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Acta Cryst. (2009). E65, m170    [ doi:10.1107/S1600536809000439 ]

fac-Aquadichloridotris(tetramethylene sulfoxide-[kappa]S)ruthenium(II)

R. S. Srivastava, C. F. Gonzales and F. R. Fronczek

Abstract top

The title molecule, [RuCl2(C4H8OS)3(H2O)], is the isomer with the two chloride ligands cis and the three S-coordinated tetramethylene sulfoxide ligands facial relative to the Ru(II) center. The Ru-Cl distances are 2.4161 (7) and 2.4317 (7) Å, the Ru-O distance is 2.1540 (19) Å, and the Ru-S distances are in the range 2.2254 (8)-2.2657 (7) Å, with the shortest being that trans to the aqua ligand. The coordinated water molecule forms intermolecular hydrogen bonds with Cl and sulfoxide O atoms.

Comment top

During the course of our studies on ruthenium-DMSO/TMSO complexes, mer-RuCl3(TMSO)3 was refluxed with methyl-p-tolylsulfide in absolute ethanol for 1 h. In view of anticancer properties of Ru-DMSO/TMSO complexes, we envision to interact mer-RuCl3(TMSO)3, (1) with sulfur donor ligands, because sulfur-containing ligands are able to bind the metal center strongly and prevent interactions with sulfur-containing enzymes (Aldinucci et al., 2007). In fact, these reactions are believed to be responsible for the nephrotoxicity induced by the platinum (II)-based drugs. However, the compound (2) was hydrolyzed on long standing in solution, and finally the title compound, fac-[RuCl2(TMSO)3(H2O)] (3) was isolated. A plausible mechanism of the formation of (3) is shown in scheme 2.

There are three geometrical isomers of the title compound: trans,mer; cis,mer; and fac. The reported structure is found to be the latter, with chloro groups cis and TMSO groups facial, as shown in Fig. 1. More isomers are possible, considering that the TMSO ligands may be coordinated to Ru through either S or O in the same complex, (Srivastava & Fronczek, 2003; Srivastava et al., 2004); however, all are S-coordinated here. Relevant bond distances are given in the supplementary Tables. Most noteworthy is that the Ru—S3 distance, trans to water, is 0.03–0.04 Å shorter than the two Ru—S distances trans to Cl. While a search of the Cambridge Structural Database (version 5.29, Jan. 2008; Allen, 2002) for Ru complexes with S-bonded TMSO trans to water produced no hits, eleven examples of such DMSO complexes were found, refcodes AQAXIZ, AQAXOF, AQAXUL, BINBAC, CECSUZ, QUDRUC, TEXMOZ, TEXNEQ, TEXNIU, WOHNEM, AND WOHNIQ. Those have mean Ru—O distance 2.142 Å and mean Ru—S distance 2.256 Å. Our Ru—O distance, 2.1540 (19) Å, is near the high end of that sample, and our Ru—S distance, Ru1 S3 2.2254 (8) Å, is shorter than any in that sample.

The coordinated water molecule donates an intermolecular hydrogen bond to sulfoxide O and another to Cl, on two different molecules related by unit translation in the b direction. Thus, rings of graph set (Etter, 1990) symbol R22(9) form chains along [010], propagated by the 21 axis, as shown in Fig. 2.

Related literature top

For background literature, see: Aldinucci et al. (2007). For related structures, see: Srivastava & Fronczek (2003); Srivastava et al. (2004); Allen (2002). For hydrogen-bonding patterns, see: Etter (1990).

Experimental top

mer-RuCl3(TMSO)3 (0.166 g, 0.233 mmol) was refluxed with methyl-p-tolylsulfide (73 µl, 0.533 mmol) in absolute ethanol (15 ml) for 2 h, followed by cooling to room temperature. Upon standing for eight months, colorless needles of the title compound formed.

Refinement top

H atoms on C were placed in idealized positions with C—H distances 0.99 Å and thereafter treated as riding. Water H atoms were located in difference maps, idealized to have O–H distance 0.80 Å, and treated as riding. Uiso for H was assigned as 1.2 times Ueq of the attached atoms (1.5 for H2O). The largest negative feature in the final difference map was located 0.75 Å from the Ru position.

