TY - JOUR
T1 - Understanding the differences between iron and palladium in cross-coupling reactions
AU - Sun, Xiaobo
AU - Rocha, Marcus V.J.
AU - Hamlin, Trevor A.
AU - Poater, Jordi
AU - Matthias Bickelhaupt, F.
PY - 2019/5/21
Y1 - 2019/5/21
N2 - We aim at developing design principles, based on quantum chemical analyses, for a novel type of iron-based catalysts that mimic the behavior of their well-known palladium analogs in the bond activation step of cross coupling reactions. To this end, we have systematically explored C-X bond activation via oxidative addition of CH 3 X substrates (X = H, Cl, CH 3 ) to model catalysts m Fe(CO) 4 q (q = 0, -2; m = singlet, triplet) and, for comparison, Pd(PH 3 ) 2 and Pd(CO) 2 , using relativistic density functional theory at the ZORA-OPBE/TZ2P level. We find that the neutral singlet iron catalyst 1 Fe(CO) 4 activates all three C-X bonds via barriers that are lower than those for Pd(PH 3 ) 2 and Pd(CO) 2 . This is a direct consequence of the capability of the iron complex to engage not only in π-backdonation, but also in comparably strong σ-donation. Interestingly, whereas the palladium complexes favor C-Cl activation, 1 Fe(CO) 4 shows a strong preference for activating the C-H bond, with a barrier as low as 10.4 kcal mol -1 . Our results suggest a high potential for iron to feature in palladium-type cross-coupling reactions.
AB - We aim at developing design principles, based on quantum chemical analyses, for a novel type of iron-based catalysts that mimic the behavior of their well-known palladium analogs in the bond activation step of cross coupling reactions. To this end, we have systematically explored C-X bond activation via oxidative addition of CH 3 X substrates (X = H, Cl, CH 3 ) to model catalysts m Fe(CO) 4 q (q = 0, -2; m = singlet, triplet) and, for comparison, Pd(PH 3 ) 2 and Pd(CO) 2 , using relativistic density functional theory at the ZORA-OPBE/TZ2P level. We find that the neutral singlet iron catalyst 1 Fe(CO) 4 activates all three C-X bonds via barriers that are lower than those for Pd(PH 3 ) 2 and Pd(CO) 2 . This is a direct consequence of the capability of the iron complex to engage not only in π-backdonation, but also in comparably strong σ-donation. Interestingly, whereas the palladium complexes favor C-Cl activation, 1 Fe(CO) 4 shows a strong preference for activating the C-H bond, with a barrier as low as 10.4 kcal mol -1 . Our results suggest a high potential for iron to feature in palladium-type cross-coupling reactions.
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U2 - 10.1039/c8cp07671e
DO - 10.1039/c8cp07671e
M3 - Article
C2 - 30847454
AN - SCOPUS:85065990140
VL - 21
SP - 9651
EP - 9664
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 19
ER -