2,8-Dimethyl-10-p-tolyl-10H-phenoxaphosphine

Marimuthu, T.; Bala, M.D.; Friedrich, H.B.

doi:10.1107/S1600536809009817

organic compounds

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ISSN: 2056-9890

Volume 65| Part 4| April 2009| Page o828

doi:10.1107/S1600536809009817

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2,8-Dimethyl-10-p-tolyl-10H-phenoxaphosphine

Thashree Marimuthu,^a Muhammad D. Bala ^a ^* and Holger B. Friedrich ^a

^aSchool of Chemistry, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa
^*Correspondence e-mail: bala@ukzn.ac.za

(Received 5 March 2009; accepted 17 March 2009; online 25 March 2009)

The title compound (systematic name: 3,6-dimethyl-10-p-tolyl-9-oxa-10-phosphaanthracene), C₂₁H₁₉OP, is a precursor for the preparation of a bidentate xanthene-based ligand, in which the dihedral angle between the toluene ring and the phenoxaphosphine ring system is 83.26 (3)°. The geometry at the P atom is pyramidal, resulting in a longer C—P bond length as compared to the two ring C—P bonds.

Related literature

For related structures based on the xanthene backbone, see: Marimuthu et al. (2008a ,b ,c ). For a related phenoxaphosphine compound, see: Mann et al. (1976 ). The title compound was synthesised by a modified literature method (Bronger et al., 2004 ). For other structurally related ligands, see: Levy et al. (1965 ); Seibold et al. (2008 ); Shau et al. (2002 ).

Experimental

Crystal data

C₂₁H₁₉OP
M_r = 318.33
Monoclinic, P 2₁ /c
a = 10.9363 (3) Å
b = 11.6323 (3) Å
c = 14.0458 (4) Å
β = 111.532 (1)°
V = 1662.13 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.17 mm⁻¹
T = 173 K
0.51 × 0.49 × 0.48 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: none
29900 measured reflections
4013 independent reflections
3507 reflections with I > 2σ(I)
R_int = 0.046

Refinement

R[F² > 2σ(F²)] = 0.037
wR(F²) = 0.108
S = 1.07
4013 reflections
211 parameters
H-atom parameters constrained
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809009817/rz2300sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809009817/rz2300Isup2.hkl

checkCIF report

Comment top

The title compound was prepared as part of an ongoing study of bidentate and tridentate xanthene-based ligands (Marimuthu et al. (2008a,b,c). Similar ligands have shown relative success for the Rh-catalysed hydroformylation of alkenes. The title compound is an example of a modified xanthene backbone where a phosphorous atom has been substituted into the central ring in order to investigate the electronic properties of the final target ligand when complexed to a metal centre. In addition, methyl groups are present on the outer rings in order to increase the solubility of a resulting catalyst. The outer rings of the phenoxaphosphine backbone are nearly coplanar (dihedral angle of 6.56 (2)°). This value is significantly different from the dihedral angle of 15° reported by Mann et al.(1976) for 10-phenylphenoxaphosphine, which was observed to have a boat-like conformation about the P—O axis. The C15—P1 bond length for the tolyl group is 1.835 (13) Å, which is longer than the C—P bond lengths of the backbone heterocycle (1.805 (13) and 1.809 (13) Å for C1—P1 and C12—P1, respectively). The longer C15—P1 bond length is due to the pyramidal geometry at the P atom. Hence, the C—P—C angles range from 98.0087 (6) to 101.04 (6)°. The ring of the toluene group is nearly perpendicular to the mean plane through the phenoxaphosphine backbone, forming a dihedral angle of 83.26 (3)°

Related literature top

For related structures based on the xanthene backbone, see: Marimuthu et al. (2008a,b,c). For a related phenoxaphosphine compound, see: Mann et al. (1976). For a related experimental procedure, see: Bronger et al. (2004). For other structurally related ligands, see: Levy et al. (1965); Seibold et al. (2008); Shau et al. (2002).

