[Tris(3,5-diphenyl­pyrazol­yl)hydro­borato]nickel(II) bromide

Harding, D.J.; Harding, P.; Adams, H.

doi:10.1107/S1600536809021606

metal-organic compounds

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Volume 65| Part 7| July 2009| Page m773

doi:10.1107/S1600536809021606

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[Tris(3,5-diphenylpyrazolyl)hydroborato]nickel(II) bromide

David J. Harding,^a ^* Phimphaka Harding ^a and Harry Adams ^b

^aMolecular Technology Research Unit, Department of Chemistry, Walailak University, Thasala, Nakhon Si Thammarat 80161, Thailand, and ^bDepartment of Chemistry, Faculty of Science, University of Sheffield, Brook Hill, Sheffield S3 7HF, England
^*Correspondence e-mail: hdavid@wu.ac.th

(Received 14 May 2009; accepted 6 June 2009; online 13 June 2009)

In the title tris(pyrazolyl)borate (Tp^Ph2) complex, [NiBr(C₄₅H₃₄BN₆)], the Ni, Br and B atoms lie on a crystallographic threefold axis and a distorted NiN₃Br tetrahedral geometry arises for the metal ion. In the crystal, C—H⋯(C=C) and C—H⋯π interactions help to establish the polar crystal packing.

Related literature

For other Tp^RNiX (X = Cl, Br) complexes, see: Desrochers et al. (2003 , 2006 ); Kunrath et al. (2003 ); Uehara et al. (2002 ); Guo et al. (1998 ); Harding et al. (2007 ). For ionic radius data, see: Shannon (1976 ).

Experimental

Crystal data

[NiBr(C₄₅H₃₄BN₆)]
M_r = 808.21
Trigonal, R 3
a = 12.8227 (8) Å
c = 19.327 (3) Å
V = 2752.0 (5) Å³
Z = 3
Mo Kα radiation
μ = 1.66 mm⁻¹
T = 150 K
0.24 × 0.24 × 0.21 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1997 ) T_min = 0.691, T_max = 0.722
5609 measured reflections
2075 independent reflections
1943 reflections with I > 2σ(I)
R_int = 0.037

Refinement

R[F² > 2σ(F²)] = 0.028
wR(F²) = 0.063
S = 1.06
2075 reflections
163 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.27 e Å⁻³
Δρ_min = −0.29 e Å⁻³
Absolute structure: Flack (1983 ), 670 Friedel pairs
Flack parameter: 0.020 (8)

Table 1
Selected geometric parameters (Å, °)

Ni1—Br1	2.3523 (6)
Ni1—N1	2.041 (2)

N1—Ni1—N1ⁱ	93.11 (8)
N1—Ni1—Br1	123.04 (6)
Symmetry code: (i) -x+y+1, -x+1, z.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯Cg1ⁱⁱ	0.95	2.73	3.589 (3)	151
Symmetry code: (ii) $[-x+y+{\script{5\over 3}}, -x+{\script{1\over 3}}, z-{\script{2\over 3}}]$ .

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); 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.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809021606/hb2976sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809021606/hb2976Isup2.hkl

checkCIF report

Comment top

Tris(pyrazolyl)borates are versatile and popular ligands in coordination chemistry with many complexes now known. Despite the C₃ symmetry present in many tris(pyrazolyl)borate ligands few tetrahedral complexes crystallize in space groups containing a C₃ axis (Desrochers et al., 2003, 2006; Kunrath et al., 2003; Uehara et al., 2002). Rare examples which do contain a C₃ axis include [Tp^Ph2NiCl] and [Tp^Ph2Ni(OAc)] despite the later being formally five-coordinate (Guo et al., 1998; Harding et al., 2007). In the following paper we report a further example namely, the title compound, [Tp^Ph2NiBr], (I).

