Abstract
The spectral (UV–Vis and IR) and electrochemical behavior of the nitrile bonded complexes [Ru(NH 3) 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(NH 3) 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 ( k obs) at 25 °C are 2.9 × 10 −3 s −1 for [Ru(NH 3) 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(NH 3) 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(NH 3) 5(OH 2)] 2+ and free ligand, and the other an intramolecular linkage isomerization forming [Ru(NH 3) 5(NC-bz-4-NH 2C(O))] 2+ and [Ru(NH 3) 5(NC-bz-2-NH 2C(O))] 2+. The oxidized1,2-cyanobenzamide complex [Ru(NH 3) 5( NHC( OH)-bz-2-CN)] 3+ undergoes an amide to nitrile intramolecular linkage isomerization, followed by a cyclization reaction resulting in [Ru(NH 3) 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) (p K a = 4.3). The rates of these reactions, which occur with neighboring group participation, increase with acidity. The reduced form, [Ru(NH 3) 5( NH-( C)(HN-C(O)-2-bz))] 2+, is relatively substitution inert.
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