Imine Palladacycles: Synthesis, Structural Analysis and Application in Suzuki-Miyaura Cross Coupling in Semi-Aqueous Media.

Treatment of the imines a-c with palladium(II) acetate in acetic acid yielded the µ-acetate dinuclear complexes 1a-c, which readily reacted with sodium chloride or bromide to provide µ-halide analogues. The reaction of the latter with nitrogen, phosphorus and oxygen donor nucleophiles yielded new imine palladacycles following the cleavage of the Pd2X2 unit. The complexes were fully characterized by microanalysis, 1H, 13C and 31P NMR spectroscopies, as appropriate. The compounds were applied as catalysts in the Suzuki-Miyaura coupling reaction in aqueous and semi-aqueous media.

Solvent-dependent nuclearity, geometry and catalytic activity of [(SPhos)Pd(Ph)Cl]2.

The nuclearity and structures of the palladium complex [(SPhos)Pd(Ph)Cl]2 in the solid and solution states are revisited using a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, NMR spectroscopy, mass spectrometry, DFT calculations and trapping experiments. The complex was tested for its catalytic activity in the coupling reaction between chlorobenzene and n-hexylamine, where different deactivation behaviours were observed in toluene, 1,4-dioxane and DMF.

Palladacycle catalysis: an innovation to the Suzuki-Miyaura cross-coupling reaction.

Herein we report a Suzuki-Miyaura type cross-coupling between an aryl halide and a functionalized boronic acid palladacycle in the absence of an external catalyst. This reaction is an unprecedented case of catalysis in palladium metallacycle chemistry.

Electronic structures of cyclometalated palladium complexes in the higher oxidation states.

The electronic and redox properties of a series of cyclometalated Pd complexes with oxidation states of +2, +3 and +4 were examined using a range of currently available spectroscopic and electrochemical techniques. Changes in metal-ligand bond lengths were established by X-ray crystallography and correctly predicted by DFT calculations, from which the frontier orbitals and partial atomic charges can be obtained. X-ray absorption spectroscopy (XAS) revealed interesting XANES features that suggest a synergistic relationship between metal-ligand interactions. The electrochemical study of the Pd(ii) dimer was found to contain two sequential oxidative potentials indicative of a weak metal-metal interaction.

One-pot direct C-H arylation of arenes in water catalysed by RuCl3·nH2O-NaOAc in the presence of Zn.

The inexpensive and commercially available catalytic system RuCl3·nH2O-NaOAc-Zn is active in water for the direct C-H arylation of arenes with aryl/heteroaryl chlorides. The reaction can be accelerated by the use of microwave irradiation and can also be scaled up to a multi-gram scale with excellent isolated yields.

Silver-catalysed enantioselective addition of O-H and N-H bonds to allenes: a new model for stereoselectivity based on noncovalent interactions.

The ability of silver complexes to catalyse the enantioselective addition of O-H and N-H bonds to allenes is demonstrated for the first time by using optically active anionic ligands that were derived from oxophosphorus(V) acids as the sources of chirality. The intramolecular addition of acids, alcohols, and amines to allenes can be achieved with up to 73% ee. The exploitation of a C-H anomeric effect allowed the absolute configuration of a sample of 2-substituted tetrahydrofuran of low ee to be unambiguously assigned by comparison of the chiroptical ORD and VCD measurements with calculated spectra. In the second part of the work, the origin of the stereoselectivity was probed by DFT free-energy calculations of the transition states. A new model of enantiomeric differentiation was developed that was based on noncovalent interactions. This model allowed us to identify the source of stereoselectivity as weak attractive interactions; such dispersive forces are often overlooked in asymmetric catalysis. A new computational approach was developed that represents these interactions as colour-coded isosurfaces that are characterised by the reduced density-gradient profile.

Hydroamination reactions by metal triflates: Brønsted acid vs. metal catalysis?

Catalytic hydroamination reactions involving the addition of carboxamides (X = CO), carbamates (X = CO(2)) and sulfonamides (X = SO(2)) to unactivated C=C bonds are briefly reviewed. Development in this field of catalytic research is briefly charted, followed by a discussion of possible mechanisms, including arguments to support the operation of both metal and Brønsted acid catalysis in these systems. Future developments in the area are summarised.

A recyclable copper(ii) catalyst for the annulation of phenols with 1,3-dienes.

Air- and moisture-stable Cu(OTf)(2)-bipy catalyses the addition of phenols to 1,3-dienes under aerobic conditions in a tandem hydroalkoxylation-rearrangement-hydroalkylation sequence, furnishing O-heterocycles in moderate to good yields, and can be recycled without any loss in catalytic activity.