Organometallic Derivatives of Cyclotriphosphazene as Precursors of Nanostructured Metallic Materials: A New Solid State Method

The cyclic phosphazene trimers [N3P3(OC6H5)(5)OC5H4N center dot Ti(Cp)(2)Cl][PF6] (3), [N3P3(OC6H4CH2CN center dot Ti(Cp)(2)Cl)(6)][PF6](6) (4), [N3P3(OC6H4-Bu-t)(5)(OC6H4CH2CN center dot Ti(Cp)(2)Cl)][PF6] (5), [N3P3(OC6H5)(5)C6H4CH2CN center dot Ru(Cp)(PPh3)(2)][PF6] (6), [N3P3(OC6H5)(5)C6H4CH2CN center dot Fe(Cp)(dppe)][PF6] (7) and N3P3(OC6H5)(5)OC5H4N center dot W(CO)(5) (8) were prepared and characterized. As a model, the simple compounds [HOC5H5N center dot Ti(Cp)(2)Cl]PF6 (1) and [HOC6H4CH2CN center dot Ti(Cp)(2)Cl]PF6 (2) were also prepared and characterized. Pyrolysis of the organometallic cyclic trimers in air yields metallic nanostructured materials, which according to transmission and scanning electron microscopy (TEM/SEM), energy-dispersive X-ray microanalysis (EDX), and IR data, can be formulated as either a metal oxide, metal pyrophosphate or a mixture in some cases, depending on the nature and quantity of the metal, characteristics of the organic spacer and the auxiliary substituent attached to the phosphorus cycle. Atomic force microscopy (AFM) data indicate the formation of small island and striate nanostructures. A plausible formation mechanism which involves the formation of a cyclomatrix is proposed, and the pyrolysis of the organometallic cyclic phosphazene polymer as a new and general method for obtaining metallic nanostructured materials is discussed.