Migration from B to C or

But now B is electron-deficient again, and it wants an octet again, so the process repeats itself until all the B C bonds have been broken. The trialkylborate that is ultimately obtained undergoes hydrolysis to give the alcohol. 

the whiniest element in the periodic table, is never satisfied with its electron count. When it lacks its octet, it complains about being electron-deficient, but when a nucleophile comes along to give it its octet, it complains about its formal negative charge. 

The alkyl groups in boranes can migrate to C, too. For example, addition of the carbenoid equivalent LiCHCl2, obtained by deprotonation of CH2CI2 with LDA at low temperatures, to an alkylboronate gives the one-carbon homologous product. Other carbenoid equivalents such as diazo compounds and CO can undergo similar reactions. 

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