The fundamental aminophosphines have the formulae PH(NH) (n = 1, 2, 3).  These species cannot be isolated in a practical quantities, although they have been examined theoretically.  HNPH is predicted to be more stable than the P(V) tautomer HN=PH.
With secondary amines, the chemistry is more straightforward.  Trisaminophosphines are prepared by treatment of phosphorus trichloride with secondary amines:
:PCl  +  6 HNMe   →   (MeN)P  +  3 [HNMe]Cl