A centrosymmetric hydro­xo-bridged penta­methyl­diethyl­enetri­amine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

The title compound, di-μ-hydroxo-bis­[(1,1,4,7,7-penta­methyl­diethyl­enetri­amine)copper(II)] dibromide aceto­nitrile disolvate, [Cu₂(OH)₂(C₉H₂₃N₃)₂]Br₂·2CH₃CN, is the reaction product of CuBr with 1,1,4,7,7-penta­methyl­diethyl­enetri­amine (pmdeta) in water-containing aceto­nitrile. The cation is the dimer of an asymmetrically hydro­xo-bridged complex of copper(II) coordinated by 1,1,4,7,7-penta­methyl­diethyl­enetri­amine. The centrosymmetric structure contains distorted square-pyramidally coordinated Cu atoms.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.031
• wR factor = 0.080
• Data-to-parameter ratio = 17.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



THETM_01  Alert C The value of sine(theta_max)/wavelength is less than 0.590
          Calculated sin(theta_max)/wavelength =    0.5884


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Di-µ-hydroxo-bridged complexes of transition metals are a widely known structural type. Due to the rather small bridging ligands, there is often the possibility of a metal–metal interaction. If this takes place, a spin–spin interaction is possible when unpaired electrons are present, which makes such molecules interesting model compounds for spin-coupling phenomena.

The complex described in this study, (I) has two Cu^II centers with a separation of 3.0022 (7) Å. The asymmetric unit of the crystal contains only half of the cation. Therefore, a centrosymmetric dimeric structure is obtained (Fig. 1). The bromide counter-ions as well as the acetonitrile molecules included in the crystal do not show any interactions with the copper centers, as illustrated in the packing diagram (Fig. 2). Although the compound was synthesized from a Cu^I halide, the structure contains Cu^II ions. A possible explanation for the oxidation process is a disproportionation reaction which is known for Cu^I amine complexes. This structure is related to another (pmdeta)Cu^II compound bridged by two hydroxo ligands, which contains perchlorate as the anion (Scott et al., 1995). This related complex also shows a distorted square pyramidal coordination sphere around the Cu atoms and two hydroxo bridges with similar Cu—O distances [1.964 (4) and 1.893 (5) Å] to those in the present structure [1.904 (2) and 1.988 (2) Å]. This bonding situation seems to be common in this type of Cu^II complex and was also observed in the hydroxo-bridged cyclic triamine Cu^II compoounds N,N',N''-trimethyl-1,4,7-triazacyclononane [Cu—O 1.936 (4) and 1.939 (4) Å] (Chaudhuri et al., 1985), N-4-but-1-ene-1,4,7-triazacyclononane [Cu—O 1.929 (2) Å; Farrugia et al., 1996] and other triazacyclononane complexes with different substitution patterns (Mahapatra et al., 1996). A special feature of the title compound is its distortion of the square-pyramidal coordination sphere. None of the above related structures displays such large differences in the equatorial Cu—N distances [Cu—N_equatorial 2.040 (3) and 2.137 (3) Å; Cu—N_axial 2.340 (2) Å]. While usually the equatorial N atoms have the same distances to the Cu atom (within experimental uncertainties), the difference of the Cu—N distances in the title compound is nearly 0.1 Å.

S2. Experimental

CuBr (4.53 g, 0.0316 mol) was suspended under stirring in water-saturated acetonitrile (50 ml) under an argon atmosphere in a Schlenk flask. Pentamethlyethylenediamine (5.48 g, 0.0316 mol) was slowly added and the mixture was heated to 323 K for 15 min. The solution was cooled to room temperature and was allowed to stand for two weeks. The solvent was evaporated and dark-green crystals were isolated.

S3. Refinement

H atoms were located by difference Fourier maps and refined with a riding model.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The structure of the dimeric cation with ellipsoids at the 50% probability level. The asymmetric unit contains also one Br^- anion and one molecule of acetonitrile. For clarity, H atoms have been omitted.
	Fig. 2. Projection of the structure along [100], showing ellipsoids at the 50% probability level. For clarity, H atoms have been omitted.

