The tetrasilacyclobutadiene dication

Cyclobutadiene dication, 61, is a 2jr-aromatic cation. In the carbon case, tetramethyl- and tetraphenyl-substituted derivatives of this dication were characterized in superacidic media already in 1976 [66]. A related persila-analogue, the tetrasilacyclobutadiene dication 62, was obtained only recently in an unexpected reaction between donor-stabilized silylene 63 and Cp ZrCl3. in 29% yield (Scheme 20) [67]. As an intermediate, a silicon(ll) cation, [LSi]", resulting from... 

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