ISSN:
0268-2605
Schlagwort(e):
Palladium
;
allylic complexes
;
alkenes
;
H/D exchange
;
kinetics
;
mechanism
;
acidolysis
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Evidence is presented that the dimeric π-allylic species [(η3-allyl)PdCl]2 is not intermediate in the Li2Pd2Cl6-catalysed allylic H/D exchange in alkenes. Neither H/D exchange in α-methylstyrene, nor enrichment of [(η3-2-PhC3H4)PdCl]2, was observed when the latter complex was incubated at 100°C in D3CCOOD either in the presence or in the absence of PhC(CH3)=CH2, respectively. The kinetics of H/D exchange in α-methylstyrene catalysed by Li2Pd2Cl6 were studied in some detail. The exchange proceeds at highest rates when reduction of palladium(II) takes place and is much slower in the presence of 1,4-benzoquinone as a palladium reoxidant. The exchange rate is directly proportional to the alkene and catalyst concentrations and independent of the reoxidant concentration. It is suggested that the palladium(II)-catalysed exchange involves an intermediate hydrid-allyl species where palladium has a formal oxidation state of IV.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/aoc.590020203
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