Parent-amido (NH2) palladium(II) complexes: Synthesis, reactions, and catalytic hydroamination

Article abstract of DOI:10.1016/j.crci.2015.12.008

The treatment of [PdL₃(NH₃)](OTf)_n (n = 1; L₃ = (PEt₃)₂(Ph), (2,6-(Cy₂PCH₂)₂C₆H₃), n = 2; L₃ = (dppe)(NH₃)) with NaNH₂ in tetrahydrofuran at ambient temperature or -78 °C afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-[Pd(PEt₃)(Ph)(μ-NH₂)]₂ (1), [Pd(dppe)(μ-NH₂)]₂(OTf)₂ (2), and Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂) (3), respectively. The molecular structures of the amido-bridged (μ-NH₂) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography. The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo complex, Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(OH) (4). Exposing complex 3 to an excess of water resulted in the complete conversion of the complex into two species [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(OH₂)]⁺ and [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₃)]⁺. Complex 3 reacted with diphenyliodonium triflate ([Ph₂I]OTf) to give the aniline complex [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂Ph)]OTf. The reaction of 3 with phenylacetylene (HCCPh) yielded a palladium(II) acetylenide Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(CCPh) (5), quantitatively, along with the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(CRCR(NH₂)) (R = CO₂Me (6a), CO₂Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol produced Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(OC₆H₄-p-NO₂) (7) and cis-CHRCR(NH₂), exclusively. Reactions of 3 with either dialkyl maleate (cis-(CO₂R)CHCH(CO₂R)) (R = CH₃, CH₂CH₃) or cis-stilbene (cis-CHPhCHPh) did not result in any addition product. Instead, isomerization of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH₂CHCN) to generate a metastable insertion product, Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(CH(CN)CH₂NH₂). On the other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric species of acrylonitrile. The catalytic hydroamination of olefins with NH₃ was examined in the presence of Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(OTf), producing a range of hydroaminated products of primary, secondary, and tertiary amines with different molar ratios of more than 99% overall yield. A mechanistic feature for the observed catalytic hydroamination is described with regard to the aminated derivatives of palladium(II).

Full text of DOI:10.1016/j.crci.2015.12.008

C. R. Chimie 19 (2016) 614e629
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Full paper/Memoire
Parent-amido (NH2) palladium(II) complexes: Synthesis,
reactions, and catalytic hydroamination*
Youngwon Kim, Soonheum Park*
Department of Chemistry, Dongguk University-Gyeongju, 123 Dongdae-ro, Gyeongju, Gyeongbuk, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
The treatment of [PdL3(NH3)](OTf)n (n ¼ 1; L3 ¼ (PEt3)2(Ph), (2,6-(Cy2PCH2)2C6H3), n ¼ 2;
L3 ¼ (dppe)(NH3)) with NaNH2 in tetrahydrofuran at ambient temperature or ꢀ78 ꢁC
afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-
Received 3 November 2015
Accepted 15 December 2015
Available online 31 March 2016
[Pd(PEt3)(Ph)(
m
-NH2)]2
(1),
[Pd(dppe)(
m
-NH2)]2(OTf)2
(2),
and
Pd(2,6-
(Cy2PCH2)2C6H3)(NH2) (3), respectively. The molecular structures of the amido-bridged (
m
-
Keywords:
NH2) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography.
The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo
complex, Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4). Exposing complex 3 to an excess of water
resulted in the complete conversion of the complex into two species [Pd(2,6-
(Cy2PCH2)2C6H3)(OH2)]þ and [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]þ. Complex 3 reacted with
diphenyliodonium triflate ([Ph2I]OTf) to give the aniline complex [Pd(2,6-
(Cy2PCH2)2C6H3)(NH2Ph)]OTf. The reaction of 3 with phenylacetylene (HC^CPh) yielded a
palladium(II) acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(C^CPh) (5), quantitatively, along with
the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded
diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CR]CR(NH2))
(R ¼ CO2Me (6a), CO2Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol
produced Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) and cis-CHR]CR(NH2), exclusively.
Reactions of 3 with either dialkyl maleate (cis-(CO2R)CH]CH(CO2R)) (R ¼ CH3, CH2CH3) or
cis-stilbene (cis-CHPh]CHPh) did not result in any addition product. Instead, isomeriza-
tion of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts
of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH2CHCN) to
generate a metastable insertion product, Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2). On the
other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric
species of acrylonitrile. The catalytic hydroamination of olefins with NH3 was examined in
the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), producing a range of hydroaminated prod-
ucts of primary, secondary, and tertiary amines with different molar ratios of more than
99% overall yield. A mechanistic feature for the observed catalytic hydroamination is
described with regard to the aminated derivatives of palladium(II).
Ammonia
Parent-amido (NH2) palladium(II)
CeN bond formation
Syn-insertion
Regiospecific addition
Catalytic hydroamination
ꢀ
© 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
The amido complexes of late transition metals
have attracted considerable interest because of their
potential involvement as intermediates in metal-catalyzed
*
A part of this work has been reported as a preliminary communica-
tion in Y. Kim, S. Park, C. R. Chimie. 18 (2015) 816.
* Corresponding author.
carbonenitrogen bond formation [1,2]. Recent studies on
E-mail address: shpark@dongguk.ac.kr (S. Park).
http://dx.doi.org/10.1016/j.crci.2015.12.008
ꢀ
1631-0748/© 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
615
the chemistry of these complexes have focused mostly on
arylamido complexes, in which the metal-amido bond may
be stabilized by partial delocalization of the electron den-
sity on the amido nitrogen to an aryl substituent [2]. On the
other hand, complexes with a parent-amido ligand (NH2)
have attracted less attention [1,3e5]. Despite this, such
species are important as feasible intermediates in metal-
catalyzed amination reactions with ammonia [6]. Further-
more, considering the importance of palladium as a pri-
mary metal used in homogeneous catalysis, it is essential to
develop the chemistry with this metal [6a,7].
In this study, the catalytic hydroamination of olefins with
ammonia in the presence of the relevant title complex was
also examined. The mechanistic feature of the catalytic
hydroamination is discussed in regard to the probed reac-
tion profiles in palladium(II) aminated derivatives.
2. Results and discussion
2.1. NH2-bridged dimeric complexes
2.1.1. anti-[Pd(PEt3)(Ph)(m-NH2)]2 (1) and [Pd(dppe)(NH2)]2
Monomeric amido complexes have strong affinity to
undergo substitutional dimerization or oligomerization,
yielding amido-bridged species, which are particularly
crucial for coordinatively unsaturated complexes. There-
fore, a common synthetic strategy for preparing mono-
meric metal amides is to use a sterically hindered ancillary
ligand, such as bulky tertiary phosphines and chelates
including pincer-type ligands, to avoid substitutional
dimerization [5e7]. An earlier report on the synthesis and
thermal stability of a dimethylamido palladium(II), Pd(2,6-
(Ph2PCH2)2C6H3)(NMe2), showed that the monomeric
amido complex with a terdentate PCP pincer is resistant to
(OTf)2 (2)
The reaction of a tetrahydrofuran (THF) solution of
trans-[Pd(PEt3)2(Ph)(NH3)]OTf with NaNH2 at ambient
temperature produced a gray suspension containing a
single compound of palladium(II) along with dissociated
triethylphosphine, as evidenced by the 31P{1H} NMR
spectroscopy (Scheme 1). A pure off-white palladium(II)
dimer anti-[Pd(PEt3)(Ph)(m-NH2)]2 (1) was obtained from
an n-pentane extract of the residues resulting from the
reaction mixture. The 31P{1H} NMR spectrum of complex 1
in d6-benzene showed a single peak at
d 20.2, which is
indicative of a single compound in solution. In the 13C{1H}
NMR spectrum, the methylene carbon attached directly to
b
-hydrogen elimination and thermal decomposition at low
temperatures of less than ꢀ10 ꢁC [8a]. A previous study on
the phosphorus resonates at
d
15.61 (1J(CP) ¼ 26.7 Hz) as a
doublet. In the 1H NMR spectrum, the bridged-amide pro-
the regiospecific reactivity of an arylamido platinum(II)
containing
the
same
pincer
Pt(2,6-
tons (
m
-NH2) were observed at
d
ꢀ1.35 as a broad signal.
(Ph2PCH2)2C6H3)(NH(Tol-p)) toward the C]C bond of
acrylonitrile to yield the addition product of aminoalkyl
complex, Pt(2,6-(Ph2PCH2)2C6H3)(CH(CN)CH2NH(Tol-p))
provided a mechanistic information on one of the key steps
in the catalytic hydroamination of acrylonitrile with
NH2(Tol-p) [8b].
This article reports on a series of dimeric and mono-
meric parent-amido (NH2) complexes of palladium(II) with
an ancillary ligand framework of a different coordination
mode as part of an ongoing study of the stability and
reactivity of the parent-amido complexes. In the present
study for the synthesis of a monomeric parent-amido pal-
ladium(II) complex, a sterically hindered cyclohexyl deriv-
ative of PCP pincer was used to preclude substitutional
dimerization. The title complex exhibited unique reactivity
toward activated olefins and acetylenes to produce regio-
and diastereospecific aminated derivatives of palladium(II),
respectively, via nucleophilic attack of the coordinated NH2.
Attempts to prepare a parent-amido complex with a
chelate ligand dppe under similar reaction conditions as for
complex
[Pd(dppe)(NH3)2](OTf)2 with NaNH2 in THF at ambient
temperature resulted in a deep red solution containing a
palladium(0) complex Pd(dppe), which was trapped in situ
by treatment with dimethyl acetylenedicarboxylate (dmad)
to yield Pd(dppe)(dmad), as verified by the 31P{1H} NMR
1
were unsuccessful. The reaction of
spectrum, showing a single resonance at
d 48.0 in d6-ben-
zene [9]. The formation of Pd(dppe) from the reaction is
likely a consequence of the feasible generation of a
monomeric bis(amido) species Pd(dppe)(NH2)2, which
undergoes facile reductive elimination by releasing hy-
drazine (N2H4), although electron transfer from a base
(NHꢀ2 ) cannot be excluded. Previous studies showed that
hydrazine formation from the oxidation of coordinated
ammonia to a diruthenium complex [10] or from adsorbed
NH2 species on transition metal surfaces [11] is feasible. On
PEt3
NaNH2
Ph
Pd NH3
PEt3
PEt3
+
1/2 anti-[Pd(Ph)(PEt3)(μ-NH2)]2
OTf
THF
H2
Ph
Et3P
Ph
N
Pd
Pd
N
H2
PEt3
1
Scheme 1. Synthesis of anti-[Pd(PEt3)(Ph)(m-NH2)]2 (1).

