Dichlorido[1-(2-methyl­benz­yl)-3-(η6-2,4,6-trimethyl­benz­yl)-1H-2,3-dihydro­benzimidazol-2-yl­idene]ruthenium(II) dichloro­methane solvate

Hakan Arslan; Don VanDerveer; Sedat Yaşar; İsmail Özdemir; Bekir Çetinkaya

doi:10.1107/S160053680900350X

. 2009 Feb 4;65(Pt 3):m243–m244. doi: 10.1107/S160053680900350X

Dichlorido[1-(2-methylbenzyl)-3-(η⁶-2,4,6-trimethylbenzyl)-1H-2,3-dihydrobenzimidazol-2-ylidene]ruthenium(II) dichloromethane solvate

Hakan Arslan ^a,^b,^*, Don VanDerveer ^c, Sedat Yaşar ^d, İsmail Özdemir ^d, Bekir Çetinkaya ^e

PMCID: PMC2968587 PMID: 21582038

Abstract

The title complex, [RuCl₂(C₂₅H₂₆N₂)]·CH₂Cl₂, is best thought of as containing an octahedrally coordinated Ru center with the arene occupying three sites. Two Ru—Cl bonds and one Ru–carbene bond complete the distorted octahedron. The carbene portion of the ligand is a benzimidazole ring. This ring is connected to the C₆H₂(CH₃)₃ arene group by a CH₂ bridge. This leads to a system with very little apparent strain. A dichloromethane solvent molecule completes the crystal structure. Further stabilization is accomplished via C—H⋯N and C—H⋯Cl interactions.

Related literature

For synthesis, see: Yaşar et al. (2008 ▶); Çetinkaya et al. (2001 ▶, 2003 ▶); Özdemir et al. (2001 ▶, 2004 ▶). For general background, see: Herrmann (2002 ▶); Herrmann et al. (1995 ▶); Navarro et al. (2006 ▶); Arduengo & Krafczyc (1998 ▶). For related compounds, see: Begley et al. (1991 ▶); Steedman & Burrell (1997 ▶); Arslan et al. (2004 ▶, 2005 ▶, 2007 ▶).

Experimental

Crystal data

[RuCl₂(C₂₅H₂₆N₂)]·CH₂Cl₂
M _r = 611.37
Monoclinic,
a = 31.362 (6) Å
b = 8.1014 (16) Å
c = 20.484 (4) Å
β = 100.11 (3)°
V = 5123.8 (18) Å³
Z = 8
Mo Kα radiation
μ = 1.05 mm⁻¹
T = 153 (2) K
0.46 × 0.14 × 0.06 mm

Data collection

Rigaku Mercury CCD diffractometer
Absorption correction: multi-scan (REQAB; Jacobson, 1998 ▶) T _min = 0.644, T _max = 0.940
15807 measured reflections
4501 independent reflections
3825 reflections with I > 2σ(I)
R _int = 0.054

Refinement

R[F ² > 2σ(F ²)] = 0.049
wR(F ²) = 0.115
S = 1.08
4501 reflections
298 parameters
H-atom parameters constrained
Δρ_max = 0.92 e Å⁻³
Δρ_min = −0.73 e Å⁻³

Data collection: CrystalClear (Rigaku/MSC, 2006 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680900350X/at2716sup1.cif

e-65-0m243-sup1.cif^{(31.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053680900350X/at2716Isup2.hkl

e-65-0m243-Isup2.hkl^{(220.6KB, 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
C15—H15C⋯N2	0.98	2.60	3.244 (7)	123
C18—H18A⋯Cl2	0.99	2.67	3.468 (5)	138
C23—H23A⋯Cl1ⁱ	0.95	2.78	3.730 (5)	175
C26—H26A⋯Cl2ⁱⁱ	0.99	2.46	3.431 (6)	168

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

Acknowledgments

We thank the Technological and Scientific Research Council of Turkey TÜBİTAK-CNRS [grant No. TBAG-U/181(106 T716)] and İnönü University Research Fund (BAP 2007/39) for financial support.

supplementary crystallographic information

Comment

The ruthenium complexes of N-Heterocyclic carbenes have proved to be excellent catalysts for the Suzuki-Miyura, Sonogashira, Stille and Heck reactions (Herrmann et al., 1995; Herrmann, 2002; Navarro et al., 2006; Arduengo & Krafczyc, 1998). Expressive examples are found in various catalytic reactions with ruthenium catalysts for alken metathesis, cycloisomerization, and cyclopropanation reactions (Özdemir et al., 2004).

Previous work from our research groups in this area has focused on the elaboration of olefins as electron-rich heterocyclic carbene precursors which allow the formation of chelating carbenes, on the rapidly developing chemistry of η⁶-arene ruthenium(II) complexes containing substituted imidazolidin-2-ylidenes (Özdemir et al., 2001; Çetinkaya et al., 2001, 2003), and on the synthesis, characterization and uses of palladium, platinum and ruthenium N-heterocyclic carbene complexes as catalysts (Yaşar et al., 2008; Arslan et al., 2004, 2005, 2007, and references therein).

