Synthesis, Structural Characterization, and Magnetic Studies of Polynuclear Iron Complexes with a New Disubstituted Pyridine Ligand

Abstract

A series of novel polyiron species have been prepared from the reaction of iron chloride with the 2,5-disubstituted pyridines H2L(n) (H2L1) = N,N'-bis(n-butylcarbamoyl)pyridine-2,6-dicarboxamide; H2L2 = N,N'-bis(n-ethylcarbamoyl)pyridine-2,6-dicarboxamide). By small modifications of the experimental conditions under which the reactions are carried out, it has been possible to prepare the quadruply stranded diiron(II) complex [Fe2(mu-H2L1)4(mu-Cl)2][FeCl4]2 (1), the metallamacrocycle [Fe2(mu-H2L1)2(THF)4Cl2][FeCl4]2 (2), the hexairon(III) compound [Fe6(L1)2(mu-OMe)6(mu4-O)2Cl4] (3), and the mixed-valence trinuclear iron complexes [Fe3(L(n))3(mu3-O)] (n = 1, 4; n = 2, 5). The X-ray crystal structures of 3 and 5 and magnetic studies for all the compounds are herein presented. Interestingly, the structural analysis of 5 at room temperature indicates that one of the iron centers is Fe(III) while the other two have an average valence state between Fe(II) and Fe(III). The five complexes herein presented demonstrate the great versatility that the new ligand has as a building block for the formation of supramolecular coordination assemblies.

Formation of Unsymmetrical Trinuclear Metallamacrocycles Based on Two Different Cone Calix[4]arene Macrocyclic Rings

“…Below, we focus on the formation of low-nuclearity compounds, like trinuclear species. Several examples of trinuclear metallamacrocycles based on different ligands have been documented in the literature, involving Ni(II) [32], Pt(II) and Pd(II) [33], Fe(II) [34], or Ru(II) [35], exhibiting some interesting magnetic or photoswitchable properties [36].…”

A Novel Oxo-Centred, Trinuclear Iron Nicotinato Complex: Fe3(O)(C6NO2H5)6(H2O)3·3H2O·7Cl

“…To our knowledge, complex 1 is the first oxo-centred, trinuclear iron nicotinato-complex, although many other oxo-centred, trinuclear iron complexes have been documented thus far. 15,16 A search from the CCDC shows that there are hundreds of nicotinato-complexes. However, among these compounds there are only two complexes containing iron metal.…”

SNS versus SNN Pincer Ligands: Electrochemical Studies and Their Palladium(II) Complexes as Electro‐Catalyst for Proton Reduction

“…Pincer complexes have been synthesized since the early 1970 s, and new designs (Scheme ) continue to emerge due to their rich chemistry . Complexes of pincer ligands have been employed as crystalline switches, as sensors and most commonly as precatalysts for numerous transformations .…”

“…Pincer complexes have been synthesized since the early 1970 s, [1] and new designs (Scheme 1) continue to emerge due to their rich chemistry. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Complexes of pincer ligands have been employed as crystalline switches, as sensors and most commonly as precatalysts for numerous transformations. [17] Pincer systems are ubiquitous due to their relative ease of synthesis, and most of the reported systems are planar, due to the aromatic backbone that is commonly used.…”