Cyclotetraphosphazanes2and5obtained from 1,2-diamines are 1,3,2-diazaphosphole oligomers leading to the monomeric form by either thermal equilibrium or by complexing with boron trifluoride. The dicoordinated form stabilized by an orthophenylene ring could explain the reactivity of 4,5-benzo 1,3,2-diazaphosphole3with compounds having a mobile hydrogen; these reactions were a 1.2 type addition while butanol led to a 1.1 type addition with complexed 1,3,2-diazaphospholes4and8.