Novel <i>ansa</i>-Metallocenes with a Single Boron Atom in the Bridge:  Syntheses, Reactivities, and X-ray Structures of {Ph(L)B(η⁵-C₅H₄)₂}ZrCl₂ (L = SMe₂, PMe₃)

Abstract

The syntheses and X-ray crystal structures of the boron-bridged ansa-metallocene complexes [{Ph(Me2S)B(η5-C5H4)2}ZrCl2]·C6D6 (2) and [{Ph(Me3P)B(η5-C5H4)2}ZrCl2] (3) are reported. Complex 2 is obtained as the product of a double dehalodesilylation reaction between PhB(C5H4SiMe3)2 and ZrCl4(SMe2)2. The dimethyl sulfide adduct of 2 is readily replaced with trimethylphosphine to afford 3. Efforts to alkylate 2 were unsuccessful, presumably due to the lability of the dimethyl sulfide and, hence, its inability to protect the boron bridge from nucleophilic attack by alkyl anions. In contrast, the trimethylphosphine adduct in 3 binds tightly enough to the boron bridge to protect it from nucleophilic attack. Also, unlike 2, complex 3 is activated by methylalumoxane toward the polymerization of ethylene.