Bis(ortho)-Chelated Bis(phosphanyl)aryl Ruthenium(II) Complexes Containing an η1-P-Monodentate or μ-Bridging η1-P,η1-P′ Bonded R−PCHP Arene Ligand, 1-R-3,5-(CH2PPh2)2C6H3 [R = H, Br, or, Si(n-CH2CH2C8F17)3] — Cyclometalation Reaction Intermediates and Potential Catalysts for Use in Fluorinated Biphasic Systems

Dani, Paulo; Richter, B.; Klink, Gerard P. M. van; Koten, Gerard van

doi:10.1002/1099-0682(20011)2001:1<125::aid-ejic125>3.0.co;2-q

Cited by 29 publications

(13 citation statements)

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“…The postulated intermediates 5 and 6 ( Fig. 1) [18] formed during the course of the reaction after a fast, irreversible cyclometalation step, were observed in the present study, for the first time, by monitoring aliquots of a mixture containing equivalent amounts of ligand 2d and complex 3 in refluxing benzene by 31 P-NMR spectroscopy. The chemical shift and multiplicity of the 31 P-NMR signals provide an excellent probe, which allowed for the assignment of three species: the product [RuCl{2,6-(Ph 2 PCH 2 ) 2 C 6 H 3 ]}(PPh 3 )] (4d) and two intermediates.…”

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confidence: 99%

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Medici

Gagliardo

Williams

et al. 2005

Helvetica Chimica Acta

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Dedicated to Professor AndreÂ Merbach on the occasion of his 65th birthday, for his excellent contributions to the field of inorganic chemistry and for his support and friendship were determined by X-ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh 3 )] complexes and chiral [RuCl(P*CP*)(PPh 3 )] complexes were tested as catalyst in the H-transfer reduction of acetophenone with propan-2-ol. With the chiral complexes, a modest enantioselectivity was obtained.Introduction. ± The interaction of multidentate phosphine ligands with late transition metals has been extensively studied since these ligands can be modularly designed to tune the stereochemical and electronic properties of the corresponding metal species. Complexes of the platinum-group metals with monoanionic P-donor pincer ligands of the type [2,6-(R 2 PCH 2 ) 2 C 6 H 3 ] À (R Me,

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confidence: 99%

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Medici

Gagliardo

Williams

et al. 2005

Helvetica Chimica Acta

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“…38 The structures were solved by direct methods and refined by full-matrix least-squares on F 2 using SHELXTL-97. 39 3 BICP, 4 BINAP, 5 DIPAMP, 6 JOSIPHOS, 7 have been proven to be highly enantioselecitve in organic synthetic scenarios ( Figure 21). Scheme 67.…”

Section: Methodsmentioning

confidence: 99%

“…36a-c In such reactions, imines are often transient intermediates that are often detected but usually not isolated due to their rapid reduction during the return of the borrowed hydrogen as part of the hydrogen auto-transfer process mediated by the metal catalyst. 39 For instance recent reports have focused on an efficient methodology for the direct alkylation of amines with alcohols at 115 °C for 10 h using 1 mol% [Cp*IrI 2 ] 2 in water with no added base giving high yields of the amine products. 40 Investigations revealed that complex 4 is also active for this N-alkylation reaction (Table 4).…”

Section: Catalytic N-alkylation Of Amines With Alcoholsmentioning

confidence: 99%

“…The versatility of cycloruthenation originates last but not least from the great diversity of available ruthenium precursors (Scheme 52). 38,39 Unlike for palladacycles, a whole mechanistic picture of the cycloruthenation process is far from being complete. 2,36 Currently, no compelling evidence is available for certain reaction pathways.…”

Section: Ruthenacycles In Organic Synthesismentioning

confidence: 99%

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Part I Synthesis, characterization and reactivity studies on Ir(III) and Ru(IV) complexes with sulfur ligands Part II Catalytic applications of Ru and Pd metallacycles in C-C and C-P bond formations

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His extreme kindness gave me the chance to truly enjoy my PhD study. I also thank Dr. Goh Lai Yoong, for her advice during the initial phase of my project involving the synthesis and characterization of the thiolate-thioether complexes. I also thank Prof. Leung Pak-Hing for providing constant and unrestricted access to the facilities and resources of his laboratory and to all the group members of the Leung group past and present

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“…This increased energy requirement for tridentate coordination of PCPH pincer ligands can lead to their adopting diphosphine-like bridging coordination modes when reactions are carried out under conditions where C−H cleavage is not facile. 47 To overcome the difficulty involved in breaking this strong C−H bond to achieve ligand metallation, the pincer ligands can alternatively be prepared with bromide or iodide substituents on C-2. This approach is typically combined with a starting material in the zero oxidation state (such as [Pd 2 (dba) 3 ]), as oxidative addition of the carbon-halide bond will yield the pincer halide complex [(PCP)MX].…”

