Selective cleavage of the B-O bond or B-H bond in HBpin can be achieved by adjusting the pincer ligand of a phosphorus(III) compound guided by a combination of theoretical prediction and experimental verification. Theoretical calculations reveal that a pincer-type phosphorus compound with an [ONO](3)(-) ligand reacts with HBpin, leading to cleavage of the stronger B-O bonds (Delta G degrees. = 23.2 kcal mol(-1)) rather than the weaker B-H bond (Delta G degrees double dagger = 26.4 kcal mol(-1)). A pincer-type phosphorus compound with a [NNN](3-) ligand reacts with HBpin, leading to the weaker B-H bond cleavage (Delta G degrees double dagger = 16.2 kcal mol(-1)) rather than cleavage of the stronger B-O bond (Delta G degrees double dagger = 33.0 kcal mol(-1)). The theoretical prediction for B-O bond cleavage was verified experimentally, and the final products were characterized by NMR, HRMS, and singlecrystal X-ray diffraction. The chemoselectivity of B-O bond cleavage was also observed in the presence of B-C or B-B bonds in borane substrates.