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

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ISSN: 2056-9890

Penta­carbon­yl{3-[(2S)-1-methyl­pyrrolidin-2-yl]pyridine}tungsten(0)

aUniversity of the Western Cape, Cape Town, Bellville 7535, South Africa, bDepartment of Chemistry, Rutgers, the State University of New Jersey, 73 Warren St, Newark, NJ 07102, USA, and cDepartment of Chemistry, Kenyatta University, PO Box 43844-00100, Nairobi, Kenya
*Correspondence e-mail: monani@uwc.ac.za

(Received 4 March 2010; accepted 23 March 2010; online 31 March 2010)

The title compound, [W(C10H14N2)(CO)5], contains five carbonyl ligands and a nicotine ligand in an octa­hedral arrangement around the tungsten atom. The metal atom shows cis angles in the range 87.30 (16)–94.2 (2)°, and trans angles between 175.2 (2) and 178.1 (4)°. The W—CO bond trans to the pyridine N atom [1.987 (6) Å] is noticeably shorter than the others, which range between 2.036 (3) and 2.064 (3) Å, possibly due to the well-known trans effect. The distance between the W atom and the pyridine N atom is 2.278 (4) Å.

Related literature

Attempts to understand and mimic the nature of nitro­gen fixation have led to studies on the responsible enzyme, nitro­genase (Jennings, 1991[Jennings, J. R. (1991). Editor. Catalytic Ammonia Synthesis. New York: Plenum.]; Schrock, 2006[Schrock, R. R. (2006). Proc. Natl Acad. Sci. 103, 17087.]). As part of this work, we have investigated the reactions of the precursor tungsten halogenidocarbonyl derivative, [W(CO)4X2]2, with nitro­gen bases. For possible reaction mechanisms, see: Abel et al. (1963[Abel, E. W., Butler, I. S. & Reid, I. G. (1963). J. Chem. Soc. pp. 2068-2069.]); Baker (1998[Baker, P. K. (1998). Chem. Soc. Rev. 27, 125-132.]); Heyns & Buchholtz (1976[Heyns, K. & Buchholtz, H. (1976). Chem. Ber. 109, 3707-3727.]); Tripathi & Srivasatva (1970[Tripathi, S. C. & Srivasatva, S. C. (1970). J. Organomet. Chem. 23, 193-199.]). For the preparation of tungsten dichlorido­tetracarbonyl [W(CO)4Cl2], see: Colton & Tomkins (1966[Colton, R. & Tomkins, I. B. (1966). Aust. J. Chem. 19, 1143-1145.]).

[Scheme 1]

Experimental

Crystal data
  • [W(C10H14N2)(CO)5]

  • Mr = 486.13

  • Monoclinic, P 21

  • a = 6.6303 (1) Å

  • b = 10.6720 (2) Å

  • c = 11.6748 (2) Å

  • β = 96.636 (1)°

  • V = 820.56 (2) Å3

  • Z = 2

  • Cu Kα radiation

  • μ = 13.29 mm−1

  • T = 100 K

  • 0.28 × 0.25 × 0.19 mm

Data collection
  • Bruker SMART CCD APEXII area-detector diffractometer

  • Absorption correction: numerical (SADABS; Sheldrick, 2008a[Sheldrick, G. M. (2008a). SADABS. University of Göttingen, Germany.]) Tmin = 0.119, Tmax = 0.185

  • 6704 measured reflections

  • 2676 independent reflections

  • 2673 reflections with I > 2σ(I)

  • Rint = 0.020

Refinement
  • R[F2 > 2σ(F2)] = 0.014

  • wR(F2) = 0.033

  • S = 1.13

  • 2676 reflections

  • 210 parameters

  • 1 restraint

  • H-atom parameters constrained

  • Δρmax = 0.44 e Å−3

  • Δρmin = −0.53 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 1225 Friedel pairs

  • Flack parameter: 0.041 (9)

Data collection: APEX2 (Bruker, 2006[Bruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2005[Bruker (2005). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008b[Sheldrick, G. M. (2008b). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

An effort to understand and mimic the nature of nitrogen fixation has led to wide studies on the responsible enzyme, nitrogenase (Jennings, 1991; Schrock, 2006). The focus of our study was to investigate the reactions of the precursor tungsten halocarbonyl derivative, [W(CO)4X2]2, with nitrogen bases to help contribute to this investigation. The compound nicotine (L), was reacted with the presupposed W(CO)4X2, with the hope of obtaining W(CO)4L2; however, the product which was confirmed by a single-crystal X-ray analysis was W(CO)5L, indicating that the compound was formed via a different route. It is thus envisaged that during the preparation of the precursor it is likely that such compounds as W(CO)5Cl- [Abel et al. (1963); Baker (1998)] may be formed, which in turn react with a single molecule of the ligand, nicotine, forming the obtained product. There is less likelihood of a direct substitution of the carbonyl ligands (Tripathi & Srivasatva, 1970) or a redox mechanism (Heyns & Buchholtz, 1976) that would most likely lead to a disubstituted compound. The coordination of nicotine to tungsten, as observed, is via the imine nitrogen as shown in the crystal structure of the compound (See Figure 1).

The W metal centre has cis angles in the range 87.30 (16) to 94.2 (2)°, and trans angles between 175.2 (2)° and 178.1 (4)°. The W–CO bond trans to the nitrogen [1.987 (6) Å] is noticeably shorter than the others, which range between 2.036 (3) and 2.064 (3) Å, possibly due to the known trans effect. The distance between the W atom and the nicotine imine N is 2.278 (4) Å.

The infrared absorption bands of the compound show five absorption peaks at 2006.8(m), 1921.9(w), 1884.3(s), 1816.6(m) and 1760.9(m) cm-1. Also, there is a ~1ppm shift downfield in the positions of the alpha protons on the pyridine ring of the product in both the 1H and 13C NMR spectra compared to the reactants. The CO that is trans to the pyridinyl structure has the most significant shift upfield, possibly due to the trans effect. Only one peak is observed for the carbonyls in the 13C NMR spectrum, possibly due to shielding by the ring electrons leading to a slow decay, and since they are so close they appear identical.

Related literature top

Attempts to understand and mimic the nature of nitrogen fixation have led to studies on the responsible enzyme, nitrogenase (Jennings, 1991; Schrock, 2006). As part of this work, we investigated the reactions of the precursor tungsten halocarbonyl derivative, [W(CO)4X2]2, with nitrogen bases. For possible reaction mechanisms, see: Abel et al. (1963); Baker (1998); Heyns & Buchholtz (1976); Tripathi & Srivasatva (1970). For the preparation of tungsten halocarbonyl [W(CO)4Cl2], see: Colton & Tomkins (1966).

Experimental top

The procedure by Colton and Tomkins (1966) and Schlenk techniques were used to prepare tungsten halocarbonyl [W(CO)4Cl2]. This halocarbonyl (13.13 mmol) was then reacted in situ with the base, nicotine (31.13 mmol), dissolved in freshly distilled methanol (20 ml) at -78 °C and the mixture left to warm to room temperature while stirring. The solution was stirred at room temperature for 14 h after which the solvent was removed under vacuum and the residue washed with portions of dry freshly distilled methanol and rinsed with diethylether. A yellow product was obtained in medium yield.

The crystal was grown at 4°C using a slow diffusion of dichloromethane over hexane for several days.

Refinement top

All H atoms for (I) were found in electron density difference maps. The methyl H atoms were put in ideally staggered positions with C—H distances of 0.98 Å and Uiso(H) = 1.5Ueq(C). The methylene, methine and phenyl Hs were placed in geometrically idealized positions and constrained to ride on their parent C atoms with C—H distances of 0.99, 1.00 and 0.95 Å, respectively, and Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008b); program(s) used to refine structure: SHELXTL (Sheldrick, 2008b); molecular graphics: SHELXTL (Sheldrick, 2008b); software used to prepare material for publication: SHELXTL (Sheldrick, 2008b).

Figures top
[Figure 1] Fig. 1. : The structure of the asymmetric unit of (I) with its numbering scheme. Displacement ellipsoids are drawn at the 40% probability level for non-H atoms.
Pentacarbonyl{3-[(2S)-1-methylpyrrolidin-2-yl]pyridine}tungsten(0) top
Crystal data top
[W(C10H14N2)(CO)5]F(000) = 464
Mr = 486.13Dx = 1.968 Mg m3
Monoclinic, P21Cu Kα radiation, λ = 1.54178 Å
Hall symbol: P 2ybCell parameters from 6772 reflections
a = 6.6303 (1) Åθ = 3.8–66.8°
b = 10.6720 (2) ŵ = 13.29 mm1
c = 11.6748 (2) ÅT = 100 K
β = 96.636 (1)°Plate, yellow
V = 820.56 (2) Å30.28 × 0.25 × 0.19 mm
Z = 2
Data collection top
Bruker SMART CCD APEXII area-detector
diffractometer
2676 independent reflections
Radiation source: fine-focus sealed tube2673 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.020
ϕ and ω scansθmax = 66.8°, θmin = 3.8°
Absorption correction: numerical
(SADABS; Sheldrick, 2008a)
h = 77
Tmin = 0.119, Tmax = 0.185k = 1212
6704 measured reflectionsl = 1311
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.014 w = 1/[σ2(Fo2) + (0.0071P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.033(Δ/σ)max < 0.001
S = 1.13Δρmax = 0.44 e Å3
2676 reflectionsΔρmin = 0.53 e Å3
210 parametersExtinction correction: SHELXTL (Sheldrick, 2008b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.00053 (7)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 1225 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.041 (9)
Crystal data top
[W(C10H14N2)(CO)5]V = 820.56 (2) Å3
Mr = 486.13Z = 2
Monoclinic, P21Cu Kα radiation
a = 6.6303 (1) ŵ = 13.29 mm1
b = 10.6720 (2) ÅT = 100 K
c = 11.6748 (2) Å0.28 × 0.25 × 0.19 mm
β = 96.636 (1)°
Data collection top
Bruker SMART CCD APEXII area-detector
diffractometer
2676 independent reflections
Absorption correction: numerical
(SADABS; Sheldrick, 2008a)
2673 reflections with I > 2σ(I)
Tmin = 0.119, Tmax = 0.185Rint = 0.020
6704 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.014H-atom parameters constrained
wR(F2) = 0.033Δρmax = 0.44 e Å3
S = 1.13Δρmin = 0.53 e Å3
2676 reflectionsAbsolute structure: Flack (1983), 1225 Friedel pairs
210 parametersAbsolute structure parameter: 0.041 (9)
1 restraint
Special details top

Experimental. 'crystal mounted on a Cryoloop using Paratone-N'

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
W10.975072 (14)0.99294 (4)0.798344 (8)0.01869 (6)
C11.1233 (8)1.1176 (5)0.9028 (5)0.0212 (12)
O11.2053 (6)1.1868 (3)0.9687 (3)0.0307 (8)
N10.7925 (6)0.8443 (4)0.6915 (4)0.0218 (9)
C20.8653 (6)1.1332 (4)0.6881 (4)0.0206 (10)
O20.8203 (4)1.2112 (3)0.6253 (2)0.0327 (6)
N20.3021 (3)0.5061 (4)0.6952 (2)0.0230 (6)
C31.2185 (4)0.9810 (7)0.7074 (2)0.0238 (9)
O31.3582 (3)0.9783 (5)0.6594 (2)0.0384 (8)
C41.1080 (9)0.8553 (5)0.9047 (6)0.0233 (12)
O41.1972 (6)0.7822 (3)0.9596 (3)0.0337 (8)
C50.7301 (4)1.0112 (5)0.8913 (2)0.0204 (11)
O50.5952 (4)1.0199 (2)0.9427 (2)0.0327 (8)
C60.7783 (5)0.8398 (3)0.5751 (3)0.0244 (7)
H60.84630.90170.53550.029*
C70.6690 (5)0.7487 (3)0.5122 (3)0.0289 (7)
H70.66110.74870.43040.035*
C80.5703 (5)0.6569 (3)0.5682 (3)0.0245 (7)
H80.49630.59240.52580.029*
C90.5815 (5)0.6609 (3)0.6876 (3)0.0204 (6)
C100.6930 (4)0.7558 (3)0.7446 (3)0.0190 (6)
H100.70010.75870.82630.023*
C110.4868 (5)0.5628 (3)0.7575 (3)0.0204 (6)
H110.45300.60070.83120.025*
C120.6199 (5)0.4479 (3)0.7839 (3)0.0285 (8)
H12A0.72030.46260.85220.034*
H12B0.69310.42610.71740.034*
C130.4704 (5)0.3435 (4)0.8078 (3)0.0283 (8)
H13A0.49550.26660.76420.034*
H13B0.48210.32320.89110.034*
C140.2606 (5)0.3988 (3)0.7666 (3)0.0246 (7)
H14A0.17460.33650.72100.030*
H14B0.19080.42580.83290.030*
C150.1310 (5)0.5916 (4)0.6783 (3)0.0321 (8)
H15A0.01560.54940.63430.048*
H15B0.16870.66550.63590.048*
H15C0.09300.61740.75350.048*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
W10.01884 (8)0.01807 (8)0.01892 (8)0.00160 (9)0.00110 (4)0.00046 (9)
C10.017 (2)0.024 (3)0.022 (3)0.0024 (17)0.0021 (17)0.0015 (18)
O10.0287 (18)0.0293 (18)0.033 (2)0.0064 (14)0.0007 (14)0.0016 (14)
N10.021 (2)0.0222 (18)0.0211 (18)0.0006 (15)0.0020 (14)0.0023 (12)
C20.021 (2)0.0141 (18)0.025 (2)0.0005 (17)0.0033 (17)0.0001 (13)
O20.0357 (14)0.0301 (15)0.0304 (15)0.0040 (12)0.0037 (11)0.0013 (12)
N20.0172 (10)0.0248 (18)0.0262 (12)0.0042 (15)0.0002 (8)0.0002 (15)
C30.0216 (12)0.028 (3)0.0223 (14)0.0030 (19)0.0068 (10)0.0013 (18)
O30.0368 (12)0.042 (2)0.0386 (13)0.0094 (16)0.0119 (9)0.0142 (15)
C40.024 (2)0.018 (2)0.026 (3)0.0011 (18)0.0001 (18)0.0026 (17)
O40.042 (2)0.0292 (17)0.0269 (19)0.0006 (15)0.0089 (14)0.0064 (14)
C50.0202 (12)0.022 (3)0.0200 (14)0.0013 (14)0.0070 (10)0.0048 (14)
O50.0327 (12)0.031 (3)0.0349 (14)0.0026 (10)0.0071 (9)0.0025 (9)
