metal-organic compounds
Tetrakis(μ3-2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-6-nitrophenolato)tetracopper(II)
aDepartment of Inorganic Chemistry, Taras Shevchenko National University of Kyiv, 64\13 Volodymyrska St, Kyiv 01601, Ukraine, and bSTC `Institute for Single Crystals', National Academy of Sciences of Ukraine, 60 Lenina Avenue, Kharkiv 61001, Ukraine
*Correspondence e-mail: kokozay@univ.kiev.ua
The title cluster, [Cu4(C11H12N2O6)4], was obtained from the Cu0–FeCl2·4H2O–H4L–Et3N–DMF reaction system (in air), where H4L is 2-hydroxymethyl-2{[(2-hydroxy-3-nitrophenyl)methylidene]amino}propane-1,3-diol and DMF is dimethylformamide. The consists of one Cu2+ ion and one dianionic ligand; a -4 generates the cluster, which contains a {Cu4O4} cubane-like core. The metal ion has an elongated square-based pyramidal CuNO4 coordination geometry with the N atom in a basal site. An intramolecular O—H⋯O hydrogen bond is observed. The solvent molecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65, 148–155], which indicated a solvent cavity of volume 3131 Å3 containing approximately 749 electrons. These solvent molecules are not considered in the given chemical formula.
CCDC reference: 981257
Related literature
For general background to direct synthesis (DS), see: Kokozay & Shevchenko (2005). For related structures, see: Dey et al. (2002); Dong et al. (2007); Guo et al. (2008). For successful realisation of DS, see: Chygorin et al. (2012); Nesterov et al. (2012).
Experimental
Crystal data
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Data collection: CrysAlis CCD (Agilent, 2012); cell CrysAlis RED (Agilent, 2012); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: OLEX2 (Dolomanov et al., 2009); molecular graphics: SHELXTL; software used to prepare material for publication: publCIF (Westrip, 2010).
Supporting information
CCDC reference: 981257
10.1107/S1600536814000798/hb7174sup1.cif
contains datablocks I, New_Global_Publ_Block. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814000798/hb7174Isup2.hkl
Tris(hydroxymethyl)aminomethane (0.303 g, 2.5 mmol), 3-Nitrosalicylaldehyde (0.418 g, 2.5 mmol), and triethylamine (0.35 ml, 2.5 mmol) were dissolved in dmf (25 ml) in this order, forming an orange solution and magnetically stirred at 60–70°C (15 min). Then, copper powder (0.079 g, 1.25 mmol) and FeCl2.4H2O (0.248 g, 1.25 mmol) were successfully added to the hot orange solution with stirring about 3 h. Brown blocks were isolated by adding diethylether to the dark orange-brown solution after 2 days. Yield: 0.4 g, 48%. The compound is sparingly soluble in dmso and dmf, and it is stable in air.
All H atoms were placed in idealized positions (C–H = 0.95 – 0.99 Å, O–H = 0.84 Å) and constrained to ride on their parent atoms, with Uiso = 1.2Ueq (except Uiso = 1.5Ueq for hydroxyl groups). Hydrogen atom of the hydroxyl group O4–H4 was disordered over two sites with equal occupancy factors of 0.50 in order to fit the intramolecular hydrogen bond O4–H4A···O4'. Several isolated electron density peaks were located during the
whose were believe to be a solvent molecules. Large displacement parameters were observed modeling the disordered oxygen, carbon, and sulfur atoms. SQUEEZE procedure of PLATON indicated a solvent cavity of volume 3131 Å3 centered at (0,0,0), containing approximately 749 electrons. In the final this contribution was removed from the intensity data that produced better results. The hydroxyl group O5—H5A located near the void was believed to be H-bonded with one of the removed solvent molecules. Several reflections with great differences between calculated and observed F2 were omitted during the These reflections were believed to arise because of little impurities of the crystal under study.In last few decades polynuclear complexes have been in focus of intense interest due to their relevance to the active sites of metaloenzimes, and their potential applications as magnetic materials. Thus development of synthetic approaches that could lead to new polynuclear compounds or improve their yields is quite important. Our research group is interested in employment of so-called "direct synthesis" (DS), a serendipitous self-assembling approach based on utilization of metal powders as starting materials to construct coordination compounds both homo- and heterometallic ones. Recently we have shown its ability to produce Co/Fe complexes with Schiff base ligand (Chygorin et al., 2012; Nesterov et al., 2012). It should be noted that outcome of DS is not highly predictable and sometimes we can isolated homometallic or mononuclear complexes only. Such a case was observed in the investigated system: Cu0–FeCl2.4H2O–H4L–Et3N–dmf, where H4L is 2-hydroxymethyl-2{[(2-hydroxy-3-nitrophenyl)methylene]amino}propane-1,3-diol (Fig. 1). The Schiff base ligand, that is obtained by condencation of the salicylaldehyde derivative and tris(hydroxymethyl)aminomethane is typical hydroxy-rich ligand, which can coordinate to several metal centers and accepts various coordination modes, and thus it is an attractive ligand system for serendipitous self-assembling. Despite of this fact this Schiff base ligand has recived little attention to date [only 35 hits were found by searching via CSD (http://www.ccdc.cam.ac.uk/cgi-bin/catreq.cgi?)]. Herein we report the synthesis of a new tetranuclear cubane complex starting from potentially polydentate hydroxyl-rich ligand.
