The reaction enthalpy for O atom transfer from CpReO3 to PPh(3) in to
luene solution is measured to be -28.4 +/- 0.3 kcal/mol and -28.0 +/-
0.6 kcal/mol in THF solution. This allows the strength of the Re=O bon
d in CpReO3 (in solution) to be estimated at 116.8 +/- 1.2 kcal/mol.