A T-shaped selenenyl halide

The title selenenyl halide complex, 3-iodo-2-phenyl-3H-3-selenaindazole, C₁₂H₉IN₂Se, has an almost planar conformation and a nearly ideal T-shape for the Se(INC) moiety [Se-I 2.8122 (12), Se-C 1.881 (7) and Se-N2 2.051 (6) Å; C-Se-N 79.6 (3), C-Se-I 96.8 (2) and N-Se-I 176.17 (17)°]. This arrangement, together with the two selenium lone pairs, leads to a distorted trigonal-bipyrimidal geometry about the Se atom. Intermolecular interactions are largely limited to stacking forces.

S1. Comment

X-ray structure determination of the title compound, (I), revealed the complex to be a T-shaped selenenyl iodide with the I and N atoms occupying the trans positions. The main nine-atom moeity (Se1, N1, N2, C1—C6) is essentially planar (r.m.s. atomic deviations of 0.030 Å), as is the phenyl ring (r.m.s. deviations of 0.013 Å), and the two are rotated relative to each other by 6.4 (3)° about the N2—C7 bond.

As with similar compounds investigated, (II) and (III) (Majeed, 1999), and (IV) (Jones & Ramirez de Arellano, 1995), the Se atom is formally bonded to the halogen atom and to the aromatic C1 atom, with a secondary link to N2 which is trans to the halogen. The Se1—I1 bond length in (I) is 2.8122 (12) Å, which compares very favourably with the equivalent bond in the T-shaped selenium chloroiodide complex (II) of 2.837 (2) Å. The Se1—N2 distance of 2.051 (6) Å is significantly longer than the mean value of 1.83 Å for Se—N single bonds in the Cambridge Structural Database (Allen et al., 1987), but again is close to the values determined for the selenenyl halides (II), (III) and (IV) which are 2.040 (6), 2.011 (5) and 2.025 (3) Å, respectively. The Se1—C1 bond length of 1.881 (7) Å is as expected for an Se—Csp² single covalent bond and compares favourably with the value quoted by Allen et al. (1987) of 1.893 Å.

In the Se1—N2 interaction, N2 donates an electron pair to Se1 to complete a trigonal-bipyrimidal type of coordination about the central Se atom. The two lone pairs and C1 are equatorial and the more electronegative N and I atoms are axial, this being in accord with the valence-shell electron-pair repulsion (VSEPR) theory (Gillespie, 1963). The angle N2—Se1—I1 is close to linear [176.17 (17)°], and the slight bending in the direction of C1 is probably due to lone-pair repulsion as suggested by Jones & Ramirez de Arellano (1995). The main deviation from an ideal T-shape is seen in the N2—Se1—C1 angle of 79.6 (3)°. This is characteristic of this group of compounds with (II), (III) and (IV) having angles of 80.3 (3), 80.8 (2) and 79.8 (2)°, respectively.

The main intermolecular forces are largely associated with stacking along the short a axis.

S2. Experimental

Azobenzene (55 mmol), selenium(IV) tetrachloride (5 mmol) and anhydrous aluminium chloride (5 mmol) were heated to 433 K under argon for 3 h in 50 ml of 1,2-dichlorobenzene. The reaction mixture was cooled to 353 K and methanol added until the vigorous reaction ceased. The brown precipitate of (III) which formed after cooling was recrystallized from methanol; yield 10%. (III) (1.67 mmol) was added to a solution of diiodine (1.67 mmol) in AR-grade propanone (200 ml). The mixture was heated for 10 min and the solvent removed leaving a deep-red crystalline solid; yield 33%. Crystals suitable for diffraction work were obtained by slow evaporation from propanone.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CADABS (Gould & Smith, 1986); program(s) used to solve structure: CRYSTALS (Watkin, Prout, Carruthers & Betteridge, 1996); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin, Prout & Pearce, 1996); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

(2-phenylazophenyl-C,N')selenium iodide

Crystal data

C12H9IN2Se	F(000) = 728
Mr = 387.07	Dx = 2.098 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 4.845 (2) Å	Cell parameters from 25 reflections
b = 18.369 (6) Å	θ = 9.8–17.0°
c = 13.7745 (12) Å	µ = 5.56 mm^−1
β = 91.77 (2)°	T = 293 K
V = 1225.3 (7) Å^3	Plate, red
Z = 4	0.40 × 0.32 × 0.25 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	1728 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.037
Graphite monochromator	θmax = 25.0°, θmin = 2.2°
ω/2θ scans	h = −1→5
Absorption correction: ψ scan (North et al., 1968)	k = 0→21
Tmin = 0.186, Tmax = 0.250	l = −16→16
2956 measured reflections	3 standard reflections every 120 min
2140 independent reflections	intensity decay: 1.1%

