Inorganic Chemistry Communications 6 (2003) 896–899 www.elsevier.com/locate/inoche
Novel heterometallic Cu/Cd complex containing a unique polymeric ladder-like anion [Cd2(O2CMe)6]2 n derived from elemental copper and cadmium oxide Oksana V. Pryma a, Svitlana R. Petrusenko a,*, Vladimir N. Kokozay a, Oleg V. Shishkin b, Marina V. Zhigalko b b
a Department of Inorganic Chemistry, National Taras Shevchenko University, Volodimirska str. 64, Kyiv 01033, Ukraine Scientific Research Department of Alkali Halide Crystals, STC ‘‘Institute for Single Crystals’’, National Academy of Sciences of Ukraine, Lenina Ave 60, Khar’kov 61001, Ukraine
Received 10 February 2003; accepted 12 April 2003
Abstract Copper powder reacts with cadmium oxide and ammonia acetate in methanol solution of ethylenediamine affording {[Cu(en)2 ][Cd2 (O2 CMe)6 ]}n in which seven-coordinated cadmium atoms are ligated by three bonding modes of acetate groups 2þ forming ladder-like anions [Cd2 (O2 CMe)6 ]2 are located in the lattice and serve as bridges to connect n . The cations [Cu(en)2 ] separate anionic polymer chains into a two- dimensional network via hydrogen bonds. Ó 2003 Elsevier Science B.V. All rights reserved. Keywords: Heterometallic acetates; Elemental copper; Cadmium oxide; Ethylenediamine; Crystal structure
1. Introduction Remarkable progress has been made recently in the field of coordination polymers of various dimensionality with different structural motifs [1,2]. Many of these compounds are useful in catalysis, separation, gas storage and molecular recognition [3]. A reasonable approach to the design of such polymeric coordination compounds is to link different metals with organic ligands or anions possessing bridging possibility. Manifestation of the unique coordination preferences of Cu and Cd could lead to the formation of new composite networks containing each metal in its own structural motif [4,5]. The presence of carboxylate groups which display a variety of binding geometries (monodentate bridging, bidentate bridging, chelating, monodentate terminal) [6] should increase the difference and complexity of the polymeric structures.
*
Corresponding author. Tel.: +380-44-235-4371; fax: +380-44-2962467. E-mail address:
[email protected] (S.R. Petrusenko).
Conventional synthesis of heterometallic complexes normally involves metal salts or complexes as starting materials. We have offered a novel synthetic approach (‘‘direct synthesis’’) in obtaining of number of heterometallic assemblies of various compositions and structures using elemental metal along with metal salt [7]. Developing this method we propose to exploit only elemental metal and metal oxide as a source of metals, since it avoids the problems of drying and potential anion contamination which accompany the use of metal salts. Such approach also allows to change a molar ratio M1 :M2 :X (M – metal, X – anion) in a broad range. The following system was chosen for this aim: Cu0 –CdO–NH4 O2 CMe–en–Solv because, as it has been shown before, copper powder and cadmium oxide readily react with non-aqueous solutions of ammonia salts, especially in the presence of ethylenediamine (en) [8]. In this paper, we report the direct synthesis and single crystal structure of a new heterometallic complex {[Cu(en)2 ][Cd2 (O2 CMe)6 ]}n , which contains a unique polymeric ladder-like anion [Cd2 (O2 CMe)6 ]2 n .
