[μ-N,N,N′,N′-Tetrakis(2-pyridyl­methyl)-1,2-ethanedi­amine]­bis­[di­chloro­copper(II)]

Each Cu^II atom in the title complex, [Cu₂Cl₄(tpen)], where tpen is N,N,N′,N′-tetrakis(2-pyridyl­methyl)-1,2-ethanedi­amine (C₂₆H₂₈N₆), is clearly five-coordinate with approximate square-pyramidal geometry. Four of the coordinating atoms, viz. a Cl atom and the three N atoms of a tpen ligand, lie in a distorted square plane around Cu^II. The second Cl atom occupies the apical position of the square pyramid. The Cu—Cl distances are 2.262 (1) and 2.478 (1) Å, and the Cu—N distances are 2.006 (4) to 2.089 (4) Å.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.057
• wR factor = 0.136
• Data-to-parameter ratio = 19.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The most interesting aspects in the coordination chemistry of copper(II) is the variety of coordination geometries possible fof the central Cu^II atom (Anderson et al., 1976). N,N,N',N'-Tetrakis(2-pyridylmethyl)-1,2-ethylenediamine (referred to as tpen) is a hexadentate ligand. It is expected to form a mononuclear hexadentate octahedral complex. However, because of the steric crowding in mononuclear copper(II) complexes, the formation of dinuclear copper(II) complexes is also possible (Karlin et al., 1992; Mahapatra et al., 1997; Casella et al., 1988; Farrugia et al., 1997). Recently, dinucleartransition metal complexes containing Cu^II with various chelating ligands related to tpen were reported (Jensen et al., 1997). Furthermore, the high reactivities of the chloro ligand which coordinate to Cu^II make the complexes useful as a starting material for various reactions.

We report here the crystal structure of the centrosymmetric title complex, (I). In the title complex (Fig. 1), where the dinuclear Cu^II is contained as a central dimetal unit which are connected by a tpen bridge and with four chloro ligands coordinated. In the crystal structure, each Cu^II is clearly five-coordinated with approximate square-pyramidal geometry. Bond distances and angles are summarized in Table 1. Four of the coordinating atoms, i.e. one of the Cl atoms (Cl1) and the three N atoms of the tpen ligand, lie at the corners of a distorted square plane around Cu^II. The second Cl atom (Cl2) occupies the apical position of the square pyramid. The Cu—Cl bond lengths are not identical and are 2.2618 (14) and 2.4781 (14) Å. The Cu—N bond lengths are 2.006 (4), 2.020 (5) and 2.089 (4) Å. Comparing the Cu—Cl bonds, it is found that the length of the Cu—Cl apical bond is significantly longer than that of the basal one (2.478 Å versus 2.262 Å). This axial expansion may be due to the influence of the d⁹ electronic distribution on the coordination geometry (Anderson, 1976). In addition to atomic distance, it is noteworthy to mention angles. The Cl1—Cu—Cl2 [105.24 (6)°] bond angle is greater than the other bond angles [Cl2—Cu—N1 95.6 (1)°, Cl2—Cu—N2 96.4 (1)° and Cl2—Cu—N3 95.63 (14)°]. This is believed to be a result of repulsion by the lone-pair electrons of Cl1 and Cl2. Two intermolecular C—H···Cl interactions are present in the crystal structure. Also, the Cu···Cu non-bonding distance for the (I) was 7.932 (1) Å.

S2. Experimental

A solution of CuCl₂·5H₂O (0.23 g, 1 mmol) in methanol (50 ml) was added to a solution of tpen (0.22 g, 0.5 mmol) in methanol (5 ml). A green precipitate formed immediately after mixing. The mixture containing the precipitate was stirred for 20 min. and then 5 ml of a methanolic solution of sodium acetate (0.1 g, 1.2 mmol) was added. The precipitate dissolved immediately without ligation of acetate. The resulting green solution was stirred for 1 h. After stirring, the green solution was left at room temperature for a few days. A suitable single green crystal for X-ray analysis was then formed. Analysis calculated for the title complex: C 45.03, H 4.07, N 12.12%; found: C 44.85, H 4.13, N, 12.22%.

