Closo - O -carboranylmethylamine-pyridine associations: Synthesis, characterization, and first complexation studies

Article abstract of DOI:10.1021/om1006374

The synthesis of new pyridine-substituted carboranylmethylamines is described. The strategy involved mesylation of carboranylmethanols prior to amination reaction and is particularly adapted to the reactivity of o-carborane derivatives bearing a 2-pyridinyl substituent. Preparation and characterization of a corresponding N,N-ligand-palladium complex as well as first results in a Suzuki coupling reaction are illustrated.

Full text of DOI:10.1021/om1006374

4130 Organometallics 2010, 29, 4130–4134
DOI: 10.1021/om1006374
closo-o-Carboranylmethylamine-Pyridine Associations: Synthesis,
Characterization, and First Complexation Studies
†
†
,†
,‡
Vincent Terrasson,†,‡ Jose Giner Planas, Clara Vinas, Francesc Teixidor,* Damien Prim,*
ꢀ
~
Mark E. Light,§ and Michael B. Hursthouse§
†
ꢁ
Institut de Ciencia de Materials de Barcelona, CSIC, Campus de la UAB, 08193 Bellaterra, Spain,
‡
ꢀ
Universite de Versailles Saint-Quentin, Institut Lavoisier de Versailles, UMR CNRS 8180, 45 Avenue des
Etats-Unis, 78035 Versailles, France, and School of Chemistry, University of Southampton, Highfield,
§
Southampton SO171BJ, United Kingdom
Received July 1, 2010
The synthesis of new pyridine-substituted carboranylmethylamines is described. The strategy
involved mesylation of carboranylmethanols prior to amination reaction and is particularly adapted
to the reactivity of o-carborane derivatives bearing a 2-pyridinyl substituent. Preparation and
characterization of a corresponding N,N-ligand-palladium complex as well as first results in a Suzuki
coupling reaction are illustrated.
Introduction
organophosphorus derivatives,2 thiols, thioethers, and to a
lesser extent amines, arsines, or selenols and may form a
variety of mono- or bidentate coordination complexes.3 The
past decades have witnessed the emerging use of both
metallacarboranes and closo-carborane-based coordination
compounds in a wide range of transition metal catalyzed
organic transformations.4,5 For instance, closo-carborane
frameworks bearing thioether and/or phosphine substitu-
ents at both C-vertices were recently shown to be highly
effective bidentate ligands for Pd- and Rh-catalyzed organic
transformations.4 However, the association of amine-chelat-
ing groups to a closo-carborane unit as ligands is still scarcely
reported, probably due to the well-known amine- and/or
base-generated degradation ofcloso-carboranes.6 Such carbo-
rane derivatives thus remain challenging and under-exploited
from synthetic, coordination chemistry, and, consequently,
ortho-Carboranes (icosahedral closo-1,2-C2B10H12) repre-
sent a class of boron clusters that have found applications in
fields as diverse as material science, medicinal chemistry,
selective metal ion extraction, polymers, or supramolecular
chemistry.1 These icosahedral closo-o-carboranes may be
functionalized at one or both cage carbon atoms to give
*To whom correspondence should be addressed. E-mail: teixidor@
icmab.es; prim@chimie.uvsq.fr.
