21560-19-0Relevant articles and documents
Water π-donation in trans-tetraammineruthenium(II): Effect on coordinated-water properties induced by a trans NO ligand
Bezerra, Cícero W.B.,Da Silva, Sebasti?o C.,Gambardella, Maria T.P.,Santos, Regina H.A.,Plicas, Lidia M.A.,Tfouni, Elia,Franco, Douglas W.
, p. 5660 - 5667 (1999)
The complex trans-[Ru(NH3)4NO(H2O)]Cl 3·H2O has been isolated as a decomposition product of the dimeric cation [{Ru(NH3)4NO}2(μ-S2)] 6+. The elemental analysis and electronic, infrared, X-ray, and ESR spectroscopies fit well with the formulation trans-[Ru(NH3)4NO(H2O)]Cl 3·H2O. The νNO (1912 cm-1) observed and the Z(Ru-N-O) = 178.1°(5) are consistent with the nitrosonium character of the NO ligand. Cyclic voltammetry showed only one redox process in the range -0.5 to +1.2 V, which was attributed to the reaction trans-[(H2O)(NH3)4RuII(NO +)]3+ + e- harr; trans-[(H2O)(NH3)4RuII(NO 0)]2+. The pKa values 3.1 ± 0.1 and 7.7 ± 0.1 (μ = 0.10 M, NaCl) have been measured for the reaction trans-[Ru(NH3)4L(H2O)]n++ + H2O ? trans-[Ru(NH3)4L(OH)](n-1)+ + H3O+, where L = NO+ and CO, respectively. The substitution of the coordinated water molecule in trans-[Ru(NH3)4(H2O)NO]3+ by chloride ions proceeds about 30-fold times slower than in [Ru(NH3)5(H2O)]3+ (kCl- = 8.7 × 10-5 M-1 s-1 and 3.7 × 10-6 M-1 s-1, respectively; 40°C, μ = 2.0 NaCl, [H+] = 1.0 × 10-2 mol L-1). Quantum mechanical DFT calculations show that the mixing between the lone pair of the oxygen, n in character, and the dxz orbital of the metal is linearly related to the pKa of the water ligand and to the water lability. The calculations have also shown that the π-d mixing is strongly dependent on the trans ligand L. The electronic spectra of the trans-[Ru(NH3)4(H2O)L]n+ (L = CO and NO+) species are discussed on the basis of DFT and ZINDO/S calculations.
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.
