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A new tetranuclear CuII–HgII–HgII–CuII complex, [Cu2Hg2Cl4(C18H18N2O2)2], has been prepared by means of a copper complex found in the literature. The molecular structure of this complex was determined by X-ray diffraction and the Cu–Hg–Hg–Cu chain was seen to be non-linear. The change in magnetic susceptibility with temperature was recorded for this complex and observed to abide by the Curie–Weiss law. The coordination around the HgII ions is square pyramidal. The Cu...Hg bridging distance is 3.5269 (7) Å.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101019709/br1346sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101019709/br1346Isup2.hkl
Contains datablock I

CCDC reference: 182008

Comment top

Organic structured copper complexes have been used in pharmacology because the Cu(II) ion is an essential element for all living beings. Mercury is one of the most toxic elements for people and animals and also secretion of mercury from the human body is very difficult. For this reason copper and mercury complexes are important in bioinorganic chemistry and a complex which contains both ions is very interesting. The most frequently observed coordination of the mercury(II)-organic ligand complexes in literature is the tetrahedral coordination. If the complexes contain halogen ions either dimerization or formation of planar rings in the structure HgX···HgX (The ring is defined as the Hg—Cl—Hg—Cl ring) can be observed (Canty et al., 1979; Holy et al., 1976; Davidovic et al., 1998).

It has been known for a long time that ONNO type Schiff bases form polynuclear complexes with Cu(II) and Ni(II) complexes by reaction with many Lewis acids in nonaqueous solvents (Butcher & Sinn, 1976; Aminabhavi et al., 1986; Yao et al., 1997; Atakol et al., 1999). A Cu-ONNO Schiff base complex previously prepared was put reacted with HgCl2 with the expectation that a heterometal complex CuII—HgII would tend to dimerize forming planar HgX···HgX coordination rings (Atakol et al., 1999). The molecular structure was seen to be tetranuclear through X-ray diffraction studies (Fig 1). The complex structure was also studies using IR and element analysis techniques. In addition, the magnetic behaviour of the metal complex was measured between 2–300 K. The magnetic measurements indicate that the crystals are paramagnetic. Selected geometric parameters have been presented in Table 1.

The seven components chelate ring is not seen very often and most of the transition metal ions do not form this seven member chelate ring. The seven-member chelate ring composed of atoms Cu(II), N1, C8, C9, C10, C11 and N2 has a chair conformation. Similar to the six component rings, the most stable form of the seven coordinate ring is the chair. The CuII ion has a distorted square-planar coordination involving two O and N atoms from the SALBD (salycilydene butane diamine) ligand. The HgII ion has a distorted square pyramid coordination. This coordination for HgII ion is unusual (Eliel & Wilen, 1996).

In general, a τ value can be calculated from the angles around the central atom for a coordination number of five. τ = (α-β)/60 and α and β are the largest two angles around the central atom. If τ = 1 then the coordination is an ideal trigonal bipyramid, whereas if τ = 0 then the coordination is an ideal square pyramid (Addison et al., 1984). From the bond angles seen in Table 1 τ is 0.176. As this value as close to zero the coordination around HgII is a square pyramid. The Cu···Hg and Hg···Hgi (1 - x, -1 - y, 2 - z) distances are 3.5269 (7) and 4.3613 (6), respectively. The largest Hg···Cl distance found in literature in an Hg—Cl—Hg—Cl ring is 2.976 Å (Davidovic et al., 1998). Although HgII has been reported as generally having coordination numbers 2 and 4, its coordination number in the tetranuclear complex can be taken as 5.

