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 δ 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 κ2-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 13C NMR chemical shift data of 7–10 suggest that these molecules have rather acidic copper sites and weakly donating triazapentadienyl ligands.