[μ-Bis(trimethyl­silyl)amido]bis­[μ-N,N-dimethyl-N′,N′′-bis­(trimethyl­silyl)guanidinato]-triangulo-tricopper(I)

Guo, D.; Qiao, X.; Tong, H.-B.; Zhou, M.

doi:10.1107/S1600536809008745

metal-organic compounds

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ISSN: 2056-9890

Volume 65| Part 4| April 2009| Page m405

doi:10.1107/S1600536809008745

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[μ-Bis(trimethylsilyl)amido]bis[μ-N,N-dimethyl-N′,N′′-bis(trimethylsilyl)guanidinato]-triangulo-tricopper(I)

Donglong Guo,^a Xiaoli Qiao,^b Hong-Bo Tong ^b and Meisu Zhou ^b ^*

^aSchool of Life Science and Technology, Shanxi University, Taiyuan 030006, People's Republic of China, and ^bInstitute of Applied Chemistry, Shanxi University, Taiyuan 030006, People's Republic of China
^*Correspondence e-mail: mszhou@sxu.edu.cn

(Received 9 March 2009; accepted 10 March 2009; online 14 March 2009)

The title compound, [Cu₃(C₆H₁₈NSi₂)(C₉H₂₄N₃Si₂)₂], is a trinuclear Cu^I complex. A crystallographic twofold axis passes through one Cu^I atom and the N atom of the bis(trimethylsilyl)amide ligand that bridges between the other two Cu^I atoms. The Cu—Cu bonds bridged by the guanadinate ligands [2.7913 (9) Å] are slightly longer than the Cu—Cu bond bridged by the bis(trimethylsilyl)amide ligand [2.6405 (11) Å].

Related literature

For background literature concerning the coordination chemistry of guanidinates, see: Chandra et al. (1970 ); Barker & Kilner (1994 ); Edelmann (1994 ); Bailey & Pace (2001 ); Zhou et al. (2007 ).

Experimental

Crystal data

[Cu₃(C₆H₁₈NSi₂)(C₉H₂₄N₃Si₂)₂]
M_r = 812.00
Monoclinic, C 2/c
a = 16.445 (3) Å
b = 18.653 (4) Å
c = 14.046 (3) Å
β = 96.943 (3)°
V = 4277.1 (15) Å³
Z = 4
Mo Kα radiation
μ = 1.67 mm⁻¹
T = 213 K
0.30 × 0.20 × 0.20 mm

Data collection

Siemens SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1997 ) T_min = 0.622, T_max = 0.717
8714 measured reflections
3773 independent reflections
3394 reflections with I > 2σ(I)
R_int = 0.033

Refinement

R[F² > 2σ(F²)] = 0.056
wR(F²) = 0.118
S = 1.26
3773 reflections
193 parameters
H-atom parameters constrained
Δρ_max = 0.57 e Å⁻³
Δρ_min = −0.46 e Å⁻³

Data collection: SMART (Siemens, 1996 ); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809008745/bi2357sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809008745/bi2357Isup2.hkl

checkCIF report

Comment top

Since the first guanidinato complex was reported by Lapper and coworkers (Chandra et al., 1970), the coordination chemistry of guanidinates has been well explored for main group metals as well as transition metals (Bailey & Pace, 2001; Barker & Kilner, 1994; 1994; Edelmann, 1994). The trigonal-planar CN₃ unit provides easy accessibillity and the possibility of substituent variation, which allows for tuning of the steric and electronic properties of the ligands. Recently, we reported a series of early transition metal guanidinates and their applications in the polymerization of ethylene (Zhou et al., 2007). Here we describe the synthesis and crystal structure of a new copper(I) guanidinato complex.

The molecular structure is illustrated in Fig. 1. In the trinuclear copper compound, each Cu^I atom coordinates to the other two Cu^I atoms and two N from the ligands. Atoms Cu1, Cu2, Cu1ⁱ and N4 are exactly co-planar with a crystallographic 2-fold rotation axis passing through Cu2 and N4. The bond lengths Cu1—Cu2 and Cu1ⁱ—Cu2 are therefore identical, whereas the bond length Cu1—Cu1ⁱ is slightly shorter (Table 1). The Cu1—N1 and Cu2—N3 bond lengths are 1.875 (3) and 1.885 (3) Å, respectively. In the guanidinato ligand, the bond lengths C1—N1, C1—N2 and C1—N3 are 1.329 (5), 1.386 (5) and 1.341 (5) Å, respectively. The bond angle N1—C1—N3 is 122.8 (3)°. The dihedral angle between N1/C1/N3 and Cu1/Cu2/N3 is 31.8° and that between Cu1/Cu2/Cu1ⁱ and Cu1/Cu2/N3 is 42.0°.

Related literature top

For background literature concerning the coordination chemistry of guanidinates, see: Chandra et al. (1970); Barker & Kilner (1994); Edelmann (1994); Bailey & Pace (2001); Zhou et al. (2007).

Experimental top

(CH₃)₂NCN (0.22 ml, 2.76 mmol) was added to a solution of LiN(SiMe₃)₂ (0.46 g, 2.76 mmol) in THF (30 ml) at -78°C. The resulting mixture was warmed to room temperature and stirred for 2 h. CuCl (0.27 g,2.76 mmol) was the added at -78°C and the mixture was warmed to again to room temperature and stirred for 24 h. The volatiles were removed in vacuo and the residue was extracted with dichloromethane then filtered. The filtrate was concentrated to give colorless crystals (0.14 g, 19%). M.p.: 398–400 K. ¹H NMR (CDCl₃):δ 0.10–0.43 (m, 54H, SiMe₃), 2.86 (m, 12H, N(CH₃)₂). ¹³C NMR (CDCl₃): δ 1.74~7.44 (SiMe₃), 42.16 (N(CH₃)₂), 172.8 (NCN).

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. Molecular structure showing displacement ellipsoids at 50% probability. H atoms are omitted. Symmetry code: (i) -x, y, 3/2 - z.

[µ-Bis(trimethylsilyl)amido]bis[µ-N,N-dimethyl- N',N''-bis(trimethylsilyl)guanidinato]-triangulo- tricopper(I) top

Crystal data top

[Cu₃(C₆H₁₈NSi₂)(C₉H₂₄N₃Si₂)₂]	F(000) = 1720
M_r = 812.00	D_x = 1.261 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 3322 reflections
a = 16.445 (3) Å	θ = 2.3–27.5°
b = 18.653 (4) Å	µ = 1.67 mm⁻¹
c = 14.046 (3) Å	T = 213 K
β = 96.943 (3)°	Block, colourless
V = 4277.1 (15) Å³	0.30 × 0.20 × 0.20 mm
Z = 4

Data collection top

Siemens SMART CCD diffractometer	3773 independent reflections
Radiation source: fine-focus sealed tube	3394 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.033
ω scans	θ_max = 25.0°, θ_min = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −19→16
T_min = 0.622, T_max = 0.717	k = −21→22
8714 measured reflections	l = −16→15

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.118	H-atom parameters constrained
S = 1.26	w = 1/[σ²(F_o²) + (0.0417P)² + 4.1466P] where P = (F_o² + 2F_c²)/3
3773 reflections	(Δ/σ)_max < 0.001
193 parameters	Δρ_max = 0.57 e Å⁻³
0 restraints	Δρ_min = −0.46 e Å⁻³

Crystal data top

[Cu₃(C₆H₁₈NSi₂)(C₉H₂₄N₃Si₂)₂]	V = 4277.1 (15) Å³
M_r = 812.00	Z = 4
Monoclinic, C2/c	Mo Kα radiation
a = 16.445 (3) Å	µ = 1.67 mm⁻¹
b = 18.653 (4) Å	T = 213 K
c = 14.046 (3) Å	0.30 × 0.20 × 0.20 mm
β = 96.943 (3)°