The reaction of copper powder with iron(II) chloride in dmf solution of the tetrapodal Schiff base ligand, formed in situ, in basic medium with free access of air leads to the isolation of the homometallic cuban complex [Cu4(C11H12O6N2)4]. The Schiff base ligand H4L was obtained by condensation of 3-nitro-salicylaldehyde and tris(hydroxymethyl)aminomethane (Fig. 1). The molar ratio of starting materials (Cu0: FeCl2: Schiff base ligand) was taken 1:1:2. The reaction was carried out in air with heating and stirring till total dissolution of metal powder was observed.
Tetranuclear molecular complex (Fig. 2) consists of the discrete [Cu4(H2L)4] moiety with a {Cu4O4} cubane-like core. Eight alternately arranged netal centers and oxygen atoms from methoxy groups form a distorted {Cu4O4} cube with local S4-symmetry. Each of four ligands coordinates in a tridentate mode as an (H2L)2- dianion, with the phenoxyl and one of the alkoxyl groups deprotonated. The NO2 donor set from one ligand molecule together with O-atom from methoxy arm of another ligand forms distorted square coordination polyhedra around each metal center (with RMS deviation of atoms from square plane of 0.135 Å). Coordination lengths vary in the range of 1.892 - 1.955 Å, and X—Cu—Y angles vary in the range of 84.8 - 94.9° that is comparable with the known literature data. The oxygen atom of the methoxy group of the third ligand molecule coordinates on this metal atom with Cu—O length of 2.524 Å, so that can be threated as additional coordination. In crystal, weak C4—H4B···O2' hydrogen bonds (1.25 - y,x - 0.25,z - 0.25; H···O' 2.51 Å, C—H···O' 153°) form three-dimensional-connected network with channels along (111) crystallographic direction. Minimal channel dimension is about 6.74 Å (O5···O5' distance). The crystal packing diagram is shown in Fig. 3.
For general background to direct synthesis (DS), see: Kokozay & Shevchenko (2005). For related structures, see: Dey et al. (2002); Dong et al. (2007); Guo et al. (2008). For successful realisation of DS, see: Chygorin et al. (2012); Nesterov et al. (2012).
