A NOVEL ACCESS TO THE ICOSAHEDRAL CLOSO N B11 SKELETON

At 200 degrees C, the open skeleton of NB9H12 is closed to the icosahe dral skeleton of NB11H10Y (3) by the action of three equivalents of Et (3)N . BH3, whereby one equivalent forms a bridge Y = -BH2-NEt(2)-CH2- CH2- between the adjacent cluster atoms N1 and B2; the product 3 cryst allizes in the space group $($) over bar$$ P1. With L . BH3 (L = NMe(3 ), SMe(2)) instead of Et(3)N . BH3, the nido-borane NB9H12 is transfor med into the closo-borane (LBH(2))NB11H11 (4a, b) at 140 degrees C. By allowing tBuNH(2) to react with 4b, the N-bonded ligand Me(2)SBH(2) i s removed with formation of the aza-closo-dodecaborate [tBuNH(3)][NB11 H11], thus opening a new route to closo-NB11H12.