Asymmetric exchange of cyclopalladated ligands: A new route to optically active phosphapalladacycles

Article abstract of DOI:10.1007/s11172-006-0573-8

An asymmetric version of the cyclopalladated ligand exchange reaction was developed. This procedure involves the use of prochiral phosphines in an aprotic medium. A benzylaminate palladacycle bearing the primary amino group and the bulky But substituent at the C*stereo-center serves as a chirality inductor. Springer Science+Business Media, Inc. 2006.

Full text of DOI:10.1007/s11172-006-0573-8

Russian Chemical Bulletin, International Edition, Vol. 55, No. 12, pp. 2193—2211, December, 2006
2193
Asymmetric exchange of cyclopalladated ligands:
a new route to optically active phosphapalladacycles
V. V. Dunina,aꢀ O. N. Gorunova,b E. D. Kuznetsova,a E. I. Turubanova,a M. V. Livantsov,a
Yu. K. Grishin,a L. G. Kuz´mina,c and A. V. Churakovc
aDepartment of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: dunina@org.chem.msu.ru
bInstitute of Physiologically Active Compounds, Russian Academy of Sciences,
1 Severnyi proezd, 142432 Chernogolovka, Moscow region, Russian Federation.
Eꢀmail: o.gorunova@org.chem.msu.ru
cN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 952 1279. Eꢀmail: churakov@igic.ras.ru
An asymmetric version of the cyclopalladated ligand exchange reaction was developed.
This procedure involves the use of prochiral phosphines in an aprotic medium. A benzylaminate
palladacycle bearing the primary amino group and the bulky But substituent at the C* stereoꢀ
center serves as a chirality inductor.
Key words: asymmetric induction, C—H bond activation, cyclopalladated ligand exchange,
optically active phosphaꢀ and azapalladacycles, Xꢀray diffraction analysis.
Scheme 1
Although the idea of asymmetric C—H bond activaꢀ
tion by transition metals is attractive, examples of this
process are scarce. In a special case of cyclopalladation,
two versions of asymmetric C—H bond activation under
control of either external sources of chirality (bases)1—7
or innerꢀsphere sources are known. Bidentate N,Nꢀ 8,9
and P,Pꢀdonor10,11 ligands were tested as the latter
sources. The chirality transfer from chelated ligands
proved to be highly efficient in the closure of C*Oꢀ9 and
C*Cꢀpalladacyclesꢁ (see Refs 8, 10, and 11), whereas an
attempt to generate planar chirality upon the formation of
a CNꢀpalladacycle with the use of an optically active
monodentate S*ꢀdonor ligand (sulfoxide) in a metallating
agent failed.12 Chelation of phosphinoꢀPꢀylides giving rise
to PC*ꢀpalladacycles with diastereoselectivity of ~70% de
(see Refs 13 and 14) is the only example of the use of
CNꢀpalladacycles as chirality inductors. However, conꢀ
figurational lability of such systems substantially limits
their use.
Although the starting palladacycle in the CLE reacꢀ
tion can serve not only as the metallating agent but also as
the source of chirality, only achiral versions of this reacꢀ
tion have been examined. The only attempt to perform
asymmetric CLE has been unsuccessful.17 High efficiency
of cyclopalladated complexes in optical resolution18,19
and enantioselective catalysis,20—23 as reagents for the
enantiomeric purity determination,24,25 and as matrices
for asymmetric synthesis26—28 was documented. This
stimulated the estimation of their potential as chirality
inductors in CLE reactions. The preliminary results of
our investigations in this field have been published reꢀ
cently.29
The aim of the present study was to develop a
new method of asymmetric C—H bond activation
15,16
based on cyclopalladated ligand exchange (CLEꢁꢁ
(Scheme 1).
)
Results and Discussion
ꢀ The asymmetric atom directly bound to the metal atom is
marked with an asterisk.
ꢀꢀ The more laconic term transcyclometallation has been proꢀ
posed16 for the description of such reactions; however, this term
does not reflects the essence of the process, in which ligands
rather than metal atoms (transmetallation) are exchanged.
We chose a series of benzylaminate CNꢀdimers (1a,b
and 2a—7a),ꢁ which differ in the nature of the amino
ꢀ The number of the complex corresponds to the superscript n
in the code of the starting ligand HLn, and the letters stand for
different derivatives of this palladacycle.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2112—2129, December, 2006.
1066ꢀ5285/06/5512ꢀ2193 © 2006 Springer Science+Business Media, Inc.

2194
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
group, the αꢀsubstituent, or µꢀhalide, as chirality inꢀ
ductors.
To achieve the goal to be sought, it was necessary to
optimize the reaction conditions and the structure of the
reagent and to estimate the scope of this reaction.
Complex
HLn
HL1
HL2
HL3
HL4
HL5
HL6
HL7
HL8
R1
But
But
But
Ph
Me
Me
Me
Ph
R2
H
H
Me
H
R3
H
Me
Me
H
H
H
Me
Me
1
2
3
4
5
6
7
8
Optimization of medium
H
Pri
Me
Me
The CLE reactions have as yet been carried out only
in an acidic medium, which is necessary for destruction of
the starting palladacycle through Pd—C bond protoꢀ
lysis.15,30 Since monodentate ligands are generally poorly
efficient in the chirality transfer, the main goal of the
present study was to create conditions for retention of the
chelate structure of palladating agents. As expected, the
reactions in an acidic medium produced new palladacycles
as racemates. For example, the reaction of dimer (SC)ꢀ7a
with tertiary amine HL8 in an acidic medium afforded
racemic dimer 8a (Scheme 2).
X = Cl (a), Br (1b)
Scheme 2
The Nꢀ (HL1, HL3, HL4, and HL8), Pꢀ (HL9 and
HL10), and Sꢀdonor ligands (HL11) (most of which are
prochiral) were tested as substrates. This set was intended
for estimation of the efficiency of generation of C*ꢀ and
P*ꢀcentral chirality and planar chirality upon C—H bond
activation.ꢁ
Conditions: PhMe—AcOH, 50 °C, 17 h.
The same results were obtained in the reactions with
other Nꢀ, Pꢀ, and Sꢀdonor substrates in an acidic meꢀ
dium. For example, the (SC)ꢀ1a/HL8, (SC)ꢀ1a/HL10
,
(SC)ꢀ1a/HL11, and (SCRN)ꢀ6a/HL10 systems gave new
cyclopalladated complexes 8a, 10a, and 11a as racemates
(ee <2%) in moderate yields (42—71%). In spite of the
absence of asymmetric induction under these conditions,
these results are of interest on their own. First, they proꢀ
ꢀ New dimeric cyclopalladated complexes 1b, 4a, and 11a were
2
characterized as their mononuclear derivatives [Pd(η ꢀLn)(Q)X]
(Q = PPh3, X = Cl (4b), Br (1c); Q = Py, X = Cl (11b)).

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2195
vide stereochemical evidence for the dissociative mechaꢀ
nism of the CLE reaction in acidic media.31,32 Second,
these results illustrate the possibility of efficient cycloꢀ
palladation of Pꢀ and Sꢀdonor substrates in CLE reacꢀ
tions. Only one example of this type of reactions involvꢀ
ing a phosphine substrate (PhCH2PPh2) was docuꢀ
mented.33 This reaction produced a PCꢀpalladacycle in
low yield (21%). Earlier, thioamides were not used in
CLE reactions. Of Sꢀcontaining substrates, only thioꢀ
ketone, thiourea, and bis(thioether) were tested in this
reaction.34
mation of dimer 4a was not observed both at room temꢀ
perature and upon heating (Scheme 4).
Scheme 4
We performed the CLE reaction in an aprotic medium
for the first time with the use of the (SCRN)ꢀ6a/HL10
system. This reaction in toluene under heating (in the
absence of acids) gave new dimer 10a in a yield identical
to that obtained in an acidic medium (Scheme 3).
Scheme 3
Conditions: 20 °C, 168 h or 50 °C, 192 h.
The reaction of dimer 4a with primary amine HL1
bearing the bulky But substituent at the α position
(the reaction was performed with racemates) is the only
exception. After an extremely long period of storage
(2.5 months) of this reaction mixture at room temperaꢀ
ture, the formation of new CNꢀpalladacycle 1a with a low
degree of conversion (18%) was spectroscopically estabꢀ
lished (Scheme 5).
Scheme 5
Conditions: PhMe, 60 °C, 11 h.
The CLE reaction should be performed in an aprotic
medium, which is the key prerequisite to the development
of its asymmetric version. However, to increase the deꢀ
gree of stereodifferentiation, it is necessary to optimize
the structures of the palladating agent and the substrate,
as well as the reaction conditions.
Nature of substrates
The nature of the substrate has a substantial influence
on the efficiency of C—H bond activation in an aprotic
medium. In the absence of acids, the reactions of dimers
(SC)ꢀ1a and (SC)ꢀ5a with tertiary amines HL3 and priꢀ
mary amines (HL4) stopped at the formation of the monoꢀ
nuclear adducts [Pd(η2ꢀLn)(HL´)Cl] (HL´ = HL3 (5b) or
HL4 (1d, 5c)). Neither dehalogenation of the reagent
(KPF6, MeCN) nor heating led to activation of the
(SC)ꢀ5a/HL3 system. In the (SC)ꢀ5a/HL4 system, the forꢀ
Conditions: toluene, 20 °C, 2.5 months.
The results of investigation of the reactions of
CNꢀpalladacycles with amines suggested that the depth of
CLE in an aprotic medium is determined by the relative

2196
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
ease of cyclopalladation of two benzylamines and the
strength of coordination of the incoming ligand to the
reagent. Actually, the primary amino group of the ligand
HL1 ensures its stronger coordination to PdII compared
to the tertiary analog HL3, whereas the bulky αꢀBut subꢀ
stituent more efficiently sterically promotes35 its cycloꢀ
palladation compared to the αꢀMeꢀ (HL5) or αꢀPh group
(HL4) in other primary benzylamines. Although the CLE
reaction in an aprotic medium proved to be possible even
with the involvement of the ligand containing the hard
Nꢀdonor atom, the development of the chiral version holds
little promise because of long reaction times.
to undergo cyclopalladation. Actually, of the two ligands,
HL1 and HL11, which function in the (SC)ꢀ1a/HL11 sysꢀ
tem, the former ligand may be subjected to cycloꢀ
palladation even at room temperature,37 whereas the latꢀ
ter ligand is involved in the reaction only on heating. The
problem of strong binding of the substrate to the reagent is
more radically solved with the use of phosphine ligands
bearing the soft Pꢀdonor atom. Because of this, a further
study of the factors responsible for the efficiency of CLE
was carried out with the use of prochiral phosphines
P(Tolꢀo)2But and FcCH2PBut2.
Optimization of the structure of
cyclopalladated reagents
We expected that the reactions of palladacycles with
Nꢀthiopivaloylpiperidine (HL11) could be promoted by
both the soft sulfur atom of the substrate, which can form
a strong coordination bond with palladium(II), and the
bulky But group of the acyl fragment, which is sterically
favorable for cyclopalladation.35,36 However, all attempts
to perform CLE in the (SC)ꢀ1a/HL11 system in an aprotic
medium failed. Neither heating nor dehalogenation of the
reactant promoted this reaction, and it stopped (TLC data)
at the formation of the adduct of the CNꢀpalladacycle
with thioamide (1e) (Scheme 6).
For the development of the asymmetric version of
CLE, it is necessary to have a highly efficient palladating
agent, which enables this process to be performed under
mild temperature conditions. Most of the known reacꢀ
tions of this type were performed in an acidic medium
with heating (50—118 °C).30,32,34,38,39 The belowꢀdeꢀ
scribed experiments revealed the structural factors responꢀ
sible for the efficiency of CNꢀreagents in CLE reactions
performed in an aprotic medium.
A comparison of the reactions of phosphine HL10 with
CNꢀdimers clearly shows that the position of the equilibꢀ
rium between two palladacycles depends on the ease of
C—H bond activation in the corresponding benzylamine
(Scheme 7).
Scheme 6
Actually, heating of phosphine HL10 with αꢀButꢀsubꢀ
stituted reagents (SC)ꢀ3 and (RCSN)ꢀ2a led to the formaꢀ
tion of PCꢀcomplex 10a in low yield (8%) only in the
latter system (with the reagent containing the secondary
amino group). A comparison of the reactions of phosꢀ
phine HL10 with αꢀMeꢀsubstituted dimers (SCRN)ꢀ6a and
(SC)ꢀ5a illustrates the same tendency. The reaction of
reagent 5a containing the primary amino group produces
PCꢀdimer 10a in 66% yield, which is the maximum value
for the reactions in aprotic media at room temperature,
whereas the reaction with secondary amine derivative 6a
requires heating. The influence of the size of the αꢀsubꢀ
stituent in the palladacycle of the reagent is evident
from a comparison of the reactions of HL10 with two
secondary amine derivatives. Thus, αꢀMeꢀsubstituted
dimer (SCRN)ꢀ6a provides a seven times higher yield durꢀ
ing the period of time, which is an order of magnitude
shorter than that required in the case of αꢀButꢀsubstituted
analog (RCSN)ꢀ2a.
The influence of the structure of the reagent is
even more pronounced in the reactions of ferrocenylꢀ
methylphosphine HL9 (Scheme 8) due to its lower abilꢀ
ity to undergo cyclopalladation40 compared to diarylꢀ
phosphine HL10 (see Ref. 41). Actually, the reaction of
HL9 with αꢀButꢀsubstituted reagents at 20 °C (500 h)
stopped at the formation of the mononuclear adduct
Conditions: 20 °C, 21 days or 60 °C, 10 days, or KPF6, MeCN,
20 °C, 28 h.
This failure is evidence that the efficiency of C—H
bond activation in the substrate in an aprotic medium
depends substantially on the relative ability of two ligands

