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

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.