616
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
dmad
(dppe)Pd
Pd(dppe)(dmad)
at ambient temp.
d6-benzene
NH3
NH3
NaNH
THF
2
(dppe)Pd
(OTf)2
H
N
2
2
(dppe)Pd
Pd(dppe)
(OTf)2
1/2
NaOTf
+
-78 Co
N
H
2
Scheme 2. Synthesis of [Pd(dppe)(m-NH2)]2(OTf)2 (2).
the basis of the above result, the reaction was performed at
low temperatures. The reaction of [Pd(dppe)(NH3)2](OTf)2
with NaNH2 in THF at ꢀ78 ꢁC (dry ice/acetone) afforded a
crystals suitable for X-ray crystallography were grown
either by the slow evaporation of an n-hexane solution of 1
or by the slow diffusion of a mixture of diethyl ether and n-
pentane (1:1) into a dichloromethane solution of 2. Both
complexes 1 and 2 crystallize in the monoclinic space
group P21/n. For 1, there are two crystallographically in-
dependent but chemically identical molecules. The two
dicationic amido-bridged dimeric complex [Pd(dppe)(m-
NH2)]2(OTf)2 (2) in 67% isolated yield (Scheme 2). The 1H
and 31P{1H} NMR spectra of 2 in CDCl3 exhibit an upfield
broad signal at
protons (
-NH2) and a single 31P resonance at
respectively. The counter anion CF3SO3 ꢀ can be established
by the
(SO3) at 1154 and 1266 cmꢀ1 in the IR and the 19F
{1H} NMR resonance at
ꢀ78.9. The molar conductivity
d
ꢀ0.19 corresponding to bridged-amide
m
d
53.2,
independent molecular structures of 1 contain the
respective Pd2N2 rings puckered with the dihedral angles of
53.1(2)ꢁ and 55.2(2)ꢁ. The PdePd distances are 2.9594(10)
and 2.9401(9) Å, respectively. The cation of complex 2
contains a puckered Pd2N2 ring with a dihedral angle of
28.8(0.15)ꢁ, which is smaller than that of 1. Therefore, the
PdePd distance 3.0669(8) Å in 2 is slightly larger. The
observed PdePd distances for 1 and 2 indicate that there is
no bonding between Pd and Pd [12], which are comparable
to the PtePt distances in the range of 3.087e3.134 Å,
observed in the NH2-bridged platinum(II) dimers, anti-
n
d
measurement for 2 in nitromethane reveals that the com-
plex is a 1:2 electrolyte (L ¼ 184 Uꢀ1 cm2 molꢀ1
,
M
[2] ¼ 0.50 ꢂ 10ꢀ3 M). The microanalytical data for 1 and 2
are consistent with the dimeric formulation (see Section 4).
2.1.2. Molecular structures of anti-[Pd(PEt3)(Ph)(m-NH2)]2 (1)
and [Pd(dppe)( -NH2)]2(OTf)2 (2)
m
The molecular structures of 1 and 2 were determined by
single-crystal X-ray crystallography (Figs. 1 and 2). Single
[Pt(POPh2)(PMePh2)(
m-NH2)]2
[4b],
[Pt(PMe2Ph)2(
m-NH2)]2 [5a]. The
m-
NH2)]22þ [4c], and anti-[PtMe(PPh3)(
Fig. 1. The molecular structure for one of the two crystallographically independent molecules of 1 shown with 40% thermal ellipsoids. For clarity hydrogen atoms
have been omitted.

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
617
Fig. 2. The structure of the cation of 2 shown with 40% thermal ellipsoids. The counter anions 2[CF3SO3]ꢀ and hydrogen atoms were omitted for clarity.
PdeN bond lengths for 1 and 2 are in the range of 2.067(7)e
2.127(7) Å. For the angles within the bridge about palla-
dium and nitrogen, the respective PdeNePd and NePdeN
bond angles are 88.8(3)e90.4(3)ꢁ and 77.7(3)e78.3(3)ꢁ for
1 and 95.0(2)e95.6(2)ꢁ and 79.2(2)e79.6(2)ꢁ for 2. The
selected bond lengths (in angstroms) and angles (in de-
grees) for complexes 1 and 2 are given in Tables 1 and 2,
respectively. For reference, all the X-ray crystallographic
data of 1 and 2 are provided in Supplementary Data,
including the crystal data, atomic coordinates and equiva-
lent isotropic displacement parameters, bond lengths and
angles, anisotropic displacement parameters, and
hydrogen coordinates and isotropic displacement
parameters.
2.2. Monomeric amido complex Pd(2,6-(Cy2PCH2)2C6H3)(NH2)
(3) and its reactivity
Because the formation of amido-bridged dimeric spe-
cies resulted from substitutional dimerization, a palladiu-
m(II) ammine complex containing
a trans-spanning
terdentate ligand was as a synthetic precursor for the
preparation of a monomeric parent-amido palladium(II)
complex. In a similar synthetic manner, as for 1, treatment
of
the
cationic
ammine
complex
[Pd(2,6-
(Cy2PCH2)2C6H3)(NH3)](OTf) with NaNH2 afforded the
Table 1
Selected bond lengths (Å) and angles (ꢁ) for one of the two crystallo-
graphically independent molecules of 1.
The amido-bridged dimeric complexes 1 and 2 in the
solid state and in solution are stable in air for a period of
days. No reactions with unsaturated molecules, such as
CO2, CH2]CHCN, dimethyl acetylenedicarboxylate, diethyl
maleate, and cyclohexene were observed, indicating a lack
of nucleophilicity of the bridging NH2. Considering the
observed stability, it is unanticipated that although the few
analogous platinum(II) dimers have been reported [4,5a],
the title complexes are, to the best of our knowledge, the
first structurally determined NH2-bridged palladium(II)
dimers [13].
Pd(1)eN(1)
Pd(1)eN(2)
Pd(2)eN(1)
Pd(2)eN(2)
2.104(7)
2.085(7)
2.067(7)
2.127(7)
Pd(1)eC(1)
Pd(2)eC(13)
Pd(1)eP(1)
Pd(2)eP(2)
2.000(9)
1.998(9)
2.233(3)
2.235(3)
Pd(2)eN(1)ePd(1)
Pd(1)eN(2)ePd(2)
N(2)ePd(1)eN(1)
N(1)ePd(2)eN(2)
C(1)ePd(1)eN(2)
C(1)ePd(1)eN(1)
C(1)ePd(1)eP(1)
90.4(3)
89.3(3)
77.8(3)
77.7(3)
93.5(3)
171.3(3)
89.0(3)
N(2)ePd(1)eP(1)
N(1)ePd(1)eP(1)
C(13)ePd(2)eN(1)
C(13)ePd(2)eN(2)
C(13)ePd(2)eP(2)
N(1)ePd(2)eP(2)
N(2)ePd(2)eP(2)
174.3(2)
99.5(2)
92.8(3)
170.4(3)
91.7(3)
175.1(2)
97.7(2)

618
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
ꢀ1.22 with the small value of 3J(PH) ¼ 3.3 Hz
Table 2
(PdeOH) at
d
Selected bond lengths (Å) and angles (ꢁ) for 2.
in the 1H NMR spectrum along with a single 31P NMR
resonance at d 48.7 [15,16]. For further characterization, the
Pd(1)eN(1)
Pd(1)eN(2)
Pd(2)eN(1)
Pd(2)eN(2)
2.089(6)
2.067(6)
2.069(6)
2.075(6)
Pd(1)eP(1)
Pd(1)eP(2)
Pd(2)eP(3)
Pd(2)eP(4)
2.255(2)
2.240(2)
2.240(2)
2.244(2)
hydroxo complex Pd(2,6-(Cy2PCH2)2C6H3)(OH) was pre-
pared independently by metathesis from Pd(2,6-
(Cy2PCH2)2C6H3)(OTf) and KOH in THF (see Section 4). The
Pd(2)eN(1)ePd(1)
Pd(1)eN(2)ePd(2)
N(2)ePd(1)eN(1)
N(1)ePd(2)eN(2)
N(2)ePd(1)eP(2)
N(1)ePd(1)eP(2)
N(2)ePd(1)eP(1)
95.0(2)
95.6(2)
79.6(2)
79.9(2)
93.4(2)
173.0(2)
179.1(2)
N(1)ePd(1)eP(1)
P(2)ePd(1)eP(1)
N(1)ePd(2)eP(3)
N(2)ePd(2)eP(3)
N(1)ePd(2)eP(4)
N(2)ePd(2)eP(4)
P(3)ePd(2)eP(4)
101.3(2)
85.69(7)
98.8(2)
174.6(2)
176.9(2)
98.1(2)
observed s-ligand exchange reaction of 3 with H2O com-
pares well with a previous report on the reactivity of a
parent-amido Ni(II) complex toward H2O [17]. Exposing the
complex 3 to an excess of water resulted in the immediate
conversion of the complex into two species, which exhibit
31P NMR resonance at
d 52.7 and d 54.7 (predominant),
83.03(8)
respectively. The former is assigned to the cationic ammine
species [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]þ, which was estab-
lished by the observation of an identical 31P{1H} NMR reso-
nance with the complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)](OTf).
The latter can be attributed to the cationic aqua complex
[Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]þ, as evidenced by the iden-
monomeric palladium(II) amide Pd(2,6-(Cy2PCH2)2C6H3)(NH2)
(3). When NaH was used as a deprotonating agent in place of
NaNH2, the reaction yielded a mixture of two products,
including mainly complex 3 along with a small amount of
palladium(II) hydride (2,6-(Cy2PCH2)2C6H3)PdH. The for-
mation of the palladium(II) hydride was verified by the
tical 31P{1H} NMR resonance at
d 54.7 with a complex pre-
pared from Pd(2,6-(Cy2PCH2)2C6H3)(BF4) and H2O in d6-
benzene. No formation of the hydroxo complex was observed
from the reaction of 3 with an excess of water. Therefore, the
observed results can be explained by a sequence of reactions
observation of upfield hydride resonance at
d
ꢀ3.73 (t,
2J(PH) ¼ 16 Hz) in the 1H NMR spectrum [8a,14]. On the
other hand, the metathetical replacement of the triflate
ligand in Pd(2,6-(Cy2PCH2)2C6H3)(OTf) with NaNH2 yielded
the monomeric palladium(II) amide, exclusively. Scheme 3
represents the used synthetic routes. The formation of
Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3) was established by the
involving the s-ligand exchange of the amido complex with
H2O to give the hydroxo complex, which then protonates
from excess water molecules to generate the observed
cationic aqua complex (Scheme 4). The formation of a small
amount of cationic ammine complex can be attributed to the
ligand substitution of the cationic aqua complex with the
liberated NH3.
A d6-benzene solution of 3 reacted with diphenyliodo-
nium triflate ([Ph2I]OTf) to give an N-phenylated amine
complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf (Scheme 4).
The formation of the cationic aniline complex was
confirmed by its independent preparation from a reaction
of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) with NH2Ph in d6-benzene
(see Section 4). The reaction of a d6-benzene solution of
Pd(2,6-(Cy2PCH2)2C6H3)(OTf) with NH2Ph produced
upfield shift of NH2 resonance at
d
ꢀ0.20 and the relative
intensity of the methylene protons in the pincer ligand and
NH2 resonances in the 1H NMR spectrum. On diluting a d6-
benzene solution of 3, the NH2 resonance shifts upfield,
implicating intermolecular hydrogen bonding in the
complexes.
Complex 3 is highly sensitive to air and moisture. The
monomeric amido complex slowly (over the course of
days) reacts with trace amounts of water to yield a hydroxo
complex Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4) (Scheme 4). The
hydroxo complex can be verified by the observation of
upfield triplet resonance for the coordinated hydroxide
+
PCy2
PCy2
PCy2
NaNH2
Pd NH3
NaNH2
THF
Pd NH2
Pd OTf
PCy2
THF
PCy2
PCy2
3
NaH
THF
PCy2
PCy2
Pd
PCy2
Pd NH2
H
+
PCy2
3
Scheme 3. Synthesis of Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3).

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
619
PCy2
Pd OH
PCy2
H2O (trace)
(4)
PCy2
Pd NH2
PCy2
(3)
PCy2
PCy2
H2O (excess)
+
Pd OH2
PCy2
Pd NH3
PCy2
[Ph2I]OTf
[Ph2I]Cl
(predominant)
PCy2
PCy2
Pd Cl
PCy2
NH2Ph
+
+ PhI
+
PhI
Pd NH2Ph
PCy2
(OTf)
Scheme 4. Reactions of 3 with H2O and [Ph2I]X (X ¼ OTf, Cl).
[Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf, displaying a rather
broad single 31P{1H} NMR resonance at
52.1 in accordance
1J(NH) ¼ 41 Hz) (Scheme 5) [17]. Complex 5 was prepared
from preparative scale experiment and fully characterized
(see Section 4). Complex 5 shows its characteristic ab-
d
with that of the species generated by the reaction of 3 with
[Ph2I]OTf. An attempt to isolate the cationic aniline species
was unsuccessful because of dissociation of the coordi-
nated aniline, converting to Pd(2,6-(Cy2PCH2)2C6H3)(OTf).
In the meanwhile, reaction of 3 with the chloride salt of
[Ph2I]Cl generated Pd(2,6-(Cy2PCH2)2C6H3)Cl along with
the released NH2Ph, which was identified by GCeMS
(NH2Ph: m/z ¼ 93, 66, 39).
sorption peak for the n
(C^C) at 2096 cmꢀ1 in the IR spec-
trum, and the 13C{1H} NMR resonances for the coordinated
acetylenide at
d
113.1 (t, PdeC^C, 2J(CP) ¼ 12 Hz) and at
d
118.3 (PdeC^C). These spectroscopic data are in good
agreement
with
those
reported
for
trans-
Pd(PEt3)2(C6H4eMe-p)(C^CPh) at 2092 cmꢀ1 in the IR, and
at
d
119.8 (t, PdeC^C, 2J(CP) ¼ 20 Hz) and at
d 111.3
The amido complex 3 reacted readily with phenyl-
acetylene (HC^CPh) to quantitatively yield a palladium(II)
acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(C^CPh) (5) along
with the liberation of ammonia, which was detected in the
(PdeC^C) in the 13C{1H} NMR spectrum [18]. The observed
reactivity for 3 toward phenylacetylene reveals that the
coordinated NH2 is highly basic for the complex to undergo
s
-ligand exchange via protonation rather than the migra-
1H NMR spectrum (broad 1:1:1 triplet, at
d
ꢀ0.15,
tory insertion of the C^C triple bond into the PdeNH2 via
PCy2
PCy2
PCy2
R
R
R
H
R
HOC6H4-p-NO2
RC CR
+
Pd NH2
PCy2
Pd
O
Pd
PCy2
(Z)-6a,6b
(R = CO2Me (6a), CO2Et (6b))
NH2
NH2
PCy2
cis
NO2
3
7
HC CPh
PCy2
NH3
Pd
C
CPh
+
PCy2
5
Scheme 5. Reactions of 3 with RC^CR (R ¼ CO2Me, CO2Et) and HC^CPh.

620
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
nucleophilic attack on the sp-carbon of HC^CPh. In view of
the thermodynamic aspect, the driving force for the for-
mation of the palladium(II) acetylenide parallels the rela-
tive ground state stability in the order of M-C(sp) > M-
NH2(sp3) or M-C(sp2, vinylic) [19,20].
Complex 3 undergoes clean reactions with activated
acetylenes, such as dialkyl acetylenedicarboxylate (RC^CR;
R ¼ CO2Me, CO2Et), to produce the diastereospecific
insertion derivatives of Pd(2,6-(Cy2PCH2)2C6H3)(CR]
CR(NH2)) (R ¼ CO2Me (6a), CO2Et (6b)) (Scheme 5). Com-
plexes 6a and 6b have been fully characterized by multi-
nuclear NMR (1H, 13C, and 31P) and fast atom bombardment
mass spectrometry (FABMS). The formation of aminovinylic
complexes was verified readily by the observation of res-
onances for the corresponding two methyl and two ethyl
groups for the moiety of Pd(CR]CR(NH2)) (R ¼ CO2Me,
CO2Et) in the 1H and 13C{1H} NMR spectra. The amino
stereoselective olefinic derivatives with retention of
configuration. In view of the importance of using ammonia
as a building block for the production of nitrogen-containing
compounds [6], this study on the reaction profile of the syn-
insertion of activated acetylene into the PdeNH2 bond in the
title complex is noteworthy. Prior examples of the syn-
insertion of alkynes and alkenes into the PdeN bonds have
rarely been found in arylamido complexes [21].
The insertion reaction of the C]C bond of dialkyl ma-
leate (cis-(CO2R)CH]CH(CO2R)) (R ¼ CH3, CH2CH3) into the
PdeNH2 bond of complex 3 was attempted, resulting in no
formation of the insertion derivatives. Instead, dialkyl
maleate isomerizes into dialkyl fumarate (trans-(CO2R)
CH]CH(CO2R)) in the presence of a catalytic amount of 3,
as evidenced by 1H NMR spectroscopy. The reaction pro-
ceeds rather slowly at ambient temperature, resulting in an
isomeric trans/cis ratio of 0.8 (for 4 h) and 8.9 (for 24 h) for
the dimethyl derivative (CO2Me)CH]CH(CO2Me). The
conversion of dialkyl maleate (cis-isomer) into dialkyl
fumarate (trans-isomer) was completed over a period of
5 days at ambient temperature. Similarly, a reaction of the
parent-amido complex 3 with cis-stilbene (cis-CHPh]
CHPh) was attempted, resulting in no reaction at ambient
temperature. On the other hand, at an increased tempera-
ture of 50 ꢁC, the complex 3 catalyzed the isomerization of
cis-stilbene to trans-stilbene, resulting in a trans/cis ratio of
2.0 for 2 h. No insertion product was observed in the course
of the catalytic isomerization. Isomerization did not occur
in the absence of the parent-amido complex. As a control,
no isomerization was observed in the reaction via a base,
such as NH3 or p-toluidine. The migratory insertion of the
cis-isomers into the PdeNH2 bond followed by deinsertion
cannot lead to the formation of trans-isomers because
rotation of the CeC single bond in the insertion species
erythro-Pd(CHXCHXNH2) cannot invert the configuration of
protons (NH2) resonate around d 3.9 as a broad peak, which
was confirmed by the D2O exchange experiment. In the 1H
NMR spectra, the virtual triplet methylene protons (PCH2)
in the PCP pincer ligand were observed to be diastereotopic
at
d
3.1 and 3.3 as
a
doublet of triplet
(2J(HaHb) ¼ 17.6 Hz,r2J(PH) þ 4J(PH)r y 8 Hz), respectively.
In solution, no coordination of the amino group in the
complex was observed, as evidenced by 1H and 31P{1H}
NMR spectroscopy; all signals were intact on the addition
of coordinating molecules, such as pyridine and PPh3, to the
d6-benzene solution of 6a and 6b. Endeavors to isolate
complexes 6a and 6b from solution were futile because of
the high solubility in most organic solvents including n-
pentane. Therefore, the removal of all volatiles from solu-
tion under high vacuum resulted in yellow solids, which
afforded satisfactory FABMS data, displaying a parent mo-
lecular ion peak in good accordance with the calculated
molecular weight in addition to the expected peaks
because of molecular fragmentation. Although the absolute
diastereomeric configuration of 6a and 6b could not be
determined because of the failure to obtain suitable single
crystals for an X-ray structural study, the stereochemistry
of complexes 6a and 6b (Z)-isomer was assigned by per-
forming subsequent reactions. A further reaction of 6a and
6b with an acidic phenol HOC6H4-p-NO2 produced only a
single isomeric product cis-CHR]CR(NH2) (R ¼ CO2Me,
CO2Et) with the retention of the configuration, along with
the b-carbon atom. Therefore, the observed diastereomeric
isomerization catalyzed by complex 3 can most likely be
explained by a sequence of reactions as follows. Migratory
insertion of the C]C bond of the cis-isomers into the
PdeNH2 bond leads to a transient aminoalkyl species
erythro-Pd(CHXCHXNH2), which undergoes
b-H elimina-
tion to generate a Pd(II)-hydride and cis-CHX]CXNH2. The
Pd(II)-hydride reacts with cis-CHX]CXNH2 with the
opposite regiochemistry to generate Pd(C(NH2)XCH2X), in
which the rotation of the CeC bond followed by elimina-
the
palladium(II)
p-nitrophenoxide
Pd(2,6-
(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) (Scheme 5). The for-
mation of Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) was
verified by its independent synthesis from the reaction of
Pd(2,6-(Cy2PCH2)2C6H3)(OTf) and Na(OC6H4-p-NO2) in THF
(see Section 4). As a control, reaction of a d6-benzene so-
lution of dialkyl acetylenedicarboxylate with gaseous
ammonia produces an isomeric mixture of cis- and trans-
(CHR]CR(NH2)). The diastereoselective formation of (Z)-
Pd(2,6-(Cy2PCH2)2C6H3)(CR]CR(NH2)) (6a, 6b) resulting
from the reaction of Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3) and
RC^CR implies that the insertion reaction presumably in-
volves a concerted pathway, apparently excluding disso-
ciative nucleophilic addition. The observed reactivity for
the palladium(II) aminovinylic complexes toward HOC6H4-
tion of the other b-H leads to the generation of a Pd(II)-
hydride again along with trans-CHX]CXNH2. The Pd(II)-
hydride reacts with trans-CHX]CXNH2 to afford threo-
Pd(CHXCHXNH2), from which the isomerized trans-olefin
can be released via deinsertion to regenerate complex 3. A
previous theoretical study demonstrated that
b-H elimi-
nation from the ammonioalkyl complexes of group 10
metals is kinetically competitive in the catalytic hydro-
amination of ethylene with ammonia [22].
A
stoichiometric reaction of
3 with acrylonitrile
(CH2CHCN) generated metastable insertion product,
a
Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2), which was detec-
ted by 1H and 31P NMR spectroscopy (Scheme 6). A d6-ben-
zene solution of the reaction mixture showed anticipating
proton resonances for the methyne (CH) and methylene
(CH2) protons of the PdeCH(CN)CH2NH2 moiety around at
p-NO2 in the ligand exchange reaction reveals that the
s-
vinylic ligand is more basic than the -phenoxide, liberating
s

