Crystal structure, magnetic properties and spectroscopic studies of bis[1,3-bis(pyrazol-3-yl)triazenido]dicopper(II) trihydrate: a dinuclear complex with an asymmetric double pyrazolate bridge

Abstract

The crystal and molecular structure of [{ Cu(bpzt)},]-3H20 [H2bpzt = 1,3-bis(pyrazo1-3-yl)triazene] was determined by X-ray diffraction methods. The complex has a quasi-planar dinuclear structure with an asymmetric double pyrazolate bridge. The asymmetry results from the presence, on the C3 of each bridging pyrazolate, of a pyrazolyltriazenide chelating arm which completes the equatorial CuN, co-ordination. The centrosymmetric dinuclear units have intramolecular Cu 9 Cu distances of 3.852(5) and 3.839(4) A respectively.The units are stacked in columns along the b axis. The cell also contains crossing channels filled with water molecules. The complex was characterized by spectroscopic and magnetic measurements. Magnetic susceptibility data show antiferromagnetic behaviour with an exchange parameter IJI = 15 1 cm-' significantly decreased with respect to symmetric doubly bridged complexes (IJI = ~2 0 0 cm-I). The X-band powder EPR spectrum recorded at 77 K is typical of a triplet spin state lying above the singlet ground state. The results obtained for this complex are compared to recent literature data on other planar doubly bridged pyrazolate dicopper(I1) complexes. A correlation, valid for symmetric as well as asymmetric systems, is described between the exchange parameter J and the deviation of the Cu-N-N bridge angle from the optimum value corresponding to the highest 14.

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

“…Ample precedent exists for the strong tendency of pyrazolate-based multidentate ligand systems to accomplish dimerization by means of 1,2-m-pyrazolato bridges upon deprotonation of the pyrazole NH, as also observed for 9. [37] Interestingly, all dinuclear nickel(ii) complexes with L 1 ± L 3 ligand systems described up to this point (in this work and in previous reports [13,14] ) exhibit fivefold coordination with no evidence for any increase in coordination number, either in the solid state (as confirmed by X-ray crystallography) or in solution (based on the optical absorbance spectra). This strongly supports the assumption of a synergetic effect of both nickel ions for the hydration of nitriles by 2 (Scheme 2) or the hydrolysis of other substrates (see below), as only one coordination site is accessible at each metal center, located within the bimetallic pocket of the dinuclear framework.…”

“…[36,37] Our synthetic route starts from the 3-(chloromethyl)pyrazole hydrochlorides 6 a and b (obtained in two steps from the corresponding esters [38] ). For the selective attachment of the polydentate amine side arm by nucleophilic substitution, a NH protecting group had to be introduced at the pyrazole nucleus first.…”

Siamesisches Zwillingsporphyrin: ein Pyrazol‐expandiertes Porphyrin mit Bindungstaschen für Dimetallkomplexe

“…[20,21] Die helicale Verdrillung des Makrocyclus 9·Cu 2 mit den beiden Cu1-N pz -N pz -Cu1'-Torsionswinkeln von 78.7 und 80.08 bewirkt hier eine nahezu orthogonale Anordnung der beiden magnetischen d x 2 Ày 2-Metallorbitale.…”

Pyrazolate‐Based Dinucleating Ligands in L2M2 Scaffolds: Effects of Bulky Substituents and Coligands on Structures and M···H−C Interactions

“…However, the rather large magnetic coupling in 1 is certainly due to the high degree of planarity of the Ni(NN) 2 Ni scaffold, in accordance with the magneto-structural trends observed in bis(µ-pyrazolato) dicopper() chemistry. [36,13] The controlled synthesis of a complex with low-spin square-planar metal ions was achieved by treatment of…”