Study of the Reaction of Hydroxylamine with Iridium Atomic and Cluster Anions (n = 1–5)

Abstract

Elucidating the multifaceted processes of molecular activation and subsequent reactions gives a fundamental view into the development of iridium catalysts as they apply to fuels and propellants, for example, for spacecraft thrusters. Hydroxylamine, a component of the well-known hydroxyl­ammonium nitrate (HAN) ionic liquid, is a safer alternative and mimics the chemistry and performance standards of hydrazine. The activation of hydroxylamine by anionic iridium clusters, Ir n – (n = 1–5), depicts a part of the mechanism, where two hydrogen atoms are removed, likely as H2, and Ir n (NOH)− clusters remain. The significant photoelectron spectral differences between these products and the bare clusters illustrate the substantial electronic changes imposed by the hydroxylamine fragment on the iridium clusters. In combination with DFT calculations, a preliminary reaction mechanism is proposed, identifying the possible intermediate steps leading to the formation of Ir­(NOH)−.

Iridium Dimer Anion-Mediated C≡C Triple Bond Cleavage and Successive Dehydrogenation of Acetylene in the Gas Phase

“…The [Ir 2 ] − anion is predicted to have a 6 Δ u electronic ground state with a 4 Σ u ̅ state lying 25 kJ/mol above the 6 Δ u ground state at the B3LYP/QZVP level, in agreement with previous calculations at the ωB97x-d/def2-TZVPPD/SDD level of theory . The simulated density of states (DOS) spectra for the 6 Δ u and 4 Σ u ̅ states are compared with the experimental photoelectron spectrum in Figure S3.…”

“…The [Ir 2 ] − anion is predicted to have a 6 Δ u electronic ground state with a 4 Σ u̅ state lying 25 kJ/mol above the 6 Δ u ground state at the B3LYP/QZVP level, in agreement with previous calculations at the ωB97x-d/def2-TZVPPD/SDD level of theory. 81 The simulated density of states (DOS) spectra for the 6 Δ u and 4 Σ u̅ states are compared with the experimental photoelectron spectrum in Figure S3. The first VDE of the 6 Δ u state [Ir 2 ] − , derived from electron detachment from the highest singly occupied molecular orbital is calculated to be 1.62 eV, in good agreement with the experimental VDE value of 1.84 eV.…”

Anomalously Efficient Dehydrogenation of NH3 on Ir4+ and Ir5+

“…The tetrahedral isomer with a doublet state has 0.62 eV higher energy than the lowest energy one. Similarly, it has been predicted that the structures of the neutral and negatively charged iridium tetramers are square. − The dehydrogenation of NH 3 on the most stable Ir 4 + is exothermic by 0.20 eV in the present calculation, and a possible reaction pathway of Ir 4 + + NH 3 → Ir 4 NH + + H 2 is shown in Figure . This pathway indicates that all the transition states are located energetically lower than the initial state.…”

Rate-Limiting Reaction of Dehydrogenative Dimerization of Ethanol to Ethyl Acetate and Hydrogen on Cu, Cu2, and Cu13 Clusters: Size Dependence

“…The theoretical works relevant to dimerization of ethanol to ethyl acetate on pure Cu surfaces and alloys were also reported recently. [18][19][20][21][22][23] Due to the potential applications of ethanol fuel cells, many catalytic studies of ethanol oxidation were also been conducted recently on Ir [24][25][26][27][28][29] as well as other catalysts The study of nanosized metal clusters, such as Pt, [59][60][61][62][63][64][65][66][67] Au, [68][69][70][71] Pd, [72][73][74][75][76][77][78][79] Cu, [80][81][82][83][84] Ir, [85][86][87] and the alloys, [88][89][90][91][92][93][94]…”