A family of new organometallic and coordination group 5 compounds supported by animido-diamido-pyridine ligand set are reported. Reaction of [M(NR)Cl(
3-N
2N
py)(py)](M = Nb, R =
tBu
1; M = Ta, R =
tBu
2 or Ar
3, where N
2N
py = MeC(2-C
5H
4N)(CH
2NSiMe
3)
2and Ar = 2,6-C
6H
3iPr
2) with LiOAr or LiPhC(NSiMe
3)
2 afforded the five-coordinate aryloxideand benzamidinate complexes [M(NR)(OAr)(
3-N
2N
py)] (R =
tBu, M = Nb
4 or Ta
5; R = Ar,M = Ta
6) and [Nb(N
tBu){PhC(NSiMe
3)
2}(
3-N
2N
py)] (
7), respectively. Reaction of
1 or
2with LiN(SiMe
3)
2 or LiCH(SiMe
3)
2 gave the four-coordinate compounds [M(N
tBu)(X)(
2-N
2N
py)] (M = Nb, X = N(SiMe
3)
2 8 or CH(SiMe
3)
2 9; M = Ta, X = CH(SiMe
3)
2 10). Reactionof
1 or
2 with the less sterically demanding alkyl reagent LiCH
2SiMe
3 gave, in the case ofniobium, only the four-coordinate [M(N
tBu)(CH
2SiMe
3)(
2-N
2N
py)] (
11), but for tantalum anequilibrium mixture of four- (
2-) and five- (
3-) coordinate isomers was identified by NMRspectroscopy. Reaction of
1 with PhCH
2MgCl or LiC
5H
4Me gave the corresponding
1- or
5-hydrocarbyl complexes [Nb(N
tBu)(CH
2Ph)(
3-N
2N
py)(py)] (
13) and [Nb(N
tBu)(
5-C
5H
4Me)(
2-N
2N
py)] (
14). The X-ray crystal structures of the compounds
4,
6, and
9 are reported.