Carbon monoxide with transition metals

Reactions of Carbon Monoxide with Transition Metals... 

Henrici-Olive G, Olive S Reactions of carbon monoxide with transition metal-carbon bonds, Transition Met Chem l(2) 77-93, 1976. 

Moulton and Shaw were the first to report direct reactions of carbon monoxide with transition metal pincer complexes in their seminal work in 1976 [4]. In this paper, the... 

The bonding between carbon monoxide and transition-metal atoms is particularly important because transition metals, whether deposited on soHd supports or present as discrete complexes, are required as catalysts for the reaction between carbon monoxide and most organic molecules. A metal—carbon ( -bond forms by overlapping of metal orbitals with orbitals on carbon. Multiple-bond character between the metal and carbon occurs through formation of a metal-to-CO TT-bond by overlap of metal-i -TT orbitals with empty antibonding orbitals of carbon monoxide (Fig. 1). 

This chapter is concerned entirely with the insertion of carbon monoxide into transition metal-carbon cr-bonds. Sulfur dioxide insertion 154, 239), also common among transition metal-carbon complexes, will be treated in a complementary review, which is to appear later. Subject to the restrictions given at the beginning of Section VI, an attempt has been made at a complete literature coverage of the insertion of CO. Particular emphasis focuses on recent results, especially those of a kinetic and stereochemical nature. 

Yeom and Frei [96] showed that irradiation at 266 nm of TS-1 loaded with CO and CH3OH gas at 173 K gave methyl formate as the main product. The photoreaction was monitored in situ by FT-IR spectroscopy and was attributed to reduction of CO at LMCT-excited framework Ti centers (see Sect. 3.2) under concurrent oxidation of methanol. Infrared product analysis based on experiments with isotopically labeled molecules revealed that carbon monoxide is incorporated into the ester as a carbonyl moiety. The authors proposed that CO is photoreduced by transient Ti + to HCO radical in the primary redox step. This finding opens up the possibility for synthetic chemistry of carbon monoxide in transition metal materials by photoactivation of framework metal centers. 

There have been several recent reports of the reduction of carbon dioxide to carbon monoxide by transition metal complexes. Maher and Cooper (2/) have reported that several metal carbonyl dianions can effect the disproportionation of C02 to metal bound carbon monoxide [Eq. (37)] with Li2C03... 

The vast amount of work performed with surface sensitive spectroscopic methods, notably X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), has changed drastically our notion of the preferred modes of chemisorption of carbon monoxide on transition metals. Less than one decade ago Ford (38) in his authorative review still stated tungsten to be unique among the transition metals in being able to... 

The catalytic decomposition of carbon-contaming compounds is an extensively investigated method, also known as catalytic chemical vapor deposition (CCVD). One of the advantages of this method is the potential for large-scale production at a lower energy consumption and overall cost than with other methods. The CCVD method is essentially the same as that used for a long time in the synthesis of other filamentous forms of carbon, such as nanofibers or fibrils. The CCVD method involves the catalytic decomposition of hydrocarbons or carbon monoxide on transition metal particles. The major difference with those processes that produce nanofibers is in the structure of the catalyst. To produce SWNT, the size of the metal cluster needs to be very small. Therefore, the success of a CCVD method lies in the design of the catalyst. 

The most appealing and promising strategy, however, is the carhonylation of amines and/or nitro compounds with carbon monoxide over transition metal complexes, which permits the use of safer raw materials. These reactions are catalytic and do not produce large amounts of saline by-products [34, 35]. 

Chemisorption of carbon monoxide on transition metal surfaces (either single crystals or supported clusters) is a tool of general use to study the active sites present over this type of solid surfaces [42]. CO adsorption on noble metals has been the subject of a large number of papers. For instance, the adsorption behaviour of CO on surfaces of Pt single crystals, polycrystalline Pt films, and supported Pt catalysts has been discussed in terms of adsorbed species or adsorption structures formed during interaction of CO with the metal surface. 

Carbon monoxide was discovered in 1776 by heating a mixture of charcoal and 2inc oxide. It provided a source of heat to industry and homes as a component of town gas and was used as a primary raw material in German synthetic fuel manufacture during World War II its compounds with transition metals have been studied extensively (see Carbonyls). Most recently, carbon monoxide emission from vehicle exhausts has been recognized as a primary source of air pollution (qv). 

Transition-metal organometallic catalysts in solution are more effective for hydrogenation than are metals such as platinum. They are used for reactions of carbon monoxide with olefins (hydroformyla-tion) and for some ohgomerizations. They are sometimes immobihzed on polymer supports with phosphine groups. 

The reaction of alkenes with alkenes or alkynes does not always produce an aromatic ring. An important variation of this reaction reacts dienes, diynes, or en-ynes with transition metals to form organometallic coordination complexes. In the presence of carbon monoxide, cyclopentenone derivatives are formed in what is known as the Pauson-Khand reaction The reaction involves (1) formation of a hexacarbonyldicobalt-alkyne complex and (2) decomposition of the complex in the presence of an alkene. A typical example Rhodium and tungsten ... 

A determination of dimethyl sulphoxide by Dizdar and Idjakovic" is based on the fact that it can cause changes in the visible absorption spectra of some metal compounds, especially transition metals, in aqueous solution. In these solutions water and sulphoxide evidently compete for places in the coordination sphere of the metal ions. The authors found the effect to be largest with ammonium ferric sulphate, (NH4)2S04 Fe2(S04)3T2H20, in dilute acid and related the observed increase in absorption at 410 nm with the concentration of dimethyl sulphoxide. Neither sulphide nor sulphone interfered. Toma and coworkers described a method, which may bear a relation to this group displacement in a sphere of coordination. They reacted sulphoxides (also cyanides and carbon monoxide) with excess sodium aquapentacyanoferrate" (the corresponding amminopentacyanoferrate complex was used) with which a 1 1 complex is formed. In the sulphoxide determination they then titrated spectrophotometrically with methylpyrazinium iodide, the cation of which reacts with the unused ferrate" complex to give a deep blue ion combination product (absorption maximum at 658 nm). 

Figure C shows carbon monoxide insertion reactions. There are a number of reduction reactions of carbon monoxide catalyzed by transition metals, and these, I believe, all involve an insertion of carbon monoxide into a metal hydride as an initial step. Cobalt hydrocarbonyl reacts with carbon monoxide to give formate derivatives. This is probably an insertion reaction also.

The cyanide ion, CN, is isoelectronic with carbon monoxide and has an extensive chemistry of reaction with transition metals (e.g. the formation of the hexacyanoferrate(III) ion, [Fe(CN)63 ] by reaction with iron(III) in solution) but, unlike CO, it shows a preference for the positive oxidation states of the elements. This is mainly because of its negative charge. 

J) Ichikawa, M., Sudo, M., Soma, M., Onichi, T., Tamaru, K. Catalytic Formation of Hydrocarbons (Ci-Cs) from Hydrogen and Carbon Monoxide over the Electron Donor-Acceptor Complex Films of Alkalimetals with Transition Metal Phthalocyanines orGraphite. J. Am. Chem. Soc. 91, 1538 (1969). 

A full orbital analysis for CO (see Table 4) shows that the ft-bond posses the highest Fukui index (0.62 e V) as well as the highest polarization function (0.118 eV). This agrees with the fact that carbon monoxide works most efficiently as a ft acceptor when interacts with transition metal atoms. 

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