Pulsed laser evaporated boron atoms codeposited with Ar/CO2 samples give a strong product band at 1863.4 cm-1 that shows boron, carbon, and oxygen isotopic shifts. Ab initio calculations predict two strong infrared bands for the BOCO addition product and one strong band, which scales to the observed band position, for the OBCO insertion product. The calculated and observed frequencies exhibit isotopic shifts appropriate for an ''antisymmetric'' O-B, C-O stretching fundamental in a bent OBCO molecule.