Mononuclear Copper(II) and Nickel(II) Complexes with Tetradentate Pyridylpyrazole Based Ligand: Synthesis, Characterization and Structure (original) (raw)
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Inorganic Chemistry Communications, 2003
The reaction of the ligand 3-(6-methyl-2-pyridyl)-5-(2-pyridyl)pyrazole (HL) with CuðNO 3 Þ 2 Á 3H 2 O gives a complex of formula ½Cu 4 L 4 ðNO 3 Þ 3 ðNO 3 Þ, which has been characterised by elemental analyses, infrared and electronic spectroscopies and single-crystal X-ray diffraction. The molecular structure of this complex is tetranuclear. The Cu 2þ ions are linked to four ligands, forming a macromolecular cyclic system. The co-ordination geometries of the Cu(II) are square pyramid. The formation of this complex implies a control of nuclearity by steric hindrance.
Inorganica Chimica Acta, 2001
The reaction of the pyrazole derived-ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL 0 ) and 3-phenyl-5-(6-methyl-2-pyridyl)pyrazole (HL 1 ) with Cu(CH 3 COO) 2 , Co(CH 3 COO) 2 and Ni(CH 3 COO) 2 was carried out. Products were characterised by elemental analyses, conductivity measurements and infrared and electronic spectroscopy. The IR spectra of complexes display the typical absorption bands of pyrazole-derived ligands. The nature of the complexes depends on the metal, M, the ligand, HL, and the M:HL ratio: Ni(HL) 2 (CH 3 COO) 2 , Cu(L) 2 , (HL=HL 0 , HL 1 ), Co(L 0 ) 2 . In the complexes of Co(II) and Cu(II) the pyrazole is deprotonated, the band w(N-H) was not observed in IR spectroscopy. The crystal structure of [Cu(L 0 ) 2 ] consists of discrete centrosymmetric molecules involving a co-ordinated CuN(pz) 2 N(py) 2 core with planar geometry. The anionic ligand L 0 is not completely planar.
Transition Metal Chemistry, 2017
The synthesis, structure, spectroscopic and electro-spectrochemical properties of salicylaldimine Schiffbase ligands (L n H) (n = 1, 2, and 3) (L 1 H = N-[2-amino-8-hydroxyquinoline]-salicylaldimine, L 2 H = N-[2amino-8-hydroxyquinoline]-5-bromosalicylaldimine and L 3 H = N-[2-amino-8-hydroxyquinoline]-5methoxysalicylaldimine), respectively, and their dinuclear copper(II) complexes [Cu 2 (L n) 2 ] are described. Three new dissymmetric tetradentate salicylaldimine ligands containing a donor set of NOOO were prepared by reaction of 2-amino-8-hydroxyquinoline with different salicylaldehydes. The dinuclear copper(II) metal complexes of these ligands were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac) 2 ÁH 2 O. The ligands and their copper complexes were characterized by FT-IR, UV-vis, 1 H NMR, elemental analysis, molar conductivity, mass spectra and thermal analysis methods in addition to magnetic susceptibility and spectroelectrochemical techniques. The reaction of these ligands in a 1:1 mole ratio with copper(II) acetate afforded dinuclear Cu(II) metal complexes. The room temperature magnetic moments of [Cu 2 (L n) 2 ] complexes are found between 1.12 and 1.28 BM for per Cu(II) molecule.
Polyhedron, 2001
Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL 0 ) and 3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole (HL 1 ) with Cu(NO 3 ) 2 ·3H 2 O and CuX 2 ·xH 2 O (X=Cl, Br) gives complexes with stoichiometry Cu(HL 0 ) 2 X 2 ·xH 2 O, Cu(HL 1 ) 2 X 2 ·EtOH, Cu(HL)X 2 , Cu(HL) 2 (NO 3 ) 2 ·xH 2 O (HL= HL 0 , HL 1 ) and Cu(HL 0 )(NO 3 ) 2 ·2H 2 O. The new complexes were characterised by elemental analyses, conductivity measurements and infrared and electronic spectroscopy. The crystal and molecular structure of [Cu(HL 0 )(NO 3 )(H 2 O) 2 ](NO 3 ) consists of discrete cations and NO 3 − anions linked by hydrogen bonds. The cation complex [Cu(HL 0 )(NO 3 )(H 2 O) 2 ] + contains a copper(II) with a distorted tetragonal pyramid geometry (~= 0.094), with a H 2 O ligand occupying the apical site. The penta-coordinated metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen, one nitrate and two water molecules. The ligand HL 0 is not completely planar.
Dalton Transactions, 2007
The pyrazole-based diamide ligand N,N -bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide (H 3 L) has been structurally characterised and successfully employed in the preparation of [2 × 2] grid-type complexes. Thus, the reaction of H 3 L with Cu(ClO 4 ) 2 ·6H 2 O or Ni(ClO 4 ) 2 ·6H 2 O in the presence of added base (NaOH) affords the tetranuclear complexes [M 4 (HL 4 )]·8H 2 O (1: M = Cu, 2: M = Ni). Employment of a mixture of the two metal salts under otherwise identical reaction conditions leads to the formation of the mixed-metal species [Cu x Ni 4−x (HL) 4 ]·8H 2 O (x ≤ 4; for x = 2: 3). Complexes 1-3 have been structurally characterised and found to be isomorphous, with each ligand strand acting as a hybrid N 3 -NO chelator. The copper ions in 1 are in a distorted square-pyramidal N 4 O coordination environment with rather long M-O apical distances. The coordination sphere about the nickel ions in 2 is roughly the same, but with even longer M · · · O distances, and it is therefore best described as N 4 square-planar with low-spin nickel(II) ions. The single crystal X-ray data obtained for the mixed-metal complex 3 gave the best results assuming a statistical distribution of copper and nickel ions. X-Band EPR spectra of 1 and 2 indicate magnetically coupled copper(II) ions and low-spin nickel(II), respectively. EPR spectra of a powdered sample of a complex with the general formulation [Cu x Ni 4−x (HL) 4 ]·8H 2 O with a large excess of Ni 2+ (95%) was shown to be characteristic for individual copper(II) ions in the tetranuclear grid system. Magnetic susceptibility data of 1 indicate weak antiferromagnetic spin coupling between the copper ions (J = −8.2 ± 0.4 cm −1 ), which is explained by the particular spatial arrangement of the magnetic orbitals.
