Synthesis and Characterization of Methyl-Palladium and -Platinum Complexes Supported by N,O- and N,S-Donor Ligands

Article abstract of DOI:10.1002/ejic.201501140

The methylpalladium and -platinum complexes [Pd(AcNac)(PMe₃)CH₃], [Pd(SacNac)(PMe₃)CH₃], and [Pt(SacNac)(PMe₃)CH₃] have been prepared from protonation reactions between AcNac [H₃

Full text of DOI:10.1002/ejic.201501140

DOI: 10.1002/ejic.201501140
Full Paper
Metal ꢀ-Thioketoiminates
Synthesis and Characterization of Methyl–Palladium and
–Platinum Complexes Supported by N,O- and N,S-Donor Ligands
Daniel Ruiz Plaza,[a] José C. Alvarado-Monzón,[a] Gabriel A. Andreu de Riquer,[a]
Gerardo González-García,[a] Herbert Höpfl,[b] Luis Manuel de León-Rodríguez,[a] and
Jorge A. López*[a]
Abstract: The methylpalladium and -platinum complexes the composition [M(L′)Me2] (M = Pd, L′ = tmeda = N,N,N′N′-
[Pd(AcNac)(PMe3)CH3], [Pd(SacNac)(PMe3)CH3], and [Pt(SacNac)-
(PMe3)CH3] have been prepared from protonation reactions be-
tween AcNac [H3CC(O)CHC(NAr)CH3; Ar = 2,6-iPr-C6H3 = Dipp
tetramethylethylenediamine; M = Pt, L′ = cod = 1,5-cyclooctadi-
ene) and PMe3 in acetonitrile. Only one isomer was formed in
each case and X-ray crystallographic analysis showed that the
PMe3 co-ligand is found in the cis position with respect to the
sulfur or oxygen atom in all complexes.
(L1); Ar
=
2,4,6-MeC6H2
=
Mes (L2)] or SacNac
[H3CC(S)CHC(NAr)CH3; Ar = 2,6-iPr-C6H3 = Dipp (L3); Ar = 2,4,6-
MeC6H2 = Mes (L4)] ligands and dimethyl–metal complexes of
Introduction
The development of ꢀ-diketonate (Acac) and ꢀ-diiminate (Nac-
Nac) ligands was a milestone in the fields of coordination and
organometallic chemistry (Figure 1).[1] NacNac ligands have an
advantage over the Acac analogues, because both the steric
and electronic properties can be readily tuned, which is essen-
tial for the stabilization of complexes that exhibit unusual pho-
tochemical properties, oxidation states, coordination numbers,
geometries, bonds, or reactivity.[2] Although ꢀ-dithionate li-
gands (SacSac) and their coordination and organometallic com-
plexes have been disclosed in the literature,[3] in the past two
decades most of the attention has been directed towards the
design of hybrid ligands containing at least two different types
of chemical functionalities. The vast majority of these bidentate
ligands contain only hard donor atoms, that is, oxygen and ni-
trogen. Most O,N-donor ꢀ-ketoiminate ligands (AcNac) provide
sufficient thermal and kinetic stability for their employment in
catalysis.[4] Moreover, when hard and soft donor atoms are com-
bined within a single ligand, hybrid ligands result, which have
attracted significant interest in this field.[5] Recently, Tokitoh and
co-workers reported an elegant methodology for the synthesis
of ꢀ-ketophosphenate ligands (AcPac), in which bulky substitu-
ents play a fundamental role in the kinetic stabilization of the
complexes.[6]
Figure 1. ꢀ-Diketonate (Acac), ꢀ-diiminate (NacNac), ꢀ-ketoiminate (AcNac),
ꢀ-dithioketonate (SacSac), ꢀ-ketophosphenate (AcPac), and ꢀ-thioketoiminate
(SacNac) ligands.
These classical features of X,Y-donor ligands inspired us to
develop a facile synthetic procedure for the preparation of bi-
dentate species containing sulfur as a soft donor atom. To the
best our knowledge, the chemistry of S,N-donor ꢀ-thioacetyl-
iminate ligands (SacNac) (Figure 1) and their complexes is cur-
rently poorly developed. Therefore, there are a limited number
of reports on such ligands, and these have been prepared by
different synthetic pathways.[7] Herein, we report on an im-
proved methodology for the preparation of SacNac ligands.
SacNac and AcNac ligands were then treated with dimethyl–
palladium and –platinum derivatives to give complexes with
asymmetric coordination environments. Furthermore, we de-
scribe the differences in the reactivities of the two ligands in
these protonation reactions.
[a] Departamento de Química, División de CNE, Sede Noria Alta, Universidad
de Guanajuato,
Noria Alta s/n, C.P. 36050, Guanajuato, México
E-mail: albinol@ugto.mx
http://www.posgrado-quimica-ugto.mx/profesores.htm
[b] Centro de Investigaciones Químicas, Universidad Autónoma del Estado de
Morelos,
Results and Discussion
Synthesis of the N,O and N,S Ligands
Av. Universidad 1001, C.P. 62209, Cuernavaca, México
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201501140.
