metal-organic compounds
Di-μ-acetato-κ3O,O′:O;κ3O:O,O′-bis[(acetato-κ2O,O′)(1,10-phenanthroline-κ2N,N′)cadmium(II)]
aUniversidad Nacional de la Patagonia, Sede Trelew, 9100 Trelew, Chubut, Argentina, bCenPat, CONICET, 9120 Puerto Madryn, Chubut, Argentina, cUniversidad Nacional de la Patagonia, Sede Puerto Madryn, Argentina, dDepartamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile and CIMAT, Casilla 487-3, Santiago de Chile, Chile, and eDepartamento de Física, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina
*Correspondence e-mail: unharvey@cenpat.edu.ar
The title compound, [Cd2(C2H3O2)4(C12H8N2)2], consists of dimeric units built up around a centre. Each cadmium(II) unit is chelated by a 1,10-phenanthroline (phen) group and two acetate ligands, one of which also acts as a bridge, linking both seven-coordinated cadmium(II) centres. The is governed by a single π–π interaction between stacked phen groups [centroid–centroid distance 3.5209 (11) Å], leading to a planar structure parallel to (010).
Related literature
For related literature, see: Brown & Altermatt (1985); Janiak (2000); Harvey et al. (2006).
Experimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 2001); cell SAINT (Bruker, 2001); data reduction: SAINT; 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: SHELXTL and PLATON (Spek, 2003).
Supporting information
10.1107/S1600536808029462/kj2097sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808029462/kj2097Isup2.hkl
The title compound was obtained by direct mixing of two 0.15 M solutions of cadmium acetate dihydrate and 1,10-phenanthroline in dimethylformamide. Colorless needles began to develop at once, and after one day adequate crystals for X-ray diffraction could be extracted.
The hydrogen atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms with C—H = 0.96–0.98Å and Uiso(H) = 1.2/1.5× Uequiv(C). Methyl groups were allowed to rotate around their 3-fold axis as well. A peak of ca. 1.5 eA-3 appears at 0.05 Å from Cd1. The next largest peak is less than 1.0 eA-3 in height.
Data collection: SMART (Bruker, 2001); cell
SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); 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: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).[Cd2(C2H3O2)4(C12H8N2)2] | F(000) = 1632 |
Mr = 821.40 | Dx = 1.860 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 11288 reflections |
a = 8.4422 (7) Å | θ = 2.7–27.8° |
b = 15.6384 (13) Å | µ = 1.51 mm−1 |
c = 22.2195 (18) Å | T = 150 K |
V = 2933.5 (4) Å3 | Block, colourless |
Z = 4 | 0.50 × 0.40 × 0.20 mm |
Bruker SMART CCD area-detector diffractometer | 3331 independent reflections |
Radiation source: fine-focus sealed tube | 3062 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.020 |
ϕ and ω scans | θmax = 27.9°, θmin = 1.8° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2001) | h = −10→11 |
Tmin = 0.50, Tmax = 0.74 | k = −19→20 |
22676 measured reflections | l = −28→27 |
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)] = 0.024 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.064 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0401P)2 + 1.4472P] where P = (Fo2 + 2Fc2)/3 |
3331 reflections | (Δ/σ)max = 0.003 |
210 parameters | Δρmax = 1.58 e Å−3 |
0 restraints | Δρmin = −0.40 e Å−3 |
[Cd2(C2H3O2)4(C12H8N2)2] | V = 2933.5 (4) Å3 |
Mr = 821.40 | Z = 4 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 8.4422 (7) Å | µ = 1.51 mm−1 |
b = 15.6384 (13) Å | T = 150 K |
c = 22.2195 (18) Å | 0.50 × 0.40 × 0.20 mm |
Bruker SMART CCD area-detector diffractometer | 3331 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2001) | 3062 reflections with I > 2σ(I) |
Tmin = 0.50, Tmax = 0.74 | Rint = 0.020 |
22676 measured reflections |
R[F2 > 2σ(F2)] = 0.024 | 0 restraints |
wR(F2) = 0.064 | H-atom parameters constrained |
S = 1.06 | Δρmax = 1.58 e Å−3 |
3331 reflections | Δρmin = −0.40 e Å−3 |
210 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Cd1 | 1.020491 (17) | 0.537614 (8) | 0.417981 (6) | 0.01764 (7) | |
N1 | 0.88137 (18) | 0.41531 (9) | 0.38716 (7) | 0.0202 (3) | |
N2 | 1.02282 (19) | 0.52821 (10) | 0.31067 (8) | 0.0216 (4) | |
C1 | 0.8037 (2) | 0.36453 (13) | 0.42461 (9) | 0.0235 (4) | |
H1 | 0.8129 | 0.3746 | 0.4666 | 0.028* | |
C2 | 0.7084 (2) | 0.29656 (12) | 0.40510 (9) | 0.0254 (4) | |
H2 | 0.6519 | 0.2626 | 0.4333 | 0.030* | |
C3 | 0.6983 (2) | 0.28003 (12) | 0.34466 (9) | 0.0262 (4) | |
H3 | 0.6364 | 0.2334 | 0.3305 | 0.031* | |
C4 | 0.7800 (2) | 0.33252 (12) | 0.30367 (9) | 0.0239 (4) | |
C5 | 0.7738 (2) | 0.32032 (14) | 0.23972 (9) | 0.0302 (4) | |
H5 | 0.7160 | 0.2734 | 0.2238 | 0.036* | |
C6 | 0.8487 (3) | 0.37424 (14) | 0.20153 (9) | 0.0312 (5) | |
H6 | 0.8441 | 0.3641 | 0.1594 | 0.037* | |
C7 | 0.9354 (2) | 0.44695 (13) | 0.22400 (9) | 0.0256 (4) | |
C8 | 1.0118 (2) | 0.50644 (16) | 0.18593 (10) | 0.0294 (5) | |
H8 | 1.0089 | 0.4993 | 0.1435 | 0.035* | |
C9 | 1.0896 (3) | 0.57412 (14) | 0.21075 (9) | 0.0308 (4) | |
H9 | 1.1416 | 0.6147 | 0.1858 | 0.037* | |
C10 | 1.0919 (2) | 0.58316 (13) | 0.27331 (9) | 0.0273 (4) | |
H10 | 1.1455 | 0.6310 | 0.2900 | 0.033* | |
C11 | 0.9455 (2) | 0.46042 (11) | 0.28630 (9) | 0.0209 (4) | |
C12 | 0.8686 (2) | 0.40117 (11) | 0.32713 (8) | 0.0199 (4) | |
C13 | 1.2479 (2) | 0.66285 (12) | 0.41072 (8) | 0.0207 (4) | |
C23 | 1.3877 (3) | 0.72303 (14) | 0.40927 (9) | 0.0286 (4) | |
H23A | 1.3759 | 0.7629 | 0.3755 | 0.043* | |
H23B | 1.4855 | 0.6901 | 0.4043 | 0.043* | |
H23C | 1.3923 | 0.7552 | 0.4471 | 0.043* | |
O13 | 1.27330 (18) | 0.58473 (9) | 0.42176 (6) | 0.0282 (3) | |
O23 | 1.11146 (17) | 0.69086 (10) | 0.40168 (8) | 0.0354 (3) | |
C14 | 0.7547 (2) | 0.58393 (11) | 0.48087 (8) | 0.0192 (3) | |
C24 | 0.6115 (2) | 0.59980 (13) | 0.51958 (9) | 0.0252 (4) | |
H24A | 0.6170 | 0.6576 | 0.5365 | 0.038* | |
H24B | 0.6088 | 0.5579 | 0.5523 | 0.038* | |
H24C | 0.5155 | 0.5943 | 0.4951 | 0.038* | |
O14 | 0.88527 (15) | 0.56447 (8) | 0.50710 (6) | 0.0229 (3) | |
O24 | 0.74741 (18) | 0.59082 (9) | 0.42510 (6) | 0.0247 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.01769 (10) | 0.01872 (10) | 0.01652 (10) | −0.00151 (4) | −0.00046 (4) | −0.00019 (4) |
