Reaction Of Dicobalt Octacarbonyl Research Articles

Synthesis of Dicobalt Hexacarbonyl Complex with B-Type 13,14-Didehydromisoprostol Analog

The reaction of dicobalt octacarbonyl with 8,12,13,14-tetradehydro-11-deoxymisoprostol analog and its trimethylsilyl ether afforded the corresponding dicobalt hexacarbonyl complexes. Spectral characteristics of the complexes and their cytotoxicity in comparison to the free ligands are discussed.

Organometallic Nucleosides: Synthesis and Biological Evaluation of Substituted Dicobalt Hexacarbonyl 2'-Deoxy-5-oxopropynyluridines.

Reactions of dicobalt octacarbonyl [Co2(CO)8] with 2′‐deoxy‐5‐oxopropynyluridines and related compounds gave dicobalt hexacarbonyl nucleoside complexes (83–31 %). The synthetic outcomes were confirmed by X‐ray structure determination of dicobalt hexacarbonyl 2′‐deoxy‐5‐(4‐hydroxybut‐1‐yn‐1‐yl)uridine, which exhibits intermolecular hydrogen bonding between a modified base and ribose. The electronic structure of this compound was characterized by the DFT calculations. The growth inhibition of HeLa and K562 cancer cell lines by organometallic nucleosides was examined and compared to that by alkynyl nucleoside precursors. Coordination of the dicobalt carbonyl moiety to the 2′‐deoxy‐5‐alkynyluridines led to a significant increase in the cytotoxic potency. The cobalt compounds displayed antiproliferative activities with median inhibitory values (IC50) in the range of 20 to 80 μm for the HeLa cell line and 18 to 30 μm for the K562 cell line. Coordination of an acetyl‐substituted cobalt nucleoside was expanded by using the 1,1‐bis(diphenylphosphino)methane (dppm) ligand, which exhibited cytotoxicity at comparable levels. The formation of reactive oxygen species in the presence of cobalt compounds was determined in K562 cells. The results indicate that the mechanism of action for most antiproliferative cobalt compounds may be related to the induction of oxidative stress.

Reactions of dicobalt octacarbonyl with dinucleating and mononucleating bis(imino)pyridine ligands.

This work focuses on the application of dicobalt octacarbonyl (Co2(CO)8) as a metal precursor in the chemistry of formally low-valent cobalt with redox-active bis(imino)pyridine [NNN] ligands. The reactions of both mononucleating mesityl-substituted bis(aldimino)pyridine (L1) and dinucleating macrocyclic xanthene-bridged di(bis(aldimino)pyridine) (L2) with Co2(CO)8 were investigated. Independent of the metal-to-ligand ratio (1 : 1 or 1 : 2 ligand to Co2(CO)8), the reaction of the dinucleating ligand L2 with Co2(CO)8 produces a tetranuclear complex [Co4(L2)(CO)10] featuring two discrete [Co2[NNN](CO)5] units. In contrast, a related mononucleating bis(aldimino)pyridine ligand, L1, produces different species at different ligand to Co2(CO)8 ratios, including dinuclear [Co2(CO)5(L1)] and zwitterionic [Co(L1)2][Co(CO)4]. Interestingly, [Co4(L2)(CO)10] features metal-metal bonds, and no bridging carbonyls, whereas [Co2(CO)5(L1)] contains cobalt centers bridged by one or two carbonyl ligands. In either case, treatment with excess acetonitrile leads to disproportionation to the zwitterionic [Co[NNN](NCMe)2][Co(CO)4] units. The electronic structures of the complexes described above were studied with density functional theory. All the obtained bis(imino)pyridine complexes serve as catalysts for cyclotrimerization of methyl propiolate, albeit their reactivity is inferior compared with Co2(CO)8.

