Diplatinum complexes: Chemoselective reactions of the μ-orthometalated, metal-metal bonded complex

Article abstract of DOI:10.1016/j.poly.2012.08.030

In order to investigate further the chemoselectivity of reactions involving the μ-orthometalated, metal-metal bonded dinuclear Pt(I) complex [Pt ₂(μ-o-C₆H₄PPh₂)(μ-PPh ₂)(PPh₃)₂](Pt-Pt) (1), it was reacted with HCl and HI using various stoichiometries. The first step was the breaking of the metal-carbon bond and the formation of C-H and Pt-X bonds. When a 1:1 ratio was used, the complexes [Pt₂X(μ-PPh₂)(PPh₃) ₃](Pt-Pt) (2, X = Cl; 3, X = I) have been obtained but the use of a 2:1 ratio resulted instead in the formation of the complexes [Pt ₂(μ-H)(μ-PPh₂)X₂(PPh₃) ₂](Pt-Pt) (4, X = Cl; 6, X = I). The latter transformed into [Pt ₂(μ-X)(μ-PPh₂)X₂(PPh₃) ₂] (5, X = Cl; 7, X = I) in the presence of an additional equivalent of HX. The cis,cis- and cis,trans-isomers of 7 were also obtained by oxidation of 3 with one equivalent of iodine. Whereas compounds 4, cis,cis-5, and cis,trans-7 have been characterized in solution, the complexes 2·1/2C₇H₈, 3, 6 and cis,cis-7 have been isolated and structurally characterized by X-ray diffraction.

Full text of DOI:10.1016/j.poly.2012.08.030

Polyhedron 52 (2013) 545–552
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Diplatinum complexes: Chemoselective reactions of the
metal–metal bonded complex [Pt2( -o-C6H4PPh2)( -PPh2)(PPh3)2] with acids.
Crystal structures of [Pt2Cl( -PPh2)(PPh3)3], [Pt2I( -PPh2)(PPh3)3],
[Pt2( -H)( -PPh2)I2(PPh3)2] and cis,cis-[Pt2( -I)( -PPh2)I2(PPh3)2]
l-orthometalated,
l
l
l
l
l
l
l
l
Christine Archambault a, Robert Bender a, Yves Dusausoy b, Richard Welter c, Pierre Braunstein a,
⇑
a Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Université de Strasbourg, 4 rue Blaise Pascal, F-67081 Strasbourg-Cédex, France
b Laboratoire de Cristallochimie et Modélisation des Matériaux Minéraux et Biologiques, UPRESA 7036, Université Henri Poincaré, Nancy I, Faculté des Sciences, Boîte Postale 239,
F-54026 Vandoeuvre-les-Nancy, France
c Laboratoire DECOMET, Institut de Chimie (UMR 7177 CNRS), Université de Strasbourg, 4 rue Blaise Pascal, F-67081 Strasbourg-Cédex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 25 August 2012
In order to investigate further the chemoselectivity of reactions involving the l-orthometalated, metal–
metal bonded dinuclear Pt(I) complex [Pt2(
HCl and HI using various stoichiometries. The first step was the breaking of the metal–carbon bond and
the formation of C–H and Pt–X bonds. When a 1:1 ratio was used, the complexes [Pt2X( -PPh2)(PPh3)3]
(Pt–Pt) (2, X = Cl; 3, X = I) have been obtained but the use of a 2:1 ratio resulted instead in the formation
of the complexes [Pt2( -H)( -PPh2)X2(PPh3)2](Pt–Pt) (4, X = Cl; 6, X = I). The latter transformed into
[Pt2( -X)( -PPh2)X2(PPh3)2] (5, X = Cl; 7, X = I) in the presence of an additional equivalent of HX. The
l-o-C6H4PPh2)(l-PPh2)(PPh3)2](Pt–Pt) (1), it was reacted with
Dedicated to the memory of Alfred Werner
on the 100th Anniversary of his Nobel Prize
in Chemistry in 1913.
l
l
l
l
l
Keywords:
cis,cis- and cis,trans-isomers of 7 were also obtained by oxidation of 3 with one equivalent of iodine.
Whereas compounds 4, cis,cis-5, and cis,trans-7 have been characterized in solution, the complexes
2Á1/2C7H8, 3, 6 and cis,cis-7 have been isolated and structurally characterized by X-ray diffraction.
Ó 2012 Elsevier Ltd. All rights reserved.
Diplatinum complexes
Metal–metal bonds
Platinum
Phosphido ligands
Protonation
1. Introduction
transition-metal-mediated phosphorus–carbon cleavage of phos-
phine ligands can lead to a very rich chemistry in which the phos-
The study and understanding of the reactivity of metal–ligand
bonds represents a central issue in coordination and organometallic
chemistry and the selectivity of the reactions is usually determined
by a subtle balance between different factors. Molecules in which
possible competition exists between potential reactive sites are
therefore particularly interesting to investigate. This can be ex-
tended to situations where a reaction can occur at a metal–ligand
or at a metal–metal bond. It may be considered as ironic to talk about
metal–metal bonded complexes in a special issue dedicated to
Alfred Werner since in the days of this chemistry giant and founder
of Coordination Chemistry, the notionof metal–metalbonding with-
in molecules was non-existent. Later on, the recognition that such
bonding could exist and the subsequent exponential growth of clus-
ter chemistry justified coining it ‘‘post-Wernerian chemistry’’ [1].
Already in 1999, a three volumes book was not sufficient to cover
all the aspects of metal cluster chemistry and its diverse applications
in numerous fields of modern science [2]. It is well known that the
phorus atoms occupies a bridging position between two or more
metal centers and such transformations have relevance to possible
in situ transformations of homogeneous catalysts [3]. A number of
polynuclear phosphido-bridged complexes of platinum have been
reported and this class of complexes continues to attract consider-
able attention because of their structural diversity, rich chemistry
and often unexpected reactivity [4]. In this chemistry, the stabilizing
role of the three electron donor phosphido bridge(s) is well docu-
mented and the flexibility of the Pt–(l-P)–Pt angle, which can be
readily monitored by 31P NMR spectroscopy [5,6b], allows retention
or loss of metal–metal bonding, and in the latter case, without
decomposition of the complex [3,6].
In the dinuclear, metal–metal bonded orthometalated complex
[Pt2(l-o-C6H4PPh2)(l-PPh2)(PPh3)2](Pt–Pt) (1), obtained as one of
the thermolysis products of the Pt(0) complex [Pt(C2H2)(PPh3)2]
[7], three main potential reactivity sites for electrophilic attack ex-
ist: the electron-rich metal–aryl bond, a Pt–(l-P) bond and the me-
tal–metal bond [8]. Reactions involving the Pt–phosphine bonds
appear to be less frequent. In the case of attack by protons, the
classical reaction LnM–R + HX ? LnM–X + RH usually leads to
breaking of the metal–carbon bond and formation of C–H and
⇑
Corresponding author.
E-mail address: braunstein@unistra.fr (P. Braunstein).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.030

546
C. Archambault et al. / Polyhedron 52 (2013) 545–552
Scheme 1. Reactions of the dinuclear complex 1 with acids.
M–X bonds. We have shown previously that a proton can be easily
16.5 ppm compared to 2 is due to the different trans halide, and
the chemical shifts of the terminal phosphines at d 20.1, 25.5 and
35.9 ppm are close to those for 2 (assignments are given in Table 1).
The various P–P and P–Pt coupling constants are also comparable
to those of 2, which emphasizes the similarities between the
molecular structures of 2 and 3. We shall come back to the
31P{1H} NMR spectrum of 3 below.
Single crystals of 2Á1/2C7H8 and 3 were obtained by layering a
toluene solution of these complexes with pentane and X-ray dif-
fraction studies confirmed their structural similarity (Figs. 2 and
3, Table 2).
added in a bridging position to the Pt–Pt bond of complex 1, Àpro-
vided it is associated with a poor nucleophile such as BF4 or
À
PF6 [8]. The breaking the Pt–C
r-bond required the addition of
a second proton equivalent. Here we investigate and compare the
reactions of 1 with various stoichiometries of the mineral acids
HCl and HI, which lead to incorporation of the halide into the
products.
2. Results and discussion
The chloro complex 2 crystallized with half a molecule of tolu-
ene per molecule of complex. The asymmetric unit contains two
slightly different molecules, constituted by two Pt atoms linked
by a direct metal–metal bond and bridged by a PPh2 group. In trans
positions to this PPh2 group, one finds a halogen atom, chlorine in 2
and iodine in 3, and a terminal PPh3 ligand. In addition, the coordi-
nation sphere of each Pt atom is completed by a PPh3 group, in a
transoid arrangement with respect to the metal–metal bond. The
2.1. Syntheses and molecular structures of the dinuclear complexes
[Pt2Cl(l-PPh2)(PPh3)3](Pt–Pt) (2) and [Pt2I(l-PPh2)(PPh3)3](Pt–Pt) (3)
The complex 1 [7] reacts rapidly at room temperature with one
equivalent of aqueous HCl to afford the complex [Pt2Cl(l-PPh2)-
(PPh3)3](Pt–Pt) (2) (Scheme 1).
The IR spectrum of 2 no longer contains the typical absorption
at 724 cmÀ1 indicative of orthometalation in 1. This is consistent
with the breaking of the platinum–carbon bond in 1 and formation
of a C–H bond restoring a PPh3 ligand. The 1H NMR spectrum of 2
only contains resonances for aryl protons and does not reveal the
presence of a hydride ligand. The 31P{1H} NMR spectrum of 2 con-
tains signals corresponding to four chemically different phospho-
rus nuclei, flanked with satellites due to P–195Pt couplings
(Table 1 and Fig. 1).
The most deshielded signal (d = 157.2 ppm, ddd) typically corre-
sponds to a phosphido group bridging two different Pt atoms
linked by a metal–metal bond [5,6,9]. The bridging phosphorus is
coupled to another 31P nucleus in trans position (2J(PP) = 245 Hz)
and to two phosphorus nuclei in cis positions (2J(PP) = 45 and
14 Hz). The latter three nuclei have chemical shifts typical of ter-
minal phosphines (d = 22.4, 25.7 and 38.0 ppm). These data are
fully consistent with the results of an X-ray diffraction study
which, in addition, established the presence of a chloro ligand in
a position trans to the phosphido group (see below).
Pt2(l-P)P3 core of each of these molecules is planar. The Pt–Pt dis-
tance is slightly longer in 3. The other distances and angles show
no remarkable difference between 2 in 2Á1/2C7H8 and 3 (Table 2).
Complexes 2 and 3 possess 30 valence electrons and one metal–
metal bond, which confers a 16 electron environment to each d9 Pt
center, as is the case in the precursor complex 1. The reaction of 1
with HCl thus leads to the expected reaction (LnM–R + HCl ? LnM–
Cl + R-H) and the orthometalated triphenylphosphine is trans-
formed in a terminal phosphine ligand. This reaction did not take
place when 1 was reacted with HPF6 or HBF4, the PF6À or BF4À an-
ions being not nucleophilic enough to enter the coordination
sphere of the dinuclear core of the complex [8]. Instead, these acids
led to protonation of the Pt–Pt bond. Only a second proton equiv-
alent was able to break the Pt–phenyl bond, thus affording another
series of diplatinum complexes [8].
The reaction of 1 with the adduct HFÁpyridine has also been
shown to result in the breaking of the Pt–C
r-bond with formation
of a terminal triphenylphosphine. However in this case, the liber-
ated site on the Pt atom is occupied by a molecule of pyridine,
which is a better donor than the fluoride anion [10].
The reaction of complex 2 with NaI in acetone afforded the ex-
pected iodo complex [Pt2I(l
-PPh2)(PPh3)3](Pt–Pt) (3). Its 31P{1H}
NMR spectrum at À15 °C is analogous to that of 2 (Table 1). The
Whereas the 31P{1H} NMR spectrum of complex 3 is well re-
solved in CD2Cl2 at À15 °C, it becomes broader and poorly resolved
bridging phosphorus resonates at d 173.7 ppm, the deshielding of

C. Archambault et al. / Polyhedron 52 (2013) 545–552
547
Table 1
1H and 31P{1H} NMR data, at room temperature, in CD2Cl2 for complexes 2–7.
Complex
Nucleus
31P{1H}
d (ppm)
J (Hz)a
Assignmentb
2
22.4 (dd)
25.7 (dd)
38.0 (d)
157.2 (ddd)
20.1 (dd)
25.5 (dd)
35.9 (d)
173.7 (ddd)
À4.88 (dt)
21.0 (s)
109.7 (s)
7.70 (s)
JP–Pt = 3068, 414
JP–Pt = 3625, 455
JP–Pt = 3535, nd
JP–Pt = 3062, 4273
JP–Pt = 2932, 360
JP–Pt = 3650, 456
JP–Pt = 3448, nd
JP–Pt = 3103, 4123
JH–Pt = 454
JP–P = 214, 14
JP–P = 214, 45
JP–P = 245
JP–P = 245, 45, 14
JP–P = 210, 18
JP–P = 210, 40
JP–P = 262
JP–P = 262, 40, 18
JP–H = 88, 88, 15
JP–P = 68
PPh3 (P4)
PPh3 (P1)
PPh3 (P3)
l-P
3 at 258 K
31P{1H}
PPh3 (P4)
PPh3 (P1)
PPh3 (P3)
l
l
-P
-H
4
1H
31P{1H}
JP–Pt = 4125, 338
JP–Pt = 2930
JP–Pt = 4540
PPh3
-P
PPh3
l
cis,cis-5
31P{1H}
À68.6 (s)
À4.70 (dt)
16.6 (s)
138.2 (s)
13.6 (s)
JP–Pt = 2914
JH–Pt = 433
JP–Pt = 4084, 295
JP–Pt = 2858
JP–Pt = 4194
l
l
-P
-H
6
1H
JP–H = 84, 84,11
JP–P = 70
31P{1H}
PPh3
-P
PPh3
-P
l
cis,cis-7
31P{1H}
À141.6 (s)
JP–Pt = 2653
l
a
nd: not determined.
The numbering of the P atoms corresponds to the ORTEP views.
b
Fig. 2. ORTEP view of one of the two, slightly different molecules of complex 2Á1/
2C7H8 present in the asymmetric unit, with labeling scheme. Only the ipso carbon
atoms of the phenyl rings are represented. Hydrogen atoms as well as solvent
molecules are omitted for clarity. The ellipsoids enclose 50% of the electronic
density. A complete view of one molecule is given in Fig. S1 of the Supporting
Information.
Fig. 1. 31P{1H} NMR spectrum of 2.
above 27 °C in the region of the terminal phosphines: complex sig-
nals, grouped around 27 ppm, contain three doublets with 195Pt
satellites emerging from a broad hump (see Fig. S3, Supporting
Information). The signal for the bridging phosphorus remains at
the same chemical shift, but its symmetrical pattern becomes sec-
ond order, with two intense external lines at 172.05 and
173.89 ppm, while its 195Pt satellites take asymmetric profiles.
These observations suggest that a dynamic behavior occurs at
room temperature. This dynamic process may be induced by ioni-
Fig. 3. ORTEP view of complex 3 with labeling scheme. Only the ipso carbon atoms of
the phenyl rings are represented. Hydrogen atoms are omitted for clarity. The
ellipsoids enclose 50% of the electronic density. A complete view of 3 is given in
Fig. S2 of the Supporting Information, respectively.
zation of the molecule into [Pt2(
cation would possess a free coordination site, like the related Pd
complex [Pd2(
-Pt-Bu2)(PPh3)3]+ [11], and this could initiate a dy-
l
-PPh2)(PPh3)3]+IÀ. The complex
l
namic process involving the phosphine ligands. While the reso-
nance for P1 is only little affected by the temperature change,
those of P3 and P4, observed at À15 °C at 35.9 and 20.1 ppm,
respectively, become significantly closer from each other at room
temperature, suggesting that these ligands are those most involved
in the dynamic process. A suggestion is that an oscillation of the

548
C. Archambault et al. / Polyhedron 52 (2013) 545–552
Table 2
None of these new complexes could be isolated pure and their
1H and 31P{1H} NMR data were extracted from the spectra of mix-
tures (Table 1). These spectra are analogous to those of the corre-
sponding iodo complexes 6 and cis,cis-7, whose structures have
been determined by X-ray diffraction (see below). In complex 4,
Selected interatomic distances (Å) and angles (°) in one of the molecules of [Pt2Cl(
PPh2)(PPh3)3] (2) in 2Á1/2C7H8 and in [Pt2I( -PPh2)(PPh3)3] (3).
l-
l
the 31P{1H} NMR signal of the
l-PPh2 bridge is a singlet at
109.7 ppm, flanked by satellites due to 1J(P–Pt) = 2930 Hz, and
the phosphine resonances present the typical pattern for a P–Pt–
Pt–P chain at 21 ppm with 1J(P–Pt) = 4125 Hz, 2J(P–Pt) = 338 Hz
and 3J(P–P) = 68 Hz [12]. In addition, the 1H NMR spectrum con-
tains a triplet of doublets at À4.88 ppm for the bridging hydride li-
gand, with satellites due to 1J(H–Pt) = 454 Hz, 2J(H–P) = 88 and
15 Hz. The 31P{1H} NMR spectrum of cis,cis-5 contains two singlets
with satellites, one for the PPh3 groups at 7.7 ppm with 1J(P–
Pt(1)–Pt(2)
Pt(1)–P(1)
Pt(1)–P(2)
Pt(1)–Cl(1)
Pt(1)–I(1)
Pt(2)–P(2)
Pt(2)–P(3)
Pt(2)–P(4)
P(1)–Pt(1)–P(2)
P(1)–Pt(1)–Cl(1)
P(1)–Pt(1)–I(1)
Pt(2)–Pt(1)–Cl(1)
Pt(2)–Pt(1)–I(1)
Pt(2)–Pt(1)–P(1)
Pt(2)–Pt(1)–P(2)
Pt(1)–Pt(2)–P(2)
P(2)–Pt(2)–P(3)
P(2)–Pt(2)–P(4)
P(3)–Pt(2)–P(4)
P(2)–Pt(2)–Pt(1)
P(3)–Pt(2)–Pt(1)
P(4)–Pt(2)–Pt(1)
2.7387(9)
2.2518(15)
2.1803(16)
2.3904(17)
–
2.2592(15)
2.3013(16)
2.2912(17)
107.93(6)
91.38(6)
–
2.7526(9)
2.256(3)
2.193(3)
–
2.6829(7)
2.252(3)
2.316(3)
2.308(3)
109.67(1)
–
Pt) = 4540 Hz and the second for the
l
-PPh2 group at À68.6 ppm
with 1J(P–Pt) = 2914 Hz. The negative value of the chemical shift
is typical for a phosphido ligand bridging two metals without a
metal–metal bond [4a,5,6,9]. No other isomer of cis,cis-5 has been
observed in these NMR spectra.
These results show that the reaction of 1 with more than one
equivalent HCl does not stop at the formation of complex 4, i.e.
at the attack of two protons, but that very rapidly a third proton
reacts with 4 to form the complex cis,cis-5. Ultimately, the latter
is transformed into mononuclear species. Similar results were ob-
served when 2 was reacted with HCl or when complex 1 was re-
acted with more than three equivalents HCl.
The reaction of 1 with one equivalent HCl was the only one
which afforded an isolable dinuclear halogeno complex in good
yield. All the other stoichiometries explored gave mixtures of var-
ious mononuclear and dinuclear platinum halogeno complexes.
With the hope of improving these results, similar reactions have
been undertaken with HI and these are described below.
90.50(8)
107.24(5)
–
106.26(3)
–
161.13(4)
53.22(4)
50.62(4)
144.02(6)
106.24(6)
106.91(6)
50.62(4)
95.13(4)
156.77(4)
52.70(8)
50.78(8)
144.47(11)
106.14(11)
107.35(10)
50.78(8)
97.07(8)
155.45(7)
P3–Pt2–P4 moiety would bring P3 closer to Pt1 to compensate for
its empty coordination site resulting from iodide dissociation.
However, in view of the proximity of all the chemical shifts of
the terminal phosphine ligands, the mechanism of the dynamic
process cannot be established with certainty. At 70 °C, the red solu-
tion of 3 turns yellow and contains a mixture of unidentified spe-
cies, as indicated by a completely modified 31P{1H} NMR spectrum
(C2D2Cl4) which corresponds to an irreversible transformation of 3
(see Fig. S4, Supporting Information). Several new resonances ap-
pear, that of the phosphido group typical of 3 at 173.7 ppm has dis-
appeared and has been replaced by a new resonance at 82.6 (dd,
J(P–P) = 486, 16 Hz, 1J(Pt–P) = 2713 Hz). These species formed have
not been identified.
2.3. Reaction of 1 with HI
2.3.1. Synthesis and molecular structure of [Pt2(l-H)(l-PPh2)I2-
(PPh3)2](Pt–Pt) (6)
The reaction of HI in water with 1 in a 1:1 ratio afforded the
new complex 6 in 50% yield. Reaction with two equivalents of HI
gave only compound 6, which was isolated in 68% yield. The 1H
NMR spectrum of 6 showed the presence of a bridging hydride li-
gand at À4.7 ppm (Fig. 4, top and Table 1). This signal is a triplet of
doublets (2J(H-trans-P) = 84 Hz and 2J(H-cis-P) = 11 Hz), flanked by
satellites due to 1J(H–Pt) = 433 Hz. The 31P{1H} NMR spectrum con-
tained only two signals, a singlet at 138.2 ppm for a symmetrical
bridging PPh2 group, with satellites due to a 1J(P–Pt) coupling of
2858 Hz and a signal characteristic for the P–Pt–Pt–P chain [12],
centered at 16.6 ppm (1J(P–Pt) = 4084 Hz, 2J(P–Pt) = 295 Hz, 3J(P–
P) = 70 Hz) (Fig. 4, bottom and Table 1). These data indicate the
2.2. Reaction of 1 with two or more equivalents of HCl
The reactions of 1 with two or three equivalents of HCl in
aqueous solution afforded mixtures of complexes. In both cases,
cis-[PtCl2(PPh3)2] and trans-[Pt(H)Cl(PPh3)2] were identified in situ
by 31P{1H} NMR analysis of the reaction mixture. In addition, the
reaction with two equivalents of HCl also afforded the dinuclear
presence of a [Pt2(l-H)(l-PPh2)(PPh3)2] moiety in the molecular
structure of 6.
An X-ray diffraction study on a single crystal of 6, obtained by
recrystallization of the complex from a CH2Cl2/pentane mixture,
confirmed the presence of this moiety and provided the complete
details of the molecular structure of 6 (Table 3 and Fig. 5). There
are two, very similar molecules in the asymmetric unit. The coor-
dination sphere around each Pt atom is completed by a terminal io-
complexes [Pt2(l-H)(l-PPh2)Cl2(PPh3)2](Pt–Pt) (4) and cis,cis-
[Pt2( -Cl)( -PPh2)Cl2(PPh3)2] (cis,cis-5). This latter was the only
l
l
dinuclear compound identified when 1 was reacted with three
equivalents of HCl.
dine atom, trans to the
l-PPh2 group. The molecule is rather
symmetrical, with a Pt–Pt distance of 2.847(1) Å. This distance is
longer by 0.077 Å than the Pt–Pt distance in 3, and this is consis-
tent with the presence of a bridging hydride between the metal
atoms [13,14].
Complex 6 was obtained by reaction of 1 with two equivalents
of HI. The first equivalent of HI affords compound 3, which reacted
immediately with the second equivalent of HI. The first proton
breaks the orthometalated Pt–C bond of complex 1, while the sec-

C. Archambault et al. / Polyhedron 52 (2013) 545–552
549
Table 3
Selected bond distances (Å) and angles (°) in the two, slightly different molecules of
[Pt2I2( -H)( -PPh2)(PPh3)2] (6).
l
l
Pt(1)–Pt(2)
Pt(1)–I(1)
Pt(2)–I(2)
Pt(1)–P(1)
Pt(2)–P(1)
Pt(1)–P(2)
Pt(2)–P(3)
2.847(1)
2.662(2)
2.674(2)
2.202(7)
2.206(7)
2.265(7)
2.274(7)
Pt(3)–Pt(4)
Pt(3)–I(3)
Pt(4)–I(4)
Pt(3)–P(4)
Pt(4)–P(4)
Pt(3)–P(6)
Pt(4)–P(5)
2.838(1)
2.649(2)
2.652(3)
2.235(7)
2.219(7)
2.264(7)
2.260(7)
Pt(2)–Pt(1)–P(1)
Pt(2)–Pt(1)–I(1)
P(1)–Pt(1)–P(2)
I(1)–Pt(1)–P(2)
P(1)–Pt(2)–Pt(1)
P(1)–Pt(2)–P(3)
Pt(1)–Pt(2)–I(2)
I(2)–Pt(2)–P(3)
Pt(1)–P(1)–Pt(2)
49.8(2)
113.9(1)
103.9(3)
92.3(2)
49.7(2)
104.8(2)
114.7(1)
90.6(2)
80.5(2)
Pt(4)–Pt(3)–P(4)
Pt(4)–Pt(3)–I(3)
P(4)–Pt(3)–P(6)
I(3)–Pt(3)–P(6)
P(4)–Pt(4)–Pt(3)
P(4)–Pt(4)–P(5)
Pt(3)–Pt(4)–I(4)
I(4)–Pt(4)–P(5)
Pt(3)–P(4)–Pt(4)
50.2(2)
112.7(1)
104.6(3)
92.1(2)
50.7(2)
104.2(3)
112.2(1)
95.4(2)
79.1(2)
Fig. 4. 1H (top) and 31P{1H} NMR (bottom) spectrum of [Pt2(
(PPh3)2](Pt–Pt) (6) (d in ppm).
l-H)(l-PPh2)I2
Fig. 5. ORTEP view of one of the two, slightly different molecules of complex 6
present in the asymmetric unit, with labeling scheme. Only the ipso carbon atoms
of the phenyl rings are represented. The bridging hydride and other hydrogen atoms
are omitted for clarity. The ellipsoids enclose 50% of the electronic density. A
complete view of the molecule is given in Fig. S5 of the Supporting Information.
ond adds to the Pt–Pt bond of 3, and the iodide substitutes a PPh3
ligand, without variation of the total electron count in the new
complex. Both 3 and 6 are 30 electron complexes. The d9 Pt(I) cen-
ters of 3 become d8 Pt(II) in 6, a description which is supported by
the similarity of the values of 1J(Pt–P) in 6 and cis,cis-7, which
clearly contains two Pt(II) centers. In this latter case, there is for-
mally no Pt–Pt bond and the interaction between the Pt atoms
and the bridging hydrogen in complex 6 is best described as 3 cen-
ter-2 electron bonding. The chemical behavior of the bridging
hydrogen was tested experimentally. Solutions of sodium hydro-
genocarbonate or of potassium hydroxyde did not react with 6.
In contrast, HI reacted easily with 6 and these results, detailed in
the next section, indicate a hydridic rather than an acidic character
for this ligand.
plexes 2, 3 and 6. The mean coordination planes of the Pt atoms in
cis,cis-7 make a roof angle of 13(1)°.
Complex cis,cis-7 was obtained by three different synthetic
routes. First, the reaction of complex 1 with three equivalents of
HI afforded a mixture of various compounds; among them two iso-
mers of 7, the cis,cis and the cis,trans species, could be identified by
31P{1H} NMR spectroscopy. Recrystallization of this mixture
yielded a small quantity of pure cis,cis-7 but the cis,trans isomer
could not be isolated. An analogous result was obtained from the
reaction of complex 6 with one equivalent of HI. Finally, a yield
of 59% of complex cis,cis-7 was obtained by oxidation of complex
3 with one equivalent of I2 and recrystallization of the reaction
mixture from CH2Cl2/diethyl ether.
2.3.2. Reactivity of complex 6 with HI: molecular structure of cis,cis-
[Pt2(l-I)(l-PPh2)I2(PPh3)2] (cis,cis-7)
The molecular structure of cis,cis-[Pt2(
l
-I)(
l
-PPh2)I2(PPh3)2]
The 1H NMR spectrum of cis,cis-7 no longer showed the pres-
ence of a bridging hydride as in 6, while the 31P{1H} NMR spectrum
contained only two singlets, at 13.6 and À141.6 ppm, flanked by
satellites due to 1J(P–Pt) = 4194 Hz and 2653 Hz, respectively
(Table 1). Consistent with the presence of two terminal phosphines
and one phosphido ligand, the intensity of the high field singlet
corresponding to terminal phosphines is twice that of the lower
field signal, while the satellites of the latter are twice as intense
as those of the high field signal owing to coupling with two 195Pt
(cis,cis-7) was determined by X-ray diffraction on a single crystal
obtained by layering a CH2Cl2 solution of the complex with dieth-
ylether (Fig. 6 and Table 4). In this dinuclear platinum complex,
each metal atom has an almost square planar coordination geom-
etry, with two iodines, a PPh3 and a PPh2 group in cis positions. The
two square planes share an iodine atom and a PPh2 group, which
occupy bridging positions between the metal atoms. The inter-
atomic distances and angles lie in the same range as those of com-

550
C. Archambault et al. / Polyhedron 52 (2013) 545–552
Fig. 6. ORTEP view of complex cis,cis-7 with labeling scheme (left). Only the ipso carbon atoms of the phenyl rings are represented. Hydrogen atoms are omitted for clarity. The
ellipsoids enclose 50% of the electronic density. On the right side, a perpendicular view is given. A complete view of the molecule is given in Fig. S6 of the Supporting
Information.
Table 4
Selected bond distances (Å) and angles (°) in cis,cis-[Pt2(
l
-I)(
l
-PPh2)I2(PPh3)2] (cis,cis-
7).
Scheme 2.
leads to the addition of one iodine atom to each metal center with
oxidation from Pt(I) to Pt(II) and rupture of the Pt–Pt bond. This is
followed by elimination of a phosphine ligand linked to the most
sterically encumbered Pt atom and occupancy of the bridging posi-
tion between the metal atoms by an iodo ligand of the other metal.
Pt1–P1
Pt1–P2
Pt1–I2
Pt1–I1
P1–Pt1–P2
P1–Pt1–I2
P2–Pt1–I2
P1–Pt1–I1
P2–Pt1–I1
I2–Pt1–I1
P3–Pt2–P2
Pt2–P3
Pt2–P2
Pt2–I2
Pt2–I3
P3–Pt2–I2
P2–Pt2–I2
P3–Pt2–I3
P2–Pt2–I3
I2–Pt2–I3
Pt2–I2–Pt1
2.270(2)
2.310(2)
2.639(1)
2.656(1)
99.84(6)
172.24(4)
81.21(4)
93.73(5)
163.73(4)
86.55(2)
102.30(6)
2.268(2)
2.307(2)
2.635(1)
2.684(1)
175.58(4)
81.37(4)
88.22(5)
168.67(5)
87.94(2)
89.27(2)
In conclusion, we have shown that [Pt2(l-o-C6H4PPh2)(l-
PPh2)(PPh3)2](Pt–Pt) (1) is a versatile precursor for the synthesis
of new diplatinum complexes. Depending on the stoichiometry of
the reagents, it reacts with HCl or HI to afford three new types of
dinuclear platinum complexes, exemplified by complexes 2 and
3, 4 and 6, 5 and 7. In complexes 2 and 3, the two Pt(I) centers form
a metal–metal bond bridged by the 3 electron donor PPh2 ligand. In
complexes 5 and 7, the Pt(II) centers are linked by two 3 electron
donors,
tal–metal bonding. In the symmetric complexes 4 and 6, both Pt(II)
centers are bridged by a -PPh2 group, but the metal atoms remain
linked by a metal–metal bond involved in a 3 center – 2 electron
l-PPh2 and l-X (X = Cl or I), without occurrence of me-
l
system with the l-H ligand.
3. Experimental
nuclei. These data indicate the presence in the molecular structure
of cis,cis-7 of a cis,cis-(PPh3)Pt( -PPh2)Pt(PPh3) moiety and the ab-
All experiments were performed under an inert atmosphere of
deoxygenated and dried nitrogen with the use of Schlenk tech-
l
sence of a metal–metal bond [4a,5,6,9]. The other substituents
around the Pt atoms are two terminal and one bridging iodine
atoms, as shown by X-ray diffraction. The 31P{1H} NMR data of
niques. The complex [Pt2(l-o-C6H4PPh2)(l-PPh2)(PPh3)2] (1) was
prepared as described in the literature [7]. Solvents were dried
and distilled under nitrogen prior to use. Infrared spectra were
measured in KBr pellets on a Nicolet 205 FT-IR spectrometer and
NMR spectra on Bruker AM 400 (31P at 161.977 MHz) and on a
FT-Bruker WP 200 SY instrument (31P at 81.02 MHz and 1H at
200.13 MHz). Phosphorus chemical shifts were externally refer-
enced to 85% H3PO4 in H2O, with downfield chemical shifts
reported as positive. Proton chemical shifts were positive down-
field relative to external SiMe4.
the bridging phosphido group
l-PPh2 in complex cis,trans-7 have
been extracted from the spectrum of the mixture of the isomers,
which contains a doublet at À117.2 ppm with 2J(P–P) = 405 Hz,
with two sets of satellites with 1J(P–Pt) = 1520 and 2470 Hz. This
indicates its bridging position, trans to chemically different ligands
(Scheme 2). The signals for the terminal phosphines are not clear
enough, because of the overlap of several peaks in this region of
the spectrum of the mixture.
[Pt2Cl(l-PPh2)(PPh3)3](Pt–Pt) (2). To a yellow suspension of 1
The formation of complexes 7 by reaction of 1 with HI occurs
via that of compound 6, followed by reaction of the bridging hy-
dride with a proton and substitution by iodide. Formation of com-
plex cis,cis-7 by oxidation of complex 3 with one equivalent of I2
(136 mg, 0.10 mmol) in THF (20 mL) was added slowly 1 mL HCl
0.1 M in water. The mixture turned rapidly orange and was stirred
at room temperature for 45 min. and evaporated to dryness under
reduced pressure. The solid was then dissolved in 120 mL diethyl

C. Archambault et al. / Polyhedron 52 (2013) 545–552
551
Table 5
Crystal data and details of the structure determination for 2Á1/2C7H8, 3, 6 and cis,cis-7.
Compounds
2Á1/2C7H8
69.5H59ClP4Pt2
3
6
cis,cis-7
Formula
C
C66H55IP4Pt2
1489.06
monoclinic
C2/c
35.9980(4)
16.9940(2)
24.9270(4)
90
129.20(5)
90
11816(8)
8
C48H41I2P3Pt2
1355.39
monoclinic
P21/c
18.473(5)
25.326(5)
21.085(5)
90
91.72(2)
90
9885.9(2)
8
C48H40I3P3 Pt2
1480.59
monoclinic
P21/n
12.3300(10)
17.394(2)
21.262(2)
90
99.82(5)
90
4493.2(10)
4
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
1443.68
triclinic
ꢀ
P1
13.940(5)
18.001(5)
27.267(5)
86.868(5)
85.231(5)
67.572(5)
6301(3)
4
a
(°)
b (°)
c
(°)
V (Å3)
Z
qcalc (g cmÀ3
F(000)
)
1.522
2836
4.619
1.674
5760
5.400
1.81
5080
6.404
2.189
2752
8.421
l
(mmÀ1
)
Temperature (K)
Radiation
h limits (°)
Data measurement
Data with I > 2r(I)
173
Mo K
173
Mo K
room temperature
173
Mo Ka
a
a
Mo K
1/25
a
1.70/27.42
28533
22493
0.045
0.1169
1.036
1.40 /30.03
45265
9971
0.0636
0.2072
1.037
2.04/30.04
13098
9734
0.0465
0.1270
1.038
12267
5727
0.0545
0.0573
0.85
R1
Rw2
GOF
Largest peak (e ÅÀ3
)
2.133
2.698
1.30
5.605
ether and the solution was filtered under reduced pressure and
cooled to À30 °C. Yellow crystals of complex 2 were collected
(105 mg, 75% yield). Crystals of 2Á1/2 toluene suitable for X-ray dif-
fraction were obtained by slow diffusion of pentane in a toluene
solution of 2. Anal. Calc. for C69.5H59ClP4Pt2 (Mr = 1443.72): C,
57.82; H, 4.12. Found: C, 58.75; H, 4.18%.
3.2. Reactions of [Pt2(
l
-H)(
l
-PPh2)I2(PPh3)2](Pt–Pt) (6) with bases
(a) A solution of NaHCO3 (100 mg, 0.12 mmol) in H2O (2 mL)
was added to a suspension of [Pt2( -H)( -PPh2)I2(PPh3)2](Pt–Pt)
(6) (47 mg, 0.035 mmol) in acetone (10 mL) and the mixture was
stirred overnight at room temperature. After filtration, the orange
solid was washed with water and diethyl ether, and dried in vacuo.
The IR spectrum of the solid was the same as that of 6.
l
l
[Pt2I(l
-PPh2)(PPh3)3](Pt–Pt) (3). Solid NaI (25 mg, 0.17 mmol)
-PPh2)(PPh3)3](Pt–Pt) (2) (70 mg,
was added to a solution of [Pt2Cl(
l
0.05 mmol) in acetone (40 mL) and the mixturewas stirred for 4 h. at
room temperature. The red suspension was filtered and the solid
was recrystallized from a mixture of 10 mL toluene layered with
40 mL pentane. Red crystals of 3 were isolated (20 mg, 26% yield).
