2,2′-Diselenobis(4,4-diphenylcyclohexa-2,5-dienone)

The title compound, C₃₆H₂₆O₂Se₂, displays crystallographic twofold symmetry. The packing involves corrugated linear ribbons mediated through C—H...O and C—H...Se inter­actions. The ribbons are connected through C—H...π inter­actions.

S1. Comment

The role of weak hydrogen bonds such as C—H···O, C—H···π, or in general C—H···X (X = heteroatom or metal) and X···X interactions in the stabilization of crystal structures is a theme of current interest (Desiraju & Steiner, 1999). In this context, the crystal structure of the title compound, (I), is pertinent because it has phenyl C—H donor groups, carbonyl acceptor atoms and a Se—Se bond.

The molecular geometry of (I) is shown in Fig. 1 (Johnson, 1976). The molecule lies on a twofold axis that bisects the Se1—Se1ⁱ bond [symmetry code: (i) 3/2 − x, 1/2 − y, z]; the asymmetric unit contains half a molecule of (I). The cyclohexa-2,5-dienone ring forms dihedral angles of 58.1 (1) and 89.85 (1)° with the two phenyl rings (C7—C12 and C13—C18). The diselenide geometry in (I) is normal, with a Se1—Se1ⁱ bond length of 2.3229 (6) Å and a C2—Se1—Se1ⁱ—C2ⁱ torsion angle of 79.35 (8)°. These values are comparable with those found in the crystal structure of dimesityl diselenide reported recently by Jeske et al. (1998) [Se—Se 2.3341 (6) Å and C—Se—Se—C 83.96 (12)°].

In the crystal structure of (I), space group Pccn, inversion related molecules are connected through C—H···O and C—H···Se interactions (Iwaoka & Tomoda, 1994; Narayanan et al., 1998) to produce a corrugated ribbon-like structure in (101) [C16—H16A···O1 2.82 Å, 125°; C17—H17A···Se1 3.10 Å, 141°] (Fig. 2). Such ribbons are connected by chains of C—H···O and C—H···π interactions along [001] through the C5 and C6 H-atoms of the cyclohexa-2,5-dienone as donors and the carbonyl group and phenyl ring as acceptors [C5—H5A···O1 2.93 Å, 157°; C6—H6A···π_centroid 2.57 Å, 153°]. The hydrogen bonds in this study have been considered with liberal distance and angle cut-off criteria of 2.0 < H···O < 3.0 Å and 120 < C—H···O < 180°, as advocated by Desiraju & Steiner (1999).

The approach of electrophilic and nucleophilic groups (X) to divalent Se (Y—Se—Z) has been discussed by Ramasubbu & Parthasarathy (1987) and categorized as type I or type II depending on whether the approaching atom is normal to the selenide plane and along the Se lone pair orbital (<θ> = 23°) or in the plane and along the C—Se σ* antibonding orbital (<θ> = 79°). In the spherical coordinate system, θ is the polar angle between the direction X···Se and the normal to the Y—Se—Z selenide plane. There are two interactions in (I) involving the Se-atom that deserve mention. In the C17—H17A···Se1 interaction, the C—H group approaches the Se acceptor along the direction for electrophilic donors with θ = 18.5°. Interestingly, the structure also has a C—Se···π_centroid contact of 3.59 Å (166.4°), which is shorter than the sum of the van der Waals radii (Se 2.0 and C 1.7 Å). The approach of the phenyl ring is in the C—Se—Se plane and from behind the C—Se bond, i.e. it is a type-II contact with θ = 83.9°. Based on this approach geometry, the interaction could be viewed as electrophile-nucleophile pairing, i.e. Se(δ+)···π(δ-). Thus, the stereochemical distribution of charge density at Se and its behaviour both as a donor and as an acceptor in the crystal structure of (I) is rationalized.

