Quantification of ultrasound-induced chain scission in PdII-phosphine coordination polymers

A kinetically inert, reversible coordination polymer (3) was obtained through complexation of dicyclohexyl-phosphine telechelic poly (tetrahydro furan) with palladium(II) dichloride. This coordination polymer is unreactive towards palladium(II) dichloride bis(l-diphenylphosphino)dodecane (4), because ligand dissociation in the coordination polymer is slow. However, upon ultrasonication of solutions of 3 in toluene in the presence of 4, formation of palladium(II) heterocomplexes was observed With P-31 NMR spectroscopy. Heterocomplex formation, the consumption of 4, and changes in molecular weight were used to quantify the scission process. In the presence of 60 equivalents of the alkyldiphenyl-phosphine stopper complex, the reduction in molecular weight was strongly enhanced; over a period of eight hours the weight-averaged molecular weight was reduced from 1.1 x 10(5) to 2.3 x 10(4) gmol(-1) while 47% of the palladium(n) complexes in the coordination polymer had been converted into heterocomplexes. These results show that the system of 3 in combination with scavenger 4 is a suitable system to study the efficiency of ultrasound-induced chain scission of coordination polymers.