Bis(aceto­nitrile-κN)di­aqua­bis­­(perchlorato-κO)copper(II)

In the title compound, [Cu(ClO₄)₂(CH₃CN)₂(H₂O)₂], the Cu²⁺ ion, located on a special position (site symmetry ), is coordinated by six monodentate ligands, viz. an N-coordin­ated acetonitrile, a perchlorate anion and a water mol­ecule, and their symmetry-related counterparts. The perchlorate anion is disordered over two sets of sites with occupancies of 0.53 (2) and 0.47 (2). The crystal structure is stabilized by O—H⋯O hydrogen bonds involving the perchlorate ion and aqua H atoms.

Related literature

For details of the changing Cu(II/I) redox potential with increasing acetonitrile contents in water–acetonitrile solution, see: Cox et al. (1988); Verma & Sood (1979); Sumalekshmy & Gopidas (2005); Ajayakumar et al. (2009); Drew et al. (1985). For the dependence of the luminescent properties (emission energy) of the 3-cyano-4-dicyano­methyl­ene-5-oxo-4,5-dihydro-1H-pyrrol-2-olate (A)-based salts depend on the mol­ecular environment around (A), see: Tafeenko et al. (2009, 2010). For transition metals as fluorescence quenchers, see: Xu et al. (2005, 2010). For a previous study on the formation of related compounds, see: Inamo et al. (2001).

Experimental

Crystal data

• [Cu(ClO₄)₂(C₂H₃N)₂(H₂O)₂]

• M_r = 380.59

• Triclinic,

• a = 5.581 (1) Å

• b = 7.244 (2) Å

• c = 8.733 (2) Å

• α = 82.82 (2)°

• β = 76.86 (1)°

• γ = 77.12 (1)°

• V = 334.1 (1) ų

• Z = 1

• Ag Kα radiation

• λ = 0.56085 Å

• μ = 1.09 mm⁻¹

• T = 296 K

• 0.15 × 0.1 × 0.08 mm

Data collection

• Enraf–Nonius CAD-4 diffractometer

• 2518 measured reflections

• 1259 independent reflections

• 1020 reflections with I > 2s(I)

• R_int = 0.049

• 2 standard reflections every 120 min intensity decay: none

Refinement

• R[F² > 2σ(F²)] = 0.066

• wR(F²) = 0.192

• S = 1.08

• 1259 reflections

• 138 parameters

• 11 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.70 e Å⁻³

• Δρ_min = −1.09 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H11⋯O3^i	0.83 (7)	2.03 (7)	2.758 (17)	146 (6)
O1—H12⋯O3^ii	0.79 (9)	2.22 (10)	3.00 (3)	165 (8)
Symmetry codes: (i) x, y-1, z; (ii) -x+1, -y+1, -z+1.

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: WinGX (Farrugia, 1999).

Supporting information

S1. Comment

It was found (Tafeenko et al., 2009; Tafeenko et al., 2010) that the luminescent properties (emission energy) of the 3-cyano-4-dicyanomethylene-5-oxo-4,5-dihydro-1H-pyrrol-2-olate (A)-based salts depend on the molecular environment around (A). To investigate the effect of transition metals, which act usually as fluorescence quenchers (Xu et al., 2005, 2010), we made an attempt to synthesize (A)-based salts with Cu²⁺. Acetonitrile treatment of crude crystalline mass, obtained after evaporation of CuSO₄ + BaA₂ (equivalent amounts) mixture in water-ethanol (v/v=1/1) solution, and posterior evaporation of an acetonitrile solution in an air atmosphere at room temperature resulted in formation of (A)-based salts with Cu⁺. We saw several reasons for the reduction of Cu²⁺ to Cu⁺:

- iodide anion I^- reduces Cu²⁺ in water-ethanol solution, as it was detected that BaA₂ salt used for synthesis contained I^-;

- anion (A) exhibits of reducing properties;

- acetonitrile-water mixture causes reduction of copper(II) to copper(I), as it was documented that i) copper(II) salt solution in acetonitrile-water mixture is a powerful oxidizer of organic molecules (Verma et al., 1979; Cox et al.,1988; Sumalekshmy et al., 2005; Ajayakumar et al., 2009); ii) acetonitrile can reduce Cu²⁺ to Cu⁺ (Drew et al., 1985).

To find out whether acetonitrile-water mixture can cause a reduction of Cu²⁺ to Cu⁺, we prepared a Cu(ClO₄)₂ solution in a mixture of 99.5% CH₃CN and 0.5% H₂O (volume percentage) and evaporated this solution, which yielded crystals of the title compound, [Cu(CH₃CN)₂(H₂O)₂(ClO₄)₂]. No other phases could be detected using powder-XRD. The crystal and molecular structure of the title compound (Fig.1) is presented in this paper.

The structure is composed of monomeric units built up around a Cu²⁺ on a special position (site symmetry –1). The Cu²⁺ cation is surrounded by six monodentate ligands, viz. an N–coordinated acetonitrile, a perchlorate anion and a water molecule, and their symmetry related counterparts. The perchlorate anion is disordered over two positions, with occupancies (0.53 (2) and 0.47 (2)), but it's O atoms displacement ellipsoids are still quite large, indicating possible rotational disorder, with the rotation axis passing through oxygen O1 of the perchlorate coordinated with Cu1 and Cl1. The complex adopts an elongated octahedral coordination geometry.

The axial Cu–O1 (perchlorate) bond length is 2.401 (15) and in plane Cu–N1(acetonitrile) 1.960 (5), Cu1–O2(aqua) 1.950 (5) Å respectively.

Besides ionic forces, the crystal structure is stabilized by hydrogen bonding interaction via the perchlorate and aqua H atoms (Fig. 2).

In conclusion, we have to note that the structure of the title compound differs from reported by Inamo with co-workers (Inamo et al., 2001) compounds. They reporteded the formation of [Cu(H₂O)_n(CH₃CN)_(6-n)]²⁺ (n = 0–3) in (water/acetonitrile) solutions with [Cu(H₂O)_m(CH₃CN)_6-m]²⁺ (m < 3) as the dominant species for H₂O concentration lower than 0.5 M (99% acetonitrile).

Related literature

For details of the changing Cu(II/I) redox potential with increasing acetonitrile contents in water–acetonitrile solution, see: Cox et al. (1988); Verma & Sood (1979); Cox et al. (1988); Sumalekshmy & Gopidas (2005); Ajayakumar et al. (2009); Drew et al. (1985). For the dependence of the luminescent properties (emission energy) of the 3-cyano-4-dicyanomethylene-5-oxo-4,5-dihydro-1H-pyrrol-2-olate (A)-based salts depend on the molecular environment around (A), see: Tafeenko et al. (2009, 2010). For transition metals as fluorescence quenchers, see: Xu et al. (2005, 2010). For a previous study, see: Inamo et al. (2001).

S2. Experimental

Blue crystals of the title salt were obtained by slow evaporation of 0.045 M Cu(H₂O)₆(ClO₄)₂ solution in acetonitrile at room temperature in an air atmosphere. The crystals are not stable in the open air, so suitable for X-ray investigation crystal was placed in a sealed capillary. Copper(II) perchlorate hexahydrate of 98% (Aldrich) grade was used for synthesis. Acetonitrile was boiled with phosphorus pentaoxide and then distilled at 353 K.

S3. Refinement

During the refinement a difference maps showed peaks consistent with the perchlorate atoms Cl1,O2—O5 being unequally disorder over two interpenetrating sites. This was allowed for by use of the appropriate SHELXL SAME, EADP restraints. At convergence the perchlorate disorder was modelled with occupancies (0.53 (2) and 0.47 (2)).

The positions of the H atoms of the water molecule were determined from Fourier difference maps and refined freely; the positions of the H atoms of the methyl group were placed in calculated positions and allowed to ride on their parent atoms [C—H = 0.96 Å]. U_iso(H) = xU_eq(parent atom), where x = 1.5 for attached C atoms.

Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. Only one of the two disordered positions of the perchlorate ion is shown. Symmetry code: (i) – x,1 – y, – z.
	Fig. 2. The hydrogen bonding pattern in the title compound. H bonds are drawn as dashed lines. Symmetry codes (ii) x, 1–y, z; (iii): 1–x, 1–y, 1–z; (iv) 1–x, –y, 1–z.

Bis(acetonitrile-κN)diaquabis(perchlorato-κO)copper(II)

Crystal data

[Cu(ClO4)2(C2H3N)2(H2O)2]	Z = 1
Mr = 380.59	F(000) = 191
Triclinic, P1	Dx = 1.891 Mg m^−3
Hall symbol: -P 1	Melting point: 422 K
a = 5.581 (1) Å	Ag Kα radiation, λ = 0.56085 Å
b = 7.244 (2) Å	Cell parameters from 25 reflections
c = 8.733 (2) Å	θ = 11–13°
α = 82.82 (2)°	µ = 1.09 mm^−1
β = 76.86 (1)°	T = 296 K
γ = 77.12 (1)°	Prism, light-blue
V = 334.1 (1) Å^3	0.15 × 0.1 × 0.08 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	Rint = 0.049
Radiation source: fine-focus sealed tube	θmax = 20.0°, θmin = 1.9°
Graphite monochromator	h = −6→6
non–profiled ω scans	k = −8→8
2518 measured reflections	l = −10→10
1259 independent reflections	2 standard reflections every 120 min
1020 reflections with I > 2s(I)	intensity decay: none

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)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.192	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.1161P)^2 + 0.4339P] where P = (Fo^2 + 2Fc^2)/3
1259 reflections	(Δ/σ)max = 0.042
138 parameters	Δρmax = 0.70 e Å^−3
11 restraints	Δρmin = −1.09 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	Occ. (<1)
Cu1	0.0000	0.5000	0.5000	0.0477 (4)
O1	0.2556 (10)	0.2741 (6)	0.5295 (6)	0.0574 (12)
N1	0.2362 (12)	0.5987 (8)	0.3237 (7)	0.0631 (16)
C1	0.3717 (13)	0.6605 (9)	0.2302 (8)	0.0555 (15)
C2	0.5546 (16)	0.7387 (12)	0.1089 (9)	0.072 (2)
H2A	0.7197	0.6899	0.1297	0.109*
H2B	0.5174	0.8747	0.1088	0.109*
H2C	0.5478	0.7034	0.0079	0.109*
Cl1	0.120 (3)	0.803 (2)	0.7550 (16)	0.0538 (10)	0.53 (2)
O2	0.195 (3)	0.656 (3)	0.651 (2)	0.082 (6)	0.53 (2)
O3	0.295 (5)	0.921 (3)	0.694 (3)	0.142 (9)	0.53 (2)
O4	0.143 (3)	0.729 (3)	0.9072 (14)	0.105 (6)	0.53 (2)
O5	−0.124 (3)	0.902 (2)	0.755 (2)	0.096 (5)	0.53 (2)
Cl11	0.132 (3)	0.820 (2)	0.7453 (18)	0.0538 (10)	0.47 (2)
O21	0.112 (5)	0.637 (2)	0.717 (2)	0.079 (6)	0.47 (2)
O31	0.383 (2)	0.837 (3)	0.729 (2)	0.080 (5)	0.47 (2)
O41	0.008 (6)	0.853 (6)	0.899 (3)	0.22 (2)	0.47 (2)
O51	0.017 (6)	0.955 (2)	0.644 (4)	0.156 (12)	0.47 (2)
H11	0.212 (12)	0.172 (10)	0.565 (7)	0.041 (16)*
H12	0.357 (17)	0.228 (12)	0.458 (10)	0.07 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0492 (7)	0.0344 (6)	0.0530 (7)	−0.0110 (4)	0.0021 (4)	0.0024 (4)
O1	0.063 (3)	0.034 (2)	0.064 (3)	−0.004 (2)	0.001 (2)	0.002 (2)
N1	0.060 (3)	0.045 (3)	0.068 (3)	−0.013 (3)	0.014 (3)	0.008 (2)
C1	0.057 (4)	0.042 (3)	0.060 (4)	−0.006 (3)	−0.005 (3)	0.002 (3)
C2	0.073 (5)	0.075 (5)	0.060 (4)	−0.028 (4)	0.005 (4)	0.016 (3)
Cl1	0.0544 (13)	0.040 (2)	0.0630 (16)	−0.0150 (12)	0.0034 (11)	−0.0097 (13)
O2	0.062 (9)	0.085 (11)	0.107 (13)	0.011 (7)	−0.033 (9)	−0.051 (10)
O3	0.115 (16)	0.087 (11)	0.23 (2)	−0.061 (11)	−0.042 (14)	0.062 (13)
O4	0.093 (11)	0.152 (15)	0.046 (6)	−0.002 (9)	0.000 (6)	0.013 (7)
O5	0.072 (8)	0.088 (11)	0.110 (11)	0.018 (7)	−0.007 (7)	−0.028 (8)
Cl11	0.0544 (13)	0.040 (2)	0.0630 (16)	−0.0150 (12)	0.0034 (11)	−0.0097 (13)
O21	0.111 (17)	0.047 (7)	0.090 (12)	−0.027 (9)	−0.039 (10)	0.003 (7)
O31	0.044 (7)	0.117 (14)	0.085 (9)	−0.034 (8)	0.006 (6)	−0.028 (9)
O41	0.18 (3)	0.31 (4)	0.17 (3)	−0.16 (3)	0.12 (2)	−0.15 (3)
O51	0.19 (3)	0.041 (8)	0.26 (3)	−0.028 (10)	−0.11 (2)	0.040 (11)

Geometric parameters (Å, º)

Cu1—O1	1.950 (5)	C2—H2C	0.9600
Cu1—N1	1.960 (5)	Cl1—O5	1.390 (14)
Cu1—O2	2.401 (15)	Cl1—O4	1.391 (14)
O1—H11	0.83 (7)	Cl1—O3	1.414 (14)
O1—H12	0.79 (9)	Cl1—O2	1.418 (12)
N1—C1	1.103 (9)	Cl11—O51	1.386 (15)
C1—C2	1.450 (9)	Cl11—O41	1.387 (15)
C2—H2A	0.9600	Cl11—O31	1.409 (14)
C2—H2B	0.9600	Cl11—O21	1.413 (13)
O1—Cu1—O1^i	180.000 (1)	C1—C2—H2C	109.5
O1—Cu1—N1	90.4 (2)	H2A—C2—H2C	109.5
O1^i—Cu1—N1	89.6 (2)	H2B—C2—H2C	109.5
N1—Cu1—N1^i	180.0 (3)	O5—Cl1—O4	110.2 (13)
O1—Cu1—O2^i	93.3 (4)	O5—Cl1—O3	110.9 (15)
N1—Cu1—O2^i	97.7 (6)	O4—Cl1—O3	110.2 (14)
N1^i—Cu1—O2^i	82.3 (6)	O5—Cl1—O2	112.1 (11)
O1—Cu1—O2	86.7 (4)	O4—Cl1—O2	110.3 (13)
O2^i—Cu1—O2	180.0 (7)	O3—Cl1—O2	102.9 (14)
Cu1—O1—H11	120 (4)	Cl1—O2—Cu1	137.3 (11)
Cu1—O1—H12	123 (6)	O51—Cl11—O41	109 (2)
H11—O1—H12	93 (7)	O51—Cl11—O31	109.9 (15)
C1—N1—Cu1	176.0 (7)	O41—Cl11—O31	108.2 (15)
N1—C1—C2	178.6 (8)	O51—Cl11—O21	109.8 (13)
C1—C2—H2A	109.5	O41—Cl11—O21	107.7 (16)
C1—C2—H2B	109.5	O31—Cl11—O21	112.3 (14)
H2A—C2—H2B	109.5

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H11···O3^ii	0.83 (7)	2.03 (7)	2.758 (17)	146 (6)
O1—H12···O3^iii	0.79 (9)	2.22 (10)	3.00 (3)	165 (8)

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