Poly(iminomethylenes). 8. Circular insertion mechanism of nickel(II)-catalyzed polymerization of isocyanides

Nolte, Roeland J. M.; Zwikker, Jan W.; Reedijk, Jan; Drenth, W.

doi:10.1016/0304-5102(78)80012-1

Cited by 24 publications

(9 citation statements)

References 20 publications

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“…22 This catalyst is reliable from a functional point of view, while the details of the mechanism have been elaborated and speculated on over the years. Nolte's initial work on these polymers led him to propose a merry-go-round type mechanism, 23 which can be used to infer the chirality of the resulting polymer when a nonracemic monomer is used. 12 Subsequently, Deming and Novak performed careful experiments to determine the role of the nickel (starting from the dimeric complex in Scheme 2) in the catalytic cycle [24][25][26] (which is not incompatible with a merry-go-round mechanism).…”

Section: Introductionmentioning

confidence: 99%

Long‐range effects of chirality in aromatic poly(isocyanide)s

Amabilino

Serrano

Sierra

et al. 2006

J. Polym. Sci. A Polym. Chem.

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The preparation of optically active atropoisomeric polymers which present chiral backbones, thanks to induction during their synthesis from stereogenic centers, located far away from the skeleton is possible, thanks principally to semirigid conformations of the promesogenic spacers between them. The result is that chiral “information” can be passed as far as 21 Å from the asymmetric center to the carbon atom that forms the polymeric chain in poly(isocyanide)s. The sense of chiral induction in these conformationally rigid polymers parallels the helical sense of the cholesteric phases, as well as to the helical senses of chiral smectic C phases, induced by the monomers in nematic and smectic C phases, respectively. All these phenomena obey the odd–even rules proposed for chiral sense changes in these liquid crystalline phases. Noncovalent interactions play an important part in the induction process, in which steric arguments can be used to justify the inductions observed. The methodology can be used to prepare macromolecules, which display switching behavior upon thermal or electrochemical stimulus. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3161–3174, 2006

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Section: Introductionmentioning

confidence: 99%

Long‐range effects of chirality in aromatic poly(isocyanide)s

Amabilino

Serrano

Sierra

et al. 2006

J. Polym. Sci. A Polym. Chem.

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“…We suggest that the preferred direction of attack is on the side of the smaller substituent, S. Thus, in structure I, the attack will occur on C2. As explained in the preceding article [1], concomitantly with this attack an isocyanide monomer, which had entered apically from above, substitutes for C1(X)=N-C^, while the latter group shifts down. Once the propagation has started, it continues in the same direction, which in the sequence C2 C3 -+ C4 gives rise to a left-handed screw.…”

Section: Resultsmentioning

confidence: 99%

“…The initiation step consists of attack by a nucleophile, X" , on one of the coordinated isocyanides, producing intermediate I [1]. The plane of C1(X)=N-C^is approximately perpendicular to the ligand plane C1C2C3C4, while the nickel center and the group (SML)C will be in the (Z)-position just as in similar platinum complexes [3].…”

Section: Resultsmentioning

confidence: 99%

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Poly(iminomethylenes). 9. Induction of screw sense in the nickel(II)-catalyzed polymerization of chiral isocyanides

Beijnen

Nolte

Zwikker

et al. 1978

Journal of Molecular Catalysis

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SummaryA rule is presented which predicts the screw sense of the polymers ob tained in a nickel(II)-catalyzed reaction from chiral isocyanides of the type R1R2R3C-N=C. It is based on the steric effects and on the ligand properties of R1, R2 and R3. The optical rotation data on ten chiral isocyanides and their polymers verify this rule. The results suggest that the asymmetric in duction of screw sense is controlled kinetically at the catalyst center. A ther modynamically controlled process appears to be less likely.

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“…The polymers were prepared by the nickel(II) catalytic system developed by Nolte and coworkers. 18,19 Polymerisation of (R)-3 yielded polymer (R)-11 as a yellow powder in 91% yield after precipitation in methanol, while (R)-12 was produced in the same form in 93% yield using the same procedure. The polymers are solids presumably because of their rigid nature, a result of the steric hindrance around the backbone, which gives rise to the helical secondary structure.…”

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confidence: 99%