Data collection: CrysAlis CCD (Agilent, 2012); cell
CrysAlis RED (Agilent, 2012); data reduction: CrysAlis RED (Agilent, 2012); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: OLEX2 (Dolomanov et al., 2009); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).[Cu4(C11H12N2O6)4] | Dx = 1.158 Mg m−3 |
Mr = 1327.06 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, I41/a | Cell parameters from 462 reflections |
Hall symbol: -I 4ad | θ = 3.0–25.0° |
a = 20.5587 (14) Å | µ = 1.17 mm−1 |
c = 18.010 (2) Å | T = 173 K |
V = 7612.0 (11) Å3 | Block, brown |
Z = 4 | 0.40 × 0.40 × 0.30 mm |
F(000) = 2704 |
Agilent Xcalibur Sapphire3 diffractometer | 3349 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 1395 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.000 |
Detector resolution: 16.1827 pixels mm-1 | θmax = 25.0°, θmin = 3.2° |
ω scans | h = −16→17 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | k = 0→24 |
Tmin = 0.653, Tmax = 0.721 | l = 0→21 |
3349 measured reflections |
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)] = 0.075 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.184 | H-atom parameters constrained |
S = 0.80 | w = 1/[σ2(Fo2) + (0.060P)2] where P = (Fo2 + 2Fc2)/3 |
3349 reflections | (Δ/σ)max = 0.001 |
182 parameters | Δρmax = 0.94 e Å−3 |
0 restraints | Δρmin = −0.57 e Å−3 |
[Cu4(C11H12N2O6)4] | Z = 4 |
Mr = 1327.06 | Mo Kα radiation |
Tetragonal, I41/a | µ = 1.17 mm−1 |
a = 20.5587 (14) Å | T = 173 K |
c = 18.010 (2) Å | 0.40 × 0.40 × 0.30 mm |
V = 7612.0 (11) Å3 |
Agilent Xcalibur Sapphire3 diffractometer | 3349 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | 1395 reflections with I > 2σ(I) |
Tmin = 0.653, Tmax = 0.721 | Rint = 0.000 |
3349 measured reflections |
R[F2 > 2σ(F2)] = 0.075 | 0 restraints |
wR(F2) = 0.184 | H-atom parameters constrained |
S = 0.80 | Δρmax = 0.94 e Å−3 |
3349 reflections | Δρmin = −0.57 e Å−3 |
182 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 | Occ. (<1) | |
Cu1 | 0.48941 (4) | 0.66864 (4) | 0.06731 (4) | 0.0396 (3) | |
O1 | 0.5536 (2) | 0.6041 (2) | 0.0524 (3) | 0.0451 (13) | |
N1 | 0.4460 (3) | 0.6539 (3) | −0.0276 (3) | 0.0406 (16) | |
C1 | 0.5204 (4) | 0.5693 (4) | −0.0716 (4) | 0.047 (2) | |
N2 | 0.6541 (4) | 0.5153 (3) | 0.0538 (4) | 0.0542 (19) | |
O2 | 0.6303 (3) | 0.5101 (3) | 0.1159 (3) | 0.0611 (17) | |
C2 | 0.5608 (4) | 0.5690 (4) | −0.0063 (5) | 0.047 (2) | |
O3 | 0.7144 (3) | 0.5100 (3) | 0.0436 (3) | 0.0751 (19) | |
C3 | 0.6141 (4) | 0.5230 (4) | −0.0096 (5) | 0.050 (2) | |
