Comparing the reactivity of benzenedithiolate- versus alkyldithiolate- bridged Fe₂(CO)₆ complexes with competing ligands

The reactivity of [(μ-X₂bdt)Fe₂(CO)₆] [(bdt)1, X₂bdt = 3,6-disubstituted bezenedithiolate; X = H, Cl] with ligands of different donor strengths is investigated and compared to that of [(μ-pdt)Fe₂(CO)₆] [(pdt)1, pdt = propyldithiolate] and [(μ-edt)Fe₂(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 O₂-sensitive, magnetically uncoupled species, potentially a mononuclear Fe^I complex coordinated by bdt and at least 2 CO ligands.