Two polymorphs of [Rh(μ-I)(COD)]2

Ullery, D.R.; Moore, C.E.; Thomas, C.M.

doi:10.1107/S205698902100743X

Jerry P. Jasinski tribute

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ISSN: 2056-9890

Volume 77| Part 9| September 2021| Pages 871-874

https://doi.org/10.1107/S205698902100743X

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Two polymorphs of [Rh(μ-I)(COD)]₂

David R. Ullery,^a Curtis E. Moore ^a and Christine M. Thomas ^a ^*

^a100 W. 18<sup>th</sup> Ave., Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
^*Correspondence e-mail: thomas.3877@osu.edu

Edited by M. Zeller, Purdue University, USA (Received 2 July 2021; accepted 19 July 2021; online 27 July 2021)

The solid-state structure of di-μ-iodido-bis{[(1,2,5,6-η)-cycloocta-1,4-diene]rhodium(I)}, [Rh₂I₂(C₈H₁₂)₂] or [Rh(μ-I)(COD)]₂, was determined from two crystals with different morphologies, which were found to correspond to two polymorphs containing Rh dimers with significantly different molecular structures. Both polymorphs are monoclinic and the [Rh(μ-I)(COD)]₂ molecules in each case possess C₂v symmetry. However, the core geometry of the butterfly-shaped Rh₂I₂ core differs substantially. In the C2/c polymorph, the core geometry of [Rh(μ-I)(COD)]₂^B is bent, with a hinge angle of 96.13 (8)° and a Rh⋯Rh distance of 2.9612 (11) Å. The P2₁/c polymorph features a more planar [Rh(μ-I)(COD)]₂^P core geometry, with a hinge angle of 145.69 (9)° and a Rh⋯Rh distance of 3.7646 (5) Å.

Keywords: crystal structure; polymorph; rhodium; dimer.

CCDC references: 2097568; 2097567

1. Chemical context

Compounds of the type [M(μ-X)(COD)]₂, (M = Ir, Rh, X = Cl, Br, I) are ubiquitous synthons for Rh and Ir catalysts. As a representative example, [Rh(COD)(DPEphos)]BF₄ catalyzes the hydroamination of vinylarenes with anti-Markovnikov selectivity, and is prepared via the reaction of [Rh(μ-Cl)(COD)]₂ with two equivalents of AgBF₄ and two equivalents of DPEphos (Utsunomiya et al., 2003 ). Within the series [M(μ-X)(COD)]₂ (M = Ir, Rh; X = Cl, Br, I), all compounds have been structurally characterized with the notable exception of [Rh(μ-I)(COD)]₂ (De Ridder & Imhoff, 1994 ; Pettinari et al., 2002 ; Cotton et al., 1986 ; Yamagata et al., 2007a ,b ). Thus, crystallographic characterization of the title compound was pursued to complete the series.

2. Structural commentary

Crystallization of [Rh(μ-I)(COD)]₂ in toluene at 236 K produced two types of crystals with different colors and morphologies, namely dark-orange and yellow–orange blocks. A representative crystal of each type was subjected to single crystal X-ray diffraction, revealing two different polymorphs of [Rh(μ-I)(COD)]₂ containing dimers with significantly different structural features. X-ray diffraction of the dark-orange crystals revealed that [Rh(μ-I)(COD)]₂ crystallized in the monoclinic C2/c space group in this polymorph. The molecular structure of [Rh(μ-I)(COD)]₂^B exhibited a C₂v-symmetric geometry featuring a bent Rh₂I₂ diamond core (Fig. 1). The hinge angle, defined as the angle between the intersecting planes that contain the iodide ligands and each rhodium, is 96.13 (8)° and the Rh⋯Rh distance is 2.9612 (11) Å. [Rh(μ-I)(COD)]₂^B exhibits a geometry significantly different from that of [Rh(μ-Cl)(COD)]₂ and [Rh(μ-Br)(COD)]₂, which both exhibit more planar Rh₂X₂ cores with hinge angles of 169.08 (6) and 148.74 (7)° and Rh⋯Rh distances of 3.5169 (6) and 3.5648 (14) Å, respectively (De Ridder & Imhoff, 1994; Pettinari et al., 2002). However, the hinge angle of [Rh(μ-I)(COD)]₂^B is similar to that of [Ir(μ-I)(COD)]₂ [95.26 (1)°; Yamagata et al., 2007b].

