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The title compound, poly­[[di­aqua­di­bromo­cadmium-μ-(1,3,5,7-tetra­aza­tri­cyclo[3.3.1.13,7]decane-N1:N5)-aqua­cad­mium-di-μ-bromo-aqua­cadmium-μ-(1,3,5,7-tetra­aza­tri­cyclo[3.3.1.13,7]decane-N1:N5)-di-μ-bromo] dihydrate], [Cd3­Br6­(C6­H12­N4)2­(H2O)4]·­2H2O, is made up of two-dimensional neutral rectangular coordination layers. Each rectangular subunit is enclosed by a pair of Cd32-Br)6(H2O)3 fragments and a pair of (μ2-hmt)Cd(H2O)2Br22-hmt) fragments as sides (hmt is hexa­methyl­enetetr­amine). The unique CdII atom in the Cd2Br2 ring in the Cd32-Br)6(H2O)3 fragment is in a slightly distorted octahedral CdNOBr4 geometry, surrounded by one hmt ligand [2.433 (5) Å], one aqua ligand [2.273 (4) Å] and four Br atoms [2.6409 (11)–3.0270 (14) Å]. The CdII atom in the (μ2-hmt)Cd(H2O)2Br22-hmt) fragment lies on an inversion center and is in a highly distorted octahedral CdN2O2Br2 geometry, surrounded by two trans-related N atoms of two hmt ligands [2.479 (5) Å], two trans-related aqua ligands [2.294 (4) Å] and two trans-related Br atoms [2.6755 (12) Å]. Adjacent two-dimensional coordination sheets are connected into a three-dimensional network by hydrogen bonds involving lattice water mol­ecules, and the aqua, bromo and hmt ligands belonging to different layers.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100007435/de1139sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100007435/de1139Isup2.hkl
Contains datablock I

CCDC reference: 150323

Comment top

Hexamethylenetetramine (hmt) as a potential polydendate ligand has been of interest in recent years (Miyamae et al., 1988; Mak, 1984; Pickardt & Droas, 1985). These compounds may exhibit interesting topological structures. We and others have recently reported some interesting two- and three-dimensional non-interpenetrating open-networks constructed µ-4-hmt ligand (Bertelli et al., 1997; Carlucci et al., 1997; Tong et al., 1999). We describe herein the crystal structure of the title compound, (I), with a two-dimensional rectangle-like network, in which hmt acts in a µ2 bridging mode. \sch

The title complex is made up of two-dimensional neutral layers of rectangular subunits and lattice water molecules. As shown in Fig.1, each rectangular subunit is enclosed by a pair of Cd32-Br)6(H2O)3 fragments and a pair of Cd(H2O)2Br22-hmt)2 fragments as sides. The Cd(H2O)2Br22-hmt)2 fragment has inversion symmetry with octahedral coordination by two trans-related monodentate bromo atoms [Cd1—Br1 2.6755 (12) Å], two trans-related aqua ligands [Cd1—O2W 2.294 (4) Å] and two trans-related nitrogen atoms [Cd1—N2 2.479 (5) Å] from different hmt ligands. The Cd2 atom in Cd32-Br)6(H2O)3 fragment is in a highly distorted octahedral geometry and coordinated by four bromo atoms [2.6409 (11)–3.0270 (14) Å], one aqua [2.273 (4) Å] and one hmt ligand [2.433 (5) Å]. Along the a direction, the CdII atoms share common Br atoms at the corners to form Cd(µ2-Br)2(H2O) infinite chains, similar to that in the related compounds (Rogers et al., 1993, 1996; Krishnan et al., 1991). These chains are further interlinked by (µ2-hmt)-CdBr2(H2O)2-(µ2-hmt) fragments, resulting in a two-dimensional coordination rectangular layer. The hmt ligand acts in a µ2-mode and bridges two CdII atoms belonging to two types of CdII atoms. The Cd—Br(µ2-mode) bonds are not equivalent. The Cd—Br(µ2-mode) bonds are largely inequivalent compared to those [2.668 (3) and 2.780 (4) Å] found in a related compound, catena-[(µ2-nicotinato-O,O',N)-µ2-aquacadmium(II)] (Zhang et al., 1996).

