Coadsorption of Methyl Pyruvate and (±)-1-(1-Naphthyl)Ethylamine on Pt(111): Insights on the Mechanism for Asymmetric Hydrogenation

The results of a series of adsorption and coadsorption measurements using (±)-1-(1-naphthyl)ethylamine (NEA), methyl pyruvate, ester-deuterated methyl pyruvate, methyl naphthalene and 2,3-butanedione on Pt(111) are presented. Coadsorption of NEA stabilizes a molecularly adsorbed state of methyl pyruvate. The latter state undergoes thermal decomposition to yield a methane desorption peak centred at 320 K. Experiments performed using ester-deuterated methyl pyruvate show that the methane desorption results from the decomposition of the acetyl moiety of the α-ketoester. A stabilizing interaction is not observed for coadsorbed methyl naphthalene and methyl pyruvate, presumably due to the absence of an amine group. The study provides further evidence for the existence of a 1:1 methyl pyruvate-1-(1-naphthyl)ethylamine docking complex on Pt(111) under ultrahigh vacuum conditions.