End Group Functionalization of PFpP Macromolecules Via Fp Migration Insertion Reactions

Chain-Conformation-Directed Polymerization Cyclization for Effective Synthesis of Macrocycles in Bulk

Biological cyclization is highly efficient, and this can be attributed to the conformation of the backbone of the biopolymer. Taking advantage of metal-coordination geometry, we developed a method for conformation-directed polymerization cyclization through rational design of metal carbonyl monomers that could be used to produce cyclic macromolecules, even in bulk. ^P FpR [^P Fp=(PPh₂ (CH₂ )₃ Cp)Fe(CO)₂ with the phosphine group tethered on the cyclopentadiene (Cp) ring; R=CH₃ or (CH₂ )₅ CH₃ ] was designed and synthesized for migration insertion polymerization to generate P(^P FpR) with the polymer backbone containing Cp-Fe bonds. Growth of the backbone led to a cyclic conformation with close end-to-end distances, which facilitated the cyclization. This conformation-directed cyclization was attributed to the piano-stool metal-coordination geometry of the repeating units and the low rotational barrier of the Cp-Fe bonds in the backbone. The produced macrocycles, which contain a metal carbonyl coordination structure in their backbones, are rigid, unlike many organic macrocycles. The macrocycles thus have a large excluded volume. This new type of metal carbonyl macrocycle will be of interest as a building block for supramolecular chemistry and in the exploration of novel materials.

Flexibility and Stability of Metal Coordination Macromolecules

The effect of chain structure on flexibility and stability of macromolecules containing weak P-Fe metal coordination bonds is studied. Migration insertion polymerization (MIP) of FpC_X Fp (1) and PR₂ C_Y PR₂ (2) (Fp: CpFe(CO)₂ ; C_X and C_Y : alkyl spacers; P: phosphine; R: phenyl or isopropyl) generates P(1/2), in which the P-Fe and Fe-P bonds with opposite bonding direction are alternatively arranged in the backbone. On the other hand, P(FpC_X P) synthesized from AB-type monomers (FpC_X P) has P-Fe bonds arranged in the same direction. P(1/2) is more rigid and stable than P(FpC_X P), which is attributed to the chain conformation resulting from the P-Fe bonding direction. In addition, the longer spacers render P(1/2) relatively flexible; the phenyl substituents, as compared with the isopropyl groups, improves the rigidity, thermal, and solution stability of P(1/2). It is therefore possible to incorporate weak metal coordination bonds into macromolecules with improved stability and adjustable flexibility for material processing.

Facile preparation of a novel nickel-containing metallopolymer via RAFT polymerization

While the metallocene polymers were comprehensively studied, other metallopolymers are rarely explored. The major challenge is the lack of a synthetic platform for the preparation of metal coordinated derivatives, monomers, and polymers. Therefore, the development of a facile synthesis of new metal coordinated monomers and polymers is critically needed. A novel successfully synthesized methacrylate-containing nickel complex is reported in this communication. Controlled RAFT polymerizations are further carried out to prepare a series of side-chain nickel containing polymers with different molecular weight and narrow Polydispersity Index (PDI). This new metallopolymer performs specific electrochemical and excellent thermal properties. This study provides a novel and convenient strategy to prepare metallopolymer with controllable molecular weight, which has potential applications in assembled, catalytic and magnetic materials.

Solvent-dependent chain conformation for ring closure of metal carbonyl oligomers via migration insertion polymerization (MIP) of CpFe(CO)2(CH2)6PPh2

Solvent-induced chain conformation of cyclic PFpC6P via the migration insertion polymerization of CpFe(CO)₂(CH₂)₆PPh₂ (FpC6P) in THF/hexane mixed solvents.