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Chem. 2000, 39, 4280. (d) Lee, Y.-J.; Lee, J.-D.; Kim, S.-J.; Keum, S.; Ko, J.;
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Sillanpaa, R. J. Am. Chem. Soc. 2000, 122, 1963. (b) Tutusaus, O.; Vinas,
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r
pubs.acs.org/Organometallics
Published on Web 08/24/2010
2010 American Chemical Society

Article
Scheme 1. Previous Results on Carboranylmethyl Alcohol
Chemistry
Organometallics, Vol. 29, No. 18, 2010 4131
Scheme 2. Mesylation of Carboranylbenzyl Alcohols
applications points of view.7 On the basis of our previous
experience in both carborane chemistry8 and synthesis, com-
plexation, and catalytic activity of benzylic amines,9 we have
been interested in the synthesis of new carboranyl amines. Our
efforts to date have focused on aminobenzyl-o-carboranes
bearing (hetero)aromatic rings (type III in Scheme 1). We
have recently reported a convenient and general method to
synthesize these compounds starting from monosubtituted
carboranes and commercially available aromatic aldehydes
and avoiding the cluster degradation.8g The key step of this
methodology is a selective nucleophilic amination of the
chlorides II as intermediates ((b) in Scheme 1). The use of
mild conditions allowed minimization of partial degradation
of the boron clusters by amines. Following this strategy, we
sought to develop a new series of potentially interesting
bidentate N,N-ligands incorporating both an aminomethyl-
o-carborane cluster and a pyridine heterocycle (type III0 in
Scheme 1). If the 2-aminomethylpyridine pattern is found in
many ligands recently described for coordination chemistry
and/or catalysis,10 2-aminomethylpyridine-carborane com-
binations remain to our knowledge unprecedented. Unfor-
tunately our synthetic sequence involving chlorination of
carboranyl methyl alcohols followed by nucleophilic amina-
tion proved unsuccessful with pyridine-substituted substrates
(Scheme 1), showing that in this case such transformation is
still not trivial.8f In this note, we report a new easy methodo-
logy to synthesize such N,N-diamines that overcome the
previous synthetic problems and show that this new family
of ligands can form stable Pd complexes that are highly
effective catalysts for Suzuki coupling reactions.
Results and Discussion
We previously examined the mesylation of alcohol 1a,
bearing a phenyl substituent, and obtained a very poor
conversion of the alcohol to the corresponding mesylate 2a
(Scheme 2a) even under harsh reaction conditions (2 equiv of
MeSO2Cl in refluxing CH2Cl2).8g We hypothesized that the
low reactivity of alcohol 1a could be due to its low nucleo-
philicity as a result of the presence of two electron-with-
drawing substituents (phenyl and o-carboranyl groups), in
addition to the bulkiness of the cluster. For these reasons we
turned our attention to the smaller SOCl2 reagent, and this
reacted completely to give the halogenated derivatives (type
II in Scheme 1).8g However, we were puzzled by the unusual
reactivity of these 2-pyridyl derivatives. In fact, in situ NMR
experiments showed that the latter were far more reactive
toward SOCl2 than the related phenyl derivatives, regardless
of the nature of the reaction product (Scheme 2b).8f The
oxidation process affording the pyridyl-carboranyl ketone
II0 was attributed to the fast formation of plausible pyridi-
nium-chlorosulfite intermediate A (Y = SOCl), with con-
comitant increase of the residual pseudo benzylic proton
acidity, at the early stage of the chlorination step (Scheme 2).
Taking into account the strong analogy between inter-
mediate A and the product resulting from mesylation of I
(Y = SO2Me), we were curious to test the reactivity of the
2-pyridinyl derivatives toward MeSO2Cl to see whether
oxidation or mesylation would occur. Therefore two 2-pyr-
idinyl derivatives 1b,c were treated with MeSO2Cl in the
presence of Et3N at room temperature (Scheme 2a). Gratify-
ingly, both derivatives 1b,c afforded the mesylated products
2b,c, exclusively, in excellent yields, as shown in Scheme 2.
These results further illustrate the particular behavior of the
2-pyridinyl-substituted carboranylmethanols 1b and 1c to-
ward electrophiles8f and suggest the crucial intervention of
the pyridine moiety in the reaction mechanism. All new
compounds in this work have been fully characterized
(7) Yoo, J.; Do, Y. Dalton Trans. 2009, 4978.
~
(8) (a) Teixidor, F.; Vinas, C.; Benakki, R. Inorg. Chem. 1997, 36,
€€
~
€
~
1719. (b) Vinas, C.; Cirera, M. R.; Teixidor, F.; Sillanpaa, R.; Kivekas, R.;
ꢀ
Llibre, J. Inorg. Chem. 1998, 37, 6746. (c) Teixidor, F.; Angles, P.; Vinas, C.
~
~
Inorg. Chem. 1999, 38, 3605. (d) Teixidor, F.; Nꢀunez, R.; Vinas, C.;
€€
€
Sillanpaa, R.; Kivekas, R. Angew. Chem., Int. Ed. 2000, 39, 4290.
~
(e) Oliva, J. M.; Allan, N. L.; Schleyer, P. v. R.; Vinas, C.; Teixidor, F. J.
