ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The seven-coordinate complexes (IV) with a pseudo-pentagonal bipyramidal geometry are obtained fr... more The seven-coordinate complexes (IV) with a pseudo-pentagonal bipyramidal geometry are obtained from the sodium salts (I) of the quadridentate Schiff bases ((IVa) (M: Zr) and (IVc): space group P1, Z=2). Recrystallization of (IVa) from toluene removes the THF ligand leading to the six-coordinate cis-dichloro derivatives (V) (P21/n, Z=4). In the absence of geometrical constraints Zr(IV) prefers six-coordination and a cis arrangement of the chloride ligands. This is confirmed by synthesizing the Zr(IV) complex (VI)
Scheme 1. The synthesis and reactivity of the porphyrinogen ± Ru ± vinylidene functionality. Comp... more Scheme 1. The synthesis and reactivity of the porphyrinogen ± Ru ± vinylidene functionality. Complexes 1 ± 8 were isolated and fully characterized. Complexes A ± C are speculative.
Journal of the American Chemical Society, Feb 8, 2016
It is possible to control the geometry and the composition of metallasupramolecular assemblies vi... more It is possible to control the geometry and the composition of metallasupramolecular assemblies via the aspect ratio of their ligands. This point is demonstrated for a series of iron-and palladium-based coordination cages. Functionalized clathrochelate complexes with variable aspect ratios were used as rod-like metalloligands. A cubic Fe II 8L12 cage was obtained from a metalloligand with an intermediate aspect ratio. By increasing the length or by decreasing the width of the ligand, the self-assembly process resulted in the clean formation of tetrahedral Fe II 4L6 cages instead of cubic cages. In a related fashion, it was possible to control the geometry of Pd II-based coordination cages. A metalloligand with a large aspect ratio gave an entropically-favored tetrahedral Pd II 4L8 assembly, whereas an octahedral Pd II 6L12 cage was formed with a ligand of the same length but with an increased width. The aspect ratio can also be used to control the composition of dynamic mixtures of Pd II cages. Out of two metalloligands with only a marginally different aspect ratio, one gave rise to a self-sorted collection of Pd II 4L8 and Pd II 6L12 cages, whereas the other did not.
Related Article: Alexander G. Tskhovrebov, Euro Solari, Rosario Scopelliti, and Kay Severin|2013|... more Related Article: Alexander G. Tskhovrebov, Euro Solari, Rosario Scopelliti, and Kay Severin|2013|Inorg.Chem.|52|11688|doi:10.1021/ic401524w
The one-electron reduction of nitrous oxide (N 2 O) was achievedu sing strong Lewis acids E(C 6 F... more The one-electron reduction of nitrous oxide (N 2 O) was achievedu sing strong Lewis acids E(C 6 F 5) 3 (E = Bo rA l) in combination with metallocenes.I nt he case of B(C 6 F 5) 3 , electron transfer to N 2 Or equired ap owerful reducing agent such as Cp* 2 Co (Cp* = pentamethylcyclopentadienyl). In the presence of Al(C 6 F 5) 3 ,o nt he other hand, the reactions could be performedw ith weaker reducing agents such as Cp* 2 Fe or Cp 2 Fe (Cp = cyclopentadienyl). TheL ewis acid-mediated electron transfer from the metallocene to N 2 Or esulted in cleavage of the NÀOb ond, generating N 2 and the oxyl radical anion [OE(C 6 F 5) 3 ] •À .T he latter is highly reactivea nd engages in CÀHa ctivation reactions. It was possible to trap the radicalb ya ddition of the Gomberg dimer,w hich acts as a sourceo ft he trityl radical. Scheme1.(a) The strong Lewis acids B(C 6 F 5) 3 and Al(C 6 F 5) 3 are able to promote the reduction of substrates Sv ia single-electron-transferp rocesses. (b) Reaction of the nitrous oxide adductR 3 P-N 2 O-Al(C 6 F 5) 3 with Al(C 6 F 5) 3 .