Data collection top

Siemens SMART CCD diffractometer	3773 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	3394 reflections with I > 2σ(I)
T_min = 0.622, T_max = 0.717	R_int = 0.033
8714 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.056	0 restraints
wR(F²) = 0.118	H-atom parameters constrained
S = 1.26	Δρ_max = 0.57 e Å⁻³
3773 reflections	Δρ_min = −0.46 e Å⁻³
193 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
Cu1	0.00565 (3)	0.28899 (3)	0.65704 (4)	0.03181 (17)
Cu2	0.0000	0.15714 (4)	0.7500	0.0297 (2)
N1	0.0253 (2)	0.22736 (18)	0.5568 (2)	0.0335 (8)
N2	0.1160 (3)	0.1407 (2)	0.5116 (3)	0.0489 (11)
N3	0.0812 (2)	0.14177 (18)	0.6683 (3)	0.0327 (8)
N4	0.0000	0.3629 (2)	0.7500	0.0331 (12)
Si1	−0.03059 (9)	0.24764 (8)	0.44721 (9)	0.0484 (4)
Si2	0.16644 (8)	0.10002 (7)	0.73019 (10)	0.0384 (3)
Si3	0.09487 (9)	0.40530 (7)	0.75808 (11)	0.0444 (4)
C1	0.0727 (3)	0.1708 (2)	0.5803 (3)	0.0326 (10)
C2	0.1565 (4)	0.1842 (3)	0.4465 (4)	0.0711 (18)
H2A	0.1295	0.1780	0.3817	0.107*
H2B	0.2134	0.1697	0.4493	0.107*
H2C	0.1538	0.2342	0.4648	0.107*
C3	0.1235 (4)	0.0641 (3)	0.5000 (4)	0.077 (2)
H3A	0.0899	0.0397	0.5419	0.116*
H3B	0.1803	0.0501	0.5163	0.116*
H3C	0.1055	0.0512	0.4339	0.116*
C4	−0.0495 (4)	0.1674 (4)	0.3693 (4)	0.085 (2)
H4A	0.0018	0.1512	0.3490	0.127*
H4B	−0.0875	0.1796	0.3133	0.127*
H4C	−0.0726	0.1294	0.4048	0.127*
C5	0.0166 (4)	0.3231 (4)	0.3864 (5)	0.087 (2)
H5A	0.0322	0.3609	0.4325	0.131*
H5B	−0.0226	0.3417	0.3352	0.131*
H5C	0.0648	0.3060	0.3598	0.131*
C6	−0.1333 (3)	0.2798 (4)	0.4694 (4)	0.0747 (19)
H6A	−0.1633	0.2407	0.4946	0.112*
H6B	−0.1629	0.2966	0.4097	0.112*
H6C	−0.1273	0.3187	0.5155	0.112*
C7	0.2640 (3)	0.1337 (3)	0.6908 (4)	0.0577 (15)
H7A	0.2668	0.1196	0.6248	0.087*
H7B	0.3102	0.1133	0.7315	0.087*
H7C	0.2658	0.1855	0.6957	0.087*
C8	0.1675 (3)	0.1227 (3)	0.8591 (4)	0.0543 (14)
H8A	0.1733	0.1742	0.8675	0.081*
H8B	0.2131	0.0987	0.8962	0.081*
H8C	0.1165	0.1072	0.8809	0.081*
C9	0.1591 (4)	0.0000 (2)	0.7255 (4)	0.0586 (15)
