Luminescent Di- and Tetranuclear Gold Complexes of Bis(diphenylphosphinyl)-Functionalized Dipyrido-Annulated N-Heterocyclic Carbene

Article abstract of DOI:10.1021/acs.inorgchem.9b00514

Phosphine-functionalized N-heterocyclic carbene (NHC) ligands are known to complex group 11 metal centers to form multinuclear complexes with photoluminescence properties. This study reports a structurally rigid ortho-substituted dipyrido-annulated NHC wi

Full text of DOI:10.1021/acs.inorgchem.9b00514

Article
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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Luminescent Di- and Tetranuclear Gold Complexes of
Bis(diphenylphosphinyl)-Functionalized Dipyrido-Annulated
N‑Heterocyclic Carbene
Sihan Zhang,† Rong Shang,*,† Masaaki Nakamoto,† Yohsuke Yamamoto,*,† Yohei Adachi,‡
and Joji Ohshita‡
†Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 7398526, Japan
‡Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 7398527, Japan
S
* Supporting Information
ABSTRACT: Phosphine-functionalized N-heterocyclic carbene
(NHC) ligands are known to complex group 11 metal centers to
form multinuclear complexes with photoluminescence proper-
ties. This study reports a structurally rigid ortho-substituted
dipyrido-annulated NHC with T-shape coordination geometry
and its di- and tetranuclear gold(I) complexes. The free ligand as
well as all metal complexes are found luminescent at room
temperature and phosphorescent at 77 K. Although metal d10−
d10 interactions are evident based on their solid-state structures,
their effect on the photoemission is limited, most likely due to
the weak coordination of the ligand to the metal centers in
solution.
coordination sites, permitting more diversified coordination
geometries.19−25 However, the resulting complexes usually
have longer metal−metal distances, which prevent intra-
molecular d10−d10 interactions.19,20,22,25 In addition, flexibility
of ligands are known to hamper the efficiency of luminescence
through thermal vibrations.26
Considering the above, a structurally rigid design containing
carbene and phosphine that offers different coordination
geometries would be highly desirable. Our group has
successfully introduced thio, phosphinyl, and aryl groups into
Weiss27 and Kunz’s28−32 dipyrido-annulated N-heterocyclic
carbene (dpa-NHC) to form pincer ligands. The steric
rigidity33,34 and unusual weak σ-donating, π-rich, and overall
strong donating nature of the backbone29 as carbene are of
special interest to us. Among these, the ortho-diphosphinyl-
substituted derivative (dpaP2-NHC, Chart 1C) has only been
characterized by coordination to a rhodium center previ-
ously.34
INTRODUCTION
■
Multidentate ligands1−8 containing both N-heterocyclic
carbene (NHC) and phosphine moieties can offer combined,
complementary electronic properties and coordination geo-
metries to transition metal centers to enhance the desired
physical and chemical properties.9−13 Since the first isolation of
P-functionalized imidazolium iodide by Herrmann et al. in
1996,14 a growing number of designs of this hybrid class of
ligands have been used for synthesizing multinuclear
complexes of group 11 metal cations for potential photo-
luminescent properties. The different geometric designs of the
ligand resulted in various degrees of intra- or intermolecular
d10−d10 metal interactions, which have been shown to
influence their photophysical properties.15,16
To date, most of the phosphine-functionalized NHCs used
for photoluminescent properties of multinuclear complexes
have been based on the Arduengo-type imidazole scaffold,
including the mono-17 and disubstituted bisphosphanyl NHC
ligands18 (Chart 1A) and the more flexible NHC hybrid
ligands3,5,7,17,19,20 with a spacer between the phosphine and
carbene moieties (Chart 1B). In the former design (A), the
carbene and phosphine donors align the metal cations along
one axis (x-axis in Chart 1), allowing for intramolecular metal−
metal interactions. Although free rotation along the N−P bond
(the x-axis) is possible, coordination to metal led to mostly21
rigid 2-D structures, where all carbene and phosphine ligands
and metal centers lie within the same plane. In contrast, the
latter design (Chart 1B) allows for controllable degrees of
freedom in all directions depending on the spacer between the
This work reports the isolation and characterization of the
dpaP2-NHC for the first time. Its coordination chemistry to
gold(I) complexes and the photoluminescent properties of the
resulting multinuclear complexes are investigated. Its rigid
backbone and free rotation only along the P−C bond (y-axis)
lead to previously inaccessible geometries.
Received: February 23, 2019
© XXXX American Chemical Society
A
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Chart 1. Phosphine-Functionalized NHC Ligands for
Multinuclear Group 11 Metal Complexes and ortho-
Substituted dpa-NHC Transition Metal Complexes
Figure 1. Molecular structures of 1 and 2 in the solid state. The
ellipsoids are shown at 50% probability. Ellipsoids of periphery atoms
and the counterion were removed for clarity. Selected bond lengths
(Å) and angles (°) for 1: C1−N1 1.368(2), C1−N2 1.378(2), C4−
C5 1.378(3); N1−C1−N2 100.2(2). Torsion angle ΦP1C2C3P2 = 9.6.
Selected bond lengths (Å) and angles (°) for 2: C1−N1 1.354(5),
C3−C3′ 1.395(8); N1−C1−N1′ 107.8(5). ΦP1C2C2′P1′ = 18.9. CCDC
for 1, 1894301, for 2, 1894302.
Scheme 1. Generation of the dpaP2-NHC 1 from
Deprotonation 1(H)I and the Coordination through
Phosphine Moieties
RESULTS AND DISCUSSION
■
The dpaP2-NHC 1 is generated from deprotonation of the
corresponding imidazolium salt 1(H)I. Although its in situ
generation and trapping by the rhodium(I) complex have been
described earlier, now free carbene 1 can be isolated in good
yield (69%). The solid-state molecular structure of 1 obtained
from X-ray crystallographic studies (Figure 1) shows a planar
annulated dipyrido backbone with one phosphine bending
slightly out of the plane (ΦPCCP = 9.6°). The phenyl groups of
the two phosphine moieties are on the same side of the plane
due to crystal packing. The N−C−N angle of 100.2(2)° is
slightly larger than Kunz’s substituted carbene (99.6(2)°). The
13C{1H} NMR spectrum of 1 in C6D6 showed a triplet at 198.3
ppm, which has been assigned to the carbene carbon C1, with
precarbene carbon was assigned to a singlet at 146.7 ppm, very
similar to that of 1(H)PF6, at 146.0 ppm. Meanwhile, the ESI-
MS spectrum shows an ion peak at m/z = 1113.1609, as
expected for the [(AuCl)21(H)]+ cation.
3
a JCP of 34 Hz.
Single crystals of 2 obtained from dimethylformamide
(DMF)/diethyl ether revealed a solid-state structure of a
dinuclear gold complex with a C2 rotating axis. The two gold
centers are trans to each other, pointing to either side of the
planar ligand backbone (Figure 1), and thus show no
intramolecular metal−metal interactions. In the crystal lattice,
the AuCl moieties are aligned with an intermolecular Au−Cl
distance of 3.550 Å and an Au−Au distance of 4.219 Å,
indicating no intermolecular metal−metal interactions.
The slow addition of one equivalent of [AuCl(SMe2)] in
dichloromethane (DCM) to a hexane solution of 1 afforded
complex 3 as a yellow solid precipitated from the reaction
mixture in 72% yield (Scheme 2). Upon recrystallization in a
The two phosphines of the dipyrido-backbone can
coordinate to gold(I) centers independently, shown by a
reaction of the parent imidazolium salt 1(H)PF6 and
[AuCl(SMe2)] in dichloromethane. Following complexation
of [AuCl(SMe2)] with 1(H)PF6 in a ratio of 2:1, a bright
yellow solid was isolated in 90% yield (Scheme 1). 1H,
13C{1H}, and 31P{1H} NMR spectra of 2 in deuterated DMSO
at room temperature show one set of signals, consistent to a
symmetrical structure. The upfield shift of the pro-carbenic
proton resonance [1(H)PF6, δH 8.6, vs 2, δH 8.3] and
downfield shift of the phosphine resonance [1(H)PF6, δP −3.6,
vs 2, δP 27.2] indicate coordination of phosphines to gold. The
B
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anion. Both gold(I) centers have a linear geometry, each
coordinated by a carbene. Three phosphine moieties of 3 do
not coordinate to the adjacent Au(I) center. The remaining
one coordinates to the metal center of a second monomer.
