Synthesis of Ethylene-co-Norbornene Polymers Promoted by MAO Free Catalysts Based on Group 4 Dicarbollide Complexes

Ethylene-co-norbornene polymers [P(E-co-N)s] have been synthesized with the dicarbollide catalysts (η 5 -C 2 B 9 H 12 )M(NEt 2 ) 2 (NHEt 2 ) [M = Ti (1), Zr (2)] activated with methylaluminoxane (MAO) or alkylaluminium compounds, as AIMe 3 (TMA), Al( i Bu) 3 (TIBA), AlH( i Bu) 2 (DIBALH), AlEt 2 Cl (DEAC). Polymerization results by 1-TIBA, 2-TIBA, 1-MAO and 2-MAO catalysts have been preliminary compared with those of cyclopentadienyl derivatives of the group 4 metals, (η 5 -C 5 R 5 )TiX 3 [R = H, X = Cl (3); R = Me, X = Cl (4), Me(5)], (η C 5 H 5 )ZrCl 3 (6), ethylenebis(1-indenyl) zirconium dichloride (7) and Cp-free compounds M(NEt 2 ) 4 [M = Ti (8), Zr (9)] precursors of the dicarbollide compounds 1-2, under the same conditions (T p = 50°C, [M] = 1 × 10 -3 M; P E = 1 atm; [N] = 1.75 M). The 1-TIBA and 2-TIBA catalysts exhibit productivity values greater than the corre sponding MAO activated system and incorporate high concentration of the cyclic monomer in the copolymer products (N mol-% = 38-45). Crystalline blocks of isotactic alternating NENE sequences were identified in the P(E-co-N)s copolymers produced by these catalysts by means of 13 C NMR and DSC analysis. The dicarbollide derivatives 1 and 2 were also efficiently activated with the alkyl aluminium compounds TMA, DIBALH and DEAC at very low Al/M molar ratio (Al/M = 10); the titaniun and zirconium cyclopentadienyl derivatives 3,4,6,7 are inactive under these conditions.