Bis­[bis(N,N-diethyl-1,1-di­seleno­car­bam­ato)copper(II)], [Cu(Se₂CNEt₂)₂]₂

The title centrosymmetric Cu^II binuclear complex, bis([mu]-N,N-diethyl-1,1-di­seleno­carbamato-Se,Se':Se)­bis­[(N,N-diethyl-1,1-di­seleno­carbamato-Se,Se')copper(II)], [Cu(Se₂CNEt₂)₂]₂ or [Cu₂(C₅H₁₀NSe₂)₄], is built from two symmetry-related [Cu{Se₂CN(Et)₂}₂] units by pairs of Cu-Se bonds. The coordination geometry at the unique Cu atom is distorted square pyramidal, with Cu-Se distances in the range 2.4091 (11)-2.9095 (10) Å.

S1. Comment

In sharp contrast to many studies on the chemistry of metal complexes with 1,1-dithiolate ligands, the chemistry of metal complexes with 1,1-diselenolate ligands has received scant attention. Although the 2,2-dicyanoethylence-1,1-diselenolate and N,N-diethyl-1,1-diselenocarbamate ligands were prepared many years ago (Jensen & Henriksen, 1970; Barnard et al., 1961), to our surprise, there are very few papers referring to such diselenolate ligands, among which the investigation was focused on the spectroscopic properties (Jensen & Krishnan, 1970), and very few crystal structures, such as bis(tetra-n-butylammonium) bis(2,2-dicyanoethylene-1,1-diselenolato)selenium(II) (Hummel et al., 1992) and selenium bis(1-pyrrolidinecarbodiselenoate) (Esperas et al., 1975), have been determined.

Current research interest is directed towards the understanding of the activation and cleavage of C—S and C—Se bonds in transition metal complexes featuring thiolate ligands (Hong et al., 1998; Cao et al., 1994; Jiang et al., 1993). In an attempt to observe how the C—Se bonds were activated by transition metal active centers, we prepared a series of complex containing N,N-diethyl-1,1-diselenocarbamate ligands. Herein we report a centrosymmetric binuclear Cu^II complex, [Cu{Se₂CN(Et)₂}₂]₂, which was prepared from the reaction of CuSO₄ and Se[{Se₂CN(Et)₂}₂]₂ in THF. Each bivalent Cu atom in the complex is coordinated by two N,N-diethyl-1,1-diselenocarbamate ligands in a distorted square-planar geometry forming a [Cu{Se₂CN(Et)₂}₂] unit. Two such units are linked by Cu—Se bonds to form the binuclear complex. Thus, the coordination geometry of each Cu atom is distorted square pyramidal with CuSe₅. N,N-Diethyl-1,1-diselenocarbamate acts as a chelating ligand to coordinate the Cu atom with an Se—Cu—Se angle of 79.04 (5)°. Two kinds of Cu—Se bonds are present in the complex: the shorter are in the range 2.4091 (11)–2.4455 (8) Å (average 2.428 Å) and the longer is 2.9095 (10) Å. The shorter average is compatible withthose found in the related compounds of bis(tetra-n-butyl) bis(1,1-dicyanoethene-2,2-diselenolato-Se,Se')nitridotechnetium(V) (Abram et al., 1991) and bis(tetraphenylarsonium) tris(2,2-diselenido-1,1-ethylenedicarbonitrile)nickel(IV) (Kaiser at al., 1980)

S2. Experimental

The title compound was obtained from the reaction of CuSO₄ and and Se[{Se₂CN(Et)₂}₂]₂ (molar ratio 1:1) in THF. To a solution of Se[{Se₂CN(Et)₂}₂]₂ (0.69 g, 1 mmol) in THF (20 ml) was added solid CuSO₄ (0.15 g, 1 mmol). The reaction solution turned brown–red gradually. After stirring for 2 h, the brown–red solution was filtered. The filtrate was kept in an icebox for one week to yield brown–red prisms of the title complex. Crystals suitable for X-ray diffraction analysis were obtained by recrystallization from THF/hexane at room temperature.

