RING-OPENING REACTION OF A DIHYDROZIRCONAFURAN (=2,5-DIHYDRO-1,2-OXAZIRCONOLE) - AN EQUILIBRIUM STUDIED BY NMR METHODS, AND ITS CHEMICAL CONSEQUENCES

摘要

The dihydrozirconafuran 3 (2,2-di(cyclopenta-2,4-dien-1-yl)-2,5-dihydro-5,5-dimethyl-3,4- bis(trimethylsilyl)-1,2-oxazirconole) is a valuable synthetic equivalent to the 14-electron fragment Cp(2)Zr(1)). The reactions of this metallacycle suppose an equilibrium with an 'opened' form [ZrCp(2)(RC drop CR)(acetone)], the latter paving the way to numerous ligand replacements. In a solution containing the dihydrozirconafuran and acetone, these reactions are reversible and degenerate, and can be studied by NMR methods: by two-dimensional spectroscopy and by observation of the isotope-induced chemical shifts that occur upon incorporation of(D-6)acetone into the metallacycle. The findings give an indirect proof of the described equilibrium. [References: 25]