Platinum complexes with a methoxy-amino phosphine or a nitrogen-containing bis(phosphine) ligand. Synthesis, characterization and application to hydrogenation of trans-cinnamaldehyde

Article abstract of DOI:10.1016/j.jorganchem.2016.11.036

Platinum complexes with a methoxy-amino phosphine or an ethylene-linked nitrogen-containing bis(phosphine) ligand have been synthesized and fully characterized by spectroscopic as well as crystallographic studies. The first ligand is bound to the metal in a P,N-bidentate coordination mode and with cis geometry, independently of the reaction temperature. Synthesis of a platinum complex with the second ligand at room temperature, afforded a mixture comprising 86% of a neutral cis complex, in which the ligand is bound to the metal only via the two P-donors, and 14% of a P,N,P-terdentate ionic complex where the two P atoms are trans to each other. On the other hand, synthesis of the complex at 100 °C, led almost exclusively to the formation of the cis-Pt complex in a P,P-bidentate coordination mode. The complexes were tested as catalysts without any promoting additive for the hydrogenation of trans-cinnamaldehyde under mild reaction conditions and displayed selectivity for the formation of cinnamyl alcohol of up to 67%.

Full text of DOI:10.1016/j.jorganchem.2016.11.036

Accepted Manuscript
Platinum complexes with a methoxy-amino phosphine or a nitrogen-containing
bis(phosphine) ligand. Synthesis, characterization and application to hydrogenation of
trans-cinnamaldehyde
Ioannis D. Kostas, Georgia Antonopoulou, Constantinos Potamitis, Catherine P.
Raptopoulou, Vassilis Psycharis
PII:
S0022-328X(16)30549-6
10.1016/j.jorganchem.2016.11.036
JOM 19721
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 28 July 2016
Revised Date: 21 November 2016
Accepted Date: 25 November 2016
Please cite this article as: I.D. Kostas, G. Antonopoulou, C. Potamitis, C.P. Raptopoulou, V. Psycharis,
Platinum complexes with a methoxy-amino phosphine or a nitrogen-containing bis(phosphine) ligand.
Synthesis, characterization and application to hydrogenation of trans-cinnamaldehyde, Journal of
Organometallic Chemistry (2016), doi: 10.1016/j.jorganchem.2016.11.036.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Platinum Complexes with a Methoxy-Amino Phosphine or a
Nitrogen-Containing Bis(phosphine) Ligand. Synthesis,
Characterization and Application to Hydrogenation of trans-
Cinnamaldehyde
a,
a
a
Ioannis D. Kostas ∗ , Georgia Antonopoulou , Constantinos Potamitis ,
b
b
Catherine P. Raptopoulou , Vassilis Psycharis
a
National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and
Biotechnology, Vas. Constantinou 48, 11635 Athens, Greece
b
NCSR "Demokritos", Institute of Nanoscience and Nanotechnology, 15310 Aghia
Paraskevi, Athens, Greece
_
_____________________________________________________________________
Abstract
Platinum complexes with a methoxy-amino phosphine or an ethylene-linked nitrogen-
containing bis(phosphine) ligand have been synthesized and fully characterized by
spectroscopic as well as crystallographic studies. The first ligand is bound to the metal in a
P,N-bidentate coordination mode and with cis geometry, independently of the reaction
temperature. Synthesis of a platinum complex with the second ligand at room temperature,
afforded a mixture comprising 86% of a neutral cis complex, in which the ligand is bound to
the metal only via the two P-donors, and 14% of a P,N,P-terdentate ionic complex where the
two P atoms are trans to each other. On the other hand, synthesis of the complex at 100 ºC,
led almost exclusively to the formation of the cis-Pt complex in a P,P-bidentate coordination
mode. The complexes were tested as catalysts without any promoting additive for the
hydrogenation of trans-cinnamaldehyde under mild reaction conditions and displayed
selectivity for the formation of cinnamyl alcohol of up to 67%.
Keywords: Platinum complex; PN Ligand; PNP Ligand; Hydrogenation; Cinnamaldehyde;
Homogeneous catalysis
_
_____________________________________________________________________
. Introduction
1
Hydrogenation of α,β-unsaturated aldehydes such as cinnamaldehyde (CALD), is a subject
of a much academic and industrial interest for the synthesis of specialty chemicals.
Hydrogenation of the C=C bond of CALD leads to hydrocinnamaldehyde (HCALD) used in
the flavouring industry [1] and in the synthesis of pharmaceuticals [2], while hydrogenation
of the C=O bond produces cinnamyl alcohol (CALH) used in the manufacture of perfumes
[
3]. Selective synthesis of CALH is always difficult to achieve because thermodynamics
–1
favor the hydrogenation of C=C over C=O by about 35 kJ mol , and also the kinetics of the
ethylenic double-bond hydrogenation are faster than for the carbonyl group [4]. In addition,
further hydrogenation of CALH to hydrocinnamyl alcohol (HCALH) is much faster than the
hydrogenation of CALD to CALH [5]. Selective hydrogenation of the C=O bond in
∗
Corresponding author. Tel.: +30 210 7273878; fax: +30 210 7273831.
E-mail address: ikostas@eie.gr (I.D. Kostas).
1

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unsaturated aldehydes is therefore a challenging research topic and in this area we have
previously reported the first studies concerning the evaluation of porphyrin–metal complexes
[
6] as well as Pt/TDPC nanoparticles [7] (TDPC = 3,3´-thiodipropionic acid) as catalysts for
hydrogenation of trans-cinnamaldehyde. Several unsupported transition metal (e.g. Co, Ru,
Ir) complexes have been used as homogeneous catalysts in organic or aqueous medium for
the hydrogenation of unsaturated aldehydes, providing an excellent selectivity for the
formation of unsaturated alcohols [8]. Metal colloidal nanocatalysts are also known to
improve C=O hydrogenation in a homogeneous catalytic system [9]. Heterogeneous platinum
catalysts have been widely used in this reaction and an excellent selectivity of over 90% for
C=O hydrogenation has been reported for Pt-supported catalysts, Pt-nanoparticles or Pt-
nanoclusters [10], as well as for monometallic or bimetallic Pt-nanoparticles on carbon
nanotubes [11]. According to a review by Gallezot and Richard, selective C=O hydrogenation
of CALD by unpromoted noble metals as heterogeneous catalysts follows the order Os > Ir >
Pt > Ru > Rh > Pd, and electronic and steric effects play a crucial role on this selectivity [5].
As is evident from the literature, platinum is the most studied of the above metals for this
heterogeneous hydrogenation since it is both an active and selective catalyst. On the other
hand, for homogeneous hydrogenation of α,β-unsaturated aldehydes by unsupported metal
complexes, metals such as Co, Ru, Ir were found to be beneficial for C=O hydrogenation, and
the role of these metals and of the ligands on selectivity has also been investigated [8]. To our
knowledge, however, unsupported platinum complexes as homogeneous catalysts for the
hydrogenation of α,β-unsaturated aldehydes have rarely been reported and those that have
been reported show very low selectivity for the hydrogenation of the C=O bond [12]. Thus,
additional studies are required regarding the use of platinum complexes in this reaction.
Hybrid chelating ligands which contain at least two different chemical functionalities and,
more specifically, hemilabile hybrid ligands with soft and hard donor atoms (e.g. P, N, O, S),
have received much attention in transition metal homogeneous catalysis [13]. Ligands which
bear phosphorus and nitrogen donors are amongst the most important and widely used
heterodentate ligands for homogeneous catalysis (asymmetric or otherwise) and can stabilize
intermediate oxidation states or geometries during a catalytic cycle [13,14]. As a part of our
efforts in this area [15], we have previously reported the synthesis of the methoxy-amino
phosphine 1 [16] and the nitrogen-containing bis(phosphine) 2 [17] (Scheme 1) as efficient
ligands for the Rh-catalyzed hydroformylation of styrene. We have shown that ligand 1 is
P,N-bound to rhodium and that coordination of the methoxy oxygen to the metal is not
observed [16]. A P,N-bidentate coordination mode for the analogous phosphino-amino
alcohol towards rhodium was also found by us [16], as well as recently by Kollár towards
platinum after a reaction time of more than 2 h [18]. In contrast to NP2 ligands that contain a
methylene linker between the N- and the P-atoms, which disfavour simultaneous coordination
of the three donors, with the N-atom remaining unbound [19], ethylene-linked NP2 ligands
such as 2 that impart a structural flexibility commonly coordinate to metal centres in a P,N,P-
terdentate fashion. Examples of metal complexes with ethylene-linked NP2 ligands and a
brief discussion of their coordination chemistry are given below. The P,N,P-terdentate
coordination mode has been reported in iron complexes by Beller [20], Fairweather and Guan
II
[
21], and Hazari and Neidig [22]. Gray and colleagues found dual coordination modes in Co
II
and Ni iodides, in which coordination to nickel is achieved via the three donors, in contrast
to cobalt complexes, where the central N-donor generally remains unbound, with only one
exception where a Co–N interaction was also observed [23]. Hanson reported a terdentate
II
mode in Co (CH SiMe ) complexes [24]. Terdentate coordination was also observed in
2
3
ruthenium complexes by Beller [25], Holthausen and Schneider [26], and Gusev [27], in
osmium complexes by Gusev [27], in rhenium complexes by Schneider [28], and in iridium
di(or tri)hydride complexes by Holthausen and Schneider [29] and Bianchini [30], while in
2

ACCEPTED MANUSCRIPT
monohydride iridium complexes, the ligand is bound to the metal only via the two
II
phosphorus atoms [30]. Hii (Mimi) found the formation of P,N,P-bound complexes with Pd
0
salts, as opposed to a P,P-bidentate mode with Pd [31]. Kollár reported a P,P-bidentate
coordination mode in a platinum complex with an ethylene-linked NP2 ligand, while nitrogen
is also bound to the metal in DMSO-d or by addition of SnCl or of KI or KCN in the
6
2
presence of SnCl to the platinum complex [32]. Platinum and other metal complexes with
2
analogous NP2 ligands have been reported by Taqui Khan et al., including examples of bi-
and more often terdentate coordination modes [33]. We have also shown a P,P-bidentate
I
coordination mode in a Rh complex with ligand 2 at room temperature, while at low
temperatures a Rh–N interaction is also possible [17]. In the present work, we report the
synthesis and characterization of platinum complexes with the above-mentioned ligands 1
and 2. The catalytic activity of these complexes towards the hydrogenation of trans-
cinnamaldehyde was also investigated.
2
. Results and discussion
2
.1. Synthesis and spectroscopic characterization of platinum complexes
The synthesis of platinum complexes 3 and 4 was achieved by treatment of (PhCN) PtCl2
2
with one equivalent of ligand 1 or 2, respectively (Scheme 1). All synthetic procedures
described below were performed 2–4 times to ensure repeatability and to establish the
coordination mode in the complexes, which was determined by spectroscopic techniques as
1
195
31
31
well as by X-ray studies. The J( Pt, P) coupling constants in the P NMR spectra of
platinum complexes are diagnostic and it is known that the trans P–Cl arrangement gives
1
1
JPtP higher than 3500 Hz, while the trans P–P arrangement displays JPtP in the range of
500–3000 Hz [34].
2
Scheme 1. Synthesis of platinum complexes.
Scheme to be reproduced in a single column]
[
3

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Complex 3 was prepared in an overnight experiment (18 h) at room temperature using
dichloromethane as a solvent. The same product was also obtained in toluene at 100 ºC for 3
1
13
h. H and C NMR spectra of 3 in CDCl showed that the NMe resonance is shifted
3
considerably downfield compared to the corresponding resonance in the free ligand (ꢀδ =
1
13
1
.09 ppm in the H NMR; ꢀδ = 15.35 ppm in the C NMR) providing clear evidence for Pt–
1
N coordination. On the other hand, the OMe resonance is shifted slightly upfield in the H
NMR spectrum and is at the same position in the C NMR spectrum compared to the free
ligand, indicating the absence of a Pt–O interaction. Analogous chemical shifts for the NMe
1
3
1
13
and OMe moieties in the H and C NMR spectra of 3 were also observed in acetone-d .
6
Upon complexation, the four NCH CH O protons become chemically and magnetically
2
2
1
nonequivalent. Indeed, in the H NMR spectrum of 3 in CDCl , the signals for these protons
3
are centered at δ 4.78 (1H, NCH ), 3.94 (1H, OCH ), 3.77 (1H, OCH ) and 3.64 (1H, NCH )
A
X
Z
M
corresponding to an AMXZ spin system with a ꢀν = 54JAM and ꢀνXZ = 10JXZ (see spectra
AM
2
in SI). The NCH gem coupling constant is J = 12.7 Hz and the OCH gem coupling
2
AM
2
2
constant is J = 10.7 Hz. In acetone-d , these protons appear at δ 4.68 (1H, NCH ), 3.85
XZ
6
A
(
1H, NCH ), 3.80 (1H, OCH ) and 3.72 (1H, OCH ) with a ꢀν = 40JAM and ꢀνXY = 4J ,
M X Y AM XY
2
2
31
corresponding to an AMXY spin system ( J = 12.4 Hz and J = 10.5 Hz). The P NMR
AM
XY
spectrum of 3 in CDCl or acetone-d showed a single central signal at 15.48 or 16.25 ppm,
3
6
respectively, flanked by platinum satellites in a ratio of 1:4:1. The absence of the signal
corresponding to the free ligand 1 at –13.80 ppm [16] supports the coordination of the P-atom
1
to the metal center and the formation of a five-membered chelate ring. The value of J
PtP
coupling constant (3903 Hz in CDCl or 3878 Hz in acetone-d ) provides a clear evidence for
3
6
the formation of a cis-PtCl (1) complex. The above-mentioned coordination mode and
2
geometry is also supported by the crystal structure of complex 3 as described below. Positive
+
+
ESI-MS of 3 showed bands corresponding exactly to [M–Cl] and [M+Na] (see HRMS in
the experimental section and also in SI).
Complex 4 was prepared at room temperature in 18 h using dichloromethane as a solvent
3
1
(
Method A) or in toluene at 100 ºC for 3 h (Method B). The P NMR spectrum of 4 showed
central signals flanked by platinum satellites in a ratio of 1:4:1. The absence of the signal
corresponding to the free ligand 2 at –21.22 ppm [17] and the lack of P–P coupling support
3
1
the coordination of the two equivalent P-atoms to platinum. However, the P NMR spectra
of the products obtained by each of the above-mentioned methods showed a difference,
although the spectra for the products by both syntheses were taken in CDCl over several
3
31
hours (Figure 1). In CDCl , the P NMR spectrum of the product obtained by method A
displayed a central signal at 10.37 ppm with a J coupling constant equal to 3591 Hz and
also a central signal at 27.49 ppm with 2712 Hz as a J coupling constant. In accordance to
3
1
PtP
1
PtP
Hii’s (Mimi) observation for Pd complexes with ethylene-linked NP2 ligands [31], we also
propose an isomerization between the neutral cis(P,P) and the cationic trans(P,N,P)
configuration as the ligand alternates between bi- and terdentate modes without cleavage of
1
the Pt–P bonds (Scheme 1). The value of the J coupling constant for the upfield resonance
PtP
corresponds to a cis(P,P) geometry (complex 4a), in which ligand 2 is bound to platinum
only via the two P-atoms. The downfield resonance corresponds to the trans(P,N,P) isomer
4
b, in which N-donor is also coordinated to the metal, forming two five-membered chelate
+
rings in cationic species of the formula [(PNP)Pt(Cl)] with chloride as a counterion. Relative
integration of the signals showed that the product mixture comprises 86% of 4a and 14% of
–
1
2
–1
4
b. The small Λ value (1.91 ꢁ cm mol in CH Cl ) observed from the conductivity
2 2
measurement of the product resulting from method A definitely indicates only a partial
isomerization of the neutral platinum complex to the corresponding ionic form. Analogous
cationic complexes as unique species have previously been reported for palladium [31] and
4

