Bis(1-ethyl-3-methyl­imidazolium) 3,6-diselanyl­­idene-1,2,4,5-tetra­selena-3,6-diphospha­cyclo­hexane-3,6-di­selen­olate

In the title compound, 2C₆H₁₁N₂⁺·P₂Se₈²⁻ or [EMIM]₂P₂Se₈ (EMIM = 1-ethyl-3-methyl­imidazolium), the anions, located about inversion centers between EMIM cations, exhibit a cyclo­hexane-like chair conformation. The cations are found in columns along the a axis, with centroid–centroid distances of 3.8399 (3) and 4.7530 (2) Å. The observed P—Se distances and Se—P—Se angles agree with other salts of this anion.

Related literature

For similar seleno­phosphate compounds, see: Biswas et al. (2010); Lin et al. (2012). For ionothermal reactions in room-temperature ionic liquids, see: Morris (2009); Parnham & Morris (2007); Cody et al. (2012). For the preparation of EMIM(BF₄), see: Egashira et al. (2006). For the structure of the P₂Se₈²⁻ anion, see: Zhao et al. (1992); Rotter et al. (2008). For π–π inter­actions between imidazolium cations, see: Wilkes & Zaworotko (1993).

Experimental

Crystal data

• 2C₆H₁₁N₂⁺·P₂Se₈²⁻

• M_r = 915.96

• Triclinic,

• a = 7.8885 (4) Å

• b = 9.3783 (4) Å

• c = 9.8039 (5) Å

• α = 110.390 (3)°

• β = 96.395 (4)°

• γ = 102.992 (5)°

• V = 648.00 (5) ų

• Z = 1

• Mo Kα radiation

• μ = 11.41 mm⁻¹

• T = 293 K

• 0.19 × 0.07 × 0.03 mm

Data collection

• Nonius KappaCCD diffractometer

• Absorption correction: Gaussian [JANA2006 (Petříček et al., 2006) and X-SHAPE (Stoe & Cie, 1998)] T_min = 0.204, T_max = 0.754

• 22118 measured reflections

• 3719 independent reflections

• 2622 reflections with I > 2σ(I)

• R_int = 0.072

Refinement

• R[F² > 2σ(F²)] = 0.029

• wR(F²) = 0.063

• S = 1.02

• 3719 reflections

• 118 parameters

• H-atom parameters constrained

• Δρ_max = 0.47 e Å⁻³

• Δρ_min = −0.55 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

P1—Se4	2.1104 (8)
P1—Se3	2.1334 (8)
P1—Se1	2.2794 (9)
P1—Se2^i	2.2809 (8)
Se1—Se2	2.3442 (5)

Se4—P1—Se3	122.19 (4)
Se4—P1—Se1	113.49 (4)
Se3—P1—Se1	100.04 (3)
Se4—P1—Se2^i	113.90 (4)
Se3—P1—Se2^i	100.49 (3)
Se1—P1—Se2^i	104.32 (3)
P1—Se1—Se2	102.89 (2)
P1^i—Se2—Se1	102.37 (2)
Symmetry code: (i) -x+1, -y, -z.

Data collection: COLLECT (Hooft, 2009); cell refinement: COLLECT; data reduction: COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

Thiophosphate and selenophosphate compounds are sought for their interesting and fine-tunable electronic properties (Lin et al., 2012). As new synthetic methods are often needed to gain access to new compounds with interesting properties, ionothermal reactions of thio- and selenophosphates were explored. Recently, room-temperature ionic liquids have received much interest for the preparation of inorganic materials (Morris, 2009; Parnham & Morris, 2007; Cody, et al., 2012).

The structure of the anion in the title compound was first reported by Zhao et al. (1992) and the EMIM cation is well known. All interatomic distances and angles found in the current study (Fig. 1) are within normal ranges (Rotter et al., 2008). Although the EMIM cations are found in columns in the title compound, the centroid-to-centroid distances of 3.8399 (3) Å and 4.7530 (2) Å (Fig. 2) indicate only weak pi-pi interactions (Wilkes & Zaworotko, 1993).

Related literature

For similar selenophosphate compounds, see: Biswas et al. (2010); Lin et al. (2012). For ionothermal reactions in room-temperature ionic liquids, see: Morris (2009); Parnham & Morris (2007); Cody et al. (2012). For the preparation of EMIMBF₄, see: Egashira et al. (2006). For the structure of the P₂Se₈^2- anion, see: Zhao et al. (1992); Rotter et al. (2008). For π–π interactions between imidazolium cations, see: Wilkes & Zaworotko (1993).

