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J Am Chem Soc
; 131(1): 34-5, 2009 Jan 14.
Article
in English
| MEDLINE
| ID: mdl-19093861
ABSTRACT
Rate and equilibrium measurements for the hydrolysis of the Fe(CO)3-coordinated cyclohexadienyl cation lead to pKR = 4.7 compared with pKR = -2.1 for the uncoordinated ion. The hydrolysis yields exo-coordinated cyclohexadienol 10(7)-fold more rapidly than its endo-isomer, despite the isomers being of similar stability. DFT calculations of the energy of isodesmic transfer of Fe(CO)3 from cyclohexadiene to benzene lead to an estimate of pKa 8 for loss of a proton from the coordinated cyclohexadienyl cation to form Fe(CO)3-coordinated benzene. This implies that the coordinated cation is 33 log units (46 kcal) less acidic than the uncoordinated ion.