Compound 4

2',3',6',7'-Tetra-tert-butyl-2,2,2'',2'',5,5,5'',5''-octakis(trimethylsilyl)dispiro[silolane-1,4'-pentacyclo[4.2.0.0^1,7.0^2,5.0^3,5]octasilane-8',1''-silolane]

From: A heavy analogue of the smallest bridgehead alkene stabilized by a base