Simple Access to the Non-Oxidizing Lewis Superacid PhF→Al(ORF)3 (RF=C(CF3)3)
Lutz O. Müller Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorDaniel Himmel Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorJulia Stauffer
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorGunther Steinfeld Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorJohn Slattery Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorGustavo Santiso-Quiñones Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorVolker Brecht
Institute of Pharmaceutical and Medical Chemistry, University of Freiburg, Albertstrasse 25, 79104 Freiburg (Germany)
Search for more papers by this authorIngo Krossing Prof. Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorLutz O. Müller Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorDaniel Himmel Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorJulia Stauffer
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorGunther Steinfeld Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorJohn Slattery Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorGustavo Santiso-Quiñones Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorVolker Brecht
Institute of Pharmaceutical and Medical Chemistry, University of Freiburg, Albertstrasse 25, 79104 Freiburg (Germany)
Search for more papers by this authorIngo Krossing Prof. Dr.
Institute of Analytical and Inorganic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg (Germany)
Search for more papers by this authorGraphical Abstract
Lewis superacidity? In analogy to Brønsted superacids, Lewis superacids can be defined as Lewis acids that are stronger than the strongest conventional and commercially employed Lewis acid SbF5. The fluorobenzene complex PhF→Al(ORF)3 (RF=C(CF3)3) qualifies as an easily accessible, non-oxidizing and stable Lewis acid that conforms with our Lewis superacidity criterion.
Supporting Information
Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z800783_s.pdf or from the author.
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
References
- 1
- 1aE. Y.-X. Chen, T. J. Marks, Chem. Rev. 2000, 100, 1391–1434;
- 1bM. H. Valkenberg, C. de Castro, W. F. Hoelderich, Stud. Surf. Sci. Catal. 2001, 135, 4629–4636;
- 1cH. Li, T. J. Marks, Proc. Natl. Acad. Sci. USA 2006, 103, 15295–15302.
- 2
- 2aA. Corma, H. Garcia, Chem. Rev. 2002, 102, 3837–3892;
- 2bA. Corma, H. Garcia, Chem. Rev. 2003, 103, 4307–4365.
- 3
- 3aA. Haaland, Angew. Chem. 1989, 101, 1017–1032;
- 3bA. Y. Timoshkin, G. Frenking, Organometallics 2008, 27, 371–380.
- 4T. E. Mallouk, G. L. Rosenthal, G. Mueller, R. Brusasco, N. Bartlett, Inorg. Chem. 1984, 23, 3167–3173.
- 5K. O. Christe, D. A. Dixon, D. McLemore, W. W. Wilson, J. A. Sheehy, J. A. Boatz, J. Fluorine Chem. 2000, 101, 151–153.
- 6
- 6aI. Krossing, I. Raabe, Chem. Eur. J. 2004, 10, 5017–5030;
- 6bIn a recent contribution,[3b] Timoshkin and Frenking assessed ΔE for E(C6F5)3 and obtained values that were very similar to our FIA values (E=B 454, Al 552 and Ga 465 kJ mol−1), supports the calculated data that we presented herein.
- 7
- 7aD. Lentz, K. Seppelt, Z. Anorg. Allg. Chem. 1983, 502, 83–88;
- 7bM. J. Collins, G. J. Schrobilgen, Inorg. Chem. 1985, 24, 2608–2614.
- 8F. Sladky, H. Kropshofer, O. Leitzke, J. Chem. Soc. Chem. Commun. 1973, 134–135.
- 9V. C. Williams, W. E. Piers, W. Clegg, M. R. J. Elsegood, S. Collins, T. B. Marder, J. Am. Chem. Soc. 1999, 121, 3244–3245.
- 10The term “Lewis superacid” has been used occasionally.[14,23] However, no precise definition of this term has been given. See also:
- 10aA. Hasegawa, K. Ishihara, H. Yamamoto, Angew. Chem. 2003, 115, 5909–5911; Angew. Chem. Int. Ed. 2003, 42, 5731–5733;
- 10bM. V. Metz, D. J. Schwartz, C. L. Stern, T. J. Marks, P. N. Nickias, Organometallics 2002, 21, 4159–4168.