General: All experiments were performed inside a glovebox under an atmosphere of dinitrogen conta... more General: All experiments were performed inside a glovebox under an atmosphere of dinitrogen containing less than 1 ppm of oxygen and water. Thoroughly dried and deoxygenated solvents were used. Triphenylphosphine (PPh 3) and bicyclo[2.2.1]hepta-2,5-diene (NBD) were purchased from Fluka. Metallic Zn was a commercial product from Aldrich. t-Butylacetylene was purchased from Alfa Aesar. Tricyclohexylphosphine (PCy 3) was obtained from Strem Chemicals and RuCl 3 (H 2 O) n from Precious Metals Online. All chemicals were used as received, unless otherwise stated. 1 H, 13 C and 31 P NMR spectra were recorded on a Bruker spectrometer at 400 MHz using deuterated solvents. CD 2 Cl 2 and CDCl 3 (from Aldrich) for NMR experiments were degassed by three freeze-pump-thaw cycles and then purified by vacuum transfer at room temperature. Synthesis of complex 3: [RuCl 3 (H 2 O) n ] (500 mg, 1.90 mmol) was dissolved in 25 mL THF with heating and then the solvent was distilled off at 72 °C, normal pressure using a rotavapor. Complete removal of the solvent at this temperature led to a green insoluble material. Hence, the last portion (~5 mL) of the solvent was removed under high vacuum. The procedure was repeated and then the resulting solid (reddish brown in color) was dissolved in 10 mL of dry MeOH under nitrogen followed by the addition of tbutylacetylene (1.0 mL, 8.0 mmol). The closed flask was heated at 55 °C for 24 h and S1
The chemical activation of nitrous oxide (N 2 O) typically results in O-atom transfer and the ext... more The chemical activation of nitrous oxide (N 2 O) typically results in O-atom transfer and the extrusion of N 2 gas. In contrast, reactions of Ntrimethylsilyl (TMS)-substituted amides with N 2 O give inorganic or organic azides, with concomitant formation of silanols or siloxanes. N-TMS-substituted amides are also able to induce N−O bond cleavage in N 2 O-derived dialkylaminodiazotates, generating tetrazene salts. These results indicate the potential of silyl groups in devising transformations, in which N 2 O acts as an N-atom donor.
Dinuclear clathrochelate complexes are easily accessible by reaction of zinc(II) triflate or coba... more Dinuclear clathrochelate complexes are easily accessible by reaction of zinc(II) triflate or cobalt(II) nitrate with arylboronic acids and phenoldioximes. The utilization of brominated arylboronic acids and/or brominated phenoldioximes allows preparing clathrochelates with two, three, five or seven bromine atoms on the outside. These clathrochelates can undergo Pd-catalyzed cross-coupling reactions with 3-and 4-pyridylboronic acid to give new metalloligands featuring up to seven pyridyl groups. The pyridylcapped clathrochelates display characteristics which make them interesting building blocks for structural supramolecular chemistry: they are rigid, large (up to 2.7 nm), luminescent (for M = Zn), and anionic. The pentatopic pyridyl ligands display an unusual trigonal bipyramidal geometry.
A ditopic carbanionic N-heterocyclic carbene was found to react with the inert gas nitrous oxide,... more A ditopic carbanionic N-heterocyclic carbene was found to react with the inert gas nitrous oxide, resulting in a stable covalent adduct with two intact N2O groups attached to the heterocycle. Mesoionic N-heterocyclic carbenes derived from C2-arylated 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene are also able to form adducts with one or two N2O groups. Crystallographic analyses of all adducts reveal bent N2O groups, which can adopt a cis or trans configuration.
Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The propert... more Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The properties of these ligands were examined by synthesizing Rh I , Au I , and Pd II complexes. Experimental (NMR, IR) and theoretical investigations show that Azo-MICs are potent σ-donor ligands. Yet, they feature a small singlettriplet gap and very low-lying LUMO levels. The unique electronic properties of Azo-MICs allow for reversible one-electron reductions of the metal complexes, as evidenced by cyclic voltammetry.
Synthesis of Azoimidazolium Dyes with Nitrous Oxide.-AlCl 3-mediated coupling of a variety of are... more Synthesis of Azoimidazolium Dyes with Nitrous Oxide.-AlCl 3-mediated coupling of a variety of arenes with N 2O-adducts of NHC-carbenes offers a synthetic route to novel azoimidazolium dyes (IV) and (VI).
