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Synthesis and crystal structure of a new μ2-phenoxy oxygen bridged macrocyclic binuclear cadmium(II) complex with pendant arms
Pergamon
PolyhedronVol. 16, No. 6, pp. 915-919, 1997 Copyright© 1996Published by ElsevierScienceLtd Printed in Great Britain. All fightsreserved PII : S0277-5387(96)00361--0 0277-5387/97 $17.00+0.00
Synthesis and crystal structure of a new p2-phenoxy oxygen bridged macrocyclic binuclear cadmium(ll) complex with pendant arms X i n - Y o u X u , a Qin-Hui Luo, a* Meng-Chang Shen, a X i a o - Y u n Huang, b
and Qiang-Jin Wu b
Coordination Chemistry State Key Laboratory, Nanjing University, Nanjing 210008, P.R. China bFuzhou State Key Laboratory of Structure Chemistry, Fuzhou 350002, P.R. China (Received 20 March 1996; accepted 24 July 1996) Abstract--A new binuclear cadmium(II) macrocyclic complex has been synthesized by [2+2] Schiff-base condensation of tris(3-aminopropyl)amine with sodium 2,6-diformyl-4-methoxylphenolate in the presence of Cd(C104)2" 6H20. The crystal structure, spectral characterization and molar conductivity show that two cadmium(II) ions were bridged by two/~2-phenoxy oxygen atoms. Each cadmium(II) is located in a trigonal prismatic coordination environment (N402). Copyright © 1996 Published by Elsevier Science Ltd Keywords: cadmium(II) ; binuclear complex ; macrocycle ; oxygen bridge ; crystal structure ; trigonal prism.
Pilkington and Robson [1] obtained a new kind of macrocyclic ligand for the first time by the template condensation of 2,6-diformyl-4-methylphenol with diamines. The ligands contain strong donors, namely, phenoxy oxygen atoms as well as amine nitrogen atoms, therefore they are excellent for catalysis and biological simulation [2,3] because of their special coordination ability with transition metal ions. The polyaza macrocyclic ligands also have these properties and have attracted much attention [4-6]. Cadmium is an environmental pollutant which inhibits RNA polymerase activity in vivo [7,8] and reacts readily with proteins and other biological molecules, and so the macrocyclic chemistry of cadmium has been developed recently [9]. Although many studies have been made on cadmium(II) macrocyclic complexes [10-12], only a few crystal structures have been reported, and most were found to be mononuclear complexes [13-17]. In this paper we report the synthesis, characterization and X-ray crystal structure of a new ~/-oxo-bridged binuclear cadmium(II) com-
* Author to whom correspondence should be addressed.
plex of a 28-membered macrocyclic complex with pendant arms (Fig. 1). To our knowledge, only a few of these kinds of structures have hitherto been reported. EXPERIMENTAL Materials
2,6-Diformyl-4-methoxylphenol (dmop) was prepared using the method described in the literature [18]. Sodium 2,6-diformyl-4-methoxylphenolate (sdmop) was obtained by mixing equimolar amounts of dmop and NaOH in ethanol. Tris(3-aminopropyl)amine was prepared by a modified literature method [19] with a purity of over 99%. All starting materials were of chemical purity. Physical measurements
Solution electrical conductivity was measured by a BDS-A numerical conductometer (Jiangsu, China) with solution concentrations of c a 10 - 4 mol dm -3 in acetonitrile. IR spectra were measured as KBr discs
915
Xin-You Xu et al.
916 OCH
L
" 7 2+
OCtt
3 Fig. 1. The structure of the binuclear complex cation [Cd~(H_2L)]2+.
using a Nicolet 5DX FT-IR spectrophotometer. Electronic spectra were recorded on Shimadazu UV-240 spectrophotometer.
Preparation of the complex
[Cdz(H_2L)](C104)2 RESULTS AND DISCUSSION
• 0.5CH3OH To a stirred solution of sodium 2,6-diformyl-4methoxyphenolate (0.101 g, 0.5 mmol) and Cd(CIO4)2" 6H20 (0.261 g, 0.625 retool) in absolute methanol (30 cm 3) was added dropwise a solution of tris(3-aminopropyl)amine (0.094 g, 0.5 retool) in absolute methanol (15 cm 3) at 0°C. After stirring for 2 h at 35°C, yellowish microcrystals were precipitated and filtered off, washed with methanol and dried in vacuo (yield 45%). Found : C, 40.2 ; H, 5.5 ; N, 10.5 ; Cd, 19.9. Calc. for C36.sH56NsO12.5 Cd2C12; C, 39.8; H, 5.1 ; N, 10.2 ; Cd, 20.4%. IR (KBr, c m - l) : 3400 br, v(OH)(CH3OH); 3354s, Vas(NH2); 3300s, vs(NH2); 1641s, v(C--N) ; 1544s, v(Ar--O) ; 1102 (C104). U V vis (2m,~ rim, CH3CN) ; 270 (9763 tool -1 dm 3 cm-1) ; 430 (10078). AM (CH3CN, 279 K) : 236 S cm 2 tool i. The yellowish crystals of [Cd2(H_2L)](CIO4)2 • 5CH3OH suitable for X-ray structure determination were obtained by slow evaporation of the mother liquor at ambient temperature. CAUTION. Perchlorate salts of metal complexes with organic ligands are potentially explosive. Only small amounts of material should be prepared, and these should be handled with caution. The complex described in this report has, so far, been found to be safe when used in small quantities.
