Hydrazine Complexes of B-Triorganylboroxins,

Abstract : B-Triorganylboroxins, (-BRO-)3 (R = C2H5, C6H5), form 1:1 molar complexes with hydrazine, N,N' -dimethylhydrazine, and N,N'-dimethylhydrazine. At room temperature, the complexes exhibit only one 11B NMR signal suggesting that the species are fluxional with nitrogen coordinating to all three boron atoms of the boroxin ring. The signals broaden on lowering of the temperature and, at -50 C, the signal of (BC2H5O-)3(CH3)2NNH2 appears as two separate peaks in 2:1 ratio indicating that fluxion has been arrested. The complexes (-BRO-)3L with R = C2H5 or C6H5 and L = N2H4 and with R = C6H5 and L = (CH3)2NNH2 can form solvates with excess of the hydrazine and solid 1:2 molar complexes were isolated. However, the second hydrazine is readily lost under reduced pressure or at evaluated temperatures. The complexes of B-triphenylboroxin are thermally much less than those of B-triethylboroxin.