Synthesis and Reactivity of NHC‐Stabilized Iron(II)–Mesityl Complexes

Abstract

We present the synthesis of a series of NHC‐stabilized iron(II) complexes of the type [Fe(NHC)2Mes2] and [Fe(NHC)Mes2], starting from [Fe2Mes4] and the NHC. Depending on the steric demand of the NHC used, tetrahedral {[Fe(Me2Im)2Mes2] 1 and [Fe(MeiPrIm)2Mes2] 2}, square‐planar {trans‐[Fe(iPr2Im)2Mes2] 3}, or trigonal‐planar {[Fe(R2Im)Mes2]; R = tBu 6, Dipp 7, Dipp2H2 8} complexes were isolated. Three‐coordinate complexes [Fe(R2Im)Mes2] (R = Me 4, iPr 5) of smaller carbenes were synthesized via ligand exchange of [Fe(NHC)2Mes2] and [Fe2Mes4]. The reactivity of trans‐[Fe(iPr2Im)2Mes2] 3 towards small molecules and element–hydrogen compounds was investigated. The reaction of 3 and 2 with dioxygen led to the tetrameric‐cluster complexes [{Fe(R2Im)(OMes)(µ2‐O)}4] 9 and 10 (R = iPr 9, Me 10). The reaction of 3 with CO afforded [Fe(iPr2Im)2(CO)3] 11. Reactions of 3 with E–H compounds (E = O, S, N, P, Sn), with substitution of the mesityl ligands, produced the complexes [Fe(iPr2Im)2(OtBu)2] 12, [Fe(iPr2Im)2(OPh)2] 13, [Fe(iPr2Im)2(SPh)2] 14, [Fe(iPr2Im)2(NHPh)2] 15, cis‐[Fe(iPr2Im)2{o‐C6H4(NH)2}] 16, [Fe(iPr2Im)2(PHPh)2] 17, [Fe(iPr2Im)2(PPh2)2] 18, trans‐[Fe(Me2Im)2(SnnBu3)2] 19, and trans‐[Fe(iPr2Im)2(SnnBu3)2] 20. The complexes 16, 17, 19, and 20 adopt square‐planar structures. The reaction of 3 with phenylsilane afforded crystallographically characterized [Fe(iPr2Im)2(µ2‐H)3(SiPh2H){SiH2(iPr2Im)}] 21.