Ligand Contributions to the Electronic Structures of the Oxidized Cobalt(II) salen Complexes

Kochem, Amélie; Kanso, Hussein; Baptiste, Benoı̂t; Arora, Himanshu; Philouze, Christian; Jarjayes, Olivier; Vezin, Hervé; Luneau, Dominique; Orio, Maylis; Thomas, Fabrice

doi:10.1021/ic300763t

Cited by 82 publications

(75 citation statements)

References 142 publications

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“…The Co complexes CoSal R1,R2 were synthesised in good yields from the metallation of the corresponding ligands H 2 Sal R1,R2 with Co(OAc) 2 •4H 2 O. [50][51][52][53][54][55] CoSal tBu,NO2 yielded crystals suitable for X-ray analysis, using THF-pentane as the recrystallisation solvents. The molecular structure of CoSal tBu,NO2 •THF is shown in Fig.…”

Section: Synthesis and Characterisationmentioning

confidence: 99%

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Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

et al. 2014

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A series of cobalt salen complexes, where salen represents an N2O2 bis-Schiff-base bis-phenolate framework, are prepared, characterised and investigated for reversible-termination organometallic mediated radical polymerisation (RT-OMRP). The salen ligands contain a cyclohexane diimine bridge and systematically altered para-substituted phenoxide moieties as a method to examine the electronic impact of the ligand on complex structure and reactivity. The complexes are characterised by single crystal X-ray diffraction, cyclic voltammetry, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and computational methods. Structural studies all support a tailorable metal centre reactivity altered by the electron-donating ability of the salen ligand. RT-OMRP of styrene, methyl methacrylate and vinyl acetate is reported and suggests that cobalt-carbon bond strength varies with the ligand substitution. Competing β-hydrogen abstraction affords long-chain olefin-terminated polymer chains and well controlled vinyl acetate polymerisations, contrasting with the lower temperature associative exchange mechanism of degenerative transfer OMRP.

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Section: Synthesis and Characterisationmentioning

confidence: 99%

“…S1 ‡). 53,56 The more positive redox potential for the NO 2 derivative is due to the presence of electron-withdrawing groups in the para position. The positive shift in the potential for the NO 2 derivative (and the use of THF as the solvent) results in only one of the redox processes being visible by CV in this work.…”

Section: Electrochemistrymentioning

confidence: 99%

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

et al. 2014

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“…Recently, Fujii and co‐workers reported Co(salen)(X) complex with the 40 % character of Co II (salen •+ )(X) and 60 % character of Co III (salen)(X) . Thomas and co‐workers have shown similar kind of cobalt(II) salen complex and one electron oxidized complex was found to have 70 % electron density over the cobalt ion and remaining 30 % electron density spreading over the ligand . In another report by the same group, phenolato donor was replaced by the anilido donor and the resultant complex was found to have 75 % contribution of metal ion in SOMO …”

Section: Figurementioning

confidence: 90%

Non‐Innocent Property of Tridentate Ligand in Novel Cobalt Complex : Crystal Structure and Evidences for Cobalt(II) Phenoxyl Radical Complex Formation

