Isolable Adducts of Tertiary Amines and Dinitrogen Trioxide

Anhydrous dinitrogen trioxide, N 2 O 3 , dissolved in toluene or dichloromethane rapidly forms stable adducts with tertiary amines such triethyl‐, tribenzyl‐, or trihexyl‐amine. With DABCO, 1,4‐diazabicyclo[2.2.2]octane it forms a free flowing orange solid. The analytical and spectroscopic data for the DABCO adduct indicate a formula of DABCO(N 2 O 3 ) 2 which has been characterized by IR, Raman, and UV/Vis spectroscopy. The R 3 N‐N 2 O 3 adducts are hydrolytically sensitive oils or solids which rapidly react quantitatively with thiols to give RSNO. The reactivity of the amine adducts is variable, and the products include amine N ‐oxides, ammonium nitrites, and ammonium nitrates depending upon the adduct, conditions, and substrate. Density functional theory, B3LYP/aug‐cc‐pvtz, has been used to compare the predicted structures and spectroscopic data for mono and bis adducts. Geometry optimization of the R 3 N N 2 O 3 adduct gives a weakly bound Lewis acid/base adduct with the amine nitrogen closest to the nitrosyl N with a strongly tilted planar ONNO 2 unit.