Formation of unexpected silicon- and disiloxane-bridged multiferrocenyl derivatives bearing Si-O-CH[double bond, length as m-dash]CH2 and Si-(CH2)2C(CH3)3 substituents via cleavage of tetrahydrofuran and trapping of its ring fragments

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 46; no. 35; pp. 11584 - 11597
• Main Authors: Bruña, Sonia, González-Vadillo, Ana Mª, Ferrández, Marta, Perles, Josefina, Montero-Campillo, M Merced, Mó, Otilia, Cuadrado, Isabel
• Format: Journal Article
• Language: English
• Published: 21.09.2017
• ISSN: 1477-9234
• DOI: 10.1039/c7dt02286g

The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc2(CH3)3C(CH2)2SiCH[double bond, length as m-dash]CH2 (5), Fc2(CH2[double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH2 (6), Fc2(OH)SiCH[double bond, length as m-dash]CH2 (7), Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH2)Fc2 (8) and Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-SiFc3 (9) is described. Silyl vinyl ether molecules 6, 8 and 9 and the heteroleptic vinylsilane 5 resulted from the competing metathesis reaction of lithioferrocene (FcLi), CH2[double bond, length as m-dash]CH-OLi or (CH3)3C(CH2)2Li with the corresponding multifunctional chlorosilane, Cl3SiCH[double bond, length as m-dash]CH2 or Cl3Si-O-SiCl3. The last two organolithium species have been likely formed in situ by fragmentation of the tetrahydrofuran solvent. Diferrocenylvinyloxyvinylsilane 6 is noteworthy since it represents a rare example of a redox-active silyl mononomer in which two different C[double bond, length as m-dash]C polymerisable groups are directly connected to silicon. The molecular structures of the silicon-containing multiferrocenyl species 5, 6, 8 and 9 have been investigated by single-crystal X-ray diffraction studies, demonstrating the capture and storage processes of two ring fragments resulting from the cleavage of cyclic THF in redox-active and stable crystalline organometallic compounds. From electrochemical studies we found that by changing the anion of the supporting electrolyte from [PF6]- to [B(C6F5)4]-, the redox behaviour of tetrametallic disiloxane 8 can be switched from a poorly resolved multistep redox process to four consecutive well-separated one-electron oxidations, corresponding to the sequential oxidation of the four ferrocenyl moieties.