Dichlorido(η6-p-cymene)(4-fluoro­aniline-κN)ruthenium(II)

Richard E Sykora; Andrew G Harris; Jason W Clements; Norris W Hoffman

doi:10.1107/S1600536810051962

. 2010 Dec 18;67(Pt 1):m99–m100. doi: 10.1107/S1600536810051962

Dichlorido(η⁶-p-cymene)(4-fluoroaniline-κN)ruthenium(II)

Richard E Sykora ^a, Andrew G Harris ^a, Jason W Clements ^a, Norris W Hoffman ^a,^*

PMCID: PMC3050405 PMID: 21522611

Abstract

The title compound, [RuCl₂(C₁₀H₁₄)(C₆H₆FN)], a pseudo-octahedral d ⁶ complex, has the expected piano-stool geometry around the Ru(II) atom. The fluoroaniline ring forms a dihedral angle of 19.3 (2)° with the p-cymene ring. In the crystal, two molecules form an inversion dimer via a pair of N—H⋯Cl hydrogen bonds. Weak intermolecular C—H⋯Cl interactions involving the p-cymene ring consolidate the crystal packing.

Related literature

For applications of (η⁶-p-cymene)Ru(II) dihalides in organic synthesis, see: Boutadla et al. (2010 ▶). For studies of (η⁶-arene)Ru(II) dihalides in bioinorganic chemistry, see: den Heeten et al. (2010 ▶). For anti-tumor medical applications of (η⁶-arene)Ru(II) systems, see: Hanif et al. (2010 ▶). For conversion of [(η⁶-p-cymene)RuCl₂]₂ with two molar equivalents of neutral unidentate nitrogen ligands into monomeric pseudo-octahedral piano-stool complexes of general formula (η⁶-p-cymene)Ru(N-ligand)Cl₂, see: Burrell & Steedman (1997 ▶); Govindaswamy & Kollipara (2006 ▶); Begley et al. (1991 ▶). For crystal structures of Ni-triad complexes of 4-fluoroaniline, see: Randell et al. (2006 ▶); Fawcett et al. (2005 ▶); Padmanabhan et al. (1985 ▶). For applications of ¹⁹F-NMR reporter moieties in monitoring ligand-substitution equilibria, see: Hoffman et al. (2009 ▶); Carter et al. (2004 ▶).

Experimental

Crystal data

[RuCl₂(C₁₀H₁₄)(C₆H₆FN)]
M _r = 417.30
Monoclinic,
a = 8.6492 (9) Å
b = 12.2458 (13) Å
c = 15.6471 (16) Å
β = 93.271 (8)°
V = 1654.6 (3) Å³
Z = 4
Mo Kα radiation
μ = 1.27 mm⁻¹
T = 290 K
0.26 × 0.25 × 0.20 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.635, T _max = 0.779
3234 measured reflections
3027 independent reflections
2284 reflections with I > 2σ(I)
R _int = 0.048
3 standard reflections every 120 min intensity decay: none

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.090
S = 1.00
3027 reflections
193 parameters
H-atom parameters constrained
Δρ_max = 0.57 e Å⁻³
Δρ_min = −0.67 e Å⁻³

Data collection: CAD-4-PC (Enraf–Nonius, 1993 ▶); cell refinement: CAD-4-PC; data reduction: XCAD-4PC (Harms & Wocadlo, 1995) ▶; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: OLEX2 (Dolomanov et al., 2009 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810051962/is2638sup1.cif

e-67-00m99-sup1.cif^{(18.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810051962/is2638Isup2.hkl

e-67-00m99-Isup2.hkl^{(148.6KB, hkl)}

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
N1—H1B⋯Cl2ⁱ	0.90	2.39	3.225 (3)	154
C6—H6⋯Cl1ⁱⁱ	0.93	2.72	3.384 (4)	129

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

Acknowledgments

The authors gratefully acknowledge the Department of Chemistry and the Univeristy Committee for Undergraduate Research at USA for their generous support and the Department of Energy and Oak Ridge National Laboratory for the diffractometer used in this study.

supplementary crystallographic information

Comment

The (η⁶-p-cymene)ruthenium(II)-dihalide motif has been used extensively for promotion of organic reactions (Boutadla et al., 2010), bioinorganic studies (den Heeten et al., 2010), and anti-tumor medical trials (Hanif et al., 2010). Treating the commercially available dimer, di-µ-chloridobis-[chlorido(p-cymene)ruthenium(II)], with two molar equivalents of many neutral unidentate ligands (L) generates two moles of (η⁶-p-cymene)Ru(L)Cl₂. The structures of several with aniline ligands (2,6-diisopropylphenyl, Burrell & Steedman, 1997; 4-chloro, Govindaswamy & Kollipara, 2006; 4-methyl, Begley, 1991) have been crystallographically determined. Structures of 4-fluoroaniline complexes have been reported for other late d-transition metals [palladium(II), Randell et al., 2006; Padmanabhan et al., 1985; nickel(II), Fawcett et al., 2005].

