Regioselective Nitration and/or Halogenation of Iridabenzofurans through Electrophilic Substitution
Regioselective electrophilic substitution reactions of the iridabenzofurans [Ir(C7H5O{OMe 7}(CO)(PPh3)2][OTf] (1) and IrCl(C7H5O{OMe 7}(PPh3)2 (2) provide a convenient route to mononitro dinitro and mixed nitro /halo substituted derivatives. Treatment of cationic 1 with copper(II) nitrate in acetic anhydride "Menke" nitration conditions) gives the mononitrated iridabenzofuran [Ir(C7H4O{NO2 2}{OMe 7}(CO)(PPh3)2][O3SCF3] (3) Under the same conditions neutral 2 undergoes dinitration to form IrCl(C7H3O{NO2 2}{NO2 6}{OMe 7}(PPh3)2 (5) Simple substitution of the carbonyl ligand in 3 with chloride gives the neutral mononitro derivative IrCl(C7H4O{NO2 2}{OMe 7}(PPh3)2 (4) Depending on the conditions employed, treatment of the iridabenzofurans 1 and 2 with Cu(NO3)2 and either lithium chloride or lithium bromide in acetic anhydride gives either the mixed nitro /halo substituted iridabenzofurans IrCl(C7H3O{NO2 2}{Cl 6}{OMe 7}(PPh3)2 (6) and IrCl(C7H2O{NO2 2}{NO2 4}{Cl 6}{OMe 7}(PPh3)2 (7) or the simpl.