Crystal and molecular structure of 2-methyl-9,9-diphenyl-9,10-dihydro-9-sila-3-azaanthracene

The crystal and molecular structure of 2-methyl-9,9-diphenyl-9,10-dihydro-9-sila-3-azaanthracene has been determined by three-dimensional X-ray analysis. The crystal data are: space group P1, a 11.339(2), b 11.151(2), c 19.808(4) Å, α 100.11(1), β 100.00(1), γ 121.20(2)°, C25H21NSi, Z = 4, Dc = 1.20 g cm-3. The intensity data were measured on a 4-circle automatic diffractometer (Mo-Kα radiation). The structure was solved by direct methods using a multiple-solution procedure, and it was refined by large-blocks least-squares methods with anisotropic temperature factors for Si, N and C atoms and with isotropic temperature factors for the H atoms. The final R-factors are R = 0.024 and Rw = 0.027 for 2049 reflections with I>3σ(I). The investigated compound belongs to the family of quasi-heteromolecular crystals. Within the standard deviation limits the symmetrical non-bonded molecules A and A′ are characterised by equal bond lengths and slight differences of the valency angles in the central heterocycles, but differ in the conformation of the tricyclic fragments. The planes of the benzene and pyridine rings constitute a dihedral angle of 132.1° for A and 147.0° for A′, and the planes of the phenyl substituents 87.0° and 55.0°, respectively. The organosilicon heterocycles investigated have a boat conformation. Bond lengths SiC lie in the range 1.8531.871 Å, the average value of the endocyclic angle CSiC is 101.5(2)°. Average bond length NC 1.339(7) Å and angle CNC 117.2(4)°. © 1981.