Tetracobalt Dodecacarbonyl Research Articles

Functionalized cobalt clusters. Properties of carboxylate clusters (CO) 6Co 2HCCCOOH and (CO) 10Co 4HCCCOOH as related to their structures

Reaction of propiolic acid (HCCCOOH) with dicobalt octacarbonyl (Co 2(CO) 8) and tetracobalt dodecacarbonyl (Co 4(CO) 12) leads to the organometallic carboxylic acids (CO) 6Co 2HCCCOOH ( 1) and (CO) 10Co 4HCCCOOH ( 2) in good yield. Both organometallic compounds show a cobalt carbonyl core bonded to a carboxylate function. The structure of the acetylene–carboxylic group in both clusters deviates from that of ethylene. The C(1)C(2)C(3) fragment is half way between acrylic and acetylene–carboxylic acid. The comparative acidity of the carboxylic group measured in methanol reveals that ( 1) is a stronger acid than ( 2), but less acidic than propiolic acid. Both organometallic carboxylic acids are thermally decomposed into phases with high metal content at relatively low temperatures. Fenske–Hall calculations on this series of cobaltocarbonyl cluster carboxylic acids confirm that the Co(CO) 3 donates electron density to the HCCCOOH fragment, thus decreasing the acidity of the carboxylic function. The redox properties and the electronic spectra are also well correlated to the HOMO–LUMO gap thus calculated by this non-parametric SCF method.

Electrophilic reactivity and π-complexation studies in 1,8-naphthylene-bridged [3.2]paracyclophane with a cyclobutane calliper

The 1,8-naphthylene-bridged [3.2]paracyclophane 1, a novel syn-paracyclophane which is further rigidified via a cyclobutane calliper, reacts with 2.2 equivalents of Br2 in CCl4 in the dark to give the symmetrical dibromo derivative 2. Bromination with excess Br2 (6 equiv.) leads to further bromination at the 4-position of the naphthalene ring to give the tribromide 3. In contrast to [2.2]paracyclophane and naphthalene, compound 1 does not produce a persistent π-complex with NO+. Reaction of 1 with AgOTf results in cycloreversion to form a silver-complexed divinyl derivative 4 which could be decomplexed with excess 18-crown-6 to form 5. With tetracobalt dodecacarbonyl a metal π-complex on the exterior of the cyclophane unit was formed (6) with the cyclobutane ring remaining intact. NMR spectral features of the resulting products are examined. AM1 minimizations were used as a guide to structures and relative energies. The nitration, benzoylation, benzylation and ethylation of 1 were also studied.

Selective Reactions of Functionalized Ruthenium(II) σ-Alkynyl Complexes with Dicobalt Octacarbonyl and Tetracobalt Dodecacarbonyl: Synthesis of Cyclopentenone Derivatives via Intermolecular Pauson−Khand Reactions

Treatment of [Ru{C⋮CCPh2(C⋮CH)}(η5-C9H7)(PPh3)2] (1) with [Co2(CO)8] leads to the formation of the adduct [Ru{C⋮CCPh2(μ2-η2-C⋮CH)Co2(CO)6}(η5-C9H7)(PPh3)2] (3) through the selective coordination of the Co2(CO)6 fragment at the terminal alkyne group on 1. Similarly, the enynyl complex [Ru{C⋮CCHCH(C⋮CPh)}(η5-C9H7)(PPh3)2] ((E,Z)-2), prepared via a Wittig reaction from [Ru{C⋮CCH2(PPh3)}(η5-C9H7)(PPh3)2][PF6] (5) and phenylpropargyl aldehyde, also reacts with [Co2(CO)8] to yield selectively the adduct [Ru{C⋮CCHCH(μ2-η2-C⋮CPh)Co2(CO)6}(η5-C9H7)(PPh3)2] ((E,Z)-6). Protonation of complexes 3 and (E,Z)-6 with HBF4·Et2O affords the cationic vinylidene derivatives [Ru{CC(H)CPh2(μ2-η2-C⋮CH)Co2(CO)6}(η5-C9H7)(PPh3)2][BF4] (4) and [Ru{CC(H)CHCH(μ2-η2-C⋮CPh)Co2(CO)6}(η5-C9H7)(PPh3)2][BF4] ((E,Z)-7), respectively. Dicobalt adduct complexes 3 and (E,Z)-6 undergo Pauson−Khand cyclization processes with strained cyclic alkenes (norbornadiene and norbornene) to afford regioselectively the tricyclic cyclopentenone derivatives 8a,b, 9a,b, (E,Z)-10, and 11. (E,Z)-6 reacts with [Co4(CO)12] to give an unprecedented ruthenium(II) vinylidene complex containing a tetranuclear “butterfly” type cobalt cluster (12), which has been characterized by X-ray diffraction.

Physical properties and Fischer-Tropsch activities of Co/Al 2O 3 catalysts prepared from the decomposition of Co 4(CO) 12

Carbonyl-derived cobalt/alumina catalysts were prepared in an attempt to obtain supported cobalt Fischer-Tropsch catalysts which are both highly dispersed and highly reduced. Catalysts prepared from the decomposition of tetracobalt dodecacarbonyl on partially dehydroxylated alumina were found to have twice the dispersion and twice the extent of reduction of conventionally prepared catalysts, resulting in catalysts with higher active surface area. Catalyst dispersion was optimized at a reduction temperature of 350°C. The carbonyl-derived catalysts have slightly higher specific activities than corresponding conventional catalysts, while their selectivity properties are very similar. The carbonyl-derived catalysts are stable under reaction conditions, losing only about 13% of their initial activities after 24 hours of reaction.

Interactions of cobalt carbonyls with oxide surfaces. 3. Dicobalt octacarbonyl and tetracobalt dodecacarbonyl in zeolites

Etudes des reactions de Co 2 (CO) 8 et de Co 4 (CO) 12 avec les zeolites A, X et Y par spectrometrie IR et des analyses des gaz formes au cours des reactions. Les cobalt carbonyls sont deposes sur les zeolites par sublimation

Interactions of cobalt carbonyls with oxide surfaces. 2. Dicobalt octacarbonyl and tetracobalt dodecacarbonyl on silicas and aluminas

Interactions of cobalt carbonyls with oxide surfaces. 2. Dicobalt octacarbonyl and tetracobalt dodecacarbonyl on silicas and aluminas

The formation of HCo(CO) 4 from Co 2(CO) 8 or Co 4(CO) 12. A high pressure IR and UV spectroscopic study

Under high pressure tetracobalt dodecacarbonyl reacts first with CO to give dicobalt octacarbonyl. The latter reacts with H 2 to HCo(CO) 4 via an associative or a dissociative mechanism depending on the partial pressure of CO. Reversible kinetics of the type ▪ are applied for the equilibrium CO 2(CO) 8 + H 2 ⇌ 2HCo(CO) 4 at P(H 2) = 45 bar and 80°C. For P(CO) < P(H 2) the rate constant depend on the partial pressure of CO. For P(CO) ≥ P(H 2) the rate constants are k 1 = 0.0040 min −1 and k 2 = 0.10 l⇌mol min, independent of CO pressure.

Fundamental metal carbonyl equilibria: a quantitative infrared spectroscopic study of the equilibrium between dicobalt octacarbonyl and tetracobalt dodecacarbonyl under carbon monoxide pressure in hexane solution.

The equilibrium between Co 2(CO) 8 and Co 4(CO) 12 has been investigated in hexane solution in the temperature range 105–145°C under carbon monoxide pressure (6–14 bar). the data obtained by infrared analytical monitoring of the system in a high-pressure cell alow a reasonably precise extension of the calculated equilibrium concentration between —20 and 300°C. The thermo- dynamic parameters obtained for this system are: Δ H 0 29.5 ± 0.5 kcal mol -1, Δ S 0 135 ± 3 cal mol -1 K -1. The stability regions of Co 2(CO) 8 and Co 4(CO) 12 in terms of p(CO) and temperature are discussed.

Kinetics and mechanism of the reaction of tetracobalt dodecacarbonyl with carbon monoxide under pressure

The kinetics of the reaction of tetracobalt dodecacarbonyl with carbon monoxide to form dicobalt octacarbonyl in n-hexane have been investigated over a wide range of temperature and CO pressure. The reaction is first order in [Co 4(CO) 12]; the order in [CO] changes between one (at low pressures and high temperatures) and two (at high pressures and low temperatures). Activation parameters have been estimated and a mechanism involving initial reversible breaking of one CoCo bond, followed by irreversible breaking of a second, is proposed. The first step involves concerted addition of CO while the second can proceed with or without such addition.

Preparation and structure of a new derivative of tetrarhodium dodecacarbonyl. Further refinement of the structure of tetracobalt dodecacarbonyl

Preparation and structure of a new derivative of tetrarhodium dodecacarbonyl. Further refinement of the structure of tetracobalt dodecacarbonyl

Kinetics of tetracobalt dodecacarbonyl formation from dicobalt octacarbonyl in heptane

The decomposition of Co 2(CO) 8 to Co 4(CO) 12 in heptane can be described by the kinetic equation: ▪ Dicobalt heptacarbonyl formed in a fast pre-equilibrium: ▪ is a possible intermediate of the reaction. The values for the equilibrium constant K D 1 calculated from the kinetics of Co 2(CO) 8 decomposition are in good agreement with results from independent measurements.

Structural analyses of tetracobalt dodecacarbonyl and tetrarhodium dodecacarbonyl. Crystallographic treatments of a disordered structure and a twinned composite

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural analyses of tetracobalt dodecacarbonyl and tetrarhodium dodecacarbonyl. Crystallographic treatments of a disordered structure and a twinned compositeChin Hsuan WeiCite this: Inorg. Chem. 1969, 8, 11, 2384–2397Publication Date (Print):November 1, 1969Publication History Published online1 May 2002Published inissue 1 November 1969https://doi.org/10.1021/ic50081a030RIGHTS & PERMISSIONSArticle Views289Altmetric-Citations151LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Monosubstituted derivatives of tetracobalt dodecacarbonyl

Monosubstituted derivatives of tetracobalt dodecacarbonyl