Novel Scorpionate and Pyrazole Dioxovanadium Complexes, Catalysts for Carboxylation and Peroxidative Oxidation of Alkanes

Silva, Telma F. S.; Luzyanin, Konstantin V.; Kirillova, Marina V.; Silva, M. Fátima C. Guedes da; Martins, Luísa M. D. R. S.; Pombeiro, Armando J. L.

doi:10.1002/adsc.200900660

Cited by 103 publications

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“…The overall conversion, turnover number and selectivity obtained for complexes 1 and 2 are in the range of those values found for other oxovanadium complexes previously reported. 10,16,19,22 …”

Section: Discussionmentioning

confidence: 99%

“…[16][17][18] In this way, a number of model complexes for vanadium containing enzymes and other vanadium complexes had their catalytic properties evaluated towards the peroxidative oxidation of alkenes and aromatic hydrocarbons. 6,[19][20][21][22][23] In this work, we present the synthesis and characterization of two novel vanadium(V) cis-dioxo complexes of general formula [VO 2 (L)] and [VO 2 (HLox)], where HL = (3-[(bis-pyridin-2-yl-methylamino)-methyl]-2-hydroxy-5-methyl-benzaldehyde) and H 2 Lox = (3-[(bis-pyridin-2-ylmethylamino)-methyl]-2-hydroxy-5-methyl-benzaldehyde oxime), and preliminary reactivity studies on the catalytic oxidation of cyclohexane by these complexes employing H 2 O 2 or t-BuOOH as oxidants. …”

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Synthesis, characterization and catalytic activity of two novel cis-dioxovanadium(v) complexes: [VO2(L)] and [VO2(Hlox)]

Silva¹,

Pinheiro²,

Chacon³

et al. 2011

J. Braz. Chem. Soc.

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Dois novos complexos [VO 2 (L)] e [VO 2 (HLox)]foram sintetizados e caracterizados por espectroscopias no IV, UV-Vis e RMN, voltametria cíclica, análise elementar e difração de raios X. A síntese do ligante inédito H 2 Lox também é descrita. Os complexos 1 e 2 foram obtidos pela reação de [VO(acac) 2 ] com os respectivos ligantes HL e H 2 Lox. Alternativamente, 2 foi preparado a partir da reação de HL com [VO(acac) 2 ] na presença de hidroxilamina, e através da reação de 1 com hidroxilamina. Dados cristalográficos mostram que 1 e 2 apresentam estruturas moleculares similares, onde o centro de vanádio(V) cis-dioxo encontra-se coordenado em um ambiente octaédrico distorcido formado pelos ligantes L -e HLox -, respectivamente. A atividade catalítica destes compostos foi avaliada na oxidação do cicloexano, utilizando H 2 O 2 e t-BuOOH como oxidantes. Ambos apresentam seletividade > 70% para formação de cicloexilidroperóxido. Cálculos B3LYP/6-31G(d) foram empregados na otimização da geometria e para auxiliar na atribuição do espectro eletrônico.Two novel complexes, [VO 2 (L)] (1) and [VO 2 (HLox)] (2), were synthesized and characterized by IV, UV-Vis and NMR spectroscopy, cyclic voltammetry, elemental analysis and X-ray diffraction. The synthesis of a new ligand, H 2 Lox, is also described. Complexes 1 and 2 were obtained by the reaction of [VO(acac) 2 ] with the ligands HL and H 2 Lox, respectively. Alternatively, 2 was also obtained by the reaction of HL with [VO(acac) 2 ] in the presence of hydroxylamine, and by the reaction of 1 with hydroxylamine. Crystallographic data show that complexes 1 and 2 have similar molecular structures, in which the cis-dioxovanadium(V) center is coordinated to L -or HLox -, respectively, in a distorted octahedral environment. The catalytic activity of these compounds towards cyclohexane oxidation was evaluated using H 2 O 2 and t-BuOOH as oxidants. Both complexes presented > 70% selectivity for cyclohexylhydroperoxide formation. B3LYP/6-31G(d) calculations were used to confirm the geometry and to help assign the electronic spectra. Keywords: oxovanadium(V), bioinspired catalysts, peroxide activation IntroductionVanadium coordination chemistry has received attention in recent years due to its presence in several biological systems and its applications in catalysis. The first example of vanadium-dependent enzyme are the vanadium haloperoxidases (VHPOs), isolated from the marine algae Ascophyllum nodosum.1,2 Later, these enzymes were isolated from different sources such as seaweed, lichens and other algae and characterized as iodoperoxidases, bromoperoxidases and chloroperoxidases, depending on the most electronegative halogen the enzyme is capable of oxidizing.3 These enzymes are responsible for the two-electron oxidation catalyses of chloride, bromide Silva et al. 661 Vol. 22, No. 4, 2011 and iodide by hydrogen peroxide and are involved in the halogenation of a large variety of organic substrates in vivo. 4 The discovery of its structure initiated the investigation of vanadium...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Synthesis, characterization and catalytic activity of two novel cis-dioxovanadium(v) complexes: [VO2(L)] and [VO2(Hlox)]