C60.0282 (17)0.0266 (19)0.0185 (19)0.0014 (14)0.0029 (13)0.0036 (14)
C70.0345 (19)0.035 (2)0.0170 (18)0.0022 (15)0.0021 (13)0.0001 (13)
C80.0281 (17)0.0268 (18)0.0175 (18)0.0031 (14)0.0016 (12)0.0027 (12)
C90.0167 (14)0.0233 (17)0.0209 (18)0.0029 (12)0.0005 (11)0.0001 (12)
C100.0199 (15)0.0220 (17)0.0150 (16)0.0017 (12)0.0019 (11)0.0005 (11)
C110.0196 (16)0.0228 (18)0.0190 (18)0.0019 (14)0.0025 (11)0.0026 (14)
C120.0234 (17)0.0250 (18)0.037 (2)0.0056 (13)0.0013 (14)0.0076 (12)
C130.0271 (19)0.027 (2)0.030 (2)0.0056 (13)0.0005 (14)0.0053 (13)
C140.0224 (16)0.0218 (17)0.0299 (19)0.0067 (13)0.0039 (13)0.0018 (13)
C150.0243 (17)0.0310 (19)0.040 (2)0.0035 (14)0.0013 (14)0.0027 (15)
Geometric parameters (Å, º) top
W1—C11.987 (6)C7—H70.9500
W1—C32.035 (3)C8—C91.388 (5)
W1—C22.052 (5)C8—H80.9500
W1—C42.055 (6)C9—C101.379 (5)
W1—C52.064 (3)C9—C111.507 (5)
W1—N12.278 (4)C10—H100.9500
C1—O11.156 (7)C11—C121.522 (4)
N1—C101.344 (5)C11—H111.0000
N1—C61.352 (6)C12—C131.539 (5)
C2—O21.126 (6)C12—H12A0.9900
N2—C151.451 (5)C12—H12B0.9900
N2—C141.460 (5)C13—C141.536 (4)
N2—C111.480 (4)C13—H13A0.9900
C3—O31.138 (4)C13—H13B0.9900
C4—O41.132 (7)C14—H14A0.9900
C5—O51.138 (4)C14—H14B0.9900
C6—C71.374 (5)C15—H15A0.9800
C6—H60.9500C15—H15B0.9800
C7—C81.384 (5)C15—H15C0.9800
C1—W1—C389.8 (2)C10—C9—C11118.9 (3)
C1—W1—C290.6 (3)C8—C9—C11123.0 (3)
C3—W1—C287.9 (2)N1—C10—C9124.0 (3)
C1—W1—C487.75 (12)N1—C10—H10118.0
C3—W1—C487.7 (2)C9—C10—H10118.0
C2—W1—C4175.3 (2)N2—C11—C9113.0 (3)
C1—W1—C588.7 (2)N2—C11—C12101.4 (3)
C3—W1—C5178.1 (3)C9—C11—C12113.7 (2)
C2—W1—C590.97 (18)N2—C11—H11109.5
C4—W1—C593.4 (2)C9—C11—H11109.5
C1—W1—N1175.2 (2)C12—C11—H11109.5
C3—W1—N194.2 (2)C11—C12—C13104.5 (3)
C2—W1—N192.12 (11)C11—C12—H12A110.9
C4—W1—N189.8 (3)C13—C12—H12A110.9
C5—W1—N187.30 (16)C11—C12—H12B110.9
O1—C1—W1176.2 (5)C13—C12—H12B110.9
C10—N1—C6117.2 (4)H12A—C12—H12B108.9
C10—N1—W1119.7 (3)C14—C13—C12104.1 (3)
C6—N1—W1123.1 (3)C14—C13—H13A110.9
O2—C2—W1174.5 (4)C12—C13—H13A110.9
C15—N2—C14112.0 (2)C14—C13—H13B110.9
C15—N2—C11113.5 (3)C12—C13—H13B110.9
C14—N2—C11103.9 (3)H13A—C13—H13B109.0
O3—C3—W1177.1 (6)N2—C14—C13104.9 (3)
O4—C4—W1173.8 (5)N2—C14—H14A110.8
O5—C5—W1179.3 (5)C13—C14—H14A110.8
N1—C6—C7122.3 (3)N2—C14—H14B110.8
N1—C6—H6118.9C13—C14—H14B110.8
C7—C6—H6118.9H14A—C14—H14B108.8
C6—C7—C8119.8 (3)N2—C15—H15A109.5
C6—C7—H7120.1N2—C15—H15B109.5
C8—C7—H7120.1H15A—C15—H15B109.5
