Cobalt complexes carbonyls

3-dioxa-2-silacyclohepta-5-ynes which undergo carbonyl substitution in the case of = CO with PPha or dppm.  

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Cobalt carbonyl complexes with tertiary phosphine ligands are not volatile. This makes possible a distillative separation of the reaction products from the cobalt catalyst system (Fig. 5). 

Cobalt carbonyl complexes involving InBr form when InBr inserts into the Co—Co bond in CojtCoJg ... 

The Co2(CO)g/pyridine system can catalyze carbomethoxylation of butadiene to methyl 3-pentenoate (Eq. 6.44) [80]. The reaction mechanism of the cobalt-catalyzed carbalkoxylation of olefins was investigated and the formation of a methoxycar-bonylcobalt species, MeOC(0)Co from a cobalt carbonyl complex with methanol as an intermediate is claimed [81, 82]. 

These sites must be considered to have different catalytic properties. The sites on top (Co atoms of low coordination) would be similar to that of the central atom of cobalt carbonyl complexes, and reactions on these should be similar to those in hydroformylation. Specifically, insertion reactions between n- and cr-ligands (CO... 

DECOMPOSITION OF DIGLYME SOLUTIONS OF VARIOUS COBALT CARBONYL COMPLEXES IN THE PRESENCE OF TRIMETHYLOLPROPANE PHOSPHITE... 

ARRHENIUS PARAMETERS FOR THE DECOMPOSITION OF COBALT CARBONYL COMPLEXES... 

Preparation of arylacetic acids using a cobalt carbonyl complex... 

Selected examples of the conversion of alkyl halides into ethyl esters using cobalt carbonyl complexes... 

In the sixties it was recognised that ligand substitution on the cobalt carbonyl complex might influence the performance of the catalyst. Tertiary alkyl phosphines have a profound influence ... 

To make butyraldehyde, the precursor for NBA, the so-called Oxo process is used, reacting chemical grade propylene with hydrogen and. carbon monoxide at 250-300°F and 3500-4000 psi. See Figure 14-4.) Under those conditions, both feeds are liquids. The catalyst is an oil-soluble cobalt carbonyl complex dissolved in the propylene. If rhodium-based catalysts or complexes based on rhodium carbonyls and triphenyl phosphine... 

Cobalt carbonyl complexes react with 1,3-diynes to give a variety of complexes in which two molecules of diyne have coupled to form y-cyclobutadiene ligands slightly different conditions result in formation of cluster complexes (see Section VILE.2). In the mixture of complexes obtained from the reaction... 

Use of Co2(CO)8 in reactions involving 1,2-propadienes remains for the most part unexplored. It has been reported that terminal 1,2-propadienes react with Co2(CO)8 to form unidentified complexes, and that excess 1,2-propadiene is polymerized concurrently [30]. It has also been reported by Nakamura that a novel dimeric complex 54, in which a carbonyl ligand is connected to the central carbon of 1,2-propadiene, is produced by the reaction of 1,2-propadiene itself with Co2(CO)8 (Scheme 23) [31]. However, unlike the well-known chemistry of alkyne-Co2(CO)6 complexes, these 1,2-propadiene-cobalt carbonyl complexes have rarely been applied in synthetic reactions, probably due to their high activity in catalyzing the polymerization of 1,2-propadienes [32]. 

The alkyne-cobalt carbonyl complex 3 formed from the alkyne 1 and dicobalt octacarbonyl 2 should lose at least one of the GOs on the metal to provide the vacancy for the incoming olefins. Subsequently, an olefin-bound complex 5 rearranged oxidatively to yield a metallacyclic intermediate 6. Migratory insertion of GO of 6 would provide the homologated ring intermediate 7, and the following two successive reductive eliminations afford the cyclopentenone... 

Although the oxidative promoters have been quite effective, the reaction with less reactive olefins is still troublesome. Under the conditions with the oxidative promoter, the PKR is inevitably competing with the demetallation of the alkyne-cobalt carbonyl complex to give the metal-free alkynes. This competition is insignificant when the reactive olefins are employed, but it is prone to give more demetallated alkynes when the less reactive olefins are used (Scheme 3). This is reasoned by the fact that it is hard to expect from those promoters to oxidize only one of the COs on metal, and, in other words, the decarbonylation is not discriminative. As a result, the finding of the optimum condition is critical to favor the desired PKR product. 

One of the complexes formed in the reaction of diphenylacetylene and iron dodecacarbonyl is a red, crystalline compound of the composition [Fe2(CO)6(PhC2Ph)], which, on reduction with sodium in liquid ammonia, gives dibenzyl (117). By analogy with the cobalt carbonyl complex, structure (XXXV M = Fe) is proposed, in which the 7r-elcctrons of the triple... 

The cobalt carbonyl complex is also an effective catalyst for the siloxy-methylation of aromatic aldehydes.110 Arylethane-l,2-diol disilylethers are obtained in good yields, resulting from incorporation of one molecule of CO and two molecules of HSiR3. Good selectivity for the siloxymethylation product is observed at 0°C in hexane. At 15°C, faster reaction rates are observed, but the selectivity for the CO-incorporated product is lower. In contrast, aliphatic aldehydes react under these conditions (1 atm CO, 0°C) to give only a small amount of CO-incorporated product, with a major product resulting from hydrosilylation. 

The cobalt(O) complex shown in Entry 2 (Table 3.49) could be prepared either by heating a mixture of an alkyne cobalt carbonyl complex with polystyrene-bound tri-phenylphosphine, or by pretreating resin-bound triphenylphosphine with dicobalt octacarbonyl and then treating the resulting support with the alkyne. 

A series of cobalt carbonyl complexes of polyphosphazenes have been prepared via arene coordination sites. Examples are shown as 3.65 and 3.66.112 These are synthesized via the reactions of (NPC12) with the sodium salt of the appropriate metal-arene terminated alcohol. Mixed-substituent polymers with trifluoroethoxy or phenoxy cosubstituents have also been prepared. 

Pauson-Khand cyclization of vic-enyne derivatives of /3-lactams gave good yields of fused tricyclic compounds. The 1,4-disubstituted 2-azetidinone 391 and cobalt octacarbonyl gave the alkyne-cobalt carbonyl complex, which on thermolysis gave the tricycle 392 in 95% yield (Equation 54). When the complexes of 393 with cobalt octacarbonyl were treated with TMANO, a lower yield (65%) of 394 was obtained (Equation 55). A single diastereoisomer was formed in each case <1996TL6901>. 

Pour into an Erlenmeyer containing hexanes (200 mL) and stir for 2 h to decompose the intermediate cobalt-carbonyl complexes. 

The RCCo3(CO)9 catalysts in these reactions, however, only appear to be sources of simpler cobalt carbonyl species through their thermolysis, and it is the latter which cause the acetylene trimerization through well-established routes (73). Indeed, in some cases acetylene-derived cobalt carbonyl complexes are obtained (72) ... 

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