Reaction of a 2,4,6-triphenylphosphinine ferrate anion with electrophiles: a new route to phosphacyclohexadienyl complexes

Abstract

A novel, versatile route to phosphorus- and carbon-substituted η⁵-phosphacyclohexadienyl complexes was developed. Reaction of the anionic 2,4,6-triphenylphosphinine iron complex [K([18]crown-6)(thf)₂][Cp*Fe(PC₅Ph₃H₂)] (1) with selected main group element electrophiles afforded the new complexes [Cp*Fe(2-endo-H-PC₅Ph₃H₂)] (endo-3), [Cp*Fe(2-exo-H-PC₅Ph₃H₂)] (exo-3), [Cp*Fe(1-Me-PC₅Ph₃H₂)] (4), [Cp*Fe(1-Me₃Si-PC₅Ph₃H₂)] (5), [Cp*Fe(1-PPh₂-PC₅Ph₃H₂)] (6) and [Cp*Fe(2-BCat-PC₅Ph₃H₂)] (7, BCat = 2-benzo[d][1,3,2]dioxaborol-2-yl). Initial attack of the electrophile at phosphorus was observed, leading to a P-substitued phosphinine ligand. A subsequent rearragement occured in some cases, resulting in C-substituted phosphinine complexes endo-3, exo-3 and 7. The new complexes were characterized by ¹H, ³¹P{¹H}, and ¹³C{¹H} NMR spectroscopy, UV-vis spectroscopy and elemental analysis; their molecular structures were determined by X-ray crystallography.