Matrix Isolation Studies on Sulfur Heterocycles and Related Species

Abstract

The matrix isolation technique in combination with vacuum pyrolysis, photochemistry, and quantum mechanical computations was applied to study the structures and reactivities of dimethoxycarbene (DMC) and 1,3-dithian-2-ylidene. 1,2,4-Trithiolane was used for the generation of thioformaldehyde S-sulfide and the isomeric dithiirane. Irradiation of thioformaldehyde S-oxide in argon matrix at 10 K led to the first isolation of parent oxathiirane as well as HCSOH, a remarkable species with a rare formal carbon–sulfur triple bond.

Keywords:

• Flash vacuum pyrolysis
• nucleophilic carbenes
• thiocarbonyl S-oxides
• thiocarbonyl S-sulfides
• 1,2,4-trithiolanes

Acknowledgments

The presented work was supported by the DAAD within the Partnership of the University of Łódź and the Justus-Liebig University. G. M. thanks the Alexander von Humboldt-Stiftung (Bonn) for financial support.

Notes

Products of gas phase thermolysis of 3 were also studied by means of photoelectron spectroscopy. ^11b

Figure 2 The computed (CCSD(T)/cc-pVDZ) IR spectra of two of the three DMC conformers (top) and the difference IR spectrum of the crude pyrolysate registered at 11 K in Ar matrix (bottom).

The first dithiiranes substituted with bulky groups were reported by Nakayama, Ishii, and co-workers in the 1990s. ¹⁸

The absorption maximum localized at λ = 374 nm is attributed to a π → π* transition. ²⁴

This type of isomerization may be expected based on an earlier observation by Senning. ²⁵ Apparently, isomerization processes of thiosulfines are strongly substituent-dependent; see also the discussion in Ref. [26].

Figure 6 IR spectrum (middle) of photorearrangement of thioacetone S-sulfide (22) into 3,3-dimethyldithiirane (17d) (10 K, Ar-matrix). Computed IR spectra at B3LYP/6-311 + G(d,p) (top and bottom).