861853-10-3Relevant 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.
