SYNTHESIS AND STRUCTURES OF NOVEL DITHIABORETANES CONTAINING A GROUP-4, GROUP-14, OR GROUP-15 ELEMENT

Dilithiation of the dimercaptoborane TbtB(SH)(2) (1), which was synthe sized by the sulfurization of the corresponding overcrowded lithium ar yltrihydroborate bearing the 2,4,6-tris[bis(trimethylsilyl)methyl]phen yl (Tbt) group, followed by treatment with electrophiles such as Cp2Ti Cl2, Mes(2)GeBr(2), Ph2SnCl2, and TbtSbBr(2) resulted in the isolation of novel four-membered baracycles, 1,3,2,4-dithiaboratitanetane, 1,3, 2,4-dithiagermaboretane, 1,3,2,4-dithiastannaboretane, and 1,3,2,4-dit hiastibaboretane as stable crystals, respectively. The introduction of a C, Si, or P atom to the four-membered ring was not successful. The structures of the newly obtained four-membered boracycles were determi ned by X-ray crystallograghic analysis. The four-membered rings are al most planar and perpendicular to the aromatic ring of Tbt group. The g eometries around the boron atom in the four-membered ring are found to be almost trigonal planer, and the S-B-S angles in the ring are not m uch smaller than 90 degrees, indicating that the geometry around the b aron and sulfur atoms was not so different from that of 1 in spite of being embedded in the ring system.