Thioether Iron Complexes [(X‐SMe‐7,8‐C₂B₉H₁₀)Fe(C₆H₆)] (X = 9 or 10) as Synthons of Neutral Ferracarborane Fragments

The demethylation reactions of the cyclohexadienyl complexes [(η‐X‐SMe₂‐7,8‐C₂B₉H₁₀)Fe(η⁵‐C₆H₇)] {X = 9 (1a), 10 (1b); X is the number of the substituent position} with PhCH₂SNa in N,N‐dimethylformamide (DMF) and subsequent protonation by acetic acid lead to the iron–benzene complexes [(η‐X‐SMe‐7,8‐C₂B₉H₁₀)Fe(η‐C₆H₆)] (2a and 2b). The visible‐light irradiation of 2a in the presence of tBuNC or [Cp*Fe(η‐cyclo‐P₅)] (Cp* = pentamethylcyclopentadienyl) affords the neutral half‐sandwich complex [(η‐9‐SMe‐7,8‐C₂B₉H₁₀)Fe(tBuNC)₃] (3) or the triple‐decker complex [(η‐9‐SMe‐7,8‐C₂B₉H₁₀)Fe(µ‐η:η‐cyclo‐P₅)FeCp*] (4). The reaction of 2b with (THF)W(CO)₅ (THF = tetrahydrofuran) selectively gives the iron–tungsten dinuclear complex [(η‐10‐SMe{W(CO)₅}‐7,8‐C₂B₉H₁₀)Fe(η‐C₆H₆)] (5). The structures of 2a, 4, and 5 were determined by X‐ray diffraction. Electrochemistry revealed that the redox processes of the SMe‐substituted ferracarboranes are cathodically shifted (by ca. 350 mV) with respect to the corresponding redox changes of the SMe₂ analogs. The Fe–C₆H₆ bonding in 2a and the related benzene complexes [(η‐9‐SMe₂‐7,8‐C₂B₉H₁₀)Fe(η‐C₆H₆)]⁺ and [(η‐7,8‐C₂B₉H₁₁)Fe(η‐C₆H₆)] was analyzed by energy‐decomposition analysis.