Synthesis, Structure, and Reactivity Study of Iron(II) Complexes with Bulky Bis(anilido)thioether Ligation

The synthesis, molecular structure, and ligand substitution reactivity of iron(II) complexes bearing the bulky N,N'-dimesityl-2,2'-diamidophenyl sulfide ligand have been studied. The ligand H-2((NSN)-N-mes) (1) was synthesized by a Pd-mediated Buchwald-Hartwig amination method. An amine elimination reaction between 1 and [Fe(NTMS2)(2)](2) afforded the high-spin complex [((NSN)-N-mes)Fe(THF)] (2), displaying a distorted trigonal-monopyramidal geometry. Interaction of 2 with PMe3 and 2,5-di-tert-butylimidazol-1-ylidene (IBut) gave the ligand substitution products [((NSN)-N-mes)Fe(PMe3)] (3) and [((NSN)-N-mes)Fe(IBut)] (4), respectively. Both 3 and 4 are high spin and display molecular geometry similar to that of 2. The reaction of 2 with 3 equiv of isocyanide gave the low-spin complexes [((NSN)-N-mes)Fe(CNR)(3)] (R = But (5), Ph-2,6-Me-2 (6)). Recrystallization of 6 has led to the isolation of the carbon sulfur bond cleavage product [((NS)-N-mes)Fe(CNPh-2,6-Me-2)(3)] (7). Quite unexpectedly, the interaction of 2 with 3-hexyne and deuterated benzene could induce Fe-N(amido) bond cleavage, giving [((HNSN)-H-mes)(2)Fe(THF)] (8) and [((HNSN)-H-mes)(2)Fe] (9), respectively. The formation of 7-9 suggests the lability of the [((NSN)-N-mes)Fe] fragment, which could suffer from degradation in the presence of bulky strong field ligands.