1,1-Hydroboration and a Borane Adduct of Diphenyldiazomethane: A Potential Prelude to FLP-N2 Chemistry

Article abstract of DOI:10.1002/anie.201710337

Diphenyldiazomethane reacts with HB(C₆F₅)₂ and B(C₆F₅)₃, resulting in 1,1-hydroboration and adduct formation, respectively. The hydroboration proceeds via a concerted reaction involving ini

Full text of DOI:10.1002/anie.201710337

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: 1,1-Hydroboration and Borane Adduct of Diphenyldiazomethane:
A Prelude to FLP-N2 Chemistry?
Authors: Connie Tang, Qiuming Liang, Andy Jupp, Tim Johnstone,
Rebecca Neu, Datong Song, Stefan Grimme, and Douglas
Wade Stephan
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201710337
Angew. Chem. 10.1002/ange.201710337
Link to VoR: http://dx.doi.org/10.1002/anie.201710337
http://dx.doi.org/10.1002/ange.201710337

10.1002/anie.201710337
Angewandte Chemie International Edition
COMMUNICATION
1,1-Hydroboration and Borane Adduct of Diphenyldiazomethane:
A Prelude to FLP-N2 Chemistry?
Connie Tanga, Quiming Lianga, Andrew R. Juppa, Timothy C. Johnstonea, Rebecca C. Neua, Datong
Songa, Stefan Grimmeb and Douglas W. Stephana*
Dedicated
Abstract: Diphenyldiazomethane reacts with HB(C6F5)2 and B(C6F5)3
resulting in 1,1-hydroboration and adduct formation, respectively. The
hydroboration proceeds via a concerted reaction involving initial
formation of the Lewis adduct Ph2CN2BH(C6F5)2. The highly sensitive
adduct Ph2CN2B(C6F5)3, 5, liberates N2 and generates Ph2CB(C6F5)3.
DFT computations reveal that formation of 5 from carbene, N2 and
borane is thermodynamically favourable, suggesting steric frustration
could preclude carbene-borane adduct formation and effect FLP-N2
capture.
binding of N2 to Lewis acids has been the subject of a number
of computational studies, and the species (N2)BF3was
generated transiently via supersonic expansion at 600 torr and
170
K
and characterized spectroscopically.[16] Recent
[17]
computational work on the compound Ph3PNNPPh3
has
described this species as involving two phosphine donors
interacting with N2.[18] This description has been controversial
as this species is not derived from nor evolves N2. On the other
hand, diazomethanes are isolable yet liberate N2, thus acting
as carbene precursors.[19] In this regard, we note our previous
report of insertion of diazomethanes into B-C bonds with
liberation of N2 (Scheme 1).[20] Herein, the sterically-
encumbered diazomethane, Ph2CN2 reacts with the boranes
HB(C6F5)2 and B(C6F5)3 via adduct formation. In the former
case, 1,1-hydroboration is seen, and the diazomethane adduct
of B(C6F5)3 foreshadows the possibility of FLP-N2 chemistry.
Frustrated Lewis pair (FLP) chemistry has emerged as a
strategy to both metal-free hydrogenations and the activation
of a variety of small molecules.[1] Immediately following the
demonstration of the heterolytic activation of H2 by
combinations of Lewis acids and bases in 2006,[2] the notion of
metal-free reduction protocols garnered much attention.
Concurrent with the efforts described above, FLP
strategies have been applied to activate small molecules other
than H2. Early efforts showed the unique reactivity of FLPs with
olefins,[3] alkynes,[4] disulfides,[5] N2O[6] and cyclopropanes,[7]
while more recent studies have extended this reactivity to
include reactions with CO2,[8] CO,[9] NO,[10] SO2[11] and RNSO.[12]
Recent studies have creatively used these fundamentally new
reactions in organic synthetic applications, and others have
uncovered transition metal-based FLPs, with relevance to
hydrogenase enzyme models and surface chemistry.[13]
Notably absent from the list of small molecule substrates
for FLPs is dinitrogen. Although this has been the subject of
question and conjecture for some years, it is only recently that
the groups of Szymczak[14] and Simonneau[15] reported
interaction of boranes with metal-N2 complexes (Scheme 1).