S2. Experimental

Compound (I) was obtained as an unexpected product in 60% yield during the SeO₂ oxidation of 4,4-diphenyl-2-cyclohexenone (Zimmerman & Schuster, 1962). Yellow crystals of (I) were obtained upon crystallization from ethyl acetate and hexane (m.p. 483 K).

S3. Refinement

All the H atoms have been generated at idealized geometries and refined isotropically using a riding model.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SHELXTL (Siemens, 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976) and PLUTON (Spek, 1992); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. ORTEPII (Johnson, 1976) diagram and numbering scheme for (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii [symmetry code: (i) 3/2 − x, 1/2 − y, z].
	Fig. 2. A view of (I) showing the corrugated ribbons connected by C—H.·O and C—H···Se hydrogen bonds along [100]. Se atoms are shown as large hatched circles and O atoms as small crossed circles. The C—H···O and C—H···π interactions along [001] are omitted for clarity.

2,2'-Diselenobis(4,4-diphenylcyclohexa-2,5-dienone)

Crystal data

C36H26O2Se2	Dx = 1.522 Mg m^−3
Mr = 648.49	Melting point: 483 K
Orthorhombic, Pccn	Mo Kα radiation, λ = 0.71073 Å
a = 17.4144 (16) Å	Cell parameters from 1650 reflections
b = 10.6767 (10) Å	θ = 2.2–26.4°
c = 15.2187 (14) Å	µ = 2.65 mm^−1
V = 2829.6 (5) Å^3	T = 168 K
Z = 4	Plate, yellow
F(000) = 1304	0.8 × 0.5 × 0.14 mm

Data collection

Siemens CCD area detector diffractometer	2839 independent reflections
Radiation source: fine-focus sealed tube	2412 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
Detector resolution: 512 pixels mm^-1	θmax = 26.4°, θmin = 2.9°
ϕ and ω scans	h = −21→10
Absorption correction: multi-scan (SADABS; Blessing, 1995)	k = −13→13
Tmin = 0.218, Tmax = 0.690	l = −18→18
29316 measured reflections

