Stereochemical and structural characteristics of single- and double-site Pd(II)–N-heterocyclic carbene complexes: Promising catalysts in organic syntheses ranging from CC coupling to olefin polymerizations

A highly active chiral (S,S)-bis(oxazoline) Pd(ii) alkyl complex/activator catalytic system for vinyl polymerization of norbornene in air and water

The air/water-tolerant chiral Pd alkyl complexes/borate systems promote the norbornene polymerization both in air and water using unpretreated technical grade solvent and monomer with extremely high activity up to 1.7 × 10⁹ g PNB per mol_Pd per h.

Pd-Catalyzed Suzuki coupling reactions of aryl halides containing basic nitrogen centers with arylboronic acids in water in the absence of added base

Successful Suzuki reactions of basic nitrogen containing aryl chlorides/bromides with arylboronic acids in water without added base, partially or entirely under acidic conditions.

Geometry Constrained N-(5,6,7-Trihydroquinolin-8-ylidene)arylaminopalladium Dichloride Complexes: Catalytic Behavior toward Methyl Acrylate (MA), Methyl Acrylate-co-Norbornene (MA-co-NB) Polymerization and Heck Coupling

A new pair of plladium complexes (Pd4 and Pd5) ligated with constrained N-(5,6,7-trihydroquinolin-8-ylidene)arylamine ligands have been prepared and well characterized by ¹H-, ¹³C-NMR and FTIR spectroscopies as well as elemental analysis. The molecular structure of Pd4 and Pd5 in solid state have also been determined by X-ray diffraction, showing slightly distorted square planar geometry around the palladium metal center. All complexes Pd1–Pd5 are revealed highly efficient catalyst in methyl acrylate (MA) polymerization as well as methyl acrylate/norbornene (MA/NB) copolymerization. In the case of MA polymerization, as high as 98.4% conversion with high molecular weight up to 6282 kg·mol⁻¹ was achieved. Likewise, Pd3 complex has good capability to incorporate about 18% NB content into MA polymer chains. Furthermore, low catalyst loadings (0.002 mol %) of Pd4 or Pd5 are able to efficiently mediate the coupling of haloarenes with styrene affording up to 98% conversion.

Synthesis and characterization of trinuclear N-heterocyclic carbene–palladium(ii) complexes and their applications in the Suzuki–Miyaura cross-coupling reaction

Five novel trinuclear N-heterocyclic carbene–palladium(ii) complexes 5a–e were conveniently synthesized in one step. The obtained palladium(ii) complexes were the effective catalyst precursors for the Suzuki–Miyaura coupling.

Palladium(ii) complexes with chelating N-phosphanyl acyclic diaminocarbenes: synthesis, characterization and catalytic performance in Suzuki couplings

Novel palladium(ii) complexes with the title ligands have been prepared and tested as precatalysts in Suzuki couplings of aryl chlorides.

A mesoionic bis(Py-tzNHC) palladium(II) complex catalyses "green" Sonogashira reaction through an unprecedented mechanism

A novel bis(pyridyl-functionalized 1,2,3-triazol-5-ylidene)-palladium(II) complex [Pd(Py-tzNHC)2](2+) catalyses the copper-, amine-, phosphine-, and additive-free aerobic Sonogashira alkynylation of (hetero)aryl bromides in water as the only reaction solvent. The catalysis proceeds along two connected Pd-cycles with homogeneous bis-carbene Pd(0) and Pd(II) species, as demonstrated by electrospray ionization mass spectrometry.

