Home Physical Sciences Synthesis and crystal structure of a new homoleptic tetraarylruthenium(IV) complex Ru(2,4,5-Me3C6H2)4
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Synthesis and crystal structure of a new homoleptic tetraarylruthenium(IV) complex Ru(2,4,5-Me3C6H2)4

  • Chang-Jiu Wang , Xiu-Li Wu , Xiu-Fang Ma , Ai-Quan Jia and Qian-Feng Zhang EMAIL logo
Published/Copyright: June 12, 2017
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Zeitschrift für Naturforschung B
From the journal Zeitschrift für Naturforschung B Volume 72 Issue 7

Abstract

Treatment of [Ru(acac)3] (acac−=acetylacetonate) with (2,4,5-Me3C6H2)MgBr, followed by column chromatography in air, afforded the homoleptic tetraaryl-ruthenium(IV) complex [Ru(2,4,5-Me3C6H2)4] (1) in moderate yield. The product was characterized by proton NMR spectroscopy and microanalyses. Its crystal structure has also been established by X-ray crystallography.

Keywords: crystal structure; homoleptic complex; ruthenium(IV); synthesis

1 Introduction

Since Wilkinson and coworkers first reported the synthesis of high-valent osmium(IV)/(VI) aryl and oxo aryl compounds by arylation of [OsO4] with Grignard reagents ArMgBr (Ar=aryl), it has been found that the ortho-methyl substituent in the aryl group has a significant effect on the nature of the arylation products [1]. Up to date, compared with the osmium analogues [2], [3], [4], [5], the chemistry of homoleptic tetraarylruthenium(IV) compounds has not been well explored [6], [7]. This may probably be due to the lack of general methods to prepare the typical homoleptic [RuAr4] complexes in relatively high yields. Previously, Wilkinson and coworkers reported a series of tetraarylruthenium(IV) complexes (aryl=2-methylphenyl, mesityl, 2,6-dimethylphenyl, and p-tert-butylphenyl), e.g. [Ru(2,6-Me2C6H3)4], by reaction of [Et4N][RuCl5(MeCN)] with 2,6-Me2C6H3MgBr, isolated in a relatively low yield (ca. 13%) [6]. In an effort to study the electronic factors affecting the stability/reactivity of the homoleptic [RuAr4] complexes, we have recently synthesized the 2,5-dimethylphenyl and 4-methoxy-2-methylphenyl complexes of ruthenium(IV) and further investigated their organometallic chemistry [8]. Herein, we report the synthesis of the complex [Ru(2,4,5-Me3C6H2)4] by alkylation of [Ru(acac)3] (acac−=aceytacetonate) with a Grignard reagent, followed by column chromatography in air, and further isolated in moderate yield (ca. 37%). The results involving isolation and structural characterization of the homoleptic tetraarylruthenium(IV) complex are reported in this paper.

2 Experimental

2.1 General

All synthetic manipulations were carried out under dry nitrogen by standard Schlenk techniques. RuCl3·3H2O was used as purchased from Pressure Chemical Co. Ltd. [Ru(acac)3] (acac−=acetylacetonate) was prepared according to a literature method [9]. NMR spectra were recorded on a Bruker ALX 400 spectrometer operating at 400 MHz for 1H, and chemical shifts (δ in ppm) were reported with reference to SiMe4 (1H). Elemental analyses were carried out using a Perkin-Elmer 2400 CHN analyzer.

2.2 Synthesis of [Ru(2,4,5-Me3C6H2)4] (1)

To a solution of [Ru(acac)3] (201.7 mg, 0.50 mmol) in THF (20 mL) at −78°C was added 7 equiv. of 2,4,5-Me3C6H2MgBr (3.5 mL of 1.0 M solution in THF, 3.5 mmol). The resulting brown mixture was stirred at room temperature overnight, and the volatiles were removed in vacuo. The residue was extracted into CH2Cl2-diethyl ether (1:1 v/v) and subjected to column chromatography in air (silica gel, CH2Cl2-hexanes, 1:1 v/v). Recrystallization from hexane afforded purple needle crystals, which were suitable for X-ray diffraction analysis. Yield was 106.7 mg, 37% (based on Ru). 1H NMR (400 MHz, CDCl3): δ=2.18 (brs, 3H, o-Me), 2.27 (s, 3H, m-Me), 2.30 (s, 3H, p-Me), 6.78–6.84 (brs, 2H, ArH). Analysis for C36H44Ru: calcd. C 74.83, H 7.68; found: C 74.87, H 7.64%.

