Copper(I) Ethylene Complexes Supported by 1,3,5-Triazapentadienyl Ligands with Electron-Withdrawing Groups

The fluorinated 1,3,5-triazapentadienyl ligands [N{(C3F7)C(2-(NO2)-C6H4)N}(2)](-), [N{(C3F7)C(4-(NO2)C6H4)N}(2)](-), [N{(C3F7)C(2-(CF3)C6H4)N}(2)](-), and [N{(C3F7)C(2-F,6-(CF3)C6H3)N}(2)](-) have been used as supporting ligands in copper(I) ethylene chemistry [N{(C3F7)C(2-(NO2)C6H4)N}(2)]Cu(C2H4) (7), [N{(C3F7)C(4-(NO2)C6H4)N}(2)]Cu(C2H4) (8), [N{(C3F7)C(2-(CF3)C6H4)N}(2)]Cu(C2H4) (9), and [N{(C3F7)C(2-F,6-(CF3)C6H3)N}(2)]Cu(C2H4) (10) are easily isolable, thermally stable solids and display their ethylene proton and carbon resonances in the delta 3.68-3.48 and 85.2-87.6 ppm regions, respectively. X-ray crystal structures reveal that 7-10 feature trigonal-planar copper sites and kappa(2)-bonded, U-shaped triazapentadienyl ligands. The Cu(I) carbonyl adducts [N{(C3F7)C(2-(NO2)C6H4)N}(2)]Cu(CO)(NCCH3) (16) and [N{(C3F7)C(4-(NO2)C6H4)N}(2)]Cu(CO)(NCCH3) (17) have also been synthesized, and they have pseudotetrahedral copper sites. The CO stretching frequencies of the compounds 16 and 17 and ethylene C-13 NMR chemical shift data of 7-10 suggest that these molecules have rather acidic copper sites and weakly donating triazapentadienyl ligands.