Nine coordinate, transition state

Mechanistically the reaction is proposed to proceed via a nine-membered transition state with the chiral phosphoric acid simultaneously activating the imine by protonation and the phosphite by coordinating to the hydroxyl group (Fig. 9). 

Possible stereochemistries for eight-coordinate [Ln(H20)8]3+ are the dodecahedron, the square antiprism, and the cube, although the last seems less likely (295). The proposed nine-coordinate [Ln(H20)9]3+ tri-capped trigonal prism transition state is similar to the [Ln(H20)9]3+ structures observed in the solid state. Thus, the possible water exchange... 

Perhaps the most important result in this study is the identification of the relationship between valency and the location of transition states. For the nine hydrogenation reactions on PtOH) it was found that as the valency of the reactants decreases so too does the tendency of the adsorbates to access transition states at sites of higher coordination number. 

Bodizs and Helm investigated nine-coordinated complexes of Gd(III) and Eu(II) with acetonitrile by a combination of NMR relaxation (for H and and EPR data. By the combined experiments, the dynamic processes in solutions could be characterized in terms of rotational correlation times and exchange rates. Mayer et studied variable temperature O transverse relaxation for the caboxylate oxygens in DOTA complexes through the lanthanide series. The data provided information on kinetics of the exchange between bound and unbound carboxylates. Through combination with DPT calculations, the authors were able to characterize the transitions states in the series of lanthanides. 

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