O4 | 0.4358 (3) | 0.7332 (3) | −0.1606 (3) | 0.0761 (19) | |
H4A | 0.4728 | 0.7401 | −0.1646 | 0.114* | 0.50 |
H4C | 0.4145 | 0.7014 | −0.1769 | 0.114* | 0.50 |
C4 | 0.6276 (4) | 0.4875 (4) | −0.0723 (5) | 0.061 (2) | |
H4B | 0.6644 | 0.4596 | −0.0728 | 0.073* | |
O5 | 0.2776 (3) | 0.7029 (3) | −0.0736 (4) | 0.0732 (18) | |
H5A | 0.2430 | 0.6816 | −0.0784 | 0.110* | |
C5 | 0.5890 (4) | 0.4913 (4) | −0.1342 (5) | 0.061 (3) | |
H5B | 0.5991 | 0.4672 | −0.1777 | 0.073* | |
O6 | 0.4282 (2) | 0.7408 (2) | 0.0779 (2) | 0.0369 (12) | |
C6 | 0.5353 (4) | 0.5310 (4) | −0.1317 (4) | 0.052 (2) | |
H6A | 0.5071 | 0.5320 | −0.1735 | 0.063* | |
C7 | 0.4659 (4) | 0.6122 (4) | −0.0773 (4) | 0.048 (2) | |
H7A | 0.4416 | 0.6101 | −0.1220 | 0.057* | |
C8 | 0.3906 (4) | 0.6972 (4) | −0.0412 (4) | 0.047 (2) | |
C9 | 0.4121 (4) | 0.7530 (4) | −0.0911 (4) | 0.057 (2) | |
H9A | 0.3747 | 0.7826 | −0.0989 | 0.069* | |
H9B | 0.4465 | 0.7780 | −0.0653 | 0.069* | |
C10 | 0.3319 (4) | 0.6594 (4) | −0.0737 (5) | 0.058 (2) | |
H10A | 0.3415 | 0.6448 | −0.1249 | 0.069* | |
H10B | 0.3223 | 0.6206 | −0.0430 | 0.069* | |
C11 | 0.3712 (4) | 0.7262 (4) | 0.0359 (4) | 0.0436 (19) | |
H11A | 0.3454 | 0.7663 | 0.0285 | 0.052* | |
H11B | 0.3440 | 0.6945 | 0.0633 | 0.052* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.0337 (6) | 0.0344 (6) | 0.0509 (5) | 0.0009 (5) | −0.0021 (5) | −0.0018 (4) |
O1 | 0.044 (3) | 0.029 (3) | 0.062 (3) | −0.005 (3) | −0.002 (3) | −0.015 (3) |
N1 | 0.039 (4) | 0.037 (4) | 0.046 (3) | −0.005 (3) | −0.001 (3) | −0.006 (3) |
C1 | 0.032 (5) | 0.046 (5) | 0.064 (5) | 0.001 (4) | 0.007 (4) | −0.004 (5) |
N2 | 0.053 (5) | 0.038 (4) | 0.071 (5) | 0.012 (4) | −0.004 (4) | −0.017 (4) |
O2 | 0.059 (4) | 0.040 (4) | 0.084 (4) | 0.008 (3) | −0.019 (4) | −0.004 (3) |
C2 | 0.034 (5) | 0.022 (4) | 0.084 (6) | −0.001 (4) | 0.003 (5) | −0.009 (4) |
O3 | 0.032 (4) | 0.077 (5) | 0.116 (5) | 0.013 (3) | −0.001 (3) | −0.026 (4) |
C3 | 0.039 (5) | 0.041 (5) | 0.071 (5) | −0.023 (4) | −0.002 (5) | −0.018 (5) |
O4 | 0.082 (5) | 0.088 (5) | 0.059 (3) | −0.014 (4) | 0.006 (3) | 0.006 (3) |
C4 | 0.039 (5) | 0.045 (6) | 0.098 (6) | −0.004 (5) | 0.005 (5) | −0.024 (5) |
O5 | 0.038 (4) | 0.065 (4) | 0.116 (5) | 0.001 (3) | −0.020 (4) | 0.000 (4) |
C5 | 0.037 (5) | 0.051 (6) | 0.094 (6) | −0.004 (5) | 0.020 (5) | −0.033 (5) |
O6 | 0.019 (3) | 0.029 (3) | 0.063 (3) | 0.002 (2) | −0.007 (2) | 0.004 (2) |
C6 | 0.040 (5) | 0.054 (6) | 0.062 (5) | −0.012 (5) | 0.005 (4) | −0.016 (5) |
C7 | 0.044 (5) | 0.048 (5) | 0.051 (5) | −0.013 (4) | −0.001 (4) | 0.010 (4) |
C8 | 0.032 (5) | 0.043 (5) | 0.067 (5) | 0.005 (4) | −0.013 (4) | 0.004 (4) |
C9 | 0.048 (6) | 0.063 (6) | 0.062 (5) | −0.010 (5) | −0.017 (4) | 0.010 (5) |
C10 | 0.041 (5) | 0.061 (6) | 0.071 (5) | 0.005 (5) | 0.000 (5) | −0.007 (5) |
C11 | 0.030 (5) | 0.041 (5) | 0.059 (4) | 0.000 (4) | 0.003 (4) | −0.002 (4) |
Cu1—O1 | 1.892 (5) | C4—C5 | 1.371 (11) |
Cu1—O6i | 1.940 (5) | C4—H4B | 0.9500 |
Cu1—N1 | 1.952 (6) | O5—C10 | 1.430 (9) |
Cu1—O6 | 1.954 (4) | O5—H5A | 0.8400 |
Cu1—O6ii | 2.524 (5) | C5—C6 | 1.374 (11) |
O1—C2 | 1.288 (8) | C5—H5B | 0.9500 |
N1—C7 | 1.304 (9) | O6—C11 | 1.428 (8) |
N1—C8 | 1.467 (9) | O6—Cu1iii | 1.940 (5) |
C1—C6 | 1.373 (10) | C6—H6A | 0.9500 |
C1—C7 | 1.428 (10) | C7—H7A | 0.9500 |
C1—C2 | 1.440 (10) | C8—C9 | 1.524 (10) |
N2—O2 | 1.224 (8) | C8—C10 | 1.551 (10) |
N2—O3 | 1.259 (8) | C8—C11 | 1.562 (10) |
N2—C3 | 1.417 (10) | C9—H9A | 0.9900 |
C2—C3 | 1.449 (10) | C9—H9B | 0.9900 |
C3—C4 | 1.373 (10) | C10—H10A | 0.9900 |
O4—C9 | 1.403 (9) | C10—H10B | 0.9900 |
O4—H4A | 0.7773 | C11—H11A | 0.9900 |
O4—H4C | 0.8400 | C11—H11B | 0.9900 |
O1—Cu1—O6i | 93.6 (2) | C6—C5—H5B | 120.9 |
O1—Cu1—N1 | 94.9 (2) | C11—O6—Cu1iii | 118.5 (4) |
O6i—Cu1—N1 | 164.4 (2) | C11—O6—Cu1 | 108.5 (4) |
O1—Cu1—O6 | 174.8 (2) | Cu1iii—O6—Cu1 | 108.6 (2) |
O6i—Cu1—O6 | 87.9 (2) | C1—C6—C5 | 123.1 (8) |
O1—Cu1—O6ii | 93.45 (18) | C1—C6—H6A | 118.5 |
O6i—Cu1—O6ii | 73.19 (17) | C5—C6—H6A | 118.5 |
N1—Cu1—O6ii | 119.2 (2) | N1—C7—C1 | 127.0 (7) |
O6—Cu1—O6ii | 82.22 (17) | N1—C7—H7A | 116.5 |
N1—Cu1—O6 | 84.8 (2) | C1—C7—H7A | 116.5 |
C2—O1—Cu1 | 126.0 (5) | N1—C8—C9 | 109.3 (6) |
C7—N1—C8 | 121.9 (6) | N1—C8—C10 | 111.3 (6) |
C7—N1—Cu1 | 124.0 (5) | C9—C8—C10 | 112.3 (6) |
C8—N1—Cu1 | 114.0 (5) | N1—C8—C11 | 106.4 (6) |
C6—C1—C7 | 118.2 (8) | C9—C8—C11 | 108.1 (7) |
C6—C1—C2 | 120.9 (8) | C10—C8—C11 | 109.2 (6) |
C7—C1—C2 | 120.8 (7) | O4—C9—C8 | 114.1 (7) |
O2—N2—O3 | 121.3 (7) | O4—C9—H9A | 108.7 |
O2—N2—C3 | 120.9 (7) | C8—C9—H9A | 108.7 |
O3—N2—C3 | 117.6 (7) | O4—C9—H9B | 108.7 |
O1—C2—C1 | 127.1 (7) | C8—C9—H9B | 108.7 |
O1—C2—C3 | 119.0 (7) | H9A—C9—H9B | 107.6 |
C1—C2—C3 | 113.9 (7) | O5—C10—C8 | 107.0 (6) |
C4—C3—N2 | 119.1 (8) | O5—C10—H10A | 110.3 |
C4—C3—C2 | 122.3 (8) | C8—C10—H10A | 110.3 |
N2—C3—C2 | 118.6 (7) | O5—C10—H10B | 110.3 |
C9—O4—H4A | 111.7 | C8—C10—H10B | 110.3 |
C9—O4—H4C | 110.9 | H10A—C10—H10B | 108.6 |
H4A—O4—H4C | 128.4 | O6—C11—C8 | 110.0 (6) |