Anal. Calc. for C66H55IP4Pt2 (Mr = 1489.10): C, 53.23; H, 3.72. Found:
C, 53.09; H, 3.81%.
(b) A solution of KOH (100 mg, 0.18 mmol) in H2O (10 mL) was
added to
a suspension of [Pt2(l-H)(l-PPh2)I2(PPh3)2](Pt–Pt)
(6) (70 mg, 0.05 mmol) in acetone (20 mL) and the mixture was
stirred at room temperature for 30 min. After evaporation of the
acetone, the solid was filtered, washed with H2O and diethyl ether,
and dried under reduced pressure. The IR spectrum of the solid was
the same as that of 6.
3.1. Reactions of 1 with more than one equivalent of HCl
(a) A solution of HCl (1 mL, 0.1 M in H2O, 0.1 mmol) was added
3.3. Synthesis of cis,cis-[Pt2(l-I)(l-PPh2)I2(PPh3)2] (cis,cis-7)
dropwise to a solution of [Pt2(
l
-PPh2)Cl(PPh3)3]Á1/2C7H8, 2Á1/
2C7H8, (149 mg, 0.1 mmol) in THF (15 mL). The mixture turned yel-
low and after 2 h of stirring at room temperature, was evaporated to
dryness under reduced pressure. The 31P{1H} NMR spectrum of the
residue showed the presence of cis-[PtCl2(PPh3)2] and trans-
(a) A solution of HI (60
lL, 57% in H2O, d = 1.70, 0.45 mmol) was
added to a solution of 1 (204 mg, 0.15 mmol) in CH2Cl2 (10 mL).
The mixture was stirred at room temperature for 2 days and evap-
orated to dryness under reduced pressure. The yellow solid was
washed with diethyl ether and analyzed by 31P{1H} NMR. Three
[Pt(H)Cl(PPh3)2], and of the dinuclear complexes [Pt2(
Cl2(PPh3)2](Pt–Pt) (4) and cis,cis-[Pt2( -Cl)( -PPh2)Cl2(PPh3)2]
(Pt–Pt) (cis,cis-5). The dinuclear complexes could not be isolated
pure.(b) The reaction of a solution of [Pt2(
-PPh2)Cl(PPh3)3]Á
(1/2C7H8) in THF with two equivalents of HCl in H2O or of [Pt2(
o-C6H4PPh2)( -PPh2)(PPh3)2](Pt–Pt) (1) in acetone with two or three
l-H)(l-PPh2)-
l
l
dinuclear complexes were identified: [Pt2(
(Pt–Pt) (6) and the cis,cis- and cis,trans-isomers of [Pt2(
-PPh2)I2(PPh3)2] (7). Recrystallization of the mixture from CH2Cl2
l-H)(
l-PPh2)I2(PPh3)2]
l
-I)
l
(l
l-
layered with diethyl ether afforded 12 mg of pure yellow cis,cis-7,
l
as indicated by 31P{1H} NMR.
equivalents of HCl in H2O afforded analogous mixtures of Pt com-
(b) A solution of HI (7.5
lL, 57% in H2O, d = 1.70, 0.057 mmol)
plexes. None of the dinuclear complexes could be isolated pure.
was added to a solution of [Pt2(
l
-H)( -PPh2)I2(PPh3)2](Pt–Pt) (6)
l
[Pt2(
l
-H)(
l
-PPh2)I2(PPh3)2](Pt–Pt) (6). A solution of HI (20
l
l,
(77 mg, 0.057 mmol) in CH2Cl2 (10 mL). The mixture was stirred
at room temperature for 24 h and evaporated to dryness under re-
duced pressure. The solid contained the same compounds as those
obtained in the previous case.
(c) Solid I2 (4.6 mg, 0.018 mmol) was added to a solution of
[Pt2I(l-PPh2)(PPh3)3](Pt–Pt) (3) (28 mg, 0.018 mmol) in THF
67% in H2O, d = 1.96, 0.20 mmol) was added to a suspension of 1
(136 mg, 0.10 mmol) in THF (20 mL). The yellow mixture was stir-
red for 20 min at ambient temperature. After evaporation of the
solvent under reduced pressure, the residue was washed with
20 mL toluene, filtered and dried under reduced pressure, affording
6 (92 mg, 68% yield). Anal. Calc. for C48H41I2P3Pt2 (Mr = 1354.67): C,
42.56; H, 3.05. Found: C, 43.67; H, 3.17%.
(12 mL). After the reaction mixture was stirred for 3 h at room
temperature, the yellow solution was evaporated to dryness under

552
C. Archambault et al. / Polyhedron 52 (2013) 545–552
reduced pressure. Recrystallization of the yellow residue from CH2-
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We thank the Centre National de la Recherche Scientifique and
the Ministère de l’Enseignement Supérieur et de la Recherche for
support. We are grateful to Johnson Matthey PLC for a generous
loan of platinum salts.
Appendix A. Supplementary data
CCDC 890595, 890594, 887473 and 890596 contain the sup-
plementary crystallographic data for 2Á1/2C7H8, 3, 6, cis,cis-7,
respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2012.08.030.
[20] International Tables for X-ray Crystallography, vol. IV, Kynoch, Birmingham,
England, 1974.