Edge-bridged half-open zirconocenes: Synthesis, characterization, and reaction with diphenylacetylene

The synthesis and characterization of the new, 16 electron half-open zirconocenes, Zr(C5H5)(c-C8H11)(PR3) (R = Me, Et) are reported, together with a structural study of the PEt3 complex. As with other low valent half-open zirconocenes, the Zr–C distances are significantly shorter on average for the electronically open dienyl ligand than those for the C5H5 ligand, 2.343 vs. 2.512 Å. Reaction of either of these compounds with PhC2Ph led to the incorporation of two equivalents of the alkyne, resulting in a formally 14 electron complex with coordination from cyclopentadienyl, allyl, σ-alkyl, and σ-vinyl units.

Graphical abstractThe synthesis and characterization of the half-open zirconocene, Zr(C5H5)(c-C8H11)(PEt3) (c-C8H11 = cyclooctadienyl), is described. The compound shows shorter Zr–C distances for the cyclooctadienyl ligand, in accord with expectations of stronger Zr–C bonding relative to C5H5. This compound reacts with two equivalents of diphenylacetylene to yield a bicyclic coupling product.Figure optionsDownload full-size imageDownload as PowerPoint slide