S3. Refinement

H atoms were treated as riding atoms using SHELXL97 defaults. The highest peak in the difference map is 2.4 Å from H7 and the largest hole is 0.69 Å from the Cu atom.

Computing details

Data collection: STADI4 (Stoe & Cie, 1996); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1996); program(s) used to solve structure: SHELXS97-2 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97-2 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

Figures

Fig. 1. ORTEP-3 (Farrugia, 1997) drawing of (I) with the atom numbering; displacement ellipsolids are drawn at the 50% probability level and H atoms have been omitted for clarity.

(I)

Crystal data

[Cu2Cl4(C26H28N6)]	F(000) = 1408
Mr = 693.42	Dx = 1.589 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -p_2ac_2ab	Cell parameters from 25 reflections
a = 13.113 (1) Å	θ = 9.6–10.9°
b = 20.926 (2) Å	µ = 1.85 mm^−1
c = 10.6378 (8) Å	T = 298 K
V = 2919.1 (4) Å^3	Monoclinic, green
Z = 4	0.32 × 0.25 × 0.22 mm

Data collection

Stoe STADI4 diffractometer	2303 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.079
Graphite monochromator	θmax = 27.4°, θmin = 2.0°
ω–2θ scans	h = 0→16
Absorption correction: numerical (Stoe & Cie, 1996)	k = 0→26
Tmin = 0.665, Tmax = 0.824	l = 0→13
3548 measured reflections	3 standard reflections every 60 min
3324 independent reflections	intensity decay: 5%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.057	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.136	H-atom parameters constrained
S = 1.16	w = 1/[σ^2(Fo^2) + (0.0328P)^2 + 10.1201P] where P = (Fo^2 + 2Fc^2)/3
3324 reflections	(Δ/σ)max = 0.001
172 parameters	Δρmax = 0.79 e Å^−3
0 restraints	Δρmin = −0.46 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cu	0.26364 (4)	0.07289 (3)	0.11319 (6)	0.03140 (18)
Cl1	0.11411 (10)	0.10097 (8)	0.02276 (14)	0.0462 (4)
Cl2	0.24750 (10)	0.10513 (8)	0.33645 (13)	0.0478 (4)
N1	0.2290 (3)	−0.0194 (2)	0.1416 (4)	0.0327 (10)
N2	0.4110 (3)	0.0356 (2)	0.1274 (4)	0.0283 (9)
N3	0.3451 (3)	0.1502 (2)	0.0595 (4)	0.0379 (10)
C1	0.1404 (4)	−0.0489 (3)	0.1165 (5)	0.0388 (12)
H1	0.0872	−0.0253	0.0821	0.047*
C2	0.1256 (5)	−0.1129 (3)	0.1398 (6)	0.0499 (15)
H2	0.0627	−0.1318	0.1241	0.060*
C3	0.2043 (5)	−0.1481 (3)	0.1860 (6)	0.0517 (16)
