Knowledge Bank

Dibromoborane and dibromoborane-d have been prepared and observed spectroscopically. A vibrational analysis has been carried out using the Green's function and partitioning techniques. The calculated and observed frequencies are in good agreement. The theory for a single force constant change has been applied to the B---H stretching motion, with good qualitative correlation with our previous results on $HBCl2$. The fundamentals observed are, for $HBBr2:\nu 1=610$ and $585cm-1,B10-$ and $B11-Br$ asymmetric stretch; $\nu 2=2621cm-1,B-H$ stretch (no splitting); $\nu 4=1047$ and $1036cm-1,B10-$ and $B11-Br$ asymmetric stretch; $\nu 5=772cm-1$, in-plane H- deformation $(B11);\nu 6=730cm-1$, out-of-plane deformation $(B11)$; and for $DBBr2:\nu 1=575cm-1(B11);\nu 2=1952cm-1$ (no splitting); $\nu 4=915$ and $900cm-1;\nu 5=656cm-1(B11)$; and $\nu 6=625cm-1(B11)$. The B-Br symmetric deformation, $\nu 3$, is calculated to be at $\approx 180cm-1$, outside the range of our instrument.