Cyclopalladation of C6H4(CH2SBut)2-1,3 and the crystal structure of [PdCl{C6H3(CH2SBut)2-2,6}]

Errington, J.; McDonald, Walter S.; Shaw, Bernard L.

doi:10.1039/dt9800002312

Cited by 76 publications

(79 citation statements)

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“…If the palladacycle formation were complete (i.e., if there was no coordination complex 5 present), the S-aryl SCS palladacycles (6,7,8,9, 10, 12, or 13) could be used in Heck chemistry without formation of any visible palladium black. If the coordination complex were present as a mixture with the palladacycle or if the coordination complex itself were used, palladium black invariably formed.…”

Section: Resultsmentioning

confidence: 99%

“…Shaws group had earlier noted that PPh 3 coordinates to the palladium center of an SCS complex. [8] van Koten has also shown that unmetallated PCP ligands can react with metallated NCN complexes in a trans-cyclometallation reaction. [8,44] During this reaction, the nitrogen ligands of the NCN complexes are displaced by the phosphorus atoms of the PCP ligand, and ultimately the metal center is transferred from the NCN moiety to the PCP ligand.…”

Section: Added Phosphine Experimentsmentioning

confidence: 97%

“…[7] Palladium pincer compounds are characterized by a metal-carbon bond and two coordinating heteroatoms that chelate the metal in a cyclic fashion (e.g., 1 -3). The most common heteroatoms are P, N, and S. The SCS palladacycles discussed here were first described by Shaw [8] and they and their N-and P-substituted analogues have emerged as an interesting, actively investigated family of organometallic complexes that have been used as a palladium source for various catalytic reactions. [7,9 -12] The mechanistic studies below focus on a limited subset of these complexes, the so-called SCS-Pd pincer complexes that have two sulfur atoms of a bis(benzyl thioether) chelating the carbon-bound palladium.…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Studies of SCS-Pd Complexes Used in Heck Catalysis

Bergbreiter

Osburn

Frels

2005

Advanced Synthesis & Catalysis

150

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Air-stable SCS palladacycles that can be used to promote C À C coupling chemistry were studied mechanistically. Using a small library of electronically varied SCS ligands, a collection of palladacycles was synthesized. Kinetic studies showed that these complexes all had induction periods, induction periods that were effected by concentration of substrates, products and trace impurities. Hammet correlations showed that electronically diverse palladacycles had identical 1 values, values that suggested that aryl halide electrophilic addition to a Pd species was not the rate-determining step. Phosphine addition experiments led to increased reactivity of the starting palladacycles, possibly by trapping an in situ generated Pd(0) species. Studies that examined reactivity in biphasic thermomorphic reactions showed residual activity in phases that do not contain polymer-bound palladacycle and provided convincing evidence that palladacycles are not the actual catalyst. Poisoning experiments using mercury metal to test for the presence of a Pd colloid were very effective with low molecular weight palladacycles, completely suppressing Heck chemistry. Similar studies with polymer-bound palladacycles showed mercury poisoning too. However, since so little decomposition of the palladacycle occurred, the polymer-bound palladacycle could still be recycled multiple times. However, mercury poisoned subsequent cycles of the experiment too. The conclusion is that SCS palladacycles are actually reservoirs of a catalytically active but ill-defined form of palladium(0).

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Section: Resultsmentioning

confidence: 99%

Section: Added Phosphine Experimentsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Mechanistic Studies of SCS-Pd Complexes Used in Heck Catalysis

Bergbreiter

Osburn

Frels

2005

Advanced Synthesis & Catalysis

150

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“…These incorporate thioether-type (S-alkyl or S-aryl) coordinating heteroatom donor sites and were reported in 1980 [25]. This work was subsequently followed by the studies of Pfeffer and coworkers [26].…”

Section: Thioether Containing "Scs" Aryl Pincersmentioning

confidence: 95%

Modern Organometallic Multidentate Ligand Design Strategies: The Birth of the Privileged “Pincer” Ligand Platform

Chase

Gossage

Koten

2015

The Privileged Pincer-Metal Platform: Coordination Chemistry &Amp; Applications

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The seemingly simple tridentate ligand design, one that is now known as the "pincer," has gained increasing importance in metal-ligand chemistry and in other applications as diverse as organic synthesis, catalysis, and materials science. This chapter describes the historical context in which the pincer ligand platform developed and sketches how Shaw's research played a crucial early role. The original chemistry, emerging in the late 1970s and early 1980s, is presented which details the synthesis and properties of the first examples of pincer-based organometallic complexes along with a selection of related species. Finally, a connection is made from this early start to the excellent and striving studies that currently are ongoing in pincer chemistry and its applications thereof.

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“…1). Initially, Pincer ligands had been designed simply as platforms intended to enforce trans-spanning bisphosphine (PCP [3]) or bis-sulphide donors (SCS [4]) or to act as a rigid mer-tridentate (NCN [5,6]) ligand. However, in present times, now some 40 years later, the pincer-ligand platform has developed into a multifunctional building block that is used in a wide variety of metal complexes for a number of more diverse applications.…”

Section: Prefacementioning

confidence: 99%