supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportcited insimilar papers buy article online

Acta Cryst. (2007). E63, m1786-m1787    [ doi:10.1107/S160053680702586X ]

Bis(2-amino-6-methylpyridinium) di-[mu]-chlorido-[mu]-oxido-bis[dichloridoantimonate(III)]

W.-J. Feng, H.-B. Wang, X.-J. Ma, H.-Y. Li and Z.-M. Jin

Abstract top

The title compound, (C6H9N2)2[Sb2Cl6O], consists of one triple-bridged [Sb2Cl6O]2- anion and two 2-amino-6-methylpyridinium cations that undergo aminium-iminium tautomerism. The counter-ion pair are linked together by N-H...O and N-H...Cl hydrogen bonds.

Comment top

There are numerous examples of 2-amino-substituted pyridine compounds reported previously (Navarro Ranninger et al., 1985; Krizanovic et al., 1993; Luque et al., 1997; Qin et al., 1999; Yip et al., 1999; Lah et al., 2002; Ren et al., 2002; Rivas et al., 2003; Jin et al., 2000, 2001, 2002, 2005; Albrecht et al., 2003). Among them, the tautomerism phenominon (Scheme 1) of 2-amino-X-methylpyridine [2AXMP; X indicates the methyl position] has been proved by X-ray diffraction, such as 2 A6MP-hydrochloric acid (2/2; Jin et al., 2005) and 2 A6MP-neoabietic acid (1/1; Jin et al., 2000). All the above studies provide important references to futher research into 2-aminopyridines. Now, the title compound, (I), has been sythesized, as a continue part of research.

As shown in Fig. 1, there are two crystallographically independent 2-amino-6-methylpyridinium (HAMP) cations and a (Sb2Cl6O)2− anion in the formula unit. The anion is linked to one HAMP (N1/N2/C1/C6) by N1—H1N···O1 and N2—H2A···Cl4 hydrogen bonds, and to the other HAMP(N3/N4/C7/C12) by N3—H3N···Cl6 hydrogen bond.

In the structure, two 2-amino-6-methylpyridine molecules are protonated, and show aminium-iminium tautomerism phenominon (Inuzuka & Fujimoto, 1986 and 1990). Features of the iminium tautomer are most clearly observed in (I), suggesting that the imime tautomer play a important role in the structure. In cation HAMP (N1/N2/C1/C6), the N2—C1 bond [1.329 (8) Å] is a little but significantly shorter than the N1—C1 [1.353 (8) Å] and N1—C5 [1.353 (8) Å] bonds, coincident with the iminium tautomer (Table 1). Moreover, the existence of the iminium tautomer is testified by the fact that the C1—C2 [1.389 (9) Å] and C3—C4 [1.387 (10) Å] bonds are longer than the C2—C3 [1.343 (9) Å] and C4—C5 [1.350 (9) Å] bonds. Similar features are provided with HAMP (N3/N4/C7/C12). In the HAMP (N3/N4/C7/C12), the N4 and three H atoms of N3 and N4 are on the same plane with the matrix heterocycle. But, there is a slight difference in the cation HAMP (N1/N2/C1/C6). H2A of N2 deviates from the matrix plane at a distance of 0.2507 (8) Å, due to N2—H2A···Cl4 hydrogen bond (Fig. 1).

The structure of the (Sb2Cl6O)2− anion resembles a anionic antimony(III) oxide chloride reported previously (Hall & Sowerby, 1979). It has a discrete dimeric structure resulting from the sharing of a common face between two pseudo-octahedral units. The triple bridge involves one oxygen (O1) and two chlorine atoms (Cl3 and Cl6). The structure is based on two SbOCl4 pseudo-octahedral units. The lone pair of electrons of Sb in each case occupies the sixth octahedral posotion which is trans to the bridging oxygen atom. Bonds to terminal chlorine atoms are of normal length and are substantially shorter than those involving in bridging (Table. 1). Bridging is asymmmetrical at Cl3 but both Cl6 and O1 form symmetrical bridges. The distance between Sb1 and Sb2 is of 3.530 (8) Å, a value well within the sum of van der Waals' radius (4.4 Å).

