The new atnino-cyclophosphine (CH3) &PC4H8 (liquid, b p. est. 170') was made from (CH8) 2NPC12 and BrMgC4HsMgBr. It forms a 1: 1 adduct with CHaI and reacts with 2HC1 to make C4HSPC1 (liquid, bp est. 165'), reconvertible to (CH3) 2-NPC, H, by reaction with 2 (CHa) zNH. The slightly volatile liquid adduct (CH~)~ NPC~ HR. BH~ on heating forms the new cyclic C4HsPH (30% yield; mp-S8O; bp est. 105'), aminoborines and a trace of the ...