X-ray
crystal
F(000) = 1122, Z = 2, Dc = 1.60 g c m -3, T = 296 K, p = 11.06 cm -z. Data collection and refinement. A single crystal was mounted on a glass fibre. The crystal data were collected on an Enraf-Nonius CAD4 four-circle diffractometer with graphite-monochromated Mo-K~ radiation (2 = 0.71069 A) using an co-20 scan mode with o9 scan width 0.95 +0.350 tan 0, scan rate 5.49 ° min-I. A total of 8067 independent reflections were collected in the range 2 < 20 < 50% of which 6421 reflections with I > 3a(/) were used in the structure determination and refinement, after Lp corrections. The structure was solved by the MITHRIL direct method. The remaining non-hydrogen atoms were located from a difference Fourier map. Hydrogen atoms were introduced in calculated positions but not refined. The final least-squares cycle gave R = 0.052, Rw = 0.064(w = 1/aZ(Fo)). The maximum and minimum residuals had values of 0.63 and - 0 . 8 9 e/~ -3, respectively. All calculations were performed on a MICRO VAX-3100 computer using the programs contained in the TEXSAN [20].
structure
determination
of
[Cd2(H_2L)](C104)2" 5CH3OH
Crystal data. C36 sH56NsOI2.sCd2C12, M = 1102.65, yellowish crystal, dimensions 0.9 × 0.9 × 0.45 mm 3, triclinic, space group P_1(#2), a = 10.455(6), b = 11.451(4), c = 20.130(6) /~, ~ = 105.75(3), /~ = 82.84(3), y = 97.21(3) °, V = 2291(2) A 3,
Characterization of the complex In the infrared spectrum a strong peak appears at 1641 cm -1 corresponding to the stretching vibration ofimino ~ N bonds. The symmetric and asymmetric stretching frequencies (3300 and 3354 cm -I) for NH2 groups are also present, but no strong peaks at 16501700 cm 1 for the carbonyl groups. This means that two NHz groups and carbonyl groups have been condensed into ~ N bonds, whilst another NH2 group is unchanged. A broad band at ca 3400 era- J, characteristic of the OH group of CH3OH, showed that CH3OH molecules exist in the crystalline complex, in agreement with the elemental analysis. The strong peak at 1102 cm -1 without splitting showed that CIO~- did not take part in coordination with Cd ~ ions. This is also confirmed by the molar conductivity of the complex (AM = 236 S cm 2mol -~) which is attributable to a 2 : 1 electrolyte. Two intense absorptions in the electronic spectrum of the complex are designated to 7r-lr* transitions of the K band of the benzene rings and of C = N groups.
Description of the structure of [Cd2(H zL)](CIO4)z • 0.5CH3OH A perspective view of the cation [Cd2(H_ 2L)]2+ and a packing diagram are displayed in Figs 2 and 3, respectively. Selected bond distances and bond angles are given in Tables 1 and 2, respectively. Figure 3 shows that each unit cell contains two complex associations, each consisting of one molecule of the macrocyclic complex cation [Cd2(H_ 2L)]2+, two perchlorate anions and half of a methanol solvent
917
Synthesis and structure of a ~2-phenoxybridged macrocyclic cadmium(II) complex
~
C(36)
~)0(4) C(23) C(24) C(22)
C09) __ C08) C(21)
C(12)
C(13)
C(20) c04)
C(25)
N(5)
0(2)
C(31)
N(3)
c05)
C(30) Cd(2) ~ ' ~
C(ll)
N(4) C(34)
C(29)
O(1)
N(7)
N(8)
C(28)
C(33)
C(6) C(5) i
C(1)
C(32) c(35)
C(2)
~
~
ci4)
coo)
~
0(3)
C(3) Fig. 2. A perspective view of the cation [Cd(H :L)]2+.
O
C
B
Fig. 3. A packing diagram of the complex [Cd2(H_2L)](C104)2• 0.5CH3OH.
