Stable Imido Amido Complexes of Tungsten(VI).

Abstract

Reaction of Me₃SiNHC₃H₃Prⁱ₂-2,6 with [WC1₃(NC₆H₃Prⁱ-2,6)] in thf gives [WCl₃(NC₆H₃Prⁱ₂- 2,6)(NHC₆H₃Prⁱ₂-2,6)(thf)] (1), and reaction in CH₂Cl₂ in the presence of py gives [WCl₃(NC₆H₃Pr ⁱ₂-2,6)(NHC₆H₃Prⁱ₂-2,6)(py)] (2). Addition of 1 equiv. of NH₂C₆H₃Prⁱ₂-2,6 to [WCl₄(NC₆H₃Prⁱ₂-2,6)] in CH₂Cl₂ gives the 1 : 1 adduct [WCl4(NC6H3Prⁱ₂-2,6)(NH2C6H3Prⁱ₂-2,6)] (3) which when reacted with 1 equiv. of Me₃SiNHC₆H₃Prⁱ₂-2,6 gives rise to [WCl₃(NC₆H₃Prⁱ₂-2,6)(NHC₆H₃Prⁱ₂-2,6)(NH₂C₆H₃Prⁱ₂-2,6)] (4) and also the tris amido complex [WCl₃(NHC₆H₃Prⁱ₂-2,6)₃] (5). Complex (4) converts into complex (5), and after long reaction periods only complex (5) is isolated. Addition of 1 equiv. of Me₃SiNHC₆H₃Prⁱ₂-2,6 to [WCl₅(NC₆H₃Prⁱ₂-2,6)NEt₄ in CH₂Cl₂ gives rise to [WCl₄(NC₆H₃Prⁱ₂-2,6)(NHC₆H₃Prⁱ₂-2,6)] NEt₄ (6), and if Me₃SiNHC₆H₃Me₂-2,6 is used, instead, [WCl₄(NC₆H₃Prⁱ₂-2,6)(NHC₆H₃Me₂-2,6)] NEt₄ (7) results. Me₃SiNHC₆H₅ gives unidentified mixtures of products. Reaction of NH₂C₆H₃Prⁱ₂-2,6 with [WCl₄(O)] leads to the complex [WCl₄(NC₆H₃Prⁱ₂-2,6)(NHC₆H₃Prⁱ₂-2,6)] NH₃C₆H₃Prⁱ₂-2,6 (8) which was characterized by X-ray crystallography. The structure shows an octahedral array with cis-oriented imido and amido ligands. For the imido ligand the W-N bond length is 1·67(2) Å and W-N-C bond angle 174(2)°; for the amido ligand, the corresponding values are 1·87(2) Å and 144(2)°. The amido ligand orientates so that any NH contacts with nearby chlorine ligands are minimized. Complexes (1)-(8) give insight into an intramolecular NH proton transfer process leading to an organoimido ligand.