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14‐Electron T‐Shaped [PdRXL] Complexes: Evidence or Illusion? Mechanistic Consequences for the Stille Reaction and Related Processes
Author(s) -
Casares Juan A.,
Espinet Pablo,
Salas Gorka
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20021104)8:21<4843::aid-chem4843>3.0.co;2-i
Subject(s) - transmetalation , stille reaction , chemistry , dissociation (chemistry) , stereochemistry , catalysis , photochemistry , medicinal chemistry , organic chemistry
A recent claimed spectroscopic observation (by 1 H NMR) of 14‐electron T‐shaped 3‐coordinated palladium complexes turns out to be a misinterpretation. A thorough study of the species formed by [PdRX(AsPh 3 ) 2 ] (R=Ph, C 6 Cl 2 F 3 ; X=Cl, I) in different solvents (S=CDCl 3 , THF, DMF) suggests that: 1) there is no NMR‐detectable amount of [PdRX(AsPh 3 )], and 2) in the presence of free arsine (AsPh 3 /[PdRX(AsPh 3 ) 2 ] 2:1) the concentration of [PdRX(AsPh 3 )(S)] is negligible. This clearly settles matters in the controversy of dissociative or associative pathways for the transmetalation step involved in the Stille coupling in favor of the latter: under catalytic conditions the dominant pathway is the associative reaction of the stannane with the square‐planar complex [PdRX(AsPh 3 ) 2 ].