The synthesis of 1,4-[(RCp)2Ti]2Se4 (R = H (3a), Me (3b), i-Pr (3c) is described together with their applications to the preparation of 1,2,5,6-Se4S4 (4). The deselenization of (RCp)2TiSe5 (2a-c) with organophosphines gives 3a-c isolated as purple microcrystalline solids. The same compounds could also be prepared from the reaction of (RCp)2TiCl2 with solutions of Li2Se2. RCp labeling studies show that these Ti2Se4 compounds do not exchange their (RCp)2TiSe2 fragments. 77Se NMR studies indicate that 3c has one type of Se atom while three resonances are observed for the pentaselenide 2c. Compound 3b crystallizes in the triclinic space group C1 with a = 9.577 (2) Å, b = 15.145 (2) Å, c = 8.359 (1) Å, α = 97.08 (1)°, β = 92.02 (1)°, γ = 89.89 (1)°. A total of 1772 data were processed to a final RF = 0.0382, RwF. = 0.0444. The compound adopts a centrosymmetric chair conformation with Ti-Se and Se-Se distances of 2.55 and 2.34 Å, respectively. The reaction of 3a and 3b with CS2 solutions of S2Cl2 in a molar ratio 1:2 gave 4 in good yield. The single-crystal X-ray diffraction analysis of 4 indicates the presence of a cyclic crown conformer with the atomic positions occupied statistically by either S or Se due to rotational disorder. Raman spectra show three sets of lines assigned to bond stretching modes vSe-Se, vSe-S, and vS-S. The 77Se NMR spectrum of 4 exhibits only one line at 651.5 ppm. Upon heating, 4 undergoes two endothermic transformations assigned to polymerization to (Se2S2)n followed by melting at 112.5 °C.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry