X-ray diffraction investigation of siloxanes. I. Effects of organic substituents at the silicon atoms on the structure of acyclic trisiloxane-1,5-diols and on formation of different hydrogen bond systems

摘要: The molecular and crystal structure of four acyclic trisiloxane compounds, which differ in substituents at the silicon atoms (Ph-phenyl, mPh-methoxyphenyl, 2mPh-dimethoxyphenyl), was investigated by X-ray diffraction analysis. Due to intermolecular hydrogen bonding between oxygen diol fragments, 1,1,5,5-tetramethyl-3,3-diphenyl-1,3,5-trisiloxane-1,5-diol (C16H24O4Si3) (I) is a double chain architecture with hydrogen-bonded dimeric motifs C(8)R 4 (12) type graph set representation. In 1,1,5,5-tetramethyl-3,3-(2-methoxybenzo)-1,3,5-trisiloxane-1,5-diol (C18H28O6Si3) (II) 1,1,5,5-tetramethyl-3,3-(2,6-dimethoxybenzo)-1,3,5-trisiloxane-1,5-diol (C20H32O8Si3) (III), R 3 (8)D (10) formed. contrast I–III, 1,1,3,3,5,5-hexaphenyl-1,3,5-trisiloxane-1,5-diol (C36H32O4Si3) (IV) has an intramolecular bond S(8). independent molecules are joined O-H...O bonds into centrosymmetrical dimers; system general may be described as S(8)R (8).