Chemoselectivity for B-O and B-H Bond Cleavage by Pincer-Type Phosphorus Compounds: Theoretical and Experimental Studies.

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 (ΔG°⧧ = 23.2 kcal mol-1) rather than the weaker B-H bond (ΔG°⧧ = 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 (ΔG°⧧ = 16.2 kcal mol-1) rather than cleavage of the stronger B-O bond (ΔG°⧧ = 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 single-crystal 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.