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Although trimethylamine [(CH3)3N] and ammonia [H3N] are both recognized as classic Lewis bases, their reactions with the classic Lewis acid borane [BH3 from diborane] was very different. Trimethylamine gave the expected trimethylamine borane [(CH3)3NBH3] while ammonia gave a product called "the diammoniate of diborane." Its structure was shown to be [H2B(NH3)2]+[BH4]- in the late nineteen fifties. The Compound [H2B(NH3)2]+[BH4]- can be viewed as a classic coordination compound in which four-coordinate boron +3 ions are coordinated to the hydride ion and the ammonia molecule as ligands. It is noted that CoCl2 reacts with (CH3)3N and with NH3 in different ways. The "anomaly" is in the bases, not the borane acid.
The paper discusses the early studies on "the diammoniate of diborane" and emphasizes how continuing work done by Sheldon Shore at Ohio State University extended the work on the boranes and answered here-to-fore vexing structural problems on intermediates in the borane and borane-ammonia system. His work made major contributions to synthesis. He worked out techniques to prepare significant quantities of pure [H2B(NH3)2][BH4] and of pure H3NBH3. He also prepared the fascinating, theoretically anticipated compounds K2BH3 and K2B2H6.
The story, as told, shows how a brilliant, imaginative, and thoughtful person, using superb experimental techniques, has been able to develop a difficult experimental system from "black art" to sound science.
Note: This article was prepared from a talk given by the author at a Symposium (8/23/95) honoring Sheldon G. Shore on his sixty-fifth birthday. Dr. Shore is the Charles H. Kimberly Professor of Chemistry at Ohio State University.
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