Inspired by our ML results, we investigate the relationships further from a chemical standpoint. Carbenes in the singlet state have an sp 2 hybridized lone pair of electrons and an empty atomic p orbital in their valence shell. The structures of diazo compounds can be explained by sharing of the lone pair of the N 2 dimer with the empty atomic p orbital of the carbene. Conversely, the lone pair of carbenes overlaps with the π * orbital of molecular nitrogen (Scheme 3(a)).