Complexes rehybridization energies

The effect of rf coordination on the arenes was studied in the context of the phe-nol-ketodiene equilibrium . It was shown that this equilibrium for the free ligands favors heavily the phenol tautomer vide supra) whereas for the complexes [Os(NH3)5-2,3- -arene)] + (arene = phenol 2-, 3-, 4-methylphenol 3,4-dimethylphenol) the corresponding equilibrium constants approach unity (20 °C). The conversion of phenol 67 into the 2,4-cyclohexadien-l-one 68 was kinetically favored over the formation of the 2,5-isomer 69, although the latter is the thermodynamically favored product (equation 26). It was assumed that osmium rehybridizes the C(5) and C(6) atoms to form a metallocy-clopropane. This removes much of the resonance energy and therefore destabilizes the enohc form of the free hgand. The free energies of ketonization (25 °C) for the /j -phenol complex in comparison with free phenol are shown in equations 27 and 28 . 

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