Bis­(acetone-[kappa]O)­bis(N,N'-di­methyl­ethyl­enedi­amine-[kappa]²N,N')copper(II) diperchlorate

The title compound, [Cu(C₄H₁₂N₂)₂(C₃H₆O)₂](ClO₄)₂, is the first structurally characterized Cu^II complex having acetone as axial ligands. The complex adopts an elongated octahedral trans-[CuN₄O₂] coordination geometry, with the Cu atom having 222 site symmetry. The axial Cu-O(acetone) and in-plane Cu-N bond lengths are 2.507 (5) and 2.041 (3) Å, respectively.

S1. Comment

One of the most promising strategies for development of optical switching materials of metal complexes is to investigate candidates exhibiting thermal phase transition or having physical properties described by bistable potentials. Since there have been reported on intercalated hybrid materials (Choy et al., 2002), thermochromism (Narayanan & Bhadbhade, 1998) and photochromism (Takahashi et al., 2002), Cu^II complexes with ethylenediamine derivatives have been of interest as candidates for such functional materials.

Varied stereochemistry of the Cu^II complexes, for instance distortion (Simmons, 1993) and semi-coordination (Hathaway, 1984), has been the subject of the Jahn–Teller effect (Murphy & Hathaway, 2003). Strictly speaking, the pseudo-Jahn–Teller effect can be applied to the systems involving non-equivalent ligands, such as trans-[CuA₄B₂] in D_{4 h} symmetry. Mixing between non-degenerated ground states and excited states through spin-orbit vibronic coupling results in stabilization of potential energy by a pseudo-Jahn–Teller effect. Elongated axial (semi-coordination) bonds under appropriate conditions may occur thermally accessible distortion, and there is also possibility for photo-controlling.

So far, the structures of semi-coordinated Cu^II complexes with N-substituted ethylenediamine ligands have been investigated: ethylenediamine (en) by Maxcy & Turnbull (1999), N-methylethylenediamine (N-Meen) by Akitsu & Einaga (2003), N-ethylethylenediamine (N-Eten) by Grenthe et al. (1979) and N,N-dimethylethylenediamine (N—Me₂en) by Akitsu & Einaga (2004). We have determined the crystal structure of bis(acetone-κO)bis(N,N'-dimethylethylenediamine-κ²N,N')copper(II) diperchlorate, (I). This is the first structurally characterized example of the Cu^II complexes coordinated by acetone as axial ligands.

Complex (I) adopts an elongated octahedral trans-[CuN₄O₂] coordination geometry, where atom Cu1 lies on 222 site symmetry (Fig. 1 and Table 1). The axial Cu1—O1 bond length of 2.507 (5) Å is in the range of semi-coordination (2.22–2.89 Å for H₂O; Hathaway, 1973) caused by a Jahn–Teller effect. As for analogous Cu^II complexes with axial perchlorate ligands, the corresponding Cu—O(perchlorate) bond lengths are 2.579 (4), 2.569 (2), 2.594 (3) and 2.605 (4) Å for the en, N-Meen, N-Eten and N—Me₂en complexes, respectively. Interestingly, the axial Cu—O(acetone) bond is relatively shorter than the Cu—O(perchlorate) bond, regardless of the acetone ligands being neutral; however, it is considerably longer than corresponding values for dimeric Cu^II complexes having acetone ligands, which range from 2.1379 (5) (Agterberg et al., 1997) to 2.206 (3) Å (Castellari et al., 1999). Furthermore, in these similar complexes, the Cu—O═C(acetone) bond angles are bent (133°; Steward et al., 1996), whereas the Cu—O—C bond angles are 180° in (I). The Cu1—N1 bond length of 2.041 (3) Å for (I) is comparable to that of 2.057 (2) Å for the N-Meen complex. Indeed, the number of substituted groups on the N atom is reflected in the Cu—N bond distance for a series of these complexes: Cu—N(H₂) = 2.012 (2) Å for the en, Cu—N(HMe) = 2.057 (2) Å for the N-Meen, Cu—N(HEt) = 2.031 (3) Å for the N-Eten and Cu—N(Me₂) = 2.098 (2) Å for the N—Me₂en complex. The T values, i.e. the Cu—N(in-plane)/Cu—O(axial) bond-length ratio (Hathaway et al., 1970) of 0.81 for (I) is comparable or slightly larger than those of the perchlorate complexes (0.76–0.81).

