Di-μ-iodido-bis­[(η⁴-cyclo­octa-1,5-diene)­iridium(I)]

The mol­ecular structure of the title compound, [Ir₂I₂(C₈H₁₂)₂], has C₂ symmetry. The dinuclear structure features two bridging I atoms and a bent geometry for the Ir₂(μ-I)₂ core, with a hinge angle of 95.26 (1)°.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.012 Å
• R factor = 0.042
• wR factor = 0.102
• Data-to-parameter ratio = 32.0

checkCIF/PLATON results

No syntax errors found



Alert level C
DIFMX01_ALERT_2_C  The maximum difference density is > 0.1*ZMAX*0.75
            _refine_diff_density_max given =      5.910
            Test value =      5.775
DIFMX02_ALERT_1_C  The maximum difference density is > 0.1*ZMAX*0.75
            The relevant atom site should be identified.
PLAT097_ALERT_2_C Maximum (Positive) Residual Density ............       5.91 e/A   
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT342_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...         12
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.14 Ratio

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

Crystal data for binuclear complexes of d⁸ transition metals of the type [L₂M(µ-X)]₂ (M= Rh or Ir; X = halide) and their theoretical analyses have been reported (Aullón et al., 1998; Cotton, et al., 1999). However, their iodide analogues are fairly rare. Among the known complexes, cyclooctadiene derivatives of the Group 8 transition metals, i.e. [M(µ-Cl)(COD)]₂ (M = Ir^I or Rh^I; cod = cis,cis-1,5-cyclooctadiene), have been used as key starting materials for the preparation of various kinds of Ir^I or Rh^I complexes, that are efficient catalyst precursors. For example, the molecular structure of [Ir(µ-Cl){(R)-binap}]₂ has been reported (Yamagata et al., 1997), which was prepared from the reaction of [Ir(µ-Cl)(cod)]₂ with two equivalents of (R)-binap, where (R)-binap is (R)-(+)-2,2'-bis(diphenylphosphanyl)-1,1'-binaphthyl, as well as its use as an efficient catalyst for the asymmetric hydrogenation of prochiral imines (Tani et al., 1995).

The catalytic asymmetric olefin hydroamination with [Ir(µ-Cl)(diphosphine)]₂ and the structure of [Ir(µ-Cl){(R)-binap}]₂ have also been investigated by Togni and co-workers (Dorta et al., 1997). Although [Rh(µ-Cl)(cod)]₂ (De Ridder & Imhoff, 1994) has an almost planar structure (the hinge angle is 169.1 (3)°), [Ir(µ-Br)(cod)]₂ (Yamagata et al., 2007), [Ir(µ-Cl)(cod)]₂ (Cotton et al., 1986), and [Rh(µ-Br)(cod)]₂ (Pettinari et al., 2002) show bent structures; with hinge angles of 101.58 (3)°, 109.4 (3)°, and 148.7 (3)°, respectively. Thus, it was thought of interest to examine the structure of [Ir(µ-I)(cod)]₂, (I), Fig. 1 & Table 1. The structure of (I) resembles those of the aforementioned [M(µ-X)(cod)]₂ structures, indeed the structures are isomorphous. In (I), the Ir₂(µ-I)₂ core shows a bent geometry with the hinge angle of 95.26 (1)°. The M···M distances in (I), [Ir(µ-Br)(cod)]₂, [Ir(µ-Cl)(cod)]₂, and [Rh(µ-Br)(cod)]₂ are 2.9228 (6), 2.9034 (5), 2.910 (1), and 3.565 Å, respectively. The degree of bending is Ir > Rh and I > Br > Cl. These tendencies can be explained by the differences in diffuseness of the metal's d orbitals and by analyzing the <p_z²/d_z²> and <d_z²/d_z²> overlap integrals between the Slater orbitals (EH calculations) (Aullón et al., 1998).

