Bis(perchlorocatecholato)silane—A Neutral Silicon Lewis Super Acid

Article abstract of DOI:10.1002/anie.201712155

No neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO-CCSD(T)) and experiment (fluoride abstraction from SbF₆^?). The exceptional affinity towards donors is further demonstrated by, for example, the characterization of an unprecedented SiO₄F₂ dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.

Full text of DOI:10.1002/anie.201712155

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Accepted Article
Title: Bis(perchlorocatecholato)silane - A neutral silicon Lewis super
acid
Authors: Rezisha Maskey, Marcel Schädler, Claudia Legler, and Lutz
Greb
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201712155
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Bis(perchlorocatecholato)silane - A neutral silicon Lewis super
acid
Rezisha Maskey, Marcel Schädler, Claudia Legler and Lutz Greb*[a]
Abstract: No neutral silicon Lewis super acids are known to date. We
report on the synthesis of bis(perchlorocatecholato)silane and verify
its Lewis super acidity by computation (DLPNO-CCSD(T)) and
More positive Hammett parameters denote more effective
electron-withdrawal for substituents in aromatic systems.
Although chlorine is not as electronegative as fluorine, its
Hammett parameter (σpCl = 0.227) is much greater (σpF = 0.062),
as a result of weaker π-backbonding to the aromatic nucleus.[9]
The aromatic π-electron density should be related to the electron
deficiency at silicon in catecholato silanes, hence we expected
the unknown bis(perchlorocatecholato)silane 1 to be more Lewis
acidic than the perfluorinated derivative Si(catF)2. Similar
strategies led to very potent borane and antimony Lewis acids.[10]
For an assessment of the impact of substituents on the Lewis
acidity of neutral silicon(IV) species, the FIAs for strong silicon
Lewis acids (Figure 1) and SiF4 were determined computationally
at the highly correlated and accurate DLPNO-CCSD(T)/aug-cc-
pVQZ level of theory (see table 1, for all computational details,
see SI).[11] Compared to SiF4, (310 kJ mol-1) the presence of
perfluoroaryl (SiF(C6F5)3, 361 kJ mol-1) or perfluoroalkyl
(SiF(C2F5)3, 443 kJ mol-1) groups increases the FIA significantly.
The substitution with perhalogenated catechols (Si(catF)2, 490
kJ mol-1and 1, 507 kJ mol-1) boosts the FIA even more. However,
only the aspired silane 1 exceeds the FIA of SbF5, and thus
qualifies it as a neutral silicon(IV) Lewis super acid. Not only the
first FIA of 1 is remarkably high, but also its second FIA (71
-
experiment (fluoride abstraction from SbF6 ). The exceptional affinity
towards donors is further demonstrated by e.g. the characterization of
an unprecedented SiO4F2 dianion and applied in the first
hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid.
Given the strength and convenient access to this new Lewis acid,
versatile applications might be foreseen.
The success of molecular, main group element Lewis acids for
the activation of inert bonds and catalysis evoked high research
interests in recent years.[1] Especially the search for ever more
powerful, yet bottleable and easy-to-handle, so-called Lewis
super acids is an active field. The Lewis acidity is usually gauged
by the fluoride ion affinity (FIA) and the threshold to Lewis super
acidity was defined as the capability to abstract a fluoride ion from
-
the monomeric SbF6 anion in the gas phase.[2] Unfortunately,
most known Lewis super acids are not accessible in bulk
quantities, hydrolyze under liberation of HF or are highly oxidizing.
Several of these drawbacks have been overcome by the
installation of fluorinated aryl, alkyl or pentafluoroorthotellurate
4]
substituents in boron,[3] aluminum,[2a,
arsenic[5] or
-
kJ mol-1), being 275 kJ mol-1 higher as for SiF5 . The theoretical
phosphonium[6] species. Also for silicon(IV) as the central atom,
strong neutral Lewis acids have been described (Figure 1). HOGE
used pentafluoroethyl as electron-withdrawing substituents for the
preparation of remarkably stable and strong silicon Lewis acids.[7]
Bis(perfluorocatecholato)silane (Si(catF)2, catF = o-C6F4O2) was
presented by TILLEY and applied in the catalytic hydrosilylation of
aldehydes.[8] Yet, a neutral silicon Lewis super acid (FIA > SbF5)
is unprecedented so far. Herein, we describe a straightforward
synthetic access to bis(perchlorocatecholato)silane 1 and verify
its Lewis super acidity by experiment and quantum theory.
results clearly revealed exceptional acceptor properties of 1 and
prompted us for the experimental realization.