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) = 0.086	H-atom parameters constrained
S = 1.06	Calculated w = 1/[σ^2(Fo^2) + (0.05P)^2 + 1.9536P] where P = (Fo^2 + 2Fc^2)/3
2839 reflections	(Δ/σ)max = −0.002
181 parameters	Δρmax = 0.55 e Å^−3
0 restraints	Δρmin = −0.73 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 on F² for ALL reflections. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating R-factor 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
Se1	0.690398 (14)	0.29881 (2)	0.005848 (14)	0.03246 (11)
C2	0.64543 (12)	0.20752 (18)	0.10268 (13)	0.0242 (4)
C17	0.51527 (14)	−0.1935 (2)	0.06012 (15)	0.0337 (5)
H17A	0.4720	−0.1866	0.0224	0.040*
C7	0.69311 (12)	−0.00199 (19)	0.27886 (14)	0.0244 (4)
C14	0.64115 (12)	−0.21193 (19)	0.17006 (15)	0.0281 (5)
H14A	0.6846	−0.2191	0.2075	0.034*
C3	0.66978 (12)	0.09658 (19)	0.13137 (13)	0.0236 (4)
H3A	0.7128	0.0602	0.1028	0.028*
O1	0.55606 (10)	0.37295 (15)	0.11616 (12)	0.0404 (4)
C18	0.54083 (12)	−0.0895 (2)	0.10593 (14)	0.0276 (5)
H18A	0.5148	−0.0119	0.0993	0.033*
C6	0.54353 (13)	0.2069 (2)	0.21818 (16)	0.0324 (5)
H6A	0.5018	0.2462	0.2475	0.039*
C15	0.61504 (14)	−0.3167 (2)	0.12408 (16)	0.0344 (5)
H15A	0.6406	−0.3947	0.1308	0.041*
C16	0.55240 (14)	−0.3077 (2)	0.06900 (15)	0.0350 (5)
H16A	0.5349	−0.3790	0.0375	0.042*
C12	0.67207 (14)	−0.0728 (2)	0.35236 (14)	0.0304 (5)
H12A	0.6210	−0.1031	0.3577	0.036*
C1	0.57948 (13)	0.27135 (19)	0.14399 (14)	0.0286 (5)
C10	0.79998 (16)	−0.0566 (3)	0.41067 (17)	0.0440 (6)
H10A	0.8366	−0.0771	0.4546	0.053*
C4	0.63378 (11)	0.02471 (19)	0.20601 (13)	0.0224 (4)
C13	0.60417 (11)	−0.09720 (18)	0.16161 (13)	0.0217 (4)
C5	0.56725 (12)	0.0948 (2)	0.24623 (14)	0.0277 (5)
H5A	0.5408	0.0573	0.2941	0.033*
C11	0.72541 (15)	−0.0988 (2)	0.41727 (15)	0.0384 (6)
H11A	0.7104	−0.1466	0.4671	0.046*
C8	0.76782 (13)	0.0434 (2)	0.27405 (16)	0.0345 (5)
H8A	0.7827	0.0937	0.2255	0.041*
C9	0.82077 (14)	0.0162 (3)	0.33917 (18)	0.0449 (6)
H9A	0.8717	0.0476	0.3348	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.03660 (18)	0.03212 (17)	0.02865 (15)	−0.01437 (9)	−0.00976 (9)	0.00822 (8)
C2	0.0255 (11)	0.0233 (10)	0.0238 (10)	−0.0074 (8)	−0.0048 (8)	−0.0006 (8)
C17	0.0326 (12)	0.0397 (13)	0.0290 (11)	−0.0112 (10)	−0.0077 (9)	0.0023 (9)
C7	0.0275 (11)	0.0219 (10)	0.0239 (10)	0.0005 (8)	−0.0010 (8)	−0.0041 (8)
C14	0.0236 (11)	0.0286 (11)	0.0322 (11)	0.0017 (8)	−0.0010 (9)	−0.0044 (8)
C3	0.0211 (10)	0.0257 (10)	0.0239 (10)	−0.0044 (8)	0.0000 (8)	−0.0011 (8)
O1	0.0475 (10)	0.0254 (8)	0.0483 (10)	0.0073 (7)	−0.0081 (8)	0.0006 (7)
C18	0.0247 (10)	0.0289 (11)	0.0292 (11)	−0.0036 (9)	−0.0016 (9)	0.0056 (9)
C6	0.0290 (12)	0.0345 (12)	0.0337 (12)	0.0067 (9)	0.0029 (10)	−0.0071 (9)
C15	0.0381 (13)	0.0275 (11)	0.0376 (12)	0.0041 (10)	0.0024 (10)	−0.0066 (9)
C16	0.0408 (13)	0.0347 (13)	0.0296 (11)	−0.0113 (10)	0.0014 (10)	−0.0066 (9)
C12	0.0373 (12)	0.0273 (11)	0.0265 (11)	0.0012 (9)	0.0015 (9)	−0.0009 (9)
C1	0.0309 (11)	0.0220 (10)	0.0328 (11)	0.0003 (9)	−0.0096 (9)	−0.0050 (8)
C10	0.0507 (16)	0.0467 (15)	0.0345 (13)	0.0149 (12)	−0.0170 (11)	−0.0101 (11)
C4	0.0202 (9)	0.0223 (9)	0.0246 (9)	0.0000 (8)	0.0025 (8)	−0.0001 (8)
C13	0.0190 (9)	0.0248 (10)	0.0214 (9)	−0.0033 (8)	0.0046 (8)	−0.0006 (8)
C5	0.0259 (11)	0.0308 (11)	0.0265 (10)	0.0016 (9)	0.0056 (9)	−0.0023 (8)
C11	0.0558 (16)	0.0344 (13)	0.0250 (11)	0.0108 (11)	−0.0027 (11)	−0.0021 (9)
C8	0.0296 (12)	0.0396 (13)	0.0342 (12)	−0.0035 (10)	−0.0039 (9)	0.0011 (10)
C9	0.0319 (13)	0.0568 (17)	0.0462 (15)	−0.0042 (12)	−0.0115 (11)	−0.0048 (13)

Geometric parameters (Å, º)

Se1—C2	1.932 (2)	C6—C5	1.336 (3)
Se1—Se1^i	2.3229 (6)	C6—C1	1.463 (3)
C2—C3	1.332 (3)	C6—H6A	0.950
C2—C1	1.476 (3)	C15—C16	1.379 (3)
C17—C18	1.384 (3)	C15—H15A	0.950
C17—C16	1.386 (3)	C16—H16A	0.950
C17—H17A	0.950	C12—C11	1.384 (3)
C7—C8	1.390 (3)	C12—H12A	0.950
C7—C12	1.399 (3)	C10—C11	1.379 (4)
C7—C4	1.542 (3)	C10—C9	1.385 (4)
C14—C13	1.390 (3)	C10—H10A	0.950
C14—C15	1.395 (3)	C4—C5	1.509 (3)
C14—H14A	0.950	C4—C13	1.555 (3)
C3—C4	1.507 (3)	C5—H5A	0.950
C3—H3A	0.950	C11—H11A	0.950
O1—C1	1.234 (3)	C8—C9	1.385 (3)
C18—C13	1.393 (3)	C8—H8A	0.950
C18—H18A	0.950	C9—H9A	0.950
C2—Se1—Se1^i	97.81 (6)	C11—C12—H12A	119.9
C3—C2—C1	121.25 (19)	C7—C12—H12A	119.9
C3—C2—Se1	124.72 (17)	O1—C1—C6	122.5 (2)
C1—C2—Se1	114.03 (14)	O1—C1—C2	121.1 (2)
C18—C17—C16	120.4 (2)	C6—C1—C2	116.39 (18)
C18—C17—H17A	119.8	C11—C10—C9	119.2 (2)
C16—C17—H17A	119.8	C11—C10—H10A	120.4
C8—C7—C12	118.4 (2)	C9—C10—H10A	120.4
C8—C7—C4	121.65 (19)	C3—C4—C5	111.86 (17)
C12—C7—C4	119.95 (19)	C3—C4—C7	110.93 (16)
C13—C14—C15	120.6 (2)	C5—C4—C7	108.32 (16)
C13—C14—H14A	119.7	C3—C4—C13	103.69 (15)
C15—C14—H14A	119.7	C5—C4—C13	109.70 (16)
C2—C3—C4	124.57 (19)	C7—C4—C13	112.33 (16)
C2—C3—H3A	117.7	C14—C13—C18	118.36 (19)
C4—C3—H3A	117.7	C14—C13—C4	122.95 (18)
C17—C18—C13	120.9 (2)	C18—C13—C4	118.53 (18)
C17—C18—H18A	119.6	C6—C5—C4	123.5 (2)
C13—C18—H18A	119.5	C6—C5—H5A	118.2
C5—C6—C1	122.4 (2)	C4—C5—H5A	118.2
C5—C6—H6A	118.8	C10—C11—C12	121.0 (2)
C1—C6—H6A	118.8	C10—C11—H11A	119.5
C16—C15—C14	120.5 (2)	C12—C11—H11A	119.5
C16—C15—H15A	119.7	C9—C8—C7	120.8 (2)
C14—C15—H15A	119.8	C9—C8—H8A	119.5
C15—C16—C17	119.3 (2)	C7—C8—H8A	119.6
C15—C16—H16A	120.4	C10—C9—C8	120.4 (2)
C17—C16—H16A	120.3	C10—C9—H9A	119.8
C11—C12—C7	120.2 (2)	C8—C9—H9A	119.8

Symmetry code: (i) −x+3/2, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5A···O1^ii	0.95	2.93	3.822 (3)	157
C16—H16A···O1^iii	0.95	2.82	3.463 (3)	125
C17—H17A···Se1^iii	0.95	3.10	3.886 (2)	141

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