Polymerization of Allenes by Using an Iron(II) β-Diketiminate Pre-Catalyst to Generate High M_n Polymers

Area of Science:

• Polymer Chemistry
• Organometallic Catalysis
• Materials Science

Background:

• Arylallenes are versatile monomers for polymer synthesis.
• Developing efficient catalytic systems for arylallene polymerization is crucial for creating novel polymeric materials.

Purpose of the Study:

• To report a novel iron(II)-catalyzed polymerization of arylallenes.
• To elucidate the reaction mechanism and identify key intermediates.
• To characterize the resulting polymers and investigate side-product formation.

Main Methods:

• Iron(II)-catalyzed polymerization reactions.
• Nuclear Magnetic Resonance (NMR) spectroscopy.
• Differential Scanning Calorimetry (DSC).
• Gel Permeation Chromatography (GPC).
• Kinetic and isotopic labeling experiments.

Main Results:

• Achieved rapid polymerization of arylallenes at room temperature using an iron(II) catalyst and hydride co-catalyst.
• Synthesized polymers with molecular weights up to M_n = 189,000 Da.
• Postulated a mechanism involving a reactive Fe(III) species, not an iron(II) hydride.
• Identified the formation of a 1,3-substituted cyclobutane side-product.

Conclusions:

• The iron(II)-catalyzed polymerization of arylallenes is an efficient method for producing high molecular weight polymers.
• The reaction mechanism likely involves a Fe(III) intermediate, offering new insights into iron-mediated polymerization.
• Further investigation into the cyclobutane side-product may reveal novel reaction pathways.