Aminolysis of Bis[bis(trimethylsilyl)amido]iron and -cobalt as a Versatile Route to N-Heterocyclic Carbene Complexes Andreas A. Danopoulos,* Pierre Braunstein, Neoklis Stylianides, and Marcel Wesolek Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universite ́ de Strasbourg, 4 rue Blaise Pascal, F-67081 Strasbourg Cedex, France * S Supporting Information ABSTRACT: A range of new N-heterocyclic carbene complexes of iron(II) and cobalt(II) have been conveniently obtained by the aminolysis of bis[bis(trimethylsilyl)amido]iron and -cobalt precursors with imidazol(in)ium salts. Whereas sterically less hindered salts produced the tetrahedral complexes [M- (carbene) 2 Cl 2 ] (M = Fe), bulkier salts gave the three-coordinate [M(carbene){N(SiMe 3 ) 2 }Cl] (M = Fe, Co), which serve as versatile precursors to a range of derivatives; mechanistic aspects of the reaction are discussed. T he chemistry of the N-heterocyclic carbene complexes of iron and cobalt is less developed than that of other transition metals. Recently, important catalytic reactions have been reported in which the in situ formed catalyst, from an imidazolium salt and a basic organometallic reagent in the presence of iron or cobalt precursors, is presumably an N- heterocyclic carbene metal complex. 1,2 Furthermore, a few examples where well-defined iron NHC complexes are involved in catalytic transformations 3-6 or structurally mimicking [FeFe] hydrogenase enzymes have also appeared. 7,8 However, the majority of well-characterized NHC complexes of Fe and Co bear carbonyl, 9-11 cyclopentadienyl, 3,11-16 or nitrosyl 17 stabi- Received: October 10, 2011 Published: December 2, 2011 Scheme 1. Summary of the NHC Complexes Obtained by Aminolysis of [M{N(SiMe 3 } 2 ] (M = Fe, Co) with Azolium Salts a a Legend: (i) 2 equiv per Fe of azolium salt in THF, room temperature, 12 h; (ii) 1 equiv of 1,3-bis(tert butyl)imidazolinium chloride, toluene, room temperature, 12 h; (iii) 1 equiv of azolium or azolinium chloride, toluene, room temperature, 12 h. Figure 1. Molecular structure of 1b. Selected bond lengths (Å) and angles (deg): C(1)-Fe(1), 2.132(3); C(1)-N(1), 1.348(3); C(1)- N(2), 1.349(3); N(1)-C(1)-N(2), 106.0(2); C(1)#1-Fe(1)-C(1), 103.33(13); Cl(1)#1-Fe(1)-Cl(1), 106.90(4); C(1)#1-Fe(1)- Cl(1), 104.90(7). Communication pubs.acs.org/Organometallics © 2011 American Chemical Society 6514 dx.doi.org/10.1021/om200951m | Organometallics 2011, 30, 6514-6517