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The isomorphous title compounds, [Tr(S
4O
6)(C
12H
12N
2)
2]·2C
3H
7NO (Tr = Cd
II and Zn
II), consist of metal centres to which one tetrathionate and two 4,4′-dimethyl-2,2′-bipyridine chelating ligands bind. The structures are completed by two symmetry-related dimethylformamide solvent molecules. Each metal-centred complex is bisected by a twofold axis running through the metal centre and halving the chelating tetrathionate dianion through the central S—S bond. The ancillary symmetry-related 4,4′-dimethyl-2,2′-bipyridine ligands act as chelates. This results in a distorted six-coordinate geometry, with similar Tr—O/N distances but central angles differing substantially from 90 and 180°. Both ligands are basically featureless from a geometric point of view, with torsion angles in both coordinated tetrathionate groups suggesting a trend linking metal size (covalent radius) and ligand `openness'. Packing is directed by (C—H)
aromaticO bridges and π–π offset stacked interactions defining chains along [001], further linked by weaker (C—H)
methylO bridges, some of them mediated by the dimethylformamide solvent molecules.
Supporting information
CCDC references: 957000; 957001
In several previous attempts to obtain hybrid organic tetrathionate transition
metal complexes using aqueous solutions, the anion decomposed systematically,
rendering thiosulfate. In view of these failures, we thought of using a
solvent in which the organic ligand is soluble but the other two components
only slightly soluble. In doing so, it was expected that the components would
mix slowly to form the complex, while simultaneously displacing the solubility
equilibrium. After some tests, we selected dimethylformamide (DMF) as an
appropriate solvent. To a solution of 4,4'-dimethyl-2,2'-bipyridine in DMF (5 ml, 0.050 M), solid Cd or Zn diacetate dihydrate and potassium
tetrathionate were added in a mass:volume ratio so as to obtain a 0.050
M solution of each component. On standing, in both cases, a poorly
crystallized precipitate appeared, to be digested after a while (one week in
the Cd case and one month for Zn) to give rise finally to crystals of the
expected complexes in the form of well faceted colourless blocks suitable for
X-ray diffraction.
All H atoms were visible in difference maps, but were subsequently placed in
geometrically idealized positions and allowed to ride on their parent atoms,
with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C) for aromatic
H, and C—H = 0.96 Å and Uiso(H) = 1.5Ueq(C) for methyl
H. In (I), conventional weighting led to a rather low goodness-of-fit, for
which a special scheme with enhanced weighting for high-angle reflections
(provided in SHELXL97; Sheldrick, 2008) was applied.
For both compounds, data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).
(I) Bis(4,4'-dimethyl-2,2'-bipyridine-
κ2N,
N')(tetrathionato-
κ2S,
S')cadmium(II) dimethylformamide disolvate
top
Crystal data top
[Cd(S4O6)(C12H12N2)2]·2C3H7NO | F(000) = 1744 |
Mr = 851.30 | Dx = 1.522 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2418 reflections |
a = 20.7076 (7) Å | θ = 3.7–28.1° |
b = 10.7885 (3) Å | µ = 0.87 mm−1 |
c = 17.5044 (5) Å | T = 294 K |
β = 108.187 (3)° | Prism, colourless |
V = 3715.2 (2) Å3 | 0.15 × 0.05 × 0.04 mm |
Z = 4 | |
Data collection top
Oxford Gemini S Ultra CCD area-detector diffractometer | 2693 reflections with I > 2σ(I) |
ω scans, thick slices | Rint = 0.025 |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | θmax = 26.5°, θmin = 3.6° |
Tmin = 0.94, Tmax = 0.96 | h = −25→24 |
9819 measured reflections | k = −13→13 |
3844 independent reflections | l = −13→21 |
Refinement top
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)] = 0.029 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.065 | H-atom parameters constrained |
S = 1.00 | w = [exp(1.20(sinθ/λ)2)]/[σ2(Fo2) + (0.0331P)2]
where P = 0.33333Fo2 + 0.66667Fc2 |
3844 reflections | (Δ/σ)max = 0.001 |
226 parameters | Δρmax = 0.34 e Å−3 |
