Half-sandwich rhodium and iridium fragments and carboxylate ligands as building blocks for the formation of metallamacrocycles

Abstract

A series of half-sandwich rhodium and iridium complexes containing carboxylate ligands were synthesized and characterized. Reactions between [Cp∗MCl2]2 (M = Ir or Rh) and 1,3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (L1) gave binuclear complexes 1 and 2 under different conditions. The half-sandwich iridium and rhodium metallamacrocycles complexes 3–5 were constructed in a stepwise manner by the addition of carboxylate ligands (sodium acetate or the conjugate bases of pyrazine-2,3-dicarboxylic acid or 3-(2-pyridyl)acrylic acid) to the solution of the binuclear precursors prepared from the reactions of [Cp∗MCl2]2 (M = Rh or Ir) with linear N,N′-donor ligands (4,4′-bipyridine or trans-1,2-bis(4-pyridyl)ethylene), respectively. The structures of binuclear complexes and tetranuclear macrocycles were confirmed by elemental analysis, IR, 1H NMR spectroscopy and single-crystal X-ray diffraction.