B-H bond protonation in mono- and diprotonated borane complexes H3BX (X = N2H4, NH2OH, and H2O2) involving hypercoordinate boron

Structures of mono- and diprotonated borane complexes H3BX (X = N2H4, NH2OH , and H2O2) as well as their neutral analogues were calculated using the de nsity functional theory method at the B3LVP/6-311+G** level. Global minimum structures (3, 9, and 14) for all of the monocations N4BX+ are B-N protona ted with a three-center two-electron bond. Remarkably, in the case of monop rotonated hydrazine-borane H3BNH2NH2 (1), the B-H protonated H4BNH2NH2+ (3) was calculated to be 6.3 kcal/mol more stable than the N-protonated H3BNH2 NH3+ (2), unexpectedly indicating that: the bonded electron pair of the B-H bond is a better donor than the nonbonded nitrogen electron pair in hydraz ine-borane complex 1.