The enthalpy of sulfur atom transfer to stable cyclic carbenes has been measured by solution calorimetry. Absolute values of the R2CS bond strengths (≈100 kcal/mol) are in a range comparable to those of R3PS bond strengths. These data are compared to reported enthalpies of binding of carbenes and phosphines to metal complexes. Similar patterns of donor abilities are displayed for both oxidative addition of sulfur and binding to metal complexes.
