Carbon−Fluorine Bond Activation in Thermolysis Reactions of the Osmium(IV) Perfluorothiolate Compounds [Os(SC6F5)4(P(C6H4X-4)3)] (X = CF3, Cl, F, H, CH3, and OCH3)

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Thermolysis reactions of [Os(SC6F5)4(P(C6H4X-4)3)] (X = CF3 1, Cl 2, F 3, H 4, CH3 5, and OCH3 6) in refluxing toluene yield compounds [OsF(SC6F5)2(SC6F4(SC6F5)-2)(P(C6H4X-4)3)] (1a−6a) and [Os(SC6F5)2(SC6F4(SC6F5)-2)(C6H4X-4)] (1b−6b). In addition, [Os(SC6F5)3(SC6F4(SC6F5)-2)] (c) is yielded from 1−4 and 6, compounds [OsF(SC6F5)3(P(C6H4X-4)3)] [X = CF3 (1e), X = Cl (2e)] are also identified as products of the thermolysis reactions of 1 and 2, while [Os(SC6F5)2(S2C6F4)(P(C6H4CH3-4)3)] (5d) is obtained from 5. Compounds c, e, and d are produced in low yields (ca. 2−4%). Formation of all products involves the rupture of ortho C−F bonds. The first complexes systematically detected in these thermolysis reactions are compounds a, which are isomers of the starting complexes. Thus, the C−F activation involves the metal-mediated generation of the covalent Os−F bond. Single-crystal X-ray diffraction studies of the new compounds 4a, 5a, 2b−6b, 2e, and 5d indicate that these compounds consist of five-coordinated metal ions in essentially trigonal-bipyramidal geometries. In addition, thermolysis of the isolated compound [OsF(SC6F5)2(SC6F4(SC6F5)-2)(P(C6H4CH3-4)3)] (5a) in refluxing toluene gives rise to [Os(SC6F5)2(SC6F4(SC6F5)-2)(C6H4CH3-4)] (5b) and [Os(SC6F5)2(S2C6F4)(P(C6H4CH3-4)3)] (5d), confirming that compounds a can generate compounds b when the thermolysis is prolonged. Compounds 1a−6a, 2b−6b, 1e, and 2e are investigated in solution by NMR studies, including variable-temperature 19F NMR experiments. These molecules are fluxional. Some of the activation parameters for the dynamic processes are determined.