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

[TiCp₂S₅] (phase ), [TiCp₂Se₅] (phase ), and five solid solutions of mixed titanocene selenide sulfides [TiCp₂SeS₅] (Cp = C₅H₅) with the initial Se:S ranging from 1:4 to 4:1 (phases ⁻) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp₂Cl₂]. Their Se and C NMR spectra were recorded from the CS₂ solution. The definite assignment of the Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the Se chemical shifts and is supported by C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS₂ solutions of the phases ⁻: [TiCp₂Se₅] (₁), [TiCp₂Se₄S] (₁), [TiCp₂Se₃S₂] (₁), [TiCp₂SSe₃S] (₆), [TiCp₂SSe₂S₂] (₅), [TiCp₂SSeS₃] (₂), and [TiCp₂S₅] (₁). The disorder scheme in the chalcogen atom positions of the phases ⁻ observed upon crystal structure determinations is consistent with the spectral assignment. The enthalpies of formation calculated for all twenty [TiCp₂SeS] ( = 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 Se and C NMR spectroscopy.