BEITRAEGE ZUR CHEMIE DES BORS CLXXVII. DITHIADIBORETANE UND TRITHIATRIBORANE (BORTHIINE): KINETISCHE UND THERMODYNAMISCHE PRODUKT-KONTROLLE

Article abstract of DOI:10.1016/0022-328X(86)80292-3

Thermal decomposition of μ-(aminoborondithiolato)bis(tricarbonyliron) compounds gives the 2,4-diamino-1,3,2,4-dithiadiboretanes (R2NBS)2 (R2N = NMe, NⁱPr2, tmp) at ca. 200 deg C. (Me2NBS)2 thus obtained reacts with itself in solution to give (Me2NBS)3.Therefore, the B2S2 compounds are the kinetically controlled products while the B3S3 ring systems represent the thermodynamic products.This is further substantiated by the thermolysis of PhBS2Fe2(CO)6 at 200 deg C which yields a mixture of (PhBS)2 with (PhBS)3, while pure (PhBS)2 is readily obtained from PhBCl2 and (Me3Si)2S under mild conditions.Pyrolysis of the diboron compound (Me2N)2B2S2Fe2(CO)6 proceeds with disproportionation leading to (Me2NBS)2 as the volatile products, while the spirocyclic iron cluster μ-(2,5,7,10-tetramethyl-2,10-diaza-5,7-diazonia-1,6-diboratotricyclo<5.3.0.0^1,5>decane-6,6-dithiolato)bis(tricarbonyliron) yields bis(1,3-dimethyl-1,3,2-diazaborolidin-2-yl)sulfide.Silthiane cleavage of (Me2Si)2S with aminoboron halides R2NBX₂ and (Me2N)2BCl require reflux conditions in toluene to give (R2NBS)2,3 heterocycles.