cis-Tetrakis(μ-N-phenylacetamidato)-κ4 N:O;κ4 O:N-bis[(benzonitrile-κN)rhodium(II)](Rh—Rh)

The complex molecule of the title compound, [Rh2{N(C6H5)COCH3}4(C6H5CN)2], exhibits crystallographically imposed centrosymmetry. The four acetamide ligands bridging the dirhodium core are arranged in a 2,2-cis manner, with two N atoms and two O atoms coordinating to the unique RhII atom cis to one another. The Neq—Rh—Rh—Oeq torsion angles on the acetamide bridges vary between 1.62 (4) and 1.78 (4)°. The Rh—Rh bond length is 2.4319 (3) Å. The axial nitrile ligand completes the distorted octahedral coordination sphere and shows a non-linear coordination with an Rh—N—C bond angle of 167.14 (15)°, while the N—C bond length is 1.135 (3) Å.

The complex molecule of the title compound, [Rh 2 {N(C 6 H 5 )COCH 3 } 4 (C 6 H 5 CN) 2 ], exhibits crystallographically imposed centrosymmetry. The four acetamide ligands bridging the dirhodium core are arranged in a 2,2-cis manner, with two N atoms and two O atoms coordinating to the unique Rh II atom cis to one another. The N eq -Rh-Rh-O eq torsion angles on the acetamide bridges vary between 1.62 (4) and 1.78 (4) . The Rh-Rh bond length is 2.4319 (3) Å . The axial nitrile ligand completes the distorted octahedral coordination sphere and shows a non-linear coordination with an Rh-N-C bond angle of 167.14 (15) , while the N-C bond length is 1.135 (3) Å .
The infrared absorption spectrum of 1 showed bands at 2359 and 2320 cm -1 attributable to carbon-nitrogen bond stretching modes. The corresponding band for uncomplexed benzonitrile appears at 2228 cm -1 . This indicates that there is a shortening of the carbon-nitrogen bond and a stronger σ-interaction to the rhodium metal compared to the π-backbonding which occurs upon complexation with cis-tetrakis [µ-N-(phenyl)

Experimental
Approximately 10 mg of 2,2-cis-[Rh 2 (N(C 6 H 5 )COCH 3 ) 4 ] was dissolved in 18 mL of dichloromethane. 10 µL of benzonitrile was then added to this solution, via a gas tight syringe, turning the solution from a green to a light blue color. Atoms C22 and C23 exhibit slightly extended displacement perpendicular to the plane of the ring containing them. This is likely due to a combination of some rotational disorder about the N3-Rh1 bond and also due to normal stacking errors, as evidenced in similar displacement amplitudes in the adjacent ring (C5 to C10).
There are three strong reflections missing. They may have been low-angle reflections behind the beamstop shadow or the relections may have overloaded in the detector (even in the overload-correction mode).

Figure 1
ORTEP of the title compound showing 30% probability ellipsoids. Hydrogen atoms are drawn as small spheres.

Figure 2
Packing diagram for the title compound as seen along the b axis. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.005 Δρ max = 0.39 e Å −3 Δρ min = −0.34 e Å −3 Special details Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).