21393-88-4Relevant academic research and scientific papers
Reactions of pentaammineruthenium complexes with 1,2- and 1,4-dicyanobenzene and cyanobenzamides: Evidences of neighboring group participation
Tfouni, Elia,Macêdo, Ant?nio Marcos De Souza,Cardoso, Luciana Nunes,Ferreira, Kleber Queiroz,Oliveira, érica Cristina De,Da Rocha, Zênis Novais
, p. 2909 - 2920 (2008/10/09)
The spectral (UV-Vis and IR) and electrochemical behavior of the nitrile bonded complexes [Ru(NH3)5L]2+ (L = 1,4-dicyanobenzene (1,4-dcb), 1,2-dicyanobenzene (1,2-dcb)), [Ru(NH 3)5(NHC(OH)-bz-4-CN)]3+, [Ru(NH 3)5(NHC(O)-bz-2-CN)]2+ and [Ru(NH 3)5(NH(C)NHC(O)bz)]3+ (NH(C)NHC(O)-bz = 3-imino-1-oxo-isoindoline) are described. Oxidation of [Ru(NH3) 5L]2+, at 0 ≤ pH ≥ 6, is followed by hydrolysis of the coordinated nitrile to give amide complexes in which the amide is through the nitrogen, with pH-dependent rate constants. The estimated values of the rate constant of hydrolysis (kobs) at 25 °C are 2.9 × 10 -3 s-1 for [Ru(NH3)5(1,4-dcb)] 3+ and 5.6 × 10-3 s-1 for [Ru(NH 3)5(1,2-dcb)]3+ at pH 4.65. Reduction of [Ru(NH3)5(NHC(O)-bz-4-CN)]2+ and [Ru(NH 3)5(NHC(O)-bz-2-CN)]2+ is followed by two reactions, one is an aquation forming [Ru(NH3)5(OH 2)]2+ and free ligand, and the other an intramolecular linkage isomerization forming [Ru(NH3)5(NC-bz-4-NH 2C(O))]2+ and [Ru(NH3)5(NC-bz-2- NH2C(O))]2+. The oxidized1,2-cyanobenzamide complex [Ru(NH3)5(NHC(OH)-bz-2-CN)]3+ undergoes an amide to nitrile intramolecular linkage isomerization, followed by a cyclization reaction resulting in [Ru(NH3)5(NH-(C)(HN-C(O)-2-bz))] 3+ ((NH-(C)(HN-C(O)-2-bz)) = 3-imino-1-oxo-isoindoline bonded through the exocyclic nitrogen) (pKa = 4.3). The rates of these reactions, which occur with neighboring group participation, increase with acidity. The reduced form, [Ru(NH3)5(NH-(C)(HN-C(O)-2-bz))] 2+, is relatively substitution inert.
Reactivity of imidazoliumruthenium ammine complexes: Nitrogen- to carbon-bound rearrangement, trans labilization, and redox behavior
Tweedle,Taube
, p. 3361 - 3371 (2008/10/08)
In trans-H2O(NH3)4RuIIIL, where L is carbon-bound4,5 dimethylimidazole, the affinity for imidazole, pyridine, isonicotinamide, Cl-, Br-, or I- is reduced to such a degree that Kassoc could not be measured directly and the upper limit on Kassoc is ca. 5. For isonicotinamide, it was calculated as 1.2 from the relevant redox potentials and the measured value of Kassoc for the Ru(II) form of the complex. The reaction with NCS- is rather rapid, and this points to a large kinetic labilization produced in Ru(III) by the C-bound ligand replacing NH3. In this case, the affinity remains high - Kassoc = 3.3 × 104. The value of pKa governing the deprotonation of H2O trans to C-bound imidazole on Ru(III) is 6.9; that governing the deprotonation of the C-bound imidazole itself in the pentaammine complex is 11.0. The rate of isomerization of N-bound imidazole to the C-bound form on Ru(II) was studied as a function of acidity. In each case, isomerization is accompanied by aquation, and each reaction is first order in [H+]. The percent yields of the C-bound products are 0, 5, 20, and 85 for 1-methylimidazole, imidazole, 4,5-dimethylimidazole, and histidine, respectively. Rearrangement is an intramolecular process. The oxidation by H2O2 of trans-H2O(NH3)4RuIIL (where L is C-bound 4,5-dimethylimidazole) to the Ru(III) product is complicated by destruction of the ligand and by decomposition of H2O2. The specific rate governing the disappearance of Ru(II) is 1.9 × 103 M-1 s-1, and we infer that it involves substitution on the metal center. An inner-sphere mode also obtains in the oxidation with O2. The specific rate governing the disappearance of Ru(II) where L now is C-bound imidazole is 1.36 × 102 M-1 s-1. All the data cited in the foregoing were obtained at 25°C.
Studies on oxidation-reduction reactions of ruthenium ammines
Endicott, John F.,Taube, Henry
, p. 437 - 445 (2008/10/08)
Kinetic and stoichiometric measurements of the reductions of Ru(NH3)6+3 by Cr+2(aq) (Cl- independent as well as Cl- catalyzed paths) and stoichiometries of the reaction of Ru(NH3)5Cl+2 with Cr+2 are reported. Evidence is presented that the reduced species is in each case a Ru(II) ammine and that the ammine ligands remain in the Ru(II) coordination sphere for reasonable periods of time. The standard oxidation potential of Ru(NH83)6+2 = Ru(NH3)6+3 + e- has been determined as -0.214 v. Further kinetic studies of oxidation of Ru(II) species by ClO4- and Co(III) ammines are reported. Equilibrium quotients for the anation of Ru(NH3)5OH2+3 by Cl-, Br-, and I- have been determined taking advantage of the catalysis of the reactions by Ru(NH3)5OH2+2. Copyright 1965 by the American Chemical Society.
