Correlated Coordination and Redox Activity of a Hemilabile Noninnocent Ligand in Nickel Complexes

The compound [Ni(QM)2], QM=4,6‐di‐tert‐butyl‐N‐(2‐methylthiomethylphenyl)‐o‐iminobenzoquinone, is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom and without any NiS bonding interaction. One‐electron oxidation results in additional twofold NiS...

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Veröffentlicht in:Chemistry : a European journal Jg. 20; H. 18; S. 5414 - 5422
Hauptverfasser: Paretzki, Alexa, Bubrin, Martina, Fiedler, Jan, Záliš, Stanislav, Kaim, Wolfgang
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Weinheim WILEY-VCH Verlag 25.04.2014
WILEY‐VCH Verlag
Wiley
Wiley Subscription Services, Inc
Schlagworte:
Absorption
Anisotropy
Binding
Cations
Charge transfer
Chemistry
Chemistry, Multidisciplinary
coordination change
Coordination compounds
hemilabile ligands
Ligands
Nickel
noninnocent ligands
Oxidation
Physical Sciences
redox chemistry
Science & Technology
nickel
coordination change
TRANSITION-METAL-COMPLEXES
APPROXIMATION
BEHAVIOR
OXIDATIVE ADDITION
redox chemistry
ELECTRONIC-STRUCTURES
MONONUCLEAR
noninnocent ligands
CHEMISTRY
SYSTEMATICS
ATOMS
hemilabile ligands
4-COORDINATE
ISSN:0947-6539, 1521-3765, 1521-3765
Online-Zugang:Volltext
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Zusammenfassung:The compound [Ni(QM)2], QM=4,6‐di‐tert‐butyl‐N‐(2‐methylthiomethylphenyl)‐o‐iminobenzoquinone, is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom and without any NiS bonding interaction. One‐electron oxidation results in additional twofold NiS coordination (dNiS≈2.38 Å) to produce a complex cation of [Ni(QM)2](PF6) with hexacoordinate NiII and two distinctly different mer‐configurated tridentate ligands. The O,O′‐trans arrangement in the neutral precursor is changed to an O,O′‐cis configuration in the cation. The EPR signal of [Ni(QM)2](PF6) has a very large g anisotropy and the magnetic measurements indicate an S=3/2 state. The dication was structurally characterized as [Ni(QM)2](ClO4)2 to exhibit a similar NiN2O2S2 framework as the monocation. However, the two tridentate (O,N,S) ligands are now equivalent according to the formulation [NiII(QM0)2]2+. Cyclic voltammetry reflects the qualitative structure change on the first, but not on the second oxidation of [Ni(QM)2], and spectroelectrochemistry reveals a pronounced dependence of the 800–900 nm absorption on the solvent and counterion. Reduction of the neutral form occurs in an electrochemically reversible step to yield an anion with an intense near‐infrared absorption at 1345 nm (ε=10400 M−1 cm−1) and a conventional g factor splitting for a largely metal‐based spin (S=1/2), suggesting a [(QM.−)NiII(QM2−)]− configuration with a tetracoordinate metal atom with antiferromagnetic NiII–(QM.−) interactions and symmetry‐allowed ligand‐to‐ligand intervalence charge transfer (LLIVCT). Calculations are used to understand the NiS binding activity as induced by remote electron transfer at the iminobenzoquinone redox system. Radical change: Oxidation of the singlet diradical species [NiII(QM.−)2], which contains the hemilabile redox‐active ligand QM, results in coordination of the S‐donor functions and spin‐crossover at the nickel atom, although the electron is removed not from the metal but from the noninnocent chelate ligand (see scheme).
Bibliographie:EU
Land Baden-Württemberg
COST programme CM1202
Ministry of Education of the Czech Republic - No. LD11086
istex:61D00040876BA890BE74E9607C4A5F30CF35472C
ark:/67375/WNG-BW1X1JXT-B
ArticleID:CHEM201304316
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
content type line 23
ISSN:0947-6539
1521-3765
1521-3765
DOI:10.1002/chem.201304316