S2. Experimental

The title compound was prepared by the literature method (Cody et al., 2012) for ionothermal synthesis of related sulfur compounds. A total mass of 125 mg of the elements with a stoichiometry of Ni: 4P: 16Se was ground together in a glove box and then placed in a Pyrex tube. An aliquot of 1.25 ml of the ionic liquid EMIMBF₄, prepared according to the literature (Egashira, et al., 2006), was added to the tube in a glove bag. The tube was then evacuated and sealed. The reaction mixture was heated at 150 °C for 96 h and then slowly cooled to room temperature at a rate of 0.5 °C/min. The tube was opened, the product mixture was filtered, and individual crystals were selected for analysis by hand. The products included black powder, large red blocks, and small yellow plates. The latter were both the title compound; the color difference is attributed to absorption effects from the thickness of the crystals. Although elemental nickel was included in the reaction mixture, it was not observed in the isolated crystalline products.

S3. Refinement

All H atoms were positioned with idealized geometry and were refined isotropically with U_iso(H) = 1.2 U_eq(C) (1.5 for methyl H atoms) using a riding model with C—H = 0.93 Å for aromatic, 0.97 Å for methylene and 0.96 Å for methyl H-atoms.

Computing details

Data collection: COLLECT (Hooft, 2009); cell refinement: COLLECT (Hooft, 2009); data reduction: COLLECT (Hooft, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. Molecular structure and atomic labeling scheme for the title compound. Thermal elipsoids are shown at the 50% level. Symmetry code for the generation of equivalent atoms: i = 1 - x, -y, -z.
	Fig. 2. A packing diagram of the title compound showing the column of EMIM cations along the a axis.

Bis(1-ethyl-3-methylimidazolium) 3,6-diselanylidene-1,2,4,5-tetraselena-3,6-diphosphacyclohexane-3,6-diselenolate

Crystal data

2C6H11N2^+·P2Se8^2^−	Z = 1
Mr = 915.96	F(000) = 424
Triclinic, P1	Dx = 2.347 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.8885 (4) Å	Cell parameters from 3719 reflections
b = 9.3783 (4) Å	θ = 6.5–30.0°
c = 9.8039 (5) Å	µ = 11.41 mm^−1
α = 110.390 (3)°	T = 293 K
β = 96.395 (4)°	Plate, yellow
γ = 102.992 (5)°	0.19 × 0.07 × 0.03 mm
V = 648.00 (5) Å^3

Data collection

Nonius KappaCCD diffractometer	3719 independent reflections
Radiation source: fine-focus sealed tube	2622 reflections with I > 2σ(I)
Unknown monochromator	Rint = 0.072
ω scans	θmax = 30.0°, θmin = 6.5°
Absorption correction: gaussian [JANA2006 (Petříček et al., 2006) and X-SHAPE (Stoe & Cie, 1998)]	h = −10→11
Tmin = 0.204, Tmax = 0.754	k = −13→13
22118 measured reflections	l = −13→13

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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.063	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0252P)^2 + 0.2292P] where P = (Fo^2 + 2Fc^2)/3
3719 reflections	(Δ/σ)max < 0.001
118 parameters	Δρmax = 0.47 e Å^−3
0 restraints	Δρmin = −0.55 e Å^−3

Special details

Experimental. A set of 280 frames were collected with a rotation of 2° per frame and an exposure time of 190 s; the crystal to detector distance was 25.00 mm. Refinements were done with the SHELXTL97 (Sheldrick, 2008) software package; absorption correction was made with the program Jana2006 (Petricek et al., 2006) using the program X-SHAPE (Stoe & Cie, 1998).

