Karplus-Type Dependence of Vicinal (119)Sn-(13)C and (119)Sn-(1)H Spin-Spin Couplings in Organotin(IV) Derivatives: A DFT Study

The empirical Karplus-type dependence of (3)J((119)Sn,(13)C) and (3)J((119)Sn,(1)H) couplings in organotin(IV) derivatives has been computationally validated by DFT methods both at the nonrelativistic and scalar ZORA relativistic level. A preliminary calibration of the computational protocols, by comparing experimental and calculated couplings for a Set Of Suitable rigid molecules, revealed their high predictive power: in particular, relativistic results for (3)J((119)Sn,(13)C) have a mean absolute error of just above 2 Hz, over a range of values up to about 70 Hz. The latter protocol has then been used to study in detail the influence of substituents and multiple paths connecting the coupled nuclei on the vicinal coupling constants, Some conformational issues have been also considered. Significant effects have been observed and theoretical Karplus-type curves for some representative systems have been proposed and discussed. It appears that general equations for vicinal (119)Sn-(1)H and (119)Sn-(13)C couplings cannot be derived, although the shape of the curves is preserved with vertical bar(3)J(0 degrees)vertical bar < vertical bar(3)J(180 degrees)vertical bar and (3)J(90 degrees)vertical bar approximate to 0 Hz.