H9A	0.1034	−0.0146	0.7321	0.088*
H9B	0.1962	−0.0205	0.7774	0.088*
H9C	0.1738	−0.0169	0.6646	0.088*
C10	0.1033 (4)	0.4625 (3)	0.6504 (5)	0.085 (2)
H10A	0.0660	0.5027	0.6504	0.128*
H10B	0.0894	0.4343	0.5927	0.128*
H10C	0.1590	0.4801	0.6523	0.128*
C11	0.1138 (4)	0.4635 (3)	0.8661 (5)	0.080 (2)
H11A	0.0990	0.4379	0.9216	0.120*
H11B	0.0808	0.5067	0.8564	0.120*
H11C	0.1713	0.4765	0.8767	0.120*
C12	0.1783 (3)	0.3378 (3)	0.7637 (4)	0.0574 (15)
H12A	0.2309	0.3620	0.7708	0.086*
H12B	0.1725	0.3097	0.7052	0.086*
H12C	0.1751	0.3064	0.8182	0.086*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0350 (3)	0.0301 (3)	0.0309 (3)	0.0019 (2)	0.0064 (2)	0.0008 (2)
Cu2	0.0272 (4)	0.0326 (4)	0.0308 (4)	0.000	0.0095 (3)	0.000
N1	0.037 (2)	0.040 (2)	0.0247 (19)	0.0004 (18)	0.0059 (15)	−0.0007 (16)
N2	0.058 (3)	0.053 (3)	0.040 (2)	0.002 (2)	0.025 (2)	−0.0066 (19)
N3	0.032 (2)	0.0316 (19)	0.037 (2)	0.0019 (16)	0.0125 (16)	−0.0031 (16)
N4	0.035 (3)	0.031 (3)	0.035 (3)	0.000	0.007 (2)	0.000
Si1	0.0512 (9)	0.0670 (10)	0.0269 (7)	−0.0083 (7)	0.0038 (6)	0.0050 (6)
Si2	0.0318 (7)	0.0326 (7)	0.0523 (8)	0.0043 (6)	0.0111 (6)	0.0007 (6)
Si3	0.0451 (8)	0.0317 (7)	0.0583 (9)	−0.0068 (6)	0.0139 (7)	−0.0011 (6)
C1	0.032 (3)	0.039 (3)	0.029 (2)	−0.008 (2)	0.0146 (19)	−0.0080 (19)
C2	0.065 (4)	0.104 (5)	0.051 (4)	0.006 (4)	0.033 (3)	0.002 (3)
C3	0.106 (5)	0.069 (4)	0.060 (4)	0.018 (4)	0.024 (4)	−0.023 (3)
C4	0.082 (5)	0.118 (6)	0.052 (4)	−0.026 (4)	−0.003 (3)	−0.024 (4)
C5	0.092 (5)	0.107 (5)	0.062 (4)	−0.017 (4)	0.005 (4)	0.042 (4)
C6	0.061 (4)	0.107 (5)	0.054 (4)	0.014 (4)	−0.004 (3)	0.017 (3)
C7	0.035 (3)	0.056 (3)	0.085 (4)	0.002 (3)	0.020 (3)	0.007 (3)
C8	0.048 (3)	0.053 (3)	0.059 (3)	0.007 (3)	−0.003 (3)	0.004 (3)
C9	0.063 (4)	0.038 (3)	0.077 (4)	0.007 (3)	0.019 (3)	0.005 (3)
C10	0.074 (5)	0.074 (4)	0.109 (6)	−0.022 (4)	0.017 (4)	0.041 (4)
C11	0.074 (4)	0.064 (4)	0.105 (5)	−0.029 (3)	0.021 (4)	−0.042 (4)
C12	0.041 (3)	0.046 (3)	0.086 (4)	−0.008 (2)	0.013 (3)	−0.010 (3)

Geometric parameters (Å, º) top

Cu1—Cu1ⁱ	2.6405 (11)	C3—H3B	0.970
Cu1—Cu2	2.7913 (9)	C3—H3C	0.970
Cu2—Cu1ⁱ	2.7912 (9)	C4—H4A	0.970
Cu1—N1	1.875 (3)	C4—H4B	0.970
Cu1—N4	1.908 (3)	C4—H4C	0.970
Cu2—N3	1.885 (3)	C5—H5A	0.970
Cu2—N3ⁱ	1.885 (3)	C5—H5B	0.970
N1—C1	1.329 (5)	C5—H5C	0.970
N1—Si1	1.737 (4)	C6—H6A	0.970
N2—C1	1.386 (5)	C6—H6B	0.970
N2—C3	1.444 (6)	C6—H6C	0.970
N2—C2	1.445 (6)	C7—H7A	0.970
N3—C1	1.341 (5)	C7—H7B	0.970
N3—Si2	1.742 (4)	C7—H7C	0.970
N4—Si3	1.741 (3)	C8—H8A	0.970
N4—Si3ⁱ	1.741 (3)	C8—H8B	0.970
N4—Cu1ⁱ	1.909 (3)	C8—H8C	0.970
Si1—C6	1.853 (6)	C9—H9A	0.970
Si1—C4	1.859 (6)	C9—H9B	0.970
Si1—C5	1.865 (6)	C9—H9C	0.970
Si2—C8	1.858 (5)	C10—H10A	0.970
Si2—C7	1.868 (5)	C10—H10B	0.970
Si2—C9	1.871 (5)	C10—H10C	0.970
Si3—C12	1.856 (5)	C11—H11A	0.970
Si3—C11	1.862 (6)	C11—H11B	0.970
Si3—C10	1.870 (6)	C11—H11C	0.970
C2—H2A	0.970	C12—H12A	0.970
C2—H2B	0.970	C12—H12B	0.970
C2—H2C	0.970	C12—H12C	0.970
C3—H3A	0.970

