Two pyridylphosphine ligands, 2-(diphenylphosphino)pyridine (DPPP) and 2-[(diphenylphosphino)methyl]pyridine (DPPP), were investigated as complexing ligands in the iron-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and styrene with various initiators and solvents. In studies of their ATRP behavior, the FeBi2,/DPPP catalytic system was a more efficient ATRP catalyst for the MMA polymerization than the other complexes studied in this paper. Most of these systems were well controlled with a linear increase in the number-average molecular weights (M-n) vs. Conversion and relatively low molecular weight distributions (M-w/M-n = 1.15-1.3) being observed throughout the reactions, and the measured molecular weights matched the predicted values with the DPPP ligand. The polymerization rate of MMA attained a maximum at a ratio of ligand to metal of 2:1 in p-xylene at 80 degrees C. The polymerization was faster in polar solvents than in p-xylene. The 2-bromopropionitrile (BPN) initiated ATRP of MMA with the FeX2/DPPP catalytic system (X = Cl, Br) was able to be controlled in P-xylene at 80 degrees C. The polymerization of styrene was able to be controlled using the PECI/FeCl2/DPPP system in DMF at 110 degrees C. (c) 2007 Elsevier Ltd. All rights reserved.