Mono(cyclopentadienyl) and ansa-bis(cyclopentadienyl)imido derivatives of Group 5 and 6 transition metals; crystal structures of [M{(η-C5H4)CMe2(η-C5H4)}(NR)X] (M = Nb, R = SiMe3, X = Cl; R = But, X = Cl, Br or I; M = Ta, R = But, X = Cl)†

Abstract

The new half-sandwich mono(cyclopentadienyl)tungsten compounds [W(η-C₅H₄Me)(NBu^t)Cl₃] and [W(η-C₅H₄Me)(NBu^t)(L)Cl] (L = η-C₂H₄ or η-MeC₂Me) have been synthesized. In addition, the ansa-bis(cyclopentadienyl) Group 5 compounds [M{(η-C₅H₄)CMe₂(η-C₅H₄)}(NR)X] (M = V, R = Bu^t, X = Cl; M = Nb, R = SiMe₃, X = Cl;* R = Bu^t, X = Cl,* Br,* I* or Me; M = Ta, R = Bu^t, X = Cl* or Me) are reported. An asterisk indicates that the compound has been structurally characterized. Attempts to prepare the related dichloride compounds by replacement of the imido functionality in [M{(η-C₅H₄)CMe₂(η-C₅H₄)}(NBu^t)Cl] (M = V, Nb or Ta) using HCl led to decomposition, suggestive of a labilising of the cyclopentadienyl rings by the strongly bonding imido ligand.