Thermochemical insight into the reduction of CO to CH3OH with [Re(CO)]+ and [Mn(CO)]+ complexes

  • Wiedner E
  • Appel A
  • 18


    Mendeley users who have this article in their library.
  • 9


    Citations of this article.


To gain insight into thermodynamic barriers for reduction of CO into CH3OH, free energies for reduction of [CpRe(PPh3)(NO)(CO)](+) into CpRe(PPh3)(NO)(CH2OH) have been determined from experimental measurements. Using model complexes, the free energies for the transfer of H(+), H(-), and e(-) have been determined. A pKa of 10.6 was estimated for [CpRe(PPh3)(NO)(CHOH)](+) by measuring the pKa for the analogous [CpRe(PPh3)(NO)(CMeOH)](+). The hydride donor ability (DeltaG degrees H(-)) of CpRe(PPh3)(NO)(CH2OH) was estimated to be 58.0 kcal mol(-1), based on calorimetry measurements of the hydride-transfer reaction between CpRe(PPh3)(NO)(CHO) and [CpRe(PPh3)(NO)(CHOMe)](+) to generate the methylated analogue, CpRe(PPh3)(NO)(CH2OMe). Cyclic voltammograms recorded on CpRe(PPh3)(NO)(CMeO), CpRe(PPh3)(NO)(CH2OMe), and [CpRe(PPh3)(NO)(CHOMe)](+) displayed either a quasireversible oxidation (neutral species) or reduction (cationic species). These potentials were used as estimates for the oxidation of CpRe(PPh3)(NO)(CHO) or CpRe(PPh3)(NO)(CH2OH) or the reduction of [CpRe(PPh3)(NO)(CHOH)](+). Combination of the thermodynamic data permits construction of three-dimensional free energy landscapes under varying conditions of pH and PH2. The free energy for H2 addition (DeltaG degrees H2) to [CpRe(PPh3)(NO)(CO)](+) (+15 kcal mol(-1)) was identified as the most significant thermodynamic impediment for the reduction of CO. DFT computations on a series of [Cp(X)M(L)(NO)(CO)](+) (M = Re, Mn) complexes indicate that DeltaG degrees H2 can be varied by 11 kcal mol(-1) through variation of both the ancillary ligands and the metal.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Get full text


  • Eric S. Wiedner

  • Aaron M. Appel

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free