Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104017378/ob1187sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270104017378/ob1187Isup2.hkl |
CCDC reference: 251298
A mixture of 8-hydroxyquinoline (0.5 mmol), pyridine-2,6-dicarboxylic acid (0.5 mmol), CdCl2·2H2O (0.5 mmol), dry ethanol (25 ml) and H2SO4 (98%, 1 ml) was stirred at ca 333 K for 2 h and then filtered. The filtrate was kept at room temperature for several days to give pale-red crystals of the title compound (yield 8%).
H atoms bonded to C atoms were located geometrically, with C—H distances of 0.93 Å, and treated as riding atoms, with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C). H atoms bonded to O atoms were located from difference density maps and refined with O—H bond distances restrained to 0.81–0.84 Å and with Uiso(H) = 1.5Ueq(O). The highest residual peak is 1.02 Å from atom C8, and the deepest hole is 0.99 Å from atom Cd1.
Data collection: SMART (Siemens, 1996); cell refinement: SMART and SAINT (Siemens, 1994); data reduction: XPREP in SHELXTL (Siemens, 1994); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
[Cd2(C9H8NO4)2Cl2(H2O)4]·2H2O | Z = 1 |
Mr = 792.12 | F(000) = 392 |
Triclinic, P1 | Dx = 1.948 Mg m−3 |
a = 6.8414 (6) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 10.7408 (9) Å | Cell parameters from 2630 reflections |
c = 10.7597 (9) Å | θ = 2.1–25.1° |
α = 64.042 (2)° | µ = 1.84 mm−1 |
β = 77.298 (2)° | T = 293 K |
γ = 72.810 (2)° | Prism, pale red |
V = 675.35 (10) Å3 | 0.60 × 0.28 × 0.26 mm |
Siemens SMART CCD area-detector diffractometer | 2371 independent reflections |
Radiation source: fine-focus sealed tube | 2167 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
ϕ and ω scans | θmax = 25.1°, θmin = 2.1° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −6→8 |
Tmin = 0.416, Tmax = 0.620 | k = −12→12 |
3540 measured reflections | l = −11→12 |
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)] = 0.033 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.089 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0526P)2 + 0.9504P] where P = (Fo2 + 2Fc2)/3 |
2371 reflections | (Δ/σ)max = 0.005 |
190 parameters | Δρmax = 1.04 e Å−3 |
8 restraints | Δρmin = −0.51 e Å−3 |
[Cd2(C9H8NO4)2Cl2(H2O)4]·2H2O | γ = 72.810 (2)° |
Mr = 792.12 | V = 675.35 (10) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.8414 (6) Å | Mo Kα radiation |
b = 10.7408 (9) Å | µ = 1.84 mm−1 |
c = 10.7597 (9) Å | T = 293 K |
α = 64.042 (2)° | 0.60 × 0.28 × 0.26 mm |
β = 77.298 (2)° |
Siemens SMART CCD area-detector diffractometer | 2371 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2167 reflections with I > 2σ(I) |
Tmin = 0.416, Tmax = 0.620 | Rint = 0.021 |
3540 measured reflections |
R[F2 > 2σ(F2)] = 0.033 | 8 restraints |
wR(F2) = 0.089 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 1.04 e Å−3 |
2371 reflections | Δρmin = −0.51 e Å−3 |
190 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Cd1 | 0.45433 (5) | 0.43106 (3) | 0.19947 (3) | 0.03411 (14) | |