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S1387-7003(03)00138-2
O.V. Pryma et al. / Inorganic Chemistry Communications 6 (2003) 896–899
2. Experimental section 2.1. Synthesis of {[Cu(en)2 ][Cd2 (O2 CMe)6 ]}n Copper powder (0.16 g, 0.0025 mol), CdO (0.64 g, 0.005 mol), NH4 O2 CMe (1.17 g, 0.015), CH3 OH (25 cm3 ) and ethylenediamine (0.35 cm3 , 0.005 mol) were heated to 50–60 °C and magnetically stirred until total dissolution of the copper and cadmium oxide was observed (60 min). Solution was filtered out and subsequently red crystals suitable for X-ray crystallography separated in one day after the successive addition of 15 cm3 isopropanol into the resulting violet solution. Crystals were filtered out, washed with dry isopropanol and finally dried in vacuo at room temperature. Yield: 1.2 g, 62.5% (per copper). Elemental analyses for metals were performed by atomic absorption spectroscopy. Anal. Calcd for C16 H34 Cd2 CuN4 O12 (Mr ¼ 762.82): C, 25.19; H, 4.49; N, 7.34; Cu, 8.33; Cd, 29.47. Found: C, 25.3; H, 4.6; N, 7.4; Cu, 8.7; Cd, 29.4%. IR (Nujol mulls, cm1 ): 3315 (br), 3230 (sh), 3220 (sh), 3200 (sh), 3180 (sh), 3170 (sh), 2980 (s, Nujol), 1620 (sh), 1580 (s, C ¼ O), 1570 (sh), 1550 (sh), 1530 (sh), 1470 (s, C@O), 1450 (sh, Nujol), 1390 (s, Nujol), 1360 (sh), 1320 (sh), 1280 (w), 1190 (m), 1115 (m), 1060 (s), 1030 (m), 940 (m), 890 (w), 740 (m), 675 (s), 660 (sh), 630 (w), 620 (w), 550 (m), 505 (w), 470 (w), 435 (w).
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177 parameters) was converged to wR2 ¼ 0.092 (R1 ¼ 0.036 for 1943 reflections with F > 4rðF Þ, S ¼ 1:011). Graphical visualisation of the structure was made using the SHELXTL package [14] and the program Diamond [15].
3. Results and discussion The open-air reaction of copper powder with cadmium oxide and ammonia acetate in a methanol solution of ethylenediamine, using a molar ratio of Cu:CdO:NH4 O2 CMe:en ¼ 1:2:2:2 gave red microcrystals that showed analytical data accounting for the presence of Cu(II) and Cd(II) in a 1:2 stoichiometry. The reaction proceeds in the following way: Cu0 þ 2CdO þ 6NH4 O2 CMe þ 2en þ 1=2O2 ! ½CuðenÞ2 ½Cd2 ðO2 CMeÞ6 þ 6NH3 þ 3H2 O
2.3. X-ray structure determination
The IR spectrum of the compound confirmed that the ethylenediamine was present. Two strong m(NH) and m(CN) vibrations (3315 and 1115 cm1 ) and middle m(CC) absorption (940 cm1 ) of the ligand can be easily identified. But m(CH) and d(NH2 ) frequencies of en is obscured by stretching vibrations of the Nujol and carboxylate group, respectively. The difference in wavenumbers, D ¼ 110 cm1 , between the antisymmetric (1580 cm1 ) and symmetric (1470 cm1 ) COO stretching frequencies demonstrated the existence of bridging or chelating acetate ligands [9], in line with the X-ray structure determination. The diffuse reflectance spectrum of the complex exhibited an absorption in the visible region centered between 19 500 and 21 000 cm1 , which corresponds to a d–d transition in a square planar environment around copper (II) [10] and which is in agreement with the crystal structure. Besides the d–d
C16 H34 Cd2 CuN4 O12 (fw ¼ 762:82), 293 K, triclinic, , , a ¼ 6:662ð1Þ, b ¼ 10:460ð2Þ, c ¼ 10:822ð2Þ A P1 a ¼ 111:61ð1Þ, b ¼ 103:52ð2Þ, c ¼ 97:12ð2Þ°, V ¼ 3 , Z ¼ 1, l(Mo-KaÞ ¼ 2.445 mm1 , dcal ¼ 663:0ð2Þ A 1.911 g/cm3 , F ð0 0 0Þ ¼ 379. Unit cell parameters and intensities of 2531 reflections (2309 unique, Rint ¼ 0.017) were measured using a four-circle diffractometer ‘‘Siemens P3/PC’’ (Mo-Ka, graphite monochromator, 2h= h-scan, hmax ¼ 25°). The absorption was calculated semiempirically by means of W-scan data (Tmin ¼ 0.4413, Tmax ¼ 0.6405). The structure was solved by direct method using the SHELXTL package [14]. Positions of the hydrogen atoms were located from the difference map of electron density and refined by ‘‘riding’’ model with Uiso ¼ nUeq of non-hydrogen atom bonded to Hatom (n ¼ 1:5 for methyl and 1.2 for other H-atoms). Full-matrix least-squared refinement against F2 in anisotropic approximation for non-hydrogen atoms (total
Fig. 1. ORTEP drawing of the crystal structure of {[Cu(en)2 ][Cd2 (O2 CMe)6 ]} n with 50% probability thermal ellipsoids, showing the atom numbering scheme (H atoms are omitted for clarity).
2.2. Physical measurements Infrared spectra were recorded in Nujol mulls on a UR-10 spectrophotometer in the 4000–2900 and 1800– 400 cm1 regions using conventional techniques. UV/Vis spectra were recorded on Perkin–Elmer 330 (diffuse-reflectance technique) spectrometer.
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O.V. Pryma et al. / Inorganic Chemistry Communications 6 (2003) 896–899 Table 1 ) and angles (°) for [Cu(en)2 Cd2 (O2 CMe)6 ]a Selected bond distances (A Cd(1)–O(1) Cd(1)–O(2) Cd(1)–O(3) Cd(1)–O(4) Cd(1)–O(5) O(1)–Cd(1)–O(2) O(1)–Cd(1)–O(3) O(1)–Cd(1)–O(4) O(1)–Cd(1)–O(5) O(1)–Cd(1)–O(6) O(2)–Cd(1)–O(3) O(2)–Cd(1)–O(4) O(2)–Cd(1)–O(5) O(2)–Cd(1)–O(6) O(3)–Cd(1)–O(4)
2.358(4) 2.566(4) 2.363(4) 2.392(4) 2.289(4) 52.1(1) 147.1(1) 157.9(1) 90.6(2) 90.4(1) 95.0(1) 149.8(1) 82.5(2) 78.1(1) 54.9(1)
Cd(1)–O(6) Cd(1)–O(1A) Cu(1)–N(1) Cu(1)–N(2) O(3)–Cd(1)–O(5) O(3)–Cd(1)–O(6) O(4)–Cd(1)–O(5) O(4)–Cd(1)–O(6) O(5)–Cd(1)–O(1A) O(5)–Cd(1)–O(6) O(6)–Cd(1)–O(1A) N(1)–Cu(1)–N(2) N(2)–Cu(1)–N(1A)
2.298(3) 2.319(4) 1.989(5) 1.983(5) 84.8(2) 80.6(1) 95.2(2) 93.4(2) 105.7(2) 154.5(2) 98.5(1) 84.9(2) 95.1(2)
a
Symmetry transformations used to generate equivalent atoms: A hx; y; zi.
Fig. 2. (a) The infinite ladder structure of anion [Cd2 (O2 CMe)6 ]2 n . (b) Fragment of 2D layer structure projecting onto the ab plane. The dashed lines represent hydrogen bonds.