The former demonstrated the prospect of protonation of the
N2 fragment and the latter explored related borylation and
silylation of the N2 bound between the metal and boron.
Metal-free systems that capture N2 are unknown however,
Scheme 1. Metal-N2-borane and diazomethane-borane
reactions.
Combination of Ph2CN2 and Piers borane, HB(C6F5)2, results
in a rapid reaction that affords a robust product
spectrum of showed a diagnostic resonance at 8.77 ppm,
1
. The 1H NMR
1
corresponding to a single NH proton. The corresponding 11B
NMR signal was seen at 35.3 ppm, while the 19F NMR spectrum
showed six signals, attributable to inequivalent C6F5 rings.
Miss C. Tang, Mr. Q. Liang, Dr. A.R. Jupp, Dr. T.C. Johnstone, Dr.
R.C. Neu, Professor Dr. Datong Song, Professor Dr. D.W. Stephan
Department of Chemistry,
University of Toronto,
80 St. George St., Toronto, Ontario, Canada M5S3H6
E-mail: dstephan@chem.utoronto.ca
Collectively these data support the formulation of 1 as
Ph2CNNHB(C6F5)2. This assignment was confirmed via a
crystallographic study (Figure 1). The structural data reveal a
pseudo trigonal planar geometry at B with N-B-C and C-B-C
angles of 118.2(2)°, 121.1(1)° and 120.6(1)°. The C=N, N-N and
N-B bond lengths are 1.287(2) Å, 1.394(2) Å and 1.385(2) Å,
respectively. These data are consistent with considerable B-
Professor Dr. Stefan Grimme,
Mulliken Center for Theoretical Chemistry, Institut fuer Physikalische
und Theoretische Chemie,Universitaet Bonn, Beringstrasse 4, D-
53115 Bonn, Germany
Supporting information for this article is given via a link at the end of
the document.
N-bonding, which gives rise to a trans-diene type structure,
This article is protected by copyright. All rights reserved.

10.1002/anie.201710337
Angewandte Chemie International Edition
COMMUNICATION
inhibits rotation about the B-N bond, and renders the centre. X-ray data confirmed the formulation of
2
(Figure 3a)
with pyramidal geometry at B and C=N, N-N and B-N bond
distances of 1.287(3) Å, 1.453(3) and 1.610(4) Å,
respectively. Gentle heating of at 50 °C for 2 h resulted in the
loss of H2 affording (Scheme 2). In a third synthetic route,
fluoroaryl rings inequivalent.
Å
2
1
1
was prepared directly in 69% yield via reaction Ph2CNNH2 with
1.2 equivalents of HB(C6F5)2 at room temperature.
Figure 1. POV-ray depiction of molecular structure of
1 as
determined by X-ray crystallography. H-atoms (except NH) are
omitted for clarity. C: black, N: blue, B: yellow-green, F: pink.
It is noteworthy that conventional hydroborations give 1,2-
substitution.[21] Although there are rare examples of 1,1-
hydroborations,[22] the formation of
1 represents the first
reported 1,1-hydroboration of an N-N bond. Mechanistically,
two options were considered. In the first, initial 1,2-
hydroboration occurs, followed by proton migration. In the
second, direct 1,1-hydroboration occurs. Computational work
using the dispersion-corrected PBEh-3c[23] (DSD-BLYP/def2-
Scheme 2. Synthetic routes to 1-4.
TZVPP//PBEh-3c+COSMO-RS) revealed
a
rather early
transition state in which the B-H hydride exhibited a bond
order of 0.54 to the B and 0.33 to the N. Localized orbitals
show a 3-centre, 2-electron-bond for the B-H-N unit, inferring
the participation of a low-lying orbital (*) on the N=N unit
that accepts electron density from the B-H bond (Figure 2).
The negative charge on the H atom is small (0.1 e more
negative than H-atoms on carbon). Thus, the 1,1-
hydroboration affording
1 is best described as a H-atom
migration from boron to the proximal nitrogen.
Figure 2. TS structure for H atom migration with a plot of the
localized 3-centre, 2-electron MO which is characteristic of
bond formation.
