Bis{μ-N-[(dimethylamino)dimethylsilyl]-2,6-dimethylanilido}-κ2 N:N′;κ2 N′:N-dicopper(I)

The title compound, [Cu2(C12H21N2Si)2], is a binuclear CuI complex. The dimeric molecule has an inversion center located at the mid-point of the Cu—Cu bond [Cu—Cu = 2.7209 (7) Å]. The bidentate ligand behaves in an N:N′-bridging mode, coordinating the metal atoms. The N—Cu—N unit is close to being linear [176.60 (8)°]. The two N atoms exhibit different affinities for the metal atom. The Cu—Namino bond is longer than the Cu—Nanilido bond by 0.079 Å. The core of the molecule, the [Cu—N—Si—N]2 eight-membered ring, adopts a chair configuration.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: VM2052).

Comment
In the past decades, considerable attention was paid to monovalent copper amides because of their potential applications in chemical vapor deposition (CVD), organic electroluminescent devices (EL), as well as their structural diversity. The tetranuclear copper(I) amide, [CuN(SiMe 3 ) 2 ] 4 , has proved to be a useful precursor in these areas (Chen et al., 1992;James et al., 1998;Noto et al., 2003). In contrast to the traditional monodentate amido ligands, the N-silylated anilido ligands with a pendant amino group were developed and supposed to be bidentate. They were employed for synthesizing compounds with different metals including Zn (Schumann et al., 2000), Zr (Chen, 2009;Yuan et al., 2010) and Fe (Chen, 2008). Here, the synthesis and crystal structure of a new copper(I) anilido complex will be described.
The molecular structure is illustrated in Fig. 1. The N-silylated anilido ligand has an N-Si-N chelating moiety, which is presumed to be a "quasi" conjugated unit owing to d-π interaction between the Si and N atoms. In the binuclear copper compound, each Cu I atom coordinates to two N from two ligands, one being an anilido group and another being an amino group. Therefore, the bidentate ligand behaves as N,N'-µ-bridging mode. Each N-Cu-N unit is close to linear and the two N-Cu-N units are nearly co-planar. The two silyl groups are located above and beneath the plane, respectively, which leads to the "chair" configuration of the [Cu-N-Si-N] 2 eight-membered ring. The bond lengths N1-Cu1, N2-Cu1A (Cu1A is generated by symmetry operation 1-x, 2-y, 2-z), N1-Si1 and N2-Si1 are 1.848 (2), 1.927 (2), 1.687 (2) and 1.819 (2) Å, respectively. The central Cu-Cu bond is 2.7209 (7) Å, which is comparable to the metal-metal interaction in another reported copper(I) compound (Guo et al., 2009). It is noteworthy that the packing is stablized by a C-H···π interaction between H12A and the phenyl ring C1-C6.

Experimental
CuCl (0.25 g, 2.50 mmol) was added into the solution of [LiN(SiMe 2 NMe 2 )(2,6-Me 2 C 6 H 3 )] 2 (0.57 g, 1.25 mmol) in tetrahydrofuran (30 ml) at 273 K. The reaction mixture was warmed to room temperature and kept stirring for 12 h. It was dried in vacuum to remove all volatiles and the residue was extracted with CH 2 Cl 2 (30 ml). Concentration of the filtrate under reduced pressure and recrystallization in hexane gave the title compound as colorless crystals (yield 0.51 g, 71%).

Refinement
The methyl H atoms were constrained to an ideal geometry, with C-H distances of 0.97 Å and U iso (H) = 1.5U eq (C), but each group was allowed to rotate freely about its C-C, C-N or C-Si bonds. The other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances of 0.94 Å and U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures Fig. 1. The molecular structure, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Symmetry code used to generate second part: 1-x, 2-y, 2-z.