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GAS, SOLID AND MATRIX SPECTRA OF $CH_{3}(SiH_{3})_{2}N$ AND $SiH_{3}(CH_{3})_{2}N$---EVIDENCE FOR POLYMERIZATION IN THE CONDENSED PHASE$^{\ast}$

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  • Physics

Abstract

The infrared spectra of $CH_{3}(SiH_{3})_{2}N$ and $SiH_{2}(CH_{3})_{2}N$ have been examined in the region 4000 to $250 cm^{-1}$ in gas, solid and matrix phases. The gaseous spectra of both molecules at pressures up to 10 mm have been observed and tentative assignments of the fundamental frequencies made assuming that the molecules belong to the point group $C_{x}$. The corresponding solid spectra at $77^{\circ}K$ was found to be much more complex for $SiH_{3}(CH_{3})_{2}N$ even after annealing, than for $CH_{2}(SiH_{2})_{2}N$. A comparative study of the spectra of $(CH_{3})_{3}N_{1}, SiH_{3}(CH_{3})_{2}N, CH_{3}(SiH_{3})_{2}N$, and $(SiH_{3})_{3}N_{1}$ in the gas, solid and crystalline conditions also revealed more bands and broadening for the $SiH_{3}(CH_{3})_{2}N$ molecule. This is believed to be due to some polymerization in the solid phase. Such a possibility has been assumed by Sujishi and $Witz^{2}$ to explain the high melting point of $SiH_{3}(CH_{3})_{2}N$. The polymerization in the solid phase has been studied by using the matrix isolation technique of Pimentel and $coworkers^{3,4}$. The spectra of mixtures of matrix argon (M) and silyl dimethylamine (A) at mole ratios $M/A = 1600, 800, 400, 200, 100$, and 50 have been obtained and the features of the spectra compared with that of methydisilylamine. The gross changes in the spectra of silyldimethylamine occur primarily in the Si---H and Si---N vibrational regions and a discussion of the implications of these changes with respect of polymer formation will be presented.

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