Syntheses and Crystal Structures of Copper(II) Bis(pyrazolyl)acetic Acid Complexes
The reaction of bis(pyrazol-1-yl)acetic acid (L) with copper(II) bromide provides two new complexes: [Cu(L-H)Br(µ-Br)]2 (1) and [Cu(L)2]⋅4H2O (2). Complex 1 is prepared by the stoichiometric reaction of L-H with copper(II) bromide in tetrahydrofuran. Dissolution of 1 in methanol causes its conversion into the bis-ligated complex (2), a highly hygroscopic material. Complex 2 can also be synthesized directly by the stoichiometric reaction of L-H with CuBr2 in methanol. Complex 1 is dimeric, interlinked by two bridging bromide ligands, and possesses terminal bromide ligands on each copper atom. The two pyrazolyl ligands in 1 coordinate with the nitrogen atoms to complete the coordination sphere of copper, resulting in a highly distorted geometry that lies between a trigonal bipyramidal or square pyramidal geometry with wide bond angles between the trans-oriented pyrazolyl nitrogen atoms and bromide ligands. Complex 2 assumes a pseudo-trigonal prismatic geometry with the deprotonated carboxylic acid that interacts weakly with copper.
Reaction of bis(pyrazol-1-yl)acetic acid (L-H) with copper(II) bromide provides two new complexes: [Cu(L-H)Br(µ-Br)]2 (1) and [Cu(L)2]⋅4H2O (2), these compounds represent the first, well-defined, independent copper(II) compounds supported by the base bis(pyrazolyl)acetic acid ligand.
KeywordsCrystal structures Synthesis Pyrazole Copper(II) complexes Scorpionate ligands
BQ would like to acknowledge the American Chemical Society Petroleum Research Fund for support or partial support of this research (PRF# 53848-UNI3).
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Conflict of interest
The authors declare no competing financial interest.
- 1.Otero A, Fernandez-Baeza J, Tejeda J, Carrillo-Hermosilla F, Diez-Barra E, Lara-Sanchez A, Fernandez-Lopez M, Lanfranchi M, Pellinghelli MA (1999) J Chem Soc Dalton Trans. https://doi.org/10.1039/A907505DGoogle Scholar
- 14.Corporation R (1999) Software user’s guide. Rigaku Molecular Structure Corporation, ©2000, Utah.Google Scholar
- 17.Sheldrick GM (2015) Acta Crystallogr C C71:1–3Google Scholar