C5—C4—C3 | 121.4 (8) | O6—C11—H11A | 109.7 |
C5—C4—H4B | 119.3 | C8—C11—H11A | 109.7 |
C3—C4—H4B | 119.3 | O6—C11—H11B | 109.7 |
C10—O5—H5A | 109.5 | C8—C11—H11B | 109.7 |
C4—C5—C6 | 118.2 (8) | H11A—C11—H11B | 108.2 |
C4—C5—H5B | 120.9 | ||
O6i—Cu1—O1—C2 | 170.0 (6) | O6i—Cu1—O6—C11 | −139.6 (4) |
N1—Cu1—O1—C2 | 3.0 (6) | N1—Cu1—O6—C11 | 26.7 (4) |
O6—Cu1—O1—C2 | −84 (2) | O1—Cu1—O6—Cu1iii | −116 (2) |
O6ii—Cu1—O1—C2 | −116.7 (6) | O6i—Cu1—O6—Cu1iii | −9.5 (2) |
O1—Cu1—N1—C7 | −2.5 (6) | N1—Cu1—O6—Cu1iii | 156.7 (3) |
O6i—Cu1—N1—C7 | −125.4 (8) | C7—C1—C6—C5 | 175.5 (7) |
O6—Cu1—N1—C7 | 172.3 (6) | C2—C1—C6—C5 | −0.9 (12) |
O6ii—Cu1—N1—C7 | 94.2 (6) | C4—C5—C6—C1 | 3.4 (13) |
O1—Cu1—N1—C8 | −178.6 (5) | C8—N1—C7—C1 | 177.6 (7) |
O6i—Cu1—N1—C8 | 58.5 (11) | Cu1—N1—C7—C1 | 1.8 (11) |
O6—Cu1—N1—C8 | −3.8 (5) | C6—C1—C7—N1 | −177.0 (7) |
O6ii—Cu1—N1—C8 | −81.9 (5) | C2—C1—C7—N1 | −0.6 (12) |
Cu1—O1—C2—C1 | −2.8 (11) | C7—N1—C8—C9 | −77.3 (8) |
Cu1—O1—C2—C3 | 178.0 (5) | Cu1—N1—C8—C9 | 98.9 (6) |
C6—C1—C2—O1 | 177.4 (7) | C7—N1—C8—C10 | 47.3 (9) |
C7—C1—C2—O1 | 1.0 (12) | Cu1—N1—C8—C10 | −136.5 (5) |
C6—C1—C2—C3 | −3.4 (11) | C7—N1—C8—C11 | 166.2 (6) |
C7—C1—C2—C3 | −179.7 (7) | Cu1—N1—C8—C11 | −17.6 (7) |
O2—N2—C3—C4 | −135.5 (8) | N1—C8—C9—O4 | 59.8 (8) |
O3—N2—C3—C4 | 40.2 (11) | C10—C8—C9—O4 | −64.2 (9) |
O2—N2—C3—C2 | 45.5 (10) | C11—C8—C9—O4 | 175.3 (6) |
O3—N2—C3—C2 | −138.8 (8) | N1—C8—C10—O5 | 170.8 (6) |
O1—C2—C3—C4 | −175.1 (7) | C9—C8—C10—O5 | −66.3 (8) |
C1—C2—C3—C4 | 5.5 (11) | C11—C8—C10—O5 | 53.6 (8) |
O1—C2—C3—N2 | 3.8 (11) | Cu1iii—O6—C11—C8 | −167.6 (4) |
C1—C2—C3—N2 | −175.5 (7) | Cu1—O6—C11—C8 | −43.2 (6) |
N2—C3—C4—C5 | 177.6 (8) | N1—C8—C11—O6 | 39.5 (8) |
C2—C3—C4—C5 | −3.5 (13) | C9—C8—C11—O6 | −77.8 (7) |
C3—C4—C5—C6 | −1.2 (13) | C10—C8—C11—O6 | 159.8 (6) |
O1—Cu1—O6—C11 | 114 (2) |
Symmetry codes: (i) −y+5/4, x+1/4, −z+1/4; (ii) −x+1, −y+3/2, z; (iii) y−1/4, −x+5/4, −z+1/4. |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O4ii | 0.78 | 1.96 | 2.729 (9) | 171 |
Symmetry code: (ii) −x+1, −y+3/2, z. |
Cu1—O1 | 1.892 (5) | Cu1—O6 | 1.954 (4) |
Cu1—O6i | 1.940 (5) | Cu1—O6ii | 2.524 (5) |
Cu1—N1 | 1.952 (6) |
Symmetry codes: (i) −y+5/4, x+1/4, −z+1/4; (ii) −x+1, −y+3/2, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O4ii | 0.78 | 1.96 | 2.729 (9) | 171 |
Symmetry code: (ii) −x+1, −y+3/2, z. |
Acknowledgements
This work was partly supported by the State Fund for Fundamental Research of Ukraine (project 54.3/005).
