Synthesis of diiron μ-allenyl complexes by electrophilic addition to propen-2-yl-dimetallacyclopentenone species: A joint experimental and DFT study

The propen-2-yl-dimetallacyclopentenone complex [Fe2Cp2(CO)(μ-CO){μ-η1:η3-Cα(H)double bond; length as m-dashCβ(Cγ(CH3)CH2)C(double bond; length as m-dashO)}] (1) underwent electrophilic additions at the propenyl moiety to afford the μ-allenyl complexes [Fe2Cp2(CO)2(μ-CO){μ-η1:η2α,β-CαHdouble bond; length as m-dashCβdouble bond; length as m-dashCγ(CH3)(CH2E)}][BF4] (E = CPh3, [2][BF4]; E = H, [3][BF4]), in ca. 85% yield. The molecular structure of ([2][BF4]) was ascertained by X-ray diffractometry; X-ray, NMR and DFT results agreed in that one single isomer formed, bearing the [CH2CPh3] group pointing far from the Fe–Fe axis. The reaction of [3][BF4] with NHEt2 in the presence of PhSSPh resulted in the prevalent formation of [FeCp(CO)2SPh] (7).