Reactions of cyclopalladated complexes with lithium diphenylphosphide

Article abstract of DOI:10.1021/om9005615

Reactions of the cyclopalladated dimer {Pd(η²-L ¹)(μ-Cl)}₂ (7) derived from N,N-dimethylbenzylamine (HL¹) with lithium diphenylphosphide were studied under varied conditions. The LiPPh₂ reagents used

Full text of DOI:10.1021/om9005615

6546 Organometallics 2009, 28, 6546–6558
DOI: 10.1021/om9005615
Reactions of Cyclopalladated Complexes with Lithium
Diphenylphosphide
Valeria A. Stepanova,† Valery V. Dunina,‡ and Irina P. Smoliakova*,†
†Chemistry Department, University of North Dakota, 151 Cornell Street, Stop 9024, Grand Forks,
North Dakota 58202-9024, and Chemistry Department, M.V. Lomonosov Moscow State University,
‡
1 Leninskie Gory, 119991 Moscow, Russian Federation
Received June 30, 2009
Reactions of the cyclopalladated dimer {Pd(η2-L1)(μ-Cl)}2 (7) derived from N,N-dimethylbenzyl-
amine (HL1) with lithium diphenylphosphide were studied under varied conditions. The LiPPh2
reagents used were purchased from Sigma-Aldrich Co. or synthesized from PPh3, ClPPh2, or HPPh2
by known general methods. Depending on the source of lithium phosphide, solvent, and reagent
ratio, reactions of LiPPh2 with complex 7 resulted in the formation of different products. The
commercial LiPPh2 solutions reacted with compound 7 and several other cyclopalladated dimeric
complexes in THF to form the corresponding mononuclear derivatives with Ph2P(CH2)4OH as an
auxiliary ligand, Pd(η2-L)Cl{PPh2(CH2)4OH}. The monophosphido-bridged analogue of dimer 7,
{Pd(η2-L1)}2(μ-Cl)(μ-PPh2) (17), was the most common product of the 1:2 reactions of dimer 7 with
other LiPPh2 solutions in THF. ortho-(Diphenylphosphino)-N,N-dimethylbenzylamine (20) was
obtained in the reactions of complex 7 with the synthesized solutions of LiPPh2 using a 1:4.5 molar
ratio of the reagents in THF or a 1:2 ratio in toluene. Possible mechanisms of these reactions are
discussed.
I. Introduction
excess Li was used; however, (Spl,Spl)-1 was added to LiPPh2
along with PPh3.
Since the discovery of cyclopalladated complexes (CPCs) a
half a century ago, these organometallic compounds have
found a plethora of applications.1 In particular, CPCs can be
used for ligand transformations using reactions of the Pd-C
bond.2 Almost all reported transformations of this type
include reactions of alkenes, alkynes, allenes, carbon mon-
oxide, isocyanides, acyl halides, or halogens.2 We have been
interested in studying reactions of CPCs with LiPAr2. Inser-
tion of the PAr2 moiety into the Pd-C bond of C,N- or C,P-
palladacycles would provide a general approach for synth-
esis of aminophosphines, diphosphines, and related ligands
valuable in asymmetric reactions.
The idea of using CPCs in reactions with metal phosphides
is not new; however, there are only four communications
related to this research field. In 1980, the Sokolov group
reported preparation of aminophosphines (Spl)-2 and rac-2
by reactions of CPCs (Spl,Spl)-1 and rac-1 with LiPPh2
(Scheme 1).3 The authors reported two different procedures.
In one of them, LiPPh2 was synthesized from PPh3 and Li
using an excess of the former reagent. In the other procedure,
Later, the same group reported a reaction of (Spl,Spl)-1
with the prochiral phosphide LiPMePh (Scheme 1).4 The
corresponding two diastereomers of aminophosphine 3 were
obtained in 52% total yield and were separated using column
chromatography on silica gel.
The Bolm group studied preparation of (SC,Rpl) and(SC,Spl)
diastereomers of the oxazolynyl[2.2]paracyclophane-derived
phosphine 5 by reacting each of the two corresponding
diastereomers of the mononuclear CPC 4 with KPPh2
(Scheme 2).5 Purification of phosphine 5 in the form of the
BH3 adduct followed by deprotection afforded two diastere-
omers in 67% and 61% yield. Surprisingly, the same group in a
later paper did not apply this method for synthesis of the
isopropyl analogue of phosphine 5; instead, the compound was
obtained using a multistep synthesis in a low overall yield.6
As a part of the study directed toward the development of
new Pd-coordinated aminophosphine catalysts, Dunina et
al. reported the NMR spectroscopic evidence of the in situ
formation of Pd(0) complexes of the composition (amino-
phosphine)Pd(PPh3)2.7 These complexes were prepared by
*To whom correspondence should be addressed. E-mail: ismoliakova@
chem.und.edu.
(4) Troitskaya, L. L.; Starikova, Z. A.; Demeshchik, T. V.; Sokolov,
V. I. Russ. Chem. Bull. 1999, 1738–1743.
(1) (a) Palladacycles. Synthesis, Characterization and Applications;
Dupont, J.; Pfeffer, M., Eds.; Wiley-VCH Verlag GmbH: Weinheim, 2008.
(b) Dupont, J.; Consorti, C. S.; Spencer, J. Chem. Rev. 2005, 105, 2527–
2571.
(5) Bolm, C.; Wenz, K.; Raabe, G. J. Organomet. Chem. 2002, 662,
23–33.
(6) Whelligan, D. K.; Bolm, C. J. Org. Chem. 2006, 71, 4609–4618.
(7) (a) Dunina, V. V.; Kuz0mina, L. G.; Howard, J. A. K.; Kataeva,
N. A.; Rubina, M. Y.; Parfyonov, A. G.; Veits, Y. A.; Grishin, Y. K.,
Direct Route from Chiral Palladacyclesto Enantioselective Aminophos-
phine Palladium(0) Catalysts. In 10th IUPAC Symposium on Organo-
Metallic Chemistry Directed toward Organic Synthesis (OMCOS-10);
Versailles, France, 1999; p 124. (b) Grishin, Y. K.; Rubina, M. Y.; Kataeva, N.
A.; Churakov, A. V.; Kuz0mina, L. G.; Howard, J. A. K.; Dunina, V. V.
CCDC, XOZPIL, 2002, private communication.
(2) Vila, J. M.; Pereira, M. T. The Pd-C Building Block of Pallada-
cycles: A Cornerstone for Stoichiometric C-C and C-X Bond Assem-
blage. In Palladacycles. Synthesis, Characterization and Applications;
Dupont, J.; Pfeffer, M., Eds.; Wiley-VCH Verlag GmbH: Weinheim, 2008; pp
87-108.
(3) Sokolov, V. I.; Troitskaya, L. L.; Reutov, O. A. J. Organomet.
Chem. 1980, 202, C58–C60.
r
pubs.acs.org/Organometallics
Published on Web 10/21/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 22, 2009 6547
Scheme 1
Scheme 2
Table 1. Reactions of Dimeric CPCs with the LiPPh2 Reagent
Aldrich-1
Scheme 3
reacting dimeric CPCs with LiPPh2 in the presence of excess
PPh3. Inspired by the results of these groups, we undertook
our study of the reactions of CPCs with LiPPh2 under
different conditions; the results are presented in this paper.
II. Results and Discussion
II.1. Reaction of μ-Cl Dimeric CPCs with a Commercial
(Sigma-Aldrich Co.) Solution of LiPPh2 in THF. This part of
the study was conducted using a 0.5 M solution of LiPPh2 in
THF purchased from Sigma-Aldrich Co. We have found
that, in the absence of PPh3, reaction of 2 molar equiv of
LiPPh2 with dimeric CPC rac-1 did not result in the insertion
of the phosphide moiety into the Pd-C bond in the tem-
perature range from -78 to þ25 °C. Instead, the major
product of the reaction was complex rac-6, in which the
phosphide moiety was converted to a tertiary phosphine with
one 4-hydroxybutyl group (Scheme 3 and Table 1, entry 1).
The appearance of this alkyl fragment in the final product
was a result of the formal insertion of the PPh2 moiety in one
of the two C-O bonds of THF used in the reaction as a
solvent.
Scheme 4
In order to determine whether this transformation is
applicable to other cyclopalladated amines, two dimeric
complexes, 7 and (SC,SC)-8, were also subjected to the same
reaction conditions with the same solution of LiPPh2. In
both cases, the corresponding air- and moisture-stable
mononuclear complexes 9 and (SC)-10 were isolated after
purification of the crude mixtures using preparative column
chromatography in 85% and 78%, respectively (Table 1,
entries 2 and 3).
Two oxazoline-derived dimeric CPCs, (SC,SC)-11, with a
five-membered exo-palladacycle containing the (sp2)C-Pd
bond, and complex 13, with an aliphatic five-membered
palladacycle and the (sp3)C-Pd bond, were tested as well.
As expected, the PPh2(CH2)4OH adducts (SC)-12 and 13
were obtained in good yield (Table 1, entries 4 and 5).
Reaction of LiPPh2 with the dimer 15, containing a six-
membered endo-palladacycle, provided exo-16 in 61% yield.
When the concentration of the complex was increased by
3-fold, a 1:1 mixture of two complexes, exo-16 and endo-16,
in a total yield of 20% was obtained (Scheme 4). The obser-
ved intramolecular trans-cyclopalladation is especially inter-
esting considering that cyclopalladation of (SC)-2,4-dibenzyl-
2-oxazoline under different conditions results exclusively in the

6548 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
Figure 1. Molecular structure of complex 9.
formation of CPC (SC,SC)-15 with the endo-palladacycle.8
However, this case of intramolecular trans-cyclopalladation is
not unique; this type of transformation has been previously
reported for other CPCs under different conditions.9-13
The structures of complexes 6, 9, 10, 12, 14, endo-(SC)-16,
1
and exo-(SC)-16 were proven by IR and H, 13C{1H}, and
31P{1H} NMR spectroscopy data, as well as by COSY,
HMQC, and DEPT NMR spectra. Purity of all new com-
plexes was confirmed by satisfactory elemental analyses. The
31P NMR spectra of the complexes with the Ph2P(CH2)4OH
ligand exhibited a single signal within the 13.1-20.1 ppm
region. For comparison, the spectra of similar PPh3 deriva-
tives usually have signals around 30 ( 4 ppm.8,10 The
trans-{N,P} geometry of complexes 6, 9, 10, 12, 14, endo-
16, and exo-16 in solutions is supported by the characteristic
values of coupling constants in the 1H and 13C NMR spectra:
4
(i) JHP = 1.6-2.9 Hz found for the NMe2 group in the
spectra of 6, 9, and 10; (ii) 3JHP=4.6 Hz for the PdCH2 signal
of 14, and (iii) 3JCP 9.7-13.0 Hz for H(6) in the spectra of 6,
9, 10, 12, endo-16, and exo-16. The unambiguous proof of the
proposed structure for complex 9 was obtained by the X-ray
crystallographic study (Figure 1).
When we were about to submit a manuscript describing
these data, we learned that another 0.5 M solution of LiPPh2
in THF (reagent Aldrich-2) also purchased from Sigma-
Aldrich Co. did not react with dimeric CPC 7 to form
complex 9. A representative of Sigma-Aldrich Co. informed
us that “the material continues to meet our specifications and
is considered fine” and refused to provide any data on
preparation of the LiPPh2 samples. Interestingly enough,
(8) Mawo, R. Y.; Johnson, D. M.; Wood, J. L.; Smoliakova, I. P. J.
Organomet. Chem. 2008, 693, 33–45.
(9) Ryabov, A. D. Inorg. Chem. 1987, 26, 1252–1260.
(10) Mawo, R. Y.; Mustakim, S.; Young, V. G.Jr.; Hoffmann, M. R.;
Smoliakova, I. P. Organometallics 2007, 26, 1801–1810.
(11) Dunina, V. V.; Gorunova, O. N.; Grishin, Y. K.; Kuz’mina, L.
G.; Churakov, A. V.; Kuchin, A. V.; Howard, J. A. K. Russ. Chem. Bull.
2005, 2073–2082.
Figure 2. 31P{1H} NMR spectra the LiPPh2 solutions in THF
purchased from Sigma-Aldrich Co.: (a) Aldrich-1; (b) Aldrich-2
upon receiving; (c) Aldrich-2 after 12 months; and (d) Aldrich-2
after 12 month and dilution (see the text for details).
(12) Kind, L.; Klaus, A. J.; Rys, P.; Gramlich, V. Helv. Chim. Acta
1998, 81, 307–316.
(13) Benito, M.; Lopez, C.; Morvan, X. Polyhedron 1999, 18, 2583–
2595.
ꢀ

Article
Organometallics, Vol. 28, No. 22, 2009 6549
Chart 1. Reported Structures of Lithium Phosphides
Chart 2. Structures of the Products Formed in the Reactions of
CPC 7 with the LiPPh2 Reagents
Scheme 5
the chemical shift value of the major signal slightly moved to
δ -31.3 ppm (Figure 2d). These data indicate that LiPPh2 in
THF solutions may form different structures, and these
structures change upon both storing and diluting the re-
agents.
after one year, the LiPPh2 reagent kept in the same bottle at
rt did react with CPC 7 to give compound 9. To attempt
explaining these results, we synthesized LiPPh2 by several
methods and studied if preparation methods or other factors
affect the structure of the phosphide as well as the products
formed in reactions with dimeric CPCs.
Since the method used by Sigma-Aldrich Co. for prepara-
tion of LiPPh2 is proprietary knowledge, we synthesized this
reagent by three different general methods (Scheme 5) and
analyzed all samples by 31P{1H} NMR spectroscopy. The
31P{1H} NMR spectrum of the LiPPh2 reagent A1 prepared
by reacting PPh3 with Li (1:2.2 molar ratio) in THF at rt for
18 h contained two signals, PPh3 (δ -22.5 ppm) and LiPPh2
(δ -39.1 ppm) in a ca. 2:1 ratio (signal delay, τ, was 2 s).14-16
When this reaction mixture was treated with t-BuCl to
remove PhLi,17,18 the spectrum of the new LiPPh2 reagent
B1 exhibited four signals assigned to PPh3 (δ -20.4 ppm),
LiPPh2 (δ -30.4 and -31.4 ppm in a ratio of 2:1), and HPPh2
(δ -55.4 ppm). The LiPPh2 reagent A2 was prepared by
reacting PPh3 with 6 equiv of Li. The spectrum of reagent
A2 contained only one signal at δ -37.4 in the range -30 to
-40 ppm; however, a trace amount of PPh3 was detected as
well. After quenching PhLi in A2 with t-BuCl, the new
reagent B2 exhibited two 31P{1H} NMR signals in the range
-30 to -40 ppm, similar to reagent B1.
II.2. 31P{1H} NMR Spectra of the Lithium Diphenylphos-
phide Reagents Obtained by Different Methods. Two LiPPh2
solutions purchased from Sigma-Aldrich Co. have been
analyzed by 31P{1H} NMR spectroscopy. The first reagent,
Aldrich-1, which reacted with CPC 7 to form complex 9, had
a single sharp 31P{1H} NMR signal at δ -31.6 ppm, ω/2 =
8.5 Hz (Figure 2a). The second reagent, Aldrich-2, when
purchased, showed several peaks in its 31P{1H} NMR spec-
trum (Figure 2b) and reacted with the dimeric CPC 7 to give
several unidentified compounds with no traces of complex 9
(TLC and 31P NMR data). In one year, the LiPPh2 reagent
Aldrich-2 reacted with dimer 7 to yield complex 9 in 59%
yield (along with 14% of complex 17, see Part II.3 and Chart
2). The 31P{1H} NMR spectrum of this reagent changed
significantly and had three signals, δ -30.4, -31.2 ppm
(ω/2 = 47.1 Hz) and -31.6 (ω/2 = 6.3 Hz), in a ratio of ca.
1:38:37 (Figure 2c). After diluting the sample with THF-d8 to
a concentration of 0.35 M, the spectrum was quite different:
the weak signal at δ -30.4 ppm remained unchanged, but
two major signals became one, with the chemical shift, δ,
-31.4 ppm; the signal ratio became 1:60. Diluting the sample
again (0.27 M) gave a signal ratio of 1:62. When the 31P{1H}
NMR spectra of the same sample were taken again in 24 and
48 h, the ratio changed to 1:78 and 1:117, respectively, and
The LiPPh2 reagent C1 was obtained using method 2
(Scheme 5) by dropwise addition of ClPPh2 to Li (1:3 molar
(14) According to our NMR experiments, the ratio of signals as-
signed to PPh3 and LiPPh2 species does not reflect the exact PPh3:LiPPh2
ratio when the signal delay, τ, is less than 10 s due to a diffrence in
relaxation time for different P-containing species.
(15) Bianco, V. D.; Doronzo, S.; Chan, J.; Bennett, M. A. Inorg.
Synth. 1976, 16, 161–163.
(16) Aguiar, A. M.; Beisler, J.; Mills, A. J. Org. Chem. 1962, 27, 1001–
1005.
(17) Bianco, V. D.; Doronzo, S. Inorg. Synth. 1976, 16, 155–161.
(18) Luther, G. W. I.; Beyerle, G. Inorg. Synth. 1977, 17, 186–188.

6550 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
ratio) in THF.19-21 The 31P{1H} NMR spectrum of
the reaction mixture had only one signal, δ -35.3 ppm.
When a mixture of two LiPPh2 reagents, C1 and Aldrich-1
(δ -31.6 ppm), was prepared, its 31P{1H} NMR spectrum
contained two signals at δ -30.7 and -35.8 ppm, suggesting
different structures of these two samples of the LiPPh2
reagent. Interestingly, in two weeks, the 31P{1H} NMR
spectrum of the LiPPh2 reagent C1, which had one signal
after its preparation, contained two peaks of an approxi-
mately equal intensity at δ -31.7 and -35.8 ppm. We also
monitored the 31P{1H} NMR spectra of the LiPPh2 reagent
C1 while heating it. Immediately after preparing reagent C1,
a sample was taken and heated at 43 °C for 12 h. Its spectrum
contained two signals, δ -31.8 and -36.2 ppm, in ca. 1:18
ratio. While keeping the sample at 43 °C, the 31P{1H}
NMR spectra were measured every two hours, and the
signal ratio gradually changed to 1:6.8 after 10 h. After
storing the sample for an additional 12 h at rt, the signal
ratio changed very slightly, 1:6.5. Finally, after 2 h at 7 °C
and 6 h at 48-61 °C, the ratio became 1:3.3. Therefore, one
can suggest that reagent C1 changes its structure upon
heating.
Second, alkali metal phosphides in solutions can be mon-
omeric, dimeric, trimeric, or even more complex. According
to Reich and Dykstra, LiPPh2 is dimeric in ether and
monomeric in 3:2 THF-Et2O (-120 °C); the reagent was
obtained from HPPh2 and n-BuLi.25 Zschunke et al. re-
ported a tetrameric structure of LiPPh2 in THF, which was
also prepared by the same general method.26 The McFarlene
group analyzed low-temperature (-73 °C) 31P and 7Li NMR
spectra of the LiPPh2 solution in THF also obtained from
HPPh2 and n-BuLi.27 The authors concluded that the re-
agent had the symmetric dimeric structure (Chart 1). The
same group proposed that PhMePLi in Et2O solutions exists
as a mixture of a dimer and a trimer, while PhHPLi in Et2O
has a trimeric structure.27,28 Cryoscopic data for LiPPh2 in
1,4-dioxane indicated the presence of both dimeric and
monomeric structures in solution.29
Several crystallographic structures of lithium phosphides
with coordinating ligands, including THF and Et2O, have
been reported as well. A crystal of a tetrameric complex with
the unusual tricyclic Li4P4 core was obtained from LiPBut2 in
THF (Chart 1).30 The dimeric structure of LiP(CH(TMS)2)2
in the solid state was confirmed by its X-ray analysis.31
A
We also checked if the amount of Li used affected the
structure of the LiPPh2 reagent obtained by method 2.
Addition of ClPPh2 to excess Li (1:10 molar ratio) resulted
in the formation of reagent C2, which, like reagent C1,
exhibited one 31P{1H} NMR signal at δ -35.3. Therefore,
there is no need to use more than a 3-fold excess of the metal
for synthesis of LiPPh2, and a large excess of Li appears to
have no influence on the structure of the reagent obtained by
this general method. In the case of the ClPPh2 addition to 2
molar equiv of Li, the obtained reagent C3 had three 31P{1H}
NMR signals, -30.6 (broad), -31.2 (sharp), and -36.2
(broad), which points at a different structure of C3 compared
to other phosphides.
polymeric structure was found for the solvate complex of
LiPPh2 obtained from HPPh2 and n-BuLi in Et2O/THF
(Chart 1).32
Consideration of our 31P{1H} NMR data for all obtained
samples of LiPPh2 in THF indicates that the structure of
LiPPh2 in this solvent may depend on (i) preparation meth-
od, (ii) ratio of reagents, (iii) concentration, and (iv) length
of storage. It is reasonable to suggest that the signal at
δ -39.1 ppm observed only for the LiPPh2 reagent A1 is
likely to belong to the LiPPh2 LiPh dimer because (i) this
3
signal is not observed in the spectra of other LiPPh2 reagents
and (ii) it disappears after quenching this reagent with
t-BuCl. Because of the specific reactivity of reagent Aldrich-1,
giving one major 31P{1H} NMR signal at δ -31.6 ppm, one
can suggest that the LiPPh2 molecules in this reagent are
coordinated to THF molecules. Also, because the reactivity
of reagent Aldrich-2 changed after one year and became similar
to that observed for Aldrich-1, it is reasonable to suggest that
both reagents, in addition to being coordinated to THF
molecules, may have a polymeric structure similar to those
reported for solid samples by Bartlett et al.32 Other reagents
are expected to be of a dimeric, trimeric, or even more complex
structure of LiPPh2 with or without coordinated THF mole-
cules. Those more complex structures can be homoaggregates
or mixed aggregates. Species of the latter type contain other
lithium compounds, e.g., LiPh or LiCl. Broadening of many
31P{1H} NMR signals in the spectra of many reagents may
suggest the presence of equilibria between different forms of
LiPPh2.
The LiPPh2 reagent D was obtained using method 3
(Scheme 5) by adding n-BuLi to a solution of HPPh2 in
THF at -78 °C (4% excess of n-BuLi).22,23 The obtained
reagent had one rather broad 31P{1H} NMR signal of
LiPPh2 at δ -38.0 ppm.
There is some literature information about possible struc-
tures of alkali metal phosphides. First, it has been reported
that solutions of these reagents can be paramagnetic or
diamagnetic.24 For example, reaction of PPh3 with excess
K in THF produces a red solution of the radical anion,
KPPh2•-, which has a characteristic ESP spectrum showing a
triplet with a hyperfine constant of ap = 8 G.24 The same
reaction in a dilute solution or without excess metal produces
a yellow solution with no paramagnetic species.24 According
to Grim and Molenda, paramagnetic species present in metal
phosphide solutions have no effect on the signal broadening
in 31P{1H} NMR spectra.24 The same authors reported that
KPPh2•- is fairly unstable, while paramagnetic solutions of
LiPPh2•- are stable at least for two weeks at rt under N2.
(25) Reich, H. J.; Dykstra, R. R. Organometallics 1994, 13, 4578–
4585.
(26) Zschunke, A.; Bauer, E.; Schmidt, H.; Issleib, K. Z. Anorg.
Chem. 1982, 115-119, 115–119.
(27) Colquhoun, I. J.; McFarlane, H. C. E.; McFarlane, W. Phos-
phorus Sulfur 1983, 18, 61–64.
(28) Colquhoun, I. J.; McFarlane, H. C. E.; McFarlane, W. J. Chem.
(19) Tamborski, C.; Ford, F. E.; Lehn, W. L.; Moore, G. J.; Soloski,
E. J. J. Org. Chem. 1962, 27, 619–621.
(20) Clark, P. W. Org. Prep. Proc. Int. 1979, 11, 103–106.
(21) Singh, G.; Singh, A. K.; Drake, J. E.; Hursthouse, M. B.; Light,
M. E. Polyhedron 2006, 25, 2915–2919.
Soc., Chem. Commun. 1982, 220–221.
(29) Issleib, K.; Tzschach, A. Chem. Ber. 1959, 92, 1118–1126.
(30) Jones, R. A.; Stuart, A. L.; Wright, T. C. J. Am. Chem. Soc. 1983,
105, 7459–7460.
(22) Fries, G.; Wolf, J.; Stalke, D.; Werner, H. Angew. Chem., Int. Ed.
2000, 39, 564–566.
(23) Mansfield, N. E.; Coles, M. P.; Hitchcock, P. B. Dalton Trans.
2005, 2833–2841.
(31) Hitchcock, P. B.; Lappert, M. F.; Power, P. P.; Smith, S. J. J.
Chem. Soc., Chem. Commun. 1984, 1669–1700.
(32) Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Inorg. Chem.
1986, 25, 1243–1247.
(24) Grim, S. O.; Molenda, R. P. Phosphorus 1974, 4, 189–193.

