The reactions of ground-state boron atoms with CO in solid argon have been reinvestigated. The BCO molecule was formed by codeposition of laser-ablated boron atoms with CO in argon. The v(1), v(2), v(3), 2v(1), 2v(3), and v(1) + v(3) modes of isotopic BCO molecules have been measured. The linear dicarbonyl, B(CO)(2), and the dimer OCBBCO were produced on sample annealing. Quantum chemical calculations of the geometry structures, vibrational frequencies, and intensities strongly support the experimental assignments. It is found that OCBBCO has a linear singlet ground state with some boron-boron triple-bond character. Bonding analysis shows that s to p (or sigma to pi) promotion plays a significant role in these boron carbonyl species.