Synthesis and Structural Characterization of Macrocyclic Half-Sandwich Rhodium(III) and Iridium(III) Complexes Bearing Bipyridyl Derivatives and Terephthalate

Abstract

The reactions of half-sandwich rhodium and iridium complexes [Cp‘MCl(μ-Cl)]2 with bidentate ligands (L) such as pyrazine, 4,4‘-bipyridine (bpy), and trans-4,4‘-azopyridine gave the corresponding binuclear complexes [{Cp‘MCl2}2(L)] (M = Ir, Cp‘ = Cp* = η5-C5Me5, L = pyrazine (3a), bpy (3b); M = Rh, Cp‘ = Cpt = η5-1,3-tBu2C5H3, L = bpy (3c), 4,4‘-azopyridine (3d)), which can be converted into tetranuclear complexes [{Cp‘2M2(μ-Cl)2}2(L)2]4+ (M = Ir, Cp‘ = Cp*, L = bpy (4a and 4b); M = Rh, Cp‘ = Cpt, L = bpy (4c, 4e), L = 4,4‘-azopyridine (4d)) on treatment with Ag(OTf) or AgBF4 (OTf = CF3SO3). Treatment of Cl-bridged complexes 4c and 4e with terephthalate (L‘) resulted in replacing the Cl bridges to produce macrocyclic complexes [(Cp‘M)4{(L)(L‘)}2]4+ (M = Rh, Cp‘ = Cpt, L = bpy, L‘ = terephthalate (5)). The molecular structures of [{Cp*IrCl2}2(μ-pyrazine)] (3a), [{Cp*Ir}4(μ-Cl)4-(μ-bpy)2](BF4)4·6(CH2Cl2) (4a), [(Cp*Ir)4(μ-Cl)4(μ-bpy)2](OTf)4·5(CH2ClCH2Cl) (4b), [(CptRh)4(μ-Cl)4(μ-bpy)2](OTf)4 (4c), [(CptRh)4(μ-Cl)4(μ-trans-4,4‘-azopyridine)2](OTf)4 (4d) and [(CptRh)4(μ-tere-phthalate)2(μ-bpy)2] (BF4)4·2(C6H12) (5) have been determined by single-crystal X-ray analysis. The molecular structure of the cation in macrocyclic complex 5 contains two different types of ligand “edges”, and the dimensions of the cavity are 10.8 × 11.2 Å.