Article
II. 3. Reactions of CPC 7 with Different LiPPh2 Reagents.
Organometallics, Vol. 28, No. 22, 2009 6551
number of Pd(II)- and Pt(II)-catalyzed reactions leading to
the formation of a P-C bond.37,38 The next step of the
reaction is likely to be the insertion of the Pd atom into the
C-O bond of THF, resulting in the formation of the Pd(IV)
intermediate, presumably G. Somewhat related Pd(IV) com-
plexes with a palladacycle have been either synthesized or
proposed as intermediates in catalytic processes.39 In a
reductive elimination step, complex G is expected to yield
compound H. It is noteworthy that the cleavage of C-N and
C-S bonds in the presence of Pd complexes has been reported;
however, those reactions presumably take place through
the oxidative addition of organic substrates to Pd(0).40-42
Complex 17. This complex was isolated from most of the
reactions using a 1:2 molar ratio of dimeric CPC 7 and
lithium phosphide (a 1:1 Pd:PPh2 ratio). The best yield of
60% was obtained in the reaction of compound 7 with
phosphide D at room temperature (Table 2, entry 23),
although the transformation proceeded readily even at
-78 °C (entry 22). Its formation can be attributed to
exchange of one Cl ion in 7 for the PPh2 moiety. It is
noteworthy that μ-halogen-μ-PPh2 Pd(II) complexes are
very rare.43-45 Isolation and X-ray data of the R-tert-bu-
tyl-substituted derivative Pd2(η2-N∩C)2(μ-PPh2)(μ-Cl), the
only known cyclopalladated complex of this type, have been
reported by Dunina et al.7
The dimeric cyclopalladated complex 7 was used as a model
compound to study reactions with the LiPPh2 reagents
obtained by different methods. In all reactions, unless spe-
cified, addition order, solvent, ratio of reagents, concentra-
tion of complex 7 in the reaction mixture, molarity of the
LiPPh2 solution, temperature, and reaction time were the
same. Depending on the LiPPh2 reagent and conditions
used, one or more of six compounds 9 and 17-21 were
isolated in each reaction (Chart 2 and Table 2).
Complex 9. One of the most unexpected results of this
study was the isolation of complex 9 in good to excellent yield
in the reactions of CPC 7 with Aldrich-1 and aged Aldrich-2
(see Part II.1 and entries 1-8 of Table 2). Insignificant
amounts of 9 were also formed in the reactions of phosphides
B2 and C2 (entries 15 and 17). It is noteworthy that reagent
A2 after storing at rt for 4.5 months reacted with CPC 7 to
produce 14% of complex 9 and 34% of 17, while freshly
prepared phosphide A2 provided only the latter product
(entries 12 and 13). Reagent C3 practically did not change
its reactivity after 2.5 months in contrast to reagent D, which
lost its reactivity after six months and reacted with dimer 7 to
give only 3% of 17.
The observed cleavage of a C-O bond in THF by LiPPh2
is not unique. As early as 1962, Garner and Tedeschi
reported that refluxing a 2:1 mixture of Li and Ph2PCl in
THF for 24 h furnished 44% of Ph2P(CH2)4OH.33 In a year,
Mallion and Mann described the preparation of Ph2P-
(CH2)4OH in 22% yield by heating a 1:1 mixture of Ph2PH
and BuLi in THF for 7 h.34 Similar results have also been
disclosed by other groups, although heating time and yields
of Ph2P(CH2)4OH vary.35,36
The LiPPh2 solutions in THF purchased from Sigma-
Aldrich Co. were checked for the presence of Ph2P-
(CH2)4OLi before reacting with a CPC. According to the
31P{1H} NMR data for the original LiPPh2 solutions and the
1H NMR data for the crude product obtained after quench-
ing these solutions with H2O, the reagents did not have even
traces of Ph2P(CH2)4OLi. Considering this information and
the fact that the formation of complex 9 took place under
much milder conditions than those reported for the forma-
tion of Ph2P(CH2)4OH from THF and LiPPh2, one can
conclude that cyclopalladated complexes act as promoters
in this transformation. To the best of our knowledge, the use
of any catalysts or promoters in the reaction of THF with
LiPPh2 has never been reported.
The 1H, 13C{1H}, and 31P{1H} NMR spectra of this
complex are consistent with the proposed structure. The
1H NMR spectrum features four well-separated signals of
the C6H4 fragment of the palladacycle. Integration of all
aromatic signals in the spectrum suggests the presence of two
C6H4Pd fragments per one PPh2 moiety. The existence of the
Pd-N bond in 17 is supported by the appearance of the
NMe2 signal in the 13C{1H} NMR spectrum as a doublet
with 3JCP=1.6 Hz. One set of signals in both 1H and 13C{1H}
NMR spectra suggests the syn configuration of the dinuclear
complex in CDCl3 solutions. The signals of the C6H4 group
have chemical shift values between 6.35 and 6.82 ppm due to
magnetic anisotropy of the PPh2 fragment. This suggests the
cis position of the PPh2 group with respect to both Pd-C6H4
moieties and, therefore, supports the syn configuration of
the dimer. The only known μ-Cl-μ-PPh2 cyclopalladated
complex has the syn configuration in the solid state.7 For
(37) (a) Wicht, D. K.; Kourkine, I. V.; Lew, B. M.; Nthenge, J. M.;
Glueck, D. S. J. Am. Chem. Soc. 1997, 119, 5039–5040. (b) Schwan, A. L.
Chem. Soc. Rev. 2004, 33, 218–224.
~
It is reasonable to suggest that molecules of LiPPh2, at
least in reagents Aldrich-1 and aged Aldrich-2, are coordi-
nated to THF molecules. A strong coordination of Li with
THF is supported by obtaining complex 9 in 65% yield in the
reaction of a solution of CPC 7 in C6H6 with the LiPPh2
sample prepared by evaporating THF from Aldrich-2 and
drying the remaining solid in vacuum, 1 mbar, at 40 °C for
1.5 h (Table 2, entry 8). We propose that the reaction begins
(38) Baranano, D.; Mann, G.; Hartwig, J. F. Curr. Org. Chem. 1997,
1, 287–305.
(39) (a) Canty, A. J.; Jin, H.; Roberts, A. S.; Skelton, B. W.; White, A.
H. Organometallics 1996, 15, 5713–5722. (b) Canty, A. J.; Rodemann, T.;
Skelton, B. W.; White, A. H. Organometallics 2006, 25, 3996–4001. (c)
Dick, A. R.; Kampf, J. W.; Sanford, M. S. J. Am. Chem. Soc. 2005, 127,
12790–12791. (d) Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007,
129, 15142–15143. (e) Dick, A. R.; Sanford, M. S. Tetrahedron 2006, 62,
2439–2463. (f) Deprez, N. R.; Sanford, M. S. Inorg. Chem. 2007, 46, 1924–
1935.
(40) Kim, Y.-J.; Lee, S.-C.; Cho, M. H.; Lee, S.-W. J. Organomet.
Chem. 1999, 588, 268–277.
(41) Ozerov, O. V.; Guo, C.; Fan, L.; Foxman, B. M. Organometallics
2004, 23, 5573–5580.
with the formation of the mononuclear CPC F with PPh2Li
3
(THF)n (Scheme 6; for simplicity, n = 1). It is worth men-
tioning that related phosphido complexes of the platinum
group metals are considered to be active intermediates in a
ꢀ
ꢀ
ꢁ
(42) Hernandez, M.; Miralrio, G.; Arevalo, A.; Bernes, S.; Garcꢀıa, J. J.;
ꢀ
Lopez, C.; Maitlis, P. M.; del Rio, F. Organometallics 2001, 20, 4061–4071.
ꢀ
~
(43) Alonso, E.; Fornies, J.; Fortuno, C.; Martꢀın, A.; Rosair, G. M.;
Welch, A. J. Inorg. Chem. 1997, 36, 4426–4431.
(44) Cartwright, S. J.; Dixon, K. R.; Rattray, A. D. Inorg. Chem.
1980, 19, 1120–1124.
(33) Garner, A. Y.; Tedeschi, A. A. J. Am. Chem. Soc. 1962, 4734–
4737.
(34) Mallion, K. B.; Mann, F. G. Chem. Ind. 1963, 654.
(35) Purdum, W. R.; Berlin, K. D. J. Org. Chem. 1975, 40, 2801–2806.
(36) Ushakov, N. V.; Vdovin, V. M.; Pozdnyakova, M. V.; Pritula, N.
A. Izv. Akad. Nauk SSSR, Ser. Khim. 1983, 2125–2129.
ꢀ
~
(45) Chaouche, N.; Fornies, J.; Fortuno, C.; Kribii, A.; Martın, A.;
´
Karipidis, P.; Tsipis, A. C.; Tsipis, C. A. Organometallics 2004, 23, 1797–
1810.

6552 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
Table 2. Reactions of Dimeric CPC 7 with the LiPPh2 Reagentsa
related dinuclear complex Pd2(μ-PPh2)(μ-Cl)(C6F5)2Py2 ap-
pear at 21.5 ppm [in CDCl3 relative to P(OEt)3], 34.6 ppm
(in CDCl3 relative to H3PO4),7 and 23.8 ppm (in acetone-d6
relative to H3PO4).43
Pd:
PPh2
temp.,
°C
time,
h product yield, %
entry
LiPPh2
Aldrich-1
Aldrich-1
Aldrich-1
ratiob
Complex 18. This previously reported complex46 was one
of the products obtained in the reactions of CPC 7 with the
LiPPh2 reagents A1 and B1,2 synthesized from PPh3 and Li
(Table 2, entries 9-11 and 15). It is assumed that complex 18
is formed as a result of the reaction of dimeric CPC 7 with
PPh3, which was spectroscopically detected in these solutions
of lithium phosphide.
1
2
3
1:1
1:1
1:1
rt
rt
18
3
0.1
1
9
9
9
85
53
66
0, then
0 f rt
4
Aldrich-1c
1:1
-78, then 0.5
9
28
-78 f rt
2.5
0.4
5
6
Aldrich-1c
Aldrich-2
1:1
1:1
rt
rt
9
9
58
59
18
Complex 19. This compound was isolated in 12% yield in
the reaction of dimeric CPC 7 with 2 molar equiv of the
LiPPh2 reagent C2 (Table 2, entry 17). Traces of complex 19
were also detected among the products formed in reactions
of the LiPPh2 reagents C1 and C3 (entries 16 and 18).
Interestingly, this complex was also isolated in 25% yield
after storing a solution of complex 17 in CH2Cl2 at rt for two
months; Pd(0) was formed as well.
(after one year)
Aldrich-2
(after one year)
Aldrich-2d
(after one year)
17
9
20
9
14
85
traces
65
22
traces
81
traces
58
17
52
12
62
34
14
35
32
9
4
23
traces
28
12
traces
55
5
traces
49
28
81
17
40
60
27
35
7
8
1:2.25 rt
4
1:1
rt
18
17
20
18
17
18
17
18
17
17
17
9
20
17
18
9
17
19
17
19
9
17
21
19
20
20
20
17
17
17
20
20
9
A1
A1
B1
1:1
1:1
1:1
rt
rt
rt
18
5
10
11
Surprisingly, little is known about complexes of Pd(II)
with PPh2PPh2 or its oxide;47-50 none of them contain a
palladacycle. The structure of compound 19 as a mono-
nuclear cyclopalladated complex with PPh2P(O)Ph2 as an
auxiliary ligand is proposed on the basis of the 1H, 13C{1H},
31P{1H}, and 2D NMR spectra. In the 1H NMR spectrum of
19, there are four Ph groups per one cyclopalladated C6H4
fragment. In contrast to the 1H NMR spectra of 17 and 18,
signals of the PPh hydrogens of complex 19 are not well
resolved, which may suggest nonequivalence of four Ph
rings. The chemical shift values, 6.09-6.73 ppm, of four
well-resolved signals of the PdC6H4 moiety and the appear-
ance of the H(6) signal at δ 6.09 ppm as a dd (JHH = 7.5,
JHP = 4.2) suggests that the PPh fragment is in close
proximity to the cyclopalladated aromatic ring and cis to
the Pd-C bond. The 31P{1H} NMR spectrum of 19 exhibited
two broadened nonsymmetrical doublets, δ 23.5 and 102.6 ppm,
with the large coupling constant JPP ≈ 203 Hz, suggesting two
nonequivalent PPh2 fragments. The value of this constant is
6
12
13
A2
A2
1:1
1:1
rt
rt
18
18
after 4.5 months
A2
B2
14
15
1:2.25 rt
1:1
18
18
rt
16
17
C1
C2
1:1
1:1
rt
rt
4
7
18
C3
1:1
rt
3
19
20
21
C3
1:2.25 rt
1:2.25 rt
18
18
18
C3e
C3d
1:1
rt
22
23
24
25
D
D
1:1
1:1
-78
rt
4
4
18
18
1
such that, in general, it can be attributed to either JPP or
D
1:2.25 rt
1:2.25 rt
De
47,51,52
trans-2JPP
.
For comparison, the coupling constant
1JPP for the free ligand PPh2P(O)PPh2 is 224 Hz.48 For the
recently reported trinuclear cluster Ar2Pt(μ-PPh2)(μ-Br)Pd(μ-
PPh2PPh2)PtAr2 (Ar=C6F5), the coupling constant 1JPP was
191 Hz, whereas 2JPP for the trans-Ph2P-Pd-PPh2PPh2 frag-
ment was larger, 296 Hz.47
a Unless otherwise noted, a 0.5 M solution of LiPPh2 in THF was
added dropwise to a solution of CPC 7 in THF (the total volume of THF
was 1.0 mL per 0.017-0.020 mmol of CPC). b Here and later, Pd:PPh2
ratios are given instead of molar ratios. c Reverse addition order. d Prior
to the reaction, a THF solution of LiPPh2 was evaporated and the
obtained residue was kept under vacuum (<1 mbar) at 40 °C for 1.5 h.
The reaction of CPC 7 with the obtained solid sample of LiPPh2 was
done in toluene (entry 21) or benzene (entry 8). e The total volume of
THF in the reaction mixture was 10 times higher than in other reactions.
The 31P NMR chemical shift of 23.5 ppm observed for 19 is
ordinary for the P atoms in tertiary phosphines bonded to
Pd(II),53 whereas the value of 102.6 ppm is rather unusual.
We suggest that this signal belongs to the POPh2 fragment of
the PPh2P(O)Ph2 ligand. This is supported by the presence of
an intense signal at ν 1261 cm-1 in the IR spectrum of
Scheme 6
(46) (a) Crociani, B.; Boschi, T.; Pietropaolo, R.; Belluco, U. J. Chem.
Soc. A 1970, 531–535. (b) Ryabov, A. D.; Yatsimirskii, A. K.; Berezin, I. V.
Izv. Akad. Nauk SSSR, Ser. Khim. 1981, 1378–1383.
~
ꢀ~
(47) Fornꢀıes, J.; Fortuno, C.; Ibanez, S.; Martꢀın, A. Inorg. Chem.
2008, 47, 5978–5987.
~
ꢀ~
(48) Fornꢀıes, J.; Fortuno, C.; Ibanez, S.; Martꢀın, A.; Tsipis, A. C.;
Tsipis, C. A. Angew. Chem., Int. Ed. 2005, 44, 2407–2410.
(49) Shmidt, F. K.; Belykh, L. B.; Goremyka, T. V. Russ. J. Coord.
Chem. 2002, 28, 92–103.
(50) Issleib, K.; Schwager, G. Z. Anorg. Chem. 1961, 310, 43–49.
(51) Fluck, E.; Binder, H. Inorg. Nucl. Chem. Lett. 1967, 3, 307–313.
(52) Ogilvie, F. B.; Jenkins, J. M.; Vercade, J. G. J. Am. Chem. Soc.
1970, 92, 1916–1923.
comparison, the 31P NMR signals of 17, its R-tert-butyl-
substituted analogue Pd2(η2-N∩C)2(μ-PPh2)(μ-Cl), and the
(53) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition
Metal Phosphine Complexes; Springer-Verlag: Berlin, 1979.

Article
Organometallics, Vol. 28, No. 22, 2009 6553
complex 19 in a benzene solution, which can be assigned to
the PdO group.54
Scheme 7
No signal of PPh2PPh2 was detected in the 31P NMR
spectra of the LiPPh2 reagents used in this study. Also,
attempts to generate complex 19 by reacting dimer 7 with
PPh2PPh2 followed by oxidation using different conditions
and varied reagent ratios failed. According to 31P NMR
spectra of the reaction mixtures, numerous species are
formed in these reactions; moreover, it appears that tetra-
phenyldiphosphine undergoes a P-P bond cleavage. There-
fore, direct reaction of CPC 7 with PPh2PPh2 followed by
oxidation can be ruled out as a possible route for the
formation of 19.
Scheme 8
Formation of 19 in the reaction of dimer 7 with the LiPPh2
reagent C2 in THF (Table 2, entry 17) can be explained by the
attack of LiPPh2 on the Pd atom of 17 (the major product of
this reaction) followed by elimination of LiCl, producing
{(η2-N∩C)Pd(κ1-PPh2)2}-. This intermediate can undergo
reductive elimination of PPh2PPh2 with the formation of
Pd(0). A similar intermediate, cis-{(PPh3)2Pd(κ1-PPh2)2},
was postulated by Stille in the Pd(II)-catalyzed coupling of
ArHal with Me3SnPPh2 and Me3SiPPh2,38,55 and a related
complex, {Pd(PPh2)2}n, was isolated by Abel.56 Formation
of the dimeric di-μ-PPh2 derivative {(η2-N∩C)Pd(μ-PPh2)}2
as an intermediate in the reaction of 17 with LiPPh2 cannot
be ruled out either. Although cyclopalladated dinuclear
diphosphido-bridged complexes are unknown, a crystal
structure of the Pt complex {Pt(bzq)(μ-PPh2)}2 was recently
reported.57 The Pd(II)-bonded PPh2PPh2 along with Pd(0)
can be released from this intermediate as a result of reductive
elimination. According to the 31P{1H} NMR data (CDCl3,
τ = 8 s), the reaction mixture obtained by reacting complex
17 with 3.5 molar equiv of the LiPPh2 reagent C3 in C6H6 at
rt for 18 h contained a number of compounds including
unreacted complex 17 (ca. 24%), compound 9 (ca. 16%),
and, presumably, free PPh2P(O)Ph2 (ca. 8%). The last
compound provided two doublets, δ 21.4 and -36.1 ppm,
with JPP = 228 Hz (cf. δ 32.7 and -24.9, JPP = 220 Hz, in
C6D6 for a sample of PPh2P(O)Ph2 obtained using a pub-
lished procedure58). Unfortunately, attempts to isolate
PPh2P(O)Ph2 were unsuccessful.
The fact that decomposition of complex 17 in CH2Cl2
provided 19 and Pd(0) suggests that, under these conditions,
complex 17 can be transformed to either the μ-di-PPh2
analogue or {(η2-N∩C)Pd(κ1-PPh2)2}-. These intermediates
can undergo reductive elimination with the formation of
PPh2PPh2 (cf. Scheme 8).
Aminophosphine 20. This compound is perhaps the most
desirable product of the reaction of CPC 7 with LiPPh2. As
mentioned in the Introduction, there have been three reports
of the reactions between CPCs and LiPR2, in which either
aminophosphines were synthesized3,4 or their Pd(0) com-
plexes were detected spectroscopically.7 In these studies,
reactions were carried out in the presence of PPh3; this
means that the corresponding mononuclear cyclopalladated
complexes with PPh3 as an auxiliary ligand were actual
reactants. A mechanism of the aminophosphine formation
in the reaction of dimeric CPCs with LiPPhMe in the
presence of 2 equiv of PPh2Me in THF was proposed by
Troitskaya et al.4 The authors suggested the formation of
intermediate I, which is transformed to aminophosphine J as
a result of reductive elimination (Scheme 7).4,59
All reactions of CPCs with lithium phosphide reported in
this study were carried out without addition of PPh3,
although reagents A1 and B1 contained a significant amount
of triphenylphosphine (see Section II.2). Phosphides A2 and
B1 contained only trace amounts of PPh3 (see Section II.2).
Reagents C1-3 and D were obtained from ClPPh2 and
HPPh2, respectively, and could not contain PPh3.
Aminophosphine 20 was isolated in the reactions using a
1:4.5 molar ratio of dimeric CPC 7 and the LiPPh2 reagents
A2, C3, and D (1:2.25 Pd:PPh2 ratio); all these reactions were
performed in THF (Table 2, entries 14, 19, 20, 24, and 25).
Formation of Pd(0) black was observed in these reactions. It
is notable that (i) the lithium phosphide reagents purchased
from Sigma-Aldrich Co. provided, at best, only traces of the
aminophosphine (entry 7) under the same conditions and
(ii) reagents A2, C3, and D did not contain PPh3.
When a 1:1Pd:PPh2 ratio was used inTHF, no aminophos-
phine was formed; instead, μ-Cl-μ-PPh2 complex 17 was
furnished (entries 18, 22, and 23). Remarkably, when the
reaction of dimeric CPC 7 and 2 equiv of reagent C3 (a 1:1
Pd:PPh2 ratio) was performed in toluene, aminophosphine
20 was obtained in 81% (solvent THF was removed under
vacuum prior to the reaction; see entry 21). It is noteworthy
that reagent Aldrich-2 used instead of C3 in benzene with the
same reagent ratio provided only traces of aminophosphine
20 (entry 8). Therefore, the reaction direction depends on the
preparation method of lithium phosphide, reagent ratio, and
the nature of the solvent used.
It appears that mechanisms of the reactions between CPC
7 and reagent C3 in THF and toluene are different. In the
reactions occurring in THF, a 1:2 Pd:PPh2 ratio was essential
(54) Hesse, M.; Meier, H.; Zeeh, B. Spectroscopic Methods in Organic
Chemistry; Georg Thieme Verlag: Stuttgart, 1997; p 54.
(55) Tunney, S. E.; Stille, J. K. J. Org. Chem. 1987, 52, 748–753.
(56) Abel, E. W.; McLean, R. A. N.; Sabherwal, I. H. J. Chem. Soc. A
1968, 2371–2373.
(59) In the original paper,4 the authors proposed the trans-(C-,
PhMeP-) geometry of intermediate I. According to the transphobia
concept, the cis-(C-,PhMeP-) geometry should be expected. For the
concept of transphobia, see: (a) Vicente, J.; Arcas, A.; Bautista, D.;
Jones, P. G. Organometallics 1997, 16, 2127–2138. (b) Vicente, J.; Arcas,
ꢀ
(57) (a) Dı
´
ez, A.; Fornies, J.; Garcı
´
a, A.; Lalinde, E.; Moreno, M. T.
Inorg. Chem. 2005, 44, 2443–2453. (b) Mastrorilli, P. Eur. J. Inorg. Chem.
2008, 4835–4850.
(58) McKechnie, J.; Payne, D. S.; Sim, W. J. Chem. Soc. 1965, 3500–
ꢀ
ꢀ
ꢀ
ꢀ
A.; Galvez-Lopez, M.-D.; Julia-Hernandez, F.; Bautista, D.; Jones, P.
3501.
G. Organometallics 2008, 27, 1582-1590, and references therein.