In the present study, we have synthesized and characterized a new ruthenium complex, (1-(2-methylbenzyl)-3-(2,4,6-trimethylbenzyl)-1H-benzo[d]imidazol-2(3H)-ylidene)ruthenium(II) dichloride. dichloromethane solvate, (I). The crystal structure of the title compound, (I), is depicted in Fig. 1.

The benzimidazol ring which has a carbene portion is connected to the C₆H₂(CH₃)₃arene by a CH₂ bridge. This leads to a system with very little apparent strain. The ruthenium atom in the title compound is best described as having an octahedral coordination environment, with the arene occupying three coordination sites. Two coordination sites are occupied by Cl ligands, while the sixth site is occupied by the carbene carbon of the benzimidazol ring.

The ruthenium atom is situated 1.6766 (19) Å from the ring centroid of the arene. While there are substantial differences in the C—C and Ru—C distances [Ru—C 92.099 (5), –C10 2.161 (4), –C11 2.246 (4), –C12 2.282 (5), –C13 2.203 (5), –C14 2.198 (5) Å] for the arene ring, there is no evidence of the alternating C—C bonds observed in some ruthenium-arene complexes (Begley et al., 1991).

The arene, the 2-methylbenzyl, imidazol and benzimidazol rings are almost planar with a maximum deviation of 0.038 (5) Å for atom C14, 0.015 (5) Å for atom C21, 0.004 (4) Å for atom N2, and 0.023 (5) Å for atom C5. The five-membered imidazole ring forms dihedral angles of 87.30 (4) ° and 78.53 (4) ° with the 2-methylbenzyl and 2,4,6-trimethylbenzyl rings, respectively.

The small steric demand of the benzimidazole ligand is reflected in the Cl—Ru—C1 angles, which are 87.51 (12) ° and 97.42 (12) °. These are significantly larger than the angles in the pyridine substituted complexes [RuCl₂(py)(η⁶-arene)] (Steedman & Burrell, 1997), and agree with Arslan results, (Arslan et al., 2004, 2005, 2007, and references therein). On the other side, the Ru—Cl distances in the coordination sphere are equal within experimental error [Ru—Cl1 = 2.4167 (12) Å and Ru—Cl2 = 2.4175 (13) Å]. The Cl—Ru—Cl angle is 88.52 (5) °.

The components of the title compound are assembled by two intermolecular C—H···Cl hydrogen bonds, to form a three-dimensional framework (Fig. 2 and Table 1). The intramolecular contacts, C—H···N and C—H···Cl, are also listed in Table 1.

Experimental

A suspension of 1-(2-methylbenzyl)-3-(2,4,6-trimethylbenzyl)benzimidazolium chloride (1.00 g, 2.56 mmol), Cs₂CO₃(0.84 g, 2.56 mmol), [RuCl₂(p-cymene)]₂(0.78 g, 1.28 mmol) and molecular sieves was heated under reflux in degassed dry toluene (20 ml) for 12 h. The reaction mixture was then filtered while hot, and the volume was reduced to about 10 ml before addition of n-hexane (10 ml). The precipitate formed was crystallized from CH₂Cl₂:hexane (5:10 ml) to give crystal product (Figure 3). Yield 0.58 g (86%), M.p.: 549–550 K. FT—IR (KBr pellet, cm^-1): ν_CN 1424 cm^{-1. 1}H NMR (δ, 399.9 MHz, CDCl₃): 2.18 and 2.34 [s, 9H, CH₂C₆H₂(CH₃)₃-2,4,6]; 2.39 [s, 3H, CH₂C₆H₄(CH₃)-2]; 5.08 [s, 2H, CH₂C₆H₄(CH₃)-2]; 5.59 [s, 2H, CH₂C₆H₂(CH₃)₃-2,4,6]; 5.76 [s, 2H, CH₂C₆H₂(CH₃)₃-2,4,6]; 6.80–7.50 [m, 8H, NC₆H₄N and CH₂C₆H₄(CH₃)-2]. ¹³C{H} NMR (δ, 100.5 MHz, CDCl₃): 17.0 and 17.4 [CH₂C₆H₂(CH₃)₃-2,4,6]; 19.5 [CH₂C₆H₄(CH₃)-2]; 49.7 [CH₂C₆H₂(CH₃)₃-2,4,6]; 53.5 [CH₂C₆H₄(CH₃)-2]; 90.0, 92.8, 98.6, 101.6, 110.0, 112.5, 123.4, 123.8, 126.0, 127.0, 127.1, 130.2, 133.2, 134.8, 135.0 and 135.4 [CH₂C₆H₂(CH₃)₃-2,4,6; NC₆H₄N and CH₂C₆H₄(CH₃)-2]; 185.9 [C_carbene].