SYNTHESIS AND DEGRADATION OF AZADECABORAN ES - AZA-NIDO-NONABORATE

The boranes arachno-B9H13(NRH(2)) (1a-c: R = p-ClC6H4, p-MeC(6)H(4), P hCH(2)) are dehydrogenated at 140 degrees C to give nido-RNB(9)H(11) ( 2a-c), from which the azaboranes closo-RNB(9)H(9) (3a-c) are formed on further dehydrogenation at 460 degrees C. These azaboranes are deboro nated either by the attack of the amine iPrNH(2) or by one of the fluo rides [NBu(4)]F or [S(NMe(2))(3)][Me(3)SiF(2)] in THF. One of the four boron atoms adjacent to nitrogen in the closo species is removed and then detected in the borazine (HNBiPr)(3) or the berate BF4-, respecti vely, whereas the novel anions nido-RNB(8)H(9)(-) (4a-c) remain. The s tructure of 4a-c corresponds to that of nido-SB8H9-, according to NMR spectra. Primary amines R'NH2 deboronate the closo-boranes 3a, b in a solvent less polar than THF to give the amine-azanonaboranes arachno-R NB(8)H(10)(NR'H-2) (5a-c: R'= iPr, Pr, Bu). The nido product [iPrNH(3) ][(p-ClC6H4)NB8H9] is converted into a mixture of the arachno products 5a and (p-ClC6H4)NB8H10(NPrH2) (5d) by the action of PrNH2, making pl ausible that anions of type 4 are intermediates during the transformat ion of 3 into 5.