Transformations of the cyclo-P(4) ligand in [Cp′′′Co(η(4)-P(4))]

The reactivity of the cyclo-P(4) ligand complex [Cp′′′Co(η(4)-P(4))] (1) (Cp′′′ = 1,2,4-tri-tert-butyl-cyclopentadienyl) towards reduction and main group nucleophiles was investigated. By using K[CpFe(CO)(2)], a selective reduction to the dianionic complex [(Cp′′′Co)(2)(μ,η(3):η(3)-P(8))](2−) (2) was achieved. The reaction of 1 with (t)BuLi and LiCH(2)SiMe(3) as carbon-based nucleophiles yielded [Cp′′′Co(η(3)-P(4)R)](−) (R = (t)Bu (4), CH(2)SiMe(3) (7)), which, depending on the reaction conditions, undergo subsequent reactions with another equivalent of 1 to form [(Cp′′′Co)(2)(μ,η(3):η(3)-P(8)R)](−) (R = (t)Bu (5), CH(2)SiMe(3) (8)). In the case of 4, a different pathway was observed, namely a dimerisation followed by a fragmentation into [Cp′′′Co(η(3)-P(5)(t)Bu(2))](−) (6) and [Cp′′′Co(η(3)-P(3))](−) (3). With OH(−) as an oxygen-based nucleophile, the synthesis of [Cp′′′Co(η(3)-P(4)(O)H)](−) (9) was achieved. All compounds were characterized by X-ray crystal structure analysis, NMR spectroscopy and mass spectrometry. Their electronic structures and reaction behavior were elucidated by DFT calculations.