Synthesis and Characterization of Novel Fluorophosphazene-Derived Cobaltacyclopentadienyl Metallacycles: Reagents for Assembly of Aryl-Bridged Fluorophosphazenes

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Abstract
Reaction of (β-phenylethynyl)pentafluorocyclotriphosphazene, F5P3N3C≡CPh, with in situ generated η5-(MeOC(O)C5H4)Co(PPh3)2 resulted in the formation of two isomers of cobaltacyclopentadienylmetallacycles, (η5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,5-bis(pentafluorocyclotriphosphazenyl)-3,4-diphenyl cobaltacyclopentadiene (1) and (η5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,4-bis(pentafluorocyclotriphosphazenyl)-3,5-diphenyl cobaltacyclopentadiene (2), along with the sandwich compound [η5-carbomethoxycyclopentadienyl]-[η4-1,3-bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene]cobalt (3). Formation of cobaltacyclopentadienylmetallacycles or cyclobutadienylmetallocene having two fluorophosphazene units on vicinal carbon atoms of the rings was not observed in this reaction. Reaction of 1 with diphenylacetylene resulted in the formation of a novel aryl-bridged fluorophosphazene, 1,4-bis(pentafluorocyclotriphosphazenyl)−2,3,5,6-tetraphenyl benzene (4), and the conversion of cobaltametallacycle to the sandwich compound, [η5-(MeOC(O)C5H4]Co(η4-C4Ph4) (5). Reaction of 1 with phenylacetylene resulted in the formation of aryl-bridged fluorophosphazene, 1,4-bis(pentafluorophosphazenyl)−2,3,5,-triphenyl benzene (6). New compounds 1−4 were structurally characterized. In compound 1, the two fluorophosphazene units were oriented in gauche form with respect to each other. However, in compounds 2 and 3, they were eclipsed to each other, and in compound 4, they were oriented anti to each other.