7-Benzyl-3-methyl-6-phenyl­imidazo[2,1-b][1,3]thia­zol-7-ium chloride 0.75-hydrate

Huang Guo-Li; Liu Bo; Kou Jun-Feng

doi:10.1107/S1600536813018795

. 2013 Jul 13;69(Pt 8):o1247–o1248. doi: 10.1107/S1600536813018795

7-Benzyl-3-methyl-6-phenylimidazo[2,1-b][1,3]thiazol-7-ium chloride 0.75-hydrate

Huang Guo-Li ^a,^*, Liu Bo ^a, Kou Jun-Feng ^a

PMCID: PMC3793749 PMID: 24109336

Abstract

Theasymmetric unit of the title salt, C₁₉H₁₇N₂S⁺·Cl⁻·0.75H₂O, contains two symmetrically independent formula units of the carbenium salt along with three water molecules. The water molecules are only 50% occupated, and one of them is positioned in a hydrophobic pocket not forming any hydrogen bonds. The conformation of the independent cations is very similar, with dihedral angles of 61.0 (2) and 61.5 (3)° between the benzene rings. They form quasi-centrosymmetric couples via π–π stacking interactions between the benzene and imidazo[2,1-b]thiazole rings [centroid–centroid distances = 3.718 (3) and 3.663 (3) Å]. In the crystal, O—H⋯Cl hydrogen bonds lead to the formation of a helical anion–water chain along the c-axis direction. The cations connect to the anion–water chain through C—H⋯Cl interactions, generating a three-dimensional supramolecular network. O—H⋯S hydrogen bonds and C—H⋯O interactions also occur.

Related literature

For applications in catalysis of abnormal N-heterocyclic carbenes, see: Mattson et al. (2006 ▶); Liu et al. (2008 ▶); Padmanaban et al. (2011 ▶). For related structures, see: Huang et al. (2011 ▶); Akkurt et al. (2011 ▶, 2007 ▶); Song et al. (2008 ▶). graphic file with name e-69-o1247-scheme1.jpg

Experimental

Crystal data

C₁₉H₁₇N₂S⁺·Cl⁻·0.75H₂O
M _r = 354.37
Trigonal,
a = 13.211 (1) Å
c = 19.555 (3) Å
V = 2955.7 (6) Å³
Z = 6
Mo Kα radiation
μ = 0.31 mm⁻¹
T = 291 K
0.28 × 0.24 × 0.22 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.919, T _max = 0.936
16250 measured reflections
6594 independent reflections
4827 reflections with I > 2σ(I)
R _int = 0.053

Refinement

R[F ² > 2σ(F ²)] = 0.060
wR(F ²) = 0.123
S = 1.00
6594 reflections
476 parameters
15 restraints
H-atom parameters constrained
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.28 e Å⁻³
Absolute structure: Flack (1983 ▶)
Flack parameter: 0.04 (7)

Data collection: SMART (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S1600536813018795/ld2101sup1.cif

e-69-o1247-sup1.cif^{(41.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813018795/ld2101Isup2.hkl

e-69-o1247-Isup2.hkl^{(322.7KB, 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
O1W—H1WA⋯Cl1ⁱ	0.94	2.75	3.208 (6)	111
O1W—H1WA⋯S2ⁱⁱ	0.94	2.88	3.819 (6)	174
O1W—H1WB⋯Cl2	0.86	2.61	3.240 (7)	132
O3W—H3WA⋯Cl2ⁱⁱⁱ	0.85	2.68	3.275 (10)	129
O3W—H3WB⋯Cl1ⁱ	0.85	2.60	3.301 (10)	141
C8—H8⋯Cl1	0.93	2.78	3.664 (5)	159
C10—H10⋯Cl1^iv	0.93	2.72	3.390 (5)	130
C18—H18⋯O3W ^v	0.93	2.52	3.320 (9)	144
C27—H27⋯Cl1	0.93	2.72	3.642 (5)	175

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

Acknowledgments

The authors thank the Scientific Researching Fund Projects of Yunnan Educational Department (grant No. 22012Z017) and the Youth Scientific Fund Projects of Yunnan Normal University for financial support.

supplementary crystallographic information

Comment

N-Heterocyclic carbenes (NHCs) have become ubiquitous ligands in organometallic chemistry and also serve as excellent organocatalysts primarily due to their inherent strong σ-donor ability and nucleophilicity. Recently, Mattson et al. (2006), Liu et al. (2008), Padmanaban et al. (2011) and other researchers have designed new abnormal NHCs compounds and used them as organocatalysts to catalyze umpolung reactions. According to the reports on the synthesis of imidazo[2,1-b]thiazoles (Akkurt et al. (2011, 2007), Huang et al. (2011), Song et al. (2008)), herein we report the synthesis and structure of the title compound. The molecular structure of the title compound is depicted in Fig. 1. The crystallographic asymmetric unit of I, contains two 7-benzyl-3-methyl-6-phenyl-imidazo[2,1-b]thiazol-7-ium cation, two chlorine anion and three water molecule. As shown in Fig.2, the dihedral angle between benzene ring A and B is 60.85, while C and D is 61.66, indicating the two cations in the unit cell are not equivalent. The two symmetrically independent cations are stabilized by π–π stacking interactions, with a separation of 3.718 and 3.663 Å between the centroids of the benzene and thiazole rings. Another interesting part of the structure of title compound is the helical chain (Cl1—O3w—Cl2—O1w) formed entirely by the O—H···Cl hydrogen-bonding interactions (Fig.3 & Fig.4) hydrogen-bonding interactions along c axis in this molecule. O(3w) and O(1w) atoms bridges Cl(1) and Cl(2) atoms with the bond distances of O(3w)···Cl(1) 3.300 (2) Å, O(3w)···Cl(2) 3.275 (1) Å, O(1w)···Cl(1) 3.203 (6) Å, O(1w)···Cl(2) 3.236 (6) Å, while O(2w) doesn't involve in the formation of the helical chain. Probably because O2W water molecules is disordered and isolated, lead to some OH groups without acceptor and can't form hydrogen bonds. The cations connect to the anion-water chain through C—H···Cl hydrogen bonds, and each chloride ion binds to four cations with the average bond distances of 3.389 Å. Thus in the solid-state of title compound, the cation binds to the helical anion-water chain linked by intermolecular hydrogen bonds of O—H···Cl, generating a three-dimensional supramolecular network, and the space between them are occupied by some lattice water molecules.

Experimental

A mixture of 3-methyl-6-phenylimidazo[2,1-b]thiazole (1.071 g, 5.0 mmol) and benzyl chorlide (0.759 g, 6.0 mmol,1.2 equiv) was dissolved in CH3CN, and stirred under reflux for 12 h. The solvent was then removed under vacuum. The white solids obtained were washed with diethyl ether and the crude product was re-crystallized from chloroform / toluene. The yield was 1.45 g, 85%. 1H NMR (δ, 300 MHz, CDCl3): 8.35 (s, 1H), 7.71–7.68 (m, 2H), 7.54–7.52 (m, 3H), 7.41–7.29 (m, 6H), 5.53 (s, 2H), 2.64 (d, J = 1.2 Hz, 3H); 13 C NMR (δ, 75 MHz, CDCl3) 146.9, 140.3, 131.0, 130.8, 130.7, 130.1, 129.8, 129.4, 129.3, 129.1, 125.2, 114.4, 112.3, 51.5, 13.0.