Crystal and molecular structure and magnetic properties of the adducts of copper(II) hexafluoroacetylacetonate with the nitroxide ligand 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide

Article abstract of DOI:10.1021/ic00253a032

Stable 1:1 and 1:2 adducts were isolated from the reaction of copper(II) hexafluoroacetylacetonate and the free radical 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (NITPh), namely Cu(hfac)₂(NITPh) and Cu(hfac)₂(NITPh)₂. The striking feature of the structure of the diamagnetic Cu(hfac)₂(NITPh) is the presence of two molecules in different conformations in the asymmetric unit with the copper ion in a distorted square-pyramidal environment and a trigonal-bipyramidal environment, respectively. The nitroxyl group is equatorially bound in both molecules. Crystal data for Cu(hfac)₂(NITPh): triclinic, P1, a = 11.346 (5) A, b = 14.115 (6) A, c = 20.129 (9) A, α = 70.12 (3)°, β = 76.68 (4)°, γ = 75.20 (3)°, Z = 4. In Cu(hfac)₂(NITPh)₂ the copper ion is in a tetragonally distorted octahedral environment with the axial coordination sites occupied by the oxygen atoms of the two nitroxyl ligands at bonding distances of 2.362 (5) and 2.393 (5) A. Crystal data for Cu(hfac)₂(NITPh)₂: monoclinic, P2₁/c, a = 12.358 (6) A, b = 15.428 (7) A, c = 22.61 (1) A, β = 102.33 (3)°, Z = 4. Magnetic measurements show a weak ferromagnetic interaction. EPR spectra of Cu(hfac)₂(NITPh)₂ show a g shift on varying the energy of the microwave quantum and nonparallelism of the two g tensors at X- and Q-band frequencies.