Monovalent Iron in a Sulfur-Rich Environment

A series of low-coordinate, paramagnetic iron complexes in a tris(thioether) ligand environment have been prepared. Reduction of ferrous {[PhTttBu]FeCl}2 [1; PhTttBu = phenyltris((tert-butylthio)methyl)borate] with KC8 in the presence of PR3 (R = Me or Et) yields the high-spin, monovalent iron phosphine complexes [PhTttBu]Fe(PR3) (2). These complexes provide entry into other low-valent derivatives via ligand substitution. Carbonylation led to smooth formation of the low-spin dicarbonyl [PhTttBu]Fe(CO)2 (3). Alternatively, replacement of PR3 with diphenylacetylene produced the high-spin alkyne complex [PhTttBu]Fe(PhCCPh) (4). Lastly, 2 equiv of adamantyl azide undergoes a 3 + 2 cycloaddition at 2, yielding high-spin dialkyltetraazadiene complex 5.