Density functional calculations of dinuclear organometallic carbonyl complexes. Part I: metalmetal and metalCO bond energies

One of the most fundamental properties in chemistry is the bond dissociation energy (BDE), the energy required to break a specific bond of a molecule. In this paper we apply gradient-corrected density functional theory (DFT) to the calculation of the BDEs of three prototypical organometallic complexes, Mn2(CO)10, Fe2(CO)9, and Co2(CO)8, along with the CO-loss products Mn2(CO)9 and Mn2(CO)8. We consider the dissociation of both the metalmetal bond and a metalcarbonyl bond. For Mn2(CO)10 and Fe2(CO)9, the calculated metalmetal BDE is within the error of the experimental measurements. However, the calculated metalmetal BDE for Co2(CO)8 is not within the errors of the measurements, but is improved greatly with an unrestricted wavefunction compared with a restricted wavefunction. For the first carbonyl BDE, the calculations agree within a few kcal mol−1 for each complex.