The reaction of NiBr₂.2H₂O with KTp^Ph2 readily affords the title complex as a red-purple solid in moderate yield. Crystals were grown by allowing hexanes to diffuse into a concentrated solution of the complex in CH₂Cl₂. The compound crystallizes in the trigonal R3 space group. The structure is shown in Figure 1 while important bond lengths and angles are given in the supporting tables. The geometry around the nickel centre is best described as distorted tetrahedral {N1—Ni—N1ⁱ = 93.11 (8), N1—Ni—Br1 = 123.04 (6)}. The Ni—N bond lengths are very slightly longer by ca. 0.01 Å than those found in [Tp^Ph2NiCl] (Guo et al., 1998). A similar difference is observed in the structures of [Tp*NiCl] and [Tp*NiBr] (Desrochers et al., 2003, 2006). The Ni—Br distance is 2.3523 (6) Å, ca 0.15 Å longer than the corresponding Ni—Cl distance in [Tp^Ph2NiCl], and consistent with the difference in the bromine and chlorine covalent radii (0.15 Å; Shannon, 1976). Interestingly, the Ni—Br bond length in (I) is significantly longer than that observed for [Tp*NiBr] (2.291 (2) Å). A similar increase, albeit not so marked, is also found between [Tp^Ph2NiCl] and [Tp*NiCl] (ΔNi-Cl = 0.03 Å) suggesting that the larger Tp^Ph2 ligand may be responsible for the longer nickel-halide bond distances.

The crystal packing in the structure of (I) contains several C—H···π interactions between the phenyl rings of neighbouring Tp^Ph2 ligands (see Figure 2). The hydrogen atoms H6 and H11 are directed at the π bonds between C1—N1 and C4—C5, respectively {(C1—N1)π···H6 2.657 (3) Å; (C4—C5)π···H11 2.834 (5) Å} while H5 interacts with a phenyl ring (Cg1···H5 2.730 (3) Å; Cg1 is the centroid of ring C10—C15). Similar interactions occur on all three faces of the Tp^Ph2 ligand creating a network of triangular columns such that all the [Tp^Ph2NiBr] molecules point in the same direction and the phenyl rings adopt a propeller configuration.

Related literature top

For other Tp^RNiX (X = Cl, Br) complexes, see: Desrochers et al. (2003); Desrochers et al. (2006); Kunrath et al. (2003); Uehara et al. (2002); Guo et al. (1998); Harding et al. (2007). For ionic radius data, see: Shannon (1976).

Experimental top

NiBr₂.2H₂O (34 mg, 0.14 mmol) was dissolved in THF (5 ml) giving a green solution and then stirred for 5 min. KTp^Ph2 (95 mg, 0.15 mmol) was dissolved in THF (5 ml) giving a pale yellow solution. Addition of the KTp^Ph2 solution to the Ni solution resulted in a colour change to a red-pink solution. The solution was stirred for 16 hrs. The solution was reduced to dryness, redissolved in fresh THF (2 ml) and filtered through celite. The purple-pink solution was layered with hexanes (10 ml). After two days purple-pink blocks of (I) appeared. These were washed with EtOH (3 x 3 ml) and hexanes (2 x 5 ml) (59 mg, 54%). ν_max(KBr)/cm^-1 3059w, 2966w, 2854w (νCH), 2626w (νBH). δ_H (300 MHz; CDCl₃; SiMe₄), 7.63 (br m, m- and p-Ph, 18H), 8.53 (br s, o-Ph, 6H), 8.86 (br s, o-Ph, 6H). UV–Vis λ_max(CH₂Cl₂)/nm 318 (ε/dm³mol^-1cm^-1 3140), 502 (600), 828 (120), 926 (160). m/z (ESI) 727 [M—Br^-]⁺. Anal. Calc. for C₄₅H₃₄N₆BBrNi [Tp^Ph2NiBr]: C, 66.87; H, 4.24; N 10.40 Found: C, 66.62; H, 4.29; N, 10.17%

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT (Bruker, 1997); 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

	Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level. [Symmetry codes:(i) -x + y+1, -x + 1, z; (ii) -y + 1, x-y, z].
	Fig. 2. The molecular packing in (I) showing the three C—H···π interactions. Only selected atoms are labelled or shown for clairty [Symmetry codes:(i) 4/3 - x + y, 2/3 - x, -1/3 + z; (ii) 4/3 - y, -1/3 + x-y, -1/3 + z].