H3	0.1963	−0.1917	0.2003	0.062*
C4	0.2958 (5)	−0.1187 (3)	0.2115 (6)	0.0475 (15)
H4	0.3504	−0.1421	0.2431	0.057*
C5	0.3058 (4)	−0.0541 (3)	0.1897 (5)	0.0345 (12)
C6	0.4447 (4)	0.1471 (3)	0.0930 (6)	0.0402 (13)
C7	0.5138 (5)	0.1933 (3)	0.0561 (8)	0.063 (2)
H7	0.5822	0.1898	0.0780	0.076*
C8	0.4801 (6)	0.2440 (4)	−0.0129 (9)	0.074 (2)
H8	0.5253	0.2760	−0.0370	0.089*
C9	0.3793 (6)	0.2477 (3)	−0.0467 (7)	0.0626 (18)
H9	0.3556	0.2819	−0.0941	0.075*
C10	0.3141 (5)	0.2002 (3)	−0.0096 (6)	0.0501 (15)
H10	0.2459	0.2027	−0.0331	0.060*
C11	0.4000 (4)	−0.0166 (3)	0.2199 (5)	0.0358 (12)
H11A	0.3951	0.0010	0.3040	0.043*
H11B	0.4593	−0.0443	0.2166	0.043*
C12	0.4716 (4)	0.0906 (3)	0.1722 (5)	0.0381 (13)
H12A	0.5439	0.0813	0.1649	0.046*
H12B	0.4563	0.0993	0.2597	0.046*
C13	0.4447 (3)	0.0120 (2)	0.0013 (5)	0.0302 (11)
H13A	0.4376	0.0463	−0.0593	0.036*
H13B	0.4000	−0.0225	−0.0247	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0208 (3)	0.0419 (4)	0.0315 (3)	0.0037 (3)	−0.0006 (2)	−0.0027 (3)
Cl1	0.0300 (6)	0.0605 (9)	0.0481 (8)	0.0096 (6)	−0.0093 (6)	0.0011 (7)
Cl2	0.0339 (7)	0.0755 (10)	0.0342 (6)	−0.0020 (7)	0.0014 (6)	−0.0172 (7)
N1	0.022 (2)	0.045 (3)	0.032 (2)	0.0020 (18)	−0.0004 (17)	−0.0004 (19)
N2	0.0193 (18)	0.039 (2)	0.027 (2)	0.0000 (17)	0.0002 (16)	−0.0019 (19)
N3	0.036 (2)	0.038 (3)	0.040 (3)	0.003 (2)	0.005 (2)	−0.004 (2)
C1	0.028 (2)	0.051 (3)	0.037 (3)	−0.002 (2)	0.002 (2)	−0.004 (3)
C2	0.042 (3)	0.062 (4)	0.045 (3)	−0.015 (3)	0.000 (3)	−0.007 (3)
C3	0.067 (4)	0.046 (4)	0.042 (3)	−0.013 (3)	−0.002 (3)	0.000 (3)
C4	0.050 (3)	0.050 (4)	0.042 (3)	0.003 (3)	−0.008 (3)	0.010 (3)
C5	0.029 (3)	0.050 (3)	0.024 (2)	−0.001 (2)	0.001 (2)	0.004 (2)
C6	0.032 (3)	0.039 (3)	0.050 (3)	−0.003 (2)	0.004 (2)	−0.011 (3)
C7	0.047 (4)	0.044 (4)	0.099 (6)	−0.009 (3)	0.005 (4)	−0.010 (4)
C8	0.070 (5)	0.039 (4)	0.114 (7)	−0.018 (4)	0.005 (5)	0.001 (4)
C9	0.083 (5)	0.033 (3)	0.072 (5)	0.002 (4)	−0.006 (4)	0.002 (3)
C10	0.053 (4)	0.038 (3)	0.060 (4)	0.008 (3)	0.000 (3)	−0.005 (3)
C11	0.028 (2)	0.047 (3)	0.033 (3)	0.007 (2)	−0.006 (2)	0.008 (2)
C12	0.024 (2)	0.048 (3)	0.043 (3)	0.000 (2)	0.001 (2)	−0.013 (3)
C13	0.024 (2)	0.038 (3)	0.028 (2)	0.002 (2)	0.0004 (19)	−0.001 (2)

Geometric parameters (Å, º)

