Reactivity of a Peraryl Cyclotrisilene (c-Si3R4) Toward Chalcogens

Abstract

Reactions of the peraryl-substituted cyclotrisilene 5 (c-Si3R4, R = Tip = iPr3C6H2) with chalcogens initially result in Si=Si double bond π-addition products, 2-chalcogena-1,3,4-trisila-bicyclo[1.1.0]butanes 6a–6c. Treatment with an excess of sulfur or selenium leads to the insertion of a second equivalent into the bridging Si-Si single bond of 6a and 6b and thus affords 2,4-dichalcogena-1,3,5-trisilabicyclo[1.1.1]pentanes 7a and 7b. In the solid state as well as at low temperature in solution, the monoaddition products 6a–6c show three signals in 29Si CP-MAS NMR spectroscopy. The rapid degenerate exchange of the differing aryl group conformations at the bridging silicon atoms leads to coalescence (and thus disappearance) of two of these signals in C6D6 at elevated temperature. Thermal isomerization of 6a–6c to 2-chalcogena-1,3,4-trisilacyclobutenes 8a–8c is suggested by NMR spectroscopic data and supported by the isolation of the hydrolysis product of 8c.