N1—Cu1—N4	169.49 (13)	N2—C3—H3C	109.5
N1—Cu1—Cu1ⁱ	141.39 (11)	H3A—C3—H3C	109.5
N4—Cu1—Cu1ⁱ	46.23 (10)	H3B—C3—H3C	109.5
N1—Cu1—Cu2	80.18 (11)	Si1—C4—H4A	109.5
N4—Cu1—Cu2	108.00 (10)	Si1—C4—H4B	109.5
Cu1ⁱ—Cu1—Cu2	61.768 (14)	H4A—C4—H4B	109.5
N3—Cu2—N3ⁱ	162.5 (2)	Si1—C4—H4C	109.5
N3—Cu2—Cu1ⁱ	119.01 (11)	H4A—C4—H4C	109.5
N3ⁱ—Cu2—Cu1ⁱ	77.47 (10)	H4B—C4—H4C	109.5
N3—Cu2—Cu1	77.47 (10)	Si1—C5—H5A	109.5
N3ⁱ—Cu2—Cu1	119.02 (11)	Si1—C5—H5B	109.5
Cu1ⁱ—Cu2—Cu1	56.46 (3)	H5A—C5—H5B	109.5
C1—N1—Si1	128.6 (3)	Si1—C5—H5C	109.5
C1—N1—Cu1	116.7 (3)	H5A—C5—H5C	109.5
Si1—N1—Cu1	114.3 (2)	H5B—C5—H5C	109.5
C1—N2—C3	122.5 (4)	Si1—C6—H6A	109.5
C1—N2—C2	121.9 (4)	Si1—C6—H6B	109.5
C3—N2—C2	115.6 (4)	H6A—C6—H6B	109.5
C1—N3—Si2	129.0 (3)	Si1—C6—H6C	109.5
C1—N3—Cu2	119.8 (3)	H6A—C6—H6C	109.5
Si2—N3—Cu2	110.53 (19)	H6B—C6—H6C	109.5
Si3—N4—Si3ⁱ	125.9 (3)	Si2—C7—H7A	109.5
Si3—N4—Cu1	104.80 (7)	Si2—C7—H7B	109.5
Si3ⁱ—N4—Cu1	113.64 (8)	H7A—C7—H7B	109.5
Si3—N4—Cu1ⁱ	113.64 (8)	Si2—C7—H7C	109.5
Si3ⁱ—N4—Cu1ⁱ	104.80 (7)	H7A—C7—H7C	109.5
Cu1—N4—Cu1ⁱ	87.5 (2)	H7B—C7—H7C	109.5
N1—Si1—C6	108.5 (2)	Si2—C8—H8A	109.5
N1—Si1—C4	112.3 (3)	Si2—C8—H8B	109.5
C6—Si1—C4	105.6 (3)	H8A—C8—H8B	109.5
N1—Si1—C5	111.4 (3)	Si2—C8—H8C	109.5
C6—Si1—C5	105.7 (3)	H8A—C8—H8C	109.5
C4—Si1—C5	112.8 (3)	H8B—C8—H8C	109.5
N3—Si2—C8	107.3 (2)	Si2—C9—H9A	109.5
N3—Si2—C7	111.7 (2)	Si2—C9—H9B	109.5
C8—Si2—C7	107.8 (3)	H9A—C9—H9B	109.5
N3—Si2—C9	112.6 (2)	Si2—C9—H9C	109.5
C8—Si2—C9	104.8 (2)	H9A—C9—H9C	109.5
C7—Si2—C9	112.3 (2)	H9B—C9—H9C	109.5
N4—Si3—C12	110.3 (2)	Si3—C10—H10A	109.5
N4—Si3—C11	112.2 (2)	Si3—C10—H10B	109.5
C12—Si3—C11	108.1 (3)	H10A—C10—H10B	109.5
N4—Si3—C10	111.1 (2)	Si3—C10—H10C	109.5
C12—Si3—C10	107.1 (3)	H10A—C10—H10C	109.5
C11—Si3—C10	107.7 (3)	H10B—C10—H10C	109.5
N1—C1—N3	122.8 (3)	Si3—C11—H11A	109.5
N1—C1—N2	119.0 (4)	Si3—C11—H11B	109.5
N3—C1—N2	118.2 (4)	H11A—C11—H11B	109.5
N2—C2—H2A	109.5	Si3—C11—H11C	109.5
N2—C2—H2B	109.5	H11A—C11—H11C	109.5
H2A—C2—H2B	109.5	H11B—C11—H11C	109.5
N2—C2—H2C	109.5	Si3—C12—H12A	109.5
H2A—C2—H2C	109.5	Si3—C12—H12B	109.5
H2B—C2—H2C	109.5	H12A—C12—H12B	109.5
N2—C3—H3A	109.5	Si3—C12—H12C	109.5
N2—C3—H3B	109.5	H12A—C12—H12C	109.5
H3A—C3—H3B	109.5	H12B—C12—H12C	109.5

Symmetry code: (i) −x, y, −z+3/2.

Experimental details

Crystal data
Chemical formula	[Cu₃(C₆H₁₈NSi₂)(C₉H₂₄N₃Si₂)₂]
M_r	812.00
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	213
a, b, c (Å)	16.445 (3), 18.653 (4), 14.046 (3)
β (°)	96.943 (3)
V (Å³)	4277.1 (15)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	1.67
Crystal size (mm)	0.30 × 0.20 × 0.20

Data collection
Diffractometer	Siemens SMART CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1997)
T_min, T_max	0.622, 0.717
No. of measured, independent and observed [I > 2σ(I)] reflections	8714, 3773, 3394
R_int	0.033
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.056, 0.118, 1.26
No. of reflections	3773
No. of parameters	193
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.57, −0.46

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997).

Acknowledgements

The authors thank the Natural Science Foundation of China (grant No. 20672070; M. Zhou), the Natural Science Foundation of Shanxi (grant No. 2007011020) and the Foundation for Returned Overseas Chinese Scholars of Shanxi Province (2006; M. Zhou).

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