Responsive macrocyclic and supramolecular structures powered by platinum

Abstract

Humankind's manipulation of platinum dates back more than two millennia to burial objects. Since then, its use has evolved from purely decorative purposes in jewelry to more functional applications such as in catalysts, pharmaceuticals, and bioimaging agents. Platinum offers a range of properties arguably unmatched by any other metal, including electroactivity, photoluminescence, chromic behaviour, catalysis, redox reactivity, photoreactivity, and stimuli-controlled intermetallic interactions. The vast body of knowledge generated by the exploration of these and other properties of platinum has recently merged with other areas of chemistry such as supramolecular and host–guest chemistry. This has shown us that platinum can incorporate its responsive character into supramolecular assemblies (e.g., macrocycles and polymers) to produce materials with tailorable functions and responses. In this Perspective Article, we cover some platinum-powered supramolecular structures reported by us and others, hoping to inspire new and exciting discoveries in the field.

Full text

Responsive macrocyclic and supramolecular
structures powered by platinum
Miguel A. Soto *
a
and Mark J. MacLachlan *
abc
Humankind's manipulation of platinum dates back more than two millennia to burial objects. Since then, its
use has evolved from purely decorative purposes in jewelry to more functional applications such as in
catalysts, pharmaceuticals, and bioimaging agents. Platinum offers a range of properties arguably
unmatched by any other metal, including electroactivity, photoluminescence, chromic behaviour,
catalysis, redox reactivity, photoreactivity, and stimuli-controlled intermetallic interactions. The vast body
of knowledge generated by the exploration of these and other properties of platinum has recently
merged with other areas of chemistry such as supramolecular and host–guest chemistry. This has shown
us that platinum can incorporate its responsive character into supramolecular assemblies (e.g.,
macrocycles and polymers) to produce materials with tailorable functions and responses. In this
Perspective Article, we cover some platinum-powered supramolecular structures reported by us and
others, hoping to inspire new and exciting discoveries in the field.
Introduction
The potential of non-covalent interactions and reversible cova-
lent bonds has been gradually uncovered since the seminal
work of 1987 Nobel laureates Cram, Lehn, and Pedersen.
1–4
Today, literature abounds with examples of craily designed
supramolecular structures and materials, in which dynamic
bonds are key to enabling responsiveness.
5–7
These systems
undergo unique electronic, stereochemical, and constitutional
changes upon physical and chemical stimulation. This is
attractive to various elds of chemistry and biochemistry, as it
can lead to systems with tailor-made functions.
8–11
Metal ions have become an important part of the available
toolkit for designing these responsive supramolecular
assemblies.
12–14
The ever-increasing number of metal–organic
cages, macrocycles, and polymers attests to this —not to
mention the fascinating work of Sauvage (2016 Nobel
Laureate)
15
on the use of copper coordination complexes to
power up molecular machines. Metal centers have become an
essential component for supramolecular design, as they unlock
a whole range of properties that are unrivaled by organic
analogues. These include tunable luminescence,
16
redox
activity,
17
magnetic susceptibility,
18
anti-aromaticity,
19
catalytic
activity,
20
and multi-responsiveness.
21
In recent years, our group has focused on incorporating
platinum into small molecules using cyclometalating ligands to
elicit responsive behavior. This research contributes to the
growing body of knowledge on Pt-containing supramolecular
systems, alongside the foundational work of other groups. In
most of the reported examples, the stimuli-responsiveness is
harnessed either from the ligands (e.g.,via photoisomerization)
or from the metal center through metallophilic interactions.
22–31
In this Perspective Article, we aim to go beyond these explored
approaches, and discuss how, in our view, other platinum-
centered responses may become crucial in the design and
realization of new supramolecular assemblies. These include
classic reactivity of platinum complexes such as redox and
ligand exchange processes that may lead to changes in, for
example, ligand distribution, oxidation state of the metal
center, nuclearity of the complex, and stereochemistry (Fig. 1).
Platinum in brief
Platinum (from the Spanish platina, meaning 'little silver') is
a transition metal with a wide range of chemical properties, and
its coordination chemistry has been extensively studied because
of its importance in biological, medical, and industrial applica-
tions. Platinum-based materials are widely used in electronics and
jewelry because of their high electrical conductivity and lustre.
32–34
In the eld of anti-cancer research, platinum complexes have
revolutionized cancer treatment by providing a new class of drugs
that act by binding to DNA, ultimately leading to cell death.
35
Amazingly, more than 50% of the platinum metal we mine today
goes into the catalytic converters in our cars.
In the eld of catalysis, platinum complexes have been
extensively used as highly active and selective catalysts in
a
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, British Columbia, V6T 1Z1, Canada. E-mail: msoto@chem.ubc.ca;
mmaclach@chem.ubc.ca
b
Quantum Matter Institute, University of British Columbia, 2355 East Mall,
Vancouver, British Columbia, V6T 1Z4, Canada
c
WPI Nano Life Science Institute, Kanazawa University, Kanazawa, 920-1192, Japan
Cite this: Chem. Sci.,2024,15,431
All publication charges for this article
have been paid for by the Royal Society
of Chemistry
Received 17th October 2023
Accepted 30th November 2023
DOI: 10.1039/d3sc05524h
rsc.li/chemical-science
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 431
Chemical
Science
PERSPECTIVE

various industrial processes.
36
Current research efforts are
focused on the design of novel platinum complexes with greater
catalytic performance and stability, while also improving their
recyclability. Platinum also nds applications in renewable
energy, particularly in fuel cells, where it serves as a catalyst for
hydrogen oxidation.
37
Furthermore, platinum has applications
in the eld of light-emitting diodes, where it is critical to
improving their efficiency and performance through advanced
material and device design strategies.
38
Platinum coordination chemistry
In coordination complexes, platinum is commonly found in +2
and +4 oxidation states. Platinum(II) complexes generally have
square planar geometry, whilst platinum(IV) complexes are
usually octahedral. The oxidation state of the Pt centre is crucial
to the reactivity and electronic properties of the complexes. In
addition to the most commonly observed Pt
II
and Pt
IV
,Pt
III
has
attracted considerable attention in the past few decades as new
methods have emerged to access Pt
III
complexes. In the +3
oxidation state, platinum shows diverse coordination geome-
tries and unique reactivity. Platinum(III) complexes oen have
distorted octahedral or square planar structures, depending on
the ligands involved. The ability to control the oxidation state of
platinum allows for the design of materials with tailored
properties and functions, expanding their use across various
applications.
