Group 5 Imido Complexes Supported by Diamido−pyridine Ligands: Aryloxide, Amide, Benzamidinate, Alkyl, and Cyclopentadienyl Derivatives

A family of new organometallic and coordination group 5 compounds supported by an
imido−diamido−pyridine ligand set are reported. Reaction of [M(NR)Cl(κ3-N2Npy)(py)]
(M = Nb, R = tBu 1; M = Ta, R = tBu 2 or Ar 3, where N2Npy = MeC(2-C5H4N)(CH2NSiMe3)2
and Ar = 2,6-C6H3iPr2) with LiOAr or LiPhC(NSiMe3)2 afforded the five-coordinate aryloxide
and benzamidinate complexes [M(NR)(OAr)(κ3-N2Npy)] (R = tBu, M = Nb 4 or Ta 5; R = Ar,
M = Ta 6) and [Nb(NtBu){PhC(NSiMe3)2}(κ3-N2Npy)] (7), respectively. Reaction of 1 or 2
with LiN(SiMe3)2 or LiCH(SiMe3)2 gave the four-coordinate compounds [M(NtBu)(X)(κ2-N2Npy)] (M = Nb, X = N(SiMe3)2 8 or CH(SiMe3)2 9; M = Ta, X = CH(SiMe3)2 10). Reaction
of 1 or 2 with the less sterically demanding alkyl reagent LiCH2SiMe3 gave, in the case of
niobium, only the four-coordinate [M(NtBu)(CH2SiMe3)(κ2-N2Npy)] (11), but for tantalum an
equilibrium mixture of four- (κ2-) and five- (κ3-) coordinate isomers was identified by NMR
spectroscopy. Reaction of 1 with PhCH2MgCl or LiC5H4Me gave the corresponding η1- or
η5-hydrocarbyl complexes [Nb(NtBu)(CH2Ph)(κ3-N2Npy)(py)] (13) and [Nb(NtBu)(η5-C5H4Me)(κ2-N2Npy)] (14). The X-ray crystal structures of the compounds 4, 6, and 9 are reported.

本文报道了一类由亚氨基-二氨基-吡啶（imido−diamido−pyridine）配体体系支撑的新型有机金属及第5族配位化合物。将[M(NR)Cl(κ³-N₂Npy)(py)]（其中M为铌（Nb），R为叔丁基（tBu）时记为化合物1；M为钽（Ta），R为叔丁基（tBu）时记为化合物2，或R为芳基（Ar）时记为化合物3，其中N₂Npy = MeC(2-C₅H₄N)(CH₂NSiMe₃)₂，Ar = 2,6-C₆H₃iPr₂）分别与芳氧基锂（LiOAr）或苯甲脒锂（LiPhC(NSiMe₃)₂）反应，可得到五配位芳氧基配合物与苯甲脒配合物[M(NR)(OAr)(κ³-N₂Npy)]（R = tBu时，M为Nb记为4、M为Ta记为5；R = Ar时，M为Ta记为6），以及[Nb(NtBu){PhC(NSiMe₃)₂}(κ³-N₂Npy)]（记为7）。将化合物1或2与双(三甲基硅基)氨基锂（LiN(SiMe₃)₂）或双(三甲基硅基)甲基锂（LiCH(SiMe₃)₂）反应，可得到四配位化合物[M(NtBu)(X)(κ²-N₂Npy)]（M为Nb时，X为N(SiMe₃)₂记为8、X为CH(SiMe₃)₂记为9；M为Ta时，X为CH(SiMe₃)₂记为10）。将化合物1或2与空间位阻更低的烷基试剂LiCH₂SiMe₃反应：对于铌体系，仅得到四配位的[M(NtBu)(CH₂SiMe₃)(κ²-N₂Npy)]（记为11）；而对于钽体系，经核磁共振波谱（NMR spectroscopy）鉴定，得到了四配位（κ²-）与五配位（κ³-）异构体的平衡混合物。将化合物1与苄基氯化镁（PhCH₂MgCl）或甲基环戊二烯锂（LiC₅H₄Me）反应，可得到对应的η¹-及η⁵-烃基配合物[Nb(NtBu)(CH₂Ph)(κ³-N₂Npy)(py)]（记为13）与[Nb(NtBu)(η⁵-C₅H₄Me)(κ²-N₂Npy)]（记为14）。本文还报道了化合物4、6及9的X射线晶体结构。