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Palladium(II)‐catalysed H/D allylic exchange in alkenes: An intermediacy of palladium(IV)?
Author(s) -
Ryabov Alexander D,
Eliseev Alexey V,
Yatsimirsky Anatoly K
Publication year - 1988
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.590020203
Subject(s) - palladium , chemistry , allylic rearrangement , catalysis , medicinal chemistry , alkene , inorganic chemistry , organic chemistry
Evidence is presented that the dimeric π‐allylic species [(η 3 ‐allyl)PdCl] 2 is not intermediate in the Li 2 Pd 2 Cl 6 ‐catalysed allylic H/D exchange in alkenes. Neither H/D exchange in α‐methylstyrene, nor enrichment of [(η 3 ‐2‐PhC 3 H 4 )PdCl] 2 , was observed when the latter complex was incubated at 100°C in D 3 CCOOD either in the presence or in the absence of PhC(CH 3 )CH 2 , respectively. The kinetics of H/D exchange in α‐methylstyrene catalysed by Li 2 Pd 2 Cl 6 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.