3-(2,4-Dichloro­phen­yl)-2-oxo-1-oxaspiro­[4.5]dec-3-en-4-yl acetate

Zhao, J.; Zhou, Y.; Cheng, J.-L.; Yu, C.-M.; Zhu, G.-N.

doi:10.1107/S1600536809053951

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 66| Part 1| January 2010| Page o208

doi:10.1107/S1600536809053951

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3-(2,4-Dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl acetate

Jin-hao Zhao,^a Yong Zhou,^b Jing-Li Cheng,^a Chuan-Ming Yu ^b and Guo-Nian Zhu ^a ^*

^aInstitute of Pesticide and Environmental Toxicology, Zhejiang University, Hangzhou 310029, People's Republic of China, and ^bCollege of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, People's Republic of China
^*Correspondence e-mail: zhugn@zj.com

(Received 30 November 2009; accepted 15 December 2009; online 19 December 2009)

In the title compound, C₁₇H₁₆Cl₂O₄, the cyclohexyl ring displays a chair conformation [the four C atoms are planar with a mean deviation of 0.001 (2) Å and the two C atoms at the flap positions deviate by 0.625 (2) and −0.680 (2) Å from the plane]. The furan ring is planar with a mean deviation of 0.004 (2) Å and forms a dihedral angle of 46.73 (2)° with the benzene ring.

Related literature

For tetronic acid, see: Fischer et al. (1993 ); Benson et al. (2000 ). For the chemistry of tetronic acid pesticides, see: BAYER Aktiengesellschaft (1995 ). For the synthesis and basic structure of the spirodiclofen derivative, see: Zhao et al. (2009 ); Zhou et al. (2009 ).

Experimental

Crystal data

C₁₇H₁₆Cl₂O₄
M_r = 355.20
Monoclinic, P 2₁ /c
a = 14.0705 (5) Å
b = 12.9731 (4) Å
c = 9.2400 (3) Å
β = 90.8920 (10)°
V = 1686.45 (10) Å³
Z = 4
Mo Kα radiation
μ = 0.40 mm⁻¹
T = 296 K
0.47 × 0.45 × 0.29 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ) T_min = 0.834, T_max = 0.893
16146 measured reflections
3835 independent reflections
2866 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.035
wR(F²) = 0.098
S = 1.00
3835 reflections
210 parameters
H-atom parameters constrained
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: PROCESS-AUTO (Rigaku, 2006 ); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2007 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ) and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809053951/si2227sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809053951/si2227Isup2.hkl

checkCIF report

Comment top

The chemistry of tetronic acid compounds has being receiving increasing attention in recent years, and references cited therein (Fischer et al.,1993; Benson et al., 2000). Bayer company have developed three tetronic acids pesticides-spirodiclofen, spiromesifen and spirotetramat(BAYER Aktiengesellschaft, 1995). The cyclohexyl chair is linked by the spiro carbon atom to the five membered furan ring and the dichlorophenyl group to form the basic structure of the spirodiclofen derivative (Zhao et al., 2009) resulting in the title compound (I), (Fig. 1) by addition of the acetate group. The furan ring is planar with a mean deviation of 0.004 (2) Å. The dihedral angle between benzene and furan rings is 46.73 (2) °. The cyclohexyl ring displays a chair conformation with the deviations of C9 and C12 being 0.625 (2) and -0.680 (2) Å, respectively. Similar distortions were observed in the structure of a spirodiclofen derivative. (Zhou et al., (2009)). As expected, C7=C15, C8=O1 and C16=O4 are typically double bonds with bond distances of 1.336 (2), 1.201 (2) and 1.183 (2) Å, respectively. In the crystal, the molecules are linked through weak intermolecular contacts of C17—H17B···O1, forming chains running along the c axis.

Related literature top

For tetronic acid, see: Fischer et al. (1993); Benson et al. (2000). For the chemistry of tetronic acid pesticides, see: BAYER Aktiengesellschaft (1995). For the synthesis and basic structure of the spirodiclofen derivative, see: Zhao et al. (2009); Zhou et al. (2009).

