The catalytic properties of neodymium tris-phosphates with various diarylphosphate ligands in the stereoregular 1,4-cis-polymerisation of butadiene and isoprene were studied. The considerable variability of the diaryl phosphate structure allowed for the systematic investigation of the dependence of the catalytic properties of neodymium tris-diarylphosphates on the electronic and steric properties of the ligand. Electron-withdrawing substituents (F, Cl, Br) in the aryl moiety increased the catalyst activity of tris-diarylphosphate. Neodymium aryl phosphates containing lipophilic bulky ligands provided the synthesis of polydienes with a monomodal molecular-weight distribution. The optimal catalytic properties demonstrated that the neodymium aryl phosphate prepared from bis(2,6-dimethy1-4-tert-butylpheny1)phosphoric acid showed high activity and ensured a monomodal MWD of polydienes (M-w/M-n similar to 2 for polybutadiene and M-w/M-n similar to 3 for polyisoprene) in various conditions. (C) 2014 Elsevier B.V. All rights reserved.