A new olefin-substituted tetrachlorocyclotri-lambda(5)-phosphazene (NPCl2)(2)(NPPr)-Pr-i{C[OC(O)Me]=CH2} (4) and an unique bicyclo-lambda(5)-triphosphazene [(NPCl2)(2)(NPPr)-Pr-i]C-2(OH)Me (5) have been prepared from the reaction of MeC(O)Cl and (NPCl2)(2)(NPPrH)-Pr-i in the presence of Et(3)N. Exclusive formation of 4 could be achieved by using an excess of both Et(3)N and MeC(O)Cl. The phosphazene rings in 5 are bridged by one carbon atom. The presence of this C(OH)Me bridge induces an asymmetric environment which renders the isopropyl ligands no longer equivalent under NMR conditions. Crystals of 4 are monoclinic, space group P2(1)/n, with a = 13.158(1) Angstrom, b = 9.555(1) Angstrom, c = 14.859(1) Angstrom, beta = 115.502(6)degrees, V = 1686.1(3) Angstrom(3), and Z = 4. Crystals of 5 are monoclinic, space group P2(1)/c. with a = 13.255(2) Angstrom, b = 12.050(2) Angstrom, c = 16.280(2) Angstrom, beta = 98.91(1)degrees, V = 2568.8(7) Angstrom(3), and Z = 4.