Experimental top

Salicylaldehyde, 1,4-butanediamine and the metal salts have been obtained from Merck. The solvents were acquired from Corlo Erba and were used without further purification. The magnetic susceptibility of the powdered sample was measured between 2.6–300 K with a Faraday-type magnetometer at 1.2 T. Experimental susceptibility data were corrected for the underlying diamagnetism. The magnetic measurements indicate that the heterometal tetranuclear complex is paramagnetic. The ligand was prepared with the condensation reaction of salicyaldehyde and 1,4-butanediamine in EtOH media (m.p. 603 K, yield: 94%). The complex was prepared in two steps. Step 1: 0.592 gr (0.002 mol) of the ligand was dissolved in 50 ml MeOH by heating. The solution of 0.400 gr Cu (CH3COO)2·H2O in 50 ml hot MeOH was added to this solution mixed and let to stand for 3–4 h. The resulting precipitate was filtered. C18H18N2O2Cu, MP > 603 K, yield: 80%. Step 2: 0.358 g of the complex prepared in Step 1 was dissolved at 363–373 K in a mixture of 20 ml dmf (dimethylformamide) + 20 ml dioxane. A solution of 0.272 g HgCl2 (0.001 mol) in 30 ml hot MeOH was added to this solution. The mixture was let to stand for 3–4 days. The precipitated crystals were filtered and let to dry in an open atmosphere. Element Analysis: Calc. for C36H36N4O4Cu2Hg2Cl4: C, 34.33; H, 2.86; N, 4.45; Cl, 11.27; Cu, 10.10%. Found: C, 34.46; H, 2.94; N, 4.54; Cl, 11.23; Cu, 10.0%. IR (cm-1); νC—H Aro=3029;νC—H Aliph =2927; νC—H imin=2984; νC=N Aro=1625; δC—H Aliph= 1472; δC—H Aro=757; νC—O Aro=1140.

Refinement top

All non-H atoms were refined with anisotropic thermal parameters. H atoms bonded to C atoms were placed geometrically from their parent atoms. For all H atoms a riding model was used with Ueq(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 EXPRESS(Enraf-Nonius, 1993); cell refinement: SHELXL97 (Sheldrick, 1997b); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: ORTEP(II) (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997b).

Figures top
[Figure 1] Fig. 1. ORTEP drawing of [(CuHgCl2)2 (C18H18N2O2)2] with the atom numbering schemes. The displacement ellipsoids are drawn at the 50% probability level.
(I) top
Crystal data top
[(CuHgCl2)2(C18H18N2O2)2]Z = 1
Mr = 1258.74Dx = 2.154 Mg m3
Triclinic, P1Mo Kα radiation, λ = 0.71073 Å
a = 8.9927 (12) ÅCell parameters from 25 reflections
b = 9.4979 (13) Åθ = 10.2–18.1°
c = 13.0245 (14) ŵ = 9.29 mm1
α = 72.440 (2)°T = 301 K
β = 69.285 (3)°Prism, dark brown
γ = 73.023 (3)°0.20 × 0.15 × 0.10 mm
V = 970.4 (2) Å3
Data collection top
CAD-4 EXPRESS (Enraf-Nonius, 1993)
diffractometer
Rint = 0.036
ω/2θ scansθmax = 26.3°
Absorption correction: ψ scan
empirical (using intensity measurements) via ψ scans (Fair, 1990)
h = 1011
Tmin = 0.258, Tmax = 0.457k = 1111
4114 measured reflectionsl = 016
3932 independent reflections3 standard reflections every 120 min
3482 reflections with I > 2σ(I) intensity decay: 0.3%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.057See text
wR(F2) = 0.149 w = 1/[σ2(Fo2) + (0.1197P)2 + 0.1203P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max = 0.003
3932 reflectionsΔρmax = 0.92 e Å3
236 parametersΔρmin = 0.19 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0026 (8)
Crystal data top
[(CuHgCl2)2(C18H18N2O2)2]γ = 73.023 (3)°
Mr = 1258.74V = 970.4 (2) Å3
Triclinic, P1Z = 1
a = 8.9927 (12) ÅMo Kα radiation
b = 9.4979 (13) ŵ = 9.29 mm1
c = 13.0245 (14) ÅT = 301 K
α = 72.440 (2)°0.20 × 0.15 × 0.10 mm
β = 69.285 (3)°
Data collection top
CAD-4 EXPRESS (Enraf-Nonius, 1993)
diffractometer
3482 reflections with I > 2σ(I)
Absorption correction: ψ scan
empirical (using intensity measurements) via ψ scans (Fair, 1990)
Rint = 0.036
Tmin = 0.258, Tmax = 0.4573 standard reflections every 120 min
4114 measured reflections intensity decay: 0.3%
3932 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0570 restraints
wR(F2) = 0.149See text
S = 1.09Δρmax = 0.92 e Å3
3932 reflectionsΔρmin = 0.19 e Å3
236 parameters
Special details top

