Diaqua­bis(ethyl­enediamine-κ2 N,N′)copper(II) bis­(4-phenyl­benzoate) 2.66-hydrate

José A Fernandes; Ana I Ramos; Patrícia Silva; Susana S Braga; Paulo Ribeiro-Claro; João Rocha; Filipe A Almeida Paz

doi:10.1107/S1600536810016223

. 2010 May 8;66(Pt 6):m626–m627. doi: 10.1107/S1600536810016223

Diaquabis(ethylenediamine-κ² N,N′)copper(II) bis(4-phenylbenzoate) 2.66-hydrate

José A Fernandes ^a, Ana I Ramos ^a, Patrícia Silva ^a, Susana S Braga ^a, Paulo Ribeiro-Claro ^a, João Rocha ^a, Filipe A Almeida Paz ^a,^*

PMCID: PMC2979460 PMID: 21579282

Abstract

In the title complex, [Cu(C₂H₈N₂)₂(H₂O)₂](C₁₃H₉O₂)₂·2.66H₂O, the Cu^II centre (located at an inversion centre) is coordinated by two bidentate ethylenediamine (en) ligands and two water O atoms in a typical Jahn–Teller distorted octahedral geometry. The amino groups and the water molecules are disordered over two distinct crystallographic positions with occupancies of 1/3 and 2/3. In the crystal, the cations and anions are disposed in alternating layers. One of the water molecules of crystallization is disordered and the other has a fractional occupation. In the 2/3 occupancy component, water molecules are organized into a chain composed of hexameric units interconnected by carboxylate bridges.

Related literature

For general background to reactions based on the copper cation, see: Graham et al. (2000 ▶); Majumder et al. (2006 ▶); Rao et al. (2004 ▶); Zhao et al. (2009 ▶). For examples of framework-type structures of hybrid materials comprising carboxylate anions, see: Eddaoudi et al. (2001 ▶). For general background to crystal engineering approaches from our research group, see: Paz & Khimyak et al. (2002 ▶); Paz & Bond et al. (2002 ▶); Paz & Klinowski (2003 ▶); Paz et al. (2005 ▶); Shi et al. (2008 ▶). For a description of the graph-set notation for hydrogen-bonded aggregates, see: Grell et al. (1999 ▶).

Experimental

Crystal data

[Cu(C₂H₈N₂)₂(H₂O)₂](C₁₃H₉O₂)₂·2.66H₂O
M _r = 662.20
Monoclinic,
a = 6.1466 (6) Å
b = 34.984 (3) Å
c = 7.3101 (7) Å
β = 95.819 (4)°
V = 1563.8 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.76 mm⁻¹
T = 150 K
0.13 × 0.10 × 0.06 mm

Data collection

Bruker X8 Kappa CCD APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1997 ▶) T _min = 0.908, T _max = 0.956
26073 measured reflections
4736 independent reflections
3908 reflections with I > 2σ(I)
R _int = 0.034

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.137
S = 1.10
4736 reflections
259 parameters
15 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.52 e Å⁻³
Δρ_min = −0.66 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: SAINT-Plus (Bruker, 2005 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810016223/tk2668sup1.cif

e-66-0m626-sup1.cif^{(27.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810016223/tk2668Isup2.hkl

e-66-0m626-Isup2.hkl^{(232KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Cu1—N1	2.019 (2)
Cu1—N1′	2.035 (4)
Cu1—N2	2.006 (2)
Cu1—N2′	2.008 (4)
Cu1—O1W	2.496 (4)
Cu1—O3W	2.605 (2)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O2ⁱⁱ	0.92	2.13	2.986 (3)	154
N1—H1B⋯O2Wⁱⁱⁱ	0.92	2.32	3.093 (3)	141
N2—H2A⋯O2ⁱⁱⁱ	0.92	2.16	3.037 (3)	158
N1′—H1E⋯O2Wⁱⁱⁱ	0.92	2.51	3.375 (4)	157
N1′—H1F⋯O1ⁱⁱⁱ	0.92	2.20	3.087 (5)	161
N2′—H2E⋯O4W^iv	0.92	2.33	3.181 (9)	154
N2′—H2F⋯O2W^v	0.92	2.21	3.055 (5)	152
O1W—H1M⋯O2ⁱⁱⁱ	0.95 (1)	1.92 (1)	2.844 (4)	163 (4)
O1W—H1N⋯O2^vi	0.95 (1)	1.88 (1)	2.814 (4)	169 (4)
O2W—H2M⋯O2^vii	0.95 (1)	1.73 (1)	2.668 (2)	168 (5)
O2W—H2N⋯O1^viii	0.95 (1)	1.87 (2)	2.765 (2)	156 (5)
O3W—H3M⋯O2W^v	0.95 (1)	2.01 (1)	2.932 (3)	163 (3)
O3W—H3N⋯O1^ix	0.95 (1)	1.82 (1)	2.721 (3)	158 (3)
O4W—H4M⋯O1^x	0.95 (1)	1.91	2.8562 (17)	178

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Symmetry codes: (ii) Inline graphic ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) ; (x) .

