Why does reduction using sodium borohydride require a protic solvent?

Question

Recently, I was looking at the chapter on chemoselectivity in Clayden et al.'s Organic Chemistry (2nd ed.). On p. 530, it is mentioned that sodium borohydride reduction only occurs in protic solvents or in the presence of electrophilic metal ions, such as $\ce {Li+}$ and $\ce {Mg^2+}$ while the more powerful reducing agent lithium aluminium hydride does not require protic solvents. Why is that the case?

Reference

Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc.

Answer 1

There are two reasons:- 1. LAH is too reactive. So it can't exist in protic solvent whereaa NaBH4 can. 2. Protic solvent hydrolyse Na+ so that BH4- can show reducing action(as it a weak reducing agent).