Syntheses and Crystal Structures of Copper(II) Bis(pyrazolyl)acetic Acid Complexes

A New Dimeric Copper(II) Complex of Hexyl Bis(pyrazolyl)acetate Ligand as an Efficient Catalyst for Allylic Oxidations

“…As for metal-involving bonds, the Cu(1)−Br(2) length of the terminal bromide ion (see Table 3 ) is about 0.06 Å shorter than the Cu(1)−Br(1) distance (2.3687 (6) vs. 2.4302 (4) Å); the Cu(1)−Br(1) I bond length of the µ-bridging Br ion is instead appreciably longer at 2.7600 (5), about 0.33 Å longer than the terminal Cu−Br bond. This value is higher than the reported average for similar compounds (2.59 Å) but fits within the reported range (2.37–3.06 Å) [ 82 , 83 , 84 , 85 , 86 , 87 , 88 ]. Similar considerations can apply to the Cu−N(1) and Cu−N(3) distances: respectively, 2.017 (2) and 2.042 (3) Å (mean: 2.00, range: 1.97–2.09 Å).…”

“…The crystal structure investigation revealed that, in the solid state, the compound exists as a dimer of formula [Cu(L OHex )Br(μ-Br)] 2 , with the Br(1) ions binding two symmetry-related units to each other. To the best of our knowledge, this complex is one of the few mono- or di-nuclear bis-pyrazolyl acetate copper complexes [ 81 , 82 ] with uncoordinated acetate moieties, and also one of the relatively not-so-abundant copper complexes showing µ-bridging bromide ions coupled with two pentacyclic N-based ligands [ 83 , 84 , 85 , 86 , 87 , 88 ], described in the CCDC repository [ 89 ].…”

“…The aliphatic chain is placed in such a way as to fold towards the N(1):C(3) ring, with C(12)/C(12A) approximately 4 Å apart from the ring centroid. The Cu atom is penta-coordinated and the environment has a distorted square planar shape; this seems to be the preferred shape in similar compounds [ 82 , 83 , 84 , 85 , 86 , 87 , 88 ]. Sitting in the pyramid basal plane are the N(1) and N(3) atoms of the two pyrazolyl rings, which are in trans position with the Br(1) and Br(2) atoms, respectively.…”

Syntheses and Biological Studies of Cu(II) Complexes Bearing Bis(pyrazol-1-yl)- and Bis(triazol-1-yl)-acetato Heteroscorpionate Ligands

“…Medium broad absorptions at 1705 and 1667 cm −1 , were observed in the spectrum of compound 1 , due to the carbonylic asymmetric stretching. They were shifted with respect to the same absorption observed for the free ligand of [HC(COOH)(pz Me2 ) 2 ] (1740 cm −1 ) and were in accordance with the presence of the uncoordinated protonated carboxylic group and coordinated to the metal center carboxylate ligand, respectively [34,47,48,50,58]. A broad absorption at 1736 cm −1 was present in the spectrum of compound 2 , due to the carbonylic asymmetric stretching of the COOH groups in the same range observed for the free ligand [HC(COOH)(pz) 2 ] (1722 cm −1 ).…”

“…Among them, complexes containing bis(pyrazol-1-yl)carboxylic acids are especially of interest, due to their κ 3 - N , N , O tripodal coordination behavior, as metalloenzyme models relevant for biochemistry [28,33,34,35,36,37,38,39,40,41,42] and as starting materials to yield bifunctional ligands [43,44,45,46]. In the nearly 15 years, the facially coordinating bis(pyazol-1-yl)acetate ligands, typically substituted at the 3,5-positions of the pyrazolyl rings, have been used to synthesize several structurally characterized copper(II) complexes [34,47,48,49,50,51,52,53,54,55,56,57,58]. Many of these coordination compounds were studied for their unique structural, electrochemical, and catalytic properties; however, to our knowledge, biological studies on the anticancer properties of bis(pyrazolyl)acetate copper(II) complexes are unknown.…”