Correlated calculations of indirect nuclear spin-spin coupling constants for XH₄ (X = Si, Ge, and Sn)

We report multiconfigurational linear response calculations of the one-bond and geminal indirect nuclear spin-spin couplings constants in SiH₄, GeH₄, and SnH₄. Results of a basis set study on SnH₄ using 13 different basis sets on Sn are given, showing the effects on the individual contributions to the coupling constant. In addition to the more conventional choice of active orbital space (one correlating orbital for each strongly occupied valence orbital), calculations employing extended active spaces were carried out. The results are compared with available experimental data showing that correlation effects are very important. For the one-bond couplings good agreement with experiment, within 1-5%, is obtained, whereas the geminai proton-proton couplings show larger deviations. The calculations reported here are, to our knowledge, the first that take into consideration correlation effects in all four contributions to the coupling constants for molecules as large as GeH₄ and SnH₄. All X-H couplings are dominated by the Fermi contact term while the picture is more diverse for the geminal couplings.