Hybrids by cluster complex-initiated polymerization

Two [Re ₆Se ₈] ²⁺ core-containing cluster complexes with a ligand capable of initiating controlled radical polymerization were prepared. The potential of using such cluster complexes to create cluster-containing hybrids was demonstrated by the polymerization of MMA with one of these complexes as initiator. The synthesis of the organic initiator (pyridin-4-ylmethyl 2-bromo-2-methylpropanoate) was achieved by acylation of pyridine-4-methanol with α-bromoisobutyryl bromide. Originally obtained using CH ₂Cl ₂ as solvent produced a complex mixture, from which pure product was obtained by chromatographic separation. Significant improvement was achieved by substituting 2,2'-dipyridyl for pentamethyldiethylenetriamine (PMDEA) as ligand for the Cu(I) catalysts and dimethylformamide (DMF) for acetonitrile (CH ₃CN) as solvent; both are less coordinating toward the cluster core.