Synthesis and Catalytic Activity of Novel Benzimidazolinylidene-Ruthenium(II) Complexes

Abstract

The reaction of [RuCl₂(p-cymene)]₂ with 1,3-dialkyl­benzimidazolium salts 1a-d in the presence of a small excess of cesium carbonate yields chelated η⁶-arene, η^¹-carbene ruthenium complexes 2a-d. All compounds were characterized by elemental analysis, NMR spectroscopy and the molecular structures of two of the complexes were determined by X-ray crystallography. The catalytic activity of RuCl₂(η⁶-arene, η^¹-benzimidazolinylidene) complexes was evaluated in the direct arylation of 2-phenylpyridine with bromobenzene derivatives.

ruthenium - benzimidazolinylidene complexes - N-heterocyclic carbene - C-H bond activation - arylation

References and Notes

1 Öfele K. J. Organomet. Chem.  1968,  12:  P42 

2 Wanzlick HW. Schonherr HJ. Angew. Chem., Int. Ed. Engl.  1968,  7:  141 

3 Arduengo AJ. Harlow RL. Kline M. J. Am. Chem. Soc.  1991,  113:  361 

4a Cardin DJ. Cetinkaya B. Lappert MF. Chem. Rev.  1972,  72:  545 

4b Bourissou D. Guerret O. Gabbai FP. Bertrand G. Chem. Rev.  2000,  100:  39 

4c Hahn FE. Angew. Chem. Int. Ed.  2006,  45:  1348 

4d Peris E. Crabtree RH. Coord. Chem. Rev.  2004,  248:  2239 

4e Corberán R. Marzá EM. Peris E. Eur. J. Inorg. Chem.  2009,  13:  1700 

4f Marion N. Frémont P. Puijk IM. Ecarnot EC. Amoroso D. Bell A. Nolan SP. Adv. Synth. Catal.  2007,  349:  2380 

4g Hahn FE. Jahnke MC. Angew. Chem. Int. Ed.  2008,  47:  3122 

5 Grubbs RH. Tetrahedron  2004,  60:  7117 

6a Özdemir I. Yaºar S. Çetinkaya B. Transition Met. Chem.  2005,  30:  831 

6b Yigit M. Yiit B. Özdemir I. Çetinkaya E. Çetinkaya B. Appl. Organomet. Chem.  2006,  20:  322 

6c Türkmen H. Pape T. Hahn FE. Çetinkaya B. Eur. J. Inorg. Chem.  2008,  5418 

7a Çetinkaya B. Özdemir I. Bruneau C. Dixneuf PH. J. Mol. Catal. A: Chem.  1997,  118:  L1 

7b Çetinkaya B. Gürbüz N. Seçkin T. Özdemir I. J. Mol. Catal. A: Chem.  2002,  184:  31 

8a Mata JA. Poyatos M. Peris E. Coord. Chem. Rev.  2007,  251:  841 

8b Normand AT. Cavell KJ. Eur. J. Inorg. Chem.  2008,  2781 

8c Jahnke MC. Hahn FE. Pape T. Z. Naturforsch., B  2007,  62:  357 

8d Hahn FE. Jahnke MC. Pape T. Organometallics  2007,  26:  150 

8e Yen SK. Koh LL. Hahn FE. Huynh HV. Hor TSA. Organometallics  2006,  25:  5105 

8f Huynh HV. Holtgrewe C. Pape T. Koh LL. Hahn FE. Organometallics  2006,  25:  245 

8g Hahn FE. Jahnke MC. Gomez-Benitez V. Morales-Morales D. Pape T. Organometallics  2005,  24:  6458 

8h Bedford RB. Cazin CSJ. Holder D. Coord. Chem. Rev.  2004,  248:  2283 

8i Marion N. Navarro O. Mei J. Stevens ED. Scott NM. Nolan SP. J. Am. Chem. Soc.  2006,  128:  4101 

8j Shore G. Morin S. Mallik D. Organ MG. Chem. Eur. J.  2008,  14:  1351 

8k Hartmann CE. Nolan SP. Cazin CSJ. Organometallics  2009,  28:  2915 

8l Zanardi A. Mata JA. Peris E. Organometallics  2009,  28:  1480 

8m Marion N. Nolan SP. Acc. Chem. Res.  2008,  41:  1440 

8n Würtz S. Glorius F. Acc. Chem. Res.  2008,  41:  1523 

9a Lappert MF. Maskell RK. J. Organomet. Chem.  1984,  264:  217 

9b Yigit M. Özdemir I. Çetinkaya B. Çetinkaya E. J. Mol. Catal. A: Chem.  2005,  241:  88 

