Detection of a .sigma.-complex in the reaction of cobalt atoms with methane

1993 ◽  
Vol 115 (5) ◽  
pp. 2039-2041 ◽  
Author(s):  
W. E. Billups ◽  
Sou Chan Chang ◽  
Robert H. Hauge ◽  
John L. Margrave
Keyword(s):  
Sigma Complex

Interaction of heterocycles and nucleophiles. II. Sigma complexes formed from methoxide ion and Methoxy-3,5-dinitropyridines in dimethyl sulphoxide

1970 ◽  
Vol 23 (5) ◽  
pp. 957 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
AG Moritz ◽  
DB Paul
Keyword(s):  
Dimethyl Sulphoxide ◽  
No Conversion ◽  
Solvation Effects ◽  
Sigma Complexes ◽  
Sigma Complex ◽  
Methoxide Ion ◽  
Rearrangement Reactions

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.

Pressure effect on rate and equilibrium constants of reversible anionic .sigma.-complex formation between polynitroaromatics and lyate ions of water and methanol

1980 ◽  
Vol 102 (24) ◽  
pp. 7268-7272 ◽  
Author(s):  
Muneo Sasaki ◽  
Noboru Takisawa ◽  
Fujitsugu Amita ◽  
Jiro Osugi
Keyword(s):  
Complex Formation ◽  
Pressure Effect ◽  
Equilibrium Constants ◽  
Sigma Complex

ChemInform Abstract: PROTON MAGNETIC RESONANCE CONFIRMATION OF CIS-TRANS ISOMERISM IN AN ANIONIC SIGMA COMPLEX

1973 ◽  
Vol 4 (31) ◽  
pp. no-no
Author(s):  
MICHAEL J. STRAUSS ◽  
STEPHAN P. B. TAYLOR
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Sigma Complex

A new approach to the generation of sigma complex structures

1990 ◽  
Vol 67 (7) ◽  
pp. 550 ◽  
Author(s):  
Joseph G. Young
Keyword(s):  
Complex Structures ◽  
New Approach ◽  
Sigma Complex

Electrochemical properties and reactivity of organonickel sigma-complex [NiBr(Mes)(bpy)] (Mes = 2,4,6-trimethylphenyl, bpy = 2,2′-bipyridine)

2015 ◽  
Vol 51 (11) ◽  
pp. 1061-1068 ◽  
Author(s):  
I. F. Sakhapov ◽  
Z. N. Gafurov ◽  
V. M. Babaev ◽  
V. A. Kurmaz ◽  
R. R. Mukhametbareev ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Sigma Complex

Meisenheimer Complex Formation Between 1,3,5-Trinitrobenzene and Hydroxide Ion. Equilibrium Constants for the Dimethylformamide–Water Solvent System

1972 ◽  
Vol 50 (11) ◽  
pp. 1729-1733 ◽  
Author(s):  
E. A. Symons ◽  
E. Buncel
Keyword(s):  
Complex Formation ◽  
Aqueous Medium ◽  
Equilibrium Constant ◽  
Equilibrium Constants ◽  
Solvent System ◽  
Medium Composition ◽  
Hydroxide Ion ◽  
Spectrophotometric Methods ◽  
Water Solvent ◽  
Sigma Complex

Sigma-complex formation between 1,3,5-trinitrobenzene (TNB) and hydroxide ion has been studied quantitatively as a function of medium composition for part of the dimethylformamide (DMF)–water solvent system by spectrophotometric methods. Only a 1:1 complex is detected under the conditions of measurement, with [TNB] ≥ [OH−]. The equilibrium constant (Keq) for complex formation in 22 mol % DMF has the value 3 × 10−3 l mol−1, compared with 3 l mol−1 in purely aqueous medium. Further increases in Kcq occur as the DMF content of the medium is raised; in 50 mol % DMF Keq ≈ 105, but reliable Keq values could not be obtained in this region of medium composition. The increase in Keq with increasing DMF content is interpreted largely on the basis of hydroxide ion desolvation.

Reaction pathways in the formation of the 1,3,5-trinitrobenzene-anilide .sigma. complex from aniline and the 1,3,5-trinitrobenzene-methoxide .sigma. complex

1977 ◽  
Vol 99 (13) ◽  
pp. 4429-4438 ◽  
Author(s):  
Erwin Buncel ◽  
John G. K. Webb ◽  
James F. Wiltshire
Keyword(s):  
Reaction Pathways ◽  
Sigma Complex
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