Figure 1
Bent structure of [Rh(μ-I)(COD)]₂^B within the monoclinic C2/c polymorph. Independent atoms are labelled, while the other half of the molecule is symmetry-generated through a twofold rotation axis. Ellipsoids are drawn at the 50% probability level. Hydrogen atoms are removed for clarity.

X-ray diffraction of the yellow–orange crystals revealed a different polymorph of [Rh(μ-I)(COD)]₂, this time crystallizing in the monoclinic P2₁/c space group. The geometry of the dirhodium dimer in the P2₁/c polymorph [Rh(μ-I)(COD)]₂^P differs significantly from the C2/c polymorph [Rh(μ-I)(COD)]₂^B. The Rh₂I₂ core geometry of [Rh(μ-I)(COD)]₂^P is more planar, with a hinge angle of 145.69 (9)° and a Rh⋯Rh distance of 3.7646 (5) Å (Fig. 2). The molecular structure of [Rh(μ-I)(COD)]₂^P is therefore similar to [Rh(μ-Cl)(COD)]₂ and [Rh(μ-Br)(COD)]₂ (De Ridder & Imhoff, 1994; Pettinari et al., 2002).

Figure 2
Planar structure of [Rh(μ-I)(COD)]₂^P within the monoclinic P2₁/c polymorph. Ellipsoids are drawn at the 50% probability level. Hydrogen atoms are removed for clarity.

A previous theoretical study found relatively small energetic differences (< 10 kcal mol⁻¹) between planar and bent [Rh(μ-X)(L)₂]₂ geometries (Aullón et al., 1998 ). By analyzing the donor–acceptor interactions between d_z² and p_z orbitals of the two metal atoms, it was determined that the stability of bent morphologies increases as the electronegativity of the bridging ligand decreases. The degree of bending was predicted to increase in the order Cl < Br < I, consistent with the observation of a bent structure for [Rh(μ-I)(COD)]₂^B but not [Rh(μ-Cl)(COD)]₂ and [Rh(μ-Br)(COD)]₂ (Aullón et al., 1998). Moreover, Aullón and coworkers predicted the bent form to be more stable for Ir than for Rh, in line with the exclusive observation of a bent geometry for [Ir(μ-I)(COD)]₂, but the possibility of both planar and bent forms for [Rh(μ-I)(COD)]₂.

There is no meaningful difference between the two independent Rh—I distances in [Rh(μ-I)(COD)]₂^B [2.7072 (7) and 2.6975 (7) Å]. The four Rh—I distances in [Rh(μ-I)(COD)]₂^P are slightly less symmetric: the bonds between I2 and the two Rh centers [2.6833 (4) and 2.6738 (4) Å] are slightly shorter than those associated with I1 [2.6998 (4) and 2.7061 (4) Å]. Similarly, the Rh—C distances in [Rh(μ-I)(COD)]₂^B are more symmetric, ranging from 2.115 (6) to 2.122 (6) Å, while the Rh—C distances in [Rh(μ-I)(COD)]₂^P range from 2.117 (4) to 2.131 (4) Å. The average Rh—C distance in the bent and planar structures are similar to the average Rh—C distances reported for the [Rh(μ-Cl)(COD)]₂ and [Rh(μ-Br)(COD)]₂ analogues (De Ridder & Imhoff, 1994; Pettinari et al., 2002), with all four compounds having an average Rh—C distance of 2.12 Å. As expected based on the inherent differences in covalent radii, the average Rh—I distances in [Rh(μ-I)(COD)]₂^B and [Rh(μ-I)(COD)]₂^P (2.70 and 2.69 Å, respectively) are considerably longer than the average Rh—Br and Rh—Cl distances in [Rh(μ-Br)(COD)]₂ and [Rh(μ-Cl)(COD)]₂ (2.54 and 2.38 Å, respectively).

