Nitrosyl and carbene iron complexes bearing a κ3-SNS thioamide pincer type ligand

Abstract

The previously reported monochelate iron complex with κ³ SNS thioamide pincer ligand, 2,6-bis(N-2,6-bis(diphenylmethyl)-4-isopropylphenyliminothiolate)pyridine (L^DPM), [Fe(THF)₂(κ³-L^DPM)], gave novel complexes, [Fe(NHC)(κ³-L^DPM)] and [Fe(NO)₂(κ³-L^DPM)], by substitution reactions with N-heterocyclic carbene (NHC) and NO molecules, respectively. The X-ray crystal structure of the [Fe(NHC)(κ³-L^DPM)] complex revealed a unique square planar iron(II) complex, which was determined to be in an intermediate spin state (S = 1) in benzene from the Evans method. The [Fe(NO)₂(κ³-L^DPM)] complex was determined to have a trigonal bipyramidal geometry from X-ray analysis and was indicated to be diamagnetic from the ¹H NMR spectrum. The ν(NO) stretching vibration of this complex showed two peaks at 1840 cm⁻¹ and 1790 cm⁻¹, and also the Fe–N–O bond angles were 168.9(2)° and 168.03(19)°. These findings suggest that the two coordinated NO molecules have neutral radical character, and they are antiferromagnetically coupled with the high-spin iron center.