Correlated molecular orbital theory at the coupled cluster CCSD(T) level with augmented correlation consistent basis sets including F12 explicit correlation has been used to predict the structure and energetic properties of the isomers of [C,N,O,P] and [C,N,S,P]. The predicted ground states are the species derived from a trivalent P with a P=0 or P=S bond and a cyano group bonded to the P. The other low energy isomers are the isonitriles and they are 1.4 kcal/mol and 6.6 less stable than the ground state for P=0 and P=S, respectively. An analysis of the bond energies is provided and the values are compared to the corresponding [N,N,C,O] isomers. Data are provided for searching for these species in interstellar regions.