Copper(I) ethylene adducts and aziridination catalysts based on fluorinated tris(pyrazolyl)borates [HB(3-(CF3),5-(R)PZ)3] (where R = CF3, C6H5, H; Pz = pyrazolyl)

The ethylene adducts of copper(I) tris(pyrazolyl)borates, [HB(3,5-(CF3)(2)PZ)(3)]Cu(C2H4), [HB(3-(CF3),5-(C6H5)Pz)(3)]Cu(C2H4), and [HB(3-(CF3)PZ)(3)]Cu(C2H4), have been prepared by reacting the corresponding sodium derivative with CF3SO3Cu in the presence of ethylene. They were characterized both in the solid state and in solution using H-1, C-13, and F-19 NMR and IR spectroscopy and by X-ray crystallography. Solid samples of these nonionic copper complexes featuring fluorinated tris(pyrazolyl)borate ligands display notably high stability toward air oxidation and ethylene loss. The H-1 NMR chemical shifts of the copper(I)-bonded ethylene protons appear in the 4.8-5.2 ppm region. The C-13 signal of copper-coordinated ethylene shows an upfield shift of about 35 ppm, whereas the W-H shows a minor change (an increase of about 2-5 Hz) compared to the values for free ethylene. X-ray structural data show the presence of pseudo-tetrahedral copper ions and eta(2)-bonded ethylene units and relatively unperturbed ethylene C-C distances. The copper adducts [HB(3,5-(CF3)(2)PZ)(3)]Cu(C2H4) and [HB(3-(CF3),5-(C6H5)PZ)(3)]Cu(C2H4) are competent aziridination catalysts, readily converting a variety of olefins into the corresponding N-tosyl aziridines with N-tosyl phenyliodinane.