The calculation of 119 Sn relative chemical shifts by DFT methods has been extensively studied (for selected examples see Ref. ). Non-relativistic calculations using the Gauge-Including Atomic Orbitals (GAIO) method and the allelectron IGLO II/III basis set are accurate for Sn compounds lacking other heavy atoms. Unfortunately, the IGLO II basis set for Sn does not appear to be in the public domain. Relativistic calculations using the zeroth order regular approximation with spin-orbit coupling (ZORA-SO) also give very good agreement with experimental results, even for Sn compounds with heavy atoms such as Br or I. In this work, we apply the ZORA-SO method for 119 Sn chemical shift calculation to the conformer geometries optimized using the PBE0-GD3BJ level of theory. Using different levels of theory for geometrical optimization and chemical shift calculations is acceptable because the chemical shift is essentially a nuclear property influenced by electronic distributions rather than an intrinsically electronic property. Figure shows the correlation between calculated and experimental 119 Sn chemical shifts for a series of non-hypercoordinate reference compounds with structural elements related to the methoxystannane substituents in this study and with a wide range of chemical shifts. The calculated geometries and 119 Sn NMR chemical shifts are for gas-phase molecules while the experimental chemical shifts were measured in a non-coordinating solvent (usually chloroform). A good linear agreement is obtained with a slope of 1.012, and a correlation coefficient of 0.9966. Because both experimental and calculated chemical shifts are relative to the chemical shift of SnMe4 defined as 0 ppm, the regression must pass through the origin. Using the same methodology, 119 Sn NMR chemical shifts were calculated for each of the methoxystannane conformers, as geometrically optimized in both gas and solvent phases (Table -3). The calculated Sn NMR chemical shifts are sharply dependent on the Sn-O distances, with extended conformers having shifts close to non-hypercoordinate analogues but hypercoordinate conformers showing significant upfield shifts. Because the optimized geometries of the hypercoordinate conformers in solvent phase typically show shorter Sn-O distances, the calculated chemical shifts tend to be shifted more upfield than for the gas-phase geometries.