Cyclo- and Polyphosphazenes with Redox Active Substituents

GRAPHICAL ABSTRACT

Co/SiO 2 catalysts prepared from Co 2(CO) 8 for CO hydrogenation into alcohols and hydrocarbons: characterization by magnetic methods and temperature-programmed hydrogenation

The hydrogenation of carbon monoxide over Co/SiO 2 catalysts obtained by reduction of precursors prepared by the reaction of dicobaltoctacarbonyl with silica gives rise to a mixture of alcohols and hydrocarbons. The chain growth probability α for hydrocarbon synthesis is similar to that observed over conventional catalysts prepared by the ammonia method ( α=0.74) with a comparable metal dispersion (metal particle size 4 nm). Alcohol formation yields a smaller chain growth probability ( α=0.42). Magnetic measurements have shown that in the latter catalyst, small cobalt clusters (∼1 nm) are likely to be present together with the cobalt particles (4 nm), this observation reconciles apparently conflicting results from the literature. It has been speculated that alcohol formation might be related to the presence of these clusters according to a concerted mechanism. Furthermore, the observation of large amounts of acetates by temperature-programmed hydrogenation, not detected in hydrocarbon selective catalysts, suggests that they may play a role in ethanol synthesis.

Thermal conversion of organosilicon cobalt precursors to mixed Si/Co/C/O ceramics

Cobalt organosilicon ceramic precursors I, I(D), III and IV were prepared by reaction of dicobalt octacarbonyl with normal and Si-deuterated 2,5-disilahexane, 2,4-disilapentane and 1,4-disilabutane respectively. Precursor II is a dimeric silicon cobalt cluster [mu;-{(CH3)Si(CH2)}2][Co(CO)3]2. Thermal decomposition of the precursors was performed under argon. Evolution of H2 in the early stage of the pyrolysis (120C) shows that an initial cross-linking of the material is induced by the remaining SiH bonds. Between 120 and 300C, the thermal decomposition of the complexes results either in the elimination of the CO ligands or in their reaction with incorporation of oxygen and carbon. At higher temperature, the elimination of hydrogen and methane corresponds to the mineralisation step of the precursors. By 1000C, the material is formed of metal-rich nodules homogeneously dispersed in a matrix. Co2Si is detected by X-ray analysis. Between 1000 and 1400C, carbothermal reduction occurs with evolution of CO. Simultaneously SiO2, SiC and CoSi phases are formed.

Transition metal-catalyzed tandem isomerization and cationic polymerization of allyl ethers. II. Structural and mechanistic studies

In the presence of organosilanes, dicobalt octacarbonyl catalyzes the polymerization of alkyl allyl ethers to give high molecular weight polymers. This article reports the results of a detailed mechanistic study of this new polymerization reaction. The evidence obtained in this study supports a stepwise process involving first, the reaction of dicobalt octacarbonyl with an organosilane to form HCo(CO)4 and R3SiCo(CO)4. In subsequent steps, HCo(CO)4 isomerizes the allyl ether to a 1-propenyl ether and then this compound is polymerized by the formal transfer of a silyl cation from R3SiCo(CO)4. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1985–1997, 1997

Reaction of dicobalt octacarbonyl with acetylene and carbon monoxide at low temperature and pressure: Formation of cyclic enone products

Dicobalt octacarbonyl is shown to react with acetylene and carbon monoxide under mild conditions in dimethoxyethane or benzene to produce, in low yields, bicyclo[3.3.0]octa-3,7-diene-2,6-dione, benzoquinone, and the cyclopentadienone-derived products 3a,4,7,7a-tetrahydro-2,7-methanoindene-1,10-dione, 1-indanone, tetracyclo[5.5.2.0 2,60 8,12]tetradeca-4,10,13-triene-3,9-dione, and tetracyclo[5.5.2.0 2,60 8,12]tetradeca-4,9,13-triene-3,11-dione. Possible mechanisms for the formation of these products are discussed.

X-Ray crystal structures of two products formed in the reaction of dicobalt octacarbonyl with carbon disulphide: dodecacarbonylcarbidohexacobalt disulphide, Co6C(CO)12S2, and bis-(enneacarbonyltricobaltcarbon) disulphide, (CO)9Co3CSSCCo3(CO)9

Two complexes formed in the reaction of dicobalt octacarbonyl with carbon disulphide were identified through X-ray crystallography as Co6C(CO)12S2(1) and [(CO)9Co3CS]2(2); the cluster core of (1) is composed of a trigonal prism of six cobalt atoms capped symmetrically by two sulphur atoms, and containing a carbide atom in the centre, whereas (2) is a trans-disulphide of the enneacarbonyltricobaltcarbon cluster, showing distortion of the idealized threefold local symmetry of the Co3CS entities presumably owing to repulsive interactions between the sulphur and (equatorial) carbonyl-C atoms.

μ 3{[Chloro-bis(η-cyclopentadienyl)titanoxy]-methylidin}- cyclo-tris(tricarbonylkobalt)(3 CoCo, (CO) 9Co 3COTi(Cl)- (π-C 5H 5) 2. Darstellung und molekulstruktur einer titan enthaltenden methylidin-trikobaltnonacarbonyl-clusterverbindung

By reaction of dicobaltoctacarbonyl with dicyclopentadienyltitaniumdichloride a novel derivative of the methylidynetricobaltnonacarbonyl cluster compounds (CO) 9Co 3CY could be prepared [Y = OTi(Cl)(C 5H 5) 2]. The structure was determined by means of three dimensional X-ray diffraction data: space group P2 1 n; a = 13.532(6), b = 22.939(10), c = 7.760(8) »; β = 90.67(4)°; Z = 4; R= 0.103. The molecule consists of the tetrahedral cluster (CO) 9Co 3C and the chloro-bis(cyclopentadienyl)titanoxy-group. The distances and angles at the titanium atom are almost unchanged compared with the starting compound (C 5H 5) 2 TiCl 2

Reactions of dicobalt octacarbonyl with fluorocarbon-bridged ligands

Reactions of dicobalt octacarbonyl with fluorocarbon-bridged ligands

Über das reaktionsverhalten von dikobaltoktacarbonyl gegenüber bor-, aluminium-, gallium-, indium- und thallium-halogeniden

Abstract The reactions of dicobalt octacarbonyl with halides of the main Group III elements are described. The boron halides BX3 (X = Cl, Br, I) and Co2(CO)8 form the unstable adducts Co2(CO)8 · BX3. AlCl3 and AlBr3 give stable complexes of composition Co2(CO)8 · AlX3. GaBr3 and InBr3 behave differently with Co2(CO)8 forming compounds of composition Ga(In)Co2Br4(CO)6. Lewis bases like tetrahydrofuran, phosphines and water lead to the derivatives GaCo2 Br4(CO)4(THF)2 and GaCo2Br4(CO)4L4 (L = phosphine, H2O). Magnetochemical investigations, conductivity measurements and chemical behavior suggest these complexes are ionic in character. TlCl3 chlorinates Co2(CO)8 toCoCl2 without formation of analogous complexes.

Some cobalt carbonyl complexes of ligands containing the ECH 2E (E = Sb, As, P) moiety

Complexes of the type, Co 2(CO) 6[(R 2E) 2CH 2] (R = CH 3, C 2H 5, p-CH 3C 6H 4; E = Sb, R = C 6H 5; E = Sb, As, P) were prepared by the reaction of dicobalt octacarbonyl with the corresponding ligands in benzene at room temperature. Treatment of these complexes with a diarylacetylene in refluxing benzene displaced two bridging carbonyl groups to give complexes of the type, Co 2(CO) 4(R′ 2C 2) [(R 2E) 2CH 2] (R′ = C 6H 5, p-CH 3C 6H 4), which also were obtained from the reaction between Co 2(CO) 6(R′ 2C 2) and (R 2E) 2CH 2. The structures of these derivatives are discussed on the basis of their infrared spectra. It was found from the PMR spectra in CH 2Cl 2 at room temperature that the coordinated stibine ligand in these complexes can be easily replaced by either a free phosphine or arsine ligand, while the coordinated arsine ligand is replaced only by a free phosphine.

Tervalent phosphorus derivatives of cobalt carbonyls : IV. Comparison of the reactions of phosphites and phosphines with dicobalt octacarbonyl

The reaction of dicobalt octacarbonyl with tertiary phosphites gives several products, which have been interconverted by chemical means. Some cobaltcobalt bonds have been formed from the nucleophilic attack by the anion [Co(CO) 4− n L n ] − on the cation [Co(CO) 5− n (PR 3) n ] + leading to known binuclear compounds. Such a reaction is not possible with tertiary phosphites because of a Michaelis—Arbuzov rearrangement, previously observed for complexes of manganese and molybdenum.

Über die reactionen von dikobaltoktacarbonyl mit borund aluminiumhalogeniden. Ein beitrag zur frage des reaktionsmechanismus der bildung von methylidyntrikobalt-nonacarbonyl-clusterverbindungen

The reactions of dicobaltoctacarbonyl with Cl3BN(C2H5)3, Br3BN(C2H5)3 and Br3AlN(C2H5)3 in benzene at 60° lead to the methylidynetricobalt-nonacarbonyl cluster compounds Co3(CO)9COBCl2N(C2H5)3, Co3(CO)9COBBr2N(C2H5)3 and Co3(CO)9COAlBr2N(C2H5)3. The IR-, 11B-, ESR- and mass spectra are discussed. The reaction of AlBr3 with Co2(CO)8 leading to the cluster system co3(CO)9COAlBr2·AlBr3 via the addition compound Co2(CO)8·AlBr3 allows conclusions on the mechanism of the formation of methylidynetricobalt-nonacarbonyl cluster compounds.

Reactions of dicobalt octacarbonyl and related compounds with gem-dihalides

Dicobalt octacarbonyl and some of its derivatives (NaCo(CO) 4, Co 4(CO) 12, Hg[Co(CO) 4] 2, [Co(CO) 3PPh 3] 2, NaCo(CO) 3PPh 3) react with activated gem-dihalides, R 2CX 2, such as dichlorodiphenylmethane, 9,9-dihalofluorenes and dimethyl dibromomalonate, to give the ‘dimer’ olefin, R 2CCR 2. The course of this conversion involves formation of the coupling product, R 2XCCXR 2, followed by dehalogenation of the latter. These separate steps have been confirmed for activated monohalides (bromodiphenylmethane, 9-bromofluorene, dimethyl bromomalonate) which were readily coupled by cobalt carbonyls, and for activated vicinal dihalides (D,L and meso-dibromostilbene, 9,9′-dichlorobisfluorenyl) which cobalt carbonyls readily dehalogenated. A radical mechanism is favored for these processes, and indirect evidence in its favor is presented.

Co 8(CO) 24C 6, a bis(tricobalt nonacarbonyl)/dicobalt hexacarbonyl derivative of 2,4-hexadiyne from the reaction of dicobalt octacarbonyl with hexachlorocyclopropane

The reaction of dicobalt octacarbonyl with hexachlorocyclopropane in THF produced Co 8(CO) 24C 6 whose structure (A) was determined by means of single crystal X-ray crystallography. ▪ The compound is obtained from hexane/benzene as black Co 8(CO) 24C 6· 1 2 C 6H 6, crystallising in the triclinic space group P 1 with a = 15.57 ± 0.02 Å, b = 16.32 ± 0.02 Å, c = 9.77 ± 0.01 Å, α = 99.78 ± 0.10°, β = 115.06 ± 0.10 °, γ = 74.39 ± 0.10 °. The final discrepancy index is R F = 10.25% for 2484 independent, nonzero reflections.

Reaction of dicobalt octacarbonyl with secondary amines: R 2NCOCo(CO) 4 derivatives

Secondary aliphatic amines were found to react with dicobalt octacarbonyl in hexane solution to form ( N-dialkylcarbamoyl)cobalt carbonyl derivatives. Compounds of the type R 2NCOCo(CO) 3(PPh 3) were isolated from the reaction products.

The reaction of dicobalt octacarbonyl with 1,1,1,5,5,5-hexafluoropentane-2,4-dione. Tris(hexafluoroacetylacetonate)cobalt(III)

The reaction of dicobalt octacarbonyl with 1,1,1,5,5,5-hexafluoropentane-2,4-dione. Tris(hexafluoroacetylacetonate)cobalt(III)

Reaction of Dicobalt Octacarbonyl with Some Acetylenic Compounds1

Reaction of Dicobalt Octacarbonyl with Some Acetylenic Compounds¹