1,2-Bis(trihalogenosilyl)benzenes are versatile synthetic building blocks and represent a unique class of ditopic Lewis acids. Building on the recently reported compound 1,2-(Cl3Si)2C6H2Me2 (1Cl; Me groups in 4,5-positions), the practical synthetic access to its sixfold fluorinated (1F), brominated (1Br), and iodinated (1I) congeners is disclosed. Compound 1F is obtained via Cl/F exchange on 1Cl using SbF3 (71%). The synthesis of 1Br involves a 4 + 2-cycloaddition reaction between Br3SiC≡CSiBr3 and 2,3-dimethyl-1,3-butadiene to furnish the corresponding 1,4-cyclohexadiene, which is subsequently dehydrogenated and aromatized using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (overall 59%). Compound 1I is formed through H/I exchange on 1,2-(H3Si)2-C6H2Me2 with BI3 (32%). All species 1F−1I are comprehensively characterized by NMR spectroscopy, X-ray crystallography, elemental analysis, and high-resolution mass spectrometry. Moreover, adducts of 1F with either 1 equiv. or 2 equiv. of F− are shown to form an inverse chelate featuring a Si−(μ-F)−Si′ bridge or a mixed bridging/terminal coordination motif, respectively.
Schmidt et al. (Thu,) studied this question.