Redox-active multinuclear Pd(<scp>ii</scp>) complexes with bis- and tris-mesoionic carbenes

Maity, Ramananda; Meer, Margarethe van der; Sarkar, Biprajit

doi:10.1039/c4dt03239j

Cited by 59 publications

(55 citation statements)

References 46 publications

(23 reference statements)

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“…In our pursuit of understanding the electronic structures, electrochemical properties, and donor properties of MICs, we have now turned our attention to MICs that are substituted with one or two ferrocenyl groups. In doing so, we wanted to test if the well‐defined electron transfer properties of the ferrocenyl group can be utilized to tune the donor properties of the MIC ligands and their metal complexes.…”

Section: Introductionmentioning

confidence: 99%

Heteromultimetallic Complexes with Redox‐Active Mesoionic Carbenes: Control of Donor Properties and Redox‐Induced Catalysis

Hettmanczyk

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Klenk

et al. 2016

Chemistry A European J

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Mesoionic carbenes (MICs) are currently hugely popular as ligands, and triazolylidenes are arguably the most prominent classes of such MICs. Mesoionic carbenes with ferrocenyl substituents are presented that can act as metalloligands for the generation of heteromultimetallic iridium(I) and gold(I) complexes. The ferrocenyl substituents allow for reversible oxidation of these heteromultimetallic complexes, and these oxidation steps have a strong influence on the donor properties of the MICs. Tolman electronic parameters (TEP) determined from analysis of the iridium-carbonyl complexes show that the neutral ferrocenyl-MIC ligands are stronger donors than the imidazolylidene based carbenes, the one-electron oxidized ferrocenyl MICs are in the range of the tricyclohexyl phosphines and the two-electron oxidized forms, which are electron-poor, lie in the range of triphenyl phosphines. Taking advantage of the generation of these electron-poor MICs, we show their gold(I) complexes are potent catalysts for the synthesis of oxazolines, with complexes of the oxidized MIC ligands, without any additional additive, outperforming their neutral counterparts by almost a factor of ten. These results thus present the first examples of MIC ligands that are reversibly electronically tunable, and show the potential of the oxidized MIC ligands in types of catalysis where electron-poor ligands are necessary. The potential of MICs for molecular electroactive materials is also shown.

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Section: Introductionmentioning

confidence: 99%

Heteromultimetallic Complexes with Redox‐Active Mesoionic Carbenes: Control of Donor Properties and Redox‐Induced Catalysis

Hettmanczyk

Suntrup

Klenk

et al. 2016

Chemistry A European J

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“…Iridium( iii ) complexes were shown to be efficient catalysts in water oxidation reactions [9,42,43,44,45] as well as other oxidation reactions and transfer hydrogenations [46,47,48,49,50,51], which are also catalyzed by ruthenium( ii ) and osmium( ii ) complexes [46,47,49,50,52,53,54,55,56,57,58]. Furthermore, 1,2,3-triazol-5-ylidenes and their metal complexes have also been investigated for their photochemical [59,60,61,62,63,64] and redox properties [60,65].…”

Section: Introductionmentioning

confidence: 99%

“…Especially palladium( ii ) 1,2,3-triazol-5-ylidene complexes obtained a lot of attention since the discovery of 1,2,3-triazol-5-ylidene complexes [22]. Various types of palladium( ii ) complexes show diversities in the coordination fashion and have different additional ligands (Figure 1) [22,38,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82]. Almost all palladium( ii ) complexes were used as catalysts in a variety of cross coupling reactions.…”

