Polymers containing nickel centers

Fig. 5 Some 2-D coordination polymers (a) nickel bis(imidazolate), containing neutral sheets of square planar metal centers,16 (b) a plan view of the europium isophthalate structure,17 showing nine-coordinate Eu3+, and (c) copper adipate,18 which consists of both chains and sheets, viewed along the chain axis. Gray spheres denote carbon, white hydrogen, blue nitrogen, red oxygen, and green nickel, with EuO, polyhedra in orange and CuOs square pyramids in blue.

A novel polysiloxane, containing the isocyanide group pendent to the backbone, has been synthesized. It is observed to react with the metal vapors of chromium, iron and nickel to afford binary metal complexes of the type M(CN-[P])n, where n = 6, 5, 4 respectively, in which the polymer-attached isocyanide group provides the stabilization for the metal center. The product obtained from the reaction with Fe was found to be photosensitive yielding the Fe2(CN-[P])q species and extensive cross-linking of the polymer. The Cr and Ni products were able to be oxidized on exposure of thin films to the air, or electrochemically in the presence of an electron relay. The availability of different oxidation states for the metals in these new materials gives hope that novel redox-active polymers may be accessible. 

The transition group compound (catalyst) and the metal alkyl compound (activator) form an organometallic complex through alkylation of the transition metal by the activator which is the active center of polymerization (Cat). With these catalysts not only can ethylene be polymerized but also a-olefins (propylene, 1-butylene, styrene) and dienes. In these cases the polymerization can be regio- and stereoselective so that tactic polymers are obtained. The possibilities of combination between catalyst and activator are limited because the catalytic systems are specific to a certain substrate. This means that a given combination is mostly useful only for a certain monomer. Thus conjugated dienes can be polymerized by catalyst systems containing cobalt or nickel, whereas those systems... 

Copper- and nickel-containing polymers 259a-259d were prepared by the Schiffbase condensation of diamino metal complexes, 258a-258d, with p-diformylbenzene (Scheme 4.54).146 GPC analysis indicated that the polymers had low molecular weights (Mn) of 610-3500. Electronic spectroscopy and CV indicated that there was no communication between adjacent metal centers in the polymers. 

These two chain-walking mechanisms have an impact upon the distribution of branches. Two consecutive methyl branches must have an even number of methylenes between them. This holds true for any odd-carbon branches because they can only be formed by having the metal center back down the chain by an odd number of carbon atoms. This mechanism would also seem to argue that there must be an odd number of methylenes between two even-carbon branches, but the fact that the catalyst has the ability to walk to any spot on the polymer backbone and insert one or more ethylenes means that this is not true. Thus, if there are an even number of methylene carbon atoms between two consecutive branches, at least one of them must contain an odd number of carbon atoms. This mechanistic argument has been nicely confirmed in the case of nickel-catalyzed... 

In order to introduce metal centers into the binaphthyl polymers, we have prepared polybinaphthyls that contain polyhydroxyl groups. Reaction of (/ )-14 with acetic anhydride generates (R)-79, in which the two hydroxyl groups of (/ )-14 are protected for the subsequent polymerization. The ester functions of R)-79 can then be easily hydrolyzed after the polymerization. (R)-79 is polymerized in a DMF solution at about 85 C in the presence of 10 mol% of nickel(II) chloride with the addition of bipyridine, triphenyl phosphine, and excess zinc [67] to generate a polybinaphthyl (/ )-80 (Scheme 34). GPC analysis of (R)-80 shows that its molecular weight is M = 6400 and M = 3600 (PDI = 1.8). LLS study shows that the of (/ )-80 is 7130. This polymer is soluble in common organic solvents. The specific optical rotation of (/ )-80 is [a] - -353 (c = 0.5, THF). When a mixture... 

---