Hexacarbonyl dicobalt complex of bis(
tert-butylsulfonylethyne) [Co
2(
![](/images/entities/mgr.gif)
-Bu
tSO
2C)
2(CO)
6,
3]experiences a thermally induced ligand exchange process with methyl
p-tolyl sulfide, dibenzylsulfide, and diethyl sulfide to give the corresponding stable sulfide complexes [Co
2(
![](/images/entities/mgr.gif)
-Bu
tSO
2C)
2(CO)
5SR
2]
4,
5, and
6, respectively, in good yield (59-65%). The reaction withtetrahydrothiophene gives a disubstituted complex
7 in 74% yield. Oxathiane
9, derivedfrom (+)-(2
R)-10-mercaptoisoborneol, also reacts with
3 to generate a chiral sulfide complex
8 (58%). The solid-state structures of
5 and
8 have been established by X-ray crystallographyand reveal the preference of the incoming sulfur ligand to occupy an equatorial coordinationsite. Further structural studies on
5 have been performed by low-temperature
1H NMRanalysis and by theoretical procedures at the PM3(tm) level of theory. Analysis of the low-temperature
1H NMR spectrum of
5 shows a signal splitting consistent with the freezing ofan equilibrium between two equatorially coordinated sulfides, and the computational studyof the different isomers of
5 shows that the equatorially coordinated complex is 3.9 kcalmol
-1 lower in energy than the most stable axially coordinated one, in agreement with solid-state and solution studies. Finally, ligand exchange experiments have been performed inorder to provide an explanation for the Pauson-Khand reactivity of alkynes containingancillary sulfide ligands and were found to support the experimentally observed rateenhancements.