Unprecedented Change of the Jahn−Teller Axis in a Centrosymmetric Cu^II Complex Induced by Lattice Water Molecules − Crystal and Molecular Structures of Bis[bis(3,5‐dimethylpyrazol‐1‐yl)acetato]copper(II) and Its Dihydrate

Abstract

Two copper coordination compounds with the tridentate (NON) ligand bis(3,5‐dimethylpyrazol‐1‐yl)acetic acid (Hbdmpza) are reported. The central coordination sphere in both compounds is fulfilled by two ligands in [CuL2]. The ligands are centrosymmetrically oriented around the copper ion, thus forming a trans‐CuN4O2 elongated octahedral chromophore. The atoms in both compounds are not positioned at the same places in the Jahn−Teller‐distorted octahedral environment. For compound [CuL2] (1) two nitrogen atoms are located on the longer axis [Cu−N: 2.438(2) Å], while the other two nitrogen atoms [Cu−N: 2.006(2) Å] and the two oxygen atoms [Cu−O: 1.983(2) Å] form the basal plane of the octahedron. The coordination sphere for [CuL2]·2H2O (2) is composed of four nitrogen atoms [Cu−N: 2.013(3), 2.038(2) Å] that form the basal plane, while the two oxygen atoms are at a longer distance [Cu−O: 2.293(2) Å]. The water molecules in 2 are hydrogen bonded to the non‐coordinated carboxylate oxygen atoms, forming bridges between two neighbouring monomeric units and leading to an infinite chain. Significant differences are observed for both compounds by spectroscopic investigations (EPR, IR, ligand field). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

IR analysis of the carboxylate forms in structurally determined [CuII(κ3-L)2] species isolated from different acidic solutions

“…Hbdmpza and the metal compounds were prepared following previously reported procedures [11][12][13][14]. The single crystals for 2 and 3 were isolated by the same procedure.…”

“…, we managed to isolate several related copper compounds with the bisligand coordination species [11,12]. The compounds were isolated from different acidic water solutions, rising to a differentiation of the network connections.…”

Activation pathways taking place at molecular copper precatalysts for the oxygen evolution reaction

“…The bdmpza − ligands of [Cu II (bdmpza) 2 ] are centrosymmetrically arranged around the copper ion, forming a trans-CuN 4 O 2 complex, wherein the copper site is coordinatively saturated [41]. However, it is not unprecedented that one of the ligand arms of bdmpza − dissociates in favor of coordination of water [42], providing an entry into catalysis at a molecular species.…”

Syntheses and structural characterization of two novel oxygen bridged dinuclear Mo-complexes containing bdmpza as ligand, trans-[Mo2O5(bdmpza)2] and trans-[Mo2O3(NCS)2(bdmpza)2] · 4CH3CN

“…Due to the growing interest in the chemistry of the non-heme iron enzymes, required in oxygen activation, as well as modelling of active sites of some zinc enzymes, several heteroscorpionate N,N,O-and N,N,S-ligands based on bis(pyrazol-1-yl)acetate, -thioacetate and -ethoxide with pyrazolyl rings substituted at 3-and 5 positions have been prepared [2]. Since the isolation of first mononuclear transition metal complex of Nb(IV) with one of the aforementioned ligands, [NbCl 2 (bdmpza) [9] and Zn(II) [8a].…”