G. A. Ardizzoia

Synthesis and characterization of copper(I)-pyrazole complexes. X-Ray crystal structure of [Cu(pzH)2Cl]2 and NMR investigation of the fluxional behaviour of [Cu(pzH)2(CO)Cl]

Abstract The product of the reduction of [Cu(pzH) 4 Cl 2 ] (pzH = pyrazole, C 3 H 4 N 2 ) with Cu powder has been shown by single crystal X-ray analysis to the dimeric species [Cu(pzH) 2 Cl] 2 . The crystals are monoclinic, space group P 2 1 / n , with a 6.327(1), b 9.610(1), c 15.066(1) A, β 96.91(1), and Z = 2. The refinements performed by full-matrix least-squares methods, for 1417 independent significant reflexions, gave a final R value of 0.030. Each dimeric unit, located on a crystallographic inversion centre, contains two Cu atoms (Cu…Cu′ 3.401(1) A), each surrounded by two bridging C1 atoms and two pzH ligands, in a pseudo-tetrahedral arrangement. The reaction of carbon monoxide with [Cu(pzH) 2 Cl] 2 gave the new species [Cu(pzH) 2 (CO)Cl], which was characterized by IR and NMR spectroscopy. Fluxional behaviour of the pyrazole ligands, equalizing their 3 and 5 positions, was revealed by both 1 H and 13 C NMR spectra. Variable temperature 13 C NMR experiments in different conditions (solvent or concentrations) lead to different E a values, indicating that the exchange process is not intramolecular, and is favoured in donor solvents, at temperatures above 250 K. In concentrated solutions in CD 2 Cl 2 a double-slope Arrhenius plot was obtained, suggesting the occurrence of two different processes, whose natures are discussed.

[ReCl3(C8H11P)2(C7H11N)2].C6H4Cl2

Trichlorobis(cyclohexyl isocyanide)bis(dimethylphenylphosphine)rhenium(III) has been synthesized from [ReOCl 3 (CNCy) 2 ] (Cy = cyclohexyl) by the removal of oxygen with excess dimethylphenylphosphine. The structure of its 1,2-dichlorobenzene adduct, determined by single-crystal X-ray methods, has a monocapped octahedral arrangement (idealized C s symmetry) of the seven ligands about the Re atom; the three Cl atoms adopt a fac geometry, opposite the face capped by one isocyanide ligand

Homogeneous Catalytic Oxidation of Organic Substrates by Copper-Pyrazolato Complexes

The synthesis of di- and polynuclear complexes having ligands which maintain the metal centers in close proximity is an important objective in transition metal chemistry, owing to their potential role in multi-metal centered catalysis. Metal assisted reactions of dioxygen are very important processes and there is increasing interest in their products and mechanisms.