Synthesis, structure, and ethene polymerisation catalysis of 1- or 2-silyl substituted bis[indenyl]zirconium(iv) dichlorides

Arylallenes and the halogeno-B(C6F5)2 reagents: facile formation of 2-borylindenes

Allenylarenes are converted to the respective 2-borylindenes by treatment with chloro- or bromobis(pentafluorophenyl)borane.

Diisobutylaluminum hydride promoted cyclization of o-(trimethylsilylethynyl)styrenes to indenes

The reaction of o-(trimethylsilylethynyl)styrenes with diisobutylaluminum hydride (DIBAL-H) provides 2-trimethylsilyl-1H-indenes efficiently. The cyclization mechanism involves regioselective hydroalumination of the alkynyl moiety, geometrical isomerization of the alkenylaluminums formed, and intramolecular carboalumination. With substrates bearing a 2-(trimethylsilyl)ethenyl group (R(1) = Me3Si, R(2) = R(3) = H), bis-silylated benzofulvenes are obtained upon treatment of the reaction mixture with an excess amount of benzaldehyde.

A general one-pot synthesis for elusive 2-substituted indenes: does bis[2-(tert-butyl)indenyl]zirconium(IV) dichloride/MAO polymerise ethene?

Among the 2-substituted indenes, 2-trifluoroindene and 2-tert-butylindene are poorly or incompletely described in the open literature. We herein describe an efficient one-pot synthesis of these compounds as a variation of the Perkin reaction which allows us to refute an earlier claim that bis(2-tert-butylindenyl)zirconium(IV) dichloride (2a) will not polymerise ethene. In fact, 2a/MAO polymerises ethene to extremely high molecular weights. Extensive DFT calculations on the polymerisation mechanism revealed an unprecedented suppression of the otherwise predominant chain termination by beta-hydride transfer due to steric congestion of the active site.