The CH3CN adduct of 1 was readily accessible in a highly scalable
2-step procedure, starting from inexpensive bulk materials.
Chlorination of catechol with H2O2/HCl according to literature[12]
and the subsequent conversion with HSiCl3 in CH3CN led to the
precipitation of 1-(CH3CN)2 and the liberation of HCl and H2 in a
good overall yield (85%) at >3 g scale. Poor solubility in common
organic solvents hampered solution phase analysis, but the
formation of a trans-bisadduct 1-(CH3CN)2 was strongly supported
by elemental analysis, IR spectroscopy and DFT computations
(see SI). The C≡N bond stretching mode in 1-(CH3CN)2
(2335 cm-1) is blue-shifted by 86 cm-1 with respect to free CH3CN
(2249 cm-1), indicating high Lewis acidity.
Table 1. Computed 1st and 2nd fluoride ion affinities (FIAs) for selected neutral
silicon(IV) Lewis acids and SbF5.
Lewis Acid (LA)/LA-F-/LA-F2
FIA (1st/2nd) [kJ mol-1]a
2-
Figure 1. Previously studied strong neutral silicon Lewis acids and the herein
presented Lewis super acid 1.
2-
SiF4 / SiF5- / SiF6
310/-204
361
SiF(C6F5)3 / SiF(C6F5)3F-
SiF(C2F5)3 / SiF(C2F5)3F-
443
2-
Si(catF)2 / Si(catF)2F-/ cis-Si(catF)2F2
490/35
507/71
501
[a]
Rezisha Maskey, Marcel Schädler, Claudia Legler, Dr. Lutz Greb
Anorganisch-Chemisches Institut
Ruprecht-Karls-Universität Heidelberg
Im Neuenheimer Feld 270, 69120 Heidelberg
E-mail: greb@uni-heidelberg.de
2-
1 / 1F- / cis-1F2
-
SbF5 / SbF6
[a] DLPNO-CCSD(T)/cc-aug-pVQZ//PW6B95-D3(BJ)/def2-TZVPP; for Sb
atoms, the cc-aug-pwcVQZ-PP basis set was used. Enthalpies obtained by
isodesmic reactions against G3/CBS anchor points (see SI).
Supporting information for this article is given via a link at the end of
the document.
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The ability of 1-(CH3CN)2 to bind halide ions was further examined.
Addition of one equivalent KF/18-crown-6 led to the formation of
the
fluorosilicate
[1F][K@18-crown-6]
(Figure
3a).
=
Pentacoordination at silicon was supported by a doublet (1JSiF
196 Hz) at -105 ppm in the 29Si-NMR spectrum and by X-ray
diffraction. The Si-F bond length (1.606 Å) is analogous to the
fluoride adduct
tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) led
to the immediate formation of the
of
Si(catF)2.[8]
Addition of
2
eq.
bisfluorido(biscatecholato)silicate dianion [1F2][S(NMe2)3]2 (see
Figure 3b), showing a triplet (1JSiF = 152 Hz) at -155 ppm in the
29Si-NMR spectrum. The number of peaks in the 13C-NMR
spectrum indicated a cis-arrangement of the fluoride substituents,
in agreement with a computed lower energy relative to the trans
isomer (see SI). The solid-state structural analysis revealed a
trans-arrangement of the fluorides instead, with Si-F bond lengths
of 1.686 Å. (cf. Na2SiF6 1.695 Å).[19] It stands thus in contrast to
Si(catF)2 and to the non-halogenated Si(cat)2, where only the
monoanions are accessible,[8, 20] and agrees with the computed
high 2nd FIA for 1. The solution and solid-state characterization of
[1F2][S(NMe2)3]2 represent the first description of a dianionic
SiO4F2 species to our knowledge and underlines the potential of
the perchlorocatechol substituents to stabilize negative charge.
