Cobalt, complexes butadiene

Many of these cobalt complexes will catalyze the reduction of organic compounds by borohydride, hydrazine, thiols, etc. Cobalt cyanide complexes will catalyze the reduction of a,j8-unsaturated acids by borohydride (105) DMG complexes the reduction of butadiene and isoprene by borohydride, but not by H2 (124) Co(II) salen, the reduction of CHCI3 and CH3CCI3 to the dichloro compounds by borohydride (116) and cyanocobalamin, the selective reduction of -CCI2- by borohydride to -CHCl- in compounds such as aldrin, isodrin, dieldrin, and endrin without... 

C18H18, Benzene, l,3-butadiene-l,4-diyl-bis-cobalt complex, 26 195 C,8H33P, Phosphine, tricyclohexyl iron complex, 26 61 nickel complexes, 26 205, 206 C H 7OP, Benzenemethanol, 2-(diphenyl-phosphino)-... 

Cobalt complexes find various applications as additives for polymers. Thus cobalt phthalocyanine acts as a smoke retardant for styrene polymers,31 and the same effect in poly(vinyl chloride) is achieved with Co(acac)2, Co(acac)3, Co203 and CoC03.5 Co(acac)2 in presence of triphenyl phosphite or tri(4-methyl-6- f-butylphenyl) phosphite has been found to act as an antioxidant for polyenes.29 Both cobalt acetate and cobalt naphthenate stabilize polyesters against degradation,73 and the cobalt complex of the benzoic acid derivative (12) (see Section 66.4) acts as an antioxidant for butadiene polymers.46 Stabilization of poly(vinyl chloride)-polybutadiene rubber blends against UV light is provided by cobalt dicyclohexyldithiophosphinate (19).74 Here again, the precise structure does not appear to be known. 

The metal carboxylate insertion mechanism has also been demonstrated in the dicobaltoctacarbonyl-catalyzed carbomethoxylation of butadiene to methyl 3-pentenoate.66,72 The reaction of independently synthesized cobalt-carboxylate complex (19) with butadiene (Scheme 8) produced ii3-cobalt complex (20) via the insertion reaction. Reaction of (20) with cobalt hydride gives the product. The pyridine-CO catalyst promotes the reaction of methanol with dicobalt octacarbonyl to give (19) and HCo(CO)4. 

The polymerization of butadiene (BD) on this site proceeds to yield a cis-1,4-polybutadiene through the addition of a cisoid monomer in the form of the cobalt complex. 

The 4% single-m-butadiene which is present in butadiene at 20° C reacts to produce almost 8% of octatriene [the formation of a cobalt complex from two single-m-butadiene molecules (0.2%) has been neglected]. 

Another cobalt complex having only hydrocarbon ligands, (1,3-butadiene)cyclopentadienylcobalt, has been obtained as a volatile red solid melting at 103°-105°C by reaction of the diene with dicyclopenta-dienylcobalt or (1-benzoyl-1,3-cyclopentadiene)cyclopentadienylcobalt (489). The compound decomposes slowly in air. 

In coordination polymerization it is generally accepted that the monomer forms a 7r-complex with the transition metal prior to insertion into the growing chain. In general these complexes are insufficiently stable to be isolated although complexes of allene [69] and butadiene [70] have been reported. With allene the complex was formed prior to polymerization with soluble nickel catalysts, and cis coordinated butadiene forms part of the cobalt complex, CoCj 2H19, which is a dimerization cateilyst. 

C H,a, Benzene, 1,3-butadiene-1,4-diyl-bis-, cobalt complex, 26 195 CjaHjaBr, Benzene, l-bromo-2,4,6-tri-tert-butyl-, 27 236... 

The stable cobalt complex LI is prepared by cocondensing cobalt atoms and butadiene at liquid nitrogen temperature This technique is also used to prepare 7t-allyl complexes of the nickel triad metals, e.g., LII . Metal hydrides are intermediates in these reactions , as shown by the reaction of nickel hydrides with dienes to yield rt-allyl complexes . The 7i-allyl complex LIII may be prepared by adding HCl and butadiene to (PPh3)4Ni in toluene or THF at —78°C, then warming to RT . ... 

Carbon-Carbon Bond-forming Reactions via Organometal1ic Electrophilies. - Functionalization of unsaturated hydrocarbons by nucleophilic attack on their metal complexes continues to receive attention. Sequential double nucleophilic addition to a cationic cobalt complex of butadiene... 

Co2(CO)8 and HCo(CO)4 using HP-IR. A cobalt carbonyl-butadiene complex and an allylcobalt carbonyl species were formed from the reaction of butadiene with Co2(CO)8. Reaction with HCo(CO)4 gradually afforded an alkenyl complex which reacted to form further byproducts. The reaction of cobalt carbonyls with hydrogen or deuterium, and the stoichiometric interaction of the resultant hydride with alkenes has also been studied with HP-IR. Ojima reported HP-IR studies into Co-Rh bimetallic carbonyl catalysts, and observed a CoRh(CO)7 species which was active for hydroformylation-amidocarbonylation. 

The [Co(CN)5] -catalysed hydrogenation of butadiene is thought to proceed via a butenyl cobalt complex the structure of which depends on the concentration of CN . At high values of [CN ] equal amounts of cis- and trans-forms (50) and (51) are present but on reduction of [CN ] the jy -7i-complex (52) is favoured. These results correlate with the observations that but-l-ene is the principal hydrogenated product at high values of [CN ] but at low values /ra s-but-2-ene is obtained preferentially. The mechanism of formation of [Co(CN)6(H)] , the precursor to butenyl complexes (50), (51), and (52), is the subject of computational studies. ... 

This simple division into polymerization and dimerization catalysts does not apply if the growing chain stabilizes as a jt-allyl—metal complex, as is the case with conjugated diolefins (i ). Certain cobalt complexes, for instance, are perfectly able to polymerize butadiene (19). 

Most organopentacyanides are stable towards [Co(CN)jH], with the exception of allyl complexes which react to liberate propylene derivatives (105). This is one of the steps in the homogeneous hydrogenation of butadienes catalyzed by cobalt cyanide complexes (see Section VII,A). 

Highly c/s-selectivity and low molecular weight distribution polymerization of l -butadiene with cobalt(II) pyridyl bis(imine) complexes in the presence of ethylaluminum sesquischloride effect of methyl position in the ligand... 

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