Chloroboration and allied reactions of unsaturated compounds. Part VI. Thiaboration, and other aspects of boron–sulphur chemistry

Abstract

The preparation of twenty organic B–S compounds, including members of the new classes R₂NB(SR′)₂, (R₂N)₂BSR′, (R₂N)BrBSR′, and (R₂N)ClBSR′, is reported. Five methods were explored, and particularly noteworthy are the general methods for synthesis of borthi-ins (XBS)_n, with use of dihalogenoboranes and either HgS or (Me₂SiS)₃. The position of B–S compounds, relative to B–N, B–Hal, etc., in boron “conversion” and “dispalcement” series is assigned. The thioboranes have been fully characterised. Especially significant is the recognition of a triplet absorption centering upon 930 cm.^–1 as diagnostic for their identification. Molar refractivities agree well with calculated values. The complexes BrB(SBuⁿ)₂,2py and Br₂BSBuⁿ,py have been prepared. Oxidation of a B–S compound has afforded the first boryl sulphone. Thioboranes act as 1,2-dipolarophiles with respect to isocyanates, but not isothiocyanates, carbon dioxide, or carbon disulphide. The novel thiourethanoboranes have been characterised.