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 H2(mesNSN) (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 [(mesNSN)­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 [(mesNSN)­Fe­(PMe3)] (3) and [(mesNSN)­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 [(mesNSN)­Fe­(CNR)3] (R = But (5), Ph-2,6-Me2 (6)). Recrystallization of 6 has led to the isolation of the carbon–sulfur bond cleavage product [(mesNS)­Fe­(CNPh-2,6-Me2)3] (7). Quite unexpectedly, the interaction of 2 with 3-hexyne and deuterated benzene could induce Fe–N­(amido) bond cleavage, giving [(mesHNSN)2Fe­(THF)] (8) and [(mesHNSN)2Fe] (9), respectively. The formation of 7–9 suggests the lability of the [(mesNSN)­Fe] fragment, which could suffer from degradation in the presence of bulky strong field ligands.