918
Xin-You Xu et al. Table 1, Selected bond distances (,~)
Cd(1)--N(7) Cd(l)--N(6) Cd(l)--N(2) Cd(1)--O(1) Cd(1)--O(2) Cd(1)--N(l) O(1)--C(6) O(3)--C(9) O(3)--C(35) Cd(1)--Cd(2) Cd(1)--N(4)
2.294(6) 2.300(5) 2.311(5) 2.282(4) 2.350(4) 2.455(5) 1.303(6) 1.374(7) 1.397(9) 3.689(2) 6.158(5)
Cd(2)--N(3) Cd(2)--N(8) Cd(2)--N(5) Cd(2)--O(1) Cd(2)--O(2) Cd(2)--N(4) O(2)--C(20) O(4)--C(23) O(4)--C(36) Cd(2)--N(1) N(I)--N(4)
2.295(5) 2.302(6) 2.305(5) 2.318(4) 2.328(4) 2.483(5) 1.315(7) 1.369(8) 1.40(1) 6.133(5) 8.608(8)
molecule. The methanol and perchlorate anions are disordered over two interpenetrating sites. It can be seen from Fig. 2 that in the cation of the complex each Cd" ion is enclosed within the polyaza macrocycle and coordinated by one bridgehead nitrogen atom, two imino nitrogen atoms, one amine nitrogen atom of the pendant arms and two oxygen atoms of phenoxy groups. Each Cd" is located in a trigonal prismatic N402 coordination environment with coordination number of six. For the Cd(1) centre, the phenoxy oxygens O(1), 0(2) and the amino nitrogen
N(6) forms one trigonal face, the Cd(1) deviates downwards by 1.5181 A from the face. The amino nitrogen atoms N(2), N(7) and the bridgehead nitrogen N(1) form another trigonal face, the Cd(1) deviates upwards by 1.2522/k from the face. The dihedral angle between the two faces is 11.13 °. For the Cd(2) centre, the phenoxy oxygens O(1), 0(2) and amino nitrogen N(3) form one trigonal face and the Cd(2) deviates upwards by 1.4849 A from the face. The amino nitrogens N(4), N(5) and the bridgehead nitrogen N(8) form another trigonal face and the Cd(2) deviates downwards by 1.2423/k from the face. The dihedral angle between the two faces is 12.74°C. The dihedral angle between the plane consisting of Cd(1), O(1), Cd(2) and the plane consisting of Cd(1), 0(2), Cd(2) is 151.00 °. The phenoxy oxygens O(1) and 0(2) bridge the two Cd n ions. The bond distances of Cd(1)--N(imino) and Cd(2)--N(imino) are approximately equal, being in the range 2.294-2.311 ,~. These C d - - N bond distances are shorter than the standard bond distance of 233_+ 0.005 A [20]. This means that these imino groups have strong coordination ability towards Cd". Conversely, the two bond distances Cd(1)--N(1), Cd(2)--N(4) are 2.455 and 2.483 A, respectively, implying weak interaction between the Cd ~I ions and the bridgehead nitrogen atoms.
Table 2. Selected bond angles (°) O(1)--Cd(1)--N(7) O(1)--Cd(1)--N(6) O(1)--Cd(I)--N(2) O(l)--Cd(1)--O(2) O(1)--Cd(1)--N(1) N(7)--Cd(1)--N(6) N(7)--Cd(1)--N(2) N(7)--Cd(I)--O(2) N(7)--Cd(I)--N(1) N(6)--Cd(1)--N(2) N(6)--Cd(1)--O(2) N(6)--Cd(1)--N(1) N(2)--Cd(l)--O(2) N(2)--Cd(1)--N(1) O(2)--Cd(1)--N(1) C(20)--O(2)--Cd(1) C(20)--O(2)--Cd(2) Cd(2)--O(2)--Cd(1) C(9)--O(3)--C(35) C(28)--N(1)--C(29) C(28)--N(1)--C(1) C(28)--N(1)--Cd(1) C(32)--N(8)--Cd(2) C(29)--N(1)--C(1) C(29)--N(1)--Cd(1) C(1)--N(1)--Cd(I) C(4)--N(2)--C(3) C(4)--N(2)--Cd(1) C(3)--N(2)--Cd(1) C(1 I)--N(3)--C(12) C(11)--N(a)--Cd(2) C(12)--N(3)--Cd(2)
