Why propene is not polymerized by (Cp*2YH)2: reactions of yttrium alkyl complexes with alkenes produce allyl and vinyl yttrium complexes
摘要:
Yttrium alkyl complexes (Cp2YR)-Y-* react with C-H bonds of alkenes to form either yttrium allyl complexes or yttrium vinyl complexes. Less substituted alkenes react faster, consistent with prior alkene coordination. The selectivity of the reaction of (Cp2YR)-Y-* with C-H bonds is allylic CH3 much greater than vinyl C-H much greater than allylic CH2. Propene is readily metallated by (Cp2YR)-Y-* giving the eta(3)-allyl complex (Cp2Y)-Y-*(eta(3)-CH2 - CH - CH2) which does not react further with propene. This explains why (Cp2YR)-Y-* (R = alkyl, H) complexes make poor propene polymerization catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.