EFFECTS OF CNN BOND ANGLE RESTRICTION IN 2,3-DIAZABICYCLO[2.1.1]HEXANE DERIVATIVES ON NITROGEN INVERSION BARRIER, EASE OF OXIDATION, AND ACIDITY

Restriction of the CNN angle of triazolidinedione 3 by the presence of the diazabicyclo[2.1.1]hexyl system causes the nitrogens to be more pyramidal than tetrahedral (alpha(av) for crystalline 3 is 109.2-degrees) and produces a double nitrogen inversion barrier of 8.7 kcal/mol at-72-degrees-C in CD2Cl2. Although the pyramidality at N in tricyclic triazolidinedione derivatives experimentally lies near the prediction by PM3 semiemprical calculations, such calculations give barriers to double nitrogen inversion that are considerably too high. The effect of enlarging the size of the fused bicyclic system on ease of oxidation was determined: 3, E-degrees' + 1.77 V [VIP = 8.77 eV]; 5, 1.53 [8.68]; 6, 1.32 [8.60]; 7, 1.32 [8.15]; 8, 1.31 [7.90]. VIP values for azo compound 4 from PE spectroscopy are 9.3, 11.1, and 12.1 eV. The acidity of protonated bicyclic azo compounds varies 5.1 pK units between 4 (pK(a) -2.1) and 12 (pK(a) + 3.0).