Formation of metallacarboxylic acids through Hieber base reaction. A density functional theory study

Using density functional theory (B97-D/ECP2/PCM//RI-BP86/ECP1 level), we have studied the effects of ligand variation on OH- uptake by transition-metal carbonyls (Hieber base reaction), i.e., LnM(CO)+OH-[LnM(CO2H)](-), M=Fe, Ru, Os, L=CO, PMe3, PF3, py, bipy, Cl, H. The viability of this step depends notably on the nature of the co-ligands, and a large span of driving forces is predicted, ranging from G=-144kJ/mol to +122kJ/mol. Based on evaluation of atomic charges from natural population analysis, it is the ability of the co-ligands to delocalize the additional negative charge (through their -acidity) that is the key factor affecting the driving force for OH- uptake. Implications for the design of new catalysts for water gas shift reaction are discussed.