C,N-Palladacycles Containing N-Heterocyclic Carbene and Azido Ligands - Effective Catalysts for Suzuki-Miyaura Cross-Coupling Reactions

Palladium(ii) complexes of 2,2′-tellurobis(N,N-diphenyl acetamide): efficient catalysts for Suzuki–Miyaura coupling at room temperature under air

Three complexes, [Pd(L2)2Br2](C1), [(L2)PdCl(μ-Cl)2PdCl(L2)](C2), and [Pd(L2)PPh3Cl2](C3), where L2 = 2,2′-tellurobis(N,N-diphenylacetamide), catalyze Suzuki–Miyaura coupling (loading: 0.001 mol % of Pd) of eleven ArX at room temperature under air.

Synthesis and Structure of Multinuclear Pd(II) Complexes Bridged by Phosphide or Azide Ligands

The synthesis and structure of phosphide- and azide-bridged multinuclear Pd(II) complexes bearing phosphine ligands [PdX(μ-X')(PR₃)] _n (X = Cl and N₃; X' = PR₂ ^' and N₃; n = 2 and 4) are reported. The oxidative addition of R₂ ^'PCl to Pd(PMe₃)₂ furnished the phosphide-bridged dinuclear Pd(II) complexes [PdCl(μ-PR₂ ^')(PMe₃)]₂ [R' = ⁱ Pr (1a) and Cy (1b)]. However, the oxidative addition of (o-tolyl)₂PCl to Pd(PMe₃)₂ produced a nonbridged mononuclear Pd(II) complex with the bis(o-tolyl)phosphinic ligand, trans-[Pd(PMe₃)₂{P(O)(o-tolyl)₂}] (2), via oxidation of the phosphinyl ligand. The reaction of the chloride-bridged dinuclear Pd(II) complexes [PdCl(μ-Cl)(PR₃)]₂ [PR₃ = PEt₃ (3a) and PPhMe₂ (3b)] with NaN₃ afforded the azide-bridged dinuclear and tetranuclear Pd(II) complexes [Pd(N₃)(μ-N₃)(PEt₃)]₂ (4) and [Pd(N₃)(μ-N₃)(PPhMe₂)]₄ (5). Comparisons of the X-ray structures of 4 and 5 show that the square-planar molecular geometry of the Pd(II) centers of 4 are more distorted than those of 5. Density functional theory calculations suggest that the tetranuclear eight-membered ring structure like 5 is more stable than the dinuclear four-membered ring structure like 4 in the gas phase in both PEt₃ and PPhMe₂ systems. However, because the relative energy difference between the four-membered and eight-membered ring structures is small in the PEt₃ system with smaller steric hindrance compared with PPhMe₂, it is assumed that this difference is compensated by the crystal packing energy, and the dinuclear four-membered ring complex 4 is actually obtained.

Synthesis of (NHC)Pd(salicylaldimine)Cl complexes through template-directed ortho-aromatic metaloxylation of NHC-palladacycles derived from arylimines

Reactions of imidazoliums with palladacycles afforded NHC-palladacycle complexes. The reactivity of the NHC-palladacycles was explored and the results demonstrated that they could be template-directed ortho-aromatic metaloxylated in the presence of tert-butyl hydroperoxide (TBHP), affording (NHC)Pd(salicylaldimine)Cl complexes. Furthermore, the NHC-palladacycles showed efficient catalytic activities toward the ortho-aromatic hydroxylation of arylimines.

Synthesis and catalytic applications of palladium N-heterocyclic carbene complexes as efficient pre-catalysts for Suzuki–Miyaura and Sonogashira coupling reactions

A new palladium complex series with N-heterocyclic carbene (NHC), pyridine and phosphine ligands, PdCl₂(L)NHC (2a–c)(L = NHC), PdCl₂(L¹)NHC(3a–c)(L¹ = pyridine), PdCl₂(L²)NHC(4a–c)(L² = triphenylphosphine) was synthesised and fully characterized.

Structure and properties of metal complexes of a pyridine based oxazolidinone synthesized by atmospheric CO2 fixation

Copper, platinum and palladium complexes of an oxazolidinone ligand show potential in catalysis or cytotoxicity, depending on the metal incorporated.