Synthesis and characterisation of 2,6-diisopropylphenylimido complexes of chromium in oxidation states IV–VI

The chromium(VI) imido complex Cr(NAr)2Cl2 (Ar 4;= 4;2,6-iPr2C6H3) reacted with pyridine and PMe3 to form the monoadducts Cr(NAr)2Cl2(py) 1 and Cr(NAr)2Cl2(PMe3) 2 respectively. The reaction between Cr(NAr)2Cl2 and LiNHAr afforded the amide complex Cr(NAr)2(NHAr)Cl 3. Attempts to generate the half-sandwich species CrCp(NAr)2Cl through treatment of the dichloride with LiCp, Mg(Cp)2 or NaCp resulted in the dimeric chromium(V) complex [Cr(NAr)(µ-NAr)Cl]2 4. Reduction of Cr(NAr)2Cl2 with magnesium in the presence of PMe3 or PMe2Ph afforded the chromium(IV) bis-phosphine complexes Cr(NAr)2(PMe3)2 5 and Cr(NAr)2(PMe2Ph)2 6 respectively. The reaction between Cr(NAr)2(PMe3)2 and phenyldiazomethane gave the diazoalkane complex Cr(NAr)2(N2CHPh)(PMe3) 7. Complexes 1, 3, 4 and 7 have been structurally characterised.