Computing details top

Data collection: COLLECT (Nonius, 2000); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A plot of the title compound with displacement ellipsoids drawn at the 50% level and H atoms having arbitrary radius.
[Figure 2] Fig. 2. A portion of a hydrogen-bonded chain in the [010] direction.
[Figure 3] Fig. 3. The formation of the title compound.
fac-Aquadichloridotris(tetramethylene sulfoxide-κS)ruthenium(II) top
Crystal data top
[RuCl2(C4H8OS)3(H2O)]F(000) = 1024
Mr = 502.48Dx = 1.848 Mg m−3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 6027 reflections
a = 14.302 (3) Åθ = 2.5–31.5°
b = 7.7877 (15) ŵ = 1.52 mm−1
c = 17.248 (3) ÅT = 90 K
β = 109.917 (9)°Needle, colorless
V = 1806.2 (6) Å30.22 × 0.10 × 0.05 mm
Z = 4
Data collection top
Nonius KappaCCD
diffractometer (with an Oxford Cryosystems Cryostream cooler)		5982 independent reflections
Radiation source: fine-focus sealed tube4610 reflections with I > 2σ(I)
graphiteRint = 0.045
ω and φ scansθmax = 31.5°, θmin = 2.9°
Absorption correction: multi-scan
(SCALEPACK; Otwinowski & Minor, 1997)		h = −20→21
Tmin = 0.731, Tmax = 0.928k = −11→11
25916 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)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.076H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.0256P)2 + 2.7566P]
where P = (Fo2 + 2Fc2)/3
5982 reflections(Δ/σ)max = 0.002
199 parametersΔρmax = 0.87 e Å−3
0 restraintsΔρmin = −1.12 e Å−3
Crystal data top
[RuCl2(C4H8OS)3(H2O)]V = 1806.2 (6) Å3
Mr = 502.48Z = 4
Monoclinic, P21/nMo Kα radiation
a = 14.302 (3) ŵ = 1.52 mm−1
b = 7.7877 (15) ÅT = 90 K
c = 17.248 (3) Å0.22 × 0.10 × 0.05 mm
β = 109.917 (9)°
Data collection top
Nonius KappaCCD
diffractometer (with an Oxford Cryosystems Cryostream cooler)		5982 independent reflections
Absorption correction: multi-scan
(SCALEPACK; Otwinowski & Minor, 1997)		4610 reflections with I > 2σ(I)
Tmin = 0.731, Tmax = 0.928Rint = 0.045
25916 measured reflectionsθmax = 31.5°
Refinement top
R[F2 > 2σ(F2)] = 0.037H-atom parameters constrained
wR(F2) = 0.076Δρmax = 0.87 e Å−3
S = 1.02Δρmin = −1.12 e Å−3
5982 reflectionsAbsolute structure: ?
199 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
Ru10.589322 (15)0.17421 (3)0.298795 (12)0.00590 (5)
Cl10.63294 (5)−0.00620 (8)0.41988 (4)0.01063 (12)
Cl20.59746 (5)−0.07251 (8)0.21491 (4)0.00956 (12)
S10.55748 (5)0.33080 (8)0.18270 (4)0.00718 (12)
S20.59211 (5)0.41572 (8)0.37280 (4)0.00785 (12)
S30.42982 (5)0.11754 (8)0.27675 (4)0.00811 (12)
O10.64973 (14)0.3915 (2)0.16851 (11)0.0112 (4)
O20.49707 (14)0.5110 (2)0.35546 (12)0.0125 (4)
O30.35604 (14)0.1775 (3)0.19762 (12)0.0133 (4)
O40.74739 (13)0.1973 (2)0.32611 (11)0.0094 (4)
H410.76970.10340.32540.014*