The N1—Cu1—N1ⁱ [symmetry code: (i) 1 − x, 1/2 − y, z] chelate angle of 84.7 (1)° is almost the same as that of the N-Meen complex [84.58 (7)°]. The perchrolate ion lies on a twofold axis and has usual geometric parameters. N—H···O hydrogen bonds are formed between the complex cation and the the perchrolate ions (Table 2). The crystal packing of (I) is illustrated in Fig. 2. The trans-O—Cu—O axial bonds lie on twofold axes parallel to the a axis. Each complex cation is linked to four perchrolate anions and each perchrolate anion is linked to two cations via hydrogen bonds. The complex cations and perchlorate anions are aligned alternately along the a axis, forming networks of two-dimensional sheets.

The crystal structures of metal complexes having two acetone ligands at axial sites, i.e. having trans-O—M—O axial bonds, have been reported for the Mn^III (Zhang et al., 1990), Zn^II (Bench, Beveridge et al., 2002) and Co^II (Bench, Brennessel et al., 2002) complexes. Despite the trans-coordination mode, the acetone ligands are inclined in the Mn^III, Zn^II and Co^{II _{complexes, whereas they are coordinated in a linear fashion in (I) as a result of the symmetry of the crystal structure. The semi-coordination sites, namely the trans-coordination mode, being ready for acetone ligands may be dominated by steric restriction of the sites in the equatorial plane occupied by chelate or macrocyclic ligands.}}

S2. Experimental

To a methanol solution (20 ml) of Cu(ClO₄)₂ (0.375 g, 1.01 mmol), N,N'-dimethylethylenediamine (0.176 g, 2.00 mmol) was added dropwise at 298 K, giving rise to blue precipitates of the precursor bis(N,N'-dimethylethylenediamine)copper(II) diperchlorate. Blue prismatic crystals of (I) suitable for X-ray analysis were grown from an acetone–methanol solution (4:1, v/v) at 298 K over a period of a few days.

S3. Refinement

Despite an epoxy coating to retain the solvent, the crystal used for analysis was seriously damaged by the X-ray radiation during the data collection. There is a positional disorder of atom C1 over two equally occupied sites. It was assumed that the ethylenediamine moiety has two possible conformations, namely N1(H1A)—C1A(H2A/H3A)—C1Aⁱ(H2Aⁱ/H3Aⁱ) and N1(H1B)—C1B(H2B/H3B)—C1Bⁱ(H2Bⁱ/H3Bⁱ) [symmetry code: (i) 1 − x, 1/2 − y, z]. In an approximation, positional disorder of atom C2 was not taken into account, because the ratio of its maximum/minimum principal r.m.s. displacements was fairly small (1.14) and there was no remarkable peak in the difference map. All H-atom positional parameters were calculated geometrically and fixed with U_iso(H) = 1.2U_eq(parent atom).

Computing details

Data collection: WinAFC Diffractometer Control Software (Rigaku, 1999); cell refinement: WinAFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 2001); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: TEXSAN.

Figures

Fig. 1. The molecular structure of (I), showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level. One of the two possible conformations of the disordered ethylenediamine moiety has been omitted for clarity. Atoms marked with a prime ('), asterisk (*), double prime ("), and hash (#) are at the symmetry-related positions (x, 1/2 − y, 1/2 − z), (1 − x, 1/2 − y, z), (-x, y, 1/2 − z) and (1/2 − x, 1 − y, z), respectively.

Fig. 2. The crystal structure of (I).

(I)

Crystal data

[Cu(C4H12N2)2(C3H6O)6](ClO4)2	F(000) = 1164.0
Mr = 554.92	Dx = 1.467 Mg m^−3
Orthorhombic, Ccca	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -C 2b 2bc	Cell parameters from 25 reflections
a = 13.145 (5) Å	θ = 11.1–12.3°
b = 13.333 (4) Å	µ = 1.13 mm^−1
c = 14.332 (4) Å	T = 297 K
V = 2511.9 (14) Å^3	Prismatic, blue
Z = 4	0.30 × 0.30 × 0.30 mm

Data collection

Rigaku AFC-7R diffractometer	Rint = 0.008
ω–2θ scans	θmax = 27.5°
Absorption correction: ψ scan (North, et al., 1968)	h = −17→0
Tmin = 0.712, Tmax = 0.719	k = 0→17
1525 measured reflections	l = 0→18
1449 independent reflections	3 standard reflections every 150 reflections
747 reflections with I > 2σ(I)	intensity decay: 87.2%