Experimental top

4-hydroxyl-3-(2,4-dichlorophenyl)-1-oxaspiro[4,5]dec- 3-en-2-one(10 mmol 3.12 g) was added to acetic anhydride (35 ml) and the mixture was stirred at reflux for 5 h. Then water (70 ml) was added and the solution was extracted with dichloromethane. The organic layer was dried over Na₂SO₄. After filtered and concentrated, the organic residue was purified by silica gel column chromatography, eluted with ethyl acetate-petroleum(1:30,v/v) to give a white solid, which was then recrystallized from 95% ethanol to give colourless blocks.

Computing details top

Data collection: PROCESS-AUTO (Rigaku, 2006); cell refinement: PROCESS-AUTO (Rigaku, 2006); data reduction: CrystalStructure (Rigaku, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Figures top

Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

3-(2,4-Dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl acetate top

Crystal data top

C₁₇H₁₆Cl₂O₄	F(000) = 736
M_r = 355.20	D_x = 1.399 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 11608 reflections
a = 14.0705 (5) Å	θ = 3.1–27.4°
b = 12.9731 (4) Å	µ = 0.40 mm⁻¹
c = 9.2400 (3) Å	T = 296 K
β = 90.892 (1)°	Chunk, colorless
V = 1686.45 (10) Å³	0.47 × 0.45 × 0.29 mm
Z = 4

Data collection top

Rigaku R-AXIS RAPID diffractometer	3835 independent reflections
Radiation source: rotating anode	2866 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
Detector resolution: 10.00 pixels mm^-1	θ_max = 27.4°, θ_min = 3.1°
ω scans	h = −17→18
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −16→16
T_min = 0.834, T_max = 0.893	l = −11→11
16146 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.035	H-atom parameters constrained
wR(F²) = 0.098	w = 1/[σ²(F_o²) + (0.040P)² + 0.650P] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max = 0.001
3835 reflections	Δρ_max = 0.22 e Å⁻³
210 parameters	Δρ_min = −0.23 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0064 (10)

Crystal data top

C₁₇H₁₆Cl₂O₄	V = 1686.45 (10) Å³
M_r = 355.20	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 14.0705 (5) Å	µ = 0.40 mm⁻¹
b = 12.9731 (4) Å	T = 296 K
c = 9.2400 (3) Å	0.47 × 0.45 × 0.29 mm
β = 90.892 (1)°

Data collection top

Rigaku R-AXIS RAPID diffractometer	3835 independent reflections
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	2866 reflections with I > 2σ(I)
T_min = 0.834, T_max = 0.893	R_int = 0.025
16146 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.035	0 restraints
wR(F²) = 0.098	H-atom parameters constrained
S = 1.00	Δρ_max = 0.22 e Å⁻³
3835 reflections	Δρ_min = −0.23 e Å⁻³
210 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl2	0.54892 (4)	0.47091 (4)	0.18788 (5)	0.06065 (17)
Cl1	0.38311 (4)	0.75742 (4)	0.51693 (6)	0.06588 (18)
O2	0.84926 (8)	0.39184 (10)	0.46610 (12)	0.0476 (3)
O1	0.75521 (9)	0.45025 (11)	0.64035 (13)	0.0536 (3)
C4	0.64126 (12)	0.56385 (12)	0.41374 (17)	0.0392 (3)
O3	0.76541 (10)	0.49671 (10)	0.13019 (13)	0.0549 (3)
C16	0.74521 (13)	0.59698 (16)	0.08843 (19)	0.0490 (4)
C7	0.72584 (12)	0.49944 (13)	0.39001 (17)	0.0401 (4)
C6	0.56414 (13)	0.69385 (14)	0.5600 (2)	0.0500 (4)
H6	0.5665	0.7404	0.6365	0.060*
C15	0.77593 (13)	0.47332 (13)	0.27392 (18)	0.0437 (4)
C3	0.55724 (12)	0.55682 (13)	0.33197 (17)	0.0417 (4)
C1	0.48284 (12)	0.68374 (13)	0.4763 (2)	0.0462 (4)
C9	0.85752 (12)	0.40299 (14)	0.30992 (18)	0.0445 (4)
C2	0.47789 (12)	0.61566 (14)	0.36203 (18)	0.0460 (4)
H2	0.4225	0.6094	0.3064	0.055*
O4	0.74584 (11)	0.66581 (11)	0.17247 (15)	0.0626 (4)
C5	0.64214 (13)	0.63370 (14)	0.52862 (19)	0.0467 (4)
H5	0.6969	0.6399	0.5857	0.056*
C8	0.77430 (12)	0.44761 (13)	0.51412 (18)	0.0424 (4)
C14	0.84764 (13)	0.29681 (15)	0.2402 (2)	0.0522 (4)
H14A	0.7892	0.2649	0.2718	0.063*
H14B	0.8438	0.3044	0.1358	0.063*
C13	0.93139 (16)	0.22725 (18)	0.2799 (3)	0.0715 (6)
H13A	0.9306	0.2126	0.3829	0.086*
H13B	0.9252	0.1624	0.2284	0.086*
C10	0.95350 (14)	0.45228 (17)	0.2795 (2)	0.0620 (5)
H10A	0.9596	0.5155	0.3348	0.074*
H10B	0.9564	0.4699	0.1776	0.074*
C11	1.03604 (15)	0.3808 (2)	0.3184 (3)	0.0772 (7)
H11A	1.0954	0.4127	0.2907	0.093*
H11B	1.0382	0.3700	0.4223	0.093*
C17	0.72453 (19)	0.6010 (2)	−0.0704 (2)	0.0764 (7)
H17A	0.6580	0.5890	−0.0877	0.092*
H17B	0.7608	0.5488	−0.1184	0.092*
H17C	0.7415	0.6676	−0.1071	0.092*
C12	1.02541 (16)	0.2775 (2)	0.2422 (3)	0.0867 (8)
H12A	1.0774	0.2326	0.2710	0.104*
H12B	1.0282	0.2876	0.1383	0.104*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl2	0.0609 (3)	0.0749 (3)	0.0461 (3)	−0.0062 (2)	−0.0021 (2)	−0.0182 (2)
Cl1	0.0520 (3)	0.0588 (3)	0.0873 (4)	0.0111 (2)	0.0151 (2)	−0.0012 (3)
O2	0.0461 (6)	0.0517 (7)	0.0450 (6)	0.0078 (6)	−0.0016 (5)	−0.0027 (5)
O1	0.0572 (8)	0.0654 (8)	0.0381 (6)	0.0063 (6)	−0.0007 (5)	−0.0010 (6)
C4	0.0433 (8)	0.0371 (8)	0.0374 (8)	−0.0017 (7)	0.0032 (7)	0.0010 (6)
O3	0.0725 (9)	0.0540 (7)	0.0385 (6)	0.0110 (7)	0.0104 (6)	−0.0009 (5)
C16	0.0452 (9)	0.0568 (11)	0.0450 (9)	0.0032 (8)	0.0047 (7)	0.0058 (9)
C7	0.0452 (9)	0.0375 (8)	0.0374 (8)	−0.0028 (7)	0.0015 (7)	−0.0027 (7)
C6	0.0523 (10)	0.0443 (9)	0.0535 (10)	−0.0017 (8)	0.0075 (8)	−0.0110 (8)
C15	0.0502 (9)	0.0409 (9)	0.0401 (8)	0.0013 (7)	0.0035 (7)	−0.0017 (7)
C3	0.0483 (9)	0.0428 (9)	0.0341 (8)	−0.0050 (7)	0.0027 (7)	0.0017 (7)
C1	0.0441 (9)	0.0409 (9)	0.0540 (10)	0.0017 (7)	0.0110 (8)	0.0058 (8)
C9	0.0434 (9)	0.0462 (9)	0.0439 (9)	0.0007 (7)	0.0021 (7)	−0.0073 (7)
C2	0.0423 (9)	0.0514 (10)	0.0444 (9)	−0.0025 (8)	0.0017 (7)	0.0078 (8)
O4	0.0823 (10)	0.0506 (8)	0.0545 (8)	0.0025 (7)	−0.0065 (7)	0.0040 (7)
C5	0.0449 (9)	0.0472 (10)	0.0478 (9)	−0.0006 (8)	−0.0014 (7)	−0.0085 (8)
C8	0.0417 (8)	0.0409 (9)	0.0445 (9)	−0.0021 (7)	−0.0019 (7)	−0.0037 (7)
C14	0.0444 (9)	0.0498 (10)	0.0621 (11)	0.0047 (8)	−0.0058 (8)	−0.0140 (9)
C13	0.0658 (13)	0.0610 (13)	0.0869 (16)	0.0216 (11)	−0.0206 (12)	−0.0258 (12)
C10	0.0538 (11)	0.0662 (13)	0.0662 (12)	−0.0137 (10)	0.0109 (10)	−0.0151 (10)
C11	0.0405 (10)	0.1057 (19)	0.0856 (16)	−0.0067 (11)	0.0009 (10)	−0.0284 (14)
C17	0.0956 (17)	0.0911 (17)	0.0426 (10)	0.0107 (14)	0.0081 (11)	0.0080 (11)
C12	0.0493 (12)	0.112 (2)	0.0985 (18)	0.0272 (13)	−0.0115 (12)	−0.0418 (16)

