Novel W(II) complexes for reversible addition-fragmentation chain transfer (RAFT) polymerizations

Alkylation of the phosphorus coordination of the diphenyl(dithioformato)phosphine ligand in [W(CO)5(PPh2CS2)]NEt4 (1) at the S atom results in the formation of the novel RAFT agent S═C[W(CO)5PPh2]S–R (2a, R = CH2Ph; 2b, R = CH2CH═CH2). These compounds have been shown to be highly effective in reversible addition-fragmentation chain transfer (RAFT) polymerization to produce polymers (homopolymer and diblock copolymer) of predetermined molecular weight and narrow polydispersity (< 1.3). Electron-withdrawing organometallic substituents can increase the activity of RAFT agents. To the best of our knowledge, this is the first report of their use as RAFT agents in polymerization.