Synthesis and Structure of a Sterically Demanding Benzo‐1,2‐Diselenete

The synthesis and characterization of a stable benzo‐1,2‐diselenete bearing 3,5‐di‐ tert ‐butylphenyl groups as steric protection groups are reported, which revealed intrinsic properties consistent with a benzo‐1,2‐diselenete with no significant electronic perturbation. The reduction of the corresponding benzo‐1,2,3‐triselenole quantitatively afforded the targeted benzo‐1,2‐diselenete, which exhibits remarkable thermal stability up to 200°C in the solid state. An X‐ray crystallographic analysis revealed a planar CSeSeC skeleton with an elongated SeSe bond (2.398 Å) relative to typical SeSe single bonds ( ca. 2.32–2.34 Å), probably due to the electronic repulsion between the lone pairs of electrons at the selenium atoms. Spectroscopic studies, including 1 H, 77 Se NMR, and UV–vis spectra, suggested extended π–conjugation between the aromatic ring and the lone pairs of electrons on the Se atoms. Furthermore, its effective transformation of the benzo‐1,2‐diselenete to the 1,2‐bis(benzylseleno)benzene derivative was also investigated.