Transformations of thecyclo-P4ligand in [Cp′′′Co(η4-P4)]

The reactivity of thecyclo-P(4)ligand complex [Cp ''' Co(eta(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)(mu,eta(3):eta(3)-P-8)](2-)(2) was achieved. The reaction of1with(t)BuLi and LiCH(2)SiMe(3)as carbon-based nucleophiles yielded [Cp ''' Co(eta(3)-P4R)](-)(R =Bu-t (4), CH2SiMe3(7)), which, depending on the reaction conditions, undergo subsequent reactions with another equivalent of1to form [(Cp ''' Co)(2)(mu,eta(3):eta(3)-P8R)](-)(R =Bu-t (5), CH2SiMe3(8)). In the case of4, a different pathway was observed, namely a dimerisation followed by a fragmentation into [Cp ''' Co(eta(3)-(P5Bu2)-Bu-t)](-)(6) and [Cp ''' Co(eta(3)-P-3)](-)(3). With OH(-)as an oxygen-based nucleophile, the synthesis of [Cp ''' Co(eta(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.