Experimental. The IR spectra were recorded in the solid state (KBr pellets) on a Mattson 1000 FTIR spectrometer. The CHN element analysis was performed on a Leco 932 CHNS instrument and the Cu analysis was performed on a Hitachi 8200 Model AAS. The magnetic susceptibility of the powdered sample was measured between 2.6–300 K with a Faraday-type magnetometer at 1.2 T. The magnetometer consists of a CAHN D-200 microbalance, a Leybold Heraeus VNK 300 helium flux cryostat and a Bruker B—Mn 200/60 power supply.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cu0.43513 (11)1.01273 (9)0.74407 (8)0.0309 (2)
Hg0.52245 (4)0.61512 (3)0.82450 (2)0.03813 (18)
N10.4372 (8)1.1446 (7)0.8376 (6)0.0335 (13)
N20.3329 (8)1.1690 (7)0.6379 (6)0.0368 (14)
O10.5871 (7)0.8521 (6)0.8092 (6)0.0423 (13)
O20.3962 (7)0.8529 (6)0.7014 (5)0.0364 (12)
C10.7126 (9)0.8761 (9)0.8245 (6)0.0341 (16)
C20.8572 (10)0.7649 (10)0.8169 (7)0.0420 (18)
H20.86340.67340.79870.050*
C30.9910 (10)0.7865 (12)0.8356 (8)0.049 (2)
H31.08830.71120.82780.059*
C40.9836 (12)0.9155 (12)0.8650 (9)0.054 (2)
H41.07450.92850.87960.064*
C50.8444 (12)1.0263 (11)0.8735 (8)0.049 (2)
H50.84051.11570.89380.059*
C60.7081 (10)1.0102 (9)0.8529 (7)0.0365 (17)
C70.5621 (11)1.1275 (9)0.8671 (7)0.0394 (17)
H70.56001.20150.90330.047*
C80.2993 (11)1.2670 (11)0.8772 (8)0.049 (2)
H8A0.26961.24650.96030.058*
H8B0.33691.36360.84710.058*
C90.1510 (10)1.2858 (10)0.8445 (8)0.046 (2)
H9A0.05591.33460.89840.056*
H9B0.13451.18470.85040.056*
C100.1582 (12)1.3805 (10)0.7242 (9)0.051 (2)
H10A0.06331.37510.70470.062*
H10B0.14961.48730.72280.062*
C110.3125 (11)1.3294 (9)0.6353 (8)0.0423 (19)
H11A0.30681.39100.55990.051*
H11B0.40741.34460.64930.051*
C120.2821 (10)1.1441 (9)0.5667 (7)0.0407 (18)
H120.23831.23060.51820.049*
C130.2835 (9)1.0001 (9)0.5511 (6)0.0348 (16)
C140.2233 (11)1.0012 (11)0.4647 (7)0.0432 (19)
H140.18601.09530.41960.052*
C150.2171 (12)0.8712 (12)0.4439 (8)0.049 (2)
H150.17500.87370.38580.059*
C160.2742 (13)0.7344 (11)0.5101 (8)0.049 (2)
H160.27120.64270.49640.059*
C170.3346 (11)0.7289 (9)0.5947 (7)0.0402 (18)
H170.37360.63350.63760.048*
C180.3398 (9)0.8611 (9)0.6192 (7)0.0323 (15)
Cl10.3030 (3)0.6226 (3)0.9871 (2)0.0550 (6)
Cl20.7183 (4)0.4980 (3)0.6866 (2)0.0641 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.039 (4)0.032 (4)0.034 (4)0.007 (3)0.013 (3)0.010 (3)
C20.045 (4)0.034 (4)0.047 (5)0.018 (4)0.014 (4)0.000 (3)
C30.033 (4)0.056 (6)0.053 (5)0.016 (4)0.012 (3)0.001 (4)
C40.045 (5)0.057 (6)0.071 (7)0.016 (5)0.022 (4)0.021 (4)
C50.057 (5)0.047 (5)0.058 (6)0.018 (4)0.023 (4)0.019 (4)
C60.045 (4)0.030 (4)0.037 (4)0.009 (3)0.010 (3)0.013 (3)
C70.053 (5)0.031 (4)0.041 (4)0.014 (3)0.014 (4)0.013 (3)
C80.056 (5)0.039 (5)0.049 (5)0.020 (4)0.007 (4)0.007 (4)
C90.043 (4)0.034 (4)0.053 (5)0.015 (4)0.000 (4)0.007 (4)
C100.054 (5)0.028 (4)0.069 (6)0.014 (4)0.020 (5)0.002 (4)
C110.061 (5)0.016 (3)0.047 (5)0.003 (3)0.017 (4)0.005 (3)
C120.046 (4)0.029 (4)0.041 (4)0.006 (3)0.014 (3)0.001 (3)
C130.041 (4)0.031 (4)0.031 (4)0.006 (3)0.011 (3)0.007 (3)
C140.051 (5)0.042 (5)0.034 (4)0.001 (3)0.014 (3)0.011 (4)
C150.062 (5)0.056 (6)0.040 (5)0.014 (4)0.020 (4)0.017 (5)