Cl1 | 0.83742 (19) | 0.31815 (14) | 0.21558 (14) | 0.0552 (3) | |
O1 | 0.3240 (6) | 0.3240 (4) | 0.4591 (3) | 0.0499 (8) | |
O1W | 0.1843 (8) | 0.5909 (5) | 0.5204 (4) | 0.0740 (12) | |
H1WA | 0.163 (14) | 0.512 (4) | 0.558 (7) | 0.111* | |
H1WB | 0.194 (13) | 0.601 (8) | 0.589 (5) | 0.111* | |
O2 | 0.1937 (5) | 0.1439 (4) | 0.6230 (3) | 0.0465 (8) | |
O3 | 0.4860 (6) | 0.2007 (4) | −0.0596 (3) | 0.0538 (9) | |
O4 | 0.4818 (5) | 0.3709 (3) | 0.0062 (3) | 0.0366 (7) | |
O3W | 0.4605 (7) | 0.5828 (4) | 0.2935 (4) | 0.0607 (10) | |
H3WB | 0.346 (6) | 0.627 (7) | 0.260 (6) | 0.091* | |
H3WA | 0.405 (9) | 0.586 (8) | 0.370 (4) | 0.091* | |
O2W | 0.1129 (5) | 0.5447 (4) | 0.1382 (4) | 0.0493 (8) | |
H2WB | 0.108 (10) | 0.581 (7) | 0.055 (2) | 0.074* | |
H2WA | 0.030 (8) | 0.498 (6) | 0.153 (7) | 0.074* | |
N1 | 0.3624 (5) | 0.2148 (4) | 0.2701 (3) | 0.0305 (7) | |
C1 | 0.2950 (6) | 0.1411 (4) | 0.4018 (4) | 0.0318 (9) | |
C2 | 0.2521 (7) | 0.0094 (5) | 0.4442 (5) | 0.0381 (10) | |
H2 | 0.2075 | −0.0404 | 0.5366 | 0.046* | |
C3 | 0.2769 (7) | −0.0462 (5) | 0.3465 (5) | 0.0414 (10) | |
H3 | 0.2487 | −0.1342 | 0.3720 | 0.050* | |
C4 | 0.3443 (7) | 0.0305 (5) | 0.2099 (5) | 0.0387 (10) | |
H4 | 0.3622 | −0.0055 | 0.1427 | 0.046* | |
C5 | 0.3848 (6) | 0.1615 (4) | 0.1749 (4) | 0.0320 (9) | |
C6 | 0.2720 (7) | 0.2138 (5) | 0.4964 (4) | 0.0374 (10) | |
C7 | 0.4579 (7) | 0.2511 (4) | 0.0274 (4) | 0.0322 (9) | |
C8 | 0.1609 (10) | 0.2139 (7) | 0.7226 (6) | 0.0605 (14) | |
H8A | 0.2895 | 0.2300 | 0.7298 | 0.073* | |
H8B | 0.0624 | 0.3046 | 0.6913 | 0.073* | |
C9 | 0.0828 (10) | 0.1165 (7) | 0.8565 (6) | 0.0710 (17) | |
H9A | 0.0600 | 0.1564 | 0.9242 | 0.106* | |
H9B | 0.1814 | 0.0272 | 0.8857 | 0.106* | |
H9C | −0.0445 | 0.1019 | 0.8477 | 0.106* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.0430 (2) | 0.0331 (2) | 0.03061 (19) | −0.01426 (14) | −0.00153 (13) | −0.01420 (14) |
Cl1 | 0.0385 (6) | 0.0551 (7) | 0.0615 (8) | −0.0117 (5) | −0.0114 (5) | −0.0106 (6) |
O1 | 0.071 (2) | 0.050 (2) | 0.0363 (18) | −0.0289 (18) | 0.0050 (16) | −0.0198 (16) |
O1W | 0.086 (3) | 0.075 (3) | 0.054 (2) | −0.013 (3) | 0.000 (2) | −0.027 (2) |
O2 | 0.055 (2) | 0.052 (2) | 0.0333 (17) | −0.0209 (16) | 0.0020 (14) | −0.0142 (15) |
O3 | 0.092 (3) | 0.0413 (18) | 0.0374 (18) | −0.0270 (18) | 0.0042 (17) | −0.0212 (15) |
O4 | 0.0541 (19) | 0.0296 (15) | 0.0286 (15) | −0.0151 (13) | −0.0006 (13) | −0.0120 (12) |
O3W | 0.100 (3) | 0.053 (2) | 0.039 (2) | −0.032 (2) | 0.0031 (18) | −0.0241 (18) |
O2W | 0.0424 (19) | 0.046 (2) | 0.056 (2) | −0.0072 (15) | −0.0055 (17) | −0.0190 (18) |
N1 | 0.0307 (18) | 0.0324 (18) | 0.0301 (17) | −0.0109 (14) | −0.0031 (14) | −0.0116 (15) |
C1 | 0.027 (2) | 0.035 (2) | 0.031 (2) | −0.0098 (16) | −0.0014 (16) | −0.0098 (18) |
C2 | 0.035 (2) | 0.038 (2) | 0.036 (2) | −0.0146 (18) | 0.0001 (18) | −0.0068 (19) |
C3 | 0.046 (3) | 0.032 (2) | 0.048 (3) | −0.018 (2) | −0.003 (2) | −0.012 (2) |
