Chiral oritho -palladated and -piatinated arylphosphite complexes

Article abstract of DOI:10.1021/om9003237

A series of chiral bis-phosphite complexes 8-11 [MCl₂(L) ₂] (M = Pd or Pt) and ortho-metalated, C-P-chelate-bonded monophosphite complexes 12-14 [M(k²-L)(μ-Cl)]₂ have been prepared by reacting enantiopure (R)-BINOL-derived arylphosphite ligands L with readily accessible palladium or platinum precursors under appropriate conditions. The reactivity of complexes 12-14 containing the chiral C,P-bidentate-bonded arylphosphite ligands toward various monodentate and bidentate ligands was studied. It was found that the ortho-palladated complexes 12 and 13 do not cleanly react with triphenylphosphine in dichloromethane, whereas ortho-pla.tma.ted complex 14 smoothly reacts with typical monodentate or bidentate ligands such as pyridine, triphenylphosphine, tricyclohexylphosphine, triphenylphosphite, and [1,2-bis(diphenylphosphino)ethane] to generate the corresponding monomeric chiral ortho-platmated complexes 18-23 in good to excellent yields. Besides the full characterization of all novel complexes by NMR techniques and mass spectroscopy as well as elemental analysis, the structures of complexes 10, 18, 19, and 23 in the solid state (X-ray crystal structure determination) were established. The purpose and potential of employing the orthoplatinated complex 14 either as a resolution reagent or as a chiral NMR shift reagent were studied. Both enantiomers of racemic a-methylbenzylamine could be resolved with promising yields.

Full text of DOI:10.1021/om9003237

Organometallics 2009, 28, 5323–5332 5323
DOI: 10.1021/om9003237
Chiral ortho-Palladated and -Platinated Arylphosphite Complexes
Jie Li,† Maxime A. Siegler,‡ Martin Lutz,‡ Anthony L. Spek,‡
Robertus J. M. Klein Gebbink,*,† and Gerard van Koten*,†
†Chemical Biology and Organic Chemistry, Debye Institute for Nanomaterials Science, Faculty of Science,
Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Crystal and Structural
‡
Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University,
Padualaan 8, 3584 CH Utrecht, The Netherlands
Received April 27, 2009
A series of chiral bis-phosphite complexes 8-11 [MCl2(L)2] (M=Pd or Pt) and ortho-metalated,
C,P-chelate-bonded monophosphite complexes 12-14 [M(κ2-L)(μ-Cl)]2 have been prepared by
reacting enantiopure (R)-BINOL-derived arylphosphite ligands L with readily accessible palladium
or platinum precursors under appropriate conditions. The reactivity of complexes 12-14 containing
the chiral C,P-bidentate-bonded arylphosphite ligands toward various monodentate and bidentate
ligands was studied. It was found that the ortho-palladated complexes 12 and 13 do not cleanly react
with triphenylphosphine in dichloromethane, whereas ortho-platinated complex 14 smoothly reacts
with typical monodentate or bidentate ligands such as pyridine, triphenylphosphine, tricyclohex-
ylphosphine, triphenylphosphite, and [1,2-bis(diphenylphosphino)ethane] to generate the corre-
sponding monomeric chiral ortho-platinated complexes 18-23 in good to excellent yields. Besides the
full characterization of all novel complexes by NMR techniques and mass spectroscopy as well as
elemental analysis, the structures of complexes 10, 18, 19, and 23 in the solid state (X-ray crystal
structure determination) were established. The purpose and potential of employing the ortho-
platinated complex 14 either as a resolution reagent or as a chiral NMR shift reagent were studied.
Both enantiomers of racemic R-methylbenzylamine could be resolved with promising yields.
Introduction
areas of synthetic stereochemistry due to their insensitivity
toward air and moisture, tunable structural features, and
recyclability.1 These complexes find a versatile use as effi-
cient resolving agents,2 sensitive diamagnetic shift reagents,3
reliable stereochemical references,4 and active catalysts in
stereoselective organic transformations.5 Among these com-
plexes, the synthesis and applications of dimeric halogen-
bridged chiral C,N-cyclopalladated complexes have been
intensively studied; see Figure 1 for examples. The chiral
informaton in the five-membered C,N-chelate ring of such
complexes is most efficiently transferred to the coordination
site cis with respect to the N atom, since this position is
stereochemically controlled by the two NMe2 methyl
groups.6 However, external donors prefer to occupy the
position trans with respect to the N-donor atom according
to the antisymbiosis effect.7 Van Koten et al. first found that
Chiral C,E-cyclopalladated (E=e.g., N-, P-donor atom
containing group) complexes have been widely used in many
*Corresponding authors. Fax: (þ31)-30-252-3615. E-mail: r.j.m.
kleingebbink@uu.nl; g.vankoten@uu.nl.
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Incarvito, A. C. D.; Rheingold, A. L. J. Am. Chem. Soc. 2007, 129, 6847.
(b) Mino, T.; Tanaka, Y.; Hattori, Y.; Yabusaki, T.; Saotome, H.; Sakamoto,
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Org. Proc. Res. Dev. 2003, 7, 379. (e) Albert, J.; Bosque, R.; Cadena, J. M.;
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r
2009 American Chemical Society
Published on Web 08/25/2009
pubs.acs.org/Organometallics

5324 Organometallics, Vol. 28, No. 18, 2009
Li et al.
Figure 1. Representative examples of chiral C,N-cyclopalla-
dated complexes.
Scheme 1. Synthesis of Complexes [MCl2(L)2] (M = Pd or Pt;
L = 6 or 7)
introduction of a group, e.g., Me or noncoordinating
CH2NMe2 group, ortho to the cyclometalated Ar-M bond
could induce a unique and unprecedented intramolecular
rearrangement in the corresponding Ir and Rh complexes,8
which implied that stereochemical control of C,N-chelated
chiral ligands might be affected by this approach. In 2003,
Leung et al. independently described that by introduction of
an ortho-substituent, i.e., a methyl group next to the Ar-Pd
bond as in 3 (Figure 1), the steric control of the coordina-
tion site trans with respect to the N-donor atom can be en-
hanced as the aryl ring is a part of the chiral backbone of the
C,N-chelated amine ligands.9
Figure 2. Displacement ellipsoid plot of 10 in the crystal (50%
probability level). Hydrogen atoms and disordered solvent
molecules have been omitted for clarity. Only the molecule with
˚
C1 symmetry is shown. Characteristic bond distances (A) and
bond angles (deg) in 10: Pt1-Cl11 2.342(3), Pt1-Cl12 2.328(3),
Pt1-P11 2.185(2), Pt1-P12 2.188(3), Cl11-Pt1-Cl12
90.11(10), P11-Pt1-P12 93.31(10).
In this paper, we report on the preparation, reactivities,
and application of chiral arylphosphite complexes 8-11
derived from (R)-BINOL and their C,P-cyclometalated
analogues 12-14. In contrast to the C,N-cyclopalladated
complexes derived from chiral amine ligands, it was found
that the present C,P-cyclometalated arylphosphite com-
plexes react with a monodentate ligand to selectively form
the cis-substituted product with respect to the P-donor atom
of the C,P-chelate-bonded arylphosphite moiety, i.e., at the
position closest to the chiral pocket. During the preparation
of this paper, Dunina et al. independently reported the
preparation of (S)-BINOL-derived C,P-cyclopalladated
complex 13 in a very similar manner as well as the reactions
of this complex with PPh3 or (R)-valinate.10
Scheme 2. Synthesis of Chiral C,P-Cyclopalladated Complexes
12 and 13
(M=Pd or Pt; L=6 or 7) 8-11 in good to excellent yields
(i.e., 65-91% isolated yields).
31P NMR spectra of complexes 8-11 nicely showed a
single unique signal, which indicates that only one of the
possible isomers was isolated. Interestingly, 31P NMR spec-
tra of complexes 8 and 10 derived from ligand 6 showed a
sharp peak, whereas those of complexes 9 and 11 derived
from ligand 7 showed a fairly broad peak. This indicates that
an increased steric interference of the sterically bulky tert-
butyl groups in the phosphite ligand 7 induces intermolecu-
lar exchange between coordinated and dissociated ligands.
The cis-configuration of platinum complexes 10 and 11 was
assigned by comparing their Pt-P coupling constants with
those of reported complexes. Complexes 10 and 11 possess a
rather large Pt-P coupling constant, i.e., JPt-P=5764 and
5805 Hz for 10 and 11, respectively, which, however
fully agrees with the Pt-P coupling constant reported for
cis-[PtCl2(P(OPh)3)2] (i.e., JPt-P = 5805 Hz).12 The cis-P,
Results and Discussion
Synthesis of Monomeric Bis-phosphite Complexes. The
reaction of either [PdCl2(MeCN)2] or [PtCl2(Me2S)2] with
2 equiv of the respective monophosphite ligand 6 or 711 gave
the corresponding bis-phosphite complexes [MCl2(L)2]
(8) (a) Van der Zeijden, A. A. H.; van Koten, G.; Luijk, R.;
Nordemann, R. A.; Spek, A. L. Organometallics 1988, 7, 1549. (b) Van
der Zeijden, A. A. H.; van Koten, G.; Luijk, R.; Grove, D. M. Organome-
tallics 1988, 7, 1556. (c) Van der Zeijden, A. A. H.; van Koten, G.;
Nordemann, R. A.; Kojic-Prodic, B.; Spek, A. L. Organometallics. 1988,
7, 1957.
(9) Li, Y. X.; Selvaratnam, S.; Vittal, J. J.; Leung, P. H. Inorg. Chem.
2003, 42, 3229.
(10) Dunina, V. V.; Zykov, P. A.; Livantsov, M. V.; Glukhov, I. V.;
Kochetkov, K. A.; Gloriozov, I. P.; Grishin, Y. K. Organometallics
2009, 28, 425.
(11) Jagt, R. B. C.; Toullec, P. Y.; Schudde, E. P.; de Vries, J. G.;
(12) Albinati, A.; Affolter, S.; Pregosin, P. S. Organometallics 1990, 9,
Feringa, B. L.; Minnaard, A. J. J. Comb. Chem. 2007, 9, 407.
379.

Article
Organometallics, Vol. 28, No. 18, 2009 5325
Scheme 3. Synthesis of ortho-Platinated Dimeric Complex 14
P’-configuration of 10 in the solid state was confirmed by
X-ray crystal structure determination (Figure 2). In the
asymmetric unit of the crystal structure there are 1.5 inde-
pendent molecules, meaning that one molecule is located on
a general position and has C1 symmetry, while the other
molecule is located on an exact, crystallographic 2-fold axis.
The determination of the Flack x parameter proves that the
crystal is enantiomerically pure. The characteristic Pd-
Cl stretches in the IR spectra of complexes 8 and 9 (i.e.,
ν(Pd-Cl): 218 and 335 cm-1 for 8; ν(Pd-Cl): 212 and 340
cm-1 for 9) indicate the presence of a cis-PdCl2 complex.13
Accordingly, this confirms that the cis-configuration found
for the structure of the bis-phosphite palladium complexes in
the solid state is retained in solution. It is obvious that the
π-acidic phosphite ligands in complexes 8-11 would prefer-
entially be trans to the π-basic chlorides.
Synthesis of Chiral C,P-Cyclometalated Complexes.
Following the reaction conditions reported by Bedford
et al.,13,14 reacting monophosphite ligands 6 and 7 with stoi-
chiometric amounts of PdCl2 in toluene at refluxing tem-
perature overnight afforded the desired C,P-cyclopalladated
complexes 12 and 13 in 65% and 55% isolated yields,
respectively (Scheme 2). The structures of the resulting com-
plexes were confirmed by NMR techniques and mass spectro-
metry as well as elemental analysis. 31P NMR spectra of
complexes 12 and 13 both showed two peaks at 25 °C, which
implies that thesecomplexes are formed asa mixture of thecis-
and trans-isomers as previously documented for the other C,
P-cyclopalladated triarylphosphite complexes.12-14 Remark-
ably, 31P NMR as well as 1H NMR spectra displayed rather
broad peaks at 25 °C, which could be due to a facile inter-
change of cis- and trans-isomers at room temperature.
103.2 ppm (JPt-P=8127 Hz) corresponding to the cis-isomer.
It is found that these JPt-P values and the quotient of
them (i.e., q =1.034) are slightly larger than those of repor-
ted analogues [Pt(μ-Cl)(P(OPh)2(OC6H4))]2 (i.e., JPt-P
7760 Hz and JPt-P =7860 Hz; q=1.013)12 and [Pt(μ-Cl)-
(P(OC6H3-2,4-tBu2)2(OC6H2-2,4-tBu2))]2 (i.e., JPt-P
=
=
7750 Hz and JPt-P = 7875 Hz; q = 1.016).15 Interestingly,
only heating complex 11 in methoxyethanol at refluxing
temperature smoothly yielded ortho-platinated adduct 15
in quantitative yield (see Experimental Section, the synthesis
of complex 15, method A). This complex comprises both an
ortho-platinated ligand 7 and a non-ortho-platinated one.
The P-P coupling constant of complex 15 (i.e., JP-P=27 Hz)
implies that the non-ortho-platinated ligand is located cis to
the ortho-platinated one,12 which is in accordance with the
analogous complex [Pt(μ-Cl)(P(OC6H3-2,4-tBu2)2(OC6H2-
2,4-tBu2))]2.15 Moreover, complex 15 could be converted
into the C,P-cycloplatinated complex 14 by refluxing it in
methoxyethanol in the presence of 1.2 equiv of K2PtCl4. To
our delight, treatment of ligand 7 with 0.5 equiv of K2PtCl4 in
refluxing m-xylene smoothly resulted in the formation of
complex 15 in excellent yield (see Experimental Section, the
synthesis of complex 15, method B).
The integrated synthetic route for the preparation of chiral
C,P-cycloplatinated complex 14 is elaborated in Scheme 3. It
is worth pointing out that the sterically encumbered tert-
butyl groups in phosphite ligand 7 play a pivotal role in both
ortho-platinated reactions. For instance, refluxing complex
10 in methoxyethanol did not result in an ortho-platinated
reaction. Moreover, treating ligand 6 with 0.5 equiv of
K2PtCl4 at refluxing temperature in m-xylene for 48 h merely
afforded bis-phosphite complex 10 instead of an ortho-
platinated product. As a result, we have been able to prepare
the chiral C,P-cyclopalladated complexes 12 and 13 and the
chiral C,P-cycloplatinated complex 14, whereas the synthesis
of the analogous Pt complex starting from ligand 6 or
complex 10 still remains a challenge.
Synthesis and Reactivities of Chiral C,P-Cyclometalated
Complexes 12-14. A distinctly different reactivity behavior
of chiral C,P-cyclometalated complexes 12-14 toward
monodentate and bidentate ligands bearing phosphorus or
nitrogen donors was observed. Palladium complexes 12 and
13 reacted with triphenylphosphine under mild conditions
(i.e., dichloromethane, room temperature, 2 h) and formed
the expected ortho-palladated complexes. The configura-
tions of these triphenylphosphine adducts were confirmed
In contrast to the straightforward synthesis of C,P-cyclo-
palladated complexes 12 and 13, the synthesis of C,P-cyclo-
platinated analogues was more challenging (see Experi-
mental Section). In the end, refluxing cis-[PtCl2(7)2] (11)
and 1.2 equiv of K2PtCl4 in methoxyethanol did yield the
desired C,P-cycloplatinated complex 14 in 55% isolated
yield (see Experimental Section, the synthesis of complex
14, method A). The structure of this complex was confirmed
by NMR techniques and mass spectroscopy as well as ele-
mental analysis. The 31P NMR spectrum showed a singlet
with platinum satellites at 102.9 ppm (JPt-P = 7858 Hz)
corresponding to the trans-isomer and a second singlet at
ꢀ
(13) Bedford, R. B.; Betham, M.; Coles, S. J.; Horton, P. N.; Lopez-
ꢀ
Saez, M. J. Polyhedron 2006, 25, 1003.
(14) Bedford, R. B.; Hazelwood, S. L.; Limmert, M. E.; Albisson, D.
A.; Draper, S. M.; Scully, P. N.; Coles, S. J.; Hursthouse, M. B. Chem.;
Eur. J. 2003, 9, 3216.
(15) Bedford, R. B.; Hazelwood, S. L.; Albisson, D. A. Organome-
tallics 2002, 21, 2599.

5326 Organometallics, Vol. 28, No. 18, 2009
Li et al.
Figure 3. (Left) Displacement ellipsoid plot of 18 in the crystal (50% probability level). Ordered and disordered solvent molecules and
hydrogen atoms have been omitted for clarity. Only one of two independent metal complexes is shown. Characteristic bond distances
˚
(A) and bond angles (deg) in 18: Pt2-C1B 2.028(3), Pt2-Cl1B 2.3463(8), Pt2-P1B 2.1296(9), Pt2-N1B 2.122(3), C1B-Pt2-P1B
80.78(9), P1B-Pt2-N1B 96.71(8), Cl1B-Pt2-N1B 86.48(8), Cl1B-Pt2-C1B 96.03(9). (Right) Displacement ellipsoid plot of 19 in
the crystal (50% probability level). Hydrogen atoms and disordered solvent molecules have been omitted for clarity. Characteristic
˚
bond distances (A) and bond angles (deg) in 19: Pt1-C1 2.052(5), Pt1-Cl1 2.3542(13), Pt1-P1 2.1592(13), Pt1-P2 2.2696(14),
C1-Pt1-P1 80.43(15), C1-Pt1-P2 175.09(16), P1-Pt1-P2 100.65(5), P1-Pt1-Cl1 173.15(5).
was established by indicative 31P NMR P-P coupling con-
stant of the two phosphorus donors. For instance, both
Scheme 4. Reactivity of Chiral C,P-Cyclopalladated Complexes
12 and 13
complexes 19 and 20 exclusively adopt a cis-configuration,
2
as indicated by their P-P coupling constants of JP-P
=
29 and 22 Hz, respectively.12 This means that strong elec-
tron-withdrawing or moderately electron-donating ligands
would preferentially locate at the cis-position with respect
to the BINOL-phosphite moiety. The X-ray structures of
18 and 19 are shown in Figure 3 and clearly show the
cis-configuration around Pt in these complexes.
Interestingly, reaction of 14 with 2 equiv of PCy3 afforded
the ortho-platinated complex 21 as a mixture of cis- and
trans-isomers in which the trans-isomer was present in excess
(i.e., cis:trans ≈ 1:2). It is worth pointing out that the
ortho-platinated complex [PtCl{κ2-P,C-P(OC6H2-2,4-tBu2)-
(OC6H3-2,4-tBu2)2}(PCy3)] bearing a bulky triarylphosphite
ligand was prepared under similar conditions as a mixture of
cis- and trans-isomers in which, however, the cis-isomer was
present in excess.14,15 It is likely that not only the strong
trans-influence of the considerably electron-donating PCy3
ligand partially overrides the strong π-acceptance of the
BINOL-phosphite ligand and leads to the formation of both
cis- and trans-isomers but that also the steric bulkiness of
PCy3 favors the trans-substitution due to the stereochemical
control of the rigid BINOL-phosphite chiral pocket.
Complex 14 also underwent clean and high-yielding reac-
tions with the chelating bidentate phosphine ligand [1,2-
bis(diphenylphosphino)ethane] (dppe) to generate the catio-
nic complexes 22 and 23 bearing Cl- or BF4- as counter-
anions, respectively. The solid-state structure of complex 23
was determined by single-crystal X-ray structure determina-
tion. As shown in Figure 4, 23 adopts a slightly distorted
square-planar structure with the two phosphine P-donor
atoms respectively occupying cis- and trans-positions with
respect to the P-donor atom of the BINOL-phosphite ligand.
It is worth pointing out that the configuration of the BINOL
moieties (i.e., R configuration) in complexes 18, 19, and 23
and assigned according to the indicative P-P coupling
constants (Scheme 4). For example, the 31P NMR spectra
of the reaction mixture of complex 12 and triphenylpho-
sphine clearly showed a pair of doublets at δ=18.70 ppm and
at δ=150.90 ppm with the coupling constant JP-P=45 Hz,
which implies that the phosphine P-donor atom coordinates
cis with respect to the BINOL-phosphite P-donor atoms.12
The isolation of products 16 and 17 was, however, frustrated
by low chemical yields and the presence of considerable
amounts of unknown byproduct. Eventually, no analytically
pure samples could be obtained. This is in contrast to the
highly selective preparation of 17 when toluene was em-
ployed as the solvent, as recently has been reported by
Dunina et al.10
In contrast with these poor results for the C,P-cyclopalla-
dated chemistry, as depicted in Scheme 5, the chiral C,
P-cycloplatinated complex 14 smoothly reacted with various
monodentate ligands, such as pyridine, triphenylphosphite,
triphenylphosphine, and tricyclohexylphosphine, to quanti-
tatively generate the corresponding ortho-platinated com-
plexes 18-21.
Although the 31P NMR spectra of 18 nicely showed
a singlet at 109.8 ppm with platinum satellites (JPt-P
=
7194 Hz), the assignment of the absolute configuration of
18 only based on NMR data was problematic since no
reference compounds were at hand. The assignment of the
configuration at the platinum centers of complexes 19-21

Article
Organometallics, Vol. 28, No. 18, 2009 5327
was completely retained during the reactions according to
the X-ray diffraction analysis. This implies that the BINOL
moieties in both their parent C,P-cycloplatinated complex 14
and the BINOL-derived ligand 7 are enantiopure as well.
In order to investigate the reactivities of complexes 18-20,
ligand exchange and interconversion studies were carried out
as depicted in Scheme 5. It was found that the pyridine
moiety in 18 can be smoothly and stoichiometrically replaced
by triphenylphosphine at room temperature in dichloro-
methane. Under the same reaction conditions, a stoichio-
metric amount of triphenylphosphite replaces most of the
pyridine moiety and leaves about 15% complex 18 unreacted.
Further increasing the loading of triphenylphosphite to 1
equiv in excess still did not complete the reaction. These
experiments show that for ortho-platinated complexes the
platinum metal center favors triphenylphosphine, triphenyl-
phosphite, and pyridine coordination in descending order.
Applications of C,P-Cycloplatinated Complex 14. Finally,
the properties of the present chiral C,P-cycloplatinated
phosphite complex 14 as a resolving reagent for separating
both enanotiomers of a racemic mixture of a primary amine
were evaluated. As described in Scheme 6, a mixture of two
diastereomers was generated by reacting 14 with 2 equiv of
(rac)-R-methylbenzylamine in dichloromethane at room
temperature. The 31P NMR spectrum of this crude reaction
mixture nicely showed two distinctly separated singlets with
platinum satellites, one at 110.9 ppm (JPt-P=7285 Hz) and a
second at 112.7 ppm (JPt-P=7281 Hz). These 31P NMR data
confirmed that a mixture of two diastereoisomers is present
that have the respective amine enantiomer located at the cis-
position with respect to the chiral phosphite ligands (cf. the
2JPt-P values with those of 18). Fractional recrystallizaton of
the samples did not properly resolve the two diastereomers.
However, easy separation of the two diastereoisomers was
accomplished by employing flash chromatography over
silica gel (pore diameter ca. 4 nm).
After separation, the respective diastereoisomers 24 and
25 were reacted with stoichiometric amounts of triphenyl-
phosphine, which smoothly released the resolved R- and
S-enantiomers, respectively. These were isolated in promis-
ing yields (i.e., 66% for R-(þ)-R-methylbenzylamine and
77% for S-(-)-R-methylbenzylamine, respectively). The
excellent enantiopurities were confirmed by comparing their
optical rotation to that of authentic samples.
Figure 4. Displacement ellipsoid plot of 23 in the crystal (50%
probability level). Disordered THF solvent molecules, hydrogen
atoms, and BF-4 anion have been omitted for clarity. Only one
orientation of the disordered tBu group is shown. Characteristic
˚
bond distances (A) and bond angles (deg) in 23: Pt1-C1
2.089(3), Pt1-P1 2.2292(9), Pt1-P2 2.3342(9), Pt1-P3
2.3260(9), C1-Pt1-P2 176.19(9), P1-Pt1-P3 175.10(3), P2-
Pt1-P3 83.37(3).
Scheme 5. Reactivities of C,P-Cycloplatinated Complex 14

5328 Organometallics, Vol. 28, No. 18, 2009
Scheme 6. Resolution of (rac)-r-Methylbenzylamine
Li et al.
Table 1. Details of the X-ray Crystal Structure Determinations
10
19
18
23
formula
C
52H34Cl2O6P2Pt þ
C52H47ClO2P2Pt þ
disordered solvent
1060.38a
2(C39H37ClNO3PPt) C3H6O þ
[C60H56O3P3Pt] (BF4) þ
disordered solvent
1199.86a
3
disordered solvent
disordered solvent
1716.49a
colorless
fw
1082.72a
colorless
cryst color
cryst size [mm3]
temp [K]
colorless
0.20 ꢀ 0.12 ꢀ 0.08
colorless
0.36 ꢀ 0.33 ꢀ 0.06
0.42 ꢀ 0.12 ꢀ 0.06
0.36 ꢀ 0.10 ꢀ 0.10
150
110
110
150
cryst syst
space group
orthorhombic
P21212 (no. 18)
34.9820(12)
23.9547(10)
10.4698(6)
orthorhombic
P212121 (no. 19)
12.0861(1)
15.9892(1)
26.1500(3)
orthorhombic
P212121 (no. 19)
13.3733(7)
19.7636(10)
29.3397(6)
monoclinic
P21 (no. 4)
14.8486(2)
10.0752(3)
20.7515(6)
99.713(1)
˚
a [A]
˚
b [A]
˚
c [A]
β [deg]
3
V [A ]
˚
8773.6(7)
6
5053.41(8)
4
7754.6(6)
4
3059.99(14)
2
Z
Dx [g/cm3]
1.230a
0.55
1.394a
0.65
1.470a
0.65
1.302a
0.65
-1
˚
(sin θ/λ)max [A
reflns measd/unique
]
43 951/11 886
2.584a
multiscan
0.17-0.86
852/468
-0.032(7)
0.0513/0.1355
0.0646/0.1423
1.077
70 304/11 614
2.938a
multiscan
0.55-0.85
565/12
0.000(5)
0.0402/0.0866
0.0495/0.0893
1.084
98 527/17 801
3.767a
analytical
0.43-0.79
910/146
-0.020(3)
0.0253/0.0451
0.0319/0.0466
1.054
50 993/14 031
2.423a
multiscan
0.36-0.87
686/82
-0.054(3)
0.0252/0.0585
0.0318/0.0605
1.061
μ [mm-1
abs corr
]
abs corr range
params/restraints
Flack x param20
R1/wR2 [I > 2σ(I)]
R1/wR2 [all reflns]
S
3
˚
res density [e/A ]
-2.26/1.28
-1.00/3.60
-0.68/0.57
-0.90/0.88
a Derived parameters do not contain the contribution of the disordered solvent.
By taking advantage of the orientation of the R-methyl-
benzylamine enantiomeric ligand in the cycloplatinated-
BINOL-phosphite chiral pocket, the chemical shifts of char-
acteristic protons of the N-coordinated R-methylbenzyla-
mine moieties are clearly distinguishable. For instance, the
1H NMR spectrum showed a doublet at δ=0.85 ppm (3JH-H
=6.8 Hz) for its R-methyl group of 24, while this resonance
appears at δ=1.44 ppm (3JH-H=8.0 Hz) for the same group
in 25. Similarly, the 1H NMR spectra showed a multiplet at
δ =3.65 ppm for the benzylic proton of 24 and a multiplet at
δ =3.25 ppm for the same proton of 25. These results provide
a proof of principle for the effectiveness of this type of chiral
C,P-cycloplatinated phosphite complexes, as chiral shift
reagents for the determination of enantiomeric ratios of
chiral amine products by NMR techniques and for the easy
separation in the pure enantiomers by employing flash
chromatography over silica gel.
chiral phosphite ligands and readily accessible palladium or
platinum precursors.16 Remarkably, both the bulkiness of
BINOL-derived phosphite ligands and the metal species play
important roles in the formation of C,P-cyclometalated
complexes. C,P-Cycloplatinated complex 14 can react with
typical monodentate or bidentate ligands such as pyridine,
triphenylphosphine, tricyclohexylphosphine, triphenylpho-
sphite, and dppe to generate the corresponding mono-
meric chiral orthoplatinated complexes 18-23 in good
to excellent yields. Ligand-exchange and interconversion
studies of ortho-platinated complexes 18-20 suggest that
(16) C,P-Cyclometallated complexes have been reported as robust
catalysts for 1,4-additions of arylboronic acids and arylsiloxanes to
enones (see: (a) Bedford, R. B.; Betham, M.; Charmant, J. P. H.;
Haddow, M. F.; Orpen, A. G.; Pilarski, L. T. Organometallics 2007, 26,
6346), 1,2-additions and 1,4 additions of arylboronic acids to aldehydes,
aldimines, R,β-unsaturated ketones, and R-ketoesters (see:. (b) He, P.; Lu, Y.;
Dong, C. G.; Hu, Q. S. Org. Lett. 2007, 9, 343. (c) Liao, Y. X.; Xing, C. H.;
He, P.; Hu, Q. S. Org. Lett. 2008, 10, 2509. (d) He, P.; Lu, Y.; Hu, Q. S.
