2,4-Bis[(3-allyl­imidazolium-1-yl)meth­yl]mesitylene bis­(hexa­fluoridophosphate)

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

doi:10.1107/S1600536811027541

. 2011 Jul 16;67(Pt 8):o2068. doi: 10.1107/S1600536811027541

2,4-Bis[(3-allylimidazolium-1-yl)methyl]mesitylene bis(hexafluoridophosphate)

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

PMCID: PMC3213513 PMID: 22091092

Abstract

In the title molecular salt, C₂₃H₃₀N₄ ²⁺·2PF₆ ⁻, the central benzene ring of the cation makes dihedral angles of 89.80 (8) and 85.23 (7)° with the pendant imidazole rings. 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 further details of imidazol-2-ylidenes, see: Arduengo et al. (1991 ▶); Scott & Nolan (2005 ▶); Scholl et al. (1999 ▶). For a related structure, see: Villegas et al. (2005 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₂₃H₃₀N₄ ²⁺·2PF₆ ⁻
M _r = 652.45
Monoclinic,
a = 11.9269 (4) Å
b = 19.1480 (6) Å
c = 12.4233 (4) Å
β = 103.479 (1)°
V = 2759.04 (15) Å³
Z = 4
Mo Kα radiation
μ = 0.26 mm⁻¹
T = 100 K
0.67 × 0.29 × 0.15 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.845, T _max = 0.961
67401 measured reflections
9961 independent reflections
8004 reflections with I > 2σ(I)
R _int = 0.030

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.117
S = 1.05
9961 reflections
397 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.94 e Å⁻³
Δρ_min = −0.38 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/S1600536811027541/hb5934sup1.cif

e-67-o2068-sup1.cif^{(26.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811027541/hb5934Isup2.hkl

e-67-o2068-Isup2.hkl^{(477.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811027541/hb5934Isup3.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
C1—H1A⋯F3ⁱ	1.00 (2)	2.49 (2)	3.411 (2)	153.1 (18)
C1—H2B⋯F7ⁱⁱ	1.01 (2)	2.47 (2)	3.480 (2)	173.7 (18)
C3—H3A⋯F6ⁱⁱ	0.97	2.53	3.3303 (17)	140
C3—H3B⋯F2ⁱ	0.97	2.48	3.4151 (17)	161
C4—H4A⋯F8ⁱⁱⁱ	0.93	2.37	3.248 (2)	157
C5—H5A⋯F4^iv	0.93	2.34	3.0754 (16)	136
C5—H5A⋯F12ⁱⁱⁱ	0.93	2.52	3.1110 (18)	122
C6—H6A⋯F6ⁱⁱ	0.93	2.31	3.1005 (16)	143
C14—H14A⋯F9^iv	0.97	2.45	3.401 (2)	167
C15—H15A⋯F6ⁱⁱ	0.93	2.42	3.1873 (16)	139
C16—H16A⋯F8^iv	0.93	2.46	3.3113 (19)	152
C17—H17A⋯F3	0.93	2.53	3.2000 (18)	129
C18—H18B⋯F4ⁱⁱ	0.97	2.54	3.2398 (17)	129
C18—H18B⋯F6ⁱⁱ	0.97	2.50	3.3781 (17)	150

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

Acknowledgments

RAH thanks Universiti Sains Malaysia (USM) 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 USM for the Research University Grant No. 1001/PFIZIK/811160. MH also thanks USM for a post-doctoral research fellowship.

supplementary crystallographic information

Comment

Since Arduengo's report of stable imidazol-2-ylidenes (Arduengo et al., 1991), there has been growing interest in the use of N-heterocyclic carbene (NHC) species (Scott & Nolan, 2005). NHC ligands act as σ-donor ligands with minimal π-accepting. NHC ligands have proved to be particularly useful in olefin metathesis and palladium-catalyzed cross-coupling reactions. Imidazol-2-ylidene and imidazolin-2-ylidene-based ruthenium alkylidenes are more active and thermally stable than the original tricyclohexylphosphine-based systems developed by Scholl et al., (1999). The title compound (I), which possesses an imidazolidine ring, is a member of this NHC family.

The asymmetric unit of the title compound, (Fig. 1), consists of one 2,4-Bis(3-allylimidazolium-1-ylmethyl)mesityleninium dication and two hexafluorophosphate anions. The central benzene (C8–C13) ring makes dihedral angles of 89.80 (8)° and 85.23 (7)° with the terminal imidazole (N1/N2/C4–C6)/(N3/N4/C15–C17) rings. The P–F distances in the anion are in the range 1.5906 (9)–1.6161 (9) Å. This values agree with a previously reported crystal structure (Villegas et al., 2005).

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

Experimental

A mixture of imidazole (0.9 g, 13.2 mmol) and sodium hydroxide (0.5 g, 12 mmol) in DMSO (5 ml) was heated to 90°C for 2 hr. The mixture was cooled to room temperature using a water bath. To this mixture, a solution of 2,4-bis(bromomethyl) mesitylene (2 g, 6.5 mmol) in DMSO (10 ml) was added. The mixture was then heated to 40°C for 1 hr, then poured into water (40 ml) followed by cooling in ice. The precipitate formed was collected, washed with water, and recrystallized from methanol/water to give product A (1,3-bis(N-imidazole-1-yl methyl) benzene) as a white solid (1.39 g, 56%). Furthermore, a mixture of A (0.5 g, 1.3 mmol) and allyl bromide (0.4 g, 3.3 mmol) in acetonitrile (30 ml) was refluxed at 90°C for 24 hr. The solvent was removed under reduced pressure to give a pale-brown oil. The resulted bromide salt was converted to its hexafluorophosphate salt by metathesis reaction using KPF₆ (0.2g, 1.1 mmol) in 20 ml of methanol. The precipitate formed was collected and washed with distilled water (2 × 5 ml) and then recrystallized from acetonitrile to give colorless solid (0.41g, 87%). Colourless blocks of (I) were obtained by slow evaporation of the salt solution in acetonitrile at room temperature.