Syntheses and crystal structures of 2-methyl-1,1,2,3,3-pentaphenyl-2-silapropane and 2-methyl-1,1,3,3-tetraphenyl-2-silapropan-2-ol

Abstract

The sterically hindered silicon compound 2-methyl-1,1,2,3,3-pentaphenyl-2-silapropane, C33H30Si (I), was prepared via the reaction of two equivalents of diphenylmethyllithium (benzhydryllithium) and dichloromethylphenylsilane. This bisbenzhydryl-substituted silicon compound was then reacted with trifluoromethanesulfonic acid, followed by hydrolysis with water to give the silanol 2-methyl-1,1,3,3-tetraphenyl-2-silapropan-2-ol, C27H26OSi (II). Key geometric features for I are the Si-C bond lengths that range from 1.86714;(2) to 1.91414;(2)14;Å and a τ4 descriptor for fourfold coordination around the Si atom of 0.97 (indicating a nearly perfect tetrahedron). Key geometric features for compound II include Si-C bond lengths that range from 1.83514;(4) to 1.90514;(3)14;Å, a Si-O bond length of 1.66514;(3)14;Å, and a τ4 descriptor for fourfold coordination around the Si atom of 0.96. In compound II, there is an intramolecular C-H..O hydrogen bond present. In the crystal of I, molecules are linked by two pairs of C-H..π interactions, forming dimers that are linked into ribbons propagating along the b-axis direction. In the crystal of II, molecules are linked by C-H..π and O-H..π interactions that result in the formation of ribbons that run along the a-axis direction.