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

Vincent O Nyamori; Siphesihle M Zulu; Bernard Omondi

doi:10.1107/S1600536812008719

. 2012 Mar 3;68(Pt 4):m353. doi: 10.1107/S1600536812008719

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

Vincent O Nyamori ^a, Siphesihle M Zulu ^a, Bernard Omondi ^a,^*

PMCID: PMC3343779 PMID: 22589753

Abstract

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.

Related literature

For background to the chemistry of ferrocenes and their potential applications, see: Štěpnička (2008 ▶), Kealy & Pauson (1951 ▶); Togni & Hayashi (1995 ▶). For related work based on ferrocenylimidazolium salts, see: Nyamori et al. (2010a ▶); Thomas et al. (2000 ▶, 2002 ▶). For the synthesis, see: Nyamori et al. (2010b ▶). For related structures, see Nyamori & Bala (2008 ▶); Nyamori et al. (2010a ▶).

Experimental

Crystal data

[Fe(C₅H₅)(C₁₀H₁₂N₂)]PF₆
M _r = 426.13
Orthorhombic,
a = 12.4226 (2) Å
b = 13.4414 (2) Å
c = 19.2137 (3) Å
V = 3208.25 (9) Å³
Z = 8
Mo Kα radiation
μ = 1.11 mm⁻¹
T = 100 K
0.27 × 0.17 × 0.11 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.755, T _max = 0.888
44208 measured reflections
4041 independent reflections
3747 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.024
wR(F ²) = 0.064
S = 1.04
4041 reflections
227 parameters
H-atom parameters constrained
Δρ_max = 0.46 e Å⁻³
Δρ_min = −0.36 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT-Plus (Bruker, 2008 ▶); data reduction: SAINT-Plus and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812008719/fj2522sup1.cif

e-68-0m353-sup1.cif^{(34.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812008719/fj2522Isup2.hkl

e-68-0m353-Isup2.hkl^{(194.1KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C14—H14⋯F1ⁱ	0.95	2.54	3.3249 (15)	140

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Symmetry code: (i) Inline graphic .

Acknowledgments

We thank the University of KwaZulu-Natal and the National Research Foundation (NRF) for financial support.

supplementary crystallographic information

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-methylimidazole hexafluoridophosphate; mp 66–68 °C; IR (ATR cm_1) 3429, 1624, 1567, 1331, 1150, 812, 619,554, 500, 480; 1H NMR (CDCl3) 9.05 (1H, s, NCH), 7.11 (1H, s, NCH), 7.0868 (1H, s, NCH), 5.22 (2H, s, CH2), 4.39 (2H, t, J 1.8, C5H4), 4.23 (7H, t, J 1.8, C5H4), 4.24 (5H, s, C5H5), 3.94 (3H, s, CH3); 13 C NMR (CDCl3) 136.06, 122.79, 121.23, 78.02, 77.23, 69.97, 69.59, 69.19, 50.18; m/z 197 (2.3%), 198.6 (100%), 199.3 (13.1%), 280.6 (M±PF6, 4.5%); Anal. Calc. for C15H17N2Fe+; [M+]-PF6, 281.07411.