Distannabarrelenes with Three Coordinated Sn^II Atoms

Crystalline 1,4-distannabarrelene compounds [(ADC^Ar )₃ Sn₂ ]SnCl₃ (3-Ar) (ADC^Ar ={ArC(NDipp)₂ CC}; Dipp=2,6-iPr₂ C₆ H₃ , Ar=Ph or DMP; DMP=4-Me₂ NC₆ H₄ ) derived from anionic dicarbenes Li(ADC^Ar ) (2-Ar) (Ar=Ph or DMP) have been reported. The cationic moiety of 3-Ar features a barrelene framework with three coordinated Sn^II atoms at the 1,4-positions, whereas the anionic unit SnCl₃ is formally derived from SnCl₂ and chloride ion. The all carbon substituted bis-stannylenes 3-Ar have been characterized by NMR spectroscopy and X-ray diffraction. DFT calculations reveal that the HOMO of 3-Ph (ϵ=-6.40 eV) is mainly the lone-pair orbital at the Sn^II atoms of the barrelene unit. 3-Ar readily react with sulfur and selenium to afford the mixed-valence Sn^II /Sn^IV compounds [(ADC^Ar )₃ SnSn(E)](SnCl₆ )_0.5 (E=S 4-Ar, Ar=Ph or DMP; E=Se 5-Ph).