H420.77350.25810.30210.014*
C10.4799 (2)0.2324 (3)0.08568 (16)0.0117 (5)
H1A0.51960.21110.04950.014*
H1B0.45270.12160.09650.014*
C20.3955 (2)0.3583 (4)0.04466 (17)0.0142 (6)
H2A0.33530.32600.05730.017*
H2B0.37900.3561−0.01590.017*
C30.4301 (2)0.5380 (4)0.07805 (16)0.0129 (5)
H3A0.47940.58310.05450.016*
H3B0.37310.61830.06450.016*
C40.4770 (2)0.5151 (3)0.17114 (16)0.0109 (5)
H4A0.42560.49340.19640.013*
H4B0.51570.61810.19700.013*
C50.6859 (2)0.5663 (3)0.36345 (16)0.0108 (5)
H5A0.71410.52490.32180.013*
H5B0.65590.68080.34630.013*
C60.7667 (2)0.5771 (4)0.44766 (17)0.0152 (6)
H6A0.80070.68970.45480.018*
H6B0.81670.48540.45380.018*
C70.7149 (2)0.5548 (4)0.51139 (17)0.0145 (6)
H7A0.76440.53660.56710.017*
H7B0.67480.65760.51280.017*
C80.6484 (2)0.3978 (3)0.48391 (16)0.0110 (5)
H8A0.59670.39640.51010.013*
H8B0.68810.29110.49900.013*
C90.3821 (2)0.1780 (4)0.35774 (17)0.0132 (5)
H9A0.43590.17910.41210.016*
H9B0.35070.29280.34710.016*
C100.3059 (2)0.0401 (4)0.35450 (18)0.0148 (6)
H10A0.24620.05300.30460.018*
H10B0.28560.04550.40390.018*
C110.3595 (2)−0.1292 (4)0.35214 (18)0.0149 (6)
H11A0.4113−0.15160.40630.018*
H11B0.3117−0.22580.33900.018*
C120.4068 (2)−0.1113 (3)0.28551 (18)0.0119 (5)
H12A0.3614−0.15620.23230.014*
H12B0.4699−0.17640.30100.014*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ru10.00693 (9)0.00402 (9)0.00659 (9)0.00017 (7)0.00210 (7)0.00032 (7)
Cl10.0146 (3)0.0069 (3)0.0095 (3)0.0008 (2)0.0030 (2)0.0025 (2)
Cl20.0109 (3)0.0061 (3)0.0119 (3)0.0004 (2)0.0042 (2)−0.0016 (2)
S10.0081 (3)0.0058 (3)0.0071 (3)−0.0008 (2)0.0020 (2)0.0000 (2)
S20.0099 (3)0.0056 (3)0.0077 (3)0.0003 (2)0.0026 (2)0.0005 (2)
S30.0086 (3)0.0069 (3)0.0087 (3)0.0000 (2)0.0028 (2)0.0008 (2)
O10.0116 (9)0.0101 (9)0.0133 (9)−0.0033 (7)0.0060 (8)0.0002 (7)
O20.0117 (9)0.0097 (9)0.0171 (10)0.0036 (7)0.0060 (8)0.0003 (8)
O30.0093 (9)0.0158 (9)0.0127 (9)−0.0009 (8)0.0009 (7)0.0055 (8)
O40.0108 (9)0.0049 (8)0.0132 (9)−0.0012 (7)0.0049 (7)−0.0001 (7)
C10.0127 (13)0.0110 (12)0.0102 (12)−0.0029 (10)0.0024 (10)−0.0015 (10)
C20.0131 (13)0.0156 (14)0.0110 (13)−0.0005 (10)0.0005 (10)0.0025 (10)
C30.0146 (13)0.0125 (12)0.0113 (13)0.0028 (11)0.0038 (10)0.0071 (10)
C40.0115 (12)0.0086 (12)0.0121 (13)0.0040 (10)0.0034 (10)0.0024 (10)
C50.0143 (13)0.0061 (11)0.0123 (12)−0.0014 (10)0.0052 (10)0.0009 (10)
C60.0160 (14)0.0133 (13)0.0135 (13)−0.0039 (11)0.0014 (11)−0.0030 (11)
C70.0197 (15)0.0130 (13)0.0083 (12)−0.0027 (11)0.0014 (11)−0.0033 (10)
C80.0161 (13)0.0092 (12)0.0080 (12)0.0007 (10)0.0044 (10)0.0006 (10)
C90.0135 (13)0.0131 (12)0.0159 (13)−0.0003 (11)0.0086 (11)−0.0031 (11)
C100.0138 (13)0.0178 (14)0.0156 (14)−0.0047 (11)0.0087 (11)0.0012 (11)
C110.0180 (14)0.0121 (12)0.0156 (14)−0.0055 (11)0.0068 (11)0.0024 (11)
