organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 67| Part 5| May 2011| Page o1244

N-tert-Butyl O-2-iso­propyl-5-methyl­cyclo­hexyl phenyl­phospho­namidate

aCollege of Chemistry and Chemical Engineering, Liaocheng University, Shandong 252059, People's Republic of China
*Correspondence e-mail: literabc@hotmail.com

(Received 3 April 2011; accepted 6 April 2011; online 29 April 2011)

In the title compound, C20H34NO2P, the P atom has an irregular tetra­hedral environment and exhibits Sp chirality. In the crystal, weak inter­molecular N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into chains extending in [010].

Related literature

For the crystal structures of related P-chiral compounds, see: Chaloner et al. (1991[Chaloner, P. A., Harrison, R. M. & Hitchcock, P. B. (1991). Acta Cryst. C47, 2241-2242.]); Meng et al. (2010[Meng, F.-J., Xu, H., Liu, L.-J., Wang, D. & Zhao, C.-Q. (2010). Acta Cryst. E66, o2352.]).

[Scheme 1]

Experimental

Crystal data
  • C20H34NO2P

  • Mr = 351.45

  • Orthorhombic, P 21 21 21

  • a = 8.305 (3) Å

  • b = 11.064 (4) Å

  • c = 22.557 (9) Å

  • V = 2072.8 (15) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.14 mm−1

  • T = 298 K

  • 0.45 × 0.40 × 0.37 mm

Data collection
  • Bruker SMART-1000 CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.938, Tmax = 0.949

  • 10336 measured reflections

  • 3610 independent reflections

  • 1993 reflections with I > 2σ(I)

  • Rint = 0.075

Refinement
  • R[F2 > 2σ(F2)] = 0.053

  • wR(F2) = 0.130

  • S = 1.02

  • 3610 reflections

  • 223 parameters

  • 114 restraints

  • H-atom parameters constrained

  • Δρmax = 0.27 e Å−3

  • Δρmin = −0.31 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 2085 Friedel pairs

  • Flack parameter: 0.06 (17)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1⋯O2i 0.86 2.52 3.326 (4) 156
C13—H13⋯O2i 0.93 2.51 3.391 (5) 157
Symmetry code: (i) [-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: SMART (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2007[Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

We recently reported the crystal stucture of 2-isopropyl-5-methylcyclohexyl N-cyclohexyl-P- phenylphosphonamidate synthesized by the reaction of (Rp)-O-menthyl phenylphosphinate with cyclohexylamine (Meng et al., 2010). Herein we report the title compound (I) obtained by the reaction of the same phosphinate with tert-butylamine.

In (I) (Fig.1), the configuration of the central P atom was detemined as S and the four groups around the P atom form an irregular tetrahedron. A stable chair conformation was observed for the 2-isopropyl-5-methylcyclohexyloxy, in which the isopropyl, methyl and oxygen atom locate at equatorial bond. The absolute configuration of C4, C7, and C11 are S, R, and R, respectively. The bond angle around the P atom are normal and comparable with those observed in the related compounds (Meng et al., 2010; Chaloner et al. 1991).

In the crystal structure, the molecules are linked by weak intermolecular N1—H1···O2 and C13—H13···O2 hodrogen bonds (Tabel 1) into chains extended in [010].

Related literature top

For the crystal structures of related P-chiral compounds, see: Chaloner et al. (1991); Meng et al. (2010).

Experimental top

Carbon tetrachloride was added to a solution of (Rp)-O-menthyl-phenylphosphonothioate dissolved in dry ether and tert-butylamine.The reaction mixture was stirred for 30 h at room temperature. The crystal suitable for X-ray diffraction was obtained by recrystallization with dichloromethane/hexane.

Refinement top

All H atoms were fixed geometrically (C—H = 0.93 - 0.98 Å; N—H = 0.86 Å), and treated as riding, with Uiso(H) = 1.2-1.5 Ueqof the parent atom.