39,40
There are many approaches to assemble platinum coordi-
nation complexes, depending on the desired features. The use
of monodentate ligands, for example, may lead to cis or trans
arrangements, which can inuence the electronic and steric
properties of the resulting complex. Bidentate or polydentate
ligands, on the other hand, produce a single (non-isomeric)
complex that is stabilized by the chelate effect. Examples of
such ligands include diamines, bis(phosphines), and 2,2
′
-
bipyridine derivatives. Another approach is to use bridging
ligands that can connect two or more platinum centres, leading
to the formation of polynuclear complexes. Molecules equipped
with carboxylic acids, imines, and pyridyl moieties are examples
of the commonly used multidentate ligands. The obtained
polynuclear complexes can show unique properties, such as
cooperative binding, catalytic activity, and redox communica-
tion between the platinum centres.
41
In addition to these approaches, recent studies have
explored the use of supramolecular self-assembly to construct
platinum-based materials with unique properties. For example,
platinum ions can be incorporated into self-assembled organic
nanostructures, such as micelles and vesicles, to provide addi-
tional functionality, including catalytic activity or drug delivery.
The use of self-assembly allows for the construction of highly
ordered and tunable materials with precise control over the
size, shape, and composition of the resulting structures.
42
The assembly of platinum coordination complexes is
a versatile and highly customizable process that allows for the
design of materials with bespoke architectures. By exploring
different ligands, bridging groups, and self-assembly strategies,
one can create platinum-based materials with intriguing prop-
erties for a wide range of applications.
Responsiveness powered by platinum
While fundamental studies of platinum have been a subject of
research for many decades, the focus is increasingly shiing to
exploiting the properties of platinum to construct responsive
systems. Platinum is being used as a key element to impart
responsiveness and advanced functionality to molecular archi-
tectures, creating opportunities for innovative applications in
areas such as sensing, drug delivery, and smart materials. In the
following sections, we discuss the advances made by our group
and others in which responsiveness to competitive species
(ligand exchange and insertion), and redox inputs are advan-
tageous for the design and realization of dynamic supramo-
lecular assemblies.
Responsiveness to competitive species
Ligand exchange. Ligand exchange processes are well known
for palladium complexes.
43
In contrast, their platinum
analogues are generally more stable and show higher kinetic
barriers and metal–ligand binding energies. There are a few
groups that have made efforts to ne-tune these parameters. On
the one hand, highly stable Pt complexes have been prepared
using strongly coordinating chelating ligands, e.g. ethylenedi-
amines, which prevent ligand exchange under ambient
conditions.
44–46
Other examples (vide infra) include more labile
structures that allow exchange under milder conditions, which
is advantageous in the design of responsive supramolecular
assemblies.
In the early 2000s, the Lusby group recognized the impor-
tance of achieving switchable supramolecular assemblies via
ligand exchange to advance the design of molecular ratchets
Fig. 1 Cartoon representation of some platinum-centered responses
that have been incorporated into supramolecular assemblies.
432 |Chem. Sci.,2024,15,431–441 © 2024 The Author(s). Published by the Royal Society of Chemistry
Chemical Science Perspective

and articial molecular machines. They relied on platinum
since greater thermodynamic biases can be introduced between
two switchable states in comparison to their palladium
counterparts.
47–49
Fig. 2a shows one of the systems studied by
the Lusby group.
50
Complex 1consists of a tridentate ligand (2,6-diphenylpyr-
idine), a Pt
II
center, and an ancillary 4-dimethylaminopyridine
(DMAP) ligand. Compound 1is stable in solution but undergoes
rapid transformation upon adding a Brønsted-Lowry acid.
Addition of p-toluenesulfonic acid selectively cleaves a C–Pt
bond, protonating and releasing a phenyl ring from the metal
complex. The resulting vacant coordination site at the Pt center
is rapidly lled by p-toluenesulfonate to yield compound 2
(Fig. 2a). Based on the solid-state structures of 1and 2(Fig. 2b),
it is suggested that this process is driven by an increase in the
binding energy of the C–Pt bond upon acidication, which
correlates well with a decrease in the d
C–Pt
, from 2.056 Å to 1.955
Å for 1and 2, respectively. This process is reversible and the
addition of base (e.g.,K
2
CO
3
) to a solution of 2quickly regen-
erates 1. The excellent conversion ratios of the forward (>70%)
and backward (>80%) reactions make this a promising platform
from which to build more complex structures.
The transformation of 1to 2is an example of partial ligand
displacement, in which neither the tridentate nor the ancillary
ligands are exchanged. In fact, both the addition of acid (which
activates the compound for exchange) and the presence of
a competitive ligand are required to observe exchange. For
example, complex 3is stable in the presence of 4(a bidentate
ligand), but rapidly converts to 5when acid is added (Fig. 2c).
51
Acid leads to partial displacement of the cyclic tridentate ligand,
followed by exchange (2,6-lutidine to 4) driven by the chelate
effect of the competing ligand. The resulting compound has
a threaded geometry in which both the ring and linear moieties
are linked by a Pt
II
centre. Furthermore, this transformation is
accompanied by (i) a change in the charge of the complex, with
3being neutral and 5being positively charged, and (ii) a change
in the binding mode: 3has one monodentate and one tridentate
ligand (3 + 1), while 4has two bidentate ligands (2 + 2). This
process is reversible and 3can be recovered from 5by addition
of base.
Fig. 2 Lusby's responsive platform. (a) Reversible transformation of 1into 2through acid–base stimuli. (b) Solid-state structures of 1and 2as
determined by SCXRD. (c) Synthesis of threaded complex 5by reversible ligand exchange. (d) pH-Responsive behaviour of complex 6to yield 7.
(e) Assembly of metal–organic structures 8and 10 using the exchange-active precursor 7. TsOH =toluenesulfonic acid; R =p-C
6
H
4
CH
3.
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 433
Perspective Chemical Science

The complexity of the system is easily increased by changing
the ancillary ligands. For example, if 4,4
′
-bipyridine (4,4
′
-bipy) is
used instead of DMAP in complex 1, the dinuclear structure 6is
obtained (Fig. 2d). Addition of acid to 6generates 7(Fig. 2d),
which is activated for exchange.
