Hydrogen-transfer catalysis with Cp*Ir^III complexes:The influence of the ancillary ligands

Fourteen Cp*IrIII complexes, bearing various combinations of N- and C-spectator ligands, are assayed in hydrogen-transfer catalysis from isopropyl alcohol to acetophenone under various conditions to investigate ligand effects in this widely used reaction. The new cationic complexes bearing monodentate pyridine and N-heterocyclic carbene (NHC) ligands were characterized crystallographically and by variable-temperature nuclear magnetic resonance (VT-NMR). Control experiments and mercury poisoning tests showed that iridium(0) nanoparticles, although active in the reaction, are not responsible for the high activity observed for the most active precatalyst [Cp*Ir(IMe) 2Cl]BF4 (6). For efficient catalysis, it was found necessary to have both NHCs in monodentate form; tying them together in a bis-NHC chelate ligand gave greatly reduced activity. The kinetics of the base-assisted reaction showed induction periods as well as deactivation processes, and H/D scrambling experiments cast some doubt on the classical monohydride mechanism. © 2013 American Chemical Society

1-(4-Nitrophenyl)-1H-imidazol-3-ium chloride

In the title salt, C9H8N3O2+·Cl−, the least-squares planes of the imidazolium and benzene rings are almost coplanar, making a dihedral angle of 4.59 (1)°. In the crystal, the chloride anion links the organic molecules through N—H...Cl hydrogen bonds, forming chains that run diagonally across the bc face, which compliment strong C—H...O hydrogen bonds between neighbouring molecules. These chains are connected to adjacent chains through two weak C—H...Cl interactions, resulting in hydrogen-bonded sheets extending along the b and c axes. The absolute structure of the title compound was determined using a Flack x parameter of 0.00 (6) and a Hooft y parameter of 0.03 (2)

Copper-catalyzed rearrangement of oximes into primary amides

The atom-efficient and cost-effective rearrangement of oximes into primary amides is catalyzed by simple copper salts. The use of homogeneous Cu(OAc)2 (1–2 mol %) was found to be effective for this transformation at 80 °C. The reaction was successful with either conventional or microwave heating. CuO and CuO/ZnO on activated carbon provided a competent reuseable heterogeneous catalyst which could be used in a batch process or in flow. Copper salts are much cheaper than the precious metals previously used for this rearrangement, and the reaction conditions are milder than those reported