Cyclopalladation in the Periphery of a NHC Ligand as the Crucial Step in the Synthesis of Highly Active Suzuki–Miyaura Cross‐Coupling Catalysts

Fizia, Agnes; Gaffga, Maximilian; Lang, Johannes; Sun, Yu; Niedner‐Schatteburg, Gereon; Thiel, Werner R.

doi:10.1002/chem.201702877

Cited by 23 publications

(9 citation statements)

References 81 publications

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“…During the last years, roll-over cyclometallation has turned out to be a versatile strategy for increasing the activity of catalysts. [11][12][13][14] However, it is also a highly efficient tool to access bimetallic complexes. For this approach, we designed ligands that create a second chelating donor site by undergoing rollover cyclometallation, thus enabling the coordination of a second transition metal.…”

Section: Synthesis Of Mono-and Binuclear Complexesmentioning

confidence: 99%

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Quantification of Cooperativity between Metal Sites in Dinuclear Transition Metal Complexes Containing the (2‐Dimethylamino)‐4‐(2‐pyrimidinyl)pyrimidine Ligand

et al. 2021

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A concept for the quantification of cooperative effects in transition-metal complexes is presented. It is demonstrated for a series of novel N,N-(mononuclear) and C,N-coordinated homo-and heterometallic binuclear complexes based on the (2-dimethylamino)-4-(2-pyrimidinyl)pyrimidine ligand, which are accessible by applying roll-over cyclometallation. These iridium-, platinum-, and palladium-containing compounds are investigated with respect to their absorption and fluorescence spectra. The cooperative effects in the electronic absorptions, i. e., the energetic shifts between mononuclear and dinuclear complexes, and free ligands are analyzed on the basis of the lowest energy π-π* transitions and compared to calculated data, obtained from TD-DFT calculations. Furthermore the corresponding fluorescence spectra are presented and analyzed with respect to the concept of cooperativity.

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Section: Synthesis Of Mono-and Binuclear Complexesmentioning

confidence: 99%

“…During the last years, roll‐over cyclometallation has turned out to be a versatile strategy for increasing the activity of catalysts [11–14] . However, it is also a highly efficient tool to access bimetallic complexes.…”

Section: Conceptsmentioning

confidence: 99%

Quantification of Cooperativity between Metal Sites in Dinuclear Transition Metal Complexes Containing the (2‐Dimethylamino)‐4‐(2‐pyrimidinyl)pyrimidine Ligand

et al. 2021

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“…As happened in the case of ylides commented above, the initial coordination of an NHC ligand to Pd(II) could evolve to give a C,C-metallacycle upon an intramolecular CÀ H activation step, usually on an aryl ring conveniently located in the NHC structure (palladacycles 82 and 83). In this sense, examples dealing with the metalation of normal [83] and abnormal [84,85] NHC's have been reported (Scheme 62 and Scheme 63).…”

Section: Coordination Of a C-donor Ligand Followed By Cà H Activation Stepmentioning

confidence: 99%

Chasing C,C‐Palladacycles

Garcı́a-López

Saura‐Llamas

2021

Eur J Inorg Chem

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The different approaches for the synthesis of C,C-palladacycles are reviewed in this manuscript. These species hold a bidentate ligand that chelates the Pd atom through two C-donor moieties. Their relevance is closely related to the fact that they are intermediates in many palladium-catalyzed transformations. Furthermore, some of them have been used as efficient catalyst in cross coupling reactions. The review is structured according to the different strategies that have been employed to achieve the synthesis of the C,C-palladacycle derivatives, starting with those involving one elemental step (such as the oxidative addition of strained CÀ C bonds to Pd(0) or the transmetalation reactions between organometallic reagents and Pd(II) precursors), and continuing with more complex processes, where at least two elementary steps of Pd chemistry are involved (for example, carbometalation of alkenes followed by a CÀ H activation process). A final section highlights some aspects of synthetic methodologies based on Pd catalysis in which one or several C,C-palladacyclic intermediates are involved.Lenarda et al. synthesized the first reported four-membered C,C-palladacycles 1 a and 1 b in 1972, [5] via the oxidative addition of 1,1,2,2-tetracyanocyclopropane to [Pd(PPh 2 R) 4 ] (R = Ph; Me) (Scheme 1). The reaction occurred with the CÀ C bond cleavage of the highly strained ring and oxidative addition of the two resulting fragments to Pd(0).

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“…In the case of cyclometalated NHCs, subtle modifications in the NHC backbone, the solvent medium, and/or the metal precursor may lead to site-selective C–H activation sites upon metal coordination . The NHC cyclometalated complexes derived thereof display distinctive physicochemical features that are known to substantially alter their intrinsic catalytic activity. − …”

Section: Introductionmentioning

confidence: 99%

Introducing Ion Mobility Mass Spectrometry to Identify Site-Selective C–H Bond Activation in N-Heterocyclic Carbene Metal Complexes

Mollar-Cuni

Ibáñez-Ibáñez

Guisado‐Barrios

et al. 2022

J. Am. Soc. Mass Spectrom.

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The activation of C−H bonds in a selective manner still constitutes a major challenge from a synthetic point of view; thus, it remains an active area of fundamental and applied research. Herein, we introduce ion mobility spectrometry mass spectrometry-based (IM-MS) approaches to uncover site-selective C−H bond activation in a series of metal complexes of general formula [(NHC)LMCl] + (NHC = N-heterocyclic carbene; L = pentamethylcyclopentadiene (Cp*) or p-cymene; M = Pd, Ru, and Ir). The C−H bond activation at the N-bound groups of the NHC ligand is promoted upon collision induced dissociation (CID). The identification of the resulting [(NHC-H)LM] + isomers relies on the distinctive topology that such cyclometalated isomers adopt upon site-selective C−H bond activation. Such topological differences can be reliably evidenced as different mobility peaks in their respective CID-IM mass spectra. Alternative isomers are also identified via dehydrogenation at the Cp*/p-cymene (L) ligands to afford [(NHC)(L-H)M] + . The fragmentation of the ion mobility-resolved peaks is also investigated by CID-IM-CID. It enables the assignment of mobility peaks to the specific isomers formed from C(sp 2 )−H or C(sp 3 )−H bond activation and distinguishes them from the Cp*/p-cymene (L) dehydrogenation isomers. The conformational change of the NHC ligands upon C−H bond activation, concomitant with cyclometalation, is also discussed on the basis of the estimated collision cross section (CCS). A unique conformation change of the pyrene-tagged NHC members is identified that involves the reorientation of the NHC ring accompanied by a folding of the pyrene moiety.

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Cyclopalladation in the Periphery of a NHC Ligand as the Crucial Step in the Synthesis of Highly Active Suzuki–Miyaura Cross‐Coupling Catalysts

Cited by 23 publications

References 81 publications

Quantification of Cooperativity between Metal Sites in Dinuclear Transition Metal Complexes Containing the (2‐Dimethylamino)‐4‐(2‐pyrimidinyl)pyrimidine Ligand

Quantification of Cooperativity between Metal Sites in Dinuclear Transition Metal Complexes Containing the (2‐Dimethylamino)‐4‐(2‐pyrimidinyl)pyrimidine Ligand

Chasing C,C‐Palladacycles

Introducing Ion Mobility Mass Spectrometry to Identify Site-Selective C–H Bond Activation in N-Heterocyclic Carbene Metal Complexes

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