Am. Chem. Soc. 2005, 127, 13538. (f) Terrasson, V.; Planas, J. G.; Prim, D.;
1
by analytical methods and H, 11B, 11B{1H}, and 13C{1H}
~
Vinas, C.; Teixidor, F.; Light, M. E.; Hursthouse, M. B. J. Org. Chem. 2008,
~
73, 9140. (g) Terrasson, V.; Planas, J. G.; Prim, D.; Teixidor, F.; Vinas, C.;
NMR spectroscopy. 11B{1H} NMR spectra for all com-
pounds are consistent with a closo-icosahedral geometry
for the boron cage.11 13C{1H} NMR spectra also show
characteristic peaks for the two cage-carbon vertices, pyr-
idine ring, and benzylic CH carbons. Only relevant 1H NMR
data will be discussed later in more detail.
Light, M. E.; Hursthouse, M. B. Chem.;Eur. J. 2009, 15, 12030.
(9) (a) Terrasson, V.; Marque, S.; Scarpacci, A.; Prim, D. Synthesis
2006, 1858. (b) Terrasson, V.; Marque, S.; Georgy, M.; Campagne, J.-M.;
Prim, D. Adv. Synth. Catal. 2006, 348, 2063. (c) Michaux, J.; Terrasson, V.;
Marque, S.; Wehbe, J.; Prim, D.; Campagne, J.-M. Eur. J. Org. Chem. 2007,
2601. (d) Terrasson, V.; Prim, D.; Marrot, J. Eur. J. Inorg. Chem. 2008, 2739.
(10) For recent examples, see: (a) Mayilmurugan, R.; Visvaganesan,
K.; Suresh, E.; Palaniandavar, M. Inorg. Chem. 2009, 48, 8771. (b) Li, R.;
Moubaraki, B.; Murray, K. S.; Brooker, S. Eur. J. Inorg. Chem. 2009, 19,
2851. (c) Felluga, F.; Baratta, W.; Fanfoni, L.; Pitacco, G.; Rigo, P.; Benedetti,
F. J. Org. Chem. 2009, 74, 3547. (d) Dickson, S. J.; Paterson, M. J.; Willans,
C. E.; Anderson, K. M.; Steed, J. W. Chem.;Eur. J. 2008, 14, 7296.
(e) Puget, B.; Roblin, J.-P.; Prim, D.; Troin, Y. Tetrahedron Lett. 2008, 49,
1706. (f) Gil-Molto, J.; Karlstrom, S.; Najera, C. Tetrahedron 2005, 61,
12168.
The successful syntheses of the mesylate derivates 2b,c
open new possibilities for the preparation of the desired N,
N-diamines by nucleophilic amination. Indeed, mesylates
2b,c were successfully converted into the targeted vicinal
(11) Todd, L. J. Prog. Nucl. Magn. Reson. Spectrosc. 1979, 13, 87.

4132 Organometallics, Vol. 29, No. 18, 2010
Terrasson et al.
Scheme 4. Preparation of the Palladium Complex 8
Scheme 3. Preparation of the Diamine Derivatives 3-7
protons H(a), H(b), H(c), and H(d) and from 0.37 to 0.92
ppm for the benzylic protons H(e) and H(f), respectively. As
expected, the chemical shift for the NH proton is the most
affected by metal coordination (δ 2.87 and 4.53 for 5 and 8,
respectively). It can be seen that an AB spin system for the
diastereotopic protons of the methylene group of the benzyl
fragment (H(f) in Figure 2) in ligand 5 became a well-
resolved ABX spin system in complex 8 [H(f) and H(f0)].
Coupling constants between the two diastereotopic nuclei,
JAB, are 13.0 and 13.7 Hz for the ligand 5 and the complex 8,
respectively. Coupling of both diastereotopic nuclei with
the NH proton is observed only in the complex and dis-
plays different coupling constants (9.2 and 2.2 Hz). Con-
sequently, the NH proton appears as a broad doublet of
about 8 Hz.
diamines by their reaction with 1.5 equiv of amine at room
temperature in acetonitrile (Scheme 3). The expected com-
pounds 3-7 were obtained in good to excellent yields (53-
86%) regardless of the nature of the nucleophile (primary
or secondary, cyclic or acyclic amine). All these new com-
pounds were fully characterized by analytical methods and
NMR spectroscopy, and the molecular structures of 5 and 6
have been unequivocally established by X-ray crystallogra-
phy. The molecular structures for both compounds are in
agreement with the NMR data showing the vicinal disposi-
tion of the pyridine and amine nitrogens. Crystal data
collection, selected bond lengths, bond angles, and torsion
angles can be found in the Supporting Information.