bands, the spectrum displays a ligand-to-metal charge transfer transition at 34 000 cm1 . The crystal structure of {[Cu(en)2 ][Cd2 (O2 CMe)6 ]}n consists of one-dimensional ladder-like polymeric an2þ ions [Cd2 (O2 CMe)6 ]2 forming n and cations [Cu(en)2 ] two-dimensional network by means of H-bonds (Figs. 1 and 2). The Cd-atoms have seven coordination. Each pair of Cd(II) atoms in the anion is linked by two acetate groups which behave simultaneously as chelating bidentate [through O(1), O(2) and O(1A), O(2A)] and bridging unidentate [through O(1) and O(1A)] ligands towards two coplanar cadmium atoms (in-plane connection) (Fig. 1). Each of the Cd(II) is further coordinated by one chelating and two additional anti–anti bridging bidentate acetates (out-of-plane connection) to form two equivalent CdO7 distorted one-cap trigonal antiprisms joined at their shared side. The long
, intermetallic Cd(1) Cd(1A) separation is 3.842(2) A indicating that there is no obvious interaction between the two metal atoms. The Cd–O distances [2.289(4)– ] are typical for Cd(II) carboxylate complexes 2.566(4) A [11] (Table 1). The difference of 51.1° between the angles C(3)–O(1)–Cd(1A) 149.9(4)° and C(3)–O(1)–Cd(1) 98.8(3)° indicates significant tilt of the carboxylate toward Cd(1) and can serve as additional evidence of mixed bridging unidentate plus chelating bidentate mode of acetate group [12]. The small difference in the values of the Cd(1)–O(3) and Cd(1)–O(4) distances , respectively] demonstrates [2.363(4) and 2.392(4) A practically a symmetrically chelating acetate group. The interesting observation is that titled complex represents the first example of heterometallic compound containing polymeric Cd(II) motif with three different kinds of bonding modes of acetate ligands. The coordination environment around the Cu atom in [Cu(en)2 ]2þ is best described as square planar. The copper ion is located on an exact crystallographic inversion center. The Cu–N bond distances are almost ) and the N–Cu–N even (from 1.983(5) to 1.989(5) A angles are close to 90° varying from 84.9(2)° to 95.1(2)° (Table 1). The en ligands reveal gauche conformations (torsion angle N(1)–C(1)–C(2)–N(2) 53.6°). In fivemembered metallocycles Cu(1)–N(1)–C(1)–C(2)–N(2) corresponding deviations from the plane Cu(1)N(1)N(2) [C(1)] and 0.34(1) A [C(2)]. The axial poare 0.37(1) A
Table 2 , °) Pertinent details of the hydrogen-bonds (A D–H A
Symmetry
d(D–H)
d(H A)
d(D A)
\DHA
N(1)–H(1D) O(2) N(2)–H(2D) O(6) N(2)–H(2C) O(3) N(1)–H(1C) O(3)
x þ 1, y þ 1, z x, y þ 1, z 1 x, 1 y, 2 z 2 x, 1 y, 2 z
0.900 0.900 0.900 0.900
2.00 2.18 2.04 2.31
2.878 3.000 2.910 3.018
164 151 163 136
O.V. Pryma et al. / Inorganic Chemistry Communications 6 (2003) 896–899
sitions of copper (II) ion are occupied by oxygen atoms from bridging bidentate acetate ligands on different [Cd2 (O2 CMe)6 ]2 n anions at a distance of 3.084(2) A, too long for even semi-coordination [13]. The [Cu(en)2 ]2þ cations are encapsulated in the interchain anionic space as shown in Fig. 2(b). All hydrogen atoms from the ethylenediamine ligands are involved in N–H O hydrogen bonds to build up a two-dimensional network (Fig. 2(b) and Table 2). In conclusion, elemental copper, cadmium oxide and ammonia acetate in methanol solution of en were successfully employed to prepare novel heterometallic Cu/ Cd complex containing unique ladder-like polymeric anions [Cd2 (O2 CMe)6 ]2 n based on three different coordination modes of acetate groups. Since {[Cu(en)2 ] [Cd2 (O2 CMe)6 ]}n is the first complex containing [Cd2 (O2 CMe)6 ]2 n it would be profitable to explore the formation of similar compounds by applying our synthetic approach and structure-directing agents. Work in this direction is now in progress. References [1] P. Gamez, P. de Hoog, O. Roubeau, M. Lutz, W.L. Driessen, A.L. Spek, J. Reedijk, Chem. Commun. (2002) 1488. [2] Z.-C. Zhu, Z.-G. Zha, Z. Xu, X.-Y. Huang, Jiegou Huaxue 18 (1999) 340; P.A. Petrenko, G.A. Kiosse, Zn. Neorg. Khim. 45 (2000) 1136; T. Kitazawa, S.-I. Nishikiori, R. Kuroda, T. Iwamoto, J. Chem. Soc., Dalton Trans. (1994) 1029; S. Nishikiori, T. Iwamoto, Chem. Lett. (1994) 1199.
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