Competing Reaction Pathways in Heterogeneously Catalyzed Hydrogenation of Allyl Cyanide: The Chemical Nature of Surface Species.

We present a mechanistic study on the formation of an active ligand layer over Pd(111), turning the catalytic surface highly active and selective in partial hydrogenation of an α,β-unsaturated aldehyde acrolein. Specifically, we investigate the chemical composition of a ligand layer consisting of allyl cyanide deposited on Pd(111) and its dynamic changes under the hydrogenation conditions. On pristine surface, allyl cyanide largely retains its chemical structure and forms a layer of molecular species with the CN bond oriented nearly parallel to the underlying metal.

Understanding Ligand-Directed Heterogeneous Catalysis: When the Dynamically Changing Nature of the Ligand Layer Controls the Hydrogenation Selectivity.

We present a mechanistic study on the formation and dynamic changes of a ligand-based heterogeneous Pd catalyst for chemoselective hydrogenation of α,β-unsaturated aldehyde acrolein. Deposition of allyl cyanide as a precursor of a ligand layer renders Pd highly active and close to 100 % selective toward propenol formation by promoting acrolein adsorption in a desired configuration via the C=O end. Employing a combination of real-space microscopic and in-operando spectroscopic surface-sensitive techniques, we show that an ordered active ligand layer is formed under operational conditions, consisting of stable N-butylimine species.

Adsorption geometry and self-assembling of chiral modifier (R)-(+)-1-(1-naphthylethylamine) on Pt(111).

A mechanistic study on interaction of a chiral modifier - (R)-(+)-1-(1-naphthylethylamine) (R-NEA) - with a single crystalline Pt(111) surface is reported. The details of the adsorption geometry of individual R-NEA molecules and their intermolecular interactions are addressed by combination of infrared reflection absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM). The spectroscopic observations suggest that the molecules are tilted with respect to the underlying metal substrate with the long axis of the naphthyl ring being parallel and the short axis tilted with respect to the surface.