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Acta Cryst. (2008). E64, m1534    [ doi:10.1107/S1600536808036465 ]

Pentacarbonyl-2[kappa]5C-chlorido-1[kappa]Cl-bis[1([eta]5)-cyclopentadienyl]([mu]-[alpha]-oxidobenzylidene-1:2[kappa]2O:C)titanium(IV)tungsten(0)

C. Esterhuysen, I. B. J. Nel, M. W. Esterhuysen and S. Cronje

Abstract top

The title compound, [TiW(C5H5)2(C7H5O)Cl(CO)5], consists of two metal centres, with a (tungstenpentacarbonyl)oxyphenylcarbene unit coordinated by a titanocene chloride. The oxycarbene group is nearly planar, with the phenyl ring twisted by an angle of 39.1 (2)° with respect to this plane. One of the cyclopentadienyl rings undergoes an offset face-to-face [pi]-[pi] interaction [3.544 (6) Å] with the symmetry-related cyclopentadienyl ring of a neighbouring molecule.

Comment top

Anionic Fischer-type carbene ligands are known to act as monodentate ligands towards transition metals like Ti and Zr (Barluenga and Fañanás, 2000). We have shown that such zirconocene complexes, Cp2Zr(Cl)OC(R)W(CO)5, catalyze the oligomerization of 1-pentene, as well as the copolymerization of ethene and 1-pentene, in the presence of MAO (Luruli et al., 2004; Luruli et al., 2006). Since Cp2TiCl2 has been shown to polymerize ethylene when activated by methylaluminoxane, MAO (Sinn et al., 1980), the title complex (I) was synthesized as part of our investigation into improved Ziegler-Natta catalysts for polymerization of ethene.

In the title compound (Fig. 1), the W=Ccarbene and Ccarbene—C distances are similar to those found in the equivalent hafnocene complex [2.177 (6) and 1.291 (6) Å, respectively; Esterhuysen et al., 2008], while the Ti—O distance is similar to the related compound Cp2Ti(Cl)OC(C6H5)Mn(CO)2(C5H4CH3) (Balzer et al., 1992). The Ti—O—C angle deviates slightly from linearity, which is similar to the related hafnocene complex [171.4 (3)°], but more linear than the manganese complex [160.8 (5)°]. These results are indicative of π delocalization through the Ti—O—C=W unit. As a result, the Cl/Ti/O1/C1/W/C3/O3 moiety is approximately planar, with the phenyl ring (C21/C22/C23/C24/C25/C26) twisted at an angle of 39.1 (2)° with respect to this plane.

The C31/C32/C33/C34/C35 Cp ring [with centroid Cg(1)] undergoes offset face-to-face π–π interactions with the symmetry related Cp ring on a neighbouring molecule [Cg(1)···Cg(1)i = 3.544 (6) Å; Symmetry code: (i) - x, 2 - y, 1 - z)].

Related literature top

For related literature regarding anionic Fischer-type carbenes, see: Barluenga & Fañanás (2000). For information regarding the catalytic activity of similar complexes, see: Luruli et al. (2004, 2006); Sinn et al. (1980). For comparable structures, see: Esterhuysen et al. (2008); Balzer et al. (1992). For related literature, see: Orpen et al. (1989).

Experimental top

A solution of LiCH3 (31.0 ml, 1.6M, 50.2 mmol) in 50 ml of diethylether was added to a well stirred suspension of W(CO)6 (17.80 g, 50.6 mmol) in 100 ml of diethylether. After solvent removal in vacuo, dissolution of the residue in 150 ml of cold water and filtration, a solution of Et4NCl (8.72 g, 52.6 mmol) in 50 ml of cold water was added to the filtrate. Upon further filtration 1.13 g (2.0 mmol) of the product {[W(CO)5C(C6H5)O][NEt4]} was dissolved in 70 ml of dichloromethane and added to a solution of Cp2TiCl2 (0.51 g, 2.0 mmol) in 40 ml of dichloromethane. After stirring for 30 min at -40°C AgBF4 (0.39 g, 2.0 mmol) was added. The red concentrate, stripped of solvent, was purified by chromatography at -20°C on silica with 400 ml of dichloromethane-pentane (2:1) followed by 200 ml of diethyl ether-hexane (2:1) (column 15 × 2 cm). The eluent was dried in vacuo, and the residue dissolved in toluene, layered with pentane and kept at -6°C, whereupon brown crystals of the title compound suitable for X-ray diffraction analysis were obtained in 38% yield.

