Integral cross sections for the bond-forming reaction CO2+ + Ar --> ArC2+ + O have been measured as a function of collision energy in a guided-ion beam mass spectrometer. The energy dependence is consistent with an endoergic reaction. Since the title reaction is in competition with several charge-transfer processes, the cross section at the maximum is only 0.023 Angstrom(2) at a collision energy of about 3 eV. Simple kinematics considerations suggest that the falloff of the cross section at higher energies might be due to the vibrational predissociation of ArC2+. State correlation diagrams are used for discussing the reaction mechanism. (C) 2000 American Institute of Physics. [S0021-9606(00)01510-5].