Stepwise Formation of Half-Sandwich Iridium-Based Rectangles Containing 2,5-Diarylamino-1,4-benzoquinone Derivatives Linkers

Abstract

Binuclear complexes [Cp*2Ir2(μ-DB)Cl2] (1−5) (Cp* = η5-C5Me5, DB = 2,5-diarylamino-1,4-benzoquinone derivatives) were obtained by the reactions of [Cp*Ir(μ-Cl)Cl]2 with 2,5-diarylamino-1,4-benzoquinone derivatives in the presence of base. Treatments of [Cp*2Ir2(μ-DB)Cl2] with bidentate ligands (L) such as pyrazine, 4,4′-bipyridine (bpy) in the presence of Ag(OTf) (OTf = CF3SO3) in CH3OH solution gave the corresponding tetranuclear complexes, with the general formulas [Cp*4Ir4(μ-DB)2(μ-L)2](OTf)4 [1a,b−5a,b: DB = 2,5-dianilino-1,4-benzoquinone (DABQ), L = pyrazine (1a); DB = DABQ, L = bpy (1b); DB = 2,5-dianilino-3,6-dichloro-1,4-benzoquinone (DCBQ), L = pyrazine (2a); DB = DCBQ, L = bpy (2b); DB = 2,5-bis(4′-chloroanilino)-3,6-dichloro-1,4-benzoquinone (BCBQ), L = pyrazine (3a); DB = BCBQ, L = bpy (3b); DB = 2,5-bis(4′-bromoanilino)-3,6-dichloro-1,4-benzoquinone (BBBQ), L = pyrazine (4a); DB = BBBQ, L = bpy (4b); DB = 2,5-bis(4′-methoxyanilino)-3,6-dichloro-1,4-benzoquinone (BMBQ), L = pyrazine (5a); DB = BMBQ, L = bpy (5b)]. The molecular structures of [Cp*2Ir2(μ-DABQ)Cl2] (1), [Cp*2Ir2(μ-DCBQ)Cl2] (2), [Cp*4Ir4(μ-BCBQ)2(μ-bpy)2](OTf)4 (3b), and [Cp*4Ir4(μ-BBBQ)2(μ-bpy)2](OTf)4 (4b) have been determined by single-crystal X-ray analysis.