Geometric parameters (Å, º) top

Cl2—C3	1.7388 (17)	C9—C14	1.526 (2)
Cl1—C1	1.7437 (17)	C2—H2	0.9300
O2—C8	1.359 (2)	C5—H5	0.9300
O2—C9	1.457 (2)	C14—C13	1.525 (3)
O1—C8	1.201 (2)	C14—H14A	0.9700
C4—C5	1.395 (2)	C14—H14B	0.9700
C4—C3	1.396 (2)	C13—C12	1.520 (4)
C4—C7	1.473 (2)	C13—H13A	0.9700
O3—C15	1.368 (2)	C13—H13B	0.9700
O3—C16	1.385 (2)	C10—C11	1.525 (3)
C16—O4	1.183 (2)	C10—H10A	0.9700
C16—C17	1.492 (3)	C10—H10B	0.9700
C7—C15	1.336 (2)	C11—C12	1.520 (3)
C7—C8	1.486 (2)	C11—H11A	0.9700
C6—C1	1.377 (3)	C11—H11B	0.9700
C6—C5	1.381 (2)	C17—H17A	0.9600
C6—H6	0.9300	C17—H17B	0.9600
C15—C9	1.500 (2)	C17—H17C	0.9600
C3—C2	1.384 (2)	C12—H12A	0.9700
C1—C2	1.377 (3)	C12—H12B	0.9700
C9—C10	1.524 (3)

C8—O2—C9	110.17 (12)	O2—C8—C7	109.76 (14)
C5—C4—C3	116.84 (15)	C13—C14—C9	111.57 (15)
C5—C4—C7	118.94 (14)	C13—C14—H14A	109.3
C3—C4—C7	124.16 (15)	C9—C14—H14A	109.3
C15—O3—C16	119.83 (14)	C13—C14—H14B	109.3
O4—C16—O3	121.77 (16)	C9—C14—H14B	109.3
O4—C16—C17	128.21 (19)	H14A—C14—H14B	108.0
O3—C16—C17	110.02 (18)	C12—C13—C14	111.3 (2)
C15—C7—C4	134.48 (15)	C12—C13—H13A	109.4
C15—C7—C8	105.27 (15)	C14—C13—H13A	109.4
C4—C7—C8	120.25 (14)	C12—C13—H13B	109.4
C1—C6—C5	118.93 (16)	C14—C13—H13B	109.4
C1—C6—H6	120.5	H13A—C13—H13B	108.0
C5—C6—H6	120.5	C9—C10—C11	112.02 (18)
C7—C15—O3	132.27 (16)	C9—C10—H10A	109.2
C7—C15—C9	112.81 (15)	C11—C10—H10A	109.2
O3—C15—C9	114.90 (14)	C9—C10—H10B	109.2
C2—C3—C4	122.29 (15)	C11—C10—H10B	109.2
C2—C3—Cl2	117.53 (13)	H10A—C10—H10B	107.9
C4—C3—Cl2	120.18 (13)	C12—C11—C10	110.95 (17)
C6—C1—C2	121.56 (16)	C12—C11—H11A	109.4
C6—C1—Cl1	119.41 (14)	C10—C11—H11A	109.4
C2—C1—Cl1	119.02 (14)	C12—C11—H11B	109.4
O2—C9—C15	101.97 (13)	C10—C11—H11B	109.4
O2—C9—C10	108.00 (14)	H11A—C11—H11B	108.0
C15—C9—C10	112.41 (16)	C16—C17—H17A	109.5
O2—C9—C14	108.69 (15)	C16—C17—H17B	109.5
C15—C9—C14	113.02 (14)	H17A—C17—H17B	109.5
C10—C9—C14	112.08 (15)	C16—C17—H17C	109.5
C1—C2—C3	118.43 (16)	H17A—C17—H17C	109.5
C1—C2—H2	120.8	H17B—C17—H17C	109.5
C3—C2—H2	120.8	C11—C12—C13	110.58 (18)
C6—C5—C4	121.95 (16)	C11—C12—H12A	109.5
C6—C5—H5	119.0	C13—C12—H12A	109.5
C4—C5—H5	119.0	C11—C12—H12B	109.5
O1—C8—O2	121.23 (15)	C13—C12—H12B	109.5
O1—C8—C7	129.01 (16)	H12A—C12—H12B	108.1