An orthogonal synthetic strategy was also developed
involving the reaction of Ph2CNNH2 and HB(C6F5)2 in a 1:1
stoichiometry. The reaction generates the Lewis acid-base
adduct (Ph2CNNH2)HB(C6F5)2 2 in 62% isolated yield (Scheme
1
2). The H NMR spectrum exhibits broad multiplets at 6.71-
Figure 3. POV-ray depictions of the molecular structures of (a)
, (b) , (c) as determined by X-ray crystallography. C-H
protons are omitted for clarity. C: black, N: blue, B: yellow-
green, F: pink
6.69 ppm and 3.89 ppm attributable to the NH2 and BH
fragments, respectively. The 11B NMR spectrum shows a
singlet at -12.1 ppm and 19F NMR signals appear at -134.5, -
157.4 and -163.4 ppm, consistent with a 4-coordinate boron
2
3
4
.
This article is protected by copyright. All rights reserved.

10.1002/anie.201710337
Angewandte Chemie International Edition
COMMUNICATION
In a similar fashion, the reaction of Ph2CNNH2 and B(C6F5)3 interesting that this interaction dramatically facilitates the
afforded the corresponding adduct (Ph2CNNH2)B(C6F5)3
62% isolated yield (Scheme 2). Compound
3 in ability of Ph2CN2 to evolve N2. Moreover, it appears that the
exhibited a H steric demands of the arene rings on Ph2CN2 preclude the
NMR singlet at 7.44 ppm, a 11B NMR signal at -6.3 ppm, and formal carbene insertion into B-C bonds that is readily seen
19F NMR peaks at -133.4, -155.4, and -162.7 ppm. Single- with smaller diazomethanes.[20] Upon warming the solution
1
3
crystal X-ray diffraction confirmed the formulation of
C=N, N-N and N-B distances of 1.291(6) Å, 1.459(6) Å and 19F resonances at -132.9, -155.8 and -162.9 ppm appear which
1.631(7) Å, respectively (Figure 3b). Compound , when is consistent with the formation of new adduct proposed to be
heated at 110 °C for 20 h in a sealed vessel, generates a
Ph2C(B(C6F5)3. While a 1H-19F HOESY NMR data further support
solution of compound and C6F5H. Workup of this reaction this proposal, efforts to isolate this species were unsuccessful
afforded in only 26% isolated yield. Interestingly, reaction of (See SI).
with tBu3P proceeds at room temperature over 22 h, and a
new product was isolated (Scheme 2). This species gives rise
3
with warm to room temperature, a 11B NMR signal at -6.4 ppm and
3
1
1
3
4
to a broad resonance in the 1H NMR spectrum at 8.57 ppm and
a doublet at 5.34 ppm (1JH-P = 456 Hz) in a 1:1 intensity ratio.
These resonances are attributed to N- and P-bound protons,
respectively. The 31P NMR spectrum shows a doublet at 58.2
ppm with a corresponding P-H coupling constant. A signal at -
6.6 ppm was observed in the 11B NMR spectrum and the 19F
NMR spectrum of
-162.7 ppm. These data support the formulation of
4
showed three peaks at -133.3, -156.0 and
as the
Figure 4. POV-ray depiction of molecular structure of
5 as
4
determined by X-ray crystallography. H-atoms are omitted for
clarity. C: black, N: blue, B: yellow-green, F: pink.
salt [tBu3PH][Ph2CN2HB(C6F5)3], which was confirmed
crystallographically (Figure 3c). The C=N, N-N and N-B
distances in the anion are 1.296(7) Å, 1.354(6) Å and 1.524(7)
Å, respectively. The metric parameters in the cation were
unexceptional.
Given the isolation of the adducts
a B(C6F5)3 adduct of diphenyldiazomethane was undertaken.
