Palladacycles − An Old Organometallic Family Revisited: New, Simple, and Efficient Catalyst Precursors for Homogeneous Catalysis

Abstract

Nitrogen-, phosphorus-, and sulfur-containing palladacycles, typically containing four-or six-electron donor anionic metallated ligands, are emerging as a new family of organometallic catalyst precursors. These thermally and air-stable complexes are easy to handle and their synthesis is often [a] interface of inorganic, organometallic, and organic chemistry, with an emphasis on metal-mediated functionalization of CϪH bonds through reactions aimed at producing new carbonϪcarbon or carbonϪheteroatom bonds. John Spencer obtained a B.Sc. (1st class, Hon.) at Sussex University in Chemistry with European Studies in 1990 before studying for a Ph.D. under the supervision of Michel Pfeffer, Strasbourg (1990Ϫ1994). After a postdoctoral stay with Antonio Togni at the ETH, Zurich, he returned to England where he first worked in the pharmaceutical industry (Xenova, Cerebrus) . He then took up his current position at the Thrombosis Research Institute (London), where he is now a Senior Research Scientist. He is a co-author of over a dozen papers and patents and his research interests include organopalladium and organoboron chemistry, as well as asymmetric catalysis.MICROREVIEWS: This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included.1917 straightforward. Palladacycles are now being successfully exploited in catalytic reactions ranging from classical hydrogenations to enantioselective aldol-type condensations. The main recent achievements pertaining to their use in homogeneous organometallic catalysis are outlined herein.

A Broadly Applicable Strategy for Entry into Homogeneous Nickel(0) Catalysts from Air-Stable Nickel(II) Complexes

“…4 Several groups (Nolan, 5 Buchwald, 6 Organ, 7 and others) have greatly advanced the ubiquity of precatalysts in organic synthesis, with much of the effort focused on palladium catalysts for cross couplings, amination, and related transformations. 8 Likewise, though by far less established than those for palladium-catalyzed reactions, single-component nickel precatalysts are not new, with the most frequently employed being complexes such as (PPh 3 ) 2 NiCl 2 .…”

Synthesis, Characterization, and Catalytic Applications of Palladacyclic Complexes Bearing C,N,S‐Donor Ligands

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Among these studies, the search for appropriate ancillary ligands that can serve as catalyst precursors is of current interest. Palladacycles bearing a metallated carbon atom and dative group(s) are the most active catalyst precursors for the promotion of such reactions.…”

“…Palladacycles bearing a metallated carbon atom and dative group(s) are the most active catalyst precursors for the promotion of such reactions. [2][3][4][5][6][7][8][11][12][13][14][15][16][17]19] These complexes are usually formed as dinuclear species with bridged ligands, or as mononuclear species in the presence of ligands with neutral dative groups. In order to improve the stability and efficiency of catalytic palladium complexes, various families of palladium based catalyst precursors have been developed.…”

Chloro{1-[(dimethylamino)methyl-κN]-1H-indolyl-κC2}(triphenylphosphine-κP)palladium(II) dichloromethane solvate

“…The presence of a tethered donor group allows the initial coordination of the ligand to the metal and favourable intramolecular cyclization. Palladacycles are amongst the most active catalysts for C-C and Cheteroatom bond formation (Herrmann et al, 1999;Albrecht & van Koten, 2001;Dupont et al, 2001). Palladacycles are amongst the most active catalysts for C-C and Cheteroatom bond formation (Herrmann et al, 1999;Albrecht & van Koten, 2001;Dupont et al, 2001).…”