Synthesis, Characterization, and Electrochemical Properties of Molecular Rectangles of Half-Sandwich Iridium Complexes Containing Bridging Chloranilate Ligands

Abstract

Binuclear complex [Cp*2Ir2(μ-CA)Cl2] (2) (CA = chloranilate) was obtained by the reaction of [Cp*IrCl2]2 (1) with H2CA in the presence of base. Treatment of 2 with pyridine or 4-(4-bromophenyl)pyridine in the presence of AgOTf (OTf = CF3SO3) in CH3OH gave the corresponding binuclear complexes [Cp*2Ir2(μ-CA)(pyridine)2](OTf)2 (4a) and [Cp*2Ir2(μ-CA){4-(4-bromophenyl) pyridine}2](OTf)2 (4b). Reactions of 2 with bidentate ligands gave tetranuclear complexes [Cp*4Ir4(μ-CA)2(μ-L)2](OTf)4 (L = pyrazine, 5a; 4,4′-dipyridyl, 5b; 2,5-bis(4-pyridyl)-1,3,5-oxadiazole, 5c; 1,4-bis(4-pyridyl)benzene, 5d; (E)-1,2-bis(4-pyridyl)ethene, 5e). X-ray analyses of 5a, 5b, and 5e revealed that each of four Cp*Ir moieties was connected by pyridyl ligands and a bis-bidentate chloranilate (CA) ligand to construct a rectangular cavity with the dimensions 8.03 × 6.92 A for 5a, 8.03 × 11.24 A for 5b, and 8.01 × 13.55 A for 5e. Toluene molecules are contained as solvent molecules in the crystals of 5a and 5b. For 5a, the toluene mole...