Addition of 1 eq. of bis(triphenylphosphine)iminium chloride
([PPN]Cl) to 1-(CH3CN)2 led to the chloridosilicate [1Cl][PPN], a
substance class made only recently accessible for the first time
(Figure 3c).[21] A singlet at -90.4 ppm in the 29Si-NMR spectrum
and X-ray diffraction revealed pentacoordination at silicon.[22]
More intriguingly, the addition of >1 eq. [PPN]Cl revealed the
partial formation of an elusive dichlorosilicate dianion, as was
visible by 13C-NMR spectroscopy.[23] The chloride ion affinity was
further shown by reaction of 1-(CH3CN)2 with trityl chloride
(Scheme 3d) causing immediate strong coloration of the solution
to deep orange upon mixing. 1H- and 13C-NMR spectra
unequivocally showed the partial (23%) formation of a trityl
carbenium ion and at the same time, 29Si- and 13C-NMR spectra
showed signals identical to the silicate anion in [1Cl][PPN].
Figure 2. a) Formation of ether adducts of 1 together with b) the molecular
structures obtained by X-ray diffraction (ellipsoids 50% probability, selected
bond lengths [Å]) of 1-(Et2O)2 (Si-O1 = 1.724(1), Si-O2 = 1.738(1), Si-
O3 = 1.957(2)),
O3 = 1.966(2)).
1-(DME)
(Si-O1 = 1.735(2),
Si-O2 = 1.725(2),
Si-
A similar blue-shift (86 cm-1) was reported for the nitrile stretching
mode in the CH3CNSbF5 adduct.[13] Further measurement of the
Lewis acidity provided the 31P-NMR shift difference (Δ31P) upon
complexation of OPEt3 according to Gutmann-Beckett.[14] The
addition of OPEt3 to a suspension of 1-(CH3CN)2 in CD2Cl2 led to
a prompt dissolution of 1-(CH3CN)2 and the liberation of 2 eq. of
1
CH3CN. 31P- and H-NMR spectroscopy, as well as ESI-MS(+)
indicated a dynamic mixture of the three compounds 1-OPEt3, 1-
(OPEt3)2 and 12-(OPEt3)3.[15] The monoadduct 1-OPEt3 revealed
Δ31P = 35 ppm, lying in accordance with the shift observed for
F
Si(cat)2 (36 ppm), and significantly above B(C6F5)3 (26 ppm),
whereas the shift in the bisadduct 1-(OPEt3)2 indicated expectedly
weaker acceptor ability (Δ31P = 23 ppm). The nature of the
bisadduct was proven by X-ray structural analysis, showing a
hexacoordinated silicon with trans arranged phosphine oxides
(see SI). Interestingly, these findings not only underline a strong
Lewis acidity of 1, but indicate also a stronger
tendency towards hexacoordination compared to
Si(cat)2 and Si(catF)2, for which only phosphine
oxide monoadducts were observed.[8, 16]
The Lewis super acidity of 1 (as 1-(CH3CN)2) was finally verified
by reaction with either [NEt4][SbF6] or [PPh4][SbF6] at rt. In both
cases, the initial formation of a silicate monofluoride was
Reaction of HSiCl3 and perchlorocatechol in
presence of Et2O or displacement of acetonitrile
from 1-(CH3CN)2 with dimethoxyethane yielded
ether adducts of 1 with hexacoordinate silicon
(Figure 2a). The strong affinity towards such donors
is remarkable for a neutral silicon(IV) species. The
measured Si-O bond lengths indicate dative
bonding for the ether oxygens towards silicon (1.957
Å in 1-(Et2O)2, 1.966 Å in 1-DME, Figure 2b).
