Cobalt-catalyzed alternating and nonalternating copolymerization of carbon monoxide with aziridine

Advances in heterometallic ring-opening (co)polymerisation catalysis

Truly sustainable plastics require renewable feedstocks coupled with efficient production and end-of-life degradation/recycling processes. Some of the most useful degradable materials are aliphatic polyesters, polycarbonates and polyamides, which are often prepared via ring-opening (co)polymerisation (RO(CO)P) using an organometallic catalyst. While there has been extensive research into ligand development, heterometallic cooperativity offers an equally promising yet underexplored strategy to improve catalyst performance, as heterometallic catalysts often exhibit significant activity and selectivity enhancements compared to their homometallic counterparts. This review describes advances in heterometallic RO(CO)P catalyst design, highlighting the overarching structure-activity trends and reactivity patterns to inform future catalyst design.

Copper(i) oxide nanoparticle-mediated C–C couplings for synthesis of polyphenylenediethynylenes: evidence for a homogeneous catalytic pathway

Polyphenylenediethynylenes have been synthesized using copper(i) oxide nanocatalysts under ligandless conditions, mild base, and atmospheric air as the oxidant in good yield and number average molecular weight.

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

The synthesis of aziridine and azetidine monomers and their ring-opening polymerization via different mechanisms is reviewed.

Metal-catalyzed synthesis of alternating copolymers

The creation of polymers with a high degree of sequence and/or stereocontrol represents an exciting frontier in materials science. In order to obtain alternating polymers, coordination polymerization using well-defined metal complexes has played a leading role in the last two decades. In the following paper, we will describe selected published efforts to achieve these research goals using discrete, structurally well-characterized metal complexes.

Poly(beta-alanoid-block-beta-alanine)s: synthesis via cobalt-catalyzed carbonylative polymerization and self-assembly

The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(beta-alanine) block is solubilized by the poly(beta-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.

Carbonylation of heterocycles by homogeneous catalysts

This article summarizes the recent developments (particularly the uses of homogeneous organometallic catalysts) in ring-opening carbonylations, ring-opening carbonylative polymerizations and ring-expansion carbonylations of heterocycles such as epoxides, aziridines, lactones and oxazolines.

Mechanistic studies of the copolymerization reaction of aziridines and carbon monoxide to produce poly-beta-peptoids

The coupling of carbon monoxide and aziridines has been shown to be selective for comonomer-alternating enchainment in the presence of PhCH2C(O)Co(CO)4 to afford poly-beta-peptoids. In this article, we have investigated the mechanistic aspects of the reaction of CO and N-butylaziridine by means of in situ infrared spectroscopy employing CH3C(O)Co(CO)3L (L = PPh3 (1) and P(o-tolyl)3 (2)) as precatalysts. Precatalyst 1 exists in solution under catalytic conditions as an equilibrium mixture of 1 and CH3C(O)Co(CO)4, and affords both poly-beta-butylalanoid and the corresponding lactam. By way of contrast, precatalyst 2 which possesses the sterically bulky and labile P(o-tolyl)3 ligand, affords only the acyl cobalt tetracarbonyl species in solution during catalysis with concomitant selective production of the copolymer. Kinetic studies conducted with precatalyst 2 showed the coupling reaction to have a first order dependence on catalyst, a first order dependence on N-butylaziridine, and only a slight dependence on the concentration of CO over the pressure range 17-69 bar. The working mechanistic model for the copolymerization reaction involves first aziridine insertion into the cobalt-acyl bond, rate determining ring opening by the cobaltate species, followed by the migratory CO insertion.