posted on 1999-02-24, 00:00authored byTimothy J. Peckham, Alan J. Lough, Ian Manners
The stable phosphonium-bridged [1]ferrocenophane [(η-C5H4)2FePPhMe][OTf] (10b) was
synthesized by the reaction of the phosphorus-bridged [1]ferrocenophane (η-C5H4)2FePPh
(3a) with methyl triflate (MeOTf). A single-crystal X-ray diffraction study of 10b revealed
an angle of 24.4(5)° between the planes of the cyclopentadienyl rings, less than the respective
angle (26.7°) for 3a. Compound 10b and a number of other tetracoordinate, phosphorus-bridged [1]ferrocenophanes, (η-C5H4)2FeP(S)Ph (5a), (η-C5H4)2FeP[Fe(CO)4]Ph (6), and [(η-C5H4)2FePFpPh][PF6] (7) (where Fp = (η-C5H5)Fe(CO)2), were investigated with respect to
their ring-opening polymerization (ROP) behavior. Only compound 10b was found to undergo
ROP, which occurred both thermally and in the presence of a transition-metal catalyst (PtCl2).
The resultant ionomeric polymer {[(η-C5H4)2FePPhMe][OTf]}n (11) was found to be soluble
in dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methanol, and acetone but
displayed only limited stability in these solvents. The thermally ring-opened polymer was
found to possess a glass transition temperature of 176 °C and was thermally stable to weight
loss up to ca. 400 °C. Analysis by wide-angle X-ray scattering (WAXS) revealed that the
polymer was amorphous. A study on the partial to full methylation of the polymer [(η-C5H4)2FePPh]n (14) gave results that were consistent with those from the ROP of 10b. Dynamic
light scattering studies on polymer 11 produced via thermal ROP and transition-metal-catalyzed ROP gave hydrodynamic radii in the range of 30−45 nm, which suggested that
the compounds were polymeric rather than oligomeric in nature. On the basis of the glass
transition temperatures for a series of samples of polymers 11 of known molecular weight
with varying numbers of repeat units (from 20 to 100), the molecular weight (Mn) of the
transition-metal-catalyzed ROP product was greater than 46 000 (ca. 100 repeat units) and
the molecular weight of the thermally produced polymer was even higher.