This reaction afforded highly unstable product but
2 and 3, the synthesis of
a
performing the reaction at -78 °C permitted its
characterization. The 11B NMR spectrum of the product
showed a resonance at 4.8 ppm and the 19F NMR spectrum
showed resonances at -132.0, -154.7 and -163.4 ppm. The
upfield 11B NMR shift and the reduced meta-para gap of the
fluorine resonances with respect to the free borane are
consistent with the formation of a Lewis adduct between
B(C6F5)3 and Ph2CN2. Infrared absorption data collected at 233
K showed bands at 1645 and 1516 cm-1 attributable to N=N
and C=N stretches. Crystals of the product proved remarkably
sensitive and evolved gas (N2) even at room temperature
under Paratone-N oil. This sensitivity stands in contrast to Scheme 3. Degradation pathway for
Ph3PNNPPh3, which only evolved N2 above 215 °C.[18] structures
Relative free energies at the DSD-BLYP/def2-
Crystallographic data collected at 150 K confirmed that the TZVPP//PBEh-3c+COSMO-RS[CH2Cl2] level are in kcal/mol.
product was indeed Ph2CN2B(C6F5)3 . The C=N, N=N and B-N
and 1.65(1) Å,
is 124.6(6)°. These acceptor interaction (bond order 0.6), an N-N double bond and
5 showing optimized DFT
.
5
distances are 1.278(8) Å, 1.177(7)
respectively, while the N-N-B angle in
Å
5
DFT computational studies for 5 revealed a N-B donor-
metric data are consistent with C-N and N-N double bond a C-N bond order of 1.5. Consideration of the instability of
character and the geometry about the N2-fragment is prompted computation of the pathway to loss of N2.
reminiscent of the M=N=N-B units seen in Dissociation of to a van der Waals complex is a low energy
M(R2PCH2CH2PR2)2N2B(C6F5)3 (R = Ph, M = Mo, W; R = Et, M = process (3.9 kcal/mol), while a transition state (TS) involving
Fe).[14-15] The B-N distance in
is significantly longer than those coordination of borane to the carbon of
in these metal complexes (M = Mo 1.567(7) Å; W 1.570(6) Å; diphenyldiazomethane is computed to be thermally accessible
M = Fe 1.575(4) Å). At the same time, the N-N bond and the N- at 19.4 kcal/mol above (Scheme 3). From this TS, loss of N2
N-B angle in are shorter/smaller than those in the metal affording the carbene adduct of B(C6F5)3 is exergonic by about
complexes (M = Mo 1.196(5) Å, 141.4(5)°; W 1.212(6) Å, 53 kcal/mol. The B-Ccarbene bonding in Ph2CB(C6F5)3 is
140.3(4)°; Fe 1.186(3) Å, 137.0(3)°). The structural data for computed to be 1.66 Å similar to that seen for the B-C bonds
are consistent with weak N-B donation. Nonetheless, it is
5
5
5
5
5
5
This article is protected by copyright. All rights reserved.

10.1002/anie.201710337
Angewandte Chemie International Edition
COMMUNICATION
[9] (a) M. Sajid, L.-M. Elmer, C. Rosorius, C. G. Daniliuc, S. Grimme,
G. Kehr, G. Erker, Angew. Chem. Int. Ed. 2013, 52, 1-5; (b) R.
Dobrovetsky, D. W. Stephan, J. Am. Chem. Soc. 2013, 135, 4974-
4977.
[10] M. Sajid, A. Stute, A. J. P. Cardenas, B. J. Culotta, J. A. M.
Hepperle, T. H. Warren, B. Schirmer, S. Grimme, A. Studer, C. G.
Daniliuc, R. Frohlich, J. L. Petersen, G. Kehr, G. Erker, J. Am.
Chem. Soc. 2012, 134, 10156-10168.
[11] (a) D. W. Stephan, G. Erker, Chem. Sci. 2014, 5, 2625-2641; (b)
K. Y. Ye, M. Bursch, Z. W. Qu, C. G. Daniliuc, S. Grimme, G.
Kehr, G. Erker, Chem. Commun. 2017, 53, 633-635.
[12] L. E. Longobardi, V. Wolter, D. W. Stephan, Angew. Chem. Int.
Ed. 2015, 54, 809-812.
[13] D. W. Stephan, Science 2016, 354, aaf7229.
[14] J. B. Geri, J. P. Shanahan, N. K. Szymczak, J. Am. Chem. Soc.
2017, 139, 5952-5956.
[15] A. Simonneau, R. Turrel, L. Vendier, M. Etienne, Angew. Chem.
Int. Ed. 2017, 56, 12268 -12272.
[16] K. C. Janda, L. S. Bernstein, J. M. Steed, S. E. Novick, W.
