Silylene and Disilene Additions to Hexa-2,4-diyne:  Formation of a Propynylsilirene and of Bicyclic Compounds¹

Tetra-tert-butyldisilene and di-tert-butylsilylene, generated by photolysis of hexa-tert-butylcyclotrisilane (1), react with the triple bonds of hexa-2,4-diyne to provide the addition products octa-tert-butyl-2-methylene-5-methyl-3, 4, 7, 8-tetrasilabicyclo[4.2.0]oct-1(6)-ene (5) and di-tert-butyl-2-methyl-3-propynylsilirene (6). Further treatment of 6 with 1 is thought to proceed via a bis(silirene) derivative to furnish the rearranged tetra-tert-butyl-3, 6-dimethyl-2, 5-disilabicyclo[2.2.0]hexa-1 (6),3-diene (12). The structures of 5 and 12 were determined by X-ray crystallography.