C160.070 (6)0.042 (5)0.047 (5)0.016 (4)0.017 (4)0.022 (4)
C170.060 (5)0.024 (4)0.041 (4)0.003 (3)0.019 (4)0.014 (3)
C180.032 (3)0.027 (4)0.039 (4)0.005 (3)0.010 (3)0.011 (3)
Cl10.0478 (12)0.0631 (15)0.0454 (12)0.0090 (11)0.0130 (9)0.0026 (11)
Cl20.0762 (17)0.0590 (16)0.0526 (14)0.0295 (12)0.0198 (12)0.0114 (13)
Cu0.0390 (5)0.0195 (4)0.0374 (5)0.0077 (4)0.0143 (4)0.0054 (3)
Hg0.0486 (2)0.0258 (2)0.0430 (2)0.01005 (14)0.01545 (15)0.00712 (14)
N10.044 (4)0.020 (3)0.039 (4)0.009 (3)0.014 (3)0.004 (3)
N20.048 (4)0.022 (3)0.039 (4)0.007 (3)0.011 (3)0.007 (3)
O10.054 (3)0.022 (3)0.064 (4)0.014 (3)0.034 (3)0.002 (2)
O20.052 (3)0.020 (2)0.043 (3)0.002 (2)0.025 (3)0.007 (2)
Geometric parameters (Å, º) top
C1—O11.304 (9)C11—H11A0.9900
C1—C21.409 (11)C11—H11B0.9900
C1—C61.416 (11)C12—N21.274 (11)
C2—C31.389 (13)C12—C131.438 (12)
C2—H20.9500C12—H120.9500
C3—C41.368 (14)C13—C141.408 (11)
C3—H30.9500C13—C181.416 (11)
C4—C51.375 (14)C14—C151.362 (13)
C4—H40.9500C14—H140.9500
C5—C61.402 (12)C15—C161.394 (14)
C5—H50.9500C15—H150.9500
C6—C71.449 (12)C16—C171.372 (12)
C7—N11.263 (11)C16—H160.9500
C7—H70.9500C17—C181.403 (11)
C8—C91.486 (13)C17—H170.9500
C8—N11.491 (11)C18—O21.313 (10)
C8—H8A0.9900Hg—Cl12.331 (2)
C8—H8B0.9900Hg—Cl1i3.2997 (17)
C9—C101.543 (13)Hg—Cl22.321 (2)
C9—H9A0.9900Hg—O12.420 (5)
C9—H9B0.9900Hg—O22.562 (5)
C10—C111.520 (13)Cu—O11.933 (6)
C10—H10A0.9900Cu—O21.921 (5)
C10—H10B0.9900Cu—N12.001 (6)
C11—N21.471 (9)Cu—N21.955 (7)
O1—C1—C2120.3 (7)C13—C12—H12116.3
O1—C1—C6122.1 (7)C14—C13—C18120.0 (8)
C2—C1—C6117.5 (7)C14—C13—C12117.0 (7)
C3—C2—C1121.4 (8)C18—C13—C12123.0 (7)
C3—C2—H2119.3C15—C14—C13121.8 (8)
C1—C2—H2119.3C15—C14—H14119.1
C4—C3—C2120.4 (8)C13—C14—H14119.1
C4—C3—H3119.8C14—C15—C16118.2 (8)
C2—C3—H3119.8C14—C15—H15120.9
C3—C4—C5119.9 (8)C16—C15—H15120.9
C3—C4—H4120.0C17—C16—C15121.7 (8)
C5—C4—H4120.0C17—C16—H16119.2
C4—C5—C6121.4 (9)C15—C16—H16119.2
C4—C5—H5119.3C16—C17—C18121.3 (8)
C6—C5—H5119.3C16—C17—H17119.3
C5—C6—C1119.4 (8)C18—C17—H17119.3
C5—C6—C7119.3 (8)O2—C18—C17120.2 (7)
C1—C6—C7121.1 (7)O2—C18—C13122.7 (7)
N1—C7—C6128.6 (7)C17—C18—C13117.1 (7)
N1—C7—H7115.7O2—Cu—O183.6 (2)
C6—C7—H7115.7O2—Cu—N292.6 (3)
C9—C8—N1115.3 (8)O1—Cu—N2163.3 (3)
C9—C8—H8A108.5O2—Cu—N1161.3 (3)
N1—C8—H8A108.5O1—Cu—N190.1 (2)
C9—C8—H8B108.5N2—Cu—N198.1 (3)
N1—C8—H8B108.5Cl2—Hg—Cl1153.80 (12)
H8A—C8—H8B107.5Cl2—Hg—O1108.68 (18)
C8—C9—C10113.8 (8)Cl1—Hg—O196.99 (18)
C8—C9—H9A108.8Cl1i—Hg—O1103.40 (3)
C10—C9—H9A108.8Cl2—Hg—O2100.32 (15)
C8—C9—H9B108.8Cl1—Hg—O296.17 (15)
C10—C9—H9B108.8Cl1i—Hg—O2164.36 (3)
H9A—C9—H9B107.7Cl1i—Hg—Cl179.96 (3)
C11—C10—C9113.7 (7)Cl1i—Hg—Cl288.92 (3)
C11—C10—H10A108.8O1—Hg—O262.04 (18)
C9—C10—H10A108.8C7—N1—C8115.1 (7)
C11—C10—H10B108.8C7—N1—Cu120.1 (5)
C9—C10—H10B108.8C8—N1—Cu124.8 (5)
H10A—C10—H10B107.7C12—N2—C11115.1 (7)
N2—C11—C10110.4 (7)C12—N2—Cu124.9 (6)
N2—C11—H11A109.6C11—N2—Cu120.0 (6)
C10—C11—H11A109.6C1—O1—Cu122.5 (5)
N2—C11—H11B109.6C1—O1—Hg129.2 (5)
C10—C11—H11B109.6Cu—O1—Hg107.7 (2)
H11A—C11—H11B108.1C18—O2—Cu128.8 (5)
N2—C12—C13127.5 (7)C18—O2—Hg127.8 (5)
N2—C12—H12116.3Cu—O2—Hg102.8 (2)
Symmetry code: (i) x+1, y+1, z+2.

