Flexibility and Stability of Metal Coordination Macromolecules

Abstract

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 Fp (1) and PR C PR (2) (Fp: CpFe(CO) ; C and C : 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 P) synthesized from AB-type monomers (FpC P) has P-Fe bonds arranged in the same direction. P(1/2) is more rigid and stable than P(FpC 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.

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

“…We developed migration insertion polymerization (MIP) that can polymerize FpP [Fp=CpFe(CO) 2 , Cp=cyclopentadiene; P=alkyldiphenylphosphine] and other metal carbonyl monomers under a step‐growth mechanism to generate P(FpP) and its analogues (Figure a) . One interesting feature of P(FpP) is the piano‐stool metal coordination geometry of the repeating units, which is nonlinear and accounts for various chain conformations depending on the solution conditions and the backbone structures . The MIP of FpP in either bulk or THF generates extended P(FpP) chains with NMR spectroscopy detectable end groups (Figure a) .…”

“…[5c, 8] This polymerization cyclization is attributed to the conformationo ft he polymer chain,but it is less studied than other routes.Bytaking advantage of the metal coordinationg eometries [9] and the nature of coordination bonds, main-chain organometallic polymers are ideal systemst oe xplore conformation-directed polymerization cyclization. [8] We developedm igration insertion polymerization (MIP) that can polymerize FpP [Fp = CpFe(CO) 2 ,C p = cyclopentadiene; P = alkyldiphenylphosphine] [10] and other metal carbonyl monomers [11] under as tep-growth mechanism [12] to generate P(FpP)a nd its analogues ( Figure 1a). [13] One interesting feature of P(FpP) is the piano-stoolm etal coordination geometry of the repeating units, [13] which is nonlineara nd accounts for various chain conformations depending on the solution conditions and the backbones tructures.…”

“…[13] One interesting feature of P(FpP) is the piano-stoolm etal coordination geometry of the repeating units, [13] which is nonlineara nd accounts for various chain conformations depending on the solution conditions and the backbones tructures. [11,14] The MIP of FpP in either bulk or THF generates extended P(FpP) chains with NMR spectroscopy detectable end groups ( Figure 1a). [10b, 12, 13, 15] This linear growth is attributed to the directional FeÀCa nd FeÀphosphine metalc oordination bonds that extend the chains and prevent intramolecular reaction of the end groupsfor cyclization.…”