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
621
d
2.2, 3.1, and 3.5 as multiplets in the 1H NMR spectrum and a
new single resonance at
49.0 in the 31P{1H} NMR spectrum.
catalytic reactions were typically performed at a fixed
concentration of olefin substrates (100 equiv) with various
d
The observed proton resonances of the Pd(CH(CN)CH2NH2)
moiety are in good agreement with those of the analo-
concentrations of NH3 in the presence of a catalyst
(1.0 equiv) for 12 h at 60 ꢁC. The results are summarized in
Table 3. For the catalytic hydroamination of acrylonitrile
(CH(CN)]CH2) with NH3 (entries 1e5), a range of hydro-
aminated products of primary (CH2(CN)CH2NH2), second-
ary ((CH2(CN)CH2)2NH), and tertiary ((CH2(CN)CH2)3N)
amines with different molar ratios were produced in an
overall yield of more than 99%, indicating that the produced
amine derivatives compete with ammonia as nucleophilic
substrates. The catalytic overall yield increased consider-
ably with increasing concentration of NH3 (entries 2e5).
The mole percent ratios of the produced amine derivatives
(primary/secondary) generally increased with increasing
concentration of ammonia (entries 3e5). On the other
gous
aminoalkyl
platinum(II)
complex,
Pt(2,6-
(Ph2PCH2)2C6H3)(CH(CN)CH2NHTol-p) at
d
2.75 (m, 1H,
CH), 3.08 (m, 1H, CHa), and 3.45 (m, 1H, CHb), respectively
[8b]. Attempts to isolate the insertion product from the
solution were unsuccessful because of decomposition to a
couple of unidentified species. The reaction of 3 with an
excess of acrylonitrile slowly produced polymeric species
of acrylonitrile at ambient temperature, which precipitated
in solution. The 31P NMR resonance at
d 49.0 because of an
aminoalkyl palladium(II) derivative observed at an early
stage of the reaction mostly disappeared to generate a
couple of new 31P NMR resonances, one at
d 59.2 corre-
sponding to a cationic acrylonitrile complex [Pd(2,6-
(Cy2PCH2)2C6H3)(CH2]CHCN)]þ (vide infra, catalytic
hydroamination of olefins with ammonia). The isolated
polymer from the reaction mixture shows the character-
hand, at a relatively low concentration of ammonia
compared to acrylonitrile (NH3/acrylonitrile ¼ 4/5), the
tertiary amine derivative ((CH2(CN)CH2)3N), 11 mol %) was
produced along with the predominant formation of sec-
ondary amine ((CH2(CN)CH2)2NH, 57 mol %) (entry 2).
Hydroaminated products were not produced at a signifi-
cantly low ratio of ammonia-to-acrylonitrile (NH3/
acrylonitrile ¼ 1/5, entry 1). For the hydroamination of
methyl acrylate (CH2]CHCO2Me) with ammonia, the re-
action rate considerably decreased in comparison with
those from acrylonitrile with ammonia, resulting in an
overall yield of 47% at 80 ꢁC for 18 days (entry 6). The
resulting products were only a mixture of the secondary
((CH2(CO2CH3)CH2)2NH, 83 mol %) and the tertiary
((CH2(CO2CH3)CH2)3N, 17 mol %) amines without the pri-
mary amine (CH2(CO2CH3)CH2NH2), apparently revealing
that the generated primary amine (more basic than NH3)
subsequently attacks methyl acrylate to produce the sec-
ondary amine predominantly. For the hydroamination of
crotononitrile (MeCH]CHCN, a mixture of cis- and trans-
isomer with a ratio of ca. 1.0) with ammonia (entries 7e9),
the reaction rate was much slower than that from acrylo-
nitrile (or methyl acrylate) with ammonia. On the other
hand, the resulting product was exclusively the primary
amine (CH2(CN)CH(CH3)NH2). No formation of the sec-
ondary and tertiary amines from the catalytic reaction can
be attributable mostly to the steric effect of the produced
primary amine. The catalytic hydroamination of other un-
saturated hydrocarbons, such as cyclohexene, styrene, 1-
hexene, 1-hexyne, and diphenylacetylene, with ammonia
was attempted without success.
istic absorption peaks for the n
(CN) at 2245 and 2204 cmꢀ1
and for the
trum. As
n
(NH2) at 3300 and 3360 cmꢀ1 in the IR spec-
control, the reaction of Pd(2,6-
a
(Cy2PCH2)2C6H3)(OTf) with an excess acrylonitrile gener-
ated [Pd(2,6-(Cy2PCH2)2C6H3)(CH2]CHCN)](OTf) without
producing any polymeric species. Therefore, the observed
results can be explained by a sequence of reactions
involving migratory insertion of the C]C bond of acrylo-
nitrile into the PdeNH2 bond at an early stages of the re-
action to generate a metastable aminoalkyl palladium(II)
complex, which undergoes the consecutive insertion of
acrylonitrile into the PdeC bond followed by the liberation
of polymeric species (Scheme 6). The present result is
comparable to a previous study on an aminoalkyl plati-
num(II) complex, which exhibited no further reactivity
toward acrylonitrile, and is in line with the migratory
insertion barriers for the
s-alkyl complexes in the order
Pd(II) < Pt(II) [23]. Attempted reactions of 3 with unac-
tivated olefins, such as 1-hexene, cyclohexene, and styrene,
were futile presumably because of the insufficient nucleo-
philicity of the coordinated amide along with the rigidity of
the sterically hindered pincer ligand in the title complex.
2.3. Catalytic hydroamination of olefins with ammonia
The catalytic hydroamination of various olefins with
NH3 was examined in the presence of Pd(2,6-
(Cy2PCH2)2C6H3)(OTf). Unless otherwise noted, the
PCy2
PCy2
PCy2
CN
CN
CH2 CHCN
nCH2 CHCN
Pd
PCy2
CN
Pd NH2
PCy2
Pd
PCy2
n
NH2
NH2
3
[Pd] + polymers
Scheme 6. Reaction of 3 with acrylonitrile.

