Catalytic C–C and C–Heteroatom Bond Formation Reactions: In Situ Generated or Preformed Catalysts? Complicated Mechanistic Picture Behind Well-Known Experimental Procedures

Abstract

In situ generated catalysts and preformed catalysts are two practical strategies widely used in cross-coupling methodology that have long been considered to involve the same active species in the catalytic cycle. Recent mechanistic studies have revealed two fundamentally different pictures of catalytic reactions in solution. Preformed catalysts with strongly bound ligands initiate transformations mainly involving single type of metal species. In contrast, in situ generated catalysts give rise to cocktail-type systems with different metal species presented in solution. The role of catalyst precursor, interconversions of catalytic species during reaction, stability and recycling of catalyst, catalysis by autocatalyst exhaust and plausible sources of metal-containing contaminants are the key points discussed in this review.

Plausible role of nanoparticle contamination in the synthesis and properties of organic electronic materials

“…Recent studies of catalytic reactions have surprisingly shown that catalytically active metal complexes do not remain unchanged during the synthetic transformation [14,15]. Indeed, several transformations involving metal complexes do take place simultaneously with the catalytic reaction ( Figure 4) [14].…”

“…Indeed, several transformations involving metal complexes do take place simultaneously with the catalytic reaction ( Figure 4) [14]. Of particular importance is the aggregation of metal complexes towards the formation of metal clusters and metal nanoparticles.…”

“…Several components of this mixture may exhibit catalytic activity and initiate the operation of the so-called "cocktail" of catalysts ( Figure 5) [14,16]. For example, molecular complexes of palladium as well as palladium clusters and nanoparticles can be formed, and each of the components can make a contribution toward the conversion of reagents to products.…”

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

“…An exceptionally high activity was found for dynamic catalytic systems with the possibility of adaptive tuning. 20,21 Yet another promising approach to increase the efficiency of catalytic reactions in fine organic synthesis is the use of specially developed heterogeneous catalysts in which the active components are immobilized metal complexes or even deposited metal particles. Indeed, heterogeneous catalysts have a number of significant advantages over homogeneous systems and, therefore, they may be considered more valuable for commercialization.…”

"Pure" method for depositing platinum nanoparticles onto the carbon material from a Pt2dba3 solution

“…8 The reaction mechanism can be of complicated nature, and the process can proceed via both the heterogeneous ca talysis and homogeneous catalysis routes, or via both routes in parallel. 9 It was shown that the study of the reaction mechanisms involving supported catalysts is impeded by the fact that the process of catalyst pre paration is affected by numerous poorly controlled fac tors (Fig. 1).…”