Orientation and Conformation of Methyl Pyruvate on Ni(111)

Abstract

The molecular orientation and conformation of methyl pyruvate on Ni(111) was studied in the temperature range 105-220 K. The full monolayer formed at 105 K was found to be almost exclusively in the bidentate cis-conformation, with the molecular plane oriented perpendicular to the surface. In contrast, the low coverage layer at 105 K was found to be composed of a mixture of trans-and cis-methyl pyruvate. However, direct exposure at 200-220 K yielded exclusively cis-bidentate adsorption at all coverages. The observation of the preferred cis-bidentate species is at odds with the adsorption geometry and conformation usually assumed in rationalizations of the enantioselective hydrogenation of methyl pyruvate on chiral-compound modified platinum metal particle catalysts.

Heterogeneous Enantioselective Hydrogenation over Cinchona Alkaloid Modified Platinum: Mechanistic Insights into a Complex Reaction

“…These calculations confirmed the strong interaction between Pt surface and the quinoline π-system. 39 As concerns the adsorption mode of the alkyl pyruvate reactant (methyl or ethyl pyruvate), ultrahigh vacuum studies on platinum single-crystal surfaces using X-ray and UV photoelectron spectroscopies (XPS and UPS), 40 NEXAFS, 41 and reflection/absorption infrared spectroscopy (RAIRS) 42 revealed that the alkyl pyruvate mainly adsorbs via lone pair-metal interaction of both carbonyl groups, that is, in cis conformation with the molecular tion for the observed rate enhancement. Generally, there are several possibilities how thermodynamic and kinetic factors can affect enantioselectivity and reaction rate, as schematically shown in Figure 6.…”

Solvent effect on CO oxidation as a novel diagnosing tool to pin down low-coverage CO at the liquid–solid interface: An in situ infrared study

“…The adsorption modes and thermal chemistry of methyl pyruvate on Ni(111) [46,61,62] and Pt(111) [63], of ethyl pyruvate on Pt(111) [64,65], and of 2,3-butandione on Ag(111) [66,67] and Ni(111) [47] have been investigated under ultrahigh vacuum conditions [46,47,61,62,[64][65][66][67] or using computational methods [63] in the absence of liquid phase. The co-adsorption and interaction of chiral modifier and α-ketoester on Pt(111) [68,69] and supported Pt/Al 2 O 3 catalysts [10,45,70] were the subject of a couple of recent studies.…”

Adsorption of activated ketones on platinum and their reactivity to hydrogenation: a DFT study

“…The adsorption of EP has been experimentally studied with different techniques on Ni and Pt [ [38][39][40][41]. While the preferred adsorption of molecular methyl pyruvate (MP) on Ni was found to be a bifurcated version of the η 1 discussed for AC, the studies on Pt point to a mixture of adsorption modes of the ethyl pyruvate.…”