Ring-Opening Alkyne Metathesis Polymerization Catalyzed by a Bench-Stable Rhenium Complex

TL;DR

A new rhenium-based catalyst enables controlled ring-opening alkyne metathesis polymerization with improved usability and versatility.

Contribution

A bench-stable rhenium complex enables controlled ROAMP with tolerance for hydroxyl groups and living polymerization characteristics.

Findings

The Re(V) complex allows controlled ROAMP with up to 700 degrees of polymerization and low dispersity.

The catalyst tolerates hydroxyl groups in monomers and allows post-polymerization cleavage via cross-metathesis.

The process exhibits living polymerization behavior, enabling block copolymer synthesis.

Abstract

In the last quarter
of a century, ring-opening alkene metathesis
polymerization has revolutionized the ability to synthesize functional
polymers. In comparison, current methods for ring-opening alkyne metathesis
polymerization (ROAMP) remain constrained by a narrow scope of monomers
and catalysts that are not user-friendly. Herein, we report that an
air-stable d2 Re­(V) alkylidyne precatalyst complex mediates
ROAMP in a controlled fashion, even tolerating free hydroxyl groups
in the monomer. This polymerization exhibits excellent control, with
up to 700 degrees of polymerization of nonyne monomers with a low
to moderate molecular weight dispersity. The metal can be cleaved
from the polymer chain by means of cross-metathesis with commercially
available phenylacetylenes. Additionally, this polymerization shows
living character, which enables the preparation of block copolymers.
These results highlight the potential of Re­(V)-mediated polymerizations
to enable a broader use of ROAMP for the synthesis of functional macromolecules.

Figures