March 2014   (Technical report   )

Surface Diastereomeric Complexes Formed by Methyl Benzoylformate and (R)-1-(1-Naphthyl)ethylamine on Pt(111)

Guillaume Goubert, Peter McBreen

The formation of diastereomeric complexes between methyl benzoylformate (MBF) and (R)-1-(1-naphthyl)ethylamine, (R)-NEA, on Pt(111) was studied using scanning tunneling microscopy. We observe several distinct geometries formed by 1:1 and 2:1 MBF/(R)-NEA complexes. The complexation patterns are compared with our previous data for 2,2,2-trifluoroacetophenone, (TFAP)/(R)-NEA, and methyl-3,3,3 trifluoropyruvate, (MTFP)/(R)-NEA, complexes on Pt(111). Steric hindrance due to the phenyl group forces MBF to form complexes that are inverted relative to those formed by MTFP. Compared to TFAP, the addition of the ester group, permitting intermolecular bonding through either the ester or the keto-carbonyl or both, increases the number of complexation geometries that the substrate can adopt. In particular, the ketoester group permits the phenyl group to be placed distant from (R)-NEA at several positions while also permitting NH···OC bonding. Overall, this leads to a decrease of the prochiral selectivity relative to TFAP/(R)-NEA complexes.