Mononuclear organometallic platinum(II) complexes and platinum(II)-copper (I) mixed complexes from symmetrical 3,5-bis(iminoacetyl)pyrazolate ligands

Article abstract of DOI:10.1021/om800403y

The reaction of symmetrical dinucleating ligands 3,5-bis(4- methoxyphenyliminoacetyl)-4-methylpyrazole (bmimpH, 1a) and 3,5-bis(2,6- dimethylphenyliminoacetyl)-4-methylpyrazole (bdmimpH, 1b) with [(μ-Me ₂S)PtMe₂]₂ or (Me₂S) ₂PtPh₂ affords selectively mononuclear complexes LPtMe(SMe₂) or LPtPh(SMe₂) (L = bmimp, bdmimp). Reaction of these complexes with CuCl gives access to ionic compounds {[LPtMe(SMe ₂)]₂Cu⁺CuCl₂^- and [LPtPh(SMe₂)]₂Cu⁺CuCl₂^-, which exhibit dynamic behavior in solution for L = bdmimp. Ligand deprotonation followed by reaction with (Me₂S)₂PtPh₂ affords mononuclear anionic complexes K⁺[LPtPh₂]^-. These react with CuCl to give dimeric structures of formula {[LPtPh ₂]₂Cu₂}, which exhibit Ptr→Cu dative bonds and a Cu-Cu contact, and dynamic behavior in solution.

Full text of DOI:10.1021/om800403y

Organometallics 2008, 27, 4903–4916
4903
Mononuclear Organometallic Platinum(II) Complexes and
Platinum(II)-Copper(I) Mixed Complexes from Symmetrical
3,5-Bis(iminoacetyl)pyrazolate Ligands
Marc-Etienne Moret and Peter Chen*
Labor fu¨r Organische Chemie, ETH Zu¨rich, CH-8093 Zu¨rich, Switzerland
ReceiVed May 6, 2008
The reaction of symmetrical dinucleating ligands 3,5-bis(4-methoxyphenyliminoacetyl)-4-methylpyrazole
(bmimpH, 1a) and 3,5-bis(2,6-dimethylphenyliminoacetyl)-4-methylpyrazole (bdmimpH, 1b) with [(µ-
Me2S)PtMe2]2 or (Me2S)2PtPh2 affords selectively mononuclear complexes LPtMe(SMe2) or LPtPh(SMe2)
(L ) bmimp, bdmimp). Reaction of these complexes with CuCl gives access to ionic compounds
{[LPtMe(SMe2)]2Cu+CuCl2- and [LPtPh(SMe2)]2Cu+CuCl2-, which exhibit dynamic behavior in solution
for L ) bdmimp. Ligand deprotonation followed by reaction with (Me2S)2PtPh2 affords mononuclear
anionic complexes K+[LPtPh2]-. These react with CuCl to give dimeric structures of formula
{[LPtPh2]2Cu2}, which exhibit PtfCu dative bonds and a CusCu contact, and dynamic behavior in
solution.
of benzene20-27 and methane28-31 to form phenyl or methyl
complexes, respectively. Higher alkanes can also be activated
to give dehydrogenation products.32-34 The mechanism of some
of these transformations has been extensively studied by several
groups,21,23,29,30,32-45 including ours.46-49 These reactions are
thought to proceed through the initial complexation of a σ C-H
Introduction
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particular, organometallic complexes of platinum incorporating
N-donor ligands have been shown to activate the C-H bonds
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* Corresponding author. E-mail: chen@org.chem.ethz.ch.
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10.1021/om800403y CCC: $40.75
2008 American Chemical Society
Publication on Web 09/03/2008

4904 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
Scheme 1.a
bond to a Pt(II) center, followed by oxidative addition to form
a transient Pt(IV) phenyl (or alkyl) hydride complex. Ligand
exchange is often rate determining.
In most cases though, the formed phenyl or methyl complexes
do not undergo the subsequent reactions that would be required
for achieving an efficient catalytic transformation of benzene
or methane. The most noticeable exception is the Catalytica
system,28 which is able to convert methane into methyl sulfate
using a N-N chelated Pt catalyst in hot sulfuric acid. Several
cases of catalytic hydroarylation of alkenes27,50-52 using related
complexes have also been reported.
a
Reaction conditions: a) Ar ) p-methoxyphenyl, cat. HCOOH,
MeOH, room temperature, 77%; b) Ar ) 2,6-dimethylphenyl, cat.
TsOH, toluene, ∆, 78%.
One possibility to tune the reactivity of a metal center is
to make use of cooperative effects in bimetallic complexes,53,54
which can result in alteration of the redox behavior of the
metal centers55 or in a variety of reaction pathways allowed
by the coordination of the substrate(s) to multiple metal
centers.56 Copper has found many uses in catalytic redox
chemistry, due to fast ligand exchange and the accessibility
of three oxidation states in solution, as well as to its ability
to activate dioxygen. Of particular interest is the recent
development of Cu-catalyzed aromatic oxidative coupling57-60
based on the century-old Ullmann chemistry. In an attempt
to couple platinum and copper activities, Tilley et al.61
recently reported the preparation of bimetallic Pt-Cu com-
plexes using a dinucleating PPNN ligand, where the plati-
num(II) center is chelated by two phosphorus atoms and the
copper(I) by two nitrogen atoms. We aim at the preparation
of Pt-Cu complexes with all-N dinucleating ligands, which
may open access to new reactivity based on C-H activation
by N-coordinated platinum(II).
of both metals, as the binding sites are identical.64,70 The readily
available, symmetrical bis(iminoacetyl)pyrazolate ligands have
been recently used to prepare homobimetallic palladium and
nickel complexes for olefin polymerization.71,72 As diimine
chelating ligands would be suitable for both platinum and
copper, we investigated the possibility of using this class of
ligands for the preparation of platinum-containing heterobime-
tallic complexes.
In this work, we used two different approaches to prepare
and characterize mononuclear organometallic platinum(II) com-
plexes of symmetrical bis(iminoacetyl)pyrazolate. In the first
strategy, we exploited a stoichiometric activation of the pyrazole
N-H bond by platinum, while the second one relied on the
steric bulk of phenyl ligands. The targeted mononuclear
platinum(II) complexes were selectively obtained in both cases,
and their coordination to copper(I) was studied using NMR,
electrospray ionization mass spectrometry (ESI-MS), and X-ray
crystallography.
The synthesis of well-defined bimetallic complexes in a
controlled way requires the use of dinucleating ligands, which
generally consist of a bridging unit attached on each side to
one or more chelating arms.62 Ligands incorporating pyrazolate
as a bridging unit have been used to produce a wide range of
bi- and polymetallic structures.63-69 Symmetrical dinucleating
ligands have the advantage of being synthetically easily acces-
sible, but often require well-controlled successive introduction
Results and Discussion
Ligand Synthesis. 3,5-Bis(4-methoxyphenyliminoacetyl)-4-
methylpyrazole (bmimpH, 1a) could be conveniently synthe-
sized in good yield by imine condensation of 3,5-diacetyl-4-
methylpyrazole and p-methoxyaniline in methanol at room
temperature, using formic acid as a catalyst (see Scheme 1).
The more bulky 2,6-dimethylaniline did not react under the same
conditions. However, using the conditions of Noe¨l et al.64
(refluxing toluene, p-toluenesulfonic acid catalyst), 3,5-bis(2,6-
dimethylphenyliminoacetyl)-4-methylpyrazole (bdmimpH, 1b)
could be prepared in good yield.
N-H Activation Based Strategy. As the pyrazole bridging
unit of ligands 1a,b have one acidic proton, we reasoned that a
complex formation reaction that involves a stoichiometric
reaction of the labile N-H bond should selectively afford
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Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4905
Scheme 2.a
Figure 1. ORTEP representations of the X-ray crystal structures
of trans-2a (top) and trans-2b (bottom). Ellipsoids are drawn at
50% probability. Selected distances [Å], angles [deg], and torsion
angles [deg]: trans-2a: Pt1-C1 2.011, Pt1-S1 2.259, Pt1-N1
2.068, Pt1-N2 2.052, C1-Pt1-N1 172.0, S1-Pt1-N2 178.5,
C1-Pt1-S285.6,C1-Pt1-N294.7,N1-Pt1-N277.4,N1-Pt1-S1
102.2, N1-Pt1-S1-C2 26.4, N1-Pt1-S1-C3 133.8. trans-2b:
Pt1-C1 2.028, Pt1-S1 2.266, Pt1-N1 2.079, Pt1-N2 2.063,
C1-Pt1-N1171.5,S1-Pt1-N2175.5,C1-Pt1-S187.6,C1-Pt1-N2
94.8, N1-Pt1-N2 77.8, N1-Pt1-S1 100.0, N1-Pt1-S1-C2
42.7, N1-Pt1-S1-C3 59.0.1.
a
Reaction conditions: a) Ar ) 4-methoxyphenyl, 60 h 110 °C,
conversion >50% (ESI-MS and 1H NMR); b) Ar ) 2,6-dimethylphenyl,
2 days, 130 °C, traces of 2b observed by ESI-MS; c) DCM, RT, 10
days.
mononuclear complexes. As activation of the N-H bond of the
related 2-(N-arylimino)pyrroles by [(Me2S)PtMe2]2 is docu-
mented,21 we investigated the reactivity of 1a,b with
[(Me2S)PtMe2]2 and (Me2S)2PtPh2 (Scheme 2).
The reaction of 1a,b with (Me2S)2PtPh2 afforded the mono-
nuclear platinum(II) phenyl complexes trans-2a,b in good yields
(the cis and trans notation are attributed according to the relative
position of the pyrazolate nitrogen and the aryl or alkyl ligand).
Remarkably, only one of the two possible isomers was formed,
which shows that the pyrazolate and imine nitrogen atoms are
electronically different.
Complexes trans-2a,b were characterized crystallographically
(see Figure 1). In both compounds, the platinum center adopts
the expected square-planar geometry, which is slightly distorted
due to the acute (∼77°) bite angle of the ligand. The free sides
of the ligands exhibit a N-C-C-N torsion angle of about 180°,
which allows conjugation of the imine group with the pyrazolate
ring but avoids the methyl-methyl repulsion that would arise
at a 0° angle. The main geometrical difference between trans-
2a and trans-2b is the orientation of the coordinated SMe2
molecule, of which the two methyl groups are located on the
same side of the coordination plane in 2a but not so in 2b. This
discrepancy is likely due mainly to crystal packing forces. In
both cases only one S-Me 1H NMR signal is observed in
solution, indicating a low rotational barrier around the Pt-S
bond.
Figure 2. δ 0-3 ppm region of the 1H NMR spectra of cis-3a
(top), trans-3a (bottom), and a solution of cis-3a equilibrated for
10 days at room temperature. Peaks assigned to the bmimp ligand,
coordinated Me2S, and Pt-Me are marked with *, ×, and °,
respectively.
The ligands 1a,b reacted with [(Me2S)PtMe2]2 to yield
mainly the cis isomer of the mononuclear complexes 3a,b,
which were isolated in moderate yield (see Scheme 2) and
were fully characterized. Upon storage of cis-3a,b in CD2Cl2
1
solution at room temperature, new peaks appeared in the H
the cis and trans isomers, respectively. Furthermore, for the
related [2-(N-arylimino)pyrrolide]PtMe(SMe2) complexes, Iver-
NMR spectra (see Figure 2), which were assigned to trans-
3a,b.
3
son et al.21 reported J(195Pt-1H) of 51 vs 58 Hz for Pt-SMe2
The stereochemical assignment of 3a,b was made mainly on
the basis of 1H NMR data as described here for 3a (see Figure
2). Going from cis-3a to trans-3a, the SMe2 signal is shifted
downfield by 0.62 ppm, while the Pt-Me signal is shifted upfield
by 1.09 ppm, which we attribute to the shielding effect of the
p-methoxyphenyl moiety on the SMe2 and Pt-Me protons of
and 2J(195Pt-1H) of 79-80 vs 73 Hz for Pt-Me coupling
constants of the cis and trans isomers, respectively. We find
very similar values for cis- and trans-3a, which support our
stereochemical assignment.
In order to confirm this assignment, we looked for conditions
that would allow the isolation of trans-3a. We found that upon

