Matrix infrared spectra of Co2CO were obtained from cobalt vapors condensed with different isotopically substituted mixtures of carbon monoxide diluted in argon at 10 K. New bands at 1953.3, 488.7, 357.9, and 270.9 cm(-1) are assigned to the nu(C-O), nu(M-CO), nu(M-C-O), and nu(M-M) fundamentals, respectively. Computations performed using density functional theory with the generalized gradient approximation (DFT-GGA) for the exchange-correlation potential predict the lowest energy state of Co2CO to be (5)A" with the angle Co-Co-C of 116degrees. Our DFT-GGA vibrational frequencies of this state agree with the experimental frequencies extremely well-within 15 cm(-1). Our estimate for the Co-2-CO bond strength is 1.60 eV. Computed vibrational frequencies for Co2CO+ and Co2CO- are included for comparison.