Ligand-Based Reduction of CO<sub>2</sub> to CO Mediated by an Anionic Niobium Nitride Complex

Silvia, Jared S.; Cummins, Christopher C.

doi:10.1021/ja910445r

Cited by 88 publications

(97 citation statements)

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“…The most stable structure of 1-Nb has a C 3 point group. As seen from Figure 21 The free-energy barrier for the formation of 2-Nb from 1-Nb + CO 2 is calculated to be 6.2 kcal/mol, indicating that 1-Nb easily traps CO 2 .…”

Section: ■ Computational Detailsmentioning

confidence: 91%

“…30 In the CPCM calculations, THF was used as the solvent, corresponding to the experimental conditions. 21 In this paper, solvation-corrected relative free energies are used to analyze the reaction pathways calculated. Wiberg bond indices (WBI) were obtained by natural bond orbital (NBO) analysis.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

“…31 The minimum-energy crossing points (MECPs) between the singlet and triplet states for some pertinent niobium and vanadium complexes were calculated using the MECP location program developed by Harvey and his co-workers. 32 21 We optimized the structures of [NNb(N t BuMe) 3 ] − (1-Nb) and [O 2 CNNb(N t BuMe) 3 ] − (2-Nb) in which the Ar substituents at N of the amide ligands were modeled with Me and displayed the calculated structures and relative energies in Figure 1.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

“…21 Scheme 1 shows that an initial binding of CO 2 to the terminal nitride nitrogen atom of 1Nb rather than the niobium metal center gives the carbamate complex 2Nb. Reaction of the carbamate complex 2Nb with MeC(O)Cl gives an isocyanate− acetate (3Nb).…”

Section: ■ Introductionmentioning

confidence: 99%

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DFT Studies on Reactions of CO₂ with Niobium and Vanadium Nitride Complexes

et al. 2011

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We have investigated the reduction of CO 2 to CO mediated by the anionic niobium nitride complex [NNb(N t BuMe) 3 ] − , a model complex of [NNb(N t BuAr) 3 ] − , using density functional theory. We mainly calculated the energetics for the interesting reaction sequence, reported recently by Cummins and his co-workers, involving reactions of the anionic niobium nitride complex [NNb(N t BuAr) 3 ] − with CO 2 to first give a carbamate complex. The carbamate complex then reacts with MeC(O)Cl to give an isocyanate−acetate, which can be reduced by SmI 2 to give the isocyanate complex (OCN)Nb(N t BuAr) 3 . Further reduction of the isocyanate complex by Na/Hg extrudes CO and regenerates [NNb(N t BuAr) 3 ] − . In addition, we compare the reaction pathways for the reduction reaction of the isocyanate complexes (OCN)M(N t BuMe) 3 (M = Nb, V), model complexes of (OCN)M(N t BuAr) 3 , with sodium and explain why these two reduction reactions give remarkably different products. ■ INTRODUCTIONCarbon dioxide (CO 2 ) is an easily available, renewable carbon resource. Therefore, there is significant interest in developing efficient transformation of CO 2 into useful chemicals. 1 However, cleavage of the CO bond(s) in carbon dioxide is not easy to achieve because of its high thermodynamic stability. A number of approaches to the transformation have been discussed in detail in a recent review article. 2 Of these approaches, many transition-metal complexes were found to be efficient in converting CO 2 to other chemicals. 3−10 In particular, (PNP)IrH 2 , 11 Li 2 [W(CO) 5 ], [WCl 2 (PMePh 2 ) 4 ], 12,13 (NHC)Ni (NHC = N-heterocyclic carbene), 14 L t-Bu Fe−N 2 − FeL t -B u (L t -B u = 2,2,6,6-tetramethyl-3,5-bis-[(2,6-diisopropylphenyl)imino]hept-4-yl), 15 [Cp 2 TiCl] 2 , Cp 2 Zr(II)-(CO) 2 , 16 Ir 2 (CO) 3 (dmpm) 2 , 17 [(Ph 2 P(CH 2 ) 2 PPh 2 ) 2 Rh]-[MgCl], 18 and a coordinatively unsaturated tris-aryloxide uranium(III) complex [(L)U] (L = 1,4,7-tris(3,5-di-tert-butyl-2-hydroxybenzylate)-1,4,7-triazacyclononane) 19 have been found to be capable of abstracting CO or O from CO 2 to form strong metal−carbonyl or metal−oxygen bonds. However, formation of strong metal−carbonyl or metal−oxygen bonds from these abstraction reactions represents a challenge to catalytic turnover. Recent studies showed that a sequence of reactions constituted a cycle for CO 2 reduction to CO when Zr(III)−O− Cu(II) 20 or [NNb(N t BuAr) 3 ] − (1Nb) 21−23 was employed. These metal complexes are believed to be promising for a catalytic reduction of CO 2 to CO.In this work, we are interested in the reaction sequence elegantly reported recently by Cummins and his co-workers (Scheme 1) involving the anionic niobium nitride complex 1Nb. 21 Scheme 1 shows that an initial binding of CO 2 to the terminal nitride nitrogen atom of 1Nb rather than the niobium metal center gives the carbamate complex 2Nb. Reaction of the

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Section: ■ Computational Detailsmentioning

confidence: 91%

Section: ■ Computational Detailsmentioning

confidence: 99%

Section: ■ Computational Detailsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

DFT Studies on Reactions of CO₂ with Niobium and Vanadium Nitride Complexes

et al. 2011

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“…As shown in Table S4, it can be found that both the lengths of C3AO1 bond and C3AO2 bond increase in TS2 compared with those in the free carbon dioxide. Referring to the increase in the length of CAO bond is used to measure the activation of carbon dioxide [28][29][30][31][32]. Besides, the lengths of NAC3 bond and O1AC1 bond shorten from 3.030 Å, 3.909 Å in compound 2 to 1.709 Å, 2.365 Å in TS2, respectively.…”

Section: The Reaction Mechanism With No Catalyst (Path I)mentioning

confidence: 99%