TY - JOUR
T1 - Direct observation of reductive elimination of MeX (X = Cl, Br, I) from RhIII complexes
T2 - Mechanistic insight and the importance of sterics
AU - Feller, Moran
AU - Diskin-Posner, Yael
AU - Leitus, Gregory
AU - Shimon, Linda J.W.
AU - Milstein, David
PY - 2013/7/31
Y1 - 2013/7/31
N2 - Rare cases of directly observed reductive elimination (RE) of methyl halides from RhIII complexes are described. Treatment of the coordinatively unsaturated complexes [(tBuPNP)Rh(CH 3)X][BF4] (1-3, X = I, Br, and Cl; tBuPNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) with coordinating and noncoordinating compounds results in the formation of the corresponding free methyl halides and RhI complexes. The rate increase of CH 3I and CH3Br RE in the presence of polar aprotic solvents argues in favor of an SN2 RE mechanism. However, the RE of CH 3Cl is faster in polar protic solvents, which argues in favor of a concerted C-Cl RE. The RE of methyl halides from complexes 1-3 is induced by steric factors, as treatment of the less bulky complexes [(iPrPNP) Rh(CH3)X][BF4] (19-21; X = I, Br, Cl, respectively) with coordinating compounds leads to the formation of the adducts complexes rather than RE of the methyl halides. The accumulated evidence suggests that the RE process is nonassociative.
AB - Rare cases of directly observed reductive elimination (RE) of methyl halides from RhIII complexes are described. Treatment of the coordinatively unsaturated complexes [(tBuPNP)Rh(CH 3)X][BF4] (1-3, X = I, Br, and Cl; tBuPNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) with coordinating and noncoordinating compounds results in the formation of the corresponding free methyl halides and RhI complexes. The rate increase of CH 3I and CH3Br RE in the presence of polar aprotic solvents argues in favor of an SN2 RE mechanism. However, the RE of CH 3Cl is faster in polar protic solvents, which argues in favor of a concerted C-Cl RE. The RE of methyl halides from complexes 1-3 is induced by steric factors, as treatment of the less bulky complexes [(iPrPNP) Rh(CH3)X][BF4] (19-21; X = I, Br, Cl, respectively) with coordinating compounds leads to the formation of the adducts complexes rather than RE of the methyl halides. The accumulated evidence suggests that the RE process is nonassociative.
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U2 - 10.1021/ja401852c
DO - 10.1021/ja401852c
M3 - Article
C2 - 23865376
AN - SCOPUS:84881037430
VL - 135
SP - 11040
EP - 11047
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 30
ER -