These distances are significantly shorter than in
the two only known adducts of an acyclic ether with
Figure 3: a,b) Fluoride ion additions 1-(CH3CN)2 with molecular structures obtained by X-ray
diffraction for [1F][K@18-crown-6] (Si-O = 1.738(1), Si-F = 1.606(1)) and [1F2][S(NMe2)3]2 (Si-
O = 1.790(1), Si-F = 1.686(1), ellipsoids 50% probability, cations and solvent molecules are
omitted for clarity) c) chloride ion additions to 1-(CH3CN)2, d) chloride abstraction with 1-(CH3CN)2
from tritylchloride.
neutral silanes (e.g. 2.27 Å in H3SiCl-Me2O, stable
only in the crystalline state at <100 K),[17] and rather
bear resemblance to ether adducts of silylium
cations.[18]
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observed (Figure 4a, 19F/29Si/13C-NMR spectra identical to [1-
F][S(NMe2)3] and a strong signal of [1-F-] in ESI-MS(-)). Due to
ligand scrambling between silicon and antimony, the isolation of
the intermediate species was not successful. However, and
similar to reactions with PF6- salts (see SI for details), the finally
identified
product
contained
the
tris(perchlorocatecholato)antimonate anion (see SI for X-ray
diffraction), likely driven by the release of SiF4 (for a proposed
reaction scheme and the identification of all observed
intermediates by 19F-NMR/ESI-MS, see SI). Clearly, the neutral
-
silicon Lewis acid 1 abstracts a fluoride ion from SbF6 , as the first
necessary elementary step in the observed reaction cascade,
serving as the experimental proof of its Lewis super acidity.[24]
Importantly, in agreement with our computational results, no
fluoride abstraction from [PPh4][SbF6] occurred with the weaker
Lewis acid Si(catF)2.
To demonstrate the utility of 1-(CH3CN)2 in catalysis, C(sp3)-F
bond activation for hydrodefluorination (HDF) was attempted –
processes well performed by silylium cations, but with no
precedence for neutral silicon species as a catalyst.[1c, 25] Indeed,
the HDF of 1-adamantylfluoride proceeded cleanly to full
conversion applying 10 mol% of 1-(CH3CN)2 in tetrachloroethane
in 15 h at rt, using Et3SiH or even deactivated PMHS as reducing
agent (Figure 4b). With a primary alkyl fluoride (1-pentylfluoride),
Figure 4: a) Fluoride abstraction from the SbF6- anion and following reactions,
b) hydrodefluorination with polymethlyhydrosiloxane (PMHS) catalyzed by 1-
(CH3CN)2, c) synthesis of donor free 1 with Oestreich’s SiH4 surrogate.
Keywords: Lewis super acids • silanes • hydrodefluorination •
main-group elements • catechol
[1]
a) A. Corma, H. García, Chem. Rev. 2003, 103, 4307-4366; b) S.
Antoniotti, V. Dalla, E. Duñach, Angew. Chem. Int. Ed. 2010, 49, 7860-
7888; c) T. Stahl, H. F. T. Klare, M. Oestreich, ACS Catalysis 2013, 3,
1578-1587; d) D. W. Stephan, J. Am. Chem. Soc. 2015, 137, 10018-
10032; e) E. I. Davydova, T. N. Sevastianova, A. Y. Timoshkin, Coord.
Chem. Rev. 2015, 297, 91-126; f) M. Oestreich, J. Hermeke, J. Mohr,
Chem. Soc. Rev. 2015, 44, 2202-2220.
no catalytic HDF was obtained, but
a
stoichiometric
dehydrofluorination with subsequent isomerization of the terminal
to an internal olefin (2-pentene) occurred.
Despite the simple preparation of 1-(CH3CN)2 and its high
reactivity, access to donor-free 1 would be finally desirable.
Comparable synthetic procedures with HSiCl3 or SiCl4 in non-
donor solvents were not successful. However, a B(C6F5)3
catalyzed, dehydrogenative protocol relying on OESTREICH’s SiH4
surrogate tris(cyclohexadienyl)silane in CH2Cl2 granted access to
free 1, with H2 and benzene as the only byproducts (Figure 4c).[26]
The formation of 1 was proven by addition of OPEt3 or KF/18-
crown-6 to the insoluble product, affording identical NMR spectra
and single crystals as those obtained from the same reactions
with 1-(CH3CN)2.
[2]
[3]
a) L. O. Müller, D. Himmel, J. Stauffer, G. Steinfeld, J. Slattery, G.
Santiso-Quiñones, V. Brecht, I. Krossing, Angew. Chem. Int. Ed. 2008,
47, 7659-7663; b) T. E. Mallouk, G. L. Rosenthal, G. Mueller, R.