Tetrahedron Lett. 2007, 48, 5283) and allylation of aldehydes (see . (e)
Bedford, R. B.; Pilarski, L. T. Tetrahedron Lett. 2008, 49, 4216). Our work
in preparing the chiral C,P-cyclopalladated and -platinated complexes 12-14
could pave a route to access the asymmetric catalytic version of these
reactions.
Conclusion
A series of chiral bis-phosphite complexes and ortho-meta-
lated, C,P-chelate-bonded chiral phosphite complexes have
been synthesized by using enantiopure (R)-BINOL-derived

Article
Organometallics, Vol. 28, No. 18, 2009 5329
ortho-platinated complexes favor triphenylphosphine, tri-
phenylphosphite, and pyridine coordination in descending
order, which indicates the bulky BINOL moiety perturbs the
expected order of interaction with external donors. Even-
tually, complex 14 was successfully employed either as
a resolution reagent or as a chiral NMR shift reagent.
7.03 (d, J=8.4 Hz, 4H, ArH), 7.33-7.38 (m, 2H, BINOLH),
7.39-7.46 (m, 6H, BINOLH), 7.52 (t, J = 7.6 Hz, 2H,
BINOLH), 7.60-7.66 (m, 4H, BINOLH), 7.98 (t, J=9.2 Hz,
4H, BINOLH), 8.10 (q, J=8.8 Hz, 6H, BINOLH). 13C{1H}
NMR (CDCl3, 100.6 Hz): δ 119.9, 121.3, 122.1, 122.6, 122.9,
125.7, 126.4, 126.6, 126.8, 127.5, 127.6, 128.7, 129.2, 131.5 (d, J=
5 Hz), 132.1, 132.5, 132.7, 146.4 (t, J=3 Hz), 147.0 (t, J=5.4 Hz),
148.9. 31P{1H} NMR (CDCl3, 161.9 Hz): δ 115.5 (s). MS
(MALDI-TOF): m/z calcd for C52H34Cl1O6P2Pd 958.63 [M -
Cl]þ; found 958.71; and calcd for C52H34O6P2Pd 923.20 [M -
2Cl]þ; found 923.42. Anal. Calcd: C, 62.83; H, 3.45; P, 6.23; Pd,
10.71. Found: C, 62.79; H, 3.41; P, 6.22; Pd, 10.69.
Experimental Section
General Remarks. All reactions were performed under a dry
N2 atmosphere using standard Schlenk techniques unless other-
wise stated. Et3N was distilled over CaH2 and was then stored
under N2 at -30 °C with molecular sieves. Toluene was freshly
dried over sodium. PCl3 was freshly distilled and stored under
N2 prior to use. (R)-1,10-Binaphthyl-2,20-diyl chlorophosphite
and (R)-1,10-binaphthane-2,20-diyl phenyl phosphite 6 (starting
from phenol 4) were prepared according to a literature proce-
dure.17 All other reagents were purchased from ACROS Or-
ganics and Sigma-Aldrich Chemical Co. Inc. and used as
Complex 9. The product was obtained as an off-white solid.
1
Yield: 0.232 g, 76%. H NMR (CDCl3, 400 MHz): δ 0.82 (s,
18H, tBu), 1.13 (s, 18H, tBu), 6.26 (apparent br d, 2H, ArH),
6.97 (d, J=8.4 Hz, 2H, ArH), 7.06 (s, 2H, ArH), 7.17 (apparent
br d, 2H, BINOLH), 7.25-7.40 (m, 8H, BINOLH), 7.45 (t, J=
8 Hz, 2H, BINOLH), 7.56 (t, J=8 Hz, 2H, BINOLH), 7.67
(apparent d, 2H, BINOLH), 7.83 (d, J=8 Hz, 2H, BINOLH),
7.90-8.10 (m br, 6H, BINOLH). 13C{1H} NMR (CDCl3, 100.6
Hz): δ 29.9, 31.6, 34.7, 119.3, 120.2, 122.6 (t, J=9.6 Hz), 123.7,
124.6, 126.3 (d, J=5.3 Hz), 127.0 (d, J=15.8 Hz), 127.3, 128.5,
129.1, 130.8, 131.7, 131.9, 132.4 (d, J=5.4 Hz), 132.6, 138.4,
164.7, 147.6, 148.1 (t, J=5 Hz). 31P{1H} NMR (CDCl3, 161.9
Hz): δ 104.9 (vbr s). MS (MALDI-TOF): m/z calcd for
C68H66Cl1O6P2Pd 1183.10 [M - Cl]þ; found 1183.00; and calcd
for C68H66O6P2Pd 1147.62 [M - 2Cl]þ; found 1147.70. Anal.
Calcd: C, 67.03; H, 5.46; P, 5.08; Pd, 8.73. Found: 66.95; H, 5.49;
P, 5.11; Pd, 8.71.
Complex 10. The product was obtained as a white solid, and
single crystals were grown by slow diffusion of CH2Cl2/hexanes.
Yield: 0.2385 g, 88%. 1H NMR (CDCl3, 400 MHz): δ 5.94 (t, J=
7.6 Hz, 2H, ArH), 6.28 (t, J=7.6 Hz, 4H, ArH), 6.94 (d, J=8 Hz,
4H, ArH), 7.32-7.38 (m, 2H, BINOLH), 7.40-7.48 (m, 6H,
BINOLH), 7.53 (t, J=6.8 Hz, 2H, BINOLH), 7.60-7.66 (m,
4H, BINOLH), 7.96 (q, J=8 Hz, 4H, BINOLH), 8.04-8.12 (m,
6H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 120.0,
121.0, 122.2, 122.6, 122.9, 125.5, 126.3, 126.4, 126.6, 126.8,
127.0, 127.3, 127.6, 128.8, 129.1, 132.6 (t, J = 12 Hz), 146.5,
146.7 (t, J=5.7 Hz), 149.3. 31P{1H} NMR (CDCl3, 161.9 Hz):
δ 90.1 (s with sat., JPt-P=5764 Hz). MS (MALDI-TOF): m/z
calcd for C52H34Cl1O6P2Pt 1047.30 [M - Cl]þ; found 1047.25;
and calcd for C52H34O6P2Pt 1011.85 [M - 2Cl]þ; found 1011.93.
Anal. Calcd: C, 57.68; H, 3.17; P, 5.72; Pt, 18.02. Found: C,
57.73; H, 3.24; P, 5.71; Pt, 17.99.
1
received. H NMR (400.0 MHz), 13C NMR (100.6 MHz), 31P
NMR (121.5 or 161.9 MHz), and 19F NMR (376.3 MHz)
spectra were recorded at room temperature in CDCl3 on a
Varian spectrometer at 300 or 400 MHz. Chemical shift values
are reported in ppm (δ) relative to (CH3)4Si (1H and 13C NMR)
or a capillary containing 85% H3PO4 in D2O (31P{1H} NMR).
Optical rotations were recorded on a Perkin-Elmer 241 polari-
meter at 20 °C. Flash chromatography was performed using
ACROS silica gel, 0.06-0.200 mm, pore diameter ca. 4 or 6 nm.
MS measurements were carried out on an Applied Biosystems
Voyager DE-STR MALDI-TOF MS. Elemental microanalyses
were performed by Dornis and Kolbe, Mikroanalytisches La-
€
boratorium, Mulheim a/d Ruhr, Germany.
Compound 7. 2,4-Di-tert-butylphenol (5) (1.050 g, 5 mmol)
was azeotropically dried over toluene (3 ꢀ 5 mL) and redis-
solved in toluene (25 mL). To this solution was dropwise added
another solution of (R)-1,10-binaphthyl-2,20-diyl chloropho-
sphite (1.760 g, 5 mmol) in toluene (10 mL) at 0 °C, and the
resulting white suspension was stirred at room temperature for
an additional 2 h. After removing the white salt by filtration, the
solution was concentrated and the resultant oily crude product
was subjected to flash chromatography with EtOAc/hexanes
(1:9) as eluent. The desired phosphite ligand was obtained as a
white solid after drying under vacuum. Yield: 2.21 g, 85%. 1H
NMR (CDCl3, 400 MHz): δ 1.35 (s, 9H, tBu), 1,41 (s, 9H, tBu),
7.18-7.22 (m, 2H, ArH), 7.24-7.31 (m, 4H, BINOLH), 7.42-
7.52 (m, 4H, BINOLH), 7.60 (d, J=8 Hz, 1H, ArH), 7.90-8.02
(m, 4H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 30.3,
31.8, 34.8, 35.2, 119.6 (d, J=15 Hz), 122.1 (d, J=14 Hz), 123.2,
124.7, 125.3 (d, J=26 Hz), 126.5 (d, J=21 Hz), 127.3 (d, J=10
Hz), 128.6 (d, J=7 Hz), 129.3, 130.0, 130.7, 131.7 (d, J=44 Hz),
133.0 (d, J=33 Hz), 139.7, 146.7, 147.4, 148.3 (d, J=5 Hz), 148.7
(d, J=9 Hz) . 31P{1H} NMR (CDCl3, 161.9 Hz): δ 146.1 (s). MS
(MALDI-TOF): m/z calcd for C34H34O3P 521.60 [M þ H]þ;
found 521.50. Anal. Calcd: C, 78.44; H, 6.39; P, 5.95. Found: C,
78.50; H, 6.31; P, 5.93;
Complex 11. The product was obtained as an off-white solid.
1
Yield: 0.2124 g, 65%. H NMR (CDCl3, 400 MHz): δ 0.86 (s,
18H, tBu), 1.18 (s, 18H, tBu), 6.34 (vbr s, 2H, ArH), 6.81 (d, J=
8.8 Hz, 2H, ArH), 7.11 (s, 2H, ArH), 7.22-7.64 (vbr m, 18H,
BINOLH), 7.81 (d, J=8 Hz, 2H, BINOLH), 7.9-8.10 (vbr m,
4H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 29.9,
31.6, 34.7, 119.4, 120.2, 122.4, 122.8, 124.5, 126.2 (d, J =
9 Hz), 126.9 (d, J = 9 Hz), 127.2, 128.5, 129.0, 130.8, 131.6,
131.8, 132.4, 132.7, 138.4, 146.7, 147.4, 147.9 (d, J = 8 Hz).
31P{1H} NMR (CDCl3, 161.9 Hz): δ 80.7 (vbr s with sat., JPt-P
=
5808 Hz). MS (MALDI-TOF): m/z calcd for C68H66Cl1O6P2Pt
1271.73 [M - Cl]þ; found 1271.72; and calcd for C68H66O6P2Pt
1236.28 [M - 2Cl]þ; found 1236.45. Anal. Calcd: C, 62.48; H,
5.09; P, 4.74; Pt, 14.92. Found: C, 62.45; H, 5.13; P, 4.79;
Pt, 14.87.
General Procedure of Synthesis of Complexes 12 and 13.
Ligand 6 (0.4084 g, 1 mmol) or ligand 7 (0.5210 g, 1 mmol)
and PdCl2 (0.1775 g, 1 mmol) were suspended in toluene (5 mL),
and the reaction mixture was refluxed under N2 at 120 °C
overnight. After cooling, the mixture was filtered over a short
pad of Celite and the filter cake was washed with toluene (3 ꢀ
10 mL). The collected filtrate was concentrated on a rotavapor
until about 2 mL, and the product was precipitated by the
addition of MeOH (30 mL). The light yellow-brown solids were
collected by centrifugation and dried under vacuum.
General Procedure of Synthesis of Complexes 8-11. Phosphite
ligand 6 or 7 (0.5 mmol) and [PdCl2(MeCN)2] or [PtCl2(Me2S)2]
(0.25 mmol) were dissolved in dichloromethane (5 mL) and
stirred at room temperature for 2 h. The solution was concen-
trated on a rotary evaporate until about 1 mL, and the product
was precipitated from this solution by the addition of hexanes.
Off-white or slightly yellow solids were collected by centrifuga-
tion and were dried under vacuum.
Complex 8. The product was obtained as a slightly yellow
solid. Yield: 0.230 g, 91%. 1H NMR (CDCl3, 400 MHz):
δ 5.81 (t, J=7.6 Hz, 2H, ArH), 6.30 (t, J=7.6 Hz, 4H, ArH),
(17) Albrow, V. E.; Blake, A. J.; Fryatt, R.; Wilson, C.; Woodward,
S. Eur. J. Org. Chem. 2006, 2549.

5330 Organometallics, Vol. 28, No. 18, 2009
Li et al.
Complex 12. Yield: 0.3020 g, 55%. 1H NMR (CDCl3,
400 MHz): δ 6.68 (vbr s, 2H, ArH), 6.96 (vbr s, 2H, ArH),
7.18 (br m, 4H, ArH), 7.28-7.58 (br m, 16H, BINOLH), 7.78 (br
s, 2H, BINOLH), 8.00 (apparent q, br, J = 8.8 Hz, 6H,
BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 112.1 (d, J=
8 Hz), 121.0, 122.0, 122.3, 124.7, 125.2, 127.1, 128.0, 128.4,
128.5, 131.3, 131.8, 132.6, 132.8, 133.0, 136.8, 138.5, 147.2, 148.6
(d, J = 4 Hz), 156.2 (m). 31P{1H} NMR (CDCl3, 161.9 Hz):
δ 140.2 (major isomer, br s), 141.0 (minor isomer, br s). MS
(MALDI-TOF): m/z calcd for C52H32Cl1O6P2Pd 1063.05 [M -
Cl]þ; found 1063.45. Anal. Calcd: C, 56.86; H, 2.94; P, 5.64; Pd,
19.38. Found: C, 56.81; H, 2.99; P, 5.61; Pd, 19.35.
until about 1 mL, and a white solid was precipitated by the
addition of MeOH (≈40 mL). The product was then collected by
filtration and further washed with cold MeOH (2 ꢀ 5 mL).
Finally, the fine white powder was thoroughly dried under
1
vacuum. Yield: 0.1880 g, 25%. H NMR (CDCl3, 400 MHz):
δ 1.11 (s, 18H, tBu), 1.22 (s, 18H, tBu), 6.91 (s, 2H, ArH), 7.06 (s,
2H, ArH), 7.30-7.36 (m, 4H, BINOLH), 7.40-7.45 (m, 6H,
BINOLH), 7.52-7.56 (m, 4H, BINOLH), 7.81 (d, J=8.8 Hz,
2H, BINOLH), 7.95-8.10 (m, 6H, BINOLH), 8.04-8.10 (m,
2H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 30.1, 31.9,
35.0 d, J=5 Hz), 120.5 (d, J=10 Hz), 121.2, 122.1, 122.2, 122.4,
126.6, 127.3 (d, J=26 Hz), 127.9, 128.9 (d, J=20 Hz), 131.1,
131.3, 132.0, 132.2, 132.5 (d, J=5 Hz), 133.3 (d, J=17 Hz),
145.2, 146.1 (d, J=6.6 Hz), 146.9 (d, J=14 Hz), 153.6 (d, J=17
Hz). 31P{1H} NMR (CDCl3, 161.9 Hz): δ 102.9 (major isomer, s
with sat., JPt-P=7858 Hz), 103.2 (monor isomer, s with sat., JPt-
1
Complex 13. Yield: 0.3310 g, 50%. H NMR (CDCl3, 400
MHz): δ 1.13 (br s, 12H, tBu), 1.21 (br s, 24H, tBu), 7.10-7.17
(br apparent d, 4H, ArH), 7.32-7.54 (vbr m, 14H, BINOLH),
7.81-8.10 (vbr m, 10H, BINOLH). 13C{1H} NMR (CDCl3,
100.6 Hz): δ 30.0, 31.9, 35.1, 120.9, 121.5, 121.7, 126.5, 126.9,
127.1, 127.5, 128.1, 128.8, 130.3, 130.6, 130.8, 131.1, 131.5,
132.1, 132.5, 132.6, 133.0, 133.9, 134.5, 134.7, 137.0, 139.3,
146.0, 147.2, 147.3, 151.5 (d, J = 5 Hz). 31P{1H} NMR
(CDCl3, 161.9 Hz): δ 139.4 (major isomer, br s), 141.7 (minor
isomer, br s). MS (MALDI-TOF): m/z calcd for C68H64-
Cl1O6P2Pd2 1287.48 [M - Cl]þ; found 1287.25. Anal. Calcd:
C, 61.74; H, 4.88; P, 4.68; Pd, 16.09. Found: C, 61.79; H, 4.81; P,
4.73; Pd, 16.11.
Synthesis of Complex 14. Refluxing stoichiometric amounts
of ligand 6 or 7 and K2PtCl4 in toluene or in higher boiling m-
xylene or 2-methoxyethanol did not give any of the desired
products. In the latter case, amorphous Pt0 black was formed.
Pregosin et al. independently reported that refluxing cis-[PtCl2-
(P(OPh)3)2] and 1.1 equiv of PtCl2 in xylene leads to the
formation of [Pt(μ-Cl)(P(OPh)2(OC6H4))]2 in 84% isolated
yield.12 Following this procedure, cis-[PtCl2(6)2] (10) and 1.2
equiv of K2PtCl4 were refluxed in m-xylene or methoxyethanol
for 3.5 h. Nevertheless, no ortho-metalation occurred.
Method A: Complex 11 (0.6430 g, 0.5 mmol) and K2PtCl4
(0.2500 g, 0.6 mmol) were suspended in 2-methoxyethanol
(5 mL), and the mixture was refluxed under N2 at 135 °C for
3.5 h. After cooling, the black mixture was filtered over a short
pad of Celite and the filter cake was washed with dichloro-
methane (3 ꢀ 5 mL). The combined filtrates were concentrated
under vacuum until about 1 mL, and a white solid was pre-
cipitated by the addition of MeOH (≈40 mL). The product was
then collected by filtration and further washed with cold MeOH
(2 ꢀ 5 mL). Finally, the fine white powder was thoroughly dried
under vacuum. Yield: 0.4160 g, 55%.
Method B: ligand 7 (0.5210 g, 1 mmol) and K2PtCl4 (0.2080 g,
0.5 mmol) were suspended in m-xylene (5 mL), and the mixture
was refluxed under N2 at 135 °C overnight. After cooling, m-
xylene was removed under vacuum to leave an off-white
solid mixture. To this mixture was added K2PtCl4 (0.2500 g,
0.6 mmol) and 2-methoxyethanol (5 mL), after which the
suspension was refluxed under N2 at 135 °C for 3.5 h. After
cooling, the black mixture was filtered over a short pad of Celite
and the filter cake was washed with dichloromethane (3 ꢀ
5 mL). The combined filtrates were concentrated under vacuum
until about 1 mL, and a white solid was precipitated by the
addition of MeOH (≈40 mL). The product was then collected by
filtration and further washed with cold MeOH (2 ꢀ 5 mL).
Finally, the fine white powder was thoroughly dried under
vacuum. Yield: 0.3780 g, 50%.
=
8127 Hz). MS (MALDI-TOF): m/z calcd for
P
C68H64Cl1O6P2Pt2 1464.79 [M - Cl]þ; found 1464.58;. Anal.
Calcd: C, 54.44; H, 4.30; P, 4.13; Pt, 26.01. Found: C, 54.41; H,
4.24; P, 4.17; Pt, 25.99.
Synthesis of Complex 15. Method A: Complex 11 (0.065 g,
0.05 mmol) was dissolved in MeOCH2CH2OH (1 mL), and this
reaction mixture was heated at 135 °C overnight under N2. After
cooling, the resulting mixture was concentrated under vacuum,
and an off-white solid was precipitated by the addition of
hexanes. The solid was collected by filtration and was comple-
tely dried under vacuum. The product was obtained as an off-
white solid. Yield: 0.075 g, 58%. Method B: Ligand 7 (0.053 g,
0.1 mmol) and K2PtCl4 (0.021 g, 0.05 mmol) were suspended in
m-xylene (2 mL), and this reaction mixture was heated at 135 °C
overnight under N2. After cooling, the resulting mixture was
concentrated under vacuum and an off-white solid was precipi-
tated by the addition of hexanes. The solid was collected by
filtration and was completely dried under vacuum. The product
was obtained as an off-white solid. Yield: 0.070 g, 54%. 1H
NMR (CDCl3, 400 MHz): δ 1.29 (s, 12H, tBu), 1.37 (s, 24H,
tBu), 5.82 (d, J=8.8 Hz, 1H, ArH), 6.10 (d, J=9.2 Hz, 1H, ArH),
6.57 (d, J=8.4 Hz, 1H, ArH), 6.64 (d, J=8.8 Hz, 1H, ArH), 6.71
(t, J=6.8 Hz, 1H, BINOLH), 6.78 (t, J=6.8 Hz, 1H, BINOLH),
6.94 (d, J = 8.4 Hz, 1H, BINOLH), 7.04-7.10 (m, 6H,
BINOLH), 7.18 (s, 1H, BINOLH), 7.24-7.38 (m, 4H,
BINOLH), 7.46 (t, J = 12 Hz, 2H, BINOLH), 7.58 (d, J =
8 Hz, 1H, BINOLH), 7.78 (q, J=8 Hz, 2H, BINOLH), 7.86 (d,
J=8 Hz, 1H, BINOLH), 7.95 (d, J=8 Hz, 1H, BINOLH), 8.07
(d, J =10 Hz, 2H, BINOLH), 8.37 (apparent dt, JC-H=10.8 Hz
and JPt-H = 22 Hz, 1H, ArH). 13C{1H} NMR (CDCl3,
100.6 Hz): δ 30.2 (d, J=32 Hz), 31.9 (d, J=18 Hz), 34.8, 35.0,
35.2, 35.5, 119.2 (d, J=10 Hz), 119.5, 119.9, 120.7, 121.0, 121.4,
121.8, 123.5, 124.8, 125.2, 125.5, 125.7, 126.0, 126.2, 126.3 (d, J=
6 Hz), 127.1 (d, J=6 Hz), 128.1, 12.5, 129.4, 130.3 (d, J=24 Hz),
130.9 (apparent t, J=18 Hz), 131.4 (d, J=11 Hz), 131.8, 132.1,
132.3, 132.6 (d, J=8 Hz), 146.1 (d, J=5 Hz), 146.9, 147.5 (d, J=
8 Hz), 148.6 (d, J=5 Hz), 155.1 (d, J=17 Hz). 31P{1H} NMR
(CDCl3, 121.4 Hz): δ 123.20 (d with sat., JP-P = 27 Hz and
JPt-P= 6478 Hz), 134.6 (d with sat., JP-P=27 Hz and JPt-P
=
3167 Hz). MS (MALDI-TOF): m/z calcd for C69H68O6P2Pt
1250.30 [M - Cl]þ; found 1250.47. Anal. Calcd: C, 64.46; H,
5.33; P, 4.82; Pt, 15.17. Found: C, 64.38; H, 5.29; P, 4.78;
Pt, 15.20.
General Procedure of Synthesis of Complexes 18-21. Pt dimer
complex 14 (0.0750 g, 0.05 mmol) and pyridine, triphenyl-
phosphine, tricyclohexylphosphine, or triphenylphosphite
(0.1 mmol) were dissolved in dichloromethane, and the reaction
mixture was stirred at room temperature for 1 h. The resulting
mixture was then concentrated on a rotavapor until about 1 mL,
and products were precipitated from this solution by the addi-
tion of hexanes (≈10 mL). The precipitate was collected by
centrifuge and was further quickly washed with cold hexanes
(2 ꢀ 5 mL). Finally, the desired products were thoroughly dried
under vacuum.
Method C: Ligand 7 (0.5210 g, 1 mmol) and K2PtCl4 (0.4155
g, 1 mmol) were suspended in m-xylene (5 mL), and the mixture
was refluxed under N2 at 135 °C overnight. After cooling, m-
xylene was removed under vacuum to leave a pink solid mixture.
To this mixture was added 2-methoxyethanol (5 mL), and the
suspension was refluxed under N2 at 135 °C for 5 h. After
cooling, the black mixture was filtered over a short pad of Celite
and the filter cake was washed with dichloromethane (3 ꢀ
5 mL). The combined filtrates were concentrated under vacuum

Article
Complex 18. The product was obtained as a white solid, and
the single crystals were grown by slow diffusion of CH2Cl2/
Organometallics, Vol. 28, No. 18, 2009 5331
31.7, 32.1, 34.7, 35.2, 35.5, 35.9 (m), 120.2, 120.8, 121.6, 122.0,
122.4, 123.5, 124.6, 126.0, 126.9 (d, J =12 Hz), 127.2, 127.6,
128.6 (d, J=26.6 Hz), 130.2, 131.2, 132.5, 133.2, 139.8, 140.1 (d,
J =10 Hz), 145.0 (d, J=5 Hz), 147.1, 147.7 (d, J=10 Hz), 148.0
(d, J=13 Hz), 153.7 (d, J=15 Hz). 31P{1H} NMR (CDCl3, 161.9
Hz): δ 29.1 (d with sat., JP-P=20.8 Hz and JPt-P=928 Hz),
126.5 (d with sat., JP-P =20.8 Hz and JPt-P =3500 Hz). MS
(MALDI-TOF): m/z calcd for C52H65O3P2Pt 955.10 [M - Cl]þ;
found 955.25. Anal. Calcd: C, 60.60; H, 6.36; P, 6.01; Pt, 18.93.
Found: C, 60.49; H, 6.28; P, 6.07; Pt, 18.85.
General Procedure for the Synthesis of Complexes 22 and 23.
Pt dimer complex 14 (0.0750 g, 0.05 mmol) and dppe (0.040 g,
0.1 mmol) (in the case of complex 23, AgBF4 (0.020 g, 0.1 mmol)
was also added.) were dissolved in dichloromethane, and the
reaction mixture was stirred at room temperature for 1 h. AgCl
salt was first removed by filtration, and the filter cake was washed
with dichloromethane (3 ꢀ 5 mL). The combined filtrates were
concentrated on a rotavapor until about 1 mL, and product was
precipitated from this solution by the addition of hexanes
(≈10 mL). The precipitate was collected by centrifuge and was
further quickly washed with cold hexanes (2 ꢀ 5 mL). Finally, the
desired products were thoroughly dried under vacuum.
1
hexanes. Yield: 0.064 g, 77%. H NMR (CDCl3, 400 MHz):
δ 1.30 (s, 9H, tBu), 1.39 (s, 9H, tBu), 6.61 (t, J=6.4 Hz, 2H,
ArH), 7.15-7.39 (m, 8H, BINOLH), 7.42-7.58 (m, 3H, PyH),
7.68 (apparent d, J=8.8 Hz, 1H, BINOLH), 8.00 (d, J=8.8 Hz,
1H, BINOLH), 8.06 (apparent d, J=8.8 Hz, 1H, BINOLH),
8.37 (apparent t, J=24 Hz, 1H, BINOLH), 8.50 (d, J=6 Hz, 2H,
PyH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 30.1, 32.1, 35.1 (d,
J =10 Hz), 119.6 (d, J=10.8 Hz), 120.8 (d, J=21.6 Hz), 122.1
(t, J =53 Hz), 124.9, 126.1 (d, J=8 Hz), 127.1, 128.3, 128.5,
128.9, 130.9, 131.5, 131.7, 131.9, 132.2, 132.4, 132.8, 137.2,
145.7, 147.1 (d, J=14 Hz), 152.0, 155.9 (d, J=18 Hz). 31P{1H}
NMR (CDCl3, 161.9 Hz): δ 109.8 (s with sat., JPt-P=7194 Hz).
MS (MALDI-TOF): m/z calcd for C39H37NO3PPt 793.77 [M -
Cl]þ; found 793.59. Anal. Calcd: C, 56.49; H, 4.50; N, 1.69;
P, 3.74; Pt, 23.53. Found: C, 56.51; H, 4.47; N, 1.67; P, 3.75;
Pt, 23.51.
Complex 19. The product was obtained as a white solid, and
its single crystals were obtained by slow evaporation of a CDCl3
solution in an NMR tube at room temperature. Yield: 0.085 g,
80%. 1H NMR (CDCl3, 400 MHz): δ 1.15 (s, 9H, tBu), 1.37 (s,
9H, tBu), 6.95-7.00 (m, 6H, OPhH), 7.03-7.07 (m, 3H, OPhH),
7.10-7.17 (m, 7H, ArH þ OPhH), 7.20-7.38 (m, 6H,
BINOLH), 7.55 (d, J = 8 Hz, 2H, BINOLH), 7.59 (d, J =
8 Hz, 2H, BINOLH), 8.06 (d, J = 8.4 Hz, 2H, BINOLH),
8.35-8.46 (br apparent dt, 1H, ArH). 13C{1H} NMR (CDCl3,
100.6 Hz): δ 30.1, 32.0, 35.0, 35.5, 121.8, 122.3, 123.7, 125.5,
125.7, 125.8, 126.2, 126.8, 126.9, 127.0, 127.6, 128.5, 128.8,
129.0, 129.3, 129.6, 129.7, 130.1, 130.3, 132.2, 132.4, 132.5,
132.9, 139.4 (d, J=9 Hz), 141.1 (d, J=9 Hz), 145.3 (d, J=
9 Hz), 147.6 (d, J=9 Hz), 147.8 (d, J=9 Hz), 150.6 (d, J=7.4
Hz), 155.2 (d, J=21 Hz). 31P{1H} NMR (CDCl3, 161.9 Hz): δ
116.1 (d with sat., JP-P=29 Hz and JPt-P=3207 Hz), 125.1 (d
with sat., JP-P =29 Hz and JPt-P =6222 Hz). MS (MALDI-
TOF): m/z calcd for C52H47O6P2Pt 1024.95 [M - Cl]þ; found
1025.05. Anal. Calcd: C, 58.90; H, 4.47; P, 5.84; Pt, 18.40.
Found: C, 58.85; H, 4.41; P, 5.90; Pt, 18.39.
