Why Nickel(II) Binds CO Best in Trigonal Bipyramidal and Square Pyramidal Geometries and Possible Consequences for CO Dehydrogenase

Macgregor, Stuart A.; Lu, Zheng; Eisenstein, Odile; Crabtree, Robert H.

doi:10.1021/ic00094a030

Cited by 34 publications

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“…The Ni(II) centers of intermediates 1 (Figure ), 2 , 3 , and 4 (Figure ) are four‐coordinate square planar structures. Notably, Crabtree and coworkers assigned the environment around Ni(II) in 2 to be five‐coordinate, partially due to the lack of precedence at the time for a four‐coordinate Ni(II)‐carbonyl species and the suggestion from an extended Hückel study that Ni(II)‐carbonyl complexes could be pentacoordinated since such a configuration could enhance π‐back bonding interactions between Ni(II) and CO . Nevertheless, the DFT level of theory does not support any Ni(II) pentacoordinated structure with the iminothiolate ligand.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Rudshteyn

Warnke

et al. 2017

Int J of Quantum Chemistry

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We investigate the CO oxidation into CO 2 catalyzed by a biomimetic Ni(II)-iminothiolate complex in the presence of the sacrificial oxidizing agent methylviologen. We propose a catalytic mechanism supported by the density functional theory analysis of reaction intermediates that agrees with available experimental observations and kinetic data. We rule out a fivecoordinate Ni(II) species as well as a Ni(III) intermediate which was previously proposed and instead identify a key four-coordinate Ni(II) carbonyl species. We find that the turnoverlimiting step is likely the formation of the Ni(II) carboxylic acid species, although if a worse oxidant were used or if the concentration was less, then the oxidation of the Ni(I) species would be the turnover-limiting step. The reported findings should enable the design of better catalysts to favor one of the two competing pathways for CO to CO 2 conversion as catalyzed by this particular complex.catalytic mechanism, CO oxidation, CO 2 conversion, DFT, nickel catalyst 1 | I N TR ODU C TI ON CO/CO 2 conversion is central to a wide range of reaction mechanisms from carbon metabolism in biology to H 2 production in industrial applications based on the water-gas shift reaction. [1] The conversion mechanism could also provide meaningful insights into the reverse reaction that converts the greenhouse gas CO 2 into CO, a key intermediate on the path to liquid fuels. [2][3][4] In Nature, reversible CO/CO 2 conversion is catalyzed by the natural enzyme carbon monoxide dehydrogenase (CODH) which has a catalytically active Ni(II) center, [5][6][7][8] We focus on a Ni(II)-iminothiolate catalyst, proposed and synthesized by Crabtree and coworkers as a functional biomimetic CODH model system (Scheme 1). The Ni(II)-iminothiolate complex converts CO to CO 2 at room temperature in the water/methanol mixed solvent (Scheme 2) in the presence of the oxidizing agent methylviologen (mv 21 ) and acetate (AcO -) as a weak base. [9,10] A five-step catalytic cycle has been suggested for the mechanism of CO to CO 2 conversion, [9,10] in which the decarboxylation of LNi I -CO 2 is the turnover limiting step, as supported by the overall reaction rate dependence on P CO , [mv 21 ], [H 2 O], [Ni], and solution pH. However, the proposed intermediates have yet to be supported (or, otherwise ruled out) by spectroscopic and theoretical studies.Herein, we carry out a theoretical analysis of the catalytic mechanism at the density functional theory (DFT) level. The reported findings provide valuable insights into the reaction intermediates as well as guidelines for computational design of molecular catalysts for CO 2 /CO conversion in this class of compounds, using inverse design methodologies demonstrated for other systems. [11] Yueshen Wu and Benjamin Rudshteyn contributed equally to this study.Int J Quantum Chem. 2018;118:e25555.We have analyzed for the first time the catalytic mechanism of CO/CO 2 conversion by the Ni(II)-iminothiolate catalyst at the DFT level. Our results and direct comparisons to experime...

