Iron(II) Mediated Desulfurization of Organosulfur Substrates Produces Nonheme Diiron(II)-hydrosulfides

A reaction system involving Fe(BF4)(2)center dot 6H(2)O and two dinucleating ligands, HBPMP and HPhBIMP, mediates the desulfurization of aliphatic and aromatic thiols at room temperature. This rare C-S bond cleavage reaction produces two nonheme diiron(II) complexes, [Fe-2(BPMP)-(SH)(2)(MeOH)(2)](1+) (1a) and [Fe-2(PhBIMP)(mu-SH)-(DMF)](2+) (2a), possibly via an active species similar to [Fe-2(PhBIMP)(H2O)(2)(DMF)(2)](3+) (2c), while the thiols are converted to the corresponding alcohols/phenols. In the case of thioacetic acid, a bidentate chelating organosulfur substrate, the use of HBPMP produces the corresponding bis-thiocarboxylato bridged complex, [Fe-2(BPMP)(CH3COS)](1+) (1b), instead of 1a. However, the use of HPhBIMP allows the Fe(II) mediated desulfurization of thioacetic acid as well to yield 2a, along with the formation of [Fe-2(PhBIMP)(CH3COS)-(MeCN)](2+) (2b). This convenient desulfurization reaction has been demonstrated for different substrates in different solvents along with the structural and spectroscopic characterizations of the diiron(II)-hydrosulfide complexes in comparison with two isostructural chloride complexes, [Fe-2(BPMP)(Cl)(2)(MeOH)(2)](1+) (1c) and [Fe-2(PhBIMP)(mu-Cl)(DMF)](2+) (2d). The role of the individual reactants in the desulfurization process has been thoroughly investigated using control reactions, and on the basis of these results and the identification of intermediate species, such as [Fe-2(PhBIMP)((SBu)-Bu-t)(DMF)(3)](2+) and [Fe-2(PhBIMP)((SBu)-Bu-t)(H2O)(DMF)(2)](2+), in solution by mass spectrometry, a possible mechanism has been proposed.