0 restraints | Δρmin = −0.33 e Å−3 |
Crystal data top
[Cd(S4O6)(C12H12N2)2]·2C3H7NO | V = 3715.2 (2) Å3 |
Mr = 851.30 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 20.7076 (7) Å | µ = 0.87 mm−1 |
b = 10.7885 (3) Å | T = 294 K |
c = 17.5044 (5) Å | 0.15 × 0.05 × 0.04 mm |
β = 108.187 (3)° | |
Data collection top
Oxford Gemini S Ultra CCD area-detector diffractometer | 3844 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | 2693 reflections with I > 2σ(I) |
Tmin = 0.94, Tmax = 0.96 | Rint = 0.025 |
9819 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.065 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.34 e Å−3 |
3844 reflections | Δρmin = −0.33 e Å−3 |
226 parameters | |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Cd1 | 0.5000 | 0.05562 (2) | 0.2500 | 0.04902 (10) | |
S1 | 0.58500 (3) | 0.31673 (6) | 0.36429 (3) | 0.04756 (15) | |
S2 | 0.50175 (4) | 0.43161 (7) | 0.30822 (5) | 0.0791 (2) | |
O1 | 0.57359 (11) | 0.19950 (18) | 0.32421 (13) | 0.0921 (7) | |
O2 | 0.64280 (10) | 0.3761 (2) | 0.35624 (13) | 0.0983 (7) | |
O3 | 0.58172 (12) | 0.3138 (2) | 0.44390 (11) | 0.0942 (7) | |
N1 | 0.57068 (10) | 0.04451 (17) | 0.17054 (11) | 0.0483 (5) | |
N2 | 0.45980 (10) | −0.09723 (18) | 0.15385 (11) | 0.0500 (5) | |
C1 | 0.62399 (13) | 0.1185 (2) | 0.17821 (15) | 0.0590 (7) | |
H1 | 0.6322 | 0.1819 | 0.2160 | 0.071* | |
C2 | 0.66702 (13) | 0.1060 (3) | 0.13347 (16) | 0.0618 (7) | |
H2 | 0.7033 | 0.1603 | 0.1407 | 0.074* | |
C3 | 0.65629 (12) | 0.0120 (3) | 0.07735 (15) | 0.0539 (6) | |
C4 | 0.60000 (12) | −0.0626 (2) | 0.06785 (14) | 0.0493 (6) | |
H4 | 0.5902 | −0.1253 | 0.0295 | 0.059* | |
C5 | 0.55803 (11) | −0.04488 (19) | 0.11482 (12) | 0.0418 (5) | |
C6 | 0.49677 (11) | −0.12373 (19) | 0.10555 (12) | 0.0415 (5) | |
C7 | 0.47863 (12) | −0.2188 (2) | 0.05011 (13) | 0.0492 (6) | |
H7 | 0.5051 | −0.2351 | 0.0170 | 0.059* | |
C8 | 0.42155 (14) | −0.2900 (2) | 0.04323 (14) | 0.0576 (6) | |
C9 | 0.38446 (14) | −0.2612 (3) | 0.09368 (16) | 0.0707 (8) | |
H9 | 0.3457 | −0.3065 | 0.0913 | 0.085* | |
C10 | 0.40441 (14) | −0.1663 (3) | 0.14700 (17) | 0.0665 (7) | |
H10 | 0.3784 | −0.1484 | 0.1804 | 0.080* | |
C11 | 0.70313 (16) | −0.0099 (3) | 0.02856 (19) | 0.0830 (9) | |
H11A | 0.7162 | 0.0682 | 0.0116 | 0.124* | |
H11B | 0.6803 | −0.0588 | −0.0178 | 0.124* | |
H11C | 0.7429 | −0.0531 | 0.0606 | 0.124* | |
C12 | 0.40119 (19) | −0.3912 (3) | −0.01794 (18) | 0.0884 (10) | |
H12A | 0.4172 | −0.4693 | 0.0071 | 0.133* | |
H12B | 0.4208 | −0.3760 | −0.0601 | 0.133* | |
H12C | 0.3526 | −0.3932 | −0.0402 | 0.133* | |
N3 | 0.20135 (10) | 0.06463 (19) | 0.18402 (12) | 0.0552 (5) | |
O4 | 0.26101 (12) | −0.1120 (2) | 0.18838 (15) | 0.0995 (7) | |
C13 | 0.15034 (16) | 0.1281 (3) | 0.2096 (2) | 0.0961 (11) | |
H13A | 0.1383 | 0.0784 | 0.2486 | 0.144* | |
H13B | 0.1108 | 0.1418 | 0.1640 | 0.144* | |
H13C | 0.1680 | 0.2063 | 0.2332 | 0.144* | |
C14 | 0.22956 (18) | 0.1295 (3) | 0.13132 (18) | 0.0917 (10) | |
H14A | 0.2649 | 0.0805 | 0.1217 | 0.138* | |
H14B | 0.2481 | 0.2069 | 0.1554 | 0.138* | |
H14C | 0.1947 | 0.1449 | 0.0813 | 0.138* | |
C15 | 0.22072 (15) | −0.0504 (3) | 0.20863 (17) | 0.0686 (7) | |
H15 | 0.2014 | −0.0861 | 0.2447 | 0.082* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.05889 (18) | 0.04432 (15) | 0.04450 (15) | 0.000 | 0.01706 (12) | 0.000 |
S1 | 0.0500 (4) | 0.0489 (3) | 0.0423 (3) | −0.0059 (3) | 0.0124 (3) | −0.0055 (3) |
S2 | 0.0822 (5) | 0.0793 (5) | 0.0635 (5) | 0.0290 (5) | 0.0051 (4) | −0.0199 (4) |
O1 | 0.0762 (14) | 0.0635 (12) | 0.1052 (16) | 0.0086 (11) | −0.0170 (11) | −0.0356 (12) |
O2 | 0.0538 (12) | 0.1241 (18) | 0.1094 (17) | −0.0224 (13) | 0.0147 (12) | 0.0315 (15) |
O3 | 0.1243 (19) | 0.1135 (17) | 0.0521 (12) | 0.0258 (15) | 0.0380 (12) | 0.0153 (11) |
N1 | 0.0502 (12) | 0.0452 (11) | 0.0474 (11) | −0.0128 (10) | 0.0120 (9) | −0.0033 (9) |
N2 | 0.0513 (12) | 0.0489 (11) | 0.0521 (12) | −0.0121 (10) | 0.0193 (10) | −0.0035 (9) |
C1 | 0.0604 (17) | 0.0532 (15) | 0.0584 (16) | −0.0182 (14) | 0.0114 (13) | −0.0055 (12) |
C2 | 0.0456 (15) | 0.0662 (16) | 0.0684 (18) | −0.0197 (14) | 0.0099 (13) | 0.0136 (15) |
C3 | 0.0420 (14) | 0.0617 (15) | 0.0554 (16) | 0.0000 (13) | 0.0114 (12) | 0.0163 (13) |
C4 | 0.0482 (14) | 0.0525 (13) | 0.0449 (13) | −0.0016 (13) | 0.0114 (11) | 0.0014 (11) |
C5 | 0.0444 (13) | 0.0385 (12) | 0.0384 (12) | −0.0020 (11) | 0.0071 (10) | 0.0058 (10) |
C6 | 0.0436 (13) | 0.0380 (12) | 0.0395 (12) | −0.0020 (11) | 0.0082 (10) | 0.0059 (10) |
C7 | 0.0562 (15) | 0.0435 (12) | 0.0465 (14) | −0.0069 (12) | 0.0142 (12) | −0.0022 (11) |
C8 | 0.0693 (18) | 0.0449 (13) | 0.0484 (15) | −0.0136 (14) | 0.0034 (13) | 0.0029 (11) |
C9 | 0.0620 (18) | 0.0752 (19) | 0.0708 (18) | −0.0324 (16) | 0.0147 (15) | −0.0018 (16) |
C10 | 0.0621 (17) | 0.0730 (19) | 0.0712 (18) | −0.0191 (16) | 0.0305 (15) | −0.0025 (15) |
C11 | 0.0598 (18) | 0.111 (2) | 0.087 (2) | −0.0010 (18) | 0.0363 (17) | 0.0148 (19) |
C12 | 0.114 (3) | 0.0622 (18) | 0.077 (2) | −0.039 (2) | 0.0127 (19) | −0.0135 (16) |
N3 | 0.0535 (12) | 0.0504 (12) | 0.0608 (13) | −0.0064 (11) | 0.0166 (10) | −0.0080 (10) |
O4 | 0.0842 (16) | 0.0774 (14) | 0.138 (2) | 0.0191 (13) | 0.0359 (15) | −0.0176 (14) |
C13 | 0.073 (2) | 0.078 (2) | 0.149 (3) | −0.0009 (19) | 0.051 (2) | −0.022 (2) |
C14 | 0.104 (3) | 0.098 (2) | 0.079 (2) | −0.026 (2) | 0.036 (2) | 0.0020 (19) |
C15 | 0.0666 (19) | 0.0639 (18) | 0.0716 (19) | −0.0112 (17) | 0.0160 (15) | −0.0053 (16) |
Geometric parameters (Å, º) top
Cd1—O1 | 2.2767 (19) | C7—C8 | 1.383 (3) |
Cd1—O1i | 2.2767 (19) | C7—H7 | 0.9300 |
Cd1—N1i | 2.3156 (18) | C8—C9 | 1.375 (3) |
Cd1—N1 | 2.3156 (18) | C8—C12 | 1.495 (3) |
Cd1—N2 | 2.3175 (19) | C9—C10 | 1.360 (4) |
Cd1—N2i | 2.3175 (19) | C9—H9 | 0.9300 |
S1—O2 | 1.403 (2) | C10—H10 | 0.9300 |
S1—O3 | 1.4165 (18) | C11—H11A | 0.9600 |
S1—O1 | 1.4297 (19) | C11—H11B | 0.9600 |
S1—S2 | 2.1011 (10) | C11—H11C | 0.9600 |
S2—S2i | 2.0169 (15) | C12—H12A | 0.9600 |
N1—C1 | 1.335 (3) | C12—H12B | 0.9600 |
N1—C5 | 1.338 (3) | C12—H12C | 0.9600 |
N2—C6 | 1.336 (3) | N3—C15 | 1.333 (3) |
N2—C10 | 1.341 (3) | N3—C14 | 1.421 (3) |
C1—C2 | 1.364 (4) | N3—C13 | 1.442 (3) |
C1—H1 | 0.9300 | O4—C15 | 1.204 (3) |
C2—C3 | 1.381 (4) | C13—H13A | 0.9600 |
C2—H2 | 0.9300 | C13—H13B | 0.9600 |
C3—C4 | 1.383 (3) | C13—H13C | 0.9600 |
C3—C11 | 1.498 (4) | C14—H14A | 0.9600 |
C4—C5 | 1.383 (3) | C14—H14B | 0.9600 |
C4—H4 | 0.9300 | C14—H14C | 0.9600 |
C5—C6 | 1.494 (3) | C15—H15 | 0.9300 |
C6—C7 | 1.381 (3) | | |
| | | |
O1—Cd1—O1i | 94.04 (10) | N2—C6—C5 | 116.37 (19) |
O1—Cd1—N1i | 97.39 (8) | C7—C6—C5 | 122.3 (2) |
O1i—Cd1—N1i | 86.67 (8) | C6—C7—C8 | 120.8 (2) |
O1—Cd1—N1 | 86.67 (8) | C6—C7—H7 | 119.6 |
O1i—Cd1—N1 | 97.39 (8) | C8—C7—H7 | 119.6 |
N1i—Cd1—N1 | 174.06 (9) | C9—C8—C7 | 116.9 (2) |
O1—Cd1—N2 | 157.56 (7) | C9—C8—C12 | 122.4 (3) |
O1i—Cd1—N2 | 92.64 (8) | C7—C8—C12 | 120.7 (3) |
N1i—Cd1—N2 | 104.38 (7) | C10—C9—C8 | 120.0 (2) |
N1—Cd1—N2 | 71.22 (6) | C10—C9—H9 | 120.0 |
O1—Cd1—N2i | 92.64 (8) | C8—C9—H9 | 120.0 |
O1i—Cd1—N2i | 157.56 (7) | N2—C10—C9 | 123.2 (2) |
N1i—Cd1—N2i | 71.22 (6) | N2—C10—H10 | 118.4 |
N1—Cd1—N2i | 104.38 (7) | C9—C10—H10 | 118.4 |
N2—Cd1—N2i | 89.27 (10) | C3—C11—H11A | 109.5 |
O2—S1—O3 | 114.41 (14) | C3—C11—H11B | 109.5 |
O2—S1—O1 | 111.72 (15) | H11A—C11—H11B | 109.5 |
O3—S1—O1 | 114.31 (14) | C3—C11—H11C | 109.5 |
O2—S1—S2 | 106.56 (10) | H11A—C11—H11C | 109.5 |
O3—S1—S2 | 100.87 (10) | H11B—C11—H11C | 109.5 |
O1—S1—S2 | 107.87 (9) | C8—C12—H12A | 109.5 |
S2i—S2—S1 | 103.74 (5) | C8—C12—H12B | 109.5 |
S1—O1—Cd1 | 149.51 (13) | H12A—C12—H12B | 109.5 |
C1—N1—C5 | 118.2 (2) | C8—C12—H12C | 109.5 |
C1—N1—Cd1 | 124.52 (16) | H12A—C12—H12C | 109.5 |
C5—N1—Cd1 | 117.29 (14) | H12B—C12—H12C | 109.5 |
C6—N2—C10 | 117.9 (2) | C15—N3—C14 | 121.7 (2) |
C6—N2—Cd1 | 117.70 (14) | C15—N3—C13 | 121.2 (2) |
C10—N2—Cd1 | 124.29 (16) | C14—N3—C13 | 117.2 (3) |
N1—C1—C2 | 123.4 (2) | N3—C13—H13A | 109.5 |
N1—C1—H1 | 118.3 | N3—C13—H13B | 109.5 |
C2—C1—H1 | 118.3 | H13A—C13—H13B | 109.5 |
C1—C2—C3 | 119.5 (2) | N3—C13—H13C | 109.5 |