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing the atomic numbering and 30% probability displacement ellipsoids. H atoms have been omitted for clarity.
N-tert-Butyl O-2-isopropyl-5-methylcyclohexyl phenylphosphonamidate top
Crystal data top
C20H34NO2PF(000) = 768
Mr = 351.45Dx = 1.126 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 1474 reflections
a = 8.305 (3) Åθ = 2.6–18.0°
b = 11.064 (4) ŵ = 0.14 mm1
c = 22.557 (9) ÅT = 298 K
V = 2072.8 (15) Å3Block, colourless
Z = 40.45 × 0.40 × 0.37 mm
Data collection top
Bruker SMART-1000 CCD area-detector
diffractometer
3610 independent reflections
Radiation source: fine-focus sealed tube1993 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.075
ϕ and ω scansθmax = 25.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 99
Tmin = 0.938, Tmax = 0.949k = 1013
10336 measured reflectionsl = 2625
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.053H-atom parameters constrained
wR(F2) = 0.130 w = 1/[σ2(Fo2) + (0.0457P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max = 0.001
3610 reflectionsΔρmax = 0.27 e Å3
223 parametersΔρmin = 0.31 e Å3
114 restraintsAbsolute structure: Flack (1983), 2085 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.06 (17)
Crystal data top
C20H34NO2PV = 2072.8 (15) Å3
Mr = 351.45Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 8.305 (3) ŵ = 0.14 mm1
b = 11.064 (4) ÅT = 298 K
c = 22.557 (9) Å0.45 × 0.40 × 0.37 mm
Data collection top
Bruker SMART-1000 CCD area-detector
diffractometer
3610 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1993 reflections with I > 2σ(I)
Tmin = 0.938, Tmax = 0.949Rint = 0.075
10336 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.053H-atom parameters constrained
wR(F2) = 0.130Δρmax = 0.27 e Å3
S = 1.02Δρmin = 0.31 e Å3
3610 reflectionsAbsolute structure: Flack (1983), 2085 Friedel pairs
223 parametersAbsolute structure parameter: 0.06 (17)
114 restraints
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
xyzUiso*/Ueq
P10.54415 (14)0.34918 (10)0.23972 (5)0.0462 (3)
O10.6726 (3)0.2945 (3)0.19552 (12)0.0503 (8)
O20.5009 (3)0.4756 (2)0.23040 (13)0.0578 (9)
N10.3903 (4)0.2570 (3)0.23664 (16)0.0521 (9)
H10.41390.18160.23320.063*
C40.7421 (5)0.3383 (5)0.09282 (17)0.0586 (13)
H40.85420.31920.10270.070*
C50.6512 (5)0.3284 (4)0.30808 (17)0.0418 (11)
C60.7238 (7)0.4734 (5)0.1000 (2)0.0679 (14)
H60.73010.49120.14250.082*
C70.6383 (5)0.2641 (4)0.13399 (18)0.0511 (12)
H70.52470.28060.12560.061*
C80.6923 (6)0.4277 (4)0.3410 (2)0.0624 (14)
H80.66320.50440.32810.075*
C90.6699 (6)0.1301 (4)0.1270 (2)0.0636 (14)
H9A0.77950.11320.13940.076*
H9B0.59830.08610.15330.076*
C100.2175 (5)0.2851 (4)0.2390 (2)0.0605 (12)
C110.6471 (7)0.0842 (5)0.0651 (2)0.0708 (15)