9c Özdemir I. Demir S. Şahin O. Büyükgüngör O. Çetinkaya B. Appl. Organomet. Chem.  2008,  22:  59 

10a Yamamoto YE. Negishi E. J. Organomet. Chem.  1999,  576:  1 

10b Stille JK. Angew. Chem., Int. Ed. Engl.  1986,  25:  508 

10c Miyaura N. Suzuki A. Chem. Rev.  1995,  95:  457 

10d Suzuki A. J. Organomet. Chem.  1999,  576:  147 

11a Kakiuchi F. Chatani N. Adv. Synth. Catal.  2003,  345:  1077 

11b Miura M. Nomura M. Top. Curr. Chem.  2002,  219:  212 

11c Özdemir I. Demir S. Çetinkaya B. Gourlaouen C. Maseras F. Bruneau C. Dixneuf PH.
J. Am. Chem. Soc.  2008,  130:  1156 

12a Satoh T. Kawamura Y. Miura M. Nomura M. Angew. Chem., Int. Ed. Engl.  1997,  36:  1740 

12b Terao Y. Wakui H. Satoh T. Miura M. Nomura M. J. Am. Chem. Soc.  2001,  123:  10407 

12c Bedford RB. Limmert ME.
J. Org. Chem.  2003,  68:  8669 

12d Oi S. Watanabe SI. Fukita S. Inoue Y. Tetrahedron Lett.  2003,  44:  8665 

12e Ackermann L. Mulzer M. Org. Lett.  2008,  10:  5043 

13a Oi S. Fukita S. Hirata N. Watanuki N. Miyano S. Inoue Y. Org. Lett.  2001,  3:  2579 

13b Kakiuchi F. Kan S. Igi K. Chatani N. Murai S. J. Am. Chem. Soc.  2003,  125:  1698 

13c Oi S. Aizawa E. Ogino Y. Inoue Y.
J. Org. Chem.  2005,  70:  3113 

13d Özdemir I. Demir S. Gürbüz N. Çetinkaya B. Toupet L. Bruneau C. Dixneuf PH. Eur. J. Inorg. Chem.  2009,  1942 

14a Okazawa T. Satoh T. Miura M. Nomura M. J. Am. Chem. Soc.  2002,  124:  5286 

14b Ackermann L. Synthesis  2006,  1557 

14c Gracias V. Gasiecki AF. Pagano TG. Djuric SW. Tetrahedron Lett.  2006,  47:  8873 

14d Ackermann L. Althammer A. Angew. Chem. Int. Ed.  2007,  46:  1627 ; and references cited therein

14e Lewis JC. Wiedemann SH. Bergman RG. Ellman JA. Org. Lett.  2004,  6:  35 

15a In Ruthenium in Organic Synthesis   Kakiuchi F. Chatani N. Murahashi SI. Wiley-VCH; Weinheim: 2004.  p.219 

15b Oi S. Sato H. Sugawara S. Inoue Y. Org. Lett.  2008,  10:  1823 

15c Ackermann L. Novák P. Vivente R. Hofmann N. Angew. Chem. Int. Ed.  2009,  48:  1 

15d Oi S. Funayama R. Hattori T. Inoue Y. Tetrahedron  2008,  64:  6051 

15e Po˛gan F. Dixneuf PH. Adv. Synth. Catal.  2009,  351:  1737 

16 Oi S. Ogino Y. Fukita S. Inoue Y. Org. Lett.  2002,  4:  1783 

17 Fukuyama T. Chatini N. Tatsumi J. Kakiuchi F. Murai S. J. Am. Chem. Soc.  1998,  120:  11522 

18 Moore EJ. Pretzer WR. O’Connell TJ. Harris J. LaBounty L. Chou L. Grimmer SS. J. Am. Chem. Soc.  1992,  114:  5888 

19a Ackermann L. Org. Lett.  2005,  7:  3123 

19b Ackermann L. Vicente R. Althammer A. Org. Lett.  2008,  10:  2299 

19c Ackermann L. Althammer A. Born R. Tetrahedron  2008,  64:  6115 

19d Ackermann L. Althammer A. Born R. Synlett  2007,  2833 

20a Çetinkaya B. Demir S. Ozdemir I. Toupet L. Semeril D. Bruneau C. Dixneuf PH. Chem. Eur. J.  2003,  9:  2323 

20b Arslan H. VanDerveer D. Ozdemir I. Demir S. Çetinkaya B. Acta Crystallogr., Sect. E  2009,  65:  m97 

