What is an easy way to reduce a boronic acid to borane? I have a selection of boronic acids that I want to reduce to borane forms. Some of the boronic acids in question are phenylboronic acid (C6H5B(OH)2), tolylboronic acid (C7H7B(OH)2), and p-phenylenediborinic acid (C6H4(B(OH)2)2). I want to convert them into phenylborane (C6H5BH2), tolylborane (C7H7BH2), and p-phenylenediborane (C6H4(BH2)2).

I think I can do this by dissolving the boronic acid in ether and adding Lithium Aluminum Hydride (LAH). Giving a reaction that looks something like:



However, I am afraid that, given how aggressive a reducing agent LAH is I might get something like:



So I guess I have two questions:


Will LAH attack the boron-carbon bond shown in the second reaction diagram?
Can the reduction of the boronic acid be accomplished via a less aggressive reducing agent, perhaps Sodium BoroHydride?


Just a note: I am well aware that the boranes produced will be oxygen sensitive, either converting back to boric acid on exposure to oxygen, or catching fire.
LAH will attack the boron-oxygen bonds without going after the boron-carbon bond, see here (Eq. Z, p. 142).

But it also deprotonates the hydroxyl groups as a strong base like a Grignard reagent. You need to prevent that.  Convert your acid to an ester (OH -> OR), remove the water and then apply the LAH.