126.1 (2) 91.9(2) 75.1 (1) 72.0(1) 148.0(2) 121.7(2) 110.9 (2) 76.1 (2) 82.5(2) 121.6(2) 77.0(2) 82.1 (2) 142.7(1) 81.5(2) 135.5(1) 132.3(4) 111.0(3) 104.1 (1) 117.3(5) 108.4(5) 108.3(5) 112.2(4) 108.6(4) 108.1 (5) 108.2(4) 111.4(3) 117.2(5) 122.7(4) 119.2(4) I 17.1(5) 128.6(4) 114.2(4)
N(3)--Cd(2)--N(8) N(3)--Cd(2)--N(5) N(3)--Cd(2)--O(1) N(3)--Cd(2)--O(2) N(3)--Cd(2)--N(4) N(S)--Cd(2)--N(5) N (8) --Cd (2)--O ( 1) N(8)--Cd(2)--O(2) N(8)--Cd(2)--N(4) N(5)--Cd(2)--O(1) N(5)--Cd(2)--O(2) N(5)--Cd(2)--N(4) O( 1)--Cd(2)---O(2) O(1)--Cd(2)--N(4) O(2)--Cd(2)--N(4) C(6)--O(1)--Cd(1) C(6)--O(1)--Cd(2) Cd(1)--O(1)--Cd(2) C(23)--O(4)--C(36) C( 15)--N (4)--C (14) C(15)--N(4)--C(34) C(15)--N(4)--Cd(2) C(14)--N(4)--C(34) C (14)--N(4)--Cd(2) C(34)--N(4)--Cd(2) C (18)--N(5)--C (17) C(18)--N(5)--Cd(2) C(17)--N(5)--Cd(2) C(25)--N(6)--C(26) C(25)--N(6)--Cd(l) C(26)--N(6)--Cd(1) C(3 l)--N(7)--Cd(1)
121.8(2) 120.4(2) 77.9(2) 95.5(2) 81.9(2) 111.9(2) 75.5(2) 122.7(2) 82.7(2) 142.8(2) 74.2(2) 81.0(2) 71.8(1) 135.9(2) 149.6(2) 115.0(3) 130.8(3) 106.6(2) 117.9(8) 108.9(5) 107.3(5) 112.5(4) 108.7(5) 111.6(4) 107.7(4) 116.4(5) 123.1(4) 119.9(4) 116.5(5) 130.3(4) 113.2(3) 110.3(4)
Synthesis and structure of a #2-phenoxy bridged macrocyclic cadmium(II) complex However, in the cadmium cryptate synthesized by condensation of tris(2-aminoethyl)amine with 2,6diformyl-4-methylphenol [21], the corresponding bond distance of Cd--N(bridgehead) 2.787 A, was larger than that reported in this paper. The long Cd(l) • • - Cd(2) distance (3.689 A) indicates that there is no interaction between the two metal atoms. The bond distances Cd(1)--O(1), Cd(2)--O(2), Cd(2)--O(1) and Cd(2)--I(2) are 2.282, 2.350, 2.318 and 2.328 A, respectively, being close to those reported by Drew et al. [21], also implying that Cd(l) is similar to Cd(2) in coordination environment but slightly different to Cd(2) in degree of distortion. An analogous complex [Cu2L'(OH)](C104)3 which was synthesized by [2+2] Schiff-base condensation of tris(2-aminoethyl)amine with isophthalic aldehyde in the presence of Cu(C104)2" 6H20 is unstable [22]. In our complex, however, the flexibility of the carbon chain strengthened the coordination ability of the bridgehead nitrogen atoms, and the phenoxy oxygen atoms bridging the two Cd II atoms enhanced the stability of the complex as well as forming the six-membered chelate rings and so stabilizing the structure of the complex.
5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
16.
Acknowledgements--This project was supported by the Natural ScienceFoundation of China and Fuzhou State Key Laboratory of Structure Chemistry.
17.
REFERENCES
18. 19.
1. Pilkington, N. H. and Robson, R., Aust. J. Chem., 1970, 23, 2225. 2. Zanello, P., Tamburini, S., Vigato, P. A. and Mazzochim, G. A., Coord. Chem. Rev., 1987, 77, 165. 3. Vigato, P. A., Tamburini, S. and Fenton, D. E., Coord. Chem. Rev., 1990, 106, 105. 4. Bailey, N. A., Rodriguez de Barbarin, C. O., Fenton, D. E., Hellier, P. C., Hempstead, P. D.,
20. 21. 22.