Our interest in studying relative binding affinities of soft metal centers for ligands of moderate and weak donor power using ¹⁹F and ³¹P NMR spectroscopy (Hoffman et al., 2009; Carter et al., 2004) to monitor ligand-substitution equilibria led us to prepare the title complex. Single crystals were grown from vapor diffusion of heptane into a benzene solution of the 4-fluoroaniline complex. The nitrogen atom in the 4-fluoroaniline ligand is essentially coplanar with its aromatic ring, whose plane is oriented slightly down and away from the plane of the p-cymene ring. Structural parameters were similar to those reported for the other (η⁶-p-cymene)Ru(4—X—C₆H₄NH₂)Cl₂ piano-stool complexes above. The Ru—Cl, Ru—N, and Ru—C distances are quite ordinary. Somewhat greater differences exist between structural parameters of interest in the 4-fluoroaniline complexes of the divalent Pd and Ni moieties, likely because of their dissimilar combinations of dⁿ configurations, coordination geometry, and ligand sets.

Our standard ligand-substitution reaction to determine relative affinities of neutral ligands (L) of moderate and weak donor power for (η⁶-p-cymene)RuCl₂ employs the equilibrium below (eq. 1), where P* is the very sterically hindered triaryl phosphite, P(O-2,4-Bu^t₂-C₆H₃)₃. Equilibrium constants are measured for different L employing

(η⁶-p-cymene)Ru(L)Cl₂ + P* = (η⁶-p-cymene)Ru(P*)Cl₂ + L (1)

(i) the integrals of the respective ³¹P resonances for free P* and Cl₂CymRu-P* and also (ii) the integrals of respective ¹H resonances (for either free P*/Ru—P* or Cl₂CymRu-L/Cl₂CymRu-P*). For L = 4-fluoroaniline, the ³¹P-NMR spectrum of the equilibrium solution afforded by mixing equimolar amounts of (η⁶-p-cymene)Ru(4—F—C₆H₄NH₂)Cl₂ and P* in CDCl₃ displayed just the two signals expected for free P* and Ru—P* (Fig. 2). However, the ¹⁹F NMR spectrum (Fig. 3) showed three resonances, a quick indication that our standard Cl₂CymRu-L experimental design was invalid for use with anilines.

Experimental

All solvents in synthesis were Fisher reagent-grade. To a stirred solution of 0.100 mmol [(η⁶-p-cymene)RuCl₂]₂ (Strem Chemicals) in 10 ml benzene in a 100-ml roundbottom flask was added 0.200 mmol neat 4-fluoroaniline (Sigma-Aldrich). Dripped slowly into the resulting dark-orange solution with stirring were 2.0 ml methyl tert-butyl ether and then 50 ml heptane. The yellow-orange crystals afforded were filtered and washed with two 5-ml portions of hexanes and air-dried (88% yield).

NMR analysis of this product in CDCl₃ (Cambridge Laboratories) showed the following signals. ¹H δ 0.21, 6H (d, ³J_H—H=6.9 Hz); δ 2.11, 3H (s); δ 2.82, 1H (sept, ³J_H—H=6.9 Hz); δ 4.90, 2H (s); δ 4.97, 2H (d, ³J_H—H=6.1 Hz); δ 5.05, 2H (d, ³J_H—H=6.0 Hz); δ 7.09, 2H (d of d; ³J_F—H~³J_H—H~ 8.5 Hz); δ 7.40, 2H (d of d; ³J_H—H=8.5 Hz, ⁴J_F—H=4.5 Hz). ¹³C{¹H} δ 18.60(s), δ 22.06(s), δ 30.60(s), δ 79.65(s), δ 81.50(s), δ 95.91(s), δ 103.59(s), δ 116.32 (d, ¹J_C—F=22.5 Hz), δ 121.66 (d, ²J_C—F=8.1 Hz), δ 141.30 (d, ³J_C—F=1.7 Hz). ¹⁹F δ -115.71 (t of t, ³J_F—H=8.5 Hz; ⁴J_F—H=4.5 Hz); triplets overlap to form apparent "septuplet."

Suitable single crystals were grown from vapor diffusion of 30 ml heptane into a benzene solution of the 4-fluoroaniline complex (25 mg in 5 ml) over six days at room temperature. Traces of remaining liquid were removed by disposable glass pipet from the resulting red crystals which were washed twice with 5.0 ml hexanes and air-dried overnight in the dark.