50
The subsequent addition of
4,4
′
-bipy displaces the coordinated sulfonate ligand to give
a metal–organic macrocycle (8, Fig. 2e). This structure has four
4,4
′
-bipy pillars and four Pt
II
corners, all supporting a multi-
charged, square-shaped molecule. Similarly, when the activated
structure 7is treated with the tritopic ligand 9, cage 10 spon-
taneously forms (Fig. 2e). As expected, all these processes are
reversible. The addition of base triggers the dissociation of the
superstructures and yields the starting material 6(inactive for
exchange).
This platform illustrates the potential of responsive Pt
complexes to reversibly generate metal–organic structures
through hierarchical subcomponent assembly. This also opens
other interesting avenues of exploration. For example, (i) the
transformation of 6into 8and 10 occurs with a change in
electrostatic charge, which may be advantageous to tune the
solubility of the superstructures and their host performance;
and (ii) the obtained cyclometalated assemblies are emissive,
and pairing this with the neutralizing anions may lead to
intriguing applications in aggregation-induced emission
(AIE),
52
circularly polarized luminescence (CPL), and
optoelectronics.
Ligand exchange has also been explored to switch between
macrocycles of different nuclearity using acetylide-based
molecules. Trans-Pt
II
acetylide complexes with triphenylphos-
phine ancillary ligands have a linear structure, whereas their cis
analogues have a 90° bent conformation.
53
These isomeric
forms can be interchanged by switching the phosphine ligands
(Scheme 1a). The Yang group took advantage of this property to
construct a structurally switchable assembly.
54
They designed
a pyridine-containing trans-Pt
II
acetylide ligand (11) that reacts
with 12 (Scheme 1b) to form macrocycle 13.
Interestingly, treatment of compound 13 with cis-1,2-bis(di-
phenylphosphino)ethylene (14) causes ligand exchange from
triphenylphosphine to 14, bending all pillars from 180° to
nearly 90°. This in turn collapses 13 to form a new rhomboidal
macrocycle (15, Scheme 1b). Considering that triethylphos-
phine (16) is a stronger electron-donating ligand, its addition to
the medium displaces 14 from the rhombus and reshapes the
macrocycle back into a hexagon (17).
54
This approach illustrates an elegant strategy for controlling
the shape of cyclic molecules, which has proven useful for the
creation of polymer-anchored structures while maintaining
good reactivity and processability. For example, it is possible to
switch between macrocycles with four and six polymer chains
covalently anchored at their vertices, which affects the physi-
cochemical properties of the materials and their on-surface self-
assembly. Similarly, polymer anchoring with this class of met-
allomacrocycles has been achieved by host–guest interactions
alone, with the added advantage of controlling polymer chain
unanchoring by degradation of the Pt-containing macrocycles.
55
Exchange on Pt
II
acetylide complexes has also been used to
make other classes of supramolecular structures, including
helicates and linear polymers, enabling dynamic behaviour and
reversible structural changes.
56–59
In principle, this strategy
could also be useful to control the size and shape of nano/
micrometre-sized particles while maintaining the intrinsic
porosity of the materials.
In a different example, the Mirkin lab used the weak-link
approach
60
to modulate the cavity size of a Pt containing cav-
itand. Weak-link approach complexes are typically composed of
hemilabile phosphinoalkyl-chalcoether
61
(or amine,
62
or car-
bene
63
) ligands and d
8
transition metals (e.g.,Rh
I
,Pd
II
or Pt
II
).
These molecules can be switched between rigid, condensed
species and exible, open complexes via the abstraction and
introduction of a small molecule (or elemental anion) that
displaces the metal–X (weak-link) interaction, while leaving the
metal–P (strong-link) interaction intact. This is illustrated in
Scheme 1 Switchable cyclic structures through ligand exchange. (a) Exchange of ancillary ligands in Pt acetylide complexes. (b) Precursors used
for the assembly of a hexagonal macrocycle and reshaping of macrocycle 13 into 15 and 17 via ligand exchange.
434 |Chem. Sci.,2024,15,431–441 © 2024 The Author(s). Published by the Royal Society of Chemistry
Chemical Science Perspective

Scheme 2a, where complex 18 (condensed, rigid form) trans-
forms into a partially open analogue (19) and nally into 20, the
fully open and exible form of the system. The process is
reversible, so 20 reverts to 18 upon chloride abstraction.
64
This chemistry was cleverly incorporated in the design of
a responsive calixarene compound.
65
This compound (21)
contains a Pt node that blocks the opening of the host, making
it ineffective for guest recognition (Scheme 2b). However, the
addition of chloride eliminates the weak-link and generates
a new species (22) with a larger opening (Scheme 2b). It was
shown that 21 is inactive as a host, while 22 can incorporate
pyridine N-oxide into its pocket with a tight t. It is noteworthy
that Cl
−
abstraction from 22 reforms 21 and causes guest
ejection. Conversion of 21 to 22 and back to 21 can be repeated
several times with delity of guest uptake/ejection. Given that
21 has two weak-links, it was also shown that both can be
eliminated by introducing strong electron-donating ligands
such as CN
−
, yielding compound 23 (Scheme 2b), which has the
largest opening of the three species and is thus able to
accommodate a larger guest, such as N-methylpyridinium, in its
cavity. Compounds 21 and 22 show no binding to this guest.
The weak-link approach is a powerful tool not only for
reversibly controlling the shape of molecular containers, but
also for producing responsive heteroleptic complexes, metal-
lopolymers, redox-responsive structures, metallomacrocycles
and more.
66–69
The accessible synthesis and response to simple
ions also has important advantages over other strategies,
making it promising for incorporation into biologically
compatible systems and nanostructured materials. Coupling
this platform with supramolecular synthons that rely on non-
covalent interactions (e.g., H-bonding) could open interesting
new avenues for chemical discovery.
Ligand insertion. The Stang group has been a major
contributor to the eld of metallomacrocycle chemistry,
focusing on the use of Pt
II
nodes and pyridyl-containing ligands
to form cyclic structures.
70
In a seminal paper, they showed that
the reaction of cis-bis(phosphine)platinum(II) ditriate with
4,4
′
-bipy yields macrocycle 24 as the sole cyclic molecule
(Fig. 3a).
71
Following a similar strategy, many macrocyclic
structures have been reported to date,
72–79
demonstrating that
different shapes and pore sizes can be easily constructed from
readily available components.
