Vibrational study of rotational isomerism in dialkyldichlorosilanes Cl2SiR2 (R=Bun, Hexn)

Abstract

IR and Raman spectra of CI2SiR 2 (R = Hex n (1), Bu ~ (2)) in liquid, glassy, and polycrystalline states were investigated. In the liquid and glassy states, rotational isomerism about the Si--C and C--C bonds takes place, the compounds being mixtures of con formers.In the crystalline state, only one, the most stable conformer (all-tram in relation to the C--C bonds), persists. Compound 7_. in contrast to 1, was found to crystallize on cooling with great difficulty.

Order−Disorder Phase Transition in Poly(di-n-butylstannane) Observed by UV−Vis and Raman Spectroscopy

“…Their assignments are based on variable-temperature vibrational studies of the related compounds n Bu 4-nSnCl n 17 and n Bu 2 SiCl 2 . 25 The variable-temperature Raman data for [ n Bu 2 Sn] n confirm the phase transition, manifested as dramatic changes in the ν(Sn-Sn) region in the temperature interval given above. More specifically, a broad intense band at ca.…”

“…An analogous phenomenon was observed by two of us for the low-temperature glassy state of n Bu 2 SiCl 2 . 25 Thus, the Raman results show that an order-disorder phase transition for [ n Bu 2 Sn] n does not involve abrupt ordering of the side chains, but only changes in conformation of the Sn-Sn bonded main chain, presumably to an all-anti or transoid conformation. Very similar results have been observed for [ n Hex 2 Sn] n and [ n Oct 2 -Sn] n , which display analogous temperature-dependent Raman spectra but a higher temperature (ca.…”

“…All of the modes with frequencies higher than 650 cm -1 belong to internal vibrations of the n Bu groups. Their assignments are based on variable-temperature vibrational studies of the related compounds n Bu 4- n SnCl n 17 and n Bu 2 SiCl 2 …”

Regularities and Peculiarities of Solid Polydialkylsilane Order-Disorder Transitions as Studied by Optical (UV, Raman and IR) Spectroscopy

“…Investigation of rotational isomerism of model monomers Alk 2 SiX 2 with the same Alk groups as in the polymer by variable-temperature study of the vibrational spectra [17,25] is of great use here because the internal vibrations of the alkyl groups attached to silicon atom are practically the same for a monomer and the corresponding polymer. This is due to the fact that a heavier Si atom serves as a "barrier" for kinematic interactions of organic substituents.…”

“…The aim of this paper is to describe characteristic features of polydi-n-alkylsilane transitions based on generalization from the authors' experience [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and literature data, as well as to demonstrate that the three types of ordering are not necessarily interrelated.…”