Complex 20. The product was obtained as an off-white solid.
Yield: 0.069 g, 68%. 1H NMR (CDCl3, 400 MHz): δ 1.10 (s, 9H,
tBu), 1.38 (s, 9H, tBu), 6.98-7.06 (m, 6H, PPhH), 7.08-7.12 (m,
3H, PPhH), 7.14-7.20 (m, 2H, BINOLH), 7.21-7.28 (m, 2H,
BINOLH), 7.28-7.34 (m, 2H, BINOLH), 7.36-7.42 (m, 7H,
ArH þ PPhH), 7.46-7.52 (m, 3H, BINOLH), 7.80 (d, J=8 Hz,
1H, BINOLH), 7.95 (t, J = 8.8 Hz, 2H, BINOLH), 8.57
(apparent dt, JC-H= 6 Hz, JPt-H=45 Hz, 1H, ArH). 13C{1H}
NMR (CDCl3, 100.6 Hz): δ 30.0, 32.1, 34.9, 35.5, 121.5 (d, J=32
Hz), 121.7, 122.2, 122.9, 125.9 (d, J=12.5 Hz), 126.6 (d, J=19.5
Hz), 127.5, 127.8 (d, J=10 Hz), 128.0, 128.5 (d, J=18 Hz), 130.2,
130.5, 130.8, 131.1, 131.9, 132.2, 132.8, 133.9 (d, J =10 Hz),
134.9 (d, J=5 Hz), 138.7 (d, J=10 Hz), 139.7, (d, J=10 Hz),
145.2 (d, J=9 Hz), 146.6 (d, J=9 Hz), 147.1 (d, J=14 Hz), 153.7
(d, J=18 Hz). 31P{1H} NMR (CDCl3, 161.9 Hz): δ 23.1 (d with
Complex 22. The product was obtained as a white, fine
1
powder. Yield: 0.086 g, 75%. H NMR (CDCl3, 400 MHz): δ
0.75 (s, 9H, tBu), 1.10 (s, 9H, tBu), 2.02 (br s, 1H, PCH2), 2.30 (br
s, 1H, PCH2), 3.00 (br m, 1H, PCH2), 3.49 (vbr d, 1H, PCH2),
6.37-6.41 (m, 2H, PPhH), 6.51-6.56 (m, 2H, PPhH), 6.76 (t, J=
7.6 Hz, 1H, ArH), 6.89 (d, J=8 Hz, 1H, PPhH), 7.08-7.14 (m,
3H, BINOLH), 7.22-7.34 (m, 4H, BINOLH), 7.48 (t, J=8 Hz,
1H, BINOLH), 7.50-7.61 (m, 10H, PPhH), 7.68 (t, J=8 Hz,
1H, ArH), 7.78-7.98 (m, 7H, BINOLH þ PPhH), 8.19 (q, J=
8 Hz, 2H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 30.1,
31.3, 34.5, 35.4, 120.8, 121.8 (d, J=56 Hz), 124.2, 126.2 (d, J=19
Hz), 127.0-127.2 (m), 128.01, 128.8 (d, J=13 Hz), 128.8, 129.78
(d, J=11 Hz), 130.12 (t, J=12 Hz), 130.5, 131.0-131.8 (m),
131.9, 132.5 (d, J=49 Hz), 133.9 (d, J=9 Hz), 135.2 (d, J=9 Hz),
135.8 (d, J=9 Hz), 138.5 (d, J=11 Hz), 145.9 (d, J=8 Hz), 146.4,
146.7, 146.8, 155.3 (d, J = 21.6 Hz). 31P{1H} NMR (CDCl3,
161.9 Hz): δ 43.8 (dd with sat., JPt-P=1506 Hz, JP-P=8 Hz,
J
P-P =23 Hz), 55.0 (dd with sat., JPt-P=2804 Hz, JP-P=8.6 Hz,
JP-P=528 Hz), 151.3 (dd with sat., JPt-P=4528 Hz, JP-P=23.8
Hz, JP-P = 528 Hz). MS (MALDI-TOF): m/z calcd for
C60H56O3P3Pt 1113.09 [M - Cl]þ; found 1113.25. Anal. Calcd:
C, 62.74; H, 4.91; P, 8.09; Pt, 16.98. Found: C, 62.70; H, 4.99; P,
8.14; Pt, 16.93.
Complex 23. The product was obtained as a white, fine
powder, and the single crystals were grown by slow diffusion
of THF/hexanes. Yield: 0.094 g, 78%. H NMR (CDCl3, 400
1
MHz): δ 0.75 (s, 9H, tBu), 1.10 (s, 9H, tBu), 1.96 (br s, 1H,
PCH2), 2.27 (br s, 1H, PCH2), 2.86 (br d, 1H, PCH2), 3.16 (br d,
1H, PCH2), 6.42-6.44 (apparent t, 2H, PPhH), 6.65 (t, J=5.4
Hz, 2H, PPhH), 6.78 (t, J=4 Hz, 1H, ArH), 6.91 (d, J=8.8 Hz,
1H, PPhH), 7.10-7.16 (m, 3H, BINOLH), 7.24-7.28 (m, 2H,
BINOLH), 7.48-7.68 (m, 12H, BINOLH þ PPhH), 7.79-7.89
(m, 5H, PPhH), 7.94-8.05 (m, 4H, BINOLH), 8.15 (q, J=8 Hz,
2H, BINOLH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 30.1, 31.3,
34.5, 35.4, 120.8, 121.4, 121.5, 123.8, 124.2, 124.4, 126.5 (d, J=
8.6 Hz), 127.1, 127.3, 127.5, 127.8, 128.4 (d, J=11 Hz), 128.9,
129.9 (d, J=11 Hz), 130.2 (q, J=8 Hz), 130.6, 131.2, 131.4,
131.9, 132.2, 132.7, 132.9, 133.3, 133.7, 133.8, 134.8 (d, J =
10 Hz), 135.1 (d, J=10 Hz), 138.5 (d, J=11 Hz), 145.9 (d, J=8
Hz), 146.4, 146.7 (d, J=13 Hz), 155.3 (d, J=21.6 Hz). 31P{1H}
NMR (CDCl3, 161.9 Hz): δ 44.0 (dd with sat., JPt-P=1563 Hz,
sat., JP-P=22 Hz and JPt-P=1868 Hz), 123.0 (d with sat., JP-P
=
22 Hz and JPt-P=6756 Hz). MS (MALDI-TOF): m/z calcd for
C52H47O3P2Pt 976.96 [M - Cl]þ; found 977.10. Anal. Calcd: C,
61.69; H, 4.68; P, 6.12; Pt, 19.27. Found: C, 61.64; H, 4.73;
P, 6.15; Pt, 19.25.
Complex 21. Only the cis-product was isolated in analytical
purity. The cis-product was obtained as a white solid. Yield:
0.0186 g, 18% (based on Pt). 1H NMR (CDCl3, 400 MHz):
δ 0.51 (br s, 3H, CyH), 0.80-1.18 (br m, 14H, CyH þ tBu),
1.19-1.40 (br m, 17H, CyH þ tBu), 1.40-1.58 (br s, 6H, CyH),
1.60-1.80 (br m, 5H, CyH), 1.81-1.97 (br m, 4H, CyH), 2.00-
2.18 (br s, 2H, CyH), 7.09 (s, 1H, ArH), 7.22-7.34 (m, 3H,
BINOLH), 7.35-7.38 (m, 1H, BINOLH), 7.42-7.56 (m, 4H,
BINOLH), 7.90-8.01 (m, 3H, BINOLH), 8.03 (d, J=8.8 Hz,
1H, BINOLH), 8.51 (apparent dt, JC-H= 5.2 Hz, JPt-H=44
Hz, 1H, ArH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ 26.5, 27.1
(d, J=8.6 Hz), 27.6 (d, J=8.6 Hz), 29.7, 30.0, 30.7, 30.9, 31.2,
J
P-P=8.4 Hz, JP-P=23.8 Hz), 55.0 (dd with sat., JPt-P=2810
Hz, JP-P=9 Hz, JP-P=528.8 Hz), 151.3 (dd with sat., JPt-P
=
4536 Hz, JP-P = 24.3 Hz, JP-P = 521.8 Hz). 19F{1H} NMR
(CDCl3, 376.3 Hz): δ -154.0 (s). MS (MALDI-TOF): m/z calcd
for C60H56O3P3Pt 1164.44 [M - Cl]þ; found 1164.29. Anal.
Calcd: C, 60.06; H, 4.70; P, 7.74; Pt, 16.26. Found: C, 60.10; H,
4.64; P, 7.79; Pt, 16.24.

5332 Organometallics, Vol. 28, No. 18, 2009
Li et al.
Resolution of Diastereomers 24 and 25. Pt dimer complex 14
(0.1500 g, 0.1 mmol) and racemic R-methylbenzylamine
(25.8 μL, 0.2 mmol) were dissolved in dichloromethane, and
the reaction mixture was stirred at room temperature for 1 h.
The mixture was then concentrated on a rotavapor and was
subjected to flash chromatography (ACROS silica gel, 0.06-
0.200 mm, pore diameter ca. 4 nm; diameter of column ≈ 18 mm;
length of column ≈ 270 mm; positive pressure (N2) at the top of
column ≈ 1025 mbar) with EtOAc/hexanes (1:9) as eluent.
Complex 24, Rf=0.60. Complex 25, Rf=0.35.
Complex 24. The product was obtained as a white solid. Yield:
0.1290 g, 74%. 1H NMR (CDCl3, 400 MHz): δ 0.85 (d, J=6.8
Hz, 3H, Me), 1.30 (s, 9H, tBu), 1.38 (s, 9H, tBu), 2.20 (br t, J=
10 Hz, 1H, NH), 3.38 (br d, J=11.6 Hz, 1H, NH), 3.65 (br m, 1H,
PhCH(NH2)Me), 6.44 (d, J = 7.6 Hz, 2H, PhH), 7.07 (t, J =
7.2 Hz, 1H, BINOLH), 7.12 (d, J=7.2 Hz, 1H, BINOLH), 7.16
(s, 1H, ArH), 7.28-7.42 (m, 2H, BINOLH), 7.44-7.58 (m, 3H,
PhH), 7.60 (d, J=8.4 Hz, 1H, BINOLH), 7.66 (t, J=7.2 Hz, 1H,
BINOLH), 7.78 (d, J=8.8 Hz, 1H, BINOLH), 7.88 (d, J=8.8
Hz, 2H, BINOLH), 8.00 (q, J=10 Hz, 2H, BINOLH), 8.08 (d, J
=8.8 Hz, 1H, BINOLH), 8.32 (t, J=27 Hz, 1H, ArH). 13C{1H}
NMR (CDCl3, 100.6 Hz): δ 30.1, 32.1, 35.1 (d, J=11 Hz), 53.7,
55.4, 120.6, 121.2, 121.3, 122.0, 122.1 (d, J=11 Hz), 124.4, 125.7,
126.2, 126.9 (d, J=12.8 Hz), 127.3 (d, J=6.6 Hz), 128.0 (d, J=4
Hz), 128.9, 129.0, 129.3, 131.8 (d, J=17.5 Hz), 131.0 (d, J=10
Hz), 132.4, 132.5, 132.7, 132.9, 143.4, 145.5, 145.7 (d, J=6 Hz),
147.4 (d, J = 14.6 Hz), 155.6 (d, J = 18 Hz). 31P{1H} NMR
(CDCl3, 161.9 Hz): δ 110.9 (s with sat., JPt-P=7285 Hz). MS
(MALDI-TOF): m/z calcd for C42H43NO3PPt 835.85 [M -
Cl]þ; found 835.91. Anal. Calcd: C, 57.90; H, 4.97; N, 1.61; P,
3.55; Pt, 22.39. Found: C, 57.85; H, 4.99; N, 1.59; P, 3.49; Pt,
22.35.
Complex 25. The product was obtained as an off-white foam.
Yield: 0.1551 g, 89%. 1H NMR (CDCl3, 400 MHz): δ 1.28 (s,
9H, tBu), 1.39 (s, 9H, tBu), 1.44 (d, J=8 Hz, 3H, Me), 2.44 (br d,
J =8.8 Hz, 1H, NH), 3.25 (br m, 1H, PhCH(NH2)Me), 3.72 (br
t, J=11.2 Hz, 1H, NH), 6.04 (d, J=7.6 Hz, 2H, PPhH), 6.84 (t,
J =7.6 Hz, 2H, BINOLH), 7.00 (t, J=7.2 Hz, 1H, BINOLH),
7.17 (s, 1H, ArH), 7.32-7.41 (m, 3H, PPhH), 7.51 (q, J=8.8 Hz,
2H, BINOLH), 7.61 (q, J=8 Hz, 2H, BINOLH), 7.72 (q, J=
9.2 Hz, 2H, BINOLH), 7.81 (d, J=8 Hz, 1H, BINOLH), 8.02 (d,
J=8 Hz, 1H, BINOLH), 8.08 (d, J=8.8 Hz, 1H, BINOLH), 8.31
(t, J =27 Hz, 1H, ArH). 13C{1H} NMR (CDCl3, 100.6 Hz): δ
30.1, 32.1, 35.1 (d, J=13 Hz), 53.7, 56.6, 120.5, 120.8, 121.6 (d,
J=2.5 Hz), 122.1, 122.4, 122.5, 124.0, 125.2, 126.2, 126.7, 127.3,
127.5, 127.8 (d, J=3.7 Hz), 128.9, 129.0, 129.3, 129.4, 131.5,
131.9, 132.0, 132.4, 132.6, 132.8. 143.6, 145.6, 147.4 (d, J =
14 Hz), 155.5 (d, J=18 Hz). 31P{1H} NMR (CDCl3, 161.9 Hz): δ
112.7 (s with sat., JPt-P=7281 Hz). MS (MALDI-TOF): m/z
calcd for C42H43NO3PPt 835.85 [M - Cl]þ; found 835.78. Anal.
Calcd: C, 57.90; H, 4.97; N, 1.61; P, 3.55; Pt, 22.39. Found: C,
57.83; H, 5.01; N, 1.57; P, 3.57; Pt, 22.37.
Release of Enantiopure (R)- or (S)-r-Methylbenzylamine. To a
solution of complex 24 or 25 (0.088 g, 0.1 mmol) in dichlor-
omethane (2 mL) was added triphenylphosphine (0.0263 g,
0.1 mmol) in one portion at room temperature. The reaction
mixture was stirred for 1 h and was immediately subjected to
flash chromatography (ACROS silica gel, 0.06-0.200 mm, pore
diameter ca. 6 nm; diameter of column ≈ 18 mm; length of
column ≈ 270 mm; positive pressure (N2) at the top of column ≈
1025 mbar) with MeOH/EtOAc/Et3N (95:4:1) as eluent. The
fractions were concentrated and dried on a rotary evaporator
without warming. This procedure was repeated three times in the
same scale until sufficient sample was collected for measuring
optical rotation. (Caution: The amine products should be stored
under N2 at -30 °C.) Both enantiomers were obtained as a
very light yellow oil. For (R)-(þ)-R-methylbenzylamine, yield:
0.024 g, 66%, [R]2D0 = þ3.504 (c 0.1, CHCl3). For (S)-(-)-R-
methylbenzylamine, yield: 0.0250 g, 70%, [R]2D0=-3.508 (c 0.1,
CHCl3). Optical rotation of authentic samples: for (R)-(þ)-R-
methylbenzylamine, [R]2D0=þ35.100 (c 1, CHCl3); for (R)-(þ)-R-
methylbenzylamine, [R]2D0=-35.110 (c 1, CHCl3).
X-ray Crystal Structure Determinations. X-ray reflections
˚
were measured with Mo KR radiation (λ = 0.71073 A) on a
Nonius KappaCCD diffractometer with rotating anode. The
structures were solved with automated Patterson methods
(program DIRDIF-08,18 compounds 18, 19, and 23) or direct
methods (program SHELXS-9719 compound 10). Refinement
was performed with SHELXL-9719 against F2 of all reflections.
Non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were introduced in
calculated positions and refined with a riding model. Geometry
calculations and checking for higher symmetry was performed
with the PLATON program.20 Further details are given in
Table 1.
10: The crystal was cracked into two fragments. Only the
intensities of the major fragment were used. The crystal struc-
3
ture contains very large solvent-accessible voids (2852 A /unit
˚
cell, corresponding to 32%) filled with severely disordered
solvent molecules. Their contribution to the structure factors
was taken into account using back-Fourier transformation with
the SQUEEZE routine of the program PLATON,20 resulting in
388 electrons/unit cell. In the refinement of the structure strong
restraints were used for all carbon atoms to approximate
isotropic behavior. The determination of the Flack x parameter
proves that the crystal is enantiomerically pure.21
18: The crystal structure contains large solvent-accessible
3
voids (920 A /unit cell, corresponding to 12%) filled with
˚
severely disordered solvent molecules. Their contribution to
the structure factors was taken into account using back-Fourier
transformation with the SQUEEZE routine of the program
PLATON,20 resulting in 162 electrons/unit cell. In the refine-
ment of the structure rigid-bond restraints for the displacement
parameters, distance restraints were used for one disordered tBu
group and the acetone solvent molecule. The latter was also
restrained to be planar.
19: The crystal structure contains large solvent-accessible
3
voids (860 A /unit cell, corresponding to 17%) filled with
˚
severely disordered solvent molecules. Their contribution to
the structure factors was taken into account using back-Fourier
transformation with the SQUEEZE routine of the program
PLATON,20 resulting in 308 electrons/unit cell. In the refine-
ment of the structure rigid-bond restraints for the displacement
parameters were used for carbon atoms C28-C30.
23: The crystal structure contains large solvent-accessible
3
voids (602 A /unit cell, corresponding to 20%) filled with
˚
severely disordered THF solvent molecules. Their contribution
to the structure factors was taken into account using back-
Fourier transformation with the SQUEEZE routine of the
program PLATON,20 resulting in 151 electrons/unit cell.
In the refinement of the structure distance and angle restraints
were used for one disordered tBu group, and the displace-
ment parameters of this group were restrained to approximate
isotropic behavior.
Acknowledgment. We gratefully thank Utrecht Uni-
versity for financial support. This work was also
supported in part (M.L., A.L.S.) by the Council for the
Chemical Sciences of The Netherlands Organization for
Scientific Research (CW-NWO).
(18) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The
DIRDIF-08 program system, Technical Report of the Crystallography
Laboratory; University of Nijmegen: The Netherlands, 2008.
(19) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(20) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
(21) Flack, H. D. Acta Crystallogr. 1983, A39, 876.