Synthesis, structure, and ring-opening polymerization (ROP) of a phosphonium-bridged [1]ferrocenophane

The stable phosphonium-bridged [1]ferrocenophane [(eta-C5H4)(2)FePPhMe][OTf ] (10b) was synthesized by the reaction of the phosphorus-bridged [1]ferroc enophane (eta-C5H4)(2)FePPh (3a) with methyl triflate (MeOTf). A single-cry stal X-ray diffraction study of 10b revealed an angle of 24.4(5)degrees bet ween the planes of the cyclopentadienyl rings, less than the respective ang le (26.7 degrees) for 3a. Compound 10b and a number of other tetracoordinat e, phosphorus-bridged [1]ferrocenophanes, (eta-C5H4)(2)FeP(S)Ph (5a), (eta- C5H4)(2)FeP[Fe(CO)(4)]Ph (6), and [(eta-C5H4)(2)FePFpPh][PF6] (7) (where Fp = (eta-C5H5)Fe(CO)(2)), were investigated with respect to their ring-openi ng polymerization (ROP) behavior. Only compound 10b was found to undergo RO P, which occurred both thermally and in the presence of a transition-metal catalyst (PtCl2). The resultant ionomeric polymer {[(eta-C5H4)(2)FePPhMe][O Tf]}(n) (11) was found to be soluble in dimethylformamide (DMF), dimethyl s ulfoxide (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 degrees C and was thermally stable to weight loss up to ca. 400 degrees C. Analysis by wide-angle X-ray scatteri ng (WAXS) revealed that the polymer was amorphous. A study on the partial t o full methylation of the polymer [(eta-C5H4)(2)FePPh](n) (14) gave results that were consistent with those from the ROP of 10b. Dynamic light scatter ing studies on polymer 11 produced via thermal ROP and transition-metal-cat alyzed ROP gave hydrodynamic radii in the range of 30-45 nm, which suggeste d that the compounds were polymeric rather than oligomeric in nature. On th e basis of the glass transition temperatures for a series of samples of pol ymers 11 of known molecular weight with varying numbers of repeat units (fr om 20 to 100), the molecular weight (M-n) of the transition-metal-catalyzed ROP product was greater than 46 000 (ca. 100 repeat units) and the molecul ar weight of the thermally produced polymer was even higher.