6554 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
Scheme 9
The structure and composition of aminophosphine 20 and
1
its oxide 21 were proven by H, 13C, 31P, and 2D NMR
spectra, as well as HRMS data.
Conclusions
Cyclopalladated complexes react with commercial LiPPh2
reagents and lithium phosphide solutions synthesized in our
lab to furnish different types of products. The difference in
the 31P NMR spectra of the LiPPh2 reagents obtained from
Sigma-Aldrich Co. and those synthesized in our lab by
different methods suggests their different structures in
THF. Reaction of the dimeric CPC 7 with LiPPh2 is highly
sensitive to reaction conditions, especially to the reagent
ratio, addition order, solvent, and source of lithium phos-
phide. The major pathway of the reactions in THF between
dinuclear CPCs and the lithium phosphide purchased from
Sigma-Aldrich Co. is the formation of the corresponding
mononuclear complexes with Ph2P(CH2)4OH as an auxiliary
ligand. Reactions of dimeric CPC 7 in THF with the lithium
phosphide reagents synthesized in our lab from PPh3,
ClPPh2, or HPPh2 lead to the formation of either μ-Cl-μ-
PPh2 complex 17 using 1 equiv of LiPPh2 per palladacycle or
aminophosphine 20 using 2.25 equiv of the phosphide.
Aminophosphine 20 can also be obtained in toluene using
1 equiv of LiPPh2 per palladacycle. Preparation of amino-
phosphine 20 in either THF or toluene does not require the
presence of PPh3 and cannot be accomplished with the
LiPPh2 reagents in THF purchased from Sigma-Aldrich
Co. The mechanisms of the aminophosphine formation in
THF and toluene appear to be different.
for the aminophosphine formation (entries 19 and 20), while
using a 1:1 ratio in the same solvent (entry 18), μ-Cl-μ-PPh2
complex 17 was isolated as the major compound. This may
suggest that complex 17 is an intermediate of the aminophos-
phine formation in THF. To confirm this hypothesis, two
identical reactions of μ-Cl-μ-PPh2 complex 17 with 1 equiv of
LiPPh2 reagent C3 were carried out (THF, rt, 18 h). The 31
P
NMR spectrum of the first reaction mixture contained
signals of aminophosphine 20 and PPh2P(O)Ph2 in ca. 2:1
ratio. The second reaction was used to isolate products
formed. Aminophosphine 20 was obtained from this reac-
tion in 38% yield, backing up the idea that compound 17 is
an intermediate of the aminophosphine formation in THF.
Because Pd(0) was formed in all reactions in THF leading to
compound 20, the last step of the aminophosphine formation
in this solvent is expected to be reductive elimination. On the
basis of these considerations and the fact that 2 equiv of
LiPPh2 are necessary for each palladacycle, we propose that
the reaction begins with the formation of 17 followed by the
attack of LiPPh2 on the Pd(II) atom and LiCl elimination to
afford the intermediate {(η2-N∩C)Pd(κ1-PPh2)2}- (K, Scheme 8).
The reductive elimination step brings the reaction to its end,
producing Pd(0) and aminophosphine 20.
The reaction of CPC 7 with the LiPPh2 reagent C3 in
toluene furnishing aminophosphine 20 required only 1 equiv
of the PPh2 ion per palladacycle. This difference must be
related to the noncoordinating nature of this solvent and, as
one of the consequences, to a change in structure and
reactivity of LiPPh2 reagents in THF and toluene. The μ-Cl-
μ-PPh2 complex 17 is an unlikely candidate for an inter-
mediate in the reactions in toluene or benzene leading to
compound 20, because no aminophosphine is formed in the
reaction of complex 17 with 3.5 molar equiv of the LiPPh2
reagent C3 in benzene. A possible mechanism of the reaction
in a noncoordinating solvent includes the formation of the
intermediate {(η2-N∩C)Pd(μ-PPh2)}2 (N, Scheme 9) directly
from {(η2-N∩C)Pd(μ-Cl)}2 through a simple anion metathe-
sis well known for dinuclear cyclopalladated complexes.1
Formation of different intermediates in toluene and THF
(Scheme 8) can be explained by a different structure and,
therefore, reactivity of the phosphide ion in a noncoordinat-
ing solvent and THF.60 One can also hypothesize that in a
noncoordinating solvent such as toluene the neutral dimer
{(η2-N∩C)Pd(μ-PPh2)}2 may be more stable than the anionic
complex {(η2-N∩C)Pd(κ1-PPh2)2}-. For example, Pd(PPh2)2
is apparently tetrameric in benzene.56 Reductive elimination
as the final step is to afford the aminophosphine, Pd(0), and a
new portion of N, which is to undergo reductive elimination
again.
Currently, we are studying stoichiometric and catalytic
reactions of mono- and dinuclear cyclopalladated complexes
with other phosphides under different conditions in order to
shed more light on possible mechanisms of these transforma-
tions and synthesize a set of structurally different P*- and
C*P*-chiral aminophosphines, potential catalysts in asym-
metric transformations.
Experimental Section
General Methods and Materials. All reactions of LiPPh2 were
carried out under a positive pressure of argon using the Schlenk
technique. Purifications by column chromatography were car-
ried out using Natland silica gel 60 (230 mesh). Preparative thin-
layer chromatography (TLC) was carried out using 200 ꢀ
250 mm glass plates with an unfixed layer of Natland or Merck
silica gel 60 (230 mesh). Analytical TLC was performed on
Whatman silica gel 60 (F254) 250 μm precoated plates. Com-
pounds were visualized on TLC plates using UV light (254 nm)
and/or iodine stain. Routine 1H (500 MHz), 13C{1H} (126 MHz),
and 31P{1H} (202 MHz) as well as DEPT, COSY, and HSQC
spectra were recorded on a Bruker AVANCE 500 NMR spectro-
meter. Chemical shifts are reported in ppm with SiMe4 as an
internal standard (1H and 13C) or P(OEt)3 as an external standard
(31P). Spin-spin coupling constants, J, are given in Hz. Spectra of
the products obtained in reactions of the LiPPh2 reagents with
CPCs were recorded in CDCl3 unless otherwise stated. Melting
points were measured on a Laboratory Devices Mel-Temp appa-
ratus and are uncorrected. Optical rotations were measured at
room temperature on a Rudolph Autopol III automatic polari-
meter. Elemental analyses were carried out by Atlantic Microlabs
Inc., Norcross, GA. Benzene and toluene were dried by refluxing
over K/benzophenone ketyl, distilled under Ar, and kept over
potassium. Tetrahydrofuran and THF-d8 were distilled over
K/benzophenone ketyl under Ar immediately before starting a
reaction. Acetone was purified by distillation over KMnO4. Other
(60) For the conversion of mononuclear terminal phosphido com-
plexes to the corresponding dinuclear bridged phosphido derivatives of
Pt(II), see: (a) Scriban, C.; Wicht, D. K.; Glueck, D. S.; Zakharov, L. N.;
Golen, J. A.; Rheingold, A. L. Organometallics 2006, 25, 3370–3378. (b)
Maassarani, F.; Davidson, M. F.; Wehman-Ooyevaar, I. C. M.; Grove, D. M.;
van Koten, M. A.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. Inorg. Chim.
Acta 1995, 235, 327–338.

Article
Organometallics, Vol. 28, No. 22, 2009 6555
solvents were distilled over CaH2. ClPPh2 and HPPh2 were
distilled invacuum prior to use. tert-BuCl was distilled over CaCl2.
Other chemicals were used as purchased without further purifica-
tion. Lithium used was obtained from Acros, granules 99.9 þ%,
unless stated otherwise. Two 0.5 M solutions of LiPPh2 used this
study, Aldrich-1 and Aldrich-2, were purchased from Sigma-
Aldrich Co., lot # 00111CD and 17309MH, respectively.
signal delays were applied, signal ratios for the same sample
varied due to changes in relaxation time for different P-contain-
ing species.)
Preparation of Dimeric CPCs. Complex rac-di(μ-chloro)bis-
[1-(N,N-dimethylamino)methylferrocenyl-C,N]dipalladium(II)
(rac-1) was synthesized in 84% following a published proce-
dure.61 Compounds di(μ-chloro)bis[2-(N,N-dimethylamino)-
methyl]phenyl-C,N]dipalladium(II) (7) and (SC,SC)-di(μ-chloro)-
bis{2-[1-(N,N-dimethylamino)ethyl]phenyl-C,N}dipalladium(II)
((SC,SC)-8) were obtained from the corresponding benzylamines
in 95% and 98% yield, respectively, using a reported procedure.62
Complex (SC,SC)-di(μ-chloro)bis[2-(2-methyl-2-oxazolin-4-yl)-
phenyl-C,N]dipalladium(II) ((SC,SC)-11) was synthesized in 92%
yield by cyclopalladation of (S)-2-methyl-4-phenyl-2-oxazoline
with Pd(OAc)2 in AcOH followed by reaction with LiCl.63 Com-
plex di(μ-chloro)bis[2-methyl-2-(4,4-dimethyloxazolin-2-yl)pro-
pyl-C,N]dipalladium(II)64 (13) was synthesized in 76% yield by
cyclopalladation of 2-tert-butyl-4,4-dimethyl-2-oxazoline with
Pd(OAc)2 in AcOH followed by treatment with LiCl using a
procedure described for cyclopalladation of other oxazolines.10
Complex (SC)-di(μ-chloro)bis{[2-(4-benzyl-2-oxazolin-2-yl)methyl]-
phenyl-C,N}dipalladium(II) ((SC)-15) was obtained in 78% yield
following a published procedure.8
General Procedure for Preparation of Complexes 6, 9, (SC)-10,
(SC)-12, 14, and exo-(SC)-16. In the atmosphere of Ar, a 0.5 M
solution of LiPPh2 in THF (Aldrich-1, δ -31.6 ppm, 0.39 mL,
0.20 mmol) was introduced into a 15 mL Schlenk flask using
a syringe. Then a solution of a dimeric CPC (0.096 mmol) in
5.3 mL of absolute THF was added dropwise during 5 min. The
yellow solution turned red-orange after stirring for 8 h at rt.
After removal of THF using a rotavapor, the crude product was
dissolved in ca. 0.5 mL of CH2Cl2 and purified by preparative
TLC (8:1 benzene-acetone). Pure complexes 6, 9, (SC)-10, (SC)-
12, 14, and exo-(SC)-16 were obtained after crystallization from
CH2Cl2-hexane.
Synthesis of LiPPh2 Using PPh3 and Li.15,16 Reagent A1:
Granules of Li (61.1 mg, 8.8 mmol) were placed into an Ar-filled
10 mL Schlenk flask followed by addition of THF (2 mL).
In another Ar-filled flask, PPh3 (655.7 mg, 2.5 mmol) was
dissolved in THF (3 mL). Then the PPh3 solution was added
dropwise to the metal through a septum during 3-4 min. The
reaction mixture was stirred overnight for 18 h. Then the
solution was filtered to remove excess Li. The solution’s color
was dark brown-red. To take a 31P NMR spectrum of the
reaction mixture, 0.01 mL of THF-d8 and 0.25 mL of the
prepared solution were used. 31P{1H} NMR (δ, ppm): two
signals, -22.4 (PPh3) and -39.1 (ω/2=28.6 Hz, LiPPh2), with
a relative intensity of 2:1 (τ = 2 s). Reagent A2 was obtained
using 6 equiv of Li following the same procedure. 31P{1H} NMR
(δ, ppm): -37.4.
Synthesis of LiPPh2 Using PPh3 and Li Followed by Quenching
of PhLi.17,18 Reagent B1: A solution of the LiPPh2 reagent
A1 in THF (1 mL, 0.5 mmol) obtained as described above was
placed into an Ar-filled 10 mL Schlenk flask followed by
dropwise addition of t-BuCl (0.05 mL, 0.5 mmol) using a
syringe. The resulting solution was stirred at rt under Ar for
1.5 h and slowly filtered (at normal pressure and in inert
atmosphere) prior to further use. 31P{1H} NMR (δ, ppm): four
signals, -20.4 (PPh3), -30.4 and -31.4 (ω/2= 4.0 and 9.2 Hz,
respectively, LiPPh2), and -55.4 (HPPh2). Reagent B2 was
obtained from A2 using the same procedure. 31P{1H} NMR
(δ, ppm): -30.2 and -31.1 (signal ratio 1:2.3).
Preparation of LiPPh2 Using ClPPh2 and Li.19-21 Reagent
C3: Li pieces (37.2 mg, 5.4 mmol) and THF (5.4 mL) were placed
into an Ar-filled Schlenk flask. Then ClPPh2 (0.50 mL, 2.7
mmol) was added dropwise in 6 min. In ca. 30 min, the reaction
mixture turned bright orange. The reaction was slightly exother-
mic. The reaction was stirred overnight and slowly filtered (at
normal pressure and in inert atmosphere) prior to further use.
Complete conversion of ClPPh2 was confirmed by 31P NMR
data. 31P{1H} NMR (δ, ppm): overlap of -30.6 (broad) and
-31.2 (sharp), -36.2 (broad). Reagent C1 was synthesized using
a 1:3 molar ratio of ClPPh2 and Li following the same proce-
dure. 31P{1H} NMR (δ, ppm): -35.3 ppm, ω/2 = 14.6 Hz.
Reagent C2 was obtained using a 1:10 molar ratio of ClPPh2 and
Li following the same procedure. 31P{1H} NMR (δ, ppm):
-35.3 ppm.
Chloro-{2-(N,N-dimethylamino)methyl]ferrocenyl-C,N}[(4-hy-
droxybutyl)diphenylphosphine-P]palladium(II) (6). Compound 6
was obtained from rac-1 in 87% yield as orange-red crystals.
Mp: 156-157 °C (dec); Rf 0.60 (5:1 benzene-acetone). 1H NMR
(δ, ppm): 1.13 (m, 1H, PCH2CHA), 1.40 (m, 1H, PCH2CH2CHB),
1.96 (m, 1H, 3JHP = 4.3, PCH2CH2CHA), 1.96 (m, 1H, PCHA),
2.04 (m, 1H, PCH2CHB), 2.93 (s, 1H, H(5) ferrocenyl), 2.97 (d,
3H, 4JHP = 2.1, NCH3A), 3.04 (m, 2H, OH and PCHB), 3.18 (d,
3H, 4JHP =1.8, NCH3B), 3.40 (dd, 1H, 4JHP =2.4, 2JHH = 14.4,
NCHA), 3.57 (m, 2H, NCHB, CHAOH), 3.71 (s, 5H, C5H5), 3.76
(m, 2H, CHBOH and H(3) ferrocenyl), 3.96 (s, 1H, H(4)
ferrocenyl), 7.40 (m, 2H, m-PPhA), 7.47 (m, 1H, p-PPhA), 7.55
(m, 3H, m- and p-PPhB), 7.75 (m, 2H, o-PPhA), 7.98 (m, 2H,
o-PPhB). 13C{1H} NMR (δ, ppm): 20.3 (d, 2JCP=2.4, PCH2CH2),
30.3 (d, 1JCP=32.6, PCH2), 32.6 (d, 3JC3P=16.4, PCH2CH2CH2),
Preparation of the LiPPh2 Reagent D Using HPPh2 and Li.22,23
In the Ar atmosphere, HPPh2 (0.48 mL, 2.8 mmol) and THF
(5 mL) were placed into a 10 mL Schlenk flask. The solution was
cooled to -75 °C and stirred for about 20 min. Then a 0.25 M
solution of n-BuLi in hexane (1.0 mL, 2.5 mmol) was added
dropwise in 5 min. During the addition, the color of the reaction
mixturechangedfrom colorlesstoorange. The mixture was stirred
at -75 °C for 30 min and then was left to warm to rt within several
hours. To take a 31P{1H} NMR spectrum of the reaction mixture,
0.01 mL of THF-d8 and 0.25 mL of the prepared solution were
used. 31P{1H} NMR (δ, ppm): -38.0 ppm (ω/2=21.4 Hz).
Preparation of 31P NMR Samples of the LiPPh2 Reagents. For
the collection of 31P{1H} NMR spectra, 0.25 mL of 0.5 M
solutions of LiPPh2 in THF were mixed with 0.01 mL of
THF-d8 at rt, so the estimated concentration of the reagents in
NMR samples was 0.48 M. The 31P{1H} NMR spectra were
taken at rt unless otherwise noted. In some cases, concentration
of the obtained reagents was also evaluated using 31P{1H} NMR
spectroscopy. An exact volume of the reagent’s solution was
mixed with a known amount of PPh3, and a 31P{1H} NMR
spectrum was run with a signal delay, τ, of 10 s. (When shorter
3
51.2 (d, JCP = 2.5, NCH3), 52.7 (d, JCP = 1.9, NCH3), 59.8
(CH2OH), 60.5 (C(4) ferrocenyl), 65.1 (d, 3JCP=1.8, NCH2), 65.5
(d, 4JCP =3.8, C(3) ferrocenyl), 69.1 (C5H5), 71.3 (d, 3JCP =9.7,
C(5) ferrocenyl, 97.02 (d, 3JCP = 1.7, C(2) ferrocenyl), 97.17 (d,
2JCP = 2.1, PdC(1) ferrocenyl), 128.1 (d, 3JCP = 10.6, m-PPhA),
3
1
128.7 (d, JCP = 9.8, m-PPhB), 129.07 (d, JCP = 48.2, ipso-C
of PPhA), 130.3 (d, JCP = 3.1, p-PPhA), 131.0 (d, JCP = 1.4,
p-PPhB), 132.3 (d, 2JCP = 10.8, o-PPhA), 133.26 (d, 1JPC = 45.0,
ipso-C of PPhB), 135.4 (d, 2JPC=11.8, o-PPhB). 31P{1H} NMR (δ,
ppm): 20.09. Anal. Calcd for C29H34ClNOPPd: C, 54.32; H, 5.34;
N, 2.18. Found: C, 54.95; H, 5.59; N, 2.15.
4
4
(61) Gaunt, J. C.; Shaw, B. L. J. Organomet. Chem. 1975, 102, 511–
516.
(62) Zalevskaya, O. A.; Dunina, V. V.; Potapov, V. M.; Kuz’mina, L.
G.; Struchkov, Y. T. Zh. Obshch. Khim. 1985, 55, 1332–1341.
(63) Gorunova, O. N.; Keuseman, K. J.; Goebel, B. M.; Kataeva, N.
A.; Churakov, A. V.; Kuz’mina, L. G.; Dunina, V. V.; Smoliakova, I. P.
J. Organomet. Chem. 2004, 689, 2382–2394.
(64) Balavoine, G.; Clinet, J. C. J. Organomet. Chem. 1990, 390, C84–
C88.

6556 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
Chloro-{[2-(N,N-dimethylamino)methyl]phenyl-C,N}[(4-hydroxy-
butyl)diphenylphosphine-P]palladium(II) (9). Complex 9 was ob-
tained from dimer 7 in 79% yield as pale yellow crystals. Mp:
154-155 °C (dec); Rf 0.61 (5:1 benzene--acetone). 1H NMR (δ,
ppm): 1.57 (m, 2H, PCH2CH2CH2), 1.81(m,2H, PCH2CH2), 2.43
(m, 2H, 2JHP=2.6, PCH2), 2.81 (d, 6H, 4JHP =2.4, NCH3), 2.99
Chloro-[2-methyl-2-(4,4-dimethyloxazolin-2-yl)propyl-C,N]-
[(4-hydroxybutyl)diphenylphosphine-P]palladium(II) (14). Com-
pound 14 was obtained from CPC 13 as a pale yellow powder in
1
92% yield. Mp: 58-60 °C; Rf 0.26 (5:1 benzene-acetone); H
3
NMR (δ, ppm) 1.08 (s, 6H, CH3), 1.22 (d, 2H, JHP = 4.6,
PdCH2), 1.58 (s and m, 8H, two CH3 groups and PCH2CH2CH2),
1.74 (m, 2H, PCH2CH2), 2.45 (m, 2H, PCH2), 3.20 (br s, 1H, OH),
3.69 (m, 2H, CH2OH), 4.11 (s, 2H, OCH2), 7.41 (m, 6H, m- and
p-PPh), 7.65 (m, 4H, o-PPh). 13C{1H} NMR (δ, ppm): 20.3
3
(br s, 1H, OH), 3.65 (t, 2H, JHH = 5.8, CH2O), 4.03 (d, 2H,
4JHP=2.4, NCH2), 6.40 (m, 2H, H(5,6) arom), 6.82 (t, 1H, 3JHH
=
7.2, H(4) arom), 7.24 (d, 1H, 3JHH=7.2, H(3) arom), 7.39 (m, 4H,
m-PPh), 7.44 (m, 2H, p-PPh), 7.81 (m, 4H, o-PPh). 13C{1H} NMR
1
(PCH2CH2), 26.5 (d, JPC = 30.8, PCH2), 27.6 and 27.9 (two
2
1
(δ, ppm): 20.7 (d, JCP = 2.8, PCH2CH2), 29.3 (d, JCP = 33.8,
PCH2), 32.8 (d, PCH2CH2CH2, 3JCP =16.4), 50.3 (d, 3JCP =2.4,
NCH3), 59.8 (CH2OH), 72.9 (d, 3JCP = 3.1, NCH2), 122.4 (C(3)
arom), 123.9 (C(4) arom), 125.2 (d, 4JCP =5.9, C(5) arom), 128.4
CH3 groups), 32.8(d, 2JCP=15.5, PdCH2), 35.2 (PCH2CH2CH2),
41.6 (Me2CN), 59.8 (CH2OH), 67.0 (d, 3JCP=3.2, Me2CCH2Pd),
82.2 (d, 4JCP =3.7, OCH2), 128.3 (d, 3JCP =10.2, m-PPh), 130.2
(d, 4JCP=1.9, p-PPh), 132.0 (d, 1JCP=46.4, ipso-C of PPh), 133.2
3
1
2
3
(d, JCP = 10.2, m-PPh), 130.3 (d, JCP = 48.1, ipso-C of PPh),
130.7 (d, 4JCP =1.4, p-PPh), 134.5 (d, 2JCP =12.3, o-PPh), 137.5
(d, 3JCP = 11.2, C(6) arom), 148.4 (d, 2JCP =2.3, PdC(1) arom),
150.4(C(2) arom). 31P{1H} NMR (δ, ppm):21.83. Anal.Calcdfor
C25H31ClNOPPd: C, 56.19; H, 5.85; N, 2.62. Found: C, 56.08; H,
5.90; N, 2.59.
(d, JCP = 10.8, o-PPh), 182.2 (d, JCP = 2.7, NCO). 31P{1H}
NMR (δ, ppm): 15.72. Anal. Calcd for C25H35ClNO2PPd: C,
54.16; H, 6.36; N, 2.53. Found: C, 53.89; H, 6.34; N, 2.69.
(SC)-Chloro-{[2-(4-benzyl-2-oxazolin-2-yl)methyl]phenyl-C,N}-
[(4-hydroxybutyl)diphenylphosphine-P]palladium(II) (endo-(SC)-
16). Compound endo-(SC)-16 was synthesized from (SC,SC)-15
following the general procedure except for using 1/3 of the THF
amount for dissolving CPC (SC,SC)-15. The complex was isolated
as a pale yellow powder in 10% yield. Mp: 98-100 °C; Rf 0.14 (5:1
benzene-acetone). 1H NMR (δ, ppm): 1.32 (m, 2H, PCH2-
CHACHA), 1.63 (m, 2H, PCH2CHBCHB), 2.00 (m, 2H, PCHA,
OH), 2.40 (m, 1H, PCHB), 2.68 (m, 1H, PhCHA), 3.36 (m, 1H,
(SC)-Chloro-{2-[1-(N,N-dimethylamino)ethyl]phenyl-C,N}[(4-
hydroxybutyl)diphenylphosphine-P]palladium(II) ((SC)-10). Com-
pound (SC)-10 was synthesized from (SC,SC)-8 as pale yellow
crystals in 79% yield. [R]D þ22 (c 0.0034, CH2Cl2). Mp:60-61 °C;
Rf 0.71 (5:1 benzene-acetone). 1H NMR (δ, ppm): 1.49 (m, 1H,
PCH2CH2CHA), 1.64 (m, 2H, PCH2CHACHB), 1.78 (d, 3H,
3JHH = 6.5, CHCH3), 2.04 (m, 1H, PCH2CHB), 2.22 (m, 1H,
PCHA), 2.70 (m, 1H, PCHB), 2.74 (d, 3H, 4JHP = 2.9, NCH3A),
2.77 (d, 3H, 4JHP=1.6, NCH3B), 3.02 (br s, 1H, OH), 3.62 (m, 1H,
CHAOH), 3.68 (m, 1H, CHBOH), 3.79 (m, 1H, CHCH3), 6.40 (m,
2H, H(5,6) arom), 6.82(dt,1H, JHP=4.5, 3JHH=7.6, H(4) arom),
6.93 (d, 1H, 3JHH =7.2, H(3) arom), 7.32 (m, 2H, m-PPhA), 7.39
(m, 1H, p-PPhA), 7.46 (m, 3H, m- and p-PPhB), 7.68 (m, 2H,
o-PPhA), 7.92 (m, 2H, o-PPhB). 13C{1H} NMR (δ, ppm): 20.5 (d,
2
CHAOH), 3.43 (m, 1H, CHBOH), 3.58 (dd, 1H, JHH = 12.1,
3JHH = 8.7, OCHA), 3.66 (d, 1H, 2JHH = 14.1, C6H4CHA), 3.90
(dd, 1H, 2JHH = 14.0, 3JHH = 6.3, PhCHB), 4.10 (d, 1H, C6H4-
CHB), 4.50 (m, 1H, OCH2), 4.74 (m, 1H, CHN), 6.35 (m, 2H,
H(5,6) of C6H4Pd), 6.68 (m, 2H, H(3,4) of C6H4Pd), 6.90 and 7.01
(two m, 5H, C6H5 of 4-Bn), (m, 2H, m-PPhA), 7.20-7.40 (m, 6H,
m- and p-PPh2), 7.57 (m, 2H, o-PPhA), 7.69 (m, 2H, o-PPhB).
13C{1H} NMR (δ, ppm): 19.9 (PCH2CH2), 26.3 (d, 1JCP = 33.2,
1
3
2JCP = 3.0, PCH2CH2), 21.5 (CHCH3), 29.1 (d, JCP = 33.6,
PCH2), 31.8 (d, JCP = 16.4, PCH2CH2CH2), 33.7 (C6H4CH2),
PCH2), 33.6 (d, 3JCP =16.6, PCH2CH2CH2), 46.2 (d, 3JCP =1.7,
39.6 (PhCH2), 59.2 (NCH), 59.5 (CH2OH), 71.5 (OCH2), 122.7
and 125.8 (C(3) and C(4) of C6H4Pd), 124.6 (d, 4JCP=6.3, C(5) of
C6H4Pd), 127.0 (p-C of 4-Bn), 127.2 (two overlapping d, m-PPh),
128.1 (o-C of 4-Bn), 129.3 (m-C of 4-Bn), 129.7 (d, 1JCP = 47.3,
NCH3A), 50.1 (d, JCP = 2.7, NCH3B), 59.6 (CH2OH), 74.9 (d,
3
3JCP=2.9, CHCH3), 122.3 (C(3) arom), 123.9 (C(4) arom), 125.1
(d, 4JCP =5.8, C(5) arom), 128.2 (d, 3JCP =10.3, m-PPhA), 128.5
(d, 3JCP=10.4, m-PPhB), 130.5 (d, 4JCP=1.9, p-PPhA), 130.6 (br
d, 1JCP = 45.2, ipso-C of PPhA and PPhB), 130.7 (d, 4JCP = 2.3,
1
ipso-C of PPhA), 130.5 (d, JCP = 47.4, ipso-C of PPhB), 132.6
(three overlapping d, o- and p-PPh), 134.1 (d, 3JCP=10.7, C(6) of
C6H4Pd), 134.9 (PdC(1) arom), 149.1 (C(2) of C6H4Pd), 170.6 (d,
3JCP=5.0, NCO). 31P{1H} NMR (δ, ppm): 13.05. Anal. Calcd for
C33H35ClNO2PPd: C, 60.93; H, 5.42; N, 2.15. Found: C, 60.57; H,
5.72; N, 2.11.
2
2
p-PPhB), 134.3 (d, JCP = 10.9, o-PPhA), 134.4 (d, JCP = 11.1,
3
o-PPhB), 137.5 (d, JCP = 11.7, C(6) arom), 150.1 (C(2) arom),
154.3 (d, JCP = 2.1, PdC(1) arom). 31P{1H} NMR (δ, ppm):
21.83. Anal. Calcd for C26H33ClNOPPd: C, 56.94; H, 6.07; N,
2.55. Found: C, 56.74; H, 6.07; N, 2.43.
2
(SC)-{[2-(2-Benzyl-2-oxazolin-4-yl)methyl]phenyl-C,N}[(4-hydro-
xybutyl)diphenylphosphine-P]palladium(II) (exo-(SC)-16). Com-
pound exo-(SC)-16 was obtained from (SC,SC)-15 a pale yellow
powder in 61% yield. Mp: 152-154 °C; Rf 0.25 (5:1 benzene-
acetone). 1H NMR (δ, ppm): 1.40 (m, 2H, PCH2CHACHA), 1.78
(m, 2H, PCH2CHBCHB), 2.10 (m, 1H, PCHA), 2.17 (br s, OH),
(SC)-Chloro-[2-(2-methyl-2-oxazolin-4-yl)phenyl-C,N][(4-hy-
droxybutyl)diphenylphosphine-P]palladium(II) ((SC)-12). Com-
pound (SC)-12 was synthesized from (SC,SC)-11 as a pale yellow
powder in 67% yield. [R]D þ58 (c0.0030, CH2Cl2). Mp:96-97 °C;
Rf 0.61 (5:1 benzene-acetone). 1H NMR (δ, ppm): 1.45 (m, 2H,
PCH2CHACHA), 1.69 (m, 1H, PCH2CH2CHB), 2.10 (m, 2H,
PCHACHB), 2.49 (s, 3H, CH3), 2.72 (br s, 1H, OH), 2.91 (m, 1H,
PCHB), 3.61 (m, 1H, CHAOH), 3.68 (m, 1H, CHBOH), 4.31
(m, 1H, OCHA), 4.88 (m, 1H, OCHB), 5.82 (m, 1H, CHN), 6.44
(m, 2H, H(5,6) arom), 6.70 (d, 1H, 3JHH =7.3, H(3) arom), 6.87
(m, 1H, H(4) arom), 7.26 (m, 2H, m-PPhA), 7.37 (m, 1H, p-PPhA),
7.53 (m, 3H, m- and p-PPhB), 7.59 (m, 2H, o-PPhA), 8.12 (m, 2H,
o-PPhB). 13C{1H} NMR (δ, ppm): 14.1 (CH3), 20.9 (PCH2CH2),
28.8 (d, 1JCP=34.5, PCH2), 32.8 (d, 3JCP=16.4, PCH2CH2CH2),
60.3 (CH2OH), 73.6 (OCH2), 74.0 (NCH), 120.4 (C(3) arom),
2
3
2.48 (m, 1H, PCHB), 2.74 (dd, 1H, JHH = 13.7, JHH = 7.6,
C6H4CHACH), 3.18 (dd, 1H, 3JHH=4.2, C6H4CHBCH), 3.40 (d,
1H, 2JHH=16.4, C6H4CHACN), 3.47 (m, 1H, CHAOH), 3.53 (m,
1H, CHBOH), 4.14 (d, 1H, C6H4CHBCN), 4.26 (m, 1H, OCHA),
4.51 (m, 1H, OCHB), 5.30 (m, 1H, CHN), 6.55 (m, 1H, H(6) of
C6H4Pd), 6.81 (m, 1H, H(5) of C6H4Pd), 6.86 (m, 2H, H(3,4) of
C6H4Pd), 6.98 (m, 2H, o-CH of 2-Bn), 7.02 (m, 2H, m-CH of 2-
Bn), 7.08 (m, 1H, p-CH of 2-Bn), 7.20-7.55 (m, 6H, m- and
p-PPh), 7.62 (m, 2H, o-PPhA), 7.79 (m, 2H, o-PPhB). 13C{1H}
NMR (δ, ppm): 21.0 (PCH2CH2), 28.5 (d, 1JCP = 33.3, PCH2),
33.4 (d, 3JCP = 15.6, PCH2CH2CH2), 38.8 (C6H4CH2CN), 40.6
(PhCH2), 60.7 (CH2OH), 63.6 (NCH), 74.9 (OCH2), 123.7 (C(4)
of C6H4Pd), 125.8 (d, 4JCP=4.7, C(6) of C6H4Pd), 126.4 (p-CH of
2-Bn), 127.0 (C(3) of C6H4Pd), 128.3 (overlap of one s and two d,
CH of 2-Bn, m-PPhA and m-PPhB), 129.8 (CH of 2-Bn), 130.3 (d,
3JCP1=15.1, p-PPh2), 130.6 (d, 1JCP=47.3, ipso-C of PPhA), 131.5
(d, JCP = 47.0, ipso-C of PPhB), 133.8 (two overlapping d, o-
PPh2), 135.9 and 136.0 (ipso-C of 2-Bn and PdC(1) arom), 137.7
(d, 4JCP = 13.0, C(5) of C6H4Pd), 149.1 (C(2) of C6H4Pd), 171.6
4
125.0 (C(4) arom), 125.7 (d, JCP = 6.1, C(5) arom), 128.5 (d,
3JCP = 12.3, m-PPhA), 128.8 (d, 3JCP = 13.0, m-PPhB), 130.1 (d,
1
1JCP = 46.9, ipso-C of PPhA), 130.3 (d, JCP = 45.9, ipso-C of
PPhB), 130.5 (p-PPhA), 131.0 (p-PPhB), 134.1 (two overlapping d,
3
o-PPhA and o-PPhB), 138.12 (d, JCP = 12.2, C(6) arom), 147.2
(C(2) arom), 149.1 (PdC(1) arom), 171.1 (d, 3JCP = 6.7, NCO).
31P{1H} NMR (δ, ppm): 20.28. Anal. Calcd for C27H31-
ClNO2PPd: C, 56.36; H, 5.64; N, 2.43. Found: C, 56.11; H,
5.46; N, 2.46.

