An insight into the beginning stage of the aqueous ring opening metathesis polymerization of exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid with RuIII compounds: the consumption of RuIII species in the presence of carboxylic acids monitored by ESR spectroscopy

The presence of paramagnetic species in the aqueous ring opening metathesis polymerizations of the exo,exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid monomer with RuCl3 and K2[RuCl5H2O] compounds was studied using ESR techniques. It was observed that the intensities of the RuIII signals in the ESR spectra decrease on the time scale of the induction period so that the ROMP can take place. The intensity of the RuIII signal almost disappeared 50 min after reacting with K2[RuCl5H2O] and after 100 min in the case of RuCl3. Reactions of the cis-[Ru(NH3)4(H2O)2](tfms)3 and [Ru(NH3)5H2O](tfms)3 complexes with the monomer and different organic compounds representing the organic functions in the monomer (furan, norbornene, but-2-ene-1,4-diol and formic, acetic, oxalic and maleic acids) were also monitored by ESR and UV/vis spectra. It was deduced that the organic acids provide the disappearance of the RuIII signal. The proton NMR relaxation times of the residual water in D2O for reactions with oxalic acid suggested that the presence of paramagnetic ions in the solution decreases along with the disappearance of the ESR signal for RuIII. It was suggested that diamagnetic Ru species were indeed produced in the medium.