- 11In an upcoming full paper we analyze all the Lewis acids given in Table 1 in more detail, using various quantitative Lewis acidity scales not only based on the FIA, and including similar aspects as those reported for Brønsted superacids in: I. A. Koppel, P. Burke, I. Koppel, I. Leito, T. Sonoda, M. Mishima, J. Am. Chem. Soc. 2000, 122, 5114–5124.
- 12R. J. Gillespie, Can. Chem. Ed. 1969, 4, 9–10.
- 13K. O. Christe, H. D. B. Jenkins, J. Am. Chem. Soc. 2003, 125, 9457–9461.
- 14According to our definition, Me3Si[C6F5CTf2] (Tf=triflate),[10a] which reacts with F− to give Me3SiF and [C6F5CTf2]−, is not a Lewis superacid; its stable enol form (SiO bond) has a FIA of only 407 kJ mol−1.
- 15The FIA has been previously calculated with a different method.[20b] In contrast to those results, the FIA values presented herein were calculated at the BP86/SV(P) level of theory to allow comparison.
- 16The procedure for the determination of ΔHsolid for AlX3 is given in the Supporting Information.
- 17H. D. B. Jenkins, I. Krossing, J. Passmore, I. Raabe, J. Fluorine Chem. 2004, 125, 1585–1592.
- 18M. Finze, E. Bernhardt, H. Willner, C. W. Lehmann, Angew. Chem. 2003, 115, 1082–1085; Angew. Chem. Int. Ed. 2003, 42, 1052–1055.
- 19V. M. Allenger, P. S. Yarlagadda, R. N. Pandey, Erdoel Kohle Erdgas Petrochem. 1991, 44, 244–248.
- 20[AuF5]:
- 20aV. B. Sokolov, V. N. Prusakov, A. V. Ryzhkov, Y. V. Drobyshevskii, S. S. Khoroshev, Dokl. Akad. Nauk SSSR 1976, 229, 884–887;
- 20bI.-C. Hwang, K. Seppelt, Angew. Chem. 2001, 113, 3803–3805;
Angew. Chem. Int. Ed. 2001, 40, 3690–3693. [AuF6]−:
10.1002/1521-3773(20011001)40:19<3690::AID-ANIE3690>3.0.CO;2-5 CAS PubMed Web of Science® Google ScholarK. Leary, N. Bartlett, J. Chem. Soc. Chem. Commun. 1972, 903–904.
- 21Sb[OTeF5]5 has not been isolated, although attempts to synthesize it have been carried out: H. P. A. Mercier, J. C. P. Sanders, G. J. Schrobilgen, J. Am. Chem. Soc. 1994, 116, 2921–2937; see also ref. [7a].
- 22The CO adduct OCB(CF3)3 may serve as a (weaker) equivalent for free B(CF3)3. M. Finze, E. Bernhardt, M. Zaehres, H. Willner, Inorg. Chem. 2004, 43, 490–505.
- 23
- 23aT. Belgardt, J. Storre, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, Inorg. Chem. 1995, 34, 3821–3822;
- 23bJ. Klosin, G. R. Roof, E. Y. X. Chen, K. A. Abboud, Organometallics 2000, 19, 4684–4686;
- 23cN. G. Stahl, M. R. Salata, T. J. Marks, J. Am. Chem. Soc. 2005, 127, 10898–10909.
- 24T. Krahl, E. Kemnitz, Angew. Chem. 2004, 116, 6822–6825;
10.1002/ange.200460491 Google ScholarAngew. Chem. Int. Ed. 2004, 43, 6653–6656.
