The conformation and molecular structure of a 6,7-diazabicyclo[3.2.0] hept-6-ene derivative: a gas-phase electron diffraction study of perfluoro-(1,5-dimethyl-6,7-diazabicyclo[3.2.0] hept-6-ene)

Abstract

The molecular structure of perfluoro-(1,5-dimethyl-6,7-diazabicyclo[3,2,0]help-6-ene) has been studied using gas-phase electron diffraction data collected on the Balzers KDG2 instrument at UMIST. The data are compatible with C 1 endo model (boat conformation) with −CF 3 groups in independent orientations. Apart from the −CF 3 groups the symmetry is C s. The preferred refinement gave CC distances in the range 1.51–1.57 Å with the longer ones including CCF 3. The ring flap angles are 109.5(9)° across the bridge bond and 143.7° for the five-membered ring. The latter has ring torsion angles of 0, ±36 and ±24° and ∠CCC angles in the range 98–107°, while in the planar four-membered ring ∠NNC = 96.3° and ∠NCC = 83.7°with CN = 1.53(1)° and NNN = 1.17(2)». The NCCF torsion angles for corresponding F atoms of the —CF 3 groups are + 76(1) and − 21(1)°. Other parameters include CF(mean) = 1.346(2)Å, ∠NCC(F 3) = 119.8(12)°, ∠CCF(CF 3) = 111.6(5)°, ∠FCF(CF 2) = 112.7(7)° and torsion angle NNCC(F 3) = ±121.4(3)°. The geometrical parameters are similar to those of related molecules, with the principal influence of fluorination probably being the short NN bond.