Mono- and trinuclear tripodal platinum(II) chelated complexes containing a pyridine/sulfoxide based anchoring framework

Article abstract of DOI:10.1002/ejic.201300042

New tripodal ligands 2,4,6-triethyl-1,3,5-tris{[1-(2-pyridinyl)ethenyl] sulfinylmethyl}benzenes 6, characterized by three pendant chains each containing both sulfoxide and pyridine moieties, were synthesized from the corresponding sulfenic acid and 2-ethy

Full text of DOI:10.1002/ejic.201300042

FULL PAPER
DOI:10.1002/ejic.201300042
Mono- and Trinuclear Tripodal Platinum(II) Chelated
Complexes Containing a Pyridine/Sulfoxide Based
Anchoring Framework
Anna Barattucci,*[a] M. Rosaria Plutino,*[b] Cristina Faggi,[c]
Paola Bonaccorsi,[a] Luigi Monsù Scolaro,[a] and
Maria Chiara Aversa[a]
Keywords: Platinum(II) complexes / Tripodal ligands / S ligands / N ligands
New tripodal ligands 2,4,6-triethyl-1,3,5-tris{[1-(2-pyridinyl)-
ethenyl]sulfinylmethyl}benzenes 6, characterized by three
pendant chains each containing both sulfoxide and pyridine
moieties, were synthesized from the corresponding sulfenic
acid and 2-ethynylpyridine. Two diastereomeric mixtures
were obtained and separated, one racemic mixture 6a, hav-
ing a C3 symmetry axis and the other 6b with no symmetry.
With the aim of studying the coordination ability of these
chelating-κN,κS type ligands, monobranched racemic [1-(2-
pyridinyl)ethenyl]sulfinylbenzene 9 was also synthesized.
Upon addition of an equivalent amount of the monochelating
ligand 9 or the tripodal species 6a to a CD3CN solution of a
platinum(II) complex of the type cis-[PtMe2(Me2SO)2] (Pt1) or
trans-[PtMeCl(Me2SO)2] (Pt2), platinum(II) coordination and
chelation occurred, as definitively indicated by a sharp
change in the 1H NMR spectrum towards the final corre-
sponding chelated platinum(II) species and free dimethyl
sulfoxide. The prepared platinum(II) species contain one or
three fragments of the type {PtMe2}(10 or 12) and
{PtMeCl}(11 or 13) bound to the pyridinyl/sulfinyl skeleton
in the coordinating ligands 9 and 6a. All the prepared species
were fully characterized by NMR spectroscopy from the con-
nectivities in 2D-COSY, 1H-13C HSQC and phase-sensitive
2D-NOESY spectra which confirm the molecular mechanics
calculation predictions.
the most thermodynamically stable tripodal conformation,
suitable for the interaction with host species such as anions
and cations and small natural molecules.[2] Fascinating
multibranched aromatic structures, where a sulfide moiety
proximal to a trigonal nitrogen helps the coordination of
a large variety of cations, have been recently synthesized.
Depending on the kind of nitrogen, on the number of func-
tionalized arms (from two to six) and the relative position
of the two heteroatoms, they have found applications in ion-
selective electrode construction, in the formation of multi-
metallic complexes and coordination polymers.[3]
Introduction
Polyfunctionalized flexible organic systems constitute a
fascinating class of molecules owing to their general ten-
dency to optimize their conformation to satisfy the host-
guest interaction geometry and they may be employed as
building blocks for the assembly of extended supramo-
lecular architectures.[1] Hexafunctionalized 1,3,5-R-2,4,6-
RЈ-substituted benzenes, where R is a linear aliphatic chain
containing two or more carbon atoms, are known to adopt
As is evident from a large number of publications, the
sulfinyl group has played a leading role as a ditopic organic
labile ligand[4] and its corresponding transition metal com-
plexes have been widely employed in catalysis.[5] More re-
cently, organometallic systems derived from C2 disulfoxides
have been successfully used in enantioselective catalysis.[6]
[a] Dipartimento di Scienze Chimiche, Università degli Studi di
Messina,
Viale F. Stagno d’Alcontres 31, Vill. S. Agata, 98166 Messina,
Italy
Fax: +39-090-6765186
E-mail: abarattucci@unime.it
[b] Istituto per lo Studio dei Materiali Nanostrutturati, ISMN –
CNR, Unità di Messina-Sezione di Palermo, Messina, Italy
c/o Dipartimento di Scienze Chimiche, Università degli Studi However, in comparison with the corresponding sulfides,
di Messina,
very few articles deal with tri- or polysulfoxides and their
Viale F. Stagno d’Alcontres 31, Vill. S. Agata, 98166 Messina,
metallorganic derivatives,[3f,7] possibly because of the diffi-
Italy
Fax: +39-090-3974108
culty in their synthesis and purification resulting from the
stereogenicity of the sulfoxide sulfur and the subsequent
obtainment of complex diastereomeric mixtures of enantio-
mers. Tripodal species containing three pyridine rings have
been utilized in coordination chemistry and, depending on
the stoichiometry of the reaction and coordination geome-
E-mail: rosaria.plutino@pa.ismn.cnr.it
Homepage: http://www.pa.ismn.cnr.it/plutino.htm
[c] Centro Interdipartimentale di Cristallografia, Università degli
Studi di Firenze,
Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201300042.
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try of the metal ion, 1:3 or 1:1 complexes, the ones in which ethynylpyridine was almost quantitatively recovered from
the metal is completely blocked inside the tripodal cavity, the head of the chromatographic column. After the inter-
are formed.[8] However, to the best of our knowledge, noth- mediation of the achiral trisulfenic acid 5, two new dia-
ing is known in the literature about tripodal N/S(O)[9] metal stereomeric couples of enantiomers are formed: one having
derivatives.
a C3 symmetry axis (6a), where the three stereogenic sulfinyl
In this work we report the efficient synthesis of the tripo- centers have the same absolute stereochemistry, and the
dal system 6, containing three functional chelating arms other where no symmetry is present (6b). The two dia-
having both sulfoxide and pyridine moieties, and the easy stereomeric mixtures were obtained, confirming the statisti-
separation of the corresponding C3 and asymmetric dia- cal prediction, in a 1:3 ratio and a simple flash column
stereomers 6a and 6b as racemic mixtures. The synthesis chromatographic process was needed to separate each of
can be accomplished by means of the regioselective ad- them as racemate.
dition of a transient sulfenic acid[10] to triple bonds. The
All proton and carbon resonances belonging to com-
first example of the application of a tripodal N/S(O) ligand
as C3 symmetric 6a in the κN,κS coordination of the square
planar platinum(II) complexes cis-[PtMe2(Me2SO)2] (Pt1)[11]
and trans-[PtMeCl(Me2SO)2] (Pt2)[12] is also reported.
pounds 6 were assigned through NMR spectroscopy in 2D-
1
COSY and H-13C HSQC experiments, as also predicted
by molecular mechanics calculation, and by phase-sensitive
NOESY spectra. In particular, Figure 1 shows some 2D ex-
periments performed on the racemic mixture of the C3 sym-
metric compound 6a. The “three-legged stool” most popu-
lated conformation in a solution of 6a, with a mutual down-
wards disposition of the alternating three ethyl chains and
three sulfinyl/pyridinyl anchoring fragments, is fully con-
firmed by strong interligand NOE cross-peaks between H6
pyridine ortho-protons and methyl protons that lie close to
them, on the vicinal ethyl substituents (blue square in Fig-
ure 1 on the left side). As expected for this kind of structure,
the methylene protons of the ethyl groups are dia-
stereotopic, as evidenced by the pair of multiplets at δ =
3.14 and 3.28 ppm (see Exp. Sect.), as well as those bound
to the sulfinyl group, resonating as an AB system at δ =
4.45 and 4.12 ppm. Further evidence for the highly symmet-
ric “three legged stool” conformation comes from the spe-
cific NOE contacts between the two different kinds of
methylene protons, as shown in Figure 1 (right side), in par-
ticular between the three CHASO protons at 4.45 and the
Results and Discussion
Synthetic Procedures
The synthetic pathway to the tripodal 2,4,6-triethyl-1,3,5-
tris{[1-(2-pyridinyl)ethenyl] sulfinylmethyl}benzenes 6 is
shown in Scheme 1. Starting from commercially available
1,3,5-triethylbenzene (1), the trithiol 3 was obtained follow-
ing literature procedures[10c] from the tris(bromomethyl)-
benzene 2 and was transformed, in three steps, into the tris-
ulfoxides 6, by the generation of the transient trisulfenic
acid[10c,10f] 5 and its completely regioselective concerted ad-
dition to a suitable triple bond.[13] In particular, trisulfenic
acid 5 has been generated in situ through the thermolysis
of the racemic mixtures of the tripodal trisulfoxide 4 in 1,4-
dioxane at reflux temperature for four hours and in the
presence of a large excess of 2-ethynylpyridine (1:6).
Tripodal compounds 6 were obtained in 60% total yield, three methylenic protons CHBCH3 at δ = 3.14 ppm (green
after column chromatography. The unreacted excess of 2- square) and between the other three CHBSO protons at 4.12
Scheme 1. Synthetic pathway to 2,4,6-triethyl-1,3,5-tris{[1-(2-pyridinyl)ethenyl]sulfinylmethyl}benzenes 6.
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Figure 1. Phase-sensitive 2D-NOESY spectrum (left) and its aliphatic region (right) relative to a CDCl3 solution of the 6a conformer as
assumed from the selective evidenced NOE peaks. The red cross-peaks arise from NOE (500 MHz, 298 K).
and the three methylenic protons CHACH3 at δ = 3.28 ppm the crystalline state as well due to the reciprocal positions
(red square).
of substituents on the benzene ring. However, in the solid
Good crystals of the C3 symmetric racemic mixture 6a state, this symmetry is not exactly reflected, since the com-
were obtained from a CH2Cl2/Et2O mixture and the result pound crystallizes in the monoclinic crystal system, within
of the X-ray diffractometry shows that the system crys- the P21/c space group. This deviation from the expected
tallizes in the P21/c space group in a more populated tripo- highly symmetric preferred conformation is supported by
dal conformation. An ORTEP view of rel-2,4,6-triethyl- the very different values found for the significant torsion
1,3,5-tris{[(R)-1-(2-pyridinyl)ethenyl]sulfinylmethyl}benz- angles and for the angles formed among the aromatic ring
ene (6a), together with the crystal packing in the unit cell plane and the three planes of the heteroaromatic rings (see
is shown in Figure 2. When considering the above reported Supporting Information).
conformational analysis of 6a, it would be logical to expect
With the aim of studying the platinum(II) coordination
the highly symmetric “three legged stool” conformation in ability towards the pyridine/sulfoxide functionalities that
Figure 2. Left: Ortep view of rel-2,4,6-triethyl-1,3,5-tris{[(R)-1-(2-pyridinyl)ethenyl]sulfinylmethyl}benzene (6a) together with the structure
numbering. Selected bond lengths [Å] and angles [°] for 6a: S1 –O1 1.495; S1ЈЈ–O1 1.490; S1ЈЈЈ–O1 1.488; C9 –S1 –C7Ј 96.82; C9ЈЈ–S1
–
Ј
Ј
ЈЈ
ЈЈЈ
Ј
Ј
ЈЈ
C7ЈЈ 98.62; C9ЈЈЈ–S1ЈЈЈ–C7ЈЈЈ 96.10. Right: molecule crystal packing in the unit cell.
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1
characterize the three N/S branches of the tripodal ligands titatively. A typical H NMR spectroscopic comparison be-
6, we decided to start from a simple model molecule. For tween the free species and the crude reaction product is re-
this reason we synthesized compound 9, bearing only one ported in Figure 3 (spectra a and b). Taking as an example
sulfinyl and one pyridinyl anchoring moiety, in such a rela- the reaction run in CD3CN between cis-[PtMe2(Me2SO)2]
tive position that they could give the formation of a stable (Pt1) and ligand 9, the downfield shift of ca. 0.5 ppm rela-
five-membered ring after chelation, with a phenyl moiety tive to the H6Ј ortho-proton of the pyridine ring (δ =
directly bound to the sulfoxide group for enhancing its ste- 8.96 ppm) clearly indicates an established coordination
ric requirements. Simple thermolysis of the already reported which is further evidenced by the diagnostic hydrogen/plati-
sulfoxide 7[13] at the reflux temperature of toluene gave the num(II) coupling constant (3JPt,H = 22.0 Hz) for the same
intermediate benzenesulfenic acid (8) that was added in situ proton with the 195Pt nucleus that gives rise to two typical
to the triple bond of commercial 2-ethynylpyridine, present satellite peaks. Otherwise, different methyl signals of the
in excess (Scheme 2). After easy and rapid column newly formed complex 10 are present, each with the two
chromatography, a racemic mixture of the unique re- satellite peaks but each bearing different coupling constants
gioisomer 9 was obtained in almost quantitative yield and with 195Pt which are characteristic of a methyl group trans
2
it was fully characterized.
to a sulfoxide (δ = 0.85 ppm, JPt,H = 77.9 Hz, PtCH3 trans
2
to S), and to a pyridine nitrogen (δ = 0.78 ppm, JPt,H
=
90.9 Hz, PtCH3 trans to N). The presence of selective NOE
cross peaks between (i) the signals relative to the ortho-pyr-
idine proton at δ = 8.96 ppm (H6Ј) and the methyl trans to
sulfoxide at δ = 0.85 ppm (s with satellites, 2JPt,H = 77.9 Hz,
PtCH3), and (ii) the peaks at δ = 7.90 ppm (H2,6) of the
ortho-phenyl protons and δ = 0.78 ppm (s with satellites,
2JPtH = 90.9 Hz) with the methyl protons PtCH3 trans to
pyridine (see Figure 3, left side), definitively confirm the re-
sults.
Scheme 2. Synthetic pathway to the racemic [1-(2-pyridinyl)ethen-
yl]sulfinylbenzene ligand 9.
Coordination of Ligands 6 and 9 with Square Planar
Platinum(II) Complexes Pt1 and Pt2
Platinum(II) complexes of the type cis-[PtMe2-
(Me2SO)2] (Pt1)[11] and trans-[PtMeCl(Me2SO)2] (Pt2)[12]
have been employed as useful synthons for introducing the
fragments {PtMe2} and {PtMeCl}, respectively, into dif-
ferent monocoordinating or chelating heterocyclic sys-
tems.[12a,12c,14] We thought it worthwhile to extend this
methodology to the coordination of the sulfinyl sulfur and
pyridinyl nitrogen atoms of compound 9 and tripodal spe-
cies 6. In particular, we tested the reaction of the model
monocoordinating [1-(2-pyridinyl)-ethenyl]sulfinylbenzene
9 with the two selected kinds of square planar platinum(II),
complexes Pt1 and Pt2.
Scheme 3. Synthetic pathway of compound 9 towards platinum(II)
complexes 10 and 11 (in CD3CN at 298 K).
The synthetic procedure for the platinum(II) derivatives
10 and 11 was first established in situ in a 5 mm NMR tube
and then on a larger scale, at 298 K, in CD3CN, since the
A brief comment should be devoted to compound 11,
starting compounds and products showed good solubility the product of the reaction between
9 and trans-
and no trace of decomposition in this solvent for up to one [PtMeCl(Me2SO)2] (Pt2). Besides the chemical shift of the
week. Upon addition of an equivalent amount of the ligand heteroaromatic proton H6Ј that has moved to 9.49 ppm (Δδ
9 to a solution of the appropriate platinum complex in ca. 1 ppm), a methyl signal with 195Pt coupling constant (δ
2
CD3CN, there is a sharp change in the NMR spectrum, = 0.87 ppm, JPt,H = 79.7 Hz, PtCH3 trans to N) was no-
from the signals belonging to the starting platinum(II) com- ticed (Figure 3, c). This assignment was confirmed by a se-
plexes and free ligand 9 to those that may be attributed lective NOE cross peak between the signal relative to the
to the final chelated platinum(II) species and free dimethyl methyl protons and the two ortho-protons of the phenyl
sulfoxide.
ring (δ = 7.95 ppm H2,6), while no NOE contact was found
The reaction of formation of complexes 10 and 11 takes with the signal at δ = 9.49 ppm (H6Ј) relative to the ortho-
place according to Scheme 3. The two platinum(II) species pyridine proton.
10 and 11, incorporating the chelated ligand 9 coordinated
Taking into account the previous results, the racemic
at the platinum(II) center through both the pyridine nitro- mixture of the tripodal sulfinyl/pyridinyl ligands 6a was em-
gen (κN) and the sulfoxide sulfur (κS), were obtained quan- ployed in complexation reactions with square planar plati-
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Figure 3. Left: aliphatic section of the 2D-NOESY spectrum showing selective NOE between PtCH3 and the aromatic protons (300 MHz,
298 K). Right: 1H NMR spectrum of (a) ligand 9 in CD3CN (300 MHz, 298 K) and upon addition of one equiv. of (b) cis-[PtMe2-
(Me2SO)2] or (c) trans-[PtMeCl(Me2SO)2].
num(II) complexes such as cis-[PtMe2(Me2SO)2] (Pt1) and pyridine are perfectly resolved and in particular the ortho-
trans-[PtMeCl(Me2SO)2] (Pt2). As shown in Scheme 4, the protons H6Ј,6ЈЈ,6ЈЈЈ show the characteristic 195Pt coupling
syntheses of the trinuclear species of the type {[PtXY]3(6a- constants that demonstrates the chelation (δ = 9.00 ppm,
κN,κS)} (X = Y = Me, 12; X = Cl, Y = Me, 13) were 3JPt,H = 27.4 Hz), (ii) below 1 ppm it is possible to observe
performed in situ by addition of three equiv. of the corre- the signals relative to the methyl protons trans to pyridine
2
sponding platinum(II) complexes to a CD3CN solution of (δ = 0.90 ppm, JPt,H = 91.2 Hz) and to sulfoxide (δ =
the tripodal ligand 6a. Even in this case, the trinuclear plati-
num(II) derivatives and the free dimethyl sulfoxide are the
only reaction products.
Scheme 4. Synthetic pathway towards the formation of the trinu-
clear platinum(II) complexes 12 and 13 (in CD3CN at 298 K).
1
The H spectrum of the dimethylplatinum(II) derivative
12 (lower side of Figure 4) shows a lower field shift in the
pyridine proton signals in comparison with those of the
corresponding starting tripodal species 6a. The lower reso-
lution can be attributed to the low solubility of the plati-
1
Figure 4. Upper plot: H NMR spectrum of ligand 6a in CD3CN.
1
num(II) derivatives in CD3CN. In particular, from the H
Lower plot: 1H NMR spectrum of the trinuclear derivative 12 as
obtained in situ after the addition of three equiv. of cis-[PtMe2-
NMR spectra, it is possible to observe that: (i) the proton
signals H6Ј,6ЈЈ,6ЈЈЈ, H5Ј,5ЈЈ,5ЈЈЈ, H4Ј,4ЈЈ,4ЈЈЈ and H3Ј,3ЈЈ,3ЈЈЈ of the (Me2SO)2] (300 MHz, 298 K).
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2
0.84 ppm, JPt,H = 78.7 Hz) directly linked to the plati- the fairly high lability of such weakly coordinating mole-
num(II) center, (iii) the diastereotopic protons ϪCH2ϪS cules. Of particular use would be a detailed knowledge of
give a split AB system at δ = 4.20 and 4.59 (2JH,H
=
the mechanistic pathway of the dimethyl sulfoxide substitu-
14.4 Hz), and the olefinic protons give two doublets at δ = tion process. As far as the formation of the chelated species
5.92 and 6.64 ppm (2JH,H = 2.0 Hz), thus confirming the is concerned, we suggest that the pyridinic nitrogen is the
great symmetry of the newly-formed chelated system, and first coordinating group, followed by fast ring closure oper-
(iv) the methyl protons of each ethyl group resonate as a ated by the sulfur atom from the less nucleophilic sulfox-
triplet at δ = 0.68 ppm (CH2ϪCH3), while the methylene ide.[19] However, the only species that can be detected in the
protons give rise to two multiplets at δ = 2.25 and 3.09 ppm reaction mixture in solution are, in any case, the starting
(CH2ϪCH3). The proton spectrum of the trinuclear species platinum(II) complexes and free ligand (i.e. 6a or 9), to-
[{PtMe2}3(6a-κN,κS)] 12, as well as that of the mononu- gether with the final chelated species and free dimethyl sulf-
clear complex [PtMe2(3-κN,κS)] 10, shows the expected in- oxide (diagnostic signal at 2.5 ppm). Any attempts to ident-
equivalence of the two halves of the molecule, especially ify by 1H NMR spectroscopy, even at low temperatures, the
concerning the two methyl groups directly bound to the presence of other intermediate open-ring species or, in the
platinum(II) center which exhibit two different singlets with case of the trans-platinum(II) complex Pt2, other coordina-
typical 195Pt satellites. The difference in the 195Pt coupling tion isomers were unsuccessful.[20] This means that the ki-
constants is in agreement with the different trans influence netic rate constant for the sulfoxide ring-closure is too high
of the pyridine and the sulfoxide moiety.[15] The pattern of compared with that of the substitution process of the pyr-
the other signals shows a general down-field shift after idine moiety, leading to the conclusions that the open-ring
platinum(II) coordination.
species once formed is rapidly converted into the corre-
1
The H NMR spectrum of compound 13, relative to the sponding chelated species.[20,21] The overall process is imme-
chloromethylplatinum(II) derivatives with the tripodal li- diate in the case of complex Pt1 and quite slow for the
gand 6a, shows similar features as far as the signals pattern precursor complex Pt2 (ca. 10 min reaction time). This is in
of the coordinate organic moiety in 12 is concerned (see agreement with the fast dissociative substitution process of
Figure S2 in Supporting Information). As already seen in the dimethyl sulfoxide for different nucleophiles already
the comparison between the two mononuclear species 10 known for the complex Pt1, mainly due to the strong trans
and 11 (see Figure 3, spectra b and c), the ortho-pyridine effect and trans influence exerted by the two trans-methyl
proton of species 13 resonates at a higher frequency than groups.[22] On the other hand, the trans-chloromethyl spe-
that in the corresponding dimethylplatinum(II) species 12 cies Pt2 bears two less reactive dimethyl sulfoxides trans to
(9.50 vs. 9.00 ppm). In the aliphatic region there is only one each other, that, affected by the less dimethyl sulfoxide
singlet at δ = 0.71 ppm (2JPt,H = 83.8 Hz) with typical plati- trans-influence, give rise to a slower substitution process. In
num(II) satellites accounting for the unique methyl bound this regard its observed high reactivity toward a variety of
to the metal center. Phase-sensitive 2D-NOESY experi- nucleophilic agents has to be ascribed to the corresponding
ments confirmed the tripodal disposition of the substituents aqua-species trans-[PtMeCl(Me2SO)(H2O)], due to multiple
on the benzene platform of the chelated symmetric 12 and solvolysis and isomerization solution equilibria.[23]
13.
Finally we must clarify the enhanced sulfinyl affinity
Preliminary complexation experiments were also con- shown in the chelate formation: by realizing the reaction in
ducted between the non C3 symmetric ligand 6b and cis- a 1:1 ratio, no open-ring species or any kind of equilibrium
[PtMe2(Me2SO)2] (Pt1) or trans-[PtMeCl(Me2SO)2] (Pt2). between reagents and the chelated product in solution could
1H NMR spectra were obtained in each case which were be detected. Several previous kinetic studies have been de-
difficult to analyze and in which the broad signals of the voted to clarify the properties of dimethyl sulfoxide or other
pyridine protons lie in a lower field position with respect to sulfoxides when acting as monocoordinating reagents in
those of the uncoordinated 6b (see Experimental Section). square-planar platinum(II) complexes that, in substitution
As far as the diastereotopic ϪCH2ϪS, the olefinic protons reactions, can be regarded as a poor nucleophiles.[24] Inter-
and the ethylic chains are concerned, complex and difficult estingly, in our studied systems, the product formation ap-
to interpret multiplets between, respectively, δ = 7.00 and pears to be favored by the “chelate effect” of the sulfoxide
5.00 ppm, δ = 5.00 and 4.00 ppm, and δ = 4.00 and group, helped by the conformational rigidity of the chelat-
0.70 ppm were detected. The {PtMe} fragments show in ing rigid N-S framework due to the presence of a rigid link-
each case up-field singlets with typical platinum(II) satel- ing sp2 carbon.
lites with the expected 195Pt coupling constants. Even if all
data converge towards the formation of the two corre-
sponding trinuclear platinum(II) derivatives, further studies
are needed to completely clarify their structures.
Conclusions
The use of transition metal complexes containing sulfox-
ide ligands as precursors in synthetic procedures has been tris{[1-(2-pyridinyl)ethenyl]sulfinylmethyl}benzenes 6 and
known and successfully employed for many years, especially [1-(2-pyridinyl)-ethenyl]sulfinylbenzene has been ef-
A new class of ligands, namely the 2,4,6-triethyl-1,3,5-
9
in the chemistry of coordination and organometallic plati- ficiently prepared by a procedure based on the reactivity of
num(II) complexes.[17,18] The synthetic procedures exploit the corresponding sulfenic acids. In particular, compounds
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in all cases. See Supporting Information for the adopted numbering
of complexes 10–13.
6, with the substituents distributed around a benzene plat-
form in a tripodal fashion, have been separated into the
diastereomeric couples of racemic trisulfoxides, the C3 sym-
metric 6a and the asymmetric 6b, fully characterized by
NMR spectroscopy and, in the case of 6a, by single-crystal
X-ray diffraction analysis. Additionally, as a first experi-
ment in the study of the transition metal coordination abil-
ity of this type of organic ligand, we chose to treat them
CCDC-868526 contains 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.
Synthetic Procedures: The starting sulfoxides 3,3Ј,3ЈЈ-[(2,4,6-tri-
ethyl-1,3,5-benzenetriyl)tris(methylenesulfinyl)]trispropanoic acid
with platinum(II) synthons, such as cis-[PtMe2(Me2SO)2] 1,1Ј,1ЈЈ-trimethyl ester 4[10a,10c] and 3-(phenylsulfinyl)propanoic
acid methyl ester 7[10b] were synthesized following already pub-
(Pt1) and trans-[PtMeCl(Me2SO)2] (Pt2), and so the corre-
sponding mono- (10 and 11) and tris-chelated (12 and 13)
lished methods.
species, each containing one cis-{PtMe2} or cis-{PtMeCl}
fragment for each bidentate anchoring κN,κS frame, were
formed.
The synthesis of compounds 6 provides an efficient ap-
proach for obtaining a class of tripodal bidentate ligands:
the coexistence of the two coordinating N,S sites in the suit-
able relative position and the tripodal conformation has
been shown to be particularly efficient in platinum(II) coor-
dination and may open the way to bind metals with an octa-
hedral geometry.
[1-(2-Pyridinyl)ethenyl]sulfinylbenzene (9): A 1 mm solution of 1 in
toluene was added to three equiv. of 2-ethynylpyridine and main-
tained at reflux temperature for 1 h until the disappearance of 7 by
TLC. The reaction crude was then purified by column chromatog-
raphy, m.p. 40 °C, 80% yield. TLC: Rf 0.35 (petrol/EtOAc, 60:40).
C13H11NOS (229.3): calcd. C 68.09, H 4.84, N 6.11; found C 68.00,
H 4.88, N 6.20. IR (nujol): ν =1037 (S=O) cm–1. 1H NMR
˜
3
4
(300.1 MHz, CDCl3, 298 K):δ = 8.51 (ddd, JH,H = 4.6, JH,H
=
1.7, JH,H = 1.2 Hz, 1 H, H6Ј), 7.71 (m, 2 H, H2 + H6), 7.62 (dt,
5
3JH,H = 8.0, 4JH,H = 1.7 Hz, 1 H, H4Ј), 7.48 (ddd, 3JH,H = 8.0, 4JH,H
= 1.8, JH,H = 1.2 Hz, 1 H, H3Ј), 7.34 (m, 3 H, H3,5 + H4), 7.17
5
(ddd, JH,H = 8.0, 4.6, JH,H = 1.8 Hz, 1 H, H5Ј), 6.53 (d, JH,H
=
3
4
2
1.2 Hz, 1 H, C=CHA), 6.44 (d, 2JH,H = 1.2 Hz, 1 H, C=CHB) ppm.
13C NMR (75.5 MHz, CDCl3, 298 K):δ = 153.7 (C2Ј), 152.3
(C=CH2), 148.7 (C6Ј), 144.1 (C1), 136.6 (C4Ј), 130.9 (C4), 128.8
(C3,5), 125.9 (C2,6), 123.5 (C5Ј), 120.7 (C3Ј), 117.4 (C=CH2) ppm.
1H NMR (300.1 MHz, CD3CN, 298 K):δ = 8.48 (ddd, 3JH,H = 4.9,
Experimental Section
General Methods and Materials: All solvents (AR, LabScan Ltd.,
SpS, Romil Ltd.) used for synthetic procedures were obtained from
commercial suppliers and used as received. All syntheses were car-
ried out on the benchtop in atmospheric conditions unless other-
wise stated. Reactions for the preparation of all the ethenylsulfinyl
derivatives were monitored by TLC on commercially available Ald-
rich silica gel 60 F 254 precoated plates. Products were visualized
by UV or vanillin [1 g dissolved in MeOH (60 mL) and conc.
H2SO4 (0.6 mL)]. Column chromatography was performed on Ald-
rich 60 silica gel. CDCl3 (D, 99.8%) and CD3CN (D, 99.96%) for
NMR measurements were purchased from Sigma–Aldrich Co. and
used as received. All other reagents were of the highest purity grade
commercially available and used without further purification. In-
frared spectra were recorded with KBr cells in the range 4000–
400 cm–1 using a Nicolet Impact 410 spectrometer. The samples for
IR measurements were made up in nujol. NMR measurements
were performed on a Bruker ARX-300 spectrometer equipped with
a broad-band probe operating at 300.1 MHz (1H) or on Varian
Gemini-300 at 300.1 and 75.5 MHz and a Varian 500 spectrometer
operating at 500.1 and 125.7 MHz. All chemical shifts (δ) are re-
ported in parts per million (ppm) downfield of tetramethylsilane
(Me4Si) as an internal standard (δ = 0.0 ppm), or referenced to
the proton resonance resulting from incomplete deuteration of the
NMR solvents such as CDCl3 (1H NMR: 7.26 ppm and 13C NMR:
5
4JH,H = 1.8, JH,H = 1.1 Hz, 1 H, H6Ј), 7.70 (m, 2 H, H2 + H6),
3
4
3
7.68 (dt, Jav = 7.7, JH,H = 1.8 Hz, 1 H, H4Ј), 7.60 (ddd, JH,H
=
+
7.9, JH,H = 1.2, JH,H = 1.0 Hz, 1 H, H3Ј), 7.39 (m, 3 H, H3,5
4
5
H4), 7.23 (ddd, JH,H = 7.5, 4.9, JH,H = 1.2 Hz, 1 H, H5Ј), 6.54
3
4
2
2
(d, JH,H = 1.2 Hz, 1 H, C=CHA), 6.40 (d, J
= 1.2 Hz, 1 H,
H,H
C=CHB) ppm. 13C NMR (75.5 MHz, CD3CN, 298 K):δ = 153.5
(C2Ј), 152.1 (C=CH2), 149.2 (C6Ј), 144.2 (C1), 137.6 (C4Ј), 131.8
(C4), 129.6 (C3,5), 126.6 (C2,6), 124.5 (C5Ј), 121.5 (C3Ј), 117.5
(C=CH2) ppm.
