ChemInform Abstract: KRISTALLSTRUKTUR VON (1‐(P‐METHYLPHENYL)‐AETHYLDIOXY)‐BIS‐(DIMETHYLGLYOXIMATO)‐(PYRIDIN)‐KOBALT(III)

Chiaroni, A.; Pascard‐Billy, C.

doi:10.1002/chin.197320414

Cited by 8 publications

(23 citation statements)

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“… Quite in contrast, all of the [Co(Py 3 P)(OOR)] and [Co(PyPz 2 P)(OOR)] complexes with tertiary, secondary or primary R groups can be conveniently synthesized by reacting the [LCo III (OH)] complexes with excess ROOH. This method of synthesis has several advantages over other methods previously used to synthesize [LCo III −OOR] complexes. − They are as follows: There is no change in the oxidation state of the cobalt in reaction I and hence, the transformation can be followed by 1 H NMR spectroscopy. The reaction involves exchange of OH - with ROO - , and the only byproduct is water.…”

Section: Resultsmentioning

confidence: 99%

“…To date, a handful of discrete Co(III)−alkylperoxo complexes of the formula [LCo III −OOR] bearing certain ligands L have been isolated and characterized. − The structures of a few these complexes have been determined by X-ray crystallography. Synthetic methods which have been employed in the syntheses of such [LCo III −OOR] complexes include (1) addition of excess ROOH to the [LCo II ] precursor, ,, (2) dioxygen insertion into metal−alkyl bonds, ,, and (3) dioxygen insertion into metal ligand bonds under irradiation. − , Only a few of these Co(III)−alkylperoxo complexes have been used to oxidize hydrocarbons 6,12,15 and the results of at least one study have indicated that the rates of decomposition of the [LCo III −OOR] complexes and the extent of alkane oxidation depend on L. It thus appears that a systematic study with structurally characterized [LCo III −OOR] complexes with different L and R will be very useful in determining how such variations affect the stability of the [LCo III −OOR] species and their capacities of hydrocarbon oxidation under specific conditions.…”

Section: Introductionmentioning

confidence: 99%

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Syntheses, Structures, and Reactivities of Cobalt(III)−Alkylperoxo Complexes and Their Role in Stoichiometric and Catalytic Oxidation of Hydrocarbons

et al. 1998

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Although Co(III)-alkyl peroxo species have often been implicated as intermediates in industrial oxidation of hydrocarbons with cobalt catalysts, examples of discrete [LCo III -OOR] complexes and studies on their oxidizing capacities have been scarce. In this work, twelve such complexes with two different ligands, L, and various primary, secondary, and tertiary R groups have been synthesized, and seven of them have been characterized by X-ray crystallography. The dianion (L 2-) of the two ligands N, N-bis[2-(2-pyridyl)ethyl]pyridine-2,6-dicarboxamide (Py 3 PH 2 , 1) and N, N-bis[2-(1-pyrazolyl)ethyl]pyridine-2,6-dicarboxamide (PyPz 2 -PH 2 , 2) bind Co(III) centers in pentadentate fashion with two deprotonated carboxamido nitrogens in addition to three pyridine or one pyridine and two pyrazole nitrogens to afford complexes of the type [LCo III (H 2 O)] and [LCo III (OH)]. Reactions of the [LCo III (OH)] complexes with ROOH in aprotic solvents of low polarity readily afford the [LCo III -OOR] complexes in high yields. This report includes syntheses of [Co(Py 3and [Co(PyPz 2 P)(OOR)] complexes with R ) t Bu (13), Cm (14), CMe 2 CH 2 Ph (15), Cy (16), i Pr (17) or n Pr (18). The structures of 8-12 and 16 have been established by X-ray crystallography. Complexes 10 and 16 are the first examples of structurally characterized compounds containing the [Co-OOCy] unit, proposed as a key intermediate in cobalt-catalyzed oxidation of cyclohexane. The metric parameters of 7-12 and 16 have been compared with those of other reported [LCo III -OOR] complexes. When these [LCo III -OOR] complexes are warmed (60-80 °C) in dichloromethane in the presence of cyclohexane (CyH), cyclohexanol (CyOH) and cyclohexanone (CyO) are obtained in good yields. Studies on such reactions (referred to as stoichiometric oxidations) indicate that homolysis of the O-O bond in the [LCo III -OOR] complexes generates RO • radicals in the reaction mixtures which are the actual agents for alkane oxidation. [LCo-O• ], the other product of homolysis, does not promote any oxidation. A mechanism for alkane oxidation by [LCo III -OOR] complexes has been proposed on the basis of the kinetic isotope effect (KIE) value (5 at 80 °C), the requirement of dioxygen for oxidation, the dependence of yields on the stability of the RO • radicals, and the distribution of products with different substrates. Both L and R modulate the capacity for alkane oxidation of the [LCo III -OOR] complexes. The extent of oxidation is noticeably higher in solvents of low polarity, while the presence of water invariably lowers the yields of the oxidized products. Since [LCo III -OOR] complexes are converted into the [LCo III (OH)] complexes at the end of single turnover in stoichiometric oxidation reactions, it is possible to convert these systems into catalytic ones by the addition of excess ROOH to the reaction mixtures. The catalytic oxidation reactions proceed at respectable speed at moderate temperatures and involve [LCo III -OOR] species as a key intermediate. Turnover numbers over 1...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Syntheses, Structures, and Reactivities of Cobalt(III)−Alkylperoxo Complexes and Their Role in Stoichiometric and Catalytic Oxidation of Hydrocarbons

