Spectroscopic Evidence for Aminomethylene (H-C̈-NH₂ )-The Simplest Amino Carbene

Although N-heterocyclic carbenes have been well-studied, the simplest aminocarbene, aminomethylene H-C̈-NH₂ , has not been spectroscopically identified to date. Herein we report the gas-phase preparation of aminomethylene by high-vacuum flash pyrolysis of cyclopropylamine and subsequent trapping of the pyrolysate in an inert argon matrix at 12 K. Aminomethylene was characterized by matching matrix IR and UV/Vis spectroscopic data with ab initio coupled cluster computations. After UV irradiation of the matrix aminomethylene rearranges to its isomer methanimine (formaldimine) H₂ C=NH. Based on our experimental results and computations aminomethylene has a singlet ground state with a reaction barrier of almost 46 kcal mol^-1 to methanimine so that H-tunneling is excluded.