Refinement

Refinement on F^2	H-atom parameters not refined
R[F^2 > 2σ(F^2)] = 0.055	w = 1/[σ^2(Fo^2) + (0.1P)^2 where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.180	(Δ/σ)max = 0.010
S = 1.08	Δρmax = 0.44 e Å^−3
747 reflections	Δρmin = −0.46 e Å^−3
83 parameters

Special details

Refinement. Refinement using reflections with F² > 0.0 σ(F²). The weighted R-factor (wR), goodness of fit (S) and R-factor (gt) are based on F, with F set to zero for negative F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu1	0.5000	0.2500	0.2500	0.0362 (2)
Cl1	0.2500	0.5000	0.41131 (8)	0.0650 (3)
O1	0.6909 (2)	0.2500	0.2500	0.071 (1)
O2	0.2801 (3)	0.4173 (3)	0.4642 (3)	0.126 (1)
O3	0.3316 (3)	0.5270 (4)	0.3563 (3)	0.194 (2)
N1	0.4970 (2)	0.3531 (2)	0.3552 (2)	0.0482 (7)
C1A	0.5337 (5)	0.2942 (6)	0.4404 (5)	0.055 (2)	0.50
C1B	0.4757 (7)	0.2993 (7)	0.4452 (5)	0.082 (3)	0.50
C2	0.5706 (3)	0.4378 (3)	0.3533 (3)	0.081 (1)
C3	0.7824 (3)	0.2500	0.2500	0.055 (1)
C4	0.8407 (3)	0.2887 (4)	0.3298 (3)	0.085 (1)
H1A	0.4285	0.3772	0.3663	0.0582*	0.50
H1B	0.4321	0.3864	0.3460	0.0582*	0.50
H2A	0.6018	0.2780	0.4331	0.1013*	0.50
H2B	0.5065	0.3401	0.4959	0.1013*	0.50
H3A	0.5224	0.3326	0.4950	0.1013*	0.50
H3B	0.4057	0.2964	0.4569	0.1013*	0.50
H4	0.6373	0.4136	0.3462	0.1009*
H5	0.5545	0.4818	0.3022	0.1009*
H6	0.5658	0.4761	0.4098	0.1009*
H7	0.8271	0.2512	0.3846	0.1040*
H8	0.9134	0.2831	0.3170	0.1040*
H9	0.8263	0.3575	0.3405	0.1040*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0376 (3)	0.0406 (4)	0.0302 (3)	0.0000	0.0000	0.0000
Cl1	0.0669 (6)	0.0802 (8)	0.0480 (6)	0.0224 (7)	0.0000	0.0000
O1	0.037 (2)	0.097 (3)	0.078 (2)	0.0000	0.0000	−0.020 (2)
O2	0.146 (3)	0.121 (3)	0.113 (2)	0.022 (2)	−0.021 (2)	0.050 (2)
O3	0.183 (3)	0.163 (3)	0.236 (4)	0.077 (3)	0.139 (3)	0.082 (3)
N1	0.059 (1)	0.045 (1)	0.041 (1)	0.007 (1)	0.003 (1)	−0.002 (1)
C1A	0.063 (4)	0.063 (4)	0.039 (3)	0.012 (3)	0.015 (3)	−0.018 (4)
C1B	0.134 (7)	0.077 (5)	0.035 (4)	0.055 (5)	0.014 (4)	0.010 (4)
C2	0.084 (2)	0.074 (2)	0.084 (3)	−0.007 (2)	−0.009 (2)	−0.039 (2)
C3	0.046 (2)	0.049 (3)	0.069 (3)	0.0000	0.0000	−0.009 (3)
C4	0.073 (2)	0.103 (3)	0.080 (3)	−0.005 (2)	−0.017 (2)	−0.023 (3)

Geometric parameters (Å, º)