The starting AcNac ligands, H3CC(O)CHC(NAr)CH3 [Ar = Dipp =
2,6-iPr2C6H3 (L1); Ar = Mes = 2,4,6-Me3-C6H2 (L2)], were initially
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synthesized following
a
previously reported procedure rectly.[13] Furthermore, the protonation reaction with methane
(Scheme 1).[8] However, when using microwave radiation in- loss has been utilized for the synthesis of cationic active com-
stead of traditional heating, the desired products were obtained plexes in the polymerization of olefins.[14] We used the protona-
in a significantly shorter time (6 vs. 24 h) in similar yields. The tion reaction to synthesize new complexes containing N,O- and
1H and 13C NMR spectra of L1,2 are consistent with previously N,S-bidentate donor ligands.
reported data for these ligands.[9]
Thus, although the stoichiometric reaction of the N,O-donor
ligands L1,2 in acetonitrile with 1 equivalent of the dimethyl–
palladium complex [PdMe2(tmeda)] in the presence of a slight
excess of PMe3 (T = 35 °C) led to the formation of a single
isomer with the general formula [Pd(Ln)(Me)(PMe3)] (Ln = L1,2
;
M = Pd, 1, 2; Scheme 2), no reactions were observed upon the
treatment of the same ligands in acetonitrile with the dimethyl–
platinum complex [PtMe2(cod)], even after increasing the tem-
perature. Attempts to obtain the [Pt(Ln)(Me)(PMe3)] complexes
were unsuccessful either by reaction of the ligand salts NaL1,2
with [Pt(cod)(Me)Cl] or by the treatment of L1,2 with nBuLi at
–70 °C and then [PtMeCl(cod)]; invariably, the protonated ligand
was obtained.
Scheme 1. Synthesis of SacNac ligands.
The treatment of L1,2 with 1 equivalent of Lawesson's[10] rea-
gent in dichloromethane at 35 °C gave novel S,N-donor SacNac
ligands of the composition H3CC(S)CHC(NAr)CH3 [Ar = 2,6-iPr-
C6H3 = Dipp (L3); Ar = 2,4,6-MeC6H2 = Mes (L4); Scheme 1].
Compounds L3,4 were obtained in good yields (75–85 %) as yel-
low and orange solids, respectively (see the Supporting Infor-
mation).
The SacNac ligands exhibit some different and characteristic
spectroscopic features that allows them to be distinguished
from the AcNac precursors and provides considerable evidence
for successful oxygen/sulfur exchange in both cases. The IR
spectra of L3,4 show medium intensity ν(C=S) vibrations at ap-
proximately 1100 cm–1,[11] and the SH and NH stretching vibra-
tions are absent. In solution, the behavior of these ligands is
very similar to that described by Mehn and co-workers for keto-
iminato ligands.[9] Thus, in the 1H NMR spectra of L3 and L4,
broad signals at δ = 15.28 and 15.12 ppm, respectively, suggest
the presence of an intramolecular bond between the amine
and the adjacent thioketone (NH···S) or the presence of an imin-
ium proton instead of NH···O groups, which are observed at a
higher field (δ = 12.06 ppm for L1 and 11.85 ppm for L2). This
high deshielding is similar to that observed for the enol proton
of acetyl acetone. For the resonances of the methine groups of
the thioketoimine fragment, in each case downfield displace-
ments were detected (Δδ = 1.11 ppm for L1/L3 and L2/L4), be-
ing greater in the 13C{1H} NMR spectra (Δδ ≈ 17 ppm for L1/L3
and L2/L4). The fact that both ligands L3 and L4 exhibit peaks
at around 206 and 166 ppm in the 13C{1H} NMR spectra indi-
cates that the C–S and C–N bonds, respectively, show significant
double-bond character.[9,12] Although three tautomeric forms
are possible (thioketoimine, thioketamine, and enethiolimine),
we believe that these compounds are best described as proto-
nated ꢀ-thioketoiminate species, as pointed out by Mehn and
co-workers for analogous N,O-donor ligands.[9]
Scheme 2. Synthesis of the methyl–palladium and –platinum complexes.
In contrast, the N,S-donor ligands L3,4 reacted under the
same conditions with 1 equivalent of the dimethyl–metal com-
plexes [Me2M(L′)] (M = Pd, L′ = tmeda = N,N,N′N′-tetramethyl-
ethylenediamine; M = Pt, L′ = cod = 1,5-cyclooctadiene) and
PMe3 to yield the complexes with general formula cis-
[M(Ln)(Me)(PMe3)] (Ln = L3,4; M = Pd, 3,4; M = Pt, 5,6; Scheme 2).
Even in solution, all the complexes were stable under nitrogen
for weeks.
The new compounds were isolated and fully characterized.
