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, C(33)H(30)Si (I), was prepared via 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, C(27)H(26)OSi (II). Key geometric features for I are the Si-C bond lengths that range from 1.867†(2) to 1.914†(2)†à and a τ(4) descriptor for fourfold coordination around the Si atom of 0.97 (indicating a nearly perfect tetra-hedron). Key geometric features for compound II include Si-C bond lengths that range from 1.835†(4) to 1.905†(3)†à , a Si-O bond length of 1.665†(3)†à , and a τ(4) descriptor for fourfold coordination around the Si atom of 0.96. In compound II, there is an intra-molecular C-H⋯O hydrogen bond present. In the crystal of I, mol-ecules are linked by two pairs of C-H⋯π inter-actions, forming dimers that are linked into ribbons propagating along the b-axis direction. In the crystal of II, mol-ecules are linked by C-H⋯π and O-H⋯π inter-actions that result in the formation of ribbons that run along the a-axis direction.