Refinement top

H atoms were positioned geometrically, with C—H = 0.95 Å, and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C). The maximum and minimum residual electron density peaks were located 1.05 and 0.86 Å, respectively from the W atom.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN(Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001; Atwood & Barbour, 2003); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing the atomic labelling scheme and displacement ellipsoids drawn at the 50% probability level.
Pentacarbonyl-2κ5C-chlorido-1κCl-bis[1(η5)-cyclopentadienyl](µ- α-oxidobenzylidene-1:2κ2O:C)titaniumtungsten top
Crystal data top
[TiW(C5H5)2(C7H5O)Cl(CO)5]F(000) = 1232
Mr = 642.54Dx = 1.967 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3701 reflections
a = 8.553 (1) Åθ = 1.9–26.0°
b = 12.268 (1) ŵ = 5.83 mm−1
c = 20.789 (3) ÅT = 173 K
β = 95.903 (1)°Prism, brown
V = 2169.8 (3) Å30.17 × 0.14 × 0.12 mm
Z = 4
Data collection top
Nonius KappaCCD
diffractometer		4270 independent reflections
Radiation source: fine-focus sealed tube3701 reflections with I > 2σ(I)
graphiteRint = 0.048
φ and ω scans to fill Ewald sphereθmax = 26.0°, θmin = 1.9°
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)		h = −10→10
Tmin = 0.438, Tmax = 0.542k = −12→15
12664 measured reflectionsl = −25→25
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.025Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.062H-atom parameters constrained
S = 1.04 w = 1/[σ2(Fo2) + (0.0268P)2 + 1.3791P]
where P = (Fo2 + 2Fc2)/3
4270 reflections(Δ/σ)max = 0.001
280 parametersΔρmax = 1.05 e Å−3
0 restraintsΔρmin = −1.28 e Å−3
Crystal data top
[TiW(C5H5)2(C7H5O)Cl(CO)5]V = 2169.8 (3) Å3
Mr = 642.54Z = 4
Monoclinic, P21/cMo Kα radiation
a = 8.553 (1) ŵ = 5.83 mm−1
b = 12.268 (1) ÅT = 173 K
c = 20.789 (3) Å0.17 × 0.14 × 0.12 mm
β = 95.903 (1)°
Data collection top
Nonius KappaCCD
diffractometer		4270 independent reflections
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)		3701 reflections with I > 2σ(I)
Tmin = 0.438, Tmax = 0.542Rint = 0.048
12664 measured reflectionsθmax = 26.0°
Refinement top
R[F2 > 2σ(F2)] = 0.025H-atom parameters constrained
wR(F2) = 0.062Δρmax = 1.05 e Å−3
S = 1.04Δρmin = −1.28 e Å−3
4270 reflectionsAbsolute structure: ?
280 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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
xyzUiso*/Ueq
W−0.040028 (18)0.614346 (12)0.673068 (7)0.02272 (7)
Ti0.30368 (8)0.78191 (5)0.53935 (3)0.02177 (16)
Cl0.55600 (14)0.83949 (10)0.58007 (5)0.0410 (3)
O10.2431 (3)0.7285 (2)0.62039 (11)0.0245 (6)