Computing details

Data collection: SMART CCD Software (Siemens, 1994); cell refinement: SMART CCD Software; data reduction: SMART CCD Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

(I)

Crystal data

[Cu2(C5H10NSe2)4]	F(000) = 1036
Mr = 1095.32	Dx = 2.158 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.825 (2) Å	Cell parameters from 397 reflections
b = 10.904 (2) Å	θ = 12.6–19.8°
c = 16.051 (3) Å	µ = 9.92 mm^−1
β = 101.44 (3)°	T = 293 K
V = 1685.4 (6) Å^3	Prism, brown–red
Z = 2	0.29 × 0.24 × 0.22 mm

Data collection

SMART CCD diffractometer	2929 independent reflections
Radiation source: fine-focus sealed tube	2474 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.036
ω scans	θmax = 25.0°, θmin = 2.3°
Absorption correction: empirical (using intensity measurements) empirical (using intensity measurements) from equivalent reflections (XEMP in SHELXTL; Sheldrick, 1994)	h = −10→11
Tmin = 0.168, Tmax = 0.269	k = −7→12
7952 measured reflections	l = −19→16

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.032	H-atom parameters constrained
wR(F^2) = 0.086	w = 1/[σ^2(Fo^2) + (0.0439P)^2 + 0.5791P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max = 0.001
2929 reflections	Δρmax = 1.10 e Å^−3
155 parameters	Δρmin = −0.71 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0090 (4)

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. The structure was solved by direct methods. All non-H atoms were refined with anisotropic displacement parameters. The positions of all hydrogen atoms were generated geometrically (C—H bond fixed at 0.96 Å), assigned isotropic thermal parameters, and allowed to ride on their respective parent C atoms before the final cycle of least-squares refinement. All calculations were performed on an HP586 computer with SHELXTL-PC program package.

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

	x	y	z	Uiso*/Ueq
Se1	−0.31466 (6)	1.03643 (5)	−0.04538 (4)	0.0489 (2)
Se2	−0.04096 (5)	1.16813 (4)	0.03164 (3)	0.03191 (17)
Se3	0.00877 (5)	0.94118 (4)	0.20712 (3)	0.03416 (17)
Se4	−0.23439 (6)	0.78374 (5)	0.11099 (3)	0.03993 (18)
Cu	−0.12829 (6)	0.96820 (5)	0.06600 (4)	0.03389 (19)
N1	−0.2442 (4)	1.2686 (4)	−0.1006 (3)	0.0315 (9)
N2	−0.0955 (5)	0.7344 (4)	0.2780 (3)	0.0395 (10)
C11	−0.2063 (5)	1.1761 (4)	−0.0490 (3)	0.0281 (10)
C12	−0.3773 (6)	1.2730 (5)	−0.1600 (3)	0.0436 (13)
H12A	−0.4138	1.3548	−0.1615	0.080*
H12B	−0.4415	1.2195	−0.1399	0.080*
C13	−0.3664 (7)	1.2375 (6)	−0.2470 (4)	0.0650 (18)
H13A	−0.4563	1.2415	−0.2837	0.080*
H13B	−0.3038	1.2918	−0.2678	0.080*
H13C	−0.3318	1.1551	−0.2460	0.080*
C14	−0.1531 (6)	1.3751 (5)	−0.1030 (4)	0.0463 (14)
H14A	−0.1620	1.4024	−0.1607	0.080*
H14B	−0.0586	1.3504	−0.0827	0.080*
C15	−0.1873 (8)	1.4802 (6)	−0.0509 (5)	0.077 (2)
H15A	−0.1263	1.5483	−0.0532	0.080*
H15B	−0.2816	1.5052	−0.0718	0.080*
H15C	−0.1773	1.4528	0.0069	0.080*
C21	−0.1053 (5)	0.8055 (4)	0.2113 (3)	0.0321 (11)
C22	−0.1843 (7)	0.6236 (5)	0.2760 (4)	0.0556 (16)
H22A	−0.2726	0.6389	0.2396	0.080*
H22B	−0.1996	0.6058	0.3320	0.080*
C23	−0.1207 (7)	0.5152 (5)	0.2410 (5)	0.0667 (19)
H23A	−0.1782	0.4437	0.2390	0.080*
H23B	−0.1063	0.5335	0.1848	0.080*
H23C	−0.0328	0.5002	0.2779	0.080*
C24	0.0027 (6)	0.7576 (5)	0.3582 (4)	0.0540 (16)
H24A	0.0832	0.7991	0.3468	0.080*
H24B	0.0322	0.6809	0.3852	0.080*
C25	−0.0599 (8)	0.8345 (7)	0.4181 (4)	0.074 (2)
H25A	0.0053	0.8488	0.4702	0.080*
H25B	−0.0882	0.9116	0.3913	0.080*
H25C	−0.1398	0.7925	0.4301	0.080*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.0473 (4)	0.0337 (3)	0.0542 (4)	−0.0133 (2)	−0.0179 (3)	0.0155 (2)
Se2	0.0382 (3)	0.0273 (3)	0.0264 (3)	−0.0043 (2)	−0.0029 (2)	0.00270 (18)
Se3	0.0430 (3)	0.0273 (3)	0.0290 (3)	−0.0050 (2)	−0.0005 (2)	0.00396 (19)
Se4	0.0419 (3)	0.0379 (3)	0.0374 (3)	−0.0110 (2)	0.0014 (2)	0.0057 (2)
Cu	0.0425 (4)	0.0274 (4)	0.0280 (3)	−0.0042 (3)	−0.0022 (3)	0.0070 (2)
N1	0.032 (2)	0.027 (2)	0.034 (2)	0.0019 (17)	0.0022 (18)	0.0060 (17)
N2	0.047 (3)	0.035 (3)	0.037 (2)	−0.004 (2)	0.010 (2)	0.0083 (19)
C11	0.033 (3)	0.025 (3)	0.024 (2)	0.003 (2)	0.001 (2)	0.0009 (18)
C12	0.039 (3)	0.041 (3)	0.046 (3)	0.008 (2)	−0.002 (3)	0.015 (2)
C13	0.067 (4)	0.077 (5)	0.043 (4)	0.007 (4)	−0.007 (3)	0.008 (3)
C14	0.048 (3)	0.034 (3)	0.056 (4)	−0.007 (3)	0.007 (3)	0.016 (3)
C15	0.071 (5)	0.039 (4)	0.115 (7)	−0.003 (3)	0.006 (4)	−0.006 (4)
C21	0.040 (3)	0.023 (3)	0.035 (3)	0.005 (2)	0.013 (2)	0.006 (2)
C22	0.068 (4)	0.046 (4)	0.057 (4)	−0.016 (3)	0.021 (3)	0.020 (3)
C23	0.081 (5)	0.034 (4)	0.081 (5)	−0.014 (3)	0.007 (4)	0.009 (3)
C24	0.060 (4)	0.055 (4)	0.041 (3)	0.002 (3)	−0.005 (3)	0.022 (3)
C25	0.097 (6)	0.087 (6)	0.040 (4)	−0.013 (4)	0.017 (4)	−0.002 (3)

