A b i n i t i o study of the J(BB) and J(BH) coupling constants in polyboranes via the coupled-Hartree–Fock and equations-of-motion methods

Abstract

Coupled-Hartree–Fock and equations-of-motion calculations at ab initio level for the boron–boron and boron–proton indirect nuclear spin–spin coupling constants in a representative series of polyboranes (B2H6, B2H4, B2H−7, B3H−8, B4H10, and B5H9) are presented. The boron–hydrogen–boron coupling constant is very sensitive to molecular structure and shows neither a unique sign nor a constancy of absolute value. It is found to be negative in B2H6. On the other hand, the coupling constant for a two-center two-electron boron–boron bond is predicted to be invariably positive in sign. Results show that the positive sign must also be attributed to 1J(BH), irrespective of the bridged or normal nature of the boron–hydrogen bond.