2,4,6-Triethyl-1,3,5-tris{[1-(2-pyridinyl)ethenyl]sulfinylmethyl}benz-
enes (6): A 1 mm solution of 4 in 1,4-dioxane was added to six
equiv. of 2-ethynylpyridine and maintained at reflux temperature
1
for 4 h until the disappearance of the last –CO2CH3 signal by H
NMR spectroscopy. The crude reaction mixture was then purified
by column chromatography and the two racemic mixtures of dia-
stereoisomers separated. The first one to be eluted was rel-2,4,6-
Triethyl-1,3,5-tris{[(R)-1-(2-pyridinyl)ethenyl]sulfinylmethyl}benzene
(6a). White solid, m.p. 197 °C, 15% yield. TLC: Rf 0.34 (acetone/
petroleum ether, 65:35). C36H39N3O3S3 (657.9): calcd. C 65.72, H
5.97, N 6.39; found C 65.59, H 6.06, N 6.34. IR (nujol): ν = 1039
˜
(S=O) cm–1. 1H NMR (300.1 MHz, CDCl3, 298 K): δ = 8.53 (ddd,
77.0 ppm) and CD3CN (1H NMR: 1.94 ppm. 13C NMR: 118.3, 3JH,H = 4.5, JH,H = 1.8, JH,H = 1.0 Hz, 3 H, H6Ј,6ЈЈ,6ЈЈЈ), 7.74 (dt,
4
5
4
3
1.3 ppm). Coupling constants J are given in Hertz. 13C NMR spec-
tra were acquired with the APT technique. NMR peak assignments
at 298 K were performed by using homonuclear (COSY) and het-
eronuclear correlation (1H-13C) spectroscopy. Phase sensitive 1H
2D-NOESY spectra were acquired by using a standard pulse se-
quence with mixing times of 500 (9–11), 800 (12, 13) and 840 ms
(6). 1H-13C HSQC correlation experiments were also performed for
several compounds and were recorded in a gradient-selected phase-
sensitive mode. Melting points were determined on a Kofler hot-
stage apparatus and are uncorrected. The purity of all starting ma-
terials and reaction products was determined by 1H NMR spec-
troscopy and clean spectra with correct integration were obtained
3Jav = 8.0, JH,H = 1.7 Hz, 3 H, H4Ј,4ЈЈ,4ЈЈЈ), 7.68 (ddd, br, JH,H
=
8.0, JH,H = 1.2, JH,H = 1.0 Hz, 3 H, H3Ј, 3ЈЈ, 3ЈЈЈ), 7.25 (ddd, JH,H
4
5
3
= 7.2, 4.5, 4JH,H = 1.8 Hz, 3 H, H5Ј,5ЈЈ,5ЈЈЈ), 6.52 (d, 2JH,H = 1.4 Hz,
2
1 H, C=CHA), 6.51 (d, JH,H = 1.4 Hz, 1 H, C=CHB), 4.45 (AB
system, 2JA,B = 13.4 Hz, 3 H, 3ϫ CHASO), 4.12 (AB system, 2JA,B
= 13.4 Hz, 3 H, 3ϫ CHBSO), 3.14 and 3.28 (2ϫ m, 6 H, 3ϫ
CH2CH3), 1.0 (t, JH,H = 7.7 Hz, 9 H, 3ϫ CH2CH3) ppm. 13C
3
NMR (75.5 MHz, CDCl3, 298 K):δ = 154.1 and 152.8 (C2Ј,2ЈЈ,2ЈЈЈ
and 3ϫ C=CH2), 148.8 (C6Ј,6ЈЈ, 6ЈЈЈ), 146.0 (C1,3,5), 137.0 (C4Ј,4ЈЈ,4ЈЈЈ),
127.5 (C2,4,6), 123.6 (C5Ј,5ЈЈ,5ЈЈЈ), 120.6 (C3Ј,3ЈЈ,3ЈЈЈ), 118.2 (3 ϫ
C=CH2), 56.3 (3 ϫ ArCH2SO), 23.2 (3 ϫ CH2CH3), 13.9 (3 ϫ
1
CH2CH3) ppm. H NMR (300.1 MHz, CD3CN, 298 K): δ = 8.65
Eur. J. Inorg. Chem. 2013, 3412–3420
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FULL PAPER
3
4
5
1
(ddd, JH,H = 4.9, JH,H = 1.8, JH,H = 1.0, 3H, H6Ј,6ЈЈ,6ЈЈЈ), 7.93
(nujol): ν = 1147 (S=O) cm–1. H NMR (300.1, CD CN, 298 K):δ
˜
3
3
4
5
(ddd, JH,H = 8.2, JH,H = 2.0, JH,H = 1.0, 3H, H4Ј, 4ЈЈ, 4ЈЈЈ), 7.90
= 9.49 (ddd, 3JPt,H = 14.3, 3JH,H = 5.6, 4JH,H = 1.6, 5JH,H = 0.8 Hz,
(dt, JH,H = 7.8, JH,H = 1.8, 3H, H3Ј, 3ЈЈ, 3ЈЈЈ), 7.40 (ddd, JH,H
=
1 H, H6Ј), 8.12 (td, Jav = 7.8, JH,H = 1.6 Hz, 1 H, H4Ј), 7.95 (dd,
3
4
3
3
4
7.2, 4.9, JH,H = 2.0, 3H, H5Ј,5ЈЈ,5ЈЈЈ), 6.72 (d, JH,H = 1.1, 3H, 3JH,H = 8.3, JH,H = 1.4 Hz, 2 H, H2,6), 7.91 (ddd, JH,H = 7.8,
4
2
4
3
2
5
3
C=CHA), 6.44 (d, JH,H = 1.1, 3H, C=CHB), 4.61 (AB system,
4JH,H = 1.4, JH,H = 0.8 Hz, 1 H, H3Ј), 7.64 (ddd, JH,H = 5.6, 7.8,
2JA,B = 13.6, 3H, 3ϫ CHASO), 4.07 (AB system, 2JA,B = 13.6, 3H, 4JH,H = 1.4 Hz, 1 H, H5Ј), 7.56 (m, Jav = 7.9 Hz, 2 H, H3,5), 7.53
3
3
3
4
2
3ϫ CHBSO), 3.33 (m, 6H, 3ϫ CH2CH3), 0.98 (t, JH,H = 7.7,
(m, JHH = 7.3 Hz, 1 H, H4), 6.62 (AB system, JPt,H = 9.6, JA,B
= 3.1 Hz, 1 H, C=CHA), 6.55 (AB system, JPt,H = 11.2, JA,B =
4
2
9H, 3ϫ CH2CH3) ppm. The second one to be eluted was rel-2,4,6-
triethyl-1,3-bis{[(R)-1-(2-pyridinyl)ethenyl]sulfinylmethyl}-5-{[(S)-1-
(2-pyridinyl)ethenyl]sulfinylmethyl}benzene (6b). Yellow solid, m.p.
120 °C, 45% yield TLC: Rf 0.32 (acetone/petroleum ether, 65:35).
3.1 Hz, 1 H, C=CHB), 0.87 (s with satellites, 2JPt,H = 79.7 Hz, 3 H,
PtCH3 trans to N) ppm. 13C NMR (75.5 MHz, CD3CN, 298 K):δ
= 155.5 and 152.5 (C2Ј and C=CH2), 148.9 (C6Ј), 146.8 (C1), 141.1
(C4Ј), 134.4 (C4), 130.7 (C3 + C5), 127.7 (C5Ј), 126.9 (C2 + C6),
123.7 (C=CH2), 123.6 (C3Ј), –18.3 (s with satellites, 1JPtC = 726 Hz,
3 H, Pt-C) ppm.
C36H39N3O3S3 (657.9): calcd. C 65.72, H 5.97, N 6.39; found C
65.56, H 6.07, N 6.50. IR (nujol): ν = 1038 (S=O) cm–1. H NMR
1
˜
(300.1 MHz, CDCl3, 298 K):δ = 8.55 (m, 3 H, H6Ј,6ЈЈ,6ЈЈЈ), 7.72 (m,
6 H, H3Ј,4Ј,3ЈЈ,4ЈЈ,3ЈЈЈ,4ЈЈЈ), 7.27 (m, 3 H, H5Ј,5ЈЈ,5ЈЈЈ), 6.51 (m, 6 H, 3ϫ
Trinuclear Platinum(II) Complex [PtXY]3(6a-κN,κS): A solution of
6a (1 mg, 0.0015 mmol) in CD3CN (ca. 500 μL), hold into a 5 mm
NMR tube, was mixed with three equivalent amount of complexes
Pt1 or Pt2 (0.0045 mmol). Immediately after platinum(II) addition,
the color solution changes from colorless to light-yellow.
2
CH2=C), 4.53 (AB system, JA,B = 13.2 Hz, 3 H, 3ϫ CHASO),
4.13 (AB system, JA,B = 13.2 Hz, 3 H, 3ϫ CHBSO), 3.18 (m, 6
2
H, 3ϫ CH2CH3), 1.0 (t, 9 H, 3ϫ CH2CH3) ppm. 13C NMR
(75.5 MHz, CDCl3, 298 K):δ = 153.9 and 153.7 (C2Ј,2ЈЈ,2ЈЈЈ), 152.5
and 152.3 (3ϫ C=CH2), 148.8 and 148.7 (C6Ј,6ЈЈ,6ЈЈЈ), 146.1 (C1,3,5),
137.0 (C4Ј,4ЈЈ,4ЈЈЈ), 127.5 and 127.2 (C2,4,6), 123.7 and 123.6
(C5Ј,5ЈЈ,5ЈЈЈ), 120.3 (C3Ј,3ЈЈ,3ЈЈЈ), 118.1 (3ϫ C=CH2), 56.1 and 55.9
(3ϫ ArCH2SO), 23.5 and 23.1 (3ϫ CH2CH3), 14.2 and 13.9 (3ϫ
CH2CH3) ppm. 1H NMR (300.1 MHz, CD3CN, 298 K):δ = 8.67
[(PtMe2)3(6a-κN,κS)] (12): M.p. 175 °C. C42H57N3O3Pt3S3
(1333.4): calcd. C 37.83, H 4.31, N 3.15; found C 37.78, H 4.27, N
3.19. IR (nujol): ν = 1154 (S=O) cm–1. H NMR (300.1, CD CN,
1
˜
3
298 K):δ = 9.00 (d, JPt,H = 27.4, JH,H = 5.9 Hz, 3 H, H6Ј,6ЈЈ,6ЈЈЈ),
3
3
(d, JH,H = 4.9 Hz, 3 H, H6Ј,6ЈЈ,6ЈЈЈ), 7.92 (m, 3 H, H3Ј,3ЈЈ,3ЈЈЈ), 7.90
3
8.25 (td, 3Jav = 7.9 Hz, 3 H, H4Ј,4ЈЈ,4ЈЈЈ), 8.15 (d, 3Jav = 7.9 Hz, 3 H,
(m, 3 H, H4Ј,4ЈЈ,4ЈЈЈ), 7.41 (m, 3 H, H5Ј,5ЈЈ,5ЈЈЈ), 6.72 (d, JH,H
=
2
H3Ј,3ЈЈ,3ЈЈЈ), 7.55 (dd, JH,H = 5.9, 7.2 Hz, 3 H, H5Ј,5ЈЈ,5ЈЈЈ), 6.64 (d,
3
1.1 Hz, 1 H, C=CHA), 6.43 (d, 2JH,H = 1.1 Hz, 1 H, C=CHB), 4.63
2JH,H = 2.0 Hz, 3 H, 3ϫ C=CHA), 5.92 (d, JH,H = 2.0 Hz, 3 H,
2
2
(AB system, JA,B = 13.4 Hz, 3 H, 3ϫ CHASO), 4.06 (AB system,
3ϫ C=CHB), 4.59 (AB system, 2JA,B = 14.4 Hz, 3 H, 3ϫ CHASO),
4.20 (AB system, 2JA,B = 14.4 Hz, 3 H, 3ϫ CHBSO), 3.09 (m, 3JH,H
2JA,B = 13.4 Hz, 3 H, 3ϫ CHBSO), 3.31 (br. m, 6 H, 3ϫ CH2CH3),
0.99 (t, br, 9 H, 3ϫ CH2CH3) ppm.
3
= 7.6 Hz, 1 H, 3ϫ CHa–CH3), 2.25 (m, JH,H = 7.6 Hz, 3 H, 3ϫ
CHb–CH3), 0.90 (s with satellites, JPt,H = 91.2 Hz, 9 H, PtCH3
trans to N), 0.84 (s with satellites, JPt,H = 78.7 Hz, 3 H, Pt-CH3
trans to S), 0.68 (t, JH,H = 7.6 Hz, 9 H, CH2–CH3) ppm.
2
Platinum(II) Complexes Derivatives: The platinum(II) compounds
cis-[PtMe2(Me2SO)2] (Pt1)[19] and trans-[PtMeCl(Me2SO)2] (Pt2)[20]
were prepared according to already published methods and were
purified by several crystallizations from a 1:1 CH2Cl2/Et2O mixture
(v/v).
2
3
[(PtMeCl)3(6a- κN,κS)] (13): M.p. Ͼ 220 °C. C39H48Cl3N3O3Pt3S3
(1394.6): calcd. C 33.59, H 3.47, N 3.01; found C 33.65, H 3.40, N
3.05. IR (nujol): ν = 1142 (S=O) cm–1. H NMR (300.1, CD CN,
1
Mononuclear Platinum(II) Species [PtXY(9-κN,κS)], 10 and 11:
Compound 9 (2.3 mg, 0.01 mmol) was initially dissolved in CD3CN
(0.5 mL) and afterwards added of an equivalent amount (0.01 mm)
of the appropriate platinum(II) complex, cis-[PtMe2(Me2SO)2]
(Pt1) or trans-[PtMeCl(Me2SO)2] (Pt2). The colorless solutions al-
most instantly turned to light yellow. The two synthetic procedures
to obtain 10 and 11 were conducted on a larger scale too by using
the same molar ratio as above, in CH3CN as solvent, and almost
quantitative yields were obtained.
˜
3
5
298 K):δ = 9.50 (ddd, JPt,H = 20.2, 3JH,H = 5.6, JH,H = 1.6, JH,H
3
4
= 0.8 Hz, 3 H, H6Ј,6ЈЈ,6ЈЈЈ), 8.26 (td, Jav = 7.8, 4JH,H = 1.6 Hz, 3 H,
3
H4Ј,4ЈЈ,4ЈЈЈ), 8.20 (ddd, JH,H = 8.0, JH,H = 1.6, JH,H = 0.8 Hz, 3
3
4
5
H, H3Ј,3ЈЈ,3ЈЈЈ), 7.70 (ddd, JH,H = 5.6, 7.6, JH,H = 1.6 Hz, 3 H,
3
4
H5Ј,5ЈЈ,5ЈЈЈ), 6.84 (d, 2JH,H = 2.8 Hz, 1 H, C=CHA), 5.94 (d, 2JH,H
=
2
2.8 Hz, 1 H, C=CHB), 4.93 (AB system, JA,B = 15.0 Hz, 3 H, 3ϫ
CHASO), 4.57 (AB system, JA,B = 15.0 Hz, 3 H, 3ϫ CHBSO),
2
3
3
3.03 (m, JH,H = 7.6 Hz, 3 H, 3ϫ CHa–CH3), 2.29 (m, JH,H
=
7.6 Hz, 3 H, 3ϫ CHb–CH3), 0.71 (s with satellites, 2JPt,H = 83.8 Hz,
[PtMe2(9-κN,κS)] (10): M.p. 58 °C. C15H17NOPtS (454.5): calcd. C
3
9 H, PtCH3 trans to N), 0.70 (t, JH,H = 7.6 Hz, 9 H, 3ϫ
39.64, H 3.77, N 3.08; found C 39.81, H 3.69, N 3.01. IR (nujol):
ν = 1146 (S=O) cm–1. 1H NMR (300.1, CD3CN, 298 K):δ = 8.96
CH2CH3) ppm.
˜
(d, JPt,H = 22.0, JH,H = 5.7 Hz, 1 H, H6Ј), 8.06 (td, Jav = 7.9,
3
3
3
Computational Details: Molecular mechanics calculations were per-
formed on a Pentium® IV personal computer using the Spartan
package version ‘02.[16] A modified version of the MMFF94 force
field implemented for transition metal parameters was used in the
minimization on calculations. The X-ray structure of rel-2,4,6-tri-
ethyl-1,3,5-tris{[(R)-1-(2-pyridinyl)ethenyl]sulfinyl}methylbenzene
(6a) was properly modified and used as an input for the calcula-
tions to gauge the performance of the MMFF calculations. Lowest-
energy conformations of the trinuclear complexes 12–13, as well
as the monomeric species 10–11, were generated. Full geometry
optimization for each structure to a gradient convergence limit of
less than 10–5 was carried out before a final single point energy
calculation. During the minimization, no symmetry restriction was
imposed but the positions of all atoms in both of the square coordi-
nation planes, that is, Pt–S–N–CA–CB, were kept frozen.
4JH,H = 1.4 Hz, 1 H, H4Ј), 7.90 (dd, JH,H = 7.6, JH,H = 1.6 Hz, 2
3
4
H, H2,6), 7.80 (d, 3JH,H = 8.0 Hz, 1 H, H3Ј), 7.49 (ddd, 3JH,H = 5.7,
7.8, JH,H = 1.4 Hz, 1 H, H5Ј), 7.48 (m, 2 H, H3,5), 7.42 (m, 1 H,
4
H4), 6.47 (AB system, JPt,H = 7.0, JA,B = 2.1 Hz, 1 H, C=CHA),
4
2
4
2
6.44 (AB system, JPt,H = 5.8, JA,B = 2.1 Hz, 1 H, C=CHB), 0.85
2
(s with satellites, JPt,H = 77.9 Hz, 3 H, PtCH3 trans to S), 0.78 (s
with satellites, JPt,H = 90.9 Hz, 3 H, Pt-CH3 trans to N) ppm. 13C
2
NMR (75.5 MHz, CD3CN, 298 K):δ = 156.0 and 152.2 (C2Ј and
C=CH2), 148.9 (C6Ј), 144.9 (C1), 140.0 (C4Ј), 133.2 (C4), 130.3 (C3
+ C5), 126.6 (C5Ј), 126.6 (C2 + C6), 119.8 (C=CH2), 123.8 (C3Ј),
1
0.85 (s, JPtC = 797 Hz, Pt-C trans to S), –22.0 (s with satellites,
1JPtC = 940 Hz, PtC trans to N) ppm.
[PtMeCl(9-κN,κS)] (11): m.p. 125 °C. C14H14ClNOPtS (474,9):
calcd. C 35.41, H 2.97, N 2.95; found C 35.35, H 3.05, N 2.99. IR
Eur. J. Inorg. Chem. 2013, 3412–3420
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FULL PAPER
2007, 72, 4486–4496; g) M. C. Aversa, A. Barattucci, P. Bonac-
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Giannetto, J. Org. Chem. 2005, 70, 1986–1992.
Supporting Information (see footnote on the first page of this arti-
cle): Structural formulae of the platinum(II) derivatives 10 and 11,
as well as the trinuclear species 12 and 13, with the adopted num-
bering (Charts S1–S2); crystallographic data and figure (Tables S1–
S3 and Figure S1); H NMR spectrum of the trinuclear derivative
13 (Figure S2).
1
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Acknowledgments
This work was financially supported by Ministero dell’Istruzione,
Università e Ricerca (MIUR) (PRIN 2008, prot. 200859234J and
2008A9C4HZ) and by the Italian Consiglio Nazionale delle Ricer-
che (CNR). M. R. P. thanks Mr. G. Irrera (ISMN-CNR) for tech-
nical assistance.
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Received: January 14, 2013
Published Online: May 24, 2013
Eur. J. Inorg. Chem. 2013, 3412–3420
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