ChemInform Abstract: π-Complex Formation and Collapse in Electrophilic Halogenation of Aromatic Substrates.

Competition reactions using dimethylketene (DMK) – aluminum chloride complexes on a variety of substituted benzene derivatives gave partial rate factors. The logs of these Pfx values when plotted versus σ+ values gave two line segments of ρ = −6.59 for less active substrates, and ρ = −0.92 for more active substrates. Similar results were found for diphenylketene (ρ = −9.47 and −1.07).These results were rationalized by analogy to vinyl cation alkylations. A pair of π complexes (outer then inner) occur between initial approach of the reagent and final, product-determining π-complex formation. In one of these complexes the C=C bond of the ketene complex may be able to back-bond in a manner similar to that found in inorganic complexes of CO and metals.

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Proximity Effect in Arene Pi-Complex Formation

Zeitschrift für Naturforschung B ◽

10.1515/znb-1966-0902 ◽

1966 ◽

Vol 21 (9) ◽

pp. 823-827 ◽

Cited By ~ 8

Author(s):

Minoru Tsutsui ◽

Morris N. Levy

Keyword(s):

Complex Formation ◽

Proximity Effect ◽

Grignard Reagent ◽

Reaction System ◽

Coupling Reaction ◽

Reaction Products ◽

Hydrogen Elimination ◽

Trans Stilbene ◽

Π Complex ◽

Aryl Grignard Reagent

A proximity effect in arene π-complex formation from the reaction system of an aryl Grignard reagent and anhydrous chromic chloride was investigated. The yields of arene π-complexes and any accompanying reaction products were compared by the systematic variation of the aryl Grignard reagent employed. Phenyl Grignard gave the best yield of π-complex followed by the benzyl, mesityl and β-ethyl phenyl analogues. The styryl and phenylacetylenyl analogues did not form any π-complexes.The coupling reaction of benzyl groups gave a new π-complex, π-bibenzyl-π-toluene chromium, along with toluene, bibenzyl and trans-stilbene.Trans-stilbene was found without forming a trace amount of cis-stilbene. A mechanism for this stereospecific and α-hydrogen elimination coupling reaction is proposed.

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Theoretical studies on π-complex formation of organocopper compounds with acetylene. The origin of nucleophilicity of organocuprates

Journal of Molecular Structure THEOCHEM ◽

10.1016/s0166-1280(98)00458-8 ◽

1999 ◽

Vol 461-462 ◽

pp. 167-175 ◽

Cited By ~ 18

Author(s):

Seiji Mori ◽

Eiichi Nakamura

Keyword(s):

Complex Formation ◽

Theoretical Studies ◽

Π Complex

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Zum Mechanismus der Substituentenwechselwirkung bei der elektronenstoßinduzierten Äther-Spaltung in para-substituierten Methoxymethylaromaten / On the Mechanism of Substituent Interaction During the Electron Impact Induced Ether Cleavage from para-Substituted Methoxymethyl Benzenes

Zeitschrift für Naturforschung B ◽

10.1515/znb-1976-1221 ◽

1976 ◽

Vol 31 (12) ◽

pp. 1667-1672 ◽

Cited By ~ 2

Author(s):

Rupert Herrmann ◽

Helmut Schwarz

Keyword(s):

Complex Formation ◽

Electron Impact ◽

Benzene Ring ◽

Hydrogen Transfer ◽

Valence Bond ◽

Ring Expansion ◽

Ether Cleavage ◽

Π Complex ◽

Intramolecular Hydrogen ◽

Bond Isomers

The unusual methyl elimination from para-substituted methoxy-methyl benzenes has been elucidated. It can be shown that two entirely different mechanisms contribute to the reaction: i) intramolecular hydrogen transfer onto the benzene ring (π-complex formation) and ii) substituent migration via ring expansion. Alternative mechanisms as for instance transanular protonation of the ester function or substituent migration via valence bond isomers are not involved in the formation of the [M-methyl]+-ions.

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