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
P1	0.62769 (11)	−0.10004 (9)	0.13027 (9)	0.03455 (17)
Se1	0.38273 (4)	−0.24755 (3)	−0.05425 (4)	0.04208 (9)
Se2	0.21381 (4)	−0.06847 (4)	−0.03916 (4)	0.04234 (9)
Se3	0.77764 (6)	−0.26777 (5)	0.09996 (4)	0.05519 (11)
Se4	0.56642 (5)	0.01558 (4)	0.33743 (4)	0.04503 (10)
N1	0.2827 (4)	0.4858 (3)	0.3773 (3)	0.0413 (6)
N2	0.2005 (3)	0.2740 (3)	0.4218 (3)	0.0422 (6)
C1	0.2281 (4)	0.3279 (4)	0.3154 (4)	0.0415 (7)
H1	0.2122	0.2661	0.2148	0.050*
C2	0.2379 (5)	0.4007 (5)	0.5542 (4)	0.0530 (9)
H2	0.2298	0.3961	0.6465	0.064*
C3	0.2884 (5)	0.5333 (4)	0.5270 (4)	0.0525 (9)
H3	0.3210	0.6372	0.5965	0.063*
C4	0.3182 (5)	0.5911 (4)	0.2952 (4)	0.0486 (8)
H4A	0.3597	0.5382	0.2068	0.058*
H4B	0.4115	0.6869	0.3572	0.058*
C5	0.1558 (6)	0.6340 (6)	0.2513 (6)	0.0735 (13)
H5A	0.1832	0.7026	0.1986	0.110*
H5B	0.1156	0.6877	0.3388	0.110*
H5C	0.0641	0.5395	0.1883	0.110*
C6	0.1325 (5)	0.1069 (4)	0.3983 (5)	0.0606 (10)
H6A	0.1248	0.0980	0.4922	0.091*
H6B	0.2114	0.0496	0.3527	0.091*
H6C	0.0165	0.0634	0.3345	0.091*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0454 (4)	0.0353 (4)	0.0258 (4)	0.0132 (3)	0.0065 (3)	0.0144 (3)
Se1	0.0560 (2)	0.03274 (15)	0.03188 (17)	0.00568 (13)	0.00294 (14)	0.01201 (13)
Se2	0.03936 (17)	0.05217 (19)	0.03963 (19)	0.00924 (13)	0.00866 (14)	0.02474 (16)
Se3	0.0774 (3)	0.0598 (2)	0.0454 (2)	0.0411 (2)	0.01621 (19)	0.02586 (19)
Se4	0.0639 (2)	0.04233 (17)	0.02882 (17)	0.01506 (15)	0.01340 (15)	0.01247 (14)
N1	0.0472 (15)	0.0410 (14)	0.0361 (15)	0.0097 (11)	0.0087 (12)	0.0172 (12)
N2	0.0435 (14)	0.0439 (15)	0.0431 (16)	0.0089 (11)	0.0079 (12)	0.0239 (13)
C1	0.0461 (18)	0.0424 (16)	0.0338 (17)	0.0084 (13)	0.0078 (14)	0.0147 (14)
C2	0.063 (2)	0.066 (2)	0.036 (2)	0.0179 (18)	0.0138 (17)	0.0268 (19)
C3	0.071 (2)	0.0468 (18)	0.0329 (18)	0.0121 (17)	0.0126 (17)	0.0101 (16)
C4	0.054 (2)	0.0459 (18)	0.052 (2)	0.0092 (15)	0.0174 (17)	0.0277 (17)
C5	0.065 (3)	0.095 (3)	0.095 (4)	0.030 (2)	0.025 (2)	0.069 (3)
C6	0.064 (2)	0.051 (2)	0.075 (3)	0.0095 (17)	0.013 (2)	0.038 (2)

Geometric parameters (Å, º)

P1—Se4	2.1104 (8)	C2—C3	1.345 (5)
P1—Se3	2.1334 (8)	C2—H2	0.9300
P1—Se1	2.2794 (9)	C3—H3	0.9300
P1—Se2^i	2.2809 (8)	C4—C5	1.489 (5)
Se1—Se2	2.3442 (5)	C4—H4A	0.9700
Se2—P1^i	2.2809 (8)	C4—H4B	0.9700
N1—C1	1.332 (4)	C5—H5A	0.9600
N1—C3	1.370 (4)	C5—H5B	0.9600
N1—C4	1.477 (4)	C5—H5C	0.9600
N2—C1	1.327 (4)	C6—H6A	0.9600
N2—C2	1.366 (4)	C6—H6B	0.9600
N2—C6	1.463 (4)	C6—H6C	0.9600
C1—H1	0.9300
Se4—P1—Se3	122.19 (4)	C2—C3—H3	126.6
Se4—P1—Se1	113.49 (4)	N1—C3—H3	126.6
Se3—P1—Se1	100.04 (3)	N1—C4—C5	111.4 (3)
Se4—P1—Se2^i	113.90 (4)	N1—C4—H4A	109.3
Se3—P1—Se2^i	100.49 (3)	C5—C4—H4A	109.3
Se1—P1—Se2^i	104.32 (3)	N1—C4—H4B	109.3
P1—Se1—Se2	102.89 (2)	C5—C4—H4B	109.3
P1^i—Se2—Se1	102.37 (2)	H4A—C4—H4B	108.0
C1—N1—C3	108.8 (3)	C4—C5—H5A	109.5
C1—N1—C4	125.1 (3)	C4—C5—H5B	109.5
C3—N1—C4	126.0 (3)	H5A—C5—H5B	109.5
C1—N2—C2	108.5 (3)	C4—C5—H5C	109.5
C1—N2—C6	125.1 (3)	H5A—C5—H5C	109.5
C2—N2—C6	126.3 (3)	H5B—C5—H5C	109.5
N2—C1—N1	108.3 (3)	N2—C6—H6A	109.5
N2—C1—H1	125.9	N2—C6—H6B	109.5
N1—C1—H1	125.9	H6A—C6—H6B	109.5
C3—C2—N2	107.8 (3)	N2—C6—H6C	109.5
C3—C2—H2	126.1	H6A—C6—H6C	109.5
N2—C2—H2	126.1	H6B—C6—H6C	109.5
C2—C3—N1	106.7 (3)

Symmetry code: (i) −x+1, −y, −z.