18827-08-2Relevant academic research and scientific papers
Structural precursors of poly(diphenylsilane) II. Crystal and molecular structure of HO(SiPh2)4OH and HO(SiPh2)7OH
Ovchinnikov, Yu. E.,Shklover, V. E.,Struchkov, Yu. T.,Dement'ev, V. V.,Frunze, T. M.,Antipova, B. A.
, p. 157 - 166 (1987)
An X-ray diffraction study was carried out on HO(SiPh2)4OH (I) and HO(SiPh2)7OH (II), which were prepared from phenylcyclopolysilanes.H bonds, found in both cases, strongly affect the conformation of polysilane chain.The intramolecular H bond in crystal I (O...O 2.81 Angstroem) closes the six-membered pseudocycle OSi4O to give "chair" conformation, with one of the OH groups participating in the intermolecular H bond (O...O 2.75 Angstroem).Two of these bonds link the molecules into the centrosymmetric dimer.In crystal II there are intermolecular H bonds linking the molecules into head-to-tail type chains (O...O distance of 2.78 Angstroem, Si-Si-Si-Si torsion angles of 149-160 deg), and in addition there is an O-H...? intramolecular H bond formed by one of the two terminal OH groups with the ?-system of the Ph ring (the distances from the O and H atoms to the Ph plane are 3.2 and 2.52 Angstroem respectively).The Si-chain conformation of molecule II is intermediate between trans-planar and gauche, the chain is twisted and the degree of twisting increases steadily in both directions from the middle towards each chain end.The Si-Si bond lengths in I and II are 2.361-2.412 Angstroem, the terminal bonds in the molecule II (av. 2.368 Angstroem) are somewhat shorter than the others (av. 2.400 Angstroem).In I the Si-Si bond angles are 108.6 and 113.3 deg, in II the bond angle at the central Si atom is 118.9 deg, significantly exceeding other angles (109.6-117.7 deg).
