Chlorido{N-[(diethylamino)dimethylsilyl]anilido-κN}(N,N,N′,N′-tetramethylethane-1,2-diamine-κ2 N,N′)iron(II)

In the title iron(II) complex, [Fe(C12H21N2Si)Cl(C6H16N2)], the FeII cation is coordinated by two N atoms from the tetramethylethane-1,2-diamine ligand [Fe—N = 2.191 (5) and 2.215 (4) Å], one N atom from the N-[(diethylamino)dimethylsilyl]anilide ligand [Fe—N = 1.943 (4) Å] and a chloride ligand [Fe—Cl = 2.2798 (16) Å] in a distorted tetrahedral geometry. The N—Si—N angle is 113.9 (3)°. The crystal packing exhibits no short intermolecular contacts.

Group 4 metals amides supported with the N-silylated anilido ligands are active catalysts for olefin polymerization (Gibson et al., 1998;Hill & Hitchcock, 2002). Moreover, a class of monoionic N-silylated anilido ligands bearing a pendant amino group were paid much attentions. It was presumed that the empty d-orbitals on silicon would interact with the lone-pair electrons on the p-orbital of nitrogen center through d-pπ interaction throughout the N-Si-N motif.
Analogous compounds with different metals including Zn (Schumann et al., 2000) and Zr (Chen, 2009) have been synthesized. A group of zirconium amides with the similar ligand were reported showing good performance in ethylene polymerization (Yuan et al., 2010). On the other hand, some iron(II) complexes with the N-donor ligands were active in fixation of dinitrogen (Smith et al., 2001;Rodriguez et al., 2011). Here, the synthesis and crystal structure of a new iron(II) anilido-complex will be described.
The title compound, (I), was prepared by a one-pot reaction of n-LiBu, N-[(diethylamino)dimethylsilyl]aniline, 1,2-bis-(dimethylamino)ethane (tmeda) and FeCl 2 . The suitable for X-ray investigation single-crystal of (I) was obtained by recrystallization in toluene. In (I) , the metal Fe center is coordinated by a chlorido ligand, a chelating tmeda molecule and the anilido-ligand. The neutral donor molecule coordinates metal center in N,N′-chelating mode. Though the anilidoligand has a pendant amino group, exhibting an N-Si-N chelating moiety, it connects Fe(II) only with a σ-bond, Fe-N anilide being 1.943 (4) Å. It suggests the less affinity between the pendant amino-group and the metal center in comparing with tmeda. The N1-Si1-N2 angle is 113.9 (3)°. The four-coordinate Fe atom demonstrates a slightly distorted tetrahedral geometry. In an iron(III) complex with the similar ligand, the N-Si-N unit bit the Fe III metal center and the angle was 95.49 (9)° (Chen, 2008).

Experimental
A solution of n-LiBu (1.6 M, 2.1 ml, 3.3 mmol) in hexane was slowly added into a mixture of N-[(diethylamino)dimethylsilyl]aniline (0.73 g, 3.3 mmol) and tmeda (0.38 g, 3.3 mmol) in Et 2 O (20 ml) at 273 K by syringe. The mixture was stirred at room temperature for two hours and then added to a stirring suspension of FeCl 2 (0.42 g, 3.3 mmol) in Et 2 O (20 ml) at 273 K. The resulting mixture was stirred at room temperature for 8 h. Then all the volatiles were removed under vacuum. The residue was extracted with toluene (25 ml). The filtrate was concentrated to 2 ml to yield the title compound as colorless crystals (yield 1.07 g, 76%; m.p. 357-358 K

Refinement
The methyl H atoms were constrained to an ideal geometry, with C-H distances of 0.96 Å and U iso (H) = 1.5U eq (C), but each group was allowed to rotate freely about its C-C, C-N and C-Si bonds. The methylene H atoms were constrained with C-H distances of 0.97 Å and U iso (H) = 1.2U eq (C). The phenyl H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93 Å and U iso (H) = 1.2U eq (C).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.