Boronyls as Key Structural Units in Boron Oxide Clusters: B(BO)_2~- and B(BO)_3~-

摘要

BO~- is isoelectronic with CN~-. However, in comparison to CN~-, which is an important ligand in inorganic and biomolecules, the chemistry of BO~- is relatively unknown. The electron affinity (EA) of BO (2.51 eV) is much smaller than that of CN (3.86 eV), which may explain the fact that CN~- is a stable anion in solution, but BO~- is not. However, the electronic structure and bond strength of BO~- are similar to those of CN~-, suggesting that it may be a robust chemical unit and can retain its structural integrity in chemical compounds. In a recent study, we indeed found that BO behaves like a monovalent structural unit in its bonding to Au in Au_nBO~- (n = 1-3) clusters. Theoretical calculations also suggested that carbon boronyls (CBO)_n (n = 3-7) are stable species on the potential-energy surfaces. Here we report a photoelectron spectroscopy (PES) and theoretical study on two boron oxide clusters, B_3O_2~- and B_4O_3~-, which are shown to possess a D_(∞h) (~3Σ_g) linear and D_(3h) (~2A_2") triangular structure, respectively, and can be viewed as two and three boronyl groups bonded to a single B atom.