Reactivity of [Pt(PtBu3)2] with Zinc(I/II) Compounds: Bimetallic Adducts, Zn-Zn Bond Cleavage, and Cooperative Reactivity

Article abstract of DOI:10.1021/acs.organomet.1c00088

Metal-only Lewis pairs (MOLPs) based on zinc electrophiles are particularly interesting due to their relevance to Negishi cross-coupling reactions. Zinc-based ligands in bimetallic complexes also render unique reactivity to the transition metals at which

Full text of DOI:10.1021/acs.organomet.1c00088

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Reactivity of [Pt(PtBu3)2] with Zinc(I/II) Compounds: Bimetallic
Adducts, Zn−Zn Bond Cleavage, and Cooperative Reactivity
́
Nereida Hidalgo, Carlos Romero-Pérez, Celia Maya, Israel Fernández, and Jesus Campos*
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ABSTRACT: Metal-only Lewis pairs (MOLPs) based on zinc electrophiles
are particularly interesting due to their relevance to Negishi cross-coupling
reactions. Zinc-based ligands in bimetallic complexes also render unique
reactivity to the transition metals at which they are bound. Here we explore
the use of sterically hindered [Pt(PtBu3)2] (1) to access Pt/Zn bimetallic
complexes. Compounds [(PtBu3)2Pt → Zn(C6F5)2] (2) and [Pt(ZnCp*)6]
(3) (Cp* = pentamethylcyclopentadienyl) were isolated by reactions with
Zn(C6F5)2 and [Zn2Cp*2], respectively. We also disclose the cooperative
reactivity of 1/ZnX2 pairs (X = Cl, Br, I, and OTf) toward water and
dihydrogen, which can be understood in terms of bimetallic frustration.
the parent monometallic components remain inactive.12 On
these grounds, we decided to inspect the formation and
reactivity of zinc-containing MOLPs based on [Pt(PtBu3)2]
(1). In doing so, we have examined its reactivity with a range
of zinc precursors, more precisely ZnX2 (X = Cl, Br, I, and
OTf; OTf = trifluoromethanesulfonate), ZnR2 (R = Me, Et,
Ph, η5-C5Me5, and C6F5), and the more exotic Zn(I) dimer
[Zn2(η5-C5Me5)2] (Zn2Cp*2).13
INTRODUCTION
■
The unique features of bimetallic complexes are behind the
rapid development that has recently taken place in the field.1
Among these complexes, metal-only Lewis pairs (MOLPs),2
that is, bimetallic compounds in which the two metal atoms are
held together exclusively by a dative M → M bond, constitute
a fascinating family. MOLPs constructed around Lewis acidic
zinc(II) fragments are particularly appealing due to their
relevance to Negishi cross-coupling catalysis. In fact,
intermediates containing dative Pd → Zn interactions are
crucial to accessing low-energy transition states during
transmetalation3 and play essential roles in cis/trans isomer-
ization4 and deleterious homocoupling processes.5 Bergman
and Tilley have shown that biaryl reductive elimination from
Pt(II) compounds is accelerated upon Zn(C6F5)2 coordina-
tion,6 while Whittlesey and Macgregor have explored a
heterobimetallic Ru/Zn compound and demonstrated that
the unsaturated “ZnMe” terminus promotes C−H reductive
elimination and dihydrogen activation at the Ru(II) site.7
Although Zn-based MOLPs remain rare8 these findings
highlight the opportunities that may emerge from combining
zinc electrophiles with electron-rich transition metal com-
pounds.
RESULTS AND DISCUSSION
■
Treatment of [Pt(PtBu3)2] (1) with zinc (pseudo)halides in
toluene did not offer any hint of adduct formation by NMR in
the temperature range of −80 to +70 °C, which contrasts with
the readily accessible [(PCy3)2Pt → ZnBr2].10 Considering
that the basicity of 1 may be superior to that of [Pt(PCy3)2],
we ascribe the absence of MOLP formation from the former to
steric reasons. Switching to dichloromethane, fluorobenzene,
and tetrahydrofuran to improve the solubility of the zinc salt
did not alter these results. However, addition of 1 equiv of the
more acidic Zn(C6F5)2 to a colorless C6D6 solution of 1 caused
instant coloration to bright yellow. Multinuclear NMR
spectroscopic analysis suggested formation of the bimetallic
adduct [(PtBu3)2Pt → Zn(C6F5)2] (2 in Scheme 1). The most
1
distinctive feature is a pronounced decrease in the JPPt
As for Lewis basic fragments, [Pt(PCy3)2] (Cy = cyclohexyl)
is likely the most extensively investigated donor in MOLP
chemistry.9 In fact, recently reported [(PCy3)2Pt → ZnBr2] is
the first well-defined unsupported M → Zn(II) adduct.10
Combination of the bulkier analogue [Pt(PtBu3)2] (1) with a
Cu(I) species revealed bimetallic cooperation during O−H
bond activation.11 Similarly, we have explored the reactivity of
coupling constant to a value of 3328 Hz (δ = 93.1 ppm; c.f.
1
1: δ = 100.2 ppm, JPPt = 4410 Hz), a common symptom of
Received: February 12, 2021
Published: April 13, 2021
[ ( P t B u 3 ) 2 P t
→
A g N T f 2 ] ( N T f 2
=
b i s -
(trifluoromethanesulfonyl)imide), which readily cleaves X−H
(X = H, C, O, and N) bonds across the Pt−Ag linkage, while
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Scheme 1. Reaction of [Pt(PtBu3)2] (1) with Zinc
(Pseudo)halides and Organozinc Compounds
165.32(4)°). As in other bisphosphine Pt(0)-based MOLPs,
the Pt−P bond distances (2.325 Å on average) are modestly
elongated with respect to that of precursor 1 (2.25 Å).14 The
Pt−Zn bond length (2.4663(6) Å) is shorter than in the
related [(phen)Ar2PtII → Zn(C6F5)2] (phen = phenanthro-
line) adduct, which contains a less basic Pt(II) donor
(2.5526(5) Å),6 and just marginally longer than that in
[(Cy3P)2Pt → ZnBr2] (2.4040(6) Å).10 Steric constraints in 2
force the perfluorphenyl rings to bend away from the platinum
center, with the C25Zn−C31 angle of 117.73(18)° being
significantly reduced compared to those of Zn(C6F5)2
(172.6°)15 and even [(phen)Ar2PtII → Zn(C6F5)2] (134.8°).6
At variance with its fluorinated analogue, the less acidic
ZnPh2 does not react with 1, as monitored by variable
temperature NMR and visually inferred by the colorless
appearance of the reaction mixture even after prolonged
periods of time. Similarly, no Pt → Zn interactions were
detected upon addition of 10 equiv of ZnR2 (R = Me, Et, and
η5-C5Me5) to C6D6 solutions of 1, again pointing out the need
for a highly electrophilic Zn center to overcome the distortion
of the linear Pt(0) precursor to accommodate the bimetallic
dative bond. Next, we examined the reactivity of 1 with the
Zn(I) dimer [Zn2Cp*2]13 in light of its capacity to form zinc-
rich polymetallic complexes with transition metal precursors.16
For instance, Fischer has investigated the reactivity between
[Zn2Cp*2] and low-valent M(0) precursors (M = Ni, Pd, and
Pt), recurrently identifying the homolytic cleavage of the Zn−
Zn bond by insertion of the transition metal.17
a
a
Top: X = Cl, Br, I, and OTf; R = Me, Et, and Ph, C5Me5; solvent =
C6D6, CD2Cl2, THF, or C6H5F.
MOLP formation in Pt(0) compounds due to the reduced s
character of the Pt−P bonds in the bimetallic adduct.9,12
Alongside this, a new set of 19F{1H} resonances at −115.7,
−157.4, and −162.0 ppm (c.f. Zn(C6F5)2: δ = −118.0, −152.5,
and −160.5 ppm) was recorded.
The molecular structure of 2 was authenticated by single-
crystal X-ray diffraction studies (Figure 1a) confirming the
proposed bimetallic formulation. This represents the first
example of a Pt(0)/organozinc MOLP. It exhibits a T-shaped
geometry around the platinum center, slightly distorted due to
the steric pressure exerted by the tert-butyl groups in close
proximity to the perfluorinated aryl rings (P−Pt−P =
31P{1H} NMR monitoring of an equimolar mixture of 1 and
[Zn2Cp*2] in C6D6 showed the release of free phosphine (δ =
63.0 ppm) without any other detectable intermediate. It soon
became evident that a 3-fold excess of the Zn(I) dimer was
required to achieve complete consumption of 1. Under these
conditions, the highly unstable compound [Pt(ZnCp*)6] (3)
forms as the major species (ca. 80% NMR yield) by insertion
of the Pt center into the Zn−Zn bonds of three molecules of
[Zn2Cp*2]. (Scheme 2). Compound 3 slowly precipitates as
Scheme 2. Synthesis of Compound 3 by the Reaction
between 1 and [Zn2Cp*2]
bright orange crystals, which allowed us to ascertain its
heptametallic structure by X-ray diffraction analysis (Figure
1b). It can be described as an unusual 16-electron octahedral
complex in which each vertex is occupied by a neutral 1-
electron ZnCp* ligand. This is in stark contrast with all prior
Zn-rich polymetallic compounds of late transition metals,
which consistently fulfill the 18 valence electron rule.16 The
steric shrouding provided by the six planar cyclopentadienyl
ligands stabilizes the somewhat encapsulated electron-rich
platinum center.
The solid-state structure shows three pairs of ZnCp* ligands
that differ slightly from each other in terms of Zn coordination.
Two of these fragments present η5-coordination (dZn−C
≈
Figure 1. ORTEP diagram of compounds 2 and 3. Hydrogen atoms
have been excluded, and methyl groups of Cp* ligands are
represented in wire-frame format for clarity. Thermal ellipsoids are
set at 50% probability.
2.24−2.37 Å), and a second pair binds to the Cp* in an η2-
fashion. The third pair exhibits an η1-binding (shortest dZn3−C21
= 2.06(3) Å; the rest are >2.6 Å). While the former two pairs
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present Pt−Zn bond distances (2.419(3) and 2.401(4) Å)
comparable to prior examples,17 the η1-bound ZnCp*
fragment displays a Pt−Zn bond (2.238(7) Å) shortened by
0.34 Å with respect to the sum of the covalent radii (2.58 Å).18
Table 1. EDA results at ZORA-BP86-D3/TZ2P for
[Pt(ZnH)n] (n = 6 and 8) with the fragments M(s0d10) and
(ZnH)n in the Singlet State
a
compound
Pt(ZnH)6
−234.1
Pt(ZnH)8
−288.9
Pt(ZnH)8
−279.0
1
In THF-d8 solution, a single H NMR resonance at 1.92 ppm
ΔEint
indicates rapid dynamic exchange among the possible
conformations of the ZnCp* ligands. In fact, low temperature
NMR (up to −80 °C) was insufficient to freeze the dynamic
process.
ΔEPauli
434.7
468.8
486.0
−583.4 (76.3%)
−181.6 (23.7%)
b
ΔEelstat
−518.4 (77.5%)
−145.5 (21.8%)
−4.8 (0.7%)
−0.21
−575.6 (76.0%)
−175.2 (23.1%)
−6.9 (0.9%)
−0.21
b
ΔEorb
b
ΔEdisp
Compound 3 strongly resembles the closed-shell 18-electron
[Pt(ZnCp*)4(ZnR)4] species (R = Me and Et) described by
Fischer and co-workers.17b The latter compounds exhibit
rather long Zn···Zn distances (ranging from 2.812 to 3.115 Å),
which have been regarded as noninteracting or only weakly
interacting.17e Similar Zn···Zn distances were found in 3 (>3.0
Å). To confirm the negligible interaction between the zinc
centers in 3, we computationally explored the topology of the
model system Pt(ZnH)6, analogous to the model Pt(ZnH)8
used by Fischer and Frenking to understand the bonding
situation in [Pt(ZnCp*)4(ZnR)4],17b,e using the QTAIM
(Quantum Theory of Atoms in Molecules) method (see
computational details in the Supporting Information). Figure 2
c
q(Pt)
a
b
Energy values (kcal/mol) taken from ref 17b. Percentage values in
parentheses give the contributions to the total attractive energy
c
ΔEelstat + ΔEorb + ΔEdisp
platinum center.
.
Computed Hirshfeld charges at the
def2-TZVPP level including the original data reported
previously for Pt(ZnH)8 (D4d) computed at the rather similar
ZORA-BP86/TZ2P//RI-BP86/def2-TZVPP level. From the
data in Table 1, the resemblance between both Pt(0)
compounds becomes evident. Although the computed
interaction energy, ΔEint, is higher in Pt(ZnH)8 (which is
not surprising as the Pt center interacts with two additional
one-electron ZnH ligands), in both cases, the platinum atom
bears a small negative charge, which is consistent with the
chosen neutral fragments. Despite that, the main contribution
to the bonding comes from the electrostatic interactions,
representing ca. 76−77% of the total attractions. The
contribution resulting from orbital interactions (mainly
involving the d atomic orbitals of platinum) is significantly
much lower and those coming from dispersion interactions can
be considered as negligible. This therefore indicates that the
bonding in newly prepared compound 3 (and the analogous
[Pt(ZnCp*)4(ZnR)4]) can be viewed mainly as a result of the
electrostatic interactions between the platinum center and the
surrounding ZnCp* ligands.
We next interrogated the ability of these Pt/Zn bimetallic
pairs to activate both polar and nonpolar bonds using water
and dihydrogen as model substrates. We mainly directed our
efforts toward pairs containing inorganic zinc salts, as
organozinc compounds (1/ZnR2, 2 and 3) were rapidly
hydrolyzed in the presence of water. Besides, those species
remained inactive toward H2 under all attempted conditions.
In contrast, equimolar benzene suspensions of 1 and ZnX2 (X
= Cl, Br, I, and OTf) readily react with H2O (5 equiv) by
means of O−H bond activation (Scheme 3).11,12 It is
Figure 2. Contour line diagrams ∇2ρ(r) for Pt(ZnH)6 in the Zn−Pt−
Zn plane. The solid lines connecting the atomic nuclei are the bond
paths, while the small green spheres indicate the corresponding bond
critical points.
shows the Laplacian distribution of Pt(ZnH)6 computed in the
Zn−Pt−Zn plane. As expected, bond critical points (BCPs)
together with their associated bond paths (BPs) are found
between the zinc and platinum centers (computed Pt−Zn
bond distances ∼ 2.47 Å). In contrast, no BCPs or BPs were
located between the zinc atoms (computed Zn···Zn bond
Scheme 3. Activation of Polar O−H Bond by Pt(0)/Zn(II)
FLPs
distances ranging from 2.91 to 2.93 Å), which similar to
17b,e
Pt(ZnR)8
supports the above-commented noninteracting
nature of Zn···Zn in 3.
More quantitative insight into the bonding situation in 3 can
be obtained by means of the energy decomposition analysis
(EDA) method, also used by Fischer, Frenking, and co-workers
to analyze the bonding in the analogous Pt(ZnH)8 (D4d).17b
Thus, we compare the EDA data for Pt(ZnH)6 and Pt(ZnH)8
using the same partitioning scheme reported previously,
namely, Pt(0) and (ZnH)n (n = 6 and 8) in their singlet
states as fragments. Table 1 gathers the corresponding EDA
values computed at the ZORA-BP86-D3/TZ2P//BP86-D3/
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important to remark that 1 does not react with water on its
own even under more forcing conditions (80 °C, 24 h).
However, in the presence of zinc halides formation of trans-
[PtHX(PtBu3)2] (X = Cl, Br, and I; 4, Scheme 3) is evidenced
Formation of 6 suggests a catalytic role of Zn(OTf)2 during
the hydrogenation of 1, which has previously been observed
for the hydrogenation of imines catalyzed by the same zinc
species.21 In fact, decreasing the amount of Zn(OTf)2 to only 5
mol % with respect to 1 under otherwise identical conditions
led to the formation of 6 in comparable yields. In fact, the
amount of zinc and the nature of the solvent did not have any
apparent influence on the extent of dihydride produced, which
was obtained in yields between 80 and 90% in all cases.
Attempts to reach full hydrogenation of 1 were unsuccessful
despite longer reaction times, higher temperatures and
increasing loadings of zinc. These observations imply that
hydrogenation of 1 is a reversible process. We confirmed this
idea by adding Zn(OTf)2 (10 mol %) to a THF-d8/C6D6 (2:1)
solution of dihydride 6 in a sealed NMR tube (Scheme 4c).
Reaction monitoring evidenced evolution to a mixture of both
1 and 6 in a ca. 2:3 ratio after 5 h, as well a minute amount of
free H2 identified by an 1H NMR peak at 4.42 ppm. Replacing
the atmosphere by H2 (1 bar) led to 6 in around 85% yield.
The presence of zinc is also essential for dehydrogenation,
since in its absence the release of H2 could not be detected
even by heating 6 under dynamic vacuum (70 °C, 50·mbar,
Scheme 4d). This process resembles both the dehydrogenation
of [PtH2(PCy3)2] promoted by C60,22 as well as the role played
by Zn(C6F5)2 in facilitating biaryl reductive elimination from
Zn(II) complexes.6
The mechanism of reversible heterolytic dihydrogen
splitting holds great interest due to its connection to hydrogen
production and the action of hydrogenase enzymes. It has also
been largely studied as a benchmark transformation to gauge
FLP behavior and, despite its apparent simplicity, remains a
topic of intense research.23 In this line, the absence of adduct
formation from the pair 1/Zn(OTf)2 along with its cooperative
bond activation could be understood in terms of FLP
principles.24 We performed several experiments to gain some
preliminary mechanistic information. First, we determined the
kinetic isotopic effect (KIE) for H2 versus D2 splitting, which
has a strong inverse value of 0.59 0.1 (see the Supporting
Information for details). This is an uncommon finding25 that
compares well with our previously reported Pt(0)/Au(I)
1
by a distinctive low-frequency H NMR resonance due to the
metal hydride (δ = −19.2 (4a, Cl), −18.4 (4b, Br), and −16.4
(4c, I) ppm), exhibiting scalar coupling to both 31P (2JHP ≈ 12
Hz) and 195Pt (1JHPt ≈ 1100 Hz) nuclei. In the case of
Zn(OTf)2, the reduced coordinating capacity of the triflate
moiety compared to halide anions led to the cationic hydride-
aquo complex trans-[PtH(OH2)(PtBu3)2]+(5) as the only
observable product. Formation of compounds 4 and 5 is
accompanied by the appearance of a fine precipitate of zinc
hydroxide salts.
As mentioned briefly above, water activation by combining 1
11
with transition metal Lewis acids [Cu(CH3CN)4]PF6 and
AgNTf2,12 has recently been reported. Formation of an
intermediate characterized by a Pt → M dative interaction is
proposed as the initial step in both cases, after which the
cooperative cleavage of the O−H bond takes place. Our
experiments indicate that bimetallic adduct formation is not
favored for zinc salts; thus, an FLP-type mechanism seems
more likely. In fact, we have already demonstrated that
compound 1 acts as a Lewis basic site in bimetallic FLPs by
partnering it with sterically crowded Au(I) compounds.19 Our
prior mechanistic investigations allowed us to conclude that
those Pt(0)/Au(I) pairs mediate the cleavage of the H−H
bond in dihydrogen by a genuine FLP mechanism.19b We
wondered if the same would apply for the Pt/Zn pairs
investigated herein. Once again, it is worth mentioning that
neither 1 nor zinc (pseudo)halides react with H2 on their own
(Scheme 4a). Similarly, the combination of 1 and zinc halides
Scheme 4. Reactivity of Bimetallic Pair 1/Zn(OTf)2 with H2
bimetallic FLP (KIE = 0.46
0.04), where a genuine
frustrated mechanism was ascertained.19b We postulated that
the origin for such a strong inverse KIE derived from an FLP
productlike transition state whose bimetallic structure offered
an assortment of H-containing bending modes that contribute
to the zero-point energy (ZPE). We anticipate that a similar
transition state in the present system (B in Scheme 5) would
analogously derive in a strong inverse KIE, as observed
experimentally. Direct oxidative addition of dihydrogen over 1
to form cis-[PtH2(PtBu3)2] followed by Zn-assisted isomer-
ization4 could be considered an alternative mechanism (C in
Scheme 5). However, solutions of 1/Zn(OTf)2 catalyze rapid
(t1/2 < 15 min) exchange between H2 and D2 to produce HD
1
(δ = 4.36 ppm, JHD = 42.6 Hz) in a statistical amount, which
seems to disfavor a classical oxidative addition route. In fact,
the individual monometallic species mediate the exchange at a
considerable slower pace (t1/2 > 2 days). Interestingly,
compound [PtH(PtBu3)2]+, which would be an intermediate
during FLP-type H2 activation, promotes H/D scrambling at a
rate comparable to the bimetallic pair. This agrees with its
existence as a transient intermediate during the hydrogenation
of 1, thus supporting the idea of a bimetallic FLP mechanism
(through B in Scheme 5). Nevertheless, these preliminary
in benzene or THF did not provide any reactivity upon
exposure to H2 (2 bar, 70 °C). However, in the presence of the
more acidic Zn(OTf)2, dihydrogen activation proceeds
smoothly to generate Pt(II) dihydride 620 even under mild
conditions (H2 1 bar, 25 °C, 5 h; Scheme 4b). Compound 6 is
produced in ca. 85% spectroscopic yield, exhibiting a
1
characteristic H NMR resonance at −2.91 ppm (2JHP = 16.4
1
Hz, JHPt = 780.6 Hz).
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mg, 52%). Anal. Calcd for C36H54F10P2PtZn: C, 43.3; H, 5.5. Found:
Scheme 5. Potential Mechanisms for H2 Activation by 1/
Zn(OTf)2
C, 43.0; H, 5.7. 1H NMR (400 MHz, C6D6, 25 °C) δ: 1.28 (vt, 54 H,
t
3JHP = 6.3 Hz, Bu). 13C{1H} NMR (100 MHz, CD2Cl2, 25 °C) δ:
1
1
148.6 (br d, JCF = 227 Hz, o-C6F5), 139.8 (br d, JCF = 232 Hz, p-
1
C6F5), 136.6 (br d, JCF = 254 Hz, m-C6F5), 128.2 (br, ipso-C6F5),
1
40.2 (vt, JCP = 8 Hz, Pt−P(C(CH3)3), 33.0 (Pt−P(C(CH3)3).
31P{1H} NMR (160 MHz, C6D6, 25 °C) δ: 93.1 (1JPPt = 3328 Hz).
19F{1H} NMR (376 MHz, C6D6, 25 °C) δ: −115.7, −157.4, −162.0.
Compound 3. To a mixture of complex [Pt(PtBu3)2] (1) (50 mg,
0.083 mmol) and [Zn2Cp*2] (99 mg, 0.249 mmol) was added 3 mL
of benzene. The solution was stirred for 20 min at room temperature.
Complex 3 crystallized from the crude reaction after 12 h (34 mg,
30%). Anal. Calcd for C60H90PtZn6: C, 51.5; H, 6.5. Found: C, 51.5;
H, 6.8. H NMR (400 MHz, C6D6, 25 °C) δ: 1.45 (Me). 13C{1H}
NMR (100 MHz, THF-d8, 25 °C) δ: 112.0 (C5Me5), 12.0 (C5Me5).
1
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.1c00088.
■
sı
experiments cannot yet rule out a more traditional bimetallic
H2 activation route implying a transient dative Pt → Zn bond
(A in Scheme 5) or the active participation of triflate
substituents.26
Synthetic procedures, kinetic studies, X-ray structural
data, computational details, and NMR spectra (PDF)
Cartesian coordinates (XYZ)
ConclusionsIn summary, we report the formation of two
new Pt/Zn polymetallic complexes. While the metal-only
Lewis adduct [(PtBu3)2Pt → Zn(C6F5)2] (2) represents the
first Pt(0)/organozinc MOLP, the reaction between [Pt-
(PtBu3)2] (1) and [Zn2Cp*2] yields the hexametallic,
homoleptic compound [Pt(ZnCp*)6] (3). At variance with
previous Zn-rich polymetallic compounds, the latter does not
fulfill the 18 valence electron rule, since it is considered an
octahedral 16-electron species. While these complexes remain
inactive toward dihydrogen, pairing 1 with Zn(OTf)2 results in
cooperative dihydrogen cleavage. Preliminary kinetic and
isotopic exchange experiments support a bimetallic FLP-type
mechanism. Similarly, the activation of O−H bonds in water
proceeds readily in the presence of Pt/Zn pairs, while the
individual components reveal no activity.
Accession Codes
CCDC 2062801 and 2062802 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
́
Jesus Campos − Instituto de Investigaciones Químicas (IIQ),
Departamento de Química Inorgánica and Centro de
Innovación en Química Avanzada (ORFEO−CINQA),
Consejo Superior de Investigaciones Científicas (CSIC) and
University of Sevilla, 41092 Sevilla, Spain; orcid.org/
0000-0002-5155-1262; Email: jesus.campos@iiq.csic.es
EXPERIMENTAL SECTION
■
General Considerations. All preparations and manipulations
were carried out using standard Schlenk and glovebox techniques,
under an atmosphere of argon and of high purity nitrogen,
respectively. All solvents were dried, stored over 3 Å molecular
sieves, and degassed prior to use. Toluene (C7H8) and n-pentane
(C5H12) were distilled under nitrogen over sodium. Tetrahydrofuran
(THF) and diethyl ether were distilled under nitrogen over sodium/
benzophenone. (D6)Benzene was dried over molecular sieves (3 Å),
and (D8)THF was distilled under argon over sodium/benzophenone,
and CD2Cl2 and fluorobenzene over CaH2 distilled under argon.
Compounds 1,27 ZnPh2,28 [Zn2Cp*2],29 and [PtHCl(PtBu3)2]30 were
prepared as described previously. Other chemicals were commercially
available and used as received. Solution NMR spectra were recorded
on Bruker AMX-300, DRX-400 and DRX-500 spectrometers. Spectra
were referenced to external SiMe4 (δ: 0 ppm) using the residual
proton solvent peaks as internal standards (1H NMR experiments) or
the characteristic resonances of the solvent nuclei (13C NMR
experiments), while 31P was referenced to H3PO4 and 19F to CFCl3.
Spectral assignments were made by routine one- and two-dimensional
NMR experiments where appropriate. For elemental analyses, a
LECO TruSpec CHN elementary analyzer was utilized. The
supplementary crystallographic data for this paper has been deposited
in the Cambridge Crystallographic Data Centre with codes 2062801
and 2062802.
Authors
Nereida Hidalgo − Instituto de Investigaciones Químicas
(IIQ), Departamento de Química Inorgánica and Centro de
Innovación en Química Avanzada (ORFEO−CINQA),
Consejo Superior de Investigaciones Científicas (CSIC) and
University of Sevilla, 41092 Sevilla, Spain; orcid.org/
0000-0001-6966-3556
Carlos Romero-Pérez − Instituto de Investigaciones Químicas
(IIQ), Departamento de Química Inorgánica and Centro de
Innovación en Química Avanzada (ORFEO−CINQA),
Consejo Superior de Investigaciones Científicas (CSIC) and
University of Sevilla, 41092 Sevilla, Spain
Celia Maya − Instituto de Investigaciones Químicas (IIQ),
Departamento de Química Inorgánica and Centro de
Innovación en Química Avanzada (ORFEO−CINQA),
Consejo Superior de Investigaciones Científicas (CSIC) and
University of Sevilla, 41092 Sevilla, Spain
Israel Fernández − Departamento de Química Orgánica I and
Centro de Innovación en Química Avanzada
(ORFEO−CINQA), Facultad de Ciencias Químicas,
Universidad Complutense de Madrid, Madrid 28040, Spain;
orcid.org/0000-0002-0186-9774
Compound 2. To a mixture of [Pt(PtBu3)2] (1) (50 mg, 0.083
mmol) and Zn(C6F5)2 (33 mg, 0.083 mmol) was added 5 mL of
toluene, and the solution was stirred for 30 min, then kept at −30 °C.
Orange crystals of 2 were collected and washed with cold pentane (43
Complete contact information is available at:
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Article
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https://pubs.acs.org/10.1021/acs.organomet.1c00088
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the European Research Council
(ERC Starting Grant, CoopCat, Project 756575) and the
Spanish Ministry of Science and Innovation (Projects
PID2019-110856GA-I00, PID2019-106184GB-I00, and
RED2018-102387-T). We thank Dr. Rosie J. Somerville for
helpful discussions.
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