Organometallics
ARTICLE
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(23) As one could expect, this arene substitution process is easier
starting from the benzene dimer. Thus, complex 2e was quantitatively
formed after heating for 2 h the dimer 1a with 10 equiv of P(NMe2)3 in
toluene at only 50 °C. Such displacement was not observed with the
more electron-rich arenes, and the reaction of 1c or 1d with 10 equiv of
P(NMe2)3 in toluene at 70 °C only gave rise to the formation of 2c or 2d,
respectively, in which the original arene remains coordinated.
(24) For reviews on the chemistry of [{RuCl(μ-Cl)(η6-arene)}2]
dimers, see: (a) Le Bozec, H.; Touchard, D.; Dixneuf, P. H. Adv.
Organomet. Chem. 1989, 29, 163. (b) Bennett, M. A. In Comprehensive
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Organomet. Chem. 2004, 7, 3. (f) Gimeno, J.; Cadierno, V.; Crochet, P.
In Comprehensive Organometallic Chemistry III; Crabtree, R. H., Mingos,
D. M. P., Eds.; Elsevier: Oxford, U.K., 2007; Vol. 6, pp 465À550.
(g) Therrien, B. Coord. Chem. Rev. 2009, 253, 493.
(14) (a) Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and
Practice; Oxford University Press: Oxford, U.K., 1998. (b) Anastas, P. T.;
Williamson, T. C. Green Chemistry: Frontiers in Benign Chemical Synthesis
and Processes; Oxford University Press: New York, 1998. (c) Matlack,
A. S. Introduction to Green Chemistry; Marcel Dekker: New York, 2001.
(d) Lancaster, M. In Handbook of Green Chemistry and Technology;
Clark, J. H., Macquarrie, D. J., Eds.; Blackwell Publishing: Abingdon,
U.K., 2002. (e) Lancaster, M. Green Chemistry: An Introductory Text;
RSC: London, 2002. (f) Poliakoff, M.; Fitzpatrick, J. M.; Farren, T. R.;
Anastas, P. T. Science 2002, 297, 807. (g) Anastas, P. T.; Kirchhoff, M. M.
Acc. Chem. Res. 2002, 35, 686. (h) Sheldon, R. A.; Arends, I.; Hanefeld,
U. Green Chemistry and Catalysis; Wiley-VCH: Weinheim, Germany,
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(15) For leading references in this field, see: (a) Li, C.-J. Chem. Rev.
1993, 93, 2023. (b) Lubineau, A.; Auge, J.; Queneau, Y. Synthesis
1994, 741. (c) Li, C.-J.; Chan, T. H. Organic Reactions in Aqueous Media;
John Wiley & Sons: New York, 1997. (d) Lindstr€om, U. M. Chem. Rev.
2002, 102, 2751. (e) Li, C.-J. Chem. Rev. 2005, 105, 3095. (f) Andrade,
C. K. Z.; Alves, L. M. Curr. Org. Chem. 2005, 9, 195. (g) Li, C.-J.; Chen, L.
Chem. Soc. Rev. 2006, 35, 68. (h) Herrerías, C. I.; Yao, X.; Li, Z.; Li, C. J.
Chem. Rev. 2007, 107, 2546. (i) Lindstr€om, U. M., Ed. Organic Reactions
in Water; Blackwell Publishing: Oxford, U.K., 2007. (j) Li, C.-J.; Chan,
T. H. Comprehensive Organic Reactions in Aqueous Media; Wiley-VCH:
Weinheim, Germany, 2007. (k) Skouta, R. Green Chem. Lett. Rev. 2009,
2, 121.(l) Anastas, P. T., Li, C.-J., Eds. Handbook of Green Chemistry;
Wiley-VCH: Weinheim, Germany, 2010; Vol. 5.
(25) In the case of intramolecular processes, that is, formation of
tethered-arene complexes, the reactions can proceed under milder
reaction conditions. See, for example: (a) Cadierno, V.; Díez, J.;
García-Alvarez, J.; Gimeno, J. Chem. Commun. 2004, 1820. (b) Arquier,
D.; Vendier, L.; Miqueu, K.; Sotiropoulos, J.-M.; Bastin, S.; Igau, A.
Organometallics 2009, 28, 4945 and references cited therein.
(26) Formation of tolueneÀruthenium(II) complexes [RuCl2-
(η6-C6H5Me)(PR3)] usually involves the cleavage of the known dimer
[{RuCl(μ-Cl)(η6-C6H5Me)}2] by phosphines or the substitution of a
ruthenium-coordinated benzene ligand by toluene. See, for example:
(a) Redwine, K. D.; Hansen, H. D.; Bowley, S.; Isbell, J.; Sanchez, M.;
Vodak, D.; Nelson, J. H. Synth. React. Inorg. Met.-Org. Chem. 2000,
30, 379. (b) Nelson, J. H.; Ghebreyessus, K. Y. Organometallics 2000,
19, 3387. (c) Nelson, J. H.; Ghebreyessus, K. Y. Synth. React. Inorg. Met.-
Org. Chem. 2003, 33, 1329. (d) Chaplin, A. B.; Dyson, P. J. Organome-
tallics 2007, 26, 2447. (e) Wang, L.; Zhuo, X.-G.; Li, R. X. Acta
Crystallogr., Sect. E 2008, E64, m429. See also reference 18.
