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Thermal Ring‐Opening Polymerization of Hydrocarbon‐Bridged [2]Ferrocenophanes: Synthesis and Properties of Poly(ferrocenylethylene)s and Their Charge‐Transfer Polymer Salts with Tetracyanoethylene
Author(s) -
Nelson James M.,
Nguyen Paul,
Petersen Ruth,
Rengel Heiko,
Macdonald Peter M.,
Lough Alan J.,
Manners Ian,
Raju Nandyala P.,
Greedan John E.,
Barlow Stephen,
O'Hare Dermot
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030413
Subject(s) - tetracyanoethylene , polymerization , chemistry , gel permeation chromatography , thermogravimetric analysis , polymer chemistry , polymer , cyclic voltammetry , photochemistry , organic chemistry , electrochemistry , electrode
The poly(ferrocenylethylene)s [Fe(η‐C 5 H 3 RCH 2 ) 2 ] n 5a and 5b ( a : R = H, b : R = Me) have been prepared by thermal ring‐opening polymerization of the corresponding strained hydrocarbon‐bridged [2]ferrocenophanes [Fe(η‐C 5 ‐H 3 RCH 2 ) 2 ] ( 4a and 4b ). An X‐ray diffraction study of 4a indicated significant strain. Polymer 5a was crystalline and insoluble in common organic solvents and was characterized by solid‐state 13 C NMR. Polymer 5b , which was soluble in organic solvents, was characterized by 1 H and 13 C NMR, UV/visible spectroscopy and elemental analysis. Its molecular weight distribution was bimodal (gel permeation chromatography: M w = 9.6 × 10 4 , M n = 8.6 × 10 4 for the high molecular weight fraction, M w = 4.8 × 10 3 , M n = 3.5 × 10 3 for the oligomeric fraction), suggesting two polymerization mechanisms. The UV/visible spectrum implied a localized structure for the polymer backbone. Cyclic voltammetry revealed that 5b undergoes two reversible oxidations in CH 2 Cl 2 solution at–0.25 and–0.16V. The redox coupling is indicative of only a small degree of interaction between the iron centres. Thermogravimetric analysis indicated that 5a and 5b are thermally stable to ca. 300–350°C under N 2 . At higher temperatures they yield ferromagnetic iron carbide ceramics 6a and 6b (ca. 50% and 32%, respectively, at 600°C) together with molecular depolymerization products. The reaction of 5b with tetracyanoethylene (TCNE) yielded insoluble and soluble oxidized products 11 and 12 , which differed in the degree of oligomerization of the TCNE y‐ x counterions. These products were characterized by IR, elemental analysis, ESR spectroscopy, and magnetic susceptibility measurements. The last revealed the presence of significant antiferromagnetic interactions in 12 .