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Reaction of mono- and dilithioferrocene with octachlorocyclotetraphosphazene. The crystal and molecular structures of N4P4Cl6[(η-C5H 4)Fe(η-C5H5)]2 and N3P3Cl4[(η-C5H 4)Fe(η-C5H ...
Allcock, Harry R.,Lavin, Karen D.,Riding, Geoffrey H.,Whittle, Robert R.
, p. 663 - 669 (2008/10/08)
Full title: Reaction of mono- and dilithioferrocene with octachlorocyclotetraphosphazene. The crystal and molecular structures of N4P4Cl6[(η-C5H 4)Fe(η-C5H5)]2 and N3P3Cl4[(η-C5H 4)Fe(η-C5H5)]N4P 4Cl7. New and unusual derivatives of cyclophosphazenes bearing ferrocene substituents have been synthesized by the reactions of mono- and dilithioferrocene with octachlorocyclotetraphosphazene, (NPCl2)4, and with equimolar mixtures of hexachlorocyclotriphosphazene, (NPCl2)3, and (NPCl2)4. The reactions of monolithioferrocene with (NPCl2)4 gave N4P4Cl6[(η,-C5H 4)Fe(η-C5H5)]2 (4) in which the tetrameric ring has contracted to give a cyclic trimer with a phosphorus-nitrogen-phosphorus pendent chain. The two ferrocene units were found to be attached to the terminal phosphorus atom of this chain. The structure of 4 was examined by X-ray diffraction techniques. Crystals of 4 are monoclinic of space group P21/c with a = 11.199 (3) A? b = 22.774 (7) A?, c = 11.504 (7) A?, β = 104.81 (3)°, V = 2837 (4) A?3, and Z = 4. The structure was refined to discrepancy indices R = 0.055 and Rw = 0.063. The most striking feature of the molecule is the structure of the pendent chain. Here, the bond angle at nitrogen is unusually wide, being 142.7 (3)°. Also, the single bond between this nitrogen atom and the ring phosphorus (1.54 A?) is significantly shorter than the supposed double bond to the terminal phosphorus atom of the chain (1.57 A?). These observations are compatible with appreciable delocalization within the phosphorus-nitrogen skeleton. The reactions of lithioferrocene with a 1:1 molar mixture of (NPCl2)3 and (NPCl2)4 gave the bi(cyclophosphazenes), N3P3Cl4[(η-C5H 4)Fe(η-C5H4X)]N4P 4Cl7 (5a, X = H; 5b, X = Cl). The structure of 5a was also examined by X-ray diffraction techniques. Crystals of 5a were triclinic of space group P1 with a = 12 899 (5) A?, b = 14.206 (3) A?, c = 10.003 (4) A?, α = 99.77 (3)°, β = 105.76 (3)°, γ = 112.99 (2)°, V = 1543 (2) A?3, and Z = 2. The structure was refined to discrepancy indices R = 0.053 and Rw = 0.061. The most striking feature of this molecule is the linkage of the cyclic trimeric and tetrameric rings by a P-P bond. This is the first example of a trimer-tetramer bi(cyclophosphazene). Possible mechanisms leading to the formation of these ferrocenylphosphazenes are also discussed.