622
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
Table 3
Hydroamination of olefins with NH3 catalyzed by Pd(2,6-(Cy2PCH2)2C6H3)(OTf).a
[Pd] (1.0 mol%)
n
+
CHR CHX
NH
(CH2X CHR) (NH ))
(R = H, Me; X = CN, C(O)OMe)
3
n
3-n
benzene
n = 1, 2, 3,
Entry
Olefin
NH3 (molar equivb or atm)
Overall yield (%)c
HA products (mol %)c
n ¼ 1
n ¼ 2
n ¼ 3
1
2
3
4
5
6
7
8
9
CH2]CHCN
CH2]CHCN
CH2]CHCN
CH2]CHCN
CH2]CHCN
CH2]CHCO2Me
MeCH]CHCNh
MeCH]CHCN
MeCH]CHCN
20d
0e
80d
12
17
20
>99
47g
11i
9
32
21
29
84
0
100
100
100
57
79
71
15
83
0
11
0
0
0
17
0
100d
120d
7 atmf
100d
300d
7 atmf
25 atmf
0
0
0
0
29
a
Reaction conditions: Pd(2,6-(Cy2PCH2)2C6H3)(OTf) (3.0 mg, 4.0 ꢂ 10ꢀ3 mmol), [olefin] ¼ 100 ꢂ [Pd].
b
c
d
e
f
Molar equivalent to [Pd].
1H NMR integration or GC-based yield for 12 h at 60 ꢁC, unless otherwise noted. The overall yield is relative to the olefin.
In a vacuum NMR tube.
For 24 h.
In a high pressure reactor.
For 18 days at 80 ꢁC.
150 equiv.
g
h
i
For 4.5 days.
For a mechanistic feature, further experiments were
hydroaminated products. No polymeric species was pro-
duced from the catalytic reaction.
conducted by NMR spectroscopy. The 1H NMR spectrum of
a CDCl3 solution of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) in the
presence of acrylonitrile with a slight excess displayed
broad resonances at ambient temperature. The variable
temperature experiments for the 1H NMR spectra of the
CDCl3 solution revealed a dynamic process attributable to
the rapid ligand exchange between the triflate and acry-
lonitrile in the complex (Fig. 3). The rate of exchange
process is fast on the NMR time scale at >10 ꢁC and de-
creases at low temperatures. The proton resonances for
the coordinated acrylonitrile cleanly resolved at ꢀ22 ꢁC,
indicating the formation of a stable olefinic complex in
solution. On the other hand, on the addition of a large
excess amount of acrylonitrile (ca. 30 equiv) into the so-
lution, the proton resonances for the free acrylonitrile
displayed well-resolved sharp peaks at ambient temper-
ature. The 31P{1H} NMR spectrum of this solution exhibi-
In the catalytic reaction, a mechanism involving the
coordination of ammonia to a palladium(II) sphere fol-
lowed by deprotonation to generate a parent-amido com-
plex can be excluded because polymeric species, which
could be derived from a migratory insertion derivative of
palladium(II), that is, an aminoalkyl complex, was not
formed from the catalytic reaction (vide supra). A further
experiment to examine the ability of ammonia to
deprotonate the coordinated ammonia in [Pd(2,6-
(Cy2PCH2)2C6H3)(NH3)](OTf) was conducted. The treat-
ment of the amido complex 3 with NH4OTf in d6-benzene
produced [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)](OTf) and NH3,
quantitatively, as evidenced by 1H and 31P{1H} NMR
spectroscopy, apparently excluding the involvement of a
Pd(II) amido species in the catalytic reaction. Therefore,
the present catalytic reaction may proceed via the
nucleophilic attack of ammonia on the precoordinated
ted a sharp single resonance at d 59.4, which is assignable
to the cationic acrylonitrile complex [Pd(2,6-
(Cy2PCH2)2C6H3)(CH2]CHCN)](OTf) analogous to the re-
ported platinum(II) complexes [8b]. Attempts to isolate
the olefinic complex from the solution were unsuccessful
because of conversion into the palladium triflate Pd(2,6-
(Cy2PCH2)2C6H3)(OTf). The resulting cationic olefin com-
plex is stable in solution in the presence of excess acry-
lonitrile for a period of several days at ambient or
increased temperature (60 ꢁC) without producing poly-
meric species or any other side products. The addition of
NH3 (excess) to this solution, however, immediately
generated the cationic ammine complex [Pd(2,6-
(Cy2PCH2)2C6H3)(NH3)](OTf) along with the acrylonitrile
complex. Subsequently, the reaction mixture slowly un-
dergoes a catalytic reaction to produce a mixture of
olefin to palladium(II) to generate a transient alky-
lammonium complex [Pd(2,6-(Cy2PCH2)2C6H3)(CH2(CN)
CH2NH3)]þ in parallel to a previous report on catalytic
hydroamination by platinum(II) catalysts [8b]. A high
concentration of ammonia would act as a base to transfer
a proton from the suggested species to produce hydro-
aminated products (pathway A in Scheme 7). The relative
stabilities of the
s-donor amine versus the p-olefinic
acrylonitrile complexes showed that acrylonitrile practi-
cally competes with amine in the coordination spheres of
palladium(II) [24] and platinum(II) [8b,25]. The nucleo-
philic addition of amines on the coordinated olefin to
palladium(II) complexes has been well recognized [26].
An alternative pathway for the catalytic reaction likely
involves
a 5-coordinate Pd(IV)-hydride species, from

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
623
Fig. 3. The VT 1H NMR spectra of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) in the presence of CH2]CHCN in CDCl3 show that there is a fast ligand exchange between the
triflate and acrylonitrile in the complex on the NMR time scale at >10 ꢁC. The resonances of the coordinated acrylonitrile resolve at ꢀ22 ꢁC, being marked with
arrows.
which CeH reductive elimination leads to hydroaminated
products (pathway B in Scheme 7). Previous computa-
tional studies of the hydroamination of ethylene with
ammonia or aniline catalyzed by d8-metal complexes
illustrated that intramolecular transfer of an alky-
lammonium proton to the metal center to generate a 5-
coordinate (16-electron) metal-hydride intermediate is
energetically feasible [22,27]. Scheme 7 presents plau-
sible reaction pathways for the observed catalytic
hydroamination of olefins with ammonia in the presence
of the title complex.
parent-amido
showed the strong nucleophilicity of the coordinated
amide toward a range of electrophiles to undergo -ligand
complex
Pd(2,6-(Cy2PCH2)2C6H3)(NH2)
s
exchange or addition reactions with activated acetylenes
and olefins to yield diastereo- and regiospecific aminated
derivatives of palladium(II) complexes. The palladium(II)
triflate Pd(2,6-(Cy2PCH2)2C6H3)(OTf) catalyzes the hydro-
amination of olefins with ammonia to produce a range of
amine derivatives. A mechanistic feature for the observed
catalytic reaction was discussed with respect to the probed
aminoalkyl derivative of palladium(II).
3. Summary
4. Experimental
Novel parent-amido complexes of palladium(II) anti-
4.1. General methods and materials
[Pd(PEt3)(Ph)(m-NH2)]2, [Pd(dppe)(m-NH2)]2(OTf)2, and
Pd(2,6-(Cy2PCH2)2C6H3)(NH2) were prepared from the
respective ammine complexes by deprotonation of the
coordinated ammonia. The amido-bridged dimeric com-
plexes are inert to unsaturated molecules, such as CO2,
All preparations of air sensitive compounds were per-
formed on a standard Schlenk line or in an inert atmo-
sphere glovebox under argon. THF and diethyl ether were
freshly distilled from sodium/benzophenone ketyl under
nitrogen and then stored over molecular sieves. Benzene,
n-hexane, and n-pentane were distilled from sodium/
activated olefins, and acetylenes, revealing
a lack of
nucleophilicity of the bridging NH2. The monomeric

624
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
PCy2
Pd NH3
PCy2
R = H, Me
NH3 CHR=CHX
X = CN, C(O)OMe
CH2XCHRNH 2
PCy2
Pd
PCy2
Pd
X
X
R
CHR=CHX
NH3
R
CHR=CHX
H
PCy2
NH2
PCy2
CH2XCHRNH 2
NH3
NH4
B
PCy2
Pd
PCy2
Pd
A
X
X
R
R
H
PCy2
NH2
PCy2
NH3
PCy2
Pd
X
NH2
PCy2
R
NH3
NH4
Scheme 7. Plausible reaction pathways for the observed hydroamination of olefins with ammonia in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), involving an
aminoalkyl Pd(II) species (pathway A) or a Pd(IV) hydride (pathway B).
benzophenone ketyl in the presence of tetraglyme. CH2Cl2
was dried by refluxing over LiAlH4 or CaH2 under N2. PdCl2
was supplied by the Pressure Chemical Company and used
(80.950 MHz)), using the deuterium signal of the solvent as
the internal lock frequency. The chemical shifts for 1H and
13C{1H} NMR are reported in parts per million (
d) relative
as received. 1,5-Cyclooctadiene, dppe, AgOTf, NH4OTf,
a
,
a0
-
to TMS (Me4Si). For 19F{1H} and 31P{1H} NMR spectroscopy,
the chemical shifts were measured in parts per million
dibromo-m-xylene, dimethyl acetylenedicarboxylate (dmad),
diethyl acetylenedicarboxylate (dead), phenylacetylene,
acrylonitrile, dimethyl maleate, diethyl maleate, cis-stil-
bene, and NMR solvents (CDCl3, C6D6) were purchased
from Aldrich Chemical Company and used as supplied.
Dicyclohexylphosphine was obtained from Strem Chem-
icals Inc. All other reagents were acquired from various
commercial companies. Pd(dppe)Cl2 was prepared by the
displacement of cyclooctadiene from Pd(cod)Cl2 with
dppe. Complexes of trans-Pd(PEt3)2(Ph)Cl [28], Pd(2,6-
(Cy2PCH2)2C6H3)(OTf) [29], trans-[Pd(PEt3)2(Ph)(NH3)]
relative to external perfluoromethylbenzene (
d
¼ ꢀ63.73)
and 85% H3PO4 in a sealed capillary, respectively. GCeMS
was performed using an HP 6890 gas chromatograph
equipped with an HP 5973 MSD and an HP-Ultra 1 column
(Crosslinked Methyl Silicone Gum, 50 m ꢂ 0.2 mm,
0.33
mm film thickness). The injection temperature was
250 ꢁC, and the column temperature ramped from 40 to
250 ꢁC at 10ꢁ/min. The conductivity measurements were
taken using a TOA conductivity meter (CM-40S). Nitro-
methane was used as the solvent in a cell containing
OTf,
[Pd(dppe)(NH3)2](OTf)2,
and
[Pd(2,6-
platinized electrodes (cell constant
Elemental analyses were performed at the Korea Basic
Science Institute in Seoul, Korea.
¼
1.014 cmꢀ1).
(Cy2PCH2)2C6H3)(NH3)]OTf were prepared using the pro-
cedures reported elsewhere [30].
4.2. Physical measurements
4.3. Synthesis
The IR spectra were recorded on a Bruker (Tensor 37) FT-
IR spectrometer, as a pressed KBr pellets. The 1H, 13C{1H},
19F{1H}, and 31P{1H} NMR spectra were measured on a
4.3.1. anti-[Pd(PEt3)(Ph)(m-NH2)]2 (1)
In a glovebox under an argon atmosphere, a mixture of
trans-[Pd(PEt3)2(Ph)(NH3)]OTf (500 mg, 0.85 mmol) and
NaNH2 (150 mg, 3.8 mmol) was stirred in THF (20 mL) for
6 h at ambient temperature. The color of the reaction
Varian Gemini-2000 spectrometer (1H (199.975 MHz), 13
C
{1H} (50.288 MHz), 19F{1H} (188.140 MHz), 31P{1H}