Consequently, the two metal centers are put closely together
with a short Au−Au distance of 2.955(2) Å, which indicates
the presence of an aurophilic interaction.16,35−37
Scheme 2. Synthesis of Dinuclear and Tetranuclear Gold(I)
Complexes 3−5 from 1
Although crystals of 3 can be obtained reproducibly in good
yield, the solid-state structure cannot be maintained in
1
solution. H, 31P{1H}, and 13C{1H} NMR experiments of 3
showed unassignable signals in CD3CN, DMSO-d6, and CDCl3
even at low temperatures (−40 °C), indicating complicated
dynamic behavior in solution (Figure S20, Supporting
Information (SI)). This is likely due to the presence of three
dangling phosphine ligands as well as the lability of chloride,
which may dissociate or coordinate to the gold center in
solution, resulting in a mixture of monomer, dimer, or
oligomers.
In attempt to cleave the dimer and isolate pure monomeric
species, we added Lewis bases, such as phosphine or isonitrile,
to a solution of 3. However, this did not lead to any pure
product. Instead, we employed a gold precursor with weakly
coordinating ligands to favor higher-ordered structures from
ligand 1.
DMF/diethyl ether mixture, single crystals of 3 were obtained.
X-ray diffraction analysis showed an asymmetric dinuclear gold
structure with two dpaP2-NHC ligands (Figure 2). Complex 3
can be viewed as two [Au(dpaP2-NHC)Cl] monomers
condensed together with the dissociation of one chloride
The complexation behavior of gold(I) precursors often
depends on their ligands. The presence or absence of halide (X
ligand), and the coordination strength of Lewis base (L ligand)
have been reported to provide structurally different prod-
ucts.38,39 The reaction of 1 with an equimolar amount of
[Au(tht)2](OTf) in THF led to isolation of complex 4 as an
orange solid in 83% yield. The same complex 4 can also be
obtained from halide abstraction of 3 by AgOTf (Scheme 2).
Single crystal X-ray crystallographic studies revealed a
centrosymmetric dimeric structure, in which the carbene and
one phosphine of 1 coordinate to a gold center each and are
capped by a second dpaP2-NHC in complementary positions
(4, front view; Figure 2). The gold centers bend slightly
toward each other with C1−Au1−P3 and P1−Au2−C2 angles
of 174.6(1)° and 176.1(1)°, respectively. The Au−Au distance
of 3.019(2) Å is slightly longer than that in 3, lying in the
expected range of strong d10−d10 interactions.35 The distances
of Au1−P2 and Au2−P4 are 2.985(2) and 2.989(2) Å,
respectively, which are significantly longer than the Au1−P3
and Au2−P1 distances of 2.309(2) and 2.302(2) Å, revealing
two weakly or noncoordinating outer phosphine moieties (sum
of van der Waals radii, 3.46−4.22 Å).40,41 Directed by
hydrogen bonding between triflate and phenyl hydrogen
atoms, the two rigid dpaP2-NHC backbone forms a bowl
shape with phosphines orientated outward (4, side view;
Figure 2).
1
The solution H NMR of 4 in DMSO-d6 shows two sets of
signals at room temperature, assigned to the inner half and the
outer half of the ligand, consistent with the solid-state
structure. The 31P{1H} NMR spectrum showed two virtual
triplets at 29.7 and 6.8 ppm, assigned to the inner and outer
phosphorus atoms. The virtual coupling indicates that the two
sets of chemically different phosphorus atoms couple to each
other, suggesting that, at least in solution, the outer phosphines
also coordinate to the metal center. The ESI-MS spectrum
shows a signal at m/z = 845.2486, corresponding to the ion
peak of the dication of 4, indicating the robustness of the
complex.
Figure 2. Molecular structures of 3 and 4 in the solid state. The
ellipsoids are shown at 50% probability. Ellipsoids of periphery atoms
and counterions were removed for clarity. Selected bond lengths (Å)
and angles (°) for 3: Au1−Au2 2.955(2); Au1−C1 1.994(4), Au1−
P1 2.937(2), Au2−P2 2.291(2), Au2−C2 2.026(4), Au2−P3
2.895(2). Selected bond lengths (Å) and angles (°) for 4: Au1−
Au2 3.019(2); Au1−C1 2.053(4), Au1−P2 2.985(2), Au1−P3
2.309(2), Au2−P1 2.302(2), Au2−C2 2.045(4), Au2−P4 2.989(2);
C1−Au1−P3 174.6(1), P1−Au2−C2 176.1(1). CCDC for 3,
1894303, and for 4, 1894304.