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2197
Scheme 7
Scheme 8
Reagent
Structural
Conditions
Yield
ee
Reagent
Fragment
NR1R2
Conditions
Yield
9a (%)
fragment
10a (%) (%)
T/°C
τ/h
T/°C
τ/h
(toluene)
(toluene)
(SC)ꢀ3a
(SCRN)ꢀ2a
(RC)ꢀ1a
NMe2, ent
NHMe
NH2
60
60
20
60
420
420
316
48
Traces
Traces
Traces
(SC)ꢀ3a
20
60
792
—
240 Traces
NH2
26
(ee 44% (Spl))
(RCSN)ꢀ2a
(SCRN)ꢀ6a
(SC)ꢀ5a
60
60
20
132
11
8
8.8 (SP)
Actually, orthoꢀpalladation of ternary amine HL3 can
proceed in high yield even at 0 °C. This reaction with
secondary amines requires a longer reaction time (HL2)
and/or an rise of the temperature (HL2 or HL6). The
relatively high reactivity of primary αꢀButꢀsubstituted
benzylamine HL1 results from steric promotion of the
reaction. It is known35 that sterically unhindered primary
benzylamines (for example, HL5) do not form palladaꢀ
cycles under such mild conditions.
57 5.5 (RP)
66 13.4 (RP)
336
[Pd(η2ꢀL´)(HL9)Cl] (HL´ = HL1 (1f), HL2 (2b), or
HL3 (3b)). Trace amounts of PCꢀdimer 9a (TLC data)
were detected only in the reactions with the primary
benzylamine derivative (1a). The higher reactivity of reꢀ
agent 1a is evident from a comparison of the CLE reacꢀ
tions at high temperature. Dimers 2a and 3a derived from
secondary and ternary amines, respectively, virtually do
not react with phosphine HL9 even at 60 °C, whereas the
reaction with reagent (RC)ꢀ1a produces PCꢀcomplex
(Spl)ꢀ9a in 26% yield, but the enantiomeric excess is only
moderate (ee 44%).
The data presented in Schemes 7 and 8 indicate that
there is an inverse dependence of the shift of the equilibꢀ
rium between CNꢀ and PCꢀpalladacycles toward the latter
on the ability of the starting benzylamines to undergo
orthoꢀpalladation. A comparison of the conditions and
results of cyclopalladation (Li2PdCl4/AcONa, MeOH) of
a series of benzylamines, which differ in the structure of
the side chain, confirms this conclusion (Table 1).
Table 1. Cyclopalladation of benzylamines
HLn
Condition
Yield Reference
T/°C
τ/h
~8
40
HL3 0—2
78—83
60
37
42
HL2
HL6
HL1
20
65
20
3
23
∆
84
50
0
43
44
HL5
20
35, 45, 46
HL3 > HL2 ≈ HL6 ≈ HL1 >> HL5

2198
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
The presence of a free coordination site in a metallating
agent often increases its efficiency.47,48 However, an atꢀ
tempt to increase the reactivity of reagent 1a in CLE
by its dehalogenation did not meet with success. The
reactions of HL10 with the solvated palladacycles
[Pd(η2ꢀL1)(Solv)2]+ in MeCN or acetone produced
PCꢀdimer 10a in an only slightly higher yield compared to
that achieved in the reaction with µꢀchloride dimer 1a at
the same temperature (57% or 53% and 48%, respecꢀ
tively), the reaction time being substantially longer
(Scheme 9). Hence, analogous experiments with enantioꢀ
merically pure reagent (RC)ꢀ1a were not performed.
αꢀBut group ensures conformational stability of the
CNꢀpalladacycle,44 thus increasing its ability for chiral
discrimination.49
However, even this reagent ensures only moderate inꢀ
duction of planar chirality. Thus, the reaction of dimer
(RC)ꢀ1a with ferrocenylmethylphosphine HL9 produced
PCꢀcomplex (Spl)ꢀ9a with ee 44% (see Scheme 8). A relaꢀ
tively low degree of asymmetric induction in this reaction
is partially attributed to the fact that the reaction was
performed at high temperature (60 °C) because of a
low ability of trialkylphosphine HL9 to undergo cycloꢀ
palladation.40
Reagent (RC)ꢀ1a proved to be more efficient as the
inductor of the P*ꢀcentral chirality. The reaction of this
compound with phosphine HL10 even at high temperaꢀ
ture (60 °C) produced dimer (SP)ꢀ10a in satisfactory optiꢀ
cal yield (ee 66%) (Scheme 10). A further increase in
asymmetric induction in the (RC)ꢀ1a/HL10 system was
achieved by decreasing the temperature. The optical yield
of PCꢀdimer (SP)ꢀ10a increases to ee 72% at 20 °C and
then to ee 86% at –13 °C, although at the expense of an
increase in the reaction time (from 2.5 to 165 days).
Scheme 9
Scheme 10
Reagents and conditions: KPF6, MeCN or Me2CO, 20 °C,
45 days.
Enantioselectivity of cyclopalladated
ligand exchange
Although we succeeded in performing CLE with parꢀ
ticular substrates in an aprotic medium, the stereochemiꢀ
cal characteristics of this process remained unsatisfactory
(ee < 44%). To optimize the structure of reagents for
asymmetric CLE, it was necessary to find a compromise
between the opposite requirements imposed on the
CNꢀpalladacycle as the metallating agent and the chirality
inductor. It is known that palladacycles based on bulky
ligands have a pronounced chiral recognition ability, but
these ligands are less reactive in CLE compared to
cyclopalladated complexes based on sterically unhindered
benzylamines (see above). It was reasonable to expect
that enantiomers of the palladacycle based on primary
αꢀButꢀsubstituted benzylamine, viz., (RC)ꢀ1a and (SC)ꢀ1a,
might be the reagent of choice for asymmetric CLE, beꢀ
cause the primary amino group in the starting ligands
decreases its ability to undergo cyclometallation, which is
favorable for a shift of the equilibrium between the CNꢀ and
PCꢀcomplexes toward the latter, whereas the bulky
Conditions
Yield
(SP)ꢀ10a (%)
ee
(%)
T/°C
τ/h
(toluene)
60
20
–13
58
140
5.5 months
24
48
13
66
72
86.4
Then we estimated the effect of the nature of the anion
in the palladating agent on the rate and enantioselectivity
of CLE. It was expected that the replacement of the chloꢀ
ride anion by the bulkier anion would increase the steric
demands of the reagent. For this purpose, we studied the
reactions of µꢀchloride dimer (RC)ꢀ1a and its µꢀbromide
analog (RC)ꢀ1b with phosphine HL10 under identical conꢀ
ditions (Scheme 11).

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2199
Scheme 11
troscopic and TLC parameters of the corresponding auꢀ
thentic complexes isolated or generated in situ.
In the reactions with Nꢀdonor substrates, the transforꢀ
mations of mononuclear species into the corresponding
dimers were achieved by protonation of Pdꢀcoordinated
benzylamine. The course of the CLE reactions in these
systems was qualitatively monitored by TLC in the case of
a rather large difference in the chromatographic mobility
of the starting and target dimers (∆Rf 0.26—0.42). The
1
TLC and H NMR methods appeared to be inapplicable
only to the racꢀ1a/HL4 and racꢀ4a/racꢀHL1 systems beꢀ
cause of similar chromatographic mobilities of dimers 1a
and 4a (∆Rf ~0.05) and the presence of a large number of
isomers (cis/trans and meso/rac forms of dimeric cycloꢀ
palladated complexes and diastereomers of mononuclear
adducts of 4a with racemic amine HL1). These obstacles
were overcome by the in situ transformation of a mixꢀ
ture of dimers racꢀ4a/racꢀ1a into a mixture of two
mononuclear derivatives with achiral phosphine PPh3
racꢀ4b/racꢀ1g, whose ratio (4.6 : 1) was evaluated by
31P NMR spectroscopy (Scheme 12).
X = Cl (a), Br (b)
Compound
Conditions
Yield
(%)
ee
(%)
T/°C
τ/h
(toluene)
(SP)ꢀ10a
(SP)ꢀ10b
20
20
528
528
30
54
81
91
Scheme 12
The results of the study confirmed the advantages of
µꢀbromide reagent (RC)ꢀ1b concerning both the reactivity
and enantioselectivity. First, the enantiomeric purity of
PCꢀpalladacycle (SP)ꢀ10b (ee 91%) isolated in the reacꢀ
tion with (RC)ꢀ1b is higher than that observed in exꢀ
periments with µꢀchloride analog (RC)ꢀ1a at the same
temperature (ee 81%) or even at negative temperature
(ee 86%). Second, the substantially higher reactivity of
reagent 1b is evident from the almost twofold increase in
the yield of the PCꢀdimer and an increase in the reaction
rate. The 31P NMR monitoring of the reactions of phosꢀ
phine HL10 with dimers (RC)ꢀ1b and (RC)ꢀ1a showed that
after 54 h the total percentage of different forms of the
PCꢀpalladacycle was 86 and 36%, respectively. The obꢀ
served increase in the rate and enantioselectivity of CLE
in going from µꢀCl to µꢀBr is the first example of an
increase in the efficiency of palladacycles in the chiral
recognition with the use of such a simple modification of
its coordination environment.
The enantiomeric composition of CNꢀpalladacycle 8a,
which was formed in the reactions of CNꢀdimers (SC)ꢀ1a
and (SC)ꢀ5a with amine HL8 in an acidic medium, was
1
determined by H NMR spectroscopy after in situ chiral
Scheme 13
Experimental technique
The choice of the method for monitoring the course of
the reaction and its selectivity (TLC, 1H and/or 31P NMR,
polarimetry) was governed by the structures of CLE parꢀ
ticipants. To estimate the degree of conversion, mixtures
of different forms of two palladacycles were transformed
into dimeric cyclopalladated complexes, which were adꢀ
ditionally purified by chromatography. The intermediate
mononuclear adducts were identified based on the specꢀ

2200
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
Scheme 14
Conditions: MeOH, 20 °C, 4 h.
Scheme 15
derivatization of dimer 8a with (S)ꢀprolinate ((S)ꢀProl).
The signals of diastereomers of the adduct [(η2ꢀL8)Pd{(S)ꢀ
Prol}] (8b)50 are well resolved, which confirms the validꢀ
ity of the conclusion about the absence of asymmetric
induction under these conditions.
Both CSꢀdimer 11a and the adduct of CNꢀreagent 1a
with thioamide (1e) were found to be produced in the
reaction of the complex of (SC)ꢀ1a with thioamide HL11
which was monitored by chromatography and H NMR
spectroscopy (Scheme 13).
,
1
E = N or P
The fact that the reaction in an aprotic medium stops
at the formation of adduct 1e was confirmed by 1H NMR
spectroscopy. The absence of the expected adduct of the
CSꢀpalladacycle with primary amine (11c) in the reaction
mixture was also confirmed by 1H NMR spectroscopy
and the in situ generation of this adduct by the reaction of
dimer racꢀ11a with amine HL1. It should be noted that
the comparable trans effects of the Cꢀ and Sꢀdonor atoms
of the CSꢀpalladacycle leads to the formation of adduct
11c as a 3 : 1 mixture of trans(N,S)/cis(N,S) isomers.
Since coordination of CSꢀpalladacycle 11a with monoꢀ
dentate and unsymmetrical bidentate ligands is characꢀ
terized by low regioselectivity, chiral derivatization of this
compound was performed with the use of the C2ꢀsymmetꢀ
ric auxiliary ligand (1R,2R)ꢀ1,2ꢀdiphenylethaneꢀ1,2ꢀdiꢀ
amine ((R,R)ꢀ12). The formation of CSꢀdimer 11a as a
racemate in an acidic medium was confirmed by 1H NMR
spectroscopy based on the ratio of signals correspondꢀ
ing to diastereomers (1 : 1) of cationic derivative 11d
(Scheme 14).
of the formation of complex 10c as mixtures of
cis/trans isomers,41 the spectral pattern remains rather
simple for the exact integration (Scheme 16).
Scheme 16
= HL9, HL10; X = Cl (9a, 10a), Br (10b)
Reagents and conditions: 1) (S)ꢀProlK, MeOH; 2) CDCl3,
31P NMR.
In the CLE reactions with phosphines, the conversion
of their highly stable adducts with CNꢀpalladacycles into
the corresponding dimers required the use of the known51
method of decoordination of phosphine with an excess of
an easily accessible chelating agent, viz., ethylenediꢀ
amine (En), followed by protolytic removal of the auxilꢀ
iary ligand En from the intermediate cationic complex
(Scheme 15).
Stereoselectivity of CLE with phosphines was estiꢀ
mated by 31P NMR spectroscopy after in situ chiral
derivatization of dimers 9a and 10a,b with (S)ꢀprolinate
giving rise to adducts 9b and 10c, respectively. In spite
For the spectroscopic identification of intermediates
in the CLE reactions in an aprotic medium, we performed
31P NMR monitoring of the reaction of µꢀchloride dimer
(RC)ꢀ1a with phosphine HL10. Strong coordination of
phosphine HL10 and primary amine HL1 that is released
in the reaction to the starting CNꢀpalladacycle and the
resulting PCꢀpalladacycles suggests the compositions of
the reaction mixtures presented in Scheme 17.
All these species were identified by 31P NMR specꢀ
troscopy based on the parameters of the known comꢀ
pounds, the compounds prepared in the present study,

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2201
Scheme 17
N
N
N
10a
c
0.4
0.3
0.2
0.1
0.15
0.10
0.05
a
b
transꢀ(P,P)ꢀ10d
10e
0
0
200
400
t/h
200 400 t/h
1h
N
0.3
0.2
0.1
0.8
0.4
b
c
d
0
0
200
400
t/h
200
400 t/h
a
Fig. 2. Dynamics of changes with time of the percentage of
Pꢀcontaining species in the reaction mixture: dimer 10a (a), its
adducts with amine 10e (b) and phosphine 10d (c), and the
adduct of the CNꢀpalladacycle with phosphine 1h (d).
60
50
40
30
δ
Fig. 1. 31P NMR identification of Pꢀcontaining complexes in
the (RC)ꢀ1a/HL10 system in the initial (1 h, a), intermediꢀ
ate (54 h, b), and final (524 h, c) steps.
of dimer 10a (δ 63.8)41,52 and its PPh3 derivative (δ 58.3;
2JP,P = 399 Hz).41 The broad signal of the phosphine
adduct of the CNꢀpalladacycle (δ 41.6—42.7) was identiꢀ
fied based on the chemical shift of authentic complex 1h,
which was synthesized (δ 44.7) or generated in situ by the
reaction of dimer racꢀ1a with phosphine HL10 (δ 41.9).
A strong broadening of the signals in the spectra of adꢀ
duct 1h (∆δ 230—260 Hz) can be attributed to the exꢀ
change processes and hindered rotation of bulky monoꢀ
dentate phosphine HL10 about the Pd←P and P—Cipso
bonds (the Tolman cone angle is 190°).54
authentic compounds generated in situ, or their close anaꢀ
logs (Fig. 1).
The signals at δ –7.2 (s) and 63.5—63.8 (br.s) were
assigned to phosphine HL10 and PCꢀdimer 10a, respecꢀ
tively, based on their known characteristics (δ –7.33
and 63.78).41,52 The signals of the mononuclear adduct of
the PCꢀpalladacycle with αꢀButꢀbenzylamine (SP,RC)ꢀ10e
(δ 60.4—60.8) are similar to the corresponding paramꢀ
eters of the cis/trans(P,N) isomers of this complex generꢀ
ated in situ by the reaction of dimer racꢀ10a with amine
racꢀHL1 (δ 59.9 and 60.7). The characteristic pair of douꢀ
blets at δ 58.3—58.7 and 25.3—25.6 with the constant
2JP,P ≈ 373 Hz (see Ref. 53) was assigned to the adduct of
the PCꢀdimer with phosphine HL10 (10d) having the
trans(P,P) configuration. The fact that the lowꢀfield douꢀ
blet belongs to the PCꢀpalladacycle is evident from the
similarity between its chemical shift and the parameters
The validity of the above assignments is confirmed by
the dynamics of changes with time of the population of
the CLE participants in the (RC)ꢀ1a/HL10 system (Fig. 2).*
In the course of the reaction, the fractions of PCꢀdimer
* The concentrations of the complexes were calculated from
their contributions to the total intensity of all signals of
Pꢀcontaining species taking into account that the total content
of 31P nuclei in the reaction mixture is kept constant.

2202
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
10a and its adducts with amine HL1 (10e) and phosꢀ
phine HL10 (10d) increase (Fig. 2, a—c), whereas
the percentage of the adduct of the CNꢀdimer with
phosphine HL10 (1h) in the reaction mixture decreases
(Fig. 2, d).
The similar intermediate adducts [(η2ꢀL1)Pd(κ1ꢀ
HL10)Br] (1j) and [(η2ꢀL10)Pd (κ1ꢀHL)Br] (HL = HL1
(10f) or HL10 (10g)) were also identified by spectroscopic
monitoring of CLE with µꢀbromide reagent (RC)ꢀ1b/HL10.
Complex racꢀ1j was synthesized independently.
The intermediate formation of the mononuclear adꢀ
Mechanistic aspects of cyclopalladated ligand exchange
The dissociative mechanism of this reaction in an
acidic medium is commonly recognized. It is assumed
that all steps of this reaction are reversible,31,32,38,39,55—58
and the position of the equilibrium between two palladaꢀ
cycles is determined by relative stability of two σꢀPd—C
bonds to acidolysis.32,57 Two known schemes of the reacꢀ
tion differ only in the structure of the key intermediate,
which is either a coordination compound with two
monodentate ligands (Int1)38 or a bis(chelate) spiro comꢀ
plex (Int2) with two metallacycles32 (Scheme 19).
ducts [(
)Pd(κ1ꢀHL)Cl] was detected by 1H NMR
The first version (Scheme 19, path a) is based on the
data on the kinetics and thermodynamics of CLE and
experiments with Dꢀlabeled models.31,38,55 This is stereoꢀ
chemically confirmed by the absence of asymmetric inꢀ
duction in the reactions with optically active palladacycles,
which has been noted earlier15,17 for a system with an
Nꢀdonor as well as was observed in our study for the
reactions with Nꢀ, Sꢀ, and Pꢀdonor ligands. The second
version (path b) seems to be hardly probable because it
is inconsistent with both the stereochemical criterion
(C—H bond activation in the presence of a chiral palladaꢀ
cycle should be accompanied by a pronounced asymmetꢀ
ric induction) and the known conditions of the formation
of Int2ꢀtype spiro complexes (see Refs 59—61).
spectroscopy only in the reactions with primary benzylꢀ
amines. One of these adducts (4c) was synthesized indeꢀ
pendently (Scheme 18). Coordination of primary benzylꢀ
amines to the metal atom in alternative reactions, viz., the
forward reaction (racꢀ4a/racꢀHL1) and the backward reꢀ
action (racꢀ1a/HL4), is confirmed by the coordination
shifts of the signals of the amines and the diastereotopicity
of the protons of the NH2 group in the spectra of adducts
4c and 1d, respectively.
Scheme 18
It is evident that the mechanisms assumed for CLE in
acidic media are inapplicable to analogous processes in
aprotic media. The characteristic features of "acidꢀfree"
CLE, which we revealed experimentally, provide evidence
for a radically different pathway of this reaction. High
asymmetric induction under these conditions is a stereꢀ
ochemical evidence for the retention of the starting
palladacycle in the step of formation of a new palladacycle.
The progress of the reaction is determined by the relaꢀ
tive ability of two ligands to undergo cyclometallation,
Pꢀdonor substrates being preferable, whereas tertiary
Scheme 19

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2203
Scheme 20
i is the oxidative addition of the C—H bond; ii is reductive elimination.
C(11)
C(10)
benzylamines and thioamides are nonreactive. In this step,
only some speculations about the probable pathway of
CLE involving phosphine ligands in aprotic solvents can
be made (Scheme 20).
C(9)
C(37)
C(43)
C(35)
C(42)
C(8)
C(7)
C(36)
C(5)
C(4)
Like the pathways proposed for acidic media (see
Scheme 19), the reaction in an aprotic medium involves
the interconversions of dimeric and monomeric species
D1 → M3 and M4 → D3 as the first and final steps, respecꢀ
tively (Scheme 20); the key intermediates should be radiꢀ
cally different. The commonly accepted cyclometallation
mechanisms46,48,62,63 suggest that the C—H bond activaꢀ
tion should be preceded by its agostic interactions with
the metal atom (Int3); the subsequent oxidative addition
of the C—H bond to the metal atom can lead to the
closure of the phosphapalladacycle in the form of PdIV
hydride (Int4). Compounds of PdIV are well known, inꢀ
cluding the structures with palladacycles.64—66 The reacꢀ
tion comes to an end after reductive elimination to form a
C—H bond.
C(3)
C(41)
C(2)
C(34)
C(31)
C(6)
N(1)
C(1)
C(13)
C(33)
C(32)
Pd(1)
P(1)
C(44)
C(12)
C(22)
C(21)
Cl(1)
C(23)
C(27)
C(26)
C(25)
C(24)
Fig. 3. Molecular structure and the atomic numbering scheme
for phosphine adduct (SC)ꢀ3c. All atoms except for the H atoms
of the orthoꢀmethyl groups are omitted.
In addition to the spectroscopic identification of the
reaction participants (see Scheme 17), there are spectroꢀ
scopic arguments for the formation of intermediate Int3.
A decrease in the distance between the metal atom in the
axial position and the oꢀMe group of one of the Pꢀtolyl
fragments in monodentate phosphine HL10 in adducts 1h
and 1j is confirmed by 1H NMR spectroscopy. Of two
signals for the protons of the diastereotopic oꢀMe groups
(δ 2.38 and 2.66; 2.42 and 2.83), the former signal retains
its position typical of free phosphine (δ 2.38), whereas the
latter signal is shifted downfield (∆δ ~0.27 and 0.41, reꢀ
spectively) due to the anisotropy of the metal atom (which
is more pronounced in the case of bromide adduct 1j).
This provides conditions for the subsequent agostic interꢀ
action between this C—H bond and the palladium atom.
We failed to grow crystals of the adduct of CNꢀdimer
(SC)ꢀ1a with phosphine HL10 (1h) suitable for Xꢀray difꢀ
fraction. However, we used its analog, viz., [(η2ꢀL3)Pd(κ1ꢀ
HL10)Cl] (3c), for this purpose. The molecular structure
of 3c is shown in Fig. 3. Principal structural parameters of
complex (SC)ꢀ3c are similar to the corresponding paramꢀ
eters typical of phosphine adducts of orthoꢀpalladated terꢀ
tiary amines.18,43,44,67,68 This is true for the principal bond
lengths, the degree of puckering of the palladacycle
(26.28°), and a tetrahedral distortion of the coordination
sphere (8.0°), as well as for the total Λλ(SC) stereochemisꢀ
try of the complex.
The most important result of Xꢀray diffraction study
of adduct (SC)ꢀ3c is corroboration of shortened contacts
of two protons of the oꢀMe group (C(27)) of one of the
Pꢀtolyl substituents with the palladium atom (2.63(8) and
2.67(9) Å; the sum of van der Waals radii of these atoms
is 3.1 Å),69 whereas the Pd...H distances for the oꢀMe
protons of the second Pꢀtolyl group is longer than 3.15 Å.
The orientation of the first P(Tolꢀo) substituent is optimal
for the secondary interaction in the axial position. The
aromatic ring is virtually coplanar to the Pd←P bond. The

2204
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
standard), respectively. The assignments of the signals were made
with the use of homonuclear double resonance. The meltꢀ
ing points were measured using the melting point indicator
EMꢀMGU No. 49 in a sealed capillary tube. The specific rotaꢀ
tion was measured on an automated VNIEKIꢀprodmash A1ꢀEPO
polarimeter at the sodium D line. All manipulations with free
phosphines (except for PPh3) were carried out under argon in
anhydrous solvents with the use of the Schlenk technique. The
course of the reactions was monitored and the purity of the
compounds was checked by TLC on Silufol UVꢀ254. Flash chroꢀ
matography or dry column chromatography73 on Silpearl silica
gel was used for isolation of the resulting complexes.
PdPCipsoCortho(Me) torsion angle is 19.9(6)° (cf. the angle
of 59.7(6)° for the second Pꢀtolyl substituent). The atꢀ
tractive character of the secondary interaction is evidenced
by a noticeable decrease in the PdPCipso(Tolꢀo) bond angle
to 112.7(2)° for the "axial" P(Tolꢀo) group compared to
119.0(2)° for the second "skewed" Pꢀtolyl substituent. It
should be emphasized that the shortened distance to the
metal atom was observed for this of two diastereotopic
Pꢀtolyl groups (pro(RP)ꢀ(Tolꢀo)), which is subjected to
cyclopalladation in the course of asymmetric CLE in the
presence of the CNꢀpalladacycle having the (SC) configuꢀ
ration. This model accounts for the stereochemical direcꢀ
tionality of CLE in the (SC)ꢀ1a/HL10 system, in which
a high optical yield of the phosphapalladacycle was
achieved.
To conclude, we developed the asymmetric version of
CLE and established the factors responsible for its effiꢀ
ciency. The key role of an aprotic medium was estabꢀ
lished to enable the prevention of premature destruction
of the starting CNꢀpalladacycle, which serves simultaꢀ
neously as the reagent and the chirality inductor. It was
demonstrated that the easier C—H bond activation in the
substrate compared to the ligand corresponding to the
reagent is the main condition for an efficient shift of the
equilibrium between two palladacycles toward the target
product. A cyclopalladated reagent characterized by an
optimal combination of the reactivity and the ability for
chiral recognition was found. It was demonstrated for the
first time that both the efficiency and enantioselectivity of
CLE can be substantially increased by replacing the bridgꢀ
ing chloride ligand in the dimeric cyclopalladated reagent
by bromide. The CLE reactions not only at room temꢀ
perature but also at negative temperatures were carried
out for the first time.
The solvents were purified according to standard proceꢀ
dures.42 The reagents PdCl2, Pd(OAc)2, KPF6 (Aldrich), and
AgNO3 were used without additional purification; Li2PdCl4 was
synthesized according to a known procedure.45 Ethylenediamine
(highꢀpurity grade) was dried and distilled over KOH; triphenylꢀ
phosphine was purified by double recrystallization from a benꢀ
zene—hexane mixture; (S)ꢀαꢀmethylbenzylamine ([α]D –41.0)
was purified by distillation. (1R,2R)ꢀ1,2ꢀDiphenylethaneꢀ1,2ꢀ
diamine (ee 99%, Aldrich) and (S)ꢀproline (highꢀpurity grade)
with [α]D –53.0 (c 0.5, 0.5N HCl) were used without additional
purification; Nꢀacetylꢀ(R)ꢀleucine was prepared according to a
known procedure.74 Sodium and potassium (S)ꢀprolinates were
synthesized by treatment of (S)ꢀproline with an equimolar
amount of NaOH or KOH in methanol at 20 °C. After removal
of the solvent, the residue was thoroughly dried in vacuo.
Racemic αꢀtertꢀbutylbenzylamine HL1,75 its (R)ꢀ and
(S)ꢀenantiomers,37,76 (R)ꢀNꢀmethylꢀαꢀtertꢀbutylbenzylamine
(R)ꢀHL2,77
(S)ꢀN,Nꢀdimethylꢀαꢀtertꢀbutylbenzylamine,
(S)ꢀHL3,37 (S)ꢀN,Nꢀdimethylꢀαꢀmethylbenzylamine (S)ꢀHL7,78
(S)ꢀNꢀisopropylꢀαꢀmethylbenzylamine (S)ꢀHL6,43 benzhydrylꢀ
amine HL4,79 N,Nꢀdimethylbenzhydrylamine HL8,50 diꢀtertꢀ
butyl(ferrocenylmethyl)phosphine HL9,40 tertꢀbutylꢀdiꢀorthoꢀ
tolylphosphine HL10 80 and Nꢀthiopivaloylpiperidine HL11 (see
,
Ref. 81) were prepared according to known procedures.
racꢀDiꢀµꢀchlorobis[2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}phenylꢀ
C,N]dipalladium(II) (1a)44
,
(RC)ꢀ1a (see Ref. 29) and
(SC)ꢀ1a,29,82 (RCSN)ꢀdiꢀµꢀchlorobis{2ꢀ[2,2ꢀdimethylꢀ1ꢀ(methylꢀ
amino)propyl]phenylꢀC,N}dipalladium(II)
((RCSN)ꢀ2a),77
Our results shatter the myth that CLE cannot be in
principle performed in an acidꢀfree medium.15,32,39,55,58
This delusion is strange, the more so that the transfer of
cyclometallated ligands in aprotic media in reactions of
pincer PCPꢀcomplexes of other transition metals70,71 and
in transmetallation57 is well known.
Shortly after our preliminary publication on the deꢀ
velopment of the asymmetric version of CLE,29 this
method was applied72 to the efficient (ee 78—95%) genꢀ
eration of planar chirality of PCꢀpalladacycles with the
use of a bulky planar chiral cobalticene reagent. This reꢀ
sult demonstrates a high potential of the aboveꢀdescribed
method and broad prospects for its further improvement.
(SC)ꢀdiꢀµꢀchlorobis[2ꢀ(1ꢀdimethylaminoꢀ2,2ꢀdimethylpropꢀ
yl)phenylꢀC,N]dipalladium(II) ((SC)ꢀ3a),37 (SC)ꢀdiꢀµꢀchloroꢀ
bis[2ꢀ{1ꢀaminoethyl}phenylꢀC,N]dipalladium(II) ((SC)ꢀ5a)83
,
(SCRN)ꢀdiꢀµꢀchlorobis[2ꢀ{1ꢀ(isopropylamino)ethyl}phenylꢀ
C,N]dipalladium(II) ((SCRN)ꢀ6a),84 and (SC)ꢀdiꢀµꢀchlorobis[2ꢀ
{1ꢀ(dimethylamino)ethyl}phenylꢀC,N]dipalladium(II )
((SC)ꢀ7a)85 were synthesized according to known procedures.
Racemic diꢀµꢀchlorobis[2ꢀ{1ꢀ(amino)benzyl}phenylꢀC,N]diꢀ
palladium(II) (racꢀ4a). A mixture of Pd(OAc)2 (140.0 mg,
0.6168 mmol) and benzhydrylamine (114.4 mg, 0.6168 mmol)
in benzene (4 mL) was stirred at 60 °C for 9 h. Then LiCl
(136.0 mg, 3.084 mmol) was added and the mixture was stirred
for 1 h. The precipitate that formed was filtered off, washed with
benzene and chloroform, and purified by dry column chromaꢀ
tography (h = 2 cm, d = 2.5 cm, benzene—acetone mixtures in
ratios from 20 : 1 to 1 : 20 as the eluent). Dimer 4a was obtained
in a yield of 127.5 mg (64%). M.p. (with decomp.) 239—241 °C,
Rf 0.37 (benzene—acetone, 10 : 1). Found (%): C, 47.6; H, 3.7;
N, 4.1. C26H24Cl2N2Pd2. Calculated (%): C, 48.2; H, 3.7; N, 4.3.
Racemic chloro[2ꢀ{1ꢀ(amino)benzyl}phenylꢀC,N](triphenylꢀ
phosphine)palladium(II) (racꢀ4b). A mixture of dimer racꢀ4a
Experimental
1
The H and 31P{1H} NMR spectra were recorded on Varian
VXRꢀ400 and Bruker DPXꢀ400 spectrometers operating at 400
and 169.1 MHz, respectively, in CDCl3 at room temperature.
1
The chemical shifts in the H and 31P NMR spectra were meaꢀ
sured relative to Me4Si (internal standard) and H3PO4 (external

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2205
(14.1 mg, 0.0217 mmol) and PPh3 (11.5 mg, 0.044 mmol) in
benzene (4 mL) was stirred at 20 °C for 1 h and concentrated.
Complex racꢀ4b was precipitated with hexane. Adduct 4b was
obtained in a yield of 21.6 mg (85%) as a paleꢀyellow powder.
M.p. (with decomp.) 157—159 °C, Rf 0.31 (benzene—acetone,
10 : 1). Found (%): C, 63.73; H, 4.72; N, 2.21. C31H27ClNPPd.
Calculated (%): C, 63.49; H, 4.64; N, 2.39. 31P NMR, δ:
40.99 (s). 1H NMR, δ: signals for the protons of palladacycle:
1H NMR, δ: 1.22 (s, 9 H, αꢀBut); 2.94, 3.10, 3.56, and 3.94
(all br.m, 3 H, NH2, αꢀCH); 6.84—6.97 (m, 3 H, H(3), H(4),
H(5)); 7.41 (br.d, 1 H, H(6)).
(R,R)ꢀDiꢀµꢀbromobis[2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}pheꢀ
nylꢀC,N]dipalladium(II) ((R,R)ꢀ1b). A mixture of µꢀchloride
dimer (R)ꢀ1a (79.5 mg, 0.1307 mmol) and sodium bromide
(26.9 mg, 0.2614 mmol) in methanol (10 mL) was stirred under
argon for 2 h, concentrated in vacuo, and then extracted with a
dichloromethane—water mixture. The organic extract was dried
over sodium sulfate. Dimer (R)ꢀ1b was obtained in a yield of
70.7 mg (78%); m.p. (with decomp.) 223—225 °C, Rf 0.21 (diꢀ
ethyl ether—hexane, 1 : 1). The 1H NMR spectrum of dimer
(R,R)ꢀ1b is identical to that given above for the racemate.
(R,S)ꢀBromo[2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}phenylꢀ
C,N](triphenylphosphine)palladium(II) (racꢀ1c). A solution of a
mixture of µꢀbromide dimer racꢀ1b (5.0 mg, 0.0072 mmol) and
triphenylphosphine (4.2 g, 0.0157 mmol) in toluene (4 mL) was
stirred at room temperature for 6 h. The reaction mixture was
concentrated and the residue was recrystallized from a mixture
of toluene and petroleum ether. The precipitate that formed was
filtered off, washed with petroleum ether, and dried. Adduct
racꢀ1c was obtained in a yield of 7.1 mg (81%) as colorless
crystals, m.p. 224—225 °C, Rf 0.26 (diethyl ether—hexane, 1 : 1,
twofold elution). Found (%): C, 57.26; H, 5.07; N, 2.20.
3.897 (m, 1 H, NHeq, 3JH,P = 3.5 Hz, 2JH,H = 10.5 Hz, 3JHN,CH
6.4 Hz); 4.570 (m, 1 H, NHax, 3JH,P = 3.5 Hz, 2JH,H = 10.5 Hz,
=
4
3JHN,CH = 6.4 Hz); 5.537 (ddd, 1 H, αꢀCH, JH,P = 4.5 Hz,
3JHC,NH = 6.4 Hz); 7.34—7.50 (group of m, 5 H, αꢀPh; 9H,
mꢀ and pꢀH of PPh3); 6.40—6.46 (m, 2 H, C(5)H, C(6)H of the
3
C6H4 fragment); 6.774 (m, 1 H, C(4)H, JH,H = 7.8 Hz); 6.583
(d, 1 H, C(3)H, 3JH,H = 7.2 Hz); signals of PPh3: 7.33—7.50 (m,
9 H, Hm and Hp, overlap with the signals for the protons of the
αꢀPh group); 7.745 (m, 6 H, Ho, 3JH,P = 11.2 Hz).
Racemic diꢀµꢀchloroꢀbis(Nꢀthiopivaloylpiperidinꢀ2ꢀylꢀC,S)diꢀ
palladium(II) (racꢀ11a).
A mixture of PdCl2 (47.8 mg,
0.270 mmol) and Nꢀthiopivaloylpiperidine (50.0 mg,
0.270 mmol) in methanol (6 mL) was stirred at 50 °C for 6 h.
The precipitate that formed was filtered off, extracted with
dichloromethane, and purified by flash column chromatography
(h = 3 cm, d = 1.5 cm, a benzene—acetone mixture, 5 : 1, as the
eluent). After recrystallization from a dichloromethane—diethyl
ether mixture, dimer 11a was obtained in a yield of 82.7 mg
(94%) as a paleꢀyellow amorphous powder, m.p. (with decomp.)
210—212 °C, Rf 0.6 (benzene—acetone, 5 : 1). Found (%):
C, 36.66; H, 5.62; N, 3.90. C20H36Cl2N2Pd2S2. Calculated (%):
C, 36.82; H, 5.56; N, 4.29.
C
29H31BrNPPd. Calculated (%): C, 57.02; H, 5.12; N, 2.29.
1
31P NMR, δ: 40.7 (s). H NMR, δ: signals of the palladacycle:
1.31 (s, 9 H, αꢀBut); 3.81 (br.dd, 1 H, NHeq, JH,NH = 9.6 Hz,
2
3JH,P = 2.2 Hz); 3.93 (br.ddd, 1 H, NHax
,
2JH,NH = 9.6 Hz,
3JHN,CH = 6.7 Hz, JH,P = 4.0 Hz); 4.06 (dd, 1 H, αꢀCH,
3
3JHC,NH = 6.1 Hz, JH,P = 6.1 Hz); 6.39 (br.ddd, 1 H, H(6),
4
3
4
Racemic chloro(Nꢀthiopivaloylpiperidinꢀ2ꢀylꢀC,S)(pyriꢀ
dineꢀN)palladium(II) (racꢀ11b). An excess of pyridine (121.2 mg,
1.532 mmol) in benzene (20 mL) was added to a suspension of
dimer racꢀ11a (52.0 mg, 0.0766 mmol). The reaction mixture
was stirred at 20 °C for 0.5 h, filtered, and concentrated. The
residue was recrystallized from a dimethylchloromethane—hexꢀ
ane mixture on cooling to –70 °C. Complex racꢀ11b was obꢀ
tained in a yield of 51.9 mg (81%); m.p. (with decomp.)
197—198 °C. Found (%): C, 43.35; H, 5.73. C15H23ClN2PdS.
Calculated (%): C, 43.07; H, 5.54. 1H NMR, δ: signals of the
palladacycle: 1.433 (s, 9 H, But); 1.55—2.00 (group of m, 5 H,
3J6,5 = 7.6 Hz, JH,P = 6.1 Hz, J6,4 = 1.0 Hz); 6.44 (t, 1 H,
H(5), 3J5,6 = 7.6 Hz, 3J5,4 = 6.8 Hz); 6.83 (dd, 1 H, H(4), 3J4,5
=
3
3
6.8 Hz, J4,3 = 7.6 Hz); 7.02 (d, 1 H, H(3), J3,4 = 7.6 Hz);
signals of PPh3: 7.34—7.44 (m, 9 H, Hm, Hp); 7.73 (m, 6 H, Ho,
3JH,P = 11.2 Hz).
(R)ꢀBromo[2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}phenylꢀC,N](triꢀ
phenylphosphine)palladium(II) ((R)ꢀ1c). A solution of a mixture
of dimer (R)ꢀ1b (58.0 mg, 0.083 mmol) and triphenylphosphine
(47.9 mg, 0.1828 mmol) in benzene (5 mL) was stirred at 20 °C
for 1 h, the solvent was removed, and the complex was purified
by dry column chromatography (h = 2 cm, d = 1.5 cm, benꢀ
zene—acetone mixtures, from 1 : 0 to 10 : 1). Adduct (R)ꢀ1c was
isolated in a yield of 71.0 mg (85%) as a colorless powder, m.p.
(with decomp.) 222—224 °C, Rf 0.51 (benzene—acetone, 7 : 1),
[α]D +51 (c 0.4, CH2Cl2). Found (%): C, 56.80; H, 5.32; N, 2.09.
2
βꢀHax, 2β´ꢀH, 2γꢀH); 2.824 (m, 1 H, βꢀHeq, JH,H = 13.5 Hz);
3.218 (ddd, 1 H, α´ꢀHax, 2JH,H = 13.0 Hz, 3JαꢀH
ax = 9.4 Hz,
,βꢀH
ax
3JαꢀH
= 2.7 Hz); 4.433 (m, 1 H, α´ꢀHeq, 2JH,H = 13.0 Hz);
,βꢀH
ax
4.771 (dd,eq1 H, αꢀHax
,
3Jα
= 12.0 Hz, 3Jα
=
β
β
ꢀH , ꢀH
ꢀH , ꢀH
2.1 Hz); signals of coordinataexd pyridine: 7.328 (t, 2 aHx , βꢀH,
C
29H31BrNPPd. Calculated (%): C, 57.02; H, 5.12; N, 2.29.
ax
eq
3JH,H = 6.6 Hz); 7.737 (t, 1 H, γꢀH, JH,H = 7.5 Hz); 8.786 (d,
Cyclopalladated ligand exchange. The structures of the CLE
3
2 H, αꢀH, 3JH,H = 5.0 Hz).
products were confirmed by a comparison of their spectroscopic
characteristics (1H and 31P NMR) with the characteristics
published earlier. The intermediate adducts of the CNꢀ and
PCꢀdimers with the substrates were identified by spectroscopy
based on the characteristics of the corresponding species, which
were either prepared independently or generated in situ by the
reaction of the corresponding dimeric cyclopalladated complex
with a stoichiometric amount of the ligand in benzene (20 °C,
0.5—1 h).
Cyclopalladated ligand exchange reactions with benzylamines.
A. A solution of amine HL8 (92.0 mg, 0.435 mmol) in toluene
(5 mL) and glacial acetic AcOH (10 mL) was added to a suspenꢀ
sion of dimer (SC)ꢀ7a (126.3 mg, 0.2176 mmol) in toluene
(5 mL). The reaction mixture was stirred at 50 °C for 17 h,
Racemic diꢀµꢀbromoꢀbis[2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropꢀ
yl}phenylꢀC,N]dipalladium(II) (racꢀ1b). A solution of µꢀchloride
dimer racꢀ1a (43.7 mg, 0.0718 mmol) and a 20% excess of
sodium bromide (17.3 mg, 0.173 mmol) in methanol (6 mL) was
stirred for 5.5 h. Then the reaction mixture was concentrated to
dryness, the residue was dissolved in chloroform and extracted
with water (3×10 mL), the organic layer was dried over sodium
sulfate, the solvent was removed, and the residue was recrystalꢀ
lized from a CHCl3—hexane mixture. Dimer racꢀ1b was obꢀ
tained in a yield of 24.0 mg (48%) as a yellow amorphous preꢀ
cipitate. M.p. 184—186 °C, Rf 0.37 (benzene—acetone, 20 : 1;
twofold elution). Found (%): C, 37.91; H, 4.49; N, 4.20.
C22H32Br2N2Pd2. Calculated (%): C, 37.90; H, 4.63; N, 4.02.