More complex 3-D constructs can be assembled by using
non-linear linkers. For example, the Yan group showed that
ligand 25 (Fig. 3b) yields the triangular prism 26 when com-
plexed with a Pt
II
node (Fig. 3c).
80
As in many of the examples
Scheme 2 Weak-link approach. (a) Prototypical example of Mirkin
group's weak-link approach.
60
(b) Weak-link approach applied to the
opening/closing of a host's pocket.
Fig. 3 Ligand insertion for cage-to-cage transformation. (a) Classical
bipyridine-based square with Pt
II
corners (24). (b) Tetrapyridyl ligand 25
used in the construction of triangular prism 26 and cuboid cage 27. (c)
Fusion of cage 26 and macrocycle 24 to yield cage 27.
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 435
Perspective Chemical Science

shown above, the N–Pt bond in this compound is labile and,
thus, the ligands can be displaced when competitive species are
introduced into the system. More interestingly, Yan and
coworkers showed that this is still true when preformed mac-
rocycles are mixed together, resulting in reorganization of the
ligands to form a product in solution.
80
For example, the addi-
tion of 24 to a solution of 26 results in the fusion of the two
cyclic structures to form a new molecule (27, Fig. 3c) that
contains both ligands 4,4
′
-bipy and 25 in its backbone.
Although 24 is luminescent, the fused product 27 is not,
providing a macroscopic handle from which to probe molecular
rearrangement.
More sophisticated designs (e.g., using porphyrinoid linkers)
and uorescent sensors with rapid response to amino acids
have also been constructed using this type of ligand insertion
and fusion of preassembled structures.
81,82
Exploiting the
lability of the N–Pt bond is an interesting approach to induce
topological changes with precise molecular control and atom
economy. While challenges such as reversibility and limited
experimental conditions will continue to plague supramolec-
ular chemists, it is important to recognize that there are a vast
number of possibilities that can be exploited from this
approach. And this can lead to potential applications in cargo
delivery, sensing, bioimaging, and more.
Redox-active assemblies
Ligand reorganization. Cyclometalated Pt complexes with
phenylpyridine proligands were rst reported by von Zelewsky's
team, with compound 28 being the simplest of its class (Scheme
3a).
83
Aer their introduction, these compounds did not attract
much interest, perhaps because of their dull photophysical
properties in solution. Instead, some research groups focused
on the synthesis and redox reactivity of these complexes in the
hope of nding derivatives with more relevant properties for
applications.
84–89
These advances inspired us to use cyclometalated Pt
II
complexes as nodes in ring-shaped molecules.
90
In this context,
two important discoveries were crucial for the realization of our
system. First, Sanford et al. showed that oxidation of 28 with
iodobenzene dichloride (PhICl
2
) yields the Pt
IV
stereoisomers 29
and 30 (Scheme 3a).
91
Second, Rourke et al. found that phe-
nylpyridines can lead to the formation of partially cyclo-
metalated complexes, such as 31, which can also be oxidized to
form 32 (Scheme 3b) –the trans-N,Nstereoisomer of 29 and 30.
92
This rich stereochemistry and redox activity led our team to
wonder whether these species (e.g.,28) could be used to ring
close exible ligands while retaining their redox activity.
As a prototypical example, we synthesized proligand 33
(Scheme 3c), containing two phenylpyridine units bridged by
a tetraethylene glycol chain. This proligand can be ring-closed
to selectively generate macrocycles 34 and 35 (Scheme 3c).
They differ in oxidation state (Pt
II
vs. Pt
IV
) and stereochemistry
(cis vs. trans).
90
Importantly, these two compounds can be
further processed. For example, treatment of 34 with PhICl
2
yields a new macrocycle (36, Scheme 3c) with Pt
IV
and trans-N,N
stereochemistry. In addition, both 35 and 36 can be reduced to
produce complex 37, which can nally be oxidized into Pt
IV
complex 38 (Scheme 3c).
It is noteworthy that while toggling between oxidation states
and geometries of the Pt nodes in macrocycles 34–38, the ligand
distribution around the metal center also changes, subtly
reshaping the cavity of the macrocycles. This alters the host
performance of the rings and modulates their binding affinity
towards a specic guest. Importantly, when the cavity of a host,
e.g. 37, is occupied by a guest, its redox reactivity is altered,
either by the introduced steric bulk, by the modication of the
electronic properties of the host, or by both.
This platform offers new possibilities for the construction of
other classes of macrocycles (with different sizes, shapes, and
chemistries) for applications in connement reactivity, enzy-
matic mimicry, and molecular machines. However, it is
important to recognize that there are challenges that may need
to be addressed for the more diverse and faster growth of these
Scheme 3 Redox-active unbridged phenylpyridine complexes for
ligand reorganization. (a) First homoleptic, phenylpyridine-based
cyclometalated Pt
II
complex (28). (b) Products (29 and 30) of the
oxidation of 28. (c) Partially cyclometalated complex 31 and its
oxidation product (32). (d) Ring-closing reactions of proligand 33 into
34 and 35 and their postprocessing to generate rings 36–38.
436 |Chem. Sci.,2024,15,431–441 © 2024 The Author(s). Published by the Royal Society of Chemistry
Chemical Science Perspective

cyclometalated Pt nodes. These include exploring milder
reduction conditions for the transformation of, for example, 35
and 36 to 37, and investigating the reverse transformation of 36
to 34.
Dimerization. In an effort to enable photoluminescence in
phenylpyridine-containing Pt complexes, a number of
researchers have designed oxygen- and nitrogen-bridged tetra-
dentate proligands. These structures have indeed yielded
phosphorescent materials with interesting properties both in
solution and in the solid state.
93–100
Our group has also explored
bridged Pt
II
complexes to exploit their photoluminescence and
chromic behavior. In particular, our studies have focused on the
cyclometalated complex 39 (Scheme 4a), which contains an
oxygen bridge and methoxy substituents to confer good solu-
bility. In addition to its interesting photophysical and chromic
properties, we found that complex 39 can be transformed into
complex 40 by oxidation with PhICl
2
(Scheme 4a).
101
Given the
efficiency of this conversion (fast and quantitative), we
wondered if 39 would allow us to access less exploited Pt
oxidation states (e.g.,41, Scheme 4a).
Although little studied, unbridged phenylpyridine Pt
II
complexes can be oxidized to Pt
III
species to form dimeric
structures held together by intermetallic bonds.
91,102
For
example, the oxidation of 28 with N-chlorosuccinimide (NCS)
yields compound 42 in high conversion (Scheme 4b). Based on
this observation, we tested the oxidation of 39 with NCS and
found that complex 41 is the only dimeric Pt
III
species formed in
solution (Scheme 4a), which is remarkable considering that the
synthesis of Pt
III
complexes typically requires bridging ligands
to bring two Pt centers together and direct the oxidation and
metal–metal bond formation.
103,104
The stability of 41 and its
ease of synthesis led us to believe that this redox-controlled
dimerization could be useful for designing new supramolec-
ular structures. Thus, following our research on complex 39,we
targeted compound 43 (Scheme 4c), a Pt
II
complex containing
a crown ether blended to its chelating backbone.
105
As expected, 43 shows interesting photoluminescent prop-
erties in response to guests occupying its cavity. This complex is
also redox active and can be converted to a Pt
IV
analog (44,
Scheme 4c) by oxidation with PhICl
2
. More importantly, we
realized that the oxidation of 43 into a Pt
III
dimer could generate
a new form of molecular container (45, Scheme 4d) consisting of
two crown ethers linked by a Pt–Pt bond. Indeed, treatment of
43 with NCS produces compound 45 almost quantitatively. It is
noteworthy that this host can trap large cations such as Rb
+
and
Cs
+
using its two crown ether moieties, which is helpful to
remove these cations, and potentially toxic ions, from
solution.
106
It is interesting to note that the oxidation of 43 can also be
achieved photochemically. Irradiation of the compound with
blue or white light, in the presence of dichloromethane
(CH
2
Cl
2
), triggers the conversion of the Pt
II
structure to its Pt
III
parent. This is caused by the photolysis of the solvent, which
generates reactive chlorine that is ultimately responsible for the
oxidation of the metal center. Prolonged illumination facilitates
the further conversion of 45 to its Pt
IV
counterpart (44). This
whole system can function as a trap-release mechanism,
allowing the capture and precipitation of ions from solution by
successive assembly and disassembly of the container through
Pt
II
to Pt
III
to Pt
IV
photooxidation. Notably, compound 44 can be
reduced back to its precursor (43).
We believe that intermetallic bonding, which can be
accessed through the reversible oxidation of Pt
II
complexes, has
great potential for exploration and could open a variety of
avenues for scientic investigation. In particular, we are inter-
ested in studying the electrochemical formation and revers-
ibility of intermetallic bonds. We believe that this platform
could provide access to materials with high performance guest
sequestration and recovery. In addition, the reversible nature of
the dimerization could provide a new way to glue components
together in polymeric structures and nanostructured materials.
Future directions
Platinum chemistry has seen signicant research interest for
many decades, with goals mainly revolving around novel
synthetic methodologies and applications of the resulting
Scheme 4 Redox-active oxygen-bridged phenylpyridine complexes
for oxidation-dimerization. (a) Prototypical Pt
II
cyclometalated
complex 39 and its oxidation products 40 and 41. (b) Synthesis of Pt
III
dimer 42 from 28. (c) Pt
IV
product 44 resulting from the oxidation of
43. (d) Molecular container 45 resulting from the oxidation-dimer-
ization of complex 43.
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 437
Perspective Chemical Science

complexes. With the advent of supramolecular chemistry,
platinum has emerged as a unique element from which func-
tion and responsive character can be harnessed. This is evi-
denced in part by the examples described in this Perspective,
which only scratch the surface of the many possibilities that can
be uncovered when decades of Pt research intertwine with
concepts from supramolecular chemistry, materials chemistry,
systems chemistry, and nanotechnology.
Platinum's electronic properties, electroactivity, chromic
behaviour, redox reactivity, photoreactivity, and intermetallic
interactions make it a unique element from which to program
responsiveness into more functional and intricate molecules
and materials. The platforms described here can already serve
as inspiration for the design and fabrication of new platinum-
based supramolecular assemblies. For example, the Lusby
group's system could be used to synthesize quasirotaxanes
(interlocked molecules in which a threading linear molecule is
covalently linked to a ring) and molecular shuttles (Scheme
5a).
51
The design of complementary threads and macrocycles
could allow the assembly of metal–organic interlocked mole-
cules with switchable states that could differ in luminescence or
catalytic activity.
107
Given the unique properties of platinum and its potential in
supramolecular chemistry, it would also be plausible to use it in
the construction of molecular machines. One specic example
worth exploring is the case of Pt
III
dimers. Research has shown
that these structures have free rotation about the Pt–Pt bond;
see for example one of the rst Pt
III
dimers reported by Willis in
the 1990s
108
(Scheme 5b). This rotation could potentially be
controlled or modulated by the introduction of specically
designed ligands. Several factors support the idea of using these
Pt dimers in the design of molecular rotors/motors. First, the
synthesis of these complexes is relatively straightforward.
Second, they exhibit a balance of stability and dynamism,
ensuring they remain intact under various conditions, but still
allowing for their functional mobility. These characteristics
make them promising candidates as hinges to be incorporated
into molecular rotors (as depicted in Scheme 5b). An additional
advantage of these Pt
III
dimers is the potential to form them
using photochemical methods. Using light as a stimulus has
advantages, particularly due to its non-invasive nature. This
means it can be used to trigger specic reactions without
causing undesired side effects or damage to the surrounding
environment. Moreover, the ability to disassemble these struc-
tures on demand provides an added layer of control, further
highlighting their potential as building blocks for molecular
machinery.
Richard J. Puddephatt once made an important observation:
“Supramolecular chemistry and the chemistry of alkyl deriva-
tives of the transition metals [platinum] are both topics of
considerable current interest, but the combination of the two
elds is still underdeveloped. The challenges are, in large part,
experimental in nature”.
109
We can further extend this to
metalated platinum systems in general. In light of this, there is
a pressing need to draw on the skills and innovation of synthetic
chemists. By doing so, we could pave the way for the develop-
ment of sophisticated supramolecular structures that effectively
exploit the unique properties of platinum. New possibilities and
applications in molecular science could be unlocked by this
fusion.
Scheme 5 Prototypical examples of the use of Pt responsive systems for the generation of (a) switchable quasirotaxanes and (b) molecular
rotors.
438 |Chem. Sci.,2024,15,431–441 © 2024 The Author(s). Published by the Royal Society of Chemistry
Chemical Science Perspective

Author contributions
M. A. S. and M. J. M. wrote the manuscript.
Conflicts of interest
The authors declare no conict of interest to declare.
Acknowledgements
The authors are grateful to their co-workers who have explored
supramolecular Pt chemistry in the MacLachlan group. MJM
acknowledges funding from NSERC (Discovery Grant) and
thanks the Canada Research Chairs Program. We also thank
WPI NanoLSI (Kanazawa, Japan) for support.
Notes and references
1 J. W. Steed and J. L. Atwood, Supramolecular Chemistry,
Wiley, 3rd edn, 2022.
2 T. F. A. De Greef, M. M. J. Smulders, M. Wolffs,
A. P. H. J. Schenning, R. P. Sijbesma and E. W. Meijer,
Chem. Rev., 2009, 109, 5687–5754.
3 F. Huang and E. V. Anslyn, Chem. Rev., 2015, 115, 6999–
7000.
4 A. J. Savyasachi, O. Kotova, S. Shanmugaraju,
S. J. Bradberry, G. M. ´
O'M´
aille and T. Gunnlaugsson,
Chem, 2017, 3, 764–811.
5 L. Brunsveld, B. J. B. Folmer, E. W. Meijer and
R. P. Sijbesma, Chem. Rev., 2001, 101, 4071–4098.
6 D. B. Amabilino, D. K. Smith and J. W. Steed, Chem. Soc.
Rev., 2017, 46, 2404–2420.
7 X. Chen, M. A. Würbser and J. Boekhoven, Acc. Mater. Res.,
2023, 4, 416–426.
8 M. A. C. Stuart, W. T. S. Huck, J. Genzer, M. Müller, C. Ober,
M. Stamm, G. B. Sukhorukov, I. Szleifer, V. V. Tsukruk,
M. Urban, F. Winnik, S. Zauscher, I. Luzinov and
S. Minko, Nat. Mater., 2010, 9, 101–113.
9 M. Wei, Y. Gao, X. Li and M. J. Serpe, Polym. Chem., 2017, 8,
127–143.
10 M. Mrinalini and S. Prasanthkumar, ChemPlusChem, 2019,
84, 1103–1121.
11 D. Yan, Z. Wang and Z. Zhang, Acc. Chem. Res., 2022, 55,
1047–1058.
12 Transition Metals in Supramolecular Chemistry, ed. J. P.
Sauvage, Wiley, 2008.
13 T. R. Cook, Y.-R. Zheng and P. J. Stang, Chem. Rev., 2013,
113, 734–777.
14 M. H.-Y. Chan and V. W.-W. Yam, J. Am. Chem. Soc., 2022,
144, 22805–22825.
15 J.-P. Sauvage, Angew. Chem., Int. Ed., 2017, 56, 11080–11093.
16 Z. Meng, F. Yang, X. Wang, W.-L. Shan, D. Liu, L. Zhang and
G. Yuan, Inorg. Chem., 2023, 62, 1297–1305.
17 D. E. Herbert, J. B. Gilroy, W. Y. Chan, L. Chabanne,
A. Staubitz, A. J. Lough and I. Manners, J. Am. Chem. Soc.,
2009, 131, 14958–14968.
18 V. Brega, M. Zeller, Y. He, H. P. Lu and J. K. Klosterman,
Chem. Commun., 2015, 51, 5077–5080.
19 M. Yamashina, Y. Tanaka, R. Lavendomme, T. K. Ronson,
M. Pittelkow and J. R. Nitschke, Nature, 2019, 574, 511–515.
20 L. Li, L. Yang, X. Li, J. Wang, X. Liu and C. He, Inorg. Chem.,
2021, 60, 8802–8810.
21 L. Li, Y. Cong, L. He, Y. Wang, J. Wang, F.-M. Zhang and
W. Bu, Polym. Chem., 2016, 7, 6288–6292.
22 O. S. Wenger, Chem. Rev., 2013, 113, 3686–3733.
23 X. Zhang, Z. Chi, Y. Zhang, S. Liu and J. Xu, J. Mater. Chem.
C, 2013, 1, 3376–3390.
24 A. Kobayashi and M. Kato, Eur. J. Inorg. Chem., 2014, 2014,
4469–4483.
25 V. W.-W. Yam, V. K.-M. Au and S. Y.-L. Leung, Chem. Rev.,
2015, 115, 7589–7728.
26 P. Xue, J. Ding, P. Wang and R. Lu, J. Mater. Chem. C, 2016,
4, 6688–6706.
27 M. Yoshida and M. Kato, Coord. Chem. Rev., 2018, 355, 101–
115.
28 B. Li, H.-T. Fan, S.-Q. Zang, H.-Y. Li and L.-Y. Wang, Coord.
Chem. Rev., 2018, 377, 307–329.
29 M. Yoshida and M. Kato, Coord. Chem. Rev., 2020, 408,
213194.
30 B. Li, Z. Liang, H. Yan and Y. Li, Mol. Syst. Des. Eng., 2020, 5,
1578–1605.
31 M. A. Soto, R. Kandel and M. J. MacLachlan, Eur. J. Inorg.
Chem., 2021, 2021, 894–906.
32 J. Emsley, Nature's Building Blocks: An A–Z Guide to The
Elements, Oxford University Press, 2001.
33 J. Emsley, The Elements, Clarendon Press, 1998.
34 T. Bell, The Properties and Applications of Platinum,https://
www.thoughtco.com/metal-prole-platinum-2340149,
accessed 26 September 2023.
35 R. Sharma, V. J. Singh and P. A. Chawla, Anti-Cancer Agents
Med. Chem., 2022, 22, 821–835.
36 T. K. Meister, K. Riener, P. Gigler, J. Stohrer,
W. A. Herrmann and F. E. Kühn, ACS Catal., 2016, 6,
1274–1284.
37 R. J. Spiegel, Transp. Res. D: Transp. Environ., 2004, 9, 357–
371.
38 C. Cebri´
an and M. Mauro, Beilstein J. Org. Chem., 2018, 14,
1459–1481.
39 C. E. Holloway and M. Melnik, Rev. Inorg. Chem., 2005, 25,
93–270.
40 E. Lu and S. T. Liddle, in Molecular Metal–Metal Bonds:
Compounds, Synthesis, Properties, ed. S. T. Liddle, Wiley,
2015, ch. 10, pp. 352–395.
41 R. H. Crabtree and H. Torrens, Palladium: Inorganic &
Coordination Chemistry, in Encyclopedia of Inorganic
Chemistry, Wiley, 2006.
42 B. Z. Momeni and A. S. Abd-El-Aziz, Coord. Chem. Rev., 2023,
486, 215113.
43 A. C. Alb´
eniz and P. Espinet, Palladium: Inorganic &
Coordination Chemistry, in Encyclopedia of Inorganic
Chemistry, Wiley, 2006.
44 F. Ibukuro, T. Kusukawa and M. Fujita, J. Am. Chem. Soc.,
1998, 120, 8561–8562.
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 439
Perspective Chemical Science

45 M. Yoshizawa, K. Ono, K. Kumazawa, T. Kato and M. Fujita,
J. Am. Chem. Soc., 2005, 127, 10800–10801.
46 H. Takezawa, K. Shitozawa and M. Fujita, Nat. Chem., 2020,
12, 574–578.
47 S. J. Pike and P. J. Lusby, Chem. Commun., 2010, 46, 8338–
8340.
48 O. Chepelin, J. Ujma, P. E. Barran and P. J. Lusby, Angew.
Chem., Int. Ed., 2012, 51, 4194–4197.
49 J. Ujma, M. De Cecco, O. Chepelin, H. Levene, C. Moffat,
S. J. Pike, P. J. Lusby and P. E. Barran, Chem. Commun.,
2012, 48, 4423–4425.
50 P. J. Lusby, P. Müller, S. J. Pike and A. M. Z. Slawin, J. Am.
Chem. Soc., 2009, 131, 16398–16400.
51 D. Sooksawat, S. J. Pike, A. M. Z. Slawin and P. J. Lusby,
Chem. Commun., 2013, 49, 11077–11079.
52 N. Liu, T. Lin, M. Wu, H.-K. Luo, S.-L. Huang and
T. S. A. Hor, J. Am. Chem. Soc., 2019, 141, 9448–9452.
53 K. Campbell, R. McDonald, M. J. Ferguson and
R. R. Tykwinski, J. Organomet. Chem., 2003, 683, 379–387.
54 W. Zheng, W. Wang, S.-T. Jiang, G. Yang, Z. Li, X.-Q. Wang,
G.-Q. Yin, Y. Zhang, H. Tan, X. Li, H. Ding, G. Chen and
H.-B. Yang, J. Am. Chem. Soc., 2019, 141, 583–591.
55 Z. Zhang, J. Zhao, Z. Guo, H. Zhang, H. Pan, Q. Wu, W. You,
W. Yu and X. Yan, Nat. Commun., 2022, 13, 1393.
56 Y. Furusho, Y. Tanaka and E. Yashima, Org. Lett., 2006, 8,
2583–2586.
57 M. Horie, N. Ousaka, D. Taura and E. Yashima, Chem. Sci.,
2015, 6, 714–723.
58 Y. Miyagi, T. Ishida, M. Marumoto, N. Sano, T. Yajima and
F. Sanda, Macromolecules, 2018, 51, 815–824.
59 T. Ishida, T. Sotani, N. Sano, H. Sogawa and F. Sanda,
Macromolecules, 2022, 55, 309–321.
60 J. R. Farrell, C. A. Mirkin, I. A. Guzei, L. M. Liable-Sands and
A. L. Rheingold, Angew. Chem., Int. Ed., 1998, 37, 465–467.
61 M. S. Rosen, A. M. Spokoyny, C. W. Machan, C. Stern,
A. Sarjeant and C. A. Mirkin, Inorg. Chem., 2011, 50, 1411–
1419.
62 H. J. Yoon, J. Kuwabara, J.-H. Kim and C. A. Mirkin, Science,
2010, 330,66–69.
63 M. S. Rosen, C. L. Stern and C. A. Mirkin, Chem. Sci., 2013,
4, 4193–4198.
64 R. D. Kennedy, C. W. Machan, C. M. McGuirk, M. S. Rosen,
C. L. Stern, A. A. Sarjeant and C. A. Mirkin, Inorg. Chem.,
2013, 52, 5876–5888.
65 J. Mendez-Arroyo, J. Barroso-Flores, A. M. Lifschitz,
A. A. Sarjeant, C. L. Stern and C. A. Mirkin, J. Am. Chem.
Soc., 2014, 136, 10340–10348.
66 A. M. Lifschitz, M. S. Rosen, C. M. McGuirk and
C. A. Mirkin, J. Am. Chem. Soc., 2015, 137, 7252–7261.
67 A. I. d'Aquino, Z. S. Kean and C. A. Mirkin, Chem. Mater.,
2017, 29, 10284–10288.
68 H. F. Cheng, A. I. d'Aquino, J. Barroso-Flores and
C. A. Mirkin, J. Am. Chem. Soc., 2018, 140, 14590–14594.
69 B. D. Coleman, A. I. d'Aquino, Z. Kean, Y. Wang,
J. K. Hedlund Orbeck, C. L. Stern and C. A. Mirkin,
Polyhedron, 2022, 227, 116116.
70 Y. Sun, C. Chen, J. Liu and P. J. Stang, Chem. Soc. Rev., 2020,
49, 3889–3919.
71 P. J. Stang, D. H. Cao, S. Saito and A. M. Arif, J. Am. Chem.
Soc., 1995, 117, 6273–6283.
72 P. S. Mukherjee, N. Das, Y. K. Kryschenko, A. M. Arif and
P. J. Stang, J. Am. Chem. Soc., 2004, 126, 2464–2473.
73 S. Shanmugaraju, A. K. Bar, K.-W. Chi and P. S. Mukherjee,
Organometallics, 2010, 29, 2971–2980.
74 J.-L. Zhu, L. Xu, Y.-Y. Ren, Y. Zhang, X. Liu, G.-Q. Yin,
B. Sun, X. Cao, Z. Chen, X.-L. Zhao, H. Tan, J. Chen, X. Li
and H.-B. Yang, Nat. Commun., 2019, 10, 4285.
75 H. Zhu, Q. Li, B. Shi, H. Xing, Y. Sun, S. Lu, L. Shangguan,
X. Li, F. Huang and P. J. Stang, J. Am. Chem. Soc., 2020, 142,
17340–17345.
76 S. Lv, Y. Miao, D. Zheng, X. Li, D. Liu and F. Song, Mol.
Pharm., 2021, 18, 1229–1237.
77 Y. Yin, Z. Chen, R.-H. Li, C. Yuan, T.-Y. Shao, K. Wang,
H. Tan and Y. Sun, Inorg. Chem., 2021, 60, 9387–9393.
78 N. Wang, J. Zhao, Q. Xu, P. Xing, S. Feng, X.-D. Xu and
H.-B. Yang, J. Mater. Chem. C, 2022, 10, 13860–13870.
79 G. Dur´
an-Sampedro, E. Y. Xue, M. Moreno-Simoni,
C. Paramio, T. Torres, D. K. P. Ng and G. de la Torre, J.
Med. Chem., 2023, 66, 3448–3459.
80 G. Li, Z. Zhou, C. Yuan, Z. Guo, Y. Liu, D. Zhao, K. Liu,
J. Zhao, H. Tan and X. Yan, Angew. Chem., Int. Ed., 2020,
59, 10013–10017.
81 Y. Shi, I. S´
anchez-Molina, C. Cao, T. R. Cook and P. J. Stang,
Proc. Natl. Acad. Sci. U. S. A., 2014, 111, 9390–9395.
82 M. Zhang, M. L. Saha, M. Wang, Z. Zhou, B. Song, C. Lu,
X. Yan, X. Li, F. Huang, S. Yin and P. J. Stang, J. Am.
Chem. Soc., 2017, 139, 5067–5074.
83 L. Chassot, E. Mueller and A. von Zelewsky, Inorg. Chem.,
1984, 23, 4249–4253.
84 D. S. Black, G. B. Deacon and G. L. Edwards, Aust. J. Chem.,
1994, 47, 217–227.
85 M. M. Mdleleni, J. S. Bridgewater, R. J. Watts and P. C. Ford,
Inorg. Chem., 1995, 34, 2334–2342.
86 J.-Y. Cho, K. Y. Suponitsky, J. Li, T. V. Timofeeva, S. Barlow
and S. R. Marder, J. Organomet. Chem., 2005, 690, 4090–
4093.
87 C. P. Newman, K. Casey-Green, G. J. Clarkson,
G. W. V. Cave, W. Errington and J. P. Rourke, Dalton
Trans., 2007, 3170–3182.
88 W. Jiang and C. A. Schalley, Beilstein J. Org. Chem., 2010, 6,
14.
89 K. R. Neff, K. Basemann, N. Romano, J. J. Becker and
M. R. Gagn´
e, Organometallics, 2023, 42, 2177–2184.
90 M. A. Soto, V. Carta, I. Suzana, B. O. Patrick, F. Lelj and
M. J. MacLachlan, Angew. Chem., Int. Ed., 2023, 62,
e202216029.
91 S. R. Whiteld and M. S. Sanford, Organometallics, 2008, 27,
1683–1689.
92 J. Mamtora, S. H. Crosby, C. P. Newman, G. J. Clarkson and
J. P. Rourke, Organometallics, 2008, 27, 5559–5565.
93 D. A. K. Vezzu, J. C. Deaton, J. S. Jones, L. Bartolotti,
C. F. Harris, A. P. Marchetti, M. Kondakova, R. D. Pike
and S. Huo, Inorg. Chem., 2010, 49, 5107–5119.
440 |Chem. Sci.,2024,15,431–441 © 2024 The Author(s). Published by the Royal Society of Chemistry
Chemical Science Perspective

94 H. Fukagawa, T. Shimizu, H. Hanashima, Y. Osada,
M. Suzuki and H. Fujikake, Adv. Mater., 2012, 24, 5099–
5103.
95 E. Turner, N. Bakken and J. Li, Inorg. Chem., 2013, 52, 7344–
7351.
96 S. Huo, Chem. Rec., 2018, 18, 1583–1595.
97 I. Allison, H. Lim, A. Shukla, V. Ahmad, M. Hasan,
K. Deshmukh, R. Wawrzinek, S. K. M. McGregor,
J. K. Clegg, V. V. Divya, C. Govind, C. H. Suresh,
V. Karunakaran, K. N. Narayanan Unni, A. Ajayaghosh,
E. B. Namdas and S.-C. Lo, ACS Appl. Electron. Mater.,
2019, 1, 1304–1313.
98 T. Theiss, S. Buss, I. Maisuls, R. L´
opez-Arteaga, D. Brünink,
J. Kösters, A. Hepp, N. L. Doltsinis, E. A. Weiss and
C. A. Strassert, J. Am. Chem. Soc., 2023, 145, 3937–3951.
99 S. Buss, M. V. Cappellari, A. Hepp, J. Kösters and
C. A. Strassert, Chemistry, 2023, 5, 1243–1255.
100 J.-M. Kim, K. Cheong, J. Jiang, S. O. Jeon, W. P. Hong and
J. Y. Lee, Trends Chem., 2023, 5, 267–278.
101 M. A. Soto, V. Carta, R. J. Andrews, M. T. Chaudhry and
M. J. MacLachlan, Angew. Chem., Int. Ed., 2020, 59,
10348–10352.
102 T. Yamaguchi, O. Kubota and T. Ito, Chem. Lett., 2004, 33,
190–191.
103 J. J. Wilson and S. J. Lippard, Inorg. Chem., 2012, 51, 9852–
9864.
104 X. Wu, D.-G. Chen, D. Liu, S.-H. Liu, S.-W. Shen, C.-I. Wu,
G. Xie, J. Zhou, Z.-X. Huang, C.-Y. Huang, S.-J. Su, W. Zhu
and P.-T. Chou, J. Am. Chem. Soc., 2020, 142, 7469–7479.
105 M. A. Soto, V. Carta, M. T. Cano, R. J. Andrews, B. O. Patrick
and M. J. MacLachlan, Inorg. Chem., 2022, 61, 2999–3006.
106 M. A. Soto, M. T. Chaudhry, G. K. Matharu, F. Lelj and
M. J. MacLachlan, Angew. Chem., Int. Ed., 2023, 62,
e202305525.
107 D. A. Leigh, V. Marcos and M. R. Wilson, ACS Catal., 2014,
4, 4490–4497.
108 L. A. M. Baxter, G. A. Heath, R. G. Raptis and A. C. Willis, J.
Am. Chem. Soc., 1992, 114, 6944–6946.
109 R. J. Puddephatt, Dalton Trans., 2022, 51, 7011–7024.
© 2024 The Author(s). Published by the Royal Society of Chemistry Chem. Sci.,2024,15,431–441 | 441
Perspective Chemical Science