Fig. 3.

The reported pentacovalent phosphorus intermediate with β-PGM (17) is a $\mathrm{PGM}\mathrm{\text{-}}{\mathrm{MgF}}_3\mathrm{\text{-}}\mathrm{G}6\mathrm{P}\mathrm{\text{-}}\mathrm{TSA}$ complex. (A) Difference Fourier maps calculated for the structure 1o08 contoured at $+3\sigma$ and $-3\sigma$. The difference maps show significant discrepancies from the original interpretation (17) in the derived bond lengths and assignment of atoms in the TBP moiety. Positive peaks (ca. $8\sigma$, green) are observed beyond each of the equatorial atoms of the TBP indicating that the assigned equatorial bond lengths were too short. The large negative peak ($9.6\sigma$, red) for the central coordinating atom indicates that the true atomic species is lighter than phosphorus. (B) Difference Fourier maps calculated after refinement against the deposited structure factors (www.pdb.org) with ${\mathrm{MgF}}_3^{-}$ replacing ${\mathrm{PO}}_3^{-}$ as the trigonal planar species. Unrestrained refinement of the deposited coordinates against the deposited structure factors leads to equatorial bond lengths of ca. 1.9 Å, which are consistent with our observed bond lengths. Replacing ${\mathrm{PO}}_3^{-}$ with ${\mathrm{MgF}}_3^{-}$ as the trigonal planar species in the model eliminates peaks in the difference Fourier maps above $3\sigma$.