Selective Syntheses of Iron−Imide−Sulfide Cubanes, Including a Partial Representation of the Fe−S−X Environment in the FeMo Cofactor

摘要

The dinuclear precursors Fe₂(NtBu)₂Cl₂(NH₂tBu)₂, [Fe₂(NtBu)(S)Cl₄]2−, and Fe₂(NHtBu)₂(S)(N{SiMe₃}₂)₂ allowed the selective syntheses of the cubane clusters [Fe₄(NtBu)_n(S)_4−nCl₄]z with [n, z] = [3, 1−], [2, 2−], [1, 2−]. Weak-field iron−sulfur clusters with heteroleptic, nitrogen-containing cores are of interest with respect to observed or conjectured environments in the iron−molybdenum cofactor of nitrogenase. In this context, the present iron−imide−sulfide clusters constitute a new class of compounds for study, with the Fe₄NS₃ core of the [1, 2−] cluster affording the first synthetic representation of the corresponding heteroligated Fe₄S₃X subunit in the cofactor.