Polymerization isocyanide

Isocyanide polymerization has also been used to polymerize peptide-based monomers. Cornelissen et al. [31,32] prepared oligopeptides based on alanine and functionalized the N-terminus with an isocyanide moiety. These monomers were subsequently polymerized using a Ni catalyst into /3-helical poly isocyanopeptides with the dipeptides in the side chain. It was found that these polymers formed rigid rods, which were revealed by AFM to have extremely long persistence lengths. This rigidity was caused by the formation of /5-sheets between the alanines in the side chain. The same group 

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The same equipment is used as described in the procedure in Section B. The flask is charged with Fe(CO)4(2-CNC6H3Me2-l,3)(1.79g, 6.0mmol), CoCl2-2H20 (0.034 g, 0.2 mmol), and toluene (30 mL), and the mixture is heated to 85 °C with stirring. To the hot solution is added 2-isocyano-l, 3-dimethylbenzene (1.57 g, 12.0 mmol). It is crucial to add the isocyanide to the hot solution. Otherwise, catalyst deactivation (believed to be due to isocyanide polymerization) occurs. This results in sluggish and incomplete reaction.4,12... 

Scheme 7. Merry-go-Round Mechanism in Ni(II)-Catalyzed Isocyanide Polymerization...

Recently also the isocyanide polymerizations using an al-kynylnickel complex has been reported Takei, F. Tung, S. Yanai, K. Onitsuka, K. Takahashi, S. J. Organomet. Chem. 1998, 559, 91. 

Recent progress in isocyanide polymerization has largely relied on the use of transition metal complexes acting as initiators (Scheme 5). The fourth... 

Diphosphine-bridged Cu and Ag isocyanide polymeric complexes 57 are luminescent in the solid state [114]. This was proposed to arise from an MLCT excited state (d10 metal to both CNR and phosphine n systems). The properties of these polymers... 

Phenyl isocyanide, obtained from aniline, is difficult to free from unchanged aniline samples containing aniline are generally colorless, but pure phenyl isocyanide polymerizes readily to blue indigo dianil.638... 

Polymerization of l-105 with 97 (R = ethyl), a living initiator for isocyanide polymerization, simultaneously produces a mixture of diastereomeric right- and left-handed helices with different molecular weights and narrow molecular weight distributions. The two helices can be completely separated by fractionation using acetone. Fractionated polymers exhibited smectic orderings. 

Fig. 14 Synthesis of PBLG-b-poly(methylbenzyl isocyanide) (PMBI) by a combination of NCA ring-opening and isocyanide polymerization [111]...

Kros et al. reported a polymer-peptide conjugate prepared via nickel-mediated NCA polymerization and a subsequent polymerization of an isocyanide, again using the nickel complex as initiator [111]. The active catalyst is attacked by the more electrophilic isocyanide and the coordinated amine reacts with the isocyanide to yield a carbene-like initiator for the isocyanide polymerization (see Fig. 14). The product can be purified from free residual homopolymers by selective solvent... 

In the reaction of Ni(CNBu )4 and methyl iodide oligomerization of the isocyanide was observed the only isolable nickel complex was (I), shown below. This product is believed to arise through sequential insertions of three isocyanides into a nickel-carbon bond. Upon further treatment with additional isocyanide at a temperature greater than 60° C one obtains a polymer (RNC) presumably through multiple isocyanide insertion reactions. The addition of benzoyl chloride to Ni(CNBu )4 gave two isolable compounds Ni(CNBu )3(COPh)Cl (74%) and (II) (8.2%). This latter reaction, and the isolation of (II) in particular, suggests that the proposed mechanism for polymerization of isocyanides is reasonable. 

The polymerization of allenes by [Rh(CO)2Cl]2 and a ligand (phosphines, arsines, amines, isocyanides) (175) and the polymerization of cyclohexyl isocyanide by Co2(CO)g (173) have been reported. 

Mention was made earlier about insertion reactions into nickel alkyl bonds 108, 164), and about polymerizations of oleiins by isocyanide nickel complexes 31,174). 

Much of the recent interest in insertion reactions undeniably stems from the emphasis placed on development of homogeneous catalysis as a rational discipline. One or more insertion is involved in such catalytic processes as the hydroformylation (31) or the polymerization of olefins 26, 75) and isocyanides 244). In addition, many insertion reactions have been successfully employed in organic and organometallic synthesis. The research in this general area has helped systematize a large body of previously unrelated facts and opened new areas of chemistry for investigation. Heck 114) and Lappert and Prokai 161) provide a comprehensive compilation and a systematic discussion of a wide variety of insertion reactions in two relatively recent (1965 and 1967) reviews. 

This work was extended to include acetylides (alkynyls) of the type (RNG)Au-G=C-C6H4-/)-C H2 +1, with n — 6-12 (even numbers), and R as above. The compounds were prepared from (tht)AuCl and the alkynes /)-HC=C-C6H4-C H2 +1 in aqueous acetone with soda as a weak base. The resulting insoluble, polymeric alkynylgold(i) complexes were dissolved in an organic solvent by adding equivalent quantities of the isocyanides. All products show distinct transitions from a crystalline to a smectic A phase and finally to the isotropic melts.206... 

Polymeric (isocyanide)gold(i) aryls ( gold oligo-phenylene-ethynylene-isonitriles ) were tested as electrical conductors at metal-molecule-metal junctions (7r-conjugated molecular wires), but the preparation, structure, and properties of the materials were not fully disclosed (Scheme 52).218... 

The effect of mixtures of surfactants and polyelectrolytes on spontaneous, water-catalysed hydrolysis (Fadnavis and Engberts, 1982) was mentioned in Section 4, but mixtures of functionalized polyelectrolytes and cationic surfacants are effective deacylating agents (Visser et al., 1983). Polymerized isocyanides were functionalized with an imidazole group and the deacylation of 2,4-dinitrophenyl acetate in the polyelectrolyte was speeded by addition of single or twin chain quaternary ammonium ion surfactants, up to a plateau value. Anionic surfactants had essentially no effect. It is probable that the cationic surfactants accelerate the reaction by increasing the deprotonation of the imidazole groups. 

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