Starting from 9,10-dimethylphenanthrene, the title compound, C18H18Si,
was synthesized in two steps. Bond lengths and angles within the plan
ar carbon skeleton show no deviation from normal values. The five-memb
ered ring adopts an envelope conformation. Molecules pack. in a herrin
g-bone-type layer structure. There are no intermolecular C-H distances
below 2.90 Angstrom.