Synthesis and spectroscopy of tricyclo[3.3.3.03,7]undec-3(7)-ene: confirmation of computational predictions regarding the effects of pyramidalization on alkene ionization energies and electron affinities
Abstract:We have reported the syntheses of the n = 11 and 22 members of a homologous series of pyramidalized alkenes (l),3 their spectroscopic study in matrix isolation,4-5 and some of their chemistry.6 The generation of a benzo derivative of 1, n = 2,7 and a bis-ethano derivative of the n = 0 member of this series have also been described.8 In this communication we report the synthesis and some spectroscopy of 1, n = 3.
“…In order to examine the dependence of the 13 C NMR chemical shift of non-isolable, highly pyramidalized alkenes on the level of theory, calculations were performed for (i) two highly pyramidalized but isolable compounds: 1,16-dodecahedradiene (pyramidalization angle, 1a Φ = 39.9Њ), 1, 3a and hexacyclo-[6.5.1.0 2,7 .0 4,12 .0 5,10 .0 9,13 ]tetradec-9(13)-ene-3,6-dione (Φ = 46.5Њ), 2; 20 (ii) the less pyramidalized alkenes tricyclo[3.3.3.0 3,7 ]undec-3(7)-ene (Φ = 28.1Њ), 3, 8 and bicyclo[3.3.0]oct-1(5)-ene (Φ = 5.9Њ), 4, 21 and (iii) the non-pyramidalized but highly strained bicyclo[2.2.0]hex-1(4)-ene, 5, 22 (Fig. 1).…”
Section: Resultsmentioning
confidence: 99%
“…7 Ab initio methods are a powerful tool for predicting properties of unstable compounds and many computational predictions carried out on pyramidalized alkenes have experimentally been confirmed. 8 The calculation of NMR chemical shifts constitutes an important challenge for computational chemistry and during the last decade significant progress has been made in this field. 9 This work reports a DFT study of 13 C NMR chemical shifts of several pyramidalized alkenes using the GIAO method.…”
“…In order to examine the dependence of the 13 C NMR chemical shift of non-isolable, highly pyramidalized alkenes on the level of theory, calculations were performed for (i) two highly pyramidalized but isolable compounds: 1,16-dodecahedradiene (pyramidalization angle, 1a Φ = 39.9Њ), 1, 3a and hexacyclo-[6.5.1.0 2,7 .0 4,12 .0 5,10 .0 9,13 ]tetradec-9(13)-ene-3,6-dione (Φ = 46.5Њ), 2; 20 (ii) the less pyramidalized alkenes tricyclo[3.3.3.0 3,7 ]undec-3(7)-ene (Φ = 28.1Њ), 3, 8 and bicyclo[3.3.0]oct-1(5)-ene (Φ = 5.9Њ), 4, 21 and (iii) the non-pyramidalized but highly strained bicyclo[2.2.0]hex-1(4)-ene, 5, 22 (Fig. 1).…”
Section: Resultsmentioning
confidence: 99%
“…7 Ab initio methods are a powerful tool for predicting properties of unstable compounds and many computational predictions carried out on pyramidalized alkenes have experimentally been confirmed. 8 The calculation of NMR chemical shifts constitutes an important challenge for computational chemistry and during the last decade significant progress has been made in this field. 9 This work reports a DFT study of 13 C NMR chemical shifts of several pyramidalized alkenes using the GIAO method.…”
“…D e vs π is relatively constant for 2 − 5 . Simple empirical relationships between the binding energies of metal−olefin complexes and various HOMO−LUMO energies have been discussed previously. ,,, 4 Binding energies (kJ mol -1 ) of complexes 1 − 5 plotted against (a) d and b , (b) d / b , (c) π and π* energy of olefin, (d) the pyramidalization angles in the complex and in the free alkene, and (e) olefin strain energy.…”
Density functional theory and high-level ab initio molecular orbital methods have been
used to investigate complexes of platinum with highly pyramidalized olefins: Pt(PH3)2(R)
with R = C11H16, C10H14, C9H12, and C8H10. Geometries and binding energies are reported
and compared to experimental values where available. Charge decomposition analyses have
been carried out for all complexes, and they show a beautiful increase in olefin←Pt back-donation as the olefin becomes more pyramidal. Natural bond orbital analyses show a
corresponding increase in the platinum 6s and carbon 2s character in the Pt−C bond orbital,
in agreement with previous NMR studies. We also find that the binding energies of all the
complexes correlate well with the olefin strain energies calculated for the free olefins.
“…The situation is reverse for the pyramidalized alkene tricyclo [3.3.3.03,7]undec-3(7)-ene, where the positive ion is destabilized by 0.31 eV with respect to the reference compound bicyclooctene, whereas the negative ion is stabilized by 0.7 eV by pyramidalization of the CQC bond. 11 A final finding, not related to chemical reactivity but interesting from the point of view of electron scattering, is the large dependence of the magnitude of the elastic cross sections around 0.5 eV on structure, the cross section of TCO being about 45% larger.…”
Section: Discussionmentioning
confidence: 97%
“…The present work is related to the electron impact spectroscopy study of the effect of pyramidalization on the CQC bond. 11 analyzers to improve resolution, which was 16 meV (in the energy-loss mode), at an electron beam current of 300 pA. The energy scales are accurate to within AE10 meV.…”
The effect which deformation of the double bond in trans-cyclooctene (TCO), compared to cis-cyclooctene (CCO), has on its negative ion - and indirectly on the π* virtual orbital - was studied by electron-impact spectroscopy. Differential elastic and vibrational excitation cross sections were measured at a scattering angle of θ = 135°. The vertical attachment energy (VAE) derived from the vibrational excitation spectra is 1.87 eV in TCO, only 0.09 eV lower than in the unstrained CCO, 1.96 eV. The substantial deformation of the C[double bond, length as m-dash]C bond in TCO thus stabilizes its transient negative ion by a surprisingly small amount and this effect is ascribed in part to the Pauli (steric) destabilization of the TCO π* orbital by the alkyl chain facing the π* lobes. An interesting effect is observed in the elastic cross section which is about 45% larger for TCO at low energies (∼0.4 eV), despite the similar geometrical size of the two molecules. Ramsauer-Townsend minima are observed in the elastic cross section at 0.13 and 0.12 eV for CCO and TCO, respectively. Implications of the findings on enhancement of the dienophile capacity of TCO are discussed.
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