3. Supramolecular features

The structural differences between the dimers in the two polymorphs of [Rh(μ-I)(COD)]₂ are attributed to differences in crystal packing and weak interatomic forces. The bent and planar geometries are likely similar in energy. Stabilization of the bent geometry in [Rh(μ-I)(COD)]₂^B arises from intramolecular dispersion forces between the C—H bonds of the cyclooctadiene ligands on the two Rh centers within each molecule. Indeed there are four close C—H⋯H—C contacts (H2⋯H5 = 2.64 Å; H3A⋯H4B = 2.66 Å) between the alkene and methylene hydrogen atoms made possible by the bent geometry (Fig. 3). In the case of [Rh(μ-I)(COD)]₂^P, no such intramolecular C—H⋯H—C interactions are present. The shortest intermolecuar interactions in [Rh(μ-I)(COD)]₂^P are two Rh⋯H—C contacts in the apical positions of Rh2 (Rh2⋯H16A(1 − x, 1 − y, −z) = 2.67 Å; Rh2⋯H3A(2 − x, 1 − y, 1 − z) = 2.93 Å) that could, at best, be labeled as weak intermolecular agostic interactions (Fig. 4). Consistent with the intermolecular interactions in the planar structure, the P2₁/c has a higher density (2.621 g cm⁻³) than the bent C2/c polymorph (2.597 g cm⁻³), indicative of tighter crystal packing.

Figure 3
Diagram of [Rh(μ-I)(COD)]₂^B showing weak intramolecular C—H⋯H—C dispersion interactions between the two COD molecules on the two Rh centers.

Figure 4
Diagram of [Rh(μ-I)(COD)]₂^P showing weak intermolecular C—H⋯Rh interactions between adjacent molecules.

4. Synthesis and crystallization

[Rh(μ-I)(COD)]₂ was prepared according to the procedure described by J. A. Hlina et al. (2017 ). Under a nitrogen atmosphere, [Rh(μ-Cl)(COD)]₂ (312.0 mg, 0.6323 mmol) was added to toluene (5 mL) and trimethylsilyl iodide (184.6 µL, 1.297 mmol). The reaction mixture turned dark red and rust-colored crystals precipitated from the solution. The solid was isolated, washed with hexanes and dried in vacuo to yield the final product [Rh(μ-I)(COD)]₂ as a red–brown crystalline solid (358.5 mg, 84%). X-ray quality crystals were grown from a concentrated solution of toluene at 236 K, resulting in crystals with two different morphologies. ¹H NMR (C₆D₆): 1.15–1.28 (m, 8H, –CHH–), 1.90–2.05 (m, 8H, –CHH–), 4.62–4.70 (m, 8H, =CH). A single species was observed by ¹H NMR spectroscopy and the ¹H NMR spectrum did not contain any broad features indicative of dynamic behavior or interconversion between the two isomers in solution.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. Crystals were mounted on MiTeGen Micromounts with Paratone 24EX oil. Data were collected in a nitrogen gas stream at 100 (2) K using φ and ω scans. Solution by direct methods (SHELXT) produced a complete phasing model for refinement. All non-hydrogen atoms were refined anisotropically by full-matrix least-squares (SHELXL2018). All carbon-bonded methylene hydrogen atoms were placed using a riding model. Their positions were constrained relative to their parent atom using the appropriate HFIX command in SHELXL2018. All carbon-bonded methine hydrogen atoms were located in the difference map. Their C—H distances were restrained to a target value of 1.00 (2) Å. For all H atoms, displacement parameter U_iso(H) values were set to 1.2 times U_eq(C).

Table 1
Experimental details

	[Rh(μ-I)(COD)]₂^B	[Rh(μ-I)(COD)]₂^P
Crystal data
Chemical formula	[Rh₂I₂(C₈H₁₂)₂]	[Rh₂I₂(C₈H₁₂)₂]
M_r	675.97	675.97
Crystal system, space group	Monoclinic, C2/c	Monoclinic, P2₁/c
Temperature (K)	100	100
a, b, c (Å)	12.3414 (16), 11.8176 (17), 11.9374 (15)	10.4505 (5), 19.390 (1), 8.6271 (4)
β (°)	96.690 (3)	101.523 (2)
V (Å³)	1729.2 (4)	1712.92 (14)
Z	4	4
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	5.47	5.52
Crystal size (mm)	0.10 × 0.06 × 0.03	0.15 × 0.14 × 0.09

Data collection
Diffractometer	Nonius Kappa APEXII	Nonius Kappa APEXII
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )	Multi-scan (SADABS; Krause et al., 2015)
T_min, T_max	0.062, 0.093	0.057, 0.093
No. of measured, independent and observed [I > 2σ(I)] reflections	15175, 1775, 1320	38760, 3519, 2922
R_int	0.080	0.051

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.079, 1.03	0.025, 0.055, 1.07
No. of reflections	1775	3519
No. of parameters	103	205
No. of restraints	4	8
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	1.36, −0.79	1.26, −0.67
Computer programs: APEX3 and SAINT (Bruker, 2017 ), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC references: 2097568; 2097567

Crystal structure: contains datablocks global, B, P. DOI: https://doi.org/10.1107/S205698902100743X/zl5015sup1.cif

Structure factors: contains datablock B. DOI: https://doi.org/10.1107/S205698902100743X/zl5015Bsup2.hkl

Structure factors: contains datablock P. DOI: https://doi.org/10.1107/S205698902100743X/zl5015Psup3.hkl

checkCIF report

Computing details top

For both structures, data collection: APEX3 (Bruker, 2017); cell refinement: SAINT (Bruker, 2017); data reduction: SAINT (Bruker, 2017); program(s) used to solve structure: ShelXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Di-µ-iodido-bis{[(1,2,5,6-η)-cycloocta-1,4-diene]rhodium(I)} (B) top

Crystal data top

[Rh₂I₂(C₈H₁₂)₂]	F(000) = 1264
M_r = 675.97	D_x = 2.597 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.3414 (16) Å	Cell parameters from 2574 reflections
b = 11.8176 (17) Å	θ = 2.8–23.3°
c = 11.9374 (15) Å	µ = 5.47 mm⁻¹
β = 96.690 (3)°	T = 100 K
V = 1729.2 (4) Å³	Block, dark orange
Z = 4	0.10 × 0.06 × 0.03 mm

Data collection top

Nonius Kappa APEXII diffractometer	1775 independent reflections
Radiation source: sealed tube, fine-focus	1320 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.080
Detector resolution: 7.9 pixels mm^-1	θ_max = 26.4°, θ_min = 2.4°
ω and φ scans	h = −15→15
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −14→14
T_min = 0.062, T_max = 0.093	l = −14→14
15175 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.035	Hydrogen site location: mixed
wR(F²) = 0.079	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ²(F_o²) + (0.0302P)²] where P = (F_o² + 2F_c²)/3
1775 reflections	(Δ/σ)_max < 0.001
103 parameters	Δρ_max = 1.36 e Å⁻³
4 restraints	Δρ_min = −0.79 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
I1	0.52770 (3)	0.20354 (3)	0.40381 (4)	0.02475 (15)
Rh1	0.38142 (4)	0.31608 (4)	0.25934 (4)	0.02137 (15)
C1	0.2885 (6)	0.3639 (6)	0.3898 (6)	0.0274 (16)
H1	0.309 (5)	0.316 (5)	0.458 (3)	0.033*
C2	0.3652 (5)	0.4497 (6)	0.3749 (5)	0.0255 (15)
H2	0.433 (3)	0.456 (5)	0.429 (4)	0.031*
C3	0.3323 (6)	0.5616 (5)	0.3199 (6)	0.0294 (16)
H3A	0.380935	0.621981	0.354264	0.035*
H3B	0.256778	0.580087	0.333793	0.035*
C4	0.3390 (6)	0.5579 (5)	0.1903 (6)	0.0312 (17)
H4A	0.282371	0.608659	0.152182	0.037*
H4B	0.410972	0.587248	0.175166	0.037*
C5	0.3237 (5)	0.4422 (6)	0.1410 (6)	0.0273 (16)
H5	0.357 (5)	0.418 (5)	0.074 (3)	0.033*
C6	0.2378 (5)	0.3707 (5)	0.1589 (5)	0.0229 (15)
H6	0.219 (5)	0.306 (3)	0.107 (4)	0.028*
C7	0.1447 (5)	0.4044 (6)	0.2257 (5)	0.0295 (16)
H7A	0.076675	0.366941	0.192462	0.035*
H7B	0.133403	0.487216	0.219759	0.035*
C8	0.1680 (5)	0.3714 (6)	0.3502 (6)	0.0286 (16)
H8A	0.134470	0.428113	0.396580	0.034*
H8B	0.133657	0.297304	0.361920	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I1	0.0234 (3)	0.0275 (2)	0.0232 (3)	0.00135 (18)	0.00190 (18)	0.00455 (18)
Rh1	0.0203 (3)	0.0237 (3)	0.0200 (3)	0.0009 (2)	0.0018 (2)	0.0007 (2)
C1	0.031 (4)	0.029 (4)	0.024 (4)	0.000 (3)	0.007 (3)	−0.004 (3)
C2	0.028 (4)	0.027 (4)	0.022 (4)	0.004 (3)	0.003 (3)	−0.004 (3)
C3	0.030 (4)	0.020 (4)	0.038 (4)	0.005 (3)	0.006 (3)	−0.002 (3)
C4	0.028 (4)	0.024 (4)	0.042 (5)	0.003 (3)	0.006 (3)	0.008 (3)
C5	0.025 (4)	0.034 (4)	0.022 (4)	0.004 (3)	−0.001 (3)	0.004 (3)
C6	0.025 (4)	0.025 (4)	0.017 (4)	0.002 (3)	−0.006 (3)	−0.003 (3)
C7	0.024 (4)	0.029 (4)	0.034 (4)	0.005 (3)	−0.001 (3)	0.002 (3)
C8	0.029 (4)	0.026 (4)	0.031 (4)	0.002 (3)	0.006 (3)	0.005 (3)