Related literature

For related literature, see: Aullón et al. (1998); Cotton et al. (1986, 1999); Dorta et al. (1997); Pettinari et al. (2002); De Ridder & Imhoff (1994); Tani et al. (1995); Yamagata et al. (1997, 2007).

S2. Experimental

In a Schlenk flask with ether (50 ml) were added [Ir(µ-Cl)(cod)]₂ (0.429 g, 0.639 mmol) and NaI (1.33 g, 8.86 mmol). The mixture was stirred at ambient temperature for 12 h. All volatiles were removed under reduced pressure and the residual washed with five portions of water (15 ml). The washings were monitored using aqueous silver nitrate. The resulting solid was washed with ethanol (10 ml) and dried in vacuo to yield [Ir(µ-I)(cod)]₂ as a deep-red solid (0.441 g, 81%). Recrystallization from THF afforded an analytically pure product; m.pt. 522–527 K (dec.). ¹H NMR (CDCl₃, 308 K, 300 MHz, δ, p.p.m.): 4.43–4.44 (m, 8H, =CH), 2.10–2.14 (m, 8H, –CHH–), 1.13–1.36 (m, 8H, –CHH–). Analysis found: C 22.82, H 2.86%; C₁₆H₂₄I₂Ir₂ requires: C 22.49, H 2.83%.

S3. Refinement

All H-atoms were included in the riding model approximation with C—H distances in the range 0.95–0.99 Å, and with U_iso(H) = 1.2U_eq(C) [or 1.5U_eq(C) for methyl groups]. The final difference Fourier map gave a maximum peak of 5.91 e Å^-3 2.58 Å from the Ir atom and 2.35 Å from the I atom. The minimum hole of -5.04 e Å^-3 was 0.66 Å from the Ir atom.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO; data reduction: TEXSAN (Rigaku/MSC, 2004); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97; molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level. The carbon-bound H-atoms have been omitted for clarity. Symmetry code: (i) 1 - x, y, 3/2 - z.

Di-µ-iodido-bis[(η⁴-cycloocta-1,5-diene)iridium(I)]

Crystal data

[Ir2I2(C8H12)2]	F(000) = 1520
Mr = 854.56	Dx = 3.280 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71075 Å
Hall symbol: -C 2yc	Cell parameters from 41734 reflections
a = 12.3438 (4) Å	θ = 3.1–31.9°
b = 11.8161 (4) Å	µ = 18.92 mm^−1
c = 11.9435 (3) Å	T = 100 K
β = 96.6568 (14)°	Platelet, red
V = 1730.28 (10) Å^3	0.39 × 0.28 × 0.22 mm
Z = 4

Data collection

Rigaku R-AXIS RAPID imaging-plate diffractometer	2909 independent reflections
Radiation source: normal-focus sealed tube	2909 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.095
Detector resolution: 10.00 pixels mm^-1	θmax = 31.6°, θmin = 3.1°
ω scans	h = −18→18
Absorption correction: numerical (NUMABS; Higashi, 1999)	k = −17→17
Tmin = 0.018, Tmax = 0.200	l = −17→17
27799 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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.102	H-atom parameters constrained
S = 1.19	w = 1/[σ^2(Fo^2) + (0.0244P)^2 + 97.8696P] where P = (Fo^2 + 2Fc^2)/3
2909 reflections	(Δ/σ)max = 0.001
91 parameters	Δρmax = 5.91 e Å^−3
0 restraints	Δρmin = −5.04 e Å^−3

Special details

Experimental. Indexing was performed from 3 oscillations which were exposed for 2.0 minutes. The camera radius was 127.40 mm. Readout performed in the 0.100 mm pixel mode. #1 Phi=0.0, chi=55.0, omega=80.0 to 260.0 with 2.0deg step #2 Phi=180.0, chi=45.0, omega=0.0 to 180.0 with 2.0deg step #3 Phi=90.0, chi=20.0, omega=0.0 to 120.0 with 2.0deg step #4 Phi=180.0, chi= -5.0, omega=0.0 to 120.0 with 2.0deg step A total of 300 images, corresponding to 600.0 °. Osillation angles were collected with 4 different goniometer setting. Exposure time was 2.0 minutes per degree. The camera radius was 127.40 mm. Readout was performed in the 0.100 mm pixel mode.

