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

The chromium(VI) imido complex Cr(NAr)(2)Cl-2 (Ar=2,6-(Pr2C6H3)-Pr-i) react ed with pyridine and PMe3 to form the monoadducts Cr(NAr)(2)Cl-2(py) 1 and Cr(NAr)(2)Cl-2(PMe3) 2 respectively. The reaction between Cr(NAr)(2)Cl-2 an d LiNHAr afforded the amide complex Cr(NAr)(2)(NHAr)Cl 3. Attempts to gener ate the half-sandwich species CrCp(NAr)(2)Cl through treatment of the dichl oride with LiCp, Mg(Cp)(2) or NaCp resulted in the dimeric chromium(V) comp lex [Cr(NAr)(mu-NAr)Cl](2) 4. Reduction of Cr(NAr)(2)Cl-2 with magnesium in the presence of PMe3 or PMe2Ph afforded the chromium(IV) bis-phosphine com plexes 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 diazoa lkane complex Cr(NAr)(2)(N2CHPh)(PMe3) 7. Complexes 1, 3, 4 and 7 have been structurally characterised.