Organometallic compounds substitution polymerization

Different techniques have been used to study the products of photoreactions of organometallic compounds for example, irradiation of the arene complexes [CpFe() -arene)]+ resulted in the substitution of the arene by solvent or other potential ligands present in solution. In solutions containing an epoxide monomer, this photochemical reaction generated a species that initiated polymerization. Ion cyclotron resonance Fourier transform mass spectrometry and electrospray ionization mass spectrometry were used to elucidate the mechanism of these photoinitiated polymerizations. 

The chemical reactivities of the alkali metal organometallic compounds (RM) vary widely depending on metal M, basicity of the solvent systems used, and steric and electronic properties of the organic group R. In many reactions an important factor is the stabilization resulting from formation of a delocalized carbanion system as in the polymerization of dienes or aromatic substituted ethylenes, and in Reactions 3, 4, 5, and 10 in Table I. It is primarily with these delocalized carbanion systems that this review is concerned although saturated organolithium compounds are discussed briefly. 

Metal-containing polymers can be synthesized by the vapor deposition polymerization of various monomer systems including organometallic compounds and metal-monomer co-condensates. Such co-condensates are produced by simultaneous or layer-by-layer deposition of metal and monomer vapors on substrate plates at low temperatures (usually, 77 K). Polymerization can proceed in different ways. Some metal-monomer systems polymerize during cocondensation (Ge and Sn with acetylene [11], Mg with CN-substituted p-xylylene [12]), most probably due to heat released at condensation. In references 13-16, co-condensates of metals (Pd, Ag, Au, etc.) and vinyl monomers... 

Cryochemical synthesis of Ag-PPX systems and their structures were studied in references 24, 34, 36, 37, and 44. The simultaneous vapor deposition of PX-, CN-PX-, and Cl-substituted PX (Cl-PX) with Ag at 77 K does not lead to complexation or the formation of any organometallic compounds [24, 36, 44]. In the case of PX and Cl-PX, such deposition proceeds without polymerization. The co-deposition of CN-PX with Ag is accompanied by the partial polymerization of monomer. The initial condensates at 77 K contain a small amount of Ag nanocrystals that can be revealed and characterized using UV-Vis spectroscopy because such crystals have the specific absorption band of surface electron plasmons of about 430nm [3] (Figure 2.5 and 2.6). UV irradiation of these condensates at 77 K leads to the total conversion of monomers to the corresponding polymers (PPX, CIPPX, and CNPPX). However, intensity (D ), maximum position (Vax), and half-width (Ai ) of the nanocrystals plasmon band do not practically change in the course of cryopolymerization (Figures 2.5 and 2.6, Table 2.1). 

Kallio, K. Kauhanen, J. Activation of Siloxy-substituted Compounds and Homopolymerization of Ethylene by Different Soluble Alumoxane Gocatalysts. In Organometallic Catalysts and Olefin Polymerization Catalysts for a New Millenium-, Blom, R., Follestad, A., Rytter, E., Tilset, M., Ystenes, M., Eds. Springer Berlin, 2001 p 14. 

Organometallic derivatives of metal carbonyls have been shown to be intermediates in the polymerization and cyclization of acetylenes in the presence of metal carbonyls, and many acetylene derivatives of metal carbonyl compounds have been isolated 43,198). Acetylene-substituted carbonyl clusters have, in general, been prepared by one of two methods. 

Moran, M. Pascual. M.C. Cuadrado, I. Losada. J. (Dimethylamino)dimethylsilyl-substituted dimeric and siloxanyl polymeric compounds containing [(ti -C5R4)-Fe(CO)(p-CO)]2 (R = H. Me) moieties. Synthesis, characterization, and electrochemistry. Organometallics 1993. 72 811-822. 

The number of monomers that undergo chain-growth polymerization is large and includes such compounds as alkenes, alkynes, allenes, isocyanates, and cyclic compounds such as lactones, lactams, ethers, and epoxides. We concentrate on the chain-growth polymerizations of ethylene and substituted ethylenes and show how these compounds can be polymerized by radical and organometallic-mediated mechanisms. 

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