Klemperer, J. Am. Chem. Soc. 1978, 100, 8074.
in B(C6F5)3. Similarly, the bond order is computed to be 0.64
typical for B-C single bonds.
Computations also show that free carbene, free borane
and N2 are only 10.0 kcal/mol below the TS. However, in the
present system formation of the carbene-borane adduct is the
more exergonic reaction pathway. Nonetheless, this suggests
that frustration of the carbene-borane interaction could
provide an energetically favourable reaction pathway to the
TS ultimately affording an analog of
FLP approach to N2 capture.
5 and thus unveiling an
In conclusion, we have reported the 1,1-hydroboration of
Ph2CN2 with HB(C6F5)2 to give , which proceeds via a
concerted mechanism. In addition, reactions of Ph2CNNH2
with HB(C6F5)2 or B(C6F5)3 provide alternative routes to , as
well as a related salt. The isolation of the first diazomethane-
borane adduct, , is also reported. The isolation of this latter
1
1
5
species raises the possibility that judicious choice of a Lewis
acid and base could provide an avenue to metal-free capture
of N2. It is this ambitious objective that is the target of current
efforts.
[17] R. Appel, R. Schöllhorn, Angew. Chem. Int . Ed. 1964, 3, 805.
[18] N. Holzmann, D. Dange, C. Jones, G. Frenking, Angew. Chem.
Int . Ed. 2013, 52, 3004-3008.
[19] T. Itoh, Y. Nakata, K. Hirai, H. Tomioka, J. Am. Chem. Soc. 2006,
128, 957-967.
[20] R. C. Neu, C. Jiang, D. W. Stephan, Dalton Trans. 2013, 42, 726-
736.
[21](a) S. J. Geier, C. M. Vogels, S. A. Westcott, ACS Symp. Ser. 2016,
1236, 209-225; (b) J. R. Lawson, R. L. Melen, Inorg. Chem. 2017,
56, 8627-8643.
[22] (a) F. Meyer, M. U. Schmidt, P. Paetzold, Chem. Ber. 1995, 128,
947-951; (b) R. B. Brandon, C. Moore, E., A. Rheingold, L., J.
Figueroa, S., Chem. Commun. 2015, 51, 541-544; (c) D.-T. Yang,
S. K. Mellerup, X. Wang, J.-S. Lu, S. Wang, Angew. Chem., Int.
Ed. 2015, 54, 5498-5501; (d) Y.-G. Shi, N. Wang, T. Peng, S.
Wang, D.-T. Yang, K. Mellerup Soren, S. Wang, Org. Lett. 2016,
18, 1626-1629.
Keywords: diphenyldiazomethane • borane • 1,1-hydroboration
• adduct • nitrogen •
Acknowledgements
The authors gratefully acknowledge the financial support of
the NSERC of Canada. DWS is also grateful for the award of a
Canada Research Chair and an Einstein Visiting Fellowship at
TU Berlin. CT thanks Digital Speciality Chemicals for
scholarships. ARJ is grateful for the support of a Banting
Fellowship, while TCJ acknowledges the support of an NSERC
Postdoctoral Fellowship. SG thanks the DFG for financial
support in the framework of the Leibniz prize. We thank
Maotong Xu for insightful discussions and Jack Sheng for
invaluable help with NMR spectroscopic experiments.
[23] (a) R. Ahlrichs, M. Bär, M. Häser, H. Horn, C. Kölmel, Chem.
Phys. Lett. 1989, 162, 165-169; (b) TURBOMOLE, version 7.1,
2017,
TURBOMOLE
GmbH,
Karlsruhe,
See
http://www.turbomole.com; (c) F. Neese, Comput. Mol. Sci. 2012,
2, 73-78; (d) S. Grimme, C. Bannwarth, P. J. Shushkov, Chem.
Theory Comput. 2017, 13, 1989-2009; (e) S. Grimme, J. G.
Brandenburg, C. Bannwarth, A. J. Hansen, Chem. Phys. Chem.
2015, 143, 054107; (f) P. M. Zimmerman, J. Chem. Theory
Comput. 2013, 9, 3043-3050; (g) F. Weigend, R. Ahlrichs, Phys.