C4 | 0.046 (3) | 0.035 (2) | 0.041 (2) | −0.0118 (19) | −0.0029 (19) | −0.019 (2) |
C5 | 0.032 (2) | 0.030 (2) | 0.035 (2) | −0.0058 (16) | −0.0055 (17) | −0.0141 (18) |
C6 | 0.036 (2) | 0.044 (3) | 0.031 (2) | −0.0125 (19) | −0.0011 (17) | −0.0119 (19) |
C7 | 0.039 (2) | 0.028 (2) | 0.033 (2) | −0.0105 (17) | −0.0004 (17) | −0.0148 (17) |
C8 | 0.068 (4) | 0.068 (4) | 0.051 (3) | −0.025 (3) | −0.002 (3) | −0.024 (3) |
C9 | 0.075 (4) | 0.087 (5) | 0.043 (3) | −0.016 (3) | 0.006 (3) | −0.027 (3) |
Cd1—O3W | 2.277 (4) | O2W—H2WA | 0.81 (6) |
Cd1—N1 | 2.340 (3) | N1—C5 | 1.339 (5) |
Cd1—O4i | 2.370 (3) | N1—C1 | 1.340 (5) |
Cd1—O2W | 2.381 (4) | C1—C2 | 1.384 (6) |
Cd1—O4 | 2.389 (3) | C1—C6 | 1.491 (6) |
Cd1—Cl1 | 2.5508 (13) | C2—C3 | 1.379 (7) |
Cd1—O1 | 2.573 (3) | C2—H2 | 0.9300 |
O1—C6 | 1.208 (6) | C3—C4 | 1.384 (6) |
O1W—H1WA | 0.81 (6) | C3—H3 | 0.9300 |
O1W—H1WB | 0.81 (7) | C4—C5 | 1.385 (6) |
O2—C6 | 1.314 (5) | C4—H4 | 0.9300 |
O2—C8 | 1.505 (6) | C5—C7 | 1.515 (6) |
O3—C7 | 1.228 (5) | C8—C9 | 1.459 (8) |
O4—C7 | 1.259 (5) | C8—H8A | 0.9700 |
O4—Cd1i | 2.370 (3) | C8—H8B | 0.9700 |
O3W—H3WB | 0.85 (6) | C9—H9A | 0.9600 |
O3W—H3WA | 0.84 (5) | C9—H9B | 0.9600 |
O2W—H2WB | 0.81 (2) | C9—H9C | 0.9600 |
O3W—Cd1—N1 | 138.56 (13) | C1—N1—Cd1 | 122.7 (3) |
O3W—Cd1—O4i | 80.15 (12) | N1—C1—C2 | 122.3 (4) |
N1—Cd1—O4i | 140.12 (11) | N1—C1—C6 | 113.8 (4) |
O3W—Cd1—O2W | 93.61 (15) | C2—C1—C6 | 123.9 (4) |
N1—Cd1—O2W | 87.04 (12) | C3—C2—C1 | 118.6 (4) |
O4i—Cd1—O2W | 79.79 (12) | C3—C2—H2 | 120.7 |
O3W—Cd1—O4 | 152.23 (12) | C1—C2—H2 | 120.7 |
N1—Cd1—O4 | 68.90 (10) | C2—C3—C4 | 119.3 (4) |
O4i—Cd1—O4 | 72.08 (11) | C2—C3—H3 | 120.3 |
O2W—Cd1—O4 | 82.20 (12) | C4—C3—H3 | 120.3 |
O3W—Cd1—Cl1 | 92.68 (12) | C3—C4—C5 | 119.1 (4) |
N1—Cd1—Cl1 | 94.23 (9) | C3—C4—H4 | 120.5 |
O4i—Cd1—Cl1 | 92.37 (8) | C5—C4—H4 | 120.5 |
O2W—Cd1—Cl1 | 168.95 (10) | N1—C5—C4 | 121.6 (4) |
O4—Cd1—Cl1 | 88.01 (8) | N1—C5—C7 | 116.7 (3) |
O3W—Cd1—O1 | 72.30 (12) | C4—C5—C7 | 121.7 (4) |
N1—Cd1—O1 | 66.27 (11) | O1—C6—O2 | 124.5 (4) |
O4i—Cd1—O1 | 150.56 (10) | O1—C6—C1 | 122.6 (4) |
O2W—Cd1—O1 | 91.60 (13) | O2—C6—C1 | 112.8 (4) |
O4—Cd1—O1 | 134.99 (10) | O3—C7—O4 | 126.6 (4) |
Cl1—Cd1—O1 | 98.97 (9) | O3—C7—C5 | 117.1 (4) |
C6—O1—Cd1 | 114.4 (3) | O4—C7—C5 | 116.3 (3) |
H1WA—O1W—H1WB | 99 (7) | C9—C8—O2 | 106.2 (5) |
C6—O2—C8 | 115.4 (4) | C9—C8—H8A | 110.5 |
C7—O4—Cd1i | 132.6 (3) | O2—C8—H8A | 110.5 |
C7—O4—Cd1 | 119.4 (3) | C9—C8—H8B | 110.5 |
Cd1i—O4—Cd1 | 107.92 (11) | O2—C8—H8B | 110.5 |
Cd1—O3W—H3WB | 83 (5) | H8A—C8—H8B | 108.7 |
Cd1—O3W—H3WA | 129 (5) | C8—C9—H9A | 109.5 |
H3WB—O3W—H3WA | 89 (3) | C8—C9—H9B | 109.5 |
Cd1—O2W—H2WB | 112 (5) | H9A—C9—H9B | 109.5 |
Cd1—O2W—H2WA | 121 (5) | C8—C9—H9C | 109.5 |
H2WB—O2W—H2WA | 94 (7) | H9A—C9—H9C | 109.5 |
C5—N1—C1 | 119.2 (4) | H9B—C9—H9C | 109.5 |
C5—N1—Cd1 | 118.1 (3) |
Symmetry code: (i) −x+1, −y+1, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2W—H2WB···Cl1i | 0.81 (2) | 2.61 (2) | 3.405 (4) | 170 (6) |
