Selective dimerization of a trinuclear mixed-metal sandwich complex: construction of an axially chiral metal skeleton

2021 ◽  
Vol 57 (72) ◽  
pp. 9120-9123
Author(s):  
Hiroshige Yamaura ◽  
Koji Yamamoto ◽  
Tetsuro Murahashi
Keyword(s):  
Bond Formation ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Chiral Structure ◽  
Mixed Metal ◽  
Reductive Dimerization ◽  
Axially Chiral ◽  
Complex Construction

We report reductive dimerization of mixed metal Pd2Pt or PdPt2 sandwich complexes. The dimerization occurs through selective Pt–Pt bond formation, and the PdPt2 dimer has a unique axially chiral structure derived from the heterometal arrangement.

Bis(monoazacrown ethers) with an electron-donating substituent at the hinge: A pronounced participation of hydroxyl group in formation of sodium ion sandwich complexes

1989 ◽  
Vol 54 (4) ◽  
pp. 1043-1054 ◽  
Author(s):  
Jiří Závada ◽  
Juraj Koudelka ◽  
Petr Holý ◽  
Martin Bělohradský ◽  
Ivan Stibor
Keyword(s):  
Complex Formation ◽  
Sandwich Structure ◽  
Sodium Ion ◽  
Hydroxyl Group ◽  
Complex Stability ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Marked Enhancement ◽  
Stability Data ◽  
Potentiometric Data

Sodium ion complex formation has been investigated potentiometrically in four homologous bis(crown) series I-IV differing by the nature of substituent placed at the linking trimethylene chain (X = OH, OCH3, OCH2C6H5 and H respectively). A marked enhancement of the complex stability has been observed in the bis(crown) series I and attributed to participation of the lateral hydroxyl group in the sandwich complex formation. Evidence in support of the sandwich structure has been provided (i) by analysis of the potentiometric data indicating a 1:1 complex stoichiometry and (ii) by a comparison of the complex stability data from the bis(crown) series I with the corresponding values from related monocyclic ligand series V, VI and VII revealing a pronounced cooperation of both macrorings in the sodium ion-bis(crown) I complex formation.

scholarly journals Uranium(iv) cyclobutadienyl sandwich compounds: synthesis, structure and chemical bonding

2020 ◽  
Vol 56 (6) ◽  
pp. 944-947 ◽  
Author(s):  
Nikolaos Tsoureas ◽  
Akseli Mansikkamäki ◽  
Richard A. Layfield
Keyword(s):  
Chemical Bonding ◽  
Molecular Structures ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Sandwich Compounds ◽  
Bonding Properties ◽  
Half Sandwich

The synthesis, molecular structures and bonding properties of two uranium(iv) cyclobutadienyl half-sandwich complexes and a doubly activated cyclobutadienyl sandwich complex are described.

scholarly journals Synthesis and Spectroscopic Characterization of Two New Dawson Sandwich Complexes: Na18[(NaOH)2(VO)2(P2W15O56)2].40H2O and Na18[(NaOH)2(VO)2(As2W15O56)2].27H2O

2012 ◽  
Vol 9 (4) ◽  
pp. 2185-2190 ◽  
Author(s):  
Mohammad Hakimi ◽  
Mohammad Reza Mohammadi ◽  
Salma Behboupour
Keyword(s):  
Divalent Cation ◽  
31P Nmr ◽  
Spectroscopic Characterization ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Sodium Salts ◽  
Vis Spectroscopy ◽  
Sandwich Type ◽  
Anion Complexes

Reaction of the three vacant complex ofa-[P2W15O56]12-anda-[As2W15O56]12-with divalent cation of VO2+in 1:1 mole ratio yields a previously unknown sandwich-type Wells-Dawson complex; Na18[(NaOH)2(VO)2(P2W15O56)2].40H2O (represented as Na2(VO)2P4W30) and Na18[(NaOH)2(VO)2(As2W15O56)2].27H2O (represented as Na2(VO)2As4W30). These complexes contain anions in which two divalent VO2+cations with two Na+ions are symmetrically sandwiched between two α-[P2W15O56]12- or α-[As2W15O56]12-groups leading to a “lacunary” sandwich complex. The anion complexes are isolated as sodium salts and characterized by elemental analysis, TGA, IR, 31P NMR and UV-Vis spectroscopy.