C15—O3—C16—O4	7.6 (3)	C7—C15—C9—C14	115.89 (18)
C15—O3—C16—C17	−172.61 (17)	O3—C15—C9—C14	−62.8 (2)
C5—C4—C7—C15	−134.5 (2)	C6—C1—C2—C3	−0.2 (3)
C3—C4—C7—C15	48.4 (3)	Cl1—C1—C2—C3	−179.30 (13)
C5—C4—C7—C8	44.9 (2)	C4—C3—C2—C1	0.4 (3)
C3—C4—C7—C8	−132.16 (17)	Cl2—C3—C2—C1	179.61 (13)
C4—C7—C15—O3	−1.1 (3)	C1—C6—C5—C4	0.7 (3)
C8—C7—C15—O3	179.42 (18)	C3—C4—C5—C6	−0.5 (3)
C4—C7—C15—C9	−179.47 (17)	C7—C4—C5—C6	−177.72 (16)
C8—C7—C15—C9	1.07 (19)	C9—O2—C8—O1	−179.13 (16)
C16—O3—C15—C7	44.5 (3)	C9—O2—C8—C7	0.84 (18)
C16—O3—C15—C9	−137.13 (16)	C15—C7—C8—O1	178.78 (18)
C5—C4—C3—C2	−0.1 (2)	C4—C7—C8—O1	−0.8 (3)
C7—C4—C3—C2	177.04 (15)	C15—C7—C8—O2	−1.19 (19)
C5—C4—C3—Cl2	−179.29 (13)	C4—C7—C8—O2	179.26 (14)
C7—C4—C3—Cl2	−2.2 (2)	O2—C9—C14—C13	−67.2 (2)
C5—C6—C1—C2	−0.3 (3)	C15—C9—C14—C13	−179.60 (18)
C5—C6—C1—Cl1	178.78 (14)	C10—C9—C14—C13	52.1 (2)
C8—O2—C9—C15	−0.20 (17)	C9—C14—C13—C12	−55.0 (2)
C8—O2—C9—C10	118.41 (16)	O2—C9—C10—C11	67.5 (2)
C8—O2—C9—C14	−119.78 (15)	C15—C9—C10—C11	179.18 (16)
C7—C15—C9—O2	−0.60 (19)	C14—C9—C10—C11	−52.2 (2)
O3—C15—C9—O2	−179.25 (14)	C9—C10—C11—C12	54.8 (3)
C7—C15—C9—C10	−116.02 (17)	C10—C11—C12—C13	−57.3 (3)
O3—C15—C9—C10	65.3 (2)	C14—C13—C12—C11	57.6 (3)

Experimental details

Crystal data
Chemical formula	C₁₇H₁₆Cl₂O₄
M_r	355.20
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	14.0705 (5), 12.9731 (4), 9.2400 (3)
β (°)	90.892 (1)
V (Å³)	1686.45 (10)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.40
Crystal size (mm)	0.47 × 0.45 × 0.29

Data collection
Diffractometer	Rigaku R-AXIS RAPID diffractometer
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
T_min, T_max	0.834, 0.893
No. of measured, independent and observed [I > 2σ(I)] reflections	16146, 3835, 2866
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.648

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.098, 1.00
No. of reflections	3835
No. of parameters	210
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.23

Computer programs: PROCESS-AUTO (Rigaku, 2006), CrystalStructure (Rigaku, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Acknowledgements

The authors thank the National Natural Science Foundation of China (No. 30700532) and the Science and Technology Project of Zhejiang Province (No. 2009C21014) for financial support. The authors are grateful to Professor Jianming Gu for the crystal structure analysis.

References

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