Di-µ-hydroxo-bis[(1,1,4,7,7-pentamethyldiethylenetriamine)copper(II)] dibromide acetonitrile solvate

Crystal data

[Cu2(OH)2(C9H23N3)2]Br2·2C2H3N	F(000) = 772
Mr = 749.64	Dx = 1.502 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.2580 (5) Å	Cell parameters from 5499 reflections
b = 10.9165 (6) Å	θ = 2.7–24.2°
c = 16.4073 (8) Å	µ = 3.72 mm^−1
β = 91.543 (1)°	T = 293 K
V = 1657.60 (15) Å^3	Irregular, green
Z = 2	0.28 × 0.24 × 0.18 mm

Data collection

Siemens SMART CCD area-detector diffractometer	2820 independent reflections
Radiation source: fine-focus sealed tube	2389 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
ω scans	θmax = 24.7°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.390, Tmax = 0.512	k = −12→12
4696 measured reflections	l = −19→19

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.080	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0471P)^2 + 0.5272P] where P = (Fo^2 + 2Fc^2)/3
2820 reflections	(Δ/σ)max = 0.001
163 parameters	Δρmax = 0.49 e Å^−3
0 restraints	Δρmin = −0.56 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	0.46441 (4)	0.39316 (3)	0.55344 (2)	0.02289 (12)
Br1	0.18594 (4)	0.35368 (3)	0.302589 (19)	0.03915 (13)
O1	0.5469 (2)	0.5525 (2)	0.56219 (12)	0.0288 (5)
H1	0.5827	0.5937	0.6081	0.035*
N1	0.2395 (3)	0.4504 (2)	0.60299 (15)	0.0287 (6)
C2	0.1529 (3)	0.3378 (3)	0.5993 (2)	0.0372 (8)
H2A	0.0520	0.3587	0.5901	0.045*
H2B	0.1619	0.2951	0.6511	0.045*
C3	0.2014 (3)	0.2548 (3)	0.5320 (2)	0.0355 (8)
H3A	0.1494	0.1778	0.5349	0.043*
H3B	0.1775	0.2923	0.4798	0.043*
N4	0.3605 (3)	0.2298 (2)	0.53732 (14)	0.0273 (6)
C5	0.3971 (4)	0.1528 (3)	0.6091 (2)	0.0358 (8)
H5A	0.3767	0.0675	0.5967	0.043*
H5B	0.3388	0.1769	0.6547	0.043*
C6	0.5546 (4)	0.1678 (3)	0.6315 (2)	0.0373 (8)
H6A	0.5775	0.1215	0.6807	0.045*
H6B	0.6128	0.1359	0.5880	0.045*
N7	0.5894 (3)	0.2993 (2)	0.64528 (15)	0.0297 (6)
C8	0.2346 (4)	0.5087 (4)	0.6837 (2)	0.0525 (10)
H8A	0.2926	0.5816	0.6840	0.079*
H8B	0.2714	0.4530	0.7244	0.079*
H8C	0.1365	0.5297	0.6952	0.079*
C9	0.1864 (4)	0.5409 (3)	0.5434 (2)	0.0381 (8)
H9A	0.1885	0.5063	0.4896	0.057*
H9B	0.2467	0.6123	0.5460	0.057*
H9C	0.0890	0.5632	0.5555	0.057*
C10	0.4042 (4)	0.1670 (3)	0.4617 (2)	0.0381 (8)
H10A	0.3800	0.2175	0.4154	0.057*
H10B	0.3544	0.0902	0.4567	0.057*
H10C	0.5066	0.1528	0.4639	0.057*
C11	0.5478 (4)	0.3389 (4)	0.7273 (2)	0.0434 (9)
H11A	0.4452	0.3304	0.7323	0.065*
H11B	0.5745	0.4231	0.7353	0.065*
H11C	0.5965	0.2891	0.7676	0.065*
C12	0.7476 (3)	0.3144 (3)	0.6404 (2)	0.0375 (8)
H12A	0.7781	0.2894	0.5875	0.056*
H12B	0.7949	0.2649	0.6814	0.056*
H12C	0.7724	0.3989	0.6492	0.056*
N30	0.8180 (5)	0.1151 (4)	0.4675 (3)	0.0782 (13)
C31	0.8957 (5)	0.0926 (4)	0.4187 (3)	0.0498 (10)
C32	0.9964 (5)	0.0606 (5)	0.3563 (3)	0.0697 (14)
H31A	0.9487	0.0100	0.3160	0.105*
H31B	1.0766	0.0168	0.3805	0.105*
H31C	1.0307	0.1339	0.3309	0.105*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0180 (2)	0.0242 (2)	0.0265 (2)	−0.00388 (14)	0.00106 (14)	0.00275 (15)
Br1	0.0412 (2)	0.0443 (2)	0.03174 (19)	−0.00103 (15)	−0.00168 (14)	−0.00340 (14)
O1	0.0307 (12)	0.0293 (12)	0.0263 (10)	−0.0101 (9)	−0.0027 (9)	0.0004 (9)
N1	0.0195 (13)	0.0356 (16)	0.0312 (13)	0.0002 (11)	0.0032 (10)	−0.0001 (12)
C2	0.0212 (17)	0.045 (2)	0.0455 (19)	−0.0008 (14)	0.0048 (14)	0.0112 (16)
C3	0.0234 (17)	0.039 (2)	0.0436 (19)	−0.0115 (14)	−0.0014 (14)	0.0021 (16)
N4	0.0256 (14)	0.0276 (14)	0.0287 (13)	−0.0041 (11)	0.0013 (11)	0.0033 (11)
C5	0.0390 (19)	0.0301 (18)	0.0383 (18)	−0.0062 (15)	−0.0004 (15)	0.0052 (15)
C6	0.0332 (19)	0.0302 (19)	0.048 (2)	−0.0003 (14)	−0.0020 (15)	0.0111 (15)
N7	0.0238 (14)	0.0303 (15)	0.0350 (14)	−0.0028 (11)	−0.0014 (11)	0.0051 (12)
C8	0.047 (2)	0.067 (3)	0.044 (2)	0.014 (2)	0.0021 (17)	−0.0119 (19)
C9	0.0249 (17)	0.038 (2)	0.051 (2)	0.0033 (14)	0.0054 (14)	0.0062 (17)
C10	0.048 (2)	0.0298 (19)	0.0362 (18)	−0.0031 (15)	0.0049 (15)	−0.0047 (15)
C11	0.038 (2)	0.057 (2)	0.0355 (19)	0.0033 (17)	0.0023 (15)	0.0035 (17)
C12	0.0209 (17)	0.043 (2)	0.048 (2)	−0.0005 (15)	−0.0045 (14)	0.0046 (17)
N30	0.074 (3)	0.069 (3)	0.093 (3)	−0.015 (2)	0.032 (2)	−0.024 (2)
C31	0.048 (2)	0.043 (2)	0.058 (2)	−0.0175 (19)	0.004 (2)	−0.009 (2)
C32	0.072 (3)	0.082 (3)	0.056 (3)	−0.028 (3)	0.019 (2)	−0.019 (2)

