New monocyclopentadienyl complexes of Group 4 and 5 metals with chelating nitrogen ligands. Crystal and molecular structures of [Zr(η3-C3H5)(η4-Ph2N2C2Me2-2,3)Cp″] and [TaCl2{η4-C6H4(NSiMe3-1,2)2}Cp″] [Cp″ = C5H3(SiMe3)2-1,3]†

Abstract

Reduction of [MCl₃Cp″] [M = Zr or Hf; Cp″ = C₅H₃(SiMe₃)₂-1,3] with magnesium in the presence of 1,4-diphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene (DAD) gave the diazadiene complexes [MCl(DAD)Cp″] in high yield. Alkylation with RMgCl affords the alkyls [MR(DAD)Cp″] (R = CH₃ or CH₂Ph) and the more stable allyl complexes [M(η³-C₃H₅)(DAD)Cp″] as yellow to light brown solids. The reaction of Li₂[C₆H₄(NSiMe₃)₂-1,2] with [MCl₃Cp″] leads to the bis(amido) complexes [MCl{C₆H₄(NSiMe₃)₂-1,2}Cp″], while the analogous reaction with [MCl₄Cp″] (M = Nb or Ta) generates the red to red-brown niobium and tantalum half-sandwich compounds [MCl₂{C₆H₄(NSiMe₃)₂-1,2}Cp″]. The crystal structures of two representative examples, [Zr(η³-C₃H₅)(DAD)Cp″] and [TaCl₂{C₆H₄(NSiMe₃)₂-1,2}Cp″], are reported.