The presence of a Co-Co bond path and associated bond critical point in the density rho(r) for the compound CO2(CO)(6)(mu-CO)-(mu-C4H4O2) (2) has been investigated by quantum calculations on the isolated molecule at the DFT/B3LYP level, by a periodic DFT calculation on the triclinic phase of 2 and also by multipole refinement on the experimental data for the triclinic phase. In all models examined, a ring critical point is the only critical point associated with the Co-Co vector. (c) 2005 Elsevier B.V. All rights reserved.