Through-bond interactions in nonconjugated dienes and diones

7321

J . Am. Chem. SOC.1985, 107, 7321-7323

Through-Bond Interactions in Nonconjugated Dienes and Diones V. Balaji,+ K. D. Jordan,*+ Rolf Gleiter,$ Gerhard Jahne,t and Georg Muller1 Contribution f r o m the Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and the Institut f u r Organische Chemie der Unicersitat, Heidelberg, West Germany. Received June 28, 1985

Abstract: Electron transmission spectroscopy is utilized to determine the vertical electron affinities associated with electron capture into the a* orbitals of a series of nonconjugated dienes and diones. Those compounds in which the a groups are separated by three u bonds show particularly large through-bond interactions resulting in inverted (Le., a_*below a+*)ordering of the a* orbitals.

The interactions between the a orbitals of the dienes 1-3 and between the lone-pair (n) orbitals of the corresponding diketones 4-6 have been studied’ by utilizing photoelectron spectroscopy (PES) and theoretical calculations. PES yields the ionization potentials, which, according to Koopmans’ theorem (KT),2 may be associated with the negatives of the energies of the filled orbitals. These studies show that the splittings between the a+ and aorbitals of 1-3 and between the n+ and n- lone-pair orbitals of 4-6 (where the “+” denotes the bonding combination and the antibonding combination of the localized orbitals) increase along

Table I. Experimental Electron Attachment Energies and Splittings between the a* Orbitals of 1-6 compd exptl/AE’s (eV) exptl splitting” calcd split tin^'

I

1.38

2

1.55

3 4

5 6

1.18, 2.15 0.45, 1.10’ 0.54, 0.91 SO, 1.37

-0.93 0.65 -0.37