Microwave spectra, structure, and barrier to internal rotation of CH 3SnH 2D, CH 3SnHD 2 and CH 3SnD 3

The microwave spectra from 12.5 to 39.0 GHz of CH ₃SnH ₂D, CH ₃SnHD ₂, and CH ₃SnD ₃ have been measured and assigned for the ground vibrational state for the three most naturally abundant tin isotopes, ¹²⁰Sn, ¹¹⁸Sn, and ¹¹⁶Sn. From a diagnostic least-squares adjustment to fit 20 rotational constants, the following r_o structural parameters were obtained: r (Sn-H) = 1.708 ± 0.001 Å, r (CSn) = 2.140 ± 0.001 Å, r (CH) = 1.083 ± 0.005 Å, <CSnH = 109.36 ±°, and <SnCH = 110.36 ± 0.04°. The r_s structural parameters were also obtained for the SnH ₃ moiety and were found to be r (SnH) = 1.713 ± 0.005 Å and <CSnH = 110.01 ± 0.03°. The barrier to internal rotation was determined by the splitting method to be 595 ± 8 cal/mol. These data are compared to the corresponding quantities for some similar molecules.