Experimental top

The synthesis of the title compound was modified from literature (Bronger et al. 2004). In an inert nitrogen atmosphere AlCl₃ (2.5 g, 18.9 mmol) was added to p-tolylether (2.5 g, 12.6 mmol) in 9 ml phosphorous trichloride (PCl₃). The reaction mixture was refluxed for 8 h at 358 K and thereafter the excess PCl₃ was distilled off at 363 K. At this temperature, excess anhydrous toluene was added to the reaction mixture. The remaining PCl₃ and toluene was distilled off at 383 K to afford an orange-red residue. The residue was again diluted with 15 ml of toluene and cooled to 273 K, followed by the dropwise addition of 3.6 ml pyridine to the mixture while stirring. After an hour, the resulting salts were filtered off and the yellow residue extracted with toluene. The solvent was removed in vacuo, and the crude product purified by filtration through a short plug of silica gel to yield 2.45 g of the title compound as an oil that solidified at room temperature. X-ray quality crystals were grown from a 2-propanol/dichloromethane (1:1 v/v) solution (Yield: 61%; m.p. 337 – 338 K). Spectroscopic analysis: ¹H NMR: (400 MHz, C₆D₆, δ, p.p.m): 1.98 (s, 6H), 1.90 (s, 3H), 6.78 (d, 2H; J(H,H) = 7.2 Hz,), 6.85 (dd, 2H; CH; J(H,H) = 2.7, 1.7 Hz,), 7.09 (d, 2H; J(H,H) = 8.3 Hz,), 7.30 (dd, 2H; J(H,H) = 1.9, 1.6 Hz,), 7.39 (t, 2H, J(H,H)= 7.9 Hz). MS: m/z (%): 357.1 (M + K⁺) calculated = 357.1 for C₂₁H₁₉OPK⁺. FTIR: cm^-1 = 3009(w), (CH), 2920(s), 1585(w), 1489(m), 1466(vs), 1385(s), 1295(s), 1265(vs), 1231(vs), 909(m).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus (Bruker, 2005); program(s) used to solve structure: SHELXTL (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 the title compound. Thermal ellipsoids are shown at the 50% probability level.

3,6-dimethyl-10-p-tolyl-9-oxa-10-phosphaanthracene top

Crystal data top

C₂₁H₁₉OP	F(000) = 672
M_r = 318.33	D_x = 1.272 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8225 reflections
a = 10.9363 (3) Å	θ = 2.3–28.4°
b = 11.6323 (3) Å	µ = 0.17 mm⁻¹
c = 14.0458 (4) Å	T = 173 K
β = 111.532 (1)°	Needle, colourless
V = 1662.13 (8) Å³	0.51 × 0.49 × 0.48 mm
Z = 4

Data collection top

Bruker APEXII CCD area-detector diffractometer	3507 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.046
Graphite monochromator	θ_max = 28.0°, θ_min = 2.0°
ϕ and ω scans	h = −14→14
29900 measured reflections	k = −15→15
4013 independent reflections	l = −18→18

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.108	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.0534P)² + 0.586P] where P = (F_o² + 2F_c²)/3
4013 reflections	(Δ/σ)_max = 0.040
211 parameters	Δρ_max = 0.37 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₂₁H₁₉OP	V = 1662.13 (8) Å³
M_r = 318.33	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 10.9363 (3) Å	µ = 0.17 mm⁻¹
b = 11.6323 (3) Å	T = 173 K
c = 14.0458 (4) Å	0.51 × 0.49 × 0.48 mm
β = 111.532 (1)°

