Do Boranes Contain Hydrogen Bonds

In conclusion, the data support strongly the existence of complex formation between acids and aromatics acting as bases. Since there is ample evidence that the proton of the acid is specifically involved in the interaction, it can properly be called a H bond. An important implication of the conclusion that the base B can be aromatic is that the base must be a good electron donor but not necessarily a highly electronegative group. Clearly, this conclusion must influence a discussion of the theory of H bond formation. 

Since the boranes satisfy criteria 3 and 5, they meet the general requirements of H bonding. Despite this positive verification that the boranes involve structural units which resemble bent but symmetrical H bonds, it may be that the similarity is only superficial. Perhaps the bonding is very different in character and, if so, other properties can be expected to differ from the usual H bond behavior. 

Another interesting technique is the proton resonance measurement. Ogg has identified the resonances characteristic of the two types of protons of diborane, and finds the resonance of the bridge protons at higher magnetic fields (1538). Ogg offers the interpretation that the shift signifies that the bridge protons are more hydride-ion like than the terminal H atoms. Whether this is correct or not, the shift is in the opposite direction to the usual H bond effect. 

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