If the pKa of acetonitrile is taken to be 33.3, and K ≈ 1 for equation ( ) using a base with pKa BH+ = 25, as indicated by the results above, then K ≈ 10 -8 for equation (10), corresponding to a value of ∆G° ≈ +11 kcal/mol for Pd-C bond cleavage. Using the higher estimated value of 39 for the pKa of acetonitrile, KE ≈ 10 -14 and ∆G° ≈ +19 kcal/mol. Clearly there is uncertainty in this estimate, due to the uncertainty in the pKa of the solvent, but this strategy of determining heterolytic M-C bond cleavage energies through protonolysis places M-C and H-C bond energies on a single, self-consistent scale, using widely-used pKa values as a reference. The experimental uncertainties should be more accurate in solvents with better-established thermodynamic data, such as water. Crystallographic data for 1 and 2 are given in Table . The palladium complex has an overall distorted square planar structure similar to other [Pd(triphos)X] + cations that have been crystallographically characterized. There is crystallographically-imposed mirror symmetry, matching the symmetry observed in solution but rare for solid-state structures of [M(triphos)X] complexes, which usually crystallize in chiral conformations due to the arrangements of the five-membered chelate rings. The chelate bite angle is 83.73(4)°, which is very similar to the aforementioned [Pd(triphos)X] + cations but somewhat smaller than the [Pd(RP[CH2CH2PR2])(NCCH3)] 2+ complexes that have been structurally characterized;