O2−0.1363 (4)0.6408 (3)0.52255 (14)0.0404 (8)
O3−0.3832 (4)0.5174 (3)0.67496 (16)0.0509 (9)
O4−0.0034 (5)0.6032 (3)0.82667 (14)0.0521 (10)
O50.0917 (5)0.3753 (3)0.65428 (18)0.0569 (10)
O6−0.1413 (5)0.8615 (3)0.69147 (17)0.0505 (9)
C10.1989 (4)0.6800 (3)0.66995 (16)0.0207 (8)
C2−0.0937 (5)0.6307 (3)0.5758 (2)0.0282 (9)
C3−0.2601 (5)0.5542 (3)0.67555 (19)0.0326 (10)
C4−0.0115 (5)0.6062 (3)0.7719 (2)0.0331 (10)
C50.0453 (5)0.4607 (4)0.66182 (19)0.0340 (10)
C6−0.1093 (5)0.7727 (4)0.68423 (19)0.0332 (10)
C210.3261 (4)0.6812 (3)0.72524 (16)0.0227 (8)
C220.3483 (5)0.5921 (3)0.76655 (17)0.0261 (9)
H220.27800.53210.76150.031*
C230.4726 (5)0.5901 (4)0.81522 (19)0.0337 (10)
H230.48880.52810.84240.040*
C240.5731 (5)0.6791 (4)0.82394 (18)0.0359 (11)
H240.65800.67790.85720.043*
C250.5499 (5)0.7688 (4)0.7844 (2)0.0378 (10)
H250.61730.83020.79120.045*
C260.4280 (5)0.7699 (3)0.73471 (17)0.0300 (9)
H260.41410.83140.70700.036*
C310.0676 (5)0.8817 (3)0.5469 (2)0.0321 (10)
H31−0.01550.85180.56830.039*
C320.0882 (5)0.8697 (3)0.4812 (2)0.0337 (10)
H320.02250.82900.45030.040*
C330.2228 (5)0.9284 (4)0.4690 (2)0.0362 (10)
H330.26460.93430.42850.043*
C340.2847 (5)0.9768 (3)0.5274 (2)0.0335 (10)
H340.37451.02270.53300.040*
C350.1924 (5)0.9463 (3)0.57560 (19)0.0319 (10)
H350.21010.96540.62000.038*
C410.2059 (6)0.6425 (4)0.4682 (2)0.0424 (12)
H410.09600.63970.45550.051*
C420.2865 (7)0.5904 (4)0.5223 (2)0.0439 (12)
H420.24050.54420.55190.053*
C430.4452 (7)0.6184 (3)0.5251 (2)0.0458 (13)
H430.52600.59680.55730.055*
C440.4629 (6)0.6842 (4)0.4713 (2)0.0432 (12)
H440.55930.71380.46040.052*
C450.3183 (6)0.6991 (4)0.43667 (19)0.0399 (11)
H450.29830.74060.39810.048*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
W0.02340 (10)0.02525 (10)0.01927 (9)−0.00116 (7)0.00104 (7)0.00126 (6)
Ti0.0253 (4)0.0243 (4)0.0157 (3)0.0017 (3)0.0022 (3)0.0023 (3)
Cl0.0411 (7)0.0424 (6)0.0388 (6)−0.0064 (5)0.0013 (5)0.0034 (5)
O10.0297 (16)0.0257 (14)0.0179 (12)−0.0016 (12)0.0008 (11)0.0041 (11)
O20.045 (2)0.0505 (19)0.0231 (15)−0.0082 (16)−0.0072 (14)0.0014 (13)
O30.0308 (19)0.066 (2)0.057 (2)−0.0159 (18)0.0105 (16)−0.0051 (18)
O40.060 (2)0.075 (3)0.0213 (17)0.0082 (19)0.0064 (15)0.0073 (15)
O50.072 (3)0.037 (2)0.056 (2)0.0205 (18)−0.018 (2)−0.0063 (16)
O60.065 (2)0.0354 (19)0.051 (2)0.0102 (17)0.0045 (18)−0.0071 (16)
C10.024 (2)0.0187 (19)0.0199 (17)0.0039 (16)0.0048 (15)0.0006 (15)
C20.026 (2)0.028 (2)0.030 (2)−0.0050 (17)0.0034 (18)−0.0016 (17)
C30.033 (3)0.034 (3)0.030 (2)0.000 (2)0.0032 (19)0.0010 (19)
C40.034 (3)0.039 (3)0.028 (2)−0.0027 (19)0.0086 (19)0.0048 (18)
C50.035 (3)0.036 (3)0.028 (2)0.001 (2)−0.0089 (18)0.0017 (19)