The structure of (I) differs significantly from that of a closely related compound, namely bis(µ2-hexamethylenetetramine)bis(diiodocadmium)diaquadiiodocadmium dihydrate, in which the CdII atoms have an octahedral or tetrahedral coordinate geometry, resulting in a three-dimensional coordination network (Mak, 1981, 1982; Pickardt, 1981).

It is also noteworthy that the extensive interlayer hydrogen bonds between the adjacent layers may play a role in consolidating the crystal architecture. Each O1W ligand forms one hydrogen bond with a lattice water molecule and one interlayer hydrogen bond with the hmt ligand belonging to the adjacent layer. Each O2W ligand donates only one hydrogen bond, which is with the lattice water molecule. Interestingly, each lattice water molecule forms two acceptor hydrogen bonds with two aqua ligands and two donor hydrogen bonds with two bromo ligands [O1W···O3W 2.812 (7), O2W···O3Wi 2.837 (7), O3W···Br1ii 3.332 (5) and O3W···Br3iii 3.415 (5), O1W···N3ii 2.771 (7), O2W—Br1i 3.522 (5) Å; symmetry codes: (i) −x, −y, −z; (ii) x, y − 1, z; (iii) x − 1, y, z]. These hydrogen bonds extend the two-dimensional coordination layers into three-dimensional molecular networks (Fig. 2).

Experimental top

To a solution (5 cm3) of CdBr2·4H2O (1 mmol), a solution (5 cm3) of hmt (1 mmol) was slowly added with stirring at 323 K for 15 min. The resulting solution was allowed to stand in air at room temperature, colorless crystals were deposited within several days (90% yield).

