Synthesis and Reactions of DitantalumAllyl Complexes Derived from Intramolecular C–H Bond Activation of the Methylene of the Ethyl Group Bound to Ditantallacyclopentadiene

Reaction
of a dinuclear tantallacyclopentadiene complex, Ta2Cl6(μ-C4Et4) (1), with
PhSiH3 quantitatively afforded a polymeric
dinuclear tantalum η3-allyl complex, {Ta2Cl5[μ-C4Et3(CHMe)]}n (2), whose η3-allyl
moiety was derived from selective C–H bond activation of the
methylene moiety of the ethyl group bound to the tantallacyclopentadiene
fragment. Lewis bases, such as THF and PMe2Ph, coordinated
to 2 to give Ta2Cl5(L)2[μ-C4Et3(CHMe)] (3: L =
thf; 4: L = PMe2Ph). An insertion reaction
of diphenylacetylene into the η3-allyl moiety of 3 afforded the diphenylacetylene-incorporated complex 5. Similarly, unsaturated organic substrates, such as trimethylsilylacetylene,
2-vinylpyridine, and benzaldehyde, inserted into the η3-allyl moiety of 3 to afford the corresponding complexes 6–8.