Brusasco, N. Bartlett, Inorg. Chem. 1984, 23, 3167-3173; c) K. O. Christe,
D. A. Dixon, D. McLemore, W. W. Wilson, J. A. Sheehy, J. A. Boatz, J.
Fluorine Chem. 2000, 101, 151-153.
a) F. Sladky, H. Kropshofer, O. Leitzke, J. Chem. Soc., Chem. Commun.
1973, 134-135; b) V. C. Williams, W. E. Piers, W. Clegg, M. R. J.
Elsegood, S. Collins, T. B. Marder, J. Am. Chem. Soc. 1999, 121, 3244-
3245; c) M. Finze, E. Bernhardt, H. Willner, Angew. Chem. Int. Ed. 2007,
46, 9180-9196; d) L. A. Körte, J. Schwabedissen, M. Soffner, S.
Blomeyer, C. G. Reuter, Y. V. Vishnevskiy, B. Neumann, H.-G. Stammler,
N. W. Mitzel, Angew. Chem. Int. Ed. 2017, 56, 8578-8582.
In
conclusion,
we
identified
and
prepared
bis(perchlorocatecholato)silane as the first neutral silicon(IV)
Lewis super acid by a straightforward synthesis. Fluoride
-
abstraction from SbF6 experimentally verified the Lewis super
[4]
a) T. Belgardt, J. Storre, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt,
Inorg. Chem. 1995, 34, 3821-3822; b) J. Chen, E. Y. X. Chen, Angew.
Chem. Int. Ed. 2015, 54, 6842-6846; c) A. Wiesner, T. W. Gries, S.
Steinhauer, H. Beckers, S. Riedel, Angew. Chem. Int. Ed. 2017, 56,
8263-8266; d) J. F. Kögel, D. A. Sorokin, A. Khvorost, M. Scott, K. Harms,
D. Himmel, I. Krossing, J. Sundermeyer, Chem. Sci. 2018,
10.1039/C7SC03988C.
acidity. The characterization of a SiO4F2 silicate dianion and
stable chloridosilicates, as well as the catalytic activity in a
hydrodefluorination reaction exemplified the high affinity towards
halides. Given the Lewis acidity and the ease of preparation of 1-
(CH3CN)2, we are expecting versatile applications in bond
activation and other fields of research, where superior Lewis
acidity is needed.
[5]
[6]
D. Lentz, K. Seppelt, Z. Anorg. Allg. Chem. 1983, 502, 83-88.
C. B. Caputo, L. J. Hounjet, R. Dobrovetsky, D. W. Stephan, Science
2013, 341, 1374-1377.
[7]
a) S. Steinhauer, J. Bader, H.-G. Stammler, N. Ignat‘ev, B. Hoge, Angew.
Chem. Int. Ed. 2014, 53, 5206-5209; b) B. Waerder, M. Pieper, L. A.
Körte, T. A. Kinder, A. Mix, B. Neumann, H.-G. Stammler, N. W. Mitzel,
Angew. Chem. Int. Ed. 2015, 54, 13416-13419; c) N. Schwarze, B.
Kurscheid, S. Steinhauer, B. Neumann, H. G. Stammler, N. Ignat'ev, B.
Hoge, Chem. Eur. J. 2016, 22, 17460-17467.
Acknowledgements
We gratefully thank Prof. H.-J. Himmel for his support, the FCI for
financial support and the BWFor/BWUniCluster for computational
resources. D. Arian is acknowledged for ESI-MS measurements.
[8]
[9]
A. L. Liberman-Martin, R. G. Bergman, T. D. Tilley, J. Am. Chem. Soc.
2015, 137, 5328-5331.
D. H. McDaniel, H. C. Brown, J. Org. Chem. 1958, 23, 420-427.
This article is protected by copyright. All rights reserved.

10.1002/anie.201712155
Angewandte Chemie International Edition
COMMUNICATION
[10] a) A. E. Ashley, T. J. Herrington, G. G. Wildgoose, H. Zaher, A. L.
Thompson, N. H. Rees, T. Krämer, D. O’Hare, J. Am. Chem. Soc. 2011,
133, 14727-14740; b) M. Hirai, F. P. Gabbaï, Angew. Chem. Int. Ed. 2015,
54, 1205-1209.
