Bromodicyclopentadienylniobium complexes

Abstract

The reaction of NbX5 (X=Cl, Br) with an excess of NaCp (Cp=C5H5) followed by the addition of HBr gives (η5-C5H5)2NbBr2 (I) in low yield. The reduction of I with Na/Hg or NaNaph in a molar ratio 1/1 gives (η5-C5H5)2NbBr (II), whereas the same reaction in the presence of π-acid ligands gives (η5-C5H5)2NbBrL (III, L=CO; IV, L=PMe2Ph; V, L=P(OMe)3; VI, L=PhC≡CPh; VIII, L=PhC≡CH). Finally, the reduction of I with Na/Hg in a molar ratio 2/1 gives the dimer (η5-C5H5)4Nb2Br3 (VIII), which contains both niobium(III) and niobium(IV). The chemical and structural characteristics of all these compounds are described.