C1—C2—H2 | 120.3 | H13A—C13—H13C | 109.5 |
C3—C2—H2 | 120.3 | H13B—C13—H13C | 109.5 |
C2—C3—C4 | 117.1 (2) | N3—C14—H14A | 109.5 |
C2—C3—C11 | 122.1 (2) | N3—C14—H14B | 109.5 |
C4—C3—C11 | 120.8 (3) | H14A—C14—H14B | 109.5 |
C3—C4—C5 | 120.7 (2) | N3—C14—H14C | 109.5 |
C3—C4—H4 | 119.6 | H14A—C14—H14C | 109.5 |
C5—C4—H4 | 119.6 | H14B—C14—H14C | 109.5 |
N1—C5—C4 | 121.1 (2) | O4—C15—N3 | 125.9 (3) |
N1—C5—C6 | 117.13 (19) | O4—C15—H15 | 117.1 |
C4—C5—C6 | 121.8 (2) | N3—C15—H15 | 117.1 |
N2—C6—C7 | 121.3 (2) | | |
Symmetry code: (i) −x+1, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O3ii | 0.93 | 2.50 | 3.418 (3) | 170 |
C7—H7···O3ii | 0.93 | 2.48 | 3.397 (3) | 169 |
C10—H10···O4 | 0.93 | 2.51 | 3.320 (4) | 146 |
C11—H11C···O2iii | 0.96 | 2.48 | 3.427 (4) | 168 |
C12—H12A···O3iv | 0.96 | 2.49 | 3.413 (3) | 161 |
C13—H13C···O4v | 0.96 | 2.57 | 3.517 (4) | 167 |
Symmetry codes: (ii) x, −y, z−1/2; (iii) −x+3/2, y−1/2, −z+1/2; (iv) −x+1, y−1, −z+1/2; (v) −x+1/2, y+1/2, −z+1/2. |
(II) Bis(4,4'-dimethyl-2,2'-bipyridine-
κ2N,
N')(tetrathionato-
κ2S,
S')cadmium(II) dimethylformamide disolvate
top
Crystal data top
[Zn(S4O6)(C12H12N2)2]·2C3H7NO | F(000) = 1672 |
Mr = 804.27 | Dx = 1.463 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2102 reflections |
a = 20.8508 (12) Å | θ = 3.5–28.8° |
b = 10.8334 (8) Å | µ = 0.96 mm−1 |
c = 16.9888 (10) Å | T = 294 K |
β = 107.956 (7)° | Prism, colourless |
V = 3650.6 (4) Å3 | 0.10 × 0.05 × 0.04 mm |
Z = 4 | |
Data collection top
Oxford Gemini S Ultra CCD area-detector diffractometer | 3945 independent reflections |
Radiation source: fine-focus sealed tube | 2446 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.062 |
ω scans, thick slices | θmax = 27.0°, θmin = 3.5° |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | h = −26→26 |
Tmin = 0.95, Tmax = 0.97 | k = −13→13 |
12111 measured reflections | l = −21→21 |
Refinement top
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)] = 0.052 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.104 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0324P)2] where P = (Fo2 + 2Fc2)/3 |
3945 reflections | (Δ/σ)max = 0.005 |
226 parameters | Δρmax = 0.32 e Å−3 |
0 restraints | Δρmin = −0.29 e Å−3 |
Crystal data top
[Zn(S4O6)(C12H12N2)2]·2C3H7NO | V = 3650.6 (4) Å3 |
Mr = 804.27 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 20.8508 (12) Å | µ = 0.96 mm−1 |
b = 10.8334 (8) Å | T = 294 K |
c = 16.9888 (10) Å | 0.10 × 0.05 × 0.04 mm |
β = 107.956 (7)° | |
Data collection top
Oxford Gemini S Ultra CCD area-detector diffractometer | 3945 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | 2446 reflections with I > 2σ(I) |
Tmin = 0.95, Tmax = 0.97 | Rint = 0.062 |
12111 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.052 | 0 restraints |
wR(F2) = 0.104 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.32 e Å−3 |
3945 reflections | Δρmin = −0.29 e Å−3 |
226 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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Zn1 | 0.5000 | 0.05985 (5) | 0.2500 | 0.04149 (18) | |
S1 | 0.57909 (4) | 0.31202 (8) | 0.36779 (5) | 0.0424 (2) | |
S2 | 0.50021 (5) | 0.43416 (10) | 0.30940 (6) | 0.0700 (3) | |
O1 | 0.56286 (11) | 0.1942 (2) | 0.32708 (14) | 0.0652 (7) | |
O2 | 0.63916 (11) | 0.3628 (3) | 0.35902 (15) | 0.0764 (8) | |
O3 | 0.57462 (13) | 0.3140 (3) | 0.44977 (13) | 0.0748 (8) | |
N1 | 0.56672 (12) | 0.0504 (2) | 0.17879 (15) | 0.0407 (6) | |
N2 | 0.45588 (12) | −0.0803 (2) | 0.16141 (15) | 0.0414 (7) | |
C1 | 0.62052 (16) | 0.1225 (3) | 0.18716 (19) | 0.0474 (9) | |
H1 | 0.6283 | 0.1872 | 0.2249 | 0.057* | |
C2 | 0.66462 (16) | 0.1058 (3) | 0.1429 (2) | 0.0513 (9) | |
H2 | 0.7013 | 0.1583 | 0.1510 | 0.062* | |
C3 | 0.65451 (15) | 0.0105 (4) | 0.0862 (2) | 0.0480 (9) | |
C4 | 0.59720 (16) | −0.0613 (3) | 0.07514 (18) | 0.0442 (8) | |
H4 | 0.5875 | −0.1243 | 0.0360 | 0.053* | |
C5 | 0.55459 (14) | −0.0400 (3) | 0.12157 (17) | 0.0359 (7) | |
C6 | 0.49276 (15) | −0.1152 (3) | 0.11258 (18) | 0.0383 (8) | |
