The binding enthalpy of a triphenylphosphine ligand in Ru(CO)Cl (PPh3)(3)(CH=CHPh) is studied with "standard" (BP86 and B3LYP), dispersion-corrected (B3LYP-D and B97-D), and highly parametrized (M05 and M06 series) density functionals. An appropriate treatment of noncovalent interactions is mandatory because these turn out to account for a large fraction of the metal-ligand interaction energy. Among the tested methods, B97-D and the M06 series of functionals best reproduce the experimental binding enthalpy value of Sponsler et al. (Inorg. Chem. 2007, 46, 561).