Dinuclear platinum(II) complexes with bridging twofold deprotonated 2,2′:6′,2″-terpyridine. New molecules with a 3,5-diplatinated-pyridyl inner core: [Pt2(terpy-2H)(Me)2(L)2], [Pt2(terpy-2H)(X)2(L)2]

Article abstract of DOI:10.1016/j.jorganchem.2006.06.024

A series of dinuclear platinum complexes where the metal ions are linked by a twofold deprotonated 2,2′:6′,2″-terpyridine (terpy) has been synthesized. Reaction of cis-[Pt(Me)₂(DMSO)₂] with terpy in toluene at 90 °C (molar ratio Pt:terpy 2:1) results in activation of the C(3)- and C(5)-H bonds of the inner pyridinic ring to give the cyclometalated dinuclear derivative [Pt₂(terpy-2H)(Me)₂(DMSO)₂] (1a), (trans Me-Pt-N). From complex 1a, substitution of DMSO with neutral two-electron donors, L, allows isolation of a number of new species [Pt₂(terpy-2H)(Me)₂(L)₂] with the same N,C^∧C,N bridging ligand. The "Pt₂(terpy-2H)" fragment is very robust: it is not affected by alkylating reagents such as MeI or acids such as HPF₆ or even HCl. Nevertheless the latter acid cleaves the Pt-Me bond affording another series of complexes having a chloride in place of a methyl, [Pt₂(terpy-2H)(Cl)₂(L)₂], (trans-Cl-Pt-C). The structure of complex 7, [Pt₂(terpy-2H)(Cl)₂(PPh₃)₂], has been solved by X-ray analysis: the platinum atoms are in a tetrahedrally distorted square planar coordination. The inner framework of the molecule is not flat: the dihedral angle between the best planes of the metal ions is 37.2(1)°. The coordinated chlorides can be abstracted to give cationic solvento derivatives or exchanged with other anions such as iodides. Exchange with [BH₄]^- allows to obtain the corresponding hydrides, examples of very rare C,N cyclometalated platinum(II) hydrides. Finally a two step approach allows the synthesis of unsymmetric derivatives, [Pt₂(terpy-2H)(Cl)₂(L)(L′)], with different ligands around each platinum atom. The surprising deprotonation of terpy, typically a neutral ligand, points to the potential of the "Pt(Me)₂" fragment in the intramolecular C-H bond activation.

Full text of DOI:10.1016/j.jorganchem.2006.06.024

Journal of Organometallic Chemistry 691 (2006) 4135–4146
www.elsevier.com/locate/jorganchem
Dinuclear platinum(II) complexes with bridging twofold
deprotonated 2,20:60,200-terpyridine. New molecules with a
3,5-diplatinated-pyridyl inner core: [Pt2(terpy-2H)(Me)2(L)2],
[Pt2(terpy-2H)(X)2(L)2] and [Pt2(terpy-2H)(H)2(L)2]
(L = neutral ligand; X = halide) – Crystal and molecular
structure of [Pt2(terpy-2H)(Cl)2(PPh3)2]
a,
a
a
a
Sergio Stoccoro *, Antonio Zucca , Giacomo Luigi Petretto , Maria Agostina Cinellu ,
a
b
Giovanni Minghetti , Mario Manassero
a
Dipartimento di Chimica, Universita‘ di Sassari, Via Vienna 2, I-07100 Sassari, Italy
Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita‘ di Milano, Centro CNR, I-20133 Milano, Italy
b
Received 31 May 2006; received in revised form 16 June 2006; accepted 16 June 2006
Available online 27 June 2006
Abstract
A series of dinuclear platinum complexes where the metal ions are linked by a twofold deprotonated 2,20:60,200-terpyridine (terpy) has
been synthesized. Reaction of cis-[Pt(Me)2(DMSO)2] with terpy in toluene at 90 ꢀC (molar ratio Pt:terpy 2:1) results in activation of the
C(3)- and C(5)–H bonds of the inner pyridinic ring to give the cyclometalated dinuclear derivative [Pt2(terpy-2H)(Me)2(DMSO)2] (1a),
(trans Me–Pt–N). From complex 1a, substitution of DMSO with neutral two-electron donors, L, allows isolation of a number of new
species [Pt2(terpy-2H)(Me)2(L)2] with the same N,CꢁC,N bridging ligand. The ‘‘Pt2(terpy-2H)’’ fragment is very robust: it is not affected
by alkylating reagents such as MeI or acids such as HPF6 or even HCl. Nevertheless the latter acid cleaves the Pt–Me bond affording
another series of complexes having a chloride in place of a methyl, [Pt2(terpy-2H)(Cl)2(L)2], (trans-Cl–Pt–C). The structure of complex 7,
[Pt2(terpy-2H)(Cl)2(PPh3)2], has been solved by X-ray analysis: the platinum atoms are in a tetrahedrally distorted square planar coor-
dination. The inner framework of the molecule is not flat: the dihedral angle between the best planes of the metal ions is 37.2(1)ꢀ. The
coordinated chlorides can be abstracted to give cationic solvento derivatives or exchanged with other anions such as iodides. Exchange
with [BH4]ꢀ allows to obtain the corresponding hydrides, examples of very rare C,N cyclometalated platinum(II) hydrides. Finally a two
step approach allows the synthesis of unsymmetric derivatives, [Pt2(terpy-2H)(Cl)2(L)(L0)], with different ligands around each platinum
atom. The surprising deprotonation of terpy, typically a neutral ligand, points to the potential of the ‘‘Pt(Me)2’’ fragment in the intra-
molecular C–H bond activation.
ꢂ 2006 Elsevier B.V. All rights reserved.
Keywords: Platinum; Cyclometallated compounds; Nitrogen ligands; Crystal structure
1. Introduction
70 years ago [1]. Since the beginning this ligand has been
widely studied due to the outstanding properties of its
metal-bound derivatives [2]. In recent years terpyridine
transition metal complexes have attracted great interest
due to their photophysical and photochemical as well as
biological properties [3]. At present, one of the most prom-
ising fields is the application in supramolecular chemistry
The potentially terdentate ligand 2,20:60,200-terpyridine
(terpy) was firstly isolated by Morgan and Burstall nearly
*
Corresponding author. Tel.: +39 079229545; fax: +39 079229559.
E-mail address: stoccoro@uniss.it (S. Stoccoro).
0022-328X/$ - see front matter ꢂ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.06.024

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S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
(molecular wires [4], devices for the harvesting of light
energy [5]). In particular platinum(II) complexes are well-
suited to interact with proteins [6], to intercalate with
DNA [7], to oligomerize both in solution and in the solid
state [8].
of ligand, heating and a long reaction time: working at
50 ꢀC, complex 2, [Pt2(terpy-2H)(Me)2(3,5-lutidine)2], can
be obtained in fairly good yields.
Mostly 2,20:60,200-terpyridine acts as an N,N0,N00 endo-
terdentate ligand, classical examples being [Pt(terpy)Cl]
[8a,9] and [Ru(terpy)2]2+ [10,11]. Cyclometalation had been
observed only when a terminal nitrogen was protected
through quaternization [12]. Only recently have a few exam-
ples of cyclometalated derivatives been reported when it
was found that the reaction of terpy with electron-rich plat-
inum complexes, [Pt(Me)2(L)2], yields dinuclear cyclometa-
lated derivatives, [Pt2(terpy-2H)(Me)2(L)2] in which terpy
acts as a twofold deprotonated N,CꢁC,N ligand [13]. This
unexpected cyclometalation, which implies activation of
two C–H bonds of the inner pyridine ring, can be envizaged
as a particular case of the ‘‘rollover’’ NꢁC’ metalation pre-
viously observed for 6-substituted 2,20-bipyridines [14]. In
some cases, e.g. with 6-phenyl-2,20-bipyridine, the ‘‘roll-
over’’ metalation produces multi-metalated dinuclear com-
pounds [15]. In this case, with terpy, it is notable that
molecules are formed which have a diplatinated-3,5-pyridyl
inner core, a motif that, at the best of our knowledge, is
unprecedented.
N
N
N
Me
Me
Pt
Me
Pt
Me
N
N
2
Me
Me
At variance with 1b and 1c which are almost insoluble in
most solvents, complex 2 is soluble, likely due to non-
coplanarity of the coordinated lutidine. In the H NMR
1
spectrum the two metal-bonded methyl groups appear as
one singlet with satellites (d 0.94, 6H, 2J(Pt–H) =
86.4 Hz): the 195Pt–H coupling constant is in agreement
with a methyl group trans to a nitrogen atom, as in 1a.
The four methyl groups of the lutidine appear as one sin-
glet at d 2.43 (12H); in the aromatic region, in addition
to the lutidine ortho- and para-protons, five resonances in
a 2:2:2:2:1 integral ratio account for the terpyridine pro-
tons. On the whole the spectrum is indicative of a symmet-
ric species. The FAB mass spectrum (positive ions), shows
the molecular ion at m/z 865.
Owing to the novelty of these cyclometalated derivatives
we deemed worth to extend the series of the dinuclear
[Pt2(terpy-2H)(Me)2(L)2] species by substitution of the neu-
tral ligand L, and to study some aspects of their reactivity,
in particular as for the platinum–carbon bonds.
Reactions with alkenes were undertaken with the aim to
compare the behaviour of the metallorganic fragment
‘‘Pt2(terpy-2H)(Me)2’’ towards
a
r-donor/p-acceptor
ligand such as CO, with that towards p-donor/p-acceptor
molecules. The reactivity of complex 1a towards olefines
is not straightforward. The nature of the substituents on
the olefinic ligand is crucial: in the case of CH2@CH2
and CH2@CH–CN no reaction occurs whereas with the
strongly p acceptor (NC)2C@C(CN)2 (TCNE) displace-
ment of the DMSO ligands occurs and a new complex, 3,
can be isolated. Unfortunately, complex 3 is poorly soluble
in common organic solvents, thus its formulation as
[Pt2(terpy-2H)(Me)2(TCNE)2] mainly rests on analytical
2. Results and discussion
As previously reported the reaction of cis-[Pt(Me)2-
(DMSO)2] with terpy (molar ratio Pt/terpy 2:1, toluene,
90 ꢀC) yields the unusual dinuclear cyclometalated species
[Pt2(terpy-2H)(Me)2(DMSO)2] (1a), where
a twofold
deprotonated 2,20:60,200-terpyridine (terpy) links two plat-
inum atoms [13]. As far as we know this was the first
example of a cyclometalated terpy. From compound 1a
other complexes were obtained by substitution of DMSO
with neutral ligands (e.g. MeCN 1b, CO 1c, PPh3 1d,
PCy3 1e)
values and IR spectra, m(C„N) 2218, 2135 cmꢀ1
.
N
N
N
NC
CN
NC
CN
Pt
Pt
N
NC
CN
Me
Me
N
N
CN
NC
3
O
O
Pt
Me
Pt
Me
S
S
In the cyclometalated complexes 1a–3 the nitrogen atom
of the central pyridine ring is not involved in coordination
and we were eager to investigate how its donor capability
was affected by metalation. Firstly we studied the reactivity
of 1a with acids having non-coordinating anion such as
HPF6(aq), or HPF6 Æ 18-crown-6 ether. In no case, under
various conditions, protonation of the nitrogen atom was
observed. Furthermore, in some cases decomposition to
Me
Me
Me
Me
1a
Here we show that displacement from compound 1a of
both the coordinated DMSO can also be achieved with het-
erocyclic nitrogen ligands such as 3,5-lutidine, or even with
some alkenes. The reactions, however, are more difficult.
With lutidine complete substitution requires a large excess

S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
4137
metal occurs. Attempts to alkylate the nitrogen atom in 1a
likewise failed: however with methyl iodide an oxidative
addition occurs to give a number of species, possibly iso-
mers, not easily separable. At variance, in the reaction of
the phosphino complex [Pt2(terpy-2H)(Me)2(PPh3)2] (1d),
only one species, 4, is formed as indicated by the 31P{1H}
NMR spectrum which shows one singlet with satellites:
the 195Pt–P coupling constant (1JPt–P = 985.0 Hz) supports
to the carbon atom. Isomerization on going from 1a to
5 is justified taking into account the lower trans influence
of Cl compared to DMSO.
N
N
N
Pt
Pt
1
Cl
Cl
a Pt(IV) complex [16]. The H NMR spectrum shows the
O
O
presence of two different Pt–Me groups (d 1.18, d, 6H,
S
S
3
2
2JPt–H = 60.3 Hz, JP–H = 7.3 Hz; d 1.78, d, 6H, JPt–H
=
=
Me
Me
Me Me
3
3
70.6 Hz, JP–H = 7.6 Hz), one H40 proton (s, 1H, JPt–H
5
48.8 Hz) and one signal for the H600 at d 9.34. Overall the
NMR spectra give evidence for a symmetric species but
do not allow to distinguish between molecules with the
axial methyls on the same or the opposite side of the
Pt2(terpy-2H) plane. According to the literature data [17]
1H NMR parameters, in particular the 2JPt–H and 3JP–H rel-
evant to the Me resonances, support an arrangement
around each platinum atom with a methyl trans to N,
Complex 6 can be hardly characterized in solution due
1
to its scarce solubility in common organic solvents: a H
NMR spectrum can be obtained only in deuterated
DMSO. Under these conditions the spectrum of 6 is almost
superimposable to that of complex 5 in the same solvent.
Likely, 6 is a dimer with bridging chlorides derived from
5 by dissociation of DMSO; in DMSO the bridge is split
to give again complex 5. In agreement compound 5 can
be obtained as the only product when the reaction of 1a
with HCl is carried out in the presence of a small amount
of DMSO.
2
2JPt–H = 70.6 Hz, and the other one, JPt–H = 60.3 Hz,
trans to PPh3, not to the iodine atom. This implies that
an isomerization process takes place, as previously
reported in the oxidative addition of MeI to analogous sub-
strates [17c,17e]. If steric effects are also taken into account
the most probable isomer for 4 is:
N
N
N
PPh3
Me
Pt
Pt
N
N
N
Cl
Cl
Cl
Cl
Pt
Pt
I
I
Pt
Pt
Me
Me
N
N
PPh3
N
Me
4
6
Having ascertained the scarce reactivity of the uncoor-
dinated nitrogen atom, in particular towards protonation
or alkylation, we studied the reaction of complex 1a with
HCl. When the reaction was carried out in acetone with
a 1:1 Pt:HCl molar ratio two species were isolated in the
solid state, complexes 5 and 6, soluble and insoluble
respectively, in the reaction medium. Complex 5 analyses
for [Pt2(terpy-2H)(Cl)2(DMSO)2]: the 1H NMR spec-
trum, compared to that of 1a, clearly shows the absence
of methyl groups bound to platinum. The singlet due to
The result of the reaction of compound 1a with HCl,
which entails the cleavage of the methyl–platinum bond
without affecting the dinuclear ‘‘Pt2(terpy-2H)’’ fragment
suggests that a new series of complexes having a chlorine
in place of an alkyl may be synthesized.
2.1. Synthesis of [Pt2(terpy-2H)(Cl)2(L)2] (L = neutral
ligand)
3
the H40 proton at d 9.01, JPt–H = 44.7 Hz (vs. d 8.38,
3JPt–H = 53.7 Hz in 1a) is flanked by satellites in an
approximate 1:2.2:1 integral ratio characteristic of a cou-
pling with two chemically equivalent platinum atoms.
The signal at d 3.62, relevant to the DMSO protons,
In complex 5, at variance with complex 1a, the DMSO
ligands are trans to a nitrogen atom. It should therefore
be expected that substitution reactions in 5 may be more dif-
ficult than in 1a. Nevertheless, reaction of complex 5 with
PPh3 in mild conditions affords complete substitution of
the coordinated DMSOs to give [Pt2(terpy-2H)(Cl)2-
3
shows a JPt–H indicative of a ligand trans to a nitrogen
rather than to a carbon atom (3JPt–H = 24.4 Hz vs.
3JPt–H = 18.1 Hz in 1a). In agreement, in the IR spec-
(PPh3)2] (7). The 31P{1H} NMR spectrum shows a singlet
trum the value of the Pt–Cl stretch (mmax = 267 cmꢀ1
)
with satellites at d 18.15 : the high value of JPt–P
,
1
[18] is consistent with 5 being the isomer with Cl trans
4327 Hz, is consistent with a phosphorus trans to a nitrogen

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S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
1
atom. In the H NMR spectrum the resonance of the H40
proton, a singlet at d 6.72, is markedly shifted upfield with
respect to complex 5 (d 9.01) owing to the PPh3 ligands in
adjacent positions. The overall spectrum, also in this case
is indicative of a symmetric molecule so that 7 can be
described as follows:
Table 1
˚
Selected distances (A) and angles (ꢀ) in 7 with estimated standard
deviations (esd’s) on the last figure in parentheses
Pt(1)–Cl(1)
Pt(1)–N(1)
Pt(2)–Cl(2)
Pt(2)–N(3)
N(2)–C(6)
C(6)–C(7)
C(8)–C(9)
2.379(1)
2.101(3)
2.386(1)
2.100(3)
1.339(5)
1.400(5)
1.413(5)
Pt(1)–P(1)
Pt(1)–C(7)
Pt(2)–P(2)
Pt(2)–C(9)
N(2)–C(10)
C(7)–C(8)
C(9)–C(10)
2.230(1)
2.007(3)
2.237(1)
2.013(4)
1.346(5)
1.409(5)
1.398(6)
N
Cl(1)–Pt(1)–P(1)
Cl(1)–Pt(1)–C(7)
P(1)–Pt(1)–C(7)
Cl(2)–Pt(2)–P(2)
Cl(2)–Pt(2)–C(9)
P(2)–Pt(2)–C(9)
92.9(1)
170.0(1)
96.6(1)
89.7(1)
168.2(1)
100.7(1)
Cl(1)–Pt(1)–N(1)
P(1)–Pt(1)–N(1)
N(1)–Pt(1)–C(7)
Cl(2)–Pt(2)–N(3)
P(2)–Pt(2)–N(3)
N(3)–Pt(2)–C(9)
90.5(1)
168.3(1)
81.0(1)
89.6(1)
170.8(1)
81.0(1)
N
N
Pt
Pt
Cl
Cl
PPh3
Ph3P
7
Complex 7 can also be obtained by reaction of 6 with
PPh3 under the same experimental conditions. The struc-
ture of complex 7 has been solved by X-ray diffraction.
An ORTEP view of the complex molecule 7 is shown in
Fig. 1.
Principal bond parameters are listed in Table 1. Disre-
garding the phosphinic phenyl rings, the molecule possesses
an idealized C2 symmetry, with the twofold axis passing
through atoms N2 and C8. A projection of the inner core
of the molecule down the idealized twofold axis is shown
in Fig. 2.
˚
Pt2 are 0.168(3) and ꢀ0.152(4) A for N3 and C9, respec-
tively. The dihedral angle between the best planes of the
metal atoms is 37.2(1)ꢀ. All the observed Pt–ligand bond
lengths are as expected if the trans-influence of C (sp2)
and P atoms are considered. Thus, the Pt–N and Pt–C dis-
tances found here can be compared with those found in
[Pt2(terpy-2H)(Me)2(CO)2] (1c): here we find Pt1–N1 =
˚
2.101(3) and Pt2–N3 2.100(3) A, in 1c Pt1–N1 = 2.137(5)
and Pt2–N3 2.124(5) A. The slight shortening observed
˚
here is due to the trans-influence of P being lower than that
As can be seen, the inner framework of the molecule is
not flat, probably because of the need to relieve non-bond-
ing repulsions between the two bulky PPh3 ligands. Each of
the two Pt atoms displays a tetrahedrally distorted square-
planar coordination. Maximum deviations from the least-
of C(sp3). The present bond lengths of Pt1–C7 and Pt2–C9
˚
are 2.007(3) and 2.013(4) A, respectively; in 1c Pt1–
˚
C7 = 2.050(6) and Pt2–C9 2.051(5) A. Also in this case
the shortening in the present molecule is due to the lower
trans-influence of Cl with respect to that of CO. The pres-
ent Pt1–P1 and Pt2–P2 bond lengths, 2.230(1) and
˚
squares plane of Pt1 are +0.148(4) and ꢀ0.174(3) A for
C7 and N1, respectively. The corresponding values for
Fig. 1. ORTEP view of compound 7. Ellipsoids are drawn at the 30% probability level.

S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
4139
Fig. 2. A projection of 7 down the idealized twofold axis C8–N2. Only the first atoms of the phosphinic phenyl rings have been shown, for clarity.
˚
2.237(1) A, respectively, are very similar to those found in
[Pt2(L)Cl(PPh3)2], compound 17 [15b] (H3L = 6-phenyl-
N
N
N
N
N
N
0
˚
2,2 -bipyridine), Pt1–P1 2.225(1) and Pt2–P2 2.231(1) A
(in 17 the Pt–P bonds are also trans- to pyridinic nitrogen
atoms). The present Pt1–Cl1 and Pt2–Cl2 distances
PPh3
Pt
Pt
Pt
Pt
Cl
Cl
Cl
Cl
O
O
O
S
PPh3
S
S
˚
Me
2.379(1) and 2.386(1) A, respectively, are very long because
Me
Me Me
Me Me
of the trans-influence of C(sp2). They can be compared to
5
8
˚
the Pt–Cl bond length, 2.395(2) A, found in 18,
[PtCl(L)(SMe2)] (HL = 6-phenyl-2,20-bipyridine) [14a],
where the Pt–Cl bond is also trans- to a C(sp2) atom. As
previously found in 1c, the strain imposed on terpyridine
by its bridging behaviour is apparent in the intra-ring
angles of the N2 ring, which range 114.8(3)–126.3(3)ꢀ.
Bond lengths within this ring (see Table 1) indicate no loss
of aromaticity, and each of the three pyridinic rings is pla-
nar. However, as can be seen in Fig. 2, the three rings are
not coplanar, the dihedral angles between their best planes
being: N1 ring–N2 ring 10.5(4)ꢀ, N2 ring–N3 ring 11.9(5)ꢀ,
and N1 ring–N3 ring 3.5(7)ꢀ.
PPh3
N
N
N
Pt
Pt
Cl
Cl
PPh3
Ph3P
7
In the crystal packing of 7 there are couples of molecules
related by an inversion centre and kept together by gra-
phitic interactions, as shown in Fig. 3. The distance
between the planes of overlapping rings is about 3.40 A.
The couples of molecules that generate the packing are
kept together by normal van der Waals contacts.
The reaction proceeds in two steps indicating that sub-
˚
stitutions do not occur simultaneously on both the metallic
centres; the second PPh3 coordinates only after replace-
ment of one DMSO, suggesting an electronic interaction
between the metallic centres which are linked trough the
deprotonated terpy.
To check whether a selective substitution of the
DMSO ligands in 5 can be attained, the reaction with
PPh3 was carried out also with a 1:1 molar ratio. A
monosubstituted complex, [Pt2(terpy-2H)(Cl)2(DMSO)-
(PPh3)] (8), was isolated as the only product. The charac-
terization of compound 8 mainly rests on analytical and
NMR data. In particular, in the 1H NMR spectrum,
both the resonances of the coordinated DMSO and
PPh3 ligands are observed. In the aromatic region the
symmetry displayed by the species previously described
At variance with PPh3, the reaction of 5 with the more
bulky and basic PCy3 at room temperature affords mix-
tures of a mono- and a di-substituted product. The di-
substituted complex 9 can be obtained as the only product
from complex 5 or 6 working in dichloromethane at reflux.
In the 31P{1H} NMR spectrum the single resonance
observed at d 18.64 (1JPt–P = 4024 Hz) gives evidence for
a symmetric species having a trans P–Pt–N arrangement.
In complex 5 both the DMSO molecules can also be
replaced by 3,5-lutidine: in this case excess of ligand and
heating are required to obtain complex 10, [Pt2(terpy-2H)-
is missing as shown e.g. by the H6 and H600 protons
3
which are no more equivalent (H600: d 9.44, d, JPt–H
=
3
4
32 Hz; H6: d 9.85, dd, JPt–H = 28 Hz, JP–H = 4.5 Hz).
Compound 8 can further react with PPh3 to afford com-
pound 7.
1
(Cl)2(3,5-lutidine)2]. In the H NMR spectrum remarkable
is the shift of the H40 signal (d 5.80 with satellites 1:2.2:1,

4140
S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
Fig. 3. A couple of molecules showing graphitic interactions in the crystal packing of 7 (see text). Phenyl rings have been omitted.
3JPt–H = 43.5 Hz) strongly shielded with respect to 5 (d
9.01), as expected for a proton lying in the shielding cone
of the aromatic rings of the lutidine.
The new complexes 7–12, obtained in one or two steps
from compound 5 by substitution of DMSO with neutral
ligands, are collected in Scheme 1. All of them show an
extraordinary thermal stability.
Although in 5 and 7–12 the chloride is coordinated trans
to a C(sp2) atom, a high trans-influence and trans-effect
donor, the Pt–Cl bond is not cleaved by neutral nucleo-
philes (e.g. DMSO, CO, PPh3 in the case of 5 or CO in
the case of 7) even in the presence of Na[BF4] (acetone
solution). The substitution of the chloride in 5 with neutral
ligands was also attempted in dichloromethane in the
N
N
N
Pt
Pt
Cl
Cl
H
N
N
10
The reaction of complexes 5 and 7 with CO gives com-
pounds 11, [Pt2(terpy-2H)(Cl)2(DMSO)(CO)] and 12,
[Pt2(terpy-2H)(Cl)2(PPh3)(CO)], respectively. The IR spec-
tra of the isolated products show a strong band at
2093 cmꢀ1 assignable to the stretching vibration of a termi-
N
N
N
Pt
Pt
Cl
Cl
L'
L''
1
nal carbonyl. The H NMR spectrum of complex 11 gives
3
evidence for a coordinated DMSO (d 3.68, JPt–H
=
Compound
L’
L’’
22.5 Hz) suggesting that partial substitution occurred. In
agreement, complex 11 is not symmetric, as shown by
two resonances for the H6 and H600 protons (d 9.44 and
d 9.59): furthermore two different couplings of H40 with
5
7
DMSO
PPh3
DMSO
PPh3
195Pt (d 8.78, 3JPt–H = 43 Hz, 3JPt –H ¼ 67 Hz) indicate that
0
8
DMSO
PCy3
PPh3
PCy3
3,5-lut
CO
the two platinum atoms are not equivalent. Finally, the
FAB (positive ions) mass spectrum shows the molecular
ion of compound 11 at m/z 796. The reaction of 7 proceeds
under mild conditions (r.t., 1 atm) to give 12 in high yields
(>90%). The substitution by CO of only one of the neutral
ligands in complexes 5 and 7 may be due to the scarce sol-
ubility of compounds 11 and 12: after the first substitution,
coordination of the second CO might be hampered by their
precipitation in the reaction medium.
9
10
11
12
3,5-lut
DMSO
CO
PPh3
Scheme 1.

S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
4141
Complex 15 is unstable in the solid state and its charac-
terization mainly rests on the 1H NMR spectra: a signal in
the hydridic region, d ꢀ15.54, with satellites (1:4:1), gives
evidence for a terminal Pt–H bond. The high value of the
presence of the Brookhart’s salt, Na{B[C6H3(CF3)2]4} [19],
to take advantage of the insolubility of NaCl. In absence of
a coordinating solvent decomposition occurs, whereas
when a small amount of acetonitrile is added, the ionic
complex 13, [Pt2(terpy-2H)(DMSO)2(MeCN)2]{B[C6H3-
(CF3)2]4}2, is isolated. Complex 13 is extremely soluble in
common organic solvents, making its purification a difficult
1
platinum–hydrogen coupling constant, JPt–H = 1567 Hz,
is in line with that previously reported for a N,N,C-cyclo-
metallated species, 1606 Hz [21], where the hydride is trans
to an sp2 nitrogen atom: this implies that substitution of
Hꢀ for Clꢀ occurs with isomerization, as expected taking
account of the high trans-influence of both a carbon and
a hydride donor (trans-phobia) [22]. At variance, complex
16, [Pt2(terpy-2H)(H)2(PPh3)2], is stable in the solid state:
1
task. The H NMR shows signals at d 3.57 (12H) and 2.25
(6H) due to coordinated DMSO and acetonitrile, respec-
tively. The 195Pt–H coupling suggests a DMSO coordi-
nated trans to a carbon atom (3JPt–H = 19.3 Hz). A single
signal for the H6, H600 protons (d 9.58), is consistent with
a symmetric formulation
1
the analytical data fit the indicated formulation. The H
2
NMR spectrum shows a doublet at d ꢀ15.53, JP–H
=
=
24 Hz, with satellites due to coupling to 195Pt (1JPt–H
2+
1444.5 Hz); in the 31P {1H} NMR spectrum a resonance,
1
observed at d 32.89, is coupled to 195Pt with JPt–P
=
N
N
N
2072.0 Hz, a value consistent with a phosphorus trans to
a high trans-influence donor.
O
O
Pt
Pt
S
S
Complexes 15 and 16 are rare examples of cyclometa-
lated N,C platinum(II) hydrides: as far as we know the
only species isolated is [Pt(L–H)H] (L = 6-(1-methylben-
zyl)-2,20-bipyridine) where L–H is the tridentate N,N,C
ligand coordinated via the two bipyridine nitrogens and
an ortho carbon of the phenyl of the chiral methylbenzyl
Me
Me
S
S
Me
Me
S=MeCN
13
Substitution of the chloride with a coordinating anion
is easier, as shown by the reaction of 5 with lithium iodide
to give [Pt2(terpy-2H)(I)2(DMSO)2] (14). In the IR spec-
trum substitution of Iꢀ for Clꢀ is indicated by the disap-
pearance of the absorption at 267 cmꢀ1 assigned in 5 to
group [21]. Quite recently evidence for
a similar
[Pt(N,N,C)H] species has been detected in solution [23].
The reactivity of the Pt–H bond in platinum(II) derivatives
with nitrogen ligands is therefore completely unknown. It
is worth to remind that, in contrast, Pt(IV) hydride com-
plexes with nitrogen ligands have been widely investigated
in the frame of the studies on the intermolecular hydrocar-
bon C–H activation [24].
1
m(Pt–Cl). In the H NMR the single signal of the H6 ed
H600 protons is strongly deshielded, d 10.22, as previously
observed when an iodide is in close proximity of a pyrid-
inic ring [20].
3. Conclusions
We have described the synthesis of a number of plati-
num(II) complexes where two metal atoms are linked by
a twofold deprotonated 2,20:60,200terpyridine (terpy). Their
synthesis, which entails the activation of two C–H bonds,
is promoted by the electron-rich fragment ‘‘Pt(Me)2’’.
The electron- delocalized motif which bridges the platinum
atoms, (terpy-2H), is robust so that from the parent com-
pound 1a, [Pt2(terpy-2H)(Me)2(DMSO)2], an extensive ser-
ies of methyl derivatives, 1b–1e and 2–4, was easily
obtained by substitution of DMSO with neutral ligands.
Likewise, the bridging ligand is not affected by strong acids
such as HPF6, and is not cleaved even by HCl: reaction of
the latter with the methyl derivatives affords a new series of
complexes, 5–10, having a chloride in place of a methyl
group. The structure of one of them, [Pt2(terpy-2H)(Cl)2-
(PPh3)2] (7), solved by X-ray diffraction analysis gives evi-
dence for a trans Cl–Pt–C arrangement and shows that, at
least in this case, the inner framework of the molecule is
not flat. Furthermore other species can be obtained by
halide exchange, e.g. Iꢀ for Clꢀ, or by chloride abstraction
to give cationic solvento species. Exchange of the chloride
N
N
N
Pt
Pt
I
I
O
O
S
S
Me
Me
Me Me
14
In complexes 5 and 7, the chloride, coordinated trans to
the carbon atom, can also be substituted by hydride trans-
fer from Na[BH4], to give 15, [Pt2(terpy-2H)(H)2(DMSO)2]
and 16, [Pt2(terpy-2H)(H)2(PPh3)2], respectively.
N
N
N
Pt
Pt
L
L
H
H
L= DMSO, 15; PPh3, 16

4142
S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
with Hꢀ provides C,N cyclometalated platinum(II)
hydrides that are extremely rare. A two step approach
allows the synthesis of unsymmetric derivatives having dif-
ferent ligands around each platinum atom. Most of the
derivatives here described display a high thermal stability.
In conclusion we have shown that the reaction of the
fragment ‘‘Pt(Me)2’’ with terpy leads, through an unex-
pected behaviour of the ligand, to a variety of new species.
This once again calls the attention to the potential of the
diorgano platinum(II) derivatives in the intramolecular
C–H activation, as recently reported by us also in the case
of the 6-substituded 2,20-bipyridines. It is also worth noting
that the reactivity of these fragments is of paramount
importance in the intermolecular C–H activation.
The reaction was stirred at 50 ꢀC for two days and the
resulting solution was evaporated to dryness, crystallized
from dichloromethane/hexane and dried in vacuo to give
the analytical sample (58.2 mg, 60%) as a yellow solid.
M.p. 200 ꢀC (dec), (Calc. for C31H33N5Pt2: C, 43.01;
H, 3.84; N, 8.09. Found: C, 42.84; H, 3.99; N, 7.82%.)
m
max(Nujol)/cmꢀ1 1595m, 1555m, 1509m, 1145m, 1114m,
1071m; dH (300 MHz; acetone-D6; Me4Si) 0.94 (6H, s,
2
CH3–Pt, JPt–H 86.4); 2.43 (12H, s, CH3 (3,5-Me2-pyri-
dine); 7.18 (2H, td, H5, H500); 7.69 (2H, s, H4(3,5-Me2-pyr-
idine)); 7.80 (2H, dd, H3, H300); 7.96 (2H, td, H4, H400); 8.32
(2H, d, H6, H600); 8.51–8.53 (5H, m, H40, H2 (3,5-Me2-
pyridine)); m/z (FAB) 865 (M+), 850 ðM ꢀ CH3þÞ, 744
(MꢀCH3–C7H9N)+), 728 (Mꢀ2CH3–C7H9N+), 652 (Mꢀ
2(C7H9N)+), 636 (MꢀCH3–2(C7H9N)+), 621 (Mꢀ 2CH3–
2(C7H9N)+), 442 (MꢀCH3–2(C7H9N)–Pt+H+), 427
(Mꢀ2CH3–2(C7H9N)–Pt+H+).
4. Experimental
4.1. Materials
4.3.2. [Pt2(terpy-2H)(Me)2(TCNE)2] (3)
All the solvents were purified and dried before use accord-
ing to standard methods [25]. The reactions were performed
in air unless otherwise indicated. [Pt2(terpy-2H)(Me)2-
(DMSO)2] (1a) and [Pt2(terpy-2H)(Me)2(PPh3)2] (1d) have
been synthesized according to the literature procedures [13].
To a solution of 1a (50.0 mg, 0.062 mmol) in 40 ml of
dichloromethane were added 15.8 mg of tetracyanoethyl-
ene, TCNE, (0.123 mmol). The reaction was stirred at
room temperature for two days. The precipitate formed
was filtered off, washed with diethyl ether (5 · 20 ml) and
dried in vacuo to give the analytical sample (55.1 mg,
98%). M.p. > 270 ꢀC, (Calc. for C29H15N11Pt2: C, 38.37;
H, 1.67; N, 16.97. Found: C, 38.21; H, 1.75; N, 16.66%.).
4.2. Measurements
Elemental analyses were performed with a Perkin–Elmer
elemental analyser 240B by Mr. A. Canu (Dipartimento di
m
max(Nujol)/cmꢀ1 2218s, 2135s, 1610s, 1564s, 1265m,
1039m.
`
Chimica, Universita di Sassari, Italy). Infrared spectra were
recorded with FT-IR Jasco 480P or Perkin–Elmer 983 spec-
4.3.3. [Pt2(terpy-2H)(Me)4I2(PPh3)2] (4)
1
trophotometers using Nujol mulls. H and 31P{1H} NMR
To a solution of 1d (85.0 mg, 0.072 mmol) in 50 ml of
acetone were added 0.5 ml of MeI (d = 2.28 g/ml;
8.03 mmol). The mixture was stirred for 2 h at 30 ꢀC, then
concentrated and treated with diethyl ether. The yellow
precipitate formed was filtered, washed with diethyl ether
and dried in vacuo to give the analytical sample (69.4 mg,
66%) as a yellow solid. M.p. 170–172 ꢀC (Calc. for
C55H51N3I2P2Pt2: C, 45.25; H, 3.52; N, 2.88. Found: C,
45.09; H, 3.64; N, 2.79%.); mmax(Nujol)/cmꢀ1 1605(m),
1564(m), 1520(m), 1090(s), 1034(m), 745(s), 695(s); dH
spectra were recorded at room temperature (20 ꢀC) with a
Varian VXR 300 spectrometer operating at 300.0 and
121.4 MHz, respectively. Chemical shifts are given in ppm
relative to internal TMS (1H) and external 85% H3PO4
(31P); coupling constants are given in Hz. The mass spectro-
metric measurements were performed on a VG 7070EQ
instrument, equipped with a PDP 11-250J data system and
operating under positive ion fast bombardment (FAB) con-
ditions with 3-nitrobenzyl alcohol as supporting matrix.
2
(300 MHz; CDCl3Me4Si) 1.18 (6H, d, CH3–Pt, JPt–H
4
4''
3
2
3
60.3, JP–H 7.3); 1.78 (6H, d, CH3–Pt, JPt–H 70.6, JP–H
7.6); 7.04–7.45 (30H, m, aromatics); 7.53 (1H, s, H40,
3JPt–H48.8); 7.68–7.83 (4H, m, aromatics); 8.20 (2H, d,
3
5
6
3''
5''
6''
N
4'
N
N
3
aromatics, JH–H 8.0); 9.34 (2H, d, H6, H600, JPt–H 10.7,
Pt
JH–H ca. 5.4). dP (121.4 MHz, CDCl3, H3PO4) d = ꢀ11.58
Pt
1
(s, JPt–P 985.0).
numbering Scheme
4.3.4. [Pt2(terpy-2H)(Cl)2(DMSO)2] (5)
To a solution of 1a (90.0 mg, 0.112 mmol) in acetone
(50 ml) were added 1.5 mL of DMSO and 2.26 ml of aque-
ous 0.1 M HCl (0.226 mmol). After the addition of HCl the
solution colour changed to yellow. The mixture was stirred
for 3 h at room temperature, then concentrated to small
volume. The precipitate formed was filtered, washed
with H2O, EtOH and Et2O, and dried in vacuo to give
4.3. Syntheses
4.3.1. [Pt2(terpy-2H)(Me)2(3,5-Me2-pyridine)2] (2)
To a solution of 1a (90.0 mg, 0.112 mmol) in acetone
(40 ml) were added 50 ll of 3,5-Me2-pyridine (0.25 mmol).

S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
4143
1
the analytical sample (80.8 mg, 85%) as an orange-yellow
solid. M.p. > 270ꢀ (Calc. for: C19H21N3Cl2O2Pt2S2: C,
26.89; H, 2.49; N, 4.95. Found: C, 27.09; H, 2.58; N,
5.00%.); mmax(Nujol)/cmꢀ1 1609(m), 1564(m), 1518(m),
1138(m), 267(m). dH (300 MHz; acetone-D6; Me4Si) 3.62
CDCl3 H3PO4) d = 18.15 (s, JPt–P, 4327); m/z (FAB)
1215 (M)+, 1181(MꢀCl)+, 1145 (Mꢀ2Cl)+, 918 (MꢀCl–
PPh3)+, 883 ðM ꢀ 2Cl–PPh3þÞ, 689 (Mꢀ2Cl–PPh3–
Pt+H+), 621 ðM ꢀ 2Cl–2PPhþÞ, 427 (Mꢀ2Cl–2PPh3–Pt+).
3
3
(12H, s, CH3 (DMSO) JPt–H 24.4); 7.62 (2H, ddd, H5,
4.3.7. [Pt2(terpy-2H)(Cl)2(PPh3)(DMSO)] (8)
H500, JH–H 7.5, 5.7, 1.5); 8.21(2H, td, H4, H400, JH–H7.5,
1.5); 8.39 (2H, d, H3, H300, JH–H 7.5); 9.01 (1H, s, H40,
To a suspension of 5 (43.0 mg, 0,051 mmol) in dichloro-
methane (10 ml) were added 13.3 mg of PPh3 (0.051 mmol).
The resulting solution was stirred for 1 h at room tempera-
ture, then concentrated to small volume. The yellow precip-
itate formed after addition of hexane (30 ml) was filtered off,
washed with hexane and dried in vacuo to give the analytical
sample (43.2 mg, 78%) as a yellow solid. M.p. > 270 ꢀC
(Calc. for C35H30N3Cl2OPSPt2 3H2O: C, 38.68; H, 3.34;
N, 3.87. Found: C, 38.62; H, 2.83; N, 3.99%.); mmax(Nujol)/
cmꢀ1 1600m, 1565m, 1510m, 1142m, 1095s; dH (300 MHz;
3
3JPt–H 44.7); 9.60 (2H, dd, H6, H600, JPt–H 35, JH–H 5.1);
m/z (FAB) 814 (MꢀCl + H+), 770 (MꢀDMSO+), 734
(MꢀCl–DMSO+), 691 (Mꢀ2DMSO+), 656 (MꢀCl–
2DMSO+), 620 (Mꢀ2Cl–2DMSO–H+), 426 (Mꢀ2Cl–
2DMSO–Pt+).
4.3.5. Reaction between [Pt2(terpy-2H)(Me)2(DMSO)2]
and HCl
3
To a solution of 1a (75 mg, 0.088 mmol) in 150 ml of
acetone were added 1.8 ml of 0.1 M HCl (0.18 mmol).
The colour of the solution changed to yellow and an
orange precipitate formed. The mixture was stirred for
3 h at room temperature. The precipitate formed was fil-
tered and washed with acetone (3 · 30 ml) to give complex
6 (25.6 mg, yield 42%) as a dark-orange solid. The filtered
solution was concentrated: the precipitate formed was fil-
tered, washed with H2O, EtOH and Et2O, and dried in
vacuo to give complex 5 (35.8 mg, 48%) as an orange-
yellow solid.
Complex 6: m.p. > 270 ꢀC. (Calc. for C30H18N6Cl4Pt4:
C, 26.02; H, 1.31; N, 6.07. Found: C, 26.28; H, 1.24; N,
5.89%); mmax(Nujol)/cmꢀ1 1609m, 1565m, 1520m, 1290m,
327w, 250w, 243w; dH (300 MHz; DMSO; Me4Si) 7.66
(2H, t, H5, H500); 8.22 (2H, t, H4, H400); 8.33 (2H, d, H3,
H300); 8.83 (1H, s, H40, 3JPt–H, 37.2); 9.47 (2H, d, H6, H600).
CDCl3 Me4Si) 3.06 (6H, s, CH3(DMSO), JPt–H 21.5);
7.31–7.98 (20H, m, aromatics); 8.26, (1H, d, H300, JH–H
3
8.0); 8.34 (1H, d, H3, JH–H8.0); 9.44 (1H, d, H600, JPt–H
3
4
32, JH–H5.8); 9.85 (1H, dd, H6, JPt–H 28, JP–H ca. 4.5).
dP (121.4 MHz, CDCl3, H3PO4) 23.70 (s, 1JPt–P 4307).
4.3.8. [Pt2(terpy-2H)(Cl)2(PCy3)2] (9)
To a suspension of 5 (50.0 mg, 0,059 mmol) in dichloro-
methane (10 ml), under argon atmosphere, were added
45.0 mg of PCy3 (0.160 mmol). The yellow solution formed
was stirred for 7 h at reflux temperature, then evaporated
to dryness and crystallized from dichloromethane/diethyl
ether to give the analytical sample (47.3 mg, 64%) as a yel-
low solid. M.p. > 270 ꢀC; (Calc. for C51H75N3Cl2P2Pt2: C,
48.88; H, 6.03; N, 3.35. Found: C, 48.55; H, 5.96; N,
3.00%.); mmax(Nujol)/cmꢀ1 1605m, 1562m, 1506 m, 1005s;
dH (300 MHz; CDCl3; Me4Si) 1.1–2.1 (66H, m); 7.31 (2H,
3
m, H5, H500); 7.74 (1H, s, H40, JPt–H ca. 22); 7.88 (2H,
dt, H4, H400, JH–H7.6, 1.5); 8.14 (2H, d, H3, H3 ,
00
4.3.6. [Pt2(terpy-2H)(Cl)2(PPh3)2] (7)
3
4
Method A. To a suspension of 5 (40.0 mg, 0.047 mmol)
in 15 ml of dichloromethane were added 24.7 mg of PPh3
(0.094 mmol). The yellow solution formed was stirred for
1 h, then concentrated to small volume and treated with
hexane. The precipitate formed was filtered, washed with
hexane and dried in vacuo to give the analytical sample
(52.0 mg, 91%) as a yellow solid.
JH–H7.6); 9.59 (2H, m, H6, H600, JPt–H 40.0, JP–H 4.2).
1
dP (300 MHz; CDCl3; H3PO4) 18.64 (s, JPt–P 4024).
Complex 9 can also be obtained by reaction of 6 with
PCy3 in dichloromethane at reflux temperature for 7 h
(yield 50%).
4.3.9. [Pt2(terpy-2H)(Cl)2(3,5-Me2-pyridine)2] (10)
To a solution of 5 (90 mg, 0.106 mmol) in acetone
(40 ml) were added 50 lL of 3,5-Me2-pyridine (0.248
mmol). The solution was stirred at 50 ꢀC for 2 days, then
evaporated to dryness. The solid obtained was crystallized
from dichloromethane/hexane and dried in vacuo to give
the analytical sample (79.3 mg, 81%) as a yellow solid.
M.p. > 270 ꢀC. (Calc. for C29H27N5Cl2Pt2 Æ H2O: C,
37.67; H, 3.16; N, 7.57. Found: C, 37.34; H, 3.30; N,
7.43%.); mmax(Nujol)/cmꢀ1 1600m, 1559m, 1510m, 1255m,
1140m, 1110m, 1070m. dH (300 MHz; CDCl3; Me4Si)
2.23 (12H, s, CH3 (3,5-Me2-pyridine)); 5.80 (1H, s, H4,
3JPt–H 43.5); 7.23–7.29 (4H, m, H5, H500, H4 (3,5-Me2-pyr-
idine)); 7.88 (td, 2H, H4, H400, JH–H 7.8, 1.0); 8.15 (2H, d,
H3, H300, JH–H 7.8); 8.46 (4H, s, H2, H6 (3,5-Me2-pyridine),
Method B. To a suspension of 6 (76.0 mg, 0.055 mmol)
in dichloromethane (20 ml) were added 57.6 mg of PPh3
(0.220 mmol). The yellow solution formed was stirred at
room temperature for 2 h, then concentrated to small vol-
ume. The precipitate formed after addition of hexane
(40 ml) was filtered, washed with hexane (3 · 30 ml) and
dried in vacuo to give the analytical sample (51.5 mg,
77%) as a yellow solid. M.p. > 270 ꢀC (Calc. for C51H39-
N3Cl2P2Pt2: C, 50.34; H, 3.23; N, 3.45. Found: C, 50.09;
H, 3.36; N, 3.77%.); mmax(Nujol)/cmꢀ1 1607m, 1565m,
1510m, 1282w, 1187w, 1156w, 1099s, 757s, 695s; dH
3
(300 MHz; CDCl3 Me4Si) 6.72 (1H, t, H40, JPt–H 50.1,
4JP–H 2.7); 7.73–7.87 (32H, m, aromatics (PPh3), H5,
H500); 7.95 (2H, dt, H4, H400); 8.34 (2H, d, H3, H300); 9.65
3
4
3
(2H, m, H6, H600, JPt–H 23.4, JP–H 4.2). dP (121.4 MHz,
3JPt–H 44.4); 9.58 (2H, d, H6, H600, JPt–H 28.3, JH–H 6.0);

4144
S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
m/z (FAB) 905 (M+), 871 (MꢀCl+), 799 (MꢀC7H9N+),
763 (MꢀCl–C7H9N+), 728 (Mꢀ2Cl–C7H9N+), 656 (Mꢀ
Cl–2(C7H9N)+), 621 (Mꢀ2Cl–2(C7H9N)+), 463 (MꢀCl–
2(C7H9N)–Pt+), 427 (Mꢀ2Cl–2(C7H9N)–Pt+).
4.3.13. [Pt2(terpy-2H)(I)2(DMSO)2] (14)
To a suspension of 5 (65.0 mg, 0.077 mmol) in acetone
(30 ml) were added 40.3 mg (0.30 mmol) of LiI. The yellow
solution formed was stirred for 4 days, then evaporated to
dryness and crystallized from dichloromethane/diethyl
ether to give the analytical sample (34.0 mg, 40%) as a
yellow solid. M.p. > 270 ꢀC. (Calc. for C19H21N3I2O2S2-
Pt2ÆE2O (NMR criterion): C, 24.99; H, 2.83; N, 3.80.
Found: C, 25.27; H, 3.11; N, 3.46%.); mmax(Nujol)/cmꢀ1
1610m, 1563m, 1510m, 1135m. dH (300 MHz; CDCl3;
4.3.10. [Pt2(terpy-2H)(Cl)2(DMSO)(CO)] (11)
CO at atmospheric pressure was bubbled into a solution
of 5 (50.0 mg, 0.059 mmol) in 50 ml of dichloromethane.
The solution was stirred for 1 h during which a red suspen-
sion was formed. The mixture was concentrated to small
volume and treated with diethyl ether. The red-orange pre-
cipitate formed was filtered, washed with diethyl ether and
dried in vacuo to give the analytical sample (33.0 mg, 70%)
as an orange solid. M.p. > 270ꢀ (Calc. for C18H15N3-
Cl2O2Pt2S: C, 27.08; H, 1.89; N, 5.26. Found: C, 27.24;
H, 1.47; N, 5.36%.); mmax(Nujol)/cmꢀ1 2093 s, 1613m,
1565m, 1537m, 1269m, 798m, 767m, 731m. dH (300 MHz;
3
Me4Si) 3.92 (12H, s, CH3 (DMSO), JPt–H 22.9); 7.30
(2H, m, H5, H500); 7.94 (2H, t, H4, H400); 8.29 (2H, d,
3
H3, H300); 9.11 (1H, s, H400, JPt–H 45); 10.22 (2H, d, H6,
3
H600, JPt–H 36).
4.3.14. [Pt2(terpy-2H)(H)2(DMSO)2] (15)
To a suspension of 5 (50.0 mg, 0.059 mmol) in THF
(30 ml) were added 14.0 mg (0.373 mmol) of Na[BH4] dis-
solved in 10 ml of THF. A red precipitate immediately
formed. The suspension was stirred for 4 h, then it was fil-
tered and the precipitate was washed with dichloromethane
and diethyl ether to give 32.2 mg of a brown solid. dH
3
CDCl3; Me4Si) 3.68 (6H, s, CH3(DMSO), JPt–H 22.5);
7.44 (2H, m, H5, H500); 8.00 (2H, m, H4, H400); 8.22 (2H,
3
3
m, H3, H300); 8.78 (1H, s, H40, JPt–H43, JPt–H 67); 9.44
3
3
(1H, d, H6, JPt–H 24); 9.59 (1H, d, H600, JPt–H 32.4);
m/z (FAB) 796 (M+), 763 (MꢀCl+), 684 (MꢀCl–DMSO+),
656 (MꢀCl–DMSO–CO+), 621 (Mꢀ2Cl–DMSO–CO+),
426 (Mꢀ2Cl–DMSO–CO–Pt+).
1
(300 MHz; CDCl3; Me4Si) ꢀ15.54 (2H, s, JPt–H 1567).
4.3.15. [Pt2(terpy-2H)(H)2(PPh3)2] (16)
4.3.11. [Pt2(terpy-2H)(Cl)2(PPh3)(CO)] (12)
To a solution of [Pt2Cl2(PPh3)2(terpy-2H)] (85.0 mg
0.070 mmol) in THF (30 ml) were added 11.0 mg
(0.29 mmol) of Na[BH4] dissolved in 10 ml of THF. The
colour turned to red and a yellow precipitate was formed.
The mixture was stirred for 4 h, then cooled with an ice
bath and evaporated to small volume. The precipitate
formed by treatment with hexane was filtered, washed with
hexane and recrystallized from CHCl3/Et2O to give the
analytical sample (62.1 mg, 70%), m.p. 105 ꢀC (dec). (Calc.
for C51H41N3P2Pt2 Æ CHCl3: C, 49.28; H, 3.34; N, 3.32.
Found: C, 49.15; H, 2.97; N, 3.26%.). mmax(Nujol)/cmꢀ1
2209w, 1604m, 1564m, 1511m, 1095s. dH (300 MHz;
CO at atmospheric pressure was bubbled under stirring
for 3 h into a solution of 7 (40.0 mg, 0,033 mmol) in 30 ml
of acetone. The orange yellow precipitate formed was fil-
tered, washed with diethyl ether and dried in vacuo to give
the analytical sample (29.5 mg, 91%) as an orange yellow
solid. M.p. > 270 ꢀC. (Calc. for C34H24N3Cl2OPPt2: C,
41.56; H, 2.46; N, 4.28. Found: C, 41.48; H, 2.01; N,
4.21%.); mmax(Nujol)/cmꢀ1 2093s, 1607m, 1560m, 1095m.
3
dH (300 MHz; CDCl3; Me4Si) 7.09 (1H, d, H40, JPt–H 63,
4JP–H 2.9); 7.77–7.84 (17H, m, aromatics (PPh3), H5,
00
00
0 0
H5 ); 7.99 (2H, m, H4, H4 ); 8.26 (d, 1H, H3 ); 8.31 (1H,
3
1
2
m, H3); 9.30 (1H, d, H600, JPt–H 25.2); 9.85 (1H, t, H6,
CDCl3; Me4Si) ꢀ15.53 (2H, d, H–Pt, JPt–H 1444.5, JP–H
24.1); 6.68 (2H, m, H5, H500); 7.35–7.48 (20H, m, aromat-
ics), 7.56–7.76 (14H, m, aromatics); 8.37 (d, 2H, JH–H
3JPt–H 33.6 , JP–H 4.4). dP (121.4 MHz; CDCl3; H3PO4)
4
1
22.86 (s, JPt–P 4266).
3
4
7.7, aromatics); 9.14 (1H, t, H40, JPt–H 64.5, JP–H 6.2,
4.3.12. ½Pt2ðterpy-2HÞðCH3CNÞ ðDMSOÞ ꢁ½BAr0 ꢁ (13)
JH–H 6.2). dP (121.4 MHz; CDCl3; H3PO4) 32.89 (s, JPt–P
1
2
2
4 2
To a solution of 5 (61.5 mg, 0.072 mmol) in dichloro-
methane (30 ml) were added 128.4 mg of Na½BAr04ꢁ
(0.145 mmol). The mixture was stirred for 5 h at room tem-
perature under argon, then filtered to remove the NaCl
formed and concentrated to dryness. The crude obtained
was washed with pentane and dried in vacuo to give the
analytical sample (103 mg, ca. 60%) as a yellow solid.
M.p. 95–97 ꢀC; mmax(Nujol)/cmꢀ1 1610m, 1563m, 1509m,
1140br. dH (300 MHz; CDCl3; Me4Si) 2.25 (6H, s,
2072).
4.3.16. X-ray data collection and structure determination
Crystal data are summarized in Table 2. The diffraction
experiment was carried out on a Bruker SMART CCD
area-detector diffractometer at 223 K, using Mo Ka radia-
tion (k = 0.71073) with a graphite crystal monochromator
in the incident beam. No crystal decay was observed, so
that no time-decay correction was needed. The collected
frames were processed with the software SAINT [26], and
an empirical absorption correction was applied (SADABS)
[27] to the collected reflections. The calculations were per-
formed using the Personal Structure Determination Pack-
age [28] and the physical constants tabulated therein [29].
The structure was solved by direct methods (SHELXS) [30]
3
CH3CN); 3.57 (12H, s, CH3 (DMSO), JPt–H 19.3); 7.17
(2H, m, H5, H500 or H4, H400); 7.39 (2H, m, H4, H400 or
H5, H500); 7.54 (8H, s, Hp); 7.70 (16H, s, Ho); 8.26 (2H,
3
dd, H3, H300); 8.51 (1H, s, H40, JPt–H 43.2); 9.58 (d, 2H,
3
H6, H600, JPt–H 33.6). KM (3 · 10ꢀ4 M, acetone) =
120 Xꢀ1 cm2 molꢀ1
.

S. Stoccoro et al. / Journal of Organometallic Chemistry 691 (2006) 4135–4146
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4145
Table 2
Crystallographic data
[3] (a) J.P. Sauvage, J.P. Collin, J.C. Chabron, C.S. Guillerez, C.
Coudret, V. Balzani, F. Barigelletti, L. de Cola, L. Flamigni, Chem.
Rev. 94 (1994) 993–1019;
Compound
Formula
M
7
C51H39Cl2N3P2Pt2
1216.93
Yellow
Triclinic
P1
10.461(1)
13.656(1)
15.700(2)
90.11 (1)
96.09 (1)
97.01 (1)
2213.3(4)
2
1172
1.826
223
0.07 · 0.17 · 0.19
66.11
0.684–1.000
x
0.30
20
(b) U.S. Schubert, C. Eschbaumer, Angew. Chem. 41 (2002) 3016–
3050;
Angew Chem., Int. Ed. 41 (2002) 2892–2926;
(c) D.-K. Ma, T. Yuen-Ting Shum, F. Zhang, C.-M. Che, M. Yang,
Chem. Commun. (2005) 4675–4677.
Colour
Crystal system
Space group
ꢀ
˚
a (A)
[4] (a) M.D. Ward, Chem. Soc. Rev. 24 (1995) 121–134;
(b) A. Harriman, R. Ziessel, Coord. Chem. Rev. 171 (1998) 331–
339;
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(b) E.M.A. Ratilla, B.K. Scott, M.S. Moxness, N.M. Kostic, Inorg.
Chem. 29 (1990) 918.
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
3
˚
U (A )
Z
F(000)
[7] (a) M. Howe-Grant, K.C. Wu, W.R. Bauer, S.J. Lippard, Biochem-
istry 15 (1976) 4339;
Dc (g cmꢀ3
T (K)
)
(b) K.W. Jennette, J.T. Gill, A. Sadownick, S.J. Lippard, J. Am.
Chem. Soc. 98 (1976) 6159;
(c) S.J. Lippard, Acc. Chem. Res. 11 (1978) 211;
(d) J.C. Dewan, S.J. Lippard, W.R. Bauer, J. Am. Chem. Soc. 102
(1980) 858;
Crystal dimensions (mm)
l (Mo Ka) (cmꢀ1
)
Minimum and maximum transmission factors
Scan mode
Frame width (ꢀ)
Time per frame (s)
Number of frames
Detector–sample distance (cm)
h-Range
Reciprocal space explored
Number of reflections (total; independent)
Rint
`
(e) G. Arena, L. Monsu Scolaro, R.F. Pasternack, R. Romeo, Inorg.
Chem. 34 (1995) 2994.
2450
4.00
3–26
Full sphere
36179; 13206
0.0512
0.055, 0.067
0.030
[8] (a) J.A. Bailey, M.G. Hill, R.E. Marsh, V.M. Miskowski, W.P.
Schaefer, H.B. Gray, Inorg. Chem. 34 (1995) 4591–4599;
(b) M.G. Hill, J.A. Bailey, V.M. Miskowski, H.B. Gray, Inorg.
Chem. 35 (1996) 4585.
[9] (a) H.K. Yip, L.K. Cheng, K.K. Cheung, C.M. Che, J. Chem. Soc.,
Dalton Trans. (1993) 2933–2938;
(b) R. Cini, A. Donati, R. Giannettoni, Inorg. Chim. Acta 315 (2001)
73–80.
[10] (a) D.C. Craig, M.L. Scudder, W.A. McHale, H.A. Goodwin, Aust.
J. Chem. 51 (1998) 1131–1139;
Final R2 and R2w indicesa(F2, all reflections)
Conventional R1 index [I > 2r(I)]
Reflections with I > 2r(I)
Number of variables
8505
541
0.984
Goodness-of-fitb
(b) K. Lashgari, K. Mikael, R. Norrestam, T. Norrby, Acta
Crystallogr., Sect. C (1999) 64–67;
P
P
P
P
2
2 1=2
a
R2 ¼ ½ ðj F 2o ꢀ kF c2 jÞ= F 2oꢁ, R2w ¼ ½ w=ðF o2 ꢀ kF 2c Þ = wðF 2oÞ ꢁ
P
P
P
2
1=2
2
b
½
wðF 2o ꢀ kF 2c Þ =ðNo ꢀ NvÞꢁ , where w ¼ 4F o2= ðF 2oÞ ,
ðF 2oÞ ¼
´
(c) S. Pyo, E. Perez-Cordero, S.G. Bott, L. Echegoyen, Inorg. Chem.
P
2
ðF 2oÞ þ ðpF o2Þ2ꢁ1=2, No is the number of observations, Nv the number of
38 (1999) 3337–3343.
½
[11] (a) Although an N,N0 bidentate behaviour and, at least in one case,
even a monodentate behaviour have been reported, they are very rare.
g2-terpy: G.B. Deacon, J.M. Patrick, B.W. Skelton, N.C. Thomas,
A.H. White, Aust. J. Chem. (1984) 929–945;
variables, and p, the ignorance factor, =0.02.
and refined by full-matrix least-squares using all reflections
P
2
and minimizing the function
wðF 2o ꢀ kF 2cÞ (refinement
(b) N.C. Thomas, J. Fischer, J. Coord. Chem. 21 (1990) 119;
(c) E.W. Abel, V.S. Dimitrov, N.J. Long, K.G. Orrell, A.G. Osborne,
V. Sik, M.B. Hursthouse, M.A. Mazid, J. Chem. Soc., Dalton Trans.
(1993) 597–603;
(d) E.W. Abel, V.S. Dimitrov, N.J. Long, K.G. Orrell, A.G. Osborne,
V. Sik, M.B. Hursthouse, M.A. Mazid, J. Chem. Soc., Dalton Trans.
(1993) 291–298;
(e) E.W. Abel, K.G. Orrell, A.G. Osborne, H.M. Pain, V. Sik, M.B.
Hursthouse, K.M. Abdul Malik, J. Chem. Soc., Dalton Trans. (1994)
3441–3449;
(f) R. Chotalia, E.C. Constable, M.J. Hannon, D.A. Tocher, J.
Chem. Soc., Dalton Trans. (1995) 3571–3580;
on F2). All the non-hydrogen atoms were refined with
anisotropic thermal factors. The hydrogen atoms were
placed in their ideal positions (C–H = 0.97 A), with the
thermal parameter B 1.10 times that of the carbon atom
˚
to which they are attached, and not refined. In the ꢀfi3nal
˚
Fourier map the maximum residual was 1.69(54) e A at
˚
0.73 A from Pt(2). CCDC No. 604223 contains the supple-
mentary crystallographic data for this paper.
Acknowledgement
(g) S. Ramdeehul, L. Barloy, J.A. Osborn, Organometallics 15 (1996)
5442–5444;
g1-terpy:F.P. Pruchnik, F. Robert, Y. Jeannin, S. Jeannin, Inorg.
Chem. 35 (1996) 4261–4263.
Financial support from the Universita‘ di Sassari is
gratefully acknowledged.
[12] D.A. Bardwell, A.M.W. Cargill Thompson, J.C.J. Jeffery, J.A.
McCleverty, M.D. Ward, J. Chem. Soc., Dalton Trans. (1996) 873–
878.
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