Computational Study of the Thermochemistry of C5H5+ Isomers:  Which C5H5+ Isomer Is the Most Stable?

Glukhovtsev, Mikhail N.; Bach, Andreas; b, Sergei Laiter

doi:10.1021/jp961134v

Cited by 43 publications

(30 citation statements)

References 23 publications

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“…For 2 we previously calculated a value of À14.3 kcal mol À1 at the CASPT2A C H T U N G T R E N N U N G (14,15)/[4s3p2d/3s1p]// OLYP/TZ2P level, [8] and values in the range from À2.9 to À10.6 kcal mol À1 have been found with G2, CCSD(T), MPn, and B3LYP calculations. [2,39,[41][42][43]53] The OLYP/6-311GA C H T U N G T R E N N U N G (d,p) DE ST value for 2 is thus well within the expected interval.…”

mentioning

confidence: 53%

“…This feature was first discussed by Borden and Davidson, [40] and later by others. [39,[41][42][43][44][45] Recently, a photoelectron spectroscopic study has confirmed the quasidegeneracy of the two singletstate structures. [46] At the OLYP/ 6-311GA C H T U N G T R E N N U N G (d,p) level the first (2 s) has C 2v symmetry, while the second (2 s') has C 2 symmetry with a C 2v -symmetric transition state located 0.6 kcal mol À1 above.…”

Section: Singlet-state Geometriesmentioning

confidence: 94%

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Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

2008

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The pi contribution to the electron localization function (ELF) is used to compare 4npi- and (4n+2)pi-electron annulenes, with particular focus on the aromaticity of 4npi-electron annulenes in their lowest triplet state. The analysis is performed on the electron density obtained at the level of OLYP density functional theory, as well as at the CCSD and CASSCF ab initio levels. Two criteria for aromaticity of all-carbon annulenes are set up: the span in the bifurcation values DeltaBV(ELF(pi)) should be small, ideally zero, and the bifurcation value for ring closure of the pi basin RCBV(ELF(pi)) should be high (> or = 0.7). On the basis of these criteria, nearly all 4npi-electron annulenes are aromatic in their lowest triplet states, similar to (4n+2)pi-electron annulenes in their singlet ground states. For singlet biradical cyclobutadiene and cyclooctatetraene constrained to D4h and D8h symmetry, respectively, the RCBV(ELF(pi)) at the CASSCF level is lower (0.531 and 0.745) than for benzene (0.853), even though they have equal proportions of alpha- and beta-electrons.

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mentioning

confidence: 53%

Section: Singlet-state Geometriesmentioning

confidence: 94%

Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

2008

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“…This fragment ion has an apparent D f H = 12.67 ± 0.10 eV. Five isomers of C 5 H þ 5 are known either experimentally or on the basis of calculations [35,77]. In our case the m/z = 65 ion is most probably HC"CCHCH@CH þ 2 (Pent-1-en-4-yn-3-yl radical ion) which has a reported D f H = 11.73 eV [29].…”

Section: Benzimidazole C 7 H 6 Nmentioning

confidence: 99%

VUV photophysics and dissociative photoionization of pyrimidine, purine, imidazole and benzimidazole in the 7–18eV photon energy range

et al. 2008

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“…Selected bond lengths [] and angles [8] for the second independent molecule in the unit cell (P(6) is the apical phosphorus atom): P(4)ÀC (16) + ion than a square-basedpyramidal structure. [18,19] These observations encouraged us to survey systematically the potential-energy surface (PES) of the model cation [C 2 H 2 P 3 ]…”

Section: Dedicated To Professor Manfred Regitzmentioning

confidence: 99%

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

et al. 2003

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Selective Preparation of the [3, There has been significant progress in the chemistry of transition-metal complexes carrying the h 5 -3,5-tBu 2 -1,2,4-C 2 P 3 ligand.[1] Although the isolobal relationship PMCH and diagonal relationship P/C suggest that complexes carrying this ligand should behave like the corresponding h 5 -cyclopentadienyl-substituted analogues, recent work has shown that the phosphorus-containing systems exhibit subtle differences in both bonding and reactivity. [2][3][4] This situation suggests that further investigations could be rewarding. In a new approach to this chemistry we focused on the reactivity of the interesting tricyclic C 2 P 3 compound 1 (Scheme 1), first reported by Regitz et al.[5] First, we used this species as a convenient starting point for a new selective synthetic approach to the aromatic ion [3,5-tBu 2 -1,2,4-C 2 P 3 ] À (3). Second, and again reflecting on the consequences of replacing CH groups by isolobal P atoms, we explored the possibility of utilizing 1 as a precursor to cations [C 2 tBu 2 P 3 ]+ . The published synthetic pathways to the anion 3, [6][7][8] which derive from earlier work by Becker et al., [9,10] involve reaction of PCtBu with alkali metals (M). However, this procedure is unselective, and to obtain pure 3 it is necessary to repeatedly recrystallize the moisture-sensitive alkali-metal salts to remove the second product of these reactions, the [2,4,5-tBu 3 -1,3-C 3 P 2 ]À ion. Therefore, we recognized that if the full potential of this area was to be realized, it was important to devise a more efficient and selective pathway to 3. We reasoned that if the tricyclic compound 1, which is readily formed in good to excellent yield by treating the readily accessible zirconium complex 2 with PCl 3 , [5] was treated with an alkali metal in THF, the anionic species A should be generated (Scheme 1). We then hypothesized that such a species should undergo consecutive ring-opening reactions (A!B!3) and thus selectively provide the desired anion.Reaction (RT, 2 h, THF) of 1 with Li or Na metal leads to quantitative formation of the lithium or sodium salt of 3, which confirms our ring-opening hypotheses. Both Li·3 and Na·3 react quantitatively with Ph 3 SnCl to give the known compound 3,5-tBu 2 -1-SnPh 3 -1,2,4-C 2 P 3 (4), which has been shown to be a valuable reagent for the syntheses of complexes of the h 5 -C 2 P 3 ligand. [7] We believed that 1 might react with Lewis acids to provide an entry point to the cationic [C 2 tBu 2 P 3 ] + manifold, related to the isoelectronic pentamethylcyclopentadienyl cation, a species that has recently attracted considerable attention. [11][12][13][14][15] In particular, in view of the isolobal relationship PMCH, and Scheme 1. a) PCl 3 ; b) M, THF, ÀMCl; c) Ph 3 SnCl, ÀMCl (* = CtBu; .. = lone pair; M = Li, Na.

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Computational Study of the Thermochemistry of C₅H₅⁺ Isomers: Which C₅H₅⁺ Isomer Is the Most Stable?

Cited by 43 publications

References 23 publications

Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

VUV photophysics and dissociative photoionization of pyrimidine, purine, imidazole and benzimidazole in the 7–18eV photon energy range

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

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Computational Study of the Thermochemistry of C5H5+ Isomers: Which C5H5+ Isomer Is the Most Stable?

Cited by 43 publications

References 23 publications

Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

Triplet‐State Aromaticity of 4nπ‐Electron Monocycles: Analysis of Bifurcation in the π Contribution to the Electron Localization Function

VUV photophysics and dissociative photoionization of pyrimidine, purine, imidazole and benzimidazole in the 7–18eV photon energy range

Selective Preparation of the [3,5‐tBu2‐1,2,4‐C2P3]− Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu2‐1,2,4‐C2P3]+, Isoelectronic with [C5R5]+

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Computational Study of the Thermochemistry of C₅H₅⁺ Isomers: Which C₅H₅⁺ Isomer Is the Most Stable?

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