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. The replacement of the benzene ligand of the thioether‐substituted ferracarborane [(η‐9‐SMe‐7,8‐C2B9H10)Fe(η‐C6H6)] by other ligands makes it a convenient synthon of the neutral fragment [Fe(η‐9‐SMe‐7,8‐C2B9H10)]. DFT calculations suggest that the lone electron pair of the sulfur atom facilitates these reactions. The structures and electrochemistry of the complexes obtained are also described.