C7 | 0.47340 (16) | −0.2104 (3) | 0.05736 (18) | 0.0460 (8) | |
H7 | 0.4997 | −0.2311 | 0.0239 | 0.055* | |
C8 | 0.41503 (18) | −0.2761 (3) | 0.05085 (19) | 0.0508 (9) | |
C9 | 0.37809 (18) | −0.2399 (4) | 0.1009 (2) | 0.0598 (10) | |
H9 | 0.3384 | −0.2811 | 0.0983 | 0.072* | |
C10 | 0.39926 (16) | −0.1432 (4) | 0.1547 (2) | 0.0535 (10) | |
H10 | 0.3732 | −0.1204 | 0.1879 | 0.064* | |
C11 | 0.70261 (18) | −0.0158 (4) | 0.0385 (2) | 0.0716 (12) | |
H11A | 0.7169 | 0.0605 | 0.0205 | 0.107* | |
H11B | 0.6806 | −0.0657 | −0.0089 | 0.107* | |
H11C | 0.7412 | −0.0591 | 0.0732 | 0.107* | |
C12 | 0.3930 (2) | −0.3805 (4) | −0.0092 (2) | 0.0785 (13) | |
H12A | 0.4011 | −0.4575 | 0.0203 | 0.118* | |
H12B | 0.4181 | −0.3785 | −0.0480 | 0.118* | |
H12C | 0.3458 | −0.3726 | −0.0383 | 0.118* | |
N3 | 0.19834 (13) | 0.0609 (3) | 0.18132 (16) | 0.0491 (7) | |
O4 | 0.25600 (13) | −0.1184 (3) | 0.19203 (19) | 0.0871 (9) | |
C13 | 0.1478 (2) | 0.1295 (4) | 0.2038 (3) | 0.0907 (15) | |
H13A | 0.1326 | 0.0827 | 0.2426 | 0.136* | |
H13B | 0.1104 | 0.1454 | 0.1552 | 0.136* | |
H13C | 0.1665 | 0.2064 | 0.2285 | 0.136* | |
C14 | 0.2296 (2) | 0.1193 (4) | 0.1266 (2) | 0.0809 (13) | |
H14A | 0.2639 | 0.0660 | 0.1187 | 0.121* | |
H14B | 0.2496 | 0.1959 | 0.1504 | 0.121* | |
H14C | 0.1963 | 0.1349 | 0.0743 | 0.121* | |
C15 | 0.21530 (19) | −0.0527 (4) | 0.2094 (2) | 0.0590 (10) | |
H15 | 0.1940 | −0.0848 | 0.2456 | 0.071* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Zn1 | 0.0414 (3) | 0.0397 (3) | 0.0429 (3) | 0.000 | 0.0122 (2) | 0.000 |
S1 | 0.0429 (5) | 0.0435 (5) | 0.0397 (5) | −0.0051 (4) | 0.0112 (4) | −0.0032 (4) |
S2 | 0.0766 (7) | 0.0627 (7) | 0.0578 (6) | 0.0251 (6) | 0.0018 (5) | −0.0164 (5) |
O1 | 0.0612 (15) | 0.0436 (16) | 0.0741 (16) | 0.0018 (13) | −0.0036 (13) | −0.0181 (13) |
O2 | 0.0464 (14) | 0.096 (2) | 0.0844 (18) | −0.0230 (15) | 0.0161 (13) | 0.0091 (17) |
O3 | 0.104 (2) | 0.080 (2) | 0.0458 (14) | 0.0132 (17) | 0.0322 (14) | 0.0081 (14) |
N1 | 0.0386 (14) | 0.0382 (17) | 0.0420 (15) | −0.0071 (13) | 0.0078 (12) | −0.0018 (13) |
N2 | 0.0375 (15) | 0.0397 (17) | 0.0452 (15) | −0.0081 (13) | 0.0103 (12) | −0.0017 (13) |
C1 | 0.0432 (19) | 0.042 (2) | 0.051 (2) | −0.0081 (17) | 0.0059 (17) | −0.0003 (17) |
C2 | 0.0362 (19) | 0.057 (3) | 0.056 (2) | −0.0076 (18) | 0.0079 (17) | 0.0100 (19) |
C3 | 0.0362 (18) | 0.059 (2) | 0.047 (2) | 0.0035 (18) | 0.0099 (16) | 0.0205 (19) |
C4 | 0.0483 (19) | 0.046 (2) | 0.0373 (17) | 0.0021 (18) | 0.0124 (15) | 0.0014 (16) |
C5 | 0.0353 (17) | 0.036 (2) | 0.0333 (16) | −0.0002 (15) | 0.0052 (14) | 0.0066 (14) |
C6 | 0.0384 (18) | 0.039 (2) | 0.0339 (17) | 0.0006 (16) | 0.0051 (15) | 0.0031 (15) |
C7 | 0.050 (2) | 0.042 (2) | 0.0431 (18) | −0.0034 (18) | 0.0097 (16) | −0.0043 (17) |
C8 | 0.063 (2) | 0.038 (2) | 0.0419 (19) | −0.0115 (19) | 0.0027 (18) | −0.0024 (17) |
C9 | 0.052 (2) | 0.057 (3) | 0.062 (2) | −0.027 (2) | 0.006 (2) | −0.003 (2) |
C10 | 0.043 (2) | 0.061 (3) | 0.057 (2) | −0.0110 (19) | 0.0164 (17) | 0.002 (2) |
C11 | 0.057 (2) | 0.093 (3) | 0.074 (3) | 0.007 (2) | 0.034 (2) | 0.017 (2) |
C12 | 0.101 (3) | 0.049 (3) | 0.069 (3) | −0.026 (2) | 0.000 (2) | −0.009 (2) |
N3 | 0.0466 (16) | 0.0467 (19) | 0.0539 (17) | −0.0067 (16) | 0.0151 (14) | −0.0073 (16) |
O4 | 0.0615 (18) | 0.067 (2) | 0.130 (3) | 0.0112 (16) | 0.0251 (18) | −0.0105 (19) |
C13 | 0.070 (3) | 0.067 (3) | 0.141 (4) | 0.004 (3) | 0.042 (3) | −0.025 (3) |
C14 | 0.089 (3) | 0.085 (3) | 0.071 (3) | −0.019 (3) | 0.028 (2) | 0.010 (2) |
C15 | 0.055 (2) | 0.062 (3) | 0.057 (2) | −0.016 (2) | 0.0125 (19) | −0.003 (2) |
Geometric parameters (Å, º) top
Zn1—O1 | 2.119 (2) | C7—C8 | 1.384 (4) |
Zn1—O1i | 2.119 (2) | C7—H7 | 0.9300 |
Zn1—N1 | 2.109 (3) | C8—C9 | 1.368 (5) |
Zn1—N1i | 2.109 (3) | C8—C12 | 1.497 (5) |
Zn1—N2 | 2.136 (3) | C9—C10 | 1.370 (5) |
Zn1—N2i | 2.136 (3) | C9—H9 | 0.9300 |
S1—O2 | 1.417 (2) | C10—H10 | 0.9300 |
S1—O3 | 1.424 (2) | C11—H11A | 0.9600 |
S1—O1 | 1.442 (2) | C11—H11B | 0.9600 |
S1—S2 | 2.1056 (13) | C11—H11C | 0.9600 |
S2—S2i | 2.016 (2) | C12—H12A | 0.9600 |
