Copper Complexes with Neutral N4 Tripodal Ligands: Influence of the Number of Nitrogen Donors on Their Structures, Properties, and Reactivity

Abstract

Copper coordination complexes of the neutral tetradentate nitrogen‐containing ligands tris(3,5‐dimethylpyrazol‐1‐ylmethyl)amine (L0N4) and tris(3,5‐diisopropylpyrazol‐1‐ylmethyl)amine (L1N4), namely the copper(II) chlorido complexes [CuII(L0N4)Cl2] (1) and [CuII(L1N4)Cl2] (2), the copper(II) nitrato complexes [CuII(L0N4)(NO3)](NO3) (3) and [CuII(L1N4)(NO3)](NO3) (4), and the copper(II) sulfato complexes [CuII(L0N4)(SO4)] (5) and [CuII(L1N4)(SO4)] (6), and the copper(I) complexes [CuI(L0N4)](PF6) (7) and [CuI(L0N4)(PPh3)](ClO4) (8), have been systematically synthesized in order to investigate the influence of the number of nitrogen donors on their structures, properties, and reactivity. All copper(II) complexes were fully characterized by X‐ray crystallography and by IR/far‐IR, UV/Vis absorption, and ESR spectroscopy. Although the structure of 7 was not determined by X‐ray crystallography, this complex and the structurally characterized copper(I) triphenylphosphane complex 8 were fully characterized by IR/far‐IR and NMR spectroscopy. A comparison of the copper(II) complexes with two tris(pyrazol‐1‐ylmethyl)amine ligands with different bulkiness of the pyrazolyl rings has allowed us to evaluate the second coordination sphere effects of the ligands. Moreover, the structures and physicochemical properties of these complexes are compared with those of related complexes containing the neutral tridentate tris(pyrazolyl)methane ligand and the neutral bidentate bis(pyrazolyl)methane ligand. Finally, the relative stability of the copper(I) complexes is discussed. The influence of the number of nitrogen donors in copper complexes is observed from these systematic results.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Assembling novel Cd(ii) complexes with multidentate nitrogen donor ligands obtained in situ from the system: zerovalent copper, cadmium oxide, 1-hydroxymethyl-3,5-dimethylpyrazole and ammonium thiocyanate

“…Additionally, complex 1 shows prominent bands at 1224 and 1239 cm −1 because of the CN stretching of the hexamethylenetetramine (L 1 ) moiety 9 and a strong, broad (due to hydrogen bonds) band at 3447-3100 cm −1 that was assigned as the ν(OH) stretching frequency of the coordination methanol. The broad OH stretching band at 3152 cm −1 in the IR spectra of the starting ligand disappears in the infrared spectra of the Cd(II) complexes, which confirms that compounds 2 contain the new scorpionate ligands 10 The diffuse reflectance UV-Vis spectra of 1 and 2 were investigated with solid state samples in BaSO 4 pellets (Fig. 4).…”

Regulating Noncovalent Interactions in Amino‐Amide–Copper Complexes

“…The signals at 284–251 and 339–308 cm –1 are attributed to the ν(Cu–N) and ν(Cu–Cl) vibrations, respectively, and they corroborate the presence of chelate complexes. [17c], The Raman spectra can be found in the Supporting Information.…”

Anion and solvent effects on the coordination behavior of N-(2-pyridinylmethylene)benzoylhydrazone with copper(II): synthesis and structural characterization

“…Furthermore, a band is at 619 cm -1 (bending asymmetric ν 4 ). These features indicate that SO 4 2-is a bridging ligand coordinated to copper ions [30][31][32]. The absorption spectrum of the free benzoylhydrazone ligand in methanol shows bands at 232 and 370 nm.…”