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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.


ABSTRACT: The synthesis and crystal structures of two tris-(tri-alkyl-sil-yl)silyl bromide compounds, C9H27BrSi4 (I, HypSiBr) and C27H63BrSi4 (II, TipSiBr), are described. Compound I 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. The Si-Br bond distance is 2.2990?(12)?Å and the Si-Si bond lengths are 2.3477?(8)?Å. The Br-Si-Si bond angles are 104.83?(3)° and the Si-Si-Si bond angles are 113.69?(2)°, reflecting the steric hindrance inherent in the three tri-methyl-silyl groups attached to the central Si atom. Compound II was prepared in 55% yield by free-radical bromination of 1,1,1,3,3,3-hexa-isopropyl-2-(triiso-propyl-sil-yl)tris-ilane using N-bromo-succinimide and 2,2'-azobis(2-methyl-propio-nitrile) as a radical initiator at 353?K. Here the Si-Br bond length is 2.3185?(7)?Å and the Si-Si bond lengths range from 2.443?(1) to 2.4628?(9)?Å. The Br-Si-Si bond angles range from 98.44?(3) to 103.77?(3)°, indicating steric hindrance between the three triiso-propyl-silyl groups.

SUBMITTER: Gulotty EM 

PROVIDER: S-EPMC6072994 | BioStudies | 2018-01-01T00:00:00Z

REPOSITORIES: biostudies

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