A theoretical study of the lowest-energy singlet and triplet electronic states p-iminophosphaalkyne and nitrilimine

Kuhler, Kathleen; Palmer, Roger T.; Wittkamp, Brian L.; Hoffmann, Mark R.

doi:10.1016/0166-1280(95)04356-x

Cited by 6 publications

(3 citation statements)

References 21 publications

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“…These can be considered as conservative estimates, which also account for the approximations made and for neglecting higher-order correlation effects. From Tables 1, 2, 3, 4 and 5, it is evident that all isomers considered have been previously studied at different levels of theory [11,[41][42][43][44][45][46][47][48], but we report the first systematic investigation of their molecular structure. As in most cases the method and/or the basis set used are inferior to ours, a detailed comparison of these results to ours is not too meaningful.…”

Section: Molecular Structurementioning

confidence: 97%

A theoretical study on CH2N2 isomers: structure and energetics

Puzzarini

Gambi

2012

Theor Chem Acc

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Five CH2N2 isomers, namely cyanamide, carbodiimide, diazomethane, isocyanamide and nitrilimine, have been investigated at a high level of accuracy. The singles and doubles coupled-cluster method including a perturbational correction for connected triple excitations, CCSD(T), in conjunction with correlation-consistent basis sets ranging in size from triple to quintuple zeta have been employed. Extrapolation to the complete basis set limit has been used with treatments of core-valence correlation effects in order to accurately predict structures, relative energies as well as N-H and C-H bond dissociation energies. The latter required to also investigate the HNNC radical with the same methodology used for CH2N2 isomers, while HCNN and HNCN data are available in the literature by the same authors (Puzzarini and Gambi in J Chem Phys 122:064316, 2005). For all the species studied, harmonic vibrational frequencies have also been evaluated at the CCSD(T) level in order to obtain zero-point corrections to total energies

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Section: Molecular Structurementioning

confidence: 97%

A theoretical study on CH2N2 isomers: structure and energetics

Puzzarini

Gambi

2012

Theor Chem Acc

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“…Employing resonance theory, Huisgen (28) explained the observed [3+2] reactivity in nitrilimines and related systems, and generalized the 1,3-dipole concept. For nitrilimines, sev-eral resonance structures have been invoked to explain their reactivity and electronic structure (Scheme 1) (28)(29)(30)(31). In his original formulation, Huisgen (28) suggested that the electron sextet structures, the dipolar (RS-D) and carbenic (RS-C) forms, make only small contributions to the electronic structure of any 1,3-dipole owing to the lack of octet stabilization, but it was still this minor contribution that directed the course of reaction.…”

Section: Introductionmentioning

confidence: 99%

A computational study of the 1,3-dipolar cycloaddition reaction mechanism for nitrilimines

Mawhinney¹,

Muchall²,

Peslherbe³

2005

Can. J. Chem.

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The [3+2] and [1+2] cycloaddition pathways between ethene and a series of 13 nitrilimines (R1CNNR2) have been examined by density functional theory [PBE0/6-311++G(2df,pd)] calculations. All reactions have low barriers ranging from 14.14 (R1 = CH3, R2 = H) to 1.01 (R1 = R2 = F) kcal mol1, and large reaction exothermicities consistent with the transient nature of nitrilimines. The [3+2] and [1+2] transition-state structures are very similar, mainly differing in the relative orientation of their fragments and the newly forming CC bond distance, and exhibit only minor deviations from the structures of the reactants. Both reaction pathways are concerted and asynchronous, but the [1+2] reaction has a greater degree of asynchronicity. Examination of the frontier molecular orbitals reveals that both the [3+2] and [1+2] barrier heights are related to two sets of orbital interactions, with the interaction between the lowest unoccupied molecular orbital π [Formula: see text] of nitrilimine and the highest occupied molecular orbital of ethene in common. The second interaction in both cases is carbene-like. A relationship between the weights of the 1,3-dipolar resonance contribution in the various nitrilimines and the corresponding [3+2] barrier heights was not found, but a good correlation could be found between the [1+2] barrier heights and both the 1,3-dipolar and carbene contributions. Inspection of the potential energy surface in the vicinity of the two transition states for the reaction between unsubstituted nitrilimine and ethene suggests that the observed [3+2] product is a result of an initial carbene-like approach of the two fragments followed by a ridge bifurcation that leads to the [3+2] product minimum. Key words: nitrilimines, 1,3-dipole, carbene, [3+2] cycloaddition, [1+2] cycloaddition, density functional theory (DFT).

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“…Much theoretical work has been devoted to the study of the bonding nature of 1,3-dipolar cycloadditions . On the contrary, Bertrand and co-workers showed by X-ray structural analyses that all stable nitrile imines prepared in the 1990s possess bent, helical backbones. − Many theoretical studies have been undertaken on equilibrium geometries and vibrational spectra for some substituted nitrile imines including formonitrile imine to explain available experimental data. − To the best of our knowledge, however, no theoretical research has been undertaken to elucidate why the C–N–N moiety in nitrile imines examined does not take a linear structure, but a bent structure. Our concern for nitrile imines is to explicate what occurs inside the molecule as it undergoes a pseudo-Jahn–Teller (JT) distortion from a symmetrical structure to a less symmetrical structure with a bent C–N–N moiety. − Our results obtained so far suggest that non-nearest neighbor interactions are important in such structural changes that the molecules bend their molecular skeletons. − This is because, with skeletal bending, the nuclei and electron clouds are brought spatially close to each other and, concomitantly, the electrostatic interactions between them are greatly affected.…”

Section: Introductionmentioning

confidence: 99%

Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN₂–R: Energy Component Analysis of the Pseudo-Jahn–Teller Effect

2017

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Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN-R (R = Li, BeH, BH, CH, CN, CCH, CH, NH, OH, and F) (2-11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn-Teller (JT) distortion from a linear C structure to a C structure via a planar bent C structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent C structure for 2, 3, and 7 and to a C structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1-11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, energy component analyses were carried out at the MCSCF+SOCI level of theory at all of the stationary structures for the relevant molecules. In most of the molecules examined, pseudo-JT stabilizations were classified into two groups, one in which the stability arises from a lowering of the energy of the attractive term V and the other in which the stability results from a lowering of the energy of the repulsive terms V and V. In addition to the above two groups, it was also found that the following three groups are responsible for the pseudo-JT stabilizations in a certain stage of the structural changes. Namely, one is a lowering of the energy of the term V observed in 6, another is a lowering of the energy of the terms V and V observed in 9-11, and the other is a lowering of the energy of the terms V and V observed in 10. These energetic behaviors were accounted in terms of an elongation or a contraction of the molecular skeleton, a migration of electrons from one part of the molecule to other parts, and the combined effects arising from these two factors.

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A theoretical study of the lowest-energy singlet and triplet electronic states p-iminophosphaalkyne and nitrilimine

Cited by 6 publications

References 21 publications

A theoretical study on CH2N2 isomers: structure and energetics

A theoretical study on CH2N2 isomers: structure and energetics

A computational study of the 1,3-dipolar cycloaddition reaction mechanism for nitrilimines

Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN₂–R: Energy Component Analysis of the Pseudo-Jahn–Teller Effect

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A theoretical study of the lowest-energy singlet and triplet electronic states p-iminophosphaalkyne and nitrilimine

Cited by 6 publications

References 21 publications

A theoretical study on CH2N2 isomers: structure and energetics

A theoretical study on CH2N2 isomers: structure and energetics

A computational study of the 1,3-dipolar cycloaddition reaction mechanism for nitrilimines

Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN2–R: Energy Component Analysis of the Pseudo-Jahn–Teller Effect

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Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN₂–R: Energy Component Analysis of the Pseudo-Jahn–Teller Effect