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nickel complexes [23] of ligand 2 at reflux or at room temperature, respectively. Synthesis
was also performed at room temperature in a shorter reaction time (3 h), affording complex 4
in a very similar yield with the same molar ratio of isomers (4a/4b = 86:14). On the other
3
1
hand, the P NMR spectrum in CDCl of the product obtained by method B (toluene, 100 ºC,
3
3
h), provided the same resonances and coupling constants with the percentage of the major
component 4a being 99%. The same isomer ratio (99:1) for the latter method was also found
3
1
in an overnight P NMR experiment using acetone-d or DMSO-d as a solvent (see spectra
6
6
in SI), and this observation is in contrast to a platinum complex with another ethylene-linked
NP2 ligand previously reported by Kollár, in which the coordination mode changes from a
P,P-bidentate to a P,N,P-terdentate fashion in DMSO-d [32]. The multiplet pattern for the
6
1
3
PCH carbons in the C NMR spectrum of 4a is characteristic for chemically equivalent but
2
magnetically nonequivalent nuclei [19b]. Negative ESI-MS of 4a showed a band
–
corresponding exactly to [M+Cl] (see HRMS in the experimental section and also in SI). It
is obvious from the above-mentioned experiments that the reaction conditions affect the
isomer ratio, and that a reaction at 100 ºC leads almost exclusively to the formation of the
thermodynamically favoured cis-PtCl (2) complex in a P,P-bidentate mode, which is also
2
supported by the crystal structure of the complex resulting from method B (see below). It
should also be pointed out that the temperature effect on the isomer ratio of 4 is opposite to
that observed for a palladium complex with ligand 2, in which heating of the reaction mixture
+
–
leads to [(PNP)Pd(Cl)] Cl as the most thermodynamically stable product [31].
3
1
Figure 1. P NMR (121.50 MHz, CDCl ) spectrum for complex 4, synthesized by method A
3
(top) or B (bottom).
[
Fig. to be reproduced in a single column]
5

ACCEPTED MANUSCRIPT
2
.2. Crystal structures
Crystals of complexes 3 and 4a (synthesized by method B) suitable for X-ray
determination were obtained by slow diffusion of diethyl ether through a solution of the
complexes in dichloromethane. The molecular structures of 3 and 4a are shown in Figure 2,
and selected bond distances and angles are listed in Table 1.
Figure 2. Partially labeled plot of the molecular structure of 3 (top) and 4a (bottom).
[
Fig. to be reproduced in a single column]
II
Complex 3 consists of a Pt ion in square planar coordination comprised of two chloro
ions in a cis-arrangement and the P,N-donor atoms of ligand 1. The bite angle P–Pt–N is
8
6.98°. The coordination chromophore PNCl and the metal ion are coplanar within
2
experimental error. The five-membered ring in the coordination sphere, defined by atoms
Pt(1)–P(1)–C(22)–C(17)–N(1), is almost planar with largest deviation 0.13 Å for C(22). The
Pt(1)–Cl(1) (trans to N(1)) bond is ~2.29 Å, substantially shorter by 0.08 Å than the Pt(1)–
Cl(2) (trans to P(1)) bond of ~2.37 Å, in conformity with the trans effect series, i.e. ligands
coordinated through P atoms show higher trans influence than those coordinated through N
ones [35]. The longer Pt–Cl bond (~2.37 Å) is in agreement with those observed in cis-
dichloro platimum(II) complexes with PNP ligands which fall in the range 2.35-2.38 Å
[
19b,c]. Inspection of the Cambridge Structural Database (CSD) revealed only 24 cis-
6

ACCEPTED MANUSCRIPT
II
dichloro Pt complexes with P,N-ligands such as 1, with unsymmetrical Pt–Cl bond distances
in the range 2.27–2.30 and 2.35–2.38 Å, respectively [36].
II
Complex 4a consists of a Pt ion in a square planar P Cl environment. The bite angle P–
2
2
Pt–P is 99.42°. The PtP Cl atoms are almost coplanar with largest deviation 0.20 Å for
2
2
Cl(2). The two cis-chloro ions are bound with almost equal bonds at ~2.36 Å, as expected
from the fact that they are trans to the same type of atoms (P(1) and P(2)), in agreement with
other Pt(P,P) complexes [19b,c]. Ligand 2 is coordinated through the two phosphorous atoms
forming an eight-membered ring with the participation of the metal ion. The eight-membered
ring, defined by atoms Pt(1), P(1), P(2), N(1) and the two ethylene groups, is found in the
most stable boat-chair conformation. To the best of our knowledge, 4a and complex cis-
[
PtCl (Ph P-(CH ) -PPh )] [37] are the only examples of PtP Cl square planar complexes
2 2 2 5 2 2 2
with eight-membered rings in the coordination sphere as determined by crystallographic
studies. The Pt–P bond distances are ~2.24 Å, in agreement with analogous complexes
[
19b,c]. The large distance of the nitrogen atom from the metal ion at ~3.92 Å indicates
absence of interaction. The molecular structure of 4a also contains one molecule of
dichloromethane.
Table 1
Selected bond distances [Å] and angles [°] in 3 and 4a
3
4a
Distances
2.111(2)
Pt(1)–N(1)
Pt(1)–P(1)
Pt(1)–Cl(1)
Pt(1)–Cl(2)
Pt(1)–P(1)
Pt(1)–P(2)
Pt(1)–Cl(1)
Pt(1)–Cl(2)
2.2352(5)
2.2524(5)
2.3543(5)
2.3578(5)
2.1844(6)
2.2890(6)
2.3697(6)
Angles
N(1)–Pt(1)–P(1)
86.98(5)
177.57(6)
91.84(2)
92.13(5)
179.07(2)
P(1)–Pt(1)–P(2)
P(1)–Pt(1)–Cl(1)
P(2)–Pt(1)–Cl(1)
P(1)–Pt(1)–Cl(2)
P(2)–Pt(1)–Cl(2)
99.42(2)
89.73(2)
168.77(2)
171.60(2)
83.35(2)
N(1)–Pt(1)–Cl(1)
P(1)–Pt(1)–Cl(1)
N(1)–Pt(1)–Cl(2)
P(1)–Pt(1)–Cl(2)
Cl(1)–Pt(1)–Cl(2) 89.03(2)
Cl(1)–Pt(1)–Cl(2) 88.51(2)
[
Table to be reproduced in a single column]
2
.3. Hydrogenation of cinnamaldehyde
Platinum complexes 3 and 4 without any promoting additive such as SnCl , were
2
evaluated as catalysts in the hydrogenation of trans-cinnamaldehyde (CALD) which was
chosen as a model compound for α,β-unsaturated aldehydes (Scheme 2, Table 2).
Hydrogenations were carried out in acetone or dichloromethane as solvent with a
substrate/catalyst molar ratio of 100:1. In order to compare the obtained selectivity values at a
similar conversion level, selected experiments were performed by using a higher Pt loading at
the same concentration (1 mM) and with prolonged reaction times. GC–MS analyses of the
7

ACCEPTED MANUSCRIPT
resulting hydrogenation products indicated that the formation of decarbonylation by-products
or other side-products was negligible or nonexistent. Unfortunately, a significant amount of
hydrocinnamyl alcohol (HCALH) was formed in all experiments due to the hydrogenation of
both C=C and C=O bonds.
Catalysis at 40 ºC and 20 bar of hydrogen pressure by complex 3 in acetone for 2 h,
afforded 52% conversion with 59% selectivity toward cinnamyl alcohol (CALH) (entry 1),
while a reaction time of 24 h was sufficient for a quantitative conversion of CALD, but with a
considerable increase in the percentage of HCALH, resulting in a lower selectivity for
CALH, and the disappearance of hydrocinnamaldehyde (HCALD) (entry 2). On the other
hand, catalysis in dichloromethane under the same reaction conditions, led to 58% conversion
of CALD and 72% selectivity for HCALD as the major product (entry 3), and thus, it is clear
that acetone enhances the reaction rate compared to dichloromethane as solvent. A higher Pt
loading (CALD/Pt = 70:1) for a prolonged reaction time (48 h) in dichloromethane afforded a
high CALD conversion (88%), but the major product was HCALH with a selectivity of 74%
(
entry 4). The effect of temperature and hydrogen pressure in dichloromethane using a
CALD/Pt ratio of 100:1 and a reaction time of 24 h was investigated. Reaction at 60 ºC under
0 bar of hydrogen pressure did not improve the CALD conversion (58%) but increased the
selectivity for both CALH (from 6 to 46%) and HCALH (from 22 to 34%) against HCALD
compare entries 3 and 5). On the other hand, hydrogenation under a pressure of 50 bar at 40
2
(
ºC was sufficient for a quantitative conversion of CALD, forming a product mixture
comprised of only CALH and HCALH in a ratio of 34:66 (entry 6).
When complex 4 prepared by method B (4a/4b = 99:1) was used as a catalyst, replacement
of acetone by dichloromethane as a solvent under identical reaction conditions (40 ºC, 20 bar
H , CALD/Pt = 100:1, 24 h), also decreased CALD conversion from 86 to 60% but the
2
CALH selectivity increased from 53 to 66% (compare entries 8 and 10). A higher Pt loading
(CALD/Pt = 70:1) for a prolonged reaction time (70 h) in acetone afforded 95% conversion
of CALD with 52% selectivity toward CALH (entry 9). Hydrogenation in dichloromethane
for 48 h using a CALD/Pt ratio of 70:1 afforded 80% conversion of CALD with 58%
selectivity toward CALH (entry 11). A higher hydrogen pressure (50 bar) at the same
temperature (40 ºC) in dichloromethane using a CALD/Pt ratio of 100:1 for a reaction time of
2
4 h increases the CALD conversion from 60 to 82% (compare entries 10 and 12) and for a
similar level of conversion, also increases the CALH selectivity from 58 to 67% (compare
entries 11 and 12), while a higher temperature (60 ºC) at the same pressure (50 bar) did not
improve the CALD conversion, as in the case of complex 3, but only increased the amount of
HCALH, leading to a lower CALH selectivity (compare entries 12 and 13). Hydrogenation
for 24 h by complex 4 prepared by method A (4a/4b = 86:14) in dichloromethane at 40 ºC
and 20 bar of hydrogen pressure using a CALD/Pt ratio of 100:1, dramatically decreased both
CALD conversion and CALH selectivity compared to complex 4 synthesized by method B
(4a/4b = 99:1) (compare entries 10 and 14). Catalysis by complex 4 (4a/4b = 86:14; 40 ºC,
2
0 bar H , CH Cl ) for 68 h using a higher platinum loading (CALD/Pt = 40:1) gave a
2
2
2
quantitative conversion of CALD, leading to further full hydrogenation of HCALD to
HCALH, while the CALH selectivity remained exactly the same (compare entries 14 and 15).
Scheme 2. Hydrogenation of cinnamaldehyde.
[
Scheme to be reproduced in a single column]
8

ACCEPTED MANUSCRIPT
Table 2
Hydrogenation of cinnamaldehyde catalyzed by platinum complexes 3 and 4
a
b
Entry Pt Complex
Solvent P (bar) Time (h) Conv. (%)
Selectivity (%)
HCALD CALH HCALH
1
2
3
4
5
6
7
8
9
1
1
1
1
1
3
3
3
3
3
3
acetone 20
acetone 20
2
52
100
58
88
58
100
30
86
95
60
80
82
82
37
100
24
–
59
43
6
17
57
22
74
34
66
20
35
42
24
31
28
48
26
79
24
24
48
24
24
2
CH Cl2 20
72
9
2
c
CH Cl2 20
17
46
34
36
53
52
66
58
67
41
21
21
2
d
CH Cl2 20
20
–
2
CH Cl2 50
2
4 (4a/4b=99:1) acetone 20
4 (4a/4b=99:1) acetone 20
4 (4a/4b=99:1) acetone 20
44
12
6
24
70
24
48
24
24
24
68
c
0
1
2
3
4
5
4 (4a/4b=99:1) CH Cl2 20
10
11
5
2
c
d
e
4 (4a/4b=99:1) CH Cl2 20
2
4 (4a/4b=99:1) CH Cl2 50
2
4 (4a/4b=99:1) CH Cl2 50
11
53
–
2
4 (4a/4b=86:14) CH Cl2 20
2
1
a
4 (4a/4b=86:14) CH Cl2 20
2
Reaction conditions: 1 mM solution of Pt complex (6 mL, 6 ꢂmol); cinnamaldehyde: 75 ꢂL
(
0.6 mmol); CALD:Pt = 100:1; 40 ºC.
b
Initial pressure of H at r.t.
2
c
d
e
CALD:Pt = 70:1.
60 ºC.
CALD:Pt = 40:1.
[
Table to be reproduced in a two-column]
As mentioned above, the conversion of CALD is higher in acetone than dichloromethane
as a solvent for both complexes 3 and 4a under identical conditions, and this observation is
not surprising as it is known that the catalytic activity of Pt(II)-chloro complexes toward
hydrogenation is much greater in acetone than in halocarbon so1vents [38]. At a high
conversion level of over 80%, the selectivity toward CALH was higher using complex 4a
compared to 3 in both solvents (compare entries 2 vs 9 and 4 vs 11). The higher selectivity for
CALH by complex 4a compared to complex 3 was also observed at a CALD conversion level
of ca. 60% (compare entries 3 and 10). In accordance to the above-mentioned experimental
results, the type of complex, solvent, temperature and pressure all affect the selectivity for the
formation of CALH. The classical mechanism for the hydrogenation of unsaturated aldehydes
by metal complexes involves interaction of the substrate with the metal center and also
oxidative addition of hydrogen [8b]. Therefore, an explanation for the different selectivities
observed should be based on the mechanism, in accordance to which the higher selectivity
observed in some experiments for the formation of CALH compared to HCALD is probably
attributed to the interaction of CALD with platinum preferentially through the C=O rather
than the C=C bond. In complexes 4a and 3, platinum is coordinated with the ligand via P,P-
and P,N-donors, respectively. The higher CALH selectivity observed by complex 4a should
9

ACCEPTED MANUSCRIPT
probably be attributed to the lower electronegativity of P in complex 4a compared to N in
complex 3 resulting in a higher electron density on the metal, and as a consequence, a lower
probability for the C=C bond hydrogenation with respect to C=O hydrogenation, in
accordance to a previous review describing electronic effects on the heterogeneous selective
hydrogenation of α,β-unsaturated aldehydes [5]. Perhaps, the larger bite angle in complex 4a
compared to complex 3 by 12.44° also plays a role in the higher selectivity for the formation
of CALH by complex 4a. Of course, the reasonable mechanistic considerations mentioned
above are not completely confirmed by the experimental data presented here, and further
experimental and theoretical studies are required for this hydrogenation by using platinum
complexes with a number of P,P- and P,N-ligands, in order to accurately propose more
promising ligands for a higher selectivity toward the C=O hydrogenation of α,β-unsaturated
aldehydes. It should also be mentioned that, as shown in Table 2, the higher percentage of the
cationic trans-Pt(P,N,P) complex 4b in mixture 4 (4a/4b = 86:14) is responsible for the lower
activity and selectivity compared to 4 (4a/4b = 99:1), and perhaps complex 4b also
decelerates the oxidative addition of hydrogen during the catalytic cycle.
3
. Conclusions
We have found that a methoxy-amino phosphine ligand binds to platinum in a P,N-
bidentate coordination mode without any Pt–O interaction, forming a cis five-membered
chelate complex PtCl (L) with a P–Pt–N bite angle of 86.98°, and the Pt–Cl (trans to N) bond
2
shorter than the Pt–Cl (trans to P) bond. The coordination mode and geometry of the complex
is independent of the reaction conditions (room temperature or 100 ºC). On the other hand,
the coordination chemistry of an ethylene-linked nitrogen-containing bis(phosphine) ligand
with platinum, is temperature dependent. A mixture of a cis-Pt(P,P) complex and the
isomeric P,N,P-terdentate cationic complex where the two P atoms are trans to each other
and with two five-membered chelate rings was formed at room temperature in a molar ratio
of 86:14. Synthesis at 100 ºC afforded almost exclusively the cis P,P-bidentate eight-
membered chelate complex with a P–Pt–P bite angle of 99.42°, in contrast to its analogous
palladium complex previously reported, in which heating of the reaction mixture leads to the
terdentate cationic complex. The observed P,P-bidentate coordination mode is not common,
as the very high majority of ethylene-linked NP2 ligands are bound to transition metals in a
P,N,P-terdentate fashion. We also found that after syntheses and isolation of pure products
were achieved, the coordination chemistry in complexes was retained at room temperature
despite the choice of solvent (chloroform, acetone, dimethyl sulfoxide). Evaluation of
complexes without any promoting additive in the hydrogenation of cinnamaldehyde under
mild reaction conditions showed that using acetone as a solvent, the catalytic activity is
higher than using dichloromethane, and that the selectivity towards the formation of cinnamyl
alcohol is higher in acetone for the cis-Pt(P,N) complex, while this selectivity is increased up
to 67% in dichloromethane by the use of the cis-Pt(P,P) complex. A significant
contamination of the neutral cis-Pt(P,P) complex by the cationic trans-Pt(P,N,P) isomer
decreases both activity and selectivity. This study provides interesting information for the
coordination chemistry of old ligands in new platinum complexes, and although their
catalytic activity and selectivity are not as high as several other catalysts for the
hydrogenation of α,β-unsaturated aldehydes, the observed selectivity for cinnamyl alcohol of
up to 67% should be considered as the highest yet reported for unsupported platinum
complexes as homogeneous catalysts for this reaction.
4
. Experimental section
10

ACCEPTED MANUSCRIPT
4
.1. General
Ligands 1 [16] and 2 [17] were synthesized as previously described by us.
Bis(benzonitrile)dichloroplatinum was prepared by a known procedure [39]. All other
chemicals were commercially available. All syntheses were carried out under argon with dry
and degassed reagents and solvents. Diethyl ether, toluene and hexane were distilled over Na,
dichloromethane over CaH , and acetone over drierite. Hydrogenation studies were
2
performed in a stainless steel autoclave (300 mL) with magnetic stirring. NMR spectra were
1
13
1
recorded on a Varian 300 (300.13 MHz, 75.47 MHz and 121.50 MHz for H, C{ H} and
3
1
1
1
P{ H}, respectively) or a Varian 600 (599.827 MHz for H). The assignment of protons and
1
13
carbons in the H and C NMR spectra was performed by HSQC NMR spectra. Chemical
shift values in H and C NMR spectra were referenced internally to the residual solvent
resonances, and the P spectra were referenced to external 85% H PO in H O. Electron
1
13
3
1
3
4
2
impact gas chromatography – mass spectrometry was carried out using a Varian Saturn 2000
with a 30 m × 0.25 mm DB5-MS column; experimental details: initial column temperature 60
°
C, initial column hold time 3 min, rate of increasing temperature 10 ºC / min, final column
temperature 260 ºC, column hold time 37 min. HRMS was determined by a Thermo
Scientific LTQ Orbitrap Velos (ESI); experimental details for the positive ESI–MS of 3 in
CH Cl /MeOH (5:95) and the negative ESI–MS of 4a in CH Cl /MeOH (10:90): source
2
2
2
2
voltage 4 KV, source temperature 100 ºC, sheath gas flow rate 15, aux gas flow rate 15,
capillary temperature 270 ºC. Melting points were measured on a Büchi melting point
apparatus. Conductivity measurement for complex 4 synthesized by method A was carried
out at 25 ºC under argon from a solution of the complex in CH Cl (3.19 mM) on an Orion
2
2
–
1
–1
(
Model 105) instrument; Λ = K × κ × c , K (cell constant) = 1 cm , κ (measured specific
–
6
–3
conductance) = 6.1 ꢂS, and c = 3.19 × 10 mol × cm .
4
.2.
cis{o-Diphenylphosphino-[N-(2-methoxyethyl)-N-methyl]aniline}dichloroplatinum(II)
(3)
A solution of ligand 1 (35.01 mg, 100 ꢂmol) in dichloromethane (3 mL) was added
dropwise under argon to a solution of (PhCN) PtCl (47.32 mg, 100 ꢂmol) in
2
2
dichloromethane (3 mL) at room temperature and stirred overnight (18 h). The resulting pale
yellow solution was concentrated under reduced pressure to an approximate volume of 0.5
mL. Dry diethyl ether (5 mL) was added to cause precipitation of a solid which was collected
after decantation, washed with ether (2 × 10 mL) and then dried under vacuum, yielding 3
(52.6 mg, 86%) as a white solid, m.p. (dec.) > 200 ºC. As determined by the spectral data, the
same product with a similar yield was also obtained by a dropwise addition of a solution of
ligand 1 (34.93 mg, 100 ꢂmol) in toluene (3 mL) to a solution of (PhCN) PtCl (47.22 mg,
2
2
1
00 ꢂmol) in toluene (3 mL) at 100 ºC and stirring at this temperature for 3 h.
1
H NMR (600 MHz, CDCl ): δ 7.82–7.77 (m, 4H, arom), 7.69–7.67 (m, 1H, arom), 7.63–
3
7
.61 (m, 1H, arom), 7.56–7.49 (m, 3H, arom), 7.47–7.40 (m, 5H, arom), 4.78 (1H,
NCH H ), 3.94 (1H, OCH H ), 3.77 (1H, OCH H ) and 3.64 (1H, NCH H ) (NCH CH O,
A
M
X
Z
X
Z
A
M
2
2
2
2
3
3
3
AMXZ spin system, J = 12.7 Hz, J = 10.7 Hz, J = 5.0 Hz, J = 5.0 Hz, J = 6.6
Hz, J = 5.3 Hz), 3.73 (s, 3H, NCH ), 2.89 (s, 3H, OCH ); H NMR (600 MHz, acetone-
AM
XZ
AX
AZ
MX
3
1
MZ
3
3
d6): δ 8.13–8.11 (m, 1H, arom), 7.92–7.89 (m, 2H, arom), 7.85–7.81 (m, 2H, arom), 7.77–
7
3
.70 (m, 2H, arom), 7.65–7.51 (m, 7H, arom), 4.68 (1H, NCH H ), 3.85 (1H, NCH H ),
A M A M
2
.80 (1H, OCH H ) and 3.72 (1H, OCH H ) (NCH CH O, AMXY spin system, J = 12.4
X
Y
X
Y
2
2
AM
2
3
3
3
3
Hz, J = 10.5 Hz, J = 4.8 Hz, J = 5.9 Hz, J = 6.3 Hz, J = 6.3 Hz), 3.75 (s, 3H,
XY
AX
AY
MX
MY
NCH ), 2.91 (s, 3H, OCH ).
3
3
11

ACCEPTED MANUSCRIPT
1
3
1
2
C{ H} NMR (75.5 MHz, CDCl ): δ 159.79 (d, J = 14.2 Hz, Cipso(NAr), arom), 132.83–
3
CP
1
32.73 (m, arom), 132.61 (d, J = 3.4 Hz, arom), 132.12–132.11 (m, arom), 131.07 (d, J =
CP CP
2
.8 Hz, arom), 130.98 (d, J = 2.9 Hz, arom), 129.96 (s, arom), 129.19 (s, arom), 128.92 (d,
CP
JCP = 7.2 Hz, arom), 128.74 (s, arom), 128.15 (d, JCP = 4.6 Hz, arom), 127.99 (d, JCP = 4.5
Hz, arom), 127.51 (s, arom), 126.90 (s, arom), 126.60 (s, arom), 126.00 (s, arom), 121.45 (d,
J
= 10.6 Hz, arom), 70.64 (s, OCH ), 64.56 (s, NCH ), 59.03 (s, NCH ), 58.91 (s, OCH );
CP
2 2 3 3
1
3
1
C{ H} NMR (75.5 MHz, acetone-d ): δ 162.64–162.47 (m, Cipso(NAr), arom), 135.16 (d,
6
JCP = 2.2 Hz, arom), 134.86 (s, arom), 134.74 (d, JCP = 3.2 Hz, arom), 134.61 (s, arom),
34.14–134.13 (m, arom), 132.84–132.77 (m, arom), 131.03 (d, JCP = 7.2 Hz, arom), 129.91
d, JCP = 1.9 Hz, arom), 129.75 (d, JCP = 1.8 Hz, arom), 123.98 (d, JCP = 10.7 Hz, arom),
1.24 (s, OCH ), 64.63 (s, NCH ), 58.83 (s, NCH and OCH ).
1
(
7
2
2
3
3
3
1
1
1
31
1
P{ H} NMR (121.5 MHz, CDCl ): δ 15.48 ( J = 3903 Hz); P{ H} NMR (121.5 MHz,
3
PtP
1
acetone-d ): δ 16.25 ( J = 3878 Hz).
HRMS (positive ESI-MS): calcd for C H ClNOPPt [M–Cl] 579.0932, found 579.0927;
calcd for C H Cl NNaOPPt [M+Na] 637.0513, found 637.0520.
6
PtP
+
2
2
24
+
2
2
24
2
4
.3. cis{N,N-Bis[2-(diphenylphosphino)ethyl]phenylamine}dichloroplatinum(II) (4a) and its
ionic trans-Pt(P,N,P) isomer (4b)
Method A: A solution of ligand 2 (51.79 mg, 100 ꢂmol) in dichloromethane (3 mL) was
added dropwise under argon to a solution of (PhCN) PtCl (47.19 mg, 100 ꢂmol) in
2
2
dichloromethane (3 mL) at room temperature and stirred overnight (18 h). The resulting light
pale yellow solution was concentrated under reduced pressure to an approximate volume of
0
.5 mL. Dry diethyl ether (5 mL) was added to cause precipitation of a solid which was
collected after decantation, washed with ether (2 × 5 mL) and then dried under vacuum,
–
1
2
–1
31
1
yielding 4 (60.9 mg, 78%) as a white solid. Λ (ꢁ cm mol ): 1.91. P{ H} NMR (121.5
1
1
MHz, CDCl ): δ 27.49 ( J = 2712 Hz), trans-Pt(P,N,P) (4b); 10.37 ( J = 3591 Hz), cis-
3
PtP
PtP
1
13
Pt(P,P) (4a); 4a/4b = 86:14. H and C NMR spectra showed only very slight differences in
the aromatic region compared to those observed for the product synthesized by method B as
given below (see spectra in SI). A shorter reaction time (3 h) afforded complex 4 in a very
similar yield (80%) with the same isomer ratio (86:14) (see spectra in SI).
Method B: A solution of ligand 2 (51.79 mg, 100 ꢂmol) in toluene (5 mL) was added
dropwise under argon to a solution of (PhCN) PtCl (47.23 mg, 100 ꢂmol) in toluene (5 mL)
2
2
at 100 ºC and stirred at this temperature for 3 h, forming a white solid. After cooling to room
temperature, toluene was removed by vacuum. Dichloromethane (10 mL) was added and the
mixture was filtered under argon to remove traces of insoluble species. The filtrate was
concentrated under reduced pressure to an approximate volume of 0.5 mL, and addition of
dry diethyl ether (5 mL) caused the precipitation of a solid. The solid was collected after
decantation, washed with ether (2 × 5 mL), hexane (5 mL) and dried under vacuum, yielding
4
(60.0 mg, 77%) as a white solid, m.p. (dec.) > 200 ºC.
1
H NMR (600 MHz, CDCl ): δ 7.48–7.45 (m, 8H, arom), 7.33–7.29 (m, 6H, arom), 7.15 (t,
3
3
3
3
JHH = 7.3 Hz, 8H, arom), 6.86 (t, J = 7.3 Hz, 1H, CHpara(NPh), arom), 6.57 (d, J = 8.1
HH
HH
Hz, 2H, CH (NPh), arom), 4.18 (dm, J = 23.1 Hz, 4H, CH NCH ), 2.60–2.57 (br m, 4H, 2
ortho
2
2
1
×
CH P); H NMR (300.1 MHz, acetone-d ): δ 7.61–7.55 (m, 8H, arom), 7.38–7.26 (m, 6H,
2
6
3
3
arom), 7.20 (t, J = 6.9 Hz, 8H, arom), 6.82 (t, J = 7.3 Hz, 1H, CHpara(NPh), arom),
HH
HH
3
6
2
7
.76 (d, J = 8.0 Hz, 2H, CHortho(NPh), arom), 4.17 (dm, J = 23.3 Hz, 4H, CH NCH ),
H
H
2
2
1
.81–2.75 (br m, 2 × CH P, obscured with HDO); H NMR (300.1 MHz, DMSO-d ): δ 7.54–
.48 (m, 8H, arom), 7.40–7.35 (m, 6H, arom), 7.27–7.19 (m, 8H, arom), 6.80 (t, J = 7.3
Hz, 1H, CHpara(NPh), arom), 6.64 (d, J = 8.4 Hz, 2H, CHortho(NPh), arom), 3.94 (dm, J =
2
6
3
HH
3
HH
1
9.8 Hz, 4H, CH NCH ), 2.78–2.72 (br m, 4H, 2 × CH P).
2 2 2
12

ACCEPTED MANUSCRIPT
1
3
1
C{ H} NMR (75.5 MHz, CDCl ): δ 146.89 (s, Cipso(NPh), arom), 132.47–132.35 (br m and
3
virtual triplet, J = 4.8 Hz, arom), 130.62 (s, arom), 129.83 (s, arom), 128.17 (virtual triplet,
CP
JCP = 5.5 Hz, arom), 117.94 (s, C (NPh), arom), 112.28 (s, Cortho(NPh), arom), 51.43 (s,
para
1
3
1
CH N), 25.14–24.52 (m, CH P); C{ H} NMR (75.5 MHz, acetone-d ): δ 148.81 (s,
2
2
6
Cipso(NPh), arom), 133.71–133.59 (br m and virtual triplet, JCP = 4.8 Hz, arom), 131.41 (s,
arom), 130.49 (s, arom), 129.01 (virtual triplet, JCP = 5.5 Hz, arom), 118.70 (s, Cpara(NPh),
arom), 114.09 (s, C (NPh), arom), 52.31 (s, CH N), 26.22–25.68 (m, CH P).
ortho
2
2
3
1
1
1
P{ H} NMR (121.5 MHz, CDCl ): δ 27.20, trans-Pt(P,N,P) (4b); 10.38 ( J = 3591 Hz),
3
PtP
3
1
1
cis-Pt(P,P) (4a); P{ H} NMR (121.5 MHz, acetone-d ): δ 28.12, trans-Pt(P,N,P) (4b);
6
1
31
1
1
1.16 ( J = 3580 Hz), cis-Pt(P,P) (4a); P{ H} NMR (121.5 MHz, DMSO-d ): δ 28.16,
P
t
P
6
1
trans-Pt(P,N,P) (4b); 10.11 ( J = 3599 Hz), cis-Pt(P,P) (4a); 4a/4b = 99:1 in all solvents.
HRMS (negative ESI-MS): calcd for C H Cl NP Pt [M+Cl] 817.0796, found 817.0802.
PtP
–
3
4
33
3
2
4
.4. General experimental procedure for the hydrogenation of cinnamaldehyde
Α freshly prepared solution of the metal complex (3 or 4) in acetone or dichloromethane (1
mM, 6 mL, 6 ꢂmol) and cinnamaldehyde (75 ꢂL, 0.6 mmol) were transferred under argon to
an oven-dried autoclave, which was then closed, pressurized and depressurized twice with 5
bar of hydrogen, and then pressurized with hydrogen (20 or 50 bar) and brought to the
appropriate temperature (40 or 60 ºC). After stirring for the appropriate time, the autoclave
was cooled to room temperature and the pressure was carefully released. The solution was
1
removed, passed through celite and analyzed by GC–MS and H NMR. Conversions and
1
selectivities were determined by H NMR spectroscopy based on the relative integration of
1
substrate and product peaks (see spectra and characteristic H NMR chemical shifts in SI).
4
.5. X-ray crystallographic study of 3 and 4a
Crystals of 3 (0.11 × 0.23 × 0.31 mm) and 4a (0.12 × 0.37 × 0.37 mm) were taken from
the mother liquor and immediately cooled to –113 and –103 ºC, respectively. Diffraction
measurements were made on a Rigaku R-AXIS SPIDER Image Plate diffractometer using
graphite monochromated Mo Kα radiation. Data collection (ω-scans) and processing (cell
refinement, data reduction and Empirical absorption correction) were performed using the
CrystalClear program package [40]. Important crystallographic data are listed in Table 3. The
structure was solved by direct methods using SHELXS-97 and refined by full-matrix least-
2
squares techniques on F with SHELXL-97 [41]. Further experimental crystallographic
details for 3: 2θmax = 54°; reflections collected/unique/used, 42229/4861 [R = 0.0293]/4861;
int
3
3
38 parameters refined; (ꢀ/σ)max = 0.003; (ꢀρ)max/(ꢀρ)min = 1.422/–0.431 e/Å ; R1/wR2 (for
all data), 0.0184/0.0379. Further experimental crystallographic details for 4a: 2θmax = 54°;
reflections collected/unique/used, 82170/7505 [R = 0.0185]/7505; 527 parameters refined;
int
3
(ꢀ/σ)max = 0.004; (ꢀρ)max/(ꢀρ)min = 0.759/–1.180 e/Å ; R1/wR2 (for all data), 0.0171/0.0405.
All hydrogen atoms were located by difference maps and were refined isotropically or were
introduced at calculated positions as riding on bonded atoms. All non-hydrogen atoms were
refined anisotropically. Plots of the structure were drawn using the Diamond 3 program
package [42].
Table 3
Crystallographic data for 3 and 4a
.
3
4a CH Cl
2
2
Formula
C H Cl NOPPt C H Cl NP Pt
22 24 2 35 35 4 2
13

ACCEPTED MANUSCRIPT
Fw
615.38
868.47
Space group
α (Å)
b (Å)
c (Å)
α (°)
P2 /n
P2 /n
1
1
14.6852(3)
10.6060(2)
14.7022(3)
90.0
13.4966(3)
14.4529(3)
17.9852(3)
90.0
β (°)
102.642(1)
90.0
101.024(1)
90.0
γ (°)
3
V (Å )
2234.37(8)
4
3443.54(12)
4
Z
T (ºC)
Radiation
–113
–103
Mo Kα
1.829
Mo Kα
1.675
–
3
ρcalcd (g cm )
–
1
ꢁ
(mm )
6.603
4.504
Reflections
4618
7319
with I>2σ(I)
a
R1
0.0167
0.0166
0.0403
a
wR2
a
0.0374
2
2
2
2
o
2
w = 1ꢃ[σ (F )+(αP) +bP] and P = [max (F ,0)+2F ]/3; R = Σ(|F |–|F |)/Σ(|F |) and wR =
o
c
1
o
c
o
2
2
2 2
2 2 1/2
{
Σ[w(F –F ) ]/Σ[w(F ) ]} .
o c o
[
Table to be reproduced in a single column]
Acknowledgements
The authors are grateful to Professor László Kollár (University of Pécs, Hungary) for the
conductivity measurement and also to Eleni Siapi (National Hellenic Research Foundation)
for HRMS analyses.
Appendix A. Supplementary data
CCDC-1486014 (for 3) and CCDC-1486015 (for 4a) contain the supplementary
crystallographic data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. The
Supporting Information related to this article is available free of charge and contain copies of
1
NMR and HRMS spectra of complexes and H NMR spectra of hydrogenation products.
Notes
This research did not receive any specific grant from funding agencies in the public,
commercial, or not-for-profit sectors.
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1
14

