Palladium(ii) thiocarboxamide complexes: synthesis, characterisation and application to catalytic Suzuki coupling reactions

Abstract

A simple route to synthesise palladium(II) complexes from the reaction of N-substituted pyridine-2-thiocarboxamide ligands and PdCl(2)(PPh(3))(2) has been developed. The new complexes are very soluble in common solvents and have been fully characterised (elemental analysis, FT-IR, (1)H, (31)P, (13)C-NMR), including an X-ray diffraction analysis. The molecular structures of all the complexes were determined and reveal the presence of square planar geometry around Pd with little distortion. The complexes were tested in the Suzuki coupling of electronically deactivated aryl and heteroaryl bromides and were found to have much greater activity, without using any promoting additives or phase transfer agent under aerobic conditions. Higher reaction rates are obtained by varying R substituents on the aromatic ring of pyridine-2-thiocarboxamide. The effect of other variables on the cross-coupling reaction, such as temperature, solvent and base, is also reported.

Palladium complexes of (benzoimidazol-2-ylmethyl)amine ligands as catalysts for methoxycarbonylation of olefins

“…Complexes 4 and 5 displayed one singlet in their 31 P NMR spectra between 37.85 ppm and 30.63 ppm respectively (Figures S1). These values fall within typical 31 P NMR signals between 30.70-35.70 ppm for related mono-coordinated PPh 3 compounds and agrees with the proposed structures in Scheme 2[30][31][32][33][34][35][36][37]. Mass spectrometry was also used to establish the formation and identity of these complexes.…”

“…Crystal data collection and structural refinement parameters are given in [40][41][42]. Significant distortions from the ideal square planar geometry were evident in bond angles for N(2)-Pd(01)-P(003) of 94.19(5)° and C(1)-Pd(01)-P(004)of 87.54(7)° presumably due to steric demands of the two bulkier PPh 3 groups.…”

Synthesis and molecular studies of half-sandwich arene ruthenium and Cp*Rh/Cp*Ir complexes containing (3-picolyl)thiourea derivatives as N,S-bidentate donor ligands

“…For example, N-alkylbenzoylthiourea ligands can give stable complexes with various transition metals including Cu and Ni in which they act as bidentate O,S donor ligands [12,13]. In addition, the presence of hard nitrogen and soft sulfur donor atoms provides a multitude of bonding possibilities; moreover, an additional donor group such as pyridyl residue in the ligand can change the coordination behavior of benzoyl thiourea to act as a N,S-bidentate ligands [14,15].…”

A new Pd(II) complex of a sulfur ylide; Synthesis, X-ray characterization, theoretical study and catalytic activity toward the Suzuki–Miyaura reaction

“…The application of complexes containing sulfur or nitrogen as phosphine free catalytic systems were developed recently to eliminate or reduce costs, operational hazards and environmental pollution [22,23]. For example, Sindhuja et al reported the synthesis and application of palladium catalysts containing modified sulfur ligands which can accelerate the coupling reactions of aryl bromides with phenylboronic acid [24]. It was found that the release of Pd(0) species in such cross-coupling reactions depends on the nature of the ligands around the palladium centre [25].…”