The 1H NMR spectra of complexes 1–6 show signals at high
field, which have been assigned to the M–Me fragment. These
signals appear as doublets for palladium complexes 1 (δ =
3
3
–0.56 ppm, JHP = 4.02 Hz), 2 (δ = –0.66 ppm, JHP = 3.76 Hz),
3 (δ = –0.46 ppm, 3JHP = 3.54 Hz), and 4 (δ = –0.56 ppm, 3JHP
=
3.52 Hz) due to their coupling with the cis 31P nucleus of PMe3,
and as a doublet flanked by two satellite doublets in platinum
3
2
complexes 5 (δ = –0.04 ppm, JHP = 4.49, JHPt = 59.62 Hz) and
3
2
6 (δ = –0.02 ppm, JHP = 4.12, JHPt = 59.66 Hz) as a result of
their coupling with the 31P and 195Pt nucleus. Two sharp sin-
glets observed in the range 1.37–1.81 and 1.96–2.65 ppm have
been assigned to the protons of the two methyl groups of the
asymmetric ligands, CH3CN and CH3CS, respectively. The spec-
tral patterns of the diisopropyl groups, being the same in all
compounds in which they are present (L1, L3, 1, 3, 5), show two
Synthesis of Methyl–PdII and –PtII Complexes
The microscopic reverse reaction of the C–H bond activation well-resolved doublets corresponding to diastereotopic methyl
step, namely protonolysis, has been well studied, because of groups between 1.00 and 1.20 ppm (3JHH = 6.80), and the meth-
the inherent difficulties in studying C–H bond activation di- ine protons show a septet at around 3.5 ppm.[12] The resonan-
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ces due to the three CH3 groups of the mesityl groups (L2, L4, by the S–M–N and P–M–C atoms. As expected, the Mes and
2, 4, 6) were observed as two sharp singlets with integrals of Dipp rings are found to be in an almost perpendicular arrange-
3:6 in the range 2.04–2.45 ppm.
ment with respect to the coordination planes (MSCCCNMes)
The 31P{1H} NMR spectra of palladium complexes 1–4 are
characterized by singlets at δ = –3.72, –4.35, –4.33, and
4.85 ppm, respectively. Meanwhile, the PMe3 resonance in plati-
num complexes 5 and 6 appear at δ = –29.31 and –29.46 ppm,
flanked by 195Pt satellites with 1JPPt = 3697 and 1JPPt = 3712 Hz,
respectively.[15] These signals are shifted upfield by around
25 ppm compared with those of the palladium derivatives 3
and 4.
The 13C{1H} NMR spectra are in good agreement with the
proposed structures. The signal assignment of the platinum
complexes is supported by the coupling of some of the carbon
atoms with 195Pt isotope and 31P nucleus. Thus, the 13C NMR
spectra of all the complexes show a characteristic upfield dou-
blet in the range of δ = 9.1 to –5.2 ppm as a result of the
bonding of a methyl carbon to the metal center, and by the
coupling of this atom to the phosphorus nucleus in the cis posi-
tion (2JCP = 10.90–14.6 5 Hz). In addition, the complexes 5 and
6 are flanked by satellites (1JCPt = 649.8 and 637.0 Hz, respec-
tively). The methine carbon of the N,S-donor backbone ring
appears as a singlet at δ = 121.6 and 121.9 ppm in the spectra
of the platinum complexes 5 and 6, respectively, each with two
satellites due to coupling with the 195Pt nucleus (3JCPt = 57.22
and 56.31 Hz). In all complexes, the carbon of the CN fragment
(δ = 161.0–166.3 ppm) shows no significant shift compared
with the free ligands (δ = 162.8–164.8 ppm). In contrast, the CO
carbon (δ = 178.3 and 178.5 ppm, compounds 1 and 2) and CS
carbon resonances (δ = 166.3, 165.4, 162.4, and 161.7 ppm,
compounds 3–6) in the complexes are shifted upfield by
around 17 and 45 ppm, respectively, compared with in the free
ligands.[9,12] The configurations of the metal atoms in com-
plexes 3–6 were further established by 2D NOESY experiments.
Irradiation of the M–Me protons led to increases in the signals
arising from the PMe3 ligands and the methyl groups in the
Mes/Dipp substituents, which indicates that the sulfur atom is
located in the trans position with respect to the carbon atom
of the methyl group, and the N–Ar and PMe3 fragments are also
trans-oriented.
Figure 2. ORTEP-type perspective view of complex 2, with ellipsoids drawn
at the 50 % probability level. Selected bond lengths [Å] and angles [°]: Pd1–
C15 2.042(5), Pd1–P1 2.229(2), Pd1–O1 2.101(4), Pd1–N1 2.113(4), N1–C3
1.307(7), N1–C6 1.439(7), O1–C1 1.268(7), C1–C2 1.389(8), C2–C3 1.42(7), N1–
Pd1–P1 173.02(14), C15–Pd1–O1 176.6, C15–Pd1–P1 86.22(19), P1–Pd1–O1
90.94(10), O1–Pd1–N1 90.76(14), N1–Pd1–C15 92.3(2), C3–N1–Pd1 123.4(3),
C1–O1–Pd1 125.0(3), C2–C1–O1 126.2(5), C2–C3–N1 125.4(5).
