Transition metal mediated epoxidation as test case for the performance of different density functionals: A Computational Study

被引:46
作者
Cavallo, L [1 ]
Jacobsen, H [1 ]
机构
[1] Univ Salerno, Dept Chem, I-84081 Baronissi, SA, Italy
关键词
D O I
10.1021/jp034194r
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Energy profiles for olefin epoxidation with the cationic [Mn(acacen')](+) catalyst (acacen' = -O(CH)(3)N-C2H4-N(CH)(3)O-) have been calculated using pure (BP86) and hybrid (B3LYP) density functional methodologies. For the reaction, triplet and quintet energy hyper surfaces have been considered. The BP86 calculations allow for a rationalization of a reaction occurring under spin conservation. On the other hand, the B3LYP calculations suggest a reaction profile involving an early spin-crossing step, strongly supporting two-state reactivity. Further, the BP86 calculations suggest the existence of a metallacycle as possible reaction intermediate, a proposition not supported by the B3LYP approach. The two different computational approaches result not only in a quantitatively, but also in a qualitatively different description of the epoxidation reaction. This in turn implies different models for chirality transfer associated with related reactions employing chiral catalytic systems.
引用
收藏
页码:5466 / 5471
页数:6
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