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

Abstract

[TiCp2S5] (phase A), [TiCp2Se5] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp2SexS5−x] (Cp = C5H5−) 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 [TiCp2Cl2]. Their 77Se and 13C NMR spectra were recorded from the CS2 solution. The definite assignment of the 77Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the 77Se chemical shifts and is supported by 13C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS2 solutions of the phases B–E: [TiCp2Se5] (51), [TiCp2Se4S] (41), [TiCp2Se3S2] (31), [TiCp2SSe3S] (36), [TiCp2SSe2S2] (25), [TiCp2SSeS3] (12), and [TiCp2S5] (01). 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 [TiCp2SexS5−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 77Se and 13C NMR spectroscopy.

Selenium‐NMR Spectroscopy in Organic Synthesis: From Structural Characterization Toward New Investigations

“…Selenium element has proven to be a suitable nuclide in NMR spectroscopy in studies on stability, [40] reactivity, [41,42] chirality, [43,44,45,46,47,48] polymers, [49,50,51] coordination chemistry, [52,53,54,55] and bio-based experiments. [56,57,58,59] The great potential of 77 Se NMR experiments can be attributed to selenium-77 isotope properties, as spin ( 1 = 2 ), natural abundance (7.63%), no quadrupolar moment, magnetogyric ratio (5.12 × 10 7 rad.s À 1 .T À 1 ) and negligible nuclear Overhauser effect (nOe).…”