Unusual Hafnium–Pyridylamido/ER n Heterobimetallic Adducts (ER n =ZnR 2 or AlR 3 )

NMR spectroscopy and DFT studies indicate that the Symyx/Dow Hf(IV)–pyridylamido catalytic system for olefin polymerization, [{N − ,N,C Nph − }HfMe][B(C 6 F 5 ) 4 ] ( 1 , Nph=naphthyl), interacts with ER n (E=Al or Zn, R=alkyl group) to afford unusual heterobimetallic adducts [{N − ,N}HfMe(μ‐C Nph )(μ‐R)ER n −1 ][B(C 6 F 5 ) 4 ] in which the cyclometalated Nph acts as a bridge between Hf and E. 1 H VT (variable‐temperature) EXSY NMR spectroscopy provides direct evidence of reversible alkyl exchanges in heterobimetallic adducts, with ZnR 2 showing a higher tendency to participate in this exchange than AlR 3 . 1‐Hexene/ER n 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.