As thought, these new aminomethyl-o-carboranes are
characterized by the presence of two nitrogen atoms in
vicinal position and can be considered as interesting N,N-
ligands for the preparation of original transition metal
complexes. In order to illustrate the potential of this family
of compounds in coordination chemistry, we turned our
attention to the synthesis of a palladium complex. We chose
to first examine the aminomethyl-o-carborane 5 by virtue of
two different chiral centers, one at the secondary amine
nitrogen and the other at the contiguous methylene carbon.
Thus, diamine 5 was treated with Na2[PdCl4] in freshly
distilled MeOH according to recent literature12 to give the
desired PdII complex 8 in nearly quantitative yield as an air-
stable orange solid (Scheme 4). This complex was easily
purified by simple filtration through a silica gel pad and
was stable in acetone solutions for weeks. Complex 8 is to the
best of our knowledge the first palladium-diamine complex
incorporating an intact closo-boron cluster in its structure.
Complex 8 has been fully characterized by NMR spec-
troscopy and elemental analysis. There are two sources of
chirality in this complex that would lead, in principle, to four
different stereoisomers. The coordinated NH nitrogen has
four different substituents leading to a chiral center that can
adopt R and S configurations. The other source of chirality is
the contiguous methylene carbon adopting also R and S
configurations. However, only one diastereomer is observed
in solution since only one set of signals was found in the 1H,
11B, and 13C NMR spectra of 8. Metal coordination to both
nitrogen atoms of the ligand is confirmed by a characteristic
positive shielding observed between the amine 5 and its
corresponding complex 8 (Figure 1). The chemical shift
differences range from 0.27 to 0.45 ppm for the pyridine
The molecular structure of 8 has been unequivocally
confirmed by X-ray crystallography.13 The crystal structure
of the complex contains a racemic mixture of RS/SR en-
antiomeric pairs. The molecular structure of the N(2) R-
C(3) S isomer is shown in Figure 2, and selected bond
lengths, bond angles, and torsion angles are given in the
Supporting Information As expected, the chelating ligand
binds to the metal through a pyridyl donor N1 and secondary
amine donor N2, forming a five-membered ring with an
N1-Pd1-N2 angle of 81.11(10)°. The coordination sphere
at Pd(1) is close to square planar, the largest deviation of
Cl(2), Cl(3), N(1), and N(2) from their main plane being
˚
0.040 A. Whereas both Pd1-Cl bond distances are nearly
˚
identical (Pd1-Cl2, 2.2877(8) and Pd1-Cl3, 2.2887(8) A),
˚
the Pd-N1(pyridine) bond distance of 2.030(2) A is signifi-
˚
cantly shorter than the Pd-N2(H) distance of 2.049(3) A.
The nearly identical Pd-Cl bond distances reflect a similar
trans influence of the pyridyl and secondary amine groups.
Consequently, the difference of bond distances (Δ(Pd-N))
˚
of 0.019 A is probably due in part to the steric hindrance of
the diamine ligand. The other possible RR/SS enantiomeric
pair is not observed in the solid structure of 8. This is not
surprising because such configurations would have the ben-
zyl group at N(2) and the carborane substituent at C(3)
arranged in a syn fashion, with the consequent steric hindrance.
Therefore, both 1H NMR spectroscopic data in solution and
crystallographic data in the solid state strongly support that
the complexation reaction occurs in a diastereoselective way.
˚
(13) Crystal data for 8: M = 531.79, monoclinic, a = 8.9577(3) A,
˚
˚
b = 14.3902(3) A, c = 18.5339(7) A, R = 90.00°, β = 102.028(2)°, γ =
3
˚
90.00°, U = 2336.63(13) A , T = 120(2) K, space group P21/n, Z = 4,
μ(Mo KR) = 1.031 mm-1, 27 368 reflections measured, 5352 unique
reflections (Rint = 0.0645). The final R1 values were 0.0392 (I > 2σ(I)).
The final wR(F2) values were 0.0837 (I > 2σ(I)). The final R1 values were
0.0574 (all data). The final wR(F2) values were 0.0910 (all data). The
goodness of fit on F2 was 1.067. Data were collected on a Bruker Nonius
FR591 rotating anode equiped with a Roper CCD following standard
procedures. The structure was solved and refined using the SHELX suite
of programs ( Sheldrick, G. M. Acta Crystallogr. A 2008, A64,
112-122). Graphics produced using CrystalMaker Software Ltd,
Oxford, England.
(12) (a) Dunina, V. V.; Kuz’mina, L. G.; Kazakova, M. Y.; Gorunova,
Y. K.; Grishin, E. I.; Kazakova, E. I. Eur. J. Inorg. Chem. 1999, 1029.
(b) Keller, L.; Vargas-Sanchez, M.; Prim, D.; Couty, F.; Evano, G.; Marrot, J.
J. Organomet. Chem. 2005, 690, 2306.

Article
Organometallics, Vol. 29, No. 18, 2010 4133
Figure 1. Comparison of the 1H NMR spectra (CD3COCD3) of ligand 5 and its corresponding Pd complex 8.
Conclusion
We have developed an efficient synthesis of novel 2-pyr-
idinyl aminomethyl-o-carboranes through a new strategy
adapted to the particular reactivity of o-carborane deriva-
tives bearing a 2-pyridinyl substituent. Thanks to their
vicinal-diamine pattern, these compounds can be considered
as useful N,N-ligands for transition metal complexation and
catalysis. To demonstrate their potential, we have prepared
and fully characterized the first palladium-diamine complex
containing a closo-o-carborane cluster. Its catalytic activity
has been tested in Suzuki coupling reactions and proved
promising. Further investigations on the properties of this
new family of ligands for complexation with transition
metals are currently in progress.
Figure 2. Molecular structure of the palladium complex 8
(thermal ellipsoids drawn at the 35% probability level, cluster
hydrogens omitted for clarity).
Experimental Section
General Comments. All manipulations were carried out in
round-bottomed flasks equipped with a magnetic stirring bar,
capped with a septum, and under an N2 atmosphere. Chemicals
were used as follows: THF distilled from Na/benzophenone,
dichloromethane distilled from CaH2, and MeOH distilled from
Mg/I2; all the other chemicals were commercially available and
used as received. 2-Pyridinyl-o-carboranylmethanols were
synthesized according to our previously described procedure.8f
1H, 13C, and 11B spectra were recorded respectively at 300, 75,
and 96 MHz and referenced to the residual solvent peak for 1H
Of the two possible diastereoisomeric couples, the RS/SR
racemic mixture is the only one obtained.
To provide an initial test for the possible catalytic activity
of complex 8 and whether it would resist the catalytic
reaction conditions, we decided to evaluate its activity in
Suzuki-Miyaura coupling reactions.14 Preliminary results
are reported in the Supporting Information (Table S1).
Under classical conditions, complex 8 was shown to be
promising, although it does not surpass the activities of other
related cataysts.9d Catalyst loadings as low as 1 to 0.1 mol %
were sufficient to observe quantitative conversion of the
starting materials into the expected biaryl products in high
yields. It is also noteworthy that the carborane complex 8
was compatible with the use of water as an environmentally
more friendly reaction medium and that it apparently re-
sisted the operating temperature since Pd black was never
observed after the catalytic reactions. However these results
represent only preliminary data from a brief investigation,
and we remain confident that such compounds have excep-
tional promise as catalyst precursors. Finally, this study
further validates the feasibility of incorporating closo-o-
carborane clusters into N,N-diamine ligands and their co-
ordination to transition metals. This enables a wide spectrum
of new architectures to be generated, which would not be
possible with traditional ligands, as well as unique electronic
properties.
and 13C NMR or to BF3 OEt2 as an external standard for 11
B
3
NMR. All NMR spectra are measured in CDCl3 unless re-
ported. Chemical shifts are reported in ppm and coupling
constants in Hz. Multiplet nomenclature is as follows: s, singlet;
d, doublet; t, triplet; br, broad; m, multiplet.
