DICYCLOPENTADIENYLTANTALUM COMPLEXES

Article abstract of DOI:10.1016/S0022-328X(00)98732-1

The reduction of (η⁵C5H5)2TaCl2 with Na/Hg or NaNaph yields the dimer (η⁵C5H5)4Ta2Cl3 (I) containing tantalum(III) and tantalum(IV), whereas the same reduction in a 1/1 molar ratio gives (η⁵-C5H5)2TaCl (II).Use of NaBH4 gives the boranate complex (η⁵C5H5)2TaBH4 (III).Complex II behaves as a Lewis acid with ?-acid ligands and metal halides MXY2 to give (η⁵-C5H5)2TaClL (L = CO (IV), PMe2Ph (V), PPh3 (VI), PhC<*>CPh (VII)) and (η⁵-C5H5)2Ta(μ-Cl)(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 (η⁵C5H5)2TaCl(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 = C6F5 (XV)) and <(η⁵-C5H5)2Ta(μ-Cl)2MCl2>⁺ MCl4^- (M = Fe (XVI), Al (XVII)).Reaction of I with AgClO4 gives <(η⁵-C5H5)4Ta2Cl2>⁺ ClO4^- (XVIII).Complex III behaves also as a Lewis acid and reacts with ?-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.