Figure 3. ORTEP-type perspective view of complex 4, with ellipsoids drawn
at the 50 % probability level. Selected bond lengths [Å] and angles [°]: Pd1–
C15 2.08(1), Pd1–P1 2.216(2), Pd1–S1 2.307(3), Pd1–N1 2.126(7), N1–C3
1.31(1), N1–C6 1.44(1), S1–C1 1.68(1), C1–C2 1.35(1), C2–C3 1.42(1), N1–Pd1–
P1 173.1(2), C15–Pd1–S1 172.9, C15–Pd1–P1 83.6(3), P1–Pd1–S1 90.9(1), S1–
Pd1–N1 93.7(2), N1–Pd1–C15 92.3(4), C3–N1–Pd1 127.9(6), C1–S1–Pd1
111.0(4), C2–C1–S1 129.2(8), C2–C3–N1 128.2(8).
Single-Crystal X-ray Structure Determinations
For complexes 2, 4, and 5, single crystals suitable for X-ray crys-
tallography were grown by slow solvent evaporation from solu-
tions in acetonitrile (for 2 and 4) and benzene (for 5). To the
best of our knowledge, compounds 4 and 5 are the first struc-
turally characterized methyl–palladium and –platinum com-
plexes containing SacNac ligands, with PdCNSP and PtCNSP co-
ordinating frameworks. The molecular structures of 2, 4, and 5
are depicted in Figures 2–4, respectively, and selected bond
lengths and angles are presented in the corresponding cap-
tions. In agreement with the NMR spectroscopic analysis, the
PMe3 co-ligand is located in the cis position relative to the sul-
fur atom. In all these compounds, the coordination geometry
around the metal center is slightly distorted square-planar, with
dihedral angles of 6.94 (4) and 1.94° (5) for the planes formed
Figure 4. ORTEP-type perspective view of complex 5, with ellipsoids drawn
at the 50 % probability level. Selected bond lengths [Å] and angles [°]: Pt1–
C18 2.097(4), Pt1–P1 2.213(12), Pt1–S1 2.310(10), Pt1–N1 2.113(3), N1–C6
1.459(5), N1–C3 1.310(5), C3–C2 1.432(6), C1–C2 1.350(6), S1–C1 1.700(4), N1–
Pt1–P1 175.14(9), C18–Pt1–S1 174.74(13), C18–Pt1–P1 83.99(13), P1–Pt1–S1
90.75(4), S1–Pt1–N1 93.72(9), N1–Pt1–S1 93.72(9), C18–Pt1–N1 91.53(16).
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3
3JHH = 6.94 Hz, 6 H, CH(CH3)], 1.22 [d, JHH = 6.94 Hz, 6 H, CH(CH3)],
with the methyl or isopropyl substituents above and below the
metal center.[16] The dihedral angle between the mean planes
of the MC3NS rings and the Mes/Dipp groups are 86.3 (4) and
79.9° (5). In both cases, the carbon substituents above the
chelate plane (C14 for 4 and C16 for 5) are tilted towards the
M–Me group. The N–C–C–C–X (X = O, S) fragment is planar and
the bond lengths indicate electron delocalization, similarly to
that reported in the literature.[4,9,12–14] Interestingly, the C–O
bond length (1.268 Å) in complex 2 is shorter than that in
the ketoiminato complexes previously reported (i.e., C–O
1.311 Å),[17,12b] which suggests a strengthening of the bond.
The C–S distance in platinum complex 5 is slightly longer than
that in palladium complex 4, but both are in the range
described in the literature for monothio-ꢀ-diketone.[18] Finally,
the M1–N1, M1–S15, M1–C15, and M1–P1 bond lengths are
consistent with those reported for Pd/Pt–sulfur complexes.[7,19]
3
1.64 (s, 3 H, MeC=N), 2.12 (s, 3 H, MeC=O), 3.04 [h, JHH = 6.94 Hz,
2 H, CH(CH3)2], 5.21 [s, 1 H, C(=O)-CH-C(=N)], 7.17 [d, 2 H,
C6H2H(iPr)2], 7.29 [t, 1 H, C6H2H(iPr)2], 12.06 (s, 1 H, O···H-N) ppm.
13C NMR (127.5 MHz, CDCl3): δ = 18.8 (CNMe), 22.4 [CH(CH3)], 24.3
[CH(CH3)], 28.2 [CH(CH3)], 28.7 (MeCO), 95.3 [C(=O)-CH-C(=N)], 123.3,
128.0, 133.3, 146.0, 162.9 (C=N), 195.6 (C=O) ppm.
4-(2,4,6-Trimethylphenylamino)-3-penten-2-one (L2): 2,4,6-Tri-
methylphenylaniline (7.77 g, 57.5 mmol) and acetylacetone (11.51 g,
115 mmol) were dissolved in toluene (50 mL), and p-toluenesulfonic
acid (ca. 50 mg) was added. The reaction mixture was heated at
reflux in a Dean–Stark apparatus for 1 d. After this time, it was
cooled to room temperature and the solvent was removed under
reduced pressure to give an orange-brown oil. After allowing the
oil to solidify, the ligand was purified by two crystallizations from
1
hexanes in 80–86 % yield. H NMR (500 MHz, CDCl3): δ = 1.63 (s, 3
H, MeC=N), 2.10 (s, 3 H, MeCO), 2.16 [s, 6 H, (Me)2C6H2(Me)], 2.28 [s,
3 H, (Me)2C6H2(Me)], 5.20 (s, 1 H, CO-CH-CN), 6.90 [s, 2 H,
(Me)2C6H2(Me)], 11.85 (s, 1 H, O···H-N) ppm. 13C NMR (300 75.4 MHz,
CDCl3): δ = 17.9 [(Me)2C6H2(Me)], 18.6 (CNMe), 20.7 [(Me)2C6H2(Me)],
28.8 (COMe), 95.5 [C(=O)-CH-C(=N)], 128.7, 133.7, 135.5, 136.8, 162.8
(C=N), 195.6 (C=O) ppm.
Conclusions
Efficient methodologies for the facile synthesis of bidentate
N,O- (AcNac) and N,S-donor (SacNac) ligands and a series of
methyl–palladium and –platinum complexes with completely
asymmetric coordination environments have been achieved.
Whereas the SacNac ligands performed the protonation reac-
tion with both dimethyl–palladium and –platinum complexes,
the AcNac ligands only reacted with the dimethyl–palladium
complex. Compounds 4 and 5 are the first examples of fully
structurally characterized palladium and platinum complexes
containing SacNac ligands. The straightforward synthesis of
SacNac species may be extended to generate a family of biden-
tate ligands, which, according to their coordination properties,
might be interesting candidates for catalytic applications as
olefin polymerization and C–C coupling reactions.
Alternative Synthesis of Ligands L1 and L2 Using Microwave:
The arylamine (10 mmol) and acetylacetone (20 mmol) were dis-
solved in benzene (20 mL) along with p-toluenesulfonic acid
(20 mg). The reaction mixture was heated at reflux in an open
Dean–Stark apparatus mounted inside a CEM-Discovery microwave
oven. The mixture was irradiated in six cycles of 1 h each; for the
first two cycles, the irradiating power was 300 W, and for the four
remaining cycles, the power was reduced to 250 W. A flow of ice-
cold water was needed for the condenser.
After completing the cycles, the products were purified by the same
treatment as in the previous syntheses, yields of around 80 % were
obtained for each ligand.
4-(2,6-Diisopropylphenylamino)-3-penten-2-thione (L3): L1
(2.59 g, 10 mmol) and Lawesson's reagent (2.02 g, 5 mmol) were
dissolved in CH2Cl2 (20 mL) under nitrogen. The reaction mixture
was warmed at 35 °C for 1.5 h. After this time, the intense yellow
solution was cooled to room temperature, and the compound of
interest was purified by column chromatography on silica gel and
a hexane/ethyl ether mixture (5:1) as eluent. The product was ob-
tained as a yellow solid in 80–85 % yield. 1H NMR (500 MHz, CDCl3):
δ = 1.18 [d, JHH = 6.94 Hz, 6 H, CH(CH3)2], 1.23 [d, JHH = 6.94 Hz,
6 H, CH(CH3)2], 1.81 (s, 3 H, MeC=N), 2.65 (s, 3 H, MeC=S), 2.95 [h,
3JHH = 6.94 Hz, 2 H, CH(Me)2], 6.32 (s, 1 H, Me-CS-CH-CN-Me), 7.22
[d, 2 H, C6H2H(iPr)2], 7.35 [t, 1 H, C6H2H(iPr)2], 15.28 (s, 1 H, S···H-
N) ppm. 13C NMR (125.7 MHz, CDCl3): δ = 20.8 (MeCN), 22.5
[CH(CH3)], 25.0 [CH(CH3)], 28.6 [CH(CH3)], 38.7 (MeCS), 112.7 [C(=S)-
CH-C(=N)], 123.7, 128.7, 132.4, 145.1, 166.3 (C=N), 206.9 (C=S) ppm.
C17H25NS (275.45): calcd. C 74.13, H 9.15, N 5.08, S 11.64; found C
74.11, H 9.10, N 5.10, S 11.60.
Experimental Section
General: Unless otherwise stated, all reactions and manipulations
were performed by using standard Schlenk techniques. Commer-
cially available reagents were used as received without further puri-
fication unless specified otherwise. All solvents were purified by
distillation using standard methods. [Pd(Me)2(tmeda)] and
[Pt(Me)2(cod)] were prepared according to literature proce-
dures.[20,21] Microwave-assisted reactions were carried out in a CEM
Discovery MW oven. 1H, 13C, and 31P NMR spectra were recorded
by using a Bruker Avance Ultrashield 300 or 500 MHz spectrometer
in CDCl3 and C6D6 with tetramethylsilane (TMS) as an internal
standard. The signals are abbreviated as follows: s = singlet, d =
doublet, t = triplet, h = heptet, m = multiplet, td = triplet of dou-
blets. Coupling constants (J) are given in Hz. IR spectra were re-
corded with a Perkin–Elmer FT-IR 286 spectrometer.
3
3
4-(2,4,6-Trimethylphenylamino)-3-penten-2-thione
(L4):
L2
4-(2,6-Diisopropylphenylamino)-3-penten-2-one (L1): 2,6-Diiso- (2.17 g, 10 mmol) and Lawesson's reagent (2.02 g, 5 mmol) were
propylaniline (8.51 g, 48 mmol) and acetylacetone (9.61 g, 96 mmol)
were dissolved in toluene (50 mL), and p-toluenesulfonic acid (ca.
50 mg) was added. The reaction mixture was heated under reflux
in a Dean–Stark apparatus for 1 d. After this time, the mixture was
dissolved in CH2Cl2 (20 mL) under nitrogen. The reaction mixture
was warmed at 35 °C for 1.5 h. After this time, the intense orange
solution was cooled to room temperature, and the compound of
interest was purified by column chromatography on silica gel and
cooled to room temperature and the solvent removed under re- a hexane/ethyl ether mixture (5:1) as eluent. The product was ob-
duced pressure to give an orange-brown oil. After allowing the oil
to solidify, the ligand was purified by two crystallizations from hex-
anes to give 70–85 % yield. H NMR (500 MHz, CDCl3): δ = 1.15 [d,
tained as an orange solid in a good yield of 75–85 %. 1H NMR
(500 MHz, CDCl3): δ = 1.81 (s, 3 H, MeC=N), 2.17 [s, 6 H,
(Me)2C6H2(Me)], 2.30 [s, 3 H, (Me)2C6H2(Me)], 2.63 (s, 3 H, MeC=S),
1
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6.31 [s, 1 H, C(=S)-CH-C(=N)], 6.94 [s, 2 H, (Me)2C6H2(Me)], 15.12 (s,
1 H, S···H-N) ppm. 13C NMR (125.7 MHz, CDCl3): δ = 18.2
[(Me)2C6H2(Me)], 20.5 [(Me)2C6H2(Me)], 20.9 (MeCN), 38.7 (MeCS),
113.0 [C(=S)-CH-C(=N)], 129.1, 132.9, 134.4, 137.6, 166.2 (C=N), 206.6 12.95 Hz, PdMe), 15.6 (d, JCP = 35.15 Hz, PMe3-Pd), 23.5 [CH(CH3)],
(C=S) ppm. C14H19NS (233.37): calcd. C 72.05, H 8.21, N 6.00, S 13.74; 24.1 [CH(CH3)], 27.6 [CH(CH3)], 27.7 (MeC=N), 33.3 (MeC=S), 119.9
1.77 (s, 3 H, MeC=N), 2.47 (s, 3 H, MeC=S), 3.02 [h, 3JHH = 6.81 Hz, 2
H, CH(Me)2], 6.33 (s,
1
H, CS-CH-CN), 7.12–7.17 [m,
3
H,
=
2
C6H3(iPr)2] ppm. 13C NMR (125.7 MHz, CDCl3): δ = 9.1 (d, JCP
1
found C 72.03, H 8.15, N 6.03, S 13.65.
[C(=S)-CH-C(=N)], 123.3, 125.0, 139.3, 147.9, 164.3 (C=N), 166.3 (C=
S) ppm. 31P NMR (202.4 MHz, CDCl3): δ = –4.33 (s) ppm.
[Pd(L1)Me(PMe3)] (1): [Pd(Me)2(tmeda)] (0.063 g, 0.249 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
a solution (5 mL) containing L1 (0.065 g, 0.258 mmol) was added
to a Pd complex solution through a cannula. PMe3 (0.25 mL,
C21H36NPPdS (471.96): calcd. C 53.44, H 7.69, N 2.97, S 6.79; found
C 53.38, H 7.63, N 2.99, S 6.57.
[Pd(L4)(PMe3)Me] (4): [Pd(Me)2(tmeda)] (0.069 g, 0.25 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
a solution (5 mL) containing L4 (0.058 g, 0.25 mmol) was added to
the Pd complex solution through a cannula. PMe3 (0.25 mL,
0.25 mmol, 1
M) in toluene was added dropwise to the reaction
mixture through a syringe. The reaction was left under agitation at
room temperature for 24 h. After this time, the solvent was removed
under reduced pressure to leave a pale-beige oil, which was stored 0.25 mmol, 1
M) in toluene was added dropwise to the reaction
at 4 °C to allow solidification. Crystallization in CH2Cl2/hexane gave mixture through a syringe. The reaction was left under agitation at
1
3
1 in 60–65 % yield. H NMR (300 MHz, CDCl3): δ = –0.56 (d, JHP
=
30 °C for 24 h. After this time, the reaction mixture was concen-
trated, evaporating part of the solvent under reduced pressure. The
tube was stored at 4 °C to allow crystallization. The greenish yellow
crystals of 4 obtained were filtered and dried under reduced pres-
3
4.02 Hz, 3 H, PdMe), 1.11 [d, JHH = 6.82 Hz, 6 H, CH(Me)2], 1.19 [d,
3JHH = 6.82 Hz, 6 H, CH(Me)2], 1.38 (d, JHP = 10.14 Hz, 9 H, PMe3),
3
1.61 (s, 3 H, MeCN), 1.98 (s, 3 H, MeCO), 3.18 [h, 3JHH = 6.82 Hz, 2 H,
CH(Me)2], 4.99 [s, 1 H, C(=O)-CH-C(=N)], 7.11 (s, 3 H, N-C6H3) ppm.