[11] a) H. Bohrer, N. Trapp, D. Himmel, M. Schleep, I. Krossing, Dalt. Trans.
2015, 44, 7489-7499; b) F. Neese, A. Hansen, D. G. Liakos, J. Chem.
Phys. 2009, 131, 064103; c) C. Riplinger, F. Neese, J. Chem. Phys. 2013,
138, 034106; d) E. Paulechka, A. Kazakov, J. Phys. Chem. A 2017, 121,
4379-4387.
[12] H. Lübbecke, P. Boldt, Tetrahedron 1978, 34, 1577-1579.
[13] B. v. ꢀAhsen, B. Bley, S. Proemmel, R. Wartchow, H. Willner, F. Aubke,
Z. Anorg. Allg. Chem. 1998, 624, 1225-1234.
[14] a) U. Mayer, V. Gutmann, W. Gerger, Monatsh. Chem. 1975, 106, 1235-
1257; b) M. A. Beckett, G. C. Strickland, J. R. Holland, K. Sukumar
Varma, Polymer 1996, 37, 4629-4631.
[15] Substoichiometric or excess amount of OPEt3 enriched one over the
other species respectively. See SI for further details.
[16] E. Hey-Hawkins, U. Dettlaff-Weglikowska, D. Thiery, H. G. von
Schnering, Polyhedron 1992, 11, 1789-1794.
[17] a) A. J. Blake, S. Cradock, E. A. V. Ebsworth, K. C. Franklin, Angew.
Chem. Int. Ed. 1990, 29, 76-78; b) K. Vojinovic, U. Losehand, N. W.
Mitzel, Dalt. Trans. 2004, 2578-2581.
[18] a) R. J. Garant, L. M. Daniels, S. K. Das, M. N. Janakiraman, R. A.
Jacobson, J. G. Verkade, J. Am. Chem. Soc. 1991, 113, 5728-5735; b)
M. Driess, R. Barmeyer, C. Monsé, K. Merz, Angew. Chem. Int. Ed. 2001,
40, 2308-2310; c) J. Yang, P. S. White, M. Brookhart, J. Am. Chem. Soc.
2008, 130, 17509-17518.
[19] A. Zalkin, J. D. Forrester, D. H. Templeton, Act. Chryst. 1964, 17, 1408-
1412.
[20] a) J. J. Harland, R. O. Day, J. F. Vollano, A. C. Sau, R. R. Holmes, J. Am.
Chem. Soc. 1981, 103, 5269-5270; b) U. Dettlaff-Weglikowska, E. Hey-
Hawkins, H. G. von Schnering, in Z. Naturforsch. B, Vol. 46, 1991, p. 609.
[21] S. Steinhauer, T. Böttcher, N. Schwarze, B. Neumann, H.-G. Stammler,
B. Hoge, Angew. Chem. Int. Ed. 2014, 53, 13269-13272.
[22] Unfortunately, the structure refinement was not satisfying due to solvent
and anion disorder. See SI.
[23] The 13C-NMR peak dispersion in adducts of 1 serves as sensible tool for
the evaluation of the coordination at silicon (see SI for comparison).
[24] A. F. Janzen, Coord. Chem. Rev. 1994, 130, 355-426.
[25] a) S. Hashimoto, M. Hayashi, R. Noyori, Tetrahedron Lett. 1984, 25,
1379-1382; b) N. Ryoji, H. Masahiko, Chem. Lett. 1987, 16, 57-60; c) Q.
Shen, Y.-G. Huang, C. Liu, J.-C. Xiao, Q.-Y. Chen, Y. Guo, J. Fluorine
Chem. 2015, 179, 14-22.
[26] A. Simonneau, M. Oestreich, Nat. Chem. 2015, 7, 816-822.
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Entry for the Table of Contents
COMMUNICATION
Neutral, but super attractive:
Rezisha Maskey, Marcel Schädler,
Claudia Legler and Lutz Greb*
Bis(perchlorocatecholato)silane is
presented as the first neutral silicon
Lewis super acid. The Lewis acidity is
exemplified by coordination of weak
donors, halide abstractions and a
catalytic hydrodefluorination reaction.
