Experimental evidence for gaseous diaminocarbene H2NCNH2 and its radical cation

Dissociative electron impact ionization of aminoguanidine, HNC(NH2)NHNH2 cleanly produces diaminocarbene radical cations H2NCNH+2. Their reduction by single electron transfer in neutralization—reionization mass spectrometric experiments yields the prototype nucleophilic carbene H2NC̈NH2 as a stable species in the gas phase, distinct from its isomer formamidine, H2NC(H)NH. Deuterium labelling and multiple collision experiments confirm the identities of the ions and neutrals. The experimental findings are in excellent agreement with the results of ab initio calculations. Computations using GAUSSIAN-2 (G2) theory lead to ΔH0f(H2N-C̈-NH2)=39.4 kcal/mol and ΔH0f(H2NCNH+2) = 211 kcal/mol.