Next, the activation energy barriers for the dissociation of CO from the Ni(0) centers of 3a, 3c, and 3f were compared (Fig. ). The values of G ‡ (with respect to that of 3) increase in the order TS1c (+13.3 kcal mol -1 ) < TS1f (+14.2 kcal mol -1 ) < TS1a (+14.9 kcal mol -1 ). This trend is consistent with the experimental results that show that the efficiency of CO desorption increases in the order 3a (9%) < 3f (39%) < 3c (97%) under the applied experimental conditions (Fig. ). The presence of the N-phosphinoyl oxygen atom in 3c minimizes the change in the spatial environment around the Ni(0) center during the CO substitution process, which was evaluated using the percent buried volume (%Vbur) calculated based on the geometrical parameters obtained from DFT calculations . The change in %Vbur (%Vbur) (26) was found to be 3.3 when the %Vbur values of the 1c moieties in 3c, TS1c, and [2c•••CO] were compared; this value is obviously smaller than the %Vbur of 7.5 calculated for the transformation of 3f into [2f•••CO] via TS1f, thus rationalizing the faster interconversion in the former case compared to that of the latter.