Thermodynamic and Structural Factors That Influence the Redox Potentials of Tungsten–Alkylidyne Complexes

The thermodynamic
and structural factors that influence the redox
properties of an extensive set of tungsten–alkylidyne complexes
(W­(CR)­L4X) are analyzed by combining synthesis, electrochemistry,
and computational modeling based on free energy calculations of oxidation
potentials at the density functional theory level. The observed linear
correlations among oxidation potentials, HOMO energies, and gas-phase
ionization energies are found to be consistent with the approximately
constant solvation free energy differences between reduced and oxidized
species over the complete set. The W–X bond length, trans to the alkylidyne ligand, is found to be a good descriptor
of the positioning of the key frontier orbitals that regulate the
redox properties of the complexes.