Aqua(2,2'-bi-1H-imidazole)chloro­copper(II) chloro­(imino­diacetato)copper(II) monohydrate

In the title compound, [CuCl(C₆H₆N₄)(H₂O)][Cu(C₄H₅NO₄)Cl]·H₂O, the Cu^II atom in the cation is coordinated by one Cl^- ion, two N atoms of the 2,2'-biimidazole ligand and one aqua ligand. Within the anion, the Cu^II atom is bonded to one Cl^- ion, and one N and two O atoms of the imino­diacetate ligand. Neighbouring cations and anions are connected to each other by Cu...Cl semi-coordination bonds of 2.830 (12) and 3.071 (12) Å, forming a Cu₂Cl₂ rectangular unit. The dinuclear units further link into a polymeric chain along the a axis through Cu...O_aqua interactions of 2.725 (3) Å. Including the long coordination bonds, the geometries around the Cu atoms in the cation and anion are square-pyramidal and distorted octahedral, respectively.

S1. Comment

The synthesis of some 3 d metal complexes with either neutral or deprotonated 2,2'-biimidazole was reported for the first time by Holmes et al. (1961). Since then, the coordination chemistry and biochemical properties of 2,2'-biimidazole have been investigated (Usón & Gimeno, 1981; Liu & Su, 1996; Tadokoro & Nakasuji, 2000; Casas et al., 2003; Zhang et al., 2003; Mano et al., 2004). This is not only because 2,2'-biimidazole (H₂biim) is a ligand that can coordinate to transition metals in non-deprotonated (H₂biim), mono-deprotonated (Hbiim⁻) and tris-deprotonated tris-deprotonated? (biim²⁻) forms, but also because it is important as a biomimetic ligand, the imidazole ring of histidine having been frequently found in a variety of proteins and metalloenzymes (Cancela et al., 2001; Sang et al., 2002). In order to model the physical and chemical behaviour of natural systems, either unsubstituted or substituted 2,2'-biimidazole has been used as a ligand to design synthetic analogues of metalloenzymes. Thus, a variety of geometries and ligating modes of H₂biim to Cu^II, Co^II, Ni^II, V^II, Ag^I and Cd^II have been investigated (Bencini & Mani, 1988; Sigel et al., 2000; Cancela et al., 2001; Mori & Miyoshi 2004; Atencio et al., 2004). In addition, on account of the tridentate chelating property of the iminodiacetate (ida) ligand and the flexibility of the Cu^II coordination stereochemistry, we are interested in copper complexes with mixed ligands. Here, we report the synthesis and crystal structure of the title compound, (I).

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The asymmetric unit of (I) contains one [CuCl(H₂biim)(H₂O)]⁺ cation, one [CuCl(ida)]⁻ anion and one solvate water molecule (Fig. 1). Within the cation, atom Cu1 is bonded to atoms N1 and N3 of the 2,2'-biimidazole, atom O5 of the aqua ligand and atom Cl1. The Cu—N and Cu—Cl bond lengths are 1.996 (3)–2.003 (3) Å and 2.2503 (12) Å, respectively (Table 1), comparable with those reported previously [1.98 (1)–2.17 (4) Å, 2.254 (4) Å; Bencini & Mani, 1988; Liu & Su, 1996]. The coordination atoms around Cu1 are coplanar, with an r.m.s deviation of 0.09 Å. In the anion, atom Cu2 is coordinated by an O,N,O'-tridentate chelating ida ligand (with two deprotonated carboxylate groups) and atom Cl2. The coordinated atoms and Cu2 are coplanar, with an r.m.s deviation of 0.02 Å. The cations and anions are arranged alternately and vertically along the a axis. Neighbouring cations and anions are connected to each other via Cu1···Cl2 and Cu2···Cl1 interactions of 2.830 (12) Å and 3.071 (12) Å, respectively, forming a neutral dinuclear unit through an irregular Cu1/Cl1/Cu2/Cl2 quadrangle (Fig. 2). Theses neutral dinuclear units are further linked into a polymeric chain along the a axis by a Cu2···O5 interaction of 2.725 (3) Å. Including the semi-coordination bonds, the configuration around Cu1 in the cation is a square pyramid, and Cu2 in the anion has a distorted octahedral coordination, with atoms O5 and Cl1 at the apical positions.