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R.V. Maligal-Ganesh, L. Zhou, T.W. Goh, X. Li, D. Tesfagaber, A. Thiel, W. Huang,
ACS Catal. 4 (2014) 1340−1348; e) L.J. Durndell, C.M.A. Parlett, N.S. Hondow, M.A.
Isaacs, K. Wilson, A.F. Lee, Sci. Rep. 5 (2015) Article No. 9425; f) Z. Tian, Q. Li, J.
Hou, Y. Li, S. Ai, Catal. Sci. Technol. 6 (2016) 703−707; g) H. Liu, L. Chang, L. Chen,
Y. Li, ChemCatChem 8 (2016) 946−951.
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Y. Kihn, D. Plee, P. Kalck, P. Serp, J. Catal. 240 (2006) 18–22; b) Y. Li, Z.-G. Li, R.-
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Chaudret, P. Serp, Angew. Chem. Int. Ed. 48 (2009) 2529–2533; d) J. Teddy, A. Falqui,
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Zhao, J.-G. Chen, X. Liu, Z.-W. Liu, Z. Hao, J. Xiao, Z.-T. Liu, Ind. Eng. Chem. Res.
5
1 (2012) 11112−11121.
12] M. Abid, F. Ammari, K. Liberkova, R. Touroude, Stud. Surf. Sci. Catal. 145 (2002)
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2
(2006) 4473–4482; d) L.-C. Liang, Coord. Chem. Rev. 250 (2006) 1152–1177; e) W.-
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14] a) I.D. Kostas, Curr. Org. Synth. 5 (2008) 227–249; b) I.D. Kostas, Other P/N-Ligands,
in: A. Börner (Ed.), Phosphorus Ligands in Asymmetric Catalysis – Synthesis and
Applications, Vol. 2, Wiley-VCH, Weinheim, 2008, pp. 596–632; c) I.D. Kostas,
Recent Advances in P,N-Containing Ligands for Transition-Metal Homogeneous
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B.R. Steele, A. Terzis, S.V. Amosova, Tetrahedron 59 (2003) 3467–3473; c) I.D.
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Kostas, Inorg. Chim. Acta 355 (2003) 424–427; d) I.D. Kostas, B.R. Steele, F.J.
Andreadaki, V.A. Potapov, Inorg. Chim. Acta 357 (2004) 2850–2854; e) I.D. Kostas,
K.A. Vallianatou, J. Holz, A. Börner, Appl. Organomet. Chem. 19 (2005) 1090–1095;
f) E.I. Tolis, K.A. Vallianatou, F.J. Andreadaki, I.D. Kostas, Appl. Organomet. Chem.
2
0 (2006) 335–337; g) K.A. Vallianatou, D.J. Frank, G. Antonopoulou, S.
Georgakopoulos, E. Siapi, M. Zervou, I.D. Kostas, Tetrahedron Lett. 54 (2013) 397–
01; h) I.D. Kostas, A.-C. Tenchiu, C. Arbez-Gindre, V. Psycharis, C.P. Raptopoulou,
4
Catal. Commun. 51 (2014) 15–18.
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[
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16] I.D. Kostas, C.G. Screttas, J. Organomet. Chem. 585 (1999) 1–6.
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18] P. Pongrácz, I.D. Kostas, L. Kollár, J. Organomet. Chem. 723 (2013) 149–153.
19] Recent selected papers: a) M.B. Smith, S.H. Dale, S.J. Coles, T. Gelbrich, M.B.
Hursthouse, M.E. Light, P.N. Horton, CrystEngComm 9 (2007) 165–175; b) M. Stickel,
C. Maichle-Moessmer, L. Wesemann, H.A. Mayer, Polyhedron 46 (2012) 95–104; c) E.
Bálint, A. Tripolszky, E. Jablonkai, K. Karaghiosoff, M. Czugler, Z. Mucsi, L. Kollár,
P. Pongrácz, G. Keglevich, J. Organomet. Chem. 801 (2016) 111–121.
20] E. Alberico, P. Sponholz, C. Cordes, M. Nielsen, H.-J. Drexler, W. Baumann, H. Junge,
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[
[
21] S. Chakraborty, H. Dai, P. Bhattacharya, N.T. Fairweather, M.S. Gibson, J.A. Krause,
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22] K.L. Fillman, E.A. Bielinski, T J. Schmeier, J.C. Nesvet, T.M. Woodruff, C.J. Pan,
M.K. Takase, N. Hazari, M.L. Neidig, Inorg. Chem. 53 (2014) 6066–6072.
23] Q. Dong, M.J. Rose, W.-Y. Wong, H.B. Gray, Inorg. Chem. 50 (2011) 10213–10224.
24] G. Zhang, B.L. Scott, S.K. Hanson, Angew. Chem. Int. Ed. 51 (2012) 12102–12106.
25] M. Nielsen, E. Alberico, W. Baumann, H.-J. Drexler, H. Junge, S. Gladiali, M. Beller,
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[
[
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26] B. Askevold, J.T. Nieto, S. Tussupbayev, M. Diefenbach, E. Herdtweck, M.C.
Holthausen, S. Schneider, Nat. Chem. 3 (2011) 532–537.
27] M. Bertoli, A. Choualeb, A.J. Lough, B. Moore, D. Spasyuk, D.G. Gusev,
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28] I. Klopsch, M. Finger, C. Würtele, B. Milde, D.B. Werz, S. Schneider, J. Am. Chem.
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29] C. Schiwek, J. Meiners, M. Förster, C. Würtele, M. Diefenbach, M.C. Holthausen, S.
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30] C. Bianchini, L. Glendenning, M. Peruzzini, G. Purches, F. Zanobini, E. Farnetti, M.
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31] K.K. (Mimi) Hii, M. Thornton-Pett, A. Jutand, R.P. Tooze, Organometallics 18 (1999)
1
887–1896.
32] L. Jánosi, T. Kégl, L. Hajba, Z. Berente, L. Kollár, Inorg. Chim. Acta 316 (2001) 135–
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[
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34] P.S. Pregosin, S.N. Sze, Helv. Chim. Acta 61 (1978) 1848–1855.
35] S. Otto, M.H. Johansson, Inorg. Chim. Acta 329 (2002) 135–140.
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Crystallogr. C 47 (1991) 2090–2092; b) N.C. Payne, G.R. Tobin, Acta Crystallogr. C
4
6
8 (1992) 45–48; c) F. Leca, C. Lescop, L. Toupet, R. Reau, Organometallics 23 (2004)
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Organometallics 24 (2005) 1959–1965; e) C. Metallinis, J. Zaifman, L. Van Belle, L.
Dofge, M. Pilkington, Organometallics 28 (2009) 4534–4543; f) Y. Xie, Y. Wei, J.-G.
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129.
38] G.K. Anderson, C. Billard, H.C. Clark, J.A. Davies, C.S. Wong, Inorg. Chem. 22
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39] G.K. Anderson, M. Lin, A. Sen, E. Gretz, in: R.J. Angelici (Ed.), Inorganic Syntheses:
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[
40] Rigaku/MSC (2005). CrystalClear. Rigaku/MSC Inc., The Woodlands, Texas, USA.
41] G.M. Sheldrick, Acta Cryst. A 64 (2008) 112–122.
42] DIAMOND – Crystal and Molecular Structure Visualization, Ver. 3.1, Crystal Impact,
Rathausgasse 30, 53111, Bonn, Germany.
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Synthesis of a cis-Pt(P,N) complex with a methoxy-amino phosphine ligand.
Complexation of an ethylene-linked NP2 ligand with Pt is temperature dependent.
At r.t., a mixture of a cis-Pt(P,P) and a trans-Pt(P,N,P) complex was formed.
Synthesis at 100 ºC afforded almost exclusively the cis-Pt(P,P) complex.
Hydrogenation of cinnamaldehyde with selectivity for cinnamyl alcohol of up to 67%.