et al. 2016

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A phenoxyl radical complex [Co II (L)(L + )]NO 3 (where LH = (E)-2,4di-tert-butyl-6-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol and H = dissociable proton) was synthesized at room temperature in aerobic condition and was characterized. Crystal structure, UV-Vis-NIR and 1 H-NMR spectra, magnetic properties and electrochemical studies authenticated the presence of Co (II) phenoxyl radical complex.Generation of phenoxyl radical complexes and their reactivity studies are significantly important in the context of structural and functional modelling of galactose oxidase enzyme and are important areas in chemical research. [1, 2] Although phenoxyl radical complex of copper exhibit vital role in the oxidation chemistry of galactose by the native enzyme, phenoxyl radical complexes of cobalt gained considerable current interest because of their essential roles in the catalytic cycle performed by Jacobsen catalyst. [3][4][5][6] Cobalt complexes derived from salen type ligand exhibit crucial role in epoxide formation and CO 2 / polymerization reactions. [5,6] It has been found out that ligand centred oxidation and radical formation are important events in the catalytic cycle. Hence in the literature there are reports of cobalt(II) as well as cobalt(III) phenoxyl radical complexes. [2][3][4][5][6][7] Herein we report a facile synthesis and characterization of novel cobalt(II) radical complex [Co(L)(L + )]NO 3 and molecular structure of the complex was determined by X-ray crystallography.Recently, Fujii and co-workers reported Co(salen)(X) complex with the 40 % character of Co II (salen * + )(X) and 60 % character of Co III (salen)(X). [4] Thomas and co-workers have shown similar kind of cobalt(II) salen complex and one electron oxidized complex was found to have 70 % electron density over the cobalt ion and remaining 30 % electron density spreading over the ligand. [8] In another report by the same group, phenolato donor was replaced by the anilido donor and the resultant complex was found to have 75 % contribution of metal ion in SOMO. [6] Hence, to the best of our knowledge there is no report of phenoxyl radical complex of cobalt(II) in the literature in a ligand system other than salen and salen type ligands. We would like to mention here that Benisvy and co-workers synthesized octahedral cobalt(II) complex bearing imidazole-phenolato moiety and oxidation of this complex afforded a cobalt (II) phenoxyl radical complex; [12] however no crystal structure was described in this report. We have been working with a tridentate ligand [9] LH (shown in Figure 1) and in present study, deprotonated ligand having NNO donors was treated with cobalt(II) nitrate to afford a green colored complex. The resultant cobalt complex provided several interesting properties which are described below.Presence of phenolato function in the ligand frame and synthesis of complex [Co II (L)(L + )]NO 3 , one could simply expect the formation of a diamagnetic Co(III) complex with formula [Co III L 2 ]NO 3 however we have solved the molecular str...

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“…Complexes ( R , R )‐ N , N ′‐bis(3‐methoxy‐5‐ tert ‐butyl‐salicylidene)‐1,2‐cyclohexanediaminato]cobalt(II) ( 6 ), ( R , R )‐ N , N ′‐bis(3‐dimethylamino‐5‐ tert ‐butyl‐salicylidene)‐1,2‐cyclohexanediaminato]cobalt(II) ( 7 ), ( R , R )‐ N , N ′‐bis(3,5‐di‐ tert ‐butyl‐salicylidene)‐1,2‐cyclohexanediaminato]cobalt(II) ( 5 ), and ferrocenium tetrakis[(3,5‐trifluoromethyl)phenyl]borate were synthesized according to the reported procedures. Propylene oxide was distilled under argon after drying over calcium hydride.…”

Section: Methodsmentioning

confidence: 99%

“…For example, the O 2 /acid oxidation of Co II –salcy species, is not applicable to the preparation of 2 , possibly due to the potential for overoxidation. As an alternative oxidation method to form [Co III (MeO‐salcy)], milder oxidants such as AgSbF 6 + are known to be effective, but thus‐prepared Co III complexes have never been applied to epoxide/CO 2 copolymerization.…”

Section: Introductionmentioning

confidence: 99%

In Situ Generation of Co^III–Salen Complexes for Copolymerization of Propylene Oxide and CO₂

Hatazawa

Nakabayashi

Ohkoshi

et al. 2016

Chemistry A European J

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A simple admixture of Co(II) -salcy complexes with [Cp2 Fe(III) ]PF6 resulted in reproduction of the results with isolated Co(III) -salcy complexes in the copolymerization of epoxide and carbon dioxide. By using this in situ-generated active species with bis(triphenylphosphoranilydene)ammonium 2,4-dinitrophenolate, a para-methoxy-substituted Co-salcy complex was proven to be more active than the parent tert-butyl-substituted system. In contrast, the Co(II) -salcy complex substituted with the more strongly electron-donating NMe2 group did not show any activity for this copolymerization.

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Ligand Contributions to the Electronic Structures of the Oxidized Cobalt(II) salen Complexes

Cited by 82 publications

References 142 publications

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

Non‐Innocent Property of Tridentate Ligand in Novel Cobalt Complex : Crystal Structure and Evidences for Cobalt(II) Phenoxyl Radical Complex Formation

In Situ Generation of Co^III–Salen Complexes for Copolymerization of Propylene Oxide and CO₂

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Ligand Contributions to the Electronic Structures of the Oxidized Cobalt(II) salen Complexes

Cited by 82 publications

References 142 publications

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity

Non‐Innocent Property of Tridentate Ligand in Novel Cobalt Complex : Crystal Structure and Evidences for Cobalt(II) Phenoxyl Radical Complex Formation

In Situ Generation of CoIII–Salen Complexes for Copolymerization of Propylene Oxide and CO2

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In Situ Generation of Co^III–Salen Complexes for Copolymerization of Propylene Oxide and CO₂