A New Look at Molecular and Electronic Structure of Homoleptic Diiron(II,II) Complexes with N,N‐Bidentate Ligands: Combined Experimental and Theoretical Study

Abstract

Paddlewheel-type binuclear complexes featuring metalÀ metal bonding have been the subject of widespread interest due to fundamental concern in their electronic structures and potential applications. Here, we explore the molecular and electronic structures of diiron(II,II) complexes with N,N'-diarylformamidinate ligands. While a paddlewheeltype diiron(II,II) complex with N,N'-diphenylformamidinate ligands (DPhF) exhibits the centrosymmetric [Fe 2 (μ-DPhF) 4 ] structure, a minor alteration in the ligand system, i. e., switching from phenyl to p-tolyl N-substituted formamidinate ligand (DTolF), resulted in the isolation of an unprecedented non-centrosymmetric [Fe(μ-DTolF) 3 Fe(k 2 -DTolF)] complex. Both complexes were characterized using single-crystal X-ray diffraction, magnetic measurements, 57 Fe Mössbauer spectroscopy, and cyclic voltammetry along with high-level ab-initio calculations. The results provide a new view on a range of factors controlling the ground-state electronic configuration and structural diversity of homoleptic diiron(II,II) complexes. Model calculations determined that the Mayer bond orders for FeÀ Fe interactions are significantly lower than 1 and equal to 0.15 and 0.28 for [Fe 2 (μ-DPhF) 4 ] and [Fe(μ-DTolF) 3 Fe(k 2 -DTolF)], respectively.

Non-redox reactivity of V(ii) and Fe(ii) formamidinates towards CO2 resulting in the formation of novel M(ii) carbamates

“…34 In turn, recently, we revealed that the reaction of FeCl 2 with DTolF in THF resulted in the isolation of the non-centrosymmetric binuclear complex [Fe(μ-DTolF) 3 Fe(κ 2 -DTolF)]. 35 These results clearly demonstrate that subtle modification of the formamidinate ligand backbone profoundly affects the character of the resulting molecular complexes. The resulting complexes 1-3 were characterised spectroscopically (for details see Experimental section and ESI †), and their molecular structures were confirmed using single-crystal X-ray diffraction.…”

“…All the lengths of Fe–O and Fe–N bonds in 5 and 6 are consistent with other multinuclear iron( ii ) complexes containing carbamate or amidinate ligands. 1,35,42 A thorough analysis of the FTIR spectra of 5–6 (Fig. S5 and 6†) is featureless because the observed bands derived from carboxylate and amidinate groups overlap each other in the range of 1665–1544 cm −1 .…”

Factors controlling the structure of alkylzinc amidinates: on the role ofN-substituents

“…Building on the mentioned above results and our previous experience in studies on the structure and self-assembly of amidinate metal complexes, 11,20,21,34,35 we selected dipf and bza ligands as a model N,N′-diaryl substituted and N,N′-unsubstituted NCN scaffold to gain a more in-depth understanding of factors controlling the structure and stability of alkylzinc amidinates. To this aim, we investigated the reactions of dipf-H and bza-H proligands with ZnR 2 compounds (R = Me, Et, t Bu) and characterized products containing a systematically modified secondary coordination sphere of the Zn center in both the solid state and solution.…”

Synthesis and Complexation Study of New Aminoalkynyl−amidinate Ligands

“…[44] The bonding in such homoleptic diiron(II,II) complexes with N,N'-bidentate ligands has just been evaluated very recently in the course of a combined experimental and theoretical study. [45] Bright yellow, rod-like single-crystals of the dimolybdenum(II) complex 5 as the solvate 5•n-pentane were grown from a concentrated solution in n-pentane at 5 °C (cf. Table 1 and Figure 3).…”