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.