919
Kanesato. M. and Leeson, P. B., J. Chem. Soc., Dalton Trans., 1995, 765. Ngwenya, M. P., Chen, D., Martell, A. E. and Reibenspies, J., Inorg. Chem., 1991, 30, 2732. Fenton, D. E., Pure Appl. Chem,, 1986, 58, 1437. Jacobson, K. B. and Turner, J. E., Toxicology, 1980, 60, 1. Hidalgo, H. A., Koppa, V. and Bryan, E. S, FEBS Lett., 1976, 64, 159. Dakternieks, D., Coord. Chem. Rev., 1990, 98, 288. Marchetti, P. S., Bank, S., Bell, T. W., Kennedy, M. A. and Ellis, P. D., J. Am. Chem. Soc., 1989, 111, 2063. Thom, V. J., Hosken, G. D. and Hancock, R. D., Inorg. Chem., 1985, 24, 3378. Richens, D. T., in Annual Reports on the Progress of Chemistry, 86 (sect. A), The Royal Society of Chemistry, Cambridge, 1989, p. 66. Adam, K. R., Dancey, K. P., Leong, A. J., Lindoy, L. F., McCool, B. J., McPartlin, M. and Tasker, P. A., J. Am. Chem. Soc., 1988, 110, 8471. Drew, M. G. B., Mcfall, S. G. and Nelson, S. M., J. Chem. Soc., Dalton Trans., 1979, 575. Adam, K. R., Arshad, S. P. H., Baldwin, D. S., Duckworth, P. A., Leong, A. J., McCool, B. J., McPartlin, M., Tailor, B. A. and Tasker, P. A., lnorg. Chem., 1994, 33, 1194. Drew, M. G. B., Howarth, O. W., Morgan, G. G. and Nelson, J., J. Chem. Soc., Dalton Trans., 1994, 3149. Bencini, A., Bianch, A., Castello, M., Varia, M. D., Garcia-Espana, E., Micheloni, M. and Paoletti, P., Inorg. Chem., 1989, 28, 347. Taniguchi, S., Bull. Chem. Soc. Jpn, 1984, 57, 268. Chin, J., Banaszczyk, M., Jubian, V. and Zou, X., J. Am. Chem. Soc., 1989, 111, 186. TEXSAN, TEXRA Y Structure Analysis Package, Molecular Structure Corporation, The Woodlands, TX, U.S.A. 1989. Drew, M. G. B., Howarth, O. W., Morgan, G. G. and Nelson, J., J. Chem. Soc. Dalton Trans., 1994, 3149. Harding, C. J., Lu, Q., Malone, J. M., Marrs, D. J., Martin, N., McKee, V. and Nelson, J., J. Chem. Soc., Dalton Trans., 1995, 1739.
PolyhedronVol. 16, No. 6, pp. 915-919, 1997 Copyright© 1996Published by ElsevierScienceLtd Printed in Great Britain. All fightsreserved PII : S0277-5387(96)00361--0 0277-5387/97 $17.00+0.00
Synthesis and crystal structure of a new p2-phenoxy oxygen bridged macrocyclic binuclear cadmium(ll) complex with pendant arms X i n - Y o u X u , a Qin-Hui Luo, a* Meng-Chang Shen, a X i a o - Y u n Huang, b
and Qiang-Jin Wu b
Coordination Chemistry State Key Laboratory, Nanjing University, Nanjing 210008, P.R. China bFuzhou State Key Laboratory of Structure Chemistry, Fuzhou 350002, P.R. China (Received 20 March 1996; accepted 24 July 1996) Abstract--A new binuclear cadmium(II) macrocyclic complex has been synthesized by [2+2] Schiff-base condensation of tris(3-aminopropyl)amine with sodium 2,6-diformyl-4-methoxylphenolate in the presence of Cd(C104)2" 6H20. The crystal structure, spectral characterization and molar conductivity show that two cadmium(II) ions were bridged by two/~2-phenoxy oxygen atoms. Each cadmium(II) is located in a trigonal prismatic coordination environment (N402). Copyright © 1996 Published by Elsevier Science Ltd Keywords: cadmium(II) ; binuclear complex ; macrocycle ; oxygen bridge ; crystal structure ; trigonal prism.
Pilkington and Robson [1] obtained a new kind of macrocyclic ligand for the first time by the template condensation of 2,6-diformyl-4-methylphenol with diamines. The ligands contain strong donors, namely, phenoxy oxygen atoms as well as amine nitrogen atoms, therefore they are excellent for catalysis and biological simulation [2,3] because of their special coordination ability with transition metal ions. The polyaza macrocyclic ligands also have these properties and have attracted much attention [4-6]. Cadmium is an environmental pollutant which inhibits RNA polymerase activity in vivo [7,8] and reacts readily with proteins and other biological molecules, and so the macrocyclic chemistry of cadmium has been developed recently [9]. Although many studies have been made on cadmium(II) macrocyclic complexes [10-12], only a few crystal structures have been reported, and most were found to be mononuclear complexes [13-17]. In this paper we report the synthesis, characterization and X-ray crystal structure of a new ~/-oxo-bridged binuclear cadmium(II) com-
* Author to whom correspondence should be addressed.
plex of a 28-membered macrocyclic complex with pendant arms (Fig. 1). To our knowledge, only a few of these kinds of structures have hitherto been reported. EXPERIMENTAL Materials
2,6-Diformyl-4-methoxylphenol (dmop) was prepared using the method described in the literature [18]. Sodium 2,6-diformyl-4-methoxylphenolate (sdmop) was obtained by mixing equimolar amounts of dmop and NaOH in ethanol. Tris(3-aminopropyl)amine was prepared by a modified literature method [19] with a purity of over 99%. All starting materials were of chemical purity. Physical measurements
Solution electrical conductivity was measured by a BDS-A numerical conductometer (Jiangsu, China) with solution concentrations of c a 10 - 4 mol dm -3 in acetonitrile. IR spectra were measured as KBr discs
915
Xin-You Xu et al.