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(27) Aktas, H.; Slootweg, J. C.; Schakel, M.; Ehlers, A. W.; Lutz, M.;
Spek, A. L.; Lammertsma, K. J. Am. Chem. Soc. 2009, 131, 6666.
(28) Mitzel, N. W.; Smart, B. A.; Dreih€aupl, K.-H.; Rankin, D. W. H.;
Schmidbaur, H. J. Am. Chem. Soc. 1996, 118, 12673.
(29) See, for example: (a) Wang, K.; Emge, T. J.; Goldman, A. S.
Organometallics 1994, 13, 2135. (b) Brunet, J.-J.; Diallo, O.; Donnadieu,
B.; Roblou, E. Organometallics 2002, 21, 3388. (c) Blagg, R. J.; Adams,
C. J.; Charmant, J. P. H.; Connelly, N. G.; Haddow, M. F.; Hamilton, A.;
Knight, J.; Orpen, A. G.; Ridgway, B. M. Dalton Trans. 2009, 8724.
(30) Complex [RuCl(NCMe)(η6-C6Me6){P(NMe2)3}][PF6] was
prepared by treatment of 2d with NaPF6 in acetonitrile at room
temperature for 2 h. Spectroscopic data: 31P{1H} NMR (CDCl3) δ
115.9 (s) ppm. 1H NMR (CDCl3) δ 2.66 (d, 18H, 3JPH = 9 Hz, NMe),
2.17 (s, 3H, NCMe), 2.05 (s, 18H, C6Me6). IR (Nujol, cmÀ1): ν 2360
(CtN). Complex [RuCl(NCMe)(η6-C6Me6){P(NMe2)3}][PF6] has
shown to promote efficiently the hydration of NCMe, yielding to 97% of
acetamide after 1 h (1 mol of NCMe, 5 mol % of Ru, 3 mL of water,
100 °C). Similar activity was obtained with catalyst 2d (see Table 3,
entry 1).
(31) Complex 2d has also proven to promote the hydration of
nitriles in different organic solvents in the presence of a small quantity of
water, albeit with lower catalytic activities than in pure aqueous medium.
For example, benzonitrile was completely transformed into benzamide
after 2 h when toluene was used as a solvent, whereas 40% and 75%
conversions were reached after 24 h in 1,4-dioxane and 1,2-dimethox-
yethane, respectively (5 mol % of 2d, 100 °C, 3 mL of the corresponding
solvent, 4 equiv of water).
(16) See, for example: (a) Nelson, W. M. Green Solvents for
Chemistry: Perspectives and Practice; Oxford University Press: New York,
2003. (b) Clark, J. H.; Taverner, S. J. Org. Process Res. Dev. 2007, 11, 149.
(c) Kerton, F. M. Alternative Solvents for Green Chemistry; RSC Publish-
ing: Cambridge, U.K., 2009.
(17) Application of complex [RuCl2(η6-C6Me6){P(NMe2)3}] to
the catalytic synthesis of the nonsteroidal anti-inflammatory drug
ibuprofenamide by hydration of 2-(4-isobutylphenyl)propionitrile
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has been communicated in a preliminary report: García-Alvarez, R.;
Francos, J.; Crochet, P.; Cadierno, V. Tetrahedron Lett. 2011, 52, 4218.
(18) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974,
233.
(19) Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K.
Inorg. Synth. 1982, 21, 74.
(20) Hull, J. W.; Gladfelter, W. L. Organometallics 1984, 3, 605.
(21) Preparation of complex 2a by heating a benzene solution of 1a
with an excess of P(NMe2)3 has been previously described in the
literature. The only spectroscopic data given for 2a in the article were
1H NMR resonances: Werner, H.; Werner, R. Chem. Ber. 1982, 115,
3766.
(32) For reviews and a recent book on this topic, see: (a) Dallinger,
D.; Kappe, O. C. Chem. Rev. 2007, 107, 2563. (b) Polshettiwar, V.;
Varma, R. S. Chem. Soc. Rev. 2008, 37, 1546. (c) Polshettiwar, V.; Varma,
R. S. Acc. Chem. Res. 2008, 41, 629. (d) Polshettiwar, V., Varma, R. S.,
(22) Synthesis of complex 2b, byreacting dimer 1b with a large excess
of P(NMe2)3 (33 equiv) in dichloromethane for 24 h, has also been
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dx.doi.org/10.1021/om2006563 |Organometallics 2011, 30, 5442–5451