Computing details top

Data collection: R3M Software (Siemens, 1990); cell refinement: R3M Software; data reduction: R3M Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1998); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. ORTEP (Sheldrick, 1998) plot (35% probability displacement ellipsoids) of the coordination layer with rectangular cavities in (I).
[Figure 2] Fig. 2. Perspective view of the molecular packing of (I).
bis(µ2-hexamethylenetetramine)bis(aquadi(µ2-bromo)- cadmium)diaquadibromocadmium dihydrate top
Crystal data top
[Cd3Br6(C6H12N4)2(H2O)4]·2H2OZ = 1
Mr = 1205.15F(000) = 566
Triclinic, P1Dx = 2.533 Mg m3
a = 7.577 (2) ÅMo Kα radiation, λ = 0.71073 Å
b = 8.030 (2) ÅCell parameters from 25 reflections
c = 13.464 (3) Åθ = 7.5–15°
α = 76.60 (3)°µ = 9.63 mm1
β = 89.17 (3)°T = 293 K
γ = 82.60 (3)°Block, colorless
V = 790.2 (3) Å30.3 × 0.2 × 0.16 mm
Data collection top
Siemens R3m
diffractometer
2716 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.000
Graphite monochromatorθmax = 27.6°, θmin = 1.6°
ω scanh = 09
Absorption correction: ψ scan
semi-empirical (using intensity measurements) absorption based on ψ scan (North et al., 1968)
k = 1010
Tmin = 0.112, Tmax = 0.214l = 1717
3630 measured reflections2 standard reflections every 150 reflections
3630 independent reflections intensity decay: none
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)] = 0.043H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.104Calculated w = 1/[σ2(Fo2) + (0.0557P)2 + 0.0981P]
where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max = 0.002
3630 reflectionsΔρmax = 1.00 e Å3
161 parametersΔρmin = 0.93 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0046 (5)
Crystal data top
[Cd3Br6(C6H12N4)2(H2O)4]·2H2Oγ = 82.60 (3)°
Mr = 1205.15V = 790.2 (3) Å3
Triclinic, P1Z = 1
a = 7.577 (2) ÅMo Kα radiation
b = 8.030 (2) ŵ = 9.63 mm1
c = 13.464 (3) ÅT = 293 K
α = 76.60 (3)°0.3 × 0.2 × 0.16 mm
β = 89.17 (3)°
Data collection top
Siemens R3m
diffractometer
2716 reflections with I > 2σ(I)
Absorption correction: ψ scan
semi-empirical (using intensity measurements) absorption based on ψ scan (North et al., 1968)
Rint = 0.000
Tmin = 0.112, Tmax = 0.2142 standard reflections every 150 reflections
3630 measured reflections intensity decay: none
3630 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0430 restraints
wR(F2) = 0.104H atoms treated by a mixture of independent and constrained refinement
S = 1.03Δρmax = 1.00 e Å3
3630 reflectionsΔρmin = 0.93 e Å3
161 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
Cd10.00000.00000.00000.02334 (18)
Cd20.23094 (7)0.43802 (7)0.44138 (3)0.02542 (15)
Br10.19458 (11)0.29096 (11)0.02279 (6)0.0431 (2)
Br20.10841 (10)0.27189 (10)0.44681 (6)0.0362 (2)
Br30.58513 (10)0.64476 (10)0.41609 (5)0.03300 (19)
N10.2884 (7)0.1805 (7)0.3157 (3)0.0187 (11)
N20.1977 (7)0.0043 (7)0.1460 (3)0.0188 (11)
N30.2941 (7)0.1291 (7)0.2770 (4)0.0248 (12)
N40.5083 (7)0.0491 (7)0.2004 (4)0.0235 (12)
C10.2605 (9)0.0233 (9)0.3558 (4)0.0258 (14)
H1A0.33920.03690.41320.080*
H1B0.14040.00700.37880.080*
C20.4719 (8)0.2008 (9)0.2789 (5)0.0235 (14)
H2A0.49310.30210.25190.080*
H2B0.55230.21550.33560.080*
C30.1679 (8)0.1577 (8)0.2264 (4)0.0197 (13)
H3A0.04690.14340.24830.080*
H3B0.18520.25850.19880.080*
C40.4778 (9)0.1030 (9)0.2435 (5)0.0287 (15)
H4A0.55840.09000.29990.080*
H4B0.50060.20270.19230.080*
C50.3839 (8)0.0262 (9)0.1142 (4)0.0239 (14)
H5A0.40550.07420.06320.080*
H5B0.40440.12420.08410.080*