In the structure, the Sb2Cl6O entities link to their neighbouring ones through coordinated bonds of Sb1—Cl5 (−x + 1/2, y + 1/2, −z + 1/2) [3.530 (8) Å] in chains (Fig. 2). The chains link to their antiparallel neighbouring ones by Sb2—Cl3 (−x, −y + 2, −z) coordinated bonds [3.481 (8) Å]. Every two corresponding Sb2Cl6O entities in the two antiparallel neighbouring chains submit centrosymmetrically. The whole crystal structure is formed by extensive network of moderate intermolecular hydrogen bonds of N4—H4A···Cl6, N2—H2B···Cl3 (−x + 1, −y + 2, −z), N4—H4B···Cl2 (−x + 1, −y + 2, −z) and N4—H4b···Cl1 (−x + 1, −y + 2, −z), including the above three strong intromolecular hydrogen bonds and coordinated Sb—Cl bonds (Fig. 3).

Related literature top

For related literature, see: Albrecht et al. (2003); Jin et al. (2001, 2002, 2000, 2005); Krizanovic et al. (1993); Lah et al. (2002); Luque et al. (1997); Hall & Sowerby (1979); Navarro et al. (1985); Qin et al. (1999); Ren et al. (2002); Rivas et al. (2003); Yip et al. (1999); Inuzuka & Fujimoto (1986, 1990).

Experimental top

The preparation of the single-crystal of (I): dissolving 1.5 g antimony trichloride in 10 ml absolute acetone to form a solution, then adding 1 ml hydrochloride acid and 2 ml 2-amino-6-methylpyridine to the solution. Keeping stir and heating, until it became a clear solution, then the reaction system was cooled slowly to room temperature. Crystals of (I) were formed by gradual evaporation of the acetone over a period of three days at 300 K. Analysis calculated for Sb2Cl6O(C6H9N2)2: C 20.33, H 2.42, N 7.90%. Found: C 20.28, H 2.45, N 7.97%.