The title compound is different from previously reported biimidazole copper complexes, not only in its constituent species and their structures but also in the interactions between the species. For example, in [Cu_1.5Cl₃(H₂biim)_2], there are two species, [CuCl₂(H₂biim)] and [Cu(H₂biim)₂]²⁺, with a Cl⁻ counterion. The [CuCl₂(H₂biim)] molecules are linked into a polymeric structure by one of the coordinated Cl atoms as a bridge, and the [Cu(H₂biim)₂]²⁺ cations exist as mononclear complexes (Bencini & Mani, 1988). The compound [Cu₂(Me₅dien)₂(biim)](BPh₄)₂ (Me₅dien is 1,1,4,7,7-pentamethyldiethylenetriamine) is a dinuclear complex with biimidazole as a bridging ligand (Muni et al., 1979). The compounds [Cu(H₂biim)(dien)]ClO₄ (dien is diethylenetriamine) and [Cu(H₂biim)(salenNMe₂)]ClO₄ (salenNMe₂ is N-salicylidene-N',N'-dimethylethylenediamine) are mononuclear mixed-ligand complexes (Liu & Su, 1996; Tadokoro & Nakasuji, 2000).

As illustrated in Fig 2, three hydrogen bonds, N2—H2A······O2B, N4—H4A······O1B and O5—H5B······O3C (Table 2), link neigbouring cations and anions alternately into a chain along the b axis. The water molecule of crystallization (O6) is involved in five hydrogen bonds, joining four neigbouring ions, one cation and three anions together.

S2. Experimental

The ligand 2,2'-biimidazole was synthesized by a modification of the published procedure of Melloni et al. (1972). CuCl₂·6H₂O (0.17 g, 1 mmol) and 2,2'-biimidazole (0.134 g, 1 mmol) were suspended in water. To the resulting mixture, concentrated HCl solution was added until the suspension became clear. Then, an aqueous solution (5 ml) containing iminodiacetic acid (0.133 g, 1 mmol) was added dropwise. The solution was stirred for 1 h and then filtered, and the filtrate was allowed to stand at room temperature. Blue crystals of (I) appeared after two months by slow evaporation of the aqueous solution.

S3. Refinement

H atoms attached to C atoms were placed in geometrically idealized positions, with C—H distances in the range 0.93–0.97 Å, and were constrained to ride on their carrier atoms, with U_iso(H) = 1.2U_eq(C). H atoms attached to N and O atoms (water) were located in difference Fourier maps and constrained to ride on their carrier atoms, with N—H distances in the range 0.79–0.86 Å and O—H distances in the range 0.86–0.94 Å, and with U_iso(H) = 1.2U_eq(N) or 1.5U_eq(O).

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1999); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The hydrogen-bond network and weak coordination (dashed lines) in (I). [Symmetry codes: (A) 1 + x, y, z; (B) 1 − x, 2 − y, −z; (C) 1 − x, 2 − y, 1 − z; (D) x − 1, y, z.]

Aquachloro(2,2'-bi-1H-imidazole)copper(II) chloro(iminodiacetato)copper(II) monohydrate

Crystal data

[CuCl(C6H6N4)(H2O)][Cu(C4H5NO4)Cl]·H2O	Z = 2
Mr = 499.25	F(000) = 500
Triclinic, P1	Dx = 2.020 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.7053 (18) Å	Cell parameters from 1069 reflections
b = 8.823 (2) Å	θ = 2.4–27°
c = 14.547 (4) Å	µ = 2.96 mm^−1
α = 90.272 (3)°	T = 298 K
β = 101.316 (3)°	Block, blue
γ = 103.116 (4)°	0.40 × 0.10 × 0.10 mm
V = 820.8 (4) Å^3

Data collection

SMART 1K CCD area-detector diffractometer	2826 independent reflections
Radiation source: fine-focus sealed tube	2279 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
ϕ and ω scans	θmax = 25.0°, θmin = 1.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→7
Tmin = 0.384, Tmax = 0.756	k = −9→10
3388 measured reflections	l = −16→17

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.100	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0483P)^2] where P = (Fo^2 + 2Fc^2)/3
2826 reflections	(Δ/σ)max < 0.001
226 parameters	Δρmax = 0.54 e Å^−3
0 restraints	Δρmin = −0.54 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
Cu1	0.29122 (8)	0.93475 (6)	0.23287 (3)	0.02826 (18)
Cu2	0.80200 (8)	0.86047 (6)	0.31754 (3)	0.03050 (18)
Cl1	0.33462 (17)	0.69999 (13)	0.28056 (7)	0.0332 (3)
Cl2	0.72017 (17)	1.08734 (13)	0.28003 (7)	0.0342 (3)
O1	0.7872 (6)	0.5806 (4)	0.1031 (2)	0.0478 (9)
O2	0.8241 (4)	0.7963 (3)	0.19106 (18)	0.0308 (7)
O3	0.6793 (5)	0.7285 (4)	0.5606 (2)	0.0425 (8)
O4	0.7748 (5)	0.8765 (3)	0.44701 (19)	0.0346 (7)
O5	0.2221 (5)	0.9821 (3)	0.35400 (18)	0.0325 (7)
H5A	0.2522	0.9264	0.4010	0.049*
H5B	0.2553	1.0676	0.3729	0.049*
O6	0.2551 (5)	0.7925 (4)	0.5000 (2)	0.0425 (8)
H6B	0.2727	0.8527	0.5508	0.064*
H6A	0.3930	0.7799	0.5194	0.064*
N1	0.2873 (5)	0.8868 (4)	0.0977 (2)	0.0272 (8)
N2	0.2509 (5)	0.9654 (4)	−0.0463 (2)	0.0298 (8)
H2A	0.2314	1.0231	−0.0932	0.036*
N3	0.2366 (5)	1.1346 (4)	0.1823 (2)	0.0247 (8)
N4	0.2121 (5)	1.2793 (4)	0.0606 (2)	0.0307 (9)
H4	0.2061	1.3097	0.0097	0.037*
N5	0.8575 (5)	0.6532 (4)	0.3511 (2)	0.0269 (8)
H5C	0.9804	0.6726	0.3665	0.032*
C1	0.3043 (6)	0.7708 (5)	0.0390 (3)	0.0326 (11)
H1	0.3274	0.6744	0.0573	0.039*
C2	0.2823 (6)	0.8185 (5)	−0.0499 (3)	0.0307 (10)
H2	0.2876	0.7619	−0.1032	0.037*
C3	0.2561 (6)	1.0043 (5)	0.0442 (3)	0.0247 (9)
C4	0.2346 (6)	1.1416 (5)	0.0904 (3)	0.0240 (9)
C5	0.2146 (6)	1.2755 (5)	0.2111 (3)	0.0309 (10)
H5	0.2123	1.3050	0.2723	0.037*
C6	0.1964 (7)	1.3659 (5)	0.1364 (3)	0.0339 (11)
H6	0.1770	1.4670	0.1364	0.041*
C7	0.8025 (7)	0.6494 (5)	0.1785 (3)	0.0314 (10)
C8	0.7919 (7)	0.5514 (5)	0.2650 (3)	0.0301 (10)
H8A	0.6500	0.4909	0.2612	0.036*
H8B	0.8825	0.4795	0.2668	0.036*
C9	0.7588 (7)	0.6040 (5)	0.4318 (3)	0.0305 (10)
