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.

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.

Although examples of nickel(II), palladium(II) and platinum(II)N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(II) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(II) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1′-diisopropyl-3,3′-methylenediimidazoline-2,2′-diylidene)platinum(II) dibromide.

Although examples of nickel(II), palladium(II) and platinum(II)N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(II) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(II) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1′-diisopropyl-3,3′-methylenediimidazoline-2,2′-diylidene)platinum(II) dibromide.

Three Re(V) N-heterocyclic carbene complexes [ReO(OH)(LMe)2][PF6]1.4[ReO4]0.6, [ReO(OH)(LiPr)2][PF6]1.4[ReO4]0.6 and [ReO(OH)(LBn)2][PF6]1.3[ReO4]0.7 (LMe = 1,1′-methylene-bis(3-methylimidazole-2-ylidene); LiPr = 1,1′-methylene-bis(3-isopropylimidazole-2-ylidene) and LBn = 1,1′-methylene-bis(3-benzylimidazole-2-ylidene)) with trans oxo and hydroxo at axial positions have been synthesized.

Three Re(V) N-heterocyclic carbene complexes [ReO(OH)(LMe)2][PF6]1.4[ReO4]0.6, [ReO(OH)(LiPr)2][PF6]1.4[ReO4]0.6 and [ReO(OH)(LBn)2][PF6]1.3[ReO4]0.7 (LMe = 1,1′-methylene-bis(3-methylimidazole-2-ylidene); LiPr = 1,1′-methylene-bis(3-isopropylimidazole-2-ylidene) and LBn = 1,1′-methylene-bis(3-benzylimidazole-2-ylidene)) with trans oxo and hydroxo at axial positions have been synthesized.

A transmetallation route, using silver(I) precursors, to several zero- and di-valent palladium complexes with chelating bis(N-heterocyclic carbene) ligands bearing various N-substituents has been established. The resulting complexes have been characterized by NMR and mass spectroscopy. In addition, the structure of a representative compound, [Pd0(bis-(Mes)NHC)(η2-ma)] (3a), was confirmed by X-ray crystal structure determination. In contrast to the transfer semihydrogenation, in which only low activity was observed, complex 3a showed activity (TOF = 49 molsub molcat−1 h−1) and selectivity comparable to its monodentate counterparts in the semihydrogenation of 1-phenyl-1-propyne with molecular hydrogen.

A transmetallation route, using silver(I) precursors, to several zero- and di-valent palladium complexes with chelating bis(N-heterocyclic carbene) ligands bearing various N-substituents has been established. The resulting complexes have been characterized by NMR and mass spectroscopy. In addition, the structure of a representative compound, [Pd0(bis-(Mes)NHC)(η2-ma)] (3a), was confirmed by X-ray crystal structure determination. In contrast to the transfer semihydrogenation, in which only low activity was observed, complex 3a showed activity (TOF = 49 molsub molcat−1 h−1) and selectivity comparable to its monodentate counterparts in the semihydrogenation of 1-phenyl-1-propyne with molecular hydrogen.

A series of eight Rhenium(I)-N-heterocyclic carbene (NHC) complexes of the general form [ReCl(CO)3(C^C)] (where C^C is a bis(NHC) bidentate ligand), [ReCl(CO)3(C^C)]2 (where C^C is a bis-bidentate tetra-NHC ligand) and [Re(CO)3(C^N^C)]+[X]− (where C^N^C is a bis(NHC)-amine ligand and the counter ion X is either the ReO4− or PF6−) have been synthesised using a Ag2O transmetallation protocol. The novel precursor imidazolium salts and Re(I) complexes were characterized by elemental analysis, 1H and 13C NMR spectroscopy and the molecular structures for two imidazolium salt and six Re(I) complexes were determined by single crystal X-ray diffraction. These NHC ligand systems are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and as such the stability of two complexes of the form [ReCl(CO)3(C^C)] and [Re(CO)3(C^N^C)][ReO4] were evaluated in ligand challenge experiments using the metal binding amino acids L-histidine or L-cysteine. These studies showed that the former was unstable, with the chloride ligand being replaced by either cysteine or histidine, while no evidence for transchelation was observed for the latter suggesting that bis(NHC)-amine ligands of this type may be suitable for biological applications.

A series of eight Rhenium(I)-N-heterocyclic carbene (NHC) complexes of the general form [ReCl(CO)3(C^C)] (where C^C is a bis(NHC) bidentate ligand), [ReCl(CO)3(C^C)]2 (where C^C is a bis-bidentate tetra-NHC ligand) and [Re(CO)3(C^N^C)]+[X]− (where C^N^C is a bis(NHC)-amine ligand and the counter ion X is either the ReO4− or PF6−) have been synthesised using a Ag2O transmetallation protocol. The novel precursor imidazolium salts and Re(I) complexes were characterized by elemental analysis, 1H and 13C NMR spectroscopy and the molecular structures for two imidazolium salt and six Re(I) complexes were determined by single crystal X-ray diffraction. These NHC ligand systems are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and as such the stability of two complexes of the form [ReCl(CO)3(C^C)] and [Re(CO)3(C^N^C)][ReO4] were evaluated in ligand challenge experiments using the metal binding amino acids L-histidine or L-cysteine. These studies showed that the former was unstable, with the chloride ligand being replaced by either cysteine or histidine, while no evidence for transchelation was observed for the latter suggesting that bis(NHC)-amine ligands of this type may be suitable for biological applications.