Cobalt hydrogenation

Preparation of Cobalt Hydrogenation Catalysts. K3Co(CN)6 was prepared following Brauer (8), HCo[P(OPh)3L was prepared following an Inorganic Synthesis procedure (9), and K3Co(CN)5 was prepared following the procedure of Adamson (10). 

Iron or Cobalt Hydrogenation of CO and C02 to form hydrocarbons (Fischer-Tropsch synthesis)... 

Recently another family of dendrimers has become commercially available. These polyamines were developed by Meijer and de Brabander-van den Berg of DSM Research and are based on Vogtle s initial synthesis [7]. In this case the troublesome reduction step was performed using a Raney cobalt hydrogenation catalyst and other process improvements have permitted this synthesis to be continued up to the fifth generation with multikilogram quantities available. 

If the formation of formate esters under hydroformylation conditions involves the carbonylation of an alkoxycobalt carbonyl as suggested previously (90), this would be evidence that cobalt hydrocarbonyl adds the reverse way to acyl groups. Since the formation of formate esters can be explained as well by a CO insertion into a cobalt-hydrogen group followed by alcoholysis, however, the data would be explained best if a cobalt-carbon bond was formed in the hydride reduction of acyl compounds. 

The n complex 1 has not been isolated or observed directly, but its involvement is strongly supported by indirect evidence. In the second step the alkene inserts into the cobalt-hydrogen bond to yield an alkylcobalt complex (2), which is transformed via the migratory insertion of CO into a coordinatively unsaturated acylcobalt complex (3). 

Occlusion of Hydrogen by Cobalt.—Hydrogen is readily occluded by cobalt to an extent dependent upon a variety of factors. Chief amongst these are ... 

Only two reports deal with the reactions of cobalt complexes with HFA. Insertion into the cobalt-hydrogen bond of a hydride complex affords a cobalt hexafluoroisopropylate 136a). An oxolene(2) is formed from an alkylcobalt compound and HFA 66). For mechanistic reasons the authors favor the depicted structure 157 over the isomeric oxolene (3) ring reported for the analogous iron complex 149 174). 

In this example, the unreduced network (without the side reaction to the tetracarbonyl-acyl) has twelve rate equations, one for each participant, and fourteen coefficients. Four rate equations can be replaced by stoichiometric constraints, namely, the carbon skeleton, cobalt, hydrogen, and CO balances. This still leaves eight rate equations with ten coefficients. Pathway reduction has reduced this to a single rate equation, eqn 6.12, with two coefficients. 

Aqueous solutions of cobalt salts containing cyanide ions have long been known to absorb molecular hydrogen (11, 182, 218). Only recently, however, has it been shown by proton magnetic resonance studies that under certain conditions these solutions contain cobalt-hydrogen species (108, 111). The concentration of the cobalt-hydride complex depends on the... 

Fast 1,2-insertion of the olefin into the cobalt-hydrogen bond in HCo(CO)3(RCH=CH2) give the alkylcobalt tricarbonyl, RC2H4Co(CO)3. Carbon monoxide and HCo(CO)4 compete for this intermediate complex in fast reactions leading to carbonylated and saturated products, respectively. Using the steady-state approximation for the alkylcobalt tricarbonyl compound, rate equations for carbon monoxide uptake and for the saturated product formation were obtained. These rate equations revealed that the experimentally obtained constant in the expression rCO/rH = constant [CO]/[HCo(CO)4] is the ratio of the rate constants... 

The reaction is catalyzed by cobalt hydrogen is necessary whatever the starting material, which can be aldehydes, olefins or benzyl hahdes. The yields are generally good (50% to 98%) and the selectivities are excellent. 

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