N1 | 0.0207 (7) | 0.0190 (7) | 0.0210 (7) | 0.0005 (6) | −0.0011 (6) | −0.0009 (6) |
N2 | 0.0212 (9) | 0.0241 (8) | 0.0196 (8) | −0.0004 (6) | 0.0005 (6) | −0.0009 (6) |
C1 | 0.0231 (10) | 0.0235 (10) | 0.0238 (9) | 0.0010 (8) | −0.0003 (7) | 0.0000 (7) |
C2 | 0.0223 (9) | 0.0189 (9) | 0.0350 (10) | −0.0002 (7) | 0.0037 (8) | 0.0016 (8) |
C3 | 0.0209 (9) | 0.0206 (9) | 0.0372 (11) | −0.0006 (7) | −0.0017 (8) | −0.0047 (8) |
C4 | 0.0205 (9) | 0.0224 (9) | 0.0290 (10) | 0.0038 (7) | −0.0037 (7) | −0.0060 (7) |
C5 | 0.0285 (10) | 0.0310 (11) | 0.0310 (10) | −0.0005 (8) | −0.0076 (8) | −0.0124 (9) |
C6 | 0.0326 (11) | 0.0398 (12) | 0.0213 (9) | 0.0053 (9) | −0.0055 (8) | −0.0101 (8) |
C7 | 0.0231 (10) | 0.0318 (10) | 0.0220 (9) | 0.0070 (8) | −0.0013 (8) | −0.0021 (8) |
C8 | 0.0299 (11) | 0.0401 (13) | 0.0180 (9) | 0.0071 (9) | 0.0009 (7) | 0.0013 (9) |
C9 | 0.0321 (11) | 0.0364 (12) | 0.0240 (10) | 0.0012 (9) | 0.0056 (8) | 0.0074 (8) |
C10 | 0.0273 (10) | 0.0292 (10) | 0.0255 (10) | −0.0034 (8) | 0.0028 (8) | 0.0029 (8) |
C11 | 0.0168 (9) | 0.0213 (9) | 0.0248 (10) | 0.0044 (7) | −0.0034 (8) | −0.0024 (7) |
C12 | 0.0169 (8) | 0.0213 (9) | 0.0217 (9) | 0.0032 (7) | −0.0018 (7) | −0.0028 (7) |
C13 | 0.0198 (9) | 0.0245 (10) | 0.0179 (8) | −0.0030 (8) | 0.0003 (7) | −0.0008 (7) |
C23 | 0.0239 (10) | 0.0263 (10) | 0.0355 (11) | −0.0050 (8) | −0.0032 (8) | 0.0055 (8) |
O13 | 0.0225 (7) | 0.0234 (7) | 0.0387 (8) | −0.0037 (6) | −0.0055 (6) | 0.0065 (6) |
O23 | 0.0200 (7) | 0.0277 (8) | 0.0584 (10) | 0.0019 (6) | −0.0047 (7) | −0.0034 (7) |
C14 | 0.0204 (8) | 0.0138 (8) | 0.0233 (9) | −0.0002 (6) | −0.0008 (7) | 0.0005 (7) |
C24 | 0.0228 (9) | 0.0286 (10) | 0.0243 (9) | 0.0047 (8) | 0.0014 (7) | 0.0004 (8) |
O14 | 0.0195 (6) | 0.0261 (7) | 0.0229 (6) | 0.0029 (5) | −0.0011 (5) | 0.0022 (5) |
O24 | 0.0248 (7) | 0.0291 (7) | 0.0201 (6) | 0.0023 (6) | −0.0005 (5) | 0.0011 (5) |
Cd1—O13 | 2.2594 (15) | C6—H6 | 0.9500 |
Cd1—O14 | 2.3239 (13) | C7—C11 | 1.403 (3) |
Cd1—N1 | 2.3466 (15) | C7—C8 | 1.413 (3) |
Cd1—N2 | 2.3890 (18) | C8—C9 | 1.362 (3) |
Cd1—O14i | 2.4398 (13) | C8—H8 | 0.9500 |
Cd1—O24 | 2.4561 (15) | C9—C10 | 1.397 (3) |
Cd1—O23 | 2.5425 (16) | C9—H9 | 0.9500 |
N1—C1 | 1.324 (2) | C10—H10 | 0.9500 |
N1—C12 | 1.356 (2) | C11—C12 | 1.450 (3) |
N2—C10 | 1.329 (3) | C13—O23 | 1.248 (2) |
N2—C11 | 1.358 (2) | C13—O13 | 1.265 (2) |
C1—C2 | 1.402 (3) | C13—C23 | 1.510 (3) |
C1—H1 | 0.9500 | C23—H23A | 0.9800 |
C2—C3 | 1.370 (3) | C23—H23B | 0.9800 |
C2—H2 | 0.9500 | C23—H23C | 0.9800 |
C3—C4 | 1.407 (3) | C14—O24 | 1.246 (2) |
C3—H3 | 0.9500 | C14—O14 | 1.283 (2) |
C4—C12 | 1.409 (3) | C14—C24 | 1.504 (2) |
C4—C5 | 1.435 (3) | C24—H24A | 0.9800 |
C5—C6 | 1.353 (3) | C24—H24B | 0.9800 |
C5—H5 | 0.9500 | C24—H24C | 0.9800 |
C6—C7 | 1.442 (3) | O14—Cd1i | 2.4398 (13) |
O13—Cd1—O14 | 111.92 (5) | C8—C7—C6 | 122.93 (19) |
O13—Cd1—N1 | 138.54 (5) | C9—C8—C7 | 119.28 (19) |
O14—Cd1—N1 | 98.64 (5) | C9—C8—H8 | 120.4 |
