Dicyclopentadienyltantalum complexes

The reduction of (η5-C5H52TaCl2 with Na/Hg or NaNaph yields the dimer (η5-C5H5)4Ta2Cl3(I) containing tantalum(III) and tantalum(IV), whereas the same reduction in a 1/1 molar ratio gives (η5-C5H52 TaCl(II). Use of NaBH4 gives the boranate complex (η5-C5H5)2TaBH4 (III). Complex II behaves as a Lewis acid with π-acid ligands and metal halides MXY2 to give (η5-C5H5)2TaCIL (L = CO (IV), PMe2 Ph(V), PPh3 (VI), PhC CPh(VII)) and(η5-C5H5)2Ta(μ-X)MY2, (M = Fe, X = Y = Cl (VIII), M = Tl, X = Y = Cl (IX), M = Al, X = Y = Cl (X), M = Tl, X = Br, Y = C6F5 (XI)). Reactions of (η5-C5H5)2TaCl2 with metal halides MXY2 give (η5-C5H52 TaCl(μ-Cl)MXY2 (M = Al, X = Y = Cl (XII), M = Fe, X = Y = Cl (XIII), M = Tl, X = Y = Cl (XIV), M = Tl, X = Br, Y = Br, Y = C6F5 (XV)) and [(η5-C5H52Ta(μ-Cl)2]+ MCl4- (M = Fe (XVI), Al (XVII)). Reaction of I with AgCIO4 gives [(η5-C5H5)4Ta2Cl2]+ ClO4- (XVIII). Complex III behaves also as a Lewis acid and reacts with π-acid ligands to give (η5-C5H5)2Ta(H)(L) (L = CO (XIX), PEt3 (XX), PPh3 (XXI)). The chemical and structural behaviour of these complexes are described.We gratefully acknowledge financial support from the Comisión Asesora de Investigación Científica y Técnica (Spain)