General Procedure for the Mesylation of the o-Carboranyl-
methanols. MsCl (242 μL, 358 mg, 3.13 mmol, 2.5 equiv) was
added dropwise to a CH2Cl2 solution (10 mL) containing the
carboranyl alcohol (1.25 mmol) and triethylamine (527 μL, 379
mg, 3.75 mmol, 3 equiv) at 0 °C (ice/water bath), and the mixture
was stirred for 18 h at room temperature. After the addition of
a saturated aqueous solution of NaHCO3 (25 mL) to the reac-
tion mixture, the aqueous phase was extracted with CH2Cl2 (3 ꢀ
25 mL), and the combined organic phases were dried over
MgSO4 and filtered. Chromatographic separation on silica gel
of the residue obtained upon evaporation afforded the expected
mesylate.
Mesylate 2b. The general procedure was followed starting
from alcohol 1b (332 mg, 1.25 mmol): pale yellow oil (382 mg,
1.11 mmol, 89%). 1H NMR: δ 2.32 (s, 3H, CH3Ccluster), 2.86 (s,
3H, CH3SO3), 5.99 (s, 1H, CHOMs), 7.37 (ddd, J = 1.1, 4.9, and
7.5, 1H, C5H4N), 7.55 (dd, J = 0.8 and 7.9, 1H, C5H4N), 7.82
(td, J = 1.6 and 7.7, 1H, C5H4N), 8.60 (m, 1H, C5H4N). 13C
NMR: δ 23.5, 39.2, 76.9, 77.4, 79.0, 122.3, 124.8, 137.3, 149.1,
(14) For reviews, see: (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995,
95, 2457. (b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147. (c) Alonso,
F.; Beletskaya, I. P.; Yus, M. Tetrahedron 2008, 64, 3047.

4134 Organometallics, Vol. 29, No. 18, 2010
Terrasson et al.
154.3. 11B NMR: δ -0.7 (d, JB,H = 145, 1B), -4.9 (d, JB,H
=
Preparation of the Palladium Complex 8. Na2PdCl4 (74 mg,
0.25 mmol) was added to a stirred solution of the amine 5
(89 mg, 0.25 mmol) in freshly distilled MeOH (5 mL). The
mixture was stirred at room temperature for 16 h, and the
solvent was removed by evaporation under vacuum. The residue
was then filtered through a silica gel pad [first eluting with
cyclohexane/EtOAc (7:3) to remove traces of free amine, then
eluting with EtOAc] to give the expected palladium complex
151, 1B), -7.9 to -11.9 (m, 8B). IR (film): ν 3088, 3052, 3011,
2960, 2929, 2868, 2586 (BH), 1588, 1572, 1470, 1439, 1408, 1362,
1178, 1101, 1004, 963, 912, 855, 799, 671, 568, 517 cm-1. MS
(ESI): m/z (%) 366 (100) [M þ Na]þ, 344 (10) [M þ H]þ, 248
(10). HRMS (ESI): calcd for [M þ H]þ 344.2324; found
344.2324; calcd for [M þ H]þ 346.2266; found 346.2269.
General Procedure for the Synthesis of the o-Carboranylmethyl-
amines. The aza-nucleophile (0.75 mmol, 1.5 equiv) and triethyl-
amine (211 μL, 152 mg, 1.5 mmol, 3 equiv) were successively added
to a MeCN solution (5 mL) of the mesylate (0.5 mmol, 1 equiv),
and the mixture was stirred at room temperature until the disap-
pearance of the starting material was observed by TLC analysis
(typically 24-48 h). After the addition of a saturated aqueous
solution of NaHCO3 (20 mL) to the reaction mixture, the aqueous
phase was extracted with EtOAc (3 ꢀ 25 mL), and the combined
organic phases were dried over MgSO4 and filtered. Chromato-
graphic separation on silica gel of the residue obtained upon eva-
poration of the filtered solution afforded the pure expected amine.
Amine 5. The general procedure was followed starting from
mesylate 2b (172 mg, 0.5 mmol) and benzylamine (82 μL, 80 mg,
0.75 mmol): white solid (121 mg, 0.34 mmol, 68%); mp 129 °C.
