Halides reductive polymerization

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

Reversible redox reactions can initiate radical chemistry without a follow-up reduction or oxidation reaction. In successful reactions of this type, the redox step that produces the radical is thermodynamically disfavored. For example, Cu(I) complexes react reversibly with alkyl hahdes to give Cu(II) hahde complexes and an alkyl radical. The alkyl radical can react in, for example, an addition reaction, and the product radical will react with the Cu(II) hahde to give a new alkyl halide. This type of reaction sequence, which has been apphed in living radical polymerizations, is in the general family of nonchain radical reactions discussed earlier. ... 

There are no well-characterized polymeric bismuth catenates, although a black ether-insoluble substance, described as (PhBi)x, results from the reduction of phenylbismuth halides with LiAlH4.200 A polymeric bismuthine is thought to result from the decomposition of l,T-bibismolane.201 To date, bismuth catenation is limited to Bi2 in the case of free molecules and to some complex anionic and cationic clusters. 

Poly-p-xylylenes were prepared in excellent yield by electrolytic reduction of a,a -dihalo-/>-xylenes at controlled cathode potentials (28). Polymer and halides are formed at the cathode at the anode the halide is oxidized to halogen. It has been known that some of the a-a -dihalo- -xylene type of compounds have been polymerized by a variety of reducing agents, such as zinc, copper, phenyllithium, sodium and iron ... 

There are two principal synthetic routes to dicarboxylate complexes. One of these uses an aqueous solution of the alkali metal dicarboxylate and the corresponding metal halide,93 while the other depends upon the dicarboxylic acid reduction of higher oxidation state metals. This reductive property of oxalic acid results in its ready dissolution of iron oxides and hence a cleaning utility in nuclear power plants.94 Mention must also be made of the successful ligand exchange synthesis of molybdenum dicarboxylates, Mo(dicarboxylate)2 H2 O, from the corresponding acetate complex. Unfortunately the polymeric, amorphous and insoluble nature of these complexes has restricted the study of these systems, which may well provide examples of multiple M—M bonding in dicarboxylate coordination chemistry.95... 

Bis(cyclopentadienyl)titanium(II) dicarbonyl complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium(II) dinitrogen complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium halides ligand metathesis reactions, 4, 537 olefin polymerization, 4, 538 organic reactions, 4, 540 properties, 4, 530 reductions, 4, 532 synthesis, 4, 510... 

The solubility of neodymium carboxylates in organic solvents is also improved by the addition of electron donors such as acetylacetone, tetrahy-drofuran, N,N -dimethylformamide, thiophene, diphenylether, triethylamine, pyridine, organic phosphorus compounds etc. Also the storage stability of neodymium carboxylates in organic solutions (reduction of sediment formation) is increased by these additives. Mixtures of the Nd-precursor and the respective additives are reacted in the temperature range 0-80 °C. The sequential addition of Al-compound and halide donor yield the active polymerization catalysts [409,410]. 

A sequence of chemical reactions is postulated to account for the features observed in the kinetics of BD polymerization catalyzed by NdV/DIBAH/ EASC [178]. From the reaction scheme which is hypothetically put forward 3 to 7 eq. of DIBAH are required for the generation of one active Nd species starting from one equivalent of NdV (Scheme 24). In the first reaction step the reduction of Nd carboxylate to Nd alcoholate is assumed to occur. Experimental evidence in favor of the reduction of Nd-carboxylate comes from NMR studies in which the reduction of the respective lanthanum carboxylate by DIBAH was observed (halide donor EASC) (Windisch, 2006, personal communication). This reduction does not occur when Nd carboxylates are reacted with TMA (Anwander and Fischbach, 2006, personal communication). DIBAH might be capable of reducing carboxylic acids to the respective al-... 

Reduction of the copper(II) halides to copper(I) halides may be carried out using sulfite or copper metal. If the reduction with copper metal is carried out in concentrated HC1 solution, the solution takes on an intermediate black color before fading to the colorless CuCl ion. The black color is probably due to dimeric or polymeric ions having copper in both the +1 and +2 states, for example, Cl—Cu—Cl—CuC12(H20) . The reduction of divalent copper by cyanide to form the cyano complex, Cu(CN)73, was mentioned in Chapter 10, and the reaction between cupric and iodide ions is similar to this, releasing iodine and forming the very insoluble copper iodide ... 

Regeneratable polymeric organotin dihydride beads have been used to reduce halides selectively (e.g. 3-bromocamphor to camphor).52 /3-Unsubstituted cyclohex-enones undergo exclusive and almost quantitative 1,4-reduction by potassium tri-s-butylborohydride to the corresponding saturated ketone [e.g. (16)] 53 reductive alkylation of carvone proceeds similarly to (17 R = Me, X = H).53 In contrast,... 

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