6533b854fe1ef96bd12ade62

RESEARCH PRODUCT

Hindering the formation of ferrocenes: mono(cyclopentadienyl)halo iron complexes [Fe(C5R5)X] containing a sterically bulky cyclopentadienyl ligand

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Abstract The reaction of lithium 1,2,4-tris(trimethylsilyl)cyclopentadienide Li(Si 3 Cp) with ferrous halide FeX 2 (X=Cl, Br, I) in THF at −95 °C gives a thermally extremely sensitive compound that can be regarded as a functional equivalent for the 14-electron fragment [Fe(Si 3 Cp)X]. Experiments to trap this species with TMEDA gives thermally sensitive, colorless, paramagnetic crystals of the composition [LiFe(Si 3 Cp)Cl 2 (TMEDA) 3 ]. Trimethylphosphite gives isolable 18-electron half-sandwich complexes [Fe(Si 3 Cp){P(OMe) 3 } 2 X]. [Fe(Si 3 Cp)X] is also formed by reducing the ferric derivative [Fe(Si 3 Cp)Cl 2 ] with zinc. Analogous reactivity towards ferrous halides is observed for the lithium derivatives of the similarly bulky 1,2-bis(trimethylsilyl)-4- tert -butyl- and 2,4-di- tert -butyl-1-trimethylsilylcyclopentadienide, Li(BuSi 2 Cp) and Li(Bu 2 SiCp). Trapping with carbon monoxide gives complexes of the type [Fe(Bu n Si 3− n Cp)(CO) 2 X].