Synthesis of Coordinatively Unsaturated Mesityliron Thiolate Complexes and Their Reactions with Elemental Sulfur

The reactions of Fe2Mes4 (1; Mes = mesityl) with bulky thiols, namely, HSDmp (Dmp = 2,6-dimesitylphenyl), HSDxp (Dxp = 2,6-dixylylphenyl), and HSBtip [Btip = 2,6-(2,4,6-iPr3C6H2)2C6H3], provided a series of iron(II) mesityl complexes bearing bulky thiolate ligands. These iron complexes are the thiolate-bridged dinuclear complexes Fe2Mes2(μ-SAr)(μ-Mes) (2a, Ar = Dmp; 2b, Ar = Dxp), the 1,2-dimethoxyethane (DME) adducts (DME)Fe(SAr)(Mes) (3a, Ar = Dmp; 3b, Ar = Dxp), the mixed-valence FeI−FeII dinuclear complexes (Mes)Fe(μ-SAr)(μ-SAr)Fe (4a, Ar = Dmp; 4b, Ar = Dxp), and a low-coordinate mononuclear complex (BtipS)Fe(Mes) (5). An [Fe8S7] cluster [Fe4S3(SDmp)]2(μ-SDmp)2(μ-SMes)(μ6-S) (6), the core structure of which is topologically relevant to that of the FeMo-cofactor of nitrogenase, was obtained from the reaction of 3a or 4a with S8. The μ-SMes ligand in 6 is formed via insertion of a sulfur atom into the Fe−C(Mes) bond. The formation of cluster 6 from 3a or 4a demonstrates that organoiron complexes are applicable as precursors for iron−sulfur clusters.