Density functional calculations have been performed on [(trichlorosilyl)amino]dichloroborane (TADB, Cl3SiNHBCl2), a molecular precursor of the recently synthesized ceramic Si3B3N7. An infrared spectrum of the substance was determined both experimentally using a Fourier transform infrared spectrometer and by means of quantum chemical. calculations. The computed infrared spectrum is in good agreement with experiment and allows the assignment of the more intense peaks to the various vibrational modes. Electronic structure calculations show that the nitrogen atom in TADB is not pyramidally coordinated; the molecule rather contains a planar Si-NH-BCl2 unit with a partial N-B double bond.