Geometric parameters (Å, º) top

I1—Rh1	2.6975 (7)	C1—C8	1.509 (9)
I1—Rh1ⁱ	2.7072 (7)	C2—C3	1.510 (9)
Rh1—Rh1ⁱ	2.9612 (11)	C3—C4	1.560 (9)
Rh1—C1	2.115 (6)	C4—C5	1.492 (9)
Rh1—C2	2.122 (6)	C5—C6	1.392 (9)
Rh1—C5	2.119 (7)	C6—C7	1.526 (9)
Rh1—C6	2.121 (6)	C7—C8	1.532 (9)
C1—C2	1.413 (9)

Rh1—I1—Rh1ⁱ	66.45 (2)	C6—Rh1—I1	164.61 (18)
I1—Rh1—I1ⁱ	85.13 (2)	C6—Rh1—Rh1ⁱ	136.51 (18)
I1ⁱ—Rh1—Rh1ⁱ	56.621 (18)	C6—Rh1—C2	90.3 (2)
I1—Rh1—Rh1ⁱ	56.933 (19)	C2—C1—Rh1	70.8 (4)
C1—Rh1—I1ⁱ	165.07 (19)	C2—C1—C8	124.6 (6)
C1—Rh1—I1	92.3 (2)	C8—C1—Rh1	112.6 (4)
C1—Rh1—Rh1ⁱ	132.91 (19)	C1—C2—Rh1	70.3 (4)
C1—Rh1—C2	39.0 (2)	C1—C2—C3	122.2 (6)
C1—Rh1—C5	97.7 (3)	C3—C2—Rh1	114.2 (5)
C1—Rh1—C6	81.1 (3)	C2—C3—C4	111.4 (5)
C2—Rh1—I1ⁱ	155.75 (18)	C5—C4—C3	113.4 (5)
C2—Rh1—I1	93.32 (18)	C4—C5—Rh1	111.4 (5)
C2—Rh1—Rh1ⁱ	102.57 (18)	C6—C5—Rh1	70.9 (4)
C5—Rh1—I1	157.07 (18)	C6—C5—C4	124.1 (6)
C5—Rh1—I1ⁱ	90.08 (18)	C5—C6—Rh1	70.8 (4)
C5—Rh1—Rh1ⁱ	102.03 (18)	C5—C6—C7	123.7 (6)
C5—Rh1—C2	82.0 (3)	C7—C6—Rh1	114.5 (4)
C5—Rh1—C6	38.3 (2)	C6—C7—C8	111.9 (5)
C6—Rh1—I1ⁱ	97.57 (17)	C1—C8—C7	112.7 (5)

Symmetry code: (i) −x+1, y, −z+1/2.