H9A	0.8435	0.5469	0.4734	0.037*
H9B	0.6217	0.5359	0.4098	0.037*
C10	0.7384 (6)	0.7467 (5)	0.4842 (3)	0.0319 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0376 (3)	0.0292 (3)	0.0219 (3)	0.0137 (2)	0.0083 (2)	0.0047 (2)
Cu2	0.0429 (4)	0.0295 (3)	0.0239 (3)	0.0154 (3)	0.0100 (3)	0.0047 (2)
Cl1	0.0426 (7)	0.0289 (6)	0.0315 (6)	0.0146 (5)	0.0079 (5)	0.0044 (5)
Cl2	0.0430 (7)	0.0301 (6)	0.0341 (6)	0.0152 (5)	0.0108 (5)	0.0075 (5)
O1	0.088 (3)	0.036 (2)	0.0240 (17)	0.0192 (18)	0.0151 (17)	0.0005 (15)
O2	0.0486 (19)	0.0281 (18)	0.0202 (15)	0.0156 (14)	0.0101 (14)	0.0038 (13)
O3	0.064 (2)	0.044 (2)	0.0248 (17)	0.0154 (16)	0.0196 (16)	0.0045 (15)
O4	0.055 (2)	0.0297 (19)	0.0236 (16)	0.0161 (15)	0.0103 (15)	0.0012 (14)
O5	0.052 (2)	0.0287 (18)	0.0202 (15)	0.0135 (14)	0.0105 (14)	0.0014 (13)
O6	0.050 (2)	0.051 (2)	0.0291 (18)	0.0197 (16)	0.0039 (15)	−0.0014 (15)
N1	0.030 (2)	0.031 (2)	0.0219 (19)	0.0094 (16)	0.0063 (16)	0.0041 (16)
N2	0.034 (2)	0.037 (2)	0.0207 (19)	0.0083 (16)	0.0089 (16)	0.0060 (16)
N3	0.030 (2)	0.027 (2)	0.0203 (18)	0.0106 (16)	0.0064 (15)	0.0030 (15)
N4	0.040 (2)	0.030 (2)	0.0241 (19)	0.0089 (17)	0.0104 (17)	0.0070 (17)
N5	0.0262 (19)	0.031 (2)	0.0261 (19)	0.0116 (16)	0.0068 (16)	0.0034 (16)
C1	0.036 (3)	0.030 (3)	0.034 (3)	0.009 (2)	0.011 (2)	−0.001 (2)
C2	0.032 (3)	0.036 (3)	0.024 (2)	0.007 (2)	0.0068 (19)	−0.007 (2)
C3	0.019 (2)	0.033 (3)	0.023 (2)	0.0038 (18)	0.0078 (18)	0.0023 (19)
C4	0.017 (2)	0.030 (2)	0.023 (2)	0.0045 (17)	0.0002 (17)	0.0020 (18)
C5	0.040 (3)	0.035 (3)	0.020 (2)	0.010 (2)	0.009 (2)	0.000 (2)
C6	0.044 (3)	0.022 (2)	0.038 (3)	0.010 (2)	0.011 (2)	0.002 (2)
C7	0.033 (3)	0.036 (3)	0.027 (2)	0.012 (2)	0.007 (2)	0.004 (2)
C8	0.040 (3)	0.026 (3)	0.028 (2)	0.012 (2)	0.009 (2)	−0.0001 (19)
C9	0.037 (3)	0.035 (3)	0.024 (2)	0.014 (2)	0.010 (2)	0.008 (2)
C10	0.030 (3)	0.041 (3)	0.026 (2)	0.012 (2)	0.003 (2)	0.000 (2)

