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

A novel, versatile route to phosphorus- and carbon-substituted η(5)-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 (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR spectroscopy, UV-vis spectroscopy and elemental analysis; their molecular structures were determined by X-ray crystallography.