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(H(2)dhbq) 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)center dot CH(2)Cl(2 center dot)5H(2)O (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, H-1 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 x 6.9 angstrom (Ir-Ir separations) for 2, 8.0 x 11.2 angstrom (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 center dot center dot center dot H-O-H center dot center dot center dot 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. (C) 2010 Elsevier B.V. All rights reserved.