Functionalized Cyclic Disilenes via Ring Expansion of Cyclotrisilenes with Isocyanides

The reaction of cyclotrisilenes 1 with 1 equiv of alkyl and aryl isocyanides at 25 °C affords the four-membered trisilacyclobutenes 2 with an exocyclic imine functionality as the major products of formal insertion into one of the Si–Si single bonds of 1. Minor quantities of the iminotrisilabicyclo[1.1.0]­butanes 3 are obtained as side products, formally resulting from [1 + 2] cycloaddition of the isocyanides to the Si–Si double bond of 1. The bicyclo[1.1.0]­butanes 3 become dominant at lower temperatures and may react with an additional 1 equiv of isonitriles to give the diiminotrisilabicyclo[1.1.1]­pentanes 4.