Triferrocenylsilane and unexpected formation of diferrocenyl(3,3-dimethylbutyl)silane via cleavage and trapping of a tetrahydrofuran fragment. Redox chemistry and synthesis of (Fc)3Si–Co(CO)4 through oxidative addition of the Si–H bond

Triferrocenylsilane (Fc)3SiH (1) and the unexpected Si–H-functionalized diferrocenyl(3,3-dimethylbutyl)silane (Fc)2(CH3)3C(CH2)2SiH (3) have been synthesized via the salt metathesis reaction of monolithioferrocene and trichlorosilane. The mysterious heteroleptic hydrosilane 3 resulted from the competitive reaction of FcLi and 3,3-dimethylbutyllithium with Cl3SiH. The organolithium species (CH3)3C(CH2)2Li has been generated in situ via the carbolithiation reaction of ethene, which was formed by the α-deprotonation and subsequent reverse [3 + 2] cycloaddition of the tetrahydrofuran solvent. Compound 3 is noteworthy since, for the first time, a ring fragment resulting from the cleavage of cyclic ether THF has been captured and stored in a redox-active and stable crystalline compound. The Si–H bond of hydrosilane 1 oxidatively adds to the Co(0) metal center of Co2(CO)8 to give (Fc)3Si–Co(CO)4 (4), which is exceptionally air-stable and shows a good thermal stability. The molecular structures of multiferrocenes 1, 3 and 4 have been investigated by single-crystal X-ray diffraction studies. From electrochemical studies we observed that, using either [PF6]− (in CH2Cl2/CH3CN 3:0.5) or [B(C6F5)4]− (in CH2Cl2) as supporting electrolyte anions of different coordinating ability, the newly synthesized multiferrocenylsilyl derivatives exhibit a three (for 1 and 4) or two (for 3) well-resolved one electron waves, indicating appreciable electronic interactions between the silicon-bridged ferrocenyl moieties.