Recent advances in the experimental and computational characterization of carbocations: Silyl effects in bicyclobutonium ions

Abstract

Two trialkylsilyl substituted bicyclobutonium ion were investigated by NMR spectroscopy in superacid solution and by quantum chemical ab initio calculations. The 1-(trimethylsilyl)bicyclobutonium ion undergoes a threefold degenerate methylene rearrangement. The 3-endo-(tert-buryldimethylsilyl)bicyclobutonium ion is the first static bicyclobutonium ion. The NMR-spectra of this carbocation are a direct proof for the hypercoordinated and puckered structure of bicyclobutonium ions.