Fig. 4

Transition state in the concurrent reactions. a Methyl triphosphate fully deprotonated (number of protons n_P = 0), b γ-protonated (n_P = 1), c αγ-protonated (n_P = 2), d βγ-protonated (n_P = 2) and e αβγ-protonated (n_P = 3). See also caption of Fig. 3. Coordination bonds to Mg²⁺ are shown as dotted line. The four water molecules coordinating the Mg²⁺ are not shown, but are present in the calculations. The distance from the P_γ to the leaving and attacking oxygen atoms is indicated in Å