Di-µ-iodido-bis{[(1,2,5,6-η)-cycloocta-1,4-diene]rhodium(I)} (P) top

Crystal data top

[Rh₂I₂(C₈H₁₂)₂]	F(000) = 1264
M_r = 675.97	D_x = 2.621 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.4505 (5) Å	Cell parameters from 9797 reflections
b = 19.390 (1) Å	θ = 2.6–26.4°
c = 8.6271 (4) Å	µ = 5.52 mm⁻¹
β = 101.523 (2)°	T = 100 K
V = 1712.92 (14) Å³	Block, yellow-orange
Z = 4	0.14 × 0.14 × 0.09 mm

Data collection top

Nonius Kappa APEXII diffractometer	3519 independent reflections
Radiation source: sealed tube, fine-focus	2922 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.051
Detector resolution: 7.9 pixels mm^-1	θ_max = 26.4°, θ_min = 2.0°
ω and φ scans	h = −13→13
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −24→24
T_min = 0.057, T_max = 0.093	l = −9→10
38760 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.025	Hydrogen site location: mixed
wR(F²) = 0.055	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ²(F_o²) + (0.0284P)²] where P = (F_o² + 2F_c²)/3
3519 reflections	(Δ/σ)_max = 0.001
205 parameters	Δρ_max = 1.26 e Å⁻³
8 restraints	Δρ_min = −0.67 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
I1	0.73024 (3)	0.56233 (2)	0.46409 (3)	0.02018 (8)
I2	0.89372 (2)	0.46580 (2)	0.19408 (3)	0.02188 (8)
Rh1	0.80485 (3)	0.42940 (2)	0.45350 (4)	0.01765 (9)
Rh2	0.72305 (3)	0.57016 (2)	0.14928 (4)	0.01730 (9)
C1	0.7956 (4)	0.3230 (2)	0.3955 (5)	0.0205 (9)
H1	0.778 (4)	0.318 (2)	0.280 (2)	0.025*
C2	0.9215 (4)	0.3392 (2)	0.4781 (5)	0.0229 (9)
H2	0.990 (3)	0.346 (2)	0.416 (4)	0.027*
C3	0.9741 (4)	0.3226 (2)	0.6498 (5)	0.0253 (10)
H3A	1.059815	0.345583	0.683485	0.030*
H3B	0.988454	0.272270	0.660875	0.030*
C4	0.8836 (4)	0.3453 (2)	0.7597 (5)	0.0261 (10)
H4A	0.827646	0.306003	0.776878	0.031*
H4B	0.937029	0.358549	0.863519	0.031*
C5	0.7978 (4)	0.4056 (2)	0.6927 (5)	0.0241 (10)
H5	0.814 (4)	0.4466 (15)	0.756 (5)	0.029*
C6	0.6732 (4)	0.3985 (2)	0.5982 (5)	0.0198 (9)
H6	0.607 (3)	0.4340 (16)	0.602 (5)	0.024*
C7	0.6093 (4)	0.3303 (2)	0.5424 (5)	0.0234 (9)
H7A	0.529071	0.339182	0.462128	0.028*
H7B	0.583454	0.306526	0.632950	0.028*
C8	0.6995 (4)	0.2832 (2)	0.4711 (5)	0.0240 (9)
H8A	0.748312	0.253106	0.555256	0.029*
H8B	0.645911	0.253237	0.390385	0.029*
C9	0.6610 (4)	0.5469 (2)	−0.0943 (5)	0.0206 (9)
H9	0.679 (4)	0.4967 (11)	−0.103 (5)	0.025*