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Both complexes 3 and 4 are dinuclear species with each
tridentate dpaP2-NHC capturing only one metal center. In
order to obtain complexes with higher metal content, the
reaction of 1 with two or more equivalents of [Au(tht)2](OTf)
was carried out. Among many attempts, the reactions of 1 or 4
with [Au(tht)2](OTf) in an 1:2 ratio lead to isolation of a pure
isolable complex as an orange solid (5) in 71% yield.
Recrystallization from DMF and hexane lead to single crystals
of 5, which showed a symmetrical dimeric tetranuclear
complex of formula {Au2[dpaP2-NHC](DMF)}2 (5, Figure
3). Two Au(I) were captured at the carbene donors, lying in
transitions of the gold complexes are mostly attributed to
ligand-centered (LC) transitions. Although complex 3 shows a
relatively broad absorption, its excitation spectrum is similar to
that of 1 and other complexes, again suggesting that LC
transition is primarily involved for 3 (Figure S2). At 77 K, all
these compounds provided phosphorescence. As shown in
Figure S3, the PL spectra that are obtained with a 50 μs delay
after excitation show no bands around 500 nm, indicating that
the PL bands observed at room temperature are likely ascribed
to fluorescence. The phosphorescence bands of 3−5, however,
were slightly shifted from that of 1, indicating electronic
perturbation of the gold cation to the triplet state of the
carbene to a limited extent (Figure S3). Lifetimes of the
phosphorescence of compounds 1−5 range between 85.1 and
772.0 μs (Figure S4).
CONCLUSION
■
On the basis of the newly isolated bis(diphenylphosphinyl)-
functionalized dipyrido-annulated NHC (1, dpaP2-NHC) and
its imidazolium salt precursors, di- and tetranuclear gold(I)
complexes (2−5) have been synthesized and fully charac-
terized by X-ray crystallography. The two phosphine groups
fixed in proximity to the central carbene within a rigid
framework allowed for the formation of multinuclear species
with Au(I)−Au(I) interactions in complexes 3−5. Dynamic
behaviors observed from solution of 3 and 5 by NMR
spectroscopy suggest weak coordination. All the obtained gold
complexes are luminescent at room temperature and
phosphorescent at 77 K. However, the presence of gold(I)
centers and their d10−d10 did not lead to dramatic changes of
the emission. We are currently exploring the coordination
chemistry of dpaP2-NHC toward silver and copper ions and
their photophysical properties of the resulting complexes.
Figure 3. Molecular structures of 5 in the solid state. The ellipsoids
are shown at 50% probability. Ellipsoids of periphery atoms and
counterions were removed for clarity. Selected bond lengths (Å) and
angles (°) for 5: Au1−Au2 3.1176(7), Au2′-Au1 3.0976(7), Au1−
Au1′ 3.318(1), Au1−C1 1.98(2), Au1−O 2.15(2); P2−Au2−P1′
157.4(2), P1−Au2′-P2′ 158.4(2).42 CCDC for 5, 1894305.
plane with the dpaP2-NHC backbone. Two more Au(I) were
captured by the phosphine donors between the two antiparallel
dpaP2-NHC ligands. The four gold cations form a four-
membered planar gold(I) ring connecting each other by
aurophilic interactions. Although the distances35 of Au1−Au2
3.1176(7), and Au1−Au2′ 3.0976(7) Å are slightly longer than
those in complexes 3 and 4, each outer phosphine-coordinated
Au(I) displays a deviation from the linear P2−Au2−P1′
arrangement (157.4(2)°) toward the central carbene-coordi-
nated gold(I) atoms, which is attributed to the attractive
aurophilic interactions. This dimeric molecular 3D lattice
arrangement is unique from all previously reported heteroleptic
phosphine/carbene multinuclear complexes because the three
donors are restricted to one plane with only rotation possible
at the phosphines.
