Syntheses and crystal structures of the anhydride 4-oxa-tetra-cyclo-[5.3.2.0.0]dodec-11-ene-3,5-dione and the related imide 4-(4-bromo-phen-yl)-4-aza-tetra-cyclo-[5.3.2.0.0]dodec-11-ene-3,5-dione.

The syntheses and crystal structures of the two title compounds, CHO () and CHBrNO (), both containing the bi-cyclo-[2.2.2]octene ring system, are reported here [the structure of has been reported previously: White & Goh (2014 ▸).

Computational and dynamic NMR investigation of 2,2-dimesityl-1,1,1,3,3,3-hexamethyltrisilane.

The structure and rotational barrier for the mesityl-silicon bond of 2,2-dimesityl-1,1,1,3,3,3-hexamethyltrisilane have been investigated by H- and C-variable temperature nuclear magnetic resonance (NMR) as well as by density functional theory structural calculations. The calculations show that the lowest energy structure has C symmetry with nonequivalent ortho methyl groups, consistent with the crystal structure and solution NMR. The nonequivalent ortho methyl groups exchange through a C transition state with a calculated relative free energy of 11.

Syntheses and crystal structures of 2-methyl-1,1,2,3,3-penta-phenyl-2-sila-propane and 2-methyl-1,1,3,3-tetra-phenyl-2-silapropan-2-ol.

The sterically hindered silicon compound 2-methyl-1,1,2,3,3-penta-phenyl-2-sila-propane, CHSi (), was prepared the reaction of two equivalents of di-phenyl-methyl-lithium (benzhydryllithium) and di-chloro-methyl-phenyl-silane. This bis-benzhydryl-substituted silicon compound was then reacted with tri-fluoro-methane-sulfonic acid, followed by hydrolysis with water to give the silanol 2-methyl-1,1,3,3-tetra-phenyl-2-silapropan-2-ol, CHOSi (). Key geometric features for are the Si-C bond lengths that range from 1.

Crystal structures of 2-bromo-1,1,1,3,3,3-hexa-methyl-2-(tri-methyl-sil-yl)tris-ilane and 2-bromo-1,1,1,3,3,3-hexa-isopropyl-2-(triiso-propyl-sil-yl)tri-silane.

The synthesis and crystal structures of two tris-(tri-alkyl-sil-yl)silyl bromide compounds, CHBrSi (, HypSiBr) and CHBrSi (, TipSiBr), are described. Compound was prepared in 85% yield by free-radical bromination of 1,1,1,3,3,3-hexa-methyl-2-(tri-methyl-sil-yl)tris-ilane using bromo-butane and 2,2'-azobis(2-methyl-propio-nitrile) as a radical initiator at 333 K. The mol-ecule possesses threefold rotational symmetry, with the central Si atom and the Br atom being located on the threefold rotation axis.