C60.036 (3)0.037 (3)0.026 (2)0.000 (2)0.0020 (18)−0.0027 (19)
C210.024 (2)0.027 (2)0.0166 (16)0.0010 (17)0.0020 (15)0.0004 (15)
C220.028 (2)0.028 (2)0.0224 (18)0.0026 (17)0.0045 (16)0.0019 (16)
C230.033 (2)0.044 (3)0.024 (2)0.008 (2)0.0022 (18)0.0088 (19)
C240.027 (2)0.058 (3)0.022 (2)0.007 (2)−0.0016 (17)−0.004 (2)
C250.031 (2)0.047 (3)0.034 (2)−0.011 (2)−0.0023 (19)0.001 (2)
C260.032 (2)0.038 (2)0.0194 (18)−0.0063 (19)0.0004 (17)0.0061 (17)
C310.029 (2)0.031 (2)0.038 (2)0.0088 (19)0.0072 (19)0.0127 (18)
C320.035 (3)0.036 (3)0.027 (2)0.010 (2)−0.0108 (19)0.0062 (17)
C330.041 (3)0.040 (3)0.029 (2)0.006 (2)0.0071 (19)0.0161 (19)
C340.037 (3)0.021 (2)0.043 (2)−0.0007 (19)0.004 (2)0.0065 (18)
C350.041 (3)0.024 (2)0.031 (2)0.0067 (19)0.0072 (19)−0.0009 (17)
C410.049 (3)0.044 (3)0.035 (2)−0.003 (2)0.004 (2)−0.022 (2)
C420.070 (4)0.027 (2)0.038 (2)−0.003 (2)0.018 (2)−0.010 (2)
C430.063 (4)0.034 (3)0.041 (3)0.021 (2)0.007 (2)−0.005 (2)
C440.046 (3)0.049 (3)0.038 (2)0.012 (2)0.018 (2)−0.007 (2)
C450.055 (3)0.043 (3)0.023 (2)0.010 (2)0.010 (2)−0.0064 (19)
Geometric parameters (Å, °) top
W—C32.028 (5)C22—H220.9500
W—C22.038 (4)C23—C241.389 (7)
W—C52.043 (5)C23—H230.9500
W—C42.047 (4)C24—C251.375 (6)
W—C62.051 (5)C24—H240.9500
W—C12.204 (4)C25—C261.391 (5)
Ti—O11.927 (2)C25—H250.9500
Ti—Cl2.3446 (14)C26—H260.9500
Ti—C412.358 (4)C31—C321.404 (6)
Ti—C322.358 (4)C31—C351.411 (6)
Ti—C332.374 (4)C31—H310.9500
Ti—C432.377 (4)C32—C331.402 (6)
Ti—C422.378 (4)C32—H320.9500
Ti—C452.379 (4)C33—C341.406 (6)
Ti—C312.381 (4)C33—H330.9500
Ti—C352.385 (4)C34—C351.389 (5)
Ti—C442.385 (4)C34—H340.9500
Ti—C342.408 (4)C35—H350.9500
O1—C11.280 (4)C41—C451.403 (6)
O2—C21.135 (5)C41—C421.410 (7)
O3—C31.144 (5)C41—H410.9500
O4—C41.134 (5)C42—C431.395 (7)
O5—C51.138 (5)C42—H420.9500
O6—C61.137 (5)C43—C441.399 (6)
C1—C211.499 (5)C43—H430.9500
C21—C221.391 (5)C44—C451.377 (7)
C21—C261.396 (5)C44—H440.9500
C22—C231.390 (6)C45—H450.9500
C3—W—C286.90 (16)C21—C1—W125.7 (2)
C3—W—C590.63 (17)O2—C2—W174.3 (4)
C2—W—C591.35 (16)O3—C3—W177.2 (4)
C3—W—C488.38 (17)O4—C4—W176.6 (4)
C2—W—C4173.19 (17)O5—C5—W178.6 (4)
C5—W—C493.62 (16)O6—C6—W177.1 (4)
C3—W—C693.55 (17)C22—C21—C26118.8 (4)
C2—W—C688.91 (16)C22—C21—C1120.5 (3)
C5—W—C6175.82 (17)C26—C21—C1120.6 (3)
C4—W—C686.47 (16)C23—C22—C21120.6 (4)
C3—W—C1179.75 (15)C23—C22—H22119.7
C2—W—C192.86 (14)C21—C22—H22119.7
C5—W—C189.45 (15)C24—C23—C22119.8 (4)
C4—W—C191.85 (15)C24—C23—H23120.1
C6—W—C186.37 (15)C22—C23—H23120.1
O1—Ti—Cl96.14 (8)C25—C24—C23120.1 (4)
O1—Ti—C41101.07 (14)C25—C24—H24120.0
Cl—Ti—C41134.35 (14)C23—C24—H24120.0
O1—Ti—C32109.71 (14)C24—C25—C26120.2 (4)
