(E)-2-[(2-Amino­phen­yl)imino­meth­yl]-4,6-di-tert-butyl­phenol

Ding, L.; Lü, X.; Zhao, S.; Zhu, Y.

doi:10.1107/S1600536812038615

organic compounds

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ISSN: 2056-9890

Volume 68| Part 10| October 2012| Page o2942

https://doi.org/10.1107/S1600536812038615

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(E)-2-[(2-Aminophenyl)iminomethyl]-4,6-di-tert-butylphenol

Liqin Ding,^a ^* Xingqiang Lü,^b Shunsheng Zhao ^c and Yuqin Zhu ^a

^aSchool of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065, Shaanxi, People's Republic of China, ^bCollege of Chemical Engineering, Northwest University, Xi'an 710069, Shaanxi, People's Republic of China, and ^cCollege of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an 710054, Shaanxi, People's Republic of China
^*Correspondence e-mail: lqding@xsyu.edu.cn

(Received 1 August 2012; accepted 8 September 2012; online 15 September 2012)

In the title compound, C₂₁H₂₈N₂O, the dihedral angle between the rings is 35.2 (2)°. A weak intramolecular O—H⋯N hydrogen bond is observed between the O—H H atom and the imine N atom. In the crystal, molecules are linked by additional intermolecular N—H⋯O hydrogen bonding, resulting in a wave-like chain along the b-axis direction.

Related literature

For related structures, see: Kochem et al. (2010 ); Belmonte et al. (2010 ); Liu et al. (2010 ). Details of the synthesis can be found in Muñoz-Hernández et al. (2000 ).

Experimental

Crystal data

C₂₁H₂₈N₂O
M_r = 324.45
Monoclinic, P 2₁
a = 10.898 (5) Å
b = 6.230 (3) Å
c = 15.095 (8) Å
β = 108.928 (6)°
V = 969.5 (8) Å³
Z = 2
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 296 K
0.38 × 0.26 × 0.20 mm

Data collection

Bruker SMART 1K CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ) T_min = 0.979, T_max = 0.986
3718 measured reflections
1357 independent reflections
1224 reflections with I > 2σ(I)
R_int = 0.025
θ_max = 22.2°

Refinement

R[F² > 2σ(F²)] = 0.044
wR(F²) = 0.129
S = 1.10
1357 reflections
218 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1A⋯N1	0.82	1.87	2.608 (4)	149
N2—H2A⋯O1ⁱ	0.86	2.54	3.342 (4)	155
Symmetry code: (i) $[-x+1, y+{\script{1\over 2}}, -z+2]$ .

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2001); 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 and local programs.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536812038615/nc2289sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812038615/nc2289Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S1600536812038615/nc2289Isup3.cml

checkCIF report

Comment top

The title compound is an important synthetic intermediate for design and synthesis of asymmetric Schiff base complexes showing excellent catalytic activity in various reactions. In the structure of the title compound the dihedral angle between the two phenyl rings amount to 35.2 (2) ° and all bond lengths are comparable to those observed in similar compounds (Kochem et al., 2010; Belmonte et al., 2010; Liu et al., 2010) (Fig. 1). An intramolecular O—H···N hydrogen bond between the O-H H atom and the N atom N1 is observed (Table 1). In the crystal structure the molecules are linked into chains along the b axis by intermolecular N—H···O hydrogen bonding between the amino group and the hydroxy O atom which act as acceptor (Table 1 and Fig. 2).

Related literature top

For related structures, see: Kochem et al. (2010); Belmonte et al. (2010); Liu et al. (2010). Details of the synthesis can be found in Muñoz-Hernández et al. (2000).

Experimental top

The title compound was obtained according to the synthetic procedure of Muñoz-Hernández et al. (2000). 1,2-diaminobenzene (1.0 g, 9.2 mmol) was added to a solution of 3,5-Di-tert-butyl-2- hydroxybenzaldehyde (1.1 g, 4.6 mmol) in absolute ethanol (40 ml) and heated to reflux for 4 h, then concentrated to 20 ml by distillation. An orange solid precipitated from the reaction mixture and collected by filtration and dried open air. The orange solid was recrystalized from ethanol to give an orange crystal, which was collected by filtration and dried under vacuum, yield 71.0%. The single-crystal of the title compound suitble for X-ray diffraction was obtained by slow evaporation of an ethanol solution of the title compound.