Article
Organometallics, Vol. 28, No. 22, 2009 6557
(NCO). 31P{1H} NMR (δ, ppm): 14.91. Anal. Calcd for C33H35-
ClNO2PPd: C, 60.93; H, 5.42; N, 2.15; Cl, 5.45. Found: C, 61.22;
H, 5.67; N, 2.23; Cl, 5.59.
complex was also isolated from the reaction of CPC 7 with 2 molar
equiv of reagent C2 (THF, rt, 7 h) in 12% yield. The complex was
isolated from reaction mixtures using preparative TLC (silica gel,
benzene). Mp: 156-157 °C (dec); Rf 0.17 (5:1 benzene-acetone).
1H NMR (δ, ppm): 2.68 (s, 6H, N(CH3)2), 3.76 (s, 2H, CH2N),
μ-Chloro-μ-diphenylphosphido-{[2-(N,N-dimethylamino)methyl]-
phenyl-C,N}dipalladium(II) (17). Method I. Complex CPC 7
(21.0 mg, 0.0380 mmol) was placed into an Ar-filled 10 mL Schlenk
flask. The flask was vacuumed and THF (2.1 mL) was added. Then
a 0.5 M solution of LiPPh2 in THF (reagent D) was added dropwise
in 8 min. The colorless mixture turned red. The reaction mixture was
stirred in Ar at rt for 4 h. After solvent removal, the crude product
was dissolved in CH2Cl2 and the solution was filtered through a
layer of Celite. The filtrate was concentrated and the crude product
was purified using preparative TLC (silica gel, 6:1 benzene-
acetone). Complex 17 was isolated in 60% yield as a yellow solid.
Method II. A solution of LiPPh2 in THF (0.14 mL, 0.068 mmol)
obtained from PPh3 and Li (reagent A1) was placed into an Ar-filled
10 mL Schlenk flask. Then a solution of CPC 7 (18.3 mg, 0.0340
mmol) in THF (1.8 mL) was added dropwise to the LiPPh2 solution
in 4 min. During the addition, the color of the mixture changed from
dark brown to dark red. The reaction mixture was stirred at rt in Ar
for 5 h. After solvent evaporation using a rotavapor, the crude
product was dissolved in CH2Cl2 and filtered through a layer of
Celite. The filtrate was concentrated and the crude product was
purified using preparative TLC (silica gel, 6:1 benzene-acetone).
Complex 17 was obtained in 17% yield along with 58% of
compound 18. Method III. Complex 7 (20.0 mg, 0.0371 mmol)
was placed into an Ar-filled 10 mL Schlenk flask. The flask was
vacuumed and filled with Ar followed by addition of THF (3 mL).
Then a 0.5 M solution of LiPPh2 in THF (reagent B1, 0.15 mL,
0.074 mmol) was added dropwise in 2 min. The color of the mixture
changed from yellow to orange-red. The reaction mixture was stirred
in Ar at rt for 6 h. After solvent removal, the residue was dissolved in
CH2Cl2 and filtered through a layer of Celite. The filtrate was
concentrated and purified using preparative TLC (silica gel, 6:1
benzene-acetone). Complex 17 was obtained in 12% yield, com-
pound 18 in 52% yield. Mp: 165-168 °C; Rf 0.91 (5:1 benzene-
acetone). 1H NMR (δ, ppm): 2.59 (s, 6H, N(CH3)2), 3.78 (s, 2H,
CH2N), 6.35 (dd, 1H, 3JHH =7.5, JHP =4.2, C(6)H arom), 6.42 (t,
1H, 3JHH=7.5,C(5)Harom),6.72(t,1H,3JHH=7.5,C(4)Harom),
6.82 (d, 1H, 3JHH=7.5, C(3)H arom), 7.17 (m, 3H, p- and m-PPh),
7.79 (m, 2H, o-PPh). 13C{1H} NMR (δ, ppm): 48.2 (d, 3JCP =1.6,
NCH3), 69.9 (d, 3JCP=2.0, NCH2), 121.2 (C(3) arom), 122.3 (C(4)
arom), 124.1 (d, 4JCP =4.5, C(5) arom), 126.7 (d, 3JCP =10.2, m-
PPh), 127.7 (d, 4JCP = 2.5, p-PPh), 134.4 (d, 2JCP = 12.2, o-PPh),
134.7 (d, 1JCP =28.4, ipso-PPh), 136.5 (d, 3JCP =8.5, C(6) arom),
147.1 (d, 2JCP=2.9, PdC(1) arom), 147.3(d,3JCP=1.8,C(2) arom).
31P{1H} NMR (δ, ppm): 25.1. Anal. Calcd for C66H74Cl2N4P2Pd4
(2 molecules of 17 and 1 of benzene): C, 53.49; H, 5.03; N, 3.78.
Found: C, 53.64; H, 5.08; N, 3.62 (the benzene signal was present in
both the 1H and 13C spectra of the sample used for the analysis).
Chloro-{[2-(N,N-dimethylamino)methyl]phenyl-C,N}(triphenyl-
phosphine-P)palladium(II) (18). This previously reported complex
was a side product in reactions of CPC 7 with the LiPPh2 reagents
synthesized using PPh3. Mp: 158-160 °C; Rf 0.82 (5:1 benzene-
acetone). 1H NMR (δ, ppm): 2.85 (s, 6H, N(CH3)2), 4.07 (s, 2H,
CH2N), 6.32 (dd, 1H, 3JHH=7.3, JHP=6.6, C(6)H arom), 6.37 (t,
3
6.09 (dd, 1H, JHH = 7.4, JHP = 5.3, C(6)H arom), 6.24 (t, 1H,
3JHH =7.4, C(5)H arom), 6.61 (t, 1H, 3JHH =7.4, C(4)H arom),
6.73 (d, 1H, 3JHH=7.4, C(3)H arom), 6.96(br m, 4H, p-PPh), 7.08
(br m, 8H, m-PPh), 7.44 (m, 4H, o-PPh), 7.69 (m, 4H, o-PPh).
3
13C{1H} NMR (δ, ppm): 49.4 (d, JCP = 1.5, NCH3), 69.9 (d,
3JCP = 2.5, NCH2), 120.7 (C(3) arom), 122.0 (C(4) arom), 123.8
(d, 4JCP=4.8, C(5) arom), 126.1 (d, 3JCP=10.4, m-PPh), 127.1 (s,
p-PPh), 130.4 (d, 2JCP=11.4, o-PPh), 134.1 (br m, o-PPh and C(6)
arom), 139.5 (d, 1JCP = 58.4, ipso-PPh), 146.3 (s, PdC(1) arom),
147.4 (C(2) arom). 31P{1H} NMR (δ, ppm): PPh2 23.2 (d, 1JPP
=
203.1), P(O) 103.2 (d, 1JPP = 203.1), and the other isomer PPh2
23.8, P(O) 103.0. Anal. Calcd for C34H32DCl4NOP2Pd (1 mole-
cule of 19 and 1 of CDCl3): C, 52.17; H, 4.38; N, 1.79. Found: C,
51.63; H, 4.53; N, 1.78.
ortho-(Diphenylphosphino)-N,N-dimethylbenzylamine (20).
Method I. A 0.5 M solution of LiPPh2 in THF (reagent C3) was
placed into an Ar-filled 10 mL Schlenk flask. Then THF was
removed using a pump, and the formed pale yellow solid was kept
under vacuum (<1 mbar) for 1.5 h at 40 °C. A solution of CPC 7
(25.7 mg, 0.0465 mmol) intoluene (9.1 mL) was added dropwisein
4 min. The yellow reaction mixture was stirred in Ar at rt for 18 h.
After solvent removal, a solid residue was dissolvedinCH2Cl2 and
purified using preparative TLC (silica gel, 8:1 benzene-acetone).
Aminophosphine 20 was obtained in 81% yield, complex 17 was
isolated in 17% yield. Method II. In the Ar atmosphere, HPPh2
(0.015 mL, 0.084 mmol) was placed into a 10 mL Schlenk flask
followed by addition of THF (0.25 mL). The solution was
cooled to -78 °C, and then a 0.25 M solution of n-BuLi in hexane
(0.034 mL, 0.084 mmol) was added dropwise in 5 min. During the
addition, the colorless reaction mixture turned first yellow, then
orange and finally back to colorless. The mixture was stirred at
-78 °C for 30 min. Then it was slowly (within several hours)
warmed to rt and stirred for 30 min. The estimated molarity of the
obtained reagent was 0.3 M. Then a solution of CPC 4 (22.6 mg,
0.0409 mmol) in THF (3.5 mL) was added dropwise in 5 min.
During the addition, the color of the mixture changed to bright
red. The reaction mixture was stirred at rt in Ar for 18 h. Inthe end
of the reaction, the mixture became dark red. After solvent
removal, the solid residue was dissolved in CH2Cl2 and purified
using preparative TLC (silica gel, 7:1 benzene-acetone). Amino-
phosphine 20 was obtained in 37% yield as a pale yellow syrup:
1
Rf 0.61 (7:1 benzene-acetone). H NMR (δ, ppm): 2.05 (s, 6H,
N(CH3)2), 3.61 (d, 2H, 4JHP=1.6, NCH2), 6.90 (ddd, 1H, 3JHH
=
7.5, 3JHP=4.3, 4JHH=1.0, C(6)H arom), 7.14(dt, 1H, 3JHH=7.5,
4JHP = 1.0, C(5)H arom), 7.25 (m, 4H, o-PPh), 7.30 (m, 6H, m-
and p-PPh), 7.34 (br m, 1H, C(4)H arom), 7.46 (br dd, 4JHP=4.3,
3JHH = 7.3, C(3)H arom). 13C{1H} NMR (δ, ppm): 44.5 (s,
NCH3), 62.0 (br s, NCH2), 127.2 (C(4) arom), 128.3 (br s,
1
3
m-PPh), 128.5 (d, JCP = 39.0, ipso-PPh), 129.2 (d, JCP = 2.9,
C(5) arom), 131.7 (d, 3JCP=9.3, C(3) arom), 133.7 (d, 2JCP=5.7,
o-PPh), 133.8 (s, p-PPh), 136.7 (d, 1JCP =15.3, C(1) arom), 137.7
(br s, C(2) arom). 31P{1H} NMR (δ, ppm): -30.3. HRMS: [M þ
H]þ calcd for C21H23NP 320.1523, found 320.1565.
3
3
1H, JHH = 7.3, C(5)H arom), 6.82 (t, 1H, JHH = 7.3, C(4)H
arom), 6.99 (d, 1H, JHH = 7.3, C(3)H arom), 7.34 (m, 6H,
3
m-PPh), 7.41 (m, 3H, p-PPh), 7.72 (m, 6H, o-PPh). 13C{1H}
ortho-(Diphenyloxophosphino)-N,N-dimethylbenzylamine (21).
This compound was obtained as a slightly yellow sticky oil in 5%
yield in the reaction of CPC 7 with reagent C3 (1:2 molar ratio) in
THF at rt for 3 h: Rf 0.23 (7:1 benzene-acetone). 1H NMR (δ,
ppm): 1.99 (s, 6H, N(CH3)2), 3.78 (br s, 2H, NCH2), 7.02 (dd, 1H,
3JHH = 7.3, 3JHP = 14.1, C(6)H arom), 7.18 (t, 1H, 3JHH = 7.3,
C(5)H arom), 7.46 (m, 4H, o-PPh), 7.5 (br m, 1H, C(4)H arom),
7.53 (m, 2H, p-PPh), 7.62 (m, 4H, m-PPh), 7.76 (br m, 1H, C(3)H
arom). 13C{1H} NMR (δ, ppm): 44.9 (s, NCH3), 61.3 (br s,
NCH2), 126.2 (d, 3JCP = 13.8, C(5) arom), 128.4 (d, 2JCP = 15.1,
o-PPh), 130.2 (br s, C(3) arom), 130.7 (d, 1JCP=100.6, ipso-PPh),
131.5 (s, p-PPh), 131.7 (d, 3JCP = 8.8, m-PPh), 132.1 (br s, C(4)
NMR (δ, ppm): 50.5 (d, 3JCP =2.4, NCH3), 73.2 (d, 3JCP =2.9,
NCH2), 122.3 (C(3) arom), 123.8 (C(4) arom), 124.9 (d, JCP =
4
5.8, C(5) arom), 128.0 (d, 3JCP = 10.7, m-PPh), 130.5 (d, 4JCP
=
2.4, p-PPh), 131.4(d, 1JCP=49.9, ipso-PPh), 135.3(d, 2JCP=11.9,
o-PPh), 137.9 (d, 3JCP = 10.8, C(6) arom), 148.5 (d, 2JPC = 1.9,
PdC(1) arom), 150.8 (C(2) arom). 31P{1H} NMR (δ, ppm): 27.3.
Chloro{[2-(N,N-dimethylamino)methyl]phenyl-C,N}(tetraphe-
nyldiphosphine oxide-P)palladium(II) (19). Complex 19 was for-
med from complex 17 after storing in CH2Cl2 for two months in
25% yield. Compound 19 was also obtained from complex 17
while heating in toluene at 60 °C for a week in 12% yield. This

6558 Organometallics, Vol. 28, No. 22, 2009
Stepanova et al.
arom), 133.1 (br s, C(1) arom), 133.6 (d, 2JCP=13.8, C(6) arom),
134.0(br s, C(2) arom). 31P{1H} NMR (δ, ppm): 16.6. HRMS: [M
þ H]þ calcd for C21H23NOP 336.1517, found 336.1522.
Crystallographic data for 9 have been deposited with the
Cambridge Crystallographic Data Centre as Supplementary
Publication No. CCDC-736136. Copies of the data can be
obtained free of charge on application to the CCDC, 12 Union
Road, Cambridge CB2 1EZ, U.K. (fax: þ44(1223)-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
The authors would like to acknowledge Victor G. Young,
Jr., Benjamin E. Kuchera, and the X-ray Crystallographic
Laboratory in the Department of Chemistry of the Uni-
versity of Minnesota for the X-ray crystallographic analysis
of complex 9.
Supporting Information Available: 1H, 13C{1H}, and 31P{1H}
NMR spectra of compounds rac-6, 9, (SC)-10, (SC)-12, 14,
endo-(SC)-16, exo-(SC)-16, and 17-21 and the CIF file with
the data of the X-ray crystallographical analysis of complex 9.
This material is available free of charge via the Internet at http://
pubs.acs.org.
Acknowledgment. Financial support has been received
from ND EPSCoR through NSF grant No. EPS-0447679.