Synthesis and Structural Characterization of Cationic Rhenium(V) and Technetium(V) Dioxo Complexes Containing Four N-Heterocyclic Carbene Ligands

2003 ◽  
Vol 42 (20) ◽  
pp. 6160-6162 ◽  
Author(s):  
Henrik Braband ◽  
Theresa I. Zahn ◽  
Ulrich Abram
Keyword(s):  
Structural Characterization ◽  
Carbene Ligands

Synthesis and structural characterization of iridium(I) complexes of 20-membered macrocyclic rings bearing chelating bis(N-heterocyclic carbene) ligands

2019 ◽  
Vol 75 (12) ◽  
pp. 1652-1657
Author(s):  
Rajesh Thapa ◽  
Stefan M. Kilyanek
Keyword(s):  
Structural Characterization ◽  
Macrocyclic Ligands ◽  
Iridium Complex ◽  
Amine Group ◽  
Carbene Ligands ◽  
Bimetallic Complex ◽  
Amine Groups

The reactivities of two 20-membered macrocyclic ligands, each containing two N-heterocyclic carbene (NHC) and two amine groups, towards [IrCl(COD)]2 (COD is cycloocta-1,5-diene) were investigated. Macrocycles containing imidazolin-2-ylidene groups formed the monometallic complex [(1,2,5,6-η)-cycloocta-1,5-diene](5,16-dibenzyl-1,5,9,12,16,20-hexaazatricyclo[18.2.1.19,12]tetracosa-10,21-dien-21,22-diylidene)iridium(I) bromide dichloromethane monosolvate, [Ir(C8H12)(C32H42N6)]Br·CH2Cl2, 2a. The structure of iridium complex 2a at 100 K has triclinic P\overline{1} symmetry. The ligand in 2a coordinates to the Ir center through the NHC moieties in a cis fashion. Additionally, the ligand adopts an umbrella-like structure that appears to envelope the Ir center. The structure displays C—H...Br interactions. Macrocycles containing benzimidazolin-2-ylidene groups formed the bimetallic complex [μ-5,20-dibenzyl-1,5,9,16,20,24-hexaazapentacyclo[22.6.1.19,16.010,15.025,30]dotriaconta-10(15),11,13,25(30),26,28-hexaene-31,32-diylidene]bis{bromido[(1,2,5,6-η)-cycloocta-1,5-diene]iridium(I)}, [Ir2Br2(C8H12)2(C40H46N6)], 2b. The structure of complex 2b at 100 K has orthorhombic Pbca symmetry. Each NHC moiety in 2b coordinates in a monodentate fashion to an Ir(COD) fragment. The structure exhibits disorder of the main molecule. This disorder is found in the portion of the macrocycle containing an amine group. This structure also displays C—H...Br interactions. Finally, the structure of the hexafluorophosphate salt of the imidazolin-2-ylidene-containing macrocycle, namely 5,16-dibenzyl-1λ5,5,9,12λ5,16,20-hexaazatricyclo[18.2.1.19,12]tetracosa-1(23),10,12(24),21-tetraene-1,12-diium bis(hexafluorophosphate), C32H44N6 2+·2PF6 −, 1c, was determined. The structure of macrocycle 1c at 100 K has triclinic P\overline{1} symmetry and was found to contain C—H...F interactions.

scholarly journals Synthesis and structural characterization of 20-membered macrocyclic rings bearing trans-chelating bis(N-heterocyclic carbene) ligands and the catalytic activity of their palladium(ii) complexes

2019 ◽  
Vol 48 (33) ◽  
pp. 12577-12590 ◽  
Author(s):  
Rajesh Thapa ◽  
Stefan M. Kilyanek
Keyword(s):  
Catalytic Activity ◽  
Coordination Chemistry ◽  
Structural Characterization ◽  
Metal Coordination ◽  
Carbene Ligands

20-Membered macrocyclic rings containing NHCs and amines were synthesized, and their late metal coordination chemistry explored.

Synthesis and Structural Characterization of Half-Sandwich Nickel Complexes Bearing Two Different N-Heterocyclic Carbene Ligands

2011 ◽  
Vol 30 (24) ◽  
pp. 6685-6691 ◽  
Author(s):  
Anna Magdalena Oertel ◽  
Vincent Ritleng ◽  
Loïc Burr ◽  
Michael J. Chetcuti
Keyword(s):  
Structural Characterization ◽  
Nickel Complexes ◽  
Carbene Ligands ◽  
Half Sandwich

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

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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