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 Fe_2(N'Bu)_2Cl_2(NH_2'Bu)_2, [Fe_2(N(Bu)(S)Cl_4]~(2-), and Fe_2(NH'Bu)_2(S)(N{SiMe_3}_2)_2 allowed the selective syntheses of the cubane clusters [Fe4(N'Bu)_n(S)_(4-n)C_I4]~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 Fe_4NS_3 core of the [1, 2-] cluster affording the first synthetic representation of the corresponding heteroligated Fe_4S_3X subunit in the cofactor.