H110.53360.09700.05510.085*
C120.7434 (7)0.1585 (6)0.0229 (2)0.0831 (17)
H12A0.71650.13480.01730.100*
H12B0.85680.14180.02910.100*
C130.6942 (6)0.2165 (4)0.3286 (2)0.0627 (14)
H130.66880.14820.30650.075*
C140.7741 (6)0.2041 (5)0.3811 (2)0.0750 (16)
H140.79920.12750.39520.090*
C150.8169 (6)0.3034 (6)0.4129 (2)0.0723 (16)
H150.87390.29410.44810.087*
C160.7145 (6)0.2930 (5)0.0299 (2)0.0732 (16)
H16A0.60460.31110.01830.088*
H16B0.78560.33620.00320.088*
C170.1234 (6)0.1719 (5)0.2447 (3)0.1004 (18)
H17A0.15500.13040.28020.151*
H17B0.14350.12110.21100.151*
H17C0.01070.19080.24670.151*
C180.6792 (8)0.0509 (5)0.0587 (2)0.103 (2)
H18A0.66480.07440.01810.154*
H18B0.60540.09510.08330.154*
H18C0.78760.06830.07080.154*
C190.5637 (7)0.5245 (5)0.0774 (2)0.0915 (19)
H19A0.55230.50650.03600.137*
H19B0.56210.61050.08300.137*
H19C0.47640.48850.09900.137*
C200.7781 (7)0.4143 (5)0.3941 (2)0.0723 (16)
H200.80770.48190.41600.087*
C210.8611 (8)0.5424 (6)0.0696 (3)0.109 (2)
H21A0.96260.50890.08170.163*
H21B0.85660.62610.08070.163*
H21C0.85020.53540.02740.163*
C220.1788 (8)0.3622 (6)0.2900 (3)0.136 (2)
H22A0.06410.36650.29480.204*
H22B0.22100.44190.28350.204*
H22C0.22600.32860.32520.204*
C230.1671 (8)0.3533 (7)0.1851 (3)0.137 (2)
H23A0.05650.37700.18900.206*
H23B0.17930.30280.15080.206*
H23C0.23320.42400.18090.206*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P10.0430 (6)0.0520 (7)0.0436 (7)0.0011 (6)0.0006 (6)0.0021 (6)
O10.0398 (17)0.071 (2)0.0398 (17)0.0001 (16)0.0011 (14)0.0013 (14)
O20.054 (2)0.0493 (18)0.070 (2)0.0005 (15)0.0028 (16)0.0074 (15)
N10.037 (2)0.052 (2)0.068 (2)0.0012 (17)0.0005 (19)0.0009 (19)
C40.042 (3)0.093 (4)0.041 (3)0.000 (3)0.004 (2)0.006 (3)
C50.040 (3)0.051 (3)0.035 (2)0.003 (2)0.0010 (19)0.005 (2)
C60.067 (4)0.075 (4)0.062 (3)0.014 (3)0.004 (3)0.001 (3)
C70.040 (3)0.076 (4)0.038 (3)0.002 (3)0.003 (2)0.009 (2)
C80.077 (4)0.057 (3)0.053 (3)0.008 (3)0.009 (3)0.005 (3)
C90.053 (3)0.080 (4)0.058 (3)0.005 (3)0.003 (2)0.005 (3)
C100.042 (3)0.065 (3)0.074 (3)0.004 (2)0.001 (3)0.003 (3)
C110.065 (4)0.090 (4)0.057 (3)0.004 (3)0.001 (3)0.011 (3)
C120.078 (4)0.115 (5)0.056 (3)0.008 (4)0.008 (3)0.014 (3)
C130.074 (4)0.050 (3)0.064 (3)0.001 (3)0.017 (3)0.002 (2)
C140.076 (4)0.076 (4)0.073 (4)0.001 (3)0.028 (3)0.010 (3)
C150.067 (4)0.101 (5)0.048 (3)0.004 (3)0.019 (3)0.002 (3)
C160.072 (4)0.104 (5)0.044 (3)0.003 (3)0.002 (3)0.001 (3)
C170.055 (3)0.079 (4)0.168 (5)0.013 (3)0.010 (4)0.014 (4)
C180.120 (6)0.098 (5)0.090 (4)0.020 (4)0.006 (4)0.037 (3)
C190.097 (5)0.084 (4)0.093 (4)0.006 (4)0.017 (4)0.014 (3)
C200.093 (5)0.064 (4)0.059 (4)0.002 (4)0.018 (3)0.016 (3)
C210.098 (5)0.118 (5)0.110 (5)0.046 (4)0.018 (4)0.020 (4)
C220.081 (4)0.143 (5)0.183 (6)0.013 (4)0.033 (4)0.072 (5)