- 25
- 25aA. G. Massey, A. J. Park, J. Organomet. Chem. 1964, 2, 245–250;
- 25bD. Naumann, W. Tyrra, J. Chem. Soc. Chem. Commun. 1989, 47–50;
- 25cM. V. Metz, D. J. Schwartz, C. L. Stern, T. J. Marks, P. N. Nickias, Organometallics 2002, 21, 4159–4168; M.-C. Chen, J. A. S. Roberts, T. J. Marks, Organometallics 2004, 23, 932–935;
- 25dK. Fujiki, S.-Y. Ikeda, H. Kobayashi, A. Mori, A. Nagira, J. Nie, T. Sonoda, Y. Yagupolskii, Chem. Lett. 2000, 62–63;
- 25eL. Li, T. J. Marks, Organometallics 1998, 17, 3996–4003;
- 25fY.-X. Chen, C. L. Stern, S. Yang, T. J. Marks, J. Am. Chem. Soc. 1996, 118, 12451–12452.
- 26I. Krossing, M. Gonsior, L. Mueller, WO 2004-EP12220 2005054254, 2005.
- 27Suitable crystals of 1 were formed by cooling a fluorobenzene solution to 253 K. Data was collected on a Bruker Diffraction Apex II using MoKα radiation (λ=0.71073 Å) at 106 K. A single crystal was mounted in perfluoroether oil on top of glass fiber and then placed in the cold stream of low-temperature device so that the oil solidified. The structure was solved with direct methods in SHELXS and successive interpretation of the difference Fourier maps using SHELXL-97 (G. M. Sheldrick, SHELXL-97, University of Göttingen, 1997). Refinement against F2 was carried out with SHELXL-97. All non-hydrogen atoms were included anisotropically in the refinement. Crystal structure determination of PhF→Al(ORF)3 (1): T=173(2) K, Lorentz, polarization, and numerical absorption corrections, P21/n, Z=4, a=10.6289(4), b=21.3339(8), c=11.8219(5) Å, β=96.733(2)°, V=2662.20(18) Å3, μ=0.297 mm−1, ρcalc=2.066 Mg m−3, θmax=26.61°, reflections: 72 201 collected, 5486 unique (Rint=0.0497), R1=0.0445, wR2(all data)=0.1016, GOF=1.064. CCDC-662085 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
- 28M. W. Bouwkamp, P. H. M. Budzelaar, J. Gercama, I. D. H. Morales, J. de Wolf, A. Meetsma, S. I. Troyanov, J. H. Teuben, B. Hessen, J. Am. Chem. Soc. 2005, 127, 14310–14319.
- 29G. Portalone, G. Schultz, A. Domenicano, I. Hargittai, J. Mol. Struct. 1984, 118, 53–61.
- 30L. O. Müller, Ph.D. Thesis, University of Freiburg, 2008.
- 31
- 31aA. Bihlmeier, M. Gonsior, I. Raabe, N. Trapp, I. Krossing, Chem. Eur. J. 2004, 10, 5041–5051;
- 31bM. Gonsior, L. Müller, I. Krossing, Chem. Eur. J. 2006, 12, 5815–5822.
- 32I. Krossing, Chem. Eur. J. 2001, 7, 490–502.
10.1002/1521-3765(20010119)7:2<490::AID-CHEM490>3.0.CO;2-I CAS PubMed Web of Science® Google Scholar
- 33Owing to the weak internal Al1F2 interaction (2.778 Å) one of the ORF ligands adopts a smaller Al-O-C angle (138.1°).
- 34This assignment is further supported by a reaction of SbF5 with fluorobenzene: liquid SbF5 was added to liquid fluorobenzene at room temperature in a glove box; an oxidation occurs, and the solution turns an intense green. In reactions according to Equation (4), the green coloration was never observed. This suggests that the fluoride ion is removed from [SbF6]− in an associative process, that is: [(RFO)3AlF⋅⋅⋅SbF5⋅⋅⋅SbF6]2−→[(RFO)3AlF]−+[Sb2F11]−.
- 35J.-C. Culmann, M. Fauconet, R. Jost, J. Sommer, New J. Chem. 1999, 23, 863–867.
- 36Unfortunately, the quality of the structure is not good owing to twinning and disorder. Selected details of the refinement: P1; cell constant: 11.3443, 11.3787, 12.8865 Å; 109.202, 97.371, 118.639 °; R1=26.1 %; 39 402 reflections, completeness: 98 %, θ: 28°, 11 493 data, 852 parameters.