Refinement top

H atoms attaching to N atoms were deduced from difference Fourier maps, and incorporated in refinement freely. Others were placed in calculated positions and allowed to ride on their parent atoms at distances of 0.93Å for aromatic group and 0.96Å for methyl, with Uiso(H) = 1.2–1.5 Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), 30% probability displacement ellipsoids is shown. Hydrogn bonds are illustrated as dashed lines.
[Figure 2] Fig. 2. The packing diagram of Sb2Cl6O anions viewed down along the c axis.
[Figure 3] Fig. 3. The packing diagram of (I) viewed down along the a axis. Hydrogen bonds are illustrated by dashed lines.
[Figure 4] Fig. 4. The tautomerism in the 2-amino-6-methylpyridinium cation.
Bis(2-amino-6-methylpyridinium) di-µ-chlorido-µ-oxido-bis[dichloridoantimonate(III)] top
Crystal data top
(C6H9N2)2[Sb2Cl6O]F000 = 1320.0
Mr = 690.52Dx = 1.978 Mg m−3
Monoclinic, P21/nMo Kα radiation
λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 5386 reflections
a = 10.0746 (10) Åθ = 2.2–24.9º
b = 15.1972 (16) ŵ = 3.03 mm−1
c = 15.4631 (14) ÅT = 298 (2) K
β = 101.597 (6)ºBlock, colourless
V = 2319.2 (4) Å30.30 × 0.30 × 0.30 mm
Z = 4
Data collection top
Bruker APEX area-detector
diffractometer		4154 independent reflections
Radiation source: fine-focus sealed tube3876 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.026
T = 298(2) Kθmax = 25.2º
φ and ω scansθmin = 1.9º
Absorption correction: multi-scan
(SADABS; Bruker, 2000)		h = −12→8
Tmin = 0.419, Tmax = 0.419k = −18→18
12055 measured reflectionsl = −17→18
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.048H atoms treated by a mixture of
independent and constrained refinement
wR(F2) = 0.095  w = 1/[σ2(Fo2) + (0.03P)2 + 5.7532P]
where P = (Fo2 + 2Fc2)/3
S = 1.24(Δ/σ)max < 0.001
4137 reflectionsΔρmax = 0.86 e Å−3
250 parametersΔρmin = −0.50 e Å−3
8 restraintsExtinction correction: none
Primary atom site location: structure-invariant direct methods
Crystal data top
(C6H9N2)2[Sb2Cl6O]V = 2319.2 (4) Å3
Mr = 690.52Z = 4
Monoclinic, P21/nMo Kα
a = 10.0746 (10) ŵ = 3.03 mm−1
b = 15.1972 (16) ÅT = 298 (2) K
c = 15.4631 (14) Å0.30 × 0.30 × 0.30 mm
β = 101.597 (6)º
Data collection top
Bruker APEX area-detector
diffractometer		4154 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2000)		3876 reflections with I > 2σ(I)
Tmin = 0.419, Tmax = 0.419Rint = 0.026
12055 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0488 restraints
wR(F2) = 0.095H atoms treated by a mixture of
independent and constrained refinement
S = 1.24Δρmax = 0.86 e Å−3
4137 reflectionsΔρmin = −0.50 e Å−3
250 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
xyzUiso*/Ueq
Sb10.31762 (4)0.91360 (3)0.22353 (3)0.03853 (13)
Sb20.11872 (4)1.06417 (3)0.10221 (3)0.03951 (13)
Cl50.1190 (2)1.20568 (13)0.17485 (18)0.0883 (7)
Cl40.2383 (2)1.12353 (18)−0.00553 (15)0.0899 (8)
Cl60.0414 (2)0.96108 (14)0.24743 (13)0.0676 (5)
Cl20.52714 (18)0.90105 (13)0.17034 (12)0.0612 (5)
Cl30.17591 (17)0.88522 (11)0.04966 (10)0.0502 (4)
Cl10.44172 (18)0.96909 (13)0.36800 (11)0.0607 (5)
O10.2946 (4)1.0349 (2)0.1794 (3)0.0369 (9)
N10.5322 (5)1.1474 (3)0.1987 (4)0.0428 (12)