Chem. Chem. Phys. 2005, 7, 3297-3305; (h) S. Kozuch, D.
Gruzman, J. M. L. Martin, J. Phys. Chem. C, 2010, 114, 20801-
20808; (i) S. Grimme, S. Ehrlich, L. Goerigk, J. Comput. Chem.
2011, 32, 1456-1465; (j) S. Grimme, J. Antony, S. Ehrlich, H.
Krieg, J. Chem. Phys. 2010, 132, 154104; (k) F. Eckert, A. Klamt,
AIChE J. 2002, 48, 369-385; (l) A. J. Klamt, Phys. Chem. 1995, 99,
2224-2235.
[1] (a) D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2015, 54, 6400-
6441; (b) D. W. Stephan, J. Am. Chem. Soc. 2015, 137, 10018-
10032; (c) D. W. Stephan, Acc. Chem. Res. 2015, 48, 306-316; (d)
D. W. Stephan, G. Erker, Top. Curr. Chem. 2013, 332, 1-311; (e)
D. W. Stephan, G. Erker, Top. Curr. Chem. 2013, 334, 1-345; (f)
D. W. Stephan, Org. Biomol. Chem. 2012, 10, 5740-5746; (g) D.
W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2010, 49, 46-76.
[2] G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science
2006, 314, 1124-1126.
[3] J. S. J. McCahill, G. C. Welch, D. W. Stephan, Angew. Chem. Int.
Ed. 2007, 46, 4968-4971.
[4] (a) M. A. Dureen, C. C. Brown, D. W. Stephan, Organometallics
2010, 29, 6594-6607; (b) M. A. Dureen, D. W. Stephan, J. Am.
Chem. Soc. 2009, 131, 8396-8398.
[5] M. A. Dureen, G. C. Welch, T. M. Gilbert, D. W. Stephan, Inorg.
Chem. 2009, 48, 9910-9917.
[6] (a) E. Otten, R. C. Neu, D. W. Stephan, J. Am. Chem. Soc. 2009,
131, 9918-9919; (b) R. C. Neu, E. Otten, D. W. Stephan, Angew.
Chem., Int. Ed. 2009, 48, 9709-9712.
[7] J. G. M. Morton, M. A. Dureen, D. W. Stephan, Chem. Commun.
2010, 46, 8947-8949.
[8] (a) J. J. Chi, T. C. Johnstone, D. Voicu, P. Mehlmann, F. Dielmann,
E. Kumacheva, D. W. Stephan, Chem. Sci. 2017, 8, 3270-3275; (b)
J. Chen, L. Falivene, L. Caporaso, L. Cavallo, E. Y. Chen, J. Am.
Chem. Soc. 2016, 138, 5321-5333.
This article is protected by copyright. All rights reserved.

10.1002/anie.201710337
Angewandte Chemie International Edition
COMMUNICATION
Connie Tanga, Qiuming Lianga, Andrew R. Juppa, Timothy C. Johnstonea, Rebecca
C. Neua, Datong Songa, Stefan Grimmeb and Douglas W. Stephana*
Page No. – Page No.
1,1-Hydroboration and Borane Adduct of Diphenyldiazomethane: A Prelude to
FLP-N2 Chemistry?
N2 the breach… Diphenyldiazomethane reacts with HB(C6F5)2 and B(C6F5)3 affording
1,1-hydroboration and adduct formation, respectively. The adduct Ph2CN2B(C6F5)3
liberates N2 and the diphenylcarbene-borane adduct. Computational studies suggest
that N2 capture is thermodynamically favourable, but for the exothermicity of carbene–
borane adduct formation.
Miss C. Tang, Mr. Q. Liang, Dr. A.R. Jupp, Dr. T.C. Johnstone, Dr.
R.C. Neu, Professor Dr. Datong Song, Professor Dr. D.W. Stephan
Department of Chemistry,
University of Toronto,
80 St. George St., Toronto, Ontario, Canada M5S3H6
E-mail: dstephan@chem.utoronto.ca
Professor Dr. Stefan Grimme,
Mulliken Center for Theoretical Chemistry, Institut fuer Physikalische
und Theoretische Chemie,Universitaet Bonn, Beringstrasse 4, D-
53115 Bonn, Germany
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.