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

8.2950 (0.0021) x - 8.7297 (0.0018) y - 1.5346 (0.0022) z = 0.3948 (0.0020)

* 0.0000 (0.0000) Ir * 0.0000 (0.0000) I * 0.0000 (0.0000) I_$1

Rms deviation of fitted atoms = 0.0000

8.2950 (0.0021) x + 8.7297 (0.0019) y - 1.5346 (0.0022) z = 5.5983 (0.0018)

Angle to previous plane (with approximate e.s.d.) = 84.74 (0.01)

* 0.0000 (0.0000) Ir_$1 * 0.0000 (0.0000) I * 0.0000 (0.0000) I_$1

Rms deviation of fitted atoms = 0.0000

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
Ir	0.38310 (2)	0.18522 (2)	0.75987 (2)	0.01168 (9)
I	0.52845 (4)	0.29804 (4)	0.90380 (4)	0.01538 (11)
C1	0.3674 (7)	0.0519 (7)	0.8752 (7)	0.0168 (13)
H1	0.4422	0.0649	0.9002	0.020*
C2	0.2902 (6)	0.1384 (7)	0.8903 (7)	0.0167 (13)
H2	0.3161	0.2062	0.9269	0.020*
C3	0.1697 (7)	0.1290 (8)	0.8517 (8)	0.0223 (16)
H3A	0.1338	0.2018	0.8654	0.027*
H3B	0.1375	0.0700	0.8966	0.027*
C4	0.1472 (7)	0.0988 (8)	0.7252 (7)	0.0214 (15)
H4A	0.1357	0.0161	0.7176	0.026*
H4B	0.0793	0.1368	0.6928	0.026*
C5	0.2387 (6)	0.1330 (7)	0.6594 (7)	0.0179 (14)
H5	0.2383	0.2069	0.6280	0.021*
C6	0.3252 (7)	0.0589 (7)	0.6427 (7)	0.0180 (14)
H6	0.3789	0.0844	0.5977	0.022*
C7	0.3372 (8)	−0.0590 (8)	0.6926 (8)	0.0255 (17)
H7A	0.4074	−0.0915	0.6758	0.031*
H7B	0.2779	−0.1074	0.6560	0.031*
C8	0.3333 (8)	−0.0612 (7)	0.8202 (8)	0.0223 (16)
H8A	0.2583	−0.0797	0.8358	0.027*
H8B	0.3825	−0.1214	0.8539	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ir	0.01187 (13)	0.01351 (13)	0.00961 (13)	−0.00130 (8)	0.00106 (9)	−0.00053 (8)
I	0.0146 (2)	0.0182 (2)	0.0131 (2)	−0.00157 (16)	0.00073 (16)	−0.00549 (16)
C1	0.017 (3)	0.016 (3)	0.018 (3)	−0.002 (3)	0.003 (3)	0.003 (3)
C2	0.015 (3)	0.019 (3)	0.018 (3)	−0.006 (3)	0.007 (3)	−0.003 (3)
C3	0.022 (4)	0.021 (4)	0.025 (4)	0.001 (3)	0.004 (3)	−0.004 (3)
C4	0.013 (3)	0.028 (4)	0.023 (4)	−0.005 (3)	0.004 (3)	−0.004 (3)
C5	0.012 (3)	0.023 (4)	0.018 (3)	0.000 (3)	−0.002 (3)	−0.003 (3)
C6	0.016 (3)	0.023 (4)	0.015 (3)	−0.004 (3)	0.002 (3)	−0.003 (3)
C7	0.024 (4)	0.022 (4)	0.032 (5)	−0.002 (3)	0.006 (3)	−0.011 (3)
C8	0.023 (4)	0.017 (3)	0.028 (4)	−0.003 (3)	0.006 (3)	0.000 (3)

Geometric parameters (Å, º)

Ir—C1	2.116 (8)	C3—H3A	0.9900
Ir—C2	2.112 (7)	C3—H3B	0.9900
Ir—C5	2.122 (8)	C4—C5	1.504 (12)
Ir—C6	2.113 (8)	C4—H4A	0.9900
Ir—I	2.6901 (5)	C4—H4B	0.9900
Ir—I^i	2.6991 (6)	C5—C6	1.413 (12)
Ir—Ir^i	2.9228 (6)	C5—H5	0.9500
I—Ir^i	2.6991 (5)	C6—C7	1.516 (13)
C1—C2	1.422 (11)	C6—H6	0.9500
C1—C8	1.527 (12)	C7—C8	1.529 (14)
C1—H1	0.9500	C7—H7A	0.9900
C2—C3	1.511 (12)	C7—H7B	0.9900
C2—H2	0.9500	C8—H8A	0.9900
C3—C4	1.545 (12)	C8—H8B	0.9900
C2—Ir—C6	97.6 (3)	C2—C3—H3A	109.2
C2—Ir—C1	39.3 (3)	C4—C3—H3A	109.2
C6—Ir—C1	81.7 (3)	C2—C3—H3B	109.2
C2—Ir—C5	81.3 (3)	C4—C3—H3B	109.2
C6—Ir—C5	39.0 (3)	H3A—C3—H3B	107.9
C1—Ir—C5	91.0 (3)	C5—C4—C3	112.9 (7)
C2—Ir—I	92.1 (2)	C5—C4—H4A	109.0
C6—Ir—I	157.3 (2)	C3—C4—H4A	109.0
C1—Ir—I	93.3 (2)	C5—C4—H4B	109.0
C5—Ir—I	163.7 (2)	C3—C4—H4B	109.0
C2—Ir—I^i	164.4 (2)	H4A—C4—H4B	107.8
C6—Ir—I^i	90.2 (2)	C6—C5—C4	122.1 (8)
C1—Ir—I^i	156.1 (2)	C6—C5—Ir	70.2 (4)
C5—Ir—I^i	96.8 (2)	C4—C5—Ir	114.5 (5)
I—Ir—I^i	85.54 (2)	C6—C5—H5	118.9
C2—Ir—Ir^i	133.2 (2)	C4—C5—H5	118.9
C6—Ir—Ir^i	102.0 (2)	Ir—C5—H5	85.5
C1—Ir—Ir^i	102.6 (2)	C5—C6—C7	123.7 (8)
C5—Ir—Ir^i	136.6 (2)	C5—C6—Ir	70.9 (5)
I—Ir—Ir^i	57.305 (13)	C7—C6—Ir	112.3 (6)
I^i—Ir—Ir^i	57.008 (13)	C5—C6—H6	118.1
Ir—I—Ir^i	65.687 (15)	C7—C6—H6	118.1
C2—C1—C8	121.9 (7)	Ir—C6—H6	86.9
C2—C1—Ir	70.2 (4)	C6—C7—C8	113.2 (7)
C8—C1—Ir	114.3 (6)	C6—C7—H7A	108.9
C2—C1—H1	119.0	C8—C7—H7A	108.9
C8—C1—H1	119.0	C6—C7—H7B	108.9
Ir—C1—H1	85.7	C8—C7—H7B	108.9
C1—C2—C3	124.0 (7)	H7A—C7—H7B	107.7
C1—C2—Ir	70.5 (4)	C1—C8—C7	112.1 (7)
C3—C2—Ir	113.2 (6)	C1—C8—H8A	109.2
C1—C2—H2	118.0	C7—C8—H8A	109.2