2206
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
Pd0 was removed by filtration, and the filtrate was concentrated
to dryness. The residue was dissolved in CH2Cl2 (10 mL), the
solution was vigorously shaken with 1 M aqueous HCl (2×5 mL),
and the combined aqueous extracts were extracted with diꢀ
chloromethane. The organic layer was dried over Na2SO4, the
solvent was removed in vacuo, and the dimeric complexes were
separated by flash column chromatography (h = 16 cm, d =
2 cm; benzene—acetone mixtures, from 80 : 1 to 10 : 1). Dimer
racꢀ8a (ee <2%), m.p. (with decomp.) 195—196 °C, was isoꢀ
lated in a yield of 63.7 mg (42%). Reagent (SC)ꢀ7a, m.p. (with
decomp.) 182—183 °C; [α]D +73.4 (c 0.36, benzene), was reꢀ
covered in a yield of 39.5 mg (54%). For dimers 8a and 7a, Rf are
0.53 and 0.59 (diethyl ether—heptane, 3 : 1), respectively.
B. Analogously, after chromatography (h = 10.5 cm, d =
1.2 cm) of the mixture prepared by the reaction of dimer (SC)ꢀ1a
(52.4 mg, 0.0861 mmol) with amine HL8 (36.4 mg, 0.172 mmol)
at 50 °C (5.5 h), dimer racꢀ8a ([α]D <5, ee <4%), m.p.
(with decomp.) 195—196 °C, and reagent (SC)ꢀ1a, m.p. (with
decomp.) 217—219 °C; [α]D +146 (c 0.4, CH2Cl2—pyridine),
were isolated in yields of 25.4 (42%) and 21.0 mg (69%), respecꢀ
tively. For dimers 1a and 8a, Rf are 0.44 and 0.80 (benꢀ
zene—acetone, 10 : 1), respectively.
C. A mixture of racemic dimer 4a (17.8 mg, 0.0275 mmol)
and amine HL1 (9.0 mg, 0.0551 mmol) in toluene (5 mL) was
stirred at 20 °C for 75 days, the solvent was removed in vacuo, a
solution of the residue in dichloromethane (5 mL) was treated
with 1 M HCl (2×5 mL), and the aqueous extracts were exꢀ
tracted with dichloromethane. The organic layer was dried over
Na2SO4, the solvent was removed, and the residue was subjected
to dry column chromatography (h = 2 cm, d = 1 cm; benꢀ
zene—acetone mixtures, from 20 : 1 to 1 : 1). Since dimers 1a
and 4a have similar chromatographic mobilities (Rf 0.44 and 0.39,
respectively; benzene—acetone, 10 : 1), the composition of the
reaction mixture was estimated after the transformation of the
dimers into the mononuclear phosphine derivatives by the reacꢀ
tion with PPh3 (15.9 mg, 0.0606 mmol) in benzene (2 mL) at
20 °C (30 min). 31P NMR spectroscopy revealed the presence of
two phosphine adducts, 1g and 4b (δ 39.68 and 41.16, respecꢀ
tively), in a ratio of 1 : 4.6, which corresponds to the degree of
conversion of 18%. The 1H NMR spectra of these adducts are
identical to the spectra of individual adducts 1g 44 and 4b (see
below).
ether—hexane, 5 : 1) in the reaction of dimer (SC)ꢀ5a (79.5 mg,
0.1517 mmol) with amine HL4 (55.6 mg, 0.303 mmol) in toluꢀ
ene (5 mL) (20 °C, 144 h; 60 °C, 192 h). After chromatography
(h = 2 cm, d = 1 cm, benzene—acetone mixtures, from 20 : 1
to 1 : 1) of the reaction mixture containing dimer 5a (Rf 0.23)
and its adduct with amine HL4 (5c, Rf 0.39), dimer (SC)ꢀ5a was
recovered in a yield of 72.5 mg (91%), m.p. (with decomp.)
188—190 °C, [α]D +21 (c 0.25, CH2Cl2).
F. A mixture of dimer (SC)ꢀ5a (68.4 mg, 0.1306 mmol) and
amine racꢀHL3 (50.0 mg, 0.261 mmol) in acetonitrile (6 mL)
was treated with KPF6 (480.0 mg, 0.2612 mmol). After removal
of KCl and stirring (20 °C, 120 h; 50 °C, 48 h), dimer 3a
(Rf 0.79) was not detected by TLC* (benzene—acetone, 10 : 1).
After chromatography (h = 3 cm, d = 1.5 cm, benzene—acetone
mixtures, from 10 : 1 to 1 : 1) of the reaction mixture containing
the starting dimer (SC)ꢀ5a (Rf 0.34) and its adduct with amine
HL3 (5b, Rf 0.46), dimer (SC)ꢀ5a was recovered in a yield of
62.0 mg (91%), m.p. (with decomp.) 188—190 °C, [α]D +23
(c 0.25, CH2Cl2).
Cyclopalladated ligand exchange reactions with thioamide.
A. A solution of dimer (SC)ꢀ1a (56.5 mg, 0.0928 mmol) and
thioamide HL11 (36.6 mg, 0.1856 mmol) in a 1 : 1 mixture of
toluene and AcOH (6 mL) was stirred at 20 °C for 7 days. The
solvent was removed and the residue was subjected to dry colꢀ
umn chromatography (h = 2.5 cm, d = 1.5 cm, benzene—acꢀ
etone mixtures, from 60 : 1 to 1 : 1); CSꢀdimer 11a and the
starting CNꢀdimer (SC)ꢀ1a were isolated in yields of 31.0 (49%)
and 26.8 mg (47%), respectively. For dimers 11a and 1a, Rf are
0.64 and 0.57 (benzene—acetone, 5 : 1), respectively; CSꢀdimer
11a was identified based on the 1H NMR spectrum of its
d5ꢀpyridine adduct generated in situ (see above).
B. The formation of dimer 11a in the reaction of dimer
(SC)ꢀ1a (56.5 mg, 0.0928 mmol) with thioamide HL11 (36.6 mg,
0.186 mmol) in toluene (5 mL) in the absence of AcOH (20 °C,
21 days) was not detected by the TLC method. The solvent was
removed, and the residue was treated with a KPF6 solution
(34.2 mg, 0.186 mmol) in MeCN (3 mL). After prolonged stirꢀ
ring at 20 °C for 28 h and at 50 °C for 10 days, neither dimer 11a
nor its adduct with amine HL1 (11c) was detected. According to
TLC, the reaction mixture contained only the adduct of the
starting dimer 1a and thioamide HL11 (1e); Rf 0.38 (benꢀ
1
zene—acetone, 5 : 1). H NMR of adduct 1e (δ): signals of the
D. In the reaction of dimer (SC)ꢀ1a (60.0 mg, 0.0986 mmol)
with amine HL4 (36.1 mg, 0.197 mmol) under the analogous
conditions (20 °C, 37 days; 50 °C, 70 h) followed by treatment
with PPh3 (56.9 mg, 0.2169 mmol), the formation of dimer 4a
(based on its adduct 4b) was not observed. The 31P NMR specꢀ
trum shows one signal (δ 39.65) corresponding to the adduct of
the starting CNꢀdimer (SC)ꢀ1a with phosphine PPh3, viz.,
(SC)ꢀ1g.44 1H NMR of intermediate adduct (SC)ꢀ1d (δ): signals
of the palladacycle: 0.856 (s, 9 H, But); 3.673 (d, 1 H, αꢀCH,
palladacycle: 1.191 (s, 9 H, But); 3.912 (d, 1 H, αꢀCH,
3JHC,NH = 5.8 Hz); 4.007 (br.m, 1 H, NHeq); 3.297 (br.m, 1 H,
ax
NHax); 6.932 (m, 3 H, C(4)H—C(6)H); 7.395 (m, 1 H, C(3)H);
signals of HL11: 1.517 (s, 9 H, But); 4.128 (br.m, 2 H, αꢀCH2);
1.75 (group of br.m, 8 H, α´ꢀCH2, βꢀCH2, β´ꢀCH2, γꢀCH2).
1H NMR of adduct 11c (two sets of signals of Z/E isomers, 3 : 1)
(δ, J/Hz): signals of the palladacycle: 1.288 and 1.303 (both s,
9 H each, But); 1.44—1.80 (group of m, 5 H, βꢀHax, β´ꢀCH2,
γꢀCH2); 2.625 and 2.700 (both m, 1 H, βꢀHeq); 3.038 and 3.060
3JHC,NH = 5.7 Hz); 5.400 (br.s, 1 H, NHeq); 2.855 (br.dd, 1 H,
(both m, 1 H, α´ꢀHax); 4.288 and 4.346 (both br.d, 1 H, α´ꢀHeq
,
ax
3
NHax
C(6)H, J6,5 = 7.4 Hz); 6.608 (dd, 1 H, C(5)H, J5,4 = 7.3 Hz,
,
2JH,NH = 10.7 Hz, JHN,CH = 5.7 Hz); 6.649 (d, 1 H,
2JH,H =13.3 Hz); 4.511, 4.527 (dd, 1 H, αꢀHax, 2JH,H = 11.6 Hz,
3
3
3Jα
eq = 2.4 Hz); signals of HL1: 0.920 and 0.933 (both s,
β
, ꢀH
ꢀH
3J5,6 = 7.4 Hz); 6.766 (ddd, 1 H, C(4)H, 3J4,3 = 7.5 Hz, J4,5
=
9 H,axBut); 2.328 and 2.490 (both br.m, 1 H, NH1); 2.532
and 2.684 (both br.d, 1 H, NH2); 3.621 and 3.648 (both t,
3
4
3
7.3 Hz, J4,6 = 1.4 Hz); 6.844 (dd, 1 H, C(3)H, J3,4 = 7.5 Hz,
4J3,5 = 1.2 Hz); signals of coordinated amine HL4: 2.524 (br.s,
1 H, NH1); 3.214 (br.s, 1 H, NH2); 5.329 (d, 1 H, αꢀCH,
3
1 H, αꢀCH, JHC,NH = 4.0 Hz); 7.15—7.34 (group of m,
10 H, Ph).
3JHC,NH = 7.3 Hz); 7.18—7.40 (group m, 10 H, 2 αꢀPh).
1
E. The formation of neither dimer 4a (Rf 0.60) nor its adduct
with amine HL5 (Rf 0.52) was detected by TLC (diethyl
* To control the course of the reaction by TLC, the sample was
treated with a solution of LiCl in acetone.

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2207
Cyclopalladated ligand exchange reactions with ferrocenylꢀ
methylphosphine. A. A solution of dimer (SC)ꢀ3a (32.0 mg,
0.0481 mmol) and phosphine HL9 (41.3 mg, 0.120 mmol) in
toluene (4 mL) was stirred (20 °C, 500 h; 60 °C, 420 h), the
solvent was removed, the residue was dissolved in CH2Cl2
(6 mL), and the PCꢀpalladacycle was twice extracted with an
aqueous solution of a 20ꢀfold excess of ethylenediamine (En) as
the cationic derivative (see Scheme 15). Dichloromethane was
added to the combined aqueous extracts, and the mixture was
acidified with 1 M HCl to pH 3—4 with cooling and stirring.
The aqueous fraction was extracted with dichloromethane
(2×10 mL), and the organic layer was washed with water and
dried over Na2SO4 (method I).51 According to TLC, the solution
contained trace amounts of dimer 9a and reagent 3a (Rf 0.96
and 0.75, respectively; benzene—acetone, 10 : 1). Dry column
chromatography (h = 3 cm, d = 2 cm; benzene—acetone mixꢀ
tures, from 80 : 1 to 10 : 1) of the solution afforded a ∼1 : 10
mixture (4.0 mg) of PCꢀdimer 9a and CNꢀdimer 3a (the yield of
dimer 9a <1%) and dimer (SC)ꢀ3a (20.0 mg, 71%).
B. After the analogous reaction of dimer (RCSN)ꢀ2a (30.8 mg,
0.0484 mmol) with phosphine HL9 (41.3 mg, 0.1200 mmol) in
toluene (4 mL), the starting CNꢀdimer 2a, its adduct with phosꢀ
phine 2b, and PCꢀdimer 9a were detected by TLC (Rf 0.35, 0.63,
and 0.77, respectively; diethyl ether—hexane, 3 : 1). After workꢀ
up of the reaction mixture according to method I, dry column
chromatography (h = 3 cm, d = 2 cm, benzene—acetone mixꢀ
tures, from 80 : 1 to 10 : 1) afforded a ∼1 : 6 mixture of PCꢀdimer
9a and the starting reagent 2a in a yield of 6.0 mg (the yield
of 9a <2%), and dimer 2a was recovered in a yield of
20.0 mg (81%).
C. A mixture of dimer (RC)ꢀ1a (30.7 mg, 0.0504 mmol) and
phosphine HL9 (41.3 mg, 0.120 mmol) in toluene (4 mL) was
stirred at 20 °C for 306 h. In this step, the predominance of the
phosphine adduct of the CNꢀreagent (1f) against traces of reꢀ
agent 1a and PCꢀdimer 9a were detected by TLC (Rf 0.66, 0.49,
and 0.77, respectively, diethyl ether—hexane, 3 : 1). After heatꢀ
ing (60 °C, 96 h), dry column chromatography (h = 2 cm, d =
2 cm, benzene—acetone mixtures, from 30 : 1 to 1 : 30) afforded
PCꢀdimer (SP)ꢀ9a (ee 44%) in a yield of 12.8 mg (26%), and
reagent (RC)ꢀ1a was recovered in a yield of 21.0 mg (93%);
[α]D –146 (c 0.4, CH2Cl2ꢀPy).
Cyclopalladated ligand exchange reactions with diꢀorthoꢀtolylꢀ
tertꢀbutylphosphine. A. A solution of reagent (SCRN)ꢀ6a (69.9 mg,
0.110 mmol) and phosphine HL10 (60.1 mg, 0.220 mmol) in a
mixture of toluene and AcOH (1 : 1, 6 mL) was stirred at 60 °C
for 12.5 h. The precipitate that formed was filtered off and
washed with toluene. Dimer 10a with ee 2.3% (RP) was obtained
in a yield of 51.4 mg (57%). For dimers 10a and 6a, Rf are 0.69
and 0.32 (diethyl ether—hexane, 3 : 1), respectively.
CNꢀdimer with phosphine HL10 (3c, δ 42.88, br.s) and free
phosphine HL10 (δ –7.43, s). After prolonged heating in toluene
(60 °C, 240 h), only trace amounts of PCꢀdimer 10a (δ 63.8)
were detected. In the 31P NMR spectrum, the signal of adꢀ
duct 3c (was identified based on the 1H and 31P NMR spectra of
racemic complex 3c prepared by the independent synthesis, see
below) dominates. Slow evaporation of a solution of the reacꢀ
tion mixture in toluene afforded crystalline adduct (SC)ꢀ3c in a
yield of 22.8 mg (31%).
D. A solution of dimer (RCSN)ꢀ2a (50.0 mg, 0.079 mmol)
and phosphine HL10 (42.4 mg, 0.158 mmol) in toluene (3 mL)
was stirred at 60 °C for 132 h. The precipitate that formed was
filtered off, washed with benzene and hexane, and dried;
PCꢀdimer (SP)ꢀ10a with ee 8.8% was obtained as an amorꢀ
phous creamꢀcolored powder in a yield of 5.2 mg (8%). Reꢀ
agent (RCSN)ꢀ2a was recovered in a yield of 86% (43.3 mg,
0.0680 mmol). For dimers 2a and 10a, Rf are 0.45 and
0.85 (benzene—acetone, 7 : 1), respectively.
E. The reaction of dimer (SCRN)ꢀ6a (69.9 mg, 0.110 mmol)
with phosphine HL10 (60.0 mg, 0.220 mmol) was performed in
toluene (6 mL) (60 °C, 11 h; 20 °C, 72 h). The precipitate that
formed was filtered off and washed with toluene; PCꢀdimer (RP)ꢀ
10a with ee 5.5% was obtained in a yield of 51.4 mg (57%). For
dimers 6a and 10a, Rf are 0.33 and 0.69 (diethyl ether—hexane,
3 : 1), respectively.
F. A mixture of dimer (SC)ꢀ5a (66.4 mg, 0.1266 mmol) and
phosphine HL10 (68.5 mg, 0.253 mmol) in toluene (4.5 mL) was
stirred at 20 °C for 14 days. The precipitate that formed was
filtered off and washed with toluene, benzene, and dichloroꢀ
methane to give 58.9 mg (0.0716 mmol) of PCꢀdimer 10a. The
combined mother liquors were treated with ethylenediamine
according to method I. Subsequent separation of the mixture of
the dimers by dry column chromatography (h = 3 cm, d = 2 cm,
a mixture of diethyl ether—hexane as the eluent, from 1 : 10
to 3 : 1) affroded an additional portion of PCꢀdimer 10a
(10.0 mg), and reagent (SC)ꢀ5a was recovered in a yield of
21.0 mg (95%). As a result, dimer (RP)ꢀ10a with ee 13.4% (R)
was isolated in a yield of 68.9 mg (66%). For dimers 5a and 10a,
Rf are 0.05 and 0.46 (diethyl ether—hexane, 1 : 1), respectively.
G. Solutions of phosphine HL10 (8.2 mg, 0.0302 mmol) and
KPF6 (11.2 mg, 0.0604 mmol) in MeCN (4 mL) were sucꢀ
cessively added to a suspension of dimer racꢀ1a (9.2 mg,
00151 mmol) in MeCN (1 mL). The reaction mixture was stirred
at 20 °C for 45 days and then LiCl (2.6 mg, 0.0604 mmol) was
added. After 1 h, the precipitate was filtered off and washed
with water. Dimer racꢀ10a was obtained in a yield of 7.0 mg
(56.5%). For dimers 1a and 10a, Rf are 0.15 and 0.46 (diethyl
ether—hexane, 1 : 1), respectively.
H. The analogous reaction of dimer racꢀ1a (9.5 mg,
0.0156 mmol) with phosphine HL10 (8.4 mg, 0.0312 mmol) and
KPF6 (11.4 mg, 0.0624 mmol) in acetone (3 mL) produced
(45 days) dimer racꢀ10a in a yield of 6.8 mg (53%).
K. Heating of dimer (RC)ꢀ1a (50.0 mg, 0.0822 mmol) with
phosphine HL10 (44.4 mg, 0.1644 mmol) in toluene (3 mL)
(60 °C, 58 h) afforded a precipitate, which was filtered off and
washed with cold hexane to give PCꢀdimer (SP)ꢀ10a with ee 66%
in a yield of 16.2 mg (24%).
L. After treatment of dimer (RC)ꢀ1a (52.2 mg, 0.0858 mmol)
with phosphine HL10 (46.4 mg, 0.1716 mmol) in toluene (4 mL),
the adduct of the CN reagent with (1h) was detected spectroꢀ
scopically (31P NMR). The reaction mixture was stirred at 20 °C
B. The analogous reaction of dimer (RC)ꢀ1a (60.0 mg,
0.0986 mmol) with phosphine HL10 (53.3 mg, 0.1972 mmol) in
an acidic medium (60 °C, 1 h) produced dimer 10a with ee 2% (S)
in a yield of 57.6 mg (71%). For dimers 1a and 10a, Rf are 0.60
and 0.79 (diethyl ether—hexane, 5 : 1), respectively.
C. A solution of CNꢀdimer (SC)ꢀ3a (40.6 mg, 0.0611 mmol)
and phosphine HL10 (33.0 mg, 0.122 mmol) in toluene (3 mL)
was stirred at 20 °C for 33 days. Since dimers 3a and 10a have
similar chromatographic mobilities (Rf 0.79 and 0.81, respecꢀ
tively; benzene—acetone, 10 : 1), the course of the reaction was
monitored by 31P NMR. In this step, PCꢀdimer 10a was not
detected. The spectrum showed signals of the adduct of the

2208
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
for 140 h and concentrated to dryness. The residue was subꢀ
jected to dry column chromatography (h = 4 cm, d = 2 cm;
hexane and hexane—benzene and benzene—acetone mixtures
were used as the eluents, gradient elution). Reagent (RC)ꢀ1a was
recovered in a yield of 18.8 mg (69%). The combined fractions
of the eluates containing PCꢀdimer 10a and its phosphine adꢀ
duct 10d were treated with ethylenediamine according to
method I. The resulting dimer 10a was purified by dry column
chromatography (h = 2.0 cm, d = 3 cm; benzene—acetone
mixtures as the eluents, with polarity gradient). Dimer (SP)ꢀ10a
with ee 72% was isolated in a yield of 33.6 mg (48%). Adduct 1h
was identified based on the 1H and 31P NMR spectra of complex
racꢀ1h (see below). 31P NMR spectrum of intermediate 10e
(adduct of PCꢀdimer 10a with benzylamine HL1; a 8 : 1 mixture
of Z/E isomers): δ 60.73 (s) and 59.85 (s). 31P NMR spectrum of
M.p. (with decomp.) 189—191 °C, Rf 0.57 (benzene—acetone,
5 : 1)*. Found (%): C, 59.32; H, 6.17; N, 5.62. C24H29ClN2Pd.
1
Calculated (%): C, 59.15; H, 6.00; N, 5.75. H NMR of comꢀ
plex 4c (δ) (two sets of signals of two diastereomers, ~1 : 1):
3
signals of the palladacycle: 3.884 (m, 1 H, αꢀCH, JHC,NH
=
=
ax
9.3 Hz); 4.103 (dd, 1 H, αꢀCH, 3JHC,NH = 9.5 Hz, 3JHC,NH
4.0 Hz); 3.154 and 3.417 (both br.s, 1 Haexach, NHax); 4.923 eaqnd
4.991 (both m, 1 H each, NHeq); 6.62—6.99 (group of m, 8 H,
2C6H4Pd); 7.1—7.4 (group of m, 20 H, αꢀPh groups of the
palladacycle and amine HL1); signals of coordinated amine HL1:
0.938 and 0.946 (both s, 9 H each, But); 3.285 (br.d, 1 H, αꢀCH,
3JHC,NH1 = 9.3 Hz); 1.711, 2.544, 3.095, and 3.285 (group of m,
5 H, 2 NH1, 2 NH2 and αꢀCH).
Chloro[(R,S)ꢀ2ꢀ{1ꢀdimethylaminoꢀ2,2ꢀdimethylpropyl}pheꢀ
nylꢀC,N](tertꢀbutylꢀdiꢀoꢀtolylphosphineꢀP)palladium(II) (racꢀ3c).
A mixture of dimer racꢀ3a (40.0 mg, 0.075 mmol) and phosꢀ
phine HL10 (33.0 mg, 0.1504 mmol) in MeCN (8 mL) was
stirred at 20 °C for 5 h. The precipitate was filtered off, and the
mother liquor was concentrated to dryness. The dry residue was
recrystallized from a benzene—hexane mixture. The precipitate
was washed with hexane and dried in vacuo. Adduct 3c was
obtained as a yellow finely crystalline precipitate in a yield of
22.8 mg (25%). M.p. (with decomp.) 156—158 °C, Rf 0.27 (diꢀ
ethyl ether—hexane, 1 : 1). Found (%): C, 61.43; H, 7.30;
N, 2.47. C31H43ClNPPd. Calculated (%): C, 61.80; H, 7.19;
N, 2.32. 31P NMR, δ: 42.3 (br.s).
2
adduct transꢀ10d (δ): 58.66 (d, palladacycle, JP,P = 373 Hz);
25.65 (d, phosphine HL10, 2JP,P = 373 Hz).
M. In the analogous reaction of dimer (RC)ꢀ1a (50.0 mg,
0.082 mmol) with phosphine HL10 (44.4 mg, 0.164 mmol) in
toluene (5 mL) at 20 °C (528 h), reagent (RC)ꢀ1a was recovered
chromatographically (h = 3 cm, d = 2.5 cm) in a yield of
35.0 mg (50%), and dimer (SP)ꢀ10a with ee 81% was isolated
from the combined eluates according to method I in a yield of
20.2 mg (30%).
N. A solution of dimer (RC)ꢀ1a (66.9 mg, 0.110 mmol) and
phosphine HL10 (59.5 mg, 0.220 mmol) in toluene (4 mL) was
kept at –13 °C for 5.5 months. After the workꢀup of the reaction
mixture according to the aboveꢀdescribed procedure, reagent
(RC)ꢀ1a was recovered in a yield of 40.9 mg (70%), and PCꢀdimer
(SP)ꢀ10a with ee 86.4% was isolated in a yield of 11.5 mg (13%).
O. The reaction of µꢀbromide dimer (RC)ꢀ1b (50.0 mg,
0.072 mmol) with phosphine HL10 (38.8 mg, 0.1430 mmol) in
toluene (5 mL) at 20 °C (528 h) according to the same proceꢀ
dure produced PCꢀdimer (SP)ꢀ10b with ee 91% in a yield of
35.3 mg (54%), and reagent (RC)ꢀ1b was recovered in a yield of
6.8 mg (62%). 31P NMR of dimer 10b, δ: 65.06 (br.s).* 31P NMR
spectrum of intermediate 1j (adduct of dimer 1b with phosꢀ
phine HL10), δ: 42.76 (br.s). 31P NMR spectrum of intermediate
racꢀ10f (diastereomers of the adduct of PCꢀdimer racꢀ10b with
benzylamine racꢀHL1), δ: 61.96 and 60.50 (two singlets, 22 : 1).
31P NMR spectrum of intermediate transꢀ10g (δ) (adduct of
PCꢀdimer racꢀ10b with phosphine HL10): 58.64 (d, PCꢀpalladaꢀ
cycle, 2JP,P = 373 Hz); 25.60 (d, coordinated phosphine HL10).
Synthesis of intermediate mononuclear adducts. Chloro[2ꢀ
{1ꢀ(amino)benzyl}phenylꢀC,N](1ꢀphenylꢀ2,2ꢀdimethylpropylꢀ
amineꢀN)]palladium(II) (racꢀ4c). A mixture of racemic dimer 4a
(30.0 mg, 0.0463 mmol) and amine HL1 (15.1 mg, 0.0926 mmol)
in benzene (7 mL) was stirred at 20 °C for 17 h and concenꢀ
trated. Then hexane (5 drops) was added until the mixture beꢀ
came turbid. The precipitate that formed upon cooling was filꢀ
tered off, washed with hexane, and dried in vacuo. After addiꢀ
tional recrystallization from a benzene—hexane mixture in the
presence of 1 equiv. of amine HL1, adduct 4c was obtained as a
colorless amorphous precipitate in a yield of 10.7 mg (24%).
Chloro[(S)ꢀ2ꢀ{1ꢀdimethylaminoꢀ2,2ꢀdimethylpropyl}phenylꢀ
C,N](tertꢀbutylꢀdiꢀoꢀtolylphosphineꢀP)palladium(II) ((S)ꢀ3c).
A solution of dimer (S,S)ꢀ3a (20.0 mg, 0.0301 mmol) and phosꢀ
phine HL10 (22.8 mg, 0.0843 mmol) in toluene (6 mL) was
stirred (20 °C, 6.5 h; 50 °C, 2 h). The reaction mixture was
concentrated and treated with heptane. The precipitate that
formed was filtered off, washed with heptane, and dried. After
repeated recrystallization from a toluene—heptane mixture, adꢀ
duct (S)ꢀ3c was isolated as a paleꢀyellow crystalline precipitate
in a yield of 8.5 mg (24%). M.p. (with decomp.) 158.5—159 °C,
Rf 0.15 (toluene—acetone, 20 : 1); [α]D +149.4 (c 0.4, CH2Cl2).
1
31P NMR, δ: 42.3 (br.s). H NMR: signals of the palladacycle:
4
1.447 (s, 9 H, But); 2.993 (br.d, 3 H, NMeeq, JH,P = 2.9 Hz);
3.242 (d, 1 H, αꢀCH, 4JH,P = 5.5 Hz); 2.615 (br.s, 3 H, NMeax);
3
5.856 (br.m, 1 H, H(6)); 6.210 (dt, 1 H, H(5), JH,H = 7.5 Hz,
4JH,H = 1.5 Hz); 6.728 (t, 1 H, H(4), 3JH,H = 7.4 Hz); signals of
3
coordinated phosphine: 1.657 (d, 9 H, But, JH,P = 14.5 Hz);
2.421 and 2.849 (both s, 3 H each, Me); 7.615 (dd, 1 H, Ho,
JH,P = 11.7 Hz, 3JH,H = 7.8 Hz); 6.8—7.42 (group of m, 8 H, Ho,
4Hm, 2Hp (HL10), C(3)H (C6H4Pd)).
Chloro[(R,S)ꢀ2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}phenylꢀ
C,N](tertꢀbutylꢀdiꢀoꢀtolylphosphineꢀP)palladium(II) (racꢀ1h).
A solution of dimer 1a (28.6 mg, 0.0470 mmol) and phosphine
HL10 (27.9 mg, 0.0987 mmol) in toluene (5 mL) was stirred at
20 °C for 19 h. The precipitate that formed was filtered off,
washed with toluene, and dried in vacuo. Complex racꢀ1h
was obtained as a colorless amorphous precipitate in a yield of
16.7 mg (31%). M.p. (with decomp.) 148—150 °C, Rf 0.25 (benꢀ
zene—acetone, 10 : 1). Found (%): C, 60.97; H, 6.91; N, 2.47.
* The chemical shift of insoluble PCꢀdimer 10b was determined
from the spectrum of its mixture with adduct 10d (1 : 1), which
was generated in situ by the reaction of dimer 10b with 1 equiv.
of phosphine HL10; the signals of adduct transꢀ10d (δ): 58.64 (d,
2JP,P = 373 Hz, PCꢀpalladacycle) and 25.60 (d, 2JP,P = 373 Hz,
coordinated phosphine HL10).
C
29H39ClNPPd. Calculated (%): C, 60.63; H, 6.84; N, 2.44.
31P NMR, δ: 44.71 (br.s). 1H NMR, δ: signals of the palladacycle:
1.32 (s, 9 H, αꢀBut); 3.66 (br.d, 1 H, NHeq, 2JH,NH = 11.1 Hz);
* The complex partially decomposes on the sorbent to recover
the starting dimer.