Section: Synthesis Of Pcp and Pnp Pincer Complexesmentioning

confidence: 99%

Late Transition Metal Complexes of Pentafluorophenylphosphino-Pincer Ligands

Anderson¹

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<p>This thesis details the synthesis of new examples of electron-poor pincer ligands, featuring bis(pentafluorophenyl)phosphine donors attached to 1,3-substituted phenylene or 2,6-substituted pyridine backbones, to create tridentate PCP and PNP ligands. The effect of the ligands’ electronic nature on the coordination chemistry and ease of pincer complex synthesis with late transition metals is discussed, as is the catalytic activity of the resultant palladium pincer complexes in the Heck and Suzuki reactions. Symmetric PCP and PNP ligands possessing bis(pentafluorophenyl)phosphinite and bis(pentafluorophenyl)phosphoramine functionalities were synthesised by reaction of bis(pentafluorophenyl)phosphine bromide with resorcinol, 3-hydroxybenzyl-di- tert -butylphosphine, 2,6-diaminopyridine, or 2,6-dihydroxypyridine, affording 1,3- [(C6F5)2PO]2C6H4 (POCOPH, 1), 1-[(C6F5)2PO]-3-(tBu2PCH2)2C6H4 (POCCPH, 3), 2,6-[(C6F5)2PNH]2C6H3N (PNNNP, 10), and 2,6-[(C6F5)2PO]2C6H3N (PONOP, 11) respectively. The previously reported 1,3-[(C6F5)2PCH2]2C6H4 (PCCCPH, 2) was also synthesised, with the literature yield improved upon by the use of magnesium-anthracene to generate the required Grignard reagent. The coordination chemistry of the POCOPH ligand 1 with platinum(0) alkene and platinum(II) dimethyl precursors revealed an affinity for the formation of cis-bridged oligomeric structures. The dimer [(POCOPH)Pt(nb)]2 (14, nb = norbornene) was isolated and crystallographically characterised from the reaction between 1 and [Pt(nb)3]. The solid state structure revealed the presence of stabilising - interactions between the aromatic ligand backbones, which were also observed in solution by 1H NMR spectroscopy. Reactions of ligand 1 with platinum and palladium dichloride or chloromethyl starting materials led to rare examples of cis,trans-dimers of the type cis,trans-[(POCOPH)MClX]2 (M = Pd, Pt; X = Cl, Me). In part due to facile dimer formation with 1, metallation of the ligand backbone to form the tridentate pincer complex [(POCOP)PtCl] (25) required long reaction times and high temperatures. It was observed that platinum dichloride starting materials with more strongly binding ancillary ligands were less prone to oligomer formation, and could facilitate more rapid metallation to from 25. More facile pincer complex formation was also observed for more electron-rich ligands with both PCP and PNP pincer ligands. The electron poor platinum and palladium POCOP, PCCCP, and POCCP pincer complexes (where the free ligand had been deprotonated upon metallation) were synthesised and subsequently converted into the metal carbonyl species [(PCP)M(CO)]+. Analysis of C−O stretching frequencies by infrared spectroscopy confirmed complexes of POCOP ligand 1 were the most electron poor, while those of POCCP ligand 3 were the most electron rich. Decarbonylation of the palladium pincer complexes was observed in solution and in the solid state, and was more facile for complexes with a higher wavenumber C−O stretch. Reaction of the [(PCP)PtCl] pincer complexes with methyl nucleophiles revealed that treatment with methylmagnesium iodide resulted in halide exchange, while methyllithium promoted nucleophilic attack at phosphorus. Spectroscopic data indicated that in one instance this led to pentafluorophenyl migration to the metal centre to form a [(PCP)Pt(C6F5)] complex. Dimethylzinc was successful in methylating the platinum PCP complexes; however, it was observed to degrade the palladium PCP pincer complexes. Treatment of the rhodium PNP pincer complex [(PNNNP)RhCl] (49) with dimethylzinc also resulted in degradation, which spectroscopic evidence indicated proceeded via ligand deprotonation and the formation of a zinc adduct of 49. Low temperature protonolysis of the [(PCP)PtMe] species did not reveal any information about possible interactions between the metal and liberated methane. The catalytic activity of the electron-poor [(PCP)PdCl] complexes were assessed in the Heck and Suzuki cross-coupling reactions. The complexes of 1, 2, and 3 were all found to possess only modest activity in the Heck reaction, functioning as precatalysts which decomposed to give catalytically-active Pd(0) colloids. Under milder Suzuki reaction conditions, the most electron-poor complex, [(POCOP)PdCl] (28) proved to be one of the most active pincer catalysts known for this reaction, able to achieve a turnover number of 176,000 for the coupling of electronically-deactivated aryl bromides and phenylboronic acid. Mercury poisoning tests revealed that Suzuki reactions catalysed by 28 proceeded via a homogeneous active species.</p>

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Cited by 29 publications

References 37 publications

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Part I Synthesis, characterization and reactivity studies on Ir(III) and Ru(IV) complexes with sulfur ligands Part II Catalytic applications of Ru and Pd metallacycles in C-C and C-P bond formations

Late Transition Metal Complexes of Pentafluorophenylphosphino-Pincer Ligands

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