[Tris(3,5-diphenylpyrazolyl)hydroborato]nickel(II) bromide top

Crystal data top

[NiBr(C₄₅H₃₄BN₆)]	D_x = 1.463 Mg m⁻³
M_r = 808.21	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 2851 reflections
Hall symbol: R 3	θ = 2.8–30.6°
a = 12.8227 (8) Å	µ = 1.66 mm⁻¹
c = 19.327 (3) Å	T = 150 K
V = 2752.0 (5) Å³	Block, purple–pink
Z = 3	0.24 × 0.24 × 0.21 mm
F(000) = 1242

Data collection top

Bruker SMART CCD diffractometer	2075 independent reflections
Radiation source: fine-focus sealed tube	1943 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
Detector resolution: 100 pixels mm^-1	θ_max = 27.5°, θ_min = 2.1°
ϕ scans	h = −16→16
Absorption correction: multi-scan (SADABS; Bruker, 1997)	k = −11→16
T_min = 0.691, T_max = 0.722	l = −21→25
5609 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)] = 0.028	H-atom parameters constrained
wR(F²) = 0.063	w = 1/[σ²(F_o²) + (0.0169P)²] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max = 0.001
2075 reflections	Δρ_max = 0.27 e Å⁻³
163 parameters	Δρ_min = −0.29 e Å⁻³
1 restraint	Absolute structure: Flack (1983), 670 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.020 (8)

Crystal data top

[NiBr(C₄₅H₃₄BN₆)]	Z = 3
M_r = 808.21	Mo Kα radiation
Trigonal, R3	µ = 1.66 mm⁻¹
a = 12.8227 (8) Å	T = 150 K
c = 19.327 (3) Å	0.24 × 0.24 × 0.21 mm
V = 2752.0 (5) Å³

Data collection top

Bruker SMART CCD diffractometer	2075 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 1997)	1943 reflections with I > 2σ(I)
T_min = 0.691, T_max = 0.722	R_int = 0.037
5609 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.028	H-atom parameters constrained
wR(F²) = 0.063	Δρ_max = 0.27 e Å⁻³
S = 1.06	Δρ_min = −0.29 e Å⁻³
2075 reflections	Absolute structure: Flack (1983), 670 Friedel pairs
163 parameters	Absolute structure parameter: 0.020 (8)
1 restraint

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
Br1	0.6667	0.3333	0.732391 (16)	0.02249 (14)
Ni1	0.6667	0.3333	0.61068 (2)	0.01335 (14)
N1	0.75319 (18)	0.26622 (19)	0.55312 (10)	0.0127 (4)
N2	0.75175 (19)	0.29001 (19)	0.48407 (10)	0.0128 (4)
B1	0.6667	0.3333	0.4567 (3)	0.0139 (10)
H1B	0.6667	0.3333	0.3983	0.017*
C1	0.8082 (2)	0.2003 (2)	0.55910 (12)	0.0146 (5)
C2	0.8419 (3)	0.1815 (3)	0.49355 (13)	0.0166 (6)
H2	0.8812	0.1373	0.4829	0.020*
C3	0.8064 (2)	0.2405 (2)	0.44716 (12)	0.0136 (5)
C4	0.8224 (3)	0.2532 (3)	0.37198 (14)	0.0135 (5)
C5	0.7922 (2)	0.1509 (2)	0.33065 (13)	0.0173 (6)
H5	0.7601	0.0738	0.3515	0.021*
C6	0.8094 (3)	0.1632 (3)	0.25990 (16)	0.0182 (7)
H6	0.7890	0.0942	0.2325	0.022*
C7	0.8557 (2)	0.2743 (3)	0.22844 (13)	0.0201 (6)
H7	0.8668	0.2814	0.1797	0.024*
C8	0.8860 (3)	0.3759 (3)	0.26839 (13)	0.0215 (6)
H8	0.9179	0.4525	0.2469	0.026*
C9	0.8698 (3)	0.3652 (3)	0.33951 (14)	0.0190 (6)
H9	0.8913	0.4350	0.3665	0.023*
C10	0.8239 (2)	0.1510 (3)	0.62468 (13)	0.0163 (6)
C11	0.8460 (2)	0.2131 (3)	0.68680 (14)	0.0185 (6)
H11	0.8564	0.2919	0.6872	0.022*
C12	0.8530 (3)	0.1605 (3)	0.74866 (17)	0.0230 (7)
H12	0.8650	0.2023	0.7912	0.028*
C13	0.8422 (3)	0.0472 (3)	0.74807 (16)	0.0269 (7)
H13	0.8468	0.0113	0.7901	0.032*
C14	0.8246 (3)	−0.0137 (3)	0.68574 (15)	0.0234 (7)
H14	0.8191	−0.0904	0.6849	0.028*
C15	0.8150 (3)	0.0381 (3)	0.62476 (16)	0.0209 (6)
H15	0.8022	−0.0041	0.5824	0.025*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.02665 (19)	0.02665 (19)	0.0142 (2)	0.01332 (9)	0.000	0.000
Ni1	0.0140 (2)	0.0140 (2)	0.0120 (3)	0.00702 (10)	0.000	0.000
N1	0.0107 (10)	0.0149 (11)	0.0121 (9)	0.0061 (9)	−0.0007 (8)	0.0007 (8)
N2	0.0137 (11)	0.0146 (11)	0.0096 (8)	0.0068 (9)	0.0007 (8)	0.0006 (8)
B1	0.0112 (15)	0.0112 (15)	0.019 (2)	0.0056 (8)	0.000	0.000
C1	0.0121 (13)	0.0105 (13)	0.0199 (12)	0.0047 (11)	−0.0016 (10)	0.0005 (10)
C2	0.0186 (14)	0.0165 (15)	0.0191 (16)	0.0122 (13)	−0.0028 (13)	0.0009 (12)
C3	0.0097 (13)	0.0094 (12)	0.0189 (12)	0.0026 (11)	−0.0001 (9)	0.0010 (9)
C4	0.0106 (13)	0.0148 (14)	0.0169 (12)	0.0077 (11)	0.0010 (10)	−0.0012 (11)
C5	0.0171 (15)	0.0124 (14)	0.0221 (13)	0.0071 (12)	0.0005 (11)	0.0031 (11)
C6	0.0191 (16)	0.0155 (15)	0.0234 (16)	0.0113 (13)	−0.0015 (13)	−0.0039 (13)
C7	0.0180 (15)	0.0237 (15)	0.0153 (12)	0.0080 (13)	0.0044 (11)	0.0003 (11)
C8	0.0210 (15)	0.0179 (15)	0.0210 (12)	0.0062 (12)	0.0060 (11)	0.0053 (11)
C9	0.0199 (16)	0.0172 (15)	0.0193 (13)	0.0087 (13)	0.0016 (11)	−0.0029 (11)
C10	0.0089 (13)	0.0166 (14)	0.0215 (13)	0.0049 (11)	0.0001 (10)	0.0043 (11)
C11	0.0136 (14)	0.0155 (14)	0.0233 (13)	0.0050 (12)	−0.0050 (11)	0.0012 (11)
C12	0.0204 (17)	0.0291 (19)	0.0180 (15)	0.0112 (15)	−0.0034 (13)	0.0002 (14)
C13	0.0206 (16)	0.0304 (17)	0.0268 (14)	0.0105 (14)	−0.0022 (13)	0.0126 (13)
C14	0.0206 (16)	0.0195 (16)	0.0333 (16)	0.0124 (13)	−0.0008 (12)	0.0075 (13)
C15	0.0185 (15)	0.0194 (16)	0.0257 (14)	0.0101 (14)	−0.0019 (12)	−0.0011 (12)

Geometric parameters (Å, º) top

Ni1—Br1	2.3523 (6)	C5—H5	0.9500
Ni1—N1	2.041 (2)	C6—C7	1.380 (4)
Ni1—N1ⁱ	2.041 (2)	C6—H6	0.9500
Ni1—N1ⁱⁱ	2.041 (2)	C7—C8	1.392 (4)
N1—C1	1.350 (3)	C7—H7	0.9500
N1—N2	1.371 (3)	C8—C9	1.387 (4)
N2—C3	1.360 (3)	C8—H8	0.9500
N2—B1	1.544 (3)	C9—H9	0.9500
B1—N2ⁱ	1.544 (3)	C10—C11	1.389 (4)
B1—N2ⁱⁱ	1.544 (3)	C10—C15	1.394 (4)
B1—H1B	1.1278	C11—C12	1.397 (4)
C1—C2	1.398 (4)	C11—H11	0.9500
C1—C10	1.475 (3)	C12—C13	1.390 (5)
C2—C3	1.388 (3)	C12—H12	0.9500
C2—H2	0.9500	C13—C14	1.391 (5)
C3—C4	1.465 (4)	C13—H13	0.9500
C4—C9	1.397 (4)	C14—C15	1.388 (4)
C4—C5	1.415 (4)	C14—H14	0.9500
C5—C6	1.381 (4)	C15—H15	0.9500

