Titanocene Selenide Sulfides Revisited: Formation, Stabilities, and NMR Spectroscopic Properties

[TiCp(2)S(5)] (phase A), [TiCp(2)Se(5)] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp(2)Se(x)S(5−x)] (Cp = C(5)H(5)(−)) with the initial Se:S ranging from 1:4 to 4:1 (phases B–E) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp(2)Cl(2)]. Their (77)Se and (13)C NMR spectra were recorded from the CS(2) solution. The definite assignment of the (77)Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the (77)Se chemical shifts and is supported by (13)C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS(2) solutions of the phases B–E: [TiCp(2)Se(5)] (5(1)), [TiCp(2)Se(4)S] (4(1)), [TiCp(2)Se(3)S(2)] (3(1)), [TiCp(2)SSe(3)S] (3(6)), [TiCp(2)SSe(2)S(2)] (2(5)), [TiCp(2)SSeS(3)] (1(2)), and [TiCp(2)S(5)] (0(1)). The disorder scheme in the chalcogen atom positions of the phases B–E observed upon crystal structure determinations is consistent with the spectral assignment. The enthalpies of formation calculated for all twenty [TiCp(2)Se(x)S(5−x)] (x = 0–5) at DLPNO-CCSD(T)/CBS level including corrections for core-valence correlation and scalar relativistic, as well as spin-orbit coupling contributions indicated that within a given chemical composition, the isomers of most favourable enthalpy of formation were those, which were observed by (77)Se and (13)C NMR spectroscopy.