PENTAMETHYLCYCLOPENTADIENYL LIGAND ACTIVATION IN A CATIONIC ZIRCONOCENE COMPLEX - FORMATION OF AN UNUSUAL PENDANT ALLYL LIGAND WITH 1,3-BUTADIENE

Activation of a C5Me5 ligand on reaction of (C5Me5)2ZrMe{B(4-C6H4F)4} (1) with excess 1,3-butadiene affords an unusual linked cyclopentadienyl-allyl ligand in [(C5Me5)Zr{eta5:eta3-C5Me4(CH2CH2CHCHCH2)}]+ (2). Formation of 2 proceeds via elimination of 2-pentene from an observable eta3-allyl intermediate, followed by trapping of the putative tetramethylfulvene product by diene insertion. Stable Lewis-base-free eta3-allyl complexes, [Cp'2Zr{eta3-CH2C(Me)CH2}]+ (Cp' = C5Me5 (3b), (Me3C)C5H4 (3c)), are obtained with 1,2-propadiene.