Cl—Ti—C32133.57 (12)C24—C25—H25119.9
C41—Ti—C3278.56 (17)C26—C25—H25119.9
O1—Ti—C33135.06 (13)C25—C26—C21120.5 (4)
Cl—Ti—C33101.17 (12)C25—C26—H26119.8
C41—Ti—C3395.76 (17)C21—C26—H26119.8
C32—Ti—C3334.46 (15)C32—C31—C35107.7 (4)
O1—Ti—C4390.49 (14)C32—C31—Ti71.9 (2)
Cl—Ti—C4380.67 (15)C35—C31—Ti72.9 (2)
C41—Ti—C4357.43 (19)C32—C31—H31126.1
C32—Ti—C43134.63 (17)C35—C31—H31126.1
C33—Ti—C43132.96 (16)Ti—C31—H31120.8
O1—Ti—C4277.09 (13)C33—C32—C31108.0 (4)
Cl—Ti—C42113.08 (15)C33—C32—Ti73.4 (2)
C41—Ti—C4234.65 (17)C31—C32—Ti73.6 (2)
C32—Ti—C42109.99 (18)C33—C32—H32126.0
C33—Ti—C42130.25 (17)C31—C32—H32126.0
C43—Ti—C4234.13 (18)Ti—C32—H32118.9
O1—Ti—C45133.08 (14)C32—C33—C34107.7 (4)
Cl—Ti—C45108.73 (13)C32—C33—Ti72.1 (2)
C41—Ti—C4534.45 (16)C34—C33—Ti74.2 (2)
C32—Ti—C4581.11 (16)C32—C33—H33126.2
C33—Ti—C4579.00 (16)C34—C33—H33126.2
C43—Ti—C4556.85 (17)Ti—C33—H33119.4
C42—Ti—C4556.82 (16)C35—C34—C33108.5 (4)
O1—Ti—C3179.09 (13)C35—C34—Ti72.3 (2)
Cl—Ti—C31125.21 (12)C33—C34—Ti71.6 (2)
C41—Ti—C3199.57 (17)C35—C34—H34125.8
C32—Ti—C3134.47 (14)C33—C34—H34125.8
C33—Ti—C3157.05 (14)Ti—C34—H34122.1
C43—Ti—C31152.69 (18)C34—C35—C31108.0 (4)
C42—Ti—C31118.56 (17)C34—C35—Ti74.1 (2)
C45—Ti—C31113.73 (16)C31—C35—Ti72.6 (2)
O1—Ti—C3581.89 (12)C34—C35—H35126.0
Cl—Ti—C3590.79 (11)C31—C35—H35126.0
C41—Ti—C35133.17 (17)Ti—C35—H35119.2
C32—Ti—C3557.28 (15)C45—C41—C42107.1 (5)
C33—Ti—C3556.94 (15)C45—C41—Ti73.6 (3)
C43—Ti—C35167.92 (17)C42—C41—Ti73.5 (3)
C42—Ti—C35149.50 (17)C45—C41—H41126.4
C45—Ti—C35134.76 (15)C42—C41—H41126.4
C31—Ti—C3534.43 (14)Ti—C41—H41118.5
O1—Ti—C44124.66 (14)C43—C42—C41108.4 (4)
Cl—Ti—C4478.77 (13)C43—C42—Ti72.9 (2)
C41—Ti—C4456.67 (18)C41—C42—Ti71.9 (3)
C32—Ti—C44112.91 (16)C43—C42—H42125.8
C33—Ti—C4499.40 (16)C41—C42—H42125.8
C43—Ti—C4434.17 (16)Ti—C42—H42121.1
C42—Ti—C4456.31 (17)C42—C43—C44107.1 (5)
C45—Ti—C4433.62 (16)C42—C43—Ti73.0 (3)
C31—Ti—C44146.91 (16)C44—C43—Ti73.2 (2)
C35—Ti—C44152.05 (16)C42—C43—H43126.5
O1—Ti—C34113.94 (12)C44—C43—H43126.5
Cl—Ti—C3477.75 (11)Ti—C43—H43119.3
C41—Ti—C34129.81 (17)C45—C44—C43109.2 (5)
C32—Ti—C3456.81 (15)C45—C44—Ti72.9 (2)
C33—Ti—C3434.20 (15)C43—C44—Ti72.6 (2)
C43—Ti—C34148.78 (17)C45—C44—H44125.4
C42—Ti—C34164.43 (16)C43—C44—H44125.4
C45—Ti—C34109.94 (15)Ti—C44—H44120.7
C31—Ti—C3456.44 (14)C44—C45—C41108.1 (4)
C35—Ti—C3433.69 (13)C44—C45—Ti73.4 (2)
C44—Ti—C34118.36 (16)C41—C45—Ti72.0 (2)
C1—O1—Ti171.7 (2)C44—C45—H45125.9
O1—C1—C21111.2 (3)C41—C45—H45125.9
O1—C1—W123.0 (3)Ti—C45—H45120.4
Table 1
Selected geometric parameters (Å, °) top
W—C12.204 (4)O1—C11.280 (4)
Ti—O11.927 (2)
C1—O1—Ti171.7 (2)
Acknowledgements top

