Synthesis, Structural Characterization And Catalytic Properties Of Iron N-Heterocyclic Carbene Complexes

N-Heterocyclic carbenes NHC are stable singlet carbenes that can act as excellent two electron donor ligands towards almost any element in the periodic table. Transition metal complexes of NHCs have been extensively studied in homogeneously catalytic reactions especially in cross-coupling reactions. Iron has much research potential due to its low price and nontoxicity compared with commonly used precious metals. Iron-NHC complexes would offer opportunities to study their catalytic application in organic reaction. The dissertation describes the synthesis, structures and catalytic properties:(I) Iron-NHC complex [Fe(L)2(CH3CN)2]2+(L N-pyrimid-2-ylimidazolylidene) was prepared from the reaction of Ag-N-pyrimid-2-ylimidazolylidene complex with iron powder. Reactions of [Fe(L)2(CH3CN)2]2+with various N-, P-, O-, and S-donors have been investigated. Replacement of the labile acetonitrile led to the isolation of various iron-NHC complexes containing additional N-, P-, O-, and S-ligands. All the iron-NHC complexes have been fully characterized.[Fe(L)2(CH3CN)2]2+can efficiently catalyze the coupling reaction of various Grignard reagents with heteroaryl bromides or chlorides.(Ⅱ) Iron-NHC complexes [Fe(L)2]2+(L3-(1,10-phenanthrolin-2-yl)-1-methy limidazolylidene,3-(1,10-phenanthrolin-2-yl)-1-mesity limidazolylidene and3-(2,2’-bypridin-6-yl)-1-methyl imidazolylidene have been synthesized and fully characterized by NMR, elemental analysis, and X-ray crystallography. All the complexes contain one iron and two NHC ligands having disordered octahedral coordination sphere. The electrochemical properties of these iron-NHC complexes have also been studied.