2.3 X-ray crystallography

A summary of crystallographic data and experimental details for [Ru(2,4,5-Me3C6H2)4] (1) are summarized in Table 1. Intensity data were collected on a Bruker Smart APEX 2000 CCD diffractometer using graphite-monochromatized MoKα radiation (λ=0.71073 Å) at 293(2) K. The collected frames were processed with the software Saint [10]. The data were corrected for absorption using the program Sadabs [11]. This structure was solved by direct methods and refined by full-matrix least-squares on F2 using the Shelxtl software package [12], [13]. All non-hydrogen atoms were refined anisotropically. The positions of all hydrogen atoms were generated geometrically (Csp3−H=0.97 and Csp2−H=0.93 Å), assigned isotropic displacement parameters, and allowed to ride on their respective parent carbon atoms before the final cycle of least-squares refinement.

Table 1:

Crystallographic data and experimental details for complex [Ru(2,4,5-Me3C6H2)4] (1).

Complex1
Empirical formulaC36H44Ru
Formula weight577.78
Crystal systemMonoclinic
a, Å37.438(4)
b, Å9.2020(11)
c, Å18.606(2)
β, deg98.948(3)
V, Å36331.8(12)
Space groupC2/c
Z8
Dcalcd., g/cm1.21
Temperature, K296(2)
F(000), e2432
μ(MoKα), mm−10.52
Total refln20 609
Independent refln/Rint7697/0.0378
Ref. parameters346
R1a/wR2b (I>2 (I))0.0362/0.0786
R1a/wR2 b (all data)0.0662/0.0906
GoFc1.006
Final max/min diff. peaks, e Å−3+0.29/−0.44

  1. aR1=Σ||Fo|–|Fc||/Σ|Fo|; bwR2=[Σw(Fo2–Fc2)2/Σw(Fo2)2]1/2, w=[σ2(Fo2)+(AP)2+BP]−1, where P=(Max(Fo2, 0)+2Fc2)/3; cGoF=S=[Σw(Fo2–Fc2)2/(nobs–nparam)]1/2.

CCDC 1510576 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif.

3 Results and discussion

Usually, syntheses of the homoleptic tetraaryl (aryl=o-methylphenyl, 2,6-dimethylphenyl, mesityl, p-tert-butylphenyl, and 4-methoxy-2-methylphenyl) ruthenium(IV) complexes involved the use of [Et4N][RuCl5(solv)] (solv=acetonitrile or tetrahydrofuran), [Ru2(μ-O2CMe)4], [RuCl3(tht)3] (tht=tetrahydrothiophene), and/or [Ru(acac)3] [3], [7], [8]. In this research, treatment of [Ru(acac)3] with 7 equiv. of (2,4,5-Me3C6H2)MgBr in THF, followed by column chromatography in air, afforded the homoleptic tetraaryl ruthenium(IV) complex [Ru(2,4,5-Me3C6H2)4] (1) as a purple crystalline solid in 37% isolated yield. In the 1H NMR spectrum of 1, three singlets at δ 2.18, 2.27, and 2.30 ppm are assigned to the proton atoms of ortho-, meta-, and para-methyl substituents. Signals of the aryl resonances appear at around δ=6.7 ppm, which compares well to other related tetraaryl ruthenium(IV) complexes [3], [7], [8]. The molecular structure of complex 1 is shown in Fig. 1, together with its selected bond lengths and bond angles. The geometry around the central ruthenium atom is a slightly distorted tetrahedral with the C-Ru-C bond angles ranging from 107.64(10) to 110.94(10)°, while the C-Ru-C bond angles in the similar complex [Ru(2,4,6-Me3C6H2)4] are 98.9(6)–117.4(6)° [7], possibly arising from the steric effect of two ortho-methyl moieties in mesityl groups. The four Ru-C bond lengths in 1 are 1.989(2), 1.994(2), 1.993(2), and 1.998(2) Å, confirming its almost ideal tetrahedral geometry. In the already known complex [Ru(2,4,6-Me3C6H2)4], the four Ru-C bond lengths are 2.010(14), 2.012(14), 2.018(14), and 2.022(14) Å [7], with the average being 2.016(14) Å, almost the same as that in complex 1 (1.994(2) Å).

