Metallation of functional resins with copper acetate: control of metal speciation and catalytic activity in C-N coupling reactions

Moderately cross-linked gel-type acidic ion-exchangers (0.8-1.0 meq. H+/g) obtained upon copolymerization of dimethylacrylamide (DMAA), methylenebisacrylamide (MBAA) and methacrylic acid (MAA) or sulfoethyl methacrylate (SEMA) were reacted with Cu(OAc)(2) under different initial H+/Cu(II) molar ratios. The metal speciation inside the polymer networks was characterized on the basis of analytical and spectroscopic data. Depending on the kind of ion-exchanger and reaction conditions employed, different species were identified. The kind of metal speciation appears to have a profound influence on the catalytic activity of the resulting resin-supported copper species in C-N coupling reactions. Use of a resin containing the proper copper species results in a catalytic performance superior to that of unsupported copper acetate.