N1—C1 | 1.338 (4) | C12—H12B | 0.9600 |
N1—C5 | 1.348 (4) | C12—H12C | 0.9600 |
N2—C10 | 1.337 (4) | N3—C15 | 1.328 (4) |
N2—C6 | 1.348 (4) | N3—C13 | 1.435 (4) |
C1—C2 | 1.367 (4) | N3—C14 | 1.436 (4) |
C1—H1 | 0.9300 | O4—C15 | 1.211 (4) |
C2—C3 | 1.383 (5) | C13—H13A | 0.9600 |
C2—H2 | 0.9300 | C13—H13B | 0.9600 |
C3—C4 | 1.389 (4) | C13—H13C | 0.9600 |
C3—C11 | 1.499 (4) | C14—H14A | 0.9600 |
C4—C5 | 1.377 (4) | C14—H14B | 0.9600 |
C4—H4 | 0.9300 | C14—H14C | 0.9600 |
C5—C6 | 1.493 (4) | C15—H15 | 0.9300 |
C6—C7 | 1.368 (4) | | |
| | | |
N1—Zn1—N1i | 174.45 (15) | N2—C6—C5 | 115.0 (3) |
N1—Zn1—O1 | 89.77 (10) | C7—C6—C5 | 123.0 (3) |
N1i—Zn1—O1 | 94.04 (10) | C6—C7—C8 | 120.5 (3) |
N1—Zn1—O1i | 94.04 (10) | C6—C7—H7 | 119.7 |
N1i—Zn1—O1i | 89.77 (10) | C8—C7—H7 | 119.7 |
O1—Zn1—O1i | 93.27 (13) | C9—C8—C7 | 116.9 (3) |
N1—Zn1—N2 | 77.20 (10) | C9—C8—C12 | 121.8 (3) |
N1i—Zn1—N2 | 98.79 (10) | C7—C8—C12 | 121.3 (3) |
O1—Zn1—N2 | 166.73 (9) | C8—C9—C10 | 120.4 (3) |
O1i—Zn1—N2 | 90.15 (9) | C8—C9—H9 | 119.8 |
N1—Zn1—N2i | 98.79 (10) | C10—C9—H9 | 119.8 |
N1i—Zn1—N2i | 77.20 (10) | N2—C10—C9 | 122.8 (3) |
O1—Zn1—N2i | 90.15 (9) | N2—C10—H10 | 118.6 |
O1i—Zn1—N2i | 166.73 (9) | C9—C10—H10 | 118.6 |
N2—Zn1—N2i | 89.42 (14) | C3—C11—H11A | 109.5 |
O2—S1—O3 | 115.04 (16) | C3—C11—H11B | 109.5 |
O2—S1—O1 | 112.20 (17) | H11A—C11—H11B | 109.5 |
O3—S1—O1 | 113.95 (17) | C3—C11—H11C | 109.5 |
O2—S1—S2 | 107.08 (13) | H11A—C11—H11C | 109.5 |
O3—S1—S2 | 100.03 (12) | H11B—C11—H11C | 109.5 |
O1—S1—S2 | 107.26 (10) | C8—C12—H12A | 109.5 |
S2i—S2—S1 | 103.49 (7) | C8—C12—H12B | 109.5 |
S1—O1—Zn1 | 155.98 (15) | H12A—C12—H12B | 109.5 |
C1—N1—C5 | 117.7 (3) | C8—C12—H12C | 109.5 |
C1—N1—Zn1 | 126.2 (2) | H12A—C12—H12C | 109.5 |
C5—N1—Zn1 | 116.0 (2) | H12B—C12—H12C | 109.5 |
C10—N2—C6 | 117.4 (3) | C15—N3—C13 | 121.4 (4) |
C10—N2—Zn1 | 126.9 (2) | C15—N3—C14 | 121.1 (3) |
C6—N2—Zn1 | 115.47 (19) | C13—N3—C14 | 117.5 (4) |
N1—C1—C2 | 123.2 (3) | N3—C13—H13A | 109.5 |
N1—C1—H1 | 118.4 | N3—C13—H13B | 109.5 |
C2—C1—H1 | 118.4 | H13A—C13—H13B | 109.5 |
C1—C2—C3 | 119.9 (3) | N3—C13—H13C | 109.5 |
C1—C2—H2 | 120.1 | H13A—C13—H13C | 109.5 |
C3—C2—H2 | 120.1 | H13B—C13—H13C | 109.5 |
C2—C3—C4 | 116.9 (3) | N3—C14—H14A | 109.5 |
C2—C3—C11 | 122.4 (3) | N3—C14—H14B | 109.5 |
C4—C3—C11 | 120.8 (3) | H14A—C14—H14B | 109.5 |
C5—C4—C3 | 120.6 (3) | N3—C14—H14C | 109.5 |
C5—C4—H4 | 119.7 | H14A—C14—H14C | 109.5 |
C3—C4—H4 | 119.7 | H14B—C14—H14C | 109.5 |
N1—C5—C4 | 121.6 (3) | O4—C15—N3 | 125.9 (4) |
N1—C5—C6 | 115.8 (3) | O4—C15—H15 | 117.1 |
C4—C5—C6 | 122.6 (3) | N3—C15—H15 | 117.1 |
N2—C6—C7 | 122.0 (3) | | |
Symmetry code: (i) −x+1, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O3ii | 0.93 | 2.49 | 3.411 (4) | 170 |
C7—H7···O3ii | 0.93 | 2.46 | 3.381 (4) | 171 |
C10—H10···O4 | 0.93 | 2.47 | 3.250 (5) | 142 |
C11—H11C···O2iii | 0.96 | 2.55 | 3.479 (5) | 163 |
C12—H12A···O3iv | 0.96 | 2.55 | 3.465 (5) | 160 |
C13—H13C···O4v | 0.96 | 2.59 | 3.525 (5) | 166 |
Symmetry codes: (ii) x, −y, z−1/2; (iii) −x+3/2, y−1/2, −z+1/2; (iv) −x+1, y−1, −z+1/2; (v) −x+1/2, y+1/2, −z+1/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | [Cd(S4O6)(C12H12N2)2]·2C3H7NO | [Zn(S4O6)(C12H12N2)2]·2C3H7NO |
Mr | 851.30 | 804.27 |
Crystal system, space group | Monoclinic, C2/c | Monoclinic, C2/c |
Temperature (K) | 294 | 294 |
a, b, c (Å) | 20.7076 (7), 10.7885 (3), 17.5044 (5) | 20.8508 (12), 10.8334 (8), 16.9888 (10) |
β (°) | 108.187 (3) | 107.956 (7) |
V (Å3) | 3715.2 (2) | 3650.6 (4) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.87 | 0.96 |
Crystal size (mm) | 0.15 × 0.05 × 0.04 | 0.10 × 0.05 × 0.04 |
|
Data collection |
Diffractometer | Oxford Gemini S Ultra CCD area-detector diffractometer | Oxford Gemini S Ultra CCD area-detector diffractometer |
Absorption correction | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) |
Tmin, Tmax | 0.94, 0.96 | 0.95, 0.97 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9819, 3844, 2693 | 12111, 3945, 2446 |
Rint | 0.025 | 0.062 |