Structure description top

For related structures, see: Kochem et al. (2010); Belmonte et al. (2010); Liu et al. (2010). Details of the synthesis can be found in Muñoz-Hernández et al. (2000).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); 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) and local programs.

Figures top

	Fig. 1. The molecular structure of the title compound with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. Crystal structure of the title compound with view along the b axis. Intermolecular hydrogen bonding is shown as dashed lines.

(E)-2-[(2-Aminophenyl)iminomethyl]-4,6-di-tert-butylphenol top

Crystal data top

C₂₁H₂₈N₂O	F(000) = 352
M_r = 324.45	D_x = 1.111 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 2451 reflections
a = 10.898 (5) Å	θ = 1.9–26.6°
b = 6.230 (3) Å	µ = 0.07 mm⁻¹
c = 15.095 (8) Å	T = 296 K
β = 108.928 (6)°	Stick, orange
V = 969.5 (8) Å³	0.38 × 0.26 × 0.20 mm
Z = 2

Data collection top

Bruker SMART 1K CCD area-detector diffractometer	1357 independent reflections
Radiation source: fine-focus sealed tube	1224 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
thin–slice ω scans	θ_max = 22.2°, θ_min = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	h = −11→11
T_min = 0.979, T_max = 0.986	k = −6→6
3718 measured reflections	l = −10→16

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)] = 0.044	H-atom parameters constrained
wR(F²) = 0.129	w = 1/[σ²(F_o²) + (0.0864P)² + 0.0703P] where P = (F_o² + 2F_c²)/3
S = 1.10	(Δ/σ)_max < 0.001
1357 reflections	Δρ_max = 0.22 e Å⁻³
218 parameters	Δρ_min = −0.15 e Å⁻³
1 restraint	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.018 (7)

Crystal data top

C₂₁H₂₈N₂O	V = 969.5 (8) Å³
M_r = 324.45	Z = 2
Monoclinic, P2₁	Mo Kα radiation
a = 10.898 (5) Å	µ = 0.07 mm⁻¹
b = 6.230 (3) Å	T = 296 K
c = 15.095 (8) Å	0.38 × 0.26 × 0.20 mm
β = 108.928 (6)°

Data collection top

Bruker SMART 1K CCD area-detector diffractometer	1357 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	1224 reflections with I > 2σ(I)
T_min = 0.979, T_max = 0.986	R_int = 0.025
3718 measured reflections	θ_max = 22.2°

Refinement top

R[F² > 2σ(F²)] = 0.044	1 restraint
wR(F²) = 0.129	H-atom parameters constrained
S = 1.10	Δρ_max = 0.22 e Å⁻³
1357 reflections	Δρ_min = −0.15 e Å⁻³
218 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
O1	0.5353 (2)	0.2087 (4)	0.80055 (16)	0.0705 (8)
H1A	0.5635	0.3048	0.8389	0.106*
N1	0.6999 (3)	0.4874 (5)	0.9023 (2)	0.0643 (8)
C7	0.6019 (3)	−0.0180 (6)	0.6967 (2)	0.0588 (9)
C6	0.7034 (3)	−0.0771 (7)	0.6648 (2)	0.0603 (9)
H6A	0.6874	−0.1838	0.6193	0.072*
C13	0.7507 (3)	0.2450 (6)	0.7952 (2)	0.0576 (9)
C12	0.6285 (3)	0.1469 (6)	0.7643 (2)	0.0587 (9)
C5	0.8277 (3)	0.0122 (7)	0.6961 (2)	0.0587 (9)
C14	0.8484 (3)	0.1742 (7)	0.7605 (2)	0.0629 (10)
H14A	0.9295	0.2392	0.7818	0.075*
C3	0.9334 (3)	−0.0683 (7)	0.6571 (3)	0.0670 (10)
C15	0.7804 (3)	0.4156 (6)	0.8635 (2)	0.0646 (10)
H15A	0.8626	0.4771	0.8803	0.078*
C8	0.4673 (3)	−0.1218 (7)	0.6579 (2)	0.0669 (11)
C4	1.0650 (4)	0.0253 (13)	0.7108 (4)	0.126 (2)
H4A	1.0608	0.1791	0.7071	0.189*
H4B	1.1284	−0.0257	0.6841	0.189*
H4C	1.0892	−0.0183	0.7752	0.189*
C16	0.7344 (3)	0.6617 (6)	0.9657 (2)	0.0634 (10)
C21	0.6777 (4)	0.6701 (8)	1.0365 (2)	0.0738 (11)
C17	0.8160 (4)	0.8258 (7)	0.9580 (3)	0.0790 (12)
H17A	0.8523	0.8223	0.9102	0.095*
N2	0.5933 (4)	0.5117 (8)	1.0433 (3)	0.1113 (15)
H2A	0.5580	0.5178	1.0866	0.134*
H2B	0.5758	0.4066	1.0043	0.134*
C20	0.7066 (4)	0.8395 (9)	1.0986 (3)	0.0887 (14)
H20A	0.6707	0.8450	1.1466	0.106*
C18	0.8438 (4)	0.9946 (8)	1.0206 (3)	0.0912 (13)
H18A	0.8998	1.1033	1.0157	0.109*
C2	0.9446 (5)	−0.3129 (9)	0.6651 (4)	0.1065 (16)
H2C	0.8623	−0.3766	0.6316	0.160*
H2D	0.9695	−0.3538	0.7298	0.160*
H2E	1.0088	−0.3617	0.6388	0.160*
C9	0.4638 (4)	−0.2935 (10)	0.5856 (4)	0.1117 (19)
H9A	0.5266	−0.4026	0.6137	0.168*
H9B	0.4838	−0.2300	0.5340	0.168*
H9C	0.3789	−0.3564	0.5636	0.168*
C19	0.7882 (4)	1.0003 (10)	1.0899 (3)	0.0961 (15)
H19A	0.8059	1.1147	1.1317	0.115*
C11	0.3664 (3)	0.0476 (9)	0.6095 (3)	0.0846 (14)
H11A	0.3904	0.1140	0.5601	0.127*
H11B	0.3624	0.1547	0.6543	0.127*
H11C	0.2831	−0.0193	0.5838	0.127*
C1	0.8970 (4)	−0.0129 (12)	0.5548 (3)	0.116 (2)
H1C	0.8888	0.1400	0.5473	0.174*
H1D	0.8158	−0.0796	0.5213	0.174*
H1E	0.9631	−0.0636	0.5307	0.174*
C10	0.4275 (4)	−0.2250 (8)	0.7362 (3)	0.0870 (13)
H10A	0.4906	−0.3310	0.7675	0.130*
H10B	0.3443	−0.2921	0.7101	0.130*
H10C	0.4227	−0.1167	0.7802	0.130*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0581 (13)	0.0762 (17)	0.0891 (16)	−0.0028 (14)	0.0405 (13)	−0.0106 (15)
N1	0.0622 (17)	0.067 (2)	0.0671 (17)	0.0028 (16)	0.0262 (14)	−0.0019 (17)
C7	0.0492 (17)	0.062 (2)	0.0684 (19)	0.0013 (17)	0.0239 (15)	0.0010 (19)
C6	0.0470 (18)	0.068 (2)	0.070 (2)	−0.0007 (17)	0.0236 (15)	−0.010 (2)
C13	0.0491 (18)	0.062 (2)	0.0648 (19)	−0.0041 (16)	0.0224 (15)	0.0008 (18)
C12	0.0481 (18)	0.068 (2)	0.0668 (19)	0.0069 (17)	0.0280 (15)	0.004 (2)
C5	0.0445 (17)	0.065 (2)	0.069 (2)	0.0028 (18)	0.0222 (15)	0.003 (2)
C14	0.0468 (17)	0.071 (2)	0.074 (2)	−0.0040 (18)	0.0243 (16)	0.001 (2)
C3	0.050 (2)	0.075 (3)	0.081 (2)	0.0068 (19)	0.0296 (17)	0.001 (2)
C15	0.0577 (19)	0.068 (2)	0.069 (2)	−0.0031 (19)	0.0217 (17)	−0.001 (2)
C8	0.0463 (18)	0.081 (3)	0.076 (2)	−0.0073 (19)	0.0246 (16)	−0.008 (2)
C4	0.051 (2)	0.154 (5)	0.174 (5)	−0.001 (3)	0.039 (3)	−0.047 (5)
C16	0.0574 (19)	0.064 (2)	0.065 (2)	0.005 (2)	0.0137 (16)	−0.001 (2)
C21	0.065 (2)	0.088 (3)	0.065 (2)	0.009 (2)	0.0157 (18)	−0.005 (2)
C17	0.076 (2)	0.075 (3)	0.081 (3)	0.001 (2)	0.018 (2)	0.000 (2)
N2	0.110 (3)	0.137 (4)	0.110 (3)	−0.035 (3)	0.068 (2)	−0.031 (3)
C20	0.075 (3)	0.104 (4)	0.084 (3)	0.010 (3)	0.020 (2)	−0.018 (3)
C18	0.078 (2)	0.074 (3)	0.103 (3)	0.001 (2)	0.004 (2)	−0.002 (3)
C2	0.090 (3)	0.089 (3)	0.151 (4)	0.014 (3)	0.052 (3)	−0.001 (4)
C9	0.068 (2)	0.133 (5)	0.139 (4)	−0.033 (3)	0.039 (3)	−0.061 (4)
C19	0.088 (3)	0.098 (4)	0.083 (3)	0.017 (3)	0.001 (2)	−0.025 (3)
C11	0.0501 (19)	0.115 (4)	0.087 (3)	−0.003 (2)	0.0198 (18)	0.015 (3)
C1	0.096 (3)	0.162 (6)	0.111 (3)	0.032 (4)	0.063 (3)	0.026 (4)
C10	0.069 (2)	0.091 (3)	0.101 (3)	−0.014 (2)	0.027 (2)	0.013 (3)

