N‐Heterocyclic Carbene Palladium(II) Amine Complexes: The Role of Primary Aryl‐ or Alkylamine Binding and Applications in the Buchwald‐Hartwig Amination Reaction

Chen, Ming‐Tsz; Hsu, Yu-Cheng

doi:10.1002/ejic.202100828

Cited by 5 publications

(1 citation statement)

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“…Coordination compounds of the B 2 Pz 4 Py ligand have provided complexes of Fe and Co relevant to nitrogen fixation, [25][26][27] vitamin B12, [28] and dioxygen reduction. [29] Considering the rich chemistry of coordination complexes supported by monodentate, [30][31][32] bidentate, [33][34][35][36][37][38] tripodal [39][40][41][42] and macrocyclic [43][44][45][46][47] ligands consisting of N-heterocyclic carbene (NHC) donors a particularly striking absence in the tetrapodal pentadentate family of ligands are those composed of equatorial and axial NHC donor groups. Intrigued by the impact a pentadentate framework composed entirely of NHC donors would have on the chemistry of first-row transition metals we undertook the preparation of the tricationic protoligand [CC 4H5 Me ](OTf) 3 (3).…”

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confidence: 99%

A Tetrapodal Penta‐Carbene Ligand and Iron(III) Complex

et al. 2023

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We report the first tetrapodal pentadentate ligand composed of five N‐heterocyclic carbene donors. The proto‐ligand [CC4H5Me](OTf)3 (3) is formed in good yields from commercially available reagents. Upon removal of 5 proton equivalents from 3 with bulky non‐nucleophilic bases a dianionic penta‐carbene framework is provided in good yields as a dilithium complex CC4MeLi2 (4). Addition of FeCl3 to a solution of 4 formed in situ provides CC4MeFeCl (5) in moderate yield. Solution‐state magnetism measurements of 5 are consistent with a S=1/2 Fe(III) center. The related diamagnetic Fe(II) compound CC4MeFe (6) can be formed through reduction of 5 using KC8 though poor solubility characteristics have hampered its formation on a preparative scale and full characterization.

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Section: Introductionmentioning

confidence: 99%

A Tetrapodal Penta‐Carbene Ligand and Iron(III) Complex

et al. 2023

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Abnormal NHC Palladium(II) Complex Containing CNN Pincer Skeleton and Its Application to Suzuki‐Miyaura Coupling of Aryl Chlorides in Water

et al. 2023

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The excellent catalytic activities of abnormal NHC carbene complexes, where the C2 position remains unaffected, and coordination occurs at the C4 or C5 position of the imidazolium ring, is still a fascinating but scarce area of research. This present work reports a palladium complex (LPdBr) bearing abnormal NHC with CNN pincer architecture. It is synthesized from imidazolium‐based quinoline ligand (LH) with Pd(OAc)2 via ‐NH and carbene deprotonation. The complex was fully characterized by NMR spectroscopy (1D and 2D) and high‐resolution mass spectrometry (HRMS). The structure and abnormal coordination modes of the complex are further confirmed with the help of single‐crystal X‐ray diffraction. The studies revealed the abnormal coordination mode in LPdBr where C5 carbon of the imidazolium ring participates in bonding, leaving the C2 position unaffected. The catalytic potential of complex LPdBr was investigated in the Pd‐catalyzed Suzuki‐Miyaura coupling of various aryl/heteroaryl chlorides with different aryl/naphthyl/phenanthryl boronic acids. The catalyst LPdBr successfully activated various less‐activated aryl chloride substrates. LPdBr also exhibited good catalytic activity at 1 mol% Pd loading under microwave irradiation and in green solvent water. The mechanism of the catalytic cycle is investigated and proposed by HRMS.

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A S=3/2 Cr(III) Complex In A Square‐Capping NHC Framework

Gau,

Scepaniak

2024

ChemistrySelect

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Deprotonation of our pentadentate N‐Heterocyclic Carbene (NHC) ligand with lithium diisopropylamine in tetrahydrofuran and subsequent salt metathesis with CrCl3THF3 readily forms the complex PhCC4MeCrCl (1), a S=3/2 species in moderate yield. DFT calculations reveal three singly occupied molecular orbitals with π‐backbonding character to the square‐capping framework, UV‐Vis spectroscopy reveals 3 bands ascribed to d‐to‐d transitions, and cyclic voltammetry reveals an irreversible and quazi‐reversible reduction events as well as an irreversible oxidation event. We attempted to exchange the chloride ligand of 1 through salt‐metathesis with lithium phenylacetylide without success, the absence of reactivity is rationalized considering our XRD and DFT results.

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N‐Heterocyclic Carbene Palladium(II) Amine Complexes: The Role of Primary Aryl‐ or Alkylamine Binding and Applications in the Buchwald‐Hartwig Amination Reaction

Cited by 5 publications

References 58 publications

A Tetrapodal Penta‐Carbene Ligand and Iron(III) Complex

A Tetrapodal Penta‐Carbene Ligand and Iron(III) Complex

Abnormal NHC Palladium(II) Complex Containing CNN Pincer Skeleton and Its Application to Suzuki‐Miyaura Coupling of Aryl Chlorides in Water

A S=3/2 Cr(III) Complex In A Square‐Capping NHC Framework

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