Data collection top

Bruker APEXII CCD area-detector diffractometer	3507 reflections with I > 2σ(I)
29900 measured reflections	R_int = 0.046
4013 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.037	0 restraints
wR(F²) = 0.108	H-atom parameters constrained
S = 1.07	Δρ_max = 0.37 e Å⁻³
4013 reflections	Δρ_min = −0.27 e Å⁻³
211 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
C1	0.59638 (12)	1.06591 (11)	0.15703 (10)	0.0274 (3)
C2	0.53669 (13)	1.05047 (12)	0.22849 (10)	0.0303 (3)
H2	0.5484	0.9791	0.2636	0.036*
C3	0.46153 (13)	1.13388 (12)	0.25049 (10)	0.0313 (3)
C4	0.44183 (14)	1.23579 (12)	0.19518 (11)	0.0361 (3)
H4	0.3880	1.2940	0.2069	0.043*
C5	0.49875 (14)	1.25429 (12)	0.12363 (11)	0.0357 (3)
H5	0.4843	1.3247	0.0868	0.043*
C6	0.57734 (13)	1.16977 (11)	0.10547 (10)	0.0289 (3)
C7	0.69900 (12)	1.12246 (11)	−0.00204 (10)	0.0284 (3)
C8	0.73269 (14)	1.16321 (12)	−0.08200 (10)	0.0340 (3)
H8	0.7092	1.2391	−0.1071	0.041*
C9	0.80050 (14)	1.09313 (13)	−0.12506 (10)	0.0347 (3)
H9	0.8246	1.1222	−0.1789	0.042*
C10	0.83423 (13)	0.98126 (12)	−0.09135 (10)	0.0310 (3)
C11	0.79734 (12)	0.94259 (11)	−0.01249 (10)	0.0294 (3)
H11	0.8177	0.8657	0.0106	0.035*
C12	0.73184 (12)	1.01137 (11)	0.03436 (9)	0.0264 (2)
C13	0.40629 (15)	1.11516 (14)	0.33266 (11)	0.0399 (3)
H13A	0.3553	1.0437	0.3190	0.060*
H13B	0.3491	1.1798	0.3333	0.060*
H13C	0.4784	1.1098	0.3993	0.060*
C14	0.90781 (15)	0.90328 (14)	−0.13659 (11)	0.0387 (3)
H14A	0.9981	0.8935	−0.0878	0.058*
H14B	0.9093	0.9371	−0.2001	0.058*
H14C	0.8641	0.8283	−0.1515	0.058*
C15	0.85437 (13)	0.98293 (12)	0.24735 (9)	0.0286 (3)
C16	0.94457 (15)	0.89406 (13)	0.28148 (11)	0.0377 (3)
H16	0.9249	0.8209	0.2493	0.045*
C17	1.06328 (16)	0.91088 (17)	0.36216 (12)	0.0474 (4)
H17	1.1246	0.8494	0.3837	0.057*
C18	1.09347 (15)	1.01549 (17)	0.41141 (11)	0.0463 (4)
C19	1.00354 (15)	1.10404 (16)	0.37752 (11)	0.0440 (4)
H19	1.0230	1.1767	0.4106	0.053*
C20	0.88574 (14)	1.08866 (13)	0.29636 (11)	0.0358 (3)
H20	0.8258	1.1509	0.2739	0.043*
C21	1.22049 (18)	1.0331 (2)	0.50093 (13)	0.0681 (6)
H21A	1.2587	1.1074	0.4940	0.102*
H21B	1.2821	0.9713	0.5024	0.102*
H21C	1.2033	1.0322	0.5647	0.102*
O1	0.63326 (10)	1.20048 (8)	0.03575 (8)	0.0356 (2)
P1	0.69921 (3)	0.95166 (3)	0.14160 (2)	0.02660 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0250 (6)	0.0274 (6)	0.0299 (6)	−0.0007 (5)	0.0102 (5)	−0.0010 (5)
C2	0.0298 (6)	0.0307 (6)	0.0311 (6)	−0.0013 (5)	0.0122 (5)	0.0003 (5)
C3	0.0279 (6)	0.0352 (7)	0.0316 (6)	−0.0036 (5)	0.0119 (5)	−0.0059 (5)
C4	0.0349 (7)	0.0322 (7)	0.0445 (8)	0.0023 (5)	0.0185 (6)	−0.0054 (6)
C5	0.0383 (7)	0.0273 (6)	0.0439 (8)	0.0038 (5)	0.0179 (6)	0.0021 (6)
C6	0.0287 (6)	0.0280 (6)	0.0313 (6)	−0.0008 (5)	0.0125 (5)	0.0000 (5)
C7	0.0277 (6)	0.0290 (6)	0.0288 (6)	−0.0008 (5)	0.0105 (5)	0.0001 (5)
C8	0.0373 (7)	0.0331 (7)	0.0332 (7)	−0.0006 (5)	0.0147 (6)	0.0059 (5)
C9	0.0370 (7)	0.0418 (8)	0.0279 (6)	−0.0051 (6)	0.0150 (5)	0.0011 (5)
C10	0.0295 (6)	0.0372 (7)	0.0267 (6)	−0.0050 (5)	0.0110 (5)	−0.0063 (5)
C11	0.0308 (6)	0.0289 (6)	0.0279 (6)	−0.0016 (5)	0.0100 (5)	−0.0026 (5)
C12	0.0263 (6)	0.0285 (6)	0.0239 (5)	−0.0034 (5)	0.0084 (5)	−0.0013 (5)
C13	0.0402 (8)	0.0469 (9)	0.0385 (7)	0.0005 (6)	0.0214 (6)	−0.0047 (6)
C14	0.0404 (8)	0.0456 (8)	0.0346 (7)	−0.0017 (6)	0.0190 (6)	−0.0073 (6)
C15	0.0304 (6)	0.0337 (6)	0.0250 (6)	0.0017 (5)	0.0140 (5)	0.0048 (5)
C16	0.0413 (8)	0.0374 (7)	0.0366 (7)	0.0062 (6)	0.0168 (6)	0.0111 (6)
C17	0.0379 (8)	0.0626 (10)	0.0412 (8)	0.0109 (7)	0.0140 (7)	0.0220 (8)
C18	0.0342 (7)	0.0774 (12)	0.0272 (7)	−0.0079 (8)	0.0111 (6)	0.0112 (7)
C19	0.0416 (8)	0.0588 (10)	0.0334 (7)	−0.0115 (7)	0.0159 (6)	−0.0083 (7)
C20	0.0350 (7)	0.0398 (7)	0.0338 (7)	−0.0013 (6)	0.0141 (6)	−0.0030 (6)
C21	0.0400 (9)	0.1219 (19)	0.0356 (8)	−0.0161 (10)	0.0060 (7)	0.0136 (10)
O1	0.0444 (6)	0.0277 (5)	0.0431 (5)	0.0054 (4)	0.0261 (5)	0.0070 (4)
P1	0.02996 (18)	0.02340 (17)	0.02918 (18)	0.00000 (12)	0.01410 (14)	0.00138 (12)