C7—C8—C9118.7 (3)N2—C15—H15C109.5
C7—C8—H8120.7H15A—C15—H15C109.5
C9—C8—H8120.7H15B—C15—H15C109.5
C10—C9—C8118.1 (3)
C3—W1—C1—O1139 (7)C1—W1—C5—O5122 (22)
C2—W1—C1—O1133 (7)C3—W1—C5—O5159 (22)
C4—W1—C1—O151 (7)C2—W1—C5—O5147 (22)
C5—W1—C1—O142 (7)C4—W1—C5—O535 (22)
N1—W1—C1—O18 (9)N1—W1—C5—O555 (22)
C1—W1—N1—C1011 (3)C10—N1—C6—C70.5 (6)
C3—W1—N1—C10135.7 (3)W1—N1—C6—C7179.4 (3)
C2—W1—N1—C10136.2 (3)N1—C6—C7—C80.6 (6)
C4—W1—N1—C1048.1 (3)C6—C7—C8—C91.2 (5)
C5—W1—N1—C1045.3 (3)C7—C8—C9—C100.8 (5)
C1—W1—N1—C6169 (2)C7—C8—C9—C11177.5 (3)
C3—W1—N1—C644.1 (4)C6—N1—C10—C91.0 (5)
C2—W1—N1—C644.0 (4)W1—N1—C10—C9178.9 (2)
C4—W1—N1—C6131.8 (4)C8—C9—C10—N10.3 (5)
C5—W1—N1—C6134.8 (4)C11—C9—C10—N1176.5 (3)
C1—W1—C2—O271 (4)C15—N2—C11—C969.3 (3)
C3—W1—C2—O218 (4)C14—N2—C11—C9168.8 (3)
C4—W1—C2—O22 (7)C15—N2—C11—C12168.6 (3)
C5—W1—C2—O2160 (4)C14—N2—C11—C1246.7 (3)
N1—W1—C2—O2113 (4)C10—C9—C11—N2152.7 (3)
C1—W1—C3—O37 (10)C8—C9—C11—N230.6 (5)
C2—W1—C3—O384 (10)C10—C9—C11—C1292.4 (4)
C4—W1—C3—O394 (10)C8—C9—C11—C1284.2 (4)
C5—W1—C3—O330 (13)N2—C11—C12—C1335.7 (3)
N1—W1—C3—O3176 (10)C9—C11—C12—C13157.3 (3)
C1—W1—C4—O471 (5)C11—C12—C13—C1412.4 (4)
C3—W1—C4—O419 (5)C15—N2—C14—C13162.2 (3)
C2—W1—C4—O41 (8)C11—N2—C14—C1339.3 (3)
C5—W1—C4—O4159 (5)C12—C13—C14—N215.9 (4)
N1—W1—C4—O4113 (5)

Experimental details

Crystal data
Chemical formula[W(C10H14N2)(CO)5]
Mr486.13
Crystal system, space groupMonoclinic, P21
Temperature (K)100
a, b, c (Å)6.6303 (1), 10.6720 (2), 11.6748 (2)
β (°) 96.636 (1)
V3)820.56 (2)
Z2
Radiation typeCu Kα
µ (mm1)13.29
Crystal size (mm)0.28 × 0.25 × 0.19
Data collection
DiffractometerBruker SMART CCD APEXII area-detector
diffractometer
Absorption correctionNumerical
(SADABS; Sheldrick, 2008a)
Tmin, Tmax0.119, 0.185
No. of measured, independent and
observed [I > 2σ(I)] reflections
6704, 2676, 2673
Rint0.020
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.014, 0.033, 1.13
No. of reflections2676
No. of parameters210
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.44, 0.53
Absolute structureFlack (1983), 1225 Friedel pairs
Absolute structure parameter0.041 (9)

Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008b).

 

Acknowledgements

We acknowledge the UWC SR for funding and RAL acknowledges support by NSF-CRIF (grant No. 0443538) for the X-ray instrument.

References

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