Vibrational frequencies and structural determinations of 3,5-dibromo-1,2,4-trithia-3,5-diborolane

The vibrational frequencies and corresponding normal mode assignments of 3,5-dibromo-1,2,4-trithia-3,5-diborolane (B2S3Br2) are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of six types of motion predicted by a group theoretical analysis (B-S stretch, B-Br stretch, S-S stretch, S-B-S bend, B-Br wag, B(SSBr) umbrella motion) utilizing the C2v symmetry of the molecule. The vibrational modes of the naturally isotopically substituted (1-10B and 2-10B) forms of B2S3Br2 were also calculated and compared against experimental data. The molecular orbitals of B2S3Br2 are examined. The calculations suggest that a considerable amount of pi bonding occurs in B2S2Br2.