Niobium pentaethoxide

Recently, we succeeded in the synthesis and structural characterization of first niobium-containing metallasilsesquioxane complex. In analogy to the corresponding reactions with titanium tetraalkoxides, niobium pentaethoxide cleanly reacts with 3 in a 1 1 molar ratio to give high yields of dimeric [Cy7Si70i2Nb0Et( U-OEt)]2 (149) as a colorless, crystalline solid (Scheme 49). 

Similarly, the reaction of niobium pentaethoxide with isopropyl alcohol yielded monoethoxide tetra-isopropoxide ... 

Whitleyshowed that Ta2(OEt)io reacted with excess benzoylacetone (bzac) to give Ta(OEt)2(bzac)3 which may contain eight-coordinated tantalum. Mehroira and co-workers have also investigated the reactions of niobium and tantalum pentaethoxides with acetylacetone, benzoylacetone, dibenzoylmethane, methyl and ethyl acetoacetates and ethylbenzoylacetate and only observed partial replacement in these cases. It has been shown that the above reactions proceeded quite smoothly up to the formation of the bis-derivative, and slowed down considerably beyond that stage, but could be forced to trisubstitution for some jS-diketone or ketoester molecules similar results have been reported in the reactions of U(OMe)5 with S-diketones ... 

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