Tricarbonyl(η6-flavone)chromium(0)

In the title compound, [Cr(C15H10O2)(CO)3], the Cr(CO)3 unit exhibits a three-legged piano-stool conformation. The chromium metal centre is coordinated by the phenyl ring of the flavone ligand [Cr—(phenyl centroid) distance = 1.709 (1) Å]. The ligand is approximately planar, the dihedral angles between the γ-pyrone ring and the phenyl ring and between the γ-pyrone and the phenylene ring being 2.91 (5) and 3.90 (5)°, respectively. The molecular packing shows π–π stacking between the flavone ligands of neighbouring molecules.

In the title compound, [Cr(C 15 H 10 O 2 )(CO) 3 ], the Cr(CO) 3 unit exhibits a three-legged piano-stool conformation. The chromium metal centre is coordinated by the phenyl ring of the flavone ligand [Cr-(phenyl centroid) distance = 1.709 (1) Å ]. The ligand is approximately planar, the dihedral angles between the -pyrone ring and the phenyl ring and between the -pyrone and the phenylene ring being 2.91 (5) and 3.90 (5) , respectively. The molecular packing showsstacking between the flavone ligands of neighbouring molecules.

Experimental
Crystal data [Cr(C 15  The steric influence from a Cr(CO) 3 moiety combined with the electronic alteration of an arene ring, via metal coordination, made the tricarbonyl(arene)chromium complexes very popular intermediates in regioselective organic synthesis (Dominique et al., 1999).
In the course of our work on flavanoids we isolated and characterized the title compound, (I), [Cr(CO)  The phenyl ring of the flavone backbone is essentialy planar (r.m.s of fitted atoms C1'-C6' = 0.0083 Å). The γ-pyrone and the benzene ring of the flavone skeleton is in the same plane as the phenyl ring. A small molecular disorder is displayed by the dihedral angle of 2.91° between the γ-pyrone and the phenyl ring and the torsion angle of -178.78 (15)° formed by atoms C2'-C1'-C2-O5. The benzene ring is lifted out of the molecular plane, with a 3.90 (5)° dihedral angle between the γ-pyrone and the benzene ring. Other molecular geometrical parameters is in good agreement with literature values, see Allen (2002). Selected geometrical parameters is presented in Table 1.
The molecular packing displays two types of ligand to ligand π-π stacking. This is on opposite sides of the 2-phenylchromane backbone (Fig.2). One type of packing is where the tricarbonyl-metal moieties of neighbouring molecules are directed away from one another resulting in a ligand to ligand π-π stacking between the γ-pyrone and phenyl rings, with a plane to plane distance of 3.354 Å. The other type of π-π stacking is between the γ-pyrone and benzene rings of neighbouring molecules, with a plane to plane distance of 3.418 Å, this π-π stacking is secondarily stabilized by soft contacts between O1···H5 [2.761 (3) Å] and a O1···H5-C5 angle of 129.8 (1)°.

Refinement
The H atoms were positioned geometrically and refined using a riding model with fixed C-H distances of 0.93 Å (CH) [U iso (H) = 1.2U eq ] and 0.96 Å.
The highest density peak is 0.36 located 0.76 Å from C3 and the deepest hole is -0.35 located at 0.61 Å from Cr. Fig. 1. A view of (I) showing the atom-numbering scheme with displacement ellipsoids at the 30% probability level. Tricarbonyl(η 6 -flavone)chromium (0) Crystal data [Cr(C 15

Special details
Experimental. The intensity data was collected on a Bruker Apex II CCD diffractometer using an exposure time of 10 s/frame. The 509 frames were collected with a frame width of 0.5° covering up to θ = 28° with 99.8% completeness accomplished.