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

Graphical Abstract

Unrolling Tin Conformations: The Karplus-type dependence on the dihedral angle φ of vicinal spin-spin couplings involving ¹¹⁹Sn in organotin(IV) derivatives has been studied computationally at the scalar ZORA relativistic and at non-relativistic DFT levels. Several factors influencing the shape of the curve have been highlighted.

Abstract

The empirical Karplus-type dependence of ³J(¹¹⁹Sn,¹³C) and ³J(¹¹⁹Sn,¹H) couplings in organotin(IV) derivatives has been computationally validated by DFT methods both at the non-relativistic 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 ³J(¹¹⁹Sn,¹³C) 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 ¹¹⁹Sn-¹H and ¹¹⁹Sn-¹³C couplings cannot be derived, although the shape of the curves is preserved with |³J(0°)| < |³J(180°)| and ³J(90°) ≈ 0 Hz.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)