VICINAL N,N INTERACTIONS IN N-CHLORO SUBSTITUTED DIAZIRIDINES AND OXAZIRIDINES - PHOTOELECTRON-SPECTRA AND ELECTRONIC-STRUCTURES

The He(I) photoelectron spectra of five bicyclic N-chlorodiaziridines (6-10) and three N-chlorooxaziridines (14-16), as well as of the corre sponding N-H compounds (1-5 and 11,13), have been recorded and analyse d using AM1 calculations. The N-chlorodiaziridines show exo-endo isome rism; however, only one endo isomer (10a) is sufficiently stable for t he measurement. The N-chlorooxaziridines are more stable than their N- H precursors. The compounds are characterized by three non-bonding orb itals n(NN)(+), n(NN)(-) and n(Cl) (N-chlorodiaziridines); n(NO)(-) n( Cl) and n(O) (N-chlorooxaziridines). These orbitals give rise to the f irst three ionization bands of the compounds. The energy separation of the two n(NN) MOs of the exo isomers 6b-10b (Delta epsilon approximat e to 0.3 eV) is smaller than in the corresponding N-H compounds 1-5 (D elta epsilon approximate to 0.6 eV), while in the endo isomer 10a (Del ta epsilon approximate to 1.2 eV) it is larger than in 5. In the oxazi ridines, replacement of the hydrogen atom by a chlorine atom leads to a small stabilization of the n(O) orbital. These findings can be inter preted by vicinal n(X)/sigma(N-Hal) interactions (X = N or O).