Synthesis of the long-sought unsubstituted aminodiboranate Na(H3B-NH2-BH3) and its N-alkyl analogs.

Reduction of ammonia borane, NH(3) x BH(3), with Na or NaNH(2) in refluxing tetrahydrofuran (thf) affords the new compound, the unsubstituted aminodiboranate Na(BH(3)-NH(2)-BH(3)) (1a). Similar N-alkyl- and N,N-dialkylaminodiboranate salts, Na(H(3)B-NHMe-BH(3)) (1b), Na(H(3)B-NHEt-BH(3)) (1c), Na(H(3)B-NMeEt-BH(3)) (1d), Na[H(3)B-N(C(4)H(8))-BH(3)] (1e), and Na[H(3)B-N(C(5)H(10))-BH(3)] (1f), where N(C(4)H(8)) = pyrrolido and N(C(5)H(10)) = piperido, have also been prepared, along with their adducts with dioxane Na[H(3)B-NRR'-BH(3)](diox)(x) where x = 0.5 or 1.0 (2a-f). Crystal structures of 2b, 2c, and 2e are reported. Treatment of ErCl(3) with Na(H(3)B-NH(2)-BH(3)) in thf affords the new erbium complex Er(H(3)B-NH(2)-BH(3))Cl(2)(thf)(3), 3, which has been crystallographically characterized. (1)H and (11)B NMR spectra of the new compounds are reported.