C60.1737 (9)0.1481 (8)0.1898 (4)0.0243 (14)
H6A0.05300.16460.21170.080*
H6B0.19370.24830.13820.080*
O1W0.1851 (7)0.5399 (6)0.3011 (3)0.0309 (11)
H1WA0.20820.66610.29700.080*
H1WB0.06010.56480.29140.080*
O2W0.1886 (6)0.1593 (7)0.1054 (3)0.0368 (12)
H2WA0.18970.25970.12490.080*
H2WB0.18870.12250.15970.080*
O3W0.1538 (7)0.5112 (7)0.2116 (4)0.0421 (13)
H3WA0.13300.48010.14390.080*
H3WB0.25950.56990.23000.080*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.0218 (4)0.0251 (4)0.0232 (3)0.0016 (3)0.0004 (2)0.0066 (3)
Cd20.0284 (3)0.0250 (3)0.0238 (2)0.0087 (2)0.00364 (18)0.00442 (19)
Br10.0433 (5)0.0393 (5)0.0509 (5)0.0089 (4)0.0098 (3)0.0258 (4)
Br20.0270 (4)0.0315 (4)0.0459 (4)0.0054 (3)0.0043 (3)0.0002 (3)
Br30.0347 (4)0.0340 (4)0.0324 (3)0.0033 (3)0.0088 (3)0.0119 (3)
N10.020 (3)0.018 (3)0.019 (2)0.004 (2)0.0049 (19)0.006 (2)
N20.019 (3)0.016 (3)0.020 (2)0.001 (2)0.0007 (19)0.004 (2)
N30.031 (3)0.021 (3)0.026 (3)0.005 (3)0.001 (2)0.010 (2)
N40.017 (3)0.026 (3)0.028 (3)0.002 (2)0.002 (2)0.009 (2)
C10.034 (4)0.025 (4)0.020 (3)0.005 (3)0.000 (2)0.006 (3)
C20.011 (3)0.025 (4)0.034 (3)0.001 (3)0.005 (2)0.007 (3)
C30.018 (3)0.023 (3)0.020 (3)0.006 (3)0.003 (2)0.007 (2)
C40.028 (4)0.031 (4)0.032 (3)0.011 (3)0.004 (3)0.012 (3)
C50.020 (3)0.027 (4)0.023 (3)0.001 (3)0.000 (2)0.004 (3)
C60.030 (4)0.017 (3)0.026 (3)0.000 (3)0.004 (2)0.005 (3)
O1W0.039 (3)0.020 (3)0.037 (2)0.002 (2)0.012 (2)0.014 (2)
O2W0.035 (3)0.029 (3)0.041 (3)0.003 (2)0.010 (2)0.000 (2)
O3W0.042 (3)0.045 (4)0.041 (3)0.001 (3)0.003 (2)0.016 (3)
Geometric parameters (Å, º) top
Cd1—O2W2.294 (4)N1—C31.483 (7)
Cd1—O2Wi2.294 (4)N2—C61.467 (8)
Cd1—N22.479 (5)N2—C51.469 (8)
Cd1—N2i2.479 (5)N2—C31.479 (7)
Cd1—Br12.6755 (12)N3—C41.462 (8)
Cd1—Br1i2.6755 (12)N3—C61.465 (8)
Cd2—O1W2.273 (4)N3—C11.469 (8)
Cd2—N12.433 (5)N4—C41.460 (9)
Cd2—Br3ii2.6409 (11)N4—C51.469 (7)
Cd2—Br2iii2.7287 (13)N4—C21.469 (8)
Cd2—Br22.7482 (13)O1W—N3iv2.771 (7)
Cd2—Br33.0270 (14)O1W—O3W2.812 (7)
Br2—Cd2iii2.7287 (13)O2W—O3Wi2.837 (7)
Br3—Cd2ii2.6409 (11)O3W—Br1iv3.332 (5)
N1—C21.471 (7)O3W—Br3v3.415 (5)
N1—C11.475 (8)
O2W—Cd1—O2Wi180.0C2—N1—C1108.5 (5)
O2W—Cd1—N288.47 (17)C2—N1—C3107.2 (4)
O2Wi—Cd1—N291.53 (17)C1—N1—C3109.0 (5)
O2W—Cd1—N2i91.53 (17)C2—N1—Cd2110.6 (4)
O2Wi—Cd1—N2i88.47 (17)C1—N1—Cd2112.8 (3)
N2—Cd1—N2i180.0C3—N1—Cd2108.6 (3)
O2W—Cd1—Br190.06 (13)C6—N2—C5107.0 (5)
O2Wi—Cd1—Br189.94 (13)C6—N2—C3108.8 (4)
N2—Cd1—Br191.75 (13)C5—N2—C3108.3 (5)
N2i—Cd1—Br188.25 (13)C6—N2—Cd1116.8 (4)
O2W—Cd1—Br1i89.94 (13)C5—N2—Cd1109.1 (3)
O2Wi—Cd1—Br1i90.06 (13)C3—N2—Cd1106.5 (3)
N2—Cd1—Br1i88.25 (13)C4—N3—C6108.9 (5)
N2i—Cd1—Br1i91.75 (13)C4—N3—C1108.7 (5)
Br1—Cd1—Br1i180.0C6—N3—C1109.1 (5)
O1W—Cd2—N183.48 (17)C4—N4—C5108.8 (5)
O1W—Cd2—Br3ii157.16 (13)C4—N4—C2108.7 (5)
N1—Cd2—Br3ii91.96 (12)C5—N4—C2108.5 (5)
O1W—Cd2—Br2iii86.88 (12)N3—C1—N1110.9 (5)
N1—Cd2—Br2iii167.46 (11)N4—C2—N1111.7 (5)
Br3ii—Cd2—Br2iii99.99 (4)N2—C3—N1111.5 (5)
O1W—Cd2—Br296.00 (13)N4—C4—N3110.8 (5)
N1—Cd2—Br285.88 (13)N4—C5—N2111.7 (5)
Br3ii—Cd2—Br2106.02 (4)N3—C6—N2112.0 (5)
Br2iii—Cd2—Br287.17 (4)Cd2—O1W—N3iv126.4 (2)
O1W—Cd2—Br376.72 (13)Cd2—O1W—O3W122.6 (2)
N1—Cd2—Br395.03 (13)N3iv—O1W—O3W95.3 (2)
Br3ii—Cd2—Br381.43 (4)Cd1—O2W—O3Wi132.2 (2)
Br2iii—Cd2—Br390.53 (4)O3Wi—O2W—Br1i167.6 (2)
Br2—Cd2—Br3172.48 (3)O1W—O3W—Br1iv118.1 (2)
Cd2iii—Br2—Cd292.83 (4)O1W—O3W—Br3v103.18 (17)
Cd2ii—Br3—Cd298.57 (4)Br1iv—O3W—Br3v113.62 (16)
Symmetry codes: (i) x, y, z; (ii) x+1, y1, z+1; (iii) x, y1, z+1; (iv) x, y1, z; (v) x1, y, z.

