Synthesis of Spirocyclic Diphosphite-Supported Gold Metallomacrocycles via a Protodeauration/Cyclization Strategy: Mechanistic and Binding Studies

Article abstract of DOI:10.1021/acs.inorgchem.8b01805

A spirocylic diphosphite was used to generate P-metalated bimetallic complexes through protodeauration reactions involving LAuC₆H₄^tBu (L = JohnPhos, ^tBuXPhos) and metallomacrocycles through protodeauration/cycli

Full text of DOI:10.1021/acs.inorgchem.8b01805

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Synthesis of Spirocyclic Diphosphite-Supported Gold
Metallomacrocycles via a Protodeauration/Cyclization Strategy:
Mechanistic and Binding Studies
Lindsay J. Schafer,† Kevin J. Garcia,† Andrew W. Baggett,‡ Taylor M. Lord,† Peter M. Findeis,†
Robert D. Pike,§ and Robert A. Stockland, Jr.*,†
†Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, United States
‡Department of Chemistry, Linfield College, McMinnville, Oregon 97128, United States
§Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187, United States
S
* Supporting Information
ABSTRACT: A spirocylic diphosphite was used to generate P-
metalated bimetallic complexes through protodeauration reac-
t
t
tions involving LAuC6H4 Bu (L = JohnPhos, BuXPhos) and
metallomacrocycles through protodeauration/cyclization using
tBuC6H4AuP^PAuC6H4 Bu precursors (P^P = flexible diphos-
t
phine). While the synthesis of the bimetallic complexes followed
a stepwise process, generation of the metallomacrocycles was
highly complex because of a series of reversible ligand
redistribution reactions. The self-assembly was monitored, and
key intermediates were identified by NMR spectroscopy and
high-resolution mass spectrometry. The mechanistic investiga-
tion showed that using flexible diphosphine linkers was critical to the selective synthesis of metallomacrocycles because rigid
diphosphines generated intractable mixtures of linear and cyclic compounds. The X-ray structure of a 32-membered
metallomacrocycle revealed that the compound crystallized in an unsymmetrical collapsed form that was held together by two
supported aurophilic interactions while the flexible diphosphines were folded along opposite sides of the metallomacrocycle. The
solution structure was consistent with a symmetric species, which suggested interconversion between an open and collapsed
form and/or rapid twisting of a collapsed form. The 32-membered metallomacrocycle was used to bind estrogen primarily
through the formation of AuP−O−···H−OR hydrogen bonds.
chemistry to well-defined coordination architectures based
upon phosphorus-metalated M[PO3R2] fragments has been
challenging, partly because of the paucity of precursors.
To this end, we surmised that the spirocyclic diphosphite (1,
shown in Figure 1 in its hydrogen phosphonate form) and its
derivatives could be effective “rigid” linkers for metallomacro-
cycles and MOFs.21 Indeed, tertiary phosphites based upon a
pentaerythritol core have been used to generate dinuclear
complexes and coordination polymers.22 One of the common
methods used for the preparation of late-metal-containing
INTRODUCTION
■
The selection of the linker remains a critical choice in the
design of a new metallomacrocycle or metal−organic frame-
work (MOF). While a host of functional groups have been
used to link metal centers, phosphonates remain a popular
choice.1−4 The majority of phosphonate-based linkers found in
metallomacrocycles and MOFs use the oxygen atoms from the
RPO3 groups to bind metal centers.5 With the noteworthy
2−
exception of pyrophosphite and its derivatives,6,7 using
phosphonates and related compounds to link metal centers
through M−P bonds has received less attention and could
generate frameworks and architectures with unique geometries
and unconventional substrate binding sites. The well-known
8−10
̈
Klaui ligand is the small-molecule version of this approach.
This cobalt-based metalloligand provides an all-oxygen donor
environment and has been used to bind a variety of metals
including lanthanides and actinides,11−13 transition metals,14,15
and main-group elements such as bismuth.16 Furthermore,
there is considerable interest in the preparation of dynamic
coordination polymers, metallomacrocycles, and MOFs.17,18
One approach to the construction of these systems entails the
use of both rigid and flexible components.17−20 Extending this
Figure 1. Spirocyclic linker for the construction of phosphorus-
metalated coordination architectures.
Received: June 29, 2018
© XXXX American Chemical Society
A
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metallomacrocycles and MOFs utilizes a metal precursor
bearing a weakly coordinating ligand such as water, nitrate, or
solvent.23−26 Displacement of this poorly held ligand from the
metal by a donor from the linker is a key step in the self-
assembly process, and a staggering array of metallomacrocycles
and MOFs have been generated using this methodology.
Linker 1 could be used for such a process if the hydrogen
phosphonate form shown in Figure 1 tautomerized to a
secondary phosphite. Although the equilibrium favors the
hydrogen phosphonate form in solution,27,28 the phosphite
form can be trapped by a metal center.6 If the newly attached
metal center contains a sufficiently basic group that was able to
remove the hydrogen from the MPOH fragment (proto-
demetalation),29−33 it would generate a formally neutral
connection between the metal and linker. One version of
this approach begins with an organometallic fragment and
eliminates a small organic molecule that can be easily removed
by evaporation or extraction. Schmidbaur and our group
reported that organogold compounds are quite susceptible to
protodeauration using reagents bearing labile P−H
groups.34−37 Building on this, we have investigated the
susceptibility of 1 to generate well-defined frameworks/
architectures upon treatment with suitable dinuclear organo-
gold precursors.
follow using 1H NMR spectroscopy when monitoring the
protodeauration reactions (vide infra). The bulky dialkylbiar-
ylphosphines were used because of their ability to inhibit the
dynamic solution behavior34 and to provide a model system for
the reaction of 1 with arylgold species. The diphosphines
shown in Scheme 1 were chosen in order to provide flexibility
or rigidity to the coordination architectures. All of the arylgold
precursors exhibited a singlet in the 31P{1H} NMR spectrum
and were isolated as off-white solids.
The molecular structures of 9 and 10 were determined by X-
ray crystallography (Figure 2). In general, diphosphine-linked
dinuclear gold compounds tend to crystallize in one of three
forms: macrocycle, folded polymer, and a stretched (open)
polymer, where the gold compounds are held together by
noncovalent interactions such as hydrogen-bonding and
aurophilic interactions.41,42 It is often unpredictable which
form will crystallize and whether or not close Au···Au contacts
will be observed. Crystals of 9 were grown by cooling a
saturated dichloromethane (CH2Cl2)/tetrahydrofuran (THF)
solution to −10 °C. After several days, colorless crystals were
isolated by filtration. Compound 9 crystallized in the triclinic
̅
system P1 with two independent molecules of 9 per
asymmetric unit. The P−Au−C angles are between
167.49(8) and 174.77(8)°, the Au−C bond lengths are
between 2.043(3) and 2.048(3) Å, and the Au−P distances
are between 2.2814(7) and 2.3000(7) Å. Compound 9
aggregated into 12-membered metallomacrocycles using two
molecules of 9. Noncovalent (aurophilic) interactions were
found between the gold centers of each molecule of 9 with
Au···Au distances of 3.0452(2) and 3.0307(2) Å. No
aurophilic interactions were observed between adjacent
metallomacrocycles because the closest Au···Au contact was
over 8 Å. Crystals of 10 were grown by cooling a saturated
ethyl acetate (EtOAc)/hexane solution to 25 °C from 60 °C.
RESULTS AND DISCUSSION
■
Synthesis of Arylgold Precursors. The approach to the
preparation of the arylgold precursors is summarized in
Scheme 1. For both the mononuclear and dinuclear gold
substrates, the treatment of R3PAuCl or (Ph2P^PPh2)Au2Cl2
with 4-tert-butylphenylboronic acid along with cesium
carbonate generated arylgold precursors (2−11) in moderate
yields.38−40 The 4-tert-butylphenyl (C6H5 Bu) group was
t
selected for this chemistry because it was easy to observe/
̅
10 crystallizes in the triclinic space group P1 with two
molecules of 10 per unit cell along with two molecules of
EtOAc. Similar to 9, complex 10 (Figure 2) crystallized in the
metallomacrocycle form, and a comparison of the bond angles
and distances between the two structures is given in Table 1.
Protodeauration Reactions. In order to probe the ability
of 1 to link two metal centers, protodeauration reactions were
carried out using the mononuclear precursors 2 and 3. Stirring
an acetonitrile (CH3CN)/THF (5:1) suspension of 1 with 2
equiv of 2 or 3 cleanly generated phosphorus-metalated
bimetallic complexes (12 and 13; Scheme 2). Monitoring the
reaction of 1 with 2 in dimethyl sulfoxide (DMSO)-d6 revealed
Scheme 1. Synthesis of Arylgold Precursors
t
a stepwise process beginning with the loss of C6H5 Bu (1H: δ
1.27; −tBu) and formation of the monoaurated intermediate
(C12H9 Bu2PA-Au-[PBO3C5H8PCO3H]). The latter was char-
t
1
acterized by a new doublet (δ 6.97, JHP = 688.8 Hz) for the
unreacted −P(O)−H end in the 1H NMR spectrum along with
two doublets [31P: δ 67.4 (d, PA); 114.4 (d, PB); 2JP P = 461.0
Hz] and a singlet (δ 7.4, PC) in the 31P{1H} NMR spectrum. It
should be noted that 1 was highly soluble in DMSO-d6, while 2
was quite insoluble (ca. <1%). Only under these substrate-
starved conditions were we able to observe the reactive
intermediate. Similar experiments carried out under homoge-
neous conditions (2:1 DMSO-d6/CDCl3) yielded only signals
for 12 when 1 was treated with 2. After ca. 20% conversion
into the monoaurated complex, two new doublets appeared in
A
B
2
the 31P NMR spectrum [δ 67.6 (d), 113.9 (d); JPP = 459.1
Hz] and were assigned to 12 by comparison to an isolated
B
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Table 1. Selected Bond Distances (Å) and Angles (deg)
9
10
Au---Au
3.0307(2)
3.18789(17)
Au−Cipso
Au−P
P−CCC,CC
CC, CC
P−Au−CCC,CC
CC−P,CC−P
2.048(3), 2.044(3)
2.3000(7), 2.2840(7)
1.765(3), 1.770(3)
1.207(4)
171.94(8), 174.77(8)
174.6(3), 175.4(3)
2.049(3), 2.055(3)
2.2937(8), 2.055(3)
1.807(3), 1.808(3)
1.330(5)
174.73(8), 175.51(9)
124.1(2), 127.7(2)
Scheme 2. Synthesis of Bimetallic Complexes through
a
Protodeauration
a
t
(i) LAu(C6H4 Bu) (2.1 equiv), CH3CN/THF (5:1), 16 h, 25 °C.
strongly suggest that the spirocyclic framework is attached to
the gold centers through phosphorus. For these bimetallic
complexes and related compounds, the [PO3R2]− group can be
characterized as either a k1-O-anionic phosphorus(III)
phosphito or a k1-phosphorus(V) phosphonato donor.43
Evidence for the former includes an electron localization
function and natural bond orbital investigation of the bonding
in related ruthenium compounds.44 Igau and co-workers found
that the oxygen had high anionic character, and the Ru−P
bonding was consistent with a dative interaction. Furthermore,
the 31P chemical shifts of the [PO3R2]− fragments from 12 and
13 are in the region (>100 ppm) typically associated with gold
phosphites such as (PhO)3PAuCl, (MeO)3PAuCl, and [P-
(OH)(OR)2]AuCl.36,45,46 As a result, the bonding description
of the [PO3R2]− fragment in 12 and 13 is more congruent with
an L-type donor.47
The molecular structure of 13 is shown in Figure 3 and
t
shows that the two BuXPhosAu (tBuXPhos = 2-di-tert-
butylphosphino-2′,4′,6′-triisopropylbiphenyl) fragments are
located on the same side of the spirocyclic linker with an
intramolecular Au−Au distance of 8.1114(3) Å. This results in
the positioning of the two P−O− groups on the opposite side
of the rigid spirocyclic framework. No aurophilic interactions
were found in this structure. The distance between the two
phosphorus centers in the linker is 5.9413(16) Å. One of the
P−Au−P angles was close to linearity [174.37(4)°], while the
second deviated more significantly [166.31(4)°]. It is note-
worthy that 13 crystallized as a single enantiomer in the chiral
space group P212121. Comparing the Au−P bond lengths from
the Au−PR3 ends with the Au−P−O− groups revealed that the
bulky phosphine formed slightly longer [2.3229(12) and
2.3408(11) Å] bonds than the O-anionic phosphito groups
[2.2989(11) and 2.3084(11) Å]. The two fused 6-membered
Figure 2. Structures of 9 and 10: aggregation into 12-membered
metallomacrocycles linked by aurophilic interactions. Thermal
elipsoids shown at 50% probability with hydrogen atoms and
EtOAc (for compound 10) removed.
sample. Continued stirring resulted in the complete con-
sumption of 1 and 2 and the exclusive formation of 12.
Because of the nature of the spirocyclic linker, the
attachment to gold could occur through oxygen or phosphorus.
2
The large JPP in the 31P{1H} NMR spectra for 12 and 13
C
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However, stirring for 24 h (60 °C) resulted in intractable
mixtures of compounds that exhibited low solubility in all
common solvents including DMSO.
In order to increase the solubility of the reaction products,
analogous reactions were carried out using longer and more
flexible diphosphine-linked diaryldigold precursors (5−7 and
11). Initially, these reactions gave results similar to those of 4
and 8−10. As a representative example, monitoring the
reaction of 1 with 6 yielded signals for the single
protodeauration product [(tBuC6H4)Au[PDPh2(CH2)4Ph2PA]-
Au(PBO3C5H8O3PCH) [31P: δ 42.6 (d, PA, JP P = 507.2 Hz),
116.0 (d, PB), 7.5 (s, PC), 40.3 (s, PD); [m + Na]+ found m/z
1203.1683; calcd m/z 1203.1781] within a few minutes of
mixing along with the {[HPO3(C5H8)O3P]2tAu}− anion and
2
A
B
Figure 3. Molecular structure of 13. Thermal elipsoids shown at 50%
probability with hydrogen atoms removed. Selected bond distances
(Å) and bond angles (deg): Au1−P1 = 2.2989(11), Au1−P3 =
2.3229(12), Au2−P2 = 2.3084(11), Au2−P4 = 2.3408(11), P1−O1 =
1.485(4), P2−O4 = 1.475(3); P4−Au2−P2 = 174.37(4), P1−Au1−
P3 = 166.31(4), Au1−P1−O1 = 126.39(14), Au2−P2−O4 =
121.30(14).
the [(C6H4 Bu)Au(dppb)Au(dppb)Au(C6H4 Bu)]+ [dppb =
t
1,4-bis(diphenylphosphino)butane] cation [31P: δ 44.0 (s),
40.3 (s); found m/z 1709.4266; calcd m/z 1709.4364]. As the
reaction proceeded, [(dppb)2Au2]+2 (found m/z 623.1290;
calcd m/z 623.1326)48 was also identified along with a number
of transient signals. Increasing the temperature to 60 °C and
stirring for 16 h consumed 1 and 6, as well as all of the charged
and transient species. The reaction mixture displayed higher
solubility in DMSO and exhibited a single set of broad signals
rings from the spirocyclic framework result in the generation of
a twisted linker. The extent of the twist was determined by
linking the two phosphorus atoms from the linker and
calculating the dihedral angle [81.71(4)°] between the gold
centers (Au−P−P−Au, across the linker). The angles at the
ends of the linker [114.51(4)° and 108.07(3)°] were
determined by calculating the P−P−Au angles (across the
linker). Thus, the structure of 13 contains a twisted linker with
approximately tetrahedral “corners.”
2
in the 31P NMR spectrum (δ 115.1 and 42.7; JPP = 506 Hz).
While this suggested that the product could be an oligomer/
polymer or framework, we were unable to find end groups in
1
the 31P or H NMR spectra. If the molecular weight of the
material was high, clearly identifying end groups would be
challenging. Alternatively, the product could be cyclic.
Working under this premise, analysis of the crude reaction
mixture revealed the 30-membered metallomacrocycle,49
dppb2Au4[PO3(C5H8)O3P]2 ([m + H]+ found m/z
2093.1609; calcd m/z 2093.1661). However, the crude
reaction mixture was still highly insoluble and contained
several reaction products that were unable to be separated.
The reaction between 1 and 11 initially mirrored these
results. However, in contrast to the reactions of 1 with 4−10,
two sharp doublets were observed in the 31P NMR spectrum
[δ 111.0 (d), 37.5 (d); 2JPP = 519.7 Hz] after heating (16 h, 60
°C). The product from this reaction was identified as the 32-
m e m b e r e d m e t a l l o m a c r o c y c l e { [ P h 2 P -
(CH2)2]2O}2Au4[PO3(C5H8)O3P]2 (14, Scheme 3; ([m +
In contrast to the clean chemistry observed when 1 was
treated with 2 or 3, reactions between 1 and the diphosphine-
t
linked diaryldigold precursors (P^P)Au2(C6H4 Bu)2 (4−11)
were considerably more complex. Stirring a solution (2.4 mM,
t
15:5 DMSO/THF) of 1 with (dppe)Au2(C6H4 Bu)2 [4; dppe
= 1,2-bis(diphenylphosphino)ethane] generated an intractable
mixture after stirring for 24 h at 60 °C. This mixture was highly
insoluble in common solvents and only marginally soluble in
DMSO. Monitoring this reaction by NMR spectroscopy (25
°C, DMSO-d6) and high-resolution mass spectrometry
(HRMS) revealed the formation of tert-butylbenzene within
a few minutes of mixing along with small broad signals in the
31P NMR spectrum assigned to a −Ph2PAAuPBO3− fragment
[δ 40.3 (d, PA), 112.6 (d, PB); 2JP P = 497.0 Hz]. However, the
dominant species observed by 31P NMR was the homoleptic
anion {[HPO3(C5H8)O3P]2Au}− [δ 127.6 (s); found m/z
650.9404; calcd m/z 650.9420] along with the chelate complex
[dppe2Au]+ [δ 22.5 (s); found m/z 993.2308; calcd m/z
993.2372]. Stirring this solution for 24 h resulted in the slow
consumption of 1 and 4. The broad signals at δ 40.3 and 112.6
continued to grow, although significant amounts of the
[dppe2Au]+ chelate as well as the {[HPO3(C5H8)O3P]2}Au−
anion remained after stirring. During the course of the
reaction, a broad signal in the 31P NMR spectrum (δ 127.7)
that was nearly coincident with the signal from the
{[HPO3(C5H8)O3P]2Au}− anion grew and was assigned to
an internal (vide infra) or chain-end −{[PO3(C5H8)O3P]Au-
[PO3(C5H8)O3P]}− anionic fragment. Discrete species were
unable to be isolated from the crude product mixture using
extraction or crystallization. Similar results were obtained using
the dinuclear gold precursors linked by rigid diphosphines (8−
10). In the early stages of these reactions, the dominant species
observed in the 31P NMR spectra were gold phosphito
fragments along with the {[HPO3(C5H8)O3P]2Au}− anion.
A
B
Scheme 3. Synthesis of a Metallomacrocycle through
Protodeauration/Cyclization
D
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H]+ found m/z 2125.1477; calcd m/z 2125.1559). It should be
noted that we cannot distinguish between a closed macrocycle
where the fragments are in similar magnetic environments and
a dynamic system characterized by rapid cleavage/reassembly.
In contrast to the other reaction products, 14 was soluble in
chloroform as well as boiling CH3CN. No dynamic behavior
was observed in the 1H or 31P NMR spectra between −40 and
+65 °C (CDCl3). It was noteworthy that the formation of 14
was relatively insensitive to the concentration of the
protodeauration/cyclization reaction. Increasing the concen-
tration of the reaction by a factor of 4 to promote the
formation of oligomers/polymers still resulted in the sole
formation of 14.
of the tetramer) were 84.87(8) and 85.22(8)°. The angles at
the phosphorus corners (P−P−Au) are between 110.49(7)
and 125.81(7)°.
These results from the mechanistic studies are consistent
with the process shown in Scheme 4. The initial protodeaura-
tion between 1 and 4−11 generated the monoaurated
intermediate. This species underwent reversible ligand
redistribution to generate the homoleptic anion and cation
{[HPO3(C5H8)O3P]2Au}− and [ArAu(P^P)Au(P^P)AuAr]+.
Similar reactions have been reported for mononuclear
systems.36 These ligand-exchange processes were not observed
in the reactions of 1 with 2 or 3 because of the steric bulk of
the dialkylbiarylphosphine ligands.34 Further redistribution
+2
generated a (P^P)2Au+ chelate or (P^P)2Au2 bridged
While 14 could be readily crystallized from CH3CN, the
crystals were extremely fragile. Fortunately, diffusion of EtOAc
into a saturated DMSO solution of 14 afforded single crystals
that were suitable for X-ray diffraction (Figure 4). Instead of
bimetallic complex/oligomers depending on the length and
flexibility of the diphosphine. Indeed, significant amounts of
(dppe)2Au+ were observed in the reaction between 1 and 4
because of the stability of the 5-membered chelate. For
reactions involving rigid and shorter diphosphines, these
redistribution products persisted for the duration of the
reaction, while reactions involving longer and more flexible
diphosphines (5−7 and 11) consumed these charged species.
