Development of Palladium Precatalysts that Efficiently Generate LPd(0) Active Species

Abstract

Palladium catalysts have become central to modern organic synthesis, particularly in the context of crosscoupling reactions to form CÀ C and C-heteroatom bonds. The development of highly efficient catalyst systems has seen a transition from the use of in situ-generated catalysts derived from a ligand source and palladium precursor to the use of preformed palladium-ligand complexes that can efficiently generate the active species. The design of these systems has focused on optimizing the generation of the LPd(0) species presumed to be the active catalysts with most state-of-the-art ligand systems. This review will highlight the development of Pd(0), Pd(I), and Pd(II) precatalysts that efficiently generate LPd(0) active species with a focus on their activation mechanisms and applications in catalysis. Scheme 3. Synthesis of diene-stabilized LPd(0).Scheme 4. COD-stabilized LPd(0) and application to fluorination reactions. Scheme 14. Activation routes for Pd(allyl) precatalysts. Scheme 15. Competition between formation of active species and inactive μ-allyl palladium(I) dimers.

Isolation and Catalytic Reactivity of Mononuclear Palladium(I) Complexes

“…[1][2][3][4] In these systems, while the general reaction mechanism involves a Pd 0 /Pd II catalytic cycle, 1,5 several reports proposed the involvement of Pd I intermediates. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Additionally, while there are many examples of transient Pd I species [23][24][25][26][27][28][29][30] as well as isolated Pd I dimers, [31][32][33][34] there are very few examples of well-established monomeric Pd complexes bearing a formal +1 oxidation state at Pd. To the best of our knowledge, only two structurally characterized examples of isolated Pd I complexes -the cationic [Pd I (P t Bu3)2] + species and the [Pd I (MeCN)(P t Bu3)2] + complex, have been reported independently by Chaplin's and Ozerov's groups, respectively.…”

Isolation and Catalytic Reactivity of Mononuclear Palladium(I) Complexes

“…[1][2][3][4] In these systems, while the general reaction mechanism involves a Pd 0 /Pd II catalytic cycle, 1,5 several reports proposed the involvement of Pd I intermediates. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Additionally, while there are many examples of transient Pd I species [23][24][25][26][27][28][29][30] as well as isolated Pd I dimers, [31][32][33][34] there are very few examples of well-established monomeric Pd complexes bearing a formal +1 oxidation state at Pd. To the best of our knowledge, only two structurally characterized examples of isolated Pd I complexes -the cationic [Pd I (P t Bu3)2] + species and the [Pd I (MeCN)(P t Bu3)2] + complex, have been reported independently by Chaplin's and Ozerov's groups, respectively.…”

Halogen‐Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions

“…[13] However, excess ligands continuously compete with the substrates for the coordination site at the Pd center. [14] Moreover,h omoleptic PdL 2 complexes tend to be rather air-sensitive. [14] Alternatively,the catalyst is generated in situ from Pd II or Pd 0 precursors and phosphine or carbene ligands (Figure 1b).…”

“…[14] Moreover,h omoleptic PdL 2 complexes tend to be rather air-sensitive. [14] Alternatively,the catalyst is generated in situ from Pd II or Pd 0 precursors and phosphine or carbene ligands (Figure 1b). However,incomplete reduction of Pd II precursors to Pd 0 can Figure 1.…”