14282-91-8Relevant articles and documents
CO2 Hydrogenation over Ru-NPs Supported Amine-Functionalized SBA-15 Catalyst: Structure–Reactivity Relationship Study
Srivastava, Vivek
, p. 3704 - 3720 (2021)
We gave an effective protocol to support Ru NPs on amine-functionalized SBA-15 mesoporous silica to catalyze the CO2 hydrogenation reaction. The amine groups present in the catalytic system performed an essential role in stabilizing the Ru NPs, delivering the robust metal-support interaction and improved catalytic activities to material in formic acid synthesis. We also demonstrated a comprehensive study of different amine groups on the catalytic performance of ultrafine uniformly dispersed Ru NPs over mesoporous SBA-15 support. The effect of various compositional and steric properties of amine groups on the size/distribution of the Ru NPs were closely studied and correlated with their catalytic performance in the CO2 hydrogenation reaction. The in situ DRIFTS analysis of CO2 hydrogenation into formic acid in presence of developed CATALYST-1 showed active surface species bonded to support sites and to Ru NPs. This interaction proposed the formation of important intermediates such as hydrides, formates and bicarbonates, which are significant for the formation of formic acid. We successfully recycled the catalysts up to 5 runs with good catalytic activity. Graphic Abstract: [Figure not available: see fulltext.].
Influence of the metal centers on the pKa of the pyrrole hydrogen of imidazole complexes of (NH3)5M3+, M(III) = Co(III), Rh(III), Ir(III), Ru(III)
Fazlul Hoq,Shepherd, Rex E.
, p. 1851 - 1858 (2008/10/08)
The pKa's at 298 K, μ = 0.10 (NaCl), and the temperature dependence (273-343 K) for the deprotonation of the pyrrole NH of several imidazoles coordinated to (NH3)5M3+ moieties (M = CoIII, RhIII, IrIII, RuIII) are reported. A greater importance of dn configuration over ion size is found. Data summarized for various systems are as follows (ligand, M (pK298, ΔHa° in kcal/mol, ΔSa° in eu)): imidazole = imH, CoIII (9.99, 14.0 ± 0.5, 1.3 ± 1.6), RhIII (9.97, 13.6 ± 0.3, 0.1 ± 1.3), IrIII (10.05, 13.4 ± 0.3, 1.2 ± 1.0), RuIII (8.9, 10.0 ± 0.8, 3.7 ± 1.2); 2-methylimidazole = 2-MeimH, CoIII (10.67, 17.8 ± 0.7, 11.2 ± 2.4); 2,4(5)-dimethylimidazole = 2,5-Me2imH, CoIII (11.04, 13.4 ± 0.5, 5.3 ± 1.6), RuIII (10.20, 13.2 ± 0.6, -2.1 ± 1.6). 1H NMR spectra of low-spin d6 complexes of imidazoles and ring-methylated imidazoles are discussed for CoIII, RhIII, IrIII, and RuIII. C-2 and remote ring, C-5, substituents are shifted downfield relative to the free imidazole ligand in the order H+ > CoIII > RhIII > IrIII. The C-4 position is influenced competitively by σ-withdrawal ring substituents and TIP effects for CoIII. Assignments of the remote isomer for (NH3)5M(2,5-Me2imH)3+ (M = CoIII, RuIII) are made from the 1H NMR spectra of the CoIII and RuII complexes. The RuIII complexes of 2,5-Me2imH and the imidazolate form (2,5-Me2im-) both exhibit LMCT spectra. The imidazolato form has three bands at 655, 377, and 272 nm, proposed for II1 → IId, II2 → IId, and n → IId transitions, where II1, II2, and n are the highest HOMO's of the imidazolato ring.