EXPERIMENTAL SECTION
■
General Procedure. Unless otherwise noted, all the manipu-
lations were carried out using standard Schlenk techniques under an
argon atmosphere. THF and hexane were purified by passing through
a glass contour solvent dispensing system under an N2 atmosphere;
other solvents used were purified and dried by standard methods. The
starting material 1(H)I was prepared according to the literature
procedure.33 1H (400 MHz, 600 MHz), 13C{1H} (100 MHz, 150
MHz), and 31P{1H} (162 MHz, 243 MHz) NMR spectra were
recorded on JEOL AL-400S spectrometer and were referenced to
CDCl3 (1H: δ = 7.26 ppm; 13C: δ = 77.1 ppm), C6D6 (1H: δ = 7.16
ppm; 13C: δ = 128.0 ppm), or DMSO-d6 (1H: δ = 2.50 ppm; 13C: δ =
39.5 ppm) as external standards. 31P{1H} NMR spectra are referenced
to 85% H3PO4 (δ = 0.0 ppm) as external standards.
Complex 5 dissolved in DMSO-d6 provided the sharpest
Synthesis of Free Carbene 1 (dpaP2-NHC). The solution of
1(H)I (400.0 mg, 0.515 mmol) and KOtBu (69.3 mg, 0.618 mmol) in
THF (40 mL) was stirred at room temperature for 2 h, and then
volatiles were removed under reduced pressure. Hexane (60 mL) was
added, and the solution was filtered through Celite. After removal of
volatiles, 1 was obtained as an orange solid. Yield: 68.7% (230.1 mg,
0.354 mmol). Suitable crystals for X-ray analysis were obtained by
slow evaporation of the solution of 1 in THF/hexane. 1H NMR (600
MHz, C6D6, δ): 1.08 (s, 18H, CH3), 6.54 (s, 2H, Ha), 6.93−7.06 (m,
12H, m-/p-CHPh), 7.42 (m, 8H, o-CHPh), 7.53 (s, 2H, Hb). 31P{1H}
NMR (243 MHz, C6D6, δ): −13.8. 13C{1H} NMR (150 MHz, C6D6,
δ): 30.3 (CH3), 34.7 (C(CH3)), 111.5 (C1/C9), 121.1 (C3/C7),
signals in 1H and 31P{1H} NMR experiments in comparison to
1
other solvents. The H NMR spectrum showed a singlet at
1.12 ppm, assigned to the tBu group of the ligand backbone.
The 31P{1H} NMR spectrum showed one singlet at 36.3 ppm.
These are consistent with the solid-state structure of 5. In
comparison, the 13C{1H} NMR experiment showed a less well-
resolved spectrum, suggesting dynamic behaviors in solution at
room temperature, possibly due to the rotation of the
phosphine groups.
The photophysical properties of the gold complexes (2−5)
and the free carbene 1 were investigated in 2-methyl-THF.
The absorption and emission bands of gold complexes
observed at room temperature lie in the range of 320−420
and 450−600 nm, respectively, similar to those of 1 (Figures
S1 and S2). It seems likely, therefore, that these electronic
1
3
122.7 (d, JPC = 2 Hz, C4/C6), 128.5 (d, JPC = 8 Hz, m-CPh), 128.8
(p-CPh), 134.7 (d, 1JPC = 21 Hz, o-CPh), 136.9 (d, 2JPC = 12 Hz, i-CPh),
140.3 (C10/C11), 142.0 (d, 3JPC = 14 Hz, C2/C8), 198.3 (t, 3JPC = 33
Hz, Ccarbene). Element analysis calcd for C43H42N2P2 (648.77): C
79.61, H 6.53, N 4.32; found: C 79.37, H 6.20, N 4.84.
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spectrum could not be obtained due to the poor solubility and harsh
measurement condition, long time (more than 1 days) and low
temperature (around −10 °C). 31P{1H} NMR (243 MHz, CDCl3, δ):
26.2 (s), 27.3 (s), 28.5 (s), 30.3 (s). HRMS (ESI) (m/z): [M-2Cl]2+,
845.2498. Element analysis calcd for C86H84Au2Cl2N4P4 (1762.37): C
58.61, H 4.80, N 3.18; found: C 58.37, H 4.99, N 3.18.