Silva¹,

Pinheiro²,

Chacon³

et al. 2011

J. Braz. Chem. Soc.

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“…The main applications of C-homoscorpionate complexes as catalysts for oxidative reactions, where the involvement of metal redox processes is crucial for the catalytic activity, are the important and challenging single-pot oxidation of gaseous (e.g., direct oxidation of methane to carboxylic acids, Scheme 1) [47,62]) and liquid (e.g., cyclohexane to the correspondent alcohol-ketone mixture, Scheme 2) alkanes [7,8,13,43,[46][47][48][49]53,57,58,[63][64][65][66][67][68]. Indeed, oxidation of alkanes has been the object of considerable research [69][70][71][72][73][74][75][76][77][78], but still constitutes a serious challenge to modern chemistry, owing to the high inertness of these substrates.…”

Section: Introductionmentioning

confidence: 99%

“…A systematic investigation of the coordination behavior of new C-scorpionates, as well as some of the known ones, toward a variety of transition metals (e.g., V [44,[46][47][48][49], Mo [17,19,50], Re [51,52], Fe [44,46,49,53], Ru [54], Co [12,13], Ni [44,49,55], Pd [44], Cu [43,45,46,56,57], Ag [14], Au [58] or Zn [44,56]) followed, leading to new classes of complexes exhibiting different types of coordination modes (Figures 4 and 5). Like the pincer of a scorpion, these versatile tripodal ligands bind metal centers with nitrogen atoms from two pyrazolyl rings attached to the central carbon atom; the third pyrazolyl attached to carbon rotates forward like a scorpion's tail to "sting" the metal; hence the name of "scorpionates" (Figure 4).…”

Section: Introductionmentioning

confidence: 99%

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C-Homoscorpionate Oxidation Catalysts—Electrochemical and Catalytic Activity

Martins

2017

Catalysts

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Borate(1-), hydrotris(1H-pyrazolato-κN1)-, potassium & Borate(1-), hydrotris(1H-pyrazolato-κN1)-, sodium

Frederick

2017

Encyclopedia of Reagents for Organic Synthesis

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Novel Scorpionate and Pyrazole Dioxovanadium Complexes, Catalysts for Carboxylation and Peroxidative Oxidation of Alkanes

Cited by 103 publications

References 122 publications

Synthesis, characterization and catalytic activity of two novel cis-dioxovanadium(v) complexes: [VO2(L)] and [VO2(Hlox)]

Synthesis, characterization and catalytic activity of two novel cis-dioxovanadium(v) complexes: [VO2(L)] and [VO2(Hlox)]

C-Homoscorpionate Oxidation Catalysts—Electrochemical and Catalytic Activity

Borate(1-), hydrotris(1H-pyrazolato-κN1)-, potassium & Borate(1-), hydrotris(1H-pyrazolato-κN1)-, sodium

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