1-Piperidinecarbonitrile in tetrahydrofuran (THF) reacts with a solution of piperidyl lithium in THF at 0°C to yield lithium[1,1,3,3-bis(pentamethylene)guanidinate]. It participates in thermal decomposition of the 2H-azaphosphirene metal complexes to yield the Δ3-1,3,2-oxazaphospholene complexes and the Δ3-1,3,2-thiazaphospholene complexes.