Synthesis of (β-phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene and its reaction with RCpCo(PPh3)2 [R = MeOC(O)]

Reaction of gem-diphenyltetrafluorocyclotriphosphazene with in situ generated lithiated phenylacetylene resulted in the formation of the first example of a gem-diphenyltrifluorophosphazene based alkyne (β-phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene (NPPh2)(NPF2)[NP(F)CCPh] 1. Reaction of this alkyne with η5-(MeOC(O)C5H4)Co(PPh3)2 resulted in the formation of a CpCo stabilized cyclobutadiene complex [η5-carbomethoxycyclopentadienyl][η4-1,3-bis(gem-diphenyltrifluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene]cobalt 2, having two gem-diphenyltrifluorophosphazene moieties trans to each other on the cyclobutadiene ring. The reaction also yielded two structural isomers of the PPh3 stabilized cobaltacyclopentadiene compounds 3 and 4 having gem diphenyl trifluorophosphazene moieties present in the 2,4 and 2,5 positions of the metallacycle. The reaction in addition yielded a novel spirocyclic phosphazacyclopentadiene compound bound to a CpCo unit in the η4-mode 5. All the compounds were characterized by 1H, 13C, 31P and 19F NMR spectroscopy and compounds 2, 3 and 5 were also structurally characterized by X-ray crystallography.

Graphical abstractThe first example of a gem-diphenyltrifluorophosphazene derived alkyne has been prepared by the reaction of lithiated phenylacetylene with gem-diphenyltetrafluorophosphazene. Its reaction with CpCo(PPh3)2, in addition to fluorophosphazene derived cobaltacyclopentadienes and a CpCo derived cyclobutadiene sandwich compound, yielded a novel spirocyclic phosphazacyclopentadiene bound to a CpCo unit.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Synthesis and characterization of the new cyclophosphazene based alkynes: (β-phenylethynyl)-gem-diphenyltrifluorocyclotriphosphazene. ► Reaction of the new alkyne with RCpCo(PPh3)2 leading to phosphazene derived cobaltametallacycles, cobalt cyclobutadiene sandwich compounds and η4 complexes. ► Preparation and X-ray structural characterization of the first example of a novel phosphaza cyclopentadiene unit coordinated to the RCpCo unit.