TRIS(DIETHYLAMINO)CYCLOTRIBORANE AND CONSTITUTIONAL ISOMERISM BETWEEN CYCLO AND CLOSO-HEXAKIS(DIETHYLAMINO)HEXABORANE(6)

The reaction of Et2NBCl2 with potassium in boiling cyclohexane provides a mixture of aminopolyboranes, containing 20 - 25 mol-% (BNEt2)3 (1), (BNEt2)4 (2), and cyclo-(BNEt2)6 (3), respectively, as well as varying amounts of closo-(BNEt2)6 (4). Whereas 1 and 3 have been highly enriched by means of HPLC, 4 has been isolated by column chromatography and crystallization. On standing in solution at room temperature, the cyclo-isomer 3 slowly rearranges to the closo-isomer 4, while at elevated temperatures the reverse conversion occurs. Hence 4, which is the first neutral B6 compound with octahedral structure, has a relatively higher thermodynamic stability at normal conditions.