4906 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
of an extra CuCl unit in the cation is observed, but this ion is
likely to be formed during the electrospray process. Furthermore,
the [CuCl2]- anion is observed for all four compounds,
sometimes accompanied by a low signal corresponding to
[Cu2Cl3]-.
1
The H and 13C NMR spectra of 4a and 5a exhibit sharp
signals corresponding to a single species, which were assigned
to the ionic structure depicted in Scheme 3.
In order to confirm this assignment, we grew crystals of 4a
suitable for X-ray crystallography from a benzene solution. The
crystal structure of 4a (Figure 4) contains two independent but
similar C2 symmetrical cations. The copper(I) center has a
distorted tetrahedral coordination sphere, the planes of the two
ligands making an angle of approximately 90°. The length
difference of ∼0.05 Å between the Cu-N3 and Cu-N4 bonds
shows that the pyrazolate bridge is a slightly better σ-donor
than the N-arylimine. The opposite trend seen in Pt-N bonds
for both trans-2a,b and 4a,b is likely due to the strong trans
influence of the phenyl ligand that weakens, and thus lengthens,
the pyrazolate N-Pt bond. In both independent cations, the
Me2S ligand is oriented in such a way that the remaining lone
pair on the sulfur atom would point toward the Cu(I) center.
However, the S-Cu distance of more than 3.6 Å is too large
for chemical binding, and thus the orientation of the Me2S
ligands is most probably driven by the minimization of steric
repulsion. Besides this orientation change of the Me2S ligand,
the geometry around the Pt(II) centers is rather unaffected by
coordination to copper(I). The Pt-Cu distance of about 4.4 Å
is too large for metal-metal binding, but could in principle
allow cooperative behavior.61
Very broad signals were observed in the room-temperature
1H NMR spectra of 4b and 5b, suggesting chemical exchange,
and therefore the temperature dependence was studied. The
methyl regions of 1H NMR spectra of 4b at temperatures ranging
from -40 °C to room temperature are presented in Figure 5.
When cooling the sample, the sharp signal assigned to the
pyrazolate-bound methyl group at δ 2.58 ppm broadens and
finally splits into two signals in an approximate 3:4 ratio,
indicating the presence of two interchanging species. The most
common structures for CuCl adducts of diimine (NN) ligands,
depicted in Scheme 3, are the ionic, four-coordinate complex
[(NN)2Cu][CuCl2]73-76 (4b), the monomeric, T-shaped three-
coordinate complex (NN)CuCl76,77 (6b), and the corresponding
dimer (NN)Cu(µ-Cl2)Cu(NN)76 (6b′). Structures 6b and 6b′
possess a symmetry plane perpendicular to the plane of the 2,6-
dimethylphenyl unit, while 4b does not. Thus, for structure 4b,
the two S-Me groups as well as the two ortho-methyl groups
of the ligand phenyl ring are magnetically different if the
corresponding rotations are hindered, which would yield nine
different signals of equal intensities. On the other hand, species
6b or 6b′, in which the two sides of the ligand are symmetry
equivalent, should yield three signals with a relative intensity
of 1 (the three methyl groups of the central unit) and three
signals with an intensity of 2 (both 2,6-dimethylphenyl units
and the SMe2 ligand), a total of six signals. At -40 °C, 13
peaks are resolved in the methyl region. Band width and overlap
Figure 3. Time evolution of the mass spectra obtained from samples
of a ca. 7 mM solution of cis-3a in benzene heated at 110 °C, and
observed (black) and calculated (red) isotope patterns for peaks B
and D. Peak assignment: A: [3a + H]+, B: [2a + H]+, C:
[(bmimp)2Pt2CH3]+, D: [(bmimp)2Pt2C6H5]+, E: {[(bmimp)2Pt2-
(CH3)(C6H5)]+ + H} F: {[(bmimp)2Pt2(C6H5)]+ + H}.
reaction of 1a and [(Me2S)PtMe2]2 in toluene, cis-3a precipitates,
leaving mainly trans-3a in the liquid phase, from which it was
isolated in 8% yield and fully characterized. Equilibration at
room temperature over 10 days starting from either pure cis- or
pure trans-3a yielded a cis/trans mixture in an approximate 3:1
ratio. An equilibrium ratio of about 2:1 was observed for cis-
3b to trans-3b.
In order to test their ability to activate aromatic C-H bonds,
3a and 3b were heated in benzene, and the reaction was
monitored by recording ESI-MS spectra of samples diluted in
dichloromethane. As seen in Figure 3, when a solution of 3a in
benzene is heated at 110 °C in a closed vessel, the peak of
protonated 3a (m/z 648), gradually disappears, while the peak
of protonated 2a (m/z 710) grows, showing that the C-H
activation reaction 3a + C6H6 f 2a + CH4 is taking place.
Simultaneously, other peaks appear at higher masses, corre-
sponding to dimeric species presumably formed by the substitu-
tion of SMe2 in 2a or 3a by one of the free nitrogens of a second
molecule. In order to check the identity of the main product,
the mixture was evaporated to dryness after 60 h reaction time,
and a 1H NMR spectrum of the residue in CD2Cl2 was recorded
(see Supporting Information). The main peaks correspond to
those of independently synthesized trans-2a.
When a solution of 3b was heated to 130 °C for several
days, only traces of the C-H activation product could be
observed by ESI-MS, together with dimeric species. As the
cis-trans equilibration takes place already at room temper-
ature for both 3a and 3b, it is expected to be fast at 110-130
°C. Thus, the actual C-H activation step could proceed from
either isomer. Therefore, the lower reactivity of 3b as
compared to 3a cannot be explained by slow isomerization,
but likely stems from the increased steric bulk around the
Pt(II) center that slows down the presumably associative
exchange of SMe2 for benzene, which is likely to be the rate-
determining step in this reaction.34
The ability of the free binding site of cis-2a,b and trans-
3a,b to accept a metal ion was tested by reacting these
compounds with copper(I) chloride (Scheme 3), affording deep
red colored solutions of the mixed complexes 4a,b and 5a,b.
The positive ion ESI-MS spectra of these solutions all feature
the 2:1 complex cations of 4a,b and 5a,b, respectively, as the
most intense signal, and both the isotope pattern and the
fragmentation products are consistent with this assignment. In
most cases, a weak signal corresponding to the incorporation
(73) Skelton, B. W.; Waters, A. F.; White, A. H. Aust. J. Chem. 1991,
44, 1207–1215.
(74) Mirkhani, V.; Harkema, S.; Kia, R. Acta Crystallogr. 2004, C60,
m343-m344.
(75) Yu, J.-H.; Lu¨, Z.-L.; Xu, J.-Q.; Bie, H-Y.; Lu, J.; Zhang, X. New
J. Chem. 2004, 28, 940–945.
(76) Dieck, H. T.; Stamp, L. Z. Naturforsch. 1990, 45b, 1396–1382.
(77) Healy, P. C.; Pakawatchai, C.; White, A. H. J. Chem. Soc., Dalton
Trans. 1985, 2531–2539.

Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4907
Scheme 3.a ,b
a
b
The rightmost equilibrium was observed only for Ar ) 2,6-Me2C6H4. The dimeric structure in parentheses was ruled out by the concentration
independence of the ratio between the equilibrating species (see text).
Figure 4. ORTEP plot of one of the two crystallographically
independent cations in the crystal cell of 4a. Ellipsoids are drawn
at 50% probability. Selected distances [Å], angles [deg], and torsion
angles [deg] (values for the second cation given in parentheses):
Pt1-C1 2.025 (2.033), Pt1-S1 2.262 (2.262), Pt1-N1 2.055
(2.048), Pt1-N2 2.072 (2.094), Pt1-Cu1 4.409 (4.382), Pt1-Pt1′
6.321 (6.135), Cu1-N3 2.019 (1.998), Cu1-N4 2.065 (2.047),
N2-N3 1.334 (1.341), Cu1-S1 3.670 (3.649), C1-Pt1-S1 91.2
(92.6), C1-Pt1-N1 95.7 (93.5), N1-Pt1-N2 78.2 (77.6),
S1-Pt1-N2 94.9 (97.0), C1-Pt1-N2 173.9 (170.0), S1-Pt-N1
1
172.6 (173.4), N3-Cu1-N4 79.3 (80.5), N3-Cu-N3′ 125.4
Figure 5. Plot of the methyl region of the H NMR spectra of 4b
(126.2), N3-Cu1-N4′ 130.2 (128.4), N4-Cu1-N4′ 119.9 (119.4),
Pt1-Cu1-Pt1′ 91.6 (88.9), Pt1-N2-N3-Cu1 30.9 (19.8).
a 6b in solution recorded at different temperatures. Peak assign-
ments based on the EXSY spectrum (see Supporting Information):
pyrazolate-Me, 0; 2,6-Me2Ph-N(Cu), O; 2,6-Me2Ph-N(Pt), ∆;
NdCMe, 3; SMe2, ]. Open symbols label peaks assigned to 4b,
preclude an accurate integration of many peaks, but one can
count 10 peaks with an intensity corresponding to one methyl
group, two peaks (δ 2.08 and 1.84 ppm) corresponding to two
methyl groups, and one peak (δ 2.13 ppm) corresponding to
four methyl groups. Assuming some peak overlap, the observed
spectrum is consistent with the presence of one symmetrical
and one unsymmetrical species in equilibrium. This was
confirmed by an EXSY spectrum recorded at -25 °C, which
allowed us to partially assign the resonances as shown in Figure
5 (see Supporting Information for details). Thus, consistently
with the ESI-MS data, we propose that one of the structures is
the unsymmetrical 4b. In order to distinguish between 6b and
filled symbols label peaks assigned to 6b, and half-filled symbols
label peaks that could belong to either 4b or 6b. The residual water
signal is marked with *.
equal intensities in the methyl region (see Figure 6). The peak
2
at δ 0.83 ppm has 195Pt satellites with J(195Pt-1H) ) 75 Hz
and is assigned to the Pt-Me group. The number of peaks and
their relative intensities suggest that the unsymmetrical ionic
structure 5b is the main species in solution. However, the small
2
peak at δ 1.49 ppm with J(195Pt-1H) ) 76 Hz indicates the
presence of a second species in an approximate 1:6 equilibrium
ratio. Not all the peaks arising from this second species could
be observed, as some are most probably hidden under the peaks
of 5b, but we tentatively assign it to a monomeric (7b) or
dimeric (7b′) symmetrical structure. The equilibrium ratio was
found to shift from ca. 1:6 to ca. 1:4 when the concentration
was taken down from 88 mM to 22 mM. If the second species
were dimeric (7b′), the ratio should decrease rather than increase
at lower concentration, and thus the latter hypothesis can be
ruled out. The observed equilibrium shift is too small to be due
to a monomer-dimer equilibrium, but could be explained by
1
6b′, we recorded H NMR spectra of ca. 20, 40, and 60 mM
solutions at -40 °C and observed no concentration dependence
of the ratio between the two species. Consequently, there must
be the same number of species on both sides of the equilibrium
depicted in Scheme 3, and the second structure must be 6b.
The existence of a second species is likely due to the steric
bulk introduced by the ortho-methyl groups of the ligand phenyl
ring, which destabilizes the 2:1 complex cation of 4b.
1
The H NMR spectrum of a ca. 88 mM solution of 5b in
CD2Cl2 at -40 °C exhibits mainly 10 peaks with approximately

4908 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
acetonitrile content upon drying. However, crystallization of 9b
from warm acetonitrile allowed its characterization by X-ray
diffractometry. The asymmetric unit of the crystal structure
(Figure 8) consists of a monomeric heterobimetallic complex
and two unbound acetonitrile molecules. The Cu(I) center is
chelated by the free binding site of the bdmimp ligand, and its
slightly distorted tetrahedral coordination sphere is completed
by two η1-bound acetonitrile molecules. The slightly distorted
square-planar Pt(II) coordination is roughly identical to the one
found in 8b, except for a somewhat longer Pt1-N2 bond (2.106
vs 2.060 Å), which can be attributed to a decrease in the
σ-donating ability of one of the pyrazolate nitrogen atoms arising
when the second one is coordinated to copper. Further charac-
terization of 9b in solution was hampered by its ability to lose
acetonitrile and convert to 10b when dissolved in other solvents.
Vapor diffusion of hexane into solutions of 10a and 10b in
benzene and dioxane, respectively, afforded crystals suitable
for X-ray diffraction. The structure of 10a (Figure 9) is
tetranuclear with approximate C2 symmetry, in which both
copper atoms lie on the quasi-C2 axis with one platinum atom
on each side, resulting in an almost planar arrangement of the
four metals. The Cu-Cu distance is 2.753 Å, which is typical
for a cuprophilic interaction.78 The Cu2 center is chelated by
two nitrogen atoms of each bmimp ligand, forming a highly
distorted tetrahedral coordination environment, in which the
N3-Cu2-N3′ angle opens up to 150.7° to allow for the close
Cu-Cu contact. The large difference in Cu-N3 and Cu-N4
bond lengths (∼1.97 vs ∼2.21 Å) is noteworthy, indicating that
the pyrazolate nitrogens are more tightly bound than the imine
nitrogens. The most peculiar feature of 10a, though, is the
coordination environment of the Cu1 center. In addition to the
aforementioned Cu-Cu interaction, it consists of two close
contacts with the Pt(II) centers (2.66 and 2.74 Å), supported
by a coordination to the ipso carbons of two platinum-bound
phenyl ligands. One of the ortho carbons of these phenyl groups
is at a shorter distance from the Cu1 center than the other (2.51
and 2.41 vs 2.82 and 3.06 Å). This orientation could indicate a
distorted η2-coordination, but may also be due mainly to steric
repulsion, as it places the phenyl rings parallel to the neighboring
bmimp ligand plane. Therefore, the much shorter Cipso-Cu
distances (2.07 and 2.14 Å) entice us to describe this interaction
mainly as η1-phenyl coordination.
The structure of 10b (Figure 10) shows a planar tetrametallic
arrangement similar to that for 10a. The main difference is the
rotation of the arm of one of the bdmimp ligands by 180°,
breaking one imine-N-Cu bond. This discrepancy is most likely
due to the increased steric bulk of the 2,6-dimethylphenyl moiety
as compared to that of 4-methoxyphenyl, which prevents the
two imine nitrogens from being coordinated at the same time
to the Cu2 atom. As a result, the Cu2 center adopts a distorted
planar, T-shaped coordination. The remaining Cu2-N4 bond
is strikingly longer than in 10a (2.44 vs 2.21 Å) and, thus, is
expected to be relatively weak. The coordination around Cu1
is hardly affected by this change in the Cu2 environment, the
main difference being a slight shortening of the Pt-Cu contacts
from 2.74 and 2.66 Å in 10a to 2.57 and 2.57 Å in 10b.
The preparation of compounds with Pt(II)-Cu(I) contacts
supported by two R2PCH2PR2 (R ) phenyl,79 cyclohexyl80)
ligands and of Cu(I) complexes of a metallamacrocycle incor-
porating two Pt(II)Me2 units81 has been documented, but to our
knowledge, 10a and 10b are the first structurally characterized
compounds that exhibit a dative PtfCu bond without a bridging
1
Figure 6. Plot of the methyl region of the H NMR spectra of 5b
a 7b in solution recorded at -40 °C. The peaks assigned to 5b
are marked with *.
some extent of ion pairing of 5b at high concentration. One
could argue that with a 1:6 equilibrium ratio, the 5b a 7b
exchange should cause only a slight broadening of the peaks
of the most abundant species 5b. However, one has to consider
that the magnetically nonequivalent 2- and 6- methyl groups
do exchange via the sequence 5b f 7b f 5b, as the 2- and 6-
positions are equivalent in the symmetrical species 7b. This
exchange causes the extensive broadening observed at higher
temperatures.
Steric Repulsion Based Strategy. C-H activation by the
mononuclear complexes 3a,b has been found to be slow even
at high temperatures, which is likely due to strong binding of
the dimethylsulfide ligand that slows down its exchange for
benzene in the first coordination sphere of platinum. One way
to generate similar species with a weaker protecting ligand is
the in situ protolysis of dialkyl or diaryl species with a weakly
coordinating acid. Thus, we prepared and characterized mono-
nuclear platinum(II) diphenyl complexes of the 3,5-bis(imi-
noacetyl)pyrazole ligands, anticipating that the bulk of the
phenyl ligands would hamper the formation of dinuclear species.
Deprotonation of 1a,b with KOtBu followed by reaction with
(Me2S)2PtPh2 afforded the mononuclear anionic complexes 8a,b
in good yields (see Scheme 4). Both complexes were fully
characterized, and 8b was studied by X-ray diffraction (Figure
7).
In the crystal structure of 8b, the ligands coordinated to
platinum(II) adopt the expected distorted square-planar geom-
etry. The Pt-C bond lengths (2.005 and 2.004 Å) are almost
identical and are significantly shorter than in the monophenyl
complex 2b (2.025 Å), while the imine-N-Pt bond is longer
by 0.068 Å, which we attribute to the larger trans influence of
a phenyl ligand as compared to Me2S. The potassium ion is
chelated by two nitrogen atoms of the ligand in a highly
unsymmetrical way, with K-N distances of 2.741 and 2.955
Å for the pyrazolate and imine nitrogens, respectively, and with
an acute bite angle of 57°. The coordination sphere of the
potassium ion is completed by one phenyl ligand from the same
molecule and two from the neighboring one, building an
aromatic pocket around the ion.
With the mononuclear anionic complexes 8a,b at hand, we
investigated their ability to coordinate Cu(I) (Scheme 5). When
a solution of 1 equiv of CuCl in acetonitrile is added to a
solution of 8a,b in the same solvent, a yellow precipitate forms,
which contains KCl and the solvated Cu(I) complex 9a,b.
Extraction of this solid with benzene yielded orange solutions
of the 2:2 complexes 10a,b, which crystallized as red needles
(10a) or orange plates (10b) upon vapor diffusion with hexane.
The accurate stoichiometry of the solvento complexes 9a,b
was not determined because the solid releases part of its
(78) Hermann, H. L.; Boche, G.; Schwerdtfeger, P. Chem.-Eur. J. 2001,
7, 5333–5342.

Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4909
Scheme 4
Scheme 5.a
a
The coordination represented by a dashed line is observed only for 10a.
ligand. The Pt(II)-Cu(I) binding in 10a,b is structurally related
to the dative PtfAg bond observed in several compounds
incorporating hard σ-donor ligands on platinum,82-87 where the
electron-rich Pt(II) center acts as a Lewis base.
The behavior of 10a,b in solution was investigated by means
1
1
of H NMR. At room temperature, the H NMR spectrum of
Figure 8. ORTEP representation of the X-ray crystal structure of
9b. Ellipsoids drawn at 50% probability. For clarity, two unbound
molecules of acetonitrile present in the asymmetric unit are omitted.
Selected distances [Å], angles [deg], and torsion angles [deg]:
Pt1-C1 2.022, Pt1-C2 1.990, Pt1-N1 2.111, Pt1-N2 2.106,
Pt1-Cu1 4.369, Cu1-N3 2.042, Cu1-N4 2.143, Cu1-N5 1.999,
Cu1-N6 1.952, N2-N3 1.325, C1-Pt1-C2 88.1,C1-Pt1-N1
96.2, N1-Pt1-N2 76.6, C2-Pt2-N2 99.2, C1-Pt1-N2 172.3,
C2-Pt1-N1 175.7, N3-Cu1-N4 78.8, N3-Cu1-N5 120.3,
N3-Cu1-N6 119.4, N4-Cu1-N5 119.9, N4-Cu1-N6 99.6,
N5-Cu1-N6 112.5, Cu1-N5-C3 170.7, Cu1-N6-C4 172.2,
Pt1-N2-N3-Cu1 1.1.
10a exhibits two sharp lines at 3.78 and 3.68 ppm, corresponding
to the Ar-OMe protons, but only two broad peaks between 2
and 2.7 ppm, where one would expect three for an unsymetri-
cally coordinated bmimp ligand. In order to elucidate whether
this behavior would be due to some chemical exchange process,
we recorded spectra at temperatures ranging from -30 °C up
to room temperature (Figure 11). The spectra clearly show that
there are two different species present, for which the intercon-
version rate is fast compared to the 1H NMR time scale at room
temperature and slow at -30 °C. The ratio between the two
species is temperature dependent, which rules out the possibility
that all the signals belong to a single species containing two
different ligands. Our first hypothesis on the nature of the two
species was that there would be an equilibrium between a
monomeric form and the dimer observed in the crystal structure.
If this were the case, then the ratio between the two species
Figure 7. ORTEP plot of the X-ray crystal structure of 8b.
Ellipsoids drawn at 50% probability. Top: view of the asymmetric
cell. Bottom: view of the atoms within 5 Å of K1. The centroids
of aromatic rings are labeled X. Selected distances [Å], angles [deg],
and torsion angles [deg]: Pt1-C1 2.005, Pt1-C2 2.004, Pt1-N1
2.123, Pt1-N2 2.060, Pt1-K1 4.390, N2-N3 1.321, K1-N3
2.741, K1-N4 2.955, K1-X1 3.056, K1-X1′ 3.350, K1-X2 3.111,
C1-Pt1-N196.9,N1-Pt1-N276.8,N2-Pt1-C296.8,C1-Pt1-C2
89.6, N1-Pt1-C2 172.9, N2-Pt1-C1 173.6, N1-K1-N4 57.3,
Pt1-N2-N3-K1 33.7.

4910 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
Figure 10. ORTEP representation of the X-ray crystal structure of
10b. Ellipsoids drawn at 50% probability. For clarity, 1.5 molecules
of 1,4-dioxane present in the asymmetric unit are omitted. Selected
distances [Å], angles [deg], and torsion angles [deg]: Pt1-C1 2.013,
Pt1′-C1′ 2.004, Pt1-C2 2.042, Pt1′-C2′ 2.031, Pt1-N1 2.106,
Pt1′-N1′ 2.094, Pt1-N2 2.095, Pt1′-N2′ 2.122, Pt1-Cu1 2.570,
Pt1′-Cu1 2.574, C2-Cu1 2.110, C2′-Cu1 2.144, C3-Cu1 2.530,
C3′-Cu1 2.476, Cu1-Cu2 2.760, Cu2-N3 1.944, Cu2-N3′ 1.937,
Cu2-N4 2.444, C1-Pt1-C2 87.6, C1′-Pt1′-C2′ 86.7, C1-Pt1-N1
96.0, C1′-Pt1′-N1′ 94.6, N1-Pt1-N2 76.6, N1′-Pt1′-N2′ 77.5,
C2-Pt1-N2 100.1, C2′-Pt2′-N2′ 101.2, C1-Pt1-N2 172.2,
C1′-Pt1′-N2′ 172.1, N1-Pt1-C2 169.8, N1′-Pt1′-C2′ 176.0,
Pt1-C2-Cu1 76.5, Pt1′-C2′-Cu1 76.1, Pt1-Cu1-Pt1′ 165.1,
Pt1-Cu1-Cu2 100.1, Pt1′-Cu1-Cu2 94.6, C2-Cu1-C2′ 144.0,
C2-Pt1-Cu1 53.0, C2′-Pt1′-Cu1 53.9, N3-Cu2-N4 74.9,
N3-Cu2-N3′ 161.6, N3′-Cu2-N4 123.2, N2-Pt1-C2-C3
146.8, N2′-Pt1′-C2′-C3′ 139.5, Pt1-Cu2-Cu1-Pt1′ 177.1,
Pt1-N2-N3-Cu2 7.4, Pt1′-N2′-N3′-Cu2 3.0.
Figure 9. ORTEP representation of the X-ray crystal structure of
10a. Ellipsoids drawn at 50% probability. Selected distances [Å],
angles [deg], and torsion angles [deg] (values for the approximate
C2 symmetry equivalents given in parentheses): Pt1-C1 1.990
(1.992), Pt1-C2 2.024 (2.015), Pt1-N1 2.117 (2.128), Pt1-N2
2.064 (2.058), Pt1-Cu1 2.744 (2.658), C2-Cu1 2.069 (2.145),
C3-Cu1 2.514 (2.409), C4-Cu1 2.824 (3.056), Cu1-Cu2 2.753,
Cu2-N3 1.983 (1.963), Cu2-N4 2.206 (2.206), N2-N3 1.342
(1.346), C1-Pt1-C2 87.0 (88.6), C1-Pt1-N1 96.0 (96.1),
N1-Pt1-N2 77.3 (76.3), C2-Pt1-N2 100.1 (99.2), C1-Pt1-N2
172.4 (172.1), C2-Pt1-N1 172.5 (172.5), Pt1-C2-Cu1 84.2
(79.4),Pt1-Cu1-Pt1′155.2,Pt1-Cu1-Cu2101.8(99.0),C2-Cu1-C2′
165.6, C2-Pt1-Cu1 48.6 (52.5), N3-Cu2-N4 79.1 (78.2),
N3-Cu2-N3′ 150.7, N4-Cu2-N4′ 89.1, N2-Pt1-C2-C3 138.7
(142.4), Pt1-Cu2-Cu1-Pt1′ 166.6, Pt1-N2-N3-Cu2 17.5
(-12.9).
should be dependent on the overall concentration of the sample.
However, this ratio was found to be identical for 15, 30, and
45 mM solutions of 10a. Consequently, we propose the
following interpretation of our data, summarized in Figure 12:
considering the fact that an “open” form is found in the crystal
structure of 10b (Figure 10), we postulate that a similar structure
A also exists for 10a. At room temperature, it rapidly inter-
converts with the “closed” structure B, yielding only one set of
signals, some of which are broadened due to incomplete
coalescence. This interconversion is frozen at -30 °C, while
the intramolecular ligand exchange A a A′ is still fast. This
means that the free energy barrier for the fourth nitrogen atom
coordination A a B is higher than the barrier for the exchange
A a A′, implying that the latter has to be dissociative in nature.
The spectrum of 10b, recorded at room temperature, exhibits
seven peaks with comparable integrals in the methyl region,
which indicates the presence of only one type of bdmimp ligand
in which the two ortho-methyl groups on the imine aromatic
ring are different. Thus, we can rule out the hypothesis of a
rapid dissociation/recombination of the dimeric structure of 10b,
because it would involve the existence of a symmetrical
intermediate in which the aforementioned methyl groups would
be equivalent, affording two peaks with a relative integral of 2
and three with integral 1 instead of the actual seven equally
intense peaks. The observation of only seven peaks shows that,
although there are two different ligands in the crystal structure
of 10b, they must rapidly interconvert via aspresumably
dissociativesligand exchange at the Cu2 ion, depicted as the
A a A′ equilibrium in Figure 12. In order to test this
interpretation, we recorded a spectrum at -70 °C, which
exhibited an important broadening of several peaks. Even though
no splitting of the peaks could be observed, this broadening
supports the existence of the two species A and A′, whose
interconversion becomes slow at low temperature. The fact that
species B is not observed for 10b is a result of the increased
steric repulsion between the imine aromatic moieties of both
bdmimp ligands, which would destabilize B.
The dynamic behavior exhibited in solution by the dimeric
structures 10a,b involving several coordination states around
the copper atoms suggests that coordination and activation of
small molecules should be possible. Furthermore, these dimers
have the ability to break down to monomeric dinuclear
complexes in the presence of coordinating ligands, as exempli-
fied by the isolation of the acetonitrile adduct 9b. Thus, they
could possibly act as a reservoir for dinuclear complexes in a
catalytic cycle.
Conclusions
Symmetrical, pyrazolate based bis-diimine ligands are easily
accessible and can be used to prepare heteronuclear complexes
in which each binding site is coordinated to a different metal.
We applied two different strategies to prepare mononuclear

Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4911
critical for future catalytic application. The reactivity and
possible catalytic activity of the described complexes is the
subject of further investigation in our laboratories.
Experimental Part
General Procedures. Solvents were obtained commercially in
p.a. quality and used as received. For reactions involving metal
complexes, solvents were distilled under nitrogen over sodium
(hexane, toluene), Na/K alloy (diethylether), potassium (tetrahy-
drofuran), or CaH2 (acetonitrile, dichloromethane). All chemical
manipulations involving metal complexes were performed in an
inert atmosphere using standard Schlenk and glovebox techniques
1
unless otherwise stated. H and 13C NMR spectra were recorded
1
on Varian Gemini 300 and Varian Mercury 300 instruments. H
and 13C chemical shifts are reported in ppm relative to tetrameth-
ylsilane, using residual solvent proton and 13C resonances as internal
references. Multiplicities are indicated as s (singlet), d (doublet), t
(triplet), and dd (doublet doublet), while apparent singlets, doublets,
and triplets are indicated by “s”, “d”, and “t”, respectively. For
peak assignment, benzenic rings are abbreviated Ar and pyrazole
rings Pz. Elemental analyses were carried out by the Mikrolabor
of the Laboratorium fu¨r Organische Chemie of ETH Zu¨rich. Melting
points are uncorrected and were measured in unsealed capillaries.
Organolithium reagents were titrated using the procedure of Watson
and Eastham.88 3,5-Diacetyl-4-methylpyrazole89,90 and Pt2(CH3)4(µ-
Figure 11. Methyl region of the 1H NMR spectra of 10a recorded
at different temperatures in CD2Cl2. Peaks assigned to NdCMe
groups are marked with triangles, pyrazolate-Me with squares, and
MeO with circles. The two equilibrating species are distinguished
by filled and open symbols.
91
Me2S)2 were prepared according to literature procedures. cis-
PtPh2(SMe2)2 was prepared using a modification of a literature
procedure.92 All other chemicals were obtained commercially and
used as received.
Ligand Syntheses. 3,5-Bis(4-methoxyphenyliminoacetyl)-4-
methylpyrazole (bmimpH, 1a). A mixture of 3,5-diacetyl-4-
methylpyrazole (700 mg, 5 mmol), p-methoxyaniline (2.5 g, 20
mmol), and formic acid (50 mg, 1 mmol) in methanol (10 mL)
was stirred for 15 h at room temperature. Filtration, washing with
methanol (4 × 5 mL) and diethyl ether (5 mL), and drying in Vacuo
yielded the product as an off-white powder (1.44 g, 77%). Mp: g
1
219 °C (dec). H NMR (DMSO-d6, 300 MHz): δ 13.46 (br, 1H,
NH), 6.94 (d, 3J(H-H) ) 8.7 Hz, 4H, ArH2,6), 6.77 (d, 3J(H-H)
) 8.6 Hz, 4H, ArH3,5), 3.75 (s, 3H, OCH3), 2.57 (s, 3H, Pz-CH3),
2.22 (s, 6H, ArNdC(CH3)-Pz). No 13C NMR spectrum could be
recorded due to poor solubility in common solvents. ESI-MS
(DCM), positive ion scan: m/z 377 ([M + H]+). Anal. Calcd for
C18H20N4O: C 70.11, H 6.54, N 18.17. Found: C 69.85, H 6.63, N
18.24.
3,5-Bis(2,6-dimethylphenyliminoacetyl)-4-methylpyrazole (bd-
mimpH, 1b). A solution of 3,5-diacetyl-4-methylpyrazole (434 mg,
2.6 mmol), 2,6-dimethylaniline (1.9 g, 15.7 mmol), and p-
toluenesulfonic acid monohydrate (50 mg, 0.26 mmol) in toluene
(30 mL) was refluxed for 64 h using a Dean-Stark water separator.
The solvent was then evaporated under reduced pressure, and the
residue was washed with methanol (10 mL + 3 × 4 mL) and dried
Figure 12. Proposed schematic potential energy surface for 10a
(solid) and 10b (dashed) in solution.
complexes incorporating an organometallic platinum(II) moiety
and their copper(I) adducts, using two electronically similar but
sterically different ligands. First, we took advantage of the single
acidic N-H bond in the protonated ligand, making it react with
organometallic Pt(II) precursors in order to selectively prepare
mononuclear Pt(II) complexes. One of these mononuclear
complexes is active for the stoichiometric C-H activation of
benzene, but only at high temperatures, while the more sterically
hindered complex yielded only traces of the C-H activation
product. These complexes can accommodate a Cu(I) center in
their empty coordination site. Second, we made use of the
sterical bulk of the PtPh2 fragment to synthesize mononuclear
anionic complexes as their potassium salt. Their complexation
to copper(I) yielded neutral, dimeric structures built by several
weak ligand-metal and metal-metal interactions, including
dative PtfCu bonds. These dimers exhibit fluxional behavior
in solution, and we expect them to easily break down to
monomeric species in the presence of coordinating substrates,
as demonstrated by the isolation of a solvated monomeric
structure from acetonitrile. Throughout the study, we observed
several differences in both structure and reactivity of the
complexes induced by the different steric bulk of the two ligands
we considered, which leads us to think that this factor could be
(79) Cooper, G. R.; Hutton, A. T.; Langrick, C. R.; McEwan, D. M.;
Pringle, P. G.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1984, 855–862.
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L.; Zhu, N.; Zhou, Z.-Y. J. Am. Chem. Soc. 2003, 125, 10362–10374.
(81) Song, H.-B.; Zhang, Z.-Z.; Hui, Z.; Che, C.-M.; Mak, T. C. W.
Inorg. Chem. 2002, 41, 3146–3154.
(82) Arsenault, G. J.; Anderson, C. M.; Puddephatt, R. J. Organome-
tallics 1988, 7, 2094–2097.
(83) Uso´n, R.; Fornie´s, J.; Toma´s, M.; Ara, I.; Casas, J. M.; Martin, A.
J. Chem. Soc., Dalton Trans. 1991, 2253–2264.
(84) Fornie´s, J.; Navarro, R.; Toma´s, M.; Urriolabeitia, E. P. Organo-
metallics 1993, 12, 940–943.
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Lalinde, E.; Torroba, J. Organometallics 2006, 25, 4331–4340.
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743–744.

4912 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
Table 1. Crystallographic Data for Compounds 2a,b, 4a, and 8b
2a
2b
4a
8b
chem formula
fw
cryst syst
space group
a [Å]
b [Å]
C30H34N4O2PtS
709.76
monoclinic
P21/c
16.9605(13)
7.6043(12)
22.6425(15)
90
92.823(11)
90
C32H38N4PtS
705.81
C66H74Cl2Cu2N8O4Pt2S2
847.81
monoclinic
P2/c
24.8131(13)
15.2421(12)
17.6737(15)
90
96.919(13)
90 deg
C36H37KN4Pt
759.89
monoclinic
P21/c
12.5793(12)
9.2999(11)
28.4841(15)
90
92.192(11)
90
3329.8(5)
4
triclinic
j
P1
7.8393(14)
13.7453(17)
14.5500(17)
94.905(12)
97.696(12)
97.360(13)
1532.5(4)
2
c [Å]
R [deg]
ꢀ [deg]
γ [deg]
V [Å3]
2916.7(5)
4
6635.6(8)
8
Z
Dcalcd [g cm]
F(000)
1.616
1408
1.530
704
1.697
3352
1.516
1512
µ [mm]
temp [K]
4.915
220(2)
4.672
220(2)
5.032
220(2)
4.368
220(2)
wavelength [Å]
no. of measd rflns
no. of unique rflns
no. of data/restraints/ params
R(F) (I > 2σ(I))
wR(F2) (I > 2σ(I))
GOF
0.71070
10 229
6516
6516/0/351
0.0433
0.1083
0.71070
11 179
6719
6719/0/353
0.0501
0.1182
0.71070
25 361
13 371
13 371/0/793
0.0704
0.1623
0.71070
11 901
7439
7439/0/387
0.0412
0.1098
1.036
1.018
1.095
1.080
Table 2. Crystallographic Data for Compounds 9b and 10a,b
9b
10a
10b
chem formula
fw
cryst syst
space group
a [Å]
b [Å]
C44H49CuN8Pt
948.54
C68H66Cu2N8O4Pt2
1576.55
C78H86Cu2N8O3Pt2
1700.81
monoclinic
P21/c
19.7025(13)
13.3495(12)
28.314(2)
90
108.050(11)
90
7080.7(10)
4
triclinic
triclinic
j
j
P1
P1
12.5439(12)
12.6310(12)
14.1299(13)
69.921(12)
85.038(11)
89.992(10)
2093.8(3)
2
11.3102(12)
16.5428(13)
18.7782(13)
112.169(11)
95.433(10)
108.142(11)
3000.8(6)
2
c [Å]
R [deg]
ꢀ [deg]
γ [deg]
V [Å3]
Z
Dcalcd [g cm]
F(000)
1.505
952
1.745
1552
1.595
3392
µ [mm]
temp [K]
3.885
220(2)
5.403
220(2)
4.585
220(2)
wavelength [Å]
no. of measd rflns
no. of unique rflns
no. of data/restraints/ params
R(F) (I > 2σ(I))
wR(F2) (I > 2σ(I))
GOF
0.71070
16 067
9582
9582/0/499
0.0436
0.1090
0.71070
24 103
13 645
13 645/0/768
0.0543
0.1365
0.71070
27 193
16 238
16 238/0/853
0.0419
0.0952
1.034
1.026
0.987
in Vacuo to yield the product as a white powder (751 mg, 78%).
An analytically pure sample was obtained by vapor diffusion of
pentane into a solution of 1b in dichloromethane. Mp: 228-229
°C. 1H NMR (DMSO-d6, 300 MHz): δ 13.61 (s, 1H, NH) 7.06 (d,
3J(H-H) ) 7.5 Hz, 4H, ArH3,5), 6.88 (t, 3J(H-H) ) 7.4 Hz, 2H,
ArH4), 2.69 (s, 3H, Pz-CH3), 2.05 (s, 6H, ArNdC(CH3)-Pz), 1.98
(s, 12H, ArCH3). 13C NMR (DMSO-d6, 300 MHz): δ 162.8
(CdNAr), 158.1 (CdNAr), 148.9 (CAr), 148.5 (CAr), 147.6 (CAr),
137.6 (CAr), 127.5 (CAr), 124.7 (CAr), 124.5 (CAr), 122.5 (CAr),
122.1 (CAr), 116.4 (CAr), 18.6 (NdCCH3), 18.0 (NdCCH3), 17.0
(CdNArCH3), 11.4 (Pz-CH3). ESI-MS (DCM), positive ion scan:
m/z 373 ([M + H]+). Anal. Calcd for C24H28N4: C 77.38, H 7.58,
N 15.04. Found: C 77.09, H 7.55, N 15.03.
Complex Syntheses. cis-PtPh2(SMe2)2. A solution of phenyl-
lithium in dibutyl ether (∼2 M, not titrated, 40 mL, 80 mmol) was
added at 0 °C to a suspension of finely powdered PtCl2(SMe2)2
(cis/trans mixture, 2.2 g, 5.6 mmol) in diethyl ether (80 mL), and
the resulting beige suspension was stirred for 3.5 h. All workup
was performed at 0 °C under argon. Then 40 mL of cooled, N2-
purged water was slowly added. The phases were separated, and
the water phase was extracted with dichloromethane (4 × 20 mL).
The combined organic phases were dried over MgSO4, treated with
a small quantity of activated charcoal, filtered, and evaporated in
Vacuo. The beige residue was dissolved in a mixture of dichlo-
romethane (7 mL) and Me2S (0.5 mL), and hexane (20 mL) was
added until precipitation started. Storage overnight at -20 °C,
filtration, washing with hexane (3 × 2 mL), and drying in Vacuo
yielded the product as a beige microcrystalline solid (1.86 g).
Concentration of the combined mother liquor and washings and
storage overnight at -20 °C yielded an additional crop as a beige
solid (0.51 g). Total yield: 2.37 g, 89%. Mp: g133 °C (dec) {lit.
1
3
100 °C8}. H NMR (CDCl3, 300 MHz): δ 7.37 (dd, J(H-H) )
7.9 Hz, 5J(H-H) ) 1.4 Hz, 3J(195Pt-H) ) 72.1 Hz, 4H, PtArH2,6
)
7.00-6.86 (m, 4H, PtArH3,5), 6.80-6.73 (m, 2H, PtArH4), 2.11
(s, 3J(195Pt-H) ) 23.6 Hz, SCH3). Anal. Calcd for C16H22S2Pt: C,
40.58, H, 4.68. Found: C, 40.52, H, 4.74.
trans-(bmimp)PtPh(SMe2) (trans-2a). A mixture of bmimpH
(146 mg, 0.39 mmol) and cis-PtPh2(SMe2)2 (183 mg, 0.39 mmol)
in 6 mL of dichloromethane was stirred for 3.5 h. The resulting
orange solution was filtered and vapor diffused with hexane. After
6 days, the mother solution was decanted, and the yellow crystals
were washed with hexane (3 × 3 mL) and dried in Vacuo (210
1
mg, 77%). Mp: g185 °C (dec). H NMR (CD2Cl2, 300 MHz): δ
6.49-7.02 (m, 13H, ArH), 3.80 (s, 3H, OCH3), 3.68 (s, 3H, OCH3),

Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4913
1
2.68 (s, 3H, Pz-CH3), 2.65 (s, 3J(195Pt-H) ) 58.3 Hz, 6H, SCH3),
H 4.96, N 8.54. The stereochemistry was assigned from the H
2.34 (s, 3H, ArNdC(CH3)-Pz), 2.26 (s, 3H, ArNdC(CH3)-Pz). 13
C
NMR spectrum on the basis of the shielding of the Pt-S(CH3)2
signal by the p-methoxyphenyl group and the 195Pt-H coupling
constants of the Pt-S(CH3)2 and Pt-CH3 signals.21
NMR (CD2Cl2, 75 MHz): δ 172.7 (CdNAr), 164.6(CdNAr), 157.5
(CAr), 155.6 (CAr), 151.1 (CAr), 150.6 (CAr), 145.5 (CAr), 142.0
(CAr), 139.4 (CAr), 137.6 (CAr), 126.6 (CAr), 125.5 (CAr), 122.1
(CAr), 121.6 (CAr), 121.0 (CAr), 114.3 (CAr), 113.4 (CAr), 55.8
(OCH3), 24.4 (SCH3), 18.7 (NdCCH3), 18.5 (NdCCH3), 11.4 (Pz-
CH3). ESI-MS (DCM), positive ion scan: m/z 710 ([M + H]+).
MS/MS (+710): m/z 648 (weak, - SMe2), 632 (- C6H6), 570 (-
SMe2 - C6H6), 588 (weak, - SMe2 - C6H6 + H2O), 598 (- SMe2
- C6H6 + N2). Anal. Calcd for C30H34N4O2SPt: C 50.77, H 4.83,
N 7.89. Found: C 50.99, H 4.89, N 7.87. Crystals suitable for X-ray
analysis were obtained by vapor diffusion of hexane into a solution
of trans-2a in 1:1 DCM/hexane at 4 °C.
trans-(bmimp)PtMe(SMe2) (trans-3a). A mixture of Pt2(CH3)4(µ-
Me2S)2 (175 mg, 0.30 mmol) and bmimpH (230 mg, 0.60 mmol)
in toluene (4 mL) was stirred for 15 h, yielding an orange
suspension. After filtration and washing with toluene (3 × 2 mL),
the yellow solid was dissolved in dichloromethane (6 mL),
precipitated with diethyl ether (12 mL), filtered, washed with diethyl
ether, and dried in Vacuo to yield cis-3a (110 mg, 29%). Toluene
was evaporated from the liquid phase, and the residue was dissolved
in dichloromethane (5 mL). Addition of diethyl ether (10 mL) and
concentration in Vacuo caused the precipitation of trans-3a as a
yellow solid, which was washed with diethyl ether and dried in
Vacuo (32 mg, 8%). An analytically pure sample was obtained by
vapor diffusion of hexane into a tetrahydrofuran solution of trans-
3a. Mp: g200 °C (dec). 1H NMR (CD2Cl2, 300 MHz): δ 7.05-6.85
(m, 3H, ArH), 6.78-6.72 (m, 1H, ArH), 3.84 (s, 3H, OCH3), 3.80
trans-(bdmimp)PtPh(SMe2) (trans-2b). A solution of bdmimpH
(150 mg, 0.40 mmol) and cis-PtPh2(SMe2)2 (190 mg, 0.40 mmol)
in dichloromethane (7 mL) was stirred for 66 h. The solution was
then concentrated to 2 mL, hexane (10 mL) was added, and the
mixture was stirred for 2 h. The pale yellow precipitate was
collected by filtration, washed with pentane, and dried in Vacuo.
Concentration of the combined mother solution and washings to 5
mL yielded a second crop of product. Pale yellow powder, 223
(s, 3H, OCH3), 2.78 (s, J(195Pt-H) ) 57.1 Hz, 6H, SCH3), 2.65
3
(s, 3H, Pz-CH3), 2.33 (s, 3H, ArNdC(CH3)-Pz), 2.22 (s, 3H,
ArNdC(CH3)-Pz), 0.07 (s, J(195Pt-H) ) 69.5 Hz, 3H, PtCH3).
2
13C NMR (CD2Cl2, 75 MHz): δ 173.5 (CdNAr), 165.0 (CdNAr),
158.1 (CAr), 155.9 (CAr), 150.9 (CAr), 150.4 (CAr), 145.8 (CAr),
139.5 (CAr), 125.5 (CAr), 121.3 (CAr), 121.2 (CAr), 114.4 (CAr),
114.2 (CAr), 55.8 (OCH3), 24.1 (SCH3), 18.7 (NdCCH3), 18.4
(NdCCH3), 11.4 (Pz-CH3), -13.0 (1J(195Pt-C) ) 685 Hz, PtCH3).
ESI-MS (DCM), positive ion scan: m/z 648 ([M + H]+). MS/MS
(+648): m/z 632 (- CH4), 604 (weak, - SMe2 + H2O), 598 (-
CH4 - SMe2 + N2), 588 (weak, - CH4 - SMe2 + H2O), 570 (-
CH4 - SMe2). Anal. Calcd for C25H32N4O2SPt: C 46.36, H 4.98,
N 8.65. Found: C 46.51, H 5.10, N 8.54.
1
mg (79%). Mp: g230 °C (dec). H NMR (CD2Cl2, 300 MHz): δ
7.05 (d, 3J(H-H) ) 7.5 Hz, 2H,CdNArH3,5), 6.97-6.90 (m, 2H,
3
PtArH), 6.87 (t, J(H-H) ) 7.5 Hz, 1H, CdNArH4), 6.79 (“s”,
3H, CdNArH3,4,5), 6.62-6.50 (m, 3H, PtArH), 2.75 (s, 3H, Pz-
3
CH3), 2.62 (s, J(195Pt-H) ) 59.3 Hz, 6H, SCH3), 2.164 (s, 3H,
ArNdC(CH3)-Pz),2.159(s,6H,CdNArCH3)2.14(s,3H,ArNdC(CH3)-
Pz), 2.06 (s, 6H, CdNArCH3). 13C NMR (CD2Cl2, 75 MHz): δ
172.5 (CdNAr), 164.0 (CdNAr), 150.7 (CAr), 150.2 (CAr), 149.9
(CAr), 144.0 (CAr), 140.4 (CAr), 136.7 (CAr), 131.0 (CAr), 127.8
(CAr), 127.7 (CAr), 126.3 (CAr), 126.2 (CAr), 125.9 (CAr), 122.3
(CAr), 122.2 (CAr), 121.7 (CAr), 24.3 (SCH3), 18.7 (NdCCH3/
ArCH3), 18.3 (NdCCH3/ArCH3), 17.4 (NdCCH3/ArCH3), 11.7
(Pz-CH3). ESI-MS (DCM), positive ion scan: m/z 706 ([M + H]+).
MS/MS (+706): m/z 628 (- C6H6), 566 (- C6H6 - SMe2), 594
(weak, - C6H6 - SMe2 + N2). Anal. Calcd for C32H38N4SPt: C
54.45, H 5.43, N 7.94. Found: C 54.56, H 5.31, N 7.86. Crystals
suitable for X-ray analysis were obtained by vapor diffusion of
hexane into a solution of trans-2b in 1:1 dichloromethane/hexane
at 4 °C.
cis-(bdmimp)PtMe(SMe2) (cis-3b). A solution of bdmimpH
(129 mg, 0.35 mmol) in dichloromethane (15 mL) was added over
15 min to a solution of Pt2(CH3)4(µ-Me2S)2 (100 mg, 0.17 mmol)
at 0 °C, causing a gradual color change from colorless to yellow.
The solution was stirred for 35 min, then allowed to slowly warm
to room temperature and stirred for 2 h. The solvent was evaporated,
and the yellow residue was thoroughly washed with hexane and
purified by column chromatography over neutral alumina (15 g),
using a 1:1 hexane/dichloromethane mixture as eluent. Evaporation
of the solvent and drying in Vacuo afforded the product as a yellow
solid (104 mg, 46%). An analytically pure sample was obtained
by vapor diffusion of hexane into a dichloromethane solution of
cis-3b. Mp: g194 °C (dec). 1H NMR (CD2Cl2, 300 MHz): δ
7.21-6.99 (m, 5H, ArH), 6.86 (“t”, 3J(H-H) ) 7.5 Hz, 1H, ArH4),
2.74 (s, 3H, Pz-CH3), 2.22 (s, 6H, CdNArCH3), 2.16 (s, 3H,
cis-(bmimp)PtMe(SMe2) (cis-3a). Pt2(CH3)4(µ-Me2S)2 (100
mg, 0.17 mmol) was added as a solid to a suspension of bmimpH
(131 mg, 0.35 mmol) in dichloromethane (20 mL), causing
complete dissolution and the appearance of a yellow color,
together with gas (methane) evolution. The mixture was stirred
for 1 h, after which a thin precipitate was removed by filtration
over Celite. The product was precipitated by concentration of
the solution to 5 mL followed by addition of diethyl ether (15
mL) and stirring for 10 min. Filtration, washing with diethyl
ether (3 × 2 mL), and drying in Vacuo yielded the product as a
ArNdC(CH3)-Pz), 2.11 (s, J(195Pt-H) ) 50.5 Hz, 6H, SCH3),
3
2.062 (s, 3H, ArNdC(CH3)-Pz), 2.057 (s, 6H, CdNArCH3), 1.18
(s, J(195Pt-H) ) 79.9 Hz, 3H, PtCH3). 13C NMR (CD2Cl2, 75
2
MHz): δ 168.8 (CdNAr), 164.6 (CdNAr), 151.9 (CAr), 150.2
(CAr), 149.7 (CAr), 144.8 (CAr), 130.8 (CAr), 128.4 (CAr), 128.0
(CAr), 126.3 (CAr), 126.1 (CAr), 122.3 (CAr), 121.1 (CAr), 21.6
(SCH3), 18.6 (NdCCH3), 18.3 (CdNArCH3), 17.9 (CdNArCH3),
17.3 (NdCCH3), -12.8 (1J(195Pt-C) ) 729 Hz, PtCH3). ESI-MS
(CH2Cl2), positive ion scan: m/z 644 ([M + H]+). MS/MS (+644):
m/z 628 (- CH4), 566 (- CH4 - SMe2). Anal. Calcd for
C27H36N4SPt: C 50.38, H 5.64, N 8.70. Found: C 50.57, H 5.73, N
8.58.
1
pale yellow solid (90 mg, 40%). Mp: g230 °C (dec). H NMR
(CD2Cl2, 300 MHz): δ 7.04-6.82 (m, 3H, ArH), 6.79-6.70 (m,
1H, ArH), 3.84 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 2.64 (s, 3H,
Pz-CH3),2.32(s,3H,ArNdC(CH3)-Pz),2.16(s,3H,ArNdC(CH3)-
Pz), 2.16 (s, 3J(195Pt-H) ) 50.1 Hz, 6H, S(CH3)), 1.16 (s,
2J(195Pt-H) ) 80.3 Hz, 3H, PtCH3). The two signals at δ 2.16
can be resolved by addition of about 10% C6D6 to the sample.
13C NMR (CD2Cl2, 75 MHz): δ 169.1 (CdNAr), 165.2
(CdNAr), 158.0 (CAr), 155.8 (CAr), 152.3 (CAr), 150.1 (CAr),
145.8 (CAr), 140.5 (CAr), 124.4 (CAr), 121.1 (CAr), 121.0 (CAr),
114.6 (CAr), 114.4 (CAr), 55.79 (OCH3), 55.75 (OCH3), 21.5
(SCH3), 18.4 (NdCCH3), 18.1 (NdCCH3), 11.2 (Pz-CH3, -14.1
(1J(195Pt-C) ) 726 Hz, PtCH3). ESI-MS (DCM), positive ion
scan: m/z 648 ([M + H]+). MS/MS (+648): m/z 632 (- CH4),
570 (- CH4 - SMe2), 598 (- CH4 - SMe2 + N2). Anal. Calcd
for C25H32N4O2SPt: C 46.36, H 4.98, N 8.65. Found: C 46.45,
(88) Watson, S. C.; Eastham, J. F. J. Organomet. Chem. 1967, 9, 165–
168.
(89) Wolff, L. Liebigs Ann. Chem. 1902, 325, 134–195.
(90) Wollf, L. Liebigs Ann. Chem. 1912, 394, 59–68.
(91) Hill, G. S.; Irwin, M. J.; Levy, C. J.; Rendina, L. M.; Puddephatt,
R. J. Inorg. Synth. 1998, 32, 149–152.
(92) Rashidi, M.; Fakhroeian, Z.; Puddephatt, R. J. J. Organomet. Chem.
1990, 406, 261–267.

4914 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
{[trans-(bmimp)PtPh(SMe2)]2Cu}{CuCl2} (4a). CuCl (16
mg, 162 µmol) was added to a yellow solution of trans-2a (28 mg,
39 µmol) in CD2Cl2 (0.7 mL), causing an immediate color change
to bright red. The mixture was stirred for 10 min and filtered into
a Young-type NMR tube, where the product was characterized by
1H and 13C NMR. The solvent was then evaporated in Vacuo, and
the residue was dissolved in benzene (1 mL) and stored at 4 °C for
5 days. Filtration, washing with benzene (2 × 0.5 mL), and drying
in Vacuo yielded the product as dark red microcrystals (17 mg,
56%). Mp: g180 °C (dec). 1H NMR (CD2Cl2, 300 MHz): δ
7.09-6.89 (m, 2H, br Pt satelites, PtArH), 6.88 (“s”, 4H,
NArH2,3,5,6), 6.72-6.50 (m, 7H, ArH), 3.81 (s, 3H, OCH3), 3.68
(s, 3H, OCH3), 2.59 (s, 3H, Pz-CH3), 2.35 (s, 3H, ArNdC(CH3)-
[cis-(bdmimp)PtMe(SMe2)] · CuCl (5b). An excess of CuCl
was added to a suspension of cis-3b (40 mg, 62 µmol) in CD2Cl2
(0.7 mL), and the resulting dark red mixture was stirred for 5 min
and filtered into a Young-type NMR tube. 1H NMR (CD2Cl2, 300
3
MHz): δ 7.20 (“d”, J(H-H) ) 7.2 Hz, 4H, NArH3,5), 7.10 (dd,
3
3J(H-H) ) 8.5 Hz, J(H-H) ) 6.4 Hz, 2H, NArH4), 7.04-6.70
(br m, 6H, NArH3,4,5), 2.58 (s, 6H, Pz-CH3), 2.34-1.85 (br m,
∼30H, CH3), 2.20 (“s”, ∼12H, CH3), 2.08 (“s”, ∼12H, CH3), 1.16
3
(br, ∼6H, CH3), 0.85 (br, ∼6H, J(195Pt-H) ≈ 77 Hz, PtCH3).
ESI-MS(CH2Cl2),positiveionscan:m/z1350({[(bdmimp)PtMe(SMe2)]2-
Cu}+), 707 ({[(bdmimp)PtMe(SMe2)]Cu}+). MS/MS (+1350): m/z
1334 (weak, - CH4), 1288 (weak, - SMe2), 1272 (- CH4 - SMe2),
1194 (weak, - 2 CH4 - 2 SMe2), 707 (- [(bdmimp)PtMe(SMe2)]),
691 (- [(bdmimp)PtMe(SMe2)] - CH4), 663 (- [(bdmimp)Pt-
Me(SMe2)] - SMe2 + H2O), 629 (- [(bdmimp)PtMe(SMe2)] -
CH4 - SMe2). MS/MS (+707): m/z 691 (- CH4), 663 (- SMe2 +
H2O), 645 (weak, - SMe2), 629 (- CH4 - SMe2). Negative ion
scan: m/z 135 ([CuCl2]-), 233 (weak, [Cu2Cl3]-).
3
Pz), 2.29 (s, 3H, ArNdC(CH3)-Pz), 2.05 (s, J(195Pt-H) ) 58.7
Hz, 6H, SCH3). 13C NMR (CD2Cl2, 75 MHz): δ 173.3 (CdNAr),
163.0 (CdNAr), 157.8 (CAr), 157.2 (CAr), 151.2 (CAr), 150.5 (CAr),
143.1 (CAr), 141.0 (CAr), 138.8 (CAr), 136.3 (CAr), 127.1 (CAr),
124.8 (CAr), 123.1 (CAr), 122.6 (CAr), 121.9 (CAr), 114.3 (CAr),
113.6 (CAr), 55.82 (OCH3), 55.79 (OCH3), 23.6 (SCH3), 19.7
(NdCCH3), 19.6 (NdCCH3), 11.6 (Pz-CH3). ESI-MS (CH2Cl2),
positive ion scan: m/z 1581 (weak, [M + CuCl]+), 1482 (M+),
773 ([(bmimp)PtPh(SMe2)Cu]+). MS/MS (+1581): m/z1519 (-
SMe2), 871 (weak, - [(bmimp)PtMe(SMe2)]), 773 (- {[(bmi-
[(bmimp)PtPh2]-K+ (8a). A mixture of bmimpH (200 mg,
0.53 mmol) and KOtBu (60 mg, 0.53 mmol) in tetrahydrofuran
(5 mL) was stirred for 0.5 h, resulting in a brown solution. The
solvent was evaporated in Vacuo, and dichloromethane (5 mL)
was added and evaporated in Vacuo. This cycle was repeated
two times, and dichloromethane (6 mL) was added to the residue.
The resulting beige suspension was cooled to 0 °C, and cis-
PtPh2(SMe2)2 (252 mg, 0.53 mmol) was added. The mixture was
allowed to warm to room temperature and stirred for 63 h.
Filtration, washing of the solid with dichloromethane (2 × 1
mL), and drying in Vacuo afforded the product as a yellow
powder (270 mg, 67%). An analytically pure sample was
obtained by crystallization from acetonitrile. Mp: g150 °C (dec).
mp)PtMe(SMe2)]CuCl}).
MS/MS
(+1482):
m/z
1420
(- SMe2), 1358 (- 2 SMe2), 1280 (- 2 SMe2 - C6H6), 1009
(weak, [(bmimp)2PtCu]+), 773 (- [(bmimp)PtPh(SMe2)]). Negative
ion scan: m/z 135 ([CuCl2]-). Anal. Calcd for C60H68N8O4S2-
Cl2Cu2Pt2: C 44.55, H 4.24, N 6.93. Found: C 44.65, H 4.12, N
6.77. Crystals suitable for X-ray analysis were obtained from a
freshly prepared solution of 4a in benzene.
{[cis-(bmimp)PtMe(SMe2)]2Cu}{CuCl2} (5a). An excess of
CuCl was added to a suspension of cis-3a (40 mg, 62 µmol) in
CD2Cl2 (0.7 mL), and the resulting dark red mixture was stirred
for 5 min and filtered into a Young-type NMR tube. 1H NMR
(CD2Cl2, 300 MHz): δ 7.01 (d, 3J(H-H) ) 9.1 Hz, 4H, NArH2,6/
3
1H NMR (CD3CN, 300 MHz): δ 7.41 (dd, J(H-H) ) 8.0 Hz,
3
5J(H-H) ) 1.5 Hz, J(Pt-H) ) 73.0 Hz, 2H, PtArH2,6), 6.95
3
5
3
(dd, J(H-H) ) 7.9 Hz, J(H-H) ) 1.6 Hz, J(Pt-H) ) ∼64
Hz, 2H, PtArH2,6), 6.93-6.86 (m, 2H, ArH), 6.81-6.52 (m, 9H,
ArH), 6.48-6.33 (m, 3H, ArH), 3.77 (s, 3H, OCH3), 3.68 (s,
3H, OCH3), 2.61 (s, 3H, Pz-CH3), 2.18 (s, 3H, ArNdC(CH3)-
Pz), 2.14 (s, 3H, ArNdC(CH3)-Pz). 13C NMR (THF-d8, 75
MHz): δ 167.8 (CdNAr), 164.5 (CdNAr), 157.8 (CAr), 156.6
(CAr), 153.5 (CAr), 151.7 (CAr), 150.8 (CAr), 147.9 (CAr), 146.3
(CAr), 141.8 (CAr), 141.5 (CAr), 140.0 (CAr), 126.2 (CAr), 125.7
(CAr), 125.6 (CAr), 121.8 (CAr), 120.9 (CAr), 119.8 (CAr), 114.8
(CAr), 113.6 (CAr), 55.7 (OCH3), 19.4 (NdCCH3), 12.2 (Pz-
CH3). ESI-MS (MeCN), positive ion scan: m/z 764 ([M - K+
+ H]+), 1489 ([2 M- + K+ + 2H]+). MS/MS (+764): m/z 608
(- 2 C6H6), 626 (- 2 C6H6 + H2O), 636 (- 2 C6H6 + N2), 647
(weak, - 2 C6H6 + MeCN), 704 (weak, - C6H6 + H2O), 714
(- C6H6 + N2). MS/MS (+1489): m/z 764 (- M - H+).
Negative ion scan: m/z -724 (M-), -646 ([M - C6H6]-),
-1488 ([2 M + K]-). MS/MS (-724): m/z -646 (- C6H6).
3
3,5), 6.90 (d, J(H-H) ) 8.9 Hz, 4H, NArH3,5/2,6), 6.82 (“s”, 4H,
NArH2,3,5,6), 3.85 (s, 6H, OCH3), 3.79 (s, 6H, OCH3), 2.57 (s, 6H,
Pz-CH3), 2.29 (s, 6H, ArNdC(CH3)-Pz), 2.19 (s, 3H, ArNdC(CH3)-
Pz), 2.11 (s, 4J(195Pt-H) ) 54 Hz, 12H, SCH3) 1.08 (s, 3J(195Pt-H)
) 77.4 Hz, PtCH3). 13C NMR (CD2Cl2, 75 MHz): δ 168.8
(CdNAr), 162.5 (CdNAr), 158.3 (CAr), 157.1 (CAr), 153.0 (CAr),
150.0 (CAr), 141.7 (CAr), 139.7 (CAr), 124.1 (CAr), 123.2 (CAr),
121.2 (CAr), 114.8 (CAr), 114.3 (CAr), 55.9 (OCH3), 21.6 (SCH3),
19.3 (NdCCH3), 19.1 (NdCCH3), 11.6 (Pz-CH3), -12.5 (PtCH3).
ESI-MS (CH2Cl2), positive ion scan: m/z 1358 (M+). MS/MS
(+1358): m/z 1342 (- CH4), 1296 (- SMe2), 1280 (- CH4 -
SMe2), 1264 (- 2 CH4 - SMe2), 1218 (- CH4 - 2 SMe2), 1202
(-
2 CH4 - 2
SMe2), 1154 ([(bmimp)2Pt2CH3]+ 1140
([(bmimp)2Pt2]+),1009([(bmimp)2PtCu]+),711(weak,(-[(bmimp)Pt-
Me(SMe2)]). Negative ion scan: m/z 135 ([CuCl2]-).
[trans-(bdmimp)PtPh(SMe2)] · CuCl (4b). An excess of CuCl
was added to a suspension of trans-2b in CD2Cl2 (0.7 mL), and the
resulting dark red mixture was stirred for 5 min and filtered into a
Young-type NMR tube. 1H NMR (CD2Cl2, 300 MHz): δ 7.24-6.86
(br m, 5H, ArH), 6.79 (br, 3H, ArH), 6.61 (br, 3H, ArH), 2.60 (s, 3H,
OCH3), 2.42-1.80 (br m, ∼23H, CH3), 1.12 (very br, ∼1H, CH3).
MS/MS (-1488): m/z -724 (- M - K+) -646 (- M - K+
-
C6H6). Anal. Calcd for C34H33N4O2KPt: C 53.46, H 4.35, N 7.33.
Found: C 53.50, H 4.21, N 7.39.
[(bdmimp)PtPh2]-K+ (8b). A mixture of bdmimpH (200 mg,
0.54 mmol) and KOtBu (60 mg, 0.53 mmol) in tetrahydrofuran
(5 mL) was stirred for 0.5 h, resulting in a brown solution. The
solvent was evaporated in Vacuo, and dichloromethane (5 mL)
was added and evaporated in vacuo. This cycle was repeated,
and dichloromethane (6 mL) was added to the residue. The
resulting off-white suspension was cooled to 0 °C, and cis-
PtPh2(SMe2)2 (254 mg, 0.54 mmol) was added. The mixture was
allowed to warm to room temperature and stirred for 68 h.
Filtration, washing of the solid with dichloromethane (2 × 1
mL), and drying in Vacuo afforded the product as a yellow
powder (300 mg, 73%). An analytically pure sample was
obtained by vapor diffusion of diethyl ether into an acetonitrile
solution of 8b. Mp: g 230 °C (dec). 1H NMR (CD3CN, 300
ESI-MS
(CH2Cl2),
positive
ion
scan:
m/z
1573
([(bdmimp)PtPh(SMe2)]2Cu2Cl+), 1474 ([(bdmimp)PtPh(SMe2)]2-
Cu+). MS/MS (+1573): m/z 1511 (- SMe2), 1449 (- 2SMe2), 867
(- [(bdmimp)PtPh(SMe2)]), 805 (- [(bdmimp)PtPh(SMe2)] - SMe2),
769 (weak, [(bdmimp)PtPh(SMe2)] - CuCl), 727 (- [(bdmimp)Pt-
Ph(SMe2)] - SMe2 - C6H6). MS/MS (+1474): m/z 1412 (- SMe2),
1334 (weak, - SMe2 - C6H6), 1272 (- 2SMe2 - C6H6), 1194 (weak,
- 2SMe2 - 2C6H6), 769 (- [(bdmimp)PtPh(SMe2)]), 707 (-
[(bdmimp)PtPh(SMe2)] - SMe2), 691 (- [(bdmimp)PtPh(SMe2)] -
C6H6), 629 (- [(bdmimp)PtPh(SMe2)] - SMe2 - C6H6). Negative
ion scan: m/z 135 ([CuCl2]-), 233 (weak, [Cu2Cl3]-).

Mononuclear Organometallic Pt(II) Complexes
Organometallics, Vol. 27, No. 19, 2008 4915
MHz): δ 7.44 (dd, 3J(H-H) ) 8.0 Hz, 5J(H-H) ) 1.5 Hz,
3J(Pt-H) ) 72.9 Hz, 2H, PtArH2,6), 7.11-6.60 (m, 11H, ArH),
6.42-6.26 (m, 3H, ArH), 2.68 (s, 3H, Pz-CH3), 2.18 (s, 6H,
NArCH3), 2.02 (s, 6H, NArCH3), 2.00 (s, 3H, ArNdC(CH3)-
Pz), 1.99 (s, 3H, ArNdC(CH3)-Pz). 13C NMR (CD3CN, 75
MHz): δ 168.9 (CdNAr), 164.9 (CdNAr), 152.8 (CAr), 151.2
(CAr), 150.7 (CAr), 150.2 (CAr), 147.2 (CAr), 146.7 (CAr), 140.9
(CAr), 139.3 (CAr), 131.0 (CAr), 128.5 (CAr), 127.8 (CAr), 126.8
(CAr), 126.3 (CAr), 125.6 (CAr), 125.2 (CAr), 122.9 (CAr), 121.1
(CAr), 120.3 (CAr), 120.0 (CAr), 19.3 (NdCCH3/ArCH3), 18.3
(NdCCH3/ArCH3), 17.9 (NdCCH3/ArCH3), 11.9 (Pz-CH3). ESI-
MS (MeCN), positive ion scan: m/z 760 ([M - K+ + H]+),
1481 ([2 M- + K+ + 2H]+). MS/MS (+760): m/z 604 (- 2
C6H6). MS/MS (+1481): m/z 760 (- M - H+). Negative ion
scan: m/z -720 (M-), -642 ([M - C6H6]-), -1480 ([2 M +
K]-). MS/MS (-720): m/z -642 (- C6H6). MS/MS (-1480):
m/z -720 (- M - K+) -646 (- M - K+ - C6H6). Anal. Calcd
for C36H37N4OKPt: C 56.90, H 4.91, N 7.37. Found: C 57.19, H
4.90, N 7.37. Crystals suitable for X-ray diffraction were
obtained by vapor diffusion of diethyl ether into an acetonitrile
solution of 8b.
[(bdmimp)PtPh2]Cu(NCMe)2 (9b). A solution of CuCl (3 mg,
30 µmol) in acetonitrile (0.5 mL) was added to a solution of 8b
(20 mg, 26 µmol) in acetonitrile (0.5 mL) and stirred for 1 min.
The resulting yellow suspension was immediately filtered, and
the yellow solution was stored at -35 °C overnight. The yellow
microcrystals that formed during this time were collected by
filtration, washed with acetonitrile (3 × 0.1 mL), and suspended
in acetonitrile (1 mL). Heating to 50 °C caused complete
dissolution, after which the solution was allowed to cool slowly
to room temperature. Upon standing, yellow blocks of 9b suitable
for X-ray diffraction were obtained. Further characterization was
precluded by the ability of 9b to lose acetonitrile when exposed
to vacuum and to convert to 10b in solvents other than
acetonitrile.
m/z -1512 ({[(bmimp)PtPh2]2Cu}-), -724 ([(bmimp)PtPh2]-).
MS/MS (-1512): m/z -724 ([(bmimp)PtPh2]-), -646 (weak,
[(bmimp)PtPh2 - C6H6]-). MS/MS (-724): m/z -646 (- C6H6).
Anal. Calcd for C68H66N8O2Pt2Cu2: C 51.81, H 4.22, N 7.11.
Found: C 52.04, H 4.11, N 7.07. Crystals suitable for X-ray
diffraction were obtained by vapor diffusion of hexane into a
benzene solution of 10a.
[(bdmimp)PtPh2]2Cu2 (10b). A solution of CuCl (44 mg, 0.44
mmol) in acetonitrile (2 mL) was added under stirring to a
solution of 8b (300 mg, 0.39 mmol) in acetonitrile (10 mL).
The resulting yellow suspension was concentrated to 5 mL and
stored at -20 °C overnight. Filtration at -10 °C, washing with
precooled acetonitrile (3 + 1 + 1 mL), and drying in Vacuo
afforded a yellow solid, which was taken up in benzene (6 mL).
The solvent was evaporated in Vacuo, and the orange residue
was extracted with benzene (6 + 1 mL), affording an orange
solution, which was vapor diffused with hexane (20 mL) over 7
days. Filtration, washing with hexane (3 × 1 mL), and drying
in Vacuo yielded the product as orange plates containing 2 equiv
of benzene (185 mg, 60%). Mp: g230 °C (dec). 1H NMR
(CD2Cl2, 300 MHz): δ 7.77 (d, 3J(H-H) ) 6.9 Hz, 3J(Pt-H)
≈ 63 Hz, 2H, PtArH2,6), 7.1-6.3 (m, 16H, ArH), 2.54 (s, 3H,
Pz-CH3), 2.21 (s, 3H, NArCH3/ArNdC(CH3)-Pz), 2.17 (s, 3H,
NArCH3/ArNdC(CH3)-Pz), 2.16 (s, 3H, NArCH3/ArNdC(CH3)-
Pz), 2.11 (s, 3H, NArCH3/ArNdC(CH3)-Pz), 2.04 (s, 3H,
NArCH3/ArNdC(CH3)-Pz), 1.63 (s, 3H, NArCH3/ArNdC(CH3)-
Pz). 13C NMR (CD2Cl2, 75 MHz): δ 169.1 (CdNAr), 164.5
(CdNAr), 152.1 (CAr), 149.6 (CAr), 147.2 (CAr), 144.8 (CAr),
144.6 (CAr), 140.4 (br, CAr), 137.0 (CAr), 130.0 (CAr), 129.8
(CAr), 128.5 (CAr), 128.4 (CAr), 125.7 (CAr), 125.3 (CAr), 123.9
(CAr), 120.8 (CAr), 120.4 (CAr), 119.5 (CAr), 20.6 (NdCCH3/
ArCH3), 19.6 (NdCCH3/ArCH3), 18.8 (NdCCH3/ArCH3), 18.6
(NdCCH3/ArCH3), 18.5 (NdCCH3/ArCH3), 17.8 (NdCCH3/
ArCH3), 12.3 (Pz-CH3). ESI-MS (MeCN), positive ion scan: m/z
888 ([((bmimp)PtPh2)Cu(MeCN) + Cu]+), 1631 ([(bmimp)-
PtPh2]2Cu2 + Cu+). MS/MS (1631): m/z 1553 (weak, - C6H6),
1475 (- 2C6H6), 1399 (- Ph2 - C6H6). MS/MS (888): m/z 847
(- MeCN). Negative ion scan: m/z -1504 ([(bmimp)PtPh2]2-
Cu-), -720 ([(bmimp)PtPh2]-). MS/MS (-1504): m/z -720
([(bmimp)PtPh2]-), -642 ([(bmimp)PtPh2 - C6H6]-). MS/MS
(-720): m/z -642 (- C6H6). Anal. Calcd for C72H74N8Pt2-
Cu2 · 2C6H6: C 58.49, H 5.03, N 6.50. Found: C 58.10, H 4.99,
N 6.51. Crystals suitable for X-ray diffraction were obtained by
vapor diffusion of hexane into a 1,4-dioxane solution of 10b.
[(bmimp)PtPh2]2Cu2 (10a). A solution of CuCl (69 mg, 0.70
mmol) in acetonitrile (3 mL) was added under stirring to a
solution of 8a (500 mg, 0.65 mmol) in acetonitrile (30 mL),
resulting in an immediate color change from yellow to orange
followed by the appearance of a yellow solid after 1 min. The
yellow suspension was concentrated to about 10 mL and stored
at -20 °C overnight. Filtration at -15 °C, washing with
precooled acetonitrile (3 × 3 mL), and drying in Vacuo afforded
a yellow solid, which was extracted with benzene (5 + 2 + 2
mL), resulting in a red solution. Solvent was evaporated in Vacuo,
and the brick red residue was dissolved in benzene (7 mL) and
vapor diffused with hexane (15 mL) over 12 days. Filtration,
washing with hexane (3 × 5 mL), and drying in Vacuo yielded
the product as red needles (452 mg, 88%). Mp: g260 °C (dec).
1H NMR (CD2Cl2, 300 MHz, 22 °C): δ 8.1-7.0 (v br, 2H,
PtArH2,6), 7.0-6.3 (br m, 16H, ArH), 3.78 (s, 3H, OCH3), 3.68
(s, 3H, OCH3), 2.54 (br, 3H, Pz-CH3), 2.21 (br, 6H, ArNdC(CH3)-
Crystallographic Data. Relevant details about the structure
refinements are given in Tables 1 and 2, and selected geometrical
parameters are included in the captions of the corresponding figures.
Data collection was performed on a Bruker-Nonius Kappa-CCD
(graphite monochromator, Mo KR) at a temperature of 220 K. The
structures were solved by direct methods93 and refined by full-
matrix least-squares analysis94 including an isotropic extinction
correction. All non H-atoms were refined anisotropically (H atoms
isotropic, whereby H-positions are based on stereochemical con-
siderations).
1
Pz). H NMR (CD2Cl2, 300 MHz, -30 °C), species A: δ 7.94
3
(d, br Pt satellites, J(H-H) ) 7.1 Hz, 1H, PtArH2/6), 7.1-6.2
(br m, 16H, ArH), 6.02 (“t”, 3J(H-H) ) 7.3 Hz, 1H, ArH),
3.74 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 2.56 (s, 3H, Pz-CH3),
2.26 (s, 3H, ArNdC(CH3)-Pz) 2.08 (s, 3H, ArNdC(CH3)-Pz);
species B: δ 7.90 (d, br Pt satellites, 3J(H-H) ) 7.3 Hz, 1H,
PtArH2/6), 7.32 (d, br Pt satellites, 3J(H-H) ) 6.4 Hz, 1H,
PtArH2/6), 7.1-6.2 (br m, 16H, ArH), 3.77 (s, 3H, OCH3), 3.65
(s, 3H, OCH3), 2.51 (s, 3H, Pz-CH3), 2.23 (s, 3H, ArNdC(CH3)-
Pz), 2.17 (s, 3H, ArNdC(CH3)-Pz). A/B ratio ≈ 4:3. ESI-MS
(MeCN), positive ion scan: m/z 892 ([((bmimp)PtPh2)Cu(MeCN)
+ Cu]+), 1639 ({[(bmimp)PtPh2]2Cu2 + Cu}+). MS/MS (+1639):
m/z 1561 (weak, - C6H6), 1483 (- 2 C6H6), 1407 (- Ph2 -
C6H6). MS/MS (+892): m/z 851 (- MeCN). Negative ion scan:
Acknowledgment. The authors acknowledge support from
the Swiss National Science Foundation. We thank T. Michl
for the first synthesis of 8a and Mr. Paul Seiler for the X-ray
structure determinations, as well as Dr. Marc-Olivier Ebert
for assistance with EXSY-NMR experiments.
(93) Altomare, A.; Burla, M.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1999, 32, 115–119.
(94) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Goettingen: Germany, 1997.

4916 Organometallics, Vol. 27, No. 19, 2008
Moret and Chen
Supporting Information Available: ESI-MS and 1H NMR
spectra relative to the C-H activation experiments. Variable-
temperature 1H NMR data. EXSY spectrum of 4b a 6b and
assignment. ESI-MS, 1H and 13C NMR spectra for new compounds.
Crystal data in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800403Y