The isolation and crystal structure of the powerful Lewis acid, planar tetrakispyridine cobalt(II), [Co(C5H5N)4]2+, as its mixed chloride hexafluorophosphate salt

Beattie, James K.; Hambley, Trevor W.; Klepetko, John A.; Masters, Anthony F.; Turner, Peter

doi:10.1016/0277-5387(95)00233-i

Cited by 22 publications

(15 citation statements)

References 29 publications

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“…This makes our procedure quite general for the synthesis of cubane-like tetrameric cobalt(III) complexes of the type Co 4 O 4 (O 2 CR) 4 L 4 . The significant aspect of our work is that, unlike in reported procedures, 14,15 complexes of other nuclearities are not found to occur in the isolated products. Also, while using a dichloromethane extract of the olive green products during work-up procedure for isolating the complexes in improved yields, the complexes were invariably found to be identical to the complex species present in the precipitated products obtained directly from the reaction mixtures.…”

Section: Preparation Of Co 4 O 4 (O 2 Cr) 4 Lmentioning

confidence: 53%

Cobalt(III)-oxo cubane clusters as catalysts for oxidation of organic substrates

Das

Chakrabarty

2011

J Chem Sci

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Transition metal coordination complexes play a vital role as catalysts in the oxidation of organic substrates including renewable chemicals in an economically viable and environmentally friendly way. Here we highlight the preparation, characterization and application of oxo-cubane complexes of cobalt(III) as oxidation catalysts using air and water as oxidants. Cobalt(III)-oxo complexes of the type Co 4 O 4 (O 2 CR) 4 L 4 have been prepared by a general method and these have been characterized by analytical, spectroscopic, electrochemical and crystallographic methods. These soluble complexes have shown promising utility as catalysts in the aerobic oxidation of side chains of alkylaromatic hydrocarbon compounds. Oxidation of neat ethylbenzene has shown very high conversion and selectivity for acetophenone formation. On the other hand, oxidation of p-xylene has been found to yield both p-toluic acid and terephthalic acid. It is also possible to oxidize p-xylene in an aqueous medium under moderate applied O 2 pressure. Selective epoxidation of α-pinene with air as the oxidant also takes place with the cobalt(III)-based homogeneous catalysts.

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Section: Preparation Of Co 4 O 4 (O 2 Cr) 4 Lmentioning

confidence: 53%

Cobalt(III)-oxo cubane clusters as catalysts for oxidation of organic substrates

Das

Chakrabarty

2011

J Chem Sci

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“…This cluster, Co 4 O 4 (OAc) 4 py 4 (1), was first synthesized in 1998 by Beattie et al, and is an attractive model compound due to its resemblance to a subunit of extended cobalt oxides ( Figure 1). 24 The Nocera and Britt groups have employed 1 as a model for the cobalt phosphate (CoP i ) WOC in electron paramagnetic resonance spectroscopy studies. 25 Its promise as a functional model for water oxidation catalysis has been examined by the groups of Dismukes, Scandola, Sun, and Nocera.…”

Section: ■ Introductionmentioning

confidence: 99%

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

et al. 2015

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Artificial photosynthesis (AP) promises to replace society's dependence on fossil energy resources via conversion of sunlight into sustainable, carbon-neutral fuels. However, large-scale AP implementation remains impeded by a dearth of cheap, efficient catalysts for the oxygen evolution reaction (OER). Cobalt oxide materials can catalyze the OER and are potentially scalable due to the abundance of cobalt in the Earth's crust; unfortunately, the activity of these materials is insufficient for practical AP implementation. Attempts to improve cobalt oxide's activity have been stymied by limited mechanistic understanding that stems from the inherent difficulty of characterizing structure and reactivity at surfaces of heterogeneous materials. While previous studies on cobalt oxide revealed the intermediacy of the unusual Co(IV) oxidation state, much remains unknown, including whether bridging or terminal oxo ligands form O2 and what the relevant oxidation states are. We have addressed these issues by employing a homogeneous model for cobalt oxide, the [Co(III)4] cubane (Co4O4(OAc)4py4, py = pyridine, OAc = acetate), that can be oxidized to the [Co(IV)Co(III)3] state. Upon addition of 1 equiv of sodium hydroxide, the [Co(III)4] cubane is regenerated with stoichiometric formation of O2. Oxygen isotopic labeling experiments demonstrate that the cubane core remains intact during this stoichiometric OER, implying that terminal oxo ligands are responsible for forming O2. The OER is also examined with stopped-flow UV-visible spectroscopy, and its kinetic behavior is modeled, to surprisingly reveal that O2 formation requires disproportionation of the [Co(IV)Co(III)3] state to generate an even higher oxidation state, formally [Co(V)Co(III)3] or [Co(IV)2Co(III)2]. The mechanistic understanding provided by these results should accelerate the development of OER catalysts leading to increasingly efficient AP systems.

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“…Furthermore, the Co 4 cubane core can be oxidized to 3Co(III) and Co(IV) form and more stable than the Mn(III) Mn(IV) species that are intermediates in the O 2 evolution process [4,5]. To our knowledge, the crystal structure of a few complexes containing Co 4 cubane core, [Co 4 O 4 (O 2 CMe) 2 (bpy) 4 ](ClO 4 ) 2 [5], [Co 4 O 4 (C 7 H 8 N) 4 ] AE 5CHCl 3 [6], [ [11], etc, had been reported. Vanadates have been intensively studied owing to the ability of vanadium atoms adopting a variety of co-ordination geometries and oxidation states [12].…”

mentioning

confidence: 96%

Hydrothermal synthesis and characterization of a novel crystal containing [Co4O4]4+ cubane core: [Co4O4(dpaH)4(CH3COO)2]2V4O12·5H2O

Zhang

You

Zhu

et al. 2006

Inorganic Chemistry Communications

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The isolation and crystal structure of the powerful Lewis acid, planar tetrakispyridine cobalt(II), [Co(C5H5N)4]2+, as its mixed chloride hexafluorophosphate salt

Cited by 22 publications

References 29 publications

Cobalt(III)-oxo cubane clusters as catalysts for oxidation of organic substrates

Cobalt(III)-oxo cubane clusters as catalysts for oxidation of organic substrates

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

Hydrothermal synthesis and characterization of a novel crystal containing [Co4O4]4+ cubane core: [Co4O4(dpaH)4(CH3COO)2]2V4O12·5H2O

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