Ligand-Mediated Reactivity in CO Oxidation of Niobium–Nickel Monoxide Carbonyl Complexes: The Crucial Roles of the Multiple Adsorption of CO Molecules

Abstract

The heteronuclear metal oxide complexes are of great significance in heterogeneous catalytic oxidation of CO. However, previous studies are mainly focused on the composition of metal oxide, charge state, the support and the active oxygen species, with little attention paid to adsorbed CO ligands. Herein, the ligand-mediated reactivity in CO oxidation of niobium−nickel monoxide carbonyl complexes has been successfully identified. The NbNiO(CO) n − (n = 5−6) anions are determined to be Obridged complexes. In contrast, the NbNiO(CO) n − (n = 7−8) anions are characterized to be η 2 -CO 2 -tagged complexes. The crucial roles of the multiply adsorbed CO molecules that can facilitate not only the competitive binding with bridging oxygen atom to the transition metal centers but also the electron accumulation of transition metal atoms have been discovered. The fascinating results are of substantial importance to understand the mechanisms of CO oxidation over heteronuclear metal oxide under CO-rich feed condition.

Triply Carbonyl-Bridged Ni2(CO)5Featuring Triple Three-Center Two-Electron Ni—C–Ni Bonds Instead of Ni≡Ni Triple Bond

“…Transition metal (TM) carbonyl complexes are ubiquitous in modern organometallic chemistry; their synthesis, characterization, and application have been fundamental constituents of extensively experimental and theoretical research, especially for the metal–metal interaction in these complexes. , The inherent essence of metal–metal bonding lies at the heart of the generalized understanding and specific applications in the fields of catalysis and the synthesis of metallic materials. − Mononuclear carbonyl complexes serve as a model compound for the 18-electron rule. However, the hypothetical existence of a direct or even multiple metal–metal bonds based on the 18-electron rule and the abnormally short metal–metal bond length remains a matter of discussion for some binuclear or multinuclear TM compounds supported by the bridging CO ligands in terms of Fe 2 (CO) 9 especially.…”

“…The saturation limit of CO ligand adsorption on the cationic nickel clusters has been studied in a molecular beam via the reactions of CO with the mass-selected small thermalized nickel cluster cations. 14,15 Yet the gas-phase flow-tube reactor has been employed to investigate the saturation convergences for neutral small nickel clusters with CO, as well as the rate coefficients and chemisorption efficiency for the reactions between small nickel cluster anions and CO. 16−18 Three binuclear nickel carbonyl free radicals including Ni 2 (CO) 8 + , Ni 2 (CO) 7 − , and Ni 2 (CO) 6 + complexes trapped in a Kr matrix have been detected by electron paramagnetic resonance (EPR) spectroscopy and were tentatively assigned to have two, one, and two bridging carbonyl ligands, respectively. 19 Recently, the adsorption of CO ligands on the cationic nickel clusters has been further measured by IR-MPD spectroscopy, and their structures were established by comparison of the experimental spectra with the simulated spectra derived from density functional theory (DFT) calculations.…”

Thermodynamics and Kinetics of Gas-Phase CO Oxidation on the Scandium Monoxide Carbonyl Complexes

“…Nevertheless, the consecutive CO adsorption on the ScO + core has controlled the relative stability of the CO association products and CO oxidation products. The capability of the adsorbed CO ligand to regulate the dynamic reactivity of atomic clusters toward CO oxidation has been reported. ,,, The attached CO can turn the electronic structures of clusters and promote the CO oxidation. Owing to the synergic effects of σ-donation and π back-donation, the TM–CO bonding interaction involves charge transfer between TM and CO ligand.…”

“…24 Recently, the unexpected self-promoted enhancement of catalytic performance upon CO adsorption has been identified in both condense-phase and gas-phase studies. 34,35 Our recent investigation on the NbNiO(CO) n − series has demonstrated the crucial roles of the multiple adsorptions of CO molecules in the oxidation reaction of CO. 34 Inspired by these facts, our research is extended to the scandium monoxide carbonyl complexes to understand their reactivity toward CO oxidation.…”

Photoelectron velocity-map imaging spectroscopy of nickel carbide: examination of the low-lying electronic states

“…60 Previous CASSCF calculations show that the CI weight of dominant configuration is 88% for the NiC ground state, 53 suggesting that the structural and chemical bond properties based on single determinant calculations are qualitatively reasonable. 61–63 The pure BP86 functional utilizing Becke's 1988 exchange functional and Perdew's correlation functional 64,65 was proved to be practical, 66,67 and thus was employed for geometry optimization and electronic structure analysis in conjunction with the def2-TZVPP basis sets. The dispersion forces were considered based on Grimme's approach with the Becke—Johnson damping correction (D3(BJ)).…”