We thank the NRF and the University of Stellenbosch for financial support.

references
References top

Atwood, J. L. & Barbour, L. J. (2003). Cryst. Growth Des. 3, 3–8.

Balzer, B. L., Cazanoue, M., Sabat, M. & Finn, M. G. (1992). Organometallics, 11, 1759–1761.

Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191.

Barluenga, J. & Fañanás, F. J. (2000). Tetrahedron, 56, 4597–4628.

Esterhuysen, C., Nel, I. B. J. & Cronje, S. (2008). Acta Cryst. E64, m1150.

Luruli, N., Grumel, V., Brüll, R., Du Toit, A., Pasch, H., Van Reenen, A. J. & Raubenheimer, H. G. (2004). J. Polym. Sci. A1, 5121–5133.

Luruli, N., Heinz, L. C., Grumel, V., Brüll, R., Pasch, H. & Raubenheimer, H. G. (2006). Polymer, 47, 56–66.

Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.

Orpen, A. G., Brammer, L., Allen, F. H., Kennard, O., Watson, D. G. & Taylor, R. (1989). J. Chem. Soc. Dalton Trans. pp. S1–83.

Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Sinn, H., Kaminsky, W., Vollmer, H. J. & Woldt, R. (1980). Angew. Chem. Int. Ed. Engl. 19, 390–392.

Westrip, S. P. (2008). publCIF. In preparation.