Chelated amines ring conformation

Pd(II) complexes with enantiomerically pure orthometallated benzylamines have been studied in detail because they are used for the resolution of chiral ligands. For dimethyl(l-(a-naphtyl)-ethyl)amine it is clear that the chelate prefers the conformation with the benzylic Me in axial position, thus avoiding interactions with the naphtyl ring. This leads to a 8 conformation for the R amine (Figure 4.6), and to a X conformation for the Samine [23-26]. 

SS (RR, RS, or SR) refers to the absolute configurations of the nitrogens of the secondary amines these are fixed by the chelate ring conformations. The absolute configurations of amino acids are designated S (for L) or R (for D). 

If the amine carries a chelating substituent, as for 2-methoxyethylamine, the rate of deprotonation is accelerated. For any specific imine, ring substituents also influence the imine conformation and rate of deprotonation. These relationships reflect steric, stereoelectronic, and chelation influences, and sorting out each contribution can be challenging. 

A wide range of multidentate amine ligands coordinate to platinum. The conformational analysis of chelate ring systems by NMR has been reviewed by Hawkins, and platinum complexes are included in this work.959 Amine ligands with sulfur groups can also act as chelates, and this subject has also been reviewed.960... 

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