1
3
sure, yield 50–60 %. H NMR (500 MHz, CDCl3): δ = –0.56 (d, JHP
=
13C NMR (125.7 MHz, CDCl3): δ = –2.6 [d, JCP = 14.65 Hz, Pd(CH3)],
3.52 Hz, 3 H, PdMe), 1.44 (d, JHP = 10.01 Hz, 9 H, PMe3), 1.67 (s, 3
2
2
1
14.1 (d, JCP = 30.93 Hz, PMe3), 23.7 [CH(CH3)], 24.2 [CH(CH3)], 25.1 H, MeC=N), 2.04 [s, 6 H, (Me)2Ph(Me)], 2.28 (s, 3 H, MeC=S), 2.45
(MeCN), 27.5 (MeCO), 27.6 [CH(CH3)], 96.5 [C(=O)-CH-C(=N)], 123.2,
[s, 3 H, (Me)2Ph(Me)], 6.31 (s, 1 H, Me-CS-CH-CN-Me), 6.88 [s, 2 H,
124.7, 141.1, 146.7, 164.7 (C=N), 178.3 (C=O) ppm. 31P NMR
(Me)2C6H2(Me)] ppm. 13C NMR (125.7 MHz, CDCl3): δ = 6.6 (d, 3JCP
=
1
(202.4 MHz, CDCl3): δ = –3.72 (s) ppm. C21H39NOPPd (458.92): calcd. 12.95 Hz, Pd-Me), 15.67 (d, JCP
= 35.29 Hz, PMe3), 18.7
C 54.96, H 8.57, N 3.05; found C 54.68, H 8.35, N 2.99.
[(Me)2C6H2(Me)], 20.8 [(Me)2C6H2(Me)], 26.3 (MeC=N), 33.2 (MeC=S),
120.2 [C(=S)-CH-C(=N)], 128.5, 129.0, 133.2, 147.6, 164.8 (C=N), 165.4
(C=S) ppm. 31P NMR (202.4 MHz, CDCl3): δ = –4.85 (s) ppm.
[Pd(L2)Me(PMe3)] (2): [Pd(Me)2(tmeda)] (0.065 g, 0.257 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
a solution (5 mL) containing L2 (0.054 g, 0.248 mmol) was added
to the Pd complex solution through a cannula. PMe3 (0.25 mL,
C18H30NPPdS (429.88): calcd. C 50.29, H 7.03, N 3.26, S 7.46; found
C 50.21, H 7.13, N 3.27, S 7.40.
0.25 mmol, 1
M
) in toluene was added dropwise to the reaction
[Pt(L3)Me(PMe3)] (5): [Pt(Me)2(cod)] (0.125 g, 0.375 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
a solution (5 mL) containing L3 (0.103 g, 0.375 mmol) was added
to the Pt complex solution through a cannula. PMe3 (0.25 mL,
mixture through a syringe. The reaction was left under agitation at
room temperature for 24 h. After this time, the reaction mixture
was concentrated, evaporating part of the solvent under reduced
pressure. The tube was stored at 4 °C to allow crystallization. Grayish
0.25 mmol, 1
M) in toluene was added dropwise to the reaction
white crystals of 2 were obtained and filtered and dried under re- mixture through a syringe. The reaction was left under agitation at
duced pressure; a second crystallization from the mother liquors,
30 °C for 24 h. After this time, the reaction mixture was concen-
trated, evaporating part of the solvent under reduced pressure. The
tube was stored at 4 °C to allow crystallization. The yellow micro-
1
using the same method, afforded more crystals, yield 80–90 %. H
3
NMR (300 MHz, CDCl3): δ = –0.66 (d, JHP = 3.76 Hz, 3 H, PdMe),
2
1.38 (d, JHP = 10.09 Hz, 9 H, PMe3), 1.52 (s, 3 H, MeC=N), 1.96 (s, 3 crystals of 5 obtained, were filtered and dried under reduced pres-
1
1
H, MeC=O), 2.07 [s, 6 H, (Me)2C6H2(Me)], 2.26 [s, 3 H, (Me)2C6H2(Me)],
sure, yield 60–65 %. H NMR (300 MHz, CDCl3): δ = –0.04 (d, JHP
=
=
3
2
3
4.97 (s, 1 H, Me-CO-CH-CN-Me), 6.85 [s, 2 H, (Me)2C6H2(Me)] ppm.
