1-(Ferrocen-1-ylmethyl)-3-methylimidazol-3-ium hexafluoridophosphate

The crystal structure of the title compound, [Fe(C5H5)(C10H12N2)]PF6, consists of a ferrocene-1-methyl-(3-methylimidazolium) cation and a hexafluoridophosphate anion. The ferrocenyl rings are skewed by 6.7 (4)° from the ideal eclipsed conformation. The interplanar angle between the plane of the substituted cyclopentadienyl ring and that of the imidazole ring is 89.9 (4)°. The crystal packing is stabilized by C—H⋯F hydrogen bonds.

The crystal structure of the title compound, [Fe(C 5 H 5 )-(C 10 H 12 N 2 )]PF 6 , consists of a ferrocene-1-methyl-(3-methylimidazolium) cation and a hexafluoridophosphate anion. The ferrocenyl rings are skewed by 6.7 (4) from the ideal eclipsed conformation. The interplanar angle between the plane of the substituted cyclopentadienyl ring and that of the imidazole ring is 89.9 (4) . The crystal packing is stabilized by C-HÁ Á ÁF hydrogen bonds.

Comment
The discovery of ferrocene heralded a new era in the realm of organometallic chemistry (Kealy & Pauson, 1951). The ferrocene group has unique electronic properties, such as ability to stabilize carbocations. The titled compound (I) consists of a ferrocenyl moiety linked to an imidazole group via a methylene group. The electronic system is very well conjugated and the compound exhibits resonance structures if in solution. The ferrocenyl moiety represents a quite bulky group with unique spatial requirements due to its sandwich shape, and electronically, the powerful donor capacity of ferrocene is important in the stabilization of highly reactive metal centres and other electroactive species. Some of the important properties that ferrocenyl containing imidazolium salts exhibit that makes their study significant include electronic stabilization of adjacent electron-deficient centres due to participation of the iron atom in the dispersal of the positive charge; the unique steric bulk, chemical stability and reversibility of the ferrocene/ferrocenium redox couple.
The ferrocenyl rings exhibit an eclipsed conformation with a significant staggering angle of 6.7° which is smaller than that of Nyamori & Bala (2008) however, Nyamori et al., (2010a) have also synthesized ferrocenyl moiety with a significantly small staggering angle. The interplanar angle between the plane of the substituted Cp ring and that of the imidazole ring is orthogonal (89.9 (4)°) (Fig 1). In the crystal, a weak C-H···F hydrogen bond (Table 1) connects the cations and the anions.

Experimental
In a two-neck round-bottom flask was added sodium hexafluoridophosphate (0.13 g, 0.76 mmol) and 1-(ferrocenylmethyl)-3-methylimidazolium iodide (0.30 g, 0.74 mmol) in acetone (20 ml). The mixture was stirred under a nitrogen atmosphere for 24 h at room temperature. The reaction mixture was filtered through a plug of celite and the filtrate was then concentrated in vacuo to yield 0.23 g, 72% of an orange crystals identified as 1-(Ferrocenylmethyl)-3-methyl-   The asymmetric unit of the title compound with displacement ellipsoids drawn at the 50% probability level.

Crystal data
[Fe(C 5 H 5 )(C 10 H 12 N 2 )]PF 6 M r = 426.13 Orthorhombic, Pbca Hall symbol: -P 2ac 2ab a = 12.4226 (2)  (H) = 1.2U eq (C) (1.5 for Me groups)] and were included in the refinement in the riding model approximation. The N-H H-atom was located in a difference map and freely refined with N-H = 0.88 Å (U iso (H) = 1.2U eq (N). Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 > σ(F 2 ) is used only for calculating R-factors(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. The following ALERTS were generated. Each ALERT has the format test-name_ALERT_alert-type_alert-level. PLAT244_ALERT_4_C Low ′Solvent′ U eq as Compared to Neighbors of P1 PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L= 0.600 62 PLAT960_ALERT_3_G Number of Intensities with I. LT. -2*sig(I) ··· 4 Noted: