Self-assembled supramolecular clusters based on phosphines and coinage metals: Tetrahedra, helicates, and mesocates

Article abstract of DOI:10.1021/ic302840x

An array of coordination-driven supramolecular metal-ligand clusters has been synthesized using polytopic phosphine ligands and coinage metals (Cu ⁺, Ag⁺, Au⁺). Rigid 3-fold or 2-fold symmetric phosphine ligands have been prepared: 1,3,5-tris((4-(diphenylphosphino)ethynyl) phenyl)benzene) (tppepb, L¹), 1,4-bis((diphenylphosphino)ethynyl) benzene (1,4-dppeb, L²), 1,3-bis((diphenylphosphino)ethynyl)benzene (1,3-dppeb, L³), 2,6-bis((diphenylphosphino)ethynyl)pyridine (2,6-dppep, L⁴), and 1,5-bis((diphenylphosphino)ethynyl)naphthalene (1,5-dppen, L⁵). Self-assembly of these ligands with coinage metals produces four different types of metal-ligand clusters, or in some cases coordination polymers, depending on number and relative geometry of the phosphine donor atoms. Supramolecular tetrahedral clusters of the formula M ₄(L¹)₄I₄ (M = Cu⁺, Ag⁺, Au⁺) were obtained with the tppepb ligand, encapsulating solvent molecules (either CH₂Cl₂ or DMF) as guests within the central cavity of the clusters. The ligands 1,3-dppeb (L ³) and 2,6-dppep (L⁴) give achiral, triple-stranded, dinuclear mesocates with the formula M₂(L)₃I₂ (M = Cu⁺ or Au⁺). In contrast, the ligand 1,4-dppeb (L²) generates a triple-stranded, dinuclear helicate with Cu ⁺, but a coordination polymer with Au⁺ (both with the empirical formula M₂(L²)₃I₂). Finally, coordination polymers were obtained from 1,5-dppen (L⁵) with Cu⁺. The clusters have been fully characterized by single crystal X-ray crystallography, high-resolution mass spectrometry, ¹H NMR, and ³¹P NMR.

Full text of DOI:10.1021/ic302840x

Article
pubs.acs.org/IC
Self-Assembled Supramolecular Clusters Based on Phosphines and
Coinage Metals: Tetrahedra, Helicates, and Mesocates
Sang Ho Lim and Seth M. Cohen*
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
S
* Supporting Information
ABSTRACT: An array of coordination-driven supramolecular metal−ligand
clusters has been synthesized using polytopic phosphine ligands and coinage
metals (Cu+, Ag+, Au+). Rigid 3-fold or 2-fold symmetric phosphine ligands
have been prepared: 1,3,5-tris((4-(diphenylphosphino)ethynyl)phenyl)-
benzene) (tppepb, L1), 1,4-bis((diphenylphosphino)ethynyl)benzene (1,4-
dppeb, L2), 1,3-bis((diphenylphosphino)ethynyl)benzene (1,3-dppeb, L3),
2,6-bis((diphenylphosphino)ethynyl)pyridine (2,6-dppep, L4), and 1,5-bis-
((diphenylphosphino)ethynyl)naphthalene (1,5-dppen, L5). Self-assembly of
these ligands with coinage metals produces four different types of metal−
ligand clusters, or in some cases coordination polymers, depending on number
and relative geometry of the phosphine donor atoms. Supramolecular
tetrahedral clusters of the formula M4(L1)4I4 (M = Cu+, Ag+, Au+) were
obtained with the tppepb ligand, encapsulating solvent molecules (either
CH2Cl2 or DMF) as guests within the central cavity of the clusters. The ligands 1,3-dppeb (L3) and 2,6-dppep (L4) give achiral,
triple-stranded, dinuclear mesocates with the formula M2(L)3I2 (M = Cu+ or Au+). In contrast, the ligand 1,4-dppeb (L2)
generates a triple-stranded, dinuclear helicate with Cu+, but a coordination polymer with Au+ (both with the empirical formula
M2(L2)3I2). Finally, coordination polymers were obtained from 1,5-dppen (L5) with Cu+. The clusters have been fully
1
characterized by single crystal X-ray crystallography, high-resolution mass spectrometry, H NMR, and 31P NMR.
Hahn and co-workers is the preparation of helicates, mesocates,
and tetrahedra from bis(benzene-o-dithiol),11 tris(benzene-o-
dithiol),12 and mixed benzene-o-dithiolato/catecholato deriva-
tives.13 The Hahn group has also investigated cylinder-shaped
supramolecular structures combining polydentate N-hetero-
cyclic carbene (NHC), as softer carbon-based ligands, in
combination with coinage metal ions.14 Johnson and co-
workers have also used thiol-based ligands to obtain self-
assembled clusters based on As3+, Sb3+, Bi3+, and P3+.15
Among soft Lewis base ligands that could be used for these
assemblies, phosphines are particularly attractive, having played
crucial roles in the development of coordination chemistry and
homogeneous catalysis since the 1960s.16 Although phosphines
have been widely investigated in coordination chemistry,
particularly with late transition metals, their use as building
blocks in supramolecular clusters remains quite limited
compared to other N- and O-donor ligands. This may be due
to the bulky substituents and irregular shapes often associated
with phosphine ligands, which can lead to more complicated
geometries and lower predictability of forming well-defined
supramolecular assemblies.17 However, some supramolecular
assemblies have been described with phosphine ligands,2f,18
including many from the group of Puddephatt, who have
reported elegant examples of both discrete and infinite
INTRODUCTION
■
Supramolecular metal−ligand clusters, sometimes referred to as
metal−organic polyhedra (MOPs), have been an area of great
interest over the past few decades.1 These clusters combine
polydentate organic ligands and transition metals to form
elegant assemblies held together by reversible metal−ligand
bonds. The coordination preferences of the metal ion
combined with the directionality encoded in the ligand
geometry can direct the formation of clusters of varying
geometries. Supramolecular architectures including helicates,2
tetrahedra,3 octahedra,4 dodecahedra,5 cuboctahedra,6 and
many others7 have been obtained from these coordination-
driven self-assembly reactions. The laboratories of Fujita,
Raymond, Stang, and others have shown that these clusters
can demonstrate spectacular host−guest chemistry, including
molecular encapsulation and recognition,8 stabilization of
reactive molecules and intermediates,9 and cavity controlled
catalytic reactions.10 The majority of these clusters reported in
the literature involve metal ions coordinated by polydentate
ligands that utilize nitrogen and/or oxygen donor atoms.1
In light of the vast literature on these types of self-assembled
structures, it is somewhat surprising that relatively few
constructs have been assembled from soft Lewis base ligands,
such as those derived from second row heteroatoms (e.g., S, P,
etc.). These ligands would be expected to form stable
assemblies in conjunction with lower oxidation state metal
ions or metalloids (i.e., soft Lewis acids). One example from
Received: December 24, 2012
© XXXX American Chemical Society
A
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Scheme 1. Synthetic Scheme for Each of the Supramolecular Assemblies Obtained with Rigid Phosphine Ligands: M4(L1)4I4
Tetrahedron, M2(L2)3I2 Helicate, M2(L3)3I2 and M2(L4)3I2 Mesocates, and [M2(L2)3I2]n and [M2(L5)3I2]n Coordination
Polymers
assemblies.18a The groups of Yip18b and James18c have also
prepared self-assembled structures from phosphine ligands with
coinage metals Ag+ or Au+ to obtain rings, helicates, and a
small, adamantoid-shaped cluster. In one instance, Yip and co-
workers obtained a homoleptic, trinuclear ring structure
composed of three bridging 9,10-bis(diphenylphosphino)-
Phosphine ligands have many attractive features for use in
supramolecular clusters, including the applicability of 31P NMR
spectroscopy, interesting luminescent properties (with certain
metal ions),18d,19 and their relevance to organometallic
chemistry and homogeneous catalysis.20 Also, the softer
donor character of phosphines may produce more stable
clusters because of the additional covalency in the bonding with
lower oxidation state metal ions. In light of these features, we
previously reported the first phosphine-based supramolecular
tetrahedra clusters,21 which were made by the combination of
coinage metals Cu+, Ag+, or Au+ with the rigid, 3-fold
symmetric ligand 1,3,5-tris((4-(diphenylphosphino)ethynyl)-
−
anthracene ligands and three Au+ ions with a ClO4 anion
guest in the center.18b In another example, the group of James
obtained the M6L4 “superadamantoid” cage [Ag6(CH3C-
(CH2PPh2)3)4(OTf)4](OTf)2 using a flexible, triphosphine
CH3C(CH2PPh2)3 ligand.18c
B
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
benzene) (tppeb). These tetrahedra were found to be
1
persistent in solution as shown by ESI-MS, H NMR, and 31P
NMR analysis.
The aforementioned Platonic clusters were generated by the
formation of 4-coordinate, tetrahedral metal ions centers with
three phosphine donors and a coordinated iodide ion. The
persistence of this coordination motif across all three coinage
metals (i.e., Cu+, Ag+, Au+) suggested that related clusters could
be accessed with a variety of ligands, metal ions, and
counterions. Therefore, we sought to prepare other phosphine
ligands that would produce supramolecular clusters of different
symmetry and sizes. Herein, we show that the combination of
di- and tritopic phosphine ligands and coinage metals can form
a variety of supramolecular cluster motifs including tetrahedral
M4L4I4 clusters, dinuclear M2L3I2 triple-stranded helicates,
dinuclear M2L3I2 triple-stranded mesocates, and [M2L3I2]n
coordination polymers. Soluble species have been characterized
Figure 1. Crystal structures of the M4(L1)4I4 tetrahedra. Each cluster is
shown with the ligand as sticks and the M+ ions and iodide anions as
colored spheres: Cu+ (dark green), Ag+ (light blue), Au+ (yellow), and
I− (red).
metal-phosphine and metal-iodide bond distances are in good
agreement with those of metal-phosphine and metal-iodide
bonds in other four-coordinate phosphine-based M+ iodide
complexes.24 The ligand design and cluster architecture enforce
that all of the metal ions adopt a single, identical chiral
configuration, making the overall cluster chiral. However, as
expected, both enantiomers of the cluster are present in the
crystal related by inversion symmetry. Each cluster has a
distinct packing pattern (Supporting Information, Figure S1),
with the Au4(L1)4I4 cluster showing strong π−π stacking
interactions (3.68 Å) between the central benzene rings of the
L1 ligands of adjacent clusters (no such interactions are
observed for the Cu+ and Ag+ clusters in the solid state). One
ligand of Au4(L1)4I4 is distorted inwardly, making the cavity
volume slightly reduced compared to other clusters (322, 326,
and 312 Å3 for Cu+, Ag+, and Au+, respectively).25
1
in solution by high-resolution mass spectrometry, H NMR,
and 31P NMR. The present study represents one of the most
extensive studies on phosphine-based supramolecular architec-
tures and shows the substantial potential of such ligands to
participate in self-assembled coordination clusters.
RESULTS AND DISCUSSION
■
Ligand Synthesis. The synthesis of the ligands, tppepb
(L1), 1,4-dppeb (L2), 1,3-dppeb (L3), 2,6-dppep (L4), and 1,5-
dppen (L5) was achieved using literature procedures (Support-
ing Information, Schemes S1 and S2). Using standard
Sonogashira coupling methods,22 the aryl halides 1,3,5-tris(4-
bromophenyl)benzene, 1,4-dibromobenzene, 2,6-dibromopyr-
idine, and 1,5-diiodonaphthalene were combined with
trimethylsilyl acetylene in the presence of PdCl2(PPh3)2/CuI
or Pd(PPh3)4/CuI catalyst. The corresponding terminal alkynes
were obtained by the hydrolysis of the TMS groups under basic
conditions. Adapting the method of Constable et al.,23 the
corresponding terminal alkyne compounds were treated with
nBuLi and Ph2PCl in freshly dried tetrahydrofuran (THF) to
give reasonable yields of the desired ligands L1−L5.
In our earlier communication,21 the M4(tppeb)4I4 (M = Cu+,
Ag+, and Au+) tetrahedra showed no evidence of guest binding,
presumably because of the rather small cavity volume (129,
133, 135 Å3 for Cu+, Ag+, Au+, respectively). In contrast, the
tetrahedral clusters presented here have relatively large cavity
volumes (vide supra) and subsequently one CH2Cl2 solvent
molecule is located inside the cavity in all cases. Based on
intermolecular distances, there are close C−H···π contacts
(∼2.68, 2.54, 2.52 Å for Cu+, Ag+, Au+, respectively) between
the aromatic walls of the cluster and the hydrogen atoms of the
solvate molecule (CH2Cl2) within the cluster cavity. Other
small molecules could be encapsulated; for example when
crystallized from hot DMF, a DMF solvent molecule was found
inside the cavity of Ag4(tppeb)4I4 (Figure 2, Supporting
Information,Table S1). However, no close contacts were
observed between encapsulated DMF and the aromatic walls
of the cluster. It is unclear at this stage what the driving force
Tetrahedral Clusters M4(L1)4I4 (M = Cu+, Ag+, and Au+).
A summary of all of the supramolecular clusters obtained is
provided in Scheme 1. To obtain expanded, tetrahedral clusters,
a 1:1 suspension of a coinage metal iodide and the ligand L1
were combined in CH2Cl2 for 30 min at room temperature,
resulting in the formation of a colorless solution. This solution
was filtered and evaporated to dryness. Slow diffusion of Et2O
into a saturated solution of the isolated powders in CH2Cl2
gave colorless crystals in high yield (∼80% from the powder)
within a few days. Alternatively, crystals could also be prepared
from a saturated (hot) DMF solution of the powder, upon
standing at room temperature for approximately one week. The
X-ray crystal structures of all three tetrahedral clusters,
crystallized from CH2Cl2, are shown in Figure 3 (Supporting
Information, Table S1). All of the clusters crystallize in
centrosymmetric space groups and generally are very similar
(Figure 1). In all of the clusters, the phosphine ligands occupy a
pyramidalized, 3-fold symmetric coordination around the M+
coinage metal. The overall geometry of the M+ ions is
tetrahedral, with the apical site occupied by a tightly bound
iodide ligand. The average metal-phosphine distances in the
clusters are 2.28, 2.52, and 2.39 Å in the Cu+, Ag+, and Au+
clusters, respectively. Similarly, the average metal-iodide
distances are 2.56, 2.75, and 2.82 Å in the Cu+, Ag+, and Au+
clusters, respectively (Supporting Information, Table S4). The
Figure 2. Crystal structure of Ag4(L1)4I4 with either encapsulated
CH2Cl2 (left) or DMF (right). The cluster geometry of Ag4(L1)4I4 is
highlighted by removing the phenyl groups and iodide ions, and
coloring each ligand differently. The Ag+ ions and the guest molecules
are shown in spacefilling representation.
C
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
1
Figure 3. Variable temperature H NMR spectra of Ag4(L1)4I4 in CD2Cl2.
Figure 4. High-resolution ESI-MS of Cu4(L1)4I4. The positive ion mode experimental (left), magnification of the [M−I]+ base peak (middle), and
the simulated [M−I]+ (right) spectra are shown.
for encapsulation of these molecules is, but it may simply
involve weak dispersion forces.
To examine their persistence in solution, H NMR and ESI-
M4(tppeb)4I4, which were fully assigned by a COSY NMR
experiment.21 Unfortunately, numerous attempts to obtain
1
1
variable temperature H NMR of the other clusters (Cu+ and
Au+), using several different deuterated solvents (CDCl3, d6-
DMF, d6-acetone etc.), did not produce well-resolved spectra
(data not shown).
MS analysis of these clusters was performed. Unlike the
previously reported M4(tppeb)4I4 tetrahedra, a spectrum of
Ag4(L1)4I4 collected at room temperature (25 °C) shows
several sharp signals arising from the central benzene ring and
1,3,5-phenyl groups and very broad signals from the phenyl
groups on phosphorus atoms (Figure 3). The singlet at 7.29
ppm (Ha) and doublets at 6.86 and 7.14 ppm (Hb and Hc) are
attributed to the central benzene ring and 1,3,5-phenyl groups
in L1, respectively. The broad signals of the phenyl protons are
attributed to dynamic motions. Variable temperature NMR
studies were performed (Figure 3), which showed that the
broad signals become more resolved as the temperature is
decreased down to −60 °C. In particular, proton signals at −60
°C indicate an asymmetry between the phenyl rings on each
phosphorus atom (two distinct environments for He′ and He″ at
δ = 7.01, 7.36 ppm; and for Hf′ and Hf″ at δ = 7.22, 7.66 ppm).
These signals were assigned based on the spectra of
31P NMR of the each cluster showed a distinct peak (δ =
7.73, −31.38, 7.99 ppm for Cu+, Ag+, and Au+ for respectively,
Supporting Information, Figure S2), and the peak of the free
ligand (L1) is no longer present. The chemical shift of the Ag+
cluster appears at a chemical shift close to that of the free
ligand, but is clearly distinct in terms of its expected splitting
patterns by 107Ag−P and 109Ag−P couplings (1J(107Ag−P) =
1
246 Hz and J(109Ag−P) = 284 Hz). Strangely, the chemical
shift is quite different from nearly all the other clusters
examined in this study. Although we do not have any
reasonable explanation why the signal of the Ag+ cluster is so
shifted compared to those of Cu+ and Au+ clusters (Supporting
Information, Figure S2), the 31P NMR chemical shifts of
phosphine complexes can vary depending on metal, anions, and
D
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 5. Three views of the Cu2(L2)3I2 helical cluster, shown with the ligand as sticks and the Cu+ ions and iodide anions as spheres (left); the
cluster geometry is highlighted coloring each ligand differently viewed down the Cu−Cu axis (middle); and shown in spacefill (right).
Figure 6. Three views of the Cu2(L3)3I2 pseudomesocate cluster: shown with the ligand as sticks and the Cu+ ions and iodide anions as spheres
(left); the cluster geometry is highlighted by coloring each ligand differently as viewed down the Cu···Cu axis (middle); and shown in spacefill
(right).
even coordination number. For instance, some complexes such
as [M2(dppb)2]X2 (M = Ag+ or Au+, dppb = bis-
(diphenylphosphino)butane) complexes have significantly
different chemical shifts.26 In [Au2(dppb)2]X2,26a,b the values
defined by the intranuclear Cu···Cu distance, is ∼12.9 Å
(Supporting Information,Table S5). The twelve phenyl groups
located on the exterior of the helix arrange efficiently in offset
face-to-face stacked pairs.
1
The solution structure of Cu2(L2)3I2 was examined by H
are +41.5 and +35.6 ppm for X = BF4 and I−, respectively.
−
26c
NMR spectroscopy (Supporting Information, Figure S4). In
However, those of [Ag2(dppb)2]X2
are −15.6, −5.0, and
1
the H NMR spectrum, the proton signal of free ligand L2
+0.8 ppm for X = Br−, I−, and NO3 , respectively. On the other
hand, the signals of M((p-tolyl)3P)nCl (M = Au+ or Ag+ and n
= 1, 2, 3, or 4),27 appear in a similar region (δ = 31.32 for
Au((p-tolyl)3P)Cl27a and δ = 21.4−25.3 ppm for Ag((p-
tolyl)3P)nCl).27b Although the 31P NMR spectra do not suggest
whether each cluster exists in solution with certainty, the
spectra do suggest that a single species exists in solution of each
cluster. In the case of Cu4(L1)4I4, the solution composition is
further supported by the positive ion mode ESI-MS spectra of
Cu4(L1)4I4 (Figure 4), which shows two peaks indicative of the
intact cluster ([Cu−I]+ m/z 4358.5331, [Cu+Na]+ m/z
4508.4298). Unfortunately, the Ag+ and Au+ clusters did not
yield ESI-MS spectra with the expected ions.
−
appears largely as broad multiplets between 7.3 and 7.7 ppm;
however, Cu2(L2)3I2 displays a relatively simple and well-
resolved peak pattern as expected for a highly symmetric cluster
that is intact in solution. The structural integrity in solution is
supported by the 31P NMR spectrum of Cu2(L2)3I2, where the
peak of the free L2 ligand (−33.85 ppm) is no longer present
and a new resonance at 9.84 ppm is observed (Supporting
Information, Figure S5). Finally, high resolution ESI-MS data
confirmed the presence of the cluster in solution. The positive
ion mode ESI-MS spectrum of Cu2(L2)3I2 shows several ions
indicative of the fully intact cluster (Supporting Information,
Figure S6), including ions at m/z of 1737.1703 and 1887.0631
correspond to the [M−I]+ and [M+Na]+ exact masses
(consistent with the simulated isotopic spectrum). Additional
peaks in the ESI-MS correspond to the [M+K]+ (m/z
1903.0631) and [M+Cu]+ (m/z 1927.0060) ions. The
combination of ligand L2 with AgI was also performed;
however, no suitable crystals were obtained under a variety of
Helical Cluster Cu2(L2)3I2. A series of ditopic phosphine
ligands were prepared to evaluate whether M2L3 triple-stranded
helicates (or mesocates) or possibly M4L6 tetrahedra could be
produced.1a Combining 2 equiv of CuI in CH2Cl2 with 3 equiv
of linear ligand L2 for 30 min at room temperature resulted in
the formation of a colorless solution, which was filtered and
evaporated to dryness to obtain a powder. Slow diffusion of
Et2O into a saturated CH2Cl2 solution prepared from the
isolated powder gave colorless crystals in high yield (∼90%).
The single crystal X-ray structure determination reveals that the
product is a triple-stranded helicate, which was anticipated by
analogy to other supramolecular systems. Similar to the
tetrahedral clusters, the metal centers adopt distorted
tetrahedral environments at each metal center (Figure 5)
coordinated by an iodide anion (Cu−I distance ∼2.64 Å) and
by three phosphine donor atoms from three separate ligands
(Cu−P distance ∼2.30 Å) (Supporting Information, Table S5).
The tetrahedral coordination environments of the metal centers
are homochiral, as required by their helical symmetry. The
average helical twist angle is 23.57° about the Cu−Cu axis of
the molecule (as taken from the Cu−P−P−Cu torsion angles,
Supporting Information, Figure S3). The length of the helix, as
1
conditions. H NMR, 31P NMR, and ESI-MS studies of the
reaction mixture did not produce conclusive results. In
particular, uncoordinated free ligand (L2) was observed in the
31P NMR spectrum under the reaction conditions explored (δ =
−33.85, data not shown). Interestingly, the combination of Au+
with ligand L2 yielded a compound with the same
stoichiometry as Cu2(L2)3I2, but formed a coordination
polymer [Au2(L2)3I2]n rather than a discrete helicate (vide
infra). It is unclear why Ag+ and Au+ do not produce the
analogous helicate structures. The affinity of these metal ions
for phosphine ligands may make the equilibrium between the
solution and crystalline states of the material more complicated.
As a result, the kinetic, rather than thermodynamic products,
may be the products isolated by crystallization.
Mesocate Cluster Cu2(L3)3I2. Using the linear ditopic
phosphine ligand L2, a helical cluster was selectively formed
E
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 7. Three views of the Cu2(L4)3I2 mesocate cluster: shown with the ligand as sticks and the Cu+ ions and iodide anions as spheres (left); the
cluster geometry is highlighted by coloring each ligand differently as viewed down the Cu···Cu axis (middle); and shown in spacefill (right).
both in solution and in the solid-state with Cu+. Ligand L3
possess a bent (1,3-benzene), rather than a linear (1,4-benzene
for L2), geometry and hence was expected to produce related,
but structurally distinct clusters. It was anticipated that the bent
linker of L3 would lead to syn conformations at the metal
centers because of geometric constraints (this is in contrast to
L2, which can accommodate syn, anti, and even intermediate
conformations).
−13.72 for Au+) were observed, indicative of several species in
the solutions (Supporting Information, Figure S9). Analysis by
ESI-MS revealed that the reaction with Au+ gave peaks
indicative of Au2(L3)3I2 (m/z = 2004.2507 for [M−I]+,
Supporting Information, Figure S10), but the reaction with
Ag+ did not yield expected ions.
Mesocate Cluster M2(L4)3I2, (M = Cu+, Au+). Because of
the observed edge-to-face interaction in the mesocate cluster
Cu2(L3)3I2, it was predicted that introducing a 2,6-pyridine
linker would eliminate the pore-facing hydrogen atoms and
would be expected to construct mesocate clusters with more
idealized symmetry. Indeed, higher symmetric mesocate
clusters M2(L4)3I2, (M = Cu+, Au+) were successfully isolated
in a similar manner to that of Cu2(L2)3I2. Slow diffusion of
Et2O into a saturated CH2Cl2 solution of the compounds gave
yellow crystals in near quantitative yield (>95%). Similar to
Cu2(L3)3I2, the structure reveals M2(L4)3I2 are triple-stranded
mesocates (Figure 7, Supporting Information, Figure S11). The
clusters with Cu+ and Au+ are essentially isostructural,
possessing C3h symmetry (C3 symmetry along the metal-to-
metal axis and a σh mirror plane) such that only one-sixth of the
cluster resides in the crystallographic asymmetric unit
(Supporting Information,Table S2). Consequently, the coordi-
nation environments of metal centers are identical to each
other, bound by three identical phosphorus atoms (M+−P
distance 2.28 and 2.38 Å for Cu+ and Au+, respectively) and an
iodide ion (M+−I distance 2.57 and 2.79 Å for Cu+ and Au+,
respectively). The M···M separations in each M2(L4)3I2 are
similar, at 12.12 and 12.00 Å for Cu+ and Au+, respectively
(Supporting Information,Table S5).
The mesocate of Cu2(L3)3I2 was prepared in a similar
manner to that for Cu2(L2)3I2, and crystals were obtained by
slow diffusion of Et2O into a saturated CH2Cl2 solution (∼70%
yield) within two weeks. In contrast to Cu2(L2)3I2, the single
crystal X-ray structure of Cu2(L3)3I2 reveals a heterochiral,
triple-stranded mesocate (Figure 6, Supporting Information,T-
able S2) with the metal centers possessing opposite chirality.
However, the Cu2(L3)3I2 complex is not an idealized mesocate
structure. Each Cu+ center has a slightly different coordination
environment (Supporting Information,Table S5); the average
twist angle is about 5.59° about the Cu···Cu axis of the
molecule (as taken from the Cu−P−P−Cu torsion angles,
Supporting Information, Figure S3), which is smaller than that
of Cu2(L2)3I2. The intramolecular Cu···Cu distance in
Cu2(L3)3I2 is slightly smaller (ca. 12.1 Å) than that in
Cu2(L2)3I2 because of the structure of the substituted ligand
(1,3- vs 1,4-substitution on the central benzene ring,
Supporting Information,Table S5). Interestingly, the central
benzene ring of each ligand participates in a face-to-edge
interaction with respect to the neighboring ligand.
In solution, the Cu2(L3)3I2 cluster behaves as an idealized
mesocate. Only one set of signals for all three ligands is
obtained, indicating C3 symmetry for the complexes in solution,
at room temperature, on the NMR time scale (Supporting
Information, Figure S7). In particular, only one singlet signal
for the central benzene proton (Ha) appears and is shifted
dramatically upfield (5.64 ppm) compared to the free ligand
(7.72 ppm). This upfield shift is characteristic of a proton
experiencing a ring current shielding due to edge-to-face
interactions as observed in the X-ray crystal structure. Similar to
the Cu2(L2)3I2 cluster, the signals for the phenyl rings attached
to each phosphorus atom appear as broad multiplets at 7.80
ppm (Hd), a triplet at 7.30 ppm (Hf), and a triplet at 7.16 ppm
(He) (Supporting Information, Figure S7). The positive ion
mode ESI-MS spectrum of Cu2(L3)3I2 shows two distinct
peaks, also confirming that the cluster remains intact in solution
(m/z = 1737.1673, 1887.0631 for [M−I]+ and [M+Na]+,
respectively, Supporting Information, Figure S8). Numerous
attempts to obtain suitable crystals for the other coinage metal
1
The H NMR spectra of the M2(L4)3I2 clusters show only
one set of signals for the ligand protons, indicating C3
symmetry for the complexes in solution on the NMR time
scale (Supporting Information, Figure S12). In the Cu+ cluster,
distinct upfield shifts of the protons on the central pyridine ring
are observed (Δδ = +1.18 and +0.67 compared to the free
ligand). Similar, but smaller shifts, are found for the Au+ cluster
(Δδ = +0.61 and +0.14), which suggest that these protons are
involved in face-to-edge aromatic interactions between adjacent
pyridine rings in solution. The 31P NMR spectrum supported
the solution presence of both clusters (Supporting Information,
Figure S13), where the peak of the free L3 ligand (−34.06
ppm) was no longer present and a new resonance was observed
for the clusters M2(L4)3I2 (Cu+ δ = 9.64 ppm; Au+ δ = 10.06
ppm). The positive ion mode ESI-MS spectrum of Cu2(L4)3I2
shows two distinct peaks, confirming the presence of the cluster
in solution (m/z = 1740.1607 and 1890.0528 for [M−I]+ and
[M+Na]+, respectively, Supporting Information, Figure S14).
We were unable to obtain a clean ESI-MS spectrum of
Au2(L4)3I2. As in the L2 and L3 ligand systems, we were unable
to obtain suitable crystals upon combination of L4 and Ag+, and
spectroscopic studies of the reaction mixture were inconclusive.
1
ions (Ag+, Au+) were not successful, and H NMR data of the
corresponding reaction mixtures were inconclusive. In the 31P
NMR spectra of the reaction mixtures containing either Ag+ or
Au+, the peak of the free L3 ligand (−34.06 ppm) was absent
and several new peaks (δ = 30.86, 6.47 for Ag+, and δ = 6.03,
F
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Two views of the [Au2(L2)3I2]n (top) and [Cu2(L5)3I2]n (bottom) coordination polymers: the ligands are shown as sticks and the M+ ions
and iodide anions are represented by spheres (left); the cluster geometry is highlighted coloring each ligand differently with the phenyl groups
excluded (right).
Coordination Polymer [Au2(L2)3I2]n. Although the
ligand−metal combinations described above generally led to
the anticipated supramolecular structures, other combinations
yielded products, but not the expected structures. As
mentioned above, unlike the results with the tppeb21 or L1
ligand, many of the ditopic ligand systems did not give the same
supramolecular structures across the entire coinage metal series.
One example was the combination of Au+ with ligand L2, which
yielded a compound with the same stoichiometry as Cu2(L2)3I2,
but rather than a discrete helicate was a coordination polymer
[Au2(L2)3I2]n. Suitable crystals of [Au2(L2)3]I2]n were obtained
from slow diffusion of Et2O into a saturated CH2Cl2 solution
after one day. The crystals showed poor solubility in most
common organic solvents, and the structure clearly showed an
extended coordination polymer (Figure 8) consisting of
Au2(L2)2I2 dimer units, which are linked into one-dimensional
chains by a third, bridging L2 ligand. The Au···Au distances are
∼13.1 Å across the Au2(L2)2I2 dimer unit and ∼14.4 Å across
the single L2 bridge (Supporting Information,Table S6). Within
the Au2(L2)2I2 dimer, two nearly parallel L2 ligands participate
in a π−π stacking interaction with a face-to-face distance of
∼3.9 Å between the centers of the benzene rings. The two
distinct types of L2 ligands in the structure (dimer versus
bridging ligand) adopt different conformations in the
coordination polymer as reflected in the Au−P−P−Au torsion
angles (Supporting Information,Table S6). The dimer ligands
adopt a nearly gauche conformation (torsion angle = 62.79°),
but the third, bridging ligand adopts an anti conformation
(torsion angle = 180°).
consistent with a helicate in solution (Supporting Information,
Figure S16). A peak at m/z 2004.2443 corresponds to the exact
mass of the molecular ion minus an iodide ion (i.e., [M−I]+),
which confirms the molecular formula of the cluster. Additional
peaks in the ESI-MS correspond to the [M+H]+ (m/z
2132.1525) and [M+Au]+ (m/z 2328.1127), all of which
suggests the existence of the Au2(L2)3I2 cluster in solution
(Supporting Information, Figure S16).
These results beg the question as to why the coordination
polymer [Au2(L2)3I2]n is selectively crystallized rather than the
dinuclear cluster. An earlier study by James and co-workers
examined the transformation of M2L3 cages into [M2L3]n
polymers. It was suggested that the transformation might
occur through ring-opening polymerization arising from the
equilibrium between the solution and crystalline states of the
material. In solution the discrete cage was dominant but was in
equilibrium with a coordination polymer (or oligomers). The
polymeric form was insoluble and slowly and irreversibly
crystallized out of solution. The insolubility of the polymer
leads to crystallization, and the rate-determining factor was
reported to be the ring-opening polymerization reaction, rather
than the crystallization.28 It appears that a similar equilibrium
and crystallization mechanism is occurring for the [Au2(L2)3I2]n
coordination polymer described above.
Coordination Polymer [Cu2(L5)3I2]n. One of the most
studied supramolecular clusters, reported by Raymond and co-
workers, uses a bis(catecholato) ligand with an intervening
naphthalene spacer. This backbone causes the catechol binding
units to be offset from one another, thus disfavoring the
formation of a helicate, and forming an M4L6 tetrahedron with
extensive host−guest properties.29 It was hoped that a
bis(phosphine) ligand with an identical naphthalene (L5)
backbone would generate a similar cluster. However,
combination L5 with Cu+ ions produced a coordination
polymer very similar to [Au2(L2)3I2]n. Suitable crystals for
single crystal X-ray diffraction were prepared from a saturated
(hot) DMF solution of the complex upon cooling to room
temperature. The crystals obtained were insoluble in most
common organic solvents. X-ray diffraction reveals the crystal
structure is a coordination polymer with the formula
[Cu2(L5)3I2]n. (Figure 8). Similar to [Au2(L2)3I2]n, the
structure consists of [Cu2(L5)2I2] dimer units with distorted
tetrahedral Cu+ centers, which are linked into polymer chains
by a third, bridging L5 ligand. The Cu···Cu distances are ∼13.7
Å within the [Cu2(L5)2I2] dimer and ∼14.8 Å between the L5
bridged centers (Supporting Information,Table S6). In the
[Cu2(L5)2I2] unit, the two, nearly parallel L5 ligands have π−π
Although the coordination polymer [Au2(L2)3]I2]n shares the
same stoichiometry with the helicate Cu2(L2)3I2, attempts to
obtain the analogous Au2(L2)3I2 helicate were not successful.
Variable temperature 1H NMR and ESI-MS analysis suggest the
Au2(L2)3I2 helicate, or related discrete species, may be present
in solution. Dissolution of the coordination polymer crystals in
CD2Cl2 using extensive sonication (because of the poor
solubility of the crystals) resulted in broad, overlapping signals
at room temperature (Supporting Information, Figure S15).
However, these broad signals became resolved as the
temperature was decreased to −60 °C. Interestingly, the
spectrum at −60 °C shows a highly symmetric pattern, distinct
from the free L2 ligand (Supporting Information, Figure S15).
The spectra at −60 °C is very similar to that obtained for the
helicate Cu2(L2)3I2 (Supporting Information, Figure S4),
indicating that a similar Au2(L2)3I2 structure may be formed
in solution at low temperature. The 1H NMR data is supported
by positive ion mode ESI-MS, which shows several peaks
G
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
washed with brine (2 × 20 mL) and then, the organic phase was
separated and dried with Na2SO4. After removing the solvent, the solid
mixture was separated by silica gel column chromatography using
stacking interactions at a distance of ∼3.7 Å between the
naphthyl rings. The dimer and bridging ligands adopt gauche
and anti conformations, respectively (Supporting Informa-
tion,Table S6), as described for [Au2(L2)3I2]n. It appears that
the lack of a chelating ligand, combined with the propensity for
these ligands to engage in strong π−π stacking interactions
does not allow for access to the tetrahedral structure. In
essence, the ability to obtain an analogue to the spectacular
M4L6 tetrahedron reported by Raymond is not readily accessed
by simply adopting the naphthyl backbone strategy to a
substantially different ligand system.
1
CH2Cl2 as eluent to give the title compound (2.63 g, 92%). H NMR
(CDCl3, 400 MHz): δ 7.76 (s, 3H), 7.65 (d, 6H, J = 8 Hz), 7.61 (d,
6H, J = 8 Hz), 3.16(s, 3H); 13C NMR (150 MHz, CDCl3): δ 141.7,
141.1, 132.7, 127.2, 125.3, 121.6, 83.4, 78.1. ESI-MS (+) m/z calcd. for
[M+MeOH+H]+: 411.17, found [M+MeOH+H]+: 411.32.
1,3,5-Tris[(4-(diphenylphosphino)ethynyl)phenyl]benzene
(L1). Compound 2 (3.91 g, 10.33 mmol) was dissolved in freshly dried
THF (150 mL) at −20 °C. nBuLi (2.5 M hexane, 14.9 mL, 37.2
mmol) was added to the solution. The reaction mixture was stirred for
30 min, and then Ph2PCl (6.7 mL, 37.2 mmol) was added and the
mixture stirred for an additional 1 h. Once reaction was complete (by
TLC), the solvent was evaporated, and the residue was dissolved in
CH2Cl2 (50 mL). The organic layer was washed with water (2 × 30
mL). After drying with Na2SO4, the solvent was removed in a vacuum
to yield a pale yellow solid which was recrystallized (CH2Cl2/MeOH)
CONCLUSIONS
■
In summary, phosphine coordination chemistry has mainly
focused on organometallics and homogeneous catalysis. Only
occasionally have they been considered as building blocks for
supramolecular chemistry and self-assembly. However, a new
class of supramolecular metal-phosphine clusters formed from
tritopic/ditopic phosphines and coinage metals has been
developed. The structures obtained include tetrahedra,
dinuclear triple-stranded helicates, dinuclear triple-stranded
mesocates, and coordination polymers. While tetrahedral
clusters could be obtained with all of the coinage metals
(Cu+, Ag+, Au+) when using tritopic tris(phosphine) ligands,
the same was not true when employing ditopic bis(phosphine)
ligands. For reasons as yet to be determined, Ag+ ions were
found to be particularly challenging when trying to isolate
supramolecular species. Different geometries of bis(phosphine)
ligands lead to helicates, mesocates, or coordination polymers,
all of which share a common stoichiometry [M2(L)3I2]n. The
growing use of coinage metal-phosphine complexes as
catalysts30 suggest these clusters might serve as unusual
scaffolds not only for new catalyst design and but also for
investigating the catalytic behaviors of the new types of
phosphine-based discrete and polymeric aggregates.
1
at 0 °C to give the title compound (7.31 g, 76%). H NMR (CDCl3,
400 MHz): δ 7.80 (s, 3H), 7.69−7.74 (br s, 24H), 7.39−7.41 (br s,
18H); 31P NMR (CDCl3, 202.468 MHz): δ −33.88. ESI-MS(+) m/z
calcd. for [M+H]+: 931.28, found [M+H]+: 931.47.
1,4-Bis[(2-trimethylsilyl)ethynyl]benzene (3). 1,4-Dibromo-
benzene (7.02 g, 30 mmol) was dissolved in triethylamine (100 mL)
under an atmosphere of nitrogen. CuI (136 mg, 1.2 mol %/) and
Pd(PPh3)4 (420 mg, 0.6 mol %) were added to the solution.
Trimethylsilylacetylene (10.3 mL, 72 mmol) was slowly added, and
the mixture was heated to reflux for 8 h. Once conversion was
complete (by TLC), the solvent was evaporated. The mixture was
separated by silica gel column chromatography (n-hexane) to isolate
1
the title compound (7.30 g, 90%). H NMR (CDCl3, 400 MHz): δ
7.39 (s, 4H), 0.25 (s, 18H); 13C NMR(150 MHz, CDCl3): δ 131.73,
123.11, 96.28, 95.10, −0.11.
1,4-Diethynylbenzene (4). Compound 3 (5.4 g, 20 mmol) was
dissolved in 60 mL of CH2Cl2, followed by addition of a mixture of
MeOH/NaOH (60 mL/3.2 g). The mixture was stirred for 12 h at
room temperature. Once conversion was complete (by TLC), the
solvent was evaporated. 50 mL of CH2Cl2 was added to the residue,
and the insoluble solids were filtered away. The filtrate was washed
with brine (2 × 30 mL), and the organic phase was separated and
dried with Na2SO4. After removing the solvent, the solid mixture was
separated by silica gel column chromatography using CH2Cl2 as
EXPERIMENTAL SECTION
■
1
eluent, and the title compound was obtained (2.30 g, 91%). H NMR
General Procedure. Starting materials and solvents were
purchased and used without further purification from commercial
suppliers (Sigma-Aldrich, Alfa Aesar, Acros, TCI, Cambridge Isotope
Laboratories, Inc., and others). 1H and 31P nuclear magnetic resonance
(NMR) spectra were recorded by a Varian FT-NMR spectrometer
(CDCl3, 400 MHz): δ 7.44 (s, 4H), 3.17(s, 2H). ESI-MS (+) m/z
calcd. for [M+H2O+H]+: 145.07, found [M+H2O+H]+: 145.09, calcd.
for [M+MeOH+H]+: 159.08, found [M+MeOH+H]+: 159.17.
1,4-Bis[(diphenylphosphino)ethynyl]benzene (L2). Com-
pound 4 (3.8 g, 30.0 mmol) was dissolved in freshly dried THF
(100 mL) at −20 °C. nBuLi (2.5 M hexane, 28.8 mL, 72.0 mmol) was
slowly added to the solution. The reaction mixture was stirred for 30
min, and then Ph2PCl (12.9 mL, 72.0 mmol) was added and the
mixture stirred for an additional 1 h. Once reaction was complete (by
TLC), the solvent was evaporated, and the residue was dissolved in
CH2Cl2 (50 mL). The organic layer was washed with water (2 × 30
mL). After drying with Na2SO4, the solvent was removed in vacuum to
give a white solid that was recrystallized (CH2Cl2/MeOH) at 0 °C to
give the title compound (12.9 g, 87%). 1H NMR (CDCl3, 400 MHz):
δ 7.63−7.67 (br s, 8H), 7.49 (s, 4H), 7.35−7.37 (br s, 12H); 31P NMR
(CDCl3, 202.468 MHz): δ −33.85. ESI-MS(+) m/z calcd. for [M
+H]+: 495.14, found [M+H]+: 495.36.
1
(400 MHz for H) or JEOL FT-NMR spectrometer (500 MHz for
1H/202.468 MHz for 31P). Phosphorus nuclear magnetic resonance
spectroscopy was fully decoupled by broadband decoupling. Chemical
shifts were quoted in parts per million (ppm) referenced to the
appropriate solvent peak or 0 ppm for TMS (1H NMR) and −6 ppm
for triphenylphosphine solution in CDCl3 (31P NMR).
1,3,5-Tris[4-(2-trimethylsilyl-ethynyl)phenyl]benzene (1).
1,3,5-Tris(4-bromophenyl)benzene (5.0 g, 9.2 mmol) was dissolved
in diethylamine (350 mL) under an atmosphere of nitrogen. CuI (32
mg, 0.6 mol %/Br) and PdCl2(PPh3)2 (240 mg, 1.2 mol %/Br) were
added to the solution. Trimethylsilylacetylene (13.7 mL, 33 mmol)
was slowly added, and the mixture was heated to reflux at 50 °C for 12
h. Once conversion was complete (by TLC), the solvent was
evaporated. The mixture was separated by silica gel column
chromatography (n-Hexane) to isolate the title compound (4.64 g,
85%). 1H NMR (CDCl3, 400 MHz): δ 7.74 (s, 3H), 7.63(d, 6H, J = 8
Hz), 7.57(d, 6H, J = 8 Hz), 0.28 (s, 27H).
1,3,5-Tris-(4-ethynylphenyl)benzene (2). Compound 1 (4.5 g,
7.56 mmol) was dissolved in 60 mL of CH2Cl2, followed by addition
of a mixture of MeOH/NaOH (60 mL/1.8 g). The mixture was stirred
for 12 h at room temperature. Once conversion was complete (by
TLC), the solvent was evaporated. 50 mL of CH2Cl2 was added to the
residue, and the insoluble solids were filtered away. The filtrate was
1,3-Bis[(diphenylphosphino)ethynyl]benzene (L3). The 1,3-
diethynylbenzene (1.05 mL, 7.9 mmol) was dissolved in freshly dried
n
THF (30 mL) at 253 K. BuLi (2.5 M hexane, 7.6 mL, 19.0 mmol)
was added to the solution. The reaction mixture was stirred for 30 min,
and then Ph2PCl (3.4 mL, 19.0 mmol) was added and the mixture
stirred for an additional 1 h. Once reaction was complete (by TLC),
the solvent was evaporated, and the residue was dissolved in CH2Cl2
(50 mL). The organic layer was washed with water (2 × 30 mL). After
drying with Na2SO4, the solvent was removed in a vacuum to yield a
yellow oil (3.4 g, 87%). 1H NMR (CDCl3, 400 MHz): δ 7.72 (s, 1H),
H
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
7.64−7.69 (br s, 8H), 7.51(d, 2H, J = 8 Hz), 7.35−7.39 (br s, 12H),
7.32 (t, 1H, J = 8 Hz) ; 31P NMR (CDCl3, 202.468 MHz): δ −34.06 .
ESI-MS(+) m/z calcd. for [M+H]+: 495.14, found [M+H]+: 495.27.
2,6-Bis[(trimethylsilyl)ethynyl]pyridine (5). 2,6-Dibromopyri-
dine (1.18 g, 5 mmol) was dissolved in diethylamine (50 mL) under
an atmosphere of nitrogen. CuI (11 mg, 0.6 mol %) and PdCl2(PPh3)2
(84 mg, 1.2 mol %/Br) were added to the solution. Trimethylsily-
lacetylene (1.7 mL, 12 mmol) was slowly added, and the mixture was
heated to reflux for 8 h. Once conversion was complete (by TLC), the
solvent was evaporated. The solid mixture was separated by silica gel
column chromatography (n-hexane:CH2Cl2, 1:4) to isolate the title
MeOH/NaOH (10 mL/0.75 g). The mixture was stirred for 12 h at
room temperature. Once conversion was complete (by TLC), the
solvent was evaporated. Thirty milliliters of CH2Cl2 was added to the
residue, and the insoluble solids were filtered away. The filtrate was
washed with brine (2 × 30 mL) and then the organic phase was
separated and dried with Na2SO4. After removing the solvent, the solid
mixture was separated by silica gel column chromatography using
CH2Cl2 as eluent to give the title compound (0.246 g, 93%). 1H NMR
(CDCl3, 400 MHz): δ 8.39 (d, 2H, J = 8 Hz), 7.78 (d, 2H, J = 8 Hz),
7.53 (t, 2H, J = 8 Hz), 3.49 (s, 2H); ESI-MS (+) m/z calcd. for [M
+MeOH+H]+: 129.10, found [M+MeOH+H]+: 209.11, calcd. for [M
+2MeOH+H]+: 241.13, found [M+MeOH+H]+: 241.09.
1
compound (1.15 g, 85%). H NMR (CDCl3, 400 MHz): δ 8.58(br s,
2H), 7.81 (t, 1H, J = 2.4 Hz), 0.25 (s, 18H).
1,5-Bis((diphenlyphosphino)ethynyl)naphthalene (L5). Com-
pound 9 (0.25 g, 1.42 mmol) was dissolved in freshly dried THF (30
2,6-Diethynylpyridine (6). Compound 5 (1.02 g, 3.76 mmol) was
dissolved in 20 mL of CH2Cl2, followed by addition of a mixture of
MeOH/NaOH (10 mL/1.5 g). The mixture was stirred for 12 h at
room temperature. Once conversion was complete (by TLC), the
solvent was evaporated. Twenty millilters of CH2Cl2 was added to the
residue, and the insoluble solids were filtered away. The filtrate was
washed with brine (2 × 30 mL), and the organic phase was separated
and dried over Na2SO4. After removing the solvent, the mixture was
separated by silica gel column chromatography using CH2Cl2 as eluent
n
mL) at −20 °C. BuLi (2.5 M hexane, 1.4 mL, 3.5 mmol) was slowly
added to the solution. The reaction mixture was stirred for 30 min, and
then Ph2PCl (0.6 mL, 3.5 mmol) was added and stirred for an
additional 2 h. Once the reaction was complete (by TLC), the solvent
was evaporated, and the residue dissolved in CH2Cl2 (30 mL). The
organic layer was washed with water (3 × 20 mL). After drying with
Na2SO4, the solvent was removed in a vacuum to yield a yellow solid
1
(0.58 g, 75%). H NMR (CD2Cl2, 400 MHz): δ 8.35 (d, 2H, J = 8
1
to give the title compound (0.45 g, 94%). H NMR (CDCl3, 400
Hz), 7.81 (d, 2H, J = 8 Hz), 7.72−7.76 (br s, 8H), 7.51 (t, 2H, J = 8
Hz), 7.38−7.40 (br s, 12H); 31P NMR (CDCl3, 202.468 MHz): δ
−33.57. ESI-MS(+) m/z calcd. for [M+H]+: 545.16, found [M+H]+:
545.38, [M+MeOH+H]+: 577.19, found [M+MeOH+H]+: 577.25.
Cu4(L1)4I4. CuI (38 mg, 0.2 mmol) was suspended in CH2Cl2 (50
mL), and L1 (190 mg, 0.2 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in vacuum. The pale yellow solid was collected
and washed with Et2O (212 mg, 93%). Crystals suitable for X-ray
structure determination were grown from slow diffusion of Et2O into a
saturated solution of the material in CH2Cl2 giving colorless block-
shaped crystals within a couple days (170 mg, 80% yield from the
isolated powder). 31P NMR (CD2Cl2, 202.468 MHz): δ 7.73. High
resolution ESI-MS(+) m/z: calcd. for [M−I]+ 4358.5319, found [M−
I]+ 4358.5331, calcd. for [M+Na]+ 4508.4261, found [M+Na]+
4508.4298.
MHz): δ 8.65 (d, 2H, J = 2 Hz), 7.85 (t, 1H, J = 2 Hz), 3.24 (s, 2H);
ESI-MS (+) m/z calcd. for [M+H]+: 128.05, found [M+H]+: 128.13,
calcd. for [M+MeOH+H]+: 160.08, found [M+MeOH+H]+: 160.11.
2,6-Bis[(diphenylphosphino)ethynyl]pyridine (L4). Com-
pound 6 (0.45, 3.54 mmol) was dissolved in freshly dried THF (30
n
mL) at −20 °C. BuLi (2.5 M hexane, 3.40 mL, 8.49 mmol) was
slowly added to the solution. The reaction mixture was stirred for 30
min, and then Ph2PCl (1.5 mL, 8.49 mmol) was added and the
mixture was stirred an additional 2 h. Once reaction was complete (by
TLC), the solvent was evaporated, and the residue was dissolved in
CH2Cl2 (30 mL). The organic layer was separated and washed with
water (3 × 20 mL). After drying with Na2SO4, the solvent was
1
removed in vacuum to give a yellow solid (1.42 g, 81%). H NMR
(CD2Cl2, 400 MHz): δ 8.67 (d, 2H, J = 2 Hz), 7.94 (t, 1H, J = 2 Hz),
7.62−7.66 (br s, 8H), 7.36−7.38 (br s, 12H); 31P NMR (CDCl3,
202.468 MHz): δ −34.06. ESI-MS(+) m/z calcd. for [M+H]+: 496.14,
found [M+H]+: 496.24.
Ag4(L1)4I4. AgI (47 mg, 0.2 mmol) was suspended in CH2Cl2 (50
mL), and L1 (190 mg, 0.2 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in vacuum. The pale yellow solid was collected
and washed with Et2O (219 mg, 94%). Crystals suitable for X-ray
structure determination were grown from slow diffusion of Et2O into a
saturated solution of the material in CH2Cl2 giving colorless block-
shaped crystals within a couple of days (180 mg, 82% yield from the
1,5-Diiodonaphthalene (7). A previously reported procedure was
used for the preparation of 1,5-diiodonaphthalene.31 To a solution of
sodium nitrite (3.0 g, 0.044 mol) in concentrated sulfuric acid (25 mL)
at 0 °C was added to a solution of 1,5-diaminonaphthalene (3 g, 0.019
mol) in glacial acetic acid (25 mL). The mixture was stirred for 15 min
followed by addition of ice (50 g) and urea (0.25 g). A solution of KI
(100 g, 0.6 mol) in water (100 mL) was added and stirred overnight
under house vacuum. The solvent evaporated overnight leaving a solid
residue, which was washed with CH2Cl2 (3 × 100 mL). The combined
CH2Cl2 washes were refluxed with decolorizing charcoal, filtered
through a Celite-layered glass filter, and purified by silica gel column
chromatography (eluting with hexane/dichloromethane (2:1)) to give
7 as pale-yellow powder (3.68 g, 51%). 1H NMR (CDCl3, 400 MHz):
δ 8.14 (m, 4H), 7.28 (dd, 2H, J = 16 Hz, 7.6 Hz). 13C NMR (CDCl3,
200 MHz): δ 138.87 (2C), 134.79 (2C), 133.78 (2C), 128.69 (2C),
99.76 (2C). ESI-MS(+) m/z calcd. for [M]+: 379.9, found [M]+:
380.0, calcd. for [M−I]+: 253.0, found [M]+: 253.0, calcd. for [M-2I
+H]+: 126.0, found [M-2I+H]+: 126.2.
1,5-Bis((trimethylsilyl)ethynyl)naphthalene (8). Compound 7
(0.76 g, 2 mmol) was dissolved in diethylamine (20 mL) under an
atmosphere of nitrogen. CuI (19 mg, 2.5 mol %) and PdCl2(PPh3)2
(42 mg, 1.5 mol %) were added to the solution. Trimethylsilylace-
tylene (0.7 mL, 2.4 mmol) was slowly added, and the mixture was
heated to reflux for 12 h. Once conversion was complete (by TLC),
the solvent was evaporated. The mixture was separated by silica gel
column chromatography (n-hexane) to isolate the title compound
(0.49 g, 76%). 1H NMR (CDCl3, 400 MHz): δ 8.35 (d, 2H, J = 8 Hz),
7.74 (d, 2H, J = 8 Hz), 7.52 (t, 2H, J = 8 Hz), 0.34 (s, 18H).
1,5-Diethynylnaphthalene (9). Compound 8 (0.48 g, 1.5 mmol)
was dissolved in 10 mL of CH2Cl2, followed by adding a mixture of
1
isolated powder). H NMR (CD2Cl2, 500 MHz): δ 7.87(br s, 24H),
7.75 (br s, 24H), 7.66 (t, 12H, J = 9 Hz), 7.35 (br s, 24H), 7.29 (s,
12H), 7.22 (t, 12H, J = 8 Hz), 7.14 (d, 24H, J = 8.5 Hz), 7.01 (t, 24H,
J = 8.5 Hz), 6.87 (d, 24H, J = 8.5 Hz); 31P NMR (CD2Cl2, 202.468
MHz): δ - 31.38 (1J(107Ag−P) = 246 Hz and 1J(109Ag−P) = 284 Hz).
Au4(L1)4I4. AuI (65 mg, 0.2 mmol) was suspended in CH2Cl2 (50
mL), and L1 (190 mg, 0.2 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in a vacuum. The pale yellow solid was collected
and washed with Et2O (225 mg, 88%). Crystals suitable for X-ray
structure determination were grown from slow diffusion of Et2O into a
saturated solution of the material in CH2Cl2 giving colorless block-
shaped crystals within a couple days (171 mg, 76% yield from the
isolated powder). 31P NMR (CD2Cl2, 202.468 MHz): δ 7.99.
Cu2(L2)3I2. CuI (38 mg, 0.2 mmol) was suspended in CH2Cl2 (50
mL) and L2 (150 mg, 0.3 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in a vacuum. The yellow solid was collected and
washed with Et2O (179 mg, 95%). Crystals suitable for X-ray structure
determination were grown from slow diffusion of Et2O into a saturated
solution of the material in CH2Cl2 giving colorless block-shaped
crystals within a couple days (161 mg, 90% yield from the isolated
1
powder). H NMR (CD2Cl2, 400 MHz): δ 7.77 (br s, 24H), 7.18 (t,
12H, J = 8 Hz), 7.13 (s, 12H), 7.08 (t, 24H, J = 8 Hz); 31P NMR
I
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(CD2Cl2, 202.468 MHz): δ 9.84; High resolution ESI-MS(+) m/z:
calcd. for [M−I]+ 1737.1708, found [M−I]+ 1737.1703, calcd. for [M
+Na]+ 1887.0650, found [M+Na]+ 1887.0631, calcd. for [M+K]+
1903.0388, found [M+K]+ 1903.0631, calcd. for [M+Cu]+ 1927.0040,
found [M+Cu]+ 1927.0060.
Apex diffractometer using either Cu Kα radiation or Mo Kα radiation
controlled using the APEX 2010 software package. A semiempirical
method utilizing equivalents was employed to correct for absorption.
Hydrogen atoms were added geometrically and refined with a riding
model. All structures were solved by direct methods with SIR 200432
and refined by full-matrix least-squares procedures utilizing SHELXL-
97.33 Crystallographic data collection and refinement information is
listed in Supporting Information,Table S1−S3. Most of the crystals
diffracted very weakly and are fragile upon exposure to air, leading to
some loss in crystallinity. As a result, some of crystals, including
CH2Cl2@Cu4(L1)4I4, CH2Cl2@Ag4(L1)4I4, DMF@Ag4(L1)4I4,
CH2Cl2@Au4(L1)4I4, and Cu2(L3)3I2) never reached 100% complete-
ness despite several attempts at data collection. Most of the Alert Level
A warnings in the checkCIF file come from this incompleteness. In
addition, many of the crystal structures contained a number of phenyl-
group positional disorders, which were extensively restrained using
EADP and AFIX 66, and were refined anisotropically. For further
refinement, the carbon atoms on disordered phenyl groups were split
into two positions, which were also restrained using EADP and refined
anisotropically. The crystallographic routine SQUEEZE34 was used to
account for disordered solvent molecules, which found 747, 258, 246,
323, 169, and 156 electrons per void volume (Å3) for CH2Cl2@
Cu4(L1)4I4, CH2Cl2@Ag4(L1)4I4, DMF@Ag4(L1)4I4, CH2Cl2@
Au4(L1)4I4, Cu2(L4)3I2, and Au2(L4)3I2, respectively. The other
structures reported here, Cu2(L2)3I2, Cu2(L3)3I2, [Au2(L2)3I2]n, and
[Cu2(L5)3I2]n, were refined without the use of the SQUEEZE
protocol.
Cu2(L3)3I2. CuI (92 mg, 0.24 mmol) was suspended in CH2Cl2 (50
mL) and L3 (180 mg, 0.36 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered and
the solvent removed in a vacuum. The yellow solid was collected and
washed with Et2O (260 mg, 96%). Crystals suitable for X-ray structure
determination were grown from slow diffusion of Et2O into a saturated
solution of the material in CH2Cl2 giving colorless crystals within two
weeks (182 mg, 70% yield from the isolated powder). 1H NMR
(CD2Cl2, 400 MHz): δ 7.80 (br s, 24H), 7.30 (t, 12H, J = 8 Hz), 7.19
(t, 3H, J = 8 Hz), 7.16 (t, 24H, J = 8 Hz), 6.76 (d, 6H, J = 8 Hz),
5.64(s, 3H); 31P NMR (CD2Cl2, 202.468 MHz): δ 7.53; High
resolution ESI-MS(+) m/z: calcd. for [M−I]+ 1737.1708, found [M−
I]+ 1737.1673, calcd. for [M+Na]+ 1887.0650, found [M+Na]+
1887.0631.
Cu2(L4)3I2. CuI (26 mg, 0.135 mmol) was suspended in CH2Cl2 (30
mL) and L4 (100 mg, 0.2 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in a vacuum. The yellow solid was collected and
washed with Et2O (117 mg, 93%). Crystals suitable for X-ray structure
determination were grown from slow diffusion of Et2O into a saturated
solution of the material in CH2Cl2 giving colorless block-shaped
crystals within a couple days (112 mg, 96% yield from the isolated
1
powder). H NMR (CD2Cl2, 400 MHz): δ 8.02 (d, 6H, J = 2 Hz),
ASSOCIATED CONTENT
* Supporting Information
Cystallographic data in CIF format. Further details are given in
Schemes S1−S2, Figures S1−S16, and Tables S1−S6. This
material is available free of charge via the Internet at http://
pubs.acs.org.
7.83 (br s, 24H), 7.37 (t, 12H, J = 8 Hz), 7.22 (t, 24H, J = 8 Hz), 5.78
(t, 3H, J = 2 Hz); 31P NMR (CD2Cl2, 202.468 MHz): δ 9.64; High
resolution ESI-MS(+) m/z: calcd. for [M−I]+ 1740.1607, found [M−
I]+ 1740.1607, calcd. for [M+Na]+ 1889.05, found [M+Na]+
1890.0528.
■
S
Au2(L4)3I2. AuI (44 mg, 0.135 mmol) was suspended in CH2Cl2 (30
mL), and L4 (100 mg, 0.2 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered, and
the solvent removed in a vacuum. The yellow solid was collected and
washed with Et2O (121 mg, 84%). Crystals suitable for X-ray structure
determination were grown from slow diffusion of Et2O into a saturated
solution of the material in CH2Cl2 giving yellow hexagonal plates
within 2 days (115 mg, 95% yield from the isolated powder). 1H NMR
(CD2Cl2, 400 MHz): δ 8.43 (d, 6H, J = 2.4 Hz), 7.78 (m, 24H), 7.41
(m, 12H), 7.37 (m, 24H), 7.34 (t, 3H, J = 2.4 Hz); 31P NMR (CD2Cl2,
202.468 MHz): δ 10.06.
AUTHOR INFORMATION
Corresponding Author
*E-mail: scohen@ucsd.edu. Phone: (858) 822-5596.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
[Au2(L2)3I2]n. AuI (65 mg, 0.2 mmol) was suspended in CH2Cl2 (50
mL), and L2 (150 mg, 0.3 mmol) was added. The solution was stirred
for 30 min producing a clear solution. The solution was filtered and
the solvent removed in a vacuum. The yellow solid was collected and
washed with Et2O (172 mg, 80%). Crystals suitable for X-ray structure
determination were grown from slow diffusion of Et2O into a saturated
solution of the material in CH2Cl2 giving colorless needle-shaped
crystals within two weeks (112 mg, 65% yield from the isolated
powder). 31P NMR (CD2Cl2, 202. 468 MHz): δ 7.63.
We thank Dr. David Puerta, Dr. Jean-Philippe Monserrat, Mr.
Phuong Dau, Mr. Kevin B. Daniel, and Mr. Joshua A. Day
(UCSD) for critical reading of this manuscript. We also thank
Dr. Yongxuan Su (UCSD) for assistance with ESI-MS and Dr.
Moore Curtis (UCSD) for assistance with the refinement of the
X-ray crystal structures. This work was supported by a grant
from the Department of Energy (BES Grant DE-FG02-
08ER46519).
[Cu2(L5)3I2]n. CuI (38 mg, 0.2 mmol) was suspended in CH2Cl2
(50 mL), and L5 (164 mg, 0.3 mmol) was added. The solution was
stirred for 30 min producing a clear solution. The solution was filtered,
and the solvent removed in vacuum. The yellow solid was collected
and washed with Et2O (170 mg, 84%). Colorless block-shaped crystals
suitable for X-ray structure determination were grown from saturated
(hot) DMF solution upon cooling overnight (119 mg, 70% yield from
the isolated powder). 31P NMR (CD2Cl2, 202.468 MHz): δ 6.61.
Mass Spectrometry Analysis. High-resolution electrospray
ionization mass spectrometry (ESI-MS) was performed using an
Agilent 6230 ESI-TOFMS mass spectrometer, and the data was
analyzed using the Agilent MassHunter software suite. Samples were
dissolved in CH2Cl2 and diluted with acetone. Acetone was used as the
working flow to carry the diluted sample to the ESI source.
Single Crystal X-ray Diffraction. Single crystals from the mother
liquor were mounted on nylon loops with Paratone oil and placed
under a nitrogen cold stream (100 K). Data were collected on a Bruker
DEDICATION
■
Dedicated to Prof. Kenneth N. Raymond on the occasion of his
70th birthday.
REFERENCES
■
(1) (a) Caulder, D. L.; Raymond, K. N. Acc. Chem. Res. 1999, 32, 975.
(b) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000, 100, 853.
(c) Fujita, M.; Tominaga, M.; Hori, A.; Therien, B. Acc. Chem. Res.
2005, 38, 369. (d) Chakrabarty, R.; Mukherjee, P. S.; Stang, P. J. Chem.
Rev. 2011, 111, 6810.
(2) (a) Meyer, M.; Kersting, B.; Powers, R. E.; Raymond, K. N. Inorg.
Chem. 1997, 36, 5179. (b) Caulder, D. L.; Raymond, K. N. Angew.
Chem., Int. Ed. 1997, 36, 1439. (c) Scherer, M.; Caulder, D. L.;
Johnson, D. W.; Raymond, K. N. Angew. Chem., Int. Ed. 1999, 38,
1588. (d) Yeh, R. M.; Raymond, K. N. Inorg. Chem. 2006, 45, 1130.
J
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(e) Uerpmann, C.; Malina, J.; Pascu, M.; Clarkson, G. J.; Moreno, V.;
(13) Hahn, F. E.; Isfort, C. S.; Pape, T. Angew. Chem., Int. Ed. 2004,
43, 4807.
(14) (a) Rit, A.; Pape, T.; Hahn, F. E. J. Am. Chem. Soc. 2010, 132,
4572. (b) Rit, A.; Pape, T.; Hepp, A.; Hahn, F. E. Organometallics
2011, 30, 334.
(15) (a) Cangelosi, V. M.; Sather, A. C.; Zakharov, L. N.; Berryman,
O. B.; Johnson, D. W. Inorg. Chem. 2007, 46, 9278. (b) Cangelosi, V.
M.; Zakharov, L. N.; Johnson, D. W. Angew. Chem., Int. Ed. 2010, 49,
1248.
(16) (a) Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. J.
Chem. Soc. A 1966, 1711. (b) Hidai, M.; Tominari, K.; Uchida, Y. J.
Am. Chem. Soc. 1972, 94, 110. (c) Grubbs, R. H. Adv. Synth. Catal.
2007, 349, 34.
Rodger, A.; Grandas, A.; Hannon, M. J. Chem.Eur. J. 2005, 11, 1750.
(f) Albrecht, M.; Liu, Y.; Zhu, S. S.; Schalley, C. A.; Frohlich, R. Chem.
̈
Commun. 2009, 1195. (g) Schultz, D.; Biaso, F.; Shahi, A. R. M.;
Geoffroy, M.; Rissanen, K.; Gagliardi, L.; Cramer, C. J.; Nitschke, J. R.
Chem.Eur. J. 2008, 14, 7180.
(3) (a) Saalfrank, R. W.; Burak, R.; Breit, A.; Stalke, D.; Herbst-Irmer,
R.; Daub, J.; Porsch, M.; Bill, E.; Muther, M.; Trautwein, A. X. Angew.
̈
Chem., Int. Ed. 1994, 33, 1621. (b) Caulder, D. L.; Powers, R. E.; Parac,
T.; Raymond, K. N. Angew. Chem., Int. Ed. 1998, 37, 1840.
(c) Leininger, S.; Fan, J.; Schmitz, M.; Stang, P. J. Proc. Natl. Acad.
Sci. 2000, 97, 1380. (d) Meng, W.; Clegg, J. K.; Thoburn, J. D.;
Nitschke, J. R. J. Am. Chem. Soc. 2011, 133, 13652.
(17) James, S. L. Chem. Soc. Rev. 2009, 38, 1744.
(4) (a) Hiraoka, S.; Harano, K.; Shiro, M.; Ozawa, Y.; Yasuda, N.;
Toriumi, K.; Shionoya, M. Angew. Chem., Int. Ed. 2006, 45, 6488.
(b) Harano, K.; Hiraoka, S.; Shionoya, M. J. Am. Chem. Soc. 2007, 129,
5300. (c) Ronson, T. K.; Fisher, J.; Harding, L. P.; Hardie, M. J. Angew.
Chem., Int. Ed. 2007, 46, 9086.
(5) (a) Paquette, L. A.; Balogh, D. W.; Usha, R.; Kountz, D.;
Christoph, G. G. Science 1981, 211, 575. (b) Olenyuk, B.; Levin, M.
D.; Whiteford, J. A.; Shield, J. E.; Stang, P. J. J. Am. Chem. Soc. 1999,
121, 10434. (c) Levin, M. D.; Stang, P. J. J. Am. Chem. Soc. 2000, 122,
7428.
(18) (a) Puddephatt, R. J. Chem. Soc. Rev. 2008, 37, 2012. (b) Yip, J.
H. K.; Prabhavathy, J. Angew. Chem., Int. Ed. 2001, 40, 2159. (c) James,
S. L.; Mingos, D. M. P.; White, A. J. P.; Williams, D. J. Chem. Commun.
1998, 2323. (d) Lim, S. H.; Olmstead, M. M.; Balch, A. L. Chem. Sci.
2013, 4, 311. (e) Sun, X.; Johnson, D. W.; Caulder, D. L.; Raymond,
K. N.; Wong, E. H. J. Am. Chem. Soc. 2001, 123, 2752.
(19) Lim, S. H.; Olmstead, M. M.; Balch, A. L. J. Am. Chem. Soc.
2011, 133, 10229.
(20) Macgregor, S. A. Chem, Soc. Rev. 2007, 36, 67.
(21) Lim, S. H.; Su, Y.; Cohen, S. M. Angew. Chem., Int. Ed. 2012, 51,
5106.
(6) (a) Olenyuk, B.; Whiteford, J. A.; Fechtenkotter, A.; Stang, P. J.
̈
Nature 1999, 398, 796. (b) Atwood, J. L.; Barbour, L. J.; Dalgarno, S.
J.; Hardie, M. J.; Raston, C. L.; Webb, H. R. J. Am. Chem. Soc. 2004,
126, 13170. (c) Argent, S. P.; Adams, H.; Riis-Johannessen, T.;
Jefferey, J. C.; Harding, L. P.; Ward, M. D. J. Am. Chem. Soc. 2006, 128,
72. (d) Ghosh, K.; Hu, J.; White, H. S.; Stang, P. J. J. Am. Chem. Soc.
2009, 131, 6695. (e) Li, D.; Zhou, W.; Landskron, K.; Sato, S.; Kiely,
C. J.; Fujita, M.; Liu, T. Angew. Chem., Int. Ed. 2011, 50, 5182.
(7) (a) Zheng, Y.-R.; Ghosh, K.; Yang, H.-B.; Stang, P. J. Inorg. Chem.
2010, 49, 4747. (b) Kelley, R. F.; Lee, S. J.; Wilson, T. M.; Nakamura,
Y.; Tiede, D. M.; Osuka, A.; Hupp, J. T.; Wasielewski, M. R. J. Am.
Chem. Soc. 2008, 130, 4277. (c) Caskey, D. C.; Yamamoto, T.;
Addicott, C.; Shoemaker, R. K.; Vacek, J.; Hawkridge, A. M.;
Muddiman, D. C.; Kottas, G. S.; Michl, J.; Stang, P. J. J. Am. Chem.
Soc. 2008, 130, 7620. (d) Hong, M.; Zhao, y.; Su, W.; Cao, R.; Fujita,
M.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. 2000, 122, 4819.
(8) (a) Fiedler, D.; Leung, D. H.; Bergman, R. G.; Raymond, K. N. J.
Am. Chem. Soc. 2004, 126, 3674. (b) Davis, A. V.; Fiedler, D.; Seeber,
G.; Zahl, A.; van Eldik, R.; Raymond, K. N. J. Am. Chem. Soc. 2006,
128, 1324. (c) Leung, D. H.; Bergman, R. G.; Raymond, K. N. J. Am.
Chem. Soc. 2008, 130, 2798. (d) Pluth, M. D.; Tiedemann, B. E. F.; van
Halbeek, H.; Nunlist, R.; Raymond, K. N. Inorg. Chem. 2008, 47, 1411.
(e) Kusukawa, T.; Fujita, M. J. Am. Chem. Soc. 2002, 124, 13576.
(f) Sun, W.; Kusukawa, T.; Fujita, M. J. Am. Chem. Soc. 2002, 124,
11570. (g) Murase, T.; Otsuka, K.; Fujita, M. J. Am. Chem. Soc. 2010,
132, 7864. (h) Mal, P.; Schultz, D.; Beyeh, K.; Rissanen, K.; Nitschke,
J. R. Angew. Chem., Int. Ed. 2008, 47, 8297. (i) Ousaka, N.; Clegg, J. K.;
Nitschke, J. R. Angew. Chem., Int. Ed. 2012, 51, 1464.
(9) (a) Ziegler, M.; Brumaghim, J. L.; Raymond, K. N. Angew. Chem.,
Int. Ed. 2000, 39, 4119. (b) Fiedler, D.; Bergman, R. G.; Raymond, K.
N. Angew. Chem., Int. Ed. 2006, 45, 745. (c) Kawano, M.; Kobayashi,
Y.; Ozeki, T.; Fujita, M. J. Am. Chem. Soc. 2006, 128, 6558. (d) Mal, P.;
Breiner, B.; Rissanen, K.; Nitschke, J. R. Science 2009, 324, 1697.
(10) (a) Brown, C. J.; Bergman, R. G.; Raymond, K. N. J. Am. Chem.
Soc. 2009, 131, 17530. (b) Fiedler, D.; van Halbeek, H.; Bergman, R.
G.; Raymond, K. N. J. Am. Chem. Soc. 2006, 128, 10240. (c) Pluth, M.
D.; Bergman, R. G.; Raymond, K. N. J. Am. Chem. Soc. 2008, 130,
8587. (d) Wang, Z. J.; Brown, C. J.; Bergman, R. G.; Raymond, K. N.;
Toste, F. D. J. Am. Chem. Soc. 2011, 133, 7358. (e) Noh, T. H.; Heo,
E.; Parl, K. H.; Jung, O.-S. J. Am. Chem. Soc. 2011, 133, 1236.
(f) Smulders, M. M. J.; Maarten, M. J.; Nitschke, J. R. Chem. Sci. 2012,
3, 785.
(22) Weber, E.; Hecker, M.; Koepp, E.; Orlia, W. J. Chem. Soc., Perkin
Trans. 2 1988, 1251.
(23) Constable, E. C.; Housecroft, C. E.; Krattinger, B.; Neuburger,
M.; Zehnder, M. Organometallics 1999, 18, 2565.
(24) Based on the Cambridge Structural Database (CSD), the
average bond distances of M(I)-phosphine and M(I)-iodide (M = Cu,
Ag, and Au) in other four-coordinate phosphine-based metal(I) iodide
complexes are ∼2.30, 2.54, and ∼2.40 Å for Cu-P, Ag-P, and Au-P, and
∼2.65, ∼2.84, and ∼2.94 Å for Cu-I, Ag-I, and Au-I, respectively.
(25) To get the cavity volumes of the tetrahedral clusters M4(L1)4I4
(M = Cu+, Ag+, and Au+), the average distance from the centroid of
the overall cluster to the centroids of the central benzene of each
ligand of the cluster was obtained from the crystal structure data. This
value provides an estimation of the radii for a sphere that fits in the
cavity, from which the empty cavity volume was estimated.
(26) (a) Yau, J.; Mingos, D. M. P. J. Chem. Soc., Dalton Trans. 1997,
1103. (b) Lim, S. H.; Schmitt, J. C.; Shearer, J.; Jia, J.; Olmstead, M.
M.; Fettinger, J. C.; Balch, A. L. Inorg. Chem. 2013, 52, 823.
(c) Effendy; Nicola, C. D.; Fianchini, M.; Pettinari, C.; Skelton, B. W.;
Somers, N.; White, A. H. Inorg. Chim. Acta 2005, 358, 763.
(27) (a) Nunokawa, K.; Onaka, S.; Tatematsu, T.; Ito, T.; Sakai, J.
Inorg. Chim. Acta 2001, 322, 56. (b) Muetterties, E. L.; Alegranti, C.
W. J. Am. Chem. Soc. 1972, 6383.
(28) Lozano, E.; Nieuwenhuyzen, M.; James, S. L. Chem.Eur. J.
2001, 7, 2644.
(29) Pluth, M. D.; Raymond, K. N. Chem. Soc. Rev. 2007, 36, 161.
(30) Gorin, D. J.; Toste, F. D. Chem. Soc. Rev. 2008, 3351.
(31) Rodríguez, J. G.; Tejedor, J. L. J. Org. Chem. 2002, 67, 7631.
(32) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.;
Cascarano, G. L.; De Caro, L.; Gaicovazzo, C.; Polidori, G.; Spagna, R.
J. Appl. Crystallogr. 2005, 38, 381.
(33) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(34) van der Sluis, P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.
(11) Kreickmann, T.; Diedrich, C.; Pape, T.; Hyunh, H. V.; Grimme,
S.; Hahn, F. E. J. Am. Chem. Soc. 2006, 128, 11808.
(12) Birkmann, B.; Frohlich, R.; Hahn, F. E. Chem.Eur. J. 2009, 15,
̈
9325.
K
dx.doi.org/10.1021/ic302840x | Inorg. Chem. XXXX, XXX, XXX−XXX