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.