Research Article Synthesis and Crystal Structure of 1-Methyl ...Dr. Elango Kandasamy acknowledges the DST-SERB, for nancialsupport,DepartmentofChemistry,IndianInstitute of Technology

Research ArticleSynthesis and Crystal Structure of1-Methyl-3-(2-pyridyl)imidazolium Hexafluorophosphate

Elango Kandasamy

Department of Chemistry, Vel Tech University, Chennai 600062, India

Correspondence should be addressed to Elango Kandasamy; [email protected]

Received 20 December 2013; Revised 12 May 2014; Accepted 13 May 2014; Published 17 July 2014

Academic Editor: Yan Xu

Copyright © 2014 Elango Kandasamy. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Compound 1-Methyl-3-(2-pyridyl)imidazoliumhexafluorophosphatewas crystallized inmonoclinic systemwith space group𝑃21/𝑐

and unit cell parameters 𝑎 = 7.3740(8) Å, 𝑏 = 15.5931(16) Å, 𝑐 = 10.4787(11) Å, 𝛽 = 105.310(2)∘, and ] = 1162.1 (2) Å3. Theobtained solid state structure of 1-Methyl-3-(2-pyridyl)imidazolium hexafluorophosphate shows CH⋅ ⋅ ⋅ F type weak interactionsand was analyzed.

1. Introduction

The chemistry ofN-heterocyclic carbene (NHC) has becomeemerged field after the crystal structure of free 1,3-diada-mantyl imidazol-2-ylidene was first reported in 1991 byArduengo III et al. [1–3]. The chemical durability of NHCencouraged the chemist to study their reactivity with inor-ganic and organic compounds. The synthesis of NHCnormally had been done by removal of C-2 proton ofimidazolium salt with a suitable base. Many examples ofimidazolium salts were synthesized and their correspondingNHC and NHC-metal compounds were studied [4, 5]. Theinteresting criteria of the imidazole are that, by tuningthe substitution on nitrogen center at the imidazole ring,different types of functionalized imidazolium salts havebeen synthesized [6–9]. Herein, the modified synthesis of1-Methyl-3-(2-pyridyl)imidazolium hexafluorophosphate (1)and its crystal structure have been discussed.

2. Materials and Methods

A mixture 2-chloropyridine (1.35 g, 10mmole) and 1-meth-ylimidazole (0.821 g, 10mmole) were heated at 150∘C for 20hours. To this mixture saturated aqueous solution of KPF

6

was added, while the mixture was hot and it results in therapid precipitation of white color substance. The obtained

white color precipitate was filtrated off and dried in vacuum.The colorless block type crystals of (MeIMPy)(PF

6) were

obtained after one week from methanolic solution. Yield(based on 1-methylimidazole): 1.05 g, 34%. Anal. Calcd. forC9H10N3F3P (305.17): C, 35.26; H, 3.42; N, 13.48. Found: C,

35.42; H, 3.30; N, 13.77. 1H NMR (400MHz, CD3OD, 22∘C,

𝛿): 3.93 (s, 3H), 7.61 (m, 2H), 7.76 (d, 1H), 8.07 (m, 1H), 8.12(m, 1H), 8.48 (m, 1H), 9.26 (s, 1H).

2-Chloropyridine (99.0%), 1-methylimidazole (99.0%),and KPF

6(98.0%) were purchased from Sigma-Aldrich and

used as received. 1H NMR spectra were obtained on aJEOL-JNM LAMBDA 400 model spectrometer operating at400MHz.The spectrawere recorded inCD

3ODsolution, and

the chemical shifts were referenced with respect to TMS.Crystal was coated with light hydrocarbon oil and

mounted in the 100K dinitrogen stream of Bruker SMARTAPEX CCD diffractometer equipped with CRYO Industrieslow-temperature apparatus and intensity data were collectedusing graphite monochromated Mo K𝛼 radiation (𝑘 =0.71073 Å). The data integration and reduction wereprocessed with SAINT software [10]. An absorptioncorrection was applied [11]. Structure was solved by thedirect method using SHELXS-97 and was refined on F2 byfull-matrix least-squares technique using the SHELXL-97software package [12]. Nonhydrogen atoms were refinedanisotropically. In the refinement, hydrogen atoms were

