THE VIBRATIONAL SPECTRUM OF $B_{4}Cl_{4}$
Loading...
Date
1975
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Infrared and Raman spectra of solid $B_{4}Cl_{4}$ have been measured from 35 to 3500 $cm^{-1}$. Raman depolarization measurements were made on a $CCl_{4}$ solution, and two infrared bands were obtained for the vapor. The infrared spectra are surprisingly sparse; only one band was found below $925 cm^{-1}$. The spectra can be understood very well on the assumption of a $T_{d}$ structure in which the boron atoms form a tetrahedral cage, with the $B-Cl$ bonds directed away from the center of the tetrahedron. In the crystal the symmetry is known to be distorted very slightly to $D_{2{d}}$, and the Raman spectrum shows splittings compatible with this. the eight fundamentals for $T_d$ symmetry have been assigned as follows (solid state frequencies): $a_{1}$: 1302, 358; e: 692, 117; $f_{1}$: 343 (Inferred); $f_{2}$: $978, 514, 110 cm^{-1}$. They are believed to be reliable, except that 110 and 117 may be interchanged. A normal coordinate calculation has been made. It shows that the two $a_{1}$ modes are almost completely mixed. The most interesting force constants are $k_{r} (B-C1) = 4.08$ and $k_{R} (B-B) = 2.3 \pm 0.2$ millidynes/A. The former is In the normal range, but the latter is quite low by analogy to some related compounds. This reflects the electron-deficient nature of the molecule.
Description
Author Institution: Department of Chemistry, University of Pittsburgh