Experimental details

Crystal data
Chemical formula[(CuHgCl2)2(C18H18N2O2)2]
Mr1258.74
Crystal system, space groupTriclinic, P1
Temperature (K)301
a, b, c (Å)8.9927 (12), 9.4979 (13), 13.0245 (14)
α, β, γ (°)72.440 (2), 69.285 (3), 73.023 (3)
V3)970.4 (2)
Z1
Radiation typeMo Kα
µ (mm1)9.29
Crystal size (mm)0.20 × 0.15 × 0.10
Data collection
DiffractometerCAD-4 EXPRESS (Enraf-Nonius, 1993)
diffractometer
Absorption correctionψ scan
empirical (using intensity measurements) via ψ scans (Fair, 1990)
Tmin, Tmax0.258, 0.457
No. of measured, independent and
observed [I > 2σ(I)] reflections
4114, 3932, 3482
Rint0.036
(sin θ/λ)max1)0.623
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.057, 0.149, 1.09
No. of reflections3932
No. of parameters236
H-atom treatmentSee text
Δρmax, Δρmin (e Å3)0.92, 0.19

Computer programs: CAD-4 EXPRESS(Enraf-Nonius, 1993), SHELXL97 (Sheldrick, 1997b), SHELXS97 (Sheldrick, 1997a), ORTEP(II) (Johnson, 1976).

Selected geometric parameters (Å, º) top
Hg—Cl12.331 (2)Cu—O11.933 (6)
Hg—Cl1i3.2997 (17)Cu—O21.921 (5)
Hg—Cl22.321 (2)Cu—N12.001 (6)
Hg—O12.420 (5)Cu—N21.955 (7)
Hg—O22.562 (5)
O2—Cu—O183.6 (2)Cl2—Hg—O2100.32 (15)
N2—Cu—N198.1 (3)Cl1—Hg—O296.17 (15)
Cl2—Hg—Cl1153.80 (12)Cl1i—Hg—O2164.36 (3)
Cl2—Hg—O1108.68 (18)Cl1i—Hg—Cl179.96 (3)
Cl1—Hg—O196.99 (18)Cl1i—Hg—Cl288.92 (3)
Cl1i—Hg—O1103.40 (3)O1—Hg—O262.04 (18)
Symmetry code: (i) x+1, y+1, z+2.
 

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