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A Single‐Molecule‐Level Mechanistic Study of Pd‐Catalyzed and Cu‐Catalyzed Homocoupling of Aryl Bromide on an Au(111) Surface
Author(s) -
Adisoejoso Jinne,
Lin Tao,
Shang Xue Song,
Shi Ke Ji,
Gupta Aditi,
Liu Pei Nian,
Lin Nian
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304443
Subject(s) - catalysis , chemistry , activation energy , bromide , rate determining step , reaction rate constant , yield (engineering) , reaction rate , coupling reaction , photochemistry , aryl , chemical kinetics , kinetics , inorganic chemistry , materials science , organic chemistry , alkyl , physics , quantum mechanics , metallurgy
On‐surface Pd‐ and Cu‐catalyzed CC coupling reactions between phenyl bromide functionalized porphyrin derivatives on an Au(111) surface have been investigated under ultra‐high vacuum conditions by using scanning tunneling microscopy and kinetic Monte Carlo simulations. We monitored the isothermal reaction kinetics by allowing the reaction to proceed at different temperatures. We discovered that the reactions catalyzed by Pd or Cu can be described as a two‐phase process that involves an initial activation followed by CC bond formation. However, the distinctive reaction kinetics and the CC bond‐formation yield associated with the two catalysts account for the different reaction mechanisms: the initial activation phase is the rate‐limiting step for the Cu‐catalyzed reaction at all temperatures tested, whereas the later phase of CC formation is the rate‐limiting step for the Pd‐catalyzed reaction at high temperature. Analysis of rate constants of the Pd‐catalyzed reactions allowed us to determine its activation energy as (0.41±0.03) eV.