5,5-Dimethyl-2,8-diphenyl-5H-dibenzo[b,f]silepine: a synchrotron study

The mol­ecule of the title silepine compound, C₂₈H₂₄Si, lies on a crystallographic general position but has almost exact mirror symmetry. The seven-membered silepine ring has a boat conformation, with a fold angle of 99.99 (9)° between the C-C=C-C stern and the C-Si-C prow. The planes of the phenyl substituents are rotated by 32.23 (6) and 31.80 (7)° out of the planes of the respective fused benzene rings. Similar folded conformations are found for other dibenzo[b,f]silepines, while analogous dibenzo[b,f]borepines, in which the B atom can participate in conjugation, have a more flattened heterocyclic ring.