A combined experimental and theoretical study examining the binding of N-heterocyclic carbenes (NHC) to the Cp*RuCl (Cp* = η5-C5Me5) moiety:: Insight into stereoelectronic differences between unsaturated and saturated NHC ligands

Combined solution calorimetric and quantum mechanics studies of reactions involving saturated and unsaturated N-heterocyclic carbene (NHC) ligands show that the difference in their relative bond dissociation energies is very small (1 kcal.mol(-1)). Structural and computational studies reveal small metric parameter differences. These observations in conjunction with relative reactivity profiles of NHC-modified ruthenium-based olefin metathesis catalysts suggest that very small changes in the donor properties of the NHC ligands can translate into significant differences in catalytic properties.