Syntheses and reactions of ansa-[2,2-bis(η-cyclopentadienyl)propane]-tungsten and -molybdenum compounds
- 1 January 1995
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 3,p. 395-402
- https://doi.org/10.1039/dt9950000395
Abstract
Reaction between [MCl4(dme)](M = W or Mo; dme = 1,2-dimethoxyethane) with Li2[C5H4CMe2C5H4] gave the ansa-bridged metallocene dichlorides [M{(η-C5H4)CMe2(η-C5H4)}Cl2](M = W or Mo). Treatment of these with LiAlH4 or ZnMe2 gave respectively the dihydrides [M{(η-C5H4)CMe2(η-C5H4)}H2](M = W or Mo) and the dimethyl derivatives [M{(η-C5H4)CMe2(η-C5H4)}Me2](M = W or Mo). Treatment of [W{(η-C5H4)CMe2(η-C5H4)}Me2] with HX (X = PhCO2 or NH3l) gave [W{(η-C5H4)CMe2(η-C5H4)}Me(Y)] with Y = PhCO2 or l, respectively. Both of these react with Na[AlH2(OCH2CH2OMe)2] giving the methylhydride [W{(η-C5H4)CMe2(η-C5H4)}Me(H)]. The latter is thermally stable in refluxing benzene. Ultraviolet photolysis of [Mo{(η-C5H4)CMe2(η-C5H4)}H2] in benzene gave the phenylhydride derivative [Mo{(η-C5H4)CMe2(η-C5H4)}Ph(H)]; the corresponding tungsten derivative [W{(η-C5H4)CMe2(η-C5H4)}H2] is not photosensitive. The crystal structures of [W{(η-C5H4)CMe2(η-C5H4)}Cl2], [W{(η-C5H4)CMe2(η-C5H4)}H2], (two modifications) and [Mo{(η-C5H4)CMe2(η-C5H4)}H2] have been determined by X-ray diffraction. The ansa-bridged bis(η-cyclopentadienyl) compounds show marked differences in reactivity compared to non-ansa analogues and this is discussed in terms of the modifications of the electronic structure as a consequence of the ansa bridge.Keywords
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