Geometric parameters (Å, º) top

C1—C6	1.3845 (18)	C12—P1	1.8092 (13)
C1—C2	1.3953 (18)	C13—H13A	0.9800
C1—P1	1.8046 (13)	C13—H13B	0.9800
C2—C3	1.3780 (18)	C13—H13C	0.9800
C2—H2	0.9500	C14—H14A	0.9800
C3—C4	1.390 (2)	C14—H14B	0.9800
C3—C13	1.5021 (19)	C14—H14C	0.9800
C4—C5	1.379 (2)	C15—C16	1.3873 (19)
C4—H4	0.9500	C15—C20	1.390 (2)
C5—C6	1.3896 (19)	C15—P1	1.8352 (13)
C5—H5	0.9500	C16—C17	1.389 (2)
C6—O1	1.3784 (15)	C16—H16	0.9500
C7—O1	1.3794 (16)	C17—C18	1.379 (3)
C7—C8	1.3876 (18)	C17—H17	0.9500
C7—C12	1.3876 (18)	C18—C19	1.382 (3)
C8—C9	1.382 (2)	C18—C21	1.507 (2)
C8—H8	0.9500	C19—C20	1.383 (2)
C9—C10	1.388 (2)	C19—H19	0.9500
C9—H9	0.9500	C20—H20	0.9500
C10—C11	1.3858 (18)	C21—H21A	0.9800
C10—C14	1.4999 (19)	C21—H21B	0.9800
C11—C12	1.3901 (18)	C21—H21C	0.9800
C11—H11	0.9500

C6—C1—C2	117.93 (12)	H13A—C13—H13B	109.5
C6—C1—P1	124.10 (10)	C3—C13—H13C	109.5
C2—C1—P1	117.92 (10)	H13A—C13—H13C	109.5
C3—C2—C1	123.08 (12)	H13B—C13—H13C	109.5
C3—C2—H2	118.5	C10—C14—H14A	109.5
C1—C2—H2	118.5	C10—C14—H14B	109.5
C2—C3—C4	117.25 (12)	H14A—C14—H14B	109.5
C2—C3—C13	120.76 (13)	C10—C14—H14C	109.5
C4—C3—C13	121.98 (13)	H14A—C14—H14C	109.5
C5—C4—C3	121.42 (13)	H14B—C14—H14C	109.5
C5—C4—H4	119.3	C16—C15—C20	118.26 (13)
C3—C4—H4	119.3	C16—C15—P1	117.45 (11)
C4—C5—C6	119.89 (13)	C20—C15—P1	124.28 (11)
C4—C5—H5	120.1	C15—C16—C17	120.68 (15)
C6—C5—H5	120.1	C15—C16—H16	119.7
O1—C6—C1	125.24 (12)	C17—C16—H16	119.7
O1—C6—C5	114.37 (12)	C18—C17—C16	120.93 (15)
C1—C6—C5	120.38 (12)	C18—C17—H17	119.5
O1—C7—C8	114.67 (12)	C16—C17—H17	119.5
O1—C7—C12	124.88 (11)	C17—C18—C19	118.41 (14)
C8—C7—C12	120.45 (12)	C17—C18—C21	121.11 (18)
C9—C8—C7	119.82 (13)	C19—C18—C21	120.48 (19)
C9—C8—H8	120.1	C18—C19—C20	121.14 (16)
C7—C8—H8	120.1	C18—C19—H19	119.4
C8—C9—C10	121.47 (12)	C20—C19—H19	119.4
C8—C9—H9	119.3	C19—C20—C15	120.58 (15)
C10—C9—H9	119.3	C19—C20—H20	119.7
C11—C10—C9	117.27 (12)	C15—C20—H20	119.7
C11—C10—C14	120.08 (13)	C18—C21—H21A	109.5
C9—C10—C14	122.64 (12)	C18—C21—H21B	109.5
C10—C11—C12	122.92 (12)	H21A—C21—H21B	109.5
C10—C11—H11	118.5	C18—C21—H21C	109.5
C12—C11—H11	118.5	H21A—C21—H21C	109.5
C7—C12—C11	118.04 (12)	H21B—C21—H21C	109.5
C7—C12—P1	124.12 (10)	C6—O1—C7	122.19 (10)
C11—C12—P1	117.81 (10)	C1—P1—C12	98.00 (6)
C3—C13—H13A	109.5	C1—P1—C15	100.87 (6)
C3—C13—H13B	109.5	C12—P1—C15	101.04 (6)