Experimental details

Crystal data
Chemical formula[Cd3Br6(C6H12N4)2(H2O)4]·2H2O
Mr1205.15
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)7.577 (2), 8.030 (2), 13.464 (3)
α, β, γ (°)76.60 (3), 89.17 (3), 82.60 (3)
V3)790.2 (3)
Z1
Radiation typeMo Kα
µ (mm1)9.63
Crystal size (mm)0.3 × 0.2 × 0.16
Data collection
DiffractometerSiemens R3m
diffractometer
Absorption correctionψ scan
semi-empirical (using intensity measurements) absorption based on ψ scan (North et al., 1968)
Tmin, Tmax0.112, 0.214
No. of measured, independent and
observed [I > 2σ(I)] reflections
3630, 3630, 2716
Rint0.000
(sin θ/λ)max1)0.651
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.104, 1.03
No. of reflections3630
No. of parameters161
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)1.00, 0.93

Computer programs: R3M Software (Siemens, 1990), R3M Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1998), SHELXL97.

Selected geometric parameters (Å, º) top
Cd1—O2W2.294 (4)Cd2—Br3i2.6409 (11)
Cd1—N22.479 (5)Cd2—Br2ii2.7287 (13)
Cd1—Br12.6755 (12)Cd2—Br22.7482 (13)
Cd2—O1W2.273 (4)Cd2—Br33.0270 (14)
Cd2—N12.433 (5)
O2W—Cd1—N288.47 (17)Br3i—Cd2—Br2ii99.99 (4)
O2W—Cd1—Br190.06 (13)O1W—Cd2—Br296.00 (13)
N2—Cd1—Br191.75 (13)N1—Cd2—Br285.88 (13)
O1W—Cd2—N183.48 (17)Br3i—Cd2—Br2106.02 (4)
O1W—Cd2—Br3i157.16 (13)Br2ii—Cd2—Br287.17 (4)
N1—Cd2—Br3i91.96 (12)O1W—Cd2—Br376.72 (13)
O1W—Cd2—Br2ii86.88 (12)N1—Cd2—Br395.03 (13)
N1—Cd2—Br2ii167.46 (11)
Symmetry codes: (i) x+1, y1, z+1; (ii) x, y1, z+1.
 

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