1H NMR: δ 1.99 (s, 3H, CH3Ccluster), 3.36 (d, J = 13.1, 1H,
CH2NH), 3.68 (d, J = 13.1, 1H, CH2NH), 4.13 (s, 1H, CHNH),
7.22-7.35 (m, 7H, C5H4N, C6H5), 7.74 (td, J = 1.9 and 7.7, 1H,
C5H4N), 8.67 (m, 1H, C5H4N). 1H NMR (CD3COCD3): δ 2.12
(s, 3H, CH3Ccluster), 2.87 (s, 1H, NH), 3.45 (d, J = 13.0, 1H,
CH2NH), 3.62 (d, J = 13.0, 1H, CH2NH), 4.39 (s, 1H, CHNH),
7.22-7.43 (m, 5H, C6H5), 7.41 (m, 1H, C5H4N), 7.60 (d, J = 7.7,
1H, C5H4N), 7.88 (td, J = 1.7 and 7.7, 1H, C5H4N), 8.67 (m,
1H, C5H4N). 13C NMR: δ 22.9, 51.7, 63.4, 75.9, 81.2, 123.4,
124.0, 127.4, 128.4 (2C), 128.5 (2C), 136.4, 138.8, 149.6, 157.7.
11B NMR: δ -2.1 (d, JB,H = 149 Hz, 1B), -4.8 (d, JB,H = 151
Hz, 1B), -7.0 to -13.2 (m, 8B). IR (in KBr): ν 3435, 3291, 3060,
2880, 2860, 2665, 2613 (BH), 2593 (BH), 2557 (BH), 1658, 1586,
1463, 1427, 1278, 1155, 1104, 1032, 996, 975, 883, 775, 739, 703
cm-1. MS (ESI): m/z (%) 377 (100) [M þ Na]þ, 355 (15) [M þ
H]þ. HRMS (ESI): calcd for [M þ H]þ 355.3180; found
355.3187; calcd for [M þ H]þ 353.3248; found 353.3252.
C16H26B10N2 (354.50): calcd C 54.21, H 7.39, N 7.90; found C
54.45, H 7.55, N 7.81.
1
8 as an orange solid (129 mg, 0.243 mmol, 97%). H NMR
(CD3COCD3): δ 1.79 (s, 3H, CH3Ccluster), 4.23 (dd, J = 9.2 and
13.7, 1H, CH2NH), 4.53 (d, J = 8.3, 1H, NH), 4.69 (dd, J = 2.2
and 13.7, 1H, CH2NH), 4.76 (s, 1H, CHNH), 7.38-7.46 (m, 3H,
C6H5), 7.68-7.76 (m, 3H, C6H5, C5H4N), 8.05 (d, J = 7.3, 1H,
C5H4N), 8.24 (td, J = 1.7 and 7.9, 1H, C5H4N), 8.94 (dd,
J = 1.0 and 5.6, 1H, C5H4N). 13C NMR (CD3COCD3): δ 22.9,
58.7, 68.0, 78.7, 80.7, 127.3, 127.8, 130.4 (2C), 130.6, 131.8 (2C),
134.4, 141.3, 151.6, 160.5. 11B NMR (CD3COCD3): δ -0.7 (d,
JB,H = 146, 1B), -5.0 (d, JB,H = 147, 1B), -7.0 to -12.0 (m,
8B). IR (in KBr): ν 3440, 3255, 3024, 2649, 2593 (BH), 2557
(BH), 1607, 1443, 1422, 1386, 1206, 1175, 1083, 1062, 1032, 975,
775, 759, 703, 616 cm-1. MS (ESI): m/z (%) 592 (30), 555 (30),
537 (100) [M - Cl þ MeCN]þ, 496 (20) [M - Cl]þ, 459 (20) [M -
Cl - HCl]þ. HRMS (ESI): calcd for [M - Cl - HCl]þ 459.2057;
found 459.2051; calcd for [M - Cl - HCl]þ 462.2047; found
462.2046. C16H26B10Cl2N2Pd (531.83): calcd C 36.13, H 4.93, N
5.27; found C 36.11, H 4.92, N 5.01.
Acknowledgment. We thank Generalitat de Catalunya
(2009/SGR/279) for financial support. We are grateful
to MENRT-France for a grant (V.T.) and to CNRS
ꢀ
and the Universite de Versailles for financial support.
M.B.H. thanks the UK EPSRC for continued financial
support of the National Crystallography Service at
Southampton.
Supporting Information Available: Experimental procedures,
compound characterization and crystallographic data, and
crystallographic information files (CIF). This material is avail-
able free of charge via the Internet at http://pubs.acs.org.