Click reactions of 2H-azaphosphirene chromium and molybdenum complexes and a surprisingly facile access to a 2H-1,4,2-diazaphosphole derivative

► Ring expansion reactions of 2H-azaphosphirene chromium and molybdenum complexes. ► Synthesis of 2H-1,4,2-diazaphosphole complexes. ► N-Protonation of the ligand lead to a weakening of the P,Cr and P,Mo bonds. ► An N-protonated 2H-1,4,2-diazaphosphole derivative was isolated. ► Results from NMR spectroscopic and X-ray diffraction studies are reported.