It is worth noting that, once the metallomacrocycle was
generated, no reversible ligand redistribution was observed.
Both the solution and solid-state structures of diphosphine-
linked gold compounds can be challenging to predict. There
can be a dependence on the overall length as well as the
number of methylene groups (even or odd) in the tether
between the diphenylphosphino fragments.50 In some cases,
shorter tethers between the diphenylphosphino fragments
results in the formation of discrete species, while longer tethers
generate oligomers as well as equilibrium mixtures of cyclic
and acyclic products.41 Because of the higher solubility of 14,
our remaining efforts focused on the chemistry of this
metallomacrocycle.
Over the past few decades, there has been considerable
interest in developing new types of phosphorus-containing
macrocycles because of their applications in mechanically
interlocked molecules and molecular machines.51−54 Addition-
ally, there has been growing interest in the use of macrocycles
to modify the activity of chemotherapeutic agents.55 Recent
examples include using pillar[n]arenes to enhance variations of
photodynamic therapy56 as well as to increase the solubility
and efficacy of tamoxifen.57 For breast cancer, managing the
effects of β-estradiol (estrogen) and estrogenic materials is a
critical concern for estrogen-receptor-positive breast cancer.
Given the size and flexibility of the 32-membered metal-
lomacrocycle (14) as well as the presence of eight oxygen
atoms on the interior, 14 could interact with estrogen. This
Figure 4. Structure of 14: rotated views. Thermal elipsoids at 30%
probability and hydrogen atoms omitted. Selected bond distances (Å)
and angles (deg): Au1−P1 = 2.3034(18), Au1−P5 = 2.3446(19),
Au2−P3 = 2.2960(19), Au2−P6 = 2.3375(19), Au3−P4 = 2.293(2),
Au3−P7 = 2.322(2), Au4−P2 = 2.288(2), Au4−P8 = 2.322(2), P1−
O1 = 1.482(5), P2−O4 = 1.484(6), P3−O7 = 1.493(6), P4−O10 =
1.478(6); Au1−P1−O1 = 117.9(2), Au2−P3−O7 = 119.3(3), Au3−
P4−O10 = 118.7(3), Au4−P2−O4 = 117.2(2), P1−Au1−P5 =
172.39(7), P3−Au2−P6 = 168.78(7), P4−Au3−P7 = 175.68(9), P2−
Au4−P8 = 171.88(10).
1
possibility was investigated using H and 31P NMR spectros-
copy. The treatment of 14 (4.7 mM, dry and deacidified
CDCl3) with estradiol (E2, 1 equiv) resulted in significant
changes in the chemical shifts of several hydrogen atoms from
estradiol. It should be noted that estradiol was quite insoluble
in dry (deacidified) CDCl3; however, the solution of 14 with
estradiol was completely homogeneous, suggesting that the
metallomacrocycle aids in solubilization of the estradiol. The
low solubility of estradiol also complicated our attempts to
determine the stoichiometry of the host−guest complex. The
hydrogen atom most affected by the addition of 14 was 3-OH
(Figure 5). Its resonance moves from 4.56 ppm in the free
state to 8.00 ppm (Δδ = 3.44 ppm) in the presence of 14.
Additionally, the signals for the A-ring hydrogen atoms shifted
the open/expanded system shown in Scheme 3, the cavity of
the metallomacrocycle is compressed and held together by two
aurophilic interactions [3.1699(5) and 3.4936(7) Å]. The
flexibility of the [Ph2P(CH2)2]2O linker accommodates these
aurophilic interactions and twists to bring the spirocyclic
components together and facilitate the metal−metal inter-
actions. The shortest Au−Au contact across the cavity of the
metallomacrocycle is 8.1910(6) Å. Similar to the structure of
13, the P−P distances across each side are 5.897(3) and
5.889(3) Å, while the torsion angles (Au−P−P−Au, each side
E
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Scheme 4. Ligand Redistribution Reactions Observed in the Protodeauration/Cyclization Reactions
generate metallomacrocycles. Once the metallomacrocycle was
generated, no ligand redistribution was observed. These
redistribution reactions could also be circumvented through
the use of bulky phosphine ligands. It is possible that the
observed ligand redistribution reactions are specific to gold,
and future work will answer the question of whether or not
other metal phosphito complexes undergo similar processes. In
the X-ray structure of a 32-membered metallomacrocycle, the
cavity was compressed because of the twisting of the
compound in order to accommodate two aurophilic inter-
actions. Metallomacrocycle 14 provides a flexible framework
that can bend and twist to accommodate guest molecules.
Additional binding/recognition studies using 14 and related
compounds are ongoing and will be reported in due course.
Figure 5. Interaction between the metallomacrocycle and estrogen
(25 °C, CDCl3).
closer together relative to free estradiol. Only minor changes
1
were observed in the H and 31P NMR spectra for 14 when
EXPERIMENTAL SECTION
estradiol was added. The shifting of 3-OH is likely due to
hydrogen bonding with the oxygen atom from the Au−P−O−
group.54,58,59 Additionally, the shifting of the A-ring hydrogen
atoms could be an indication that the ring was close enough for
an interaction with the gold center.60−63 Although 14 could be
readily characterized by HRMS, the estrogen adduct did not
survive the electrospray conditions. With the exception of 3-
OH, no significant changes were observed from either 14 or
estradiol upon cooling of this solution to −40 °C (see the
Supporting Information). Only 3-OH moved as the temper-
ature was lowered because of the known dependence of
hydrogen bonding on the temperature.64 The ability of 14 to
interact with testosterone was also screened. The treatment of
14 with testosterone (1 equiv) resulted in very minor changes
in the chemical shifts and coupling constants of the hydrogen
atoms from 14 and testosterone.
■
General Considerations. All solvents were dried using a Grubbs-
type solvent purification system and distilled prior to use with the
exception of CH3CN (CaH2) and DMSO (3 Å sieves). The
chlorogold precursors (P^P)Au2Cl2 were generated by the displace-
ment of dimethyl sulfide from (Me2S)AuCl using 0.5 equiv of the
diphosphine in CH2Cl2.65−70 The mononuclear precursors
t
t
[tBuXPhosAu(C6H4 Bu) and JohnPhosAu(C6H4 Bu)] ( JohnPhos =
2-biphenyldi-tert-butylphosphine) were generated following literature
procedures.71 1 was generated by a modification of the literature
procedure as described below.21 DMSO-d6 was dried over activated
molecular sieves (3 Å). CDCl3 was dried over CaH2 and distilled
1
immediately prior to use. H NMR chemical shifts were determined
by reference to residual nondeuterated solvent resonances, and
13C{1H} chemical shifts were determined by reference to deuterated
solvent resonances. Coupling constants are given in hertz. 31P{1H}
NMR spectra were referenced to external H3PO4 (0 ppm). Standard
flash silica gel [60 Å, treated with triethylamine (NEt3)] was used for
the chromatographic isolation of arylgold compounds. Silica (thin-
layer chromatography) plates were rinsed with NEt3 solutions and
dried immediately prior to use. The connectivity and individual peak
assignments were determined through analysis of standard 1D
experiments along with heteronuclear single quantum coherence,
attached proton test, and correlation NMR spectra. ABX systems were
modeled using Spinworks. Elemental analyses were determined by
Midwest Microlabs. HRMS data were obtained on a Thermo
Scientific Exactive Plus liquid chromatography/mass spectrometry
system (electrospray ionization, ESI).
