Barriers to internal rotation of cyclopropylsilane-d3 and cyclopropylgermane from combination band spectra

Abstract

Abstract The sum and difference bands of cyclopropylsilane- d 3 in the 1400–1700 cm −1 region arising from combinations of the internal rotation with the SiD stretching mode have been recorded and analyzed. The data correspond to a barrier to internal rotation of 651 cm −1 , somewhat less than the value of 694 cm −1 determined for the undeuterated species. Similarly, the combination band spectra of cyclopropylgermane in the 1950–2200 cm −1 region establish the barrier to rotation of the germyl group as 474 cm −1 . These results confirm that the attachment of a silyl group to the cyclopropyl ring results in a higher barrier than would be expected from comparisons to other silanes and to methylcyclopropane and cyclopropylgermane.