Half-sandwich rhodium and iridium metallamacrocycles constructed via C–H activation

Abstract

Half-sandwich rhodium and iridium complexes with carboxylic acid ligands were combined with pyrazine, 4,4′-bipyridine (bpy) or trans-1,2-bis(4-pyridyl)-ethylene (bpe) to give a series of tetranuclear macrocycles. The metallamacrocycles [(Cp*Rh)₄(L₁)₂(pyrazine)₂][OTf]₂ (1), [(Cp*Rh)₄(L₁)₂(bpy)₂][OTf]₂ (2), [(Cp*Rh)₄(L₁)₂(bpe)₂][OTf]₄ (3) and [(Cp*Ir)₄(L₂)₂ (pyrazine)₂] (4) (L₁ = 3-(2-pyridyl)acrylic acid, L₂ = 1,4-di(4-carboxyphenyl)benzene) were characterized by elemental analysis, NMR, IR and single-crystal X-ray analyses. Due to the different structures of the carboxylate ligands, the complexes 1a–3a, 1b–3b and 4 were synthesized through double-site C–H activation, and complexes 1c–3c were obtained by one-site C–H activation.