Interaction of [M(NBu t )(NHBu t )(H 2 NBu t )Cl 2 ] 2 , M = Nb, Ta, with five equiv. of Bu t NHLi gave {[M(NBu t ) 3 (NHBu t )]Li 2 } 2 , M = Nb (2a), M = Ta (2b), which showed the presence of three different tert-butylimido groups and resisted further metallation. Interaction of MCl 5 , M = Nb, Ta, with 1-amino-2,2,6,6-tetramethylpiperidine, C 9 H 1 8 NNH 2 , in the presence of Me 3 SiCl-Et 3 N gave (Et 3 NH)[M(C 9 H 1 8 N 2 ) 2 Cl 4 ], M = Nb (3a), M = Ta (3b). A similar interaction with NH 4 VO 3 gave low yields of [(C 9 H 1 8 N 2 ) 2 (OSiMe 3 ) 2 V(μ-O)V(O)(OsiMe 3 ) 2 ] (4). The X-ray crystal structures of (2a), (3b) and (4) have been determined.