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Section: Resultsmentioning

confidence: 99%

Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Rudshteyn

Warnke

et al. 2017

Int J of Quantum Chemistry

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“…[7][8][9][10][11] Despite this, catalytically active Ni(II)-alkyl species may likely exhibit or transition through different coordination geometries. [12][13][14] For example, other synthetic Ni(II) complexes can be found in tetrahedral geometries in addition to the more common square planar geometries. While a square planar geometry is favored due to electronic stabilization of the d 8 Ni(II) ion, a tetrahedral geometry may be favored with suitably bulky or chelating ligands.…”

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confidence: 99%

Nickel(ii)-methyl complexes adopting unusual seesaw geometries

et al. 2020

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“…As a result, a fair number of Ni II carbonyl complexes have been prepared. Most of these complexes are five‐coordinate, an observation that has been theoretically justified in terms of a more efficient π back‐donation from the Ni II center to the CO ligand 37. In fact, five‐coordinate nickel monocarbonyl derivatives containing the CO ligand in either axial or equatorial positions, show low‐frequency ν (CO) values as for instance in ( TBPY ‐5‐23)‐[NiI 2 (CO)(fdma)] (fdma=ferrocene‐1,1′‐bis(dimethylarsine); ν (CO)=2054 cm −1 ),38 ( TBPY ‐5‐22)‐[NiI 2 (CO)(PMe 3 ) 2 ] ( ν (CO)=2015 cm −1 )31 and ( TBPY ‐5‐13)‐[Ni(PP 3 E)(CO)] 2+ (PP 3 E=tris{2‐(diethylphosphino)ethyl}phosphine; ν (CO)=2050 cm −1 ) 39.…”

Section: Resultsmentioning

confidence: 99%

“…Even in the tricarbonyl derivative ( TBPY ‐5‐11)‐[Ni(SiCl 3 ) 2 (CO) 3 ], the ν (CO) absorption appears at 2079 cm −1 33. In a square‐planar geometry, the σ‐nonbonding Ni(d π ) orbitals have been calculated to be low in energy and thus to be inefficient π‐donor orbitals 37. This statement, however, should be taken with great care, since in the anionic compounds 4 and 5 as well as in the few square‐planar precedents reported, the ν (CO) values observed suggest a significant degree of π back‐donation, see: trans ‐[Ni(C 6 Cl 5 )(PR 3 ) 2 (CO)] + (PR 3 =PPhMe 2 , PPh 2 Me; ν (CO)=2100 cm −1 )40 and [Ni(SePh) 3− x (SPh) x (CO)] − ( x =0, 1, 2; ν (CO)∼2030 cm −1 ) 29, 30.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of α‐Stereogenic Amides and Ketones by Enantioselective Conjugate Addition of 1,4‐Dicarbonyl But‐2‐enes

Jiang

Yang

Pan

et al. 2009

Chemistry A European J

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In the conjugate addition reaction of a alpha,beta-unsaturated compound, the new stereogenic center is created in the beta-position. In contrast, conjugate addition to 1,4-dicarbonyl but-2-enes will generate an alpha-stereogenic center with respect to one of the carbonyl groups, which informally, can be considered as an inversion of normal reactivity patterns or Umpolung. In this paper, we demonstrate that chiral bicyclic guanidine can catalyze the addition of 1,3-dicarbonyl compounds to 1,4-dicarbonyl but-2-enes [(E)-4-oxo-4-arylbutenamides and (E)-4-oxo-4-arylbutenones] with high regioselectivity and enantioselectivity (ee values up to 97%).

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Why Nickel(II) Binds CO Best in Trigonal Bipyramidal and Square Pyramidal Geometries and Possible Consequences for CO Dehydrogenase

Cited by 34 publications

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Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Nickel(ii)-methyl complexes adopting unusual seesaw geometries

Synthesis of α‐Stereogenic Amides and Ketones by Enantioselective Conjugate Addition of 1,4‐Dicarbonyl But‐2‐enes

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Why Nickel(II) Binds CO Best in Trigonal Bipyramidal and Square Pyramidal Geometries and Possible Consequences for CO Dehydrogenase

Cited by 34 publications

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Mechanistic study of CO/CO2 conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Mechanistic study of CO/CO2 conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Nickel(ii)-methyl complexes adopting unusual seesaw geometries

Synthesis of α‐Stereogenic Amides and Ketones by Enantioselective Conjugate Addition of 1,4‐Dicarbonyl But‐2‐enes

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Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex

Mechanistic study of CO/CO₂ conversion catalyzed by a biomimetic Ni(II)‐iminothiolate complex