Vibrational spectrum, structure, and energy of [1.1.1]propellane

Abstract

The structure of [l.l.l]propellane (bond lengths and angles) was determined from an analysis of the rotational components of the infrared bands of the parent compound and of its d6 derivative, and it was found to be in good agreement with the structure calculated including electron correlation. The central C-C bond length was 1.60 ± 0.02 Á which is ~0.09 Á longer than that in cyclopropane. The infrared and Raman spectra were obtained and are in good agreement with the calculated spectrum. A constrained adjustment of the calculated force field gave a set of "best" force constants. The stretching force constant for the central C-C bond was found to be about the same as that for the symmetric combination of the other C-C bonds. The intensities of the infrared bands were determined and were converted to dipole moment derivatives. The relationship of the derivatives to the charge distribution is discussed. The enthalpy of formation of the propellane was estimated from

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 6: Propellanes

“…1 On the other hand, many arguments derived mainly from spectral studies, including those of classical vibrational spectroscopy, 24,25 low-energy electron impact spectroscopy, 26 photoelectron spectroscopy 27 and electron momentum spectroscopy, 28,29 lead to the conclusion that the bridgehead-bridgehead bond in propellane should be interpreted as an ordinary chemical bond, but with inverted bonding hybrids. In the last study, 29 the complete valence electronic structure of propellane was reported and the resulting wavefunction was determined, which enabled the authors to derive a number of its molecular properties, confirming, in particular, the physical existence of the central bridgehead-bridgehead bond with a 0.70 bond order (very similar to that of 0.73 derived by Wiberg et al 10 ). The strength of this 'bond phantom' was estimated to be ca 60 kcal mol 1 , 30 whereas according to NBO analysis 31 the occupancy of the central bonding orbital is 1.83 and that of the antibonding orbital is 0.15.…”

“…8 In spite of its remarkable deviation from tetrahedral geometry characterized by inverted carbons at bridgeheads and considerable steric strain of 98 kcal mol 1 (1 kcal D 4.184 kJ), 9 propellane was found to be surprisingly stable. 10 The relatively high chemical stability of propellane was explained 7 by the fact that breaking of the central bridgehead-bridgehead bond releases only less than one-third of its strain energy while breaking of the peripheral carbon-carbon bond is symmetryforbidden. Higher propellanes with enlarged fused rings have also received a good deal of attention and it was a challenging task to apply the second-order polarization propagator approach (SOPPA) 11 to calculate carbon-carbon spin-spin coupling constants, J(C,C), in the series of propellanes 1-6 in continuation of our previous communications dealing with the three-membered rings, symmetries are given in Table 1.…”

“…[1.1.1]Propellane (1) As follows from the pioneering non-empirical calculations by Newton and Schulman 20 (performed long before the propellane itself had been synthesized), and from more recent studies by Wiberg and co-workers 10,21 and many others, 22,23 the bridgehead-bridgehead bond of propellane shows an essentially antibonding nature because the bonding electron density and electrostatic potential are 'inverted', i.e. directed out of the molecule along the C 1 -C 3 axis.…”

Bis‐ through Tetrakis‐Adducts of C60 by Reversible Tether‐Directed Remote Functionalization and systematic investigation of the changes in fullerene properties as a function of degree, pattern, and nature of functionalization

“…Although of a relatively short distance, the fusion bond in the cyclopropane rings is subject to considerable variation as observed in the X-ray crystal structure of 11 (Sect. 2.2) and could possibly be considered a weaker than normal C-C bond, as had been discussed for [I .I .l]propellane [42]. Actually, the effective bridgehead or fusion C-C single-bond strength in both [l.l.l]propellane as well as in 6-6-closed methanofullerenes seems not to be established.…”

Interplay of Thermochemistry and Structural Chemistry, the Journal (Volume 13, 2002) and the Discipline

“…Surprisingly, there are almost no thermochemical data for any propellane except for reaction calorimetry for the simplest one, the triple cyclopropane [1.1.1] species [90], and the likewise cyclopropane-containing [3.2.1] species [91]. Even more surprisingly, calorimetric data for species with two or more cyclic ester groups (i.e.…”