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    Thermal vs Pt Catalyzed ROP

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    Please help me to discuss these two mechanisms:
    1. Pt- catalyzed ROP
    2. Thermal ROP

    © BrainMass Inc. brainmass.com December 24, 2021, 11:33 pm ad1c9bdddf
    https://brainmass.com/chemistry/inorganic-chemical-reactions/thermal-pt-catalyzed-rop-580123

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    Pt- catalyzed ROP : Transition metal catalyzed ROP is believed to follow initial oxidative addition of the strained Si-C bond to the transition metal center (in this case, Pt). This is followed by ligand transfer from the metal or ion transfer like halides to the silicon center. Transfer generates the intermediate which then takes part in the propagation step by reacting with another molecule of monomer. This cycle of oxidative addition and reductive elimination leads to the polymer. Another possible mechanism involves the formation of metallamacrocycles that form from sequential addition of a monomer to the metal. Reductive elimination leads to the polymer. When the catalyst is sterically hindered, ROP is not as effective due to hindered access to the vacant coordination site on the metal. Insertion of the metal between Si and C has recently been confirmed to be an intermediate in transition metal catalyzed ROP.

    Thermal ROP: Mechanistic studies suggest the cleavage of the metal-Cp bond rather than the Si-C bond which is supported by lower bond energies for metal-Cp bond compared to Si-C bonds. However, there is also evidence for Si-Cp bond cleavage in such reactions. The Si-Cp bonds are believed to break in a heterolytic manner rather than in a homolytic manner. This can happen if trace impurities of nucleophiles like water are present. Alternatively, such cleavage can lead to zwitterions-like species that are resonance stabilized with positively charged Si and negatively charged Cp rings. The negatively charged rings can then initiate chain propagation by nucleophilic attack at the positively charged Si center.

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    © BrainMass Inc. brainmass.com December 24, 2021, 11:33 pm ad1c9bdddf>
    https://brainmass.com/chemistry/inorganic-chemical-reactions/thermal-pt-catalyzed-rop-580123

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