Bulky 2,6-disubstituted aryl siloxanes and a disilanamine
Boeré, René T.
International Union of Crystallography (IUCr)
The crystal structures of 5-bromo-1,3-di-tert-butyl-2-[(trimethylsilyl)oxy]benzene, C17H29BrOSi, (I), 1,3-di-tert-butyl-2-[(trimethylsilyl)oxy]benzene, C17H30OSi, (II), and N-(2,6-diisopropylphenyl)-1,1,1-trimethyl-N-(trimethylsilyl)silanamine, C18H35NSi2, (III), are reported. Compound (I) crystallizes in space group P21/c with Z′ = 1, (II) in Pnma with Z′ = 0.5 and (III) in Cmcm with Z′ = 0.25. Consequently, the molecules of (II) are constrained by m and those of (III) by m2m site symmetries. Despite this, both (I) and (II) are distorted towards mild boat conformations, as is typical of 2,6-di-tert-butyl-substituted phenyl compounds, reflecting the high local steric pressure of the flanking alkyl groups. Compound (III) by contrast is planar and symmetric, and this lack of distortion is compatible with the lower steric pressure of the flanking 2,6-diisopropyl substituents.
Open access article. Creative Commons license (CC BY) applies
Crystal structure , Steric pressure , Ortho-disubstitution , Out of plane distortion , High symmetry
Marszaukowski, F., Wohnrath, K., & Boere, R. T. (2020). Bulky 2,6-disubstituted aryl siloxanes and a disilanamine. Acta Crystallographica, Section E: Crystallographic Communications, E76, 318-323. https://doi.org/10.1107/S2056989020001413