N3−0.0424 (6)1.0719 (4)0.3982 (4)0.0530 (14)
N20.5688 (7)1.0906 (5)0.0664 (4)0.0653 (18)
C10.6139 (6)1.1355 (4)0.1402 (4)0.0440 (15)
C50.5662 (7)1.1973 (4)0.2724 (4)0.0476 (16)
N4−0.2302 (7)0.9894 (6)0.3401 (5)0.079 (2)
C7−0.1687 (7)1.0454 (5)0.4007 (5)0.0534 (17)
C110.0303 (8)1.1289 (5)0.4562 (5)0.063 (2)
C60.4618 (8)1.2076 (5)0.3281 (5)0.065 (2)
H6A0.38291.17370.30320.098*
H6B0.43741.26850.33010.098*
H6C0.49811.18710.38680.098*
C20.7428 (7)1.1720 (5)0.1600 (5)0.0546 (17)
H20.80371.16300.12300.065*
C8−0.2278 (8)1.0787 (5)0.4684 (5)0.062 (2)
H8−0.31491.06190.47290.075*
C30.7781 (8)1.2206 (5)0.2336 (5)0.067 (2)
H30.86471.24460.24730.081*
C40.6893 (8)1.2359 (5)0.2898 (5)0.067 (2)
H40.71421.27230.33880.080*
C9−0.1572 (9)1.1350 (6)0.5269 (5)0.072 (2)
H9−0.19671.15760.57160.086*
C10−0.0270 (10)1.1603 (5)0.5221 (6)0.079 (3)
H100.02111.19850.56400.094*
C120.1683 (9)1.1504 (6)0.4414 (7)0.090 (3)
H12A0.18401.11960.39020.135*
H12B0.23471.13290.49200.135*
H12C0.17501.21260.43230.135*
H1N0.458 (3)1.121 (3)0.191 (3)0.024 (14)*
H4A−0.195 (6)0.970 (5)0.299 (4)0.08 (3)*
H3N−0.008 (6)1.046 (4)0.359 (3)0.046 (19)*
H2A0.487 (3)1.076 (4)0.052 (4)0.06 (2)*
H2B0.616 (5)1.085 (5)0.028 (3)0.07 (3)*
H4B−0.312 (3)0.975 (5)0.337 (4)0.08 (3)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sb10.0418 (2)0.0367 (2)0.0381 (2)0.00126 (17)0.01051 (18)0.00583 (17)
Sb20.0305 (2)0.0408 (2)0.0460 (3)0.00311 (17)0.00485 (17)−0.00017 (18)
Cl50.0748 (14)0.0531 (11)0.128 (2)0.0129 (10)−0.0002 (13)−0.0301 (12)
Cl40.0681 (13)0.1222 (19)0.0832 (15)0.0132 (13)0.0242 (11)0.0587 (14)
Cl60.0643 (12)0.0844 (13)0.0647 (12)−0.0134 (10)0.0381 (10)−0.0141 (10)
Cl20.0497 (10)0.0758 (12)0.0620 (11)0.0222 (9)0.0209 (8)0.0095 (9)
Cl30.0538 (10)0.0551 (9)0.0421 (9)−0.0001 (8)0.0110 (7)−0.0087 (7)
Cl10.0562 (11)0.0833 (13)0.0413 (9)−0.0084 (9)0.0067 (8)−0.0003 (9)
O10.031 (2)0.033 (2)0.044 (2)−0.0005 (17)0.0028 (17)0.0111 (18)
N10.036 (3)0.042 (3)0.051 (3)−0.005 (2)0.012 (3)−0.003 (3)
N30.052 (4)0.058 (4)0.052 (4)0.000 (3)0.019 (3)−0.010 (3)
N20.056 (4)0.085 (5)0.058 (4)−0.020 (4)0.018 (3)−0.024 (4)
C10.046 (4)0.040 (3)0.047 (4)−0.005 (3)0.012 (3)−0.006 (3)
C50.052 (4)0.042 (3)0.050 (4)0.002 (3)0.014 (3)−0.008 (3)
N40.051 (4)0.118 (6)0.071 (5)−0.021 (4)0.019 (4)−0.035 (5)
C70.045 (4)0.067 (5)0.050 (4)0.003 (3)0.015 (3)0.002 (4)
C110.076 (5)0.047 (4)0.068 (5)−0.008 (4)0.020 (4)0.003 (4)
C60.069 (5)0.070 (5)0.063 (5)0.008 (4)0.029 (4)−0.018 (4)
C20.043 (4)0.069 (5)0.055 (4)−0.010 (3)0.016 (3)−0.013 (4)
C80.061 (5)0.071 (5)0.060 (5)0.009 (4)0.022 (4)0.001 (4)
C30.053 (4)0.084 (6)0.068 (5)−0.027 (4)0.018 (4)−0.018 (4)
C40.070 (5)0.071 (5)0.059 (5)−0.023 (4)0.013 (4)−0.026 (4)
C90.093 (6)0.076 (6)0.058 (5)0.013 (5)0.041 (5)−0.002 (4)
C100.107 (7)0.063 (5)0.071 (6)−0.013 (5)0.031 (5)−0.022 (4)
C120.087 (6)0.077 (6)0.113 (8)−0.032 (5)0.037 (6)−0.016 (5)
Geometric parameters (Å, °) top
Sb1—O11.964 (4)N4—H4A0.85 (2)
Sb1—Cl22.4221 (18)N4—H4B0.84 (2)
Sb1—Cl12.4783 (18)C7—C81.399 (10)
Sb1—Cl32.8123 (16)C11—C101.355 (10)
Sb2—O11.977 (4)C11—C121.490 (11)
Sb2—Cl42.418 (2)C6—H6A0.9600
Sb2—Cl52.426 (2)C6—H6B0.9600
Sb2—Sb13.355 (2)C6—H6C0.9600
N1—C11.353 (8)C2—C31.343 (9)