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
625
suspension was changed slowly from light gray to deep
4.4. Stoichiometric reactions of 3 with various electrophiles
gray during the course of the reaction. The resulting sus-
pension was filtered under vacuum to give a pale yellow
solution. The removal of all volatiles from the filtrate
under high vacuum resulted in yellow residues, which
were extracted with n-pentane (4 ꢂ 10 mL) to give a pale
yellow solution. The volume of solution was reduced to ca.
10 mL to slowly give colorless precipitates, which were
filtered, washed with cold n-pentane, and dried in vacuo.
The NMR sample preparation for the stoichiometric
reactions of complex 3 with various electrophiles was
performed in a glovebox under an argon atmosphere. An
NMR sample was prepared by the addition of reactant into
a d6-benzene solution of 3 using a 5 mm screw-capped
NMR tube (Wilmad, 528-TR) or a 5 mm vacuum NMR
tube (Wilmad, 507-LPV). The reaction products were
analyzed by NMR (1H, 13C, 19F, and 31P) spectroscopy and
GCeMS.
Yield 176 mg (65%). IR (KBr):
n
(NH) ¼ 3238, 3367 cmꢀ1 (w,
br). 1H NMR (C6D6):
d
ꢀ1.35 (br, 4H, NH2),
d 0.93 (m, 18H,
CH3),
d 1.09 (m, 12H, CH2), d 7.08 (t, 2H, p-CH (Ph),
3J(HH) ¼ 7.3 Hz),
d
7.26 (t, 4H, m-CH (Ph), 3J(HH) ¼ 7.3 Hz),
4.4.1. Reaction of 3 with H2O to yield Pd(2,6-(Cy2PCH2)2C6H3)
(OH) (4)
d
7.78 (d, 4H, o-CH (Ph), 3J(HH) ¼ 7.3 Hz). 13C{1H} NMR
(C6D6):
d
8.22 (s, CH3),
d
15.61 (d, CH2, 1J(CP) ¼ 26.7 Hz),
A d6-benzene (0.3 mL) solution of 3 (ca. 10 mg) in a
5 mm screw-capped NMR tube prepared in a glovebox was
removed and stored at ambient temperature. The reaction
was monitored by 1H and 31P NMR spectroscopy, showing
that complex 3 reacts slowly (over a period of days) with
trace amounts of H2O in solution to give Pd(2,6-
(Cy2PCH2)2C6H3)(OH) (4). The hydroxo complex Pd(2,6-
(Cy2PCH2)2C6H3)(OH) can be prepared independently by a
reaction of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) with KOH in THF.
The prepared hydroxo complex was characterized by 1H
and 31P NMR spectroscopy. For the microanalytical data,
the hydrogen content was in good agreement with the
calculated values but the carbon value was deviated slightly
from an acceptable range because of its instability in air.
The data is included as a reference. Treatment of the d6-
benzene solution of 3 with an excess of water resulted in
d
122.3, 127.1, 137.6. 31P{1H} NMR (C6D6):
d 20.2 (s). Anal.
Calcd for C24H44N2P2Pd2: C, 45.4; H, 6.98; N, 4.41. Found:
C, 45.1; H, 6.84; N, 4.20.
4.3.2. [Pd(dppe)(m-NH2)]2(OTf)2 (2)
NaNH2 (170 mg, 4.36 mmol) was added to a stirred so-
lution of [Pd(dppe)(NH3)2](OTf)2 (1.20 g, 1.43 mmol) in THF
at ꢀ78 ꢁC (dry ice/acetone). The reaction mixture was
stirred for 2 h. The solvent was evaporated to dryness
under high vacuum at ca. ꢀ20 ꢁC (caution should be taken
at this step that the solution temperature should be
controlled so as not to exceed more than ꢀ20 ꢁC while the
solvent was removed, otherwise the color of the solution
changed rapidly from colorless to deep-purple, resulting
in decomposed species; see Section 2). The residue was
extracted with CH2Cl2 (3 ꢂ 5 mL) giving a pale yellow
solution. The solution volume was reduced to ca. 3 mL.
The addition of diethyl ether (10 mL) to the concentrated
solution gave colorless crystals, which were washed with
diethyl ether and dried in vacuo. Yield: 642 mg (67%). IR
two species, exhibiting the 31P NMR resonances at
(minor) and 54.7 (predominant). The former can be
attributed to cationic ammine species [Pd(2,6-
(Cy2PCH2)2C6H3)(NH3)]þ by the observation of identical 31
{1H} NMR to that of [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)](OTf) at
52.7 in d6-benzene. The latter was attributed to cationic
aqua complex [Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]þ, as evi-
denced by the identical 31P{1H} NMR at
54.7 to a complex
d 52.7
a
P
(KBr):
n
(NH) ¼ 3250, 3360 cmꢀ1 (w, br),
n
(SO3) ¼ 1154,
d
1266 (s, br). 1H NMR (CDCl3):
d
ꢀ0.19 (br, 4H, NH2),
d
2.52
(m, 8H, CH2),
(CDCl3):
Calcd for C54H52F6N2O6P4Pd2S2: C, 48.41; H, 3.91; N, 2.09;
S, 4.79. Found: C, 48.10; H, 4.11; N, 1.77; S, 4.73.
d
7.4e7.7 (m, 40H, Ph). 31P{1H} NMR
d
d
53.2 (s) 19F{1H} NMR (CDCl3):
d
ꢀ78.9 (s). Anal.
prepared from Pd(2,6-(Cy2PCH2)2C6H3)(BF4) and H2O in d6-
benzene. For Pd(2,6-(Cy2PCH2)2C6H3)(OH), 1H NMR (C6D6):
ꢀ1.22 (t,1H, OH, 3J(PH) ¼ 3.3 Hz), 0.8e2.5 (m, 44H, Cy), 3.00
(vt, 4H, CH2, r2J(PH) þ 4J(PH)r ¼ 8.2 Hz), 7.1 (m, 3H,
L
M
¼ 184
U
ꢀ1 cm2 molꢀ1 (CH3NO2, [Pd] ¼ 0.50 ꢂ 10ꢀ3 M).
CH(aryl)). 31P{1H} NMR (C6D6):
d 48.7 (s). Anal. Calcd for
4.3.3. Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3)
C32H52O1P2Pd: C, 61.9; H, 8.44. Found: C, 59.3; H, 8.64. For
Under similar reaction conditions as for complex 1, a
mixture of [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]OTf (500 mg,
0.65 mmol) and NaNH2 (100 mg, 2.6 mmol) was stirred in
THF (30 mL). The color of the reaction mixture was changed
slowly from light gray to pale yellow during the course of
the reaction. After 4 h, the resulting mixture was filtered
under vacuum to give a yellow solution. The removal of all
volatiles from the filtrate under high vacuum resulted in
orange residues, which were extracted with n-hexane
(4 ꢂ 5 mL) to give a pale yellow solution. The removal of
solvent from the extracted solution under high vacuum
[Pd(2,6-(Cy2PCH2)2C6H3)(NH3)](OTf): 31P{1H} NMR: 52.7 (s,
C6D6), 52.4 (s, CDCl3).
4.4.2. Reaction of 3 with [Ph2I](SO3CF3) or [Ph2I]Cl
A slight excess amount of [Ph2I]OTf or [Ph2I]Cl was
added to a d6-benzene (0.3 mL) solution of 3 (15 mg,
0.024 mmol) in a 5 mm screw-capped NMR tube. The re-
action of 3 with [Ph2I]OTf produced a cationic aniline
complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf, which was
confirmed by its independent preparation from the reac-
tion of Pd(2,6-(Cy2PCH2)2C6H3)OTf and NH2Ph, showing an
gave
a
spectroscopically pure compound of Pd(2,6-
identical 31P NMR peak at
d 52.1 in d6-benzene. On the
(Cy2PCH2)2C6H3)(NH2). Yield 270 mg (68%). Spectral data
other hand, attempts at isolating the cationic aniline spe-
cies were unsuccessful because of dissociation of the co-
for Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (4): 1H NMR (C6D6):
d
ꢀ0.20 (br, 2H, NH2),
d
1.0e2.4 (m, 44H, Cy),
d
3.10 (vt, 4H,
ordinated
(Cy2PCH2)2C6H3)(OTf), which displays a single 31P{1H} NMR
at 54.5 in d6-benzene. The reaction of 3 with [Ph2I]Cl
aniline
converting
to
Pd(2,6-
CH2, r2J(PH) þ 4J(PH)r ¼ 8.4 Hz),
d
7.08 (m, 3H, CH(aryl)). 31
P
{1H} NMR (C6D6):
d
50.7 (s).
d

626
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
produced Pd(2,6-(Cy2PCH2)2C6H3)Cl (31P{1H} NMR (C6D6):
calcd
for
C
38H59NO4P2Pd,
761.30.
For
Pd(2,6-
d
52.3) along with the liberated NH2Ph (GCeMS: m/z ¼ 93,
(Cy2PCH2)2C6H3)((EtO2C)C]C(CO2Et)(NH2)) (6b): 1H NMR
66, 39).
(C6D6): d 1.0e2.4 (m, 44H, Cy), d 1.08 (t, 3H, CH3,
3J(HH) ¼ 7.1 Hz),
d
1.34 (t, 3H, CH3, 3J(HH) ¼ 7.1 Hz),
d 4.12 (q,
4.4.3. Reaction of 3 with phenylacetylene to yield Pd(2,6-
(Cy2PCH2)2C6H3)(C^CPh) (5)
2H, CH2, 3J(HH)
¼
7.1 Hz),
d
4.31 (q, 2H, CH2,
3J(HH)
¼
7.1
Hz),
d
3.10
(dt,
Ha,
CH2,
A slight excess of phenylacetylene (HC^CPh) was added
to a d6-benzene (0.3 mL) solution of 3 (15 mg, 0.024 mmol)
in a 5 mm screw-capped NMR tube. The reaction proceeded
readily, in 30 min, to yield the palladium(II) acetylenide
Pd(2,6-(Cy2PCH2)2C6H3)(C^CPh) (5), quantitatively. The
acetylenido complex is extremely soluble in conventional
organic solvents including n-pentane. Therefore, the
removal of all volatiles from the reaction mixture resulted
in a pale yellow solid, which was characterized by IR and
NMR (1H, 13C{1H}, 31P{1H}) spectroscopy. A preparative
scale experiment for this reaction was conducted in a glo-
vebox as follows: an excess amount of phenylacetylene
(0.02 g, 0.38 mmol) was added to a benzene solution of 3
(150 mg, 0.24 mmol). The reaction mixture was stirred for
1 h. All volatiles were removed under high vacuum to give
yellowish residues. The residues were dissolved in n-
pentane. The n-pentane solution was filtered through a
Celite column to give a pale yellow solution. The resulting
solution was dried completely under high vacuum to
remove all volatiles, yielding an analytically pure com-
pound of Pd(2,6-(Cy2PCH2)2C6H3)(C^CPh). Spectral data
for Pd(2,6-(Cy2PCH2)2C6H3)(C^CPh) (5): IR (KBr):
2J(HaHb) ¼ 17.6 Hz,r2J(PH) þ 4J(PH)r ¼ 8.3 Hz),
d 3.30 (dt, Hb,
CH2, 2J(HaHb) ¼ 17.6 Hz,r2J(PH) þ 4J(PH)r ¼ 8.3 Hz),
d 3.94
(br, 2H, NH2),
d
7.21 (m, 3H, CH(aryl)). 13C{1H} NMR (C6D6):
d
14.47, 15.15 (CO2CH2CH3),
d
58.98, 60.30 (CO2CH2CH3),
51.9
d
162.08, 176.09 (CO2CH2CH3). 31P{1H} NMR (C6D6):
d
(s). FABMS (observed m/z 789.25): calcd for
40H63NO4P2Pd, 789.33.
C
4.4.5. Reaction of (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CR]CR(NH2))
(R ¼ CO2Me (6a), CO2Et (6b)) with HOC6H4-p-NO2 to yield cis-
CHR]CR(NH2) (R ¼ CO2Me, CO2Et) and Pd(2,6-
(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7)
HOC6H4-p-NO2 (5 mg) was added to a d6-benzene
(0.3 mL) solution of 6a or 6b (ca. 15 mg) in a 5 mm screw-
capped NMR tube. The reaction proceeded quantitatively to
produce cis-CHR]CR(NH2) (R ¼ CO2Me, CO2Et) and Pd(2,6-
(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7). All products were
analyzed by 1H and 31P NMR spectroscopy, and GCeMS. The
p-nitrophenoxide complex Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-
p-NO2) (7) was prepared independently from an equimolar
reaction of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) and NaOC6H4-p-
NO2 in THF. For cis-((MeO2C)CH]C(CO2Me)(NH2)): 1H NMR
n
(C^C) ¼ 2096 cmꢀ1 1H NMR (C6D6):
d
1.0e2.4 (m, 44H,
(C6D6):
d 3.15 (s, 3H, CH3), d 3.44 (s, 3H, CH3), d 5.77 (s, 1H,
Cy),
d
3.20 (vt, 4H, CH2, r2J(PH) þ 4J(PH)r ¼ 8.1 Hz),
d
7.00 (t,
7.21
CH). GCeMS: m/z ¼ 159, 128, 100, 68, 59. For cis-((EtO2C)
1H, p-H(Ph), 3J(HH) ¼ 7.4 Hz),
d
7.2 (m, 3H, CH (aryl)),
d
CH]C(CO2Et)(NH2)): 1H NMR (C6D6):
d 0.78 (t, 3H, CH3,
(m, 2H, m-H(Ph)),
d
7.74 (d, 2H, o-H(Ph), 3J(HH) ¼ 7.0 Hz).
3J(HH) ¼ 7.13 Hz),
d
1.02 (t, 3H, CH3, 3J(HH) ¼ 7.13 Hz),
d 3.79
13C{1H} NMR (C6D6):
d
113.1 (t, PdeC^CPh, 2J(CP) ¼ 12 Hz),
(q, 2H, CH2, 3J(HH)
¼
7.13 Hz), d 4.07 (q, 2H, CH2,
d
118.3 (PdeC^CPh). 31P{1H} NMR (C6D6):
d
56.4 (s). Anal.
3J(HH) ¼ 7.13 Hz),
5.84 (s, 1H, CH). GCeMS: m/z ¼ 187, 142,
d
Calcd for C40H56P2Pd: C, 68.1; H, 8.00. Found: C, 68.5; H,
7.89.
114, 86, 68. For Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7):
IR (KBr):
n
(NO) ¼ 1583, 1303 cmꢀ1 (sh, s). 1H NMR (C6D6):
d
0.9e2.1 (m, 44H, Cy),
d
2.84 (vt, 4H, CH2, r2J(PH) þ 4J(PH)
4.4.4. Reaction of 3 with dialkyl acetylenedicarboxylate
(RC^CR; R ¼ CO2Me, CO2Et) to yield (Z)-Pd(2,6-
r ¼ 8.4 Hz),
d
6.88 (d, 2H, 3J(HH) ¼ 9.2 Hz),
d 8.49 (d, 2H,
3J(HH) ¼ 9.2 Hz). 31P{1H} NMR (C6D6):
d 50.7 (s). Anal. Calcd
(Cy2PCH2)2C6H3)(CR]CR(NH2)) (R ¼ CO2Me (6a), CO2Et (6b))
for C38H55NO3P2Pd: C, 61.5; H, 7.47; N, 1.89. Found: C, 61.1; H,
7.52; N, 1.58.
To
a d6-benzene (0.3 mL) solution of 3 (15 mg,
0.024 mmol) in a 5 mm screw-capped NMR tube was added
a slight excess of dialkyl acetylenedicarboxylate (RC^CR;
R ¼ CO2Me, CO2Et: 0.032 mmol; 0.1 mL of a diluted d6-
benzene solution, which was prepared by the addition of
dmad (46 mg) or dead (54 mg) into 1.0 mL of d6-benzene).
The insertion product Pd(2,6-(Cy2PCH2)2C6H3)(CR]
CR(NH2)) was formed quantitatively from the reaction,
which was monitored by NMR spectroscopy. The product
was barely isolated from the solution because of its high
solubility in most organic solvents. Therefore, the removal
of all volatiles from the solution under high vacuum
resulted in yellow solids, which afforded satisfactory
FABMS data. For Pd(2,6-(Cy2PCH2)2C6H3)((MeO2C)C]
4.4.6. Reaction of dialkyl acetylenedicarboxylate with ammonia
Anhydrous gaseous ammonia was bubbled into a d6-
benzene (0.3 mL) solution of dialkyl acetylenedicarboxylate
(dmad, dead; ca. 20 mg, respectively) for ca. 30 s in a 5 mm
screw-capped NMR tube. The reaction produced an
isomeric mixture of cis- and trans-(CHR]CR(NH2)) in a
trans/cis ratio of ca. 1.3. For trans-((MeO2C)CH]
C(CO2Me)(NH2)): 1H NMR (C6D6):
(s, 3H, CH3), 4.80 (s, 1H, CH). For trans-((EtO2C)CH]
d 3.42 (s, 3H, CH3), d 3.59
d
C(CO2Et)(NH2)): 1H NMR (C6D6):
d 0.75 (t, 3H, CH3,
3J(HH) ¼ 7.13 Hz),
d
1.01 (t, 3H, CH3, 3J(HH) ¼ 7.13 Hz),
d 3.37
(q, 2H, CH2),
d 4.08 (q, 2H, CH2), d 4.90 (s, 1H, CH). For cis-
C(CO2Me)(NH2)) (6a): 1H NMR (C6D6):
d
1.0e2.4 (m, 44H,
3.10 (dt, Ha, CH2,
3.31 (dt, Hb,
((MeO2C)CH]C(CO2Me)(NH2))
and
cis-((EtO2C)CH]
Cy),
d
3.49 (s, 3H, CH3),
d
3.73 (s, 3H, CH3),
d
C(CO2Et)(NH2)) refer to the preceding experiment.
2J(HaHb) ¼ 17.6 Hz,r2J(PH) þ 4J(PH)r ¼ 7.9 Hz),
d
CH2, 2J(HaHb) ¼ 17.6 Hz,r2J(PH) þ 4J(PH)r ¼ 7.9 Hz),
d
3.89
4.4.7. Reaction of 3 with dialkyl maleate (cis-(CO2R)CH]
CH(CO2R)) (R ¼ CH3, CH2CH3)
(br, 2H, NH2), d
7.21 (m, 3H, CH (aryl)). 13C{1H} NMR (C6D6):
d
50.53, 51.45 (s, CO2CH3),
d
162.08, 176.40 (CO2CH3). 31P
An excess of dialkyl maleate (cis-(CO2R)CH]CH(CO2R),
R ¼ CH3, CH2CH3) was added to a d6-benzene (0.3 mL)
{1H} NMR (C6D6):
d
51.7 (s). FABMS (observed m/z 761.22):

Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
627
solution of 3 (15 mg, 0.024 mmol) in a 5 mm screw-capped
4.5. A typical procedure for catalytic hydroamination of
NMR tube. The dialkyl maleate slowly isomerizes to dialkyl
fumarate (trans-(CO2R)CH]CH(CO2R), R ¼ CH3, CH2CH3) in
the presence of catalytic amounts of 3 at ambient temper-
ature, as evidenced by 1H NMR spectroscopy. After 4 h, the
observed trans/cis ratio was 0.8 (for R ¼ Me) and 0.7 (for
R ¼ Et), respectively. After 24 h, the trans/cis ratio was 8.9
(for R ¼ Me). The conversion of dialkyl maleate (cis-isomer)
into dialkyl fumarate (trans-isomer) was complete in 5
olefins with ammonia
The catalytic hydroamination of olefins with ammonia
in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) was
performed in two ways. Method A using a 5 mm vacuum
NMR tube (Wilmad, 507-LPV): anhydrous ammonia was
introduced into a d6-benzene (0.5 mL) solution of Pd(2,6-
(Cy2PCH2)2C6H3)(OTf) (3 mg, 3.98 ꢂ 10ꢀ3 mmol) and
CH2]CHCN (0.026 mL, 3.98 ꢂ 10ꢀ1 mmol) in a 5 mm
vacuum NMR tube, which was precooled and evacuated
via several freeze and thaw cycles. The molar ratio of
CH2]CHCN/NH3 was calculated by integrating the cor-
responding resonance peaks in the 1H NMR spectrum of
the prepared sample. The NMR sample was kept in sili-
cone oil for 12 h at 60 ꢁC. After cooling the sample, the
reaction products were analyzed by 1H NMR spectros-
copy and GCeMS. For GCeMS analysis, the reaction
days.
CH(CO2CH3)): 1H NMR (C6D6):
2H, CH). For dimethyl fumarate (trans-(CO2CH3)CH]
CH(CO2CH3)): 1H NMR (C6D6):
3.25 (s, 6H, CH3), 6.87 (s,
2H, CH). For diethyl maleate (cis-(CO2CH2CH3)CH]
For
dimethyl
maleate
(cis-(CO2CH3)CH]
d
3.35 (s, 6H, CH3),
d
5.71 (s,
d
d
CH(CO2CH2CH3)): 1H NMR (C6D6):
d 0.96 (t, 6H, CH3,
3J(HH) ¼ 9.2 Hz),
d
3.98 (q, 4H, CH2, 3J(HH) ¼ 9.2 Hz),
d 5.77
(s, 2H, CH). For diethyl fumarate (trans-(CO2CH2CH3)CH]
CH(CO2CH2CH3)): 1H NMR (C6D6):
d 0.89 (t, 6H, CH3,
3J(HH) ¼ 7.6 Hz),
(s, 2H, CH).
d
3.88 (q, 4H, CH2, 3J(HH) ¼ 7.6 Hz),
d
6.91
mixture was transferred to a short glass-column
(0.7 ꢂ 15 cm) packed with alumina (ca. 1 cm). Eluting
the mixture with diethyl ether resulted in a clear pale
yellow solution, which was analyzed by GCeMS. Method
B using a high pressure reactor (Carl Roth, Model 1,
4.4.8. Reaction of 3 with cis-stilbene
An excess of cis-stilbene (cis-CHPh]CHPh) was added
to a d6-benzene (0.3 mL) solution of 3 (15 mg, 0.024 mmol)
in a 5 mm screw-capped NMR tube. No reaction occurred
at ambient temperature for 10 h. At an increased tem-
perature of 50 ꢁC (in a silicone oil bath), however, cis-
stilbene isomerized catalytically to trans-stilbene in the
presence of 3: trans/cis ¼ 2.0 for 2 h. For cis-stilbene (cis-
100 mL):
a mixture of Pd(2,6-(Cy2PCH2)2C6H3)(OTf)
(3 mg, 3.98 ꢂ 10ꢀ3 mmol) and CH2]CHCN (0.026 mL,
3.98 ꢂ 10ꢀ1 mmol) in d6-benzene (0.5 mL) was loaded in
a glass linear equipped with a high pressure reactor. The
reactor was then cooled at ꢀ15 ꢁC (ice/NaCl) and evacu-
ated. Anhydrous ammonia gas was introduced into the
reactor for 5 min at 0 ꢁC to reach a pressure of 8 atm.
When reactor temperature was increased to 60 ꢁC, the
pressure increased to 25 atm. The reaction mixture was
stirred for 12 h at 60 ꢁC. After cooling the reactor in an ice
bath, gaseous ammonia was removed from the reactor in
a well ventilating hood. The reaction products were
analyzed by 1H NMR spectroscopy and GCeMS in a
similar manner. Spectral data for CH2(CN)CH2NH2, 1H
CHPh]CHPh), 1H NMR (C6D6):
d 6.49 (s, (2H, CH). For
trans-stilbene (trans-CHPh]CHPh), 1H NMR (C6D6):
(s, 2H, CH).
d 7.02
4.4.9. Reaction of 3 with acrylonitrile
A slight excess of acrylonitrile (ca. 1.5 mL) was added to
a d6-benzene (0.3 mL) solution of 3 (15 mg, 0.024 mmol)
in a 5 mm screw-capped NMR tube via a microsyringe.
The reaction proceeded readily to generate a metastable
NMR (C6D6):
d
1.45 (t, 2H, CH2CN, 3J(HH) ¼ 6.4 Hz),
d 2.13
addition
product
Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)
(t, 2H, CH2N, 3J(HH) ¼ 6.4 Hz). GCeMS: m/z ¼ 69, 42, 30,
CH2NH2). Attempts at isolating the addition product from
the solution were unsuccessful because of decomposition
to a couple of unidentified species. On the other hand, in
the reaction of 3 with a large excess of acrylonitrile, the
addition product gradually disappeared to give a couple of
new complexes, as evidenced by 31P NMR spectroscopy,
along with the generation of insoluble polymeric species
of acrylonitrile in solution. After filtration of the pre-
cipitates, the 31P NMR spectrum of the solution exhibited
28. For (CH2(CN)CH2)2NH, 1H NMR (C6D6):
d 1.50 (t, 4H,
CH2CN, 3J(HH)
¼
6.4 Hz), d 1.97 (t, 4H, CH2N,
3J(HH) ¼ 6.4 Hz). GCeMS: m/z ¼ 123, 83, 54, 42, 30, 28.
For (CH2(CN)CH2)3N, 1H NMR (C6D6):
d 1.59 (t, 6H, CH2CN,
3J(HH) ¼ 6.8 Hz),
d
1.94 (t, 6H, CH2N, 3J(HH) ¼ 6.8 Hz).
GCeMS: m/z ¼ 176, 136, 109, 83, 54, 42, 30. For (CH2(CN)
CH(CH3))NH2, GCeMS: m/z ¼ 83, 69, 44, 42, 40, 28, 18, 15.
For (CH2(CO2CH3)CH2)2NH, GCeMS: m/z ¼ 187, 174, 157,
130, 102, 56. For (CH2(CO2CH3)CH2)3N, GCeMS: m/
z ¼ 275, 216, 157, 101, 56.
a couple of new resonances, one at
to cationic acrylonitrile
d
59.2 corresponding
complex [Pd(2,6-
a
(Cy2PCH2)2C6H3)(CH2]CHCN)]þ, which can be verified by
the reaction of Pd(2,6-(Cy2PCH2)2C6H3)(OTf) with CH2]
CHCN (excess) in d6-benzene. Spectral data for Pd(2,6-
(Cy2PCH2)2C6H3)(CH(CN)CH2NH2): 1H NMR (C6D6):
4.6. X-ray structure determination
All X-ray data collections were performed using Mo
K
a
radiation (
l
¼ 0.71069 Å) on an Enraf-Nonius CAD4
d
1.0e2.4 (m, 44H, Cy), ca.
d
2.2 (m, CH), ca.
d
3.1 (m, CHa),
diffractometer equipped with a graphite crystal, incident
beam monochromator. All calculations were carried out
using the SHELX-97 programs [31]. All structures were
solved by direct methods. All non-hydrogen atoms were
refined anisotropically, and all hydrogen atoms were
generated in ideal positions and refined in a riding
model.
ca.
d
3.5 (m, CHb),
d
3.16 (vt, 4H, CH2, r2J(PH) þ 4J(PH)
r ¼ 8.1 Hz). 31P{1H} NMR (C6D6):
d 49.0 (s). For polymeric
species: IR (KBr):
n
(CN)
¼
2245, 2204 cmꢀ1
,
n
(NH2)
¼
3300,
3360
cmꢀ1
.
For
[Pd(2,6-
(Cy2PCH2)2C6H3)(CH2]CHCN)](OTf), 31P{1H} NMR:
d
59.2
(C6D6),
d 59.4 (CDCl3).

628
Y. Kim, S. Park / C. R. Chimie 19 (2016) 614e629
(g) M.G. Scheibel, J. Abbenseth, M. Kinauer, F.W. Heinemann,
Acknowledgments
C. Würtele, B. de Bruin, S. Schneider, Inorg. Chem. 54 (2015) 9290.
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This work was supported by the Dongguk University
Research Fund. The authors are grateful to Prof. M. S. Lah for
the X-ray diffraction studies, and Dr. J. M. Seul and Mr. S. Y.
Ryu for the technical assistances.
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