Discrete half-sandwich Ir, Rh-based organometallic molecular boxes: synthesis, characterization, and their properties

Abstract

The treatment of binuclear complexes [Cp*₂M₂(μ-QA)Cl₂] (M = Ir, 2a; M = Rh, 2b) (H₂QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4′-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazol (bpt)) in the presence of AgOTf (OTf = CF₃SO₃) in CH₃OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp*₄M₄(μ-QA)₂(μ-L)₂](OTf)₄ (M = Ir, 3a–7a; M = Rh, 3b–7b), respectively. The molecular structure of [Cp*₄Ir₄(μ-QA)₂(μ-pyrazine)₂](OTf)₄ (3a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate QA²⁻ ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 Å. Complexes 3a and 3b were found to exhibit selective trapping of halocarbons properties.