Unusual Hafnium–Pyridylamido/ERn Heterobimetallic Adducts (ERn=ZnR2 or AlR3) |
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| Authors: | Dr. Luca Rocchigiani Prof. Vincenzo Busico Dr. Antonello Pastore Prof. Dr. Giovanni Talarico Prof. Dr. Alceo Macchioni |
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| Affiliation: | 1. Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di sotto, 8, 06123 Perugia (Italy);2. Dutch Polymer Institute (DPI), PO box 902, 5600 AX Eindhoven (The Netherlands);3. Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli (Italy) |
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| Abstract: | NMR spectroscopy and DFT studies indicate that the Symyx/Dow Hf(IV)–pyridylamido catalytic system for olefin polymerization, [{N?,N,CNph?}HfMe][B(C6F5)4] ( 1 , Nph=naphthyl), interacts with ERn (E=Al or Zn, R=alkyl group) to afford unusual heterobimetallic adducts [{N?,N}HfMe(μ‐CNph)(μ‐R)ERn?1][B(C6F5)4] in which the cyclometalated Nph acts as a bridge between Hf and E. 1H VT (variable‐temperature) EXSY NMR spectroscopy provides direct evidence of reversible alkyl exchanges in heterobimetallic adducts, with ZnR2 showing a higher tendency to participate in this exchange than AlR3. 1‐Hexene/ERn competitive reactions with 1 at 240 K reveal that the formation of adducts is strongly favored over 1‐hexene polymerization. Nevertheless, a slight increase in the temperature (to >265 K) initiates 1‐hexene polymerization. |
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| Keywords: | bimetallic compounds metal– alkyl compounds molecular modeling NMR spectroscopy polymerization |
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