Synthesis of a Tris (4-phenylfluoro)(p-tolyl) Phosphonium Salt as a Monomer for SNAr Substitution
Both poly(arylene ether ketone)s (PAEKs) and poly(phosphonium salts) (PPSs) have been areas of some interest due to their respective uses as high performance thermoplastics and ion-transfer membrances. 1,2 There has been much research on PAEK polymers and a few reports of PPSs, but we know of no report of a poly(arylene ether phenylphosphonium_ polymer (PAEP), which would combine these two structural motifs. Three separate routes have been attempted to synthesize tris(4-fluorophenyl)(p-tolyl) phosphonium (TFPP) as a monomer which can be used to produce a PAEP. First, small scale photochemical reactions of bis(4-methylphenyl) iodonium hexaflurophosphate and tris(4-flurophenyl) phospine (TFP) in acetone-d6 produced excellent conversion (100%) to TFPP. However, scaling the reaction up in acetone gave severely lowered conversion (<1%). Second, p-tolyldiazonium hexaflurophosphate was prepared and reacted with TFP giving an unexpected product. Finally, the nickel(II) chloride catalyzed reaction of p-bromotoluene with TFP in ethanol under high pressure (200 psi) and heat (160 degree C) in a microwave reactor produced low conversions to TFP (33%) (Eq 1) and were problematic due to the reaction vessels venting at the conditions required in the experimental procedure. This research is to be continued during the 2014-2015 academic year.
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