Iron-Containing Metallophosphazenes and Their Clusters Derived from Chlorophosphazenes and Organometallic Dianions

Hexachlorocyclotriphosphazene, (NPC1₂)₃, reacts with disodium octacarbonyldiferrate, Na₂Fe₂(CO)₈, to yield the diiron and triiron cyciotriphosphazene complexes 2 and 3, respectively. The analogous cyclic tetramer (NPC1₂)₄ reacts similarly to yield the diiron and triiron analogues 5 and 6, respectively. Compounds 2 and 5 are the first chlorophosphazenes that contain two metal-phosphorus covalent bonds and a three-membered spirocyclic ring at phosphorus. Compound 3 can also be obtained by the thermal reaction of 2 with the neutral carbonyl complexes Fe(CO)₅ and Fe₂(CO)₉. In addition, the thermal reaction of 2 with Ru₃(CO)₁₂ yields the mixed-metal cluster 7, similar in structure to 3, but with a Ru(CO)₃ unit in place of the nitrogen-bound Fe(CO)₃. The trimetallic clusters 3, 6, and 7 are the first phosphazene compounds in which a portion of the phosphazene ring has been incorporated into a metallic cluster unit. Compounds 3, 6, and 7 contain both phosphorus-metal and nitrogen-metal bonds, demonstrating both the covalent and coordinative capacities of phosphazene rings. The new metallophosphazenes were characterized by ³¹P NMR, Mössbauer, infrared, and mass spectral techniques and by X-ray crystal structure analyses.