Geometric parameters (Å, º)

Cu1—O1	1.904 (2)	C2—C3	1.506 (5)
Cu1—O1^i	1.988 (2)	C3—N4	1.498 (4)
Cu1—N4	2.040 (3)	N4—C5	1.480 (4)
Cu1—N7	2.137 (3)	N4—C10	1.484 (4)
Cu1—N1	2.340 (2)	C5—C6	1.503 (5)
Cu1—Cu1^i	3.0022 (7)	C6—N7	1.487 (4)
O1—Cu1^i	1.988 (2)	N7—C11	1.474 (4)
N1—C9	1.466 (4)	N7—C12	1.478 (4)
N1—C2	1.468 (4)	N30—C31	1.119 (5)
N1—C8	1.471 (4)	C31—C32	1.446 (6)
O1—Cu1—O1^i	79.06 (9)	C2—N1—Cu1	104.63 (19)
O1—Cu1—N4	174.48 (9)	C8—N1—Cu1	118.6 (2)
O1^i—Cu1—N4	97.15 (9)	N1—C2—C3	111.1 (3)
O1—Cu1—N7	100.16 (9)	N4—C3—C2	112.3 (3)
O1^i—Cu1—N7	146.06 (9)	C5—N4—C10	110.0 (3)
N4—Cu1—N7	85.23 (10)	C5—N4—C3	110.7 (2)
O1—Cu1—N1	95.09 (9)	C10—N4—C3	109.0 (2)
O1^i—Cu1—N1	103.15 (9)	C5—N4—Cu1	107.25 (18)
N4—Cu1—N1	81.80 (10)	C10—N4—Cu1	111.95 (19)
N7—Cu1—N1	110.67 (9)	C3—N4—Cu1	107.94 (19)
O1—Cu1—Cu1^i	40.55 (6)	N4—C5—C6	109.4 (3)
O1^i—Cu1—Cu1^i	38.51 (6)	N7—C6—C5	110.3 (3)
N4—Cu1—Cu1^i	135.53 (7)	C11—N7—C12	107.5 (3)
N7—Cu1—Cu1^i	131.39 (7)	C11—N7—C6	111.2 (3)
N1—Cu1—Cu1^i	101.94 (7)	C12—N7—C6	108.1 (3)
Cu1—O1—Cu1^i	100.94 (9)	C11—N7—Cu1	110.6 (2)
C9—N1—C2	111.3 (2)	C12—N7—Cu1	115.3 (2)
C9—N1—C8	106.9 (3)	C6—N7—Cu1	104.17 (19)
C2—N1—C8	111.7 (3)	N30—C31—C32	178.6 (5)
C9—N1—Cu1	103.54 (18)

Symmetry code: (i) −x+1, −y+1, −z+1.