Cu1—O1	2.507 (5)	C1A—C1A^ii	1.48 (2)
Cu1—N1	2.041 (3)	C1A—H2A	0.926
Cu1—N1^i	2.041 (3)	C1A—H3A	0.947
Cu1—N1^ii	2.041 (3)	C1B—C1B^ii	1.46 (2)
Cu1—N1^iii	2.041 (3)	C1B—H2B	0.994
Cl1—O2	1.395 (4)	C1B—H3B	0.936
Cl1—O2^iv	1.395 (4)	C2—H4	0.939
Cl1—O3	1.380 (4)	C2—H5	0.961
Cl1—O3^iv	1.380 (4)	C2—H6	0.959
O1—C3	1.203 (5)	C3—C4	1.471 (5)
N1—C1A	1.530 (8)	C3—C4^i	1.471 (5)
N1—C1B	1.503 (9)	C4—H7	0.948
N1—C2	1.488 (5)	C4—H8	0.975
N1—H1A	0.969	C4—H9	0.948
N1—H1B	0.970
O1—Cu1—N1	91.11 (7)	N1—C1A—H3A	109.4
N1—Cu1—N1^i	177.8 (1)	C1A^ii—C1A—H2A	113.2
N1—Cu1—N1^ii	84.7 (1)	C1A^ii—C1A—H3A	109.7
N1—Cu1—N1^iii	95.3 (1)	H2A—C1A—H3A	111.8
N1^i—Cu1—N1^ii	95.3 (1)	N1—C1B—C1B^ii	110.4 (5)
N1^i—Cu1—N1^iii	84.7 (1)	N1—C1B—H2B	106.8
N1^ii—Cu1—N1^iii	177.8 (1)	N1—C1B—H3B	110.9
O2—Cl1—O2^iv	114.2 (3)	C1B^ii—C1B—H2B	108.3
O2—Cl1—O3	107.2 (2)	C1B^ii—C1B—H3B	113.2
O2—Cl1—O3^iv	109.0 (3)	H2B—C1B—H3B	107.0
O2^iv—Cl1—O3	109.0 (3)	N1—C2—H4	110.3
O2^iv—Cl1—O3^iv	107.2 (2)	N1—C2—H5	109.5
O3—Cl1—O3^iv	110.3 (4)	N1—C2—H6	110.1
Cu1—N1—C1A	103.8 (3)	H4—C2—H5	109.5
Cu1—N1—C1B	108.4 (4)	H4—C2—H6	109.6
Cu1—N1—C2	119.0 (2)	H5—C2—H6	107.8
Cu1—N1—H1A	111.2	O1—C3—C4	121.4 (2)
Cu1—N1—H1B	103.0	O1—C3—C4^i	121.4 (2)
C1A—N1—C2	101.5 (4)	C4—C3—C4^i	117.2 (4)
C1A—N1—H1A	109.5	C3—C4—H7	111.1
C1B—N1—C2	120.0 (4)	C3—C4—H8	109.6
C1B—N1—H1B	99.9	C3—C4—H9	111.1
C2—N1—H1A	110.9	H7—C4—H8	107.6
C2—N1—H1B	102.8	H7—C4—H9	109.8
N1—C1A—C1A^ii	102.7 (4)	H8—C4—H9	107.5
N1—C1A—H2A	109.6
Cu1—N1—C1A—C1A^ii	−52.3 (6)	N1—Cu1—N1^ii—C2^ii	129.8 (3)
Cu1—N1—C1B—C1B^ii	35.5 (10)	N1—Cu1—N1^iii—C1A^iii	−159.7 (3)
Cu1—N1^i—C1A^i—C1A^iii	−52.3 (6)	N1—Cu1—N1^iii—C1B^iii	170.1 (4)
Cu1—N1^i—C1B^i—C1B^iii	35.5 (10)	N1—C1A—C1A^ii—N1^ii	70.2 (8)
Cu1—N1^ii—C1A^ii—C1A	−52.3 (6)	N1—C1B—C1B^ii—N1^ii	−47 (1)
Cu1—N1^ii—C1B^ii—C1B	35.5 (10)	C1A—C1A^ii—N1^ii—C2^ii	−176.3 (5)
Cu1—N1^iii—C1A^iii—C1A^i	−52.3 (6)	C1B—C1B^ii—N1^ii—C2^ii	−106.0 (8)
N1—Cu1—N1^ii—C1A^ii	18.0 (3)	C1B—C1B^ii—N1^ii—C2^ii	−106.0 (8)
N1—Cu1—N1^ii—C1B^ii	−12.2 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O2	0.97	2.46	3.362 (4)	154
N1—H1B···O2	0.97	2.65	3.362 (4)	130
N1—H1A···O3	0.97	2.37	3.177 (5)	140
N1—H1B···O3	0.97	2.30	3.177 (5)	150