Page No. – Page No.
Bis(perchlorocatecholato)silane - A
neutral silicon Lewis super acid
[1]
[2]
[3]
a) A. Corma, H. García, Chem. Rev. 2003, 103, 4307-4366; b) S. Antoniotti, V. Dalla, E.
Duñach, Angew. Chem. Int. Ed. 2010, 49, 7860-7888; c) T. Stahl, H. F. T. Klare, M. Oestreich,
ACS Catalysis 2013, 3, 1578-1587; d) D. W. Stephan, J. Am. Chem. Soc. 2015, 137, 10018-
10032; e) E. I. Davydova, T. N. Sevastianova, A. Y. Timoshkin, Coord. Chem. Rev. 2015, 297,
91-126; f) M. Oestreich, J. Hermeke, J. Mohr, Chem. Soc. Rev. 2015, 44, 2202-2220.
a) L. O. Müller, D. Himmel, J. Stauffer, G. Steinfeld, J. Slattery, G. Santiso-Quiñones, V.
Brecht, I. Krossing, Angew. Chem. Int. Ed. 2008, 47, 7659-7663; b) T. E. Mallouk, G. L.
Rosenthal, G. Mueller, R. Brusasco, N. Bartlett, Inorg. Chem. 1984, 23, 3167-3173; c) K. O.
Christe, D. A. Dixon, D. McLemore, W. W. Wilson, J. A. Sheehy, J. A. Boatz, J. Fluorine
Chem. 2000, 101, 151-153.
a) F. Sladky, H. Kropshofer, O. Leitzke, J. Chem. Soc., Chem. Commun. 1973, 134-135; b) V.
C. Williams, W. E. Piers, W. Clegg, M. R. J. Elsegood, S. Collins, T. B. Marder, J. Am. Chem.
Soc. 1999, 121, 3244-3245; c) M. Finze, E. Bernhardt, H. Willner, Angew. Chem. Int. Ed. 2007,
46, 9180-9196; d) L. A. Körte, J. Schwabedissen, M. Soffner, S. Blomeyer, C. G. Reuter, Y. V.
Vishnevskiy, B. Neumann, H.-G. Stammler, N. W. Mitzel, Angew. Chem. Int. Ed. 2017, 56,
8578-8582.
[4]
a) T. Belgardt, J. Storre, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, Inorg. Chem. 1995, 34,
3821-3822; b) J. Chen, E. Y. X. Chen, Angew. Chem. Int. Ed. 2015, 54, 6842-6846; c) A.
Wiesner, T. W. Gries, S. Steinhauer, H. Beckers, S. Riedel, Angew. Chem. Int. Ed. 2017, 56,
8263-8266; d) J. F. Kögel, D. A. Sorokin, A. Khvorost, M. Scott, K. Harms, D. Himmel, I.
Krossing, J. Sundermeyer, Chem. Sci. 2018, 10.1039/C7SC03988C.
[5]
[6]
D. Lentz, K. Seppelt, Z. Anorg. Allg. Chem. 1983, 502, 83-88.
C. B. Caputo, L. J. Hounjet, R. Dobrovetsky, D. W. Stephan, Science 2013, 341, 1374-1377.
This article is protected by copyright. All rights reserved.

10.1002/anie.201712155
Angewandte Chemie International Edition
COMMUNICATION
[7]
a) S. Steinhauer, J. Bader, H.-G. Stammler, N. Ignat‘ev, B. Hoge, Angew. Chem. Int. Ed. 2014,
53, 5206-5209; b) B. Waerder, M. Pieper, L. A. Körte, T. A. Kinder, A. Mix, B. Neumann, H.-
G. Stammler, N. W. Mitzel, Angew. Chem. Int. Ed. 2015, 54, 13416-13419; c) N. Schwarze, B.
Kurscheid, S. Steinhauer, B. Neumann, H. G. Stammler, N. Ignat'ev, B. Hoge, Chem. Eur. J.
2016, 22, 17460-17467.
[8]
[9]
A. L. Liberman-Martin, R. G. Bergman, T. D. Tilley, J. Am. Chem. Soc. 2015, 137, 5328-5331.
D. H. McDaniel, H. C. Brown, J. Org. Chem. 1958, 23, 420-427.
[10] a) A. E. Ashley, T. J. Herrington, G. G. Wildgoose, H. Zaher, A. L. Thompson, N. H. Rees, T.