C230.074 (4)0.166 (6)0.172 (6)0.017 (4)0.036 (4)0.072 (5)
Geometric parameters (Å, º) top
P1—O21.459 (3)C12—H12A0.9700
P1—O11.581 (3)C12—H12B0.9700
P1—N11.636 (3)C13—C141.365 (6)
P1—C51.794 (4)C13—H130.9300
O1—C71.456 (5)C14—C151.359 (6)
N1—C101.470 (5)C14—H140.9300
N1—H10.8600C15—C201.338 (6)
C4—C71.510 (6)C15—H150.9300
C4—C61.512 (6)C16—H16A0.9700
C4—C161.524 (6)C16—H16B0.9700
C4—H40.9800C17—H17A0.9600
C5—C131.369 (6)C17—H17B0.9600
C5—C81.370 (6)C17—H17C0.9600
C6—C191.533 (7)C18—H18A0.9600
C6—C211.534 (7)C18—H18B0.9600
C6—H60.9800C18—H18C0.9600
C7—C91.514 (6)C19—H19A0.9600
C7—H70.9800C19—H19B0.9600
C8—C201.400 (6)C19—H19C0.9600
C8—H80.9300C20—H200.9300
C9—C111.497 (6)C21—H21A0.9600
C9—H9A0.9700C21—H21B0.9600
C9—H9B0.9700C21—H21C0.9600
C10—C221.469 (7)C22—H22A0.9600
C10—C171.483 (6)C22—H22B0.9600
C10—C231.490 (7)C22—H22C0.9600
C11—C121.490 (7)C23—H23A0.9600
C11—C181.525 (7)C23—H23B0.9600
C11—H110.9800C23—H23C0.9600
C12—C161.516 (7)
O2—P1—O1116.25 (17)C16—C12—H12B109.0
O2—P1—N1113.53 (18)H12A—C12—H12B107.8
O1—P1—N1105.14 (17)C5—C13—C14120.7 (4)
O2—P1—C5111.6 (2)C5—C13—H13119.6
O1—P1—C599.14 (18)C14—C13—H13119.6
N1—P1—C5110.08 (19)C15—C14—C13120.3 (5)
C7—O1—P1123.9 (3)C15—C14—H14119.9
C10—N1—P1129.0 (3)C13—C14—H14119.9
C10—N1—H1115.5C20—C15—C14120.7 (5)
P1—N1—H1115.5C20—C15—H15119.7
C7—C4—C6114.5 (4)C14—C15—H15119.7
C7—C4—C16108.0 (4)C12—C16—C4113.3 (4)
C6—C4—C16114.2 (4)C12—C16—H16A108.9
C7—C4—H4106.5C4—C16—H16A108.9
C6—C4—H4106.5C12—C16—H16B108.9
C16—C4—H4106.5C4—C16—H16B108.9
C13—C5—C8118.5 (4)H16A—C16—H16B107.7
C13—C5—P1122.4 (4)C10—C17—H17A109.5
C8—C5—P1119.2 (4)C10—C17—H17B109.5
C4—C6—C19114.6 (4)H17A—C17—H17B109.5
C4—C6—C21111.6 (5)C10—C17—H17C109.5
C19—C6—C21108.2 (4)H17A—C17—H17C109.5
C4—C6—H6107.4H17B—C17—H17C109.5
C19—C6—H6107.4C11—C18—H18A109.5
C21—C6—H6107.4C11—C18—H18B109.5
O1—C7—C4110.4 (4)H18A—C18—H18B109.5
O1—C7—C9107.0 (3)C11—C18—H18C109.5
C4—C7—C9111.7 (4)H18A—C18—H18C109.5
O1—C7—H7109.2H18B—C18—H18C109.5
C4—C7—H7109.2C6—C19—H19A109.5
C9—C7—H7109.2C6—C19—H19B109.5
C5—C8—C20120.4 (5)H19A—C19—H19B109.5
C5—C8—H8119.8C6—C19—H19C109.5
C20—C8—H8119.8H19A—C19—H19C109.5
C11—C9—C7114.0 (4)H19B—C19—H19C109.5
C11—C9—H9A108.7C15—C20—C8119.4 (5)
C7—C9—H9A108.7C15—C20—H20120.3
C11—C9—H9B108.7C8—C20—H20120.3
C7—C9—H9B108.7C6—C21—H21A109.5
H9A—C9—H9B107.6C6—C21—H21B109.5
N1—C10—C22111.4 (4)H21A—C21—H21B109.5
N1—C10—C17109.8 (4)C6—C21—H21C109.5
C22—C10—C17107.8 (5)H21A—C21—H21C109.5
N1—C10—C23110.6 (4)H21B—C21—H21C109.5
C22—C10—C23106.5 (5)C10—C22—H22A109.5
C17—C10—C23110.6 (5)C10—C22—H22B109.5
C12—C11—C9109.9 (4)H22A—C22—H22B109.5
C12—C11—C18112.7 (5)C10—C22—H22C109.5
C9—C11—C18113.5 (4)H22A—C22—H22C109.5
C12—C11—H11106.8H22B—C22—H22C109.5
C9—C11—H11106.8C10—C23—H23A109.5
C18—C11—H11106.8C10—C23—H23B109.5
