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Chromium-salen-medi...
Chromium-salen-mediated alkene epoxidation : a theoretical and experimental study indicates the importance of spin-surface crossing and the presence of a discrete intermediate.
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Brandt, Peter (författare)
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Norrby, Per-Ola (författare)
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Daly, Adrian M (författare)
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Gilheany, Declan G (författare)
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- 2002
- 2002
- Engelska.
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Ingår i: Chemistry - A European Journal. - 0947-6539 .- 1521-3765. ; 8:18, s. 4299-307
- Relaterad länk:
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium(v) oxo complexes can adopt a stepped shape or form a more concave surface, analogous to previous results on manganese salen complexes.
Ämnesord
- NATURVETENSKAP -- Kemi -- Organisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Organic Chemistry (hsv//eng)
- NATURVETENSKAP -- Kemi -- Teoretisk kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)
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