Selective Ring-Opening Allene Metathesis: Polymerization or Ruthenium Vinylidene Formation

Area of Science:

• Polymer Chemistry
• Organometallic Chemistry

Background:

• Allene metathesis polymerization offers a route to novel polymer structures.
• Controlling polymerization pathways is crucial for material properties.

Purpose of the Study:

• To investigate selective ring-opening allene metathesis polymerization (ROAlMP) of 1,2-cyclononadiene.
• To explore catalyst-controlled ruthenium vinylidene formation.
• To characterize the resulting polyallene and its properties.

Main Methods:

• Utilized Grubbs first-generation (G1) and second-generation (G2) catalysts for selective polymerization.
• Characterized poly(1,2-cyclononadiene) using NMR analysis and MALDI-TOF.
• Investigated the use of generated ruthenium vinylidene in ring-opening metathesis polymerization (ROMP).

Main Results:

• Grubbs G2 catalyst selectively promoted ROAlMP via alkylidene formation.
• Grubbs G1 catalyst favored vinylidene formation, preventing homopolymerization.
• A well-defined polyallene with good thermal stability (T_D ca. 390 °C) and fluorescence was synthesized.
• Ruthenium vinylidene successfully polymerized a strained norbornene derivative.

Conclusions:

• Catalyst selection enables precise control over ROAlMP pathways.
• ROAlMP provides facile access to well-defined polyallenes.
• This work facilitates structure-property relationship studies in polyallenes.