O2W—H2WA···Cl1ii | 0.81 (6) | 2.43 (6) | 3.227 (4) | 168 (6) |
O1W—H1WB···Cl1iii | 0.81 (6) | 2.55 (7) | 3.348 (5) | 167 (8) |
O1W—H1WA···O1 | 0.81 (7) | 2.54 (6) | 3.054 (6) | 123 (7) |
O3W—H3WA···O1W | 0.84 (5) | 1.96 (6) | 2.757 (6) | 158 (7) |
Symmetry codes: (i) −x+1, −y+1, −z; (ii) x−1, y, z; (iii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Cd2(C9H8NO4)2Cl2(H2O)4]·2H2O |
Mr | 792.12 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.8414 (6), 10.7408 (9), 10.7597 (9) |
α, β, γ (°) | 64.042 (2), 77.298 (2), 72.810 (2) |
V (Å3) | 675.35 (10) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 1.84 |
Crystal size (mm) | 0.60 × 0.28 × 0.26 |
Data collection | |
Diffractometer | Siemens SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.416, 0.620 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3540, 2371, 2167 |
Rint | 0.021 |
(sin θ/λ)max (Å−1) | 0.596 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.089, 1.04 |
No. of reflections | 2371 |
No. of parameters | 190 |
No. of restraints | 8 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.04, −0.51 |
Computer programs: SMART (Siemens, 1996), SMART and SAINT (Siemens, 1994), XPREP in SHELXTL (Siemens, 1994), SHELXTL.
Cd1—O3W | 2.277 (4) | O1W—H1WA | 0.81 (6) |
Cd1—N1 | 2.340 (3) | O1W—H1WB | 0.81 (7) |
Cd1—O4i | 2.370 (3) | O2—C6 | 1.314 (5) |
Cd1—O2W | 2.381 (4) | O2—C8 | 1.505 (6) |
Cd1—O4 | 2.389 (3) | O3—C7 | 1.228 (5) |
Cd1—Cl1 | 2.5508 (13) | O4—C7 | 1.259 (5) |
Cd1—O1 | 2.573 (3) | O4—Cd1i | 2.370 (3) |
O1—C6 | 1.208 (6) | ||
O3W—Cd1—N1 | 138.56 (13) | N1—Cd1—Cl1 | 94.23 (9) |
O3W—Cd1—O4i | 80.15 (12) | O4i—Cd1—Cl1 | 92.37 (8) |
N1—Cd1—O4i | 140.12 (11) | O2W—Cd1—Cl1 | 168.95 (10) |
O3W—Cd1—O2W | 93.61 (15) | O4—Cd1—Cl1 | 88.01 (8) |
N1—Cd1—O2W | 87.04 (12) | O3W—Cd1—O1 | 72.30 (12) |
O4i—Cd1—O2W | 79.79 (12) | N1—Cd1—O1 | 66.27 (11) |
O3W—Cd1—O4 | 152.23 (12) | O4i—Cd1—O1 | 150.56 (10) |
N1—Cd1—O4 | 68.90 (10) | O2W—Cd1—O1 | 91.60 (13) |
O4i—Cd1—O4 | 72.08 (11) | O4—Cd1—O1 | 134.99 (10) |
O2W—Cd1—O4 | 82.20 (12) | Cl1—Cd1—O1 | 98.97 (9) |
O3W—Cd1—Cl1 | 92.68 (12) | Cd1i—O4—Cd1 | 107.92 (11) |
Symmetry code: (i) −x+1, −y+1, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2W—H2WB···Cl1i | 0.81 (2) | 2.61 (2) | 3.405 (4) | 170 (6) |
O2W—H2WA···Cl1ii | 0.81 (6) | 2.43 (6) | 3.227 (4) | 168 (6) |
O1W—H1WB···Cl1iii | 0.81 (6) | 2.55 (7) | 3.348 (5) | 167 (8) |
O1W—H1WA···O1 | 0.81 (7) | 2.54 (6) | 3.054 (6) | 123 (7) |
O3W—H3WA···O1W | 0.84 (5) | 1.96 (6) | 2.757 (6) | 158 (7) |
Symmetry codes: (i) −x+1, −y+1, −z; (ii) x−1, y, z; (iii) −x+1, −y+1, −z+1. |