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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.122	H atoms treated by a mixture of independent and constrained refinement
S = 1.17	w = 1/[σ^2(Fo^2) + (0.0489P)^2 + 5.5805P] where P = (Fo^2 + 2Fc^2)/3
2140 reflections	(Δ/σ)max < 0.001
145 parameters	Δρmax = 0.89 e Å^−3
0 restraints	Δρmin = −0.82 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
I1	0.44972 (13)	0.14327 (3)	0.18901 (5)	0.0632 (2)
Se1	0.77590 (15)	0.26988 (4)	0.19751 (5)	0.0424 (2)
N1	0.9499 (13)	0.4079 (3)	0.1265 (4)	0.0433 (14)
N2	0.9955 (12)	0.3654 (3)	0.1972 (4)	0.0402 (13)
C1	0.6271 (14)	0.3136 (4)	0.0840 (5)	0.0393 (16)
C2	0.4182 (16)	0.2877 (5)	0.0231 (5)	0.0469 (18)
H2	0.3316	0.2437	0.0360	0.056*
C3	0.3405 (17)	0.3282 (5)	−0.0570 (6)	0.055 (2)
H3	0.2002	0.3105	−0.0982	0.066*
C4	0.4607 (19)	0.3933 (5)	−0.0789 (6)	0.060 (2)
H4	0.3996	0.4194	−0.1332	0.072*
C5	0.6699 (18)	0.4198 (5)	−0.0209 (6)	0.053 (2)
H5	0.7584	0.4630	−0.0364	0.063*
C6	0.7498 (15)	0.3803 (4)	0.0634 (5)	0.0433 (17)
C7	1.1883 (14)	0.3855 (4)	0.2722 (5)	0.0385 (15)
C8	1.2188 (18)	0.3429 (5)	0.3524 (6)	0.058 (2)
H8	1.1145	0.3006	0.3571	0.069*
C9	1.4039 (17)	0.3614 (5)	0.4278 (7)	0.060 (2)
H9	1.4184	0.3331	0.4836	0.072*
C10	1.5642 (18)	0.4224 (6)	0.4180 (7)	0.063 (2)
H10	1.6919	0.4349	0.4670	0.075*
C11	1.537 (2)	0.4647 (5)	0.3369 (8)	0.067 (2)
H11	1.6487	0.5056	0.3309	0.080*
C12	1.3479 (17)	0.4478 (5)	0.2637 (6)	0.055 (2)
H12	1.3272	0.4777	0.2095	0.066*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0653 (4)	0.0558 (4)	0.0677 (4)	−0.0066 (3)	−0.0119 (3)	0.0085 (3)
Se1	0.0430 (4)	0.0461 (4)	0.0380 (4)	0.0048 (3)	−0.0014 (3)	0.0033 (3)
N1	0.049 (3)	0.045 (4)	0.037 (3)	0.001 (3)	0.005 (3)	0.001 (3)
N2	0.041 (3)	0.043 (3)	0.036 (3)	0.004 (3)	0.004 (2)	−0.001 (3)
C1	0.043 (4)	0.044 (4)	0.032 (3)	0.013 (3)	0.006 (3)	−0.002 (3)
C2	0.049 (4)	0.053 (5)	0.038 (4)	0.000 (4)	−0.003 (3)	0.001 (3)
C3	0.054 (5)	0.074 (6)	0.036 (4)	0.006 (4)	−0.006 (3)	−0.009 (4)
C4	0.069 (6)	0.068 (6)	0.042 (4)	0.012 (5)	−0.005 (4)	0.014 (4)
C5	0.069 (5)	0.051 (5)	0.038 (4)	0.002 (4)	−0.001 (4)	0.005 (3)
C6	0.048 (4)	0.051 (4)	0.031 (4)	0.008 (3)	0.003 (3)	−0.004 (3)
C7	0.034 (3)	0.044 (4)	0.037 (4)	0.004 (3)	0.003 (3)	−0.005 (3)
C8	0.054 (5)	0.071 (6)	0.047 (5)	−0.012 (4)	−0.006 (4)	0.011 (4)
C9	0.050 (5)	0.077 (7)	0.052 (5)	0.001 (4)	−0.010 (4)	0.007 (4)
C10	0.055 (5)	0.077 (6)	0.055 (5)	0.005 (5)	−0.010 (4)	−0.016 (5)
C11	0.065 (5)	0.056 (5)	0.079 (7)	−0.013 (4)	−0.008 (5)	−0.012 (5)
C12	0.061 (5)	0.048 (5)	0.056 (5)	−0.003 (4)	−0.011 (4)	0.001 (4)

Geometric parameters (Å, º)

I1—Se1	2.8122 (12)	C5—C6	1.413 (11)
Se1—C1	1.881 (7)	C5—H5	0.9300
Se1—N2	2.051 (6)	C7—C8	1.358 (11)
N1—N2	1.262 (8)	C7—C12	1.389 (11)
N1—C6	1.378 (10)	C8—C9	1.393 (12)
N2—C7	1.421 (9)	C8—H8	0.9300
C1—C2	1.379 (10)	C9—C10	1.371 (13)
C1—C6	1.394 (11)	C9—H9	0.9300
C2—C3	1.374 (11)	C10—C11	1.364 (14)
C2—H2	0.9300	C10—H10	0.9300
C3—C4	1.368 (13)	C11—C12	1.377 (12)
C3—H3	0.9300	C11—H11	0.9300
C4—C5	1.361 (12)	C12—H12	0.9300
C4—H4	0.9300
C1—Se1—N2	79.6 (3)	N1—C6—C1	119.4 (7)
C1—Se1—I1	96.8 (2)	N1—C6—C5	119.9 (7)
N2—Se1—I1	176.17 (17)	C1—C6—C5	120.7 (7)
N2—N1—C6	111.2 (6)	C8—C7—C12	119.8 (7)
N1—N2—C7	119.7 (6)	C8—C7—N2	119.7 (7)
N1—N2—Se1	116.9 (5)	C12—C7—N2	120.5 (7)
C7—N2—Se1	123.4 (5)	C7—C8—C9	121.1 (8)
C2—C1—C6	119.3 (7)	C7—C8—H8	119.5
C2—C1—Se1	127.8 (6)	C9—C8—H8	119.5
C6—C1—Se1	112.9 (5)	C10—C9—C8	118.7 (9)
C3—C2—C1	118.6 (8)	C10—C9—H9	120.6
C3—C2—H2	120.7	C8—C9—H9	120.6
C1—C2—H2	120.7	C11—C10—C9	120.3 (8)
C4—C3—C2	122.8 (8)	C11—C10—H10	119.8
C4—C3—H3	118.6	C9—C10—H10	119.8
C2—C3—H3	118.6	C10—C11—C12	121.0 (9)
C5—C4—C3	119.9 (8)	C10—C11—H11	119.5
C5—C4—H4	120.1	C12—C11—H11	119.5
C3—C4—H4	120.1	C11—C12—C7	119.0 (8)
C4—C5—C6	118.6 (8)	C11—C12—H12	120.5
C4—C5—H5	120.7	C7—C12—H12	120.5
C6—C5—H5	120.7
C6—N1—N2—C7	−177.7 (6)	Se1—C1—C6—N1	−2.4 (8)
C6—N1—N2—Se1	1.3 (7)	C2—C1—C6—C5	−2.5 (11)
C1—Se1—N2—N1	−2.1 (5)	Se1—C1—C6—C5	178.0 (6)
I1—Se1—N2—N1	−19 (3)	C4—C5—C6—N1	−176.2 (7)
C1—Se1—N2—C7	176.8 (6)	C4—C5—C6—C1	3.4 (12)
I1—Se1—N2—C7	160 (2)	N1—N2—C7—C8	174.1 (7)
N2—Se1—C1—C2	−177.2 (7)	Se1—N2—C7—C8	−4.8 (9)
I1—Se1—C1—C2	1.7 (7)	N1—N2—C7—C12	−6.7 (10)
N2—Se1—C1—C6	2.2 (5)	Se1—N2—C7—C12	174.4 (5)
I1—Se1—C1—C6	−178.9 (5)	C12—C7—C8—C9	1.5 (13)
C6—C1—C2—C3	1.0 (11)	N2—C7—C8—C9	−179.3 (8)
Se1—C1—C2—C3	−179.7 (6)	C7—C8—C9—C10	−2.6 (14)
C1—C2—C3—C4	−0.3 (13)	C8—C9—C10—C11	1.5 (14)
C2—C3—C4—C5	1.2 (14)	C9—C10—C11—C12	0.7 (15)
C3—C4—C5—C6	−2.7 (13)	C10—C11—C12—C7	−1.8 (14)
N2—N1—C6—C1	0.7 (9)	C8—C7—C12—C11	0.8 (12)
N2—N1—C6—C5	−179.7 (7)	N2—C7—C12—C11	−178.5 (8)
C2—C1—C6—N1	177.1 (7)