Silicon compounds with strong intramolecular steric interactions. Part 73.Silylene and disilene additions to an octa-1,3,5,7-tetrayne: Formation of a C-C-linked quatersilirene

Tetra-tert-butyldisilene and di-tert-butylsilylene (1), generated by photol ysis of hexa-tert-butylcyclotrisilane, react with 1,8-di-tert-butylocta-1,3 ,5,7-tetrayne to furnish a C-C-linked bis(disilacyclobutene) derivative wit h terminal alkynyl groups 7 and a quatersilirene 8 by addition of 1 to all C-C triple bonds. Upon prolonged irradiation 8 rearranges partly to the 2,5 -disilabicyclo[2.2.0]hexa-1(6),3-diene with terminal silirene groups 9. The structures of 7, 8, and 9 were determined by X-ray crystallography.