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... 

Fig. 7 Molecular structures of tetrasilacyclobutadiene dication 62 as determined by XRD in the salt 62[Zr2Cp 2Cl7]2- (Ellipsoid presentation. H-atoms are omitted for clarity, thermal ellipsoids at 50% probability level, color code Si pink, C black, N blue. Cl green.) Important bond lengths [pm] and dihedral angles [ jiSi -Si = 232.1 Si -Si = 233.1 Si. ..Si = 302.6 Si. .Si = 353.4 Si -SP-Si = 81.15 Si -Si -Si = 98.85 [67]...

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