Decomposition of Nitrous Oxide in Hydrated Cobalt(I) Clusters : A Theoretical Insight into the Mechanistic Roles of Ligand-binding Modes

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)16816-16826
Journal / PublicationPhysical Chemistry Chemical Physics
Volume23
Issue number31
Online published6 Jul 2021
Publication statusPublished - 21 Aug 2021

Abstract

Hydrated cobalt(I) cluster ions, [Co(H2O)n]+, can decompose the inert nitrous oxide molecule, N2O. Density functional theory suggests that N2O can anchor to Co+ of [Co(N2O)(H2O)n]+ through either O end-on (η1−OL) or N end-on (η1−NL) coordinate mode. The latter is thermodynamically more favorable resulting from a subtle π backdonation from Co+ to N2O. The N2O decomposition involves two major processes: (1) redox reaction and (2) N–O bond dissociation. Initial activation of N2O through an electron transfer from Co+ to N2O yields an anionic N2O, which binds to the metal center of the formally [Co2+(N2O)(H2O)n] also through either O end-on (η1−O) or N end-on (η1−N) mode and also be stabilized by water molecules through hydrogen bonding. From η1−O, subsequent N–O bond dissociation to liberate N2, producing [CoO(H2O)n]+, is straightforward via a mechanism that is commonplace for typical metal-catalyzed N2O decompositions. Unexpectedly, the N–O bond dissociation directly from η1−N is also possible and eliminates both N2 and OH, explaining the formation of [CoOH(H2O)n]+ as observed in a previous experimental study. Interestingly, formation of [CoO(H2O)n]+ is kinetically controlled by the initial redox process between Co+ and the O-bound N2O, of which the activation barrier in large water clusters (n ≥ 14) are higher than that of the unexpected N‒O bond dissociation from the N-bound structure forming [CoOH(H2O)n]+. This theoretical discovery implies that, in the present of water molecules, the metal-catalyzed N2O decomposition starting from an O-bound metal complex is not mandatory.

Citation Format(s)

Decomposition of Nitrous Oxide in Hydrated Cobalt(I) Clusters : A Theoretical Insight into the Mechanistic Roles of Ligand-binding Modes. / Demissie, Ephrem G.; Lam, Wing Ka; Thompson, Hayden; Tang, Wai Kit; Siu, Chi-Kit.

In: Physical Chemistry Chemical Physics, Vol. 23, No. 31, 21.08.2021, p. 16816-16826.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review