A forgotten chiral spiro compound revisited: 3,3'-dimethyl-3H,3'H-2,2'-spirobi[[1,3]benzothiazole]

The title compound was obtained as a side product during dimerization-oxidation steps of the carbene generated from N-methylbenzothiazolium iodide. Chromatography on (S,S)-Whelk O1 column showed on cooling a typical plateau shape chromatogram indicating an exchange between two enantiomers on the column. The thermal barrier to racemization was determined (85 kJ.mol(-1) at 10 °C) by dynamic high-performance liquid chromatography (DHPLC).The absolute configuration of the first (M) and second eluted (P) enantiomers on the (S, S)-Whelk O1 column was established by comparing the reconstructed circular dichroism (CD) spectra from the CD detector signal and the calculated CD spectrum of the (P) enantiomer. Mass spectrometry revealed that 3,3'-dimethyl-3H,3'H-2,2'-spirobi[[1,3]benzothiazole] can be viewed as a masked thiophenate attached to a benzothiazolium framework.

Selective palladium-catalysed arylation of 2,6-dibromopyridine using N-heterocyclic carbene ligands

A selective palladium-catalysed arylation of 2,6-dibromopyridine has been developed by employing N-heterocyclic carbene ligands. Selective mono-arylation was performed in water/acetonitrile solvent at ambient temperature and low catalyst loading.

Pincer CNC bis-N-heterocyclic carbenes: robust ligands for palladium-catalysed Suzuki–Miyaura arylation of bromoanthracene and related substrates

Novel pincer-type N-heterocyclic carbene ligands have been synthesised and characterised by FAB-MS and single crystal X-ray analysis. The ligands have proved to be highly active towards palladium-catalysed Suzuki–Miyaura cross-coupling of bromoanthracene and related substrates.

Chelating palladium complexes containing pyridine/pyrimidine hydroxyalkyl di-functionalized N-heterocyclic carbenes: synthesis, structure, and catalytic activity towards C–H activation

Chelating palladium complexes containing pyridine/pyrimidine hydroxyalkyl di-functionalized NHCs were synthesized, characterized and tested for C–H activation of (benzo)oxazoles.

Suzuki–Miyaura reaction by heterogeneously supported Pd in water: recent studies

This review summarizes the progress made essentially in the last fifteen years in the Suzuki–Miyaura coupling reaction by heterogeneous palladium catalysis in water as the sole solvent.

Synthesis of well defined C–C bridged Ni(ii) complexes bearing β-ketoiminato-fluorene ligands by bifluorenyl in situ coupling and application for norbornene (co)polymerization

9-Substituted fluorene C–C bridged constrained geometry configuration (CGC) Ni(ii) complexes Ni1 and Ni2 were synthesized by coordination reaction and in situ coupling reaction in the presence of (DME)NiBr₂.

Synthesis, structures, and norbornene polymerization behavior of C(sp³), N-chelated palladacycles bearing o-aryloxide-N-heterocyclic carbene ligands

Treatment of the o-hydroxyaryl imidazolium pro-ligands (2-OH-3,5-tBu2C6H2)(R)(C3H3N2)(+)Br(-) [R = Mes (1a), Ph (1b), iPr (1c), Me (1d)] with Ag2O afforded the corresponding silver complexes 2a-d. Subsequent metal-exchange reactions of 2a-d with [Pd(OAc)(8-Me-quin-H)]2 (3) yielded the desired C(sp(3)), N-chelated and o-aryloxide-NHC-ligated palladacycle complexes 4a-d in 60-80% yields. When the N-tert-butyl substituted o-hydroxyaryl imidazolium pro-ligand 1e reacted with 3 in the presence of K2CO3 in dioxane, the palladacycle complex 4e, in which the NHC adopted an abnormal binding (C4-bonding), was obtained in 20% yield. All these complexes were fully characterized using (1)H and (13)C NMR spectra, high-resolution mass spectrometry (HRMS), and elemental analysis. Single-crystal X-ray diffraction analysis results further confirmed the molecular structures of 4a-c and the abnormal binding of NHC in 4e. With methylaluminoxane (MAO) as the cocatalyst these palladacycles showed excellent catalytic activities of up to 10(7) g of PNB (mol of Pd)(-1) h(-1) in the addition polymerization of norbornene.