Molecular modeling study of the PtCl2 complexes of unsaturated S2On+1-coronands: Dynamic simulations and investigation of the ring interconversion

Maleonitrile-dithiacrown ethers mn-12S(2)O(2) - mn-21S(2)O(5) (mn = maleoni trile) are preorganized S2On+1-coronands (n = 1 - 4) which force B, AB and A class metal ions into mixed S/O coordination spheres. Moreover, they form chelate complexes with MX2 salts (M = Pd, Pt; X = Cl, Br), which were stud ied in this paper. The structures of mn-S2On+1 and [PtCl2(mn-S2On+1)] (n = 2, 3) were investigated theoretically by empirical and semiempirical method s using SYBYL (TRIPOS force field) and MSI/ DISCOVER97 (ESFF force field). mn-12S(2)O(2) was investigated experimentally by X-ray analysis and 1D and 2D NMR spectroscopy in solution and the complex formation was studied by H- 1, C-13 and Pt-195 NMR titration experiments, respectively. S-inversion was also investigated in order to determine the ring corresponding interconver sional barriers. Different orientations of the macrocyclic ring system mn-1 8S(2)O(4) and of its transition states are shown.