Transition elements polymers

N. N. Greenwood, Boron Hydride Clusters, in H. W. Roesky (ed.) Rings, Clusters and Polymers of Main Group and Transition Elements, Elsevier, Amsterdam, 1989, pp. 49-105. 

Supplement to Mellor s Comprehensive Treatise on Inorganic and Theoretical Chemistry , Vol. V, Boron Part A, Boron-Oxygen Compounds , Longman, London, 1980, 825 pp. See also J. R. Bowser and T. P. Fehlner, Chap. 1 in H. W. Roesky (ed.). Rings, Clusters and Polymers of Main Group and Transition Elements, Elsevier, Amsterdam, 1989, pp. 1-48. 

Selective extraction experiments were then performed to see transference of some transition elements (Cu ", Ni ", Co ", and Fe " ) from the aqueous phase to the organic phase by the synthesized polymeric calixarenes. Phase-transfer studies in water-chloroform confirmed that polymer 2b and 3b were Fe ion-selective as was its monomer (1). Extraction of Fe " cation with 2b and 3b was observed to be maximum at pH 5.4. Only trace amounts of other metal cations such as Cu, Ni ", and Co " were transferred from the aqueous to the organic phase (Table 3). Furthermore, the extracted quantities of these cations remained unaffected with increasing pH. The effect of pH on the extraction of 3b was lower and 56% extraction was accomplished even at pH 2.2. The extraction experiments were also performed with calix[4]arene (1) the ratio was 8.4% at pH 2.2. The polymeric calix[4]arenes were selective to extract Fe " from an aqueous solution, which contained Cu +, Ni, Co ", and Fe " cations, and it was observed that the... 

ZIEGLER-NATTA POLYMERIZATION. Polymerization of vinyl monomers under mild conditions using aluminum alkyls and TiCL lor other transition element halide) catalyst to give a stereoregulated, or tactic, polymer. These polymers, in which the stereochemistry of the chain is not random have very useful physical properties. 

The knowledge of the chemistry and structure of nucleic acids as well as their metabolic and catabolic pathways has been extensively increased. However, there is very little evidence about the role of transition elements in the biochemistry of nucleic acids. Therefore, this review should emphasize the present status of the literature about studies of transition metal interactions with the monomer and polymer units of nucleic acids. Although this survey is far from being comprehensive it is hoped that the data collected here will be helpful for further investigations on the biochemical behavior of transition metals in nucleic acid metabolism. 

The first chapter will start with a discussion of the methods being employed to elucidate the chemical and structural possibilities of metal nucleic acid interactions. This will be followed by specific reactions of some transition elements with the free bases, the nucleosides, the nucleotides and finally the polymer nucleotides. 

More recent developments in the mechanistic aspects of the alkene metathesis reaction include the observation that the alkene coordinates to the metal carbene complex prior to the formation of the metallacyclobutane complex. Thns a 2 - - 2 addition reaction of the alkene to the carbene is very unlikely, and a vacant coordination site appears to be necessary for catalytic activity. It has also been shown that the metal carbene complex can exist in different rotameric forms (equation 11) and that the two rotamers can have different reactivities toward alkenes. " The latter observation may explain why similar ROMP catalysts can produce polymers that have very different stereochemistries. Finally, the synthesis of a well-defined Ru carbene complex (equation 12) that is a good initiator for ROMP reactions suggests that carbenes are probably the active species in catalysts derived from the later transition elements. ... 

Rings, clusters, and polymers of main group and transition elements, monograph 89MI18. 

Such similarities do not hold in low oxidation states, where frequently the halides of the main group elements are monomeric species and those of the transition elements are halide bridged polymers. This divergence in bond type in lower oxidation states is connected with the non-bonding electrons, which, for the main group elements, are largely central-atom valence shell s or , and for the transition elements valence-shell d electrons. 

Based on the well-studied characteristics of transition metal complexes, the incorporation of transition elements into a polymer main chain would be expected to allow access to processable speciality materials... 

MOFs/CPs, as the majority of these materials are based on transition metal, and more recently, lanthanide chemistry, yet a review of polymeric materials containing uranium (from more of a polymer chemistry perspective) has appeared recently. We will compare and contrast some uranium specific issues to those of the transition elements as we feel that the unique coordination geometries of the actinides (in particular U(VI)) result in a number of stmctural features, synthetic challenges, relevance to environmental issues, and opportunities for development of functional materials. 

Among the transition elements, gold is the metal that is the most exploited or most successful at making coordination and organometallic polymers. The similarities with silver are often obvious, but differences are also observed. The last part of the section on singly bridged 1-D oligomers and polymers is devoted to this element. 

The technology of plasma formation of metal-containing polymers in the form of thin films dates from 1963, when Bradley and Hammes(15) prepared specimens from some forty different materials, and studied their electrical conductivities. Included in the study were organic compounds of iron, tin, titanium, mercury, selenium, and arsenic. The presence of a metal or transition element in the polymer did not lead to special electrical properties compared to the purely organic polymers studied. 

No detailed experiments have been carried out yet to determine the usefulness of these polymers as chelating agents or drug carriers. However, preliminary tests with ethanolic solutions of metal acetates show that polymers VII, VIII, and XIV give colored complexes with some of the common transition elements. In the case of VIII, a green complex is formed with cupric acetate and a yellow complex with oobaltic acetate. More complete experiments will be reported in a latter communication. 

---