916 OCH
L
" 7 2+
OCtt
3 Fig. 1. The structure of the binuclear complex cation [Cd~(H_2L)]2+.
using a Nicolet 5DX FT-IR spectrophotometer. Electronic spectra were recorded on Shimadazu UV-240 spectrophotometer.
Preparation of the complex
[Cdz(H_2L)](C104)2 RESULTS AND DISCUSSION
• 0.5CH3OH To a stirred solution of sodium 2,6-diformyl-4methoxyphenolate (0.101 g, 0.5 mmol) and Cd(CIO4)2" 6H20 (0.261 g, 0.625 retool) in absolute methanol (30 cm 3) was added dropwise a solution of tris(3-aminopropyl)amine (0.094 g, 0.5 retool) in absolute methanol (15 cm 3) at 0°C. After stirring for 2 h at 35°C, yellowish microcrystals were precipitated and filtered off, washed with methanol and dried in vacuo (yield 45%). Found : C, 40.2 ; H, 5.5 ; N, 10.5 ; Cd, 19.9. Calc. for C36.sH56NsO12.5 Cd2C12; C, 39.8; H, 5.1 ; N, 10.2 ; Cd, 20.4%. IR (KBr, c m - l) : 3400 br, v(OH)(CH3OH); 3354s, Vas(NH2); 3300s, vs(NH2); 1641s, v(C--N) ; 1544s, v(Ar--O) ; 1102 (C104). U V vis (2m,~ rim, CH3CN) ; 270 (9763 tool -1 dm 3 cm-1) ; 430 (10078). AM (CH3CN, 279 K) : 236 S cm 2 tool i. The yellowish crystals of [Cd2(H_2L)](CIO4)2 • 5CH3OH suitable for X-ray structure determination were obtained by slow evaporation of the mother liquor at ambient temperature. CAUTION. Perchlorate salts of metal complexes with organic ligands are potentially explosive. Only small amounts of material should be prepared, and these should be handled with caution. The complex described in this report has, so far, been found to be safe when used in small quantities.
X-ray
crystal
F(000) = 1122, Z = 2, Dc = 1.60 g c m -3, T = 296 K, p = 11.06 cm -z. Data collection and refinement. A single crystal was mounted on a glass fibre. The crystal data were collected on an Enraf-Nonius CAD4 four-circle diffractometer with graphite-monochromated Mo-K~ radiation (2 = 0.71069 A) using an co-20 scan mode with o9 scan width 0.95 +0.350 tan 0, scan rate 5.49 ° min-I. A total of 8067 independent reflections were collected in the range 2 < 20 < 50% of which 6421 reflections with I > 3a(/) were used in the structure determination and refinement, after Lp corrections. The structure was solved by the MITHRIL direct method. The remaining non-hydrogen atoms were located from a difference Fourier map. Hydrogen atoms were introduced in calculated positions but not refined. The final least-squares cycle gave R = 0.052, Rw = 0.064(w = 1/aZ(Fo)). The maximum and minimum residuals had values of 0.63 and - 0 . 8 9 e/~ -3, respectively. All calculations were performed on a MICRO VAX-3100 computer using the programs contained in the TEXSAN [20].
structure
determination
of
[Cd2(H_2L)](C104)2" 5CH3OH
Crystal data. C36 sH56NsOI2.sCd2C12, M = 1102.65, yellowish crystal, dimensions 0.9 × 0.9 × 0.45 mm 3, triclinic, space group P_1(#2), a = 10.455(6), b = 11.451(4), c = 20.130(6) /~, ~ = 105.75(3), /~ = 82.84(3), y = 97.21(3) °, V = 2291(2) A 3,
Characterization of the complex In the infrared spectrum a strong peak appears at 1641 cm -1 corresponding to the stretching vibration ofimino ~ N bonds. The symmetric and asymmetric stretching frequencies (3300 and 3354 cm -I) for NH2 groups are also present, but no strong peaks at 16501700 cm 1 for the carbonyl groups. This means that two NHz groups and carbonyl groups have been condensed into ~ N bonds, whilst another NH2 group is unchanged. A broad band at ca 3400 era- J, characteristic of the OH group of CH3OH, showed that CH3OH molecules exist in the crystalline complex, in agreement with the elemental analysis. The strong peak at 1102 cm -1 without splitting showed that CIO~- did not take part in coordination with Cd ~ ions. This is also confirmed by the molar conductivity of the complex (AM = 236 S cm 2mol -~) which is attributable to a 2 : 1 electrolyte. Two intense absorptions in the electronic spectrum of the complex are designated to 7r-lr* transitions of the K band of the benzene rings and of C = N groups.