Different proton-relay groups in hexadentate polypyridyl cobalt complexes induce distinct efficie... more Different proton-relay groups in hexadentate polypyridyl cobalt complexes induce distinct efficiencies and mechanisms in photo- and electrochemical H2 generation.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The seven-coordinate complexes (IV) with a pseudo-pentagonal bipyramidal geometry are obtained fr... more The seven-coordinate complexes (IV) with a pseudo-pentagonal bipyramidal geometry are obtained from the sodium salts (I) of the quadridentate Schiff bases ((IVa) (M: Zr) and (IVc): space group P1, Z=2). Recrystallization of (IVa) from toluene removes the THF ligand leading to the six-coordinate cis-dichloro derivatives (V) (P21/n, Z=4). In the absence of geometrical constraints Zr(IV) prefers six-coordination and a cis arrangement of the chloride ligands. This is confirmed by synthesizing the Zr(IV) complex (VI)
Scheme 1. The synthesis and reactivity of the porphyrinogen ± Ru ± vinylidene functionality. Comp... more Scheme 1. The synthesis and reactivity of the porphyrinogen ± Ru ± vinylidene functionality. Complexes 1 ± 8 were isolated and fully characterized. Complexes A ± C are speculative.
Journal of the American Chemical Society, Feb 8, 2016
It is possible to control the geometry and the composition of metallasupramolecular assemblies vi... more It is possible to control the geometry and the composition of metallasupramolecular assemblies via the aspect ratio of their ligands. This point is demonstrated for a series of iron-and palladium-based coordination cages. Functionalized clathrochelate complexes with variable aspect ratios were used as rod-like metalloligands. A cubic Fe II 8L12 cage was obtained from a metalloligand with an intermediate aspect ratio. By increasing the length or by decreasing the width of the ligand, the self-assembly process resulted in the clean formation of tetrahedral Fe II 4L6 cages instead of cubic cages. In a related fashion, it was possible to control the geometry of Pd II-based coordination cages. A metalloligand with a large aspect ratio gave an entropically-favored tetrahedral Pd II 4L8 assembly, whereas an octahedral Pd II 6L12 cage was formed with a ligand of the same length but with an increased width. The aspect ratio can also be used to control the composition of dynamic mixtures of Pd II cages. Out of two metalloligands with only a marginally different aspect ratio, one gave rise to a self-sorted collection of Pd II 4L8 and Pd II 6L12 cages, whereas the other did not.
Related Article: Alexander G. Tskhovrebov, Euro Solari, Rosario Scopelliti, and Kay Severin|2013|... more Related Article: Alexander G. Tskhovrebov, Euro Solari, Rosario Scopelliti, and Kay Severin|2013|Inorg.Chem.|52|11688|doi:10.1021/ic401524w
The one-electron reduction of nitrous oxide (N 2 O) was achievedu sing strong Lewis acids E(C 6 F... more The one-electron reduction of nitrous oxide (N 2 O) was achievedu sing strong Lewis acids E(C 6 F 5) 3 (E = Bo rA l) in combination with metallocenes.I nt he case of B(C 6 F 5) 3 , electron transfer to N 2 Or equired ap owerful reducing agent such as Cp* 2 Co (Cp* = pentamethylcyclopentadienyl). In the presence of Al(C 6 F 5) 3 ,o nt he other hand, the reactions could be performedw ith weaker reducing agents such as Cp* 2 Fe or Cp 2 Fe (Cp = cyclopentadienyl). TheL ewis acid-mediated electron transfer from the metallocene to N 2 Or esulted in cleavage of the NÀOb ond, generating N 2 and the oxyl radical anion [OE(C 6 F 5) 3 ] •À .T he latter is highly reactivea nd engages in CÀHa ctivation reactions. It was possible to trap the radicalb ya ddition of the Gomberg dimer,w hich acts as a sourceo ft he trityl radical. Scheme1.(a) The strong Lewis acids B(C 6 F 5) 3 and Al(C 6 F 5) 3 are able to promote the reduction of substrates Sv ia single-electron-transferp rocesses. (b) Reaction of the nitrous oxide adductR 3 P-N 2 O-Al(C 6 F 5) 3 with Al(C 6 F 5) 3 .
