Diffusion NMR spectroscopy was applied to investigate all individual components and combinations thereof for the Cp2ZrMe2/MAO (DMAO)/TBP (MAO = methylaluminoxane, DMAO = AlMe3 depleted MAO, TBP = 2,6-di-tert-butylphenol) ternary system, selected as a prototypical catalytic pool for homo- geneous olefin polymerisation. Both MAO and DMAO were found to self-aggregate in C6D6 with the latter having a higher propensity. TBP reacts with DMAO affording MeAl(2,6-di-tert-butylphenoxide)2 and causing a structural modification of DMAO, whose aggregates become much larger. The actual dimensions and self-aggregation tendency of (D)MAO, which depend on Al concentration and the poss- ible presence of TBP, turned out to carry over to [Cp2Zr(μ-Me)2AlMe2]MeMAO (1) OSIP (outer sphere ion pair) and [Cp2Zr+Me⋯MeMAO"] (2) ISIP (inner sphere ion pair) that form upon activation of Cp2ZrMe2. Once the intrinsic self-aggregation tendency of MAO has been subtracted, OSIP 1 and ISIP 2 behave exactly as analogous ion pairs with borate ions: ISIP 2 does not self-aggregate, whereas OSIP 1 exhibits the same self-aggregation trends of zirconocene OSIPs with borate counterions.
Probing the interactions between all components of the catalytic pool for homogeneous olefin polymerisation by diffusion NMR spectroscopy
ROCCHIGIANI, LUCA;MACCHIONI, Alceo
2013
Abstract
Diffusion NMR spectroscopy was applied to investigate all individual components and combinations thereof for the Cp2ZrMe2/MAO (DMAO)/TBP (MAO = methylaluminoxane, DMAO = AlMe3 depleted MAO, TBP = 2,6-di-tert-butylphenol) ternary system, selected as a prototypical catalytic pool for homo- geneous olefin polymerisation. Both MAO and DMAO were found to self-aggregate in C6D6 with the latter having a higher propensity. TBP reacts with DMAO affording MeAl(2,6-di-tert-butylphenoxide)2 and causing a structural modification of DMAO, whose aggregates become much larger. The actual dimensions and self-aggregation tendency of (D)MAO, which depend on Al concentration and the poss- ible presence of TBP, turned out to carry over to [Cp2Zr(μ-Me)2AlMe2]MeMAO (1) OSIP (outer sphere ion pair) and [Cp2Zr+Me⋯MeMAO"] (2) ISIP (inner sphere ion pair) that form upon activation of Cp2ZrMe2. Once the intrinsic self-aggregation tendency of MAO has been subtracted, OSIP 1 and ISIP 2 behave exactly as analogous ion pairs with borate ions: ISIP 2 does not self-aggregate, whereas OSIP 1 exhibits the same self-aggregation trends of zirconocene OSIPs with borate counterions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