(sin θ/λ)max (Å−1) | 0.628 | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.065, 1.00 | 0.052, 0.104, 1.03 |
No. of reflections | 3844 | 3945 |
No. of parameters | 226 | 226 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.34, −0.33 | 0.32, −0.29 |
Selected bond lengths (Å) for (I) topCd1—O1 | 2.2767 (19) | Cd1—N2 | 2.3175 (19) |
Cd1—N1 | 2.3156 (18) | | |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O3i | 0.93 | 2.50 | 3.418 (3) | 170 |
C7—H7···O3i | 0.93 | 2.48 | 3.397 (3) | 169 |
C10—H10···O4 | 0.93 | 2.51 | 3.320 (4) | 146 |
C11—H11C···O2ii | 0.96 | 2.48 | 3.427 (4) | 168 |
C12—H12A···O3iii | 0.96 | 2.49 | 3.413 (3) | 161 |
C13—H13C···O4iv | 0.96 | 2.57 | 3.517 (4) | 167 |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+3/2, y−1/2, −z+1/2; (iii) −x+1, y−1, −z+1/2; (iv) −x+1/2, y+1/2, −z+1/2. |
Selected bond lengths (Å) for (II) topZn1—O1 | 2.119 (2) | Zn1—N2 | 2.136 (3) |
Zn1—N1 | 2.109 (3) | | |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O3i | 0.93 | 2.49 | 3.411 (4) | 170 |
C7—H7···O3i | 0.93 | 2.46 | 3.381 (4) | 171 |
C10—H10···O4 | 0.93 | 2.47 | 3.250 (5) | 142 |
C11—H11C···O2ii | 0.96 | 2.55 | 3.479 (5) | 163 |
C12—H12A···O3iii | 0.96 | 2.55 | 3.465 (5) | 160 |
C13—H13C···O4iv | 0.96 | 2.59 | 3.525 (5) | 166 |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+3/2, y−1/2, −z+1/2; (iii) −x+1, y−1, −z+1/2; (iv) −x+1/2, y+1/2, −z+1/2. |
π–π contacts (Å, °) for (I) and (II) topCompound | Group 1/group 2 | IPD (Å) | CCD (Å) | SA (°) |
(I) | Cg1···Cg2v | 1.08 (12) | 4.1042 (13) | 28.32 (12) |
(II) | Cg1···Cg2v | 1.67 (15) | 4.1745 (18) | 30.0 (4) |
Symmetry code: (v) -x + 1, -y, -z.
Notes: Cg1 is the centroid of the N1/C1–C5 ring and Cg2 that of the N2/C6–C10
ring. IPD is the interplanar distance, CCD is the centre-to-centre distance and
SA is the slippage angle. For details, see Janiak (2000). |
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For an extended period of 40 years [viz. those between the reports of Baggio & Baggio (1973) and Suarez et al. (2013)], our group has been interested in the coordination affinity towards transition metals of a variety of different sulfur oxoanions (sufate, sulfite, thiosulfate, peroxodisulfate, di/tri/tetra/pentathionate etc.) in organic–inorganic coordination compounds. Even though many of them show a remarkable coordination tendency (SO42-, SSO32- etc.), others, in particular the latter `thionate' family, present extremely poor binding abilities. This is readily confirmed by a search of the Cambridge Structural database (CSD, Version 5.33; Allen, 2002), contrasting for each ligand the total number of entries (m) and the number of coordinated ones (n); in what follows we shall represent this information as (m,n), viz. dithionate (125,13), trithionate (4,1), tetrathionate (19,2) and pentathionate (8,0). The case of tetrathionate is particularly interesting; only 2 out of 19 structures in the CSD show the anion acting in a coordinating mode [Freire et al. (1998) showed Cu bridging and Freire et al. (2001) showed Mn chelating], and in both cases the ligand had been generated serendipitously during the synthesis procedure as an oxidation product of S2O32-, which thus acted as an unwitting precursor. In summary, no direct synthesis starting from any S4O62- derivative has so far resulted in any transition metal complex with a coordinated tetrathionate group. In order to explore this puzzling situation a bit further, we tried to `fine tune' the synthesis and crystallization process of different S4O62- transition metal compounds (see Experimental section for details). We present herein the first two successful results of these attempts, the isomorphous Cd and Zn title complexes, namely bis(4,4'-dimethyl-2,2'-bipyridine-κ2N,N')(tetrathionato-κ2S,S')cadmium(II) dimethylformamide disolvate, [Cd(tth)(dmbpy)2].2DMF, (I) (Fig. 1a), and the zinc(II) analogue, [Zn(tth)(dmbpy)2(tth)].2DMF, (II) (Fig. 1b), where dmbpy is 4,4'-dimethyl-2,2'-bipyridine, tth is the tetrathionate anion and DMF is dimethylformamide.