Hindawi Publishing CorporationJournal of CrystallographyVolume 2014, Article ID 219828, 4 pageshttp://dx.doi.org/10.1155/2014/219828

2 Journal of Crystallography

F1

F2

F3

F4

F5

F6P1

C1

N1

C2

N2

C3

N3 C4

C5

C6C7

C8C9

Figure 1: ORTEP drawings of molecular structure of (MeIMPy)(PF6). The thermal displacement ellipsoids are drawn at the 30% probability.

Table 1: Crystal data and data collection parameters for thecompound (MeIMPy)(PF6).

Identification code 1Empirical formula C9H10N3F6PFormula weight 305.17Temperature 100(2) KCrystal system, space group Monoclinic, 𝑃2(1)/𝑐

Unit cell dimensions

𝑎 = 7.3740(8) Å𝑏 = 15.5931(16) Å𝑐 = 10.4787(11) Å𝛽 = 105.310(2)∘

Volume 1162.1(2) Å3

𝑍, calculated density 4, 1.744mg/m3

Absorption coefficient 0.305mm−1

𝐹(000) 616Crystal size 0.07 × 0.04 × 0.01mm3

𝜃 range for data collection 2.40 to 28.31∘

Index ranges −9 ≤ ℎ ≤ 9, −20 ≤ 𝑘 ≤ 20, −8 ≤ 𝑙 ≤ 13Reflections collected 7402Independent reflections 2885 [𝑅(int) = 0.0189]Completeness to theta 98.0%Data/restraints/parameters 2826/0/173Goodness-of-fit on F2 1.190Final 𝑅 indices [𝐼 > 2(𝐼)]a 𝑅1 = 0.0446a, 𝑤𝑅2 = 0.1119𝑅 indices (all data) 𝑅1 = 0.0592a, 𝑤𝑅2 = 0.1611b

Largest diff. peak and hole 0.526 and −0.691 e⋅Å−3a∑‖Fo| − |Fc|/ ∑ |Fo|, b√∑[𝑤(Fo2 − Fc2)2]/√𝑤(Fo2)2.

treated as riding atoms using SHELXL default parameters.The crystallographic figures, except Figure 1, were generatedusingDiamond 3.1f software. Crystal data and data collectionparameters for the compound 1 are given in Table 1. CCDC851202 contains the supplementary crystallographic datafor 1. These data can be obtained free of charge from

the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/Community/Requestastructure/Pages/DataRequest.aspx.

3. Results and Discussion

1-Methyl-3-(2-pyridyl)imidazolium hexafluorophosphate(MeIMPy)(PF

6) has been synthesized by slight modification

from reported procedure [13]. The 2-chloropyridine and1-methylimidazole were heated for 20 hours with neat con-dition. During the course of reaction, the reaction mixtureslowly turned into brown viscous liquid. When the reactionmixture was in hot condition, saturated solution of KPF

6

was added. Immediately, white color precipitate appeared.The precipitates were filtered and dried in high vacuum.The precipitates were filtered and dried in high vacuum(Scheme 1).1H-NMR of 1-Methyl-3-(2-pyridyl)imidazolium hexa-

fluorophosphate (MeIMPy)(PF6) has been recorded in deu-

terated methanol (CD3OD). The spectra of (MeIMPy)(PF

6)

show resonance peak at 9.26 ppm for –CH of 2-position ofimidazolium ring and 3.93 ppm for –CH

3. The NMR spectral

analysis matches the reported NMR values (recorded inCD3CN) and supports the molecular structure of (MeIMPy)

(PF6).Single crystals of 1 were grown in methanolic solution

at room temperature and a suitable crystal was subjectedto the X-ray structural analysis. The crystal data revealsthat the compound 1 crystallizes in the monoclinic systemand centrosymmetric space group P2(1)/c. The solid statestructure of 1 consists of one cation and one anion (Figure 1).The unit cell contains four of each cation and anion. Theimportant bond lengths and bond angles are shown inTables 2 and 3.

In the anion unit, the bond distances between phospho-rous and fluorine atom are shown in the range of 1.590(19) Åto 1.608(17) Å and the bond angles suggest that the anion unitis almost perfect octahedron (Table 2). From the cation unit,the bond angle between (N1-C1-N2 108.3(2)∘) is similar to atypical bond angle of imidazolium unit and it is in plane.

Journal of Crystallography 3

N Cl N N

N NN

CH3

(i) 150∘C(ii) aq. KPF6

H PF6

+ CH3+ KCl

Scheme 1: Synthesis of (MeIMPy)(PF6).

Table 2: Bond distances and angles of hexafluorophosphate unit.

Bond distances (Å)P(1)–F(1) 1.608(2) P(1)–F(4) 1.606(2)P(1)–F(2) 1.591(2) P(1)–F(5) 1.599(2)P(1)–F(3) 1.597(2) P(1)–F(6) 1.603(2)

Bond angles (∘)F(2)–P(1)–F(3) 90.40(11) F(3)–P(1)–F(5) 90.11(11)F(2)–P(1)–F(4) 90.75(12) F(6)–P(1)–F(1) 89.59(9)F(4)–P(1)–F(1) 179.26(11) F(3)–P(1)–F(1) 90.22(9)F(5)–P(1)–F(1) 89.72(10) F(6)–P(1)–F(4) 90.21(9)F(2)–P(1)–F(1) 89.96(11) F(3)–P(1)–F(4) 89.98(10)F(5)–P(1)–F(4) 89.57(11) F(3)–P(1)–F(6) 179.69(11)F(2)–P(1)–F(5) 179.40(11) F(5)–P(1)–F(6) 89.64(10)F(2)–P(1)–F(6) 89.85(10)

Table 3: Bond distances and angles of 1-Methyl-3-(2-pyridyl) imid-azolium unit.

Bond distances (Å)N(1)–C(2) 1.321(3) N(3)–C(3) 1.323(3)N(1)–C(1) 1.470(3) N(3)–C(4) 1.343(3)N(2)–C(8) 1.379(3) C(3)–C(7) 1.388(4)C(8)–C(9) 1.355(4) C(6)–C(7) 1.383(4)N(2)–C(2) 1.341(3) C(4)–C(5) 1.386(4)N(2)–C(3) 1.438(3) C(5)–C(6) 1.382(4)N(1)–C(9) 1.374(3)

Bond angles (∘)N(1)–C(2)–N(2) 108.3(2) C(2)–N(1)–C(9) 109.1(2)C(2)–N(2)–C(8) 108.7(2) C(2)–N(2)–C(3) 124.1(2)C(9)–C(8)–N(2) 106.6(2) N(3)–C(3)–N(2) 114.2(2)C(8)–C(9)–N(1) 107.3(2) C(8)–N(2)–C(3) 127.2(2)

The pyridyl ring has slightly twisted from plane of imida-zolium moiety.

The solid state structure of 1 shows that the cationsand anions are connected through intermolecular CH⋅ ⋅ ⋅ Ftype hydrogen bond interaction (Table 4). Each cation unitis hydrogen bonded to five separate anion units (Figure 2).CH⋅ ⋅ ⋅ F interaction between C2 position of five memberedimidazolium rings and F4, C8 position of pyridyl moietyand F1 results in the 1D supramolecular polymer chains(Figures 3 and 4).

Table 4: Details of inter- and intramolecular hydrogen bond.

D–H⋅ ⋅ ⋅A H⋅ ⋅ ⋅A Å D–H⋅ ⋅ ⋅A∘ D⋅ ⋅ ⋅A ÅC8H8⋅ ⋅ ⋅ F1 2.31 171.17(18) 3.257(4)C7H7⋅ ⋅ ⋅ F2 2.66 121.27(18) 3.260(4)C6H6⋅ ⋅ ⋅ F2 2.62 123.89(19) 3.260(4)C2H2⋅ ⋅ ⋅ F4 2.27 150.07(19) 3.135(4)C5H5⋅ ⋅ ⋅ F4 2.52 132.72(17) 3.243(3)C4H4⋅ ⋅ ⋅ F5 2.60 124.51(18) 3.243(3)C5H5⋅ ⋅ ⋅ F5 2.59 123.27(18) 3.216(4)

C2

H2

F4

C8

H8

F6

C6

H6

F2

C7

H7

C5H6F4

C4

H4F5

a

b

c

Figure 2: CH⋅ ⋅ ⋅ F interactions in (MeIMPy)(PF6).

4. Summary

The solid state structure of 1-Methyl-3-(2-Pyridyl)imida-zolium hexafluorophosphate has been discussed by usingsingle crystal X-ray diffraction study. The different types ofCH⋅ ⋅ ⋅ F supramolecular interaction and the formation of 1Dsupramolecular polymer chain between cation and anion unitby CH⋅ ⋅ ⋅ F weak interaction of titled compound have beeninvestigated.

4 Journal of Crystallography

F1

F4

C8

C2

H8H2

a

bc

Figure 3: 1D supramolecular polymer chain in (MeIMPy)(PF6).

PFN

CH

b

c

Figure 4:The unit cell packing of crystal of (MeIMPy)(PF6), viewed

along a-axis.

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper.

Acknowledgments

Dr. Elango Kandasamy acknowledges the DST-SERB, forfinancial support, Department of Chemistry, Indian Instituteof Technology Kanpur for single crystal X-ray facilities,and Vel Tech Dr. RR & Dr. SR Technical University forinfrastructure.

References

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[3] A. J. Arduengo III, R. L. Harlow, andM. Kline, “A stable crystal-line carbene,” Journal of the American Chemical Society, vol. 113,no. 1, pp. 361–363, 1991.

[4] V. Nair, S. Bindu, and V. Sreekumar, “N-heterocyclic carbenes:reagents, not just ligands!,” Angewandte Chemie, vol. 43, no. 39,pp. 5130–5135, 2004.

[5] E. A. B. Kantchev, C. J. O’Brien, and M. G. Organ, “Palladiumcomplexes of N-heterocyclic carbenes as catalysts for cross-coupling reactions—a synthetic chemist’s perspective,” Ange-wandte Chemie, vol. 46, no. 16, pp. 2768–2813, 2007.

[6] F. E. Hahn and M. C. Jahnke, “Heterocyclic carbenes: synthesisand coordination chemistry,” Angewandte Chemie, vol. 47, no.17, pp. 3122–3172, 2008.

[7] P. L. Arnold and I. J. Casely, “F-block N-heterocyclic carbenecomplexes,” Chemical Reviews, vol. 109, no. 8, pp. 3599–3611,2009.

[8] O. Kuhl, Functionalised N-Heterocyclic Carbene Complexes,Wiley-InterScience, New York, NY, USA, 2010.

[9] L. Benhamou, E. Chardon, G. Lavigne, S. Bellemin-Laponnaz,and V. César, “Synthetic routes to N-heterocyclic carbeneprecursors,” Chemical Reviews, vol. 111, no. 4, pp. 2705–2733,2011.

[10] SAINT+, 6.02 ed, Bruker AXS, Madison, Wis, USA, 1999.[11] G. M. Sheldrick, SADABS 2.0, University of Göttingen,

Göttingen, Germany, 2000.[12] G. M. Sheldrick, “A short history of SHELX,” Acta Crystallo-

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[13] V. J. Catalano and A. O. Etogo, “Luminescent coordinationpolymers with extended Au(I)-Ag(I) interactions supported bya pyridyl-substituted NHC ligand,” Journal of OrganometallicChemistry, vol. 690, no. 24-25, pp. 6041–6050, 2005.

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Research Article Synthesis and Crystal Structure of 1-Methyl ...Dr. Elango Kandasamy acknowledges the DST-SERB, for nancialsupport,DepartmentofChemistry,IndianInstitute of Technology