CONCLUSIONS
■
This work demonstrated that a spirocyclic diphosphite can
successfully be used for the preparation of bimetallic
complexes through protodeauration and metallomacrocycles
through a protodeauration/cyclization process. A mechanistic
investigation revealed that the gold phosphito intermediates
undergo a series of reversible ligand redistribution reactions to
generate charged species. Depending on the size and geometry
of the tether linking the diphenylphosphino groups together,
these charged species either persisted or were consumed to
Preparation of 2,4,8,10-Tetraoxa-3,9-diphosphaspiro[5.5]-
undecane 3,9-Dioxide (1). The title compound was made by a
F
DOI: 10.1021/acs.inorgchem.8b01805
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
modification of the literature procedure.21 A round-bottom flask was
charged with pentaerythritol (1.00 g, 7.34 mmol) and a magnetic
stirring bar. After the flask was sealed with a septum and the
atmosphere was exchanged with nitrogen, diphenyl phosphite (3.00
mL, 15.7 mmol) and pyridine (10 mL) were added by syringe. The
mixture was stirred for 2 h, followed by the injection of
dichloromethane (60 mL). A white solid formed and was triturated
by vigorous stirring for 20 min. The solid was collected by filtration
and triturated a second time with dichloromethane (60 mL). The
solid was collected on a glass frit, washed with dichloromethane (50
mL), and dried under vacuum to afford 1 as a free-flowing powder
(1.03 g, 62%).
EtOAc). After drying over MgSO4, the suspension was filtered, and
the volatiles were removed to afford the title compound as a white
solid (0.993 g, 81%). Anal. Calcd for C48H54Au2P2: C, 53.05; H, 5.01.
Found: C, 53.07; H, 4.93. 1H NMR (CDCl3, 25 °C): δ 7.69 (dd, 8H,
J = 11.5, 7.5, ArH), 7.49 (m, 4H, ArH), 7.42 (m, 12H, ArH), 7.32 (d,
4H, J = 7.5, ArH), 2.41 (m, 4H, −CH2−), 1.85 (m, 4H, −CH2−).
1.30 (s, 18H, −CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 169.9 (d, J =
117.7, quat), 148.5 (s, quat), 139.2 (s, ArCH), 133.6 (d, J = 13.3,
ArCH), 132.1 (d, J = 46.4, quat), 131.3 (s, ArCH), 129.3 (d, J = 10.6,
ArCH), 124.7 (d, J = 6.4, ArCH), 34.5 (s, quat), 31.6 (s, −CH3), 28.1
(d, J = 29.7 −CH2−), 27.2 (dd, J = 16.5, 5.5, −CH2−). 31P{1H}
NMR (CDCl3, 25 °C): δ 39.2 (s).
t
t
Preparation of LAu2(C6H4 Bu)2 Precursors. General Proce-
Preparation of (dpppent)Au2(C6H4 Bu)2 [7; dpppent = 1,5-
dure A. A vial (30 mL) was charged in air with the LAu2Cl2 precursor
(1 equiv), Cs2CO3 (4 equiv), 4-tert-butylphenylboronic acid (4
equiv), and a magnetic stirring bar. The atmosphere was exchanged
for nitrogen using a vacuum manifold, and 15 mL of isopropyl alcohol
(reagent grade) was injected by syringe. After stirring at 50 °C for 16
h in a block heater, the reaction mixture was concentrated and dried
under vacuum for 24 h. The residue was triturated with 10 mL of
methanol for 2 h. The insoluble material was separated using a
centrifuge and was subsequently triturated with THF (30 mL) or
dichloromethane (30 mL) for 1 h and filtered through Celite. The
volatiles were removed under vacuum, and the crude product was
purified by column chromatography. Because of the potential for
decomposition of the arylgold compound, the silica gel was stirred
with 10% NEt3 in EtOAc for 30 min, loaded onto the column, and
flushed with eluent (3 times the column volume) immediately prior to
use.
Bis(diphenylphosphino)pentane]. General procedure A was followed
using (dpppent)Au2Cl2 (1.000 g, 1.105 mmol), Cs2CO3 (1.440 g,
4.420 mmol), and 4-tert-butylphenylboronic acid (0.787 g, 4.42
mmol). Chromatography details: 45 g of NEt3-treated silica gel,
hexane/EtOAc (gradient 100:0−80:20), Rf = 0.48 (2:1 hexane/
EtOAc). After drying over MgSO4, the suspension was filtered, and
the volatiles were removed to afford the title compound as a white
solid (0.874 g, 85%). Anal. Calcd for C49H56Au2P2: C, 53.46; H, 5.13.
Found: C, 53.49; H, 5.18. 1H NMR (CDCl3, 25 °C): δ 7.70 (m, 8H,
ArH), 7.49 (m, 4H, ArH), 7.42 (m, 12H, ArH), 7.30 (d, 4H, J = 7.9,
ArH), 2.37 (m, 4H, −CH2−), 1.72 (m, 6H, −CH2−), 1.29 (s, 18H,
−CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 169.9 (d, J = 117.2, quat),
148.4 (s, quat), 139.2 (s, ArCH), 133.6 (d, J = 13.0, ArCH), 132.3 (d,
J = 46.4, quat), 131.2 (s, ArCH), 129.2 (d, J = 10.2, ArCH), 124.7 (d,
J = 3.9, ArCH), 34.5 (s, quat), 32.0 (t, J = 14.5, −CH2−), 31.7 (s,
−CH3), 27.7 (d, J = 29.7, −CH2−), 24.8 (d, J = 4.7, −CH2−).
31P{1H} NMR (CDCl3, 25 °C): δ 39.1 (s).
t
Preparation of (dppe)Au2(C6H4 Bu)2 (4). General procedure A was
t
followed using (dppe)Au2Cl2 (1.000 g, 1.158 mmol), Cs2CO3 (1.570
g, 4.665 mmol), and 4-tert-butylphenylboronic acid (0.830 g, 4.66
mmol). Chromatography details: 61 g of NEt3-treated silica gel,
hexane/EtOAc (gradient: 100:0−0:100), Rf = 0.40 (3:1 hexane/
EtOAc). After drying over MgSO4, the suspension was filtered, and
the volatiles were removed to afford the title compound as a white
solid (0.873 g, 71%). Anal. Calcd for C46H50Au2P2: C, 52.18; H, 4.76.
Found: C, 52.02; H, 4.70. 1H NMR (CDCl3, 25 °C): δ 7.75 (m, 8H,
Ar−H), 7.55 (m, 4H, Ar−H), 7.48 (m, 12H, Ar−H), 7.38 (d, 4H, J =
Preparation of (dpephos)Au2(C6H4 Bu)2 [8; DPEphos = (Oxydi-
2,1-phenylene)bis(diphenylphosphine)]. General procedure A was
followed using (DPEphos)Au2Cl2 (1.000 g, 0.997 mmol), Cs2CO3
(1.299 g, 3.987 mmol), and 4-tert-butylphenylboronic acid (0.710 g,
3.99 mmol). Chromatography details: 70 g of NEt3-treated silica gel,
hexane/EtOAc (gradient 100:0−80:20), Rf = 0.34 (3:1 hexane/
EtOAc). After drying over MgSO4, the suspension was filtered, and
the volatiles were removed to afford the title compound as a white
solid (0.882 g, 74%). Anal. Calcd for C56H54Au2OP2: C, 56.10; H,
4.54. Found: C, 55.85; H, 4.61. 1H NMR (CDCl3, 25 °C): δ 7.53 (dd,
4H, J = 11.5, 7.7, Ar−H), 7.46 (m, 4H, ArH), 7.39 (m, 4H, ArH),
7.21−7.07 (m, 22H, ArH), 6.78 (ddd, 2H, J = 13.5, 7.8, 1.9, ArH),
1.26 (s, 18H, −CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 168.5 (d, J =
120.3, quat), 160.3 (d, J = 7.2, quat), 147.8 (s, quat), 139.1 (s,
ArCH), 135.6 (d, J = 14.1, ArCH), 134.6 (d, J = 4.2, ArCH), 133.6
(d, J = 13.8, ArCH), 133.5 (s, ArCH), 131.2 (d, J = 49.3, quat), 131.3
(d, J = 2.2, ArCH), 130.2 (d, J = 2.4, ArCH), 129.8 (d, J = 50.7, quat),
129.1 (d, J = 10.7, ArCH), 124.7 (d, J = 7.4, ArCH), 124.3 (d, J = 5.4,
ArCH), 122.2 (d, J = 47.2, quat), 120.9 (d, J = 4.5, ArCH), 34.4 (s,
quat), 31.7 (s, −CH3). 31P{1H} NMR (CDCl3, 25 °C): δ 37.3 (s).
7.7, Ar−H), 2.76 (br s, 4H, −CH2−), 1.33 (s, 18H, −CH3). 13C{1H}
2
NMR (CDCl3, 25 °C): δ 169.8 (X part of an ABX pattern, JCP
=
5
3
118.2, JCP = 0, JPP = 52.4, Δδ = 0.8 ppm, quat), 148.7 (s, quat),
139.1 (s, −CH), 133.7 (app t, J = 6.8, −CH), 131.7 (s, −CH), 130.9
1
4
3
(X part of an ABX pattern, JCP = 45.4, JCP = 1.5, JPP = 52.8, Δδ =
2.4 ppm, quat), 129.5 (app t, J = 5.2, −CH), 124.8 (br s, −CH), 34.5
(s, quat), 31.6 (s, −CH3), 24.1 (br t, J = 17.4, −CH2−). 31P{1H}
(CDCl3, 25 °C): δ 42.0 (s).
t
Preparation of (dppp)Au2(C6H4 Bu)2 [5; dppp = 1,3-Bis-
(diphenylphosphino)propane]. General procedure A was followed
using (dppp)Au2Cl2 (1.000 g, 1.140 mmol), Cs2CO3 (1.492 g, 4.580
mmol), and 4-tert-butylphenylboronic acid (0.812 g, 4.56 mmol).
Chromatography details: 55 g of NEt3-treated silica gel, hexane/
EtOAc (gradient 100:0−80:20), Rf = 0.45 (3:1 hexane/EtOAc). After
drying over MgSO4, the suspension was filtered, and the volatiles were
removed to afford the title compound as a white solid (0.960 g, 79%).
Anal. Calcd for C47H52Au2P2: C, 52.62; H, 4.89. Found: C, 52.68; H,
4.91. 1H NMR (CDCl3, 25 °C): δ 7.72 (dd, 8H, J = 11.5, 7.7, ArH),
7.48 (m, 4H, ArH), 7.42 (t, 4H, J = 7.5, ArH), 7.35 (t, 8H, J = 7.5,
ArH), 7.28 (d, 4H, J = 7.9, ArH), 2.94 (m, 4H, −CH2−), 1.98 (m,
2H, −CH2−), 1.31 (s, 18H, −CH3). 13C{1H} NMR (CDCl3, 25 °C):
δ 169.3 (d, J = 117.3, quat), 148.3 (s, quat), 139.4 (s, ArCH), 133.8
(d, J = 13.3, ArCH), 131.6 (d, J = 46.7, quat), 131.3 (s, ArCH), 129.2
(d, J = 10.4, ArCH), 124.6 (d, J = 5.9, ArCH), 34.5 (s, quat), 31.7 (s,
−CH3), 29.1 (dd, J = 29.1, 10.4, −CH2−), 20.1 (t, J = 4.4, −CH2−).
31P{1H} NMR (CDCl3, 25 °C): δ 36.7 (s).
t
Preparation of (dppa)Au2(C6H4 Bu)2 [9; dppa = 1,2-Bis-
(diphenylphosphino)acetylene]. General procedure A was followed
using (dppa)Au2Cl2 (1.000 g, 1.164 mmol), Cs2CO3 (1.517 g, 4.656
mmol), and 4-tert-butylphenylboronic acid (0.829 g, 4.66 mmol).
Chromatography details: 30 g of NEt3-treated silica gel, hexane/
EtOAc (gradient 100:0−80:20), Rf = 0.26 (3:1 hexane/EtOAc). After
drying over MgSO4, the suspension was filtered, and the volatiles were
removed to afford the title compound as a white solid (0.948 g, 77%).
X-ray-quality crystals were grown by cooling a THF/CH2Cl2 solution.
A sample of 9 (0.500 g) was suspended in THF (5 mL), and CH2Cl2
(∼20 mL) was added until a homogeneous solution was obtained.
The solution was filtered through Celite, placed in a scratched sample
vial (27 mL), and sealed with a Teflon-lined crimp cap. The vial was
allowed to stand undisturbed for 5 days (−10 °C). Colorless crystals
of 9 were separated by filtration and dried under vacuum (0.36 g
72%). Anal. Calcd for C46H46Au2P2: C, 52.38; H, 4.40. Found: C,
t
Preparation of (dppb)Au2(C6H4 Bu)2 (6). General procedure A was
1
followed using (dppb)Au2Cl2 (1.000 g, 1.122 mmol), Cs2CO3 (1.462
g, 4.487 mmol), and 4-tert-butylphenylboronic acid (0.799 g, 4.49
mmol). Chromatography details: 57 g of NEt3-treated silica gel,
hexane/EtOAc (gradient 100:0−80:20), Rf = 0.55 (3:1 hexane/
52.56; H, 4.12. H NMR (CDCl3, 25 °C): δ 7.84 (dd, 8H, J = 13.4,
7.6, ArH), 7.48 (m, 16H, ArH), 7.32 (d, 4H, J = 7.6, ArH), 1.30 (s,
18H, −CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 166.6 (d, J = 122.3,
quat), 149.0 (s, quat), 139.1 (s, ArCH), 133.7 (d, J = 15.8, ArCH),
G
DOI: 10.1021/acs.inorgchem.8b01805
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
132.2 (d, J = 2.1, ArCH), 129.7 (d, J = 55.5, quat), 129.6 (d, J = 11.9,
ArCH), 124.8 (d, J = 6.6, ArCH), 102.7 (dd, J = 68.8, 6.1, C−),
34.6 (s, quat), 31.6 (s, −CH3). 31P{1H} NMR (CDCl3, 25 °C): δ 21.1
(s).
−CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 150.3 (d, J = 15.8, q),
141.4 (d, J = 6.4, q), 134.8 (d, J = 6.5, ArCH), 133.2 (d, J = 7.3,
ArCH), 130.9 (d, J = 2.0, ArCH), 129.7 (s, ArCH), 129.5 (s, ArCH),
128.9 (s, ArCH), 128.8 (s, ArCH), 127.1 (d, J = 5.4, ArCH), 126.7
(dd, J = 36.2, 6.0, q), 64.4 (d, J = 3.2, −CH2−), 64.3 (d, J = 3.3,
−CH2−), 38.1 (d, J = 19.0, q), 37.4 (t, J = 4.3, q), 31.3 (d, J = 6.8,
−CH3), 31.2 (d, J = 6.8, −CH3). 31P{1H} NMR (CDCl3, 25 °C): δ
114.2 (d, J = 466.2, −P(O)−), 66.4 (d, J = 466.2, −PR3).
t
Preparation of (dppee)Au2(C6H4 Bu)2 [10; dppee = (E)-1,2-
Bis(diphenylphosphino)ethane]. General procedure A was followed
using (dppee)Au2Cl2 (1.000 g, 1.161 mmol), Cs2CO3 (1.513 g, 4.644
mmol), and 4-tert-butylphenylboronic acid (0.827 g, 4.65 mmol).
Chromatography details: 50 g of NEt3-treated silica gel, hexane/
EtOAc (gradient 100:0−80:20), Rf = 0.31 (3:1 hexane/EtOAc). After
drying over MgSO4, the suspension was filtered, and the volatiles were
removed to afford the title compound as a white solid (0.801 g, 65%).
Anal. Calcd for C46H48Au2P2: C, 52.28; H, 4.58. Found: C, 52.40; H,
4.37. X-ray-quality crystals were grown by cooling an EtOAc/hexane
solution. A sample of 10 (0.500 g) and a microstirring bar were added
to a 27 mL scratched sample vial and sealed with a Teflon-lined crimp
cap. While the mixture was heated (60 °C) and stirred, EtOAc was
added by syringe until the compound was fully dissolved (∼2 mL).
With continued heating, hexane (∼20 mL) was added by syringe. The
heated vial was cooled to 25 °C and allowed to stand undisturbed for
72 h. The colorless crystals were separated by filtration and dried
Preparation of [tBuXPhosAu]2[PO3C5H8O3P] (13). General method
t
B was followed using (tBuXPhos)AuC6H4 Bu (0.200 g, 0.265 mmol)
and 1 (0.029 g, 0.13 mmol). The crude reaction mixture was dried
under vacuum and extracted with benzene (30 mL). After filtering
through diatomaceous earth, the solution was concentrated under
vacuum until 5 mL remained. The addition of hexane (30 mL),
followed by stirring for 30 min, resulted in the formation of a fine
white solid, which was isolated through centrifugation and removal of
the solution. The solid was dried under vacuum to afford 0.165 g
(88%) of a white powder. HRMS ESI. Calcd for C63H99Au2O6P4 [(M
+ H)+]: m/z 1469.5719. Found: m/z 1469.5695. Anal. Calcd for
1
C63H98Au2O6P4: C, 51.50; H, 6.72. Found: C, 51.26; H, 6.32. H
NMR (CDCl3, 25 °C): δ 7.83 (brt, 2H, J = 7.4, ArH), 7.45 (m, 4H,
ArH), 7.26 (m, 2H, ArH), 7.14 (brs, 4H, ArH), 4.10 (t, 2H, J = 12.3,
−CH2−), 4.03 (dd, 2H, J = 14.5, 11.5, −CH2−), 3.73 (t, 2H, J = 12.3,
−CH2−), 3.66 (t, 2H, J = 12.1, −CH2−), 2.99 (spt, 2H, J = 6.9,
iPrCH), 2.32 (m, 4H, iPrCH), 1.40 (brd, 36H, J = 14.9, −CH3), 1.32
(d, 6H, J = 7.1, −CH3), 1.31 (d, 6H, J = 7.0, −CH3), 1.29 (d, 12H, J
= 7.0, −CH3), 0.89 (d, 12H, J = 6.7, −CH3). 13C{1H} NMR (CDCl3,
25 °C): δ 149.8 (s, quat), 148.5 (d, J = 16.6, quat), 145.7 (s, quat),
145.6 (s, quat), 135.7 (d, J = 6.3, ArCH), 135.1 (d, J = 5.4, quat),
134.9 (d, J = 7.9, ArCH), 130.4 (s, ArCH), 129.1 (dd, J = 33.6, 6.0,
quat), 126.7 (d, J = 5.6, ArCH), 122.9 (s, ArCH), 122.5 (s, ArCH),
64.0 (d, J = 3.7, −CH2−), 63.9 (d, J = 4.0, −CH2−), 38.6 (d, J = 19.8,
1
under vacuum (0.41 g, 82%). H NMR (CDCl3, 25 °C): δ 7.67 (m,
8H, Ar−H), 7.48 (m, 16H, Ar−H), 7.37 (t, 2H, J = 17.9, CH), 7.32
(m, 4H, Ar−H), 1.29 (s, 18H, −CH3). 13C{1H} NMR (CDCl3, 25
°C): δ 168.4 (X part of an ABX pattern, 2JCP = 117.9, 3JPP = 38.0, 5JCP
= 0, Δδ = 0.7 Hz, quat), 148.6 (s, quat), 142.4 (X part of an ABX
1
3
2
pattern, JCP = 36.7, JPP = 38.0, JCP = 7.5, Δδ = 4.7 Hz, CH),
138.8 (s, ArCH), 133.9 (app t, J = 7.0, ArCH), 131.7 (s, ArCH),
130.0 (X part of an ABX pattern, 1JCP = 49.4, 3JPP = 38.0, 4JCP = 0, Δδ
= 2.5 Hz, CH), 129.4 (app t, J = 5.4, ArCH), 124.5 (app t, J = 3.0,
ArCH), 34.3 (s, quat), 31.4 (s, −CH3). 31P{1H} NMR (CDCl3, 25
°C): δ 39.1 (s).
t
i
Preparation of (Ph2P(CH2)2O(CH2)2PPh2)Au2(C6H4 Bu)2 (11). Gen-
quat), 37.6 (brt, J = 4.3, quat), 33.5 (s, PrCH), 31.6 (d, J = 6.5,
i
i
eral procedure A was followed using (Ph2P(CH2)2O(CH2)2PPh2)-
Au2Cl2 (1.000 g, 1.102 mmol), Cs2CO3 (1.436 g, 4.407 mmol), and 4-
tert-butylphenylboronic acid (0.785 g, 4.41 mmol). Chromatography
details: 51 g of NEt3-treated silica gel, hexane/EtOAc (gradient
100:0−50:50), Rf = 0.54 (2:1 hexane/EtOAc). After drying (MgSO4),
the suspension was filtered, and the volatiles removed to afford the
title compound as a white solid (0.827 g, 68%). Anal. Calcd for
C48H54Au2OP2: C, 52.28; H, 4.94. Found: C, 52.57; H, 5.11. 1H
NMR (CDCl3, 25 °C): δ 7.69 (dd, 8H, J = 11.3, 7.5, ArH), 7.50 (m,
4H, ArH), 7.45−7.38 (m, 12H, ArH), 7.30 (d, 4H, J = 7.3, ArH), 3.77
(dt, 4H, J = 12.1, 7.1, −CH2−), 2.71 (dt, 4H, J = 9.7, 7.0, −CH2−),
1.29 (s, 18H, −CH3). 13C{1H} NMR (CDCl3, 25 °C): δ 169.6 (d, J =
118.5, quat), 148.4 (s, quat), 139.2 (s, ArCH), 133.7 (d, J = 13.5,
ArCH), 132.1 (d, J = 47.3, quat), 131.2 (d, J = 2.2, ArCH), 129.2 (d, J
= 10.6, ArCH), 124.7 (d, J = 6.3, ArCH), 66.9 (d, J = 9.9, −CH2−),
34.5 (s, quat), 31.7 (s, −CH3), 29.1 (d, J = 29.7, −CH2−). 31P{1H}
NMR (CDCl3, 25 °C): δ 34.6 (s).
