THERMAL RING-OPENING POLYMERIZATION OF HYDROCARBON-BRIDGED [2]FERROCENOPHANES - SYNTHESIS AND PROPERTIES OF POLY(FERROCENYLETHYLENE)S AND THEIR CHARGE-TRANSFER POLYMER SALTS WITH TETRACYANOETHYLENE

The poly(ferrocenylethylene)s [Fe(eta-C5H3RCH2)(2)](n) 5a and 5b (a: R = H, b: R = Me) have been prepared by thermal ring-opening polymeriza tion of the corresponding strained hydrocarbon-bridged [2]ferrocenopha nes [Fe(eta-C-5-H3RCH2)(2)] (4a and 4b). An X-ray diffraction study of 4a indicated significant strain. Polymer 5a was crystalline and insol uble in common organic solvents and was characterized by solid-state C -13 NMR. Polymer 5b, which was soluble in organic solvents, was charac terized by H-1 and C-13 NMR, UV/visible spectroscopy and elemental ana lysis. Its molecular weight distribution was bimodal (gel permeation c hromatography: M-w = 9.6 x 10(4), M-n = 8.6 x 10(4) for the high molec ular weight fraction, M-w = 4.8 x 10(3), M-n = 3.5 x 10(3) for the oli gomeric fraction), suggesting two polymerization mechanisms. The UV/vi sible spectrum implied a localized structure for the polymer backbone. Cyclic voltammetry revealed that 5b undergoes two reversible oxidatio ns in CH2Cl2 solution at -0.25 and -0.16 V. The redox coupling is indi cative of only a small degree of interaction between the iron centres. Thermogravimetric analysis indicated that 5a and 5b are thermally sta ble to ca. 300-350 degrees C under N-2. At higher temperatures they yi eld ferromagnetic iron carbide ceramics 6a and 6b (ca. 50% and 32%, re spectively, at 600 degrees C) together with molecular depolymerization products. The reaction of 5b with tetracyanoethylene (TCNE) yielded i nsoluble and soluble oxidized products 11 and 12, which differed in th e degree of oligomerization of the TCNxy- counterions. These products were characterized by IR, elemental analysis, ESR spectroscopy, and ma gnetic susceptibility measurements. The last revealed the presence of significant antiferromagnetic interactions in 12.