Halides, cobalt

The preparation of carbonylmetals by treating a transition metal halide either with carbon monoxide and zinc, or with iron pentacarbonyl is well-known and smooth. However, a violent eruptive reaction occurs if a methanolic solution of a cobalt halide, a rhodium halide or a ruthenium halide is treated with both zinc and iron pentacarbonyl. 

Addition of dry cobalt halides or their suspensions in DME gave a product with similar properties and reactivity. 

Bis(imino)pyridine Iron Halide/MAO and Cobalt Halide/MAO Catalysts. 120... 

Typically, the synthesis of the precursor iron(II) and cobalt(II) halide complexes proceeds by treatment of an anhydrous or hydrated divalent iron or cobalt halide (e.g. MX2 jcH20 or MX2 X = Cl or Br) with 1 (and also 2-4) in... 

Studies conducted to examine the mode of activation of MAO with bis(imino) pyridine cobalt halide systems have shown some intriguing findings. With regard to 6a/MAO, initial reduction of the cobalt(II) precatalyst to cobalt halide followed by conversion to a cobalt methyl and ultimately to a cobalt cationic species has been demonstrated (see Sect. 2.6) [108, 109], Addition of ethylene affords an eth-... 

Ruthenium, cobalt and halogen are the key elements of this catalysis (2), although ruthenium in combination with halogen-containing zirconium and titanium derivatives is also effective (3). In the case of the Ru-Oo couple, the highest yields of acetic acid may generally be achieved with ruthenium oxide, carbonyls and complex derivatives in combination with various cobalt halides dispersed in low-melting quaternary phosphonium halide salts (2). 

Data in Table I illustrate the production of acetic acid from 1/1 syngas catalyzed by ruthenium-cobalt halide bimetallic combinations dispersed in tetrabutylphosphonium bromide (m.p. 100°C). 

Recently31,32, it has been shown that the electrochemical reduction of a cobalt halide CoX2 (X = Cl or Br) in the absence or presence of a ligand leads to a cobalt(I) species able to react with aromatic halides. This can be achieved in DMF or acetonitrile (equation 28). 

C. Electrochemical Preparation of Organozinc Compounds using Cobalt Halides as Catalysts... 

This led us to find new catalytic systems able to turn the electrochemical process to the synthesis of organozinc compounds. In this context, a simple cobalt halides salt can be used advantageously6. As a matter of fact, the work devoted to the study of the... 

Based on Knochel s work59, which has employed cobalt halides as catalyst for the acylation of dialkylzinc reagents into ketones, this catalyst has been investigated for the coupling reaction of electrochemical arylzinc compounds formed in acetonitrile (equation 71)60. 

Cobaltous halides are formed with the halogen group, but only fluorine forms a stable cobaltic compound. The other cobaltic halides are stable only in complex ions. 

Azomethines bear a formal resemblance to azo compounds and many parallels exist in the coordination chemistry of the two series of compounds. Thus the bidentate azomethines (191) behave in a strictly comparable manner to the bidentate azo compounds (20) (Section 58.2.2.1). The isomeric, bidentate azomethines (192), however, form metal complexes which undergo very facile hydrolysis as a result of polarization of the azomethine linkage. The difference between the two types of complex is dramatically illustrated by the results of a study135 of metal complex formation by the bis(azomethine) (193). This cannot function as a tetradentate ligand for steric reasons and reacts with copper, nickel and cobalt halides in cold ethanolic solution to form the five-coordinate complexes (194). Crystallization of these products from ethanol gives the five-... 

The carbonyl group does not appear to be of importance in the above catalysts since similar results may be obtained using cobalt halides in combination with aluminium alkyls (81a). 

The mercury compounds HgFe(CO)4 and Fe(CO)4(HgX)2 (X = C1, Br, I), which were the first representatives of non-ionic metal derivatives of iron carbonyl hydrides, were discovered by Hock and Stuhlmann (V, 36). During investigations into the preparation of cobalt carbonyls from cobalt halides under CO pressure, in the presence of another metal as a halogen acceptor, we discovered the mixed metal carbonyls M[Co(CO)4]2 (M = Zn, Cd, Hg, Sn) and M[Co(CO)4]3 (M = In, Tl) (44), e.g.,... 

The action of fluorine or other fluorinating agents on cobalt halides at 300 to 400°C gives dark brown CoF3, commonly used as a fluorinating agent. It is reduced by water. 

Finely divided cobalt, as obtained from anydrous cobalt halides with Li/naphthalene in glyme, is converted to Co2(CO)g in good yields at 100 °C and 95 atm of pressure. 

A very dangerous fire and moderate explosion hazard when exposed to heat or flame can react vigorously with oxidizing materials. Warning pyrophoric in air. Mixtures with nitrogen oxide explode above 50°C. Violent reaction with zinc + transition metal halides (e.g., cobalt halides, rhodium halides, ruthenium halides). Mixtures with acetic acid + water produce a pyrophoric powder. To fight fire, use water, foam, CO2, dr " chemical. See also CARBONYLS and IRON COMPOUNDS. 

Soluble cobalt and nickel catalysts for conjugated diene polymerization are usually prepared in the presence of monomer with the formation of a TT-allylic structure as a relatively stable intermediate, but the nature of attachment of other ligands to the active site is not known. Aluminium halides and cobalt halides react to form complexes of the structure (IX) [57]... 

Reaction of Tm with cobalt halides leads to the formation of paramagnetic pseudotetrahedral [CoX(Tm)] (X = Cl, Br, I), [CoBr(Tm)] being structurally characterized. Mass spectrometry reveals the presence of fragments [Co(Tm)2]+ and [Co2X(Tm)2]+ in solution. Aerial oxidation leads to the formation of the [Co(Tm)2]+ cation, crys-tallographically characterized as the BF, CIO4, Br-, and I- salts. The mixed-sandwich complex [Co(Cp )(Tm)]I has been also isolated and characterized. Electrochemical measurements indicated that [Com(Tm)] species are more difficult to reduce than their Tp and Cp analogs.7 [Mn(Tm)(CO)3] has been also reported.8... 

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