Description of the structure of [Cd2(H zL)](CIO4)z • 0.5CH3OH A perspective view of the cation [Cd2(H_ 2L)]2+ and a packing diagram are displayed in Figs 2 and 3, respectively. Selected bond distances and bond angles are given in Tables 1 and 2, respectively. Figure 3 shows that each unit cell contains two complex associations, each consisting of one molecule of the macrocyclic complex cation [Cd2(H_ 2L)]2+, two perchlorate anions and half of a methanol solvent
917
Synthesis and structure of a ~2-phenoxybridged macrocyclic cadmium(II) complex
~
C(36)
~)0(4) C(23) C(24) C(22)
C09) __ C08) C(21)
C(12)
C(13)
C(20) c04)
C(25)
N(5)
0(2)
C(31)
N(3)
c05)
C(30) Cd(2) ~ ' ~
C(ll)
N(4) C(34)
C(29)
O(1)
N(7)
N(8)
C(28)
C(33)
C(6) C(5) i
C(1)
C(32) c(35)
C(2)
~
~
ci4)
coo)
~
0(3)
C(3) Fig. 2. A perspective view of the cation [Cd(H :L)]2+.
O
C
B
Fig. 3. A packing diagram of the complex [Cd2(H_2L)](C104)2• 0.5CH3OH.
918
Xin-You Xu et al. Table 1, Selected bond distances (,~)
Cd(1)--N(7) Cd(l)--N(6) Cd(l)--N(2) Cd(1)--O(1) Cd(1)--O(2) Cd(1)--N(l) O(1)--C(6) O(3)--C(9) O(3)--C(35) Cd(1)--Cd(2) Cd(1)--N(4)
2.294(6) 2.300(5) 2.311(5) 2.282(4) 2.350(4) 2.455(5) 1.303(6) 1.374(7) 1.397(9) 3.689(2) 6.158(5)
Cd(2)--N(3) Cd(2)--N(8) Cd(2)--N(5) Cd(2)--O(1) Cd(2)--O(2) Cd(2)--N(4) O(2)--C(20) O(4)--C(23) O(4)--C(36) Cd(2)--N(1) N(I)--N(4)
2.295(5) 2.302(6) 2.305(5) 2.318(4) 2.328(4) 2.483(5) 1.315(7) 1.369(8) 1.40(1) 6.133(5) 8.608(8)
molecule. The methanol and perchlorate anions are disordered over two interpenetrating sites. It can be seen from Fig. 2 that in the cation of the complex each Cd" ion is enclosed within the polyaza macrocycle and coordinated by one bridgehead nitrogen atom, two imino nitrogen atoms, one amine nitrogen atom of the pendant arms and two oxygen atoms of phenoxy groups. Each Cd" is located in a trigonal prismatic N402 coordination environment with coordination number of six. For the Cd(1) centre, the phenoxy oxygens O(1), 0(2) and the amino nitrogen
N(6) forms one trigonal face, the Cd(1) deviates downwards by 1.5181 A from the face. The amino nitrogen atoms N(2), N(7) and the bridgehead nitrogen N(1) form another trigonal face, the Cd(1) deviates upwards by 1.2522/k from the face. The dihedral angle between the two faces is 11.13 °. For the Cd(2) centre, the phenoxy oxygens O(1), 0(2) and amino nitrogen N(3) form one trigonal face and the Cd(2) deviates upwards by 1.4849 A from the face. The amino nitrogens N(4), N(5) and the bridgehead nitrogen N(8) form another trigonal face and the Cd(2) deviates downwards by 1.2423/k from the face. The dihedral angle between the two faces is 12.74°C. The dihedral angle between the plane consisting of Cd(1), O(1), Cd(2) and the plane consisting of Cd(1), 0(2), Cd(2) is 151.00 °. The phenoxy oxygens O(1) and 0(2) bridge the two Cd n ions. The bond distances of Cd(1)--N(imino) and Cd(2)--N(imino) are approximately equal, being in the range 2.294-2.311 ,~. These C d - - N bond distances are shorter than the standard bond distance of 233_+ 0.005 A [20]. This means that these imino groups have strong coordination ability towards Cd". Conversely, the two bond distances Cd(1)--N(1), Cd(2)--N(4) are 2.455 and 2.483 A, respectively, implying weak interaction between the Cd ~I ions and the bridgehead nitrogen atoms.
