Racemic tricarbonyl[7-methoxy-2-(η6-phenyl)chromane]chromium(0)

In the title compound, [Cr(C16H16O2)(CO)3], the Cr0 atom of the Cr(CO)3 unit is coordinated to the phenyl ring of the flavan ligand in an η6 mode, with a normal arene-to-metal distance. The Cr(CO)3 unit exhibits a three-legged piano-stool conformation, while the dihydropyran ring displays a distorted envelope configuration. The phenyl ring is twisted away from the fused ring system by 25.5 (2)°. The methoxy group is almost coplanar with the phenyl ring [CMe—O—Car—Car torsion angle = 8.46 (2)°]. The crystal packing is stabilized by intermolecular C—H⋯O interactions.

In the title compound, [Cr(C 16 H 16 O 2 )(CO) 3 ], the Cr 0 atom of the Cr(CO) 3 unit is coordinated to the phenyl ring of the flavan ligand in an 6 mode, with a normal arene-to-metal distance. The Cr(CO) 3 unit exhibits a three-legged piano-stool conformation, while the dihydropyran ring displays a distorted envelope configuration. The phenyl ring is twisted away from the fused ring system by 25.5 (2) . The methoxy group is almost coplanar with the phenyl ring [C Me -O-C ar -C ar torsion angle = 8.46 (2) ]. The crystal packing is stabilized by intermolecular C-HÁ Á ÁO interactions.
The title compound crystalized in the monoclinic space group P2(1)/c, with Z = 4. For the title compound the molecular structure displays the Cr(CO) 3 moiety complexed to the flavone C-ring, exhibiting the known three-legged piano-stool conformation. All bond distances and angles are within range (Allen et al., 1987). The distance between the Cr 0 atom and the centroid of the A-η 6 -coordinated phenyl ring is 1.7119 (3) (Table 1).

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (parent) of the parent atom with a C-H distance of 0.93. The methine H atoms were placed in geometrically idealized positions and constrained to ride on its parent atoms with U iso (H) = 1.5U eq (C) and at a distance of 0.97 Å. The methyl H atoms were placed in geometrically idealized positions and constrained to ride on its parent atoms with U iso (H) = 1.5U eq (C) and at a distance of 0.96 Å. Fig. 1

Special details
Experimental. The intensity data was collected on a Bruker X8 ApexII 4 K Kappa CCD diffractometer using an exposure time of 15 s/frame. A total of 1821 frames were collected with a frame width of 0.5° covering up to θ = 28.18° with 99.7% completeness accomplished.
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.