C120.0107 (12)0.0063 (11)0.0199 (14)−0.0030 (10)0.0067 (11)0.0009 (10)
Geometric parameters (Å, °) top
Ru1—O42.1540 (19)C3—H3B0.9900
Ru1—S32.2254 (8)C4—H4A0.9900
Ru1—S12.2546 (7)C4—H4B0.9900
Ru1—S22.2657 (7)C5—C61.519 (4)
Ru1—Cl12.4161 (7)C5—H5A0.9900
Ru1—Cl22.4317 (7)C5—H5B0.9900
S1—O11.498 (2)C6—C71.531 (4)
S1—C41.807 (3)C6—H6A0.9900
S1—C11.831 (3)C6—H6B0.9900
S2—O21.487 (2)C7—C81.521 (4)
S2—C81.814 (3)C7—H7A0.9900
S2—C51.830 (3)C7—H7B0.9900
S3—O31.487 (2)C8—H8A0.9900
S3—C91.813 (3)C8—H8B0.9900
S3—C121.828 (3)C9—C101.517 (4)
O4—H410.8000C9—H9A0.9900
O4—H420.8000C9—H9B0.9900
C1—C21.529 (4)C10—C111.532 (4)
C1—H1A0.9900C10—H10A0.9900
C1—H1B0.9900C10—H10B0.9900
C2—C31.530 (4)C11—C121.525 (4)
C2—H2A0.9900C11—H11A0.9900
C2—H2B0.9900C11—H11B0.9900
C3—C41.525 (4)C12—H12A0.9900
C3—H3A0.9900C12—H12B0.9900
O4—Ru1—S3172.92 (5)C3—C4—S1104.15 (18)
O4—Ru1—S191.63 (5)C3—C4—H4A110.9
S3—Ru1—S194.04 (3)S1—C4—H4A110.9
O4—Ru1—S289.52 (5)C3—C4—H4B110.9
S3—Ru1—S294.66 (3)S1—C4—H4B110.9
S1—Ru1—S290.62 (3)H4A—C4—H4B108.9
O4—Ru1—Cl185.23 (5)C6—C5—S2107.04 (18)
S3—Ru1—Cl188.86 (3)C6—C5—H5A110.3
S1—Ru1—Cl1175.45 (2)S2—C5—H5A110.3
S2—Ru1—Cl192.63 (3)C6—C5—H5B110.3
O4—Ru1—Cl286.37 (5)S2—C5—H5B110.3
S3—Ru1—Cl289.75 (2)H5A—C5—H5B108.6
S1—Ru1—Cl286.28 (3)C5—C6—C7106.5 (2)
S2—Ru1—Cl2174.78 (2)C5—C6—H6A110.4
Cl1—Ru1—Cl290.24 (3)C7—C6—H6A110.4
O1—S1—C4107.13 (12)C5—C6—H6B110.4
O1—S1—C1106.01 (12)C7—C6—H6B110.4
C4—S1—C193.82 (12)H6A—C6—H6B108.6
O1—S1—Ru1113.14 (8)C8—C7—C6105.8 (2)
C4—S1—Ru1117.12 (9)C8—C7—H7A110.6
C1—S1—Ru1117.49 (9)C6—C7—H7A110.6
O2—S2—C8107.31 (12)C8—C7—H7B110.6
O2—S2—C5108.06 (12)C6—C7—H7B110.6
C8—S2—C593.85 (12)H7A—C7—H7B108.7
O2—S2—Ru1117.48 (8)C7—C8—S2105.84 (18)
C8—S2—Ru1116.59 (9)C7—C8—H8A110.6
C5—S2—Ru1110.80 (9)S2—C8—H8A110.6
O3—S3—C9106.85 (13)C7—C8—H8B110.6
O3—S3—C12106.88 (12)S2—C8—H8B110.6
C9—S3—C1293.64 (13)H8A—C8—H8B108.7
O3—S3—Ru1117.39 (8)C10—C9—S3104.01 (19)
C9—S3—Ru1116.73 (10)C10—C9—H9A111.0
C12—S3—Ru1112.49 (9)S3—C9—H9A111.0
Ru1—O4—H41108.3C10—C9—H9B111.0
Ru1—O4—H42125.1S3—C9—H9B111.0
H41—O4—H42105.9H9A—C9—H9B109.0
C2—C1—S1106.96 (18)C9—C10—C11104.5 (2)
C2—C1—H1A110.3C9—C10—H10A110.9
S1—C1—H1A110.3C11—C10—H10A110.9
C2—C1—H1B110.3C9—C10—H10B110.9
S1—C1—H1B110.3C11—C10—H10B110.9
H1A—C1—H1B108.6H10A—C10—H10B108.9
C1—C2—C3108.0 (2)C12—C11—C10107.2 (2)
C1—C2—H2A110.1C12—C11—H11A110.3
C3—C2—H2A110.1C10—C11—H11A110.3
C1—C2—H2B110.1C12—C11—H11B110.3
C3—C2—H2B110.1C10—C11—H11B110.3
H2A—C2—H2B108.4H11A—C11—H11B108.5
C4—C3—C2105.0 (2)C11—C12—S3106.86 (19)
C4—C3—H3A110.7C11—C12—H12A110.4
C2—C3—H3A110.7S3—C12—H12A110.4
C4—C3—H3B110.7C11—C12—H12B110.4
C2—C3—H3B110.7S3—C12—H12B110.4
H3A—C3—H3B108.8H12A—C12—H12B108.6
O4—Ru1—S1—O1−0.88 (10)S1—Ru1—S3—C12129.51 (10)
S3—Ru1—S1—O1−176.63 (9)S2—Ru1—S3—C12−139.54 (10)
