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

•Synthesis of triferrocenylsilane Fc3SiH and oxidative addition of the Si–H bond to Co2(CO)8.•Unexpected formation of heteroleptic hydrosilane Fc2(CH3)3C(CH2)2SiH.•Capture of a ring fragment resulting from the cleavage of THF in a redox-active compound.•Electrochemical studies showing significant electronic interactions between silicon-bridged ferrocenyl units.

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.

Graphical abstractFrom reaction of 1-lithioferrocene and trichlorosilane, triferrocenylsilane (1) and unexpected heteroleptic (Fc)2(CH3)3C(CH2)2SiH (3) have been obtained. 3 is noteworthy since a fragment from the cleavage of THF has been captured and stored in a redox-active compound. The Si–H bond of 1 oxidatively adds to Co2(CO)8 to give stable (Fc)3Si–Co(CO)4 (4).Figure optionsDownload full-size imageDownload as PowerPoint slide