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In last few decades polynuclear complexes have been in focus of intense interest due to their relevance to the active sites of metaloenzimes, and their potential applications as magnetic materials. Thus development of synthetic approaches that could lead to new polynuclear compounds or improve their yields is quite important. Our research group is interested in employment of so-called "direct synthesis" (DS), a serendipitous self-assembling approach based on utilization of metal powders as starting materials to construct coordination compounds both homo- and heterometallic ones. Recently we have shown its ability to produce Co/Fe complexes with Schiff base ligand (Chygorin et al., 2012; Nesterov et al., 2012). It should be noted that outcome of DS is not highly predictable and sometimes we can isolated homometallic or mononuclear complexes only. Such a case was observed in the investigated system: Cu0–FeCl2.4H2O–H4L–Et3N–dmf, where H4L is 2-hydroxymethyl-2{[(2-hydroxy-3-nitrophenyl)methylene]amino}propane-1,3-diol (Fig. 1). The Schiff base ligand, that is obtained by condencation of the salicylaldehyde derivative and tris(hydroxymethyl)aminomethane is typical hydroxy-rich ligand, which can coordinate to several metal centers and accepts various coordination modes, and thus it is an attractive ligand system for serendipitous self-assembling. Despite of this fact this Schiff base ligand has recived little attention to date [only 35 hits were found by searching via CSD (http://www.ccdc.cam.ac.uk/cgi-bin/catreq.cgi?)]. Herein we report the synthesis of a new tetranuclear cubane complex starting from potentially polydentate hydroxyl-rich ligand.
The reaction of copper powder with iron(II) chloride in dmf solution of the tetrapodal Schiff base ligand, formed in situ, in basic medium with free access of air leads to the isolation of the homometallic cuban complex [Cu4(C11H12O6N2)4]. The Schiff base ligand H4L was obtained by condensation of 3-nitro-salicylaldehyde and tris(hydroxymethyl)aminomethane (Fig. 1). The molar ratio of starting materials (Cu0: FeCl2: Schiff base ligand) was taken 1:1:2. The reaction was carried out in air with heating and stirring till total dissolution of metal powder was observed.
Tetranuclear molecular complex (Fig. 2) consists of the discrete [Cu4(H2L)4] moiety with a {Cu4O4} cubane-like core. Eight alternately arranged netal centers and oxygen atoms from methoxy groups form a distorted {Cu4O4} cube with local S4-symmetry. Each of four ligands coordinates in a tridentate mode as an (H2L)2- dianion, with the phenoxyl and one of the alkoxyl groups deprotonated. The NO2 donor set from one ligand molecule together with O-atom from methoxy arm of another ligand forms distorted square coordination polyhedra around each metal center (with RMS deviation of atoms from square plane of 0.135 Å). Coordination lengths vary in the range of 1.892 - 1.955 Å, and X—Cu—Y angles vary in the range of 84.8 - 94.9° that is comparable with the known literature data. The oxygen atom of the methoxy group of the third ligand molecule coordinates on this metal atom with Cu—O length of 2.524 Å, so that can be threated as additional coordination. In crystal, weak C4—H4B···O2' hydrogen bonds (1.25 - y,x - 0.25,z - 0.25; H···O' 2.51 Å, C—H···O' 153°) form three-dimensional-connected network with channels along (111) crystallographic direction. Minimal channel dimension is about 6.74 Å (O5···O5' distance). The crystal packing diagram is shown in Fig. 3.