3,3′-Diallyl-1,1′-[o-phenyl­enebis(methyl­ene)]diimidazol-3-ium bis­(hexa­fluoro­phosphate)

Rosenani A Haque; Mohammed Z Ghdhayeb; Madhukar Hemamalini; Hoong-Kun Fun

doi:10.1107/S160053681103474X

. 2011 Aug 31;67(Pt 9):o2529–o2530. doi: 10.1107/S160053681103474X

3,3′-Diallyl-1,1′-[o-phenylenebis(methylene)]diimidazol-3-ium bis(hexafluorophosphate)

Rosenani A Haque ^a, Mohammed Z Ghdhayeb ^a, Madhukar Hemamalini ^b, Hoong-Kun Fun ^b,^*,^‡

PMCID: PMC3200788 PMID: 22065513

Abstract

In the cation of the title molecular salt, C₂₀H₂₄N₄ ²⁺·2PF₆ ⁻, the central benzene ring makes dihedral angles of 84.19 (7) and 79.10 (7)° with the pendant imidazole rings. In one of the hexafluorophosphate anions, the six F atoms are disordered over two sets of sites, with an occupancy ratio of 0.842 (3):0.158 (3). In the crystal, the cations and anions are linked by numerous C—H⋯F hydrogen bonds, thereby forming a three-dimensional network.

Related literature

For applications and properties of N-heterocyclic carbenes, see: Bielawski & Grubbs (2000 ▶); Herrmann et al. (1998 ▶); Yeung et al. (2011 ▶); Jokic et al. (2010 ▶); Yu et al. (2010 ▶); Esteruelas et al. (2003 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₂₀H₂₄N₄ ²⁺·2PF₆ ⁻
M _r = 610.37
Triclinic,
a = 7.3151 (3) Å
b = 12.4913 (4) Å
c = 13.8569 (5) Å
α = 101.810 (1)°
β = 94.603 (1)°
γ = 91.424 (1)°
V = 1234.27 (8) Å³
Z = 2
Mo Kα radiation
μ = 0.29 mm⁻¹
T = 100 K
0.82 × 0.61 × 0.48 mm

Data collection

Bruker APEXII DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.801, T _max = 0.874
38348 measured reflections
10789 independent reflections
9422 reflections with I > 2σ(I)
R _int = 0.016

Refinement

R[F ² > 2σ(F ²)] = 0.049
wR(F ²) = 0.142
S = 1.05
10789 reflections
368 parameters
15 restraints
H-atom parameters constrained
Δρ_max = 1.45 e Å⁻³
Δρ_min = −0.91 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S160053681103474X/hb6386sup1.cif

e-67-o2529-sup1.cif^{(26.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681103474X/hb6386Isup2.hkl

e-67-o2529-Isup2.hkl^{(516.9KB, hkl)}

Supplementary material file. DOI: 10.1107/S160053681103474X/hb6386Isup3.cml

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
C4—H4A⋯F5ⁱ	0.93	2.44	3.2625 (17)	148
C9—H9A⋯F8Aⁱⁱ	0.93	2.38	3.303 (3)	171
C10—H10A⋯F2ⁱⁱⁱ	0.93	2.47	3.2429 (18)	141
C14—H14A⋯F3	0.97	2.41	3.3065 (16)	154
C14—H14B⋯F9Aⁱⁱ	0.97	2.42	3.224 (2)	140
C15—H15A⋯F5	0.93	2.51	3.2100 (15)	132
C17—H17A⋯F12A^iv	0.93	2.42	3.279 (2)	154
C18—H18B⋯F1ⁱⁱ	0.97	2.55	3.349 (2)	140
C19—H19A⋯F12A^v	0.93	2.50	3.364 (2)	155
C20—H20A⋯F8A^vi	0.93	2.40	3.158 (3)	139
C20—H20B⋯F1^vii	0.93	2.45	3.267 (2)	146

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

Acknowledgments

RAH thank Universiti Sains Malaysia for the FRGS fund (203/PKIMIA/671115), short term grant (304/PKIMIA/639001) and RU grants (1001/PKIMIA/813023 and 1001/PKIMIA/811157). HKF and MH thank the Malaysian Government and Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160. MH also thanks Universiti Sains Malaysia for a post-doctoral research fellowship.

supplementary crystallographic information

Comment

N-heterocyclic carbene (NHC) ligands have long been at the forefront of catalytic research and are studied extensively for the preparation of various transition metal catalysts (Bielawski & Grubbs, 2000; Herrmann et al., 1998). NHCs, on account of their strong chelation, stability towards air and moisture, modest cost and their availability in ionic form, makes them versatile precursors in catalysis ranging from C–C coupling to olefin polymerizations (Yeung et al., 2011; Jokic et al., 2010; Yu et al., 2010). The main point of focus in the reported compound is the presence of ally and methylene groups, which rotate the molecule when treated with metal ion to form a cage-like- structure suitable for the polymerization of ethylene and other higher olefins (Esteruelas et al., 2003). Fortified by the highly active and interesting characteristics obtained from complexes ligated by bis- carbene NHC backbone, the present ligand system is designed and synthesized in view of getting stable and active olefin polymerization catalyst.

The asymmetric unit of the title compound, (Fig. 1), consists of a 1,2-bis(allylimidazole-1-ylmethyl)benzene cation and two hexafluoro phosphate anions. In one of the PF₆^- octahedral anions, all F atoms are disordered over two sets of sites, with occupancy ratio of 0.842 (3): 0.158 (3). The central benzene (C1–C6) ring makes dihedral angles of 84.19 (7)° and 79.10 (7)° with the terminal imidazole (N1,N2/C8–C10)/ (N3,N4/C15–C17) rings, respectively. The distorted octahedral geometry of phosphate ions has typical P–F distances [1.480 (9)–1.615 (7) Å] and F—P—F angles [47.5 (4)–179.59 (7)°]. All bond lengths and bond angles in (I) are in the range of expected values.

In the crystal (Fig. 2), the cations and anions are linked together via intermolecular C—H···F (Table 1) hydrogen bonds forming a three-dimensional network.

Experimental

A mixture of imidazole (0.9 g, 13.0 mmol) and sodium hydroxide (0.5 g, 12 mmol) in DMSO (5 mL) was heated to 90°C for 2 h, and then was cooled to room temperature. A solution of 1,2-bis(bromomethyl)benzene (1.5 g, 5.7 mmol) in DMSO (10 mL) was added to the mixture and heated slowly to 40°C for 1 h with constant stirring. The solution obtained was poured into ice-cold water (40 mL). The precipitate was collected, washed with water, and recrystallized from methanol/water to give 1,2-bis(N-imidazole- 1-ylmethyl)benzene [1] as a white solid (0.95 g, 79 %). Furthernore, a mixture of [1] (0.5 g, 2.1 mmol) and allyl bromide (0.7 g, 6.1 mmol) in acetonitrile (20 mL) was refluxed for 24 h. The solvent was removed under reduced pressure to yield a pale-brown oil, which was converted directly to its corresponding hexafluorophosphate salt by metathesis reaction using KPF₆ (0.76g, 4.0 mmol) in 20 ml of methanol. The precipitate formed was collected and washed with distilled water (2 × 5 ml), and recrystallized from acetonitrile to give colorless solid. (1.1 g, 80 %). Colourless blocks of (I) were obtained by slow evaporation of the salt solution in acetonitrile at room temperature.