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2209
Table 2. Selected bond lengths and bond angles in the structure of complex (S)ꢀ3c
Bond
d/Å
Angle
ω/deg
Angle
ω/deg
Pd(1)—P(1)
Pd(1)—Cl(1)
Pd(1)—C(1)
Pd(1)—N(1)
P(1)—C(21)
P(1)—C(31)
P(1)—C(41)
N(1)—C(13)
N(1)—C(7)
N(1)—C(12)
C(1)—C(6)
C(6)—C(7)
C(7)—C(8)
C(7)—H(7A)
C(8)—C(9)
C(8)—C(10)
C(8)—C(11)
2.3030(19)
2.413(2)
2.011(5)
2.154(5)
1.838(6)
1.855(5)
1.928(6)
1.475(9)
1.508(8)
1.515(9)
1.386(8)
1.512(9)
1.564(10)
0.73(5)
C(1)—Pd(1)—N(1)
C(1)—Pd(1)—P(1)
N(1)—Pd(1)—P(1)
C(1)—Pd(1)—Cl(1)
N(1)—Pd(1)—Cl(1)
P(1)—Pd(1)—Cl(1)
C(21)—P(1)—Pd(1)
C(31)—P(1)—Pd(1)
C(41)—P(1)—Pd(1)
C(13)—N(1)—Pd(1)
C(7)—N(1)—Pd(1)
C(12)—N(1)—Pd(1)
C(21)—P(1)—C(31)
C(21)—P(1)—C(41)
C(31)—P(1)—C(41)
C(13)—N(1)—C(7)
C(13)—N(1)—C(12)
79.4(2)
99.5(2)
C(7)—N(1)—C(12)
C(6)—C(1)—C(2)
C(6)—C(1)—Pd(1)
C(2)—C(1)—Pd(1)
C(5)—C(6)—C(1)
C(5)—C(6)—C(7)
C(1)—C(6)—C(7)
N(1)—C(7)—C(6)
N(1)—C(7)—C(8)
C(6)—C(7)—C(8)
N(1)—C(7)—H(7A)
C(6)—C(7)—H(7A)
C(9)—C(8)—C(7)
C(10)—C(8)—C(7)
C(11)—C(8)—C(7)
C(21)—C(26)—C(27)
C(31)—C(36)—C(37)
107.1(6)
117.1(5)
114.0(4)
128.2(5)
121.2(6)
120.5(6)
118.2(5)
104.4(5)
117.4(6)
114.4(6)
111.0(4)
115.0(4)
113.5(7)
112.9(6)
108.2(7)
124.9(6)
124.1(6)
177.45(14)
167.77(17)
90.96(13)
90.39(5)
112.7(2)
119.01(17)
110.43(19)
117.8(5)
106.7(4)
105.3(4)
100.3(3)
105.8(3)
107.5(3)
114.6(6)
104.5(6)
1.533(10)
1.541(11)
1.522(13)
3.94 (dd, 1 H, αꢀCH, 3JHC,NH = 6.5 Hz, 4JH,P = 6.1 Hz); 4.06
CDCl3, and the 1H NMR spectrum was measured. The specꢀ
trum reveals two sets of wellꢀresolved signals identical to those
described earlier50 for diastereomers of (S)ꢀprolinate adduct 8b;
their ratio was determined from the integral intensities of the
signals for the αꢀCH protons.
ax
2
3
(br.dd, 1 H, NHax, JH,NH = 11.1 Hz, JHN,CH = 6.5 Hz); 5.92
3
(br.dd, 1 H, H(6), J6,5 = 7.6 Hz, JH,P = 7.6 Hz; 6.30 (dd, 1 H,
H(5), 3J5,6 = 7.6 Hz, 3J5,4 = 7.1 Hz); 6.76 (dd, 1 H, H(4), 3J4,3
=
3
3
7.6 Hz, J4,5 = 7.1 Hz); 6.88 (d, 1 H, H(3), J3,4 = 7.6 Hz);
signals of phosphine: 1.61 (d, 9 H, PBut, 3JH,P = 14.6 Hz); 2.38
and 2.66 (both s, 3 H each, Me); 7.00—7.45 (group of m, 5 H,
3 Hm, 2 Hp); 7.32 (m, 1 H, Hm); 7.81 and 8.32 (both br.m,
1 H each, Ho, 3JH,P = 8.6 Hz).
CSꢀDimer 11a. A solution of (1R,2R)ꢀ1,2ꢀdiphenylethaneꢀ
1,2ꢀdiamine (19.4 mg, 0.091 mmol) in MeOH (1 mL) was added
to a suspension of dimer 11a (31.0 mg, 0.0456 mmol) in MeOH
(2 mL). The reaction mixture was stirred at 20 °C for 4 h and
concentrated to dryness in vacuo. 1H NMR spectrum of diamine
adduct 11d (δ) (CDCl3 : CD3OD = 5 : 1; two sets of signals in
a ratio of 1 : 1): signals of the palladacycle: 1.412 and 1.420
(both s, 9 H each, But); 1.45—2.20 (group of m, 19 H, 3βꢀH,
Bromo[(R,S)ꢀ2ꢀ{1ꢀaminoꢀ2,2ꢀdimethylpropyl}phenylꢀ
C,N](tertꢀbutylꢀdiꢀoꢀtolylphosphineꢀP)palladium(II) (racꢀ1j).
A solution of dimer racꢀ1b (20.0 mg, 0.0287 mmol) and phosꢀ
phine HL10 (15.5 mg, 0.0574 mmol) in toluene (9 mL) was
stirred at 20 °C for 6 h and concentrated. The precipitate
that formed was filtered off, dried in vacuo, and purified by
chromatography (h = 13 cm, d = 1.5 cm; CHCl3 and a 40 : 1
CHCl3—MeOH mixture as the eluents). Complex racꢀ1b was
recrystallized from a diethyl ether—hexane mixture, and the
precipitate was washed with hexane and dried in vacuo. Adduct
racꢀ1j was obtained as a paleꢀyellow crystalline precipitate in a
yield of 10.4 mg (29%). M.p. 213—215°, Rf 0.33 (chloroꢀ
form—methanol, 20 : 1). Found (%): C, 56.40; H, 6.13; N, 2.16.
4β´ꢀH, 4γꢀH, 4NH2); 3.278 (m, 1 H, βꢀHeq,
2JH,H = 13 Hz,
3Jβ
= 2.6 Hz); 4.243 and 4.301 (both dt, 1 H each,
α
, ꢀH
ꢀH
α´ꢀHeq , 2JHax,H = 13.0 Hz, 3JαꢀH
= 10.1 Hz, 3JαꢀH
=
ax
,βꢀH
ax
,βꢀH
ax
eq
2.9 Hz); 4.475 (br.d, 1 H, α´ꢀHeq
4.779 (both dd, 1 H each, αꢀHax
3JαꢀH
= 2.6 Hz); signals of diamine:* 3.357 (m, 2 H,
,
2JH,H = 13 Hz); 4a.x734 and
,
3Jα
= 12.3 Hz,
β
, ꢀH
ax ax
ꢀH
,βꢀH
ax
eq
αꢀCH); 7.1—7.4 (m, 10 H, 2Ph).
PCꢀDimers 9a and 10a,b. A mixture of PCꢀdimer 9a or 10a,b
(~0.030 mmol) and sodium (S)ꢀprolinate (~0.063 mmol) in
MeOH (5 mL) was stirred at 20 °C for 2 h and then concentrated
to dryness. The residue was dissolved in CDCl3, and the
31P NMR spectrum of a mixture of diastereomers of (S)ꢀprolinate
derivatives 9b or 10c was measured. The spectroscopic paramꢀ
eters of adducts 9b (see Ref. 40) or 10c (see Ref. 41) are consisꢀ
tent with the characteristics published earlier.
Xꢀray diffraction study of compound 3c was performed on an
automated EnrafꢀNonius CAD4 diffractometer (MoꢀKα radiaꢀ
tion, λ = 0.71073 Å) at room temperature. The experimental
intensities were corrected for the Lorentz and polarization facꢀ
tors.86 Absorption corrections were applied based on the intensiꢀ
ties of equivalent reflections.87 The structure was solved by diꢀ
rect methods (SHELXSꢀ97).88 All nonhydrogen atoms were
C
29H39BrNPPd. Calculated (%): C, 56.28; H, 6.35; N, 2.26.
31P NMR, δ: 46.56 (br.s). 1H NMR, δ, signals of the palladacycle:
1.31 (s, 9 H, αꢀBut); 3.72 (br.d, 1 H, NHeq, JH,NH = 9.4 Hz);
3.97 (dd, 1 H, αꢀCH, JHC,NH = 6.3 Hz, JH,P = 6.3 Hz); 4.04
(br.m, 1 H, NHax); 5.93 (br.dd, 1 H, H(6), 3J6,5 = 8.5 Hz, JH,P
4.4 Hz); 6.29 (dd, 1 H, H(5), 3J5,6 = 8.5 Hz, 3J5,4 = 6.9 Hz); 6.76
(dd, 1 H, H(4), J4,5 = 6.9 Hz, J4,3 = 7.5 Hz); 6.89 (d, 1 H,
H(3), 3J3,4 = 7.5 Hz); signals of coordinated phosphine: 1.62 (d,
9 H, But, JH,P = 15.1 Hz); 2.42 and 2.83 (both s, 3 H each,
2
3
4
=
3
3
3
Me); 7.00—7.45 (group of m, 6 H, 4 Hm, 2 Hp); 7.49 and 8.27
(both br.m, 1 H each, Ho).
Spectroscopic determination of the enantiomeric purity of
dimeric cyclopalladated complexes. CNꢀdimer 8a. A mixture of
dimer 8a (25.5 mg, 0.0362 mmol) and sodium (S)ꢀprolinate
(12.0 mg, 0.0875 mmol) in MeOH (5 mL) was stirred at 20 °C
for 2 h and concentrated to dryness. The residue was dissolved in
* The signals of the NH2 groups of the diamine overlap with the
signals of the piperidine ring.