−CH3), 31.23 (s, PrCH), 31.19 (s, PrCH), 26.63 (s, −CH3), 26.61
(s, −CH3), 23.9 (s, −CH3), 23.6 (s, −CH3), 23.41 (s, −CH3), 23.37
(s, −CH3). 31P{1H} NMR (CDCl3, 25 °C): δ 114.4 (d, J = 473.5,
−P(O)−), 64.6 (d, J = 473.5, −PR3).
Preparation of Metallomacrocycles [Ph2P(CH2)2O-
(CH2)2PPh2]2Au4[PO3C5H8O3P]2 (14). A vial (20 mL) was charged
with 1 (0.0105 g, 0.0460 mmol), 11 (0.050 g, 0.045 mmol), and a
magnetic stirring bar. After sealing with a septum and exchanging the
atmosphere for nitrogen using a manifold, CH3CN (18 mL) was
added by syringe. The reaction mixture was heated (60 °C) in a block
heater with stirring for 16 h. Without cooling, the reaction mixture
was rapidly filtered through Celite into a scratched vial (20 mL). The
vial was sealed with a septum, and the reaction mixture was
concentrated under a nitrogen flow until it turned cloudy. After
standing in a cabinet for 48 h, microcrystalline 14 was isolated by
filtration and dried under vacuum (0.040 g, 83%). In some reactions,
1−3% of a secondary species was observed in the 31P NMR spectrum
even after multiple recrystallizations [CDCl3; δ 112.3 (d), 35.3 (d),
2JPP = 528.1 Hz] and was tentatively assigned as a trace of an alternate
Preparation of Bimetallic Complexes: General Procedure B.
t
A vial (10 mL) was charged in air with LAuC6H4 Bu (2.1 equiv), 1 (1
equiv), and a magnetic stirring bar. The atmosphere was exchanged
for nitrogen using a manifold. CH3CN (6 mL) and THF (1 mL) were
injected by syringe, and the resulting suspension was stirred at 25 °C
for 16 h. The bimetallic complexes were separated by extraction/
precipitation as described in the following sections.
metallomacrocycle. HRMS ESI. Calcd for C66H73Au4O14P8 [(M +
H)+]: m/z 2125.1559. Found: m/z 2125.1477. Anal. Calcd for
1
C66H72Au4O14P8: C, 37.31; H, 3.42. Found: C, 36.98; H, 3.48. H
NMR (CDCl3, 25 °C): δ 7.72 (m, 16H, ArH), 7.51−7.38 (m, 24H,
ArH), 4.15 (t, 4H, J = 11.7, −POCH2−), 4.09 (t, 4H, J = 12.6,
−POCH2−), 3.99 (t, 4H, J = 12.5, −POCH2−), 3.79 (t, 4H, J = 12.7,
−POCH2−), 3.73 (m, 4H, −OCH2−), 3.60 (m, 4H, −OCH2−), 3.04
(m, 4H, −CH2P−), 2.68 (m, 4H, −CH2P−). 13C{1H} NMR (CDCl3,
25 °C): δ 134.6 (d, J = 13.5, ArH), 133.1 (d, J = 12.2, ArH), 131.8 (s,
ArH), 130.9 (s, ArH), 130.1 (d, J = 50.7, quat), 129.3 (d, J = 48.8,
quat), 64.7 (br s, −OCH2−), 64.5 (br s, −OCH2−), 63.9 (br s,
−OCH2−), 37.1 (s, quat), 29.2 (d, J = 30.3, −CH2−). 31P{1H} NMR
(CDCl3, 25 °C): δ 111.2 (d, J = 524.9, P−O−), 35.6 (d, J = 525.2,
PR3).
Preparation of [JohnPhosAu]2[PO3C5H8O3P] (12). General
t
method B was followed using (JohnPhos)AuC6H4 Bu (0.200 g,
0.318 mmol) and 1 (0.034 g, 0.15 mmol). The crude reaction mixture
was centrifuged, and the CH3CN/THF solution was discarded. The
solid was extracted with THF (5 mL × 2) and dried under vacuum to
afford 0.167 g (92%) of a white powder. HRMS ESI. Calcd for
C45H63Au2O6P4 [(M + H)+]: m/z 1217.2902. Found: m/z 1217.2873.
Anal. Calcd for C45H62Au2O6P4: C, 44.42; H, 5.14. Found: C, 44.39;
1
H, 5.35. H NMR (CDCl3, 25 °C): δ 7.82 (t, 2H, J = 7.1, ArH),
7.55−7.42 (m, 10H, ArH), 7.24 (m, 2H, ArH), 7.14 (m, 4H, ArH),
4.14 (dd, 2H, J = 17.0, 11.5, −CH2−), 4.05 (dd, 2H, J = 15.4, 11.5,
−CH2−), 3.77 (t, 2H, J = 11.4, −CH2−), 3.71 (t, 2H, J = 11.5,
−CH2−), 1.39 (d, 18H, J = 15.1, −CH3), 1.38 (d, 18H, J = 15.1,
NMR Monitoring Experiments. Bimetallic Complex and
Metallomacrocycle Synthesis. An NMR tube (5 mm) was charged
with 1 (0.0050 g, 0.022 mmol) along with the mononuclear or
dinuclear arylgold precursor (2−11; 2 equiv for 2 and 3; 1 equiv for
H
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Article
4−11). After the atmosphere was exchanged for nitrogen using a
manifold, DMSO-d6 (0.5 mL) was injected by syringe.
Metallomacrocycle 14 with Estradiol. An NMR tube (5 mm) was
charged with 14 (0.0055 g, 2.6 μmol) and estrogen (0.0007 g, 3
μmol) and capped with a rubber septum. After the atmosphere was
exchanged for nitrogen using a manifold, CDCl3 (freshly dried over
CaH2 and distilled) was injected by syringe.
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ORCID
Robert D. Pike: 0000-0002-8712-0288
Robert A. Stockland, Jr.: 0000-0002-4351-6395
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors acknowledge the National Science Foundation for
generous support of this work (Grant CHE-1300088) as well
as the funds to purchase the NMR spectrometer (Grant CHE-
0521108) and are indebted to the NSF (Grant CHE-0443345)
and the College of William and Mary for the purchase of the X-
ray equipment. The authors thank Brian Smith and Hasan
Arslan for helpful discussions.
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