DFT Investigation of Ligand-Based Reduction of CO2 to CO on an Anionic Niobium Nitride Complex: Reaction Mechanism and Role of the Na+ Counterion (Articolo in rivista)

Type
Label
  • DFT Investigation of Ligand-Based Reduction of CO2 to CO on an Anionic Niobium Nitride Complex: Reaction Mechanism and Role of the Na+ Counterion (Articolo in rivista) (literal)
Anno
  • 2011-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1021/om200322x (literal)
Alternative label
  • Edoardo Mosconi, Filippo De Angelis (2011)
    DFT Investigation of Ligand-Based Reduction of CO2 to CO on an Anionic Niobium Nitride Complex: Reaction Mechanism and Role of the Na+ Counterion
    in Organometallics
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Edoardo Mosconi, Filippo De Angelis (literal)
Pagina inizio
  • 4838 (literal)
Pagina fine
  • 4846 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url
  • http://pubs.acs.org/doi/abs/10.1021/om200322x (literal)
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  • 30 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali
  • 9 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroFascicolo
  • 18 (literal)
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  • Istituto CNR di Scienze e Tecnologie Molecolari (CNR-ISTM) and Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto 8, I-06123, Perugia, Italy (literal)
Titolo
  • DFT Investigation of Ligand-Based Reduction of CO2 to CO on an Anionic Niobium Nitride Complex: Reaction Mechanism and Role of the Na+ Counterion (literal)
Abstract
  • We have investigated the energetics and reaction mechanism of the recently reported ligand-based reduction of CO2 to CO in the coordination sphere of the [Na][NNb(N[tBu]Ar)3] (Ar = 3,5-C6H3Me2) Nb nitride complex, [Na][1], by means of density functional theory calculations. We investigated in detail the four steps of the catalytic cycle proposed by Cummins and co-workers (Silva, J. S.; Cummins, C. C. J. Am. Chem. Soc. 2010, 132, 2171). We pointed our attention to the second reaction step, involving the reaction between [Na][O2C-1] and Ac2O to lead to the [Me-2] product, highlighting the role of the Na+ counterion in the reaction profile. We find coordination of CO2 to [Na][1] to be highly exothermic, without any energy barrier, suggesting that this process is highly favored and possibly controlled by an entropic barrier. Calculation of the free energy profile for the rate-determining second reaction step has shown a stepwise pathway to be favored over a concerted one by 10.0 kcal/mol, with the reaction intermediate [I-1] lying 2.0 kcal/mol below the reagents and an associated free energy barrier of 16.0 kcal/mol. The overall reaction is thus found to proceed with rather small free energy barriers and with a sizable free energy gain, consistent with the low-temperature conditions employed experimentally. In the absence of Na+, the reaction proceeds with a concerted mechanism, with an energetic barrier 15.2 kcal/mol higher than the corresponding process with Na+, pointing at a very relevant role of the Na+ counterion in determining the reaction thermodynamics and preferred pathway. We also investigated the selective cleavage of the Nb-O bond and release of an acetate ligand occurring after reduction of the [Me-2] product by SmI2, finding this process to be energetically favored compared to the competitive Nb-N bond cleavage. (literal)
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