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Pyridine-2,6-dicarboxylate and diethylpyridine-2,6-dicarboxylate (DEPD) are pentadentate ligands which generally act as tridentate meridional ligands, with their one amino and two carboxyl (or ester) groups acting as the chelating terminals. Many of their metal complexes have been reported (Kapoor et al., 2002; MacDonald et al., 2000; Yang et al., 2002; Odoko et al., 2002). However, a metal complex of monoethylpyridine-2,6-dicarboxylate (MEPD) has not been reported to date. On the other hand, cadmium has increasingly attracted research attention over the years, due to its toxic manifestations in the environment and various animal or human organisms (Hammond & Foulkes, 1986). We report here the synthesis and crystal structure of the title compound, (I), which is the first MEPD complex. \sch
Compound (I) was prepared by reaction of cadmium(II) chloride with pyridine-2,6-dicarboxylic acid and 98% H2SO4 in ethanol. The crystallographic analysis reveals that (I) is a dinuclear complex, [Cd2(MEPD)2(H2O)4Cl2]·2H2O, in which MEPD is derived from the mono-esterification of PDA via the catalysis of sulfuric acid. It is puzzling that we have not obtained PDA or DEPD complexes, but only the mono-esterified MEPD product. At least two kinds of reactions exist in the synthetic system, esterification and self-assembly of the metal complex. MEPD is formed by the mono-esterification of PDA or the mono-hydrolysis of DEPD, or by both reactions.
In the title complex, two Cd atoms are bridged by two carboxylate µ-O atoms from MEPD ligands, forming a centrosymmetric Cd2O2 parallelogram unit. Each CdII atom is coordinated by one N and three O atoms of MEPD ligands, as well as one Cl− and two water O atoms, resulting in a distorted pentagonal-bipyramidal coordination with Cl1—Cd1—O2W in the axial direction (Fig. 1 and Table 1). The bond lengths of Cd to the µ-O atoms [Cd1—O4 2.389 (3) and Cd1—O4i 2.370 (3) Å; symmetry code: (i) 1 − x, 1 − y, −z] are apparently shorter than that of the carbonyl O atom on the ester side [Cd1—O1 2.573 (3) Å], and the bond distance to the central pyridine N atom (Cd1—N1) is 2.340 (3) Å, slightly shorter than these Cd1—O bonds.
The investigation of hydrogen bonding is important for many practical applications, such as the design of antibiotics and the development of new materials with programmed properties (Bong et al., 2001). A great variety of supramolecular assemblies owe their well defined structure to the existence of adjacent hydrogen-bond units to complementary constituent parts (MacDonald et al., 2000). In (I), there is an intramolecular O2W—H2WB···Cl1i hydrogen bond, and intermolecular O—H···Cl and O—H···O hydrogen bonds (Table 2). The metal complexes are linked into one-dimensional stairs via an O2W—H2WA···Cl1ii hydrogen bond [Fig. 2; symmetry code: (ii) x − 1, y, z]. In other words, Cd2O2 and Cl2(H2O)2 rings are arranged alternately along the extended direction of the Cd—Cl bond (Fig. 2). The Cd···Cd distance in the Cd2O2 parallelogram unit is 3.849 (5) Å, and the shortest Cd···Cd distance in the stairs is 6.841 (3) Å. The most interesting feature is that the solvate water molecule (O1W) acts as a junction to connect the one-dimensional stairs into a two-dimensional layer via O—H···O and O—H···Cl hydrogen bonds.