Fig. 1: Molecular structure of [Ru(2,4,5-Me3C6H2)4] 1. Displacement ellipsoids are drawn at the 40% probability level. Selected bond lengths (Å) and angles (deg): Ru(1)-C(11) 1.989(2), Ru(1)-C(21) 1.994(2), Ru(1)-C(31) 1.993(2), Ru(1)-C(41) 1.998(2); C(21)-Ru(1)-C(11) 109.48(10), C(31)-Ru(1)-C(41) 108.58(10), C(31)-Ru(1)-C(21) 110.94(10), C(41)-Ru(1)-C(21) 109.39(10), C(31)-Ru(1)-C(11) 107.64(10), C(41)-Ru(1)-C(11) 110.80(10).
Fig. 1:

Molecular structure of [Ru(2,4,5-Me3C6H2)4] 1. Displacement ellipsoids are drawn at the 40% probability level. Selected bond lengths (Å) and angles (deg): Ru(1)-C(11) 1.989(2), Ru(1)-C(21) 1.994(2), Ru(1)-C(31) 1.993(2), Ru(1)-C(41) 1.998(2); C(21)-Ru(1)-C(11) 109.48(10), C(31)-Ru(1)-C(41) 108.58(10), C(31)-Ru(1)-C(21) 110.94(10), C(41)-Ru(1)-C(21) 109.39(10), C(31)-Ru(1)-C(11) 107.64(10), C(41)-Ru(1)-C(11) 110.80(10).

In summary, a new homoleptic tetraarylruthenium(IV) complex [Ru(2,4,5-Me3C6H2)4] (1) has been synthesized by an alternative method in a moderate isolated yield (37%), which is obviously higher than that of the similar tetraarylruthenium(IV) complex [Ru(2,4,6-Me3C6H2)4] (18.4%) [7]. The C-Ru-C bond angles in 1 range from 107.64(10) to 110.94(10)°, showing an almost ideal tetrahedral geometry compared to those in other tetraarylruthenium(IV) complexes [Ru(2,4,6-Me3C6H2)4] (98.9(6)–117.4(6)°) [7] and [Ru(2-MeC6H4)4] (106.3(4)–114.9(6)°) [3].

Acknowledgment

This project was supported by the Natural Science Foundation of China (21372007).

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Received: 2017-4-4
Accepted: 2017-4-21
Published Online: 2017-6-12
Published in Print: 2017-6-27

©2017 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/znb-2017-0054
Keywords for this article
crystal structure; homoleptic complex; ruthenium(IV); synthesis

Articles in the same Issue

  1. Frontmatter
  2. In this Issue
  3. Synthesis and structure of large 24-mer and 36-mer oxamate-based macrocycles
  4. A [Mo2O2S2]-based ring system incorporating tartrate as the bridging ligand: synthesis, structure and catalytic activity of Cs4[Mo2O2(μ-S)2]2(μ4-tart)2 (tart=[C4H2O6]4−)
  5. Two new pyrrolo[2,3-d]pyrimidines (7-deazapurines): ultrasonic-assisted synthesis, experimental and theoretical characterizations as well as antibacterial evaluation
  6. One-pot desilylation-Sonogashira coupling
  7. Synthesis of benzodiazepines catalyzed by CoFe2O4@SiO2-PrNH2 nanoparticles as a reusable catalyst
  8. Synthesis, structural characterization, and hydrogen bonds of Co9(OH)14[SO4]2
  9. GdCuMg with ZrNiAl-type structure – an 82.2 K ferromagnet
  10. Notes
  11. Complete X-ray single-crystal structure determination and Raman spectrum of NH4[C(CN)3]
  12. Synthesis and crystal structure of a new homoleptic tetraarylruthenium(IV) complex Ru(2,4,5-Me3C6H2)4
  13. Book Review
  14. Lead: Its Effects on Environment and Health
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