CO2 Hydrogenation and Formic Acid Dehydrogenation Using Ir Catalysts with Amide-Based Ligands was written by Kanega, Ryoichi;Ertem, Mehmed Z.;Onishi, Naoya;Szalda, David J.;Fujita, Etsuko;Himeda, Yuichiro. And the article was included in Organometallics in 2020.Formula: C6H9N3O This article mentions the following:
A series of Ir catalysts [Cp*Ir(H2O)(QCXNHR)][SO4] (1–16; Q = 2-pyridyl, 4-hydroxy-2-pyridyl, 6-hydroxy-2-pyridyl, 2-imidazolyl, 1-pyrazolyl; X = O, S, NH; R = H, Me, Ph, 4-hydroxyphenyl) bearing amide-based ligands were isolated or generated in situ by a deprotonated amide moiety with the hypotheses that strong electron-donating ability of the coordinated anionic nitrogen atom and the proton-responsive OH group near the metal center will improve the catalytic activity for CO2 hydrogenation and formic acid (FA) dehydrogenation. The effects of the modifications of the ligand architecture on the catalytic activity were investigated for CO2 hydrogenation at ambient conditions (25° with 0.1 MPa H2/CO2 (volume/volume = 1/1)) and under slightly harsher conditions (50° with 1.0 MPa H2/CO2) in basic aqueous solutions together with deuterium kinetic isotope effects (KIEs) with selected catalysts. Complex [Cp*Ir(L12)(H2O)][HSO4] (12, L12 = 6-hydroxy-N-phenylpicolinamidate) that has an anionic coordinating N atom and an OH group in the second coordination sphere, exhibits a TOF of 198 h-1 based on the initial 1 h of reaction. This TOF which, to the best of our knowledge, is the highest value ever reported under ambient conditions in basic aqueous solutions However, complex [Cp*Ir(L10)(H2O)][HSO4] (L10 = 4-hydroxy-N-methylpicolinamidate) performs better in long-term CO2 hydrogenation (up to a TON of 14700 with [Ir] = 10μM after 348 h and the final formate concentration of 0.643 M with [Ir] = 250μM.) at ambient conditions. Further, the catalytic activity for FA dehydrogenation was examined under three different conditions (pH 1.6, 2.3 and 3.5). The complex 12 in any of these conditions is less active compared to the picolinamidate catalysts without ortho-OH, owing to its instability. Theor. calculations were performed to examine the catalytic mechanism, and a step-by-step mechanism has been proposed for both CO2 hydrogenation and FA dehydrogenation reactions. D. functional theory calculations of [Cp*Ir(L3)(H2O)][HSO4] (L3 = picolinamidate) and the X-ray structure of the [Cp*Ir(L7)(H)]•H2O (L7 = N-methylpicolinamidate) complex imply a pH-dependent conformational change from N,N coordination to N,O coordination upon lowering the pH of the aqueous solution In the experiment, the researchers used many compounds, for example, 3,5-Dimethyl-1H-pyrazole-1-carboxamide (cas: 934-48-5Formula: C6H9N3O).
3,5-Dimethyl-1H-pyrazole-1-carboxamide (cas: 934-48-5) belongs to pyrazole derivatives. An alternative way to synthesize multisubstituted pyrazoles is the Csingle bondH arylation of simple pyrazoles. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.Formula: C6H9N3O
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics