The first isolation of diarylstannanethione (tin-sulfur double-bond compound) and diarylstannaneselone (tin-selenium double-bond compound), Tbt (Ditp) Sn X (Tbt= 2, 4, 6- tris [bis (trimethylsilyl) methyl] phenyl; Ditp= 2, 2''-diisopropyl-m-terphenyl-2'-yl; X= S and Se) was accomplished by dechalcogenation of the corresponding highly hindered tetrachalcogenastannolanes, Tbt (Ditp) SnX4. The 119Sn NMR of stannanethione, Tbt ( ...