S2—Ru1—S1—O188.66 (9)Cl1—Ru1—S3—C12−46.99 (10)
Cl2—Ru1—S1—O1−87.14 (9)Cl2—Ru1—S3—C1243.26 (10)
O4—Ru1—S1—C4−126.24 (11)O1—S1—C1—C2−105.28 (19)
S3—Ru1—S1—C458.01 (11)C4—S1—C1—C23.8 (2)
S2—Ru1—S1—C4−36.70 (11)Ru1—S1—C1—C2127.11 (16)
Cl2—Ru1—S1—C4147.50 (11)S1—C1—C2—C323.5 (3)
O4—Ru1—S1—C1123.22 (11)C1—C2—C3—C4−46.0 (3)
S3—Ru1—S1—C1−52.53 (11)C2—C3—C4—S147.2 (2)
S2—Ru1—S1—C1−147.24 (10)O1—S1—C4—C378.5 (2)
Cl2—Ru1—S1—C136.96 (10)C1—S1—C4—C3−29.5 (2)
O4—Ru1—S2—O2158.55 (10)Ru1—S1—C4—C3−153.17 (15)
S3—Ru1—S2—O2−27.18 (9)O2—S2—C5—C6117.47 (19)
S1—Ru1—S2—O266.92 (9)C8—S2—C5—C67.9 (2)
Cl1—Ru1—S2—O2−116.25 (9)Ru1—S2—C5—C6−112.51 (17)
O4—Ru1—S2—C8−72.00 (12)S2—C5—C6—C7−33.1 (3)
S3—Ru1—S2—C8102.28 (11)C5—C6—C7—C848.6 (3)
S1—Ru1—S2—C8−163.62 (11)C6—C7—C8—S2−41.6 (3)
Cl1—Ru1—S2—C813.20 (11)O2—S2—C8—C7−90.7 (2)
O4—Ru1—S2—C533.70 (11)C5—S2—C8—C719.5 (2)
S3—Ru1—S2—C5−152.03 (9)Ru1—S2—C8—C7135.11 (16)
S1—Ru1—S2—C5−57.93 (10)O3—S3—C9—C1080.2 (2)
Cl1—Ru1—S2—C5118.90 (10)C12—S3—C9—C10−28.6 (2)
S1—Ru1—S3—O34.88 (10)Ru1—S3—C9—C10−146.10 (16)
S2—Ru1—S3—O395.83 (10)S3—C9—C10—C1148.1 (2)
Cl1—Ru1—S3—O3−171.62 (10)C9—C10—C11—C12−48.9 (3)
Cl2—Ru1—S3—O3−81.37 (10)C10—C11—C12—S326.8 (3)
S1—Ru1—S3—C9−123.92 (11)O3—S3—C12—C11−107.7 (2)
S2—Ru1—S3—C9−32.96 (11)C9—S3—C12—C111.2 (2)
Cl1—Ru1—S3—C959.59 (11)Ru1—S3—C12—C11122.10 (17)
Cl2—Ru1—S3—C9149.83 (11)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H41···O1i0.801.992.785 (3)169
O4—H42···Cl2ii0.802.373.116 (2)156
Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) −x+3/2, y+1/2, −z+1/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H41···O1i0.801.992.785 (3)169
O4—H42···Cl2ii0.802.373.116 (2)156
Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) −x+3/2, y+1/2, −z+1/2.
Acknowledgements top

Financial support provided by the Research Corporation (Cottrell College Science Award, #CC 6234 to RSS) and the BoR, Louisiana, is greatly appreciated. The purchase of the diffractometer was made possible by grant No. LEQSF (1999–2000)-ENH-TR-13, administered by the Louisiana Board of Regents.

references
References top

Aldinucci, D., Lorenzon, D., Stefani, L., Giovagnini, L., Colombatti, A. & Fregona, D. (2007). Anti-Cancer Drugs, 18, 323–332.

Allen, F. H. (2002). Acta Cryst. B58, 380–388.

Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119.

Etter, M. C. (1990). Acc. Chem. Res. 23, 120–126.

Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.

Nonius (2000). COLLECT. Nonius BV, Delft, The Netherlands.

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.

Srivastava, R. S. & Fronczek, F. R. (2003). Inorg. Chim. Acta, 355, 354–360.

Srivastava, R. S., Fronczek, F. R. & Romero, L. M. (2004). Inorg. Chim. Acta, 357, 2410–2414.