Geometric parameters (Å, º)

Se1—C11	1.866 (5)	N1—C11	1.311 (6)
Se1—Cu	2.4091 (11)	N1—C12	1.458 (6)
Se2—C11	1.867 (5)	N1—C14	1.472 (6)
Se2—Cu	2.4455 (8)	N2—C21	1.310 (6)
Se2—Cu^i	2.9095 (10)	N2—C24	1.470 (7)
Se3—C21	1.865 (5)	N2—C22	1.487 (7)
Se3—Cu	2.4127 (11)	C12—C13	1.474 (8)
Se4—C21	1.856 (5)	C14—C15	1.496 (9)
Se4—Cu	2.4397 (8)	C22—C23	1.498 (9)
Cu—Se2^i	2.9095 (10)	C24—C25	1.496 (8)
C11—Se1—Cu	85.45 (14)	C11—N1—C12	122.9 (4)
C11—Se2—Cu	84.37 (14)	C11—N1—C14	121.7 (4)
C11—Se2—Cu^i	99.31 (14)	C12—N1—C14	115.3 (4)
Cu—Se2—Cu^i	85.96 (3)	C21—N2—C24	122.9 (4)
C21—Se3—Cu	84.43 (15)	C21—N2—C22	121.1 (5)
C21—Se4—Cu	83.84 (14)	C24—N2—C22	116.0 (4)
Se1—Cu—Se3	159.22 (4)	N1—C11—Se1	123.7 (4)
Se1—Cu—Se4	99.65 (3)	N1—C11—Se2	124.9 (4)
Se3—Cu—Se4	79.23 (3)	Se1—C11—Se2	111.3 (2)
Se1—Cu—Se2	78.84 (3)	N1—C12—C13	112.8 (5)
Se3—Cu—Se2	99.51 (3)	N1—C14—C15	112.6 (5)
Se4—Cu—Se2	172.43 (3)	N2—C21—Se4	124.0 (4)
Se1—Cu—Se2^i	100.93 (3)	N2—C21—Se3	123.5 (4)
Se3—Cu—Se2^i	99.85 (3)	Se4—C21—Se3	112.5 (2)
Se4—Cu—Se2^i	93.53 (3)	N2—C22—C23	111.3 (5)
Se2—Cu—Se2^i	94.04 (3)	N2—C24—C25	112.2 (5)

Symmetry code: (i) −x, −y+2, −z.