On the Stability and Recyclability of Supported Metal–Ligand Complex Catalysts: Myths, Misconceptions and Critical Research Needs

Abstract

Research on heterogenized metal complex catalysts has been carried out for 40 years. Despite thousands of published catalysts, there are only two significant commercial processes that utilize supported metal complex catalysts. Most academic papers are simply ''demonstration of concept'' studies reporting myriad ways to support various metal complex catalysts. Too few papers focus on rigorous studies of reaction kinetics, catalyst recycle, catalyst stability and deactivation pathways. Here, preliminary stability and deactivation studies of supported enantioselective Co-salen epoxide ring-opening catalysts and enantioselective Ru-salen olefin cyclopropanation catalysts are summarized. Insights with regard to catalyst deactivation suggest methodologies for catalyst stabilization, allowing for more effective catalyst recycle and enhanced catalyst turnover. Further examples where supported metal complex catalysts are applied in commercial processes will require the field to shift focus from ''demonstration of concept'' studies to more detailed investigations of catalyst stability and recyclability.

Copper(I)@Carbon-Catalyzed Carboxylation of Terminal Alkynes with CO2 at Atmospheric Pressure

“…However, catalytic deactivation of the recovered catalyst appears in common heterogeneous catalysis. 51 Furthermore, the electronic state of the Cu element in the catalyst was analyzed by X-ray photoelectron spectroscopy (XPS), as shown in Figure 4. Figure 4a shows the binding energies of Cu 2p for the CuBr@C catalyst as prepared.…”

Pd‐Catalyzed Z‐Selective Semihydrogenation of Alkynes: Determining the Type of Active Species

“…[1,6,9,21,24,29,33,[54][55][56][57] Excellent reviews by Finke et al and Crabtree give an overview of the experiments and methods used for the determination of the type of active catalyst. [10,11] Especially the methodology by Finke et al has providedabasis in this field.…”

“…Studies on the nature of the active catalysti nt he Heck-reaction illustrate the importance of knowing the type of ac atalyst and the benefits thereof.T hese investigations provided ar ationalef or the observed reactivities, disproved wrong mechanistic assumptions, and have realized that the Heck-reaction can now be performed at ultra-low metal loadings. [3,4,[29][30][31][32] According to experts in the field of the determination of the type of active species, the number of catalyst systems that are erroneously assumed to be well-defined molecular catalysts is underestimated. [10,11] This holds especially for Pd-catalyzed coupling and hydrogenation reactions, [11,25,33] because many of those reactions can be performed by both transition metalAp rotocol was developed to distinguish between well-defined molecular and nanoparticle-based catalysts for the Pd-catalyzed semihydrogenation reaction of alkynes to Z-alkenes.T he protocola pplies quantitative partial poisoning and dynamic light scattering methods, which allow the institution of additional validation experiments.…”

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

“…Note that with an allylic electrophile, three-component coupling furnished two C7C bonds. 81 In the reactions with organozinc reagents, (bromodifluoromethyl)trimethylsilane (12) in the presence of the acetate anion was used to generate difluorocarbene.…”