Metal Ion Chelates of Lipophilic Alkyl Diazinyl Ketoximes as Hydrolytic Catalysts

Cibulka, Radek; Hampl, František; Martinů, Tomáš; Mazáč, Jiří; Totevová, S.; Liška, František

doi:10.1135/cccc19991159

Cited by 17 publications

(5 citation statements)

References 3 publications

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“…It has been previously reported that the complex formation of pyridineoximate anions with metal ions leads to an inhibitory effect on the cleavage of phosphate triesters, in contrast to an acceleration effect with carboxylic acid esters . The reason for this difference is unclear because mechanistically the nucleophilic substitution in both types of esters is quite similar.…”

Section: Resultsmentioning

confidence: 96%

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

et al. 2017

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Deprotonated zinc(II) and cadmium(II) complexes of a tridentate oxime nucleophile (1, OxH) show a very high reactivity, breaking by 2-3 orders of magnitude the previously established limiting reactivity of oximate nucleophiles in the cleavage of substituted phenyl acetates and phosphate triesters, but are unreactive with p-nitrophenyl phosphate di- and monoesters. With reactive substrates, these complexes operate as true catalysts through an acylation-deacylation mechanism. Detailed speciation and kinetic studies in a wide pH interval allowed us to establish as catalytically active forms [Cd(Ox)], [Zn(Ox)(OH)], and [Zn(Ox)(OH)] complexes. The formation of an unusual and most reactive zinc(II) oximatodihydroxo complex was confirmed by electrospray ionization mass spectrometry data and supported by density functional theory calculations, which also supported the previously noticed fact that the coordinated water in [Zn(OxH)(HO)] deprotonates before the oxime. Analysis of the leaving group effect on the cleavage of phenyl acetates shows that the rate-determining step in the reaction with the free oximate anion is the nucleophilic attack, while with both zinc(II) and cadmium(II) oximate complexes, it changes to the expulsion of the leaving phenolate anion. The major new features of these complexes are (1) a very high esterolytic activity surpassing that of enzyme hydrolysis of aryl acetate esters and (2) an increased reactivity of coordinated oxime compared to free oxime in phosphate triester cleavage, contrary to the previously observed inhibitory effect of oxime coordination with these substrates.

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Section: Resultsmentioning

confidence: 96%

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

et al. 2017

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“…Materials and General Methods: All initial chemicals were commercially purchased and used as received without further purification. The ligand mpkoH was prepared as colorless needle crystals according to the literature method . Elemental analyses for C, H, and N were carried out with a CE‐440 (Leeman‐Labs) analyzer.…”

Section: Methodsmentioning

confidence: 99%

Two Oxime‐Based {Ln^III₃Ni^II₃} Clusters with Triangular {Ln₃(μ₃‐Ο₂)}⁷⁺ Core: Solvothermal Syntheses, Crystal Structures, and Magnetic Properties

Wang

Dong

Wang

et al. 2016

Zeitschrift anorg allge chemie

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Two isostructural heterometallic complexes, {[Dy 3 Ni 3 (H 2 O) 3 (mpko) 9 (O 2 )(NO 3 ) 3 ](ClO 4 )·3CH 3 OH·3CH 3 CN} (1) and {[Gd 3 Ni 3 (H 2 O) 3 (mpko) 9 (O 2 )(NO 3 ) 3 ](NO 3 )·10.75CH 3 OH} (2) [mpkoH = 1-(pyrazin-2-yl)ethanone oxime], were solvothermally synthesized by varying lanthanide ions with different magnetic anisotropy. Structural analyses revealed that both complexes contain a peroxide anion-aggregated triangular {Ln 3 (μ 3 -O 2 )} 7+ core, which is surrounded by three Ni II octahedra through threefold oxime linkages into a hetero-1166 metallic hexanuclear cluster. Apparent antiferromagnetic interactions are observed between the adjacent spin carriers of 1 and 2 with the coupling constant J Ln···Ni ≈ 12J Ln···Ln . Additionally, 1 with highly anisotropic Dy III site shows slow magnetization relaxation under zero dc field and 2 constructed from isotropic Gd III ion displays significant cryogenic magnetocaloric effect with a maximum entropy change of 24.8 J·kg -1 ·K -1 at 3.0 K and 70 kOe.

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“…The ligand mpkoH was prepared as colorless needle crystals according to the literature method. [11] Elemental analyses for C, H, and N were …”

Section: Materials and Instrumentsmentioning

confidence: 99%

Oximato-derived metal complexes with triangular and linear magnetic subunits: Synthesis, structure, and magnetism

Zhang

Liu

et al. 2016

Inorganic and Nano-Metal Chemistry

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Three oximato-based oligomeric metal complexes, {[Cu 3 (H 2 O)(µ 3 -OH)(mpko) 3 (NO 3 )]·3H 2 O·NO 3 } (1), {[Cu 6 (μ 3 -OH) 2 (mpko) 6 (Br) 4 ]·8H 2 O} (2), and {[Fe 3 (mpko) 6 ]·ClO 4 ·2.5CH 3 CN} (3) (mpkoH = 1-(pyrazin-2-yl)ethanone oxime), were synthesized by varying different spin carriers, and structurally and magnetically characterized. Structural determinations reveal that 1 is a discrete triangular {Cu 3 ( 3 -OH)} 5+ molecule with two adjacent metal ions further bridged by chelating-bridging mpko  ligands. Complex 2 features a centrosymmetric hexanuclear entity with two triangular {Cu 3 ( 3 -OH)} 5+ subunits extended by a Downloaded by [University of Nebraska, Lincoln] at 05:18 04 June 2016 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 pair of bridging -Br  anions. By contrast, 3 exhibits an approximately linear trinuclear entity with central Fe III ion connected with two external Fe II ions by six crystallographically unique mpko  ligands. Strong antiferromagnetic interactions with the coupling constant up to 223 (1) cm 1 are observed in the triangular subunits of 1 and 2. In 3, the central Fe III ion with S = 5/2 is almost magnetically isolated with the terminal Fe II ions with S = 0.

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Metal Ion Chelates of Lipophilic Alkyl Diazinyl Ketoximes as Hydrolytic Catalysts

Cited by 17 publications

References 3 publications

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

Two Oxime‐Based {Ln^III₃Ni^II₃} Clusters with Triangular {Ln₃(μ₃‐Ο₂)}⁷⁺ Core: Solvothermal Syntheses, Crystal Structures, and Magnetic Properties

Oximato-derived metal complexes with triangular and linear magnetic subunits: Synthesis, structure, and magnetism

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Metal Ion Chelates of Lipophilic Alkyl Diazinyl Ketoximes as Hydrolytic Catalysts

Cited by 17 publications

References 3 publications

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile

Two Oxime‐Based {LnIII3NiII3} Clusters with Triangular {Ln3(μ3‐Ο2)}7+ Core: Solvothermal Syntheses, Crystal Structures, and Magnetic Properties

Oximato-derived metal complexes with triangular and linear magnetic subunits: Synthesis, structure, and magnetism

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Two Oxime‐Based {Ln^III₃Ni^II₃} Clusters with Triangular {Ln₃(μ₃‐Ο₂)}⁷⁺ Core: Solvothermal Syntheses, Crystal Structures, and Magnetic Properties