Platinum assisted cyclization of S-methyl 3-acyl-2-methyldithiocarbazates under mild conditions. Crystal structure of [Pt2(μ-SMe)-(terpy)2][ClO4]3

Article abstract of DOI:10.1039/a904859f

The reaction of the newly synthesized aqua complex [Pt(terpy)(OH₂)][BF₄]₂ with S-methyl 3-acyl-2-methyldithiocarbazates under a variety of experimental conditions has been studied. Using a 2:1 metal to ligand ratio in meth

Full text of DOI:10.1039/a904859f

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Platinum assisted cyclization of S-methyl 3-acyl-2-methyldithio-
carbazates under mild conditions. Crystal structure of [Pt (ꢀ-SMe)-
2
(
terpy) ][ClO ] †
2
4 3
a
b
b
a
Giuliano Annibale, Paola Bergamini,* Valerio Bertolasi, Michela Cattabriga,*
c
b
c
Antonio Lazzaro, Andrea Marchi and Gianni Vertuani
a
Dipartimento di Chimica, Università di Venezia, Calle Larga S. Marta, 2137, 31023 Venezia,
Italy
Dipartimento di Chimica, Università di Ferrara, via L. Borsari 46, 44100 Ferrara, Italy
Dipartimento di Scienze Farmaceutiche, Università di Ferrara, via Fossato di Mortara 17-19,
b
c
4
4100 Ferrara, Italy
Received 18th June 1999, Accepted 15th September 1999
The reaction of the newly synthesized aqua complex [Pt(terpy)(OH )][BF ] with S-methyl 3-acyl-2-methyldithio-
2
4 2
carbazates under a variety of experimental conditions has been studied. Using a 2:1 metal to ligand ratio in
2
methanol, a platinum assisted cyclization was observed. The reaction products were ∆ -1,3,4-oxadiazoline-5-thione
3ϩ
derivatives and the binuclear tricationic complex [Pt (µ-SMe)(terpy) ] whose molecular structure has been
2
2
determined by X-ray crystallography. This platinum assisted transformation is proposed as a new synthetic route
2
to ∆ -1,3,4-oxadiazoline-5-thiones under mild conditions. In the presence of an excess of a non-co-ordinating acid
(
HClO , CH SO H or CF SO H) the cyclization is completely quenched and complexes with co-ordinated S-methyl
4 3 3 3 3
3
-acyl-2-methyldithiocarbazates have been isolated. A general mechanism which accounts for the observed
1
transformations is proposed on the basis of H NMR and UV/Vis evidence.
Introduction
ing them with the aqua complex [Pt(terpy)(OH
)][BF ] (terpy =
2 4 2
2
,2Ј:6Ј,2Љ-terpyridine), where a single co-ordination position is
Largely available biomolecules such as amino acids, peptides,
carbohydrates and steroids present structural characteristics
that could be advantageously introduced in components of
co-ordination compounds designed for various applications.
For example biocompatibility and organotropism are relevant
properties for metal complexes of pharmaceutical signifi-
cance while the presence of chiral centres can be exploited in
the preparation of transition metal catalysts for asymmetric
available through substitution of the water ligand. Platinum
complexes containing the terdentate aromatic ligand terpyrid-
ine have attracted great attention both for their chemical
5
6
properties and for their activity as DNA intercalators.
Results and discussion
Although the aqua species 2 is known in solution it has never
7
1
reactions.
been isolated in the solid state. We succeeded in isolating it as its
In this context we focused our attention on new ligands based
on chemical modifications of natural amino acids. In particular
we recently reported the preparation of N-protected amino
8
tetrafluoroborate salt by treating the known hydroxo species 1
with tetrafluoroboric acid, eqn. (1). The analytical and spectro-
2
acids conjugated with S-methyl 2-methyldithiocarbazate in an
attempt to associate the natural characteristics of amino acids
with the well known co-ordinating properties of dithiocarbazic
3
acid derivatives. In principle, dithiocarbazate derivatives Ia–Ic
should behave as versatile ligands acting as monodentate
neutral sulfur or nitrogen (via N2) donors, as anionic mono-
dentate ligands (after N3 deprotonation) and finally as neutral
S–S or anionic N3–S (also after N3 deprotonation) chelating
ligands. However, to our knowledge, only the last co-ordination
3
mode has been reported for various dithiocarbazates.
We are currently interested in studying the co-ordinating abil-
ity of this series of ligands toward transition metals of recog-
scopic data for 2 are reported in the Experimental section.
Using complex 2 as a substrate for nucleophilic substitution
at platinum with the functionalized amino acids Ia–Ic we
observed that the process course and products depend on the
acidity of the reaction medium.
2
nized pharmaceutical value. We reported the preparation of
V
V
complexes of Tc and Re and planned to explore the inter-
II
actions of functionalized amino acids with Pt , whose value in
medicine has been consolidated during many years of research
and clinical application since the discovery of the antitumour
4
The reaction of complex 2 with the ligands Ia–Ie at natural pH
activity of cisplatin [Pt(NH ) Cl ]. With this aim we examined
3
2
2
the behaviour of Ia–Ic as monodentate neutral ligands by treat-
The interaction of 2 with the ligand Ia was first investigated.
After the addition of Ia to a red-orange solution of 2 in a 1:1
ratio in MeOH, eqn. (2), a prompt change of colour was
observed, followed by the formation of a green precipitate. On
†
Supplementary data available: rotatable 3-D crystal structure diagram
in CHIME format. See http://www.rsc.org/suppdata/dt/1999/3877/
J. Chem. Soc., Dalton Trans., 1999, 3877–3882
This journal is © The Royal Society of Chemistry 1999
3877

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1
a
Table 1 Selected H NMR data of ligands Ia–Ie and heterocyclic derivatives IIa–IIe
Compound
SCH3
NCH3
C Hn
α
NHCα
NHN
Others
b
Ia
2.45 (s)
2.50 (s)
3.60 (s)
3.67 (s)
3.60 (s)
3.61 (s)
3.90 (d, 5.5)
4.43 (d, 6.2)
4.35 (q d, 7.3)
4.95 (q d, 7.7)
5.50 (t, 5.5)
5.27 (t, 6.2)
5.40 (d, 7.3)
5.32 (d, 7.7)
8.90 (br s)
9.00 (br s)
5.10 (s, CH Ph)
2
IIa
5.15 (s, CH Ph)
2
b
Ib
1.46 (CH C , d, 7.3), 5.10 (CH Ph, s)
3
α
2
IIb
1.54 (CH C , d, 7.7)
3 α
5
.11, 5.05 (CH Ph, d, 4.5)
2
b
Ic
2.45 (s)
2.60 (s)
2.55 (s)
3.48 (s)
3.60 (s)
3.85 (s)
3.82 (s)
3.65 (s)
3.83 (s)
4.58 (t d, 8.0)
5.46 (d, 8.0)
8.90 (br s)
8.50 (br s)
8.36 (s)
3.20 (CH C , m), 5.20 (CH Ph, s)
2
α
2
c
c
IIc
5.15
5.15
3.18 (CH C , m), 5.09 (CH Ph, s)
2 α 2
7.5–8.0 (Ph, m)
7.5–8.0 (Ph, m)
d
Id
d
IId
d
Ie
2.8 (CH CO, s)
3
d
IIe
2.38 (CH CO, s)
3
a
b
c
d
All spectra were recorded in CDCl ; δ, J in Hz in parentheses. cf. ref. 2. Overlapped signals for C H and NHC . cf. ref. 11.
3
α
α
unchanged Ia and a second species with a similar pattern but
lacking both the SMe group and the hydrazidic proton of
CONHNCH . These observations suggest that half the amount
3
of Ia had undergone a fragmentation (with transfer of the SMe
group to the Pt–terpy moiety) and a cyclization process to give
the 1,3,4-oxadiazoline derivative IIa, eqn. (2). This experiment
indicates that two equivalents of aqua complex 2 are required
for complete conversion of Ia into IIa and in fact when the
same reaction was performed using a 2:1 platinum:ligand ratio
Ia was completely consumed and IIa was the only product
recovered from the solution.
1
The heterocycle IIa was isolated and characterized by H
NMR, infrared, mass spectrometry and elemental analysis (see
Experimental section and Table 1). Its infrared spectrum shows
single bands for the stretchings of C᎐O and N–H, at 1692 and
᎐
Ϫ1
3
293 cm respectively, while in the spectrum of the precursor
Ia there are two bands for each functional group [1686 and 1707
Ϫ1
Ϫ1
cm for ν(C᎐O); 3322 and 3391 cm for ν(N–H)]. Another
Ϫ1
new band, observed at 1624 cm , can be assigned to the endo-
cyclic C᎐N bond and finally the wavenumber for ν(C᎐S) of IIa
1179 cm ) is consistent with literature data for analogous
compounds.
10
᎐
Ϫ1
(
11
1
the basis of elemental analysis, IR, H NMR, and conductivity
measurements (see Experimental section), the green solid was
identified as the binuclear tricationic complex 3: the presence of
a SMe bridging group was unequivocally proved by the obser-
The same cyclization process occurs when two equivalents of
2 are treated with the alanine and phenylalanine derivatives Ib
2
and Ic, giving the ∆ -1,3,4-oxadiazoline-5-thiones IIb and IIc
respectively. Compounds IIa–IIc belong to a class of hetero-
cycles which has been reported to show a wide range of bio-
logical and pharmaceutical activities and a remarkable variety
1
vation of a signal in the H NMR, presenting a 1:8:18:18:8:1
pattern typical of a proton equally coupled to two platinum
nuclei. The same cationic complex isolated as its perchlorate
9
10
of uses.
salt (3Ј, see Experimental section) was recrystallized from
The platinum assisted cyclization described here can be pro-
posed as a new synthetic route to 1,3,4-oxadiazolinethiones,
alternative to the reported reaction of acylhydrazine with thio-
phosgene CSCl2. A variety of substituents can be introduced
in the ring position 2, including chiral carbon directly bonded
to the ring as in IIb and IIc.
CH NO affording crystals suitable for structure determination
3
2
(
Fig. 1), below described in detail.
12
After the separation of the platinum containing product 3 the
remaining solution was evaporated to dryness and the residue
1
analysed by H NMR; it was identified as a 1:1 mixture of
3
878
J. Chem. Soc., Dalton Trans., 1999, 3877–3882

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With the aim to check the generality of the reaction and to
prove that the amino acidic residue of Ia–Ic has no role in the
process, we carried out a series of experiments and found that
the simple acyldithiocarbazate derivatives Id and Ie are com-
pletely transformed in the presence of two equivalents of the
aqua complex 2, giving the corresponding 1,3,4-oxadiazoline-
thiones IId and IIe which have been previously prepared and
characterized. We then observed that Ia–Ie can be quanti-
tatively transformed into IIa–IIe also using a single equivalent
of the hydroxo species 1: in this case the platinum is recovered
as the monothiolate complex 4, eqn. (3). The complete charac-
322, 330, 335 and 347 nm). The final spectrum corresponds
exactly to that of the platinum monothiolate complex 4, as
shown by comparison with an authentic sample (see Experi-
mental section).
We observed that both the second and third steps are slower
at higher acid concentrations and therefore it should be possible
to accumulate the product of the first step using an excess of
acid.
11
With this aim we followed the reaction of complex 2 with Ia,
Ϫ2
Ϫ3
1
3 × 10 mol dm each, by H NMR spectrometry, in CD OD,
3
Ϫ1
Ϫ3
with added CF SO H (10 mol dm ). Under these conditions
3
3
the cyclization process does not occur at an appreciable rate and
the spectrum shows the formation of a single species where no
signal shows platinum coupling. This species was isolated as a
solid under preparative conditions and characterized by elem-
ental analysis and IR spectroscopy as complex A (see Experi-
1
mental section) where unaltered Ia is co-ordinated to platinum
(
see Scheme 1). The substantial invariance of the stretching of
terization of the newly synthesized heterocycles IIa–IIc and of
the model compounds IId and IIe is reported in the Experi-
mental section and in Table 1.
Compounds Ia–Ie do not undergo cyclization in the presence
of a base (NEt ) or an acid ( p-toluenesulfonic acid or HCl)
3
under mild conditions, but it has been reported before that
simple 3-acyl-2-methyldithiocarbazates like Id and Ie do
undergo cyclization when refluxed for four hours in EtOH in
11
the presence of NEt3. It is worth noticing that, although our
method is based on the use of expensive platinum compounds,
it requires milder conditions (no acid or base added, room tem-
perature) and shorter time and therefore can be particularly
convenient when perishable substrates are used on a small
scale.
The reaction between complex 2 and Ia in the presence of an
added acid
During a series of experiments aimed to clarify the mechanism
of the above reaction we noticed that the acidity of a solution
Ϫ3
Ϫ3
containing 3 × 10 mol dm of both complex 2 and Ia
increases from pH 3.5 to 1.4. Consequently we considered that
the addition of an acid could inhibit the cyclization process
thus allowing us to identify the primary product of the inter-
action of 2 with Ia.
Scheme 1
Ϫ1
the C᎐O group (1709 cm ) and the lack of platinum coupling
in the H NMR signal of SMe induces us to exclude the
involvement of these groups in the co-ordination of the ligand.
If complex A is redissolved in acid-free methanol it rapidly
evolves to 4 and heterocycle IIa.
We also succeeded in isolating the product of the second step
1
In two distinct experiments the reagents were mixed at a con-
Ϫ5
Ϫ3
centration of 5 × 10 mol dm in the presence of different
1
Ϫ3
amounts of the non-co-ordinating acid CH SO H (10 and
3
3
Ϫ2
Ϫ3
1
0
mol dm ) and the reaction was followed by UV/Vis
spectrophotometry. In both cases the observed spectral changes
in the region 310–400 nm (where Ia and IIa do not absorb)
indicated a three stage process. The first stage was completed in
the time required for mixing of the reagents and it was followed
by two slower processes. The last involves only two species as
indicated by the presence of several isosbestic points (at 312,
A by carrying out the reaction under the UV/Vis experimental
2
conditions but using perchloric acid instead of CH SO H. In
3
3
this way A precipitated as its perchlorate salt, was collected
2
1
and analysed by H NMR in CD NO solution. The spectrum
3
2
shows the presence of co-ordinated Ia and in particular a
3
platinum coupled SMe signal [ J(Pt–H) = 34.2 Hz] indicating
J. Chem. Soc., Dalton Trans., 1999, 3877–3882
3879

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that in this case the co-ordination occurs through the S atom of
that group (Scheme 1).
Table 2 Selected bond distances (Å) and angles (Њ) for complex 3Ј
Pt1–S1
Pt1–N1
Pt1–N2
Pt1–N3
S1–C1
2.307(2)
2.034(8)
1.945(6)
2.027(10)
1.822(10)
Pt2–S1
Pt2–N4
Pt2–N5
Pt2–N6
2.313(3)
2.033(8)
1.971(10)
2.024(9)
Mechanistic considerations
All the above described experimental observations can be
rationalized in a general picture of the reaction mechanism,
shown in Scheme 1. First of all, in an aqueous medium or in
MeOH, the aqua complex 2 is related to the hydroxo species 1
via the pH dependent equilibrium (i). However, it is well
S1–Pt1–N1
S1–Pt1–N2
S1–Pt1–N3
N1–Pt1–N2
N1–Pt1–N3
N2–Pt1–N3
Pt1–S1–C1
Pt1–S1–Pt2
103.4(2)
176.4(1)
95.5(2)
80.1(3)
161.0(3)
80.9(3)
S1–Pt2–N4
S1–Pt2–N5
S1–Pt2–N6
N4–Pt2–N5
N2–Pt2–N6
N5–Pt2–N6
Pt2–S1–C1
104.2(3)
172.5(3)
94.7(2)
79.4(4)
161.1(4)
82.0(3)
104.0(3)
II
known that hydroxo species of Pt are completely inert towards
Ϫ
13
OH substitution and therefore 2 is the only reacting species.
In step (ii) compound Ia promptly replaces the co-ordinated
water of the aqua complex 2, giving an intermediate A which
100.8(3)
121.7(2)
1
we formulate as a thionic sulfur bonded platinum complex, on
the basis of the above discussed spectroscopic data. The species
A undergoes isomerization to A where Ia is co-ordinated via
1
2
SMe [step (iii)].
The following step (iv) is the spontaneous deprotonation of
the hydrazidic NH resulting in the monocationic intermediate B
described by two canonical forms B and B . This step accounts
1
2
for the observed increase of acidity during the reaction and is
inhibited in the presence of an added acid.
The subsequent step (v) is ring closure occurring through
intramolecular nucleophilic attack of the carbonyl oxygen of B2
on the thionic carbon with simultaneous cleavage of the C–S
bond and outgoing of 4 as a stabilized leaving group.
As soon as complex 4 is formed it reacts with the residual
aqua complex 2 producing the binuclear species 3 [step (vi)]:
this side reaction is faster than the overall cyclization process
and therefore the observed Pt:ligand 2:1 stoichiometry is
required for the complete transformation of Ia. To prove this
hypothesis we prepared complex 3 by mixing 2 and 4, eqn. (4)
and Experimental section.‡
1
4
3ϩ
Fig. 1 An ORTEP view of the [Pt (µ-SMe)(terpy) ] cation showing
2
2
thermal ellipsoids at 30% probability and the atom numbering scheme.
when we carried out a comparison reaction between 2 and the
uncyclizable S-methyl 2-methyldithiocarbazate no subsequent
C–S breaking occurred after the substrate co-ordination.
It is interesting that, according to ref. 11, compounds Id
and Ie undergo cyclization to 2-alkylthio-1,3,4-thiadiazolium
cations in the presence of a stoichiometric amount of HClO4,
while in the presence of 2 we found that they give 1,3,4-
oxadiazolidine-5-thiones (Scheme 2). We suggest that this
Scheme 2
behaviour might be ascribed to the presence of Pt–terpy acting
In Scheme 1 it is assumed that the cyclization process is the
driving force for cleavage of the C–S bond in the co-ordinated
ligand. This hypothesis is supported by the observation that
as a protecting group for the C᎐S function.
᎐
Crystal structure of [Pt (ꢀ-SMe)(terpy) ][ClO ] 3Ј
2
2
4 3
Selected bond distances and angles are reported in Table 2
‡
Step (vi) requires the presence of complex 2 in an appreciable concen-
14
tration and therefore is not observed when the reaction is carried out in
a very diluted solution or when the platinum containing reagent is the
hydroxo complex 1, eqn. (3). Under this last condition equilibrium (i) is
well shifted towards the non-reactive species 1, but even in this case the
reaction proceeds since the released proton shifts the equilibrium
towards the reactive species 2. As a consequence, the reaction is self-
maintained and 2 never reaches a concentration high enough to make
step (vi) faster than the formation of 4.
and Fig. 1 shows the ORTEP drawing of the complex cation.
3ϩ
The asymmetric unit is built up by the [Pt (µ-SMe)(terpy) ]
2
2
cation and three perchlorate anions. The cation consists of two
platinum() atoms co-ordinated to a terdentate terpyridine
ligand and sharing, as fourth ligand, the sulfur of the methane-
thiolate anion. The co-ordination geometry of both platinum
atoms is considerably distorted from perfect square planar
3
880
J. Chem. Soc., Dalton Trans., 1999, 3877–3882

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owing to the constraints of the terpyridine ligand which give
rise to a narrowing of N–Pt–N(cis) angles to 79.4Њ. These dis-
tortions are associated with a significant shortening of Pt–N
complex 3 as a green-yellow powder (yield: 75 mg, 80%). The
remaining solution was completely evaporated under reduced
pressure and the residue recrystallized from EtOH–water to
form a white powder, which was analysed as a 1:1 mixture of
unchanged Ia and the corresponding heterocyclic derivative IIa,
(
middle) distances to 1.945 and 1.971 Å with respect to the
other Pt–N distances ranging from 2.024 to 2.033 Å. This is in
II
1
agreement with the structural data of similar complexes of Pt
with ter- or tetra-dentate ligands
on the basis of H NMR (see Table 1).
7,15–18
and with data derived
from a sample of 31 structures of platinum() complexes, con-
taining at least two pyridine ligands, which show that the short-
ening of the Pt–N distance is always associated with a strained
or very strained environment characterized by N(py)–Pt–X(cis)
Compounds IIa–IIe. Method (a). When the reagents 2 and Ia
were mixed in a 2:1 molar ratio under the same conditions as
the previous reaction, the only Pt containing product was com-
plex 3, while Ia was converted into IIa (yield: 70%). Under the
same conditions, Ib was converted into IIb (70%), Ic into IIc
(68%), Id into IId (74%) and Ie into IIe (72%).
15
angles ≈ 80Њ, independently of the nature of the X atom.
Ϫ
The Pt–S distances of 2.31 Å, on average, are in perfect
agreement with those observed in the structures of similar
Method (b). To an orange solution of [Pt(terpy)(OH)][BF ] 1
4
7
(
2,2Ј:6Ј,2Љ-terpyridine)thiolatoplatinum() compounds and
(50 mg, 0.095 mmol) in 15 mL of MeOH an equimolar amount
of Ia was added: the solution immediately turned purple. It was
stirred at 0 ЊC until the precipitation of complex 4 as a purple
solid was completed (ca. 30 min). A second aliquot of product 4
was precipitated on reducing the volume of the remaining
purple solution and adding diethyl ether. It was washed with
water and dried in vacuo over P O (yield: 40 mg, 75%). The
19–21
other square planar platinum() complexes.
The planes
defined by the Pt and the four co-ordinated atoms, Pt1, N1, N2,
N3, S1 and Pt2, N4, N5, N6 and S1, form an angle of 50.7(2)Њ.
No intermolecular interactions shorter than the sum of van der
Waals radii are observed.
Binuclear platinum() complexes with a bridging thiolate
2
5
9a,b,22
have been reported before,
but 3Ј represents the first
remaining colourless solution was taken to dryness under
reduced pressure and the oily residue recrystallized with EtOH
and water to give a white solid of pure product IIa (yield: 85%).
Following the same method, Ib was converted into IIb (75%),
Ic into IIc (74%), Id into IId (90%) and Ie into IIe (85%).
Compound IIa (Found: C, 51.1; H, 4.6; N, 15.05; S, 11.5.
C H N O S requires C, 51.3; H, 4.7; N, 15.0; S, 11.5%): IR
reported species with two Pt(terpy) units bridged by that group.
Moreover only a few compounds containing a single thiolate
bridge between two transition metal centres have been structur-
23
ally characterized.
12
13
3
3
Experimental
The complexes [Pt(terpy)(OH)][BF ], [Pt(terpy)(OH)][ClO4]
and [Pt(terpy)Cl]Clؒ2H O
ν(N–H) 3293, ν(C᎐O) 1692, ν(C᎐N) 1624 and ν(C᎐S) 1179
᎐
᎐
᎐
Ϫ1
ϩ
ϩ
1
8
a
8b
cm ; FAB MS: m/z 280, [MH] ; Maldi M 279; for H NMR in
each case see Table 1. Compound IIb (Found: C, 52.9; H, 5.4;
4
24
were prepared by literature
2
N, 14.1; S, 10.0. C H N O S requires C, 53.2; H, 5.15; N, 14.3;
methods. The amino acid derivatives Ia, Ib and Ic were pre-
13 15
3
3
2
S, 10.9%): IR ν(N-H) 3316, ν(C᎐O) 1690, ν(C᎐N) 1614 and
pared as we reported before. For the synthesis of Id and Ie a
᎐
᎐
Ϫ1
11
ν(C᎐S) 1179 cm . Compound IIc (Found: C, 61.8; H, 5.2; N,
literature procedure was followed.
᎐
1
8
1
1
1.1; S, 8.3. C H N O S requires C, 61.8; H, 5.2; N, 11.4; S,
All chemicals and solvents were reagent grade used without
further purification. Elemental analyses were performed using a
Carlo Erba model EA1110 instrument. The FT-IR spectra were
recorded on a Nicolet 510P FT-IR instrument in KBr, proton
19 19 3 3
.7%): IR ν(N–H) 3310, ν(C᎐O) 1697, ν(C᎐N) 1624 and ν(C᎐S)
᎐
᎐
᎐
Ϫ1
182 cm . Compound IId (Found: C, 55.9; H, 4.3; N, 14.3; S,
6.5. C H N OS requires C, 56.2; H, 4.2; N, 14.6; S, 16.7%): IR
9
8
2
Ϫ1
ν(C᎐N) 1609 and ν(C᎐S) 1184 cm . Compound IIe (Found: C,
NMR spectra on a Bruker AM 200 spectrometer with SiMe as
᎐
᎐
4
3
4
6.5; H, 4.3; N, 21.3; S, 24.0. C H N OS requires C, 36.9; H,
4 6 2
Ϫ1
internal standard, MS-FAB (fast atom bombardment) spectra
by a Hewlett Packard MS engine HP5989 A mass spectrometer
using a p-nitrobenzyl alcohol matrix, the MS-Maldi spectrum
by a Hewlett Packard Maldi-Toff G2025A spectrometer and
electronic spectra on a Perkin-Elmer Lambda 15 spectro-
photometer. Conductivity measurements were carried out with
a CDM 83 Radiometer Copenhagen conductivity meter and a
CDC 334 immersion cell. pH Measurements were made with
a Hanna HI-8417 Digital pH-meter.
.65; N, 21.5; S, 24.6%): IR ν(C᎐N) 1630 and ν(C᎐S) 1180 cm .
᎐
᎐
[
Pt(terpy)(SMe)][BF ] 4. The complex [Pt(terpy)Cl]Clؒ2H O
4 2
(
50 mg, 0.09 mmol) was dissolved in 15 ml of MeOH and solid
NaSMe (6.5 mg, 0.09 mmol) added. The solution immediately
turned deep purple and NaCl started to precipitate. The solid
was filtered off and the solution concentrated to dryness under
reduced pressure. The purple solid was washed with water and
diethyl ether and then redissolved in MeOH (10 mL); 2.7 mL of
Ϫ3
a 0.05 mol dm solution of NaBF were added to precipitate
4
Preparations
[
Pt(terpy)(SMe)][BF ] 4. The purple solid was finally separated
4
[
Pt(terpy)(OH )][BF ] 2. To a bright orange solution of
2 4 2
by centrifugation, washed with MeOH and dried in vacuo
[
Pt(terpy)(OH)][BF ] (0.2 g, 0.37 mmol) in water (10 mL), 2.5
mL of 0.15 mol dm HBF were added dropwise. The solution
4
over P O (yield: 35 mg, 70%) (Found: C, 33.95; H, 2.3; N, 7.5;
2
5
Ϫ3
4
S, 5.6. C H BF N PtS requires C, 34.2; H, 2.5; N, 7.5;
16 14 4 3
Ϫ1 2 Ϫ1 ϩ
promptly turned pale yellow: after 10 min of stirring it was
taken to dryness to give product 2 as an orange powder that was
S, 5.7%). Λ (CH NO ) = 77 Ω cm mol . FAB MS: m/z
eq
3
2
ϩ
ϩ
4
75, [Pt(terpy)(SMe)] ; and 428, [Pt(terpy)] . UV/Vis: λmax/nm
3 Ϫ1 Ϫ1
dried in vacuo over P O (0.205 g, 90%) (Found: C, 29.65;
2
5
(MeOH) 346 (ε/dm mol cm 6000), 330 (6400) and 315
1
H, 2.2; N, 7.3. C H B F N OPt requires C, 29.75; H, 2.2; N,
1
5
13
2
8
3
(6600). H NMR (CD OD): δ 7.9, 8.3–8.5 (2m, 9 H), 9.5 (d,
3
Ϫ1
ϩ
6
6Љ
3
3
7
[
(
.4%). IR: ν(co-ordinated H O) 1653 cm . FAB MS: m/z 446,
2
ϩ ϩ
H ϩ H , J = 45) and 2.15 (s, SMe, J = 41 Hz, 1:4:1).
PtH PtH
ؒ
Pt(terpy)(OH )] ; and 428, [Pt(terpy)] . UV/Vis: λmax/nm
2
3 Ϫ1 Ϫ1
NMR Experiments showed that 4 is also formed in the reaction
between the aqua complex 2 and an excess of NaSMe in
MeOH) 339 (ε/dm mol cm 6200), 326 (5600), 308 (6400)
1
and 280 (12600); H NMR (CD NO ): δ 7.9, 8.2–8.8 (2m, 9 H)
3
2
CD OD.
3
6
6Љ 3
and 9.3 (d, H ϩ H , J = 32 Hz).
PtH
[
Pt (ꢀ-SMe)(terpy) ][BF ] 3. The complex [Pt(terpy)(SMe)]-
2 2 4 3
4
Reaction between [Pt(terpy)(OH )][BF ] 2 and Ia in 1:1
[BF ] 4 (45 mg, 0.8 mmol) was dissolved in 20 ml of MeOH
2
4
2
ratio. To an orange solution of the aqua species 2 (50 mg, 0.08
mmol) in 15 mL of MeOH, 27 mg (0.08 mmol) of Ia were
added. Under stirring at room temperature, the precipitation of
a green solid was completed in 1 h. The precipitate was filtered
off, washed with water and dried in vacuo over P O , to obtain
to give a purple solution. An equimolar amount of solid
[Pt(terpy)(OH )][BF ] 2 (50 mg) was added. In 30 min the mix-
2
4 2
ture clarified and [Pt (µ-SMe)(terpy) ][BF ] 3 precipitated as a
2
2
4 3
green-yellow solid that was collected, washed with water and
dried in vacuo over P O (yield: 65 mg, 70%) (Found: C, 31.75;
2
5
2
5
J. Chem. Soc., Dalton Trans., 1999, 3877–3882
3881

View Article Online
H, 2.15; N, 7.5; S, 2.55. C H B F N Pt S requires C, 31.9;
A. Medici, Inorg. Chem. Commun., 1998, 1, 125; M. Stolmàr,
C. Floriani, G. Gervasio and D. Viterbo, J. Chem. Soc., Dalton
Trans., 1997, 1119.
M. Cattabriga, A. Marchi, L. Marvelli, R. Rossi, G. Vertuani,
R. Pecoraro, A. Scatturin, V. Bertolasi and V. Ferretti, J. Chem. Soc.,
Dalton Trans., 1998, 1453.
3 M. Das and S. E. Livingstone, Inorg. Chim Acta, 1976, 19, 5 and refs.
therein; A. Marchi, L. Uccelli, L. Marvelli, R. Rossi, M. Giganti,
V. Bertolasi and V. Ferretti, J. Chem. Soc., Dalton Trans., 1996,
31
25
3
12
6
2
Ϫ1
2
Ϫ1
H, 2.2; N, 7.2; S, 2.75%). Λ (CH NO ) = 271 Ω cm mol .
eq
3
2
ϩ
ϩ
ϩ
FAB MS: m/z 475, [Pt(terpy)(SMe)] ; and 428, [Pt(terpy)] .
UV/Vis: λmax/nm (MeOH) 345 (ε/dm mol cm 7400), 329
9600), 315 (8800) and 279 (17000). H NMR (CD NO ): δ 7.8,
.3–8.7 (2m, 9 H); 9.7 (d, H ϩ H , J = 37) and 2.9 (s,
2
3
Ϫ1
Ϫ1
1
(
8
3
2
6
6Љ
3
PtH
3
µ-SMe, J = 36 Hz, 1:8:18:8:1).
PtH
3
105.
[
Pt (ꢀ-SMe)(terpy) ][ClO ] 3Ј. 25.4 mL of an orange aque-
2 2 4 3
Ϫ3 Ϫ3
4
Metal Ions in Biological Systems, eds. A. Sigel and H. Sigel, Marcel
Dekker, New York, 1996, vol. 32.
ous solution of 7 × 10 mol dm [Pt(terpy)(OH )][ClO ] ,
generated in situ from [Pt(terpy)(OH)][ClO ] and HClO4 in
equimolar amounts, were added to a solution of the ligand Ia
60 mg, 0.18 mmol) in 10 mL of MeOH. After a few minutes
the solution clarified and the green product 3Ј precipitated. The
reaction was complete in ca. 2 h. The solid was filtered off and
washed with water (yield: 100 mg, 95%) (Found: C, 30.95; H,
2
4 2
4
5 H. M. Brothers II and N. M. Kostic, Inorg. Chem., 1988, 27,
1761; H.-K. Yip, L.-K. Cheng, K.-K. Cheung and C.-M. Che,
J. Chem. Soc., Dalton Trans., 1993, 2933; B. Pitteri, C. Marangoni,
L. Cattalini and T. Bobbo, J. Chem. Soc., Dalton Trans., 1995, 3853.
S. J. Lippard, Acc. Chem. Res., 1978, 11, 211.
K. W. Jennette, J. T. Gill, J. A. Sadownick and S. J. Lippard, J. Am.
Chem. Soc., 1976, 98, 6159.
8 (a) T. K. Aldrige, E. M. Stacey and D. R. McMillin, Inorg. Chem.,
1994, 33, 722; (b) G. Annibale, L. Cattalini, F. Guidi, A. Cornia and
A. Fabretti, Inorg. React. Mechanisms, in the press.
(
6
7
2
.15; N, 7.05; S, 2.75. C H Cl N O Pt S requires C, 30.95;
31 25 3 6 12 2
1
H, 2.1; N, 7.0; S, 2.7%). The H NMR signals are identical with
those of complex 3.
9
(a) P. L. Goggin, R. J. Goodfellow and F. J. S. Reed, J. Chem. Soc. A,
971, 2031; (b) R. J. Puddephatt, K. A. Azam, R. H. Hill, M. P.
1
[
Pt(terpy){S᎐C(SMe)NMeNHC(O)CH NHC(O)OCH Ph}]-
᎐
2 2
Brown, C. D. Nelson, R. P. Moulding, K. R. Seddon and M. C.
Grossel, J. Am. Chem. Soc., 1983, 105, 5642; (c) N. W. Alcock,
P. Bergamini, T. J. Kemp, P. G. Pringle, S. Sostero and O. Traverso,
Inorg. Chem., 1991, 30, 1594.
[
0
CF SO ] A . The complex [Pt(terpy)(OH)][BF ] 1 (24 mg,
.045 mmol) was dissolved in 2 ml of MeOH and the pH was
adjusted to 1 using CF SO H. When an equimolar amount of
Ia was added the solution turned bright yellow. After stirring
for a few minutes A was precipitated as a yellow solid by add-
ing diethyl ether (yield: 30 mg, 70%) (Found: C, 34.0; H, 2.7; N,
.1; S, 11.9. C H F N O S Pt requires C, 34.2; H, 2.7; N, 8.0;
S, 12.2%). δ (CD NO ) 3.15 (SCH , s), 3.71 (NCH , s), 4.04
3
3
2
1
4
3
3
10 J. Hill, in Comprehensive Heterocyclic Chemistry, ed. K. T. Potts,
Pergamon Press, Oxford, 1984, vol. 6, p. 427.
1 P. Molina, A. Tarraga and A. Espinosa, Synthesis, 1988, 690.
2 W. R. Sherman, J. Org. Chem., 1961, 26, 88.
3 F. Basolo and R. G. Pearson, in Mechanism of Inorganic Reactions,
Wiley, New York, 2nd edn., 1968; L. Cattalini, Prog. Inorg. Chem.,
1970, 13, 263 and refs. therein.
14 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge
National Laboratory, Oak Ridge, TN, 1976.
1
1
1
1
8
30 28 6 6 9 4
H
3
2
3
3
3
[
C H , d, J(CH –NH) = 5.8], 5.12 (CH Ph, s), 5.55 (NHC , br
2 2 2
6
α
α
s), 7.2–8.6 (aromatic protons), 8.80 [H , d, J(Pt–H) = 40.0 Hz]
and 9.94 (NHN, s).
1
1
1
1
5 G. Marangoni, B. Pitteri, V. Bertolasi, V. Ferretti and P. Gilli,
Polyhedron, 1996, 15, 2755.
6 C.-W. Chan, C.-M. Che, M.-C. Cheng and Y. Wang, Inorg. Chem.,
Crystal structure determination of complex 3Ј
1
992, 31, 4874.
Crystal data. C H Cl N O Pt S, M = 1202.16, monoclinic,
space group P2 /c (no. 14), a = 12.538(1), b = 21.802(2), c =
3.969(1) Å, β = 106.38Њ, U = 3663.5(5) Å , T = 295 K, Z = 4,
31
25
3
6
12
2
7 C.-W. Chan, T.-F. Lai, C.-M. Che and S.-M. Peng, J. Am. Chem.
Soc., 1993, 115, 11245.
1
3
1
8 E. C. Constable, R. P. G. Henney, T. A. Leese and D. A. Tocher,
J. Chem. Soc., Chem. Commun., 1990, 513.
19 K. Umakoshi, I. Kinoshita, Y. Fukui-Yasuba, K. Matsumoto,
Ϫ3 Ϫ1
D = 2.180 g cm , µ(Mo-Kα) = 79.78 cm , F(000) = 2288,
c
8
0
473 reflections measured (2 ≤ θ ≤ 30Њ), 7935 unique (Rint
.026), corrected for Lorentz-polarization and absorption
effects (ψ-scan method, minimum transmission factor = 0.820),
and used in all calculations. Final R [F ≥ 2σ(F )] = 0.051 and
wR(F ) = 0.14. Programs used DIRDIF, SHELXL 97 and
PARST.
CCDC reference number 186/1648.
See http://www.rsc.org/suppdata/dt/1999/3877/ for crystallo-
graphic files in .cif format.
=
S. Ooi, H. Nakai and M. Shiro, J. Chem. Soc., Dalton Trans., 1989,
8
15.
2
2
20 D. Cruz-Garritz, E. Martin, H. Torrens, F. A. Mayoh and J. Smith,
Acta Crystallogr., Sect. C, 1990, 46, 2377.
2
25
26
2
1 Z. Bugarcic, B. Norén, Å. Oskarsson, C. St a˚ lhandske and L. I.
Elding, Acta Chem. Scand., 1991, 45, 361.
27
22 M. I. Djuran, E. L. M. Lempers and J. Reedijk, Inorg. Chem., 1991,
3
0, 2648; A. K. Fazlur-Rahman and J. G. Verkade, Inorg. Chem.,
992, 31, 11.
1
2
3 R. Usón, M. A. Usón, S. Herrero and L. Rello, Inorg. Chem., 1998,
7, 4473.
4 G. Annibale, M. Brandolisio and B. Pitteri, Polyhedron, 1995, 14,
51.
3
2
Acknowledgements
4
This work was supported by Ministero dell’Università e della
Ricerca Scientifica e Tecnologica in the framework of the
Project “Pharmacological and Diagnostic Properties of Metal
Complexes” (co-ordinator Professor G. Natile). We thank Mr
M. Fratta for the elemental analyses and technical assistance
25 P. T. Beurskens, G. Beurskens, W. P. Bosnan, R. de Gelder,
S. Garcia-Granda, R. O. Gould, R. Israel and J. M. M. Smits,
DIRDIF, Crystallography Laboratory, University of Nijmegen,
1
996.
2
6 G. M. Sheldrick, SHELXL 97, Program for the Refinement of
Crystal Structures, University of Göttingen, 1997.
ϩ
and Mr E. Angeli for recording FAB MS spectra.
2
7 M. Nardelli, J. Appl. Crystallogr., 1995, 28, 659.
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J. Chem. Soc., Dalton Trans., 1999, 3877–3882