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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Vydané v:	Chemistry : a European journal Ročník 20; číslo 18; s. 5414 - 5422
Hlavní autori:	Paretzki, Alexa, Bubrin, Martina, Fiedler, Jan, Záliš, Stanislav, Kaim, Wolfgang
Médium:	Journal Article
Jazyk:	English
Vydavateľské údaje:	Weinheim WILEY-VCH Verlag 25.04.2014 WILEY‐VCH Verlag Wiley Wiley Subscription Services, Inc
Predmet:	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
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Popis
Shrnutí:	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).
Bibliografia:	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