The molecules of both isomorphs consist of a transition metal (Tr) cation [Tr = CdII for (I) and Tr = ZnII for (II)] to which one tth and two dmbpy chelating ligands bind. The structures are completed by two symmetry-related DMF solvent molecules. Each complex molecule is bisected by a twofold axis running through the metal centre and halving the chelating tth anion through the central S—S bond. The ancillary symmetry-related dmbpy ligands also act as chelates. The metal cations present a 2+2+2 N4O2 environment. As expected, this results in a distorted sixfold geometry, with rather even Tr···O/N distances (Tables 1 and 2) but with the central angles differing substantially from 90 and 180° [90±18.78 (6) and 180±22.44 (7)° for (I), and 90±12.80 (10) and 180±13.27 (9)° for (II)].
The dmbpy units are planar, with maximum deviations of -0.033 (2) and 0.032 (2) Å for (I), and -0.030 (2) and 0.018 (2) Å for (II), corresponding in both cases to the terminal methyl groups.
The tth ligands chelate the metals in a similar manner to that found in the Mn–bipyridine analogue (Freire et al., 2001). They present typical S—S bonds, while the terminal S—O distances are almost indistinguishable, except for a small lengthening for the coordinated atom O1 [S—O = 1.403 (2)–1.4297 (19) Å for (I) and 1.417 (2)–1.442 (2) Å for (II)] [S1═ O2 and S1═O3 are double bonds, while S1—O1 is a single bond, so why quote them all together like this?]. However, they seem to adjust their flexible spatial conformation to the different metal sizes; the O1—S1—S2—S2i and S1—S2—S2i—S1i torsion angles [symmetry code: (i) -x + 1, y, -z + 1/2] along the anion `backbone' are 56.00 (10) and 59.05 (12)° for (I), and -105.19 (4) and -99.48 (6)° for (II), respectively. Given that, in an A—B—C—D torsion angle, a 90° value corresponds to perpendicular A—B—C:B—C—D planes, and a 0 or 180° value to parallel ones, a smaller or larger departure from 90° can be indicative of a more `close/open' character of the tth anionic group. It transpires (perhaps expectedly) that this case appears more `open', with large departures from 90°. Similar results are obtained by comparing the S1···S1i distances in the coordinated anions, viz. 4.428 (2) for (I) and 4.331 (2) Å for (II).
As stated above, the donor atoms in (I) and (II) cannot fit in any regular polyhedron, but the three chelate ligands abide by the vector bond-valence postulate of the vectorial bond-valence model (for details on the theory, see Harvey et al., 2006). The three ligand vectors, as defined therein, lie in a planar trigonal geometry, with the sum of the angles being 360.0 (2)° for both (I) and (II) (ideal = 360°) and resultant vector moduli of 0.085 valence units (v.u.) for (I) and 0.049 v.u. for (II) (ideal = 0.00 v.u.). The usual bond-valence sums (BVS; Brown, 2002) for each metal atom are 2.00 v.u. for Zn and 2.17 v.u. for Cd (see footnote).
In spite of the lack of good hydrogen-bond donors, which weakens the interactions between monomers, packing indices [as calculated by PLATON (Spek, 2009), following Kitajgorodskij (1973)] are very near the expected average of ca 65% [66.15% for (I) and 67.4% for (II)].
Tables 2 and 4 present relevant C—H···O hydrogen bonds, while Table 5 gives information on the π–π interactions. The first three entries in Tables 2 and 4 correspond to the more active (C—H)aromatic group, and in fact these have a definite structural role. Fig. 2 shows the way in which the interactions presented as the first two entries serve to link self-complementarily adjacent molecules along the [001] direction, in the form of well defined chains, complemented by the π–π interactions between offset stacked dmbpy groups. The third entry in Tables 2 and 4 binds the DMF solvent molecules to the main molecule. The remaining three entries involve the less active (C—H)methyl groups, and these interactions ultimately have the role of interlinking chains together in a rather weak fashion.
This differentiated interaction scheme serves to provide, if not an explanation, at least a plausibility argument for the rather intriguing behaviour in cell metrics, viz. the increase in the c cell dimension when going from Zn to Cd (an expected fact) but a tiny decrease in the remaining two cell dimensions (a rather unusual one), more pronounced in the a dimension. Fig. 2 helps in understanding the increase along the [001] chains: this is the overall direction of the Cd—N interactions (~ 10% longer than the corresponding Zn—N ones), as well as of the bridging (C—H)arom···O and π–π bonds, thus rendering the c cell dimension longer (and more rigid).
Along the remaining two directions, chains are instead held together by much more labile forces [mainly (C—H)methyl···O contacts; Fig. 3]. These are, accordingly, `soft' directions which would not oppose resistence to any eventual compression required by the close packing of the chains.
Footnote. In our extended experience with Cd complexes, we have detected that the bond-valence parameters presented by Brown (2006) for Cd—O and Cd—N (RCd—O = 1.904 and RCd—N = 1.960) usually lead to overestimated BVS values for the cation. This is not an unexpected fact, since it is known that these parameters are not absolutely `universal' but depend on, among other features, the coordination environment (Brown, 2008). Trying to overcome this situation, we tried to find better values for both bond-valence parameters and so, while keeping `b' fixed at its standard value of 0.37, we performed a least-squares fit on ca 2000 CdOnN6-n coordination polyhedra in the CSD (Allen, 2002) of the valence sum equation
Σ (Vi) i:1>6 = V [with V = 2, the expected Cd valence and Vi = exp (Rx - Ri)/b)],
where Rx = RCd—O or RCd—N are the parameters to be refined, and Ri the actual Cd—O and Cd—N bond lengths.
Upon convergence, this procedure led to slightly different values than those given by Brown (2006) (about 1% smaller, viz. RCd—O = 1.886 and RCd—N = 1.946) and with a better performance; they resulted in a BVS for Cd1 in (I) of 2.17, versus 2.26 as calculated from Brown's data.