Synthesis, physicochemical, and thermal characterization of coordination compounds of Cu(II) with a pyrazole-type ligand
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Synthesis, physicochemical, and thermal characterization of coordination compounds of Cu(II) with a pyrazole‑type ligand Berta Barta Holló1 · Ljiljana S. Vojinović Ješić1 · Mirjana M. Radanović1 · Marko V. Rodić1 · Željko K. Jaćimović2 · Katalin Mészáros Szécsényi1 Received: 5 September 2019 / Accepted: 1 January 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Four new coordination compounds of Cu(II) were synthesized with ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) and different co-ligands. In the reaction of warm methanolic solutions of C uX2·nH2O (X = Cl, n = 2; X = Br, n = 0; X = NO3, n = 3) and the ligand in mole ratio 1:2, bis(ligand) complexes Cu(L)2Cl2 (1), Cu(L)2Br2 (2) and Cu(L)2(NO3)2 (3) were obtained. Unlike this, reaction of C uCl2 with the ligand in the presence of LiOAc yielded to the formation of dimeric complex of the formula [Cu(L)(OAc)2]2 (4), with four acetate ions as bridging ligands. In all these complexes, ligand L is coordinated in a monodentate manner through N2 nitrogen atom. The coordination environment in the dimeric complex is octahedral, while in the monomeric complexes the central atom is tetra-coordinated. The molar conductivity data in DMF show that the acetate ions in the dimeric complex are coordinated even in solution. In the monomeric compounds, the molar conductivity data increase in the order 1 2σ(F2)] wR(F2) S No. of reflections No. of parameters No. of restraints H-atom treatment Δρmax, Δρmin (e Å−3)
Gemini S (Oxford Diffraction) Gaussian 0.555, 0.977 1.38 14,115 3299 2354 0.050 0.625 0.068 0.134 1.154 3299 212 24 Mixed 0.54, − 0.36
riding model. Their displacement parameters were approximated as Uiso = kUeq of the parent atoms (k = 1.2 for NH, CH, and C H 2; 1.5 for C H 3 groups). Disorder of ethoxy group of the pyrazole moiety was treated by distance and ADP restraints, with refinement of site occupancy factors. Structure validation and additional geometrical calculations were performed by PLATON [26]. Crystallographic and refinement details are listed in Table 1. CCDC 1949958 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. Calculations of pairwise interaction energies are based on CE-HF model [27–29] embodied in CrystalExplorer17.5 [30]. For this purpose, crystallographic structural model was
Synthesis, physicochemical, and thermal characterization of coordination compounds of Cu(II)…
modified by normalizing X–H bond lengths to standard neutron diffraction values.
General preparation of the coordination compounds Bis(ligand) complexes of copper(II) of the general formula Cu(L)2X2, X = Cl, Br, N O3 (1–3), are obtained in the reaction of solid C uX2·nH2O (X = Cl, n = 2; X = Br, n = 0; X = NO 3, n = 3) and MeOH solution of ethyl-5-amino1-methyl-1H-pyrazole-4-carboxylate (L) in a mole ratio 1:2. Under the same conditions, but in the presence of LiOAc, CuCl2·2H2O and L formed the dimeric complex o
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