[(1,2,5,6-η)-Cyclo­octa-1,5-diene]bis­(1-isopropyl-3-methyl­imidazolin-2-yl­idene)rhodium(I) tetra­fluorido­borate

Gary S Nichol; Jonathan Rajaseelan; David P Walton; Edward Rajaseelan

doi:10.1107/S1600536811049890

. 2011 Nov 30;67(Pt 12):m1860–m1861. doi: 10.1107/S1600536811049890

[(1,2,5,6-η)-Cycloocta-1,5-diene]bis(1-isopropyl-3-methylimidazolin-2-ylidene)rhodium(I) tetrafluoridoborate

Gary S Nichol ^a,^*, Jonathan Rajaseelan ^b, David P Walton ^c, Edward Rajaseelan ^c

PMCID: PMC3238752 PMID: 22199629

Abstract

In the title compound, [Rh(C₈H₁₂)(C₇H₁₂N₂)₂]BF₄, the square-planar Rh complex cation and the BF₄ ⁻ anion are both bisected by a crystallographic twofold rotation axis. The Rh and B atoms lie on this axis and all others are in general positions. In the crystal, two unique C—H⋯F hydrogen-bonding interactions are present, which involve both imidazolin-2-ylidene H atoms. They form two separate C(5) motifs, the combination of which is a rippled hydrogen-bonded sheet structure in the ab plane.

Related literature

For the structure and dynamics of related N-heterocyclic carbene rhodium and iridium complexes, see: Chianese et al. (2003 ▶); Köcher & Herrmann (1997 ▶); Leung et al. (2006 ▶); Nichol et al. (2009 ▶, 2010 ▶); Herrmann et al. (2006 ▶). For the catalytic properties of these complexes, see: Albrecht et al. (2002 ▶); Frey et al. (2006 ▶); Gnanamgari et al. (2007 ▶); Voutchkova et al. (2008 ▶).

Experimental

Crystal data

[Rh(C₈H₁₂)(C₇H₁₂N₂)₂]BF₄
M _r = 546.27
Orthorhombic,
a = 11.7508 (6) Å
b = 11.9283 (6) Å
c = 17.3129 (9) Å
V = 2426.7 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.75 mm⁻¹
T = 100 K
0.38 × 0.37 × 0.37 mm

Data collection

Bruker Kappa APEXII DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.763, T _max = 0.771
234794 measured reflections
14018 independent reflections
10241 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.020
wR(F ²) = 0.059
S = 1.13
14018 reflections
218 parameters
All H-atom parameters refined
Δρ_max = 1.55 e Å⁻³
Δρ_min = −0.92 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811049890/fj2478sup1.cif

e-67-m1860-sup1.cif^{(24.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811049890/fj2478Isup2.hkl

e-67-m1860-Isup2.hkl^{(685.3KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811049890/fj2478Isup3.cdx

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯F1ⁱ	0.909 (11)	2.496 (11)	3.3975 (8)	171.4 (10)
C3—H3⋯F2ⁱⁱ	0.877 (12)	2.478 (12)	3.2415 (8)	145.9 (11)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

JR and DPW thank the Department of Chemistry, Millersville University, for project funding. The diffractometer was purchased with funding from NSF grant CHE-0741837.

supplementary crystallographic information

Comment

We are interested in rhodium and iridium complexes with N-heterocyclic carbene ligands, in particular ligands derived from 1,2,4-triazole-derived compounds (Nichol et al., 2009, 2010). The title compound, (I), was prepared as part of this study (Figure 1). The Rh center has an expected square planar geometry and bond distances are unexceptional. Both the Rh and B atoms lie on a crystallographic twofold rotation axis, which bisects the complex and BF₄^- counterion. C–H···F hydrogen bonding interactions, which involve both imidazolin-2-ylidene H atoms and all four F atoms, form a thick two-dimensional sheet structure in the ab plane (Figure 2).

Experimental

The title compound was synthesized by transmetallation. 1-Isopropyl-3-methylimidazolium bromide (268 mg, 1.31 mmol) was mixed with Ag₂O (152 mg, 0.654 mmol), and was stirred under dark at room temperature for 90 minutes in 10 ml of CH₂Cl₂. The resulting mixture was filtered through Celite into a new flask containing the neutral compound [(cod)Rh(NHC)Cl](585 mg, 1.31 mmol), and AgBF₄(254 mg, 1.31 mmol)and stirred for an additional 90 minutes under dark. The mixture was filtered once more through Celite to remove silver bromide and silver chloride, and the solvent was removed under pressure to give a yellow solid (93%). Crystals of the resulting solid of the title compound, (I), were obtained by slow diffusion of pentane into dichloromethane solution of the compound. ¹H NMR (400 MHz, CDCl₃): δ (p.p.m.) = 7.15 (s, 2 H, NCH), 6.93 (s, 2 H, NCH), 5.03 (m, ³J_H—H = 6.8 Hz, 2 H, CH of ⁱPr), 4.63 (br, 2 H, CH of COD), 4.21 (s, 6 H, N—CH₃), 3.92 (m, 2 H, CH of COD), 2.63 (m, 2 H, CH₂ of COD), 2.42 – 1.92 (m, 6 H, CH₂ of COD), 1.46 (d, ³J_H—H = 6.8 Hz, 6 H, CH₃ of ⁱPr), 1.00 (d, ³J_H—H = 6.8 Hz, 6 H, CH₃ of ⁱPr). ¹³C NMR: δ = 178.76, 178.22 (Ir—C), 124, 117 (N—CH—N), 91.34, 91.25 (N-CHMe₃), 86.36, 86.28 (N—CH₃), 52.60 (CH of COD), 38.10, 33.75, 27.99, (CH₂ of COD), 23.5, 22.90 (CH₃ of ⁱPr).