Transformations of the: Cyclo -P4ligand in [Cp′′′Co(η4-P4)]

Abstract

The reactivity of the cyclo-P4 ligand complex [Cp′′′Co(η4-P4)] (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,η3:η3-P8)]2- (2) was achieved. The reaction of 1 with tBuLi and LiCH2SiMe3 as carbon-based nucleophiles yielded [Cp′′′Co(η3-P4R)]- (R = tBu (4), CH2SiMe3 (7)), which, depending on the reaction conditions, undergo subsequent reactions with another equivalent of 1 to form [(Cp′′′Co)2(μ,η3:η3-P8R)]- (R = tBu (5), CH2SiMe3 (8)). In the case of 4, a different pathway was observed, namely a dimerisation followed by a fragmentation into [Cp′′′Co(η3-P5tBu2)]- (6) and [Cp′′′Co(η3-P3)]- (3). With OH- as an oxygen-based nucleophile, the synthesis of [Cp′′′Co(η3-P4(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.