Silicon–Carbon bond cleavage reactions of Ansa tungstenocene compounds: The [Me ₂ Si] bridge as a site for metallocene functionalization

Abstract

A nsa bridges, i.e., substituents that link together two cyclopentadienyl groups, have been shown to exert a profound effect on the reactivity of a metallocene system. For example, we have recently described how a [Me 2 Si] ansa bridge modulates the reactivity of permethylated metallocene complexes (1-10). In each of these examples, the [Me 2 Si] ansa bridge is merely a substituent that modifies the chemistry of the system due to (i) an inductive effect and (ii) a structural effect that displaces the cyclopentadienyl groups from their natural positions. )WH resulting from cleavage and functionalization of the ansa bridge (Scheme 3). The molecular structure of (Cp Me 2 )( 5 , 1 -C 5 H 2 Me 2 SiMe 2 CH 2 )WH has been determined by x-ray diffraction, as illustrated in Fig. 3.A plausible sequence for formation of (Cp Me 2 )( 5 , 1 -C 5 H 2 Me 2 SiMe 2 CH 2 )WH involves initial nucleophilic attack at the silicon atom by MeLi, thereby breaking the Si-cyclopentadienyl bond and forming a trimethylsilylcyclopentadienyl derivative (Scheme 4). Precedent for this transformation is provided by the organolithium induced ring-opening polymerization of the ferrocene derivative [Me 2 Si(Cp) 2 ]Fe (15), although the latter process is Author contributions: C.E.Z. and G.P. designed research; C.E.Z., H.L., S.H.J., and K.P. performed research; C.E.Z., H.L., S.H.J., K.P., and G.P. analyzed data; and C.E.Z., H.L., S.H.J., K.P., and G.P. wrote the paper.

Strain-Induced Cleavage of Carbon−Carbon Bonds: Bridge Rupture Reactions of Group 8 Dicarba[2]metallocenophanes

“…The second ligand is bound in an η 4 fashion and appears to have significant fulvene character. The formation of M−C bonds of this type in ‘tuck-in’ metallocenes is relatively rare, however, several structurally characterized examples incorporating a variety of transition metals have been reported …”