Quantification of ultrasound-induced chain scission in PdII-phosphine coordination polymers.
A kinetically inert, reversible coordination polymer (3) was obtained through complexation of dicyclohexylphosphine telechelic poly(tetrahydrofuran) with palladium(II) dichloride. This coordination polymer is unreactive towards palladium(II) dichloride bis(1-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 (31)P 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 alkyldiphenylphosphine stopper complex, the reduction in molecular weight was strongly enhanced; over a period of eight hours the weight-averaged molecular weight was reduced from 1.1x10(5) to 2.3x10(4) g mol(-1) while 47 % of the palladium(II) 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.
Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Jos M J
JM
Paulusse
Jeroen P J
JP
Huijbers
Rint P
RP
Sijbesma