O13—Cd1—N2 | 92.83 (5) | C7—C8—H8 | 120.4 |
O14—Cd1—N2 | 149.95 (5) | C8—C9—C10 | 119.21 (19) |
N1—Cd1—N2 | 70.28 (5) | C8—C9—H9 | 120.4 |
O13—Cd1—O14i | 83.11 (5) | C10—C9—H9 | 120.4 |
O14—Cd1—O14i | 72.37 (5) | N2—C10—C9 | 123.3 (2) |
N1—Cd1—O14i | 80.16 (5) | N2—C10—H10 | 118.3 |
N2—Cd1—O14i | 129.64 (5) | C9—C10—H10 | 118.3 |
O13—Cd1—O24 | 140.70 (6) | N2—C11—C7 | 122.70 (19) |
O14—Cd1—O24 | 54.75 (4) | N2—C11—C12 | 117.68 (18) |
N1—Cd1—O24 | 79.93 (5) | C7—C11—C12 | 119.61 (17) |
N2—Cd1—O24 | 95.33 (5) | N1—C12—C4 | 122.03 (17) |
O14i—Cd1—O24 | 118.94 (4) | N1—C12—C11 | 118.39 (16) |
O13—Cd1—O23 | 54.03 (5) | C4—C12—C11 | 119.55 (17) |
O14—Cd1—O23 | 95.70 (5) | O23—C13—O13 | 121.80 (18) |
N1—Cd1—O23 | 151.38 (5) | O23—C13—C23 | 119.94 (18) |
N2—Cd1—O23 | 85.03 (6) | O13—C13—C23 | 118.26 (18) |
O14i—Cd1—O23 | 127.99 (5) | O23—C13—Cd1 | 67.36 (11) |
O24—Cd1—O23 | 88.47 (5) | O13—C13—Cd1 | 54.44 (10) |
C1—N1—C12 | 118.75 (16) | C23—C13—Cd1 | 172.67 (14) |
C1—N1—Cd1 | 123.59 (13) | C13—C23—H23A | 109.5 |
C12—N1—Cd1 | 117.36 (12) | C13—C23—H23B | 109.5 |
C10—N2—C11 | 117.80 (18) | H23A—C23—H23B | 109.5 |
C10—N2—Cd1 | 125.95 (13) | C13—C23—H23C | 109.5 |
C11—N2—Cd1 | 116.25 (13) | H23A—C23—H23C | 109.5 |
N1—C1—C2 | 123.00 (18) | H23B—C23—H23C | 109.5 |
N1—C1—H1 | 118.5 | C13—O13—Cd1 | 98.47 (12) |
C2—C1—H1 | 118.5 | C13—O23—Cd1 | 85.70 (12) |
C3—C2—C1 | 118.82 (18) | O24—C14—O14 | 120.99 (17) |
C3—C2—H2 | 120.6 | O24—C14—C24 | 120.98 (17) |
C1—C2—H2 | 120.6 | O14—C14—C24 | 118.02 (16) |
C2—C3—C4 | 119.59 (18) | O24—C14—Cd1 | 63.65 (10) |
C2—C3—H3 | 120.2 | O14—C14—Cd1 | 57.71 (9) |
C4—C3—H3 | 120.2 | C24—C14—Cd1 | 173.24 (13) |
C3—C4—C12 | 117.74 (17) | C14—C24—H24A | 109.5 |
C3—C4—C5 | 123.09 (18) | C14—C24—H24B | 109.5 |
C12—C4—C5 | 119.15 (18) | H24A—C24—H24B | 109.5 |
C6—C5—C4 | 121.43 (19) | C14—C24—H24C | 109.5 |
C6—C5—H5 | 119.3 | H24A—C24—H24C | 109.5 |
C4—C5—H5 | 119.3 | H24B—C24—H24C | 109.5 |
C5—C6—C7 | 120.77 (18) | C14—O14—Cd1 | 94.46 (10) |
C5—C6—H6 | 119.6 | C14—O14—Cd1i | 138.16 (11) |
C7—C6—H6 | 119.6 | Cd1—O14—Cd1i | 107.63 (5) |
C11—C7—C8 | 117.7 (2) | C14—O24—Cd1 | 89.32 (11) |
C11—C7—C6 | 119.41 (19) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
C24—H24B···O13i | 0.98 | 2.51 | 3.313 (2) | 139 |
Symmetry code: (i) −x+2, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Cd2(C2H3O2)4(C12H8N2)2] |
Mr | 821.40 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 150 |
a, b, c (Å) | 8.4422 (7), 15.6384 (13), 22.2195 (18) |
V (Å3) | 2933.5 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.51 |
Crystal size (mm) | 0.50 × 0.40 × 0.20 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2001) |
Tmin, Tmax | 0.50, 0.74 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22676, 3331, 3062 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.658 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.064, 1.06 |
No. of reflections | 3331 |
No. of parameters | 210 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.58, −0.40 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).