Table 2. Selected bond angles (°) O(1)--Cd(1)--N(7) O(1)--Cd(1)--N(6) O(1)--Cd(I)--N(2) O(l)--Cd(1)--O(2) O(1)--Cd(1)--N(1) N(7)--Cd(1)--N(6) N(7)--Cd(1)--N(2) N(7)--Cd(I)--O(2) N(7)--Cd(I)--N(1) N(6)--Cd(1)--N(2) N(6)--Cd(1)--O(2) N(6)--Cd(1)--N(1) N(2)--Cd(l)--O(2) N(2)--Cd(1)--N(1) O(2)--Cd(1)--N(1) C(20)--O(2)--Cd(1) C(20)--O(2)--Cd(2) Cd(2)--O(2)--Cd(1) C(9)--O(3)--C(35) C(28)--N(1)--C(29) C(28)--N(1)--C(1) C(28)--N(1)--Cd(1) C(32)--N(8)--Cd(2) C(29)--N(1)--C(1) C(29)--N(1)--Cd(1) C(1)--N(1)--Cd(I) C(4)--N(2)--C(3) C(4)--N(2)--Cd(1) C(3)--N(2)--Cd(1) C(1 I)--N(3)--C(12) C(11)--N(a)--Cd(2) C(12)--N(3)--Cd(2)
126.1 (2) 91.9(2) 75.1 (1) 72.0(1) 148.0(2) 121.7(2) 110.9 (2) 76.1 (2) 82.5(2) 121.6(2) 77.0(2) 82.1 (2) 142.7(1) 81.5(2) 135.5(1) 132.3(4) 111.0(3) 104.1 (1) 117.3(5) 108.4(5) 108.3(5) 112.2(4) 108.6(4) 108.1 (5) 108.2(4) 111.4(3) 117.2(5) 122.7(4) 119.2(4) I 17.1(5) 128.6(4) 114.2(4)
N(3)--Cd(2)--N(8) N(3)--Cd(2)--N(5) N(3)--Cd(2)--O(1) N(3)--Cd(2)--O(2) N(3)--Cd(2)--N(4) N(S)--Cd(2)--N(5) N (8) --Cd (2)--O ( 1) N(8)--Cd(2)--O(2) N(8)--Cd(2)--N(4) N(5)--Cd(2)--O(1) N(5)--Cd(2)--O(2) N(5)--Cd(2)--N(4) O( 1)--Cd(2)---O(2) O(1)--Cd(2)--N(4) O(2)--Cd(2)--N(4) C(6)--O(1)--Cd(1) C(6)--O(1)--Cd(2) Cd(1)--O(1)--Cd(2) C(23)--O(4)--C(36) C( 15)--N (4)--C (14) C(15)--N(4)--C(34) C(15)--N(4)--Cd(2) C(14)--N(4)--C(34) C (14)--N(4)--Cd(2) C(34)--N(4)--Cd(2) C (18)--N(5)--C (17) C(18)--N(5)--Cd(2) C(17)--N(5)--Cd(2) C(25)--N(6)--C(26) C(25)--N(6)--Cd(l) C(26)--N(6)--Cd(1) C(3 l)--N(7)--Cd(1)
121.8(2) 120.4(2) 77.9(2) 95.5(2) 81.9(2) 111.9(2) 75.5(2) 122.7(2) 82.7(2) 142.8(2) 74.2(2) 81.0(2) 71.8(1) 135.9(2) 149.6(2) 115.0(3) 130.8(3) 106.6(2) 117.9(8) 108.9(5) 107.3(5) 112.5(4) 108.7(5) 111.6(4) 107.7(4) 116.4(5) 123.1(4) 119.9(4) 116.5(5) 130.3(4) 113.2(3) 110.3(4)
Synthesis and structure of a #2-phenoxy bridged macrocyclic cadmium(II) complex However, in the cadmium cryptate synthesized by condensation of tris(2-aminoethyl)amine with 2,6diformyl-4-methylphenol [21], the corresponding bond distance of Cd--N(bridgehead) 2.787 A, was larger than that reported in this paper. The long Cd(l) • • - Cd(2) distance (3.689 A) indicates that there is no interaction between the two metal atoms. The bond distances Cd(1)--O(1), Cd(2)--O(2), Cd(2)--O(1) and Cd(2)--I(2) are 2.282, 2.350, 2.318 and 2.328 A, respectively, being close to those reported by Drew et al. [21], also implying that Cd(l) is similar to Cd(2) in coordination environment but slightly different to Cd(2) in degree of distortion. An analogous complex [Cu2L'(OH)](C104)3 which was synthesized by [2+2] Schiff-base condensation of tris(2-aminoethyl)amine with isophthalic aldehyde in the presence of Cu(C104)2" 6H20 is unstable [22]. In our complex, however, the flexibility of the carbon chain strengthened the coordination ability of the bridgehead nitrogen atoms, and the phenoxy oxygen atoms bridging the two Cd II atoms enhanced the stability of the complex as well as forming the six-membered chelate rings and so stabilizing the structure of the complex.
5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
16.
Acknowledgements--This project was supported by the Natural ScienceFoundation of China and Fuzhou State Key Laboratory of Structure Chemistry.
17.
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