Synthesis and structural characterization of macrocyclic half-sandwich rhodium(III) and iridium(III) complexes bearing bipyridyl derivatives and terephthalate

The reactions of half-sandwich rhodium and iridium complexes [Cp'MCl(mu-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* = eta(5)-C5Me5, L = pyrazine (3a), bpy (3b); M = Rh, Cp' = Cp' = eta(5)-1,3'Bu2C5H3, L = bpy (3c), 4,4'-azopyridine (3d)), which can be converted into tetranuclear complexes [{Cp'M-2(2)(mu-Cl)(2)}(2)(L)(2)](4+) (M = Ir, Cp' = Cp*, L = bpy (4a and 4b); M = Rh, Cp' = Cp', 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' = Cpl, L = bpy, L' = terephthalate (5)). The molecular structures of [{Cp*IrCl2}(2)(mu-pyrazine)] (3a), [{Cp*Ir}(4)(mu-Cl)(4)-(mu-bpy)(2)](BF4)(4)center dot 6(CH2Cl2) (4a), [(Cp*Ir)(4)(mu-Cl)(4)(mu-bpy)(2)](OTf)(4)center dot 5(CH2ClCH2CI) (4b), [(Cp'Rh)(4)(mu-Cl)(4)-(mu-bpy)(2)](OTf)(4) (4c), [(Cp'Rh)(4)(mu-Cl)(4)(mu-trans-4,4'-azopyridine)(2)](OTf)(4) (4d) and [(Cp'Rh)(4)(mu-terephthalate)(2)(mu-bpy)(2)] (BF4)(4)center dot 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 x 11.2 angstrom.