Synthesis of Homo- and Heterobimetallic Ni^II–M^II (M = Fe, Co, Ni, Zn) Complexes Based on an Unsymmetric Ligand Framework: Structures, Spectroscopic Features, and Redox Properties

Authors

Denan Wang, Marquette UniversityFollow
Sergey V. Lindeman, Marquette UniversityFollow
Adam T. Fiedler, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

9 p.

Publication Date

9-2014

Publisher

Elsevier

Source Publication

Inorganica Chimica Acta

Source ISSN

0020-1693

Abstract

Several homo- and heterobimetallic Ni^II–M^II complexes (M^II = Fe, Co, Ni, Zn) supported by an unsymmetric polydentate ligand (L₁³⁻) are reported (L₁³⁻ is the trianion of 2-[bis(2-hydroxy-3,5-tert-butylphenyl)aminomethyl]-4-methyl-6-[(2-pyridylmethyl)iminomethyl]phenol). The L₁³⁻ chelate provides two distinct coordination environments: a planar tridentate {N₂O} site (A) and a tetradentate {NO₃} site (B). Reaction of L₁³⁻ with equimolar amounts of Ni^II and M^II salts provides bimetallic complexes in which the Ni^II ion exclusively occupies the tetragonal A-site and the M^II ion is found in the tripodal B-site. X-ray crystal structures revealed that the two metal centers are bridged by the central phenolate donor of L₁³⁻ and an anionic X-ligand, where X = μ-1,1-acetate, hydroxide, or methoxide. The metal ions are separated by 3.0–3.1 Å in the M_AM_B^X structures, where M_A and M_B indicate the ion located in the A and B sites, respectively, and X represents the second bridging ligand. Analysis of magnetic data and UV–Vis–NIR spectra indicate that, in all cases, the two metal ions adopt high-spin states in solution. The Ni_A^II centers undergo one-electron reduction at −1.17 V vs. SCE, while the Ni^II and Co^II ions in the phenolate-rich B-site are reduced at lower potentials. Significantly, the Ni_A^II center possesses three open or labile coordination sites in a meridional geometry, which are generally occupied by solvent-derived ligands in the crystal structures. The NiM_B^X complexes serve as structural mimics of heterometallic Ni-containing sites in biology, such as the C-cluster of carbon monoxide dehydrogenase (CODH).

Comments

Accepted version. Inorganica Chimica Acta, Vol. 421 (September, 2014): 559-567. DOI. © 2014 Elsevier. Used with permission.

Recommended Citation

Wang, Denan; Lindeman, Sergey V.; and Fiedler, Adam T., "Synthesis of Homo- and Heterobimetallic Ni^II–M^II (M = Fe, Co, Ni, Zn) Complexes Based on an Unsymmetric Ligand Framework: Structures, Spectroscopic Features, and Redox Properties" (2014). Chemistry Faculty Research and Publications. 554.
https://epublications.marquette.edu/chem_fac/554