Development of unique dianionic Ir(III) CCC pincer complexes with a favourable spirocyclic NHC framework

Yan, Zhibo; Dai, Kun-Long; Yang, Beverly; Li, Duo; Tu, Yong‐Qiang; Zhang, Fu‐Min; Zhang, Xiaoming; Peng, Meng; Chen, Qilong; Jing, Ze-Ran

doi:10.1007/s11426-020-9875-6

Cited by 14 publications

(5 citation statements)

References 49 publications

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“…The initial development of this research area dealt with the replacement of phosphine arms in the L 2 X-type [PC sp 2 P] pincer prototype by NHC moieties . The preparation of dianionic LX 2 -type cyclometalated NHC and carbodiphosphorane core complexes and the combination of three NHC and three aryl moieties in respective L 3 - and X 3 -type pincer complexes were considered later on. Our original contribution was based on the association of ubiquitous sp 2 -type NHCs with sp 3 -type phosphonium ylides, the latter being just like the NHCs, globally neutral in their free state behaving as strong σ-donors and effective Lewis bases in main-group and coordination chemistry .…”

Section: Introductionmentioning

confidence: 99%

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

et al. 2021

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The reaction of readily available imidazolium−phosphonium salt [MesIm(CH 2 ) 3 PPh 3 ](OTf) 2 with PdCl 2 in the presence of an excess of Cs 2 CO 3 afforded selectively in one step the cationic Pd(II) complex [(C,C,C)Pd(NCMe)]-(OTf) exhibiting an LX 2 -type NHC-ylide-aryl C,C,C-pincer ligand via formal triple C−H bond activation. The replacement of labile MeCN in the latter by CNtBu and CO fragments allowed to estimate the overall electronic properties of this phosphonium ylide core pincer scaffold incorporating three different carbon-based donor ends by IR spectroscopy, cyclic voltammetry, and molecular orbital analysis, revealing its significantly higher electron-rich character compared to the structurally close NHC core pincer system with two phosphonium ylide extremities. The pincer complex [(C,C,C)Pd(CO)](OTf) represents a rare example of Pd(II) carbonyl species stable at room temperature and characterized by X-ray diffraction analysis. The treatment of isostructural cationic complexes [(C,C,C)Pd(NCMe)](OTf) and [(C,C,C)Pd-(CO)](OTf) with (allyl)MgBr and nBuLi led to the formation of zwitterionic phosphonium organopalladates [

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Section: Introductionmentioning

confidence: 99%

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

et al. 2021

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“…10 In addition to the limited and highly reactive metal precursors typically required for double C−H bond activation in anionic CCC pincers, 11−13 cyclometalation via sp 2 C−H bond activation also suffers from a less favorable (smaller) bite angle. Since the first report on a dianionic CCC pincer of a hexaphenylcarbodiphosphorane system by the groups of Cavell (C4), 14 Esteruelas and Xia (C5), 15 Tu (C6), 16 and Danopoulos (C7) 17 For these reasons, a new LX 2 -type ligand system that allows easy complexation to afford stable complexes is highly desirable. Herein, we report facile access to thermally stable iridium(III) complexes bearing the LX 2 -type CCC-pincer ligand by using a bis(aryl)-substituted dipyrido-annulated Nheterocyclic carbene (dpa Ar2 NHC, 1).…”

Section: ■ Introductionmentioning

confidence: 99%

“…In addition to the limited and highly reactive metal precursors typically required for double C–H bond activation in anionic CCC pincers, − cyclometalation via sp 2 C–H bond activation also suffers from a less favorable (smaller) bite angle. Since the first report on a dianionic CCC pincer of a hexaphenylcarbodiphosphorane system by the groups of Cavell ( C4 ), Esteruelas and Xia ( C5 ), Tu ( C6 ), and Danopoulos ( C7 ) reported the osmium, iridium, and palladium complexes bearing bis(aryl)-tethered NHC pincer ligands, respectively. Each features a strained five-membered metallacycle, which makes them more susceptible to M–C bond cleavage, compromising stability and thus hindering their applications in systematic reactivity and property investigations.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

et al. 2021

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Meridional tridentate N-heterocyclic carbene (NHC)-based pincer ligands contribute to a substantial growth in modern organometallic chemistry in both homogeneous catalysis and luminescence materials. Among all NHC-based pincer ligands, the dianionic LX 2 -type CCC-pincer ones constitute the smallest subcategory owing to their limited ligand frameworks suitable for complexation. This work reports a one-pot, high-yield synthesis of a homoleptic anionic all-carbon bis-pincer iridium(III) complex (4) directly from a bis(aryl)-substituted dipyrido-annulated (dpa Ar2 ) imidazolium salt and [Ir(COD)Cl] 2 via a cascade of deprotonation/C−H activation processes. Both experimental complexation chemistry and computational mechanistic investigation suggest that the large bite angle and π-rich character of the dpa Ar2 NHC are responsible for its facile complexation as a dianionic LX 2type CCC-pincer ligand precursor. The all-carbon ligated iridium(III) complex (4) bearing a π-conjugated ligand scaffold showed remarkably low oxidation potentials, which allows future investigations in its redox chemistry and photophysical properties.

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“…Therefore, the development of new catalysts for this type of reduction is highly desirable. Due to the successful CÀ H silylation and olefin isomerization reactions that were catalyzed by our recently developed spirocyclic N-heterocyclic carbene (SNHC)-based Ir III CCC pincer complexes (SNIrÀ Cl), [8] we sought to explore the reactivities of pincer complexes in BH reactions. Once the stable Ir III À H complex (SNIrÀ H) had been isolated, we began investigating the possible formation of Ir III dihydride, which would accelerate the reduction of unactivated olefins via hydrogen transfer.…”

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Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with Spirocyclic NHC Ir^III Pincer Complex

et al. 2022

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A facile benzylic alkylation of indenes and other arenes was developed from readily available primary and secondary alcohols using our newly investigated CCC pincer IrIII catalyst (SNIr−H). Excellent regioselectivity and yield (89 %) of the C3‐alkylated indenes were obtained. Additionally, the challenging sp2C‐alkylation was readily accomplished. This method could be utilized for the synthesis of the analogs of a histamine H1 receptor antagonist and the functional material template molecule, indeno[2,1‐a]indene. A hemilabile IrIII‐dihydride intermediate was proposed based on control experiments and previous density functional theory (DFT) calculations for the borrowing hydrogen mechanism and is key to the success of this IrIII catalyst in the reduction of unactivated multi‐substituted olefin intermediates.

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Development of unique dianionic Ir(III) CCC pincer complexes with a favourable spirocyclic NHC framework

Cited by 14 publications

References 49 publications

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with Spirocyclic NHC Ir^III Pincer Complex

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Development of unique dianionic Ir(III) CCC pincer complexes with a favourable spirocyclic NHC framework

Cited by 14 publications

References 49 publications

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

Direct Access to Palladium(II) Complexes Based on AnionicC,C,C-Phosphonium Ylide Core Pincer Ligand

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with Spirocyclic NHC IrIII Pincer Complex

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Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with Spirocyclic NHC Ir^III Pincer Complex