The use of a mild, oxidative chlorination route for the synthesis of linear and cyclic carbophosphazenes is described. For example, chlorination of the linear PNCN chain Ph2P-N=C(Ph)-N(SiMe3)(2) (1) with C2Cl6 led to the clean formation of the previously known 8- and 6-membered rings [Ph2PNC(Ph)N](2) (2) and [Ph2PNC(Ph)NP(Ph)(2)N] (3), respectively. In a similar fashion, the N-alkyl-substituted PNCN derivatives, Ph2P-N=C(Ph)-N(Bu-t)SiMe3 (4) and Ph2P-N=C(Ph)-NiPr2 (7) were readily converted by C2Cl6 into the halogenated derivatives ClPh2P=N-C(Ph)=N-t-Bu (5) and [ClPh2P=N=C(Ph)-(NPr2)-Pr-i]Cl (8), respectively. Protonation of 5 was accomplished using HCl and gave the carbophosphazenium salt [ClPh2P=N-C(Ph)=N(Bu-t)H]Cl (6). In addition, the isolation of a rare 8-membered P2N4C2 heterocycle [(Cl3P=N)ClPNC(Ph)NP(Cl)(2)NC(Ph)N] (9) from the reaction of PCl5 and Li[PhC(NSiMe3)(2)] is reported. Treatment of 9 with one equivalent of GaCl3 led to the discovery of an unusual Lewis acid-induced ring contraction reaction whereby the (PNCN)(2) ring in 9 is converted into the novel 6-membered P2N3C heterocyclic adduct [(Cl3P=N)ClPNP(Cl)(2)NC(Ph)N].GaCl3 (10) with concomitant release of PhCN. Structural characterization of compounds 1, 5, 6, and 8-10 by single-crystal X-ray diffraction is also provided.