C6—C1—C2—C3	−0.7 (2)	C20—C15—C16—C17	−0.3 (2)
P1—C1—C2—C3	176.68 (10)	P1—C15—C16—C17	−179.07 (11)
C1—C2—C3—C4	2.4 (2)	C15—C16—C17—C18	1.1 (2)
C1—C2—C3—C13	−176.31 (13)	C16—C17—C18—C19	−1.0 (2)
C2—C3—C4—C5	−2.1 (2)	C16—C17—C18—C21	178.23 (14)
C13—C3—C4—C5	176.57 (13)	C17—C18—C19—C20	0.1 (2)
C3—C4—C5—C6	0.2 (2)	C21—C18—C19—C20	−179.10 (14)
C2—C1—C6—O1	177.32 (12)	C18—C19—C20—C15	0.6 (2)
P1—C1—C6—O1	0.09 (19)	C16—C15—C20—C19	−0.5 (2)
C2—C1—C6—C5	−1.29 (19)	P1—C15—C20—C19	178.12 (11)
P1—C1—C6—C5	−178.52 (10)	C1—C6—O1—C7	10.4 (2)
C4—C5—C6—O1	−177.21 (13)	C5—C6—O1—C7	−170.89 (12)
C4—C5—C6—C1	1.5 (2)	C8—C7—O1—C6	171.17 (12)
O1—C7—C8—C9	179.10 (12)	C12—C7—O1—C6	−9.1 (2)
C12—C7—C8—C9	−0.6 (2)	C6—C1—P1—C12	−8.60 (12)
C7—C8—C9—C10	1.1 (2)	C2—C1—P1—C12	174.17 (10)
C8—C9—C10—C11	−0.1 (2)	C6—C1—P1—C15	94.34 (12)
C8—C9—C10—C14	−179.98 (13)	C2—C1—P1—C15	−82.90 (11)
C9—C10—C11—C12	−1.45 (19)	C7—C12—P1—C1	9.72 (12)
C14—C10—C11—C12	178.41 (12)	C11—C12—P1—C1	−172.23 (10)
O1—C7—C12—C11	179.45 (12)	C7—C12—P1—C15	−93.08 (12)
C8—C7—C12—C11	−0.86 (19)	C11—C12—P1—C15	84.97 (11)
O1—C7—C12—P1	−2.50 (19)	C16—C15—P1—C1	159.40 (10)
C8—C7—C12—P1	177.19 (10)	C20—C15—P1—C1	−19.24 (12)
C10—C11—C12—C7	1.94 (19)	C16—C15—P1—C12	−100.12 (11)
C10—C11—C12—P1	−176.23 (10)	C20—C15—P1—C12	81.24 (12)

Experimental details

Crystal data
Chemical formula	C₂₁H₁₉OP
M_r	318.33
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	173
a, b, c (Å)	10.9363 (3), 11.6323 (3), 14.0458 (4)
β (°)	111.532 (1)
V (Å³)	1662.13 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.17
Crystal size (mm)	0.51 × 0.49 × 0.48

Data collection
Diffractometer	Bruker APEXII CCD area-detector diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	29900, 4013, 3507
R_int	0.046
(sin θ/λ)_max (Å⁻¹)	0.661

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.037, 0.108, 1.07
No. of reflections	4013
No. of parameters	211
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.37, −0.27

Computer programs: APEX2 (Bruker, 2005), SAINT-Plus (Bruker, 2005), SHELXTL (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008).

Acknowledgements

We thank Dr Manuel Fernandes for the data collection and acknowledge SASOL, THRIP and the University of KwaZulu-Natal for financial support.

References

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