Krämer, D. O’Hare, J. Am. Chem. Soc. 2011, 133, 14727-14740; b) M. Hirai, F. P. Gabbaï,
Angew. Chem. Int. Ed. 2015, 54, 1205-1209.
[11] a) H. Bohrer, N. Trapp, D. Himmel, M. Schleep, I. Krossing, Dalt. Trans. 2015, 44, 7489-7499;
b) F. Neese, A. Hansen, D. G. Liakos, J. Chem. Phys. 2009, 131, 064103; c) C. Riplinger, F.
Neese, J. Chem. Phys. 2013, 138, 034106; d) E. Paulechka, A. Kazakov, J. Phys. Chem. A 2017,
121, 4379-4387.
[12] H. Lübbecke, P. Boldt, Tetrahedron 1978, 34, 1577-1579.
[13] B. v. ꢀAhsen, B. Bley, S. Proemmel, R. Wartchow, H. Willner, F. Aubke, Z. Anorg. Allg. Chem.
1998, 624, 1225-1234.
[14] a) U. Mayer, V. Gutmann, W. Gerger, Monatsh. Chem. 1975, 106, 1235-1257; b) M. A. Beckett,
G. C. Strickland, J. R. Holland, K. Sukumar Varma, Polymer 1996, 37, 4629-4631.
[15] Substoichiometric or excess amount of OPEt3 enriched one over the other species respectively.
See SI for further details.
[16] E. Hey-Hawkins, U. Dettlaff-Weglikowska, D. Thiery, H. G. von Schnering, Polyhedron 1992,
11, 1789-1794.
[17] a) A. J. Blake, S. Cradock, E. A. V. Ebsworth, K. C. Franklin, Angew. Chem. Int. Ed. 1990, 29,
76-78; b) K. Vojinovic, U. Losehand, N. W. Mitzel, Dalt. Trans. 2004, 2578-2581.
[18] a) R. J. Garant, L. M. Daniels, S. K. Das, M. N. Janakiraman, R. A. Jacobson, J. G. Verkade, J.
Am. Chem. Soc. 1991, 113, 5728-5735; b) M. Driess, R. Barmeyer, C. Monsé, K. Merz, Angew.
Chem. Int. Ed. 2001, 40, 2308-2310; c) J. Yang, P. S. White, M. Brookhart, J. Am. Chem. Soc.
2008, 130, 17509-17518.
[19] A. Zalkin, J. D. Forrester, D. H. Templeton, Act. Chryst. 1964, 17, 1408-1412.
[20] a) J. J. Harland, R. O. Day, J. F. Vollano, A. C. Sau, R. R. Holmes, J. Am. Chem. Soc. 1981,
103, 5269-5270; b) U. Dettlaff-Weglikowska, E. Hey-Hawkins, H. G. von Schnering, in Z.
Naturforsch. B, Vol. 46, 1991, p. 609.
[21] S. Steinhauer, T. Böttcher, N. Schwarze, B. Neumann, H.-G. Stammler, B. Hoge, Angew. Chem.
Int. Ed. 2014, 53, 13269-13272.
[22] Unfortunately, the structure refinement was not satisfying due to solvent and anion disorder. See
SI.
[23] The 13C-NMR peak dispersion in adducts of 1 serves as sensible tool for the evaluation of the
coordination at silicon (see SI for comparison).
[24] A. F. Janzen, Coord. Chem. Rev. 1994, 130, 355-426.
[25] a) S. Hashimoto, M. Hayashi, R. Noyori, Tetrahedron Lett. 1984, 25, 1379-1382; b) N. Ryoji, H.
Masahiko, Chem. Lett. 1987, 16, 57-60; c) Q. Shen, Y.-G. Huang, C. Liu, J.-C. Xiao, Q.-Y.
Chen, Y. Guo, J. Fluorine Chem. 2015, 179, 14-22.
[26] A. Simonneau, M. Oestreich, Nat. Chem. 2015, 7, 816-822.
This article is protected by copyright. All rights reserved.