C10	0.7642 (4)	0.5945 (2)	−0.0773 (5)	0.0208 (9)
H10	0.847 (3)	0.5720 (19)	−0.087 (5)	0.025*
C11	0.7443 (4)	0.6700 (2)	−0.1207 (5)	0.0247 (10)
H11A	0.665144	0.675101	−0.204767	0.030*
H11B	0.819921	0.686915	−0.162912	0.030*
C12	0.7293 (4)	0.7139 (2)	0.0242 (5)	0.0237 (9)
H12A	0.816605	0.729810	0.079190	0.028*
H12B	0.676206	0.755212	−0.012730	0.028*
C13	0.6659 (4)	0.6751 (2)	0.1393 (5)	0.0228 (9)
H13	0.685 (4)	0.693 (2)	0.250 (3)	0.027*
C14	0.5529 (4)	0.6343 (2)	0.0998 (5)	0.0210 (9)
H14	0.501 (3)	0.626 (2)	0.181 (4)	0.025*
C15	0.4755 (4)	0.6267 (2)	−0.0676 (5)	0.0240 (9)
H15A	0.485798	0.669082	−0.128031	0.029*
H15B	0.381741	0.621703	−0.064695	0.029*
C16	0.5200 (4)	0.5641 (2)	−0.1526 (5)	0.0233 (9)
H16A	0.466146	0.523646	−0.136871	0.028*
H16B	0.504985	0.573709	−0.267501	0.028*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I1	0.02462 (15)	0.01759 (15)	0.01827 (15)	0.00106 (11)	0.00414 (11)	0.00015 (11)
I2	0.02106 (15)	0.02275 (16)	0.02346 (15)	0.00440 (11)	0.00840 (11)	0.00442 (12)
Rh1	0.01825 (17)	0.01641 (17)	0.01870 (17)	0.00044 (13)	0.00467 (13)	0.00062 (13)
Rh2	0.01825 (17)	0.01664 (17)	0.01712 (17)	0.00074 (13)	0.00379 (13)	0.00049 (13)
C1	0.028 (2)	0.014 (2)	0.021 (2)	0.0024 (17)	0.0100 (18)	−0.0021 (18)
C2	0.024 (2)	0.018 (2)	0.029 (2)	0.0044 (18)	0.0087 (18)	0.0019 (19)
C3	0.021 (2)	0.026 (2)	0.029 (2)	0.0061 (18)	0.0056 (18)	0.004 (2)
C4	0.032 (3)	0.022 (2)	0.023 (2)	0.0001 (19)	0.0030 (19)	−0.0015 (19)
C5	0.033 (3)	0.021 (2)	0.019 (2)	0.001 (2)	0.0093 (19)	0.0014 (19)
C6	0.019 (2)	0.019 (2)	0.022 (2)	0.0040 (17)	0.0069 (17)	−0.0012 (18)
C7	0.021 (2)	0.024 (2)	0.026 (2)	−0.0016 (18)	0.0056 (18)	0.0011 (19)
C8	0.028 (2)	0.020 (2)	0.024 (2)	0.0007 (18)	0.0052 (18)	−0.0011 (18)
C9	0.026 (2)	0.023 (2)	0.013 (2)	0.0013 (18)	0.0045 (17)	−0.0008 (18)
C10	0.023 (2)	0.025 (2)	0.018 (2)	0.0030 (18)	0.0099 (17)	−0.0014 (18)
C11	0.027 (2)	0.025 (2)	0.023 (2)	−0.0018 (19)	0.0065 (18)	0.0073 (19)
C12	0.029 (2)	0.018 (2)	0.022 (2)	−0.0015 (18)	0.0003 (18)	0.0016 (18)
C13	0.029 (2)	0.017 (2)	0.021 (2)	0.0051 (18)	−0.0001 (18)	−0.0013 (18)
C14	0.024 (2)	0.017 (2)	0.022 (2)	0.0081 (18)	0.0060 (18)	0.0019 (18)
C15	0.024 (2)	0.020 (2)	0.028 (2)	0.0031 (18)	0.0020 (19)	0.0023 (19)
C16	0.026 (2)	0.023 (2)	0.019 (2)	−0.0014 (18)	0.0011 (18)	−0.0002 (18)

