Transition metal carbon quadruple bond: viability through single electron transmutation

Kalita, Amlan J.; Rohman, Shahnaz S.; Kashyap, Chayanika; Ullah, Sabnam S.; Guha, Ankur K.

doi:10.1039/d0cp03436c

Cited by 22 publications

(14 citation statements)

References 31 publications

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“…CASSCF calculations can be an important source of insight in the electronic structure of a molecule; however, the results depend strongly on the choice of the active space, which therefore introduces some elements of arbitrariness. The choice of the active orbitals can be motivated by chemical considerations, as done by Kalita et al [1], who include in the active space all the orbitals involved in Fe-C bonds, resulting in a CASSCF calculation with 12 correlated electrons in 12 orbitals. Here, we adopt a different strategy, based on an automatic, a priori strategy to select the active orbitals.…”

Section: Methodsmentioning

confidence: 99%

“…In a recent paper [1], a computational investigation on FeC(CO) 3 revealed the unprecedented result that in such a molecule, a quadruple Fe-C bond may be present. Unfortunately, FeC(CO) 3 has never been synthetized, and therefore no experimental characterization exists to confirm such a result: a computational investigation is therefore, at the moment, the only tool available to investigate such a system.…”

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confidence: 99%

“…Equilibrium Fe-C distance (R e , in Å) and harmonic vibrational Fe-C stretching frequencies (in cm −1 ) computed with various DFT exchange-correlation functionals. The values reported with a "*" are taken from Reference [1] and reported here for comparison. The harmonic frequencies obtained at every level of theory are all real, confirming thus that the structure is a minimum.…”

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confidence: 99%

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Is There a Quadruple Fe-C Bond in FeC(CO)3?

Nottoli

Lipparini

2021

Computation

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A recent computational paper (Kalita et al., Phys. Chem. Chem. Phys. 2020, 22, 24178–24180) reports the existence of a quadruple bond between a carbon and an iron atom in the FeC(CO)3 molecule. In this communication, we perform several computations on the same system, using both density functional theory and post-Hartree–Fock methods and find that the results, and in particular the Fe-C bond length and stretching frequency depend strongly on the method used. We ascribe this behavior to a strong multireference character of the FeC(CO)3 ground state, which explains the non-conclusive results obtained with single-reference methods. We therefore conclude that, while the existence of a Fe-C quadruple bond is not disproved, further investigation is required before a conclusion can be drawn.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Is There a Quadruple Fe-C Bond in FeC(CO)3?

Nottoli

Lipparini

2021

Computation

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“…Interest in this species has been particularly sparked in the last decade by renewed discussion of its chemical bonding in the form of a proposal that it sustains a quadruple bond between the carbons as in C⩸C, 2,3,4 a claim that generated 5 much stimulating debate and continues to do so unabated. 6 Most recently, the attention has extended to species with quadruple bond patterns between carbon and other elements such as C⩸Fe 7 or related main group elements with similar four-fold bond characteristics as in B⩸Rh 8 or Si⩸Rh. 9 Such diverse reports raise the distinct possibility that room temperature/solution studies of species containing quadruple bonds to carbon will become possible and perhaps even routine.…”

Section: Introductionmentioning

confidence: 99%

Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2.

Rzepa

2021

Preprint

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Recent lively debates about the nature of the quadruple bonding in the diatomic species C2 have been heightened by recent suggestions of molecules in which carbon may be similarly bonded to other elements. The desirability of having methods for generating such species at ambient temperatures and in solution in order to study their properties may have been realized by a recent report of the first chemical synthesis of free C2 itself under mild conditions. The method involved unimolecular fragmentation of an alkynyl zwitterion 2 as generated from the precursor 1, resulting in production and then trapping of free C2 at ambient temperatures rather than the high temperature gas phase methods normally employed for C2 generation. Here, alternative mechanisms are proposed for this reaction based on DFT calculations involving bimolecular 1,1- or 1,2-iodobenzene displacement reactions from 2 directly by galvinoxyl radical, or hydride transfer from 9,10-dihydroanthracene to 2. These mechanisms result in the same trapped products as observed experimentally, but unlike that involving unimolecular generation of free C2, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 vs 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns. The same mechanism also provides an energetically facile path to polymeric synthesis of carbon rich species by extending the carbon chain attached to the iodonium group, eventually resulting in formation of amorphous carbon and discrete molecules such as C60.<div><div> </div></div>

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Section: Introductionmentioning

confidence: 99%

Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2.

Rzepa

2021

Preprint

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Trapping experiments were claimed to demonstrate the first chemical synthesis of the free diatomic species C2 at room temperatures, as generated by unimolecular fragmentation of an alkynyl iodonium salt precursor. Alternative mechanisms based on DFT energy calculations are reported here involving no free C2, but which are instead bimolecular 1,1- or 1,2-iodobenzene displacement reactions from the zwitterionic intermediate 11 by galvinoxyl radical, or by hydride transfer from 9,10-dihydroanthracene. These result in the same trapped products as observed experimentally, but unlike the mechanism involving unimolecular generation of free C2, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 vs 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns and the same mechanism also provides an energetically facile path to polymerisation by extending the carbon chain attached to the iodonium group, eventually resulting in formation of species such as amorphous carbon and C60.<div> <div> </div></div>

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Transition metal carbon quadruple bond: viability through single electron transmutation

Abstract: Quadruple bonding to main group elements is extremely rare although they have four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between carbon atom and a...

Cited by 22 publications

References 31 publications

Is There a Quadruple Fe-C Bond in FeC(CO)3?

Is There a Quadruple Fe-C Bond in FeC(CO)3?

Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2.

Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2.

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