Geometric parameters (Å, º) top

O1—C12	1.357 (4)	C21—N2	1.376 (6)
O1—H1A	0.8200	C21—C20	1.378 (6)
N1—C15	1.284 (4)	C17—C18	1.379 (6)
N1—C16	1.416 (5)	C17—H17A	0.9300
C7—C6	1.393 (4)	N2—H2A	0.8600
C7—C12	1.410 (5)	N2—H2B	0.8600
C7—C8	1.534 (5)	C20—C19	1.373 (7)
C6—C5	1.397 (4)	C20—H20A	0.9300
C6—H6A	0.9300	C18—C19	1.370 (6)
C13—C12	1.400 (5)	C18—H18A	0.9300
C13—C14	1.401 (5)	C2—H2C	0.9600
C13—C15	1.442 (5)	C2—H2D	0.9600
C5—C14	1.368 (5)	C2—H2E	0.9600
C5—C3	1.537 (5)	C9—H9A	0.9600
C14—H14A	0.9300	C9—H9B	0.9600
C3—C1	1.504 (6)	C9—H9C	0.9600
C3—C4	1.517 (6)	C19—H19A	0.9300
C3—C2	1.530 (7)	C11—H11A	0.9600
C15—H15A	0.9300	C11—H11B	0.9600
C8—C9	1.520 (6)	C11—H11C	0.9600
C8—C11	1.528 (6)	C1—H1C	0.9600
C8—C10	1.526 (6)	C1—H1D	0.9600
C4—H4A	0.9600	C1—H1E	0.9600
C4—H4B	0.9600	C10—H10A	0.9600
C4—H4C	0.9600	C10—H10B	0.9600
C16—C17	1.384 (6)	C10—H10C	0.9600
C16—C21	1.399 (5)

