(η5-Cyclopentadienyl)[(1,2,3,4,4a,12a-η)-naphtho[2,3-b][1,4]benzodioxine]iron(II) hexafluoridophosphate

At 296 (2) K, both complexed rings in the iron(II) complex cation of the title salt, [Fe(C5H5)(C16H10O2)]PF6, are almost parallel [dihedral angle between planes = 2.4 (3)°]. The quaternary C atoms of the complexed arene ring are located at the longest distance from the Fe atom, with Fe—C distances of 2.112 (4) and 2.105 (3) Å, which are slightly longer than the average Fe—C distance for this ring (2.083 Å). The Fe ion is located 1.660 (1) and 1.543 (1) Å, respectively, from the cyclopentadienyl and the complexed arene ring.

The ORTEP of the title compound is shown in Figure 1. The planes of the coordinated arene ring and Cp ring are nearly parallel, with an angle of 2.4 (3)° between them, and this value is typically reported for benzodioxine-Fe-Cp complexes (see Piórko et al., 1995, and references therein) and for arene-Fe-Cp complexes, in general (see for example Benites et al., 1996;Benites et al., 1999;Decken, 2004;Zanello et al., 2009).
The Fe ion is located at the distances 1.660 (1)Å from the Cp ring and 1.543 (1)Å from the complexed arene ring, and these values are close to those reported in the literature for similar complexes (see for example Piórko et al., 1995;Benites et al., 1999;Decken, 2004, and literature cited therein).
In a complexed arene ring, the C-C bond lengths are found within the narrow range from 1.391 (6) to 1.409 (5) Å. Both oxygen atoms show similar bond lengths toward complexed arene ring carbon atoms [1.363 (4)Å and 1.362 (4) Å] and these appear to be shorter than similar bonds toward an uncomplexed ring [both at 1.389 (4) Å]. Similar trends have been reported for other dibenzodioxine complexes (see Piórko et al., 1995). Of the C-C bonds in the uncomplexed fused carbocyclic rings of the heterocycle three appear to be markedly shorter [range 1.348 (6) to 1.356 (5) Å], one of intermediate length [1.373 (6) Å], and remaining seven appear to be longer [the range from 1.396 (7) to 1.423 (5) Å]. Some of the angles in the structure of a heterocycle appear to be distorted with angles C4a-O5-C5a and C11a-O12-C12a [116.7 (3) and 116.2 (3)°, respectively] and angles C6-C6a-C7 and C10-C10a-C11 [122.0 (4) and 122.2 (4)°, respectively, showing the largest deviations from an idealized trigonal geometry. The distribution of both the bond lengths and angles for the naphtho-moiety of this heterocycle are similar to the values reported for the naphthalene moiety of the naphthalene-2,3-diol in complex with 4-aminoantipyrine, with angles being less severely distorted from idealized geometry than those reported in the cited work (Asiri et al., 2010).

Experimental
The title complex was prepared following the procedure of Sutherland et al. (1988). A crystal used for data collection was grown by slow evaporation of solvents from a solution of the complex in acetone-diethyl ether-dichloromethane mixture at 280 K.

Refinement
The H atoms were placed in geometrically idealized positions with C-H distances of 0.98Å (complexed aromatic) and 0.93Å (aromatic). H atoms were constrained to ride on the parent C atom with Uiso(H) = 1.2Ueq(C) for aromatic and Uiso(H) = 1.2Ueq(C) for the idealized tertiary protons. The equatorial fluorines on the PF 6 anion were modelled with a disorder ratio of 49 (2):51 (2) in order to obtain an adequate model. The P-F distances in the disordered PF 6 anion were restrained to be within 1.55Å. Fig. 1. View of the complex showing the labelling of non-H atoms with the displacement ellipsoids shown at 50% probability levels.