Cyclohexene cobalt catalysts

Cobalt catalysts have been shown to hydrogenate arenes to saturated hydrocarbons. The Co(acac)2-AlHBu 2-PBun3 system hydrogenates benzene to cyclohexene, but the presence of styrene was necessary, otherwise the reaction ceased. The styrene was also hydrogenated.72... 

The hydroformylation of alkenes generally has been considered to be an industrial reaction unavailable to a laboratory scale process. Usually bench chemists are neither willing nor able to carry out such a reaction, particularly at the high pressures (200 bar) necessary for the hydrocarbonylation reactions utilizing a cobalt catalyst. (Most of the previous literature reports pressures in atmospheres or pounds per square inch. All pressures in this chapter are reported in bars (SI) the relationship is 14.696 p.s.i. = 1 atm = 101 325 Pa = 1.013 25 bar.) However, hydroformylation reactions with rhodium require much lower pressures and related carbonylation reactions can be carried out at 1-10 bar. Furthermore, pressure equipment is available from a variety of suppliers and costs less than a routine IR instrument. Provided a suitable pressure room is available, even the high pressure reactions can be carried out safely and easily. The hydroformylation of cyclohexene to cyclohexanecarbaldehyde using a rhodium catalyst is an Organic Syntheses preparation (see Section 4.5.2.5). 

Hydr/formyUttion. Swiss chemists recommend rhodium(lII) oxide as catalyst for hydroformylation of olefins. Thus they have prepared cyclohexanecarboxaldchyde (2) in 95% yield from cyclohexene (1). Lower yields were obtained using cobalt catalysts. 

Other Syntheses Related to the Fischer-Tropsch Process Comparatively little is yet known of some synthetic reactions which obviously resemble the Fischer-Tropsch process very closely, but they are worth brief mention because they are also likely to be controlled by geometrical factors. The Oxo synthesis (15) of aldehydes by the interaction of ethylene or other olefins with carbon monoxide and hydrogen is carried out in contact with cobalt catalysts at temperatures in the range 110-150°, and under a pressure of 100-200 atmospheres. Cyclic olefins react similarly for example, cyclohexene gives hexahydrobenzaldehyde. There can be little doubt that a two-point adsorption of the hydrocarbon must take place and that the adsorbed molecule then reacts with carbon monoxide and hydrogen the difference between this process and that responsible for the normal hydrocarbon synthesis is that adsorbed carbon monoxide survives as such under the less drastic temperature conditions which are employed. Owing to the fact that a variety of isomeric aldehydes are produced, this system deserves further detailed study on geometrical lines. 

Noteworthy, the hydroformylation with cobalt catalysts can draw benefit from the addition of ruthenium [9]. For example, the initial rate of the reaction with cyclohexene was 19 times faster with Co2(CO)g/Ru3(CO)j2 in comparison to the monometallic Co system [10]. By combining the superior hydroformylation properties of a rhodium catalyst with the excellent hydrogenation activity of... 

In addition to rhodium(III) oxide, cobalt(II) acetylacetonate or dicobalt octacarbonyl has been used by the submitters as catalyst precursors for the hydroformylation of cyclohexene. The results are given in Table I. 

Lee and coworkers have reported on the use of the highly active and selective cobalt(III) catalyst depicted in Fig. 12 for the terpolymerization of propylene oxide and various epoxides with CO2, including cyclohexene oxide, 1-hexene oxide, and 1-butene oxide [61]. Catalytic activities ranged from 4,400-14,000 h at a CO2... 