21

General Method for the Preparation of Ruthenium Complexes 2a-d: A suspension of benzimidazolium salt 1a-d (2.10 mmol), Cs₂CO₃ (2.14 mmol)and [RuCl₂ (p-cymene)]₂ (0.82 mmol) was heated under reflux in degassed toluene (20 mL) for 7 h. The reaction mixture was then filtered while hot, and the volume was reduced to about 10 mL before addition of n-hexane (15 mL). The precipitate formed was crystallized from CH₂Cl₂-hexane (5 mL/15 mL) to give brown crystals. Crystals suitable for single-crystal X-ray diffraction were obtained from CHCl₃-Et₂O. RuCl ₂ [η ^¹ -CN{CH ₂ ( η ⁶ -C ₆ H ₂ ( OMe) ₃ -3,4,5)}C ₆ H ₄ N(CH ₂ C ₆ H ₄ ( CMe ₃ - p )] (2a): Yield: 78% (0.96 g); mp 238-239 ˚C. IR: 1439 (CN) cm^-¹. ^¹H NMR (399.9 MHz, CDCl₃): δ = 7.18, 7.03 (m, 8 H, NC₆H₄N, CH₂C₆ H ₄CMe₃-p), 5.75 [m, 2 H, CH₂C₆ H ₂(OMe)₃-3,4,5], 5.07, 4.88 [s, 4 H, CH ₂C₆H₂(OMe)₃-3,4,5, CH ₂C₆H₄C(Me)₃-p], 4.07, 4.27 [s, 9 H, CH₂C₆H₂(OCMe)₃-3,4,5], 1.27 (s, 9 H, CH₂C₆H₄CMe ₃-p). ^¹³C NMR (100.5 MHz, CDCl₃): δ = 185.7 (C_carbene), 97.2, 97.5, 109.0, 109.3, 109.6, 113.0, 122.9, 123.4, 125.0, 127.6, 133.2, 133.3, 135.1, 138.1, 138.4, 150.0 [CH₂ C ₆H₂(OMe)₃-3,4,5, CH₂ C ₆H₄CMe₃-p, NC₆H₄N], 57.9, 58.1 [CH₂C₆H₂(OMe)₃-3,4,5], 55.7 [CH₂C₆H₂(OMe)₃-3,4,5], 53.4 (CH₂C₆H₄CMe₃-p), 34.4 (CH₂C₆H₄ CMe₃-p), 31.3 (CH₂C₆H₄CMe ₃-p). Anal. Calcd for C₂₈H₃₂N₂O₃RuCl₂: C, 54.55; H, 5.23; N, 4.54. Found: C, 54.58; H, 5.20; N: 4.58.
RuCl ₂ [η ^¹ -CN{CH ₂ ( η ⁶ -C ₆ H ₂ ( OMe) ₃ -3,4,5)}C ₆ H ₄ N(CH ₂ C ₆ H ₂ ( OMe) ₃ -3,4,5)] (2b): Yield: 82% (1.26 g); mp 196-197 ˚C. IR: 1441 (CN) cm^-¹. ^¹H NMR (399.9 MHz, CDCl₃): δ = 7.09 (s, 4 H, NC₆H₄N), 6.43 [s, 4 H, CH₂C₆ H ₂(OMe)₃-3,4,5], 6.13, 6.04 [s, 4 H, CH ₂C₆H₂(OMe)₃-3,4,5], 3.73, 3.81 [s, 18 H, CH₂C₆H₂(OMe)₃-3,4,5]. ^¹³C NMR (100.5 MHz, CDCl₃): δ = 191.7 (C_carbene), 104.6, 112.0, 123.5, 132.9 (NC₆H₄N), 135.8, 137.9, 153.8, 154.0 [free CH₂ C ₆H₂(OMe)₃-3,4,5], 56.7, 61.2 [CH₂C₆H₂(OMe)₃-3,4,5], 53.6 [CH₂C₆H₂(OMe)₃-3,4,5]. Anal. Calcd for C₂₇H₃₀N₂O₆RuCl₂˙CHCl₃: C, 43.68; H, 4.06; N, 3.64. Found: C, 43.72; H, 4.09; N: 3.68.
RuCl ₂ [η ^¹ -CN{CH 2( η ⁶ -C ₆ H ₂ Me ₃ -2,4,6)}C ₆ H ₄ N(CH ₂ CH ₂ OEt)] (2d): Yield: 70% (0.69 g); mp 293-294 ˚C. IR: 1436 (CN) cm^-¹. ^¹H NMR (399.9 MHz, CDCl₃): δ = 7.28-7.77 (m, 4 H, C₆H₄N), 5.59 (s, 2 H, CH₂C₆ H ₂Me₃-2,4,6), 5.03 (s, 2 H, CH ₂C₆H₂Me₃-2,4,6), 4.63 (t, 2 H, J = 5.0 Hz, CH ₂CH₂OEt), 3.77 (t, 2 H, J = 5.0 Hz, CH₂CH ₂OEt), 3.40 (q, 2 H, J = 7.0 Hz, OCH ₂Me), 2.13, 2.36 (s, 9 H, CH₂C₆H₂ Me ₃-2,4,6), 1.08 (t, 3 H, J = 7.0 Hz, OCH₂ Me). ^¹³C NMR (100.5 MHz, CDCl₃): δ = 184.9 (C_carbene), 109.4, 113.8, 123.2, 123.8, 132.8, 135.9 (NC₆H₄N), 89.7, 92.8, 98.9, 101.0 (CH₂ C ₆H₂Me₃-2,4,6), 72.1 (CH₂ CH₂OEt), 66.4 (CH₂CH₂OEt), 48.1 (CH₂CH₂OEt), 45.1 (CH₂C₆H₂Me₃-2,4,6), 16.9, 17.4 (CH₂C₆H₂Me₃-2,4,6), 15.3 (OCH₂ CH₃). Anal. Calcd for C₂₁H₂₆N₂ORuCl₂: C, 51.01; H, 5.30; N, 5.67. Found: C, 51.10; H, 5.35; N: 5.65.
