Density functional calculations of NMR chemical shifts with the inclusion of spin-orbit coupling in tungsten and lead compounds

Both the Pauli spin-orbit Hamiltonian and the relativistic zero order regul ar approximation (ZORA) have been used in conjunction with the gauge includ ing atomic orbital (GIAO) method based on density functional theory (DFT) t o calculate Pb-207 and W-183 NMR chemical shifts. For the tungsten series W O3S2-, WO2S22-, WOS32-, WS42-, WO42-, W(CO)(6), WCl6 and WF6, one finds the W-183 chemical shift to be dominated by paramagnetic contributions, wherea s the Fermi-contact contribution induced by spin-orbit coupling is of less importance. On the other hand, in the lead series Me3PbCl, Me3PbBr, Me3PbI, Me3PbOMe, Me3PbSMe, Me3PbSeMe, Me3PbNEt2, Me2PbCl2, and PbX4 (X = Cl, Br, I), the Fermi-contact term is the trend setting contribution. It is shown t hat ZORA in general provides chemical shift in better agreement with experi ment than the simpler Pauli spin-orbit scheme.