Closer scrutiny of the TS structures of 1-5 shows that a shorter (longer) bond length of the P(O-H) bond corresponds to a larger (smaller) imaginary frequency, giving a Badger type correlation. For instance, the P(O-H) bond at the TS for 5Me,Me with the largest u has the shortest bond length of 1.226 Å, whereas 5CF3,C2F5 with the smallest u has the longest bond length of 1.619 Å, respectively. Overall, we observed an absolute linear variation between u and P(O-H) bond length for our studied systems (R 2 = 0.99; see Figure in the Supporting Information).