C11—C12—C16113.0 (4)H23A—C23—H23B109.5
C11—C12—H12A109.0C10—C23—H23C109.5
C16—C12—H12A109.0H23A—C23—H23C109.5
C11—C12—H12B109.0H23B—C23—H23C109.5
O2—P1—O1—C773.5 (3)C16—C4—C7—C955.0 (5)
N1—P1—O1—C752.9 (3)C13—C5—C8—C200.7 (7)
C5—P1—O1—C7166.8 (3)P1—C5—C8—C20179.0 (4)
O2—P1—N1—C1014.7 (5)O1—C7—C9—C11177.5 (4)
O1—P1—N1—C10142.9 (4)C4—C7—C9—C1156.6 (5)
C5—P1—N1—C10111.2 (4)P1—N1—C10—C2251.2 (6)
O2—P1—C5—C13175.2 (4)P1—N1—C10—C17170.6 (4)
O1—P1—C5—C1361.8 (4)P1—N1—C10—C2367.1 (6)
N1—P1—C5—C1348.1 (4)C7—C9—C11—C1252.8 (6)
O2—P1—C5—C85.2 (4)C7—C9—C11—C18180.0 (5)
O1—P1—C5—C8117.9 (4)C9—C11—C12—C1651.2 (6)
N1—P1—C5—C8132.2 (3)C18—C11—C12—C16178.9 (4)
C7—C4—C6—C1971.5 (5)C8—C5—C13—C141.0 (7)
C16—C4—C6—C1953.6 (6)P1—C5—C13—C14179.3 (4)
C7—C4—C6—C21165.0 (4)C5—C13—C14—C152.3 (8)
C16—C4—C6—C2169.8 (6)C13—C14—C15—C201.7 (9)
P1—O1—C7—C4118.4 (4)C11—C12—C16—C454.8 (6)
P1—O1—C7—C9119.8 (3)C7—C4—C16—C1254.9 (6)
C6—C4—C7—O157.7 (5)C6—C4—C16—C12176.5 (4)
C16—C4—C7—O1173.9 (4)C14—C15—C20—C80.0 (9)
C6—C4—C7—C9176.6 (4)C5—C8—C20—C151.2 (8)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O2i0.862.523.326 (4)156
C13—H13···O2i0.932.513.391 (5)157
Symmetry code: (i) x+1, y1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC20H34NO2P
Mr351.45
Crystal system, space groupOrthorhombic, P212121
Temperature (K)298
a, b, c (Å)8.305 (3), 11.064 (4), 22.557 (9)
V3)2072.8 (15)
Z4
Radiation typeMo Kα
µ (mm1)0.14
Crystal size (mm)0.45 × 0.40 × 0.37
Data collection
DiffractometerBruker SMART1000 CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.938, 0.949
No. of measured, independent and
observed [I > 2σ(I)] reflections
10336, 3610, 1993
Rint0.075
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.130, 1.02
No. of reflections3610
No. of parameters223
No. of restraints114
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.27, 0.31
Absolute structureFlack (1983), 2085 Friedel pairs
Absolute structure parameter0.06 (17)

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O2i0.862.523.326 (4)156
C13—H13···O2i0.932.513.391 (5)157
Symmetry code: (i) x+1, y1/2, z+1/2.
 

Acknowledgements

We acknowledge financial support by the Natural Science Foundation of China (grant No. 20772055).

References

First citationBruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationChaloner, P. A., Harrison, R. M. & Hitchcock, P. B. (1991). Acta Cryst. C47, 2241–2242.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationMeng, F.-J., Xu, H., Liu, L.-J., Wang, D. & Zhao, C.-Q. (2010). Acta Cryst. E66, o2352.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

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Volume 67| Part 5| May 2011| Page o1244
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