Acknowledgments

We are grateful to the Fundação para a Ciência e a Tecnologia (FCT, Portugal) for their general financial support (R&D projects PTDC/QUI/65805/2006 and PDTC/QUI/69302/2006), for a post-doctoral research grant (under the former project), for the PhD grant SFRH/BD46601/2008, and also for specific funding toward the purchase of the single-crystal diffractometer.

supplementary crystallographic information

Comment

Carboxylate anions are widely used in the synthesis of coordination polymers (Eddaoudi et al., 2001). Our research group specialises on the design and preparation of these compounds (Paz & Khimyak et al., 2002; Paz et al., 2003; Paz et al., 2005; Shi et al., 2008) and following our previous interest in the biphenyldicarboxylate anion (bpdc^2-) as a bridging ligand (Paz & Bond et al., 2002), we have recently started to use 4-phenylbenzoate (pb^-). Given its ability to form stable coordination complexes, copper was chosen as metal centre for our preliminary studies (Graham et al., 2000; Majumder et al., 2006; Rao et al., 2004; Zhao et al., 2009). While reacting pb^- with [Cu(en)₂(H₂O)₂](NO₃)₂ we isolated as a secondary product, the title complex, (I), whose structure we wish to report now.

The asymmetric unit of (I) contains one 4-phenylbenzoate anion, 1.33 water molecules of crystallisation, and 1/2 of the [Cu(en)₂(H₂O)₂]²⁺ cation; the latter is situated about a centre of inversion. The species are distributed in alternating layers along the b axis (Fig. 1a). An ordered hydrophobic layer is composed by the aromatic rings from pb^- and occupies the unit cell regions located between ca. 0.1 < b < 0.4 and 0.6 < b < 0.9 (Fig. 1a). Along the c axis, these moieties are distributed in two alternating layers, from which the aromatic rings of a specific layer are off-set from those of the layers directly above and below, avoiding efficient π-π stacking (Fig. 1b). The two average planes containing the phenyl rings are mutually rotated by ca. 40°, which increases the distance between hydrogen atoms of neighbouring pb^- anions.

The hydrophilic layer, which is formed by the carboxylate groups, the [Cu(en)₂(H₂O)₂]²⁺ cations and the water molecules of crystallisation, exhibits extensive crystallographic disorder. On the one hand, the centrosymmetric cation has two possible mutually-tilted crystallographic positions (rates of occupancy of 1/3 and 2/3; see Fig. 2), which have in common the two carbon atoms and the Cu centre. For each possibility the Cu centre exhibits a typical octahedral coordination environment with a strong Jahn-Teller distortion: the Cu—N bonds (equatorial planes) range from 2.006 (2) to 2.035 (4) Å, and the Cu—O_water (apical positions) are either 2.601 (2) Å (2/3 occupancy) or 2.495 (4) Å (1/3 occupancy); however, the cis octahedral angles fall within a rather short range around the ideal value: 84.65 (15) – 95.35 (15) ° (Table 1).

The crystal structure is rich with a variety of hydrogen bonds due to the presence of amines, carboxylates and water molecules (both coordinated and uncoordinated). The formed hydrogen bonding sub-network is strongly affected by the aforementioned crystal disorder plus some additional disorder associated with the two uncoordinated water molecules (O2W and O4W). The coordinated O3W and uncoordinated O2W water molecules, plus the O1 oxygen atom of the carboxylate group are engaged in a series of strong [O···O distances ranging from 2.668 (2) to 2.932 (3) Å; Table 2] and rather directional [angles in the range 156 (5) – 168 (5) °; Table 2] O—H···O hydrogen bonds, forming an almost planar supramolecular hexagon (longest distance to the average plane of ca. 0.17 Å) with a graph set motif R₆⁴(12) (Grell et al., 1999) (Fig. 3). Remarkably, the carboxylate group further establishes bridges between adjacent supramolecular hexagons [O2W—H2M···O2 at 1.731 (10) Å; Fig. 3], leading to a 1-D hydrogen bonded chain running parallel the a axis (Fig. 3). The amino groups also participate in the hydrogen bonding network with rather directional interactions [angles are in the range 141 – 174 °; Table 2], even though the N···O distances with the O2 carboxylate atom and the water molecules are relatively long [N1···O2 2.986 (3) Å, N2···O2 3.037 (3) Å and N1···O2W 3.093 (3) Å].

Experimental

All chemicals were purchased from commercial sources and were used as received without any further purification. An aqueous solution of Cu(NO₃)₂^.3H₂O (Sigma-Aldrich, 0.80 g, 3.3 mmol, 5 ml) was added to a solution of ethylenediamine (Riedel-de Haën, 0.5 ml, 7.3 mmol) in water (5 ml). After 1 min, a deep-violet solution was formed. Slow evaporation of the aqueous solution yielded crystalline plates of [Cu(en)₂(H₂O)₂](NO₃)₂ after 15 days.

An aqueous solution of KOH (Eka, 0.106 g, 1.89 mmol, 10 ml) was added to a suspension of 4-phenylbenzoic acid (Hpb, Sigma-Aldrich, 0.375 g, 0.945 mmol) in water (40 ml). The resulting solution was filtered and added to an aqueous solution of [Cu(en)₂(H₂O)₂](NO₃)₂ (0.228 g, 0.945 mmol, 10 ml). The precipitation of a blue-violet powder was immediate. The slow evaporation of the aqueous solution yielded crystalline needles of the title complex after 60 days.

Selected FT—IR (KBr, cm^-1): ν(NH₂) = 3363s, 3307s, 3216s and 3138m; ν_asym(—COO^-) = 1596vs, 1541vs and 1577vs; 1447m; ν_sym(—COO^-) = 1395vs; 1101m; 1045s; γ(-CH, di-subs. Ph) = 838m and 800m; γ(-CH, mono-subs. Ph) = 751s; 694m; 525m; 461m.