Syntheses and structures of half-sandwich iridium(iii) and rhodium(iii) complexes with organochalcogen (S, Se) ligands bearing N-methylimidazole and their use as catalysts for norbornene polymerization

Abstract

The organochalcogen ligands derived from 3-methyl-imidazole-2-thione/selone groups, Mbit, Mbis, Ebit and Ebis [Mbit = 1,1′-methylenebis(3-methyl-imidazole-2-thione); Mbis = 1,1′-methylenebis(3-methyl-imidazole-2-selone), Ebit = 1,1′-(1,2-ethanediyl)bis(3-methyl-imidazole-2-thione), Ebis = 1,1′-(1,2-ethanediyl)bis(3-methyl-imidazole-2-selone)] have been synthesized and characterized. Reactions of [Cp*Ir(μ-Cl)Cl]₂ and [Cp*Rh(μ-Cl)Cl]₂ (Cp* = η⁵-pentamethylcyclopentadienyl) with Mbit, Mbis, Ebit and Ebis result in the formation of the complexes [Cp*Ir(Mbit)Cl]Cl (1a·Cl), [Cp*Ir(Mbis)Cl]Cl (1b·Cl), [Cp*Ir(Ebit)Cl]Cl (2a·Cl), [Cp*Ir(Ebis)Cl]Cl (2b·Cl), [Cp*Rh(Mbit)Cl]Cl (3a·Cl), Cp*Rh(Mbis)Cl][Cp*RhCl₃] (3b·[Cp*RhCl₃]), [Cp*Rh(Ebit)Cl]Cl (4a·Cl) and [Cp*Rh(Ebis)Cl]Cl (4b·Cl), respectively. All compounds have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1b, 2b, 3a, 3b and 4a have been determined by X-ray crystallography. After activation with methylaluminoxane (MAO), the iridium complexes exhibit moderate activities for the vinyl polymerization of norbornene.