Rational Design of Half-Sandwich Iridium Metallamacrocycles Assembled by C–H Activation

Both tetranuclear metallamacrocycles {(Cp*Ir)2[m-(OOC-C6H2-COO)](pyrazine)}2 (2a) and {(Cp*Ir)2{m-[OOC-(5-NH2-C6H)-COO)]}(pyrazine)}2 (3a) were formed by reactions of {[(Cp*Ir)2(pyrazine)Cl2]} (1a) with 1,3-benzenedicarboxylic acid (m-H2BDC) and 5-amino-1,3-benzenedicarboxylic acid (NH2-m-BDC) in the presence of TEA (triethylamine) under mild conditions, respectively. In order to investigate the effect of N-donor ligands in the construction of metallamacrocycles, the binuclear complexes [(Cp*Ir)2(bpy)Cl2] and [(Cp*Ir)2(bpe)Cl2] were used as precursors to react with m-H2BDC and NH2-m-BDC under the same conditions to result in tetranuclear metallamacrocycles {(Cp*Ir)2[m-(OOC-C6H2-COO)](bpy)}2 (2b), {(Cp*Ir)2[m-(OOC-C6H2-COO)] (bpe)}2 (2c), {(Cp*Ir)2{m-[OOC-(5-NH2-C6H)-COO)]}(bpy)}2 (3b), and {(Cp*Ir)2{m-[OOC-(5-NH2-C6H)-COO)]}(bpe)}2 (3c). Furthermore, in the development of building similar metallamacrocycles by dicarboxylic acid through C–H activation, 2-amino-1,4-benzenedicarboxylic acid (NH2-BDC) was employed to react with N-donor bridging binuclear complexes, resulting in complexes {(Cp*Ir)2[OOC-(2-NH2-C6H)-COO)](pyrazine)}2 (4a), {(Cp*Ir)2[OOC-(2-NH2-C6H)-COO)](bpy)}2 (4b), and {(Cp*Ir)2[OOC-(2-NH2-C6H)-COO)](bpe)}2 (4c). The molecular structures of 2a and 3a were confirmed by single-crystal X-ray crystallography. All complexes were well characterized by NMR, IR, and elemental analysis.