Observation of Aromatic\nB<sub>13</sub>(CO)<sub><i>n</i></sub><sup>+</sup> (<i>n</i> = 1–7) as\nBoron Carbonyl Analogs of Benzene

CO as a typical σ-donor is one of the most important\nligands\nin chemistry, while planar B<sub>13</sub><sup>+</sup> is experimentally\nknown as the most prominent magic-number boron cluster analogous to\nbenzene. Joint gas-phase mass spectroscopy, collision-induced dissociation,\nand first-principles theory investigations performed herein indicate\nthat B<sub>13</sub><sup>+</sup> reacts with CO successively under\nambient conditions to form a series of boron carbonyl complexes B<sub>13</sub>(CO)<sub><i>n</i></sub><sup>+</sup> up to <i>n</i> = 7, presenting the largest boron carbonyl complexes observed\nto date with a quasi-planar B<sub>13</sub><sup>+</sup> core at the\ncenter coordinated by <i>n</i>CO ligands around it. Extensive\ntheoretical analyses unveil both the chemisorption pathways and bonding\npatterns of these aromatic B<sub>13</sub>(CO)<sub><i>n</i></sub><sup>+</sup> monocations which, with three delocalized π\nbonds well-retained over the slightly wrinkled B<sub>13</sub><sup>+</sup> moiety, all prove to be boron carbonyl analogs of benzene\ntentatively named as boron carbonyl aromatics (BCAs). Their π-isovalent\nB<sub>12</sub>(CO)<sub><i>n</i></sub> (<i>n</i> = 1–6) complexes with a quasi-planar B<sub>12</sub> coordination\ncenter are predicted to be stable neutral BCAs.