Boranes fluxional processes

As usual, H- H coupling is lost in the broad lines of boranes. The bridging hydrides are seen as the broad unresolved multiple centred at -1.38 ppm. The width of this signal may be associated with B-B coupling (a second-order effect) or with some fluxional process. It is typical of bridging B-H-B resonances. The three remaining terminal hydride signals should each appear as a quartet as a result of... 

Polyhedral isomerizations may be studied using either a microscopic or macroscopic approach. The microscopic approach uses details of polyhedral topology to elucidate possible single polyhedral isomerization steps, namely which types of isomerization steps are possible. Such isomerization steps consist most commonly of so-called diamond square-diamond processes or portions thereof. The microscopic approach to polyhedral isomerizations is relevant to understanding fluxional processes in borane and metallaborane polyhedra. 

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