Synthesis, crystal structure and properties of copper(II) complexes with different axial ligands and substituted pyrazoles

This paper presents the synthesis, crystal structure and properties of thre e copper(II) complexes with different axial ligands and substituted pyrazol es, [Cu(pz(R))(4)(X)(2)] (X = Cl- and R = H for (1), X = Cl- and R = n-But for (2), X = ClO4- and R = n-But for (3); pz(R) = 3-substituted pyrazole). The structures of all the complexes were determined by X-ray diffraction. T he complex [Cu(pz)(4)Cl-2] (1) crystallizes in the monoclinic system, space group C2/c, a = 13.658(5) Angstrom, b = 9.179(3) Angstrom, c = 14.724(6) A ngstrom, beta = 116.843(6)degrees, and Z = 4. The complex [Cu(pz(3-But))(4) Cl-2] (2) crystallizes in the triclinic system, space group p (1) over bar (No. 2), a = 10.733(2) Angstrom, b = 11.290(2) Angstrom, c = 14.726(3) Angs trom, alpha = 86.93(3)degrees, beta = 89.58(3)degrees, gamma = 89.44(3)degr ees, and Z = 2. The complex [Cu(pz(3-But))(4)(ClO4)(2)] (3) crystallizes in the monoclinic system, space group P2(1)/c (No. 14), a = 11.934(2) Angstro m, h = 23.422(5) Angstrom, c = 14.027(3) Angstrom, beta = 94.72(3)degrees, and Z = 4. The Cu(II) ion in each complex is coordinated to four pyrazole n itrogen atoms and two Cl- or two oxygen atoms of ClO4-, to form an elongate d octahedron. The two Cl- or two oxygen atoms of ClO4- are located at axial positions and the four nitrogen atoms of pyrazole are located at equatoria l positions. The average Cu(II)-N bond lengths are observed to be 2.010, 2. 015 and 1.997 Angstrom for 1, 2 and 3, respectively. The average Cu(II)-X b ond lengths are observed to be 2.839, 2.849 and 2.490 Angstrom for 1, 2 and 3, respectively. In these complexes, each Cl- or O has been connected by w eak intramolecular hydrogen bond with the hydrogen atom of two pyrazoles. T he UV-Vis and ESR spectroscopic results are consistent with the crystallogr aphic results and perfectly related to each other. (C) 2001 Elsevier Scienc e B.V. All rights reserved.