Synthesis, structure, and properties of {N,N′-bis[2-(1-pyrazolyl)ethyl]pyridine-2,6-dicarboxamido}copper(II)

The pentadentate dipeptide ligand N,N'-bis[2(1-pyrazolyl)ethyl]pyridine-2,6-dicarboxamide (PyPz(2)PH(2)) (1) (H denotes dissociable amide H) has been synthesized. The Cu(II) complex of this ligand namely, [Cu(PyPz(2)P)] (2), has been isolated and structurally characterized. Complex 2 crystallizes in the triclinic space group P (1) over bar with alpha = 7.743(3), b = 9.427(2), c = 12.809(3) Angstrom, alpha = 71.01 (2), beta = 80.38(2), gamma = 70.54(2)degrees, V = 831.8 (4) Angstrom(3) and Z = 2. The structure was refined to R = 4.13% by using 3313 (I > 2 sigma(I)) data. The dianionic pentadentate ligand coordinates to Cu(II) in a distorted square pyramidal fashion. The Cu center is lifted out of the mean basal plane by 0.32 Angstrom. The spectral parameters of 2 have been compared with those of an analogous complex [Cu(Py3P)] that contains pyridine rings in place of pyrazoles on a similar ligand framework. Such comparison indicates that pyridine nitrogens coordinate to Cu(II) more strongly than 2-pyrazolyl nitrogens. (C) 1998 Elsevier Science S.A.