2210
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006
Dunina et al.
Table 3. Crystallographic data and the Xꢀray data collection and
refinement statistics for complex (S)ꢀ3c
9. B. Binotti, C. Carfagna, G. Gatti, D. Martini, L. Mosca,
and C. Pettinati, Organometallics, 2003, 22, 1115.
10. H. C. Malinakova, Chem. Eur. J., 2004, 10, 2636.
11. J. L. Portscheller, S. E. Lilley, and H. C. Malinakova, Orgaꢀ
nometallics, 2003, 22, 2961.
Parameter
(S)ꢀ3с
Molecular formula
Molecular weight
Crystal system
Space group
C31H43ClNPPd
602.48
Orthorhombic
P212121
12. A. D. Ryabov, L. M. Panyashkina, V. A. Kazankov, and
L. G. Kuz´mina, J. Organomet. Chem., 2000, 601, 51.
13. R. Navarro and E. P. Urriolabeitia, J. Chem. Soc., Dalton
Trans., 1999, 4111.
a/Å
b/Å
14.843(8)
10.925(6)
18.164(11)
2945(3)
14. L. R. Farbello, S. Fernandez, R. Navarro, and E. P.
Urriolabeitia, New. J. Chem., 1997, 21, 909.
15. A. D. Ryabov, in Perspective in Coordination Chemistry;
Eds A. F. Williams, C. Floriani, and A. Merbach, VCH,
Weinheim, 1994, pp. 271—292.
16. M. Albrecht, P. Dani, M. Lutz, A. L. Spek, and
G. van Koten, J. Am. Chem. Soc., 2000, 122, 11822.
17. A. D. Ryabov and G. M. Kazankov, Vestn. Mosk. Univ.,
Ser. 2, Khim., 1988, 29, 220 [Vestn. Mosk. Univ., Ser. 2,
Khim., 1988, 29 (Engl. Transl.)].
18. V. V. Dunina, L. G. Kuz´mina, M. Yu. Rubina, Yu. K.
Grishin, Yu. A. Veits, and E. I. Kazakova, Tetrahedron: Asymꢀ
metry, 1999, 10, 1483.
c/Å
V/Å3
Z
4
dcalc/g cm–3
1.359
0.795
1256
µ/mm–1
F(000)
θ Scan range/deg
Ranges of indices of reflections
2.18—24.99
–17 < h < 5
–2 < k < 12
–4 < l < 21
5786
Number of measured reflections
Number of independent reflections (Rint
Number of parameters in refinement
R1 (I ≥ 2σ(I ))
)
4436(0.0384)
489
19. S. B. Wild, Coord. Chem. Rev., 1997, 166, 291.
20. St. F. Kirsch and L. E. Overman, J. Am. Chem. Soc., 2005,
127, 2866.
0.0323
wR2 (based on all reflections)
0.0822
1.044
–0.04(4)
0.983/–0.916
21. K. Takenaka and Y. Uozumi, Org. Lett., 2004, 6, 1833.
22. L. E. Overman and T. P. Remarchuk, J. Am. Chem. Soc.,
2002, 124, 12.
23. T. K. Hollis and L. E. Overman, J. Organomet. Chem., 1999,
576, 290.
Goodnessꢀofꢀfit on F 2
Flack parameter
Residual electron density
(max/min)/e Å–3
24. V. V. Dunina, O. N. Gorunova, M. V. Livantsov, and Yu. K.
Grishin, Tetrahedron: Asymmetry, 2000, 11, 2907.
25. V. V. Dunina, L. G. Kuz´mina, M. Yu. Kazakova, Yu. K.
Grishin, Yu. A. Veits, and E. I. Kazakova, Tetrahedron: Asymꢀ
metry, 1997, 8, 2537.
26. W.ꢀCh. Yeo, S.ꢀY. Tee, H.ꢀB. Tan, L. L. Koh, and P.ꢀH.
Leung, Inorg. Chem., 2004, 43, 8102.
27. P.ꢀH. Leung, Acc. Chem. Res., 2004, 37, 169.
28. Y. Qin, A. J. P. White, D. J. Williams, and P.ꢀH. Leung,
Organometallics, 2002, 21, 171.
refined by the fullꢀmatrix leastꢀsquares method against F 2
with anisotropic displacement parameters (SHELXLꢀ97).89 All
hydrogen atoms were located in difference Fourier maps and
refined isotropically. Selected bond lengths and bond angles are
listed in Table 2. The crystallographic data and the Xꢀray data
collection and refinement statistics for the structure of 3c are
given in Table 3.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 04ꢀ03ꢀ32986)
and the Russian Science Support Foundation.
29. V. V. Dunina, E. D. Razmyslova, O. N. Gorunova, M. V.
Livantsov, and Yu. K. Grishin, Tetrahedron: Asymmetry,
2003, 14, 2331.
30. R. M. Ceder, M. Gomez, and J. Sales, J. Organomet. Chem.,
1989, 361, 391.
References
31. A. D. Ryabov, Zh. Obshch. Khim., 1987, 57, 249 [J. Gen.
Chem. USSR, 1987, 57 (Engl. Transl.)].
1. V. V. Dunina, L. G. Kuz´mina, E. D. Razmyslova, and V. P.
Kislyi, Khim. Geterotsikl. Soedin., 1999, 1138 [Chem. Heteroꢀ
cyclic Compd., 1999, 1138 (Engl. Transl.)].
2. I. Mamedyarova, M. Nefedova, and V. Sokolov,
J. Organomet. Chem., 1996, 524, 181.
3. V. I. Sokolov, J. Organomet. Chem., 1995, 500, 299.
4. M. Gruselle, B. Malezieux, L. L. Troitskaya, V. I. Sokolov,
L. M. Epstein, and Y. S. Shubina, Organometallics, 1994,
13, 200.
32. J. Granell, D. Sainz, D. Sales, X. Solans, and
M. FontꢀAltaba, J. Chem. Soc., Dalton Trans., 1986, 1785.
33. A. D. Ryabov, A. V. Usatov, V. N. Kalinin, and L. I.
Zakharkin, Izv. Akad. Nauk SSSR, Ser. Khim., 1986, 2790
[Bull. Acad. Sci. USSR, Div. Chem. Sci., 1986, 35 (Engl.
Transl.)].
34. J. Dupont, N. Beudoun, and M. Pfeffer, J. Chem. Soc.,
Dalton Trans., 1989, 1715.
5. V. I. Sokolov and L. L. Troitskaya, J. Organomet. Chem.,
1982, 235, 369.
6. V. I. Sokolov, L. L. Troitskaya, and O. A. Reutov,
J. Organomet. Chem., 1979, 182, 537.
7. V. I. Sokolov and L. L. Troitskaya, Chimia, 1978, 32, 122.
8. G. Lu and H. C. Malinakova, J. Org. Chem., 2004, 69, 4701.
35. V. V. Dunina, O. A. Zalevskaya, and V. M. Potapov, Usp.
Khim., 1988, 57, 434 [Russ. Chem. Rev., 1988, 57 (Engl.
Transl.)].
36. V. V. Dunina, E. B. Golovan´, E. I. Kazakova, G. P. Potapov,
and I. P. Beletskaya, Metalloorg. Khim., 1991, 4, 1391
[Metalloorgan. Chem., 1991, 4 (Engl. Transl.)].

Asymmetric exchange of cyclopalladated ligands
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 12, December, 2006 2211
37. V. V. Dunina, M. Yu. Kazakova, Yu. K. Grishin, O. R.
Malyshev, and E. I. Kazakova, Izv. Akad. Nauk, Ser. Khim.,
1997, 1375 [Russ. Chem. Bull., 1997, 46, 1321 (Engl.
Transl.)].
38. A. D. Ryabov and G. M. Kazankov, J. Organomet. Chem.,
1984, 268, 85.
64. A. R. Dick, J. W. Kampf, and M. S. Sanford, J. Am. Chem.
Soc., 2005, 127, 12790.
65. A. J. Canty, J. L. Hoare, J. Patel, M. Pfeffer, B. W. Skelton,
and A. H. White, Organometallics, 1999, 18, 2660.
66. A. J. Canty, H. Jin, A. S. Roberts, B. W. Skelton, P. R.
Traill, and A. H. White, Organometallics, 1995, 14, 199.
67. V. V. Dunina, O. N. Gorunova, Yu. K. Grishin, L. G.
Kuz´mina, A. V. Churakov, A. V. Kuchin, and J. A. K.
Howard, Izv. Akad. Nauk, Ser. Khim., 2005, 2010 [Russ.
Chem. Bull., Int. Ed., 2005, 54, 2073].
68. L. G. Kuz´mina, Yu. T. Struchkov, O. A. Zalevskaya, V. V.
Dunina, and V. M. Potapov, Zh. Obshch. Khim., 1987, 57,
2499 [J. Gen. Chem. USSR, 1987, 57 (Engl. Transl.)].
69. A. Bondi, J. Phys. Chem., 1964, 68, 441.
39. A. D. Ryabov and A. K. Yatsimirsky, Inorg. Chem., 1984,
23, 789.
40. V. V. Dunina, O. N. Gorunova, M. V. Livantsov, Yu. K.
Grishin, L. G. Kuz´mina, N. A. Kataeva, and A. V.
Churakov, Tetrahedron: Asymmetry, 2000, 11, 3967.
41. V. V. Dunina, O. N. Gorunova, L. G. Kuz´mina, M. V.
Livantsov, and Yu. K. Grishin, Tetrahedron: Asymmetry,
1999, 10, 3951.
42. V. V. Dunina, O. N. Gorunova, E. B. Averina, Yu. K.
Grishin, L. G. Kuz´mina, and J. A. K. Howard, J. Organomet.
Chem., 2000, 603, 138.
43. V. V. Dunina, O. A. Zalevskaya, and V. M. Potapov,
Zh. Obshch. Khim., 1984, 54, 389 [J. Gen. Chem. USSR,
1984, 54 (Engl. Transl.)].
70. P. Dani, M. A. M. Toorneman, G. P. M. van Klink, and
G. van Koten, Organometallics, 2000, 19, 5287.
71. P. Dani, M. Albrecht, G. P. M. van Klink, and G. van Koten,
Organometallics, 2000, 19, 4468.
72. Fr. X. Roca, M. Motevalli, and Ch. J. Richards, J. Am.
Chem. Soc., 2005, 127, 2388.
44. V. V. Dunina, L. G. Kuz´mina, M. Yu. Kazakova, O. N.
Gorunova, Yu. K. Grishin, and E. I. Kazakova, Eur. J. Inorg.
Chem., 1999, 1029.
73. J. T. Sharp, I. Gosney, and A. G. Rowley, Practical Organic
Chemistry. A Student Handbook of Techniques, London—New
York, 1989.
45. A. C. Cope and E. C. Friedrich, J. Am. Chem. Soc., 1968,
90, 909.
74. H. De Witt and A. W. Ingersoll, J. Am. Chem. Soc., 1951,
73, 3359.
46. A. D. Ryabov, Chem. Rev., 1990, 90, 403.
47. J. K.ꢀP. Ng, Y. Li, G.ꢀKh. Tan, L.ꢀL. Koh, J. J. Vittal, and
P.ꢀH. Leung, Inorg. Chem., 2005, 44, 9874.
48. V. V. Dunina and O. N. Gorunova, Usp. Khim., 2004, 73,
339 [Russ. Chem. Rev., 2004, 73, 309 (Engl. Transl.)].
49. V. V. Dunina, E. B. Golovan´, N. S. Gulyukina, and A. V.
Buyevich, Tetrahedron: Asymmetry, 1995, 6, 2731.
50. V. V. Dunina, E. D. Razmyslova, L. G. Kuz´mina, A. V.
Churakov, M. Yu. Rubina, and Yu. K. Grishin, Tetrahedron:
Asymmetry, 1999, 10, 3147.
75. P. Billon, Ann. Chim., Ser. 10, 1927, 7, 314.
76. M. T. Warren and H. T. Smith, J. Am. Chem. Soc., 1965,
87, 1757.
77. V. V. Dunina, O. N. Gorunova, M. V. Livantsov, Yu. K.
Grishin, and N. A. Kataeva, Vestn. Mosk. Univ., Ser. Khim.,
2005, 46, 333 [Vestn. Mosk. Univ., Ser. Khim., 2005, 46 (Engl.
Transl.)].
78. A. C. Cope and T. T. Foster, J. Am. Chem. Soc., 1949,
71, 3929.
79. J. S. Jochims, Monatsh. Chem., 1963, 94, 677.
80. A. J. Cheney and B. L. Shaw, J. Chem. Soc., Dalton Trans.,
1972, 754.
51. V. V. Dunina and E. B. Golovan´, Tetrahedron: Asymmetry,
1995, 6, 2747.
52. O. N. Gorunova, Ph. D. (Chem.) Thesis, M. V. Lomonosov
Moscow State University, Moscow, 2001 (in Russian).
53. Phosphorusꢀ31 NMR Spectroscopy in Stereochemical Analyꢀ
sis, Eds J. G. Verkade and J. G. Quin, VCH, Weinheim, 1987.
54. Ch. A. Tolman, Chem. Rev., 1977, 77, 313.
55. A. D. Ryabov, Inorg. Chem., 1987, 26, 1252.
56. B. J. O’Keefe and P. J. Steel, Inorg. Chem. Commun.,
1999, 2, 10.
57. A. F. M. G. van Ploeg, G. van Koten, and K. Vrieze,
J. Organomet. Chem., 1981, 222, 155.
58. A. D. Ryabov, Koord. Khim., 1985, 11, 1532 [J. Coord. Chem.
USSR, 1981, 11 (Engl. Transl.)].
81. S. Paucher and P. Klein, Tetrahedron Lett., 1980, 21, 4061.
82. V. V. Dunina, E. D. Razmyslova, O. N. Gorunova, M. V.
Livantsov, and Yu. K. Grishin, Tetrahedron: Asymmetry,
2005, 16, 817.
83. Y. Fuchita, K. Yoshinaga, Y. Ikeda, and J. Kinoshitaꢀ
Kawashima, J. Chem. Soc., Dalton Trans., 1997, 2495.
84. O. A. Zalevskaya, V. V. Dunina, V. M. Potapov, L. G.
Kuz´mina, and Yu. T. Struchkov, Zh. Obshch. Khim., 1985,
55, 1332 [J. Gen. Chem. USSR, 1985, 55 (Engl. Transl.)].
85. K. Tani, L. D. Brown, J. Ahmed, J. Ibers, M. Yokota,
A. Nakamura, and S. Otsuka, J. Am. Chem. Soc., 1977,
99, 7876.
59. H.ꢀP. Abicht and K. Issleib, J. Organomet. Chem., 1985,
289, 201.
86. K. Harms, XCAD4. Program for the LpꢀCorrection of Nonius
CAD4 Data, Marburg, Germany, 1997.
60. H.ꢀP. Abicht and K. Issleib, J. Organomet. Chem., 1978,
149, 209.
87. SHELXTLꢀPlus. Release 6.10. Bruker AXS Inc., Madison,
Wisconsin, USA, 2000.
61. G. Longoni, P. Fantucci, P. Chini, and F. Canziani,
J. Organomet. Chem., 1972, 39, 413.
62. A. J. Canty and G. van Koten, Acc. Chem. Res., 1995,
28, 406.W
88. G. M. Sheldrick, Acta Cryst., 1990, A46, 467.
89. G. M. Sheldrick, SHELXLꢀ97. Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
63. A. D. Ryabov, Metalloorg. Khim., 1988, 1, 994 [J. Organomet.
Chem. USSR, 1988, 1 (Engl. Transl.)].
Received May 19, 2006;
in revised form August 8, 2006