Cd1—O13 | 2.2594 (15) | Cd1—O14i | 2.4398 (13) |
Cd1—O14 | 2.3239 (13) | Cd1—O24 | 2.4561 (15) |
Cd1—N1 | 2.3466 (15) | Cd1—O23 | 2.5425 (16) |
Cd1—N2 | 2.3890 (18) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
C24—H24B···O13i | 0.98 | 2.51 | 3.313 (2) | 139 |
Symmetry code: (i) −x+2, −y+1, −z+1. |
Group 1/Group 2 | ccd | ipd | sa |
Cg1/Cg2ii | 3.5209 (11) | 3.50 (1) | 4(2) |
Symmetry code: (ii) 1/2+x,y,1/2-z Cg1: N2,C10,C9,C8,C7,C11 Cg2: C4,C5,C6,C7,C11,C12 ccd: center-to-center distance (distance between ring centroids); sa: mean slippage angle (angle subtended by the intercentroid vector to the plane normal); ipd: mean interplanar distance (distance from one plane to the neighbouring centroid). For details, see Janiak (2000). |
Acknowledgements
We acknowledge the Spanish Research Council (CSIC) for providing us with a free-of-charge licence for the CSD (Allen, 2002).
References
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Harvey, M. A., Baggio, S. & Baggio, R. (2006). Acta Cryst. B62, 1038–1042. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals Google Scholar
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The title compound consists of dimeric units located around a crystallographic symmetry centre (Fig. 1) and made up of two Cd cations, two 1,10-phenanthroline (phen) molecules and four acetate anions. Each cadmium(II) unit is chelated by a phen group (through both nitrogen atoms), and two acetates (through their carboxylato oxygens). A seventh coordination bond adds to these three chelating bites, by way of one of the latter oxygens which acts also as a bridge linking both cadmium(II) centres (Fig. 1). Table 1 presents the coordination distances achieved. The Cd-Cd distance (Cd1···Cd1i: 3.846 (1)Å, (i): 2-x, 1-y, 1-z) as well as the O-Cd-O angle (O14-Cd1-O14i: 72.37 (5) °) are unexceptional.
This coordination scheme of the bis(µ2-acetato)-bis(acetato)-bis(L) type (L: a chelating aromatic amine) leading to a dimeric unit is not common among transition metal cations and in fact this is the first case reported.
The description of coordination geometries when chelating ligands are involved usually poses intrinsic difficulties which can be elegantly surmounted through a vectorial description of the ligand geometry, as proposed by Harvey et al. (2006) based on the Bond Valence Theory (Brown and Altermatt, 1985). When applied to the present case, the geometrical outcome turns out to be a tetrahedron, with angles between ligand vectors spanning the range 91.3 (1)–124.6 (1)°. The fact that the two main values associated with the theory, i.e. the bond valence sum (2.01 valence units, (v.u).) and the modulus of the bond valence vector (0.06 v.u.), agree almost perfectly with expected values (2.00 v.u. and 0.00 v.u., respectively) suggests a significant stability of this coordination sphere.
Regarding non-covalent interactions, there are just a few and not too strong either. The only hydrogen bond present (Table 2) is a non conventional, intramolecular one linking one of the methyl hydrogens to a carboxylato oxygen (Fig. 1). In fact the packing is governed by a single π···π interaction (Table 3 and Fig. 2) between staked phen groups, which gives raise to weakly interacting planar structures paralell to (010).