Synthesis of 1(H)PF6. The solution of 1(H)I (100 mg, 0.129
mmol) and KPF6 (47.4 mg, 0.258 mmol) in CH2Cl2 (20 mL) was
stirred at room temperature for 24 h. After the reaction solution was
concentrated to 2−3 mL under reduced pressure, hexane (10 mL)
was added to precipitate the yellow solid 1(H)PF6 that was collected
1
by filtration. Yield: 85.7% (87.8 mg, 0.111 mmol). H NMR (400
4
MHz, DMSO-d6, δ): 1.23 (s, 18H, CH3), 6.97 (dd, JHH = 2.0 Hz,
3JPH = 2.4 Hz, 2H, Ha), 7.21−7.38 (m, 8H, o-CHPh), 7.39−7.67 (m,
4
12H, m-/p-CHPh), 8.64 (s, H, NCHN), 8.91 (d, JHH = 2.0 Hz, 2H,
Hb). 31P{1H} NMR (162 MHz, DMSO-d6, δ): −13.6 (s), −143.2
1
(sept, JPF = 720.9 Hz, PF6). 13C{1H} NMR (100 MHz, DMSO-d6,
3
δ): 29.9 (CH3), 35.1 (C(CH3)), 110.2 (t, JPC = 16 Hz, C5), 114.8
2
(C1/ C9), 123.9 (C10/C11), 126.9 (d, JPC = 6 Hz, C6/C4), 129.0
Synthesis of Complex 4. Method A. The solution of complex 3
(100.0 mg, 0.057 mmol) and AgOTf (29.3 mg, 0.114 mmol) in
CH2Cl2 (15 mL) was stirred at room temperature over 1 h in the
absence of light. Then, the resulting solution was filtered through
Celite, and the filtrate was concentrated to 2−3 mL under reduced
pressure; hexane (15 mL) was added to precipitate complex 4, which
was collected as an orange solid by filtration. Yield: 64.3% (73.0 mg,
0.0367 mmol).
(d, 1JPC = 6 Hz, C7/C3), 129.9 (d, 3JPC = 8 Hz, m-CPh), 131.2 (p-CPh),
1
2
133.1 (d, JPC = 25 Hz, i-CPh), 133.9 (d, JPC = 21 Hz, o-CPh), 146.0
(C2/C8). HRMS (ESI) (m/z): [M-PF6]+, 649.290. Element analysis
calcd for C43H43F6N2P3 (794.74): C 64.99, H 5.45, N 3.52; found: C
65.10, H 5.70, N 3.64.
Method B. The solution of free carbene 1 (50.0 mg, 0.077 mmol)
and [Au(tht)2](OTf) (40.2 mg, 0.077 mmol) in THF (10 mL) was
stirred at room temperature for 2 h and then concentrated to 2−3 mL
under reduced pressure; hexane (15 mL) was added to precipitate
complex 4 that was collected as an orange solid by filtration. Yield:
82.6% (63.3 mg, 0.0318 mmol). Suitable crystals for X-ray analysis
were obtained by slow diffusion of diethyl ether into the solution of 4
Synthesis of Complex 2. To a solution of 1(H)PF6 (20.0 mg,
0.025 mmol) in CH2Cl2 (10 mL) was added [AuCl(SMe2)] (14.8 mg,
0.051 mmol), and the resulting solution was stirred at room
temperature for 1 h. After being concentrated to 2−3 mL under
reduced pressure, hexane (15 mL) was added to precipitate the yellow
solid complex 2 that was collected by filtration. Yield: 90.5% (28.5
mg, 0.023 mmol). Suitable crystals for X-ray analysis were obtained by
slow diffusion of diethyl ether into the solution of 2 in
dimethylformamide. 1H NMR (400 MHz, DMSO-d6, δ): 1.24 (s,
1
in dimethylformamide. H NMR (400 MHz, DMSO-d6, δ): 1.04 (s,
18H, CH3), 1.20 (s, 18H, CH3), 6.76 (br s, 8H, CHPh), 6.88 (s, 4H,
Hb/Hb′), 7.10−7.70 (m, 32H, CHPh), 8.82 (s, 2H, Ha), 8.97 (s, 2