C3—C2—H2	118.0	C1—C8—H8B	109.2
Ir—C2—H2	86.3	C7—C8—H8B	109.2
C2—C3—C4	112.0 (7)	H8A—C8—H8B	107.9
C2—Ir—I—Ir^i	142.2 (2)	C3—C4—C5—C6	91.6 (10)
C6—Ir—I—Ir^i	26.6 (6)	C3—C4—C5—Ir	10.4 (10)
C1—Ir—I—Ir^i	102.9 (2)	C2—Ir—C5—C6	−113.7 (5)
C5—Ir—I—Ir^i	−152.1 (8)	C1—Ir—C5—C6	−75.5 (5)
I^i—Ir—I—Ir^i	−53.207 (18)	I—Ir—C5—C6	179.2 (6)
C6—Ir—C1—C2	−112.9 (5)	I^i—Ir—C5—C6	81.9 (5)
C5—Ir—C1—C2	−74.9 (5)	Ir^i—Ir—C5—C6	34.2 (6)
I—Ir—C1—C2	89.3 (4)	C2—Ir—C5—C4	3.5 (6)
I^i—Ir—C1—C2	175.8 (4)	C6—Ir—C5—C4	117.2 (9)
Ir^i—Ir—C1—C2	146.5 (4)	C1—Ir—C5—C4	41.7 (7)
C2—Ir—C1—C8	117.0 (8)	I—Ir—C5—C4	−63.6 (12)
C6—Ir—C1—C8	4.1 (6)	I^i—Ir—C5—C4	−160.9 (6)
C5—Ir—C1—C8	42.0 (6)	Ir^i—Ir—C5—C4	151.4 (5)
I—Ir—C1—C8	−153.7 (6)	C4—C5—C6—C7	−2.6 (12)
I^i—Ir—C1—C8	−67.3 (9)	Ir—C5—C6—C7	104.5 (8)
Ir^i—Ir—C1—C8	−96.5 (6)	C4—C5—C6—Ir	−107.1 (7)
C8—C1—C2—C3	−1.6 (12)	C2—Ir—C6—C5	66.0 (5)
Ir—C1—C2—C3	105.4 (8)	C1—Ir—C6—C5	102.0 (5)
C8—C1—C2—Ir	−107.0 (7)	I—Ir—C6—C5	−179.4 (5)
C6—Ir—C2—C1	66.9 (5)	I^i—Ir—C6—C5	−100.5 (5)
C5—Ir—C2—C1	102.4 (5)	Ir^i—Ir—C6—C5	−156.7 (4)
I—Ir—C2—C1	−92.6 (4)	C2—Ir—C6—C7	−53.6 (6)
I^i—Ir—C2—C1	−173.6 (6)	C1—Ir—C6—C7	−17.5 (6)
Ir^i—Ir—C2—C1	−47.6 (5)	C5—Ir—C6—C7	−119.5 (8)
C6—Ir—C2—C3	−52.7 (6)	I—Ir—C6—C7	61.1 (9)
C1—Ir—C2—C3	−119.5 (8)	I^i—Ir—C6—C7	139.9 (6)
C5—Ir—C2—C3	−17.1 (6)	Ir^i—Ir—C6—C7	83.7 (6)
I—Ir—C2—C3	147.9 (6)	C5—C6—C7—C8	−53.0 (11)
I^i—Ir—C2—C3	66.9 (11)	Ir—C6—C7—C8	28.2 (9)
Ir^i—Ir—C2—C3	−167.1 (4)	C2—C1—C8—C7	91.0 (10)
C1—C2—C3—C4	−54.0 (11)	Ir—C1—C8—C7	10.0 (9)
Ir—C2—C3—C4	27.4 (9)	C6—C7—C8—C1	−24.7 (11)
C2—C3—C4—C5	−24.4 (11)

Symmetry code: (i) −x+1, y, −z+3/2.