End Functionalization of Polynorbornene with Platinum–Acetylide Complexes Utilizing a Cross-Metathesis Reaction

The functionalization of the chain end of a polymer is gathering increasing attention in the field of synthetic polymer chemistry. The present study is the first example to demonstrate the incorporation of a platinum–acetylide complex at the terminal of a polynorbornene derivative. N-Benzyl-5-norbornene-2-exo,3-exo-dicarboxyimide (1) was polymerized with Grubbs 3rd-generation catalyst (G3). The polymerization was quenched with (Z)-1,4-bis(3-((trimethylsilyl)ethynyl)phenoxy)-2-butene (2) to obtain poly(1)′, followed by the cleavage of trimethylsilyl group and dehydroiodination coupling with trans-bis(tributylphosphine)phenylethynyl iodo platinum (3a) to obtain poly(1a), which was functionalized with a platinum complex at the chain end. Poly(1)′ exhibited no remarkable absorption around 330 nm, while poly(1a) exhibited an intense absorption based on ligand-to-metal charge-transfer transition. Poly(1b) functionalized with a naphthylamide ethynyl platinum complex was synthesized in a similar fashion. The photoluminescene color of a poly(1b) solution in CH2Cl2 changed from green to red with Ar bubbling and rapidly returned to green by ceasing Ar bubbling. A poly(1b)-containing polymethyl methacrylate film exhibited a similar trend, as was observed for the polymer in solution. The weight residues of poly(1a) and poly(1b) at 800 °C were higher than that of poly(1).