Comparing the Reactivity of Benzenedithiolate- versus Alkyldithiolate-Bridged Fe2(CO)6 Complexes with Competing Ligands

The reactivity of [(mu-X(2)bdt)Fe-2(CO)(6)] [(bdt)1, X(2)bdt = 3,6-di-substituted bezenedithiolate; X = H, Cl] with ligands of different donor strengths is investigated and compared to that of [(mu-pdt)Fe-2(CO)(6)] [(pdt) 1, pdt = propyldithiolate] and [(mu-edt)Fe-2(CO)(6)] [(edt)1, edt = ethyldithiolate]. Strong donor ligands (L = CN-, PMe3) when added to (bdt) 1 lead to mononuclear [(bdt)Fe(L)(2)(CO)(2)], (bdt)6(L), in a disproportionation and fragmentation reaction, while simple ligand-substitution reactions occur on (edt)1 and (pdt)1 under identical conditions. In the presence of weaker ligands such as secondary amines or dmf, the alkyldithiolate-bridged complexes are unreactive, while (bdt)1 transforms to an O-2-sensitive, magnetically uncoupled species, potentially a mononuclear Fe-I complex coordinated by bdt and at least 2 CO ligands.