The niobium N,N-dialkylcarbamates Nb(O(2)CNR(2))(n) [n = 5, R = Me, 1, Et, 2; n = 4, R = Et, 3; n = 3, R = Et, 4], in combination wits organoaluminum cocatalysts, were found to be active in the polymerization of ethylene. The effects of the main reaction parameters (solvent, ethylene pressure, time, temperature, cocatalyst, reactivator) on the polymerization reaction were investigated in detail. When 2 was used as precursor in combination with trimethylaluminum (TMA)-depleted MAO and 1,2-dichloroethane as reactivator, activity up to 110 kg(polyethylene) mol(Nb)(-1) h(-1) bar(-1) ascertained and linear, high molecular weight polyethylene was produced. The catalytic activities related to the different precursors increase along the series 2 > 1 > 3 > 4. The 1:1 reaction of 2 with Al(2)Et(3)Cl(3) proceeds via ligand exchange, giving the X-ray characterized mixed alkyl-carbamato derivative [Al(3)(mu-O(2)CNEt(2))(6)Et(2)]Cl (6), in admixture with presumable species containing niobium in lower oxidation state. The latter and not the former seem to be responsible for directing the polymerization process, according to the evidence that 6, produced by ligand exchange between Al(O(2)CNEt(2))(3) and AlEt(2)Cl, is not active under analogous experimental conditions.
F. Marchetti, G. Pampaloni, Y. Patil, A. M. Raspolli Galletti, F. Renili, S. Zacchini (2011). Ethylene Polymerization by Niobium(V) N,N-dialkylcarbamates Activated with Aluminum Co-catalysts. ORGANOMETALLICS, 30, 1682-1688 [10.1021/om101187k].
Ethylene Polymerization by Niobium(V) N,N-dialkylcarbamates Activated with Aluminum Co-catalysts
ZACCHINI, STEFANO
2011
Abstract
The niobium N,N-dialkylcarbamates Nb(O(2)CNR(2))(n) [n = 5, R = Me, 1, Et, 2; n = 4, R = Et, 3; n = 3, R = Et, 4], in combination wits organoaluminum cocatalysts, were found to be active in the polymerization of ethylene. The effects of the main reaction parameters (solvent, ethylene pressure, time, temperature, cocatalyst, reactivator) on the polymerization reaction were investigated in detail. When 2 was used as precursor in combination with trimethylaluminum (TMA)-depleted MAO and 1,2-dichloroethane as reactivator, activity up to 110 kg(polyethylene) mol(Nb)(-1) h(-1) bar(-1) ascertained and linear, high molecular weight polyethylene was produced. The catalytic activities related to the different precursors increase along the series 2 > 1 > 3 > 4. The 1:1 reaction of 2 with Al(2)Et(3)Cl(3) proceeds via ligand exchange, giving the X-ray characterized mixed alkyl-carbamato derivative [Al(3)(mu-O(2)CNEt(2))(6)Et(2)]Cl (6), in admixture with presumable species containing niobium in lower oxidation state. The latter and not the former seem to be responsible for directing the polymerization process, according to the evidence that 6, produced by ligand exchange between Al(O(2)CNEt(2))(3) and AlEt(2)Cl, is not active under analogous experimental conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
