The reaction of permanganyl chloride with olefins: intermediates and mechanism as derived from matrix-isolation studies and density functional theory calculations.
Density functional theory (DFT) calculations predict that the [2+3] addition of tetramethylethylene (TME) to the MnO2 moiety of MnO3Cl is thermodynamically favoured over [2+1] addition (epoxidation), while the kinetic barriers for both reactions are of comparable height. However, in an experimental investigation of the TME/MnO3Cl system by means of matrix-isolation techniques, selective formation of the epoxidation product [ClO2Mn[O[C(CH3)2]2]] (1) was observed. Compound 1 was characterised by IR spectroscopy with the aid of isotopic-enrich-ment experiments in combination with DFT frequency calculations. This result, at first sight surprising, is supported by studies in solution, and, even with the numerically equal energy barriers suggested by the calculations, it can be rationalised in terms of the much broader reaction channel leading to epoxidation as opposed to the much more narrow approach path for formation of the glycolate.
Wistuba
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Anorganisch-Chemisches Institut Universität Heidelberg.
Limberg
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