C12—O1—H1A	109.5	C20—C21—C16	119.2 (4)
C15—N1—C16	120.3 (3)	C18—C17—C16	120.7 (4)
C6—C7—C12	116.3 (3)	C18—C17—H17A	119.6
C6—C7—C8	121.6 (3)	C16—C17—H17A	119.6
C12—C7—C8	122.0 (3)	C21—N2—H2A	120.0
C7—C6—C5	124.7 (3)	C21—N2—H2B	120.0
C7—C6—H6A	117.6	H2A—N2—H2B	120.0
C5—C6—H6A	117.6	C19—C20—C21	120.4 (4)
C12—C13—C14	119.6 (3)	C19—C20—H20A	119.8
C12—C13—C15	121.9 (3)	C21—C20—H20A	119.8
C14—C13—C15	118.5 (3)	C19—C18—C17	119.3 (5)
O1—C12—C13	119.8 (3)	C19—C18—H18A	120.4
O1—C12—C7	119.5 (3)	C17—C18—H18A	120.4
C13—C12—C7	120.6 (3)	C3—C2—H2C	109.5
C14—C5—C6	116.9 (3)	C3—C2—H2D	109.5
C14—C5—C3	122.8 (3)	H2C—C2—H2D	109.5
C6—C5—C3	120.3 (3)	C3—C2—H2E	109.5
C5—C14—C13	121.9 (3)	H2C—C2—H2E	109.5
C5—C14—H14A	119.1	H2D—C2—H2E	109.5
C13—C14—H14A	119.1	C8—C9—H9A	109.5
C1—C3—C4	110.4 (4)	C8—C9—H9B	109.5
C1—C3—C2	107.3 (5)	H9A—C9—H9B	109.5
C4—C3—C2	107.6 (4)	C8—C9—H9C	109.5
C1—C3—C5	109.7 (3)	H9A—C9—H9C	109.5
C4—C3—C5	111.5 (3)	H9B—C9—H9C	109.5
C2—C3—C5	110.2 (4)	C18—C19—C20	121.0 (5)
N1—C15—C13	123.7 (3)	C18—C19—H19A	119.5
N1—C15—H15A	118.2	C20—C19—H19A	119.5
C13—C15—H15A	118.2	C8—C11—H11A	109.5
C9—C8—C11	107.2 (3)	C8—C11—H11B	109.5
C9—C8—C10	108.2 (4)	H11A—C11—H11B	109.5
C11—C8—C10	108.6 (3)	C8—C11—H11C	109.5
C9—C8—C7	111.7 (3)	H11A—C11—H11C	109.5
C11—C8—C7	110.0 (4)	H11B—C11—H11C	109.5
C10—C8—C7	111.0 (3)	C3—C1—H1C	109.5
C3—C4—H4A	109.5	C3—C1—H1D	109.5
C3—C4—H4B	109.5	H1C—C1—H1D	109.5
H4A—C4—H4B	109.5	C3—C1—H1E	109.5
C3—C4—H4C	109.5	H1C—C1—H1E	109.5
H4A—C4—H4C	109.5	H1D—C1—H1E	109.5
H4B—C4—H4C	109.5	C8—C10—H10A	109.5
C17—C16—C21	119.4 (4)	C8—C10—H10B	109.5
C17—C16—N1	123.2 (3)	H10A—C10—H10B	109.5
C21—C16—N1	117.3 (4)	C8—C10—H10C	109.5
N2—C21—C20	120.6 (4)	H10A—C10—H10C	109.5
N2—C21—C16	120.2 (4)	H10B—C10—H10C	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···N1	0.82	1.87	2.608 (4)	149
N2—H2A···O1ⁱ	0.86	2.54	3.342 (4)	155

Symmetry code: (i) −x+1, y+1/2, −z+2.

Experimental details

Crystal data
Chemical formula	C₂₁H₂₈N₂O
M_r	324.45
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	296
a, b, c (Å)	10.898 (5), 6.230 (3), 15.095 (8)
β (°)	108.928 (6)
V (Å³)	969.5 (8)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.07
Crystal size (mm)	0.38 × 0.26 × 0.20

Data collection
Diffractometer	Bruker SMART 1K CCD area-detector
Absorption correction	Multi-scan (SADABS; Sheldrick, 2004)
T_min, T_max	0.979, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections	3718, 1357, 1224
R_int	0.025
θ_max (°)	22.2
(sin θ/λ)_max (Å⁻¹)	0.531

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.129, 1.10
No. of reflections	1357
No. of parameters	218
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.15

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and local programs.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···N1	0.82	1.87	2.608 (4)	149.4
N2—H2A···O1ⁱ	0.86	2.54	3.342 (4)	154.7

Symmetry code: (i) −x+1, y+1/2, −z+2.

Acknowledgements

This project was Supported Scientific Research Program Funded by Shaanxi Provincial Education Department (program Nos. 11 J K0605, 11 J K0588, 11 J K0606) and the Natural Science Basic Research Plan in Shaanxi Province of China (program Nos. 2012JM2011, 2011JQ2011).

References

Belmonte, M. M., Wezenberg, S. J., Haak, R. M., Anselmo, D., Escudero-Adán, E. C., Benet-Buchholza, J. & Kleij, A. W. (2010). Dalton Trans. 39, 4541–4550. Web of Science CSD CrossRef CAS PubMed Google Scholar
Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Kochem, A., Orio, M., Jarjayes, O., Neeseb, F. & Thomas, F. (2010). Chem. Commun. 46, 6765–6767. Web of Science CrossRef CAS Google Scholar
Liu, P., Feng, X. J. & He, R. (2010). Tetrahedron, 66, 631–636. Web of Science CSD CrossRef CAS Google Scholar
Muñoz-Hernández, M. A., Keizer, T. S., Parkin, S., Patrick, B. & Patrick, D. A. (2000). Organometallics, 19, 4416–4421. Google Scholar
Sheldrick, G. M. (2004). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar