Catalytic Abilities of [(C6F5)2BR] (R=NC4H4 and NC4H8) deduced from experimental and theoretical charge-density investigations.

Marginal difference, huge impact: The topological analyses of the electron-density distributions obtained from experiment (see figure) and quantum-chemical calculations in the two title compounds can consistently explain marginal changes in bonding and rationalize different catalytic abilities. The electronic structures of the compounds bis(pentafluorophenyl)(N-pyrrolyl)borane (1) and bis(pentafluorophenyl)(N-pyrrolidinyl)borane (2) were investigated by low-temperature high-resolution X-ray diffraction experiments and subsequent multipole refinements. Additionally, DFT calculations were performed. The topological analyses of the electron-density distributions obtained from experiments and from quantum-chemical calculations are described and discussed. In this paper reasons for the different reactivities of the compounds are provided.