et al. 1998

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“…2, nous sommes en pr&ence d'un complexe r&i-culaire; la majorit6 des atomes ont leurs coordonn6es en x sensiblement 6gales au -~ du param&re a, ce qui provoque des pseudo-extinctions auxquelles il faut ajouter celles dues aux atomes Co, 0(3) et C(3) dont les coordon6es en z sont toutes 6gales au ~ du param&re c (Tableau 2). Les distances entre les diff6rents atomes des ligands 6quatoriaux sont en accord avec les r6sultats publi6s par Lenhert (1967) et Chiaroni & Pascard-Billy (1973. (2) 0,020 (6) Le Tableau 4 donne le calcul du plan moyen des ligands 6quatoriaux.…”

Section: D6termination De La Structure Et Affinementunclassified

Structure cristalline de la méthyl(diméthylglyoximato)eau-cobalt(III)

Ginderow¹

1975

Acta Crystallogr Sect B

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“…(16) Although microwave data on fulminic acid were originally interpreted in terms of a linear geometry (rHc = 1.027 Á; = 1.168 A; rN0 = 1.199 A),17 recent ir data imply that this molecule is "quasi-linear", with the linear geometry ~0.1 kcal/mol less stable than a bent species (ZHCN = 165°; rHC = 1060 A; rCN = 1.168 A; rN0 = 1.199 A). 18 Although the STO-3G calculations do not reproduce this hump at the bottom of the surface, the flatness of the HCN bending surface is reproduced: the optimized molecule with ZHCN = 165°is only 1.4 kcal/mol (4-31G) less stable than the linear. MINDO/3 calculations reproduce this hump quantitatively!4 (17) .…”

mentioning

confidence: 98%

“…Department of Chemistry, Louisiana State University Baton Rouge, Louisiana 70803 Received May 18,1976 Cyclization and Rearrangement in the Reaction of Allylbis(dimethylglyoximato)cobalt(III) Complexes with Tetracyanoethylene. Crystal Structure of frans-3,3,4,4-Tetracyano-2-phenvlcyclopentylbis-(dimethylglyoximato)imidazolecobalt(III)…”

mentioning

confidence: 99%

Cyclization and rearrangement in the reaction of allylbis(dimethylglyoximato)cobalt(III) complexes with tetracyanoethylene. Crystal structure of trans-3,3,4,4-tetracyano-2-phenylcyclopentylbis(dimethylglyoximato)imidazolecobalt(III)

Dodd¹,

Johnson²,

Steeples³

et al. 1976

J. Am. Chem. Soc.

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The nucleophilic terminus is that with greater negative charge and highest HOMO coefficient; the electrophilic terminus has largest LUMO coefficient and the least negative (or most positive) ~h a r g e . '~,~,~ (4) MINDO/2 and MIND0/3 optimized geometries: P. Caramella, R. W. Gandour, J. A. Hall, C. G. Devilie, and K. N. Houk, J. Am. Chem. Soc., in press. These calculations also predict the trends obtained here by ab initio techniques: in MIND0/3 (MINDO12) the HCN angles are 116' (1 14'), 126' (122'), and 159' (150') for the ylide, imine, and oxide, respectively. The linear nitrile oxide is only 0.1 (0.2) kcal/mol higher in energy than the bent. (5) A. Padwa. M. Dharan, J. Smolanoff, and S. I. Wetmore, Jr., J. Am. Chem.

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ChemInform Abstract: KRISTALLSTRUKTUR VON (1‐(P‐METHYLPHENYL)‐AETHYLDIOXY)‐BIS‐(DIMETHYLGLYOXIMATO)‐(PYRIDIN)‐KOBALT(III)

Cited by 8 publications

References 0 publications

Syntheses, Structures, and Reactivities of Cobalt(III)−Alkylperoxo Complexes and Their Role in Stoichiometric and Catalytic Oxidation of Hydrocarbons

Syntheses, Structures, and Reactivities of Cobalt(III)−Alkylperoxo Complexes and Their Role in Stoichiometric and Catalytic Oxidation of Hydrocarbons

Structure cristalline de la méthyl(diméthylglyoximato)eau-cobalt(III)

Cyclization and rearrangement in the reaction of allylbis(dimethylglyoximato)cobalt(III) complexes with tetracyanoethylene. Crystal structure of trans-3,3,4,4-tetracyano-2-phenylcyclopentylbis(dimethylglyoximato)imidazolecobalt(III)

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