Synthesis and redox behavior of Si-Si dimeric 9-methylsilafluorene.

Lithium-halogen exchange on 2,2'-dibromo-1,1'-biphenyl followed by salt metathesis with 1,1,2,2-tetrachloro-1,2-dimethyldisilane produced the Si-Si linked dimeric 9-methylsilafluorene (1) in 62% yield. Compound 1 was characterized in the solid state via single crystal X-ray diffraction, which revealed a highly symmetric structure. The redox behavior of 1 was studied experimentally via cyclic voltammetry, where irreversible oxidation and reduction features were observed. Density functional theory was used to further study the electronic structure of 1 as well as its reduced (1˙-) and oxidized (1˙+) forms. A decrease in bond dissociation energies from the neutral species (+75 kcal mol(-1)) to the reduced species (+43 kcal mol(-1)) supports Si-Si bond homolysis upon reduction, which is consistent with our observed electrochemical irreversibility.