Unusual Ligand Isomerization Dictated by Coordination Requirements of the Metal Ion:  A Double-Bond Shift in Cu(II)-Assisted Template Condensation between Diacetylpyridine and a Tripodal Tetramine

1999 ◽  
Vol 38 (12) ◽  
pp. 2974-2980 ◽  
Author(s):  
Elena V. Rybak-Akimova ◽  
Alexander Y. Nazarenko ◽  
Svetlana S. Silchenko
Keyword(s):  
Double Bond ◽  
Metal Ion ◽  
Template Condensation ◽  
Coordination Requirements ◽  
Double Bond Shift

Olefin Oligomerization and Isomerization Catalysts. The Preparation, Properties and Catalytic Action of Dithio Nickel(II) Complexes With Chelating Phosphines

1986 ◽  
Vol 39 (7) ◽  
pp. 1129 ◽  
Author(s):  
KJ Cavell ◽  
AF Masters
Keyword(s):  
Double Bond ◽  
General Formula ◽  
Nickel Complexes ◽  
High Specificity ◽  
Catalytic Action ◽  
Chelating Phosphines ◽  
Olefin Oligomerization ◽  
Double Bond Shift

The syntheses and properties of cationic nickel complexes containing dithio-β-diketonate and chelating bisphosphine ligands of general formula [Ni{R1C(S)CR2C(S)R3}{(PL1L2)R(PL3L4)}]X(Rj,Lj = alkyl or aryl, R = (CH2)n, n = 1-4, X = halide, BPh4, PF6, etc.) are described. The compounds are shown to be effective catalysts for the oligomerization and double bond shift isomerization of olefins with a high specificity for dimeric products rich in desirable linear and near linear isomers.

ChemInform Abstract: A REGIOSPECIFIC DOUBLE BOND SHIFT INDUCED BY TITANOCENE CATALYSTS

1980 ◽  
Vol 11 (22) ◽  
Author(s):  
F. TURECEK ◽  
H. ANTROPIUSOVA ◽  
K. MACH ◽  
V. HANUS ◽  
P. SEDMERA
Keyword(s):  
Double Bond ◽  
Double Bond Shift

First iron and cobalt(ii) hexabromoclathrochelates: structural, magnetic, redox, and electrocatalytic behavior

2015 ◽  
Vol 44 (5) ◽  
pp. 2476-2487 ◽  
Author(s):  
Alexander V. Dolganov ◽  
Alexander S. Belov ◽  
Valentin V. Novikov ◽  
Anna V. Vologzhanina ◽  
Galina V. Romanenko ◽  
...  
Keyword(s):  
Metal Ion ◽  
Template Condensation

Template condensation of dibromoglyoxime with n-butylboronic acid on a metal ion as a matrix afforded the first iron and cobalt(ii) hexabromoclathrochelates.

Infrared Study of Some Structural Changes in Natural Rubber during Vulcanization

1958 ◽  
Vol 31 (4) ◽  
pp. 719-736 ◽  
Author(s):  
Frederic J. Linnig ◽  
James E. Stewart
Keyword(s):  
Double Bond ◽  
Gamma Rays ◽  
Structural Changes ◽  
Elemental Sulfur ◽  
Carboxyl Groups ◽  
Double Bonds ◽  
Infrared Study ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber ◽  
Double Bond Shift

Abstract A knowledge of the structure of vulcanized rubber is essential to the interpretation of vulcanization and oxidation studies and the physical properties of the material. In the present work an infrared study has been made of structures resulting from a number of different methods of vulcanization. Sulfur vulcanizates show the presence of a shifted double bond, originally observed by Sheppard and Sutherland. The presence of conjugated double bonds is also indicated. Accelerators such as tetramethylthiuram disulfide and zinc dibutyl dithiocarbamate increase the rate of the double-bond shift and reduce the amount of conjugated double bonds. Neither the double-bond shift nor conjugation is observed as a result of vulcanization with tetramethylthiuram disulfide alone, hydrogen sulfide and sulfur dioxide (Peachey process), a peroxide, or gamma rays. These result in a possible decrease in carbonyl structures, and in the case of the last three, possible increased absorption due to OH and ionized carboxyl groups. Apparently, the double-bond shift and conjugation are primarily phenomena related to the use of elemental sulfur. The other vulcanization systems studied evidently involve different mechanisms. An implication of the present work is that there may be a relationship between the reported ease of oxidation of sulfur vulcanizates, accelerated vulcanizates, and sulfurless vulcanizates (tetramethylthiuram disulfide alone), which decreases in the order named, and the probable amount of conjugation in the compound, which decreases in the same order.

scholarly journals Synthesis of a Chiral Meso-Like Ansa-Zirconocene Complex and its Use for the Catalytic Formation of Low Molecular Weight Polypropylene

1995 ◽  
Vol 50 (6) ◽  
pp. 982-989 ◽  
Author(s):  
Sven Thiele ◽  
Gerhard Erker ◽  
Cornelia Fritze ◽  
Christian Psiorz ◽  
Roland Fröhlich
Keyword(s):  
Crystal Structure ◽  
Molecular Weight ◽  
Double Bond ◽  
Ambient Temperature ◽  
Organic Synthesis ◽  
Crystal Structure Analysis ◽  
Low Molecular Weight ◽  
X Ray ◽  
Catalyst Systems ◽  
Double Bond Shift

Reaction of lithium(neomenthylcyclopentadienid) 3 with dimethyldichlorosilane gives dimethylbis[3-(neomenthyl)cyclopentadienyl]silane 4 regioselectively as a mixture of double bond shift isomers (57% isolated). Deprotonation with 2 equiv. of butyllithium followed by treatment with zirconiumtetrachloride furnished a mixture of the three {dimethylsilylenbis[η5-3-(neomenthyl)cyclopentadienyl][zirconium dichloride diastereomers from which the pure meso-like isomer 6e [p -R (1′S ,3 ′R ,4 ′R),p -S (1′S ,3 ′R ,4 ′R)] was isolated by fractional crystallization. Complex 6 c was characterized by an X-ray crystal structure analysis. Its D 1 - Zr - D 2 angle of 126.8° is very similar as observed in bis(η-cyclopentadienyl) zirconium dichloride (D 1 and D 2 denote the centroids of the cyclopentadienyl rings). The homogeneous 6c/methylalumoxane Ziegler-type catalyst produces polypropylene of low molecular weight (Mη ≈ 670 at ambient temperature). Related catalyst systems may find interesting applications in organic synthesis.

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