Cyclopentadienylmolybdenum(VI) and Molybdenum(V) Oxo Chemistry: New Synthetic and Structural Features

Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives (4Cp = C5HiPr4; Cp′′′ = C5H2tBu3‐1,2,4) of formula [(Ring)2Mo2O5] are described. Compound [Cp2Mo2O5] was produced in good yields by the rapid oxidation of red [CpMoO2]4 with PhIO in CH2Cl2. [Cp*2Mo2O5] was obtained by CH3COOH acidification of aqueous solutions of [Cp*MoO3]−Na+, the latter being generated in a single step from [Cp*MoCl4] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO2]2 were also isolated from this reaction, although the formation of this by‐product may be reduced by using a two‐step basic hydrolysis procedure. Extension of the latter strategy also allowed the preparation of [4Cp2Mo2O5], [Cp′′′2Mo2O5], and [4CpMoO2Cl] in good yields, in addition to the by‐product [Cp′′′MoO2]2. X‐ray structures are reported for compounds [4Cp2Mo2O5], [Cp′′′2Mo2O5], [Cp*MoO2]2, [Cp′′′MoO2]2, and [4CpMoO2Cl]. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)