Geometric parameters (Å, º)

Cu1—O5	1.974 (3)	N3—C4	1.335 (5)
Cu1—N3	1.996 (3)	N3—C5	1.358 (5)
Cu1—N1	2.003 (3)	N4—C4	1.322 (5)
Cu1—Cl1	2.2503 (12)	N4—C6	1.373 (5)
Cu2—O4	1.935 (3)	N4—H4	0.7862
Cu2—O2	1.965 (3)	N5—C8	1.470 (5)
Cu2—N5	1.991 (3)	N5—C9	1.478 (5)
Cu2—Cl2	2.2354 (12)	N5—H5C	0.7884
O1—C7	1.227 (5)	C1—C2	1.352 (6)
O2—C7	1.279 (5)	C1—H1	0.9300
O3—C10	1.250 (5)	C2—H2	0.9300
O4—C10	1.263 (5)	C3—C4	1.432 (6)
O5—H5A	0.8625	C5—C6	1.354 (5)
O5—H5B	0.7698	C5—H5	0.9300
O6—H6A	0.9443	C6—H6	0.9300
O6—H6B	0.8806	C7—C8	1.534 (5)
N1—C3	1.329 (5)	C8—H8A	0.9700
N1—C1	1.369 (5)	C8—H8B	0.9700
N2—C3	1.351 (5)	C9—C10	1.515 (6)
N2—C2	1.362 (5)	C9—H9A	0.9700
N2—H2A	0.8599	C9—H9B	0.9700
O5—Cu1—N3	91.79 (12)	C2—C1—N1	109.3 (4)
O5—Cu1—N1	165.83 (13)	C2—C1—H1	125.3
N3—Cu1—N1	82.01 (13)	N1—C1—H1	125.3
O5—Cu1—Cl1	90.58 (9)	C1—C2—N2	106.6 (4)
N3—Cu1—Cl1	175.67 (10)	C1—C2—H2	126.7
N1—Cu1—Cl1	94.87 (10)	N2—C2—H2	126.7
O4—Cu2—O2	167.62 (12)	N1—C3—N2	110.0 (4)
O4—Cu2—N5	84.04 (13)	N1—C3—C4	116.9 (3)
O2—Cu2—N5	84.02 (12)	N2—C3—C4	133.1 (4)
O4—Cu2—Cl2	95.02 (9)	N4—C4—N3	110.9 (4)
O2—Cu2—Cl2	96.72 (9)	N4—C4—C3	132.9 (4)
N5—Cu2—Cl2	176.69 (10)	N3—C4—C3	116.2 (4)
C7—O2—Cu2	113.8 (3)	C6—C5—N3	109.0 (4)
C10—O4—Cu2	113.7 (3)	C6—C5—H5	125.5
Cu1—O5—H5A	119.2	N3—C5—H5	125.5
Cu1—O5—H5B	117.3	C5—C6—N4	106.6 (4)
H5A—O5—H5B	106.6	C5—C6—H6	126.7
H6B—O6—H6A	89.4	N4—C6—H6	126.7
C3—N1—C1	106.4 (3)	O1—C7—O2	125.4 (4)
C3—N1—Cu1	112.2 (3)	O1—C7—C8	117.5 (4)
C1—N1—Cu1	141.4 (3)	O2—C7—C8	117.1 (4)
C3—N2—C2	107.7 (3)	N5—C8—C7	110.1 (3)
C3—N2—H2A	126.2	N5—C8—H8A	109.6
C2—N2—H2A	126.1	C7—C8—H8A	109.6
C4—N3—C5	106.2 (3)	N5—C8—H8B	109.6
C4—N3—Cu1	112.5 (3)	C7—C8—H8B	109.6
C5—N3—Cu1	141.1 (3)	H8A—C8—H8B	108.2
C4—N4—C6	107.3 (3)	N5—C9—C10	109.3 (3)
C4—N4—H4	128.9	N5—C9—H9A	109.8
C6—N4—H4	123.8	C10—C9—H9A	109.8
C8—N5—C9	118.1 (3)	N5—C9—H9B	109.8
C8—N5—Cu2	107.6 (2)	C10—C9—H9B	109.8
C9—N5—Cu2	107.2 (2)	H9A—C9—H9B	108.3
C8—N5—H5C	109.6	O3—C10—O4	123.5 (4)
C9—N5—H5C	110.6	O3—C10—C9	118.1 (4)
Cu2—N5—H5C	102.4	O4—C10—C9	118.4 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N5—H5C···O6^i	0.79	2.44	3.087 (4)	140
N4—H4···O1^ii	0.79	1.91	2.689 (4)	170
N2—H2A···O2^ii	0.86	2.19	3.035 (4)	168
O6—H6A···O3	0.94	2.05	2.989 (4)	174
O6—H6B···Cl2^iii	0.88	2.50	3.327 (3)	156
O6—H6B···O4^iii	0.88	2.48	3.077 (5)	125
O5—H5B···O3^iii	0.77	1.95	2.716 (4)	170
O5—H5A···O6	0.86	1.87	2.716 (4)	168

Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y+2, −z; (iii) −x+1, −y+2, −z+1.