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Keywords:

  • Protonation;
  • Noninnocent li­gand;
  • Carbonylation;
  • Amides;
  • Phenoxide

Abstract

The effect of protonation of metal complexes of noninnocent ligands is investigated. The anilidophenolate complexes Cp*IrtBAtBu (1) and Cp*IrtBAFPh (2) were examined [H2tBAtBu = 2-tert-butylamino-4,6-di-tert-butylphenol, H2tBAFPh = 2-(2-trifluoromethyl)amino-4,6-di-tert-butylphenol]. Protonation of 1 with HBF4 gave the anilinophenolate [1H]+. Crystallographic characterization of this complex revealed an elongatated Ir–N bond, but the IrIII center remains pentacoordinate. The anilinophenolate hydride 1H(H) was prepared by treatment of [1H]+ with boron hydride reagents and with formic acid. X-ray crystallography confirmed the structure and revealed that the hydride and ammonium hydrons occupy sites on opposite sides of the IrONC6 ring. Complex 2 is protonated only by strong acids, and the resulting derivative is unstable in the absence of ligands such as CO and PMe3. Crystallographic characterization of [2(PMe3)]+ revealed that protonation occurs at O not N. The carbonylation of [2H]+ reveals the intermediacy of kinetic adducts, which are proposed to be the anilino tautomer.