Section: Introductionmentioning

confidence: 99%

Palladium(ii)-Acetylacetonato Complexes with Mesoionic Carbenes: Synthesis, Structures and Their Application in the Suzuki-Miyaura Cross Coupling Reaction

et al. 2016

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A series of novel palladium(II) acetylacetonato complexes bearing mesoionic carbenes (MICs) have been synthesized and characterized. The synthesis of the complexes of type (MIC)Pd(acac)I (MIC = 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (1), 1,4-(2,4,6-methyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (2), 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (3); acac = acetylacetonato) via direct metalation starting from the corresponding triazolium iodides and palladium(II) acetylacetonate is described herein. All complexes were characterized by 1 H-and 13 C-NMR spectroscopy and high resolution mass spectrometry. Additionally, two of the complexes were characterized by single crystal X-ray crystallography confirming a square-planar coordination geometry of the palladium(II) center. A delocalized bonding situation was observed within the triazolylidene rings as well as for the acac ligand respectively. Complex 2 was found to be an efficient pre-catalyst for the Suzuki-Miyaura cross coupling reaction between aryl-bromides or -chlorides with phenylboronic acid.

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“…A recent emerging class of carbenes are abnormal, or latterly called mesoionic carbenes, MIC [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. One interesting subclass of these MICs are 1,2,3-triazol-5-ylidenes [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Since their first report in 2008 by the Albrecht group [ 36 ] these carbenes now belong to one of the “hot topics” in organometallic chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…Since their first report in 2008 by the Albrecht group [ 36 ] these carbenes now belong to one of the “hot topics” in organometallic chemistry. In the field of catalysis, especially the carbene derivatives of 1,2,3,-triazoles, so-called triazolylidenes, have proven to show superior effects on the catalytic performances in several catalytic processes [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. One reason for this is their easy accessibility, through the copper(I) catalyzed click [3+2] cycloaddition reaction between azides and alkynes [ 51 , 52 ].…”

Section: Introductionmentioning

confidence: 99%

Copper(I) Complexes of Mesoionic Carbene: Structural Characterization and Catalytic Hydrosilylation Reactions

et al. 2015

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Abstract:Two series of different Cu(I)-complexes of "click" derived mesoionic carbenes are reported. Halide complexes of the type (MIC)CuI (with MIC = 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (for 1b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 1c)) and cationic complexes of the general formula [Cu(MIC)2]X (with MIC =1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = CuI2 − (for 2á), 1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4 − (for 2a), 1,4-(2,6-diisopropyl)phenyl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4 − (for 2b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene, X = BF4 − (for 2c)) have been prepared from CuI or [Cu(CH3CN)4](BF4) and the corresponding ligands, respectively. All complexes were characterized by elemental analysis and standard spectroscopic methods. Complexes 2á and 1b were studied by single-crystal X-ray diffraction analysis. Structural analysis revealed 2á to adopt a cationic form as [Cu(MIC)2](CuI2) and comparison of the NMR spectra of 2á and 2a confirmed this conformation in solution. In contrast, after crystallization complex 1b was found to adopt the desired neutral form. All complexes were tested for the reduction of cyclohexanone under hydrosilylation condition at elevated temperatures. These complexes were found to be efficient catalysts for this reaction. 2c was also found to catalyze this reaction at room temperature. Mechanistic studies have been carried out as well. OPEN ACCESSMolecules 2015, 20 7380

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Redox-active multinuclear Pd(ii) complexes with bis- and tris-mesoionic carbenes

Abstract: Synthesis of a ligand platform to generate di- and tri-mesoionic carbenes is reported together with their multinuclear Pd(II) complexes. Complete structural characterization and preliminary electrochemical data are presented.

Cited by 59 publications

References 46 publications

Heteromultimetallic Complexes with Redox‐Active Mesoionic Carbenes: Control of Donor Properties and Redox‐Induced Catalysis

Heteromultimetallic Complexes with Redox‐Active Mesoionic Carbenes: Control of Donor Properties and Redox‐Induced Catalysis

Palladium(ii)-Acetylacetonato Complexes with Mesoionic Carbenes: Synthesis, Structures and Their Application in the Suzuki-Miyaura Cross Coupling Reaction

Copper(I) Complexes of Mesoionic Carbene: Structural Characterization and Catalytic Hydrosilylation Reactions

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