scholarly journals Mechanically axially chiral catenanes and noncanonical chiral rotaxanes

2021 ◽  
Author(s):  
John Maynard ◽  
Peter Gallagher ◽  
David Lozano ◽  
Patrick Butler ◽  
Steve Goldup
Keyword(s):  
Building Blocks ◽  
Biological Properties ◽  
Mirror Image ◽  
Chiral Structure ◽  
Molecular Chirality ◽  
Symmetry Properties ◽  
Axially Chiral ◽  
A Chain ◽  
Stereoselective Syntheses ◽  
Molecular Rings

Chirality, the property of objects that are distinct from their own mirror image, is important in many scientific areas but particularly chemistry, where the appearance of molecular chirality because of rigid arrangements of atoms in space famously influences a molecule’s biological properties. Less generally appreciated is that two molecular rings with chemically distinct faces combined like links in a chain results in a chiral structure even when the rings are achiral. To date, no enantiopure examples of such mechanically axially chiral catenanes has been reported. We re-examined the symmetry properties of the mechanically axially chiral motif and identified a straightforward route to such molecules from simple building blocks. We also identify that common representations of axially chiral catenanes obscure that a previously overlooked stereogenic unit arises when a ring is threaded onto a dumbbell-shaped molecule to generate a rotaxane. These insights allowed us to demonstrate the first stereoselective syntheses of an axially chiral catenane and a noncanonical axially chiral rotaxane motif. With methods to access these structures in hand, the process of exploring their properties and applications can now begin.

scholarly journals Mechanically axially chiral catenanes and noncanonical chiral rotaxanes

2021 ◽  
Author(s):  
John Maynard ◽  
Peter Gallagher ◽  
David Lozano ◽  
Patrick Butler ◽  
Steve Goldup
Keyword(s):  
Building Blocks ◽  
Biological Properties ◽  
Mirror Image ◽  
Chiral Structure ◽  
Molecular Chirality ◽  
Symmetry Properties ◽  
Axially Chiral ◽  
A Chain ◽  
Stereoselective Syntheses ◽  
Molecular Rings

Chirality, the property of objects that are distinct from their own mirror image, is important in many scientific areas but particularly chemistry, where the appearance of molecular chirality because of rigid arrangements of atoms in space famously influences a molecule’s biological properties. Less generally appreciated is that two molecular rings with chemically distinct faces combined like links in a chain results in a chiral structure even when the rings are achiral. To date, no enantiopure examples of such mechanically axially chiral catenanes has been reported. We re-examined the symmetry properties of the mechanically axially chiral motif and identified a straightforward route to such molecules from simple building blocks. We also identify that common representations of axially chiral catenanes obscure that a previously overlooked stereogenic unit arises when a ring is threaded onto a dumbbell-shaped molecule to generate a rotaxane. These insights allowed us to demonstrate the first stereoselective syntheses of an axially chiral catenane and a noncanonical axially chiral rotaxane motif. With methods to access these structures in hand, the process of exploring their properties and applications can now begin.

Synthesis, Spectroscopy and Electrochemistry of Lanthanide Bis-(ethylsulfanyl)tetraazaporphyrins

1998 ◽  
Vol 02 (02) ◽  
pp. 177-188 ◽  
Author(s):  
GIAMPAOLO RICCIARDI ◽  
SANDRA BELVISO ◽  
FRANCESCO LELJ ◽  
SANDRA RISTORI
Keyword(s):  
Direct Synthesis ◽  
Lanthanide Ions ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Trivalent Lanthanide ◽  
Green Form ◽  
Radical Ligand

Reaction of the oespz2− ligand (oespz = 2,3,7,8,12,13,17,18-octakis (ethylsulfanyl)-5,10,15,20-porphyrazinato) with trivalent lanthanide ions, such as Nd 3+, Eu 3+, Dy 3+, Yb 3+ and Lu 3+, leads to the direct synthesis of the corresponding sandwich complexes, in the radical, ligand-oxidized green form, whereas the reaction with La 3+ affords the sandwich complex in the protonated, blue form. It is found that the ligand-oxidized complexes show rather weak electronic absorptions in the range 850–1150 nm and are, compared to lanthanide diporphyrins and diphthalocyanines, very stable both to oxidation and to reduction.

scholarly journals Azaborolinyl-Komplexe, XV. Bis(η5-1,2-azaborolinyI)ruthenium-Sandwichkomplexe – Darstellung und Strukturuntersuchung/ Azaborolinyl Complexes, XV. Bis(η5-1,2-azaborolinyl)ruthenium Sandwich Complexes – Synthesis and Structure Investigation

1984 ◽  
Vol 39 (8) ◽  
pp. 1082-1087 ◽  
Author(s):  
Günter Schmid ◽  
Ottmar Boltsch ◽  
Dieter Bläser ◽  
Roland Boese
Keyword(s):  
Molecular Structure ◽  
Structure Investigation ◽  
X Ray Diffraction ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Interplanar Angle ◽  
X Ray ◽  
Tert Butyl ◽  
Complex Forms ◽  
Nmr Signals

AbstractThe synthesis of bis(1-tert-butyl-2 -methyl-η5 - 1 ,2 -azaborolinyl)ruthenium (1) and bis(2-methyll- trimethylsilyl-η5 - 1 ,2 -azaborolinyl)ruthenium (2) succeeds when RuCL is reacted with the corresponding 1,2-azaborolinyl lithium compounds in THF at -70 °C. Each of the sandwich complex forms two isomers with a clockwise and an anti-clockwise conformation of the azaborolinyl rings. The anti-clockwise isomer of 1 (1a ) gives colourless crystals which were investigated by singlecrystal X-ray diffraction methods. The molecular structure shows the rings in an eclipsed orientation forming an interplanar angle of 8.6 °. The isomers of 1 as well as of 2 give different 1H and 11B NMR signals.

scholarly journals Asymmetric biomimetic transamination of α-keto amides to peptides

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weiqi Cai ◽  
Xuelong Qiao ◽  
Hao Zhang ◽  
Bo Li ◽  
Jianhua Guo ◽  
...  
Keyword(s):  
Amino Acids ◽  
High Activity ◽  
Unnatural Amino Acids ◽  
Bond Formation ◽  
Amide Bond ◽  
Efficient Strategy ◽  
Amide Bond Formation ◽  
Axially Chiral ◽  
Catalytic Chemistry

AbstractPeptides are important compounds with broad applications in many areas. Asymmetric transamination of α-keto amides can provide an efficient strategy to synthesize peptides, however, the process has not been well developed yet and still remains a great challenge in both enzymatic and catalytic chemistry. For biological transamination, the high activity is attributed to manifold structural and electronic factors of transaminases. Based on the concept of multiple imitation of transaminases, here we report N-quaternized axially chiral pyridoxamines 1 for enantioselective transamination of α-keto amides, to produce various peptides in good yields with excellent enantio- and diastereoselectivities. The reaction is especially attractive for the synthesis of peptides made of unnatural amino acids since it doesn’t need great efforts to make chiral unnatural amino acids before amide bond formation.

Rydberg state mediated multiphoton ionization of (η7-C7H7)(η5-C5H5)Cr: DFT-supported experimental insights into the molecular and electronic structures of excited sandwich complexes

2019 ◽  
Vol 21 (19) ◽  
pp. 9665-9671
Author(s):  
Sergey Yu. Ketkov ◽  
Sheng Yuan Tzeng ◽  
Elena A. Rychagova ◽  
Lyubov’ V. Kalakutskaya ◽  
Marco Fuss ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Rydberg State ◽  
Electronic Excitation ◽  
Multiphoton Ionization ◽  
Structural Transformations ◽  
Dft Study ◽  
Sandwich Complexes ◽  
Sandwich Complex ◽  
Ligand Effects

The first REMPI/DFT study of a mixed sandwich complex reveals fine ligand effects on structural transformations accompanying electronic excitation.

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