Syntheses and molecular structures of half-sandwich iridium metallarectangles containing bridging 2,5-dihydroxy-1,4- benzoquinonato (dhbq) ligands

Binuclear complex (Cp∗IrCl)2(dhbq) (dhbq = 2,5-dihydroxy-1,4-benzoquinonato) (1) was obtained by the reaction of (Cp∗IrCl2)2 with bridging ligand 2,5-dihydroxy-1,4-benzoquinone(H2dhbq) in the presence of the base n-BuNH2. After treatments of 1 with AgX (X = NO3-,SO3CF3-) and then with N-linkers (pyrazine, 4,4′-bipyridine), the corresponding tetranuclear metallarectangular complexes [(Cp∗Ir)4(dhbq)2(pyrazine)2] (NO3)4·CH2Cl2·5H2O (2) and [(Cp∗Ir)4(dhbq)2(4,4′-bipyridine)2](SO3CF3)4(3) were obtained in good yields. Both the products were characterized by IR, 1H NMR and single crystal X-ray analyses and revealed that these tetranuclear complexes were constructed from half-sandwich metal corners with both dhbq and N-linkers to form rectangular cavities with the dimensions 8.0 × 6.9 Å (Ir–Ir separations) for 2, 8.0 × 11.2 Å (Ir–Ir separations) for 3, respectively. In additionally, in the solid structure of 2 the counteranions NO3- are located out of the cavities with the observed water molecules by hydrogen bonding of the type N–O⋯H–O–H⋯O–N. One-dimensional channels are observed in 3 along the b axis with intramolecular stacking, the similar arrangement is not found in the solid of 2.

Graphical abstractThe tetranuclear metallarectangular complexes [(Cp∗Ir)4(dhbq)2(pyrazine)2] (NO3)4·CH2Cl2·5H2O (2) and [(Cp∗Ir)4(dhbq)2(4,4′-bipyridine)2] (SO3CF3)4(3) were obtained from the precursor complex (Cp∗IrCl)2(dhbq) (1) in the presence of AgX (X = NO3-,SO3CF3-), respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide