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Issue 19, 1997
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Structure, bonding, and reactivity of molybdenum η3-cyclohexenone complexes in comparison with their cyclopentenone analogues: η3-allyl/η4-diene conversion

Abstract

The neutral η3-cyclohexenone complexes [Mo(η3-C6H7O)(CO)2(MeCN)2Br] 1, [Mo(η3-C6H7O)(CO)2{HB(pz)3}] 2, [Mo(η3-C6H7O)(CO)2(bipy)Br] 3 (bipy =  2,2′-bipyridine) and [Mo(η3-C6H7O)(CO)2(dppm)Br] 4 (dppm = Ph2PCH2PPh2) have been synthesized. The structure of 2 has been determined by X-ray crystallography. All these complexes resist hydride abstraction using Ph3C+PF6, in sharp contrast to the η3-cyclopentenone analogues where η3-allyl/η4-diene conversion is a facile process. A rationale for this different behaviour is provided by extended-Hückel calculations combined with a Walsh analysis of hydrogen abstraction. Thus, while in the η3-C5H5O → η4-C5H4O conversion a Möbius system is formed upon release of hydride via electrophilic attack, this is not possible in the hypothetical η3-C6H7O → η4-C6H6O process. Therefore, η3-C6H7O is a C–H acid. Also, the occurrence of different conformations, exo for allyl and endo for diene complexes, is rationalized.

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Article type: Paper
DOI: 10.1039/A703633G
Citation: J. Chem. Soc., Dalton Trans., 1997,0, 3599-3604
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    Structure, bonding, and reactivity of molybdenum η3-cyclohexenone complexes in comparison with their cyclopentenone analogues: η3-allyl/η4-diene conversion

    V. N. Sapunov, C. Slugovc, K. Mereiter, R. Schmid and K. Kirchner, J. Chem. Soc., Dalton Trans., 1997, 0, 3599
    DOI: 10.1039/A703633G

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