General Procedure for the Arylation of 2-Phenyl-pyridine: Ruthenium complex 2 (0.025 mmol), 2-phenylpyridine (0.5 mmol), aryl bromide (1.25 mmol) and Cs₂CO₃ (1.50 mmol) were stirred in NMP (2 mL) at 120 ˚C for 20 h. H₂O and EtOAc were added to the cold reaction mixture. The organic phase was separated, dried over MgSO₄, filtered and concentrated under vacuum. The remaining residue was purified by column chromatography on silica gel (pentane-Et₂O mixture) to yield the ortho-arylated products. Conversions and product ratios were determined by ^¹H NMR and by GC analyses. X-ray Structure Determination of 2b and 2d: Brown single crystals of 2b and 2d suitable for data collection were selected and data collection was performed on a STOE IPDS II diffractometer with graphite monochromated Mo-Kα radiation at 296 K. The structures were solved by direct-methods using SHELXS-97^²³ and refined by full-matrix least-squares methods on F ^² using SHELXL-97^²³ from within the WINGX^²4 suite of software. All non-hydrogen atoms were refined with anisotropic parameters. Hydrogen atoms were added to the structure models on calculated positions.
Selected Crystallographic Details for 2b: C₂₈H₃₁Cl₅N₂O₆Ru, M = 769.87, brown crystal, 0.48 × 0.30 × 0.06 mm^³, monoclinic, space group P2₁/c, a = 15.9602 (14), b = 13.9350 (10), c = 16.6111 (15) Å, β = 119.790 (6)˚, V = 3206.2 (5) Å^³, ρ _calcd = 1.595 g cm^-³, µ = 0.95 mm^-¹, empirical absorption correction (0.723£ T £0.956), Z = 4, 18476 intensities collected (± h, ± k, ± l), 6267 independent intensities (R _int = 0.062), refinement of 383 parameters against all unique |F^²|, R = 0.047, wR = 0.111 for 4099 contributing intensities [I £ 2σ(I)].
Selected Crystallographic Details for 2d: C₂₁H₂₆Cl₂N₂ORu, M = 494.41, brown crystal, 0.48 × 0.33 × 0.11 mm^³, monoclinic, space group C2/c, a = 30.4767 (18), b = 9.8695 (4), c = 14.8978 (8) Å, β = 108.484 (4)˚, V = 4249.9 (4) Å^³, ρ _calcd = 1.545 g cm^-³, µ = 1.00 mm^-¹, empirical absorption correction (0.565£ T £0.914), Z = 8, 29964 intensities collected (± h, ± k, ± l), 5022 independent intensities (R _int = 0.040), refinement of 247 parameters against all unique |F^²|, R = 0.025, wR = 0.063 for 3897 contributing intensities [I £ 2σ(I)].
Crystallographic data (excluding structure factors) have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication (CCDC 72906 for 2b and CCDC 72907 for 2d). Copies of the data can be obtained free of charge via www.ccdc.cam.ac.uk/data.request/cif.

22a Özdemir I. Demir S. Çetinkaya B. Toupet L. Castarlenas R. Fischmeister C. Dixneuf PH. Eur. J. Inorg. Chem.  2007,  2862 

22b Çetinkaya B. Özdemir I. Dixneuf PH. J. Organomet. Chem.  1997,  534:  153 

23 Sheldrick GM. Acta Crystallogr., Sect. A  2008,  64:  112 

24 Farrugia LJ. J. Appl. Crystallogr.  1999,  32:  837