General: All experiments were performed inside a glovebox under an atmosphere of dinitrogen conta... more General: All experiments were performed inside a glovebox under an atmosphere of dinitrogen containing less than 1 ppm of oxygen and water. Thoroughly dried and deoxygenated solvents were used. Triphenylphosphine (PPh 3) and bicyclo[2.2.1]hepta-2,5-diene (NBD) were purchased from Fluka. Metallic Zn was a commercial product from Aldrich. t-Butylacetylene was purchased from Alfa Aesar. Tricyclohexylphosphine (PCy 3) was obtained from Strem Chemicals and RuCl 3 (H 2 O) n from Precious Metals Online. All chemicals were used as received, unless otherwise stated. 1 H, 13 C and 31 P NMR spectra were recorded on a Bruker spectrometer at 400 MHz using deuterated solvents. CD 2 Cl 2 and CDCl 3 (from Aldrich) for NMR experiments were degassed by three freeze-pump-thaw cycles and then purified by vacuum transfer at room temperature. Synthesis of complex 3: [RuCl 3 (H 2 O) n ] (500 mg, 1.90 mmol) was dissolved in 25 mL THF with heating and then the solvent was distilled off at 72 °C, normal pressure using a rotavapor. Complete removal of the solvent at this temperature led to a green insoluble material. Hence, the last portion (~5 mL) of the solvent was removed under high vacuum. The procedure was repeated and then the resulting solid (reddish brown in color) was dissolved in 10 mL of dry MeOH under nitrogen followed by the addition of tbutylacetylene (1.0 mL, 8.0 mmol). The closed flask was heated at 55 °C for 24 h and S1
The chemical activation of nitrous oxide (N 2 O) typically results in O-atom transfer and the ext... more The chemical activation of nitrous oxide (N 2 O) typically results in O-atom transfer and the extrusion of N 2 gas. In contrast, reactions of Ntrimethylsilyl (TMS)-substituted amides with N 2 O give inorganic or organic azides, with concomitant formation of silanols or siloxanes. N-TMS-substituted amides are also able to induce N−O bond cleavage in N 2 O-derived dialkylaminodiazotates, generating tetrazene salts. These results indicate the potential of silyl groups in devising transformations, in which N 2 O acts as an N-atom donor.
Dinuclear clathrochelate complexes are easily accessible by reaction of zinc(II) triflate or coba... more Dinuclear clathrochelate complexes are easily accessible by reaction of zinc(II) triflate or cobalt(II) nitrate with arylboronic acids and phenoldioximes. The utilization of brominated arylboronic acids and/or brominated phenoldioximes allows preparing clathrochelates with two, three, five or seven bromine atoms on the outside. These clathrochelates can undergo Pd-catalyzed cross-coupling reactions with 3-and 4-pyridylboronic acid to give new metalloligands featuring up to seven pyridyl groups. The pyridylcapped clathrochelates display characteristics which make them interesting building blocks for structural supramolecular chemistry: they are rigid, large (up to 2.7 nm), luminescent (for M = Zn), and anionic. The pentatopic pyridyl ligands display an unusual trigonal bipyramidal geometry.
A ditopic carbanionic N-heterocyclic carbene was found to react with the inert gas nitrous oxide,... more A ditopic carbanionic N-heterocyclic carbene was found to react with the inert gas nitrous oxide, resulting in a stable covalent adduct with two intact N2O groups attached to the heterocycle. Mesoionic N-heterocyclic carbenes derived from C2-arylated 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene are also able to form adducts with one or two N2O groups. Crystallographic analyses of all adducts reveal bent N2O groups, which can adopt a cis or trans configuration.
Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The propert... more Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The properties of these ligands were examined by synthesizing Rh I , Au I , and Pd II complexes. Experimental (NMR, IR) and theoretical investigations show that Azo-MICs are potent σ-donor ligands. Yet, they feature a small singlettriplet gap and very low-lying LUMO levels. The unique electronic properties of Azo-MICs allow for reversible one-electron reductions of the metal complexes, as evidenced by cyclic voltammetry.
Synthesis of Azoimidazolium Dyes with Nitrous Oxide.-AlCl 3-mediated coupling of a variety of are... more Synthesis of Azoimidazolium Dyes with Nitrous Oxide.-AlCl 3-mediated coupling of a variety of arenes with N 2O-adducts of NHC-carbenes offers a synthetic route to novel azoimidazolium dyes (IV) and (VI).
Different proton-relay groups in hexadentate polypyridyl cobalt complexes induce distinct efficie... more Different proton-relay groups in hexadentate polypyridyl cobalt complexes induce distinct efficiencies and mechanisms in photo- and electrochemical H2 generation.
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