Geometric parameters (Å, º) top

I1—Rh1	2.6998 (4)	C2—C3	1.509 (6)
I1—Rh2	2.7061 (4)	C3—C4	1.531 (6)
I2—Rh1	2.6833 (4)	C4—C5	1.516 (6)
I2—Rh2	2.6738 (4)	C5—C6	1.398 (6)
Rh1—C1	2.120 (4)	C6—C7	1.516 (6)
Rh1—C2	2.117 (4)	C7—C8	1.526 (5)
Rh1—C5	2.131 (4)	C9—C10	1.404 (6)
Rh1—C6	2.120 (4)	C9—C16	1.496 (6)
Rh2—C9	2.120 (4)	C10—C11	1.514 (6)
Rh2—C10	2.137 (4)	C11—C12	1.547 (6)
Rh2—C13	2.117 (4)	C12—C13	1.501 (6)
Rh2—C14	2.142 (4)	C13—C14	1.405 (6)
C1—C2	1.400 (6)	C14—C15	1.514 (6)
C1—C8	1.514 (6)	C15—C16	1.538 (6)

Rh1—I1—Rh2	88.274 (12)	C2—C1—Rh1	70.6 (2)
Rh2—I2—Rh1	89.290 (12)	C2—C1—C8	122.2 (4)
I2—Rh1—I1	85.839 (12)	C8—C1—Rh1	113.4 (3)
C1—Rh1—I1	159.56 (12)	C1—C2—Rh1	70.8 (2)
C1—Rh1—I2	93.80 (11)	C1—C2—C3	124.9 (4)
C1—Rh1—C5	90.54 (16)	C3—C2—Rh1	111.4 (3)
C2—Rh1—I1	161.67 (12)	C2—C3—C4	113.4 (3)
C2—Rh1—I2	90.72 (11)	C5—C4—C3	112.2 (3)
C2—Rh1—C1	38.60 (16)	C4—C5—Rh1	113.8 (3)
C2—Rh1—C5	81.67 (16)	C6—C5—Rh1	70.4 (2)
C2—Rh1—C6	97.81 (16)	C6—C5—C4	123.8 (4)
C5—Rh1—I1	96.17 (12)	C5—C6—Rh1	71.2 (2)
C5—Rh1—I2	161.76 (12)	C5—C6—C7	124.8 (4)
C6—Rh1—I1	91.38 (11)	C7—C6—Rh1	110.9 (3)
C6—Rh1—I2	159.83 (11)	C6—C7—C8	112.4 (3)
C6—Rh1—C1	81.93 (16)	C1—C8—C7	112.6 (3)
C6—Rh1—C5	38.41 (16)	C10—C9—Rh2	71.4 (2)
I2—Rh2—I1	85.902 (12)	C10—C9—C16	125.0 (4)
C9—Rh2—I1	157.60 (12)	C16—C9—Rh2	111.8 (3)
C9—Rh2—I2	92.63 (12)	C9—C10—Rh2	70.1 (2)
C9—Rh2—C10	38.52 (16)	C9—C10—C11	123.0 (4)
C9—Rh2—C14	81.27 (16)	C11—C10—Rh2	113.4 (3)
C10—Rh2—I1	163.81 (12)	C10—C11—C12	111.3 (3)
C10—Rh2—I2	92.82 (11)	C13—C12—C11	112.8 (3)
C10—Rh2—C14	89.99 (16)	C12—C13—Rh2	110.5 (3)
C13—Rh2—I1	92.62 (12)	C14—C13—Rh2	71.7 (2)
C13—Rh2—I2	155.19 (12)	C14—C13—C12	125.6 (4)
C13—Rh2—C9	97.80 (16)	C13—C14—Rh2	69.8 (2)
C13—Rh2—C10	81.78 (16)	C13—C14—C15	123.3 (4)
C13—Rh2—C14	38.53 (16)	C15—C14—Rh2	113.5 (3)
C14—Rh2—I1	95.06 (11)	C14—C15—C16	112.1 (3)
C14—Rh2—I2	166.28 (11)	C9—C16—C15	112.7 (3)

Acknowledgements

The authors are grateful for access to the X-ray Diffraction Facility located in and supported by The Ohio State University Department of Chemistry and Biochemistry, as well as the support of The Ohio State University Sustainability Institute.

Funding information

Funding for this research was provided by: U.S. Department of Energy, Office of Science (award No. DE-SC0019179 to Christine M. Thomas).

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