Cu—N1	2.006 (4)	C4—C5	1.378 (8)
Cu—N3	2.020 (5)	C4—H4	0.9300
Cu—N2	2.089 (4)	C5—C11	1.499 (7)
Cu—Cl1	2.262 (1)	C6—C7	1.381 (8)
Cu—Cl2	2.478 (1)	C6—C12	1.494 (8)
Cu—Cu^i	7.932 (1)	C7—C8	1.365 (10)
N1—C5	1.342 (6)	C7—H7	0.9300
N1—C1	1.344 (6)	C8—C9	1.372 (10)
N2—C11	1.477 (6)	C8—H8	0.9300
N2—C12	1.478 (6)	C9—C10	1.369 (9)
N2—C13	1.497 (6)	C9—H9	0.9300
N3—C10	1.342 (7)	C10—H10	0.9300
N3—C6	1.356 (7)	C11—H11A	0.9700
C1—C2	1.375 (8)	C11—H11B	0.9700
C1—H1	0.9300	C12—H12A	0.9700
C2—C3	1.359 (9)	C12—H12B	0.9700
C2—H2	0.9300	C13—C13^ii	1.534 (9)
C3—C4	1.377 (8)	C13—H13A	0.9700
C3—H3	0.9300	C13—H13B	0.9700
N1—Cu—N3	158.8 (2)	N1—C5—C11	114.6 (5)
N1—Cu—N2	80.7 (2)	C4—C5—C11	123.8 (5)
N3—Cu—N2	80.3 (2)	N3—C6—C7	121.6 (6)
N1—Cu—Cl1	96.8 (1)	N3—C6—C12	114.4 (5)
N3—Cu—Cl1	97.5 (1)	C7—C6—C12	124.0 (5)
N2—Cu—Cl1	158.4 (1)	C8—C7—C6	119.0 (6)
N1—Cu—Cl2	95.6 (1)	C8—C7—H7	120.5
N3—Cu—Cl2	95.6 (1)	C6—C7—H7	120.5
N2—Cu—Cl2	96.4 (1)	C7—C8—C9	119.7 (7)
Cl1—Cu—Cl2	105.24 (6)	C7—C8—H8	120.1
C5—N1—C1	118.4 (5)	C9—C8—H8	120.1
C5—N1—Cu	114.1 (3)	C10—C9—C8	119.1 (7)
C1—N1—Cu	127.5 (4)	C10—C9—H9	120.5
C11—N2—C12	114.4 (4)	C8—C9—H9	120.5
C11—N2—C13	112.4 (4)	N3—C10—C9	122.3 (6)
C12—N2—C13	112.8 (4)	N3—C10—H10	118.8
C11—N2—Cu	103.6 (3)	C9—C10—H10	118.8
C12—N2—Cu	103.3 (3)	N2—C11—C5	108.9 (4)
C13—N2—Cu	109.4 (3)	N2—C11—H11A	109.9
C10—N3—C6	118.2 (5)	C5—C11—H11A	109.9
C10—N3—Cu	128.3 (4)	N2—C11—H11B	109.9
C6—N3—Cu	113.4 (4)	C5—C11—H11B	109.9
N1—C1—C2	122.3 (5)	H11A—C11—H11B	108.3
N1—C1—H1	118.9	N2—C12—C6	107.9 (4)
C2—C1—H1	118.9	N2—C12—H12A	110.1
C3—C2—C1	119.1 (6)	C6—C12—H12A	110.1
C3—C2—H2	120.4	N2—C12—H12B	110.1
C1—C2—H2	120.4	C6—C12—H12B	110.1
C2—C3—C4	119.3 (6)	H12A—C12—H12B	108.4
C2—C3—H3	120.3	N2—C13—C13^ii	113.8 (5)
C4—C3—H3	120.3	N2—C13—H13A	108.8
C3—C4—C5	119.3 (6)	C13^ii—C13—H13A	108.8
C3—C4—H4	120.4	N2—C13—H13B	108.8
C5—C4—H4	120.4	C13^ii—C13—H13B	108.8
N1—C5—C4	121.6 (5)	H13A—C13—H13B	107.7

Symmetry codes: (i) −x, −y, −z; (ii) −x+1, −y, −z.