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

Abstract

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

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

“…This suggests that 2 b possesses no unreacted Fp or uncoordinated phosphine end groups (Figure S16 a, b). Compound 2 b is, therefore, a macrocycle . Further experiments indicate that the MIP of both 1 a and 1 b in either bulk or THF generates corresponding 2 a and 2 b without detectable end groups (Figures S5 c, S14, and S15).…”

“…Further experiments indicate that the MIP of both 1 a and 1 b in either bulk or THF generates corresponding 2 a and 2 b without detectable end groups (Figures S5 c, S14, and S15). The MIP of P FpR is, therefore, a cyclization process and c ‐P( P FpR) is produced …”

“…In contrast, the R e of P(FpP) (Figure b) increases from 13.84 to 62.55 Å (Figure S23 a) as the DP is varied from 5 to 30. This larger R e renders the cyclization difficult during the MIP of FpP either in bulk or THF (Figure b) . The circular chain conformation of P( P FpR) is attributed to the incorporation of Cp−Fe bonds in the main chain of the polymer.…”

“…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) .…”

“…[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.…”