A series of new complexes of type (a) cis -[Co(en)(tn)ACl]Y [en = 1,2-diminoethane, tn = 1-3-diamino propane, A = NH 3, MeNH 2, EtNH 2, n-Bu NH 2, pyridine (py), β and γ-picoline (pic), imidazole (imz); Y = ZnCl 4 2− or 2ClO − 4 ] and (
TL;DR: In this article, the kinetics of substitution of aqua-ligands from above title complex by 1,10-phenanthroline in aqueous medium has been studied spectrophotometrically at different temperatures (40-55 °C).
Abstract: The kinetics of substitution of aqua-ligands from above title complex by 1,10-phenanthroline in aqueous medium has bean studied spectrophotometrically at different temperatures (40–55 °C). The following rate law has been established for the reaction systems at pH 5.6. where L and tap represent 1,10-phenanthroline and 2-(m-tolylazo)pyridine respectively, k1 is the water dissociation rate constant of [Ru(tap)2(H2O)2]2+ (i.e. complex 1), k−1 is the aquation rate constant, and k2 is the ligand capturing rate constant of the penta coordinated intermediate, [Ru(tap)2(H2O)]2+. Ionic strength has a very little effect on the rate constants. The rate increases with the increase in pH in the range of 4.5 to 6.0. Activation parameters (ΔH≠ and ΔS≠) were also calculated. Experimental results are consistent with a dissociative mechanism. The solvent effect study was used to verify the mechanistic conclusion.
TL;DR: In this paper, the effects of high pressure on the rates of aquation reactions of Cr(bpy)33+ and Cr(phen)33+) have been measured, and the activation volumes were derived as −0.9 ± 0.5 and +5.2 ± 0.4 cm3 mol−1, respectively.
Abstract: The effects of high pressure on the rates of aquation reactions of Cr(bpy)33+ and Cr(phen)33+ have been measured. The activation volumes of aquation were derived as −0.9 ± 0.5 and +5.2 ± 0.4 cm3 mol−1 for Cr(bpy)33+ and Cr(phen)33+, respectively. These values are consistent with those expected from an interchange mechanism involving water penetration to the coordination sphere and an extension of one or both of the Cr-polypyridine bonds.
TL;DR: In this article, the anation kinetics of the title complex were investigated spectrophotometrically in 10% (v/v) ethanol-water mixtures and the following rate law has been proposed in the pH range 3.65-6.5.
Abstract: The anation kinetics of the title complex were investigated spectrophotometrically in 10% (v/v) ethanol–water mixtures and the following rate law has been proposed in the pH range 3.65–6.5. where k1 is the water dissociation rate constant of the substrate complex, k−1 is the aquation and k2 is the ligand capturing rate constant of the five-coordinate intermediate [Ru(bpy)2(H2O)]2+. The activation parameters have been calculated and compared with other substitution reactions. Considering all the results, a dissociative mechanism has been suggested.
TL;DR: In this article, the influence of change in ion background on the aquation rate constants of [CrCl3(H2O)3] was studied spectrophotometrically at 25°C over a broad range of ionic strengths (up to several moles/liter).
Abstract: The influence of change in ion background on the aquation rate constants of [CrCl3(H2O)3)] was studied spectrophotometrically at 25°C over a broad range of ionic strengths (up to several moles/liter). The electrolytes KBr, KCl, NaClO4, NaCl, NaBr, NaNO3, HClO4, HCl, LiClO4, CaCl2, LaCl3, and ethanol were used. It is shown that the rate constant decreases with increasing electrolyte concentration in the electrolytic media (to 0.3 log unit in some of them), while increasing in ethanol media with increasing content of the alcohol.