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Titolo:
Mechanisms of cyclopalladation reactions in acetic acid: Not so simple one-pot processes
Autore:
Gomez, M; Granell, J; Martinez, M;
Indirizzi:
Univ Barcelona, Dept Quim Inorgan, E-08028 Barcelona, Spain Univ Barcelona Barcelona Spain E-08028 Inorgan, E-08028 Barcelona, Spain
Titolo Testata:
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
fascicolo: 1, , anno: 2000,
pagine: 217 - 224
SICI:
1434-1948(200001):1<217:MOCRIA>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
ORTHOMETALLATED PRIMARY AMINES; LIGAND-EXCHANGE REACTIONS; C-H BONDS; INTRAMOLECULAR ACTIVATION; CYCLOMETALATION REACTIONS; PALLADIUM(II) COMPLEXES; PRIMARY BENZYLAMINES; ORGANIC-SYNTHESIS; KINETICS; ORTHOPALLADATION;
Keywords:
reaction mechanisms; cyclopalladation; acetic acid; Pd-C bond stability; polynuclear species; palladium;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Martinez, M Univ Barcelona, Dept Quim Inorgan, Marti I Franques 1-11, E-08028 Barcelona, Spain Univ Barcelona Marti I Franques 1-11 Barcelona Spain E-08028
Citazione:
M. Gomez et al., "Mechanisms of cyclopalladation reactions in acetic acid: Not so simple one-pot processes", EUR J INORG, (1), 2000, pp. 217-224

Abstract

The processes operating during the synthetic cyclopalladation reactions ofimines in acetic acid have been studied from a kinetico-mechanistic point of view. These reactions include a fast initial coordination to the palladium through the M-donor atom of the imine, followed by the proper C-H bond activation to produce the acetato bridged dimeric species. At this point, the lability of the bridging acetato groups, the hydrolysis of the C-Pd bonds, and/or the hydrolysis of C=N exo bonds contribute to the generation of dark red polynuclear compounds. The processes occurring after the C-H activation have been followed kinetically, both from palladium acetate plus imine,and the synthetically pure isolated acetato dimers as starting materials. The kinetic and activation parameters have been found identical within experimental error whatever the starting material was (k(323) = 1.5 x 10(-4) s(-1); Delta H double dagger = 51 kJ mol(-1); Delta S double dagger = - 163 JK(-1) mol(-1) Delta V double dagger = +19 cm(3) mol(-1) for the 4-ClC6H4- CH= N-CH2-C6H5 imine derivative 1a). Acidolysis of C-Pd bonds has been foundto occur in these polynuclear species. When alternative monomeric C-benzylic-Pd bond-containing complexes are possible follow ups of the reactions produce them as final dead-end complexes (k(323) = 2.2 x 10(-5) s(-1); Delta H double dagger = 63. kJ mol(-1); Delta S double dagger = JK(-1) mol(-1) Delta V double dagger approximate to 0 cm(3) cm(-1) for the [2,4,6-(CH3)(3)]C6H2-CH=N-CH2-[2-(CH3]C6H4] imine derivative 3d). The same study has been carried out with primary amines in order to check the validity of the data ifC=N bond hydrolysis is taking place in the imine derivatives with exo C=N bonds. For complexes with similar type of metallacycles, the results agree reasonably well with the proposed mechanism [k(323) = 1.2 . 10(-4) s(-1), Delta H double dagger = 46 kJ . mol(-1), Delta S double dagger = -180 J . K-1 mol(-1), Delta V double dagger = -16 cm(3) . mol(-1) for the polynuclear formation of the C6H5-CH2-NH2 derivative 4e; k(323) = 3.0 . 10(-4) s(-1), Delta H double dagger = 55 kJ . mol(-1), Delta S double dagger = -147 J . K-1 mol(-1), Delta V double dagger = -24 cm(3) . mol(-1) for the polynuclear formation of the C6H5-CH2-N=CH-2,3,6-(CH3)(3)C6H2 derivative 2c].

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Documento generato il 21/09/20 alle ore 06:19:24