4.49, JHPt = 59.62 Hz, 3 H, PtMe), 1.09 (d, JHP = 10.48, JHPt
2
13C NMR (125.7 MHz, CDCl3): δ = –5.2 (d, JCP = 13.77 Hz,
37.45 Hz, 9 H, PMe3), 1.03 [d, 3JHH = 6.89 Hz, 6 H, CH(CH3)2], 1.36 [d,
3
Me3PPdMe), 13.9 (d, JCP = 30.60 Hz, PMe3), 18.7 [(Me)2C6H2(Me)], 3JHH = 6.89 Hz, 6 H, CH(CH3)2], 1.49 (s, 1 H, MeC=N), 2.40 (s, 3 H,
3
20.8 (MeC=N), 24.0 [(Me)2C6H2(Me)], 27.4 (MeC=O), 96.4 [C(=O)-CH-
MeC=S), 3.27 [h, JHH = 6.89 Hz, 2 H, 2CH(Me)2, CH(CH3)2], 6.32 [s, 1
C(=N)], 128.2, 130.6, 132.7, 146.2, 163. 8 (C=N), 178.5 (C=O) ppm. H, C(=S)-CH-C(=N)], 7.08–7.20 (m, 3 H, N-C6H3) ppm. 13C NMR
31P NMR (202.4 MHz, CDCl3): δ = –4.35 (s) ppm. C18H33NOPPd
(416.84): calcd. C 51.86, H 7.98, N 3.36; found C 51.53, H 7.91, N
3.25.
(125.7 MHz, CDCl3): δ = 0.6 (d, JCP = 10.90, JCPt = 649.8 Hz, PtMe),
2
1
1
2
14.25 (d, JCP = 42.69, JCPt = 43.60 Hz, PtPMe3), 23.6 [CH(CH3)2],
24.1 [CH(CH3)2], 27.3 [CH(CH3)2], 28.6 (MeC=N), 32.8 (MeC=S), 121.6
[s, JCPt = 57.22 Hz, C(=S)-CH-C(=N)], 123.1, 125.6, 139.9, 147.4, 161.0
[Pd(L3)Me(PMe3)] (3): [Pd(Me)2(tmeda)] (0.063 g, 0.25 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
a solution (5 mL) containing L3 (0.069 g, 0.25 mmol) was added to
the Pd complex solution through a cannula. PMe3 (0.25 mL,
(s, JCPt = 56.30, JCP = 2.37 Hz, C=N), 162.4 (s, C=S) ppm. 31P NMR
2
3
1
(202.4 MHz, CDCl3): δ = –29.31 (s, JPPt = 3697 Hz) ppm.
C21H36NPPtS (560.65): calcd. C 44.99, H 6.47, N 2.50, S 5.72; found
C 44.87, H 6.42, N 2.43, S 5.63.
0.25 mmol, 1
M) in toluene was added dropwise to the reaction
mixture through a syringe. The reaction was left under agitation at
30 °C for 24 h. After this time, the reaction mixture was concen-
[Pt(L4)Me(PMe3)] (6): [Pt(Me)2(cod)] (0.125 g, 0.375 mmol) was
placed in a Schlenk tube and dissolved in acetonitrile (5 mL). Then
trated, evaporating part of the solvent under reduced pressure. The a solution (5 mL) containing L4 (0.86 g, 0.375 mmol) was added to
tube was stored at 4 °C to allow crystallization. The clear-yellow
the Pt complex solution through a cannula. PMe3 (0.25 mL,
microcrystals of 3 were filtered and dried under reduced pressure,
0.25 mmol, 1 ) in toluene was added dropwise to the reaction
M
3
yield 60–73 %. 1H NMR (500 MHz, CDCl3): δ = –0.46 (d, JHP
=
mixture through a syringe. The reaction was left under agitation at
30 °C for 24 h. After this time, the reaction mixture was concen-
trated, evaporating part of the solvent under reduced pressure. The
3
3.54 Hz, 3 H, PdMe), 1.08 [d, JHH = 6.81 Hz, 6 H, CH(CH3)2], 1.20 [d,
2
3JHH = 6.81 Hz, 6 H, CH(CH3)2], 1.43 (d, JHP = 10.08 Hz, 9 H, PMe3),
Eur. J. Inorg. Chem. 2016, 874–879
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Full Paper
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171.
tube was stored at 4 °C to allow crystallization. The yellow micro-
crystals of 6 obtained were filtered and dried under reduced pres-
1
3
sure, yield 62–65 %. H NMR (300 MHz, CDCl3): δ = –0.02 (d, JHP
=
=
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4.12, JHPt = 59.66 Hz, 3 H, PtMe), 1.09 (d, JHP = 10.38, JHPt
37.9 Hz, 9 H, PMe3), 1.37 (s. 3 H, MeCN), 2.21 [s, 3 H, (Me)2Ph(Me)],
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1
(125.7 MHz, CDCl3): δ = –2.0 (d, JCP = 10.90, JCPt = 637 Hz, PtMe),
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=
=
56.31 Hz), 128.3, 129.8, 133.4, 147.1, 161.5 (C=N, 2JCPt = 79.19, 3JCP
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Acknowledgments
This work was supported by grants from the Universidad de
Guanajuato (UG-2012 and SEP/CONACYT, grant number 02-
44420). D. R. P. thanks the Consejo Nacional de Ciencia y Tecno-
logía (CONACYT) for a doctoral fellowship. The National Labora-
tory of CONACYT/UGTO is thanked for support.
Keywords: Palladium · Platinum · N,S ligands
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Received: October 7, 2015
Published Online: January 15, 2016
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www.eurjic.org
879
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim