Structural characterization of molybdenum–dinitrogen complex as key species toward ammonia formation by dispersive XAFS spectroscopy

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia in the reaction with KC8 as a reductant and [HPCy3]BArF4 (Cy = cyclohexyl, ArF = 3,5-(CF3)2C6H3) as a proton source at –78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.3 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions by using rhenium-dinitrogen complexes as catalysts.

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Ammonia Formation Catalyzed by Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions

10.26434/chemrxiv.12162270.v1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Fanqiang Meng ◽

Shogo Kuriyama ◽

Hiromasa Tanaka ◽

Akihito Egi ◽

Kazunari Yoshizawa ◽

...

Keyword(s):

Nitrogen Fixation ◽

Pincer Ligands ◽

Pincer Ligand ◽

Reaction Conditions ◽

Rhenium Atom ◽

Phosphine Complexes ◽

Proton Source ◽

Dinitrogen Complexes ◽

Dinitrogen Complex ◽

Ammonia Formation

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia in the reaction with KC8 as a reductant and [HPCy3]BArF4 (Cy = cyclohexyl, ArF = 3,5-(CF3)2C6H3) as a proton source at –78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.3 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions by using rhenium-dinitrogen complexes as catalysts.

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New ultrastructural findings about Borrelia burgdorferi by cryofixation, negative staining, thin sectioning and scanning techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160467 ◽

1990 ◽

Vol 48 (3) ◽

pp. 582-583

Author(s):

S. F. Hayes ◽

M. D. Corwin ◽

T. G. Schwan ◽

D. W. Dorward ◽

W. Burgdorfer

Keyword(s):

Lyme Disease ◽

Borrelia Burgdorferi ◽

Structural Characterization ◽

Negative Staining ◽

Low Speed ◽

Thin Sectioning ◽

Ultrastructural Findings

Characterization of Borrelia burgdorferi strains by means of negative staining EM has become an integral part of many studies related to the biology of the Lyme disease organism. However, relying solely upon negative staining to compare new isolates with prototype B31 or other borreliae is often unsatisfactory. To obtain more satisfactory results, we have relied upon a correlative approach encompassing a variety EM techniques, i.e., scanning for topographical features and cryotomy, negative staining and thin sectioning to provide a more complete structural characterization of B. burgdorferi.For characterization, isolates of B. burgdorferi were cultured in BSK II media from which they were removed by low speed centrifugation. The sedimented borrelia were carefully resuspended in stabilizing buffer so as to preserve their features for scanning and negative staining. Alternatively, others were prepared for conventional thin sectioning and for cryotomy using modified procedures. For thin sectioning, the fixative described by Ito, et al.

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