Polyhedron, 1992
The monoanionic bidentate ligand N-[2-(3-ethyl-indole)]pyridoxaldimine prepared by 1 : 1 Schiff-base condensation of 3-(2-amino-ethyl)indole (tryptamine, TPA) with [3-hydroxy-5-(hydroxy-methyl)-2-methyl-4-py~din~arboxaldehyde] (pyridoxal, pyrdox) and three different copper complexes are reported. The nickel(I1) compound with the same ligand is also studied. All complexes were characterized by IR, W-vis and 'H NMR spectra, magnetic measurements and thermoanalytical data. A single-crystal of the nickel complex was subjected to X-ray diffraction analysis. The coordination of the nickel(I1) complex is truns planar (NiN,O,) with Ni-0 and Ni-N bond lengths of 1.841(l) and 1.926(2) A, respectively. The spectroscopic data for the copper(I1) complexes suggest the same chromophore group (CuN202) with a tram configuration in the solid phase for all. Finally, the dehydration reaction Cu(pyrdoxTPA), * yH,O(s)-Cu(pyrdoxTPA)&) + yHzO(g) for the two copper complexes is studied.
Journal of the Chemical Society, Dalton Transactions, 1999
Reaction of 3-(2-pyridyl)pyrazole (HL 1 ) and 6-(3-pyrazolyl)-2,2Ј-bipyridine (HL 2 ) with nickel() and zinc() salts afforded the simple mononuclear pseudo-octahedral complexes [M(HL 1 ) 3 ][PF 6 ] 2 and [M(HL 2 ) 2 ][PF 6 ] 2 respectively (M = Ni or Zn) in which the ligands co-ordinate as neutral mononucleating chelates in the same manner as e.g. 2,2Ј-bipyridine or 2,2Ј : 6Ј,2Љ-terpyridine respectively. However with Cu II the complexes [Cu 4 (L 1 ) 6 (solv) 2 ][PF 6 ] 2 (solv = dmf or MeOH) and [Cu 4 (L 2 ) 4 (dmf) 4 ][PF 6 ] 4 were isolated and crystallographically characterised, in all cases containing four tetragonally elongated square-pyramidal copper() ions which are linked by pyrazolate bridges from the now deprotonated ligands L 1 and L 2 . The approximate orthogonality of the different ligands within each complex and the approximately square array of metal ions result in a grid-like structure. In [Cu 4 (L 1 ) 6 (solv) 2 ][PF 6 ] 2 there are successively two, one, two and one pyrazolate bridges between adjacent copper() ions around the Cu 4 square resulting in two clearly different magnetic coupling pathways; in [Cu 4 (L 2 ) 4 (dmf) 4 ][PF 6 ] 4 however, which has approximate S 4 symmetry, each Cu ؒ ؒ ؒ Cu edge has a single pyrazolate bridge and the coupling pathways are all virtually equivalent. Prolonged drying of these compounds resulted in loss of the axial dmf ligands to give [Cu 4 (L 1 ) 6 ][PF 6 ] 2 and [Cu 4 (L 2 ) 4 ][PF 6 ] 4 . Magnetic susceptibility studies on these showed the presence of two antiferromagnetic exchange pathways for [Cu 4 (L 1 ) 6 ][PF 6 ] 2 with J > 172 cm Ϫ1 and JЈ < 155 cm Ϫ1 (strong correlation between the parameters precludes a more precise determination), but only one antiferromagnetic exchange pathway for [Cu 4 (L 2 ) 4 ][PF 6 ] 4 with J = 63.5 cm Ϫ1 , consistent with the crystal structures of the dmf adducts. The EPR spectra of [Cu 4 (L 1 ) 6 ][PF 6 ] 2 and [Cu 4 (L 2 ) 4 ][PF 6 ] 4 at a variety of frequencies and temperatures can be well simulated as arising from triplet species; however the spectrum of [Cu 4 (L 1 ) 6 ][PF 6 ] 2 also contains a feature which may be ascribed to the expected thermally populated quintet state.
Inorganica Chimica Acta, 2011
Binuclear cyanate bridged nickel(II) complex [Ni(L)(NCO)] 2 (PF 6) 2 (1) and copper(II) complex [Cu(L) (NCO)] 2 (PF 6) 2 (2), where L is N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine, a tetradentate N 4-coordinated ligand have been synthesized and characterized by physicochemical method. The structures of complexes 1 and 2 have been studied by single crystal X-ray diffraction analysis. The structure analysis reveals that both nickel(II) and copper(II) center are coordinated in distorted octahedral fashion and coordination mode of cyanate ligand is end-to-end (l-1,3) for complex 1 but it is double end-on (l-1,1) mode for complex 2. The variable temperature magnetic susceptibility data, measured from 2 to 300 K, show weak antiferromagnetic interaction with J value À6.2(1) cm À1 for complex 1, whereas complex 2 has very weak ferromagnetic interaction with J value +0.5(1) cm À1 .