N1—C51.353 (8)C2—H20.9300
N1—H1N0.836 (19)C8—C91.340 (11)
N3—C71.343 (9)C8—H80.9300
N3—C111.351 (9)C3—C41.387 (10)
N3—H3N0.85 (2)C3—H30.9300
N2—C11.329 (8)C4—H40.9300
N2—H2A0.835 (19)C9—C101.383 (12)
N2—H2B0.837 (19)C9—H90.9300
C1—C21.389 (9)C10—H100.9300
C5—C41.350 (9)C12—H12A0.9600
C5—C61.496 (9)C12—H12B0.9600
N4—C71.323 (9)C12—H12C0.9600
O1—Sb1—Cl290.35 (12)N3—C11—C12115.9 (7)
O1—Sb1—Cl189.82 (12)C10—C11—C12126.2 (8)
Cl2—Sb1—Cl190.96 (7)C5—C6—H6A109.5
O1—Sb1—Cl379.04 (12)C5—C6—H6B109.5
Cl2—Sb1—Cl388.44 (6)H6A—C6—H6B109.5
Cl1—Sb1—Cl3168.84 (6)C5—C6—H6C109.5
O1—Sb2—Cl489.39 (12)H6A—C6—H6C109.5
O1—Sb2—Cl590.13 (12)H6B—C6—H6C109.5
Cl4—Sb2—Cl591.95 (10)C3—C2—C1118.9 (6)
Sb1—O1—Sb2116.72 (18)C3—C2—H2120.5
C1—N1—C5123.6 (5)C1—C2—H2120.5
C1—N1—H1N119 (4)C9—C8—C7119.2 (8)
C5—N1—H1N117 (4)C9—C8—H8120.4
C7—N3—C11124.3 (6)C7—C8—H8120.4
C7—N3—H3N114 (4)C2—C3—C4122.0 (7)
C11—N3—H3N122 (5)C2—C3—H3119.0
C1—N2—H2A121 (4)C4—C3—H3119.0
C1—N2—H2B121 (4)C5—C4—C3119.0 (7)
H2A—N2—H2B117 (3)C5—C4—H4120.5
N2—C1—N1119.6 (6)C3—C4—H4120.5
N2—C1—C2122.6 (6)C8—C9—C10121.4 (7)
N1—C1—C2117.8 (6)C8—C9—H9119.3
C4—C5—N1118.6 (6)C10—C9—H9119.3
C4—C5—C6124.3 (6)C11—C10—C9119.6 (8)
N1—C5—C6117.1 (6)C11—C10—H10120.2
C7—N4—H4A124 (4)C9—C10—H10120.2
C7—N4—H4B121 (4)C11—C12—H12A109.5
H4A—N4—H4B115 (3)C11—C12—H12B109.5
N4—C7—N3118.9 (7)H12A—C12—H12B109.5
N4—C7—C8123.6 (7)C11—C12—H12C109.5
N3—C7—C8117.5 (7)H12A—C12—H12C109.5
N3—C11—C10118.0 (7)H12B—C12—H12C109.5
Cl2—Sb1—O1—Sb2127.71 (19)N2—C1—C2—C3176.4 (8)
Cl1—Sb1—O1—Sb2−141.33 (19)N1—C1—C2—C3−3.1 (10)
Cl3—Sb1—O1—Sb239.36 (17)N4—C7—C8—C9179.8 (8)
Cl4—Sb2—O1—Sb1−128.3 (2)N3—C7—C8—C90.3 (11)
Cl5—Sb2—O1—Sb1139.7 (2)C1—C2—C3—C4−0.6 (13)
C5—N1—C1—N2−175.3 (7)N1—C5—C4—C3−2.4 (11)
C5—N1—C1—C24.3 (9)C6—C5—C4—C3179.3 (7)
C1—N1—C5—C4−1.5 (10)C2—C3—C4—C53.4 (13)
C1—N1—C5—C6177.0 (6)C7—C8—C9—C10−0.6 (12)
C11—N3—C7—N4179.8 (8)N3—C11—C10—C9−1.5 (12)
C11—N3—C7—C8−0.6 (11)C12—C11—C10—C9179.3 (8)
C7—N3—C11—C101.2 (11)C8—C9—C10—C111.3 (14)
C7—N3—C11—C12−179.5 (7)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···O10.84 (2)2.08 (3)2.907 (8)169 (3)
N2—H2A···Cl40.84 (2)2.59 (6)3.329 (8)148 (3)
N2—H2B···Cl3i0.84 (2)2.67 (6)3.439 (8)157 (3)
N3—H3N···Cl60.85 (2)2.30 (5)3.127 (8)167 (4)
N4—H4A···Cl60.85 (2)2.66 (3)3.362 (8)141 (5)
N4—H4B···Cl1ii0.84 (2)2.62 (3)3.432 (8)162 (5)
Symmetry codes: (i) −x+1, −y+2, −z; (ii) x−1, y, z.
Table 1
Selected geometric parameters (Å, °) top
Sb1—O11.964 (4)Sb2—O11.977 (4)
Sb1—Cl22.4221 (18)Sb2—Cl42.418 (2)
Sb1—Cl12.4783 (18)Sb2—Cl52.426 (2)
Sb1—Cl32.8123 (16)Sb2—Sb13.355 (2)
O1—Sb1—Cl290.35 (12)Cl1—Sb1—Cl3168.84 (6)
O1—Sb1—Cl189.82 (12)O1—Sb2—Cl489.39 (12)
Cl2—Sb1—Cl190.96 (7)O1—Sb2—Cl590.13 (12)
O1—Sb1—Cl379.04 (12)Cl4—Sb2—Cl591.95 (10)
Cl2—Sb1—Cl388.44 (6)Sb1—O1—Sb2116.72 (18)
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···O10.84 (2)2.08 (3)2.907 (8)169 (3)
N2—H2A···Cl40.84 (2)2.59 (6)3.329 (8)148 (3)
N2—H2B···Cl3i0.84 (2)2.67 (6)3.439 (8)157 (3)
N3—H3N···Cl60.85 (2)2.30 (5)3.127 (8)167 (4)
N4—H4A···Cl60.85 (2)2.66 (3)3.362 (8)141 (5)
N4—H4B···Cl1ii0.84 (2)2.62 (3)3.432 (8)162 (5)
Symmetry codes: (i) −x+1, −y+2, −z; (ii) x−1, y, z.
references
References top

