Carbon-fluorine bond cleavage in the preparation of osmium(III) and osmium(IV) fluorothiolate complexes. Fluorine by fluorine NMR-assignment and fluxional processes

Abstract

Reactions of OsO4 with HSR (R = C6F5, C6F4H-4,) in refluxing ethanol afford [Os(SC6F5)(3)(SC6F4(SC6F4(SC6F5)-2)] (1) and [Os(SC6F4H-4)(3)(SC6F3H-4-(SC6F4H-4)-2)] (2) which involve the rupture of C-F bonds. At room temperature, the compound [Os(SC6F5)(3)(PMe2Ph2)] or [Os(SC6F5)(4)(PMe2Ph)] reacts with KOH(aq) in acetone, giving rise to [Os(SC6F5)(SC6F4(SC6F4O-2)-2)(PMe2Ph)(2)] (3), through a process involving the rupture of two C-F bonds, while the compound [Os(SC6F4H)(4)(PPh3)] reacts with KOH(aq) in acetone to afford [Os(SC6F4H-4)(2)(SC6F3H-4-O-2)(PPh3)] 4), which also implies a C-F bond cleavage. Single-crystal X-ray diffraction studies of 1, 2, and 4 indicate that these compounds include five-coordinated metal ions in essentially trigonal-bipyramidal geometries, whereas these studies on the paramagnetic compound 3 show a six-coordinated osmium center in a distorted octahedral geometry. F-19, H-1, P-31 {H-1}, and COSY F-19-F-19 NMR studies for the diamagnetic 1, 2, and 4 compounds, including variable-temperature F-19 NMR experiments, showed that these molecules are fluxional. Some of the activation parameters for these dynamic processes have been determined.