title: Probing the interactions between all components of the catalytic pool for homogeneous olefin polymerisation by diffusion NMR spectroscopy.
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 homogeneous 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 possible 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.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Perugia, Via Elce di Sotto 8, I-06123, Perugia, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Rocchigiani
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Busico
authors.forename: Antonello
authors.initials: A
authors.lastname: Pastore
authors.forename: Alceo
authors.initials: A
authors.lastname: Macchioni
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D002384:Catalysis; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D058105:Polymerization; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000475:Alkenes; D009942:Organometallic Compounds; D015040:Zirconium; D000535:Aluminum