Poly cobalt complexes

These complexes are stable (presumably to aerial oxidation), which is, perhaps, surprising, in view of the fact that the analogous complexes of iron(II) could not be isolated, oxidation to iron(III) taking place in each case. A number of interesting poly(bisdithiocarbamate) complexes of cobalt(II) and nickel(II) (XXI) have been prepared and... 

Relatively few hydroformylations using supported cobalt complexes have been reported. Moffat (78, 79) showed that poly-2-vinylpyridine reversibly reacted with both Co2(CO) and HCo(CO)4, the cobalt carbonyl being displaced by excess carbon monoxide. This enabled the polymer to pick up the cobalt carbonyl at the end of the reaction and, thus, allowed it to be separated from the products by filtration. The polymer acted as a catalyst reservoir by rapidly releasing the cobalt carbonyl into solution in the presence of further carbon monoxide, so that the actual catalysis was a homogeneous process. More recently, cobalt carbonyl has been irreversibly bound to a polystyrene resin... 

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. 

Nickel complexes are of considerable importance as stabilizers and antioxidants for polymers of various kinds. The nickel(II) complex of the benzoic acid derivative (12) (see Section 66.4) acts as a stabilizer against oxidation of polybutadiene,46 but is less effective in this respect than the manganese and cobalt complexes. Complex (20) is effective in decreasing the rate of photooxidation of two-phase poly(vinyl chloride)-polybutadiene rubbers 74... 

Reversible oxygen binding has also been examined using poly(ethyleneimine)-cobalt complexes in aqueous solution. Cobalt(II) complexes of linear and branched poly(ethyleneimine) in aqueous solution are able to form with oxygen a p-peroxo adduct as is evidenced from stoichiometry and spectral properties 107). 

A kinetic study of living radical polymerizations of acrylates initiated by the (tetramesitylporphyronato)-cobalt(III) organo complexes (TMP)Co—CH(CH3)C02-Me and (Br8TMP)Co—CH(CH3)C02Me has been reported by Wayland et al.122 They applied an initial excess of the free cobalt complex and obtained the equilibrium constant for the reversible dissociation of the complex—poly(methyl acrylate) bond as K = 4.2 x 10 10 M for (TMP)Co and K= 1.3 x 10 8 M for (BrgTMP)Co from the rate of monomer consumption at 50 °C. The temperature dependence led to a bond... 

Polymer-supported salen catalysts were also developed by employing poly (norbornene)-immobihzed salen complexes 139 of manganese and cobalt (Scheme 3.40) [77]. The poly(norbornene) complexes are highly active and selective catalysts for the epoxidation of olefins. The asymmetric epoxidation of cis-P-methylstyrene 132 occurred smoothly at -20 °C to give the chiral epoxide 133 in 100% conversion with 92% ee. Under the same reaction conditions, Jacobsen s catalyst (an unsupported salen complex) afforded the same product with 93% ee. 

A detailed discussion on spin crossover in poly(pyrazolyl)borate iron and cobalt complexes has been performed by Long et al.119... 

Oxygen Uptake by Cobalt Poly(ethyleneimine) Complexes and its Electroreduction at an Electrode (Section 9.4) [26,64]... 

A single report documents the study of perfluoroalkyl poly(pyrazolyl)borate cobalt complexes however, their breadth and significance is appreciable. The compounds H B(pz)4 CpCo(Rf) (x = 0, 1,2) were prepared by the interaction of the respective K[H B(pz)4 J salt with CpCo(Rf)(CO)I, and in each case exhibit bidentate coordination of the poly(pyrazolyl)borate ligand, regardless of the number of pyrazole donors potentially available. 

As has already been mentioned, divinyl silicon derivatives, similarly to monovinyl-substituted silicon compounds, are also completely inert to productive homometathesis, particularly as far as acyclic diene metathesis (ADMET) polymerization is concerned. However, we have shown in earlier reports that in the presence of ruthenium, rhodium and cobalt complexes containing or generating M-H and/or M-Si bonds, divinyl-substituted silicon compounds undergo de-ethenated (poly)condensation to yield a mixture of oligomers and cyclic unsaturated siloxanes, silazanes and caibosilanes, as shown in Scheme 2 [21-29]. 

In 2005, Peretti and co-workers reported a highly active and isoselective (TOF = 220h mm >99%) cobalt complex, [(salph- Bu)CoOAc] 19 (Scheme 18(a)) for the polymerization of racemic propylene oxide. This is the first example of highly isotactic poly(propylene oxide) generation from racemic propylene oxide without concomitant atactic byproduct. 1-Butene... 

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