Albrecht, A. S., Landee, C. P. & Turnbull, M. M. (2003). J. Chem. Crystallogr. 33, 269–276.

Bruker (2000). SADABS (Version 2.05), SMART (Version 5.618), SAINT (Version 6.02a) and SHELXTL (Version 6.10). Bruker AXS Inc., Madison, Wisconsin, USA.

Hall, M. & Sowerby, D. B. (1979). J. Chem. Soc. Chem. Commun. pp. 1134–1135.

Inuzuka, K. & Fujimoto, A. (1986). Spectrochim. Acta Part A, 42, 929–934.

Inuzuka, K. & Fujimoto, A. (1990). Bull. Chem. Soc. Jpn, 63, 971–975.

Jin, Z. M., Pan, Y. J., Hu, M. L. & Shen, L. (2001). J. Chem. Crystallogr. 31, 191–195.

Jin, Z. M., Pan, Y. J., Hu, M. L. & Zhou, J. W. (2002). J. Mol. Struct. 609, 83–87.

Jin, Z. M., Pan, Y. J., Liu, J. G. & Xu, D. J. (2000). J. Chem. Crystallogr. 30, 195–198.

Jin, Z.-M., Shun, N., Lü, Y.-P., Hu, M.-L. & Shen, L. (2005). Acta Cryst. C61, m43–m45.

Krizanovic, O., Sabat, M., Beyerle-Pfnur, R. & Lippert, B. (1993). J. Am. Chem. Soc. 115, 5538–?. [Please give final page number]

Lah, N., Segedin, P. & Leban, I. (2002). Struct. Chem. 13, 357–360.

Luque, A., Sertucha, J., Lezama, L., Rojo, T. & Roman, P. (1997). J. Chem. Soc. Dalton Trans. pp. 847–854.

Navarro Ranninger, M.-C., Martínez-Carrera, S. & García-Blanco, S. (1985). Acta Cryst. C41, 21–22.

Qin, J. G., Su, N. B., Dai, C. Y., Yang, C. L., Liu, D. Y., Day, M. W., Wu, B. C. & Chen, C. T. (1999). Polyhedron, 18, 3461–3464.

Ren, P., Su, N. B., Qin, J. G., Day, M. W. & Chen, C. T. (2002). Jiegou Huaxue (Chin. J. Struct. Chem.), 21, 38–41. (In Chinese?)

Rivas, J. C. M., Salvagni, E., Rosales, R. T. M. & Parsons, S. (2003). Dalton Trans. pp. 3339–3349.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.

Yip, J. H. K. M., Feng, R. & Vittal, J. J. (1999). Inorg. Chem. 38, 3586–3589.