One of the characteristic features of the metal-catalysed reaction of acetylene with hydrogen is that, in addition to ethylene and ethane, hydrocarbons containing more than two carbon atoms are frequently observed in appreciable yields. The hydropolymerisation of acetylene over nickel—pumice catalysts was investigated in some detail by Sheridan [169] who found that, between 200 and 250°C, extensive polymerisation to yield predominantly C4 - and C6 -polymers occurred, although small amounts of all polymers up to Cn, where n > 31, were also observed. It was also shown that the polymeric products were aliphatic hydrocarbons, although subsequent studies with nickel—alumina [176] revealed that, whilst the main products were aliphatic hydrocarbons, small amounts of cyclohexene, cyclohexane and aromatic hydrocarbons were also formed. The extent of polymerisation appears to be greater with the first row metals, iron, cobalt, nickel and copper, where up to 60% of the acetylene may polymerise, than with the second and third row noble Group VIII metals. With alumina-supported noble metals, the polymerisation prod-... 

Phosphinecarbonyl complexes of cobalt have long been known to act as hydrogenation catalysts. In a recent study involving cyclohexene the kinetics of its hydrogenation by the complex [CoH(CO)2(PBun3)2] were studied. Unlike the systems described above, the carbonyl complexes generally require elevated temperature and pressure. The proposed mechanism is given in Scheme 6. 

In 1975 Johnson and Nowack reported that benzene was hydrogenated to cyclohexene in 20.3% yield at 58% conversion over a cobalt ion (0.05%) modified 0.5% Ru-Ca(OH)2 in the presence of water at 180°C and 6.8 MPa H2.33 The yield of cyclohexene was definitely higher than those ever reported for the cyclohexene intermediate in the hydrogenation of benzene.34-36 Similar nickel- and iron-ion-modified 0.5% Ru-Ca(OH)2 or nickel-modified 0.5% Ru-A1203 also gave good selectivities to cyclohexene although in somewhat lower yields than over the cobalt-modified catalyst. It appears that the presence of water and small amounts of transition metal... 

Example 11.1. Hydroformylation of cyclohexene with phosphine-substituted cobalt hydrocarbonyl catalyst. The most probable network of cyclohexene hydroformylation catalyzed by a phosphine-substituted cobalt hydrocarbonyl is shown on the facing page. HCo(CO)3Ph (cat) is in equilibrium with the CO-deficient HCo(CO)2Ph (cat ) and CO. For greater generality, quasi-equilibrium of these species with the 7r-complex, X, is not assumed. Actual hydroformylation olefin — aldehyde proceeds via a Heck-Breslow pathway (cycle 6.9 that includes the trihydride, X2) but without... 

Example 11.2. Streamlined network for hydroformylation of n-heptene catalyzed by phosphine-substituted cobalt hydrocarbonyl. In hydroformylation of straight-chain olefins with a phosphine-substituted cobalt hydrocarbonyl catalyst, the model must account for three complications that are absent with cyclohexene isomerization by migration of the double bond along the hydrocarbon chain, formation of isomeric aldehydes and alcohols, and condensation of the straight-chain aldehyde to "heavy ends (chiefly an alcohol of twice the carbon number, such as 2-ethylhexanol from propene via n-butanal and a C8 aldol). A streamlined network for n-heptene is ... 

In the presence of metal salts, thiiranes including cyclohexene sulfide react with acetyl chloride to afford /3-chlorothioacetate 57 in good yield <2003SC2321>. Cobalt(ll) chloride (O.OSequiv) was found to be the best catalyst. Under these conditions, cyclohexene sulfide provided the ring-open product in 87% yield (Scheme 21). Similar reactions in the absence of the metal salts provided only low yield of the ring-open product <1978CJC2677>. 

Benzene and substituted benzenes are reduced under mild conditions using [Co(C3Hs) P(OMe)3 3] as catalyst. Benzene, anisole and alkylbenzenes are converted to cyclohexanes, while alkyl benzoates give l-alkoxycarbonylcyclohexenes. ° Interesting is the fact that benzene is more easily reduced than cyclohexene because of the special affinity of the benzene ring for cobalt. 

Jonas and Tadic [71] have investigated the homogeneous cobalt-catalyzed co-cyclotrimerization of acetylene and olefins. The reaction with -Ind-cobalt bis(ethylene) as the catalyst was carried out with ethylene, a-olefins and 2-butene as well as cyclohexene and cyclooctene (eq. (25)). 

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