A comparison of 2,7‐di­hydro‐2,2,7,7‐tetra­methyl‐3,6‐di­phenyl‐1,4,5‐thiadiazepine and the corresponding 1,1‐­dioxide

The structures of the highly substituted title heterocycles, C₂₀H₂₂N₂S and C₂₀H₂₂N₂O₂S, have been determined at 123 (1) K. Both mol­ecules possess exact C₂ symmetry and the seven‐membered rings have very similar twist‐boat conformations. The magnitudes of the C—S—C bond angles, 107.13 (6) and 108.27 (7)°, respectively, are influenced significantly by the four substituent methyl groups on the seven‐membered rings.