N1—Ni1—N1ⁱ	93.11 (8)	C4—C5—H5	120.0
N1—Ni1—N1ⁱⁱ	93.11 (8)	C7—C6—C5	121.0 (3)
N1ⁱ—Ni1—N1ⁱⁱ	93.11 (8)	C7—C6—H6	119.5
N1—Ni1—Br1	123.04 (6)	C5—C6—H6	119.5
N1ⁱ—Ni1—Br1	123.04 (6)	C6—C7—C8	119.7 (2)
N1ⁱⁱ—Ni1—Br1	123.04 (6)	C6—C7—H7	120.1
C1—N1—N2	106.99 (19)	C8—C7—H7	120.1
C1—N1—Ni1	141.45 (17)	C9—C8—C7	119.9 (3)
N2—N1—Ni1	111.47 (15)	C9—C8—H8	120.0
C3—N2—N1	109.82 (19)	C7—C8—H8	120.0
C3—N2—B1	127.6 (2)	C8—C9—C4	120.9 (3)
N1—N2—B1	120.3 (2)	C8—C9—H9	119.5
N2—B1—N2ⁱ	108.89 (19)	C4—C9—H9	119.5
N2—B1—N2ⁱⁱ	108.89 (19)	C11—C10—C15	118.8 (3)
N2ⁱ—B1—N2ⁱⁱ	108.89 (19)	C11—C10—C1	121.9 (3)
N2—B1—H1B	110.0	C15—C10—C1	119.2 (2)
N2ⁱ—B1—H1B	110.0	C10—C11—C12	120.4 (3)
N2ⁱⁱ—B1—H1B	110.0	C10—C11—H11	119.8
N1—C1—C2	109.5 (2)	C12—C11—H11	119.8
N1—C1—C10	124.6 (2)	C13—C12—C11	120.1 (3)
C2—C1—C10	125.8 (2)	C13—C12—H12	120.0
C3—C2—C1	106.1 (2)	C11—C12—H12	120.0
C3—C2—H2	127.0	C14—C13—C12	119.8 (3)
C1—C2—H2	127.0	C14—C13—H13	120.1
N2—C3—C2	107.6 (2)	C12—C13—H13	120.1
N2—C3—C4	122.9 (2)	C15—C14—C13	119.7 (3)
C2—C3—C4	129.5 (2)	C15—C14—H14	120.2
C9—C4—C5	118.4 (2)	C13—C14—H14	120.2
C9—C4—C3	121.7 (3)	C14—C15—C10	121.1 (3)
C5—C4—C3	119.9 (2)	C14—C15—H15	119.4
C6—C5—C4	119.9 (3)	C10—C15—H15	119.4
C6—C5—H5	120.0

Symmetry codes: (i) −x+y+1, −x+1, z; (ii) −y+1, x−y, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···Cg1ⁱⁱⁱ	0.95	2.73	3.589 (3)	151

Symmetry code: (iii) −x+y+5/3, −x+1/3, z−2/3.

Experimental details

Crystal data
Chemical formula	[NiBr(C₄₅H₃₄BN₆)]
M_r	808.21
Crystal system, space group	Trigonal, R3
Temperature (K)	150
a, c (Å)	12.8227 (8), 19.327 (3)
V (Å³)	2752.0 (5)
Z	3
Radiation type	Mo Kα
µ (mm⁻¹)	1.66
Crystal size (mm)	0.24 × 0.24 × 0.21

Data collection
Diffractometer	Bruker SMART CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1997)
T_min, T_max	0.691, 0.722
No. of measured, independent and observed [I > 2σ(I)] reflections	5609, 2075, 1943
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.063, 1.06
No. of reflections	2075
No. of parameters	163
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.29
Absolute structure	Flack (1983), 670 Friedel pairs
Absolute structure parameter	0.020 (8)

Computer programs: SMART (Bruker, 1997), SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

Ni1—Br1	2.3523 (6)	Ni1—N1	2.041 (2)

N1—Ni1—N1ⁱ	93.11 (8)	N1—Ni1—Br1	123.04 (6)

Symmetry code: (i) −x+y+1, −x+1, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···Cg1ⁱⁱ	0.95	2.73	3.589 (3)	151

Symmetry code: (ii) −x+y+5/3, −x+1/3, z−2/3.

Acknowledgements

The authors gratefully acknowledge the Thailand Research Fund (grant No. RMU5080029) and the National Research Council of Thailand (grant No. WU51106) for support of this work.

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