Cobalt Carbonyl Research Articles

Infrared Photodissociation Spectroscopy of Mass-Selected Homoleptic Cobalt Carbonyl Cluster Cations in the Gas Phase

Infrared spectra of mass-selected homoleptic cobalt carbonyl cluster cations including dinuclear Co2(CO)8(+) and Co2(CO)9(+), trinuclear Co3(CO)10(+) and Co3(CO)11(+), as well as tetranuclear Co4(CO)12(+) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric structures of these complexes are determined by comparison of the experimental spectra with those calculated by density functional theory. The Co2(CO)8(+) cation is characterized to have a Co-Co bonded structure with Cs symmetry involving a bridging CO ligand. The Co2(CO)9(+) cation is determined to be a mixture of the CO-tagged Co2(CO)8(+)-CO complex and the Co(CO)5(+)-Co(CO)4 ion-molecular complex. The Co3(CO)10(+) cation is the coordination-saturated trinuclear cluster, which is characterized to have a triangle Co3 core with C2 symmetry involving two edge-bridging and eight terminal CO ligands. The Co3(CO)11(+) cation is a weakly bound complex involving a Co3(CO)10(+) core ion. The Co4(CO)12(+) cluster cation is deduced to have a tetrahedral Co4(+) core structure with three edge-bridging and nine terminal carbonyls.

Air‐Stable Carbonyl(pentamethylcyclopentadienyl)cobalt Diiodide Complex as a Precursor for Cationic (Pentamethylcyclopentadienyl)cobalt(III) Catalysis: Application for Directed C‐2 Selective CH Amidation of Indoles

AbstractThe readily available carbonyl(pentamethylcyclopentadienyl)cobalt diiodide complex [Cp*Co(CO)I2] was successfully utilized as the precursor of a cationic cobalt(III) active catalyst for directed CH bond functionalization. The complex Cp*Co(CO)I2 (2.5–1.25 mol%), in combination with silver hexafluoroantimonate (AgSbF6) and potassium acetate (KOAc), efficiently catalyzed the directed C‐2 selective amidation of indoles with sulfonyl azides, and the corresponding products were obtained in 85–98 % yield.magnified image

Diverse bonding modes of the pentalene ligand in binuclear cobalt carbonyl complexes

The 2007 synthesis of the hexamethylpentalene complex cis-(η5,η5-C8Me6)Co2(CO)4 by O’Hare and coworkers makes of interest a theoretical study of the unsubstituted binuclear pentalene cobalt carbonyls (C8H6)Co2(CO)n (n=6, 5, 4, 3). In this connection an unbridged unsubstituted cis-(η5,η5-C8H6)Co2(CO)4 structure analogous to the experimental hexamethyl structure is found to be the lowest energy (C8H6)Co2(CO)4 structure. Furthermore, this (C8H6)Co2(CO)n structure is predicted to be the product from reactions of pentalene derivatives with cobalt carbonyls based on the thermochemistry of CO dissociation energies in the sequence n=6 → 5 → 4 → 3 → 2. The low-energy structures for the unsaturated (C8H6)Co2(CO)n (n=3, 2) derivatives also have the pentalene ligand bonded to each cobalt as a pentahapto ligand. They may be derived from either this unbridged cis-(η5,η5-C8H6)Co2(CO)4 structure or a doubly CO-bridged variation thereof by removal of one or two CO groups. The carbonyl-rich (C8H6)Co2(CO)n (n=6, 5) structures, which may be considered as precursors to cis-(η5,η5-C8H6)Co2(CO)4, illustrate considerable diversity of bonding modes of the pentalene ligand to the central Co2 unit. Structures without direct Co–Co bonds are found exhibiting either cis or trans stereochemistry in which trihapto allylic and/or pentahapto cyclopentadienylic subunits are bonded to Co(CO)3 and Co(CO)2 moieties, respectively. In addition, (C8H6)Co2(CO)n (n=6, 5) structures exhibiting cis stereochemistry are found in which CC bonds of a butadiene or fulvene subunit of the pentalene ligand replace CO groups in Co2(CO)8, retaining the formal Co–Co single bond.

Cobalt-based catalysts derived from cobalt carbonyl clusters for Fischer-Tropsch synthesis

Co catalysts supported on γ-Al 2 O 3 were prepared using Co 2 (CO) 6 HCCCOOH, Co 3 (CO) 9 CCH 2 COOH, and Co 4 (CO) 10 HCCCOOH as precursors. Co(NO 3 ) 2 was used as the precursor for preparing the reference catalyst. The results of Fischer-Tropsch synthesis tests and characterization by transmission electron microscopy, NH 3 temperature-programmed desorption, and infrared showed that the different precursors have significant effects on the dispersion of the Co, which affect their catalytic behavior. CO conversion and C 5+ selectivity over these catalysts prepared from different precursors decreased in the order Co 3 (CO) 9 CCH 2 COOH > Co 2 (CO) 6 HCCCOOH > Co 4 (CO) 10 HCCCOOH > Co(NO 3 ) 2 . A series of Co-based catalysts supported on γ-Al 2 O 3 prepared using cobalt carbonyl clusters showed higher CO conversion and C 5+ selectivity in F-T synthesis than a reference catalyst prepared using Co(NO 3 ) 2 .

ChemInform Abstract: Cobalt Carbonyl as an Effective CO Source in One‐Pot Synthesis of Esters from Aryl Halides.

AbstractCo2(CO)8 is applied for the first time as an effective carbonyl source in Pd‐catalyzed alkoxycarbonylation reactions of aryl halides under microwave conditions.

Coordination between cobalt (II) ion and carbonyl group in acetone probed by using DAOSD approach

We applied a newly developed technique of the DAOSD (Double Asynchronous Orthogonal Sample Design) approach to probe weak coordination between Co2+ ions and acetone. Subtle spectral variation on the carbonyl band of acetone and d–d transition band are revealed via cross peaks of 2D asynchronous spectra generated by using the DAOSD approach. These results suggest that coordination occur between cobalt ions and the carbonyl group of acetone. To confirm whether coordination occur between cobalt ions and acetone, EXAFS experiments are utilized. The EXAFS results reveal that a Co2+ is coordinated by six methanol molecules in anhydrous CoCl2/methanol solution. Upon addition of acetone in into the anhydrous CoCl2/methanol solution, the coordination number of Co2+ ion becomes four, and one coordinating oxygen atom is replaced by a chlorine atom. We infer that the decrease in coordination number of Co2+ ion is due to the participation of the carbonyl oxygen of acetone in the coordination since the size of acetone is larger than methanol. This result provides an alternative evidence to support the conclusion that Co2+ ions coordinate with acetone, which is separately obtained from the 2D asynchronous spectra generated by using the DAOSD approach.

Effect of Reflux Time on Nanoparticle Shape

In the present work, Pt nanoparticles were produced from a reaction mixture containing a trace amount of cobalt carbonyl salt acting as a shape inducer. Nanoparticle shape evolution during reaction mixture reflux was monitored by characterizing particles extracted from the reaction mixture at different times. It was observed that 5 min of reflux produced spherical nanoparticles, 30 min of reflux produced cube shaped nanoparticles, and 60 min of reflux produced truncated octahedron morphology nanoparticles. It is illustrated that during nanoparticle synthesis the reflux process can provide energy needed for shape transformation from a metastable cube morphology to a truncated octahedron morphology which is thermodynamically the most stable geometry for fcc crystals. An optimization of the reaction reflux is thus needed for isolating metastable shapes.

Tri-cobalt Carboxylate as a Catalyst and Catalyst Precursor in the Fischer-Tropsch Synthesis

In recent years, several groups have invested significant research capacity to investigate the effect of the metal crystallite size on the various primary and secondary reactions taking place during the Fischer–Tropsch synthesis. Most publications agree that with decreasing crystallite size (dcryst<10 nm) the surface-specific CO hydrogenation activity (turnover frequency) decreases. In parallel, an increased selectivity to the undesired methane was observed. In the present study we combined and extended previously published data on alumina-supported cobalt nanocrystallites with observations on an alumina-supported cobalt carbonyl complex ((CO)9Co3CCOOH) and its decomposition products under Fischer–Tropsch reaction conditions. We could show that with an increased degree of sintering of the complex, that is, a larger cobalt crystallite size, the turnover frequency increased and the tendency to form methane decreased. The results connect seamlessly with those obtained for the nanocrystallites suggesting that the catalyst performance features extend into the sub-2 nm range.

Theoretical investigation on the vibrational and electronic spectra of three isomeric forms of dicobalt octacarbonyl

Three isomeric forms of dicobalt octacarbonyl, [Co2(CO)8], with C2v, D3d and D2d point group were optimized by using density functional theory (DFT/B3LYP) method with LANL2DZ basis set for the cobalt atoms and 6-31G(d) basis set for the other atoms in the gas phase. Electronic structures, carbonyl stretching frequencies and Mulliken population analysis were determined from the optimized structures. Electronic structures indicate that each of the dicobalt octacarbonyl isomers have been constituted from two trigonal bipyramidal geometry. While the isomer C2v has two bridged carbonyl groups, in the isomers D3d and D2d all carbonyl groups are coordinating as terminal. The calculated C–O stretching frequencies are in a good agreement with experimental frequencies. Experimental C–O stretching frequencies were assigned to isomers according to the calculated frequencies. Mulliken population analysis show that free carbonyl ligands transfer their electron to the cobalt atoms during formation of the complexes. The electronic spectra of isomers were obtained by using time dependent density functional theory (TD-DFT/B3LYP) method with LANL2DZ basis set for the cobalt atoms and 6-31G(d) basis set for the other atoms in the gas phase. The theoretical electronic spectra of isomers are in a good agreement with experimental spectra. The calculated bands at 277.9, 278.1 and 284.1nm for isomers C2v, D2d and D3d were assigned to metal–ligand charge transfer transitions and the shoulder at 344.6nm was assigned to pure metal center transitions for isomer D3d.

Cobalt(I) and cobalt(III) cyclopentadienyl complexes with new silicon-branched fluorous tags

Two new fluorous tags based on omega-[tris(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silyl]alkyl substituents (alkyl=ethyl, propyl) were synthesized from 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl iodide as the fluorine-containing component. Cyclopentadienes (the mixtures of 1- and 2-substituted isomers) which bore the tags were prepared, cyclopentadienyl cobalt(I) dicarbonyl complexes were subsequently obtained from the reactions of the cyclopentadienes with dicobalt octacarbonyl. Oxidative additions of 1-iodoperfluoroalkanes on the cobalt(I) complexes provided cobalt(III) complexes with one of their four ponytails bonded directly to the metal and with a stereocenter at the metal.

Incorporating Cobalt Carbonyl Moieties onto Ethynylthiophene-Based Dithienylcyclopentene Switches. 1. Photochemistry

The synthesis and characterization of a series of dithienyl perhydro- and perfluorocyclopentene photochromic molecular switches appended with cobalt carbonyl binding 3-ethynylthiophene and phenyl-3-ethynylthiophene substituents are reported. Their photochromic properties, fatigue resistance, and thermal stability were examined to establish the effect of substituents on their performance as molecular photoswitches. The photochemical properties of the dithienylethene core were retained to the greatest extent by the inclusion of phenyl units and a hexafluorocyclopentene ring. The alkyne units of the switches were used to coordinate cobalt carbonyl moieties: i.e., Co2(CO)6 and Co2(CO)4(dppm). The cobalt carbonyl moieties were found to reduce the efficiency of cyclization and cycloreversion of the dithienylethene unit. Density functional theory was used to identify the excited states responsible for cyclization.

A heterogeneous water oxidation catalyst from dicobalt octacarbonyl and 1,2-bis(diphenylphosphino)ethane

We report the thermal synthesis of a heterogeneous Co–phosphine-based water oxidation catalyst that can be easily coated onto a variety of substrates. The system is active in neutral water and performs best with borate as electrolyte, in which the onset of catalytic current occurs at 1.51 V vs. RHE, with a Tafel slope of 68 mV per decade. Stable water oxidation is observed for over 40 hours; including in seawater with borate electrolyte, in which the catalyst is selective for water oxidation over chloride (85% Faradaic efficiency). The organic portion of the catalyst appears to play a crucial role in catalytic activity.

Low-temperature (≤150 °C) chemical vapor deposition of pure cobalt thin films

High purity soft-magnetic cobalt films were grown by cyclic thermal–chemical vapor deposition (CVD) process using dicobalt octacarbonyl as metal organic precursor, at an optimum substrate temperature of 125 °C. Physical, electrical, and magnetic properties of CVD grown Co films were compared with physical vapor deposition (PVD) grown Co films. Films were analyzed by x-ray photoelectron spectroscopy, x-ray diffraction, four-point resistivity probe, scanning electron microscopy, hysteresis loop tracer, vibrating sample magnetometry, and atomic force microscopy. The authors observed in-plane uniaxial magnetic anisotropy in the CVD-grown cobalt film with cyclic pulse-purge technique. Typical film properties obtained were low volume resistivity (&amp;lt;20 μΩ cm), &amp;gt;99.5% purity, 100% growth linearity as a function of number of cycles, good step coverage in a SiO2 trench, low coercivity (&amp;lt;15 Oe), high saturation magnetization (∼1.5 T), and low root-mean-square surface roughness (7 Å). Compared to our PVD films, CVD Co films are magnetically softer, smoother, and less textured.

Cobalt Carbonyl‐Based Catalyst for Hydrosilylation of Carboxamides

AbstractThe cobalt carbonyl [Co2(CO)8] complex is employed as a useful catalyst for the reduction of tertiary amides to the corresponding tertiary amines using 1,1,3,3‐tetramethyldisiloxane (TMDS) and poly(methylhydrosiloxane) (PMHS) as silane reagents under thermal (100 °C) or photo‐assisted conditions (UV, 350 nm at room temperature). Of particular interest, a low catalytic amount (0.5 mol%) of [Co2(CO)8] is used to perform the reaction with 2.2 equiv. of PMHS at 100 °C for 3 h. This reaction is the first example of a cobalt‐catalyzed hydrosilylation of amides.magnified image

Binuclear cobalt carbonyl complexes of the strong π-acceptor trifluoromethyl isocyanide

The cobalt carbonyl complexes (CF3NC)2Co2(CO)n (n=7, 6, 5, 4) and (CF3NC)Co(CO)n(n=4, 3, 2) of the strongly π-accepting trifluoromethyl isocyanide ligand have been investigated by density functional theory. The lowest energy (CF3NC)2Co2(CO)6 structures are doubly bridged structures with the global minimum having two bridging CF3NC ligands. The lowest energy unbridged (CF3NC)2Co2(CO)6 structure lies ∼19kcal/mol in energy above this global minimum. This differs from unsubstituted Co2(CO)8 for which the doubly bridged and unbridged isomers have similar energies so both can be observed experimentally. The lowest energy structures of the formally unsaturated (CF3NC)2Co2(CO)n (n=5, 4) derivatives are also doubly bridged structures. Bridging CF3NC groups are energetically preferred over bridging CO groups. Four-electron donor bridging η2-μ-CF3NC groups are found in higher energy structures. Coupling of CF3NC groups to form a coordinated bis(trifluoromethyldiimine) ligand, CF3NCCNCF3 is observed in carbonyl-rich (CF3NC)2Co2(CO)7 structures. However, such (CF3NC)2Co2(CO)7 structures do not appear to be viable since CO dissociation from the lowest energy such structure to give (CF3NC)2Co2(CO)6 is predicted to be essentially thermoneutral.

A highly selective cobalt-catalyzed carbonylative cyclization of internal alkynes with carbon monoxide and organic thiols

Despite the fact that many transition-metal-catalyzed reactions of organosulfur compounds with internal alkynes are ineffective, cobalt carbonyl (Co2(CO)8) is an excellent catalyst for carbonylative cyclization of internal alkynes with carbon monoxide. When Co2(CO)8-catalyzed reactions of internal alkynes with organic thiols are conducted in acetonitrile under 4 MPa pressure of carbon monoxide, thiolative lactonization of internal alkynes successfully takes place with incorporation of two molecules of CO. This carbonylation provides a useful tool to prepare the corresponding α,β-unsaturated γ-thio-γ-lactones (butenolide derivatives) in good yields. In the cases of unsymmetrical alkynes, such as 2-octyne and 6-methyl-2-heptyne, the thiolative lactonization proceeds with moderate regioselectivity to give the butenolide derivatives on which the carbonyl group preferentially bonds to the less hindered acetylenic carbon. Mechanistic pathways about the present thiolative lactonization are also discussed.

Focused helium ion beam deposited low resistivity cobalt metal lines with 10 nm resolution: implications for advanced circuit editing

Helium ion beam induced cobalt nanowire deposition using dicobalt octacarbonyl (Co2(CO)8) as a precursor is described. 10 nm wide metal lines were fabricated with good repeatability and extremely high purity. The metal lines were deposited on electrical test structures to determine the nanowire resistivity and contact resistance. Measurements reveal that these metal lines have 50–100 μΩ-cm resistivity. The contact resistance of a Co line on a gold pad is 15 Ω with a 0.14 × 1.4 μm contact area. The resulting metal deposit size was determined by helium ion microscopy (HIM) because of its high imaging resolution, and further characterized by high resolution transmission electron microscopy (HR-TEM) and electron energy-loss spectroscopy (EELS). HR-TEM images reveal that these metal lines are composed of 6 ± 2 nm cobalt crystallite grains; and EELS analysis shows that no measurable carbon signal was observed. Single-line and multiple-line patterns were prepared to examine proximity effects around the metal line depositions. Both HIM imaging and electrical measurements of the patterns verify that the collateral proximity deposition between individual lines can be minimized. Finally, factors determining the ultimate line width achievable with the He ion beam are discussed.

Water-Soluble-Phosphines-Assisted Cobalt Separation in Cobalt-Catalyzed Hydroformylation

The hydroformylation of octene-1 and the removal of Co2(CO)8 and HCo(CO)4 from the reaction products including commercial C9 OXO-product were studied under biphasic conditions using an aqueous solution of different electron-donating sulfonated phosphine RnP(C6H4-m-SO3Na)2 (n = 0, 1, 2; R = Me, Bu, Cp) ligands. Depending on the electronic and steric properties of the phosphines, 6–70 ppm residual cobalt concentrations could be achieved in the organic phase under 10 bar of CO/H2 (1:1) at 75 °C. The formation of several water-soluble-phosphine-substituted cobalt carbonyl species including Co2(CO)6(TPPTS)2, HCo(CO)3(TPPTS), HCo(CO)2(TPPTS)2, and [Co(CO)3(TPPTS)2]+[Co(CO)4]− were identified and monitored by in situ IR and NMR spectroscopy.

Carbonylation of halides using catalysts based on cobalt carbonyl: a promising approach to the synthesis of organic acids as intermediates in drug production

A universal method for the synthesis of fatty aromatic, aromatic, and heteroaromatic acids that was based on carbonylation under mild conditions using catalysts based on modified cobalt carbonyl was developed and could be used for drug production.

Effects of Different Pretreatment Pressures on the Catalytic Performance of Catalyst Derived from (CO)&lt;sub&gt;6&lt;/sub&gt;Co&lt;sub&gt;2&lt;/sub&gt;CC(COOH)&lt;sub&gt;2&lt;/sub&gt; for Fischer-Tropsch Synthesis

New type of Co-based catalyst was prepared using (CO)6Co2CC(COOH)2 as precursor supported on γ-Al2O3 support. The effects of pretreatment pressures on the catalysts properties and the F-T synthesis performance were investigated in details. Combined with TEM characterization technology, it was found that under different pretreatment pressures (0 MPa, 1.0 MPa, 2.0 MPa), the structure of carbonyl clusters underwent different changes. Moreover, the aggregation degree of cobalt species depends on the pretreated pressure applied. In addition, the catalytic performance of the cobalt carbonyl catalyst pretreated with different pressures was performed and both CO conversion and C5+ selectivity exhibited the order of Co2/2MPa/Al2O3 &gt; Co2/1MPa/Al2O3 &gt; Co2/0MPa/Al2O3.