Synthesis and Structural Characterization of Niobium(IV) Amido Complexes and a Niobium(V) Bisimido Complex

Oxidation Reactions of [(Me3Si)2N]2VX(THF) (X = Cl, Me, Ph) with CuCl, PhCH(O)CH2, and Ph2CN2 and the Syntheses and Structures of the Vanadium(III) Anions {[(Me3Si)2N]2VX2}- (X = Cl, Me)

“…In this paper, we report the one-electron oxidation of this latter V−Me complex, the analogous V−Ph complex, and the parent V(III) chloride complex to yield the bis(amide) V(IV) methyl−chloride, phenyl−chloride, and dichloride derivatives, respectively. This last species completes the homologous series of group 5 [(Me 3 Si) 2 N] 2 MCl 2 compounds (M = V, Nb, Ta), as the niobium , and tantalum , analogs were recently reported by Hoffman. The syntheses and structures of related four-coordinate V(III) anions, i.e., {[(Me 3 Si) 2 N] 2 VCl 2 } - and {[(Me 3 Si) 2 N] 2 VMe 2 } - , are also reported.…”

“…Hoffman and co-workers have reported congeneric group 5 species that are obtained using different synthetic methodologies. The Nb(IV) dihalide [(Me 3 Si) 2 N] 2 NbCl 2 , , available from NbCl 4 (THF) 2 and LiN(SiMe 3 ) 2 , may be converted to [(Me 3 Si) 2 N] 2 Nb(Cl)(Ph) on treatment with ZnPh 2 . Reduction of Andersen's [(Me 3 Si) 2 N] 2 TaCl 3 38 with Na/Hg affords [(Me 3 Si) 2 N] 2 TaCl 2 16,17 in 64% yield.…”

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

“…23 As anticipated, the Nb-N bond lengths in 2 (Nb1-N1 = 1.937(2), Nb1-N2 = 1.939(2) Å) are longer than those observed in 1 , consistent with the presence of the larger Nb 4+ ion, but are shorter than those found in Nb(NPh 2 ) 4 (1.985(3)–2.029(3) Å). 31 The Ta-N bond lengths in 7 (Ta1-N1 = 1.934(2), Ta1-N2 = 1.931(2) Å) are identical to those exhibited by 2 and also comparable to those exhibited by complex 5 , despite the difference in oxidation states between the two complexes. For further comparison, these values are comparable to those exhibited by MCl(tmkh)(tBu 2 pz) 2 (M = Nb, Ta; tmkh 3− = 2,2,6,6-tetramethyl-5-ketimidohept-3-en-3-imide; tBu 2 pz − = 3,5-di- tert -butylpyrazolate), 32 but longer than that in Cp*Ta(η 4 -C 4 H 6 )(κ 2 - C,N -C 6 H 4 -2-C(Me)N).…”

Synthesis and reactions of (tert-butylimido)bis(η-cyclopentadienyl)niobium cations: NMR evidence for d0 olefin cations [Nb{(η-C5H5)2}(NtBu)(η-C2H4)][B(C6F5)4] and [Nb{(η-C5H4)CMe2(η-C5H4)}(NtBu)(η-C2H3Me)][B(C6F5)4]

“…The Nb-P bond length (2.5974(7) Å) is at the low end of the range of values found for previously reported niobium() compounds (2.577-2.649 Å). 14,23- 27 The bis(η-cyclopentadienyl)niobium ring system is destabilised in a manner similar to that observed in 1; however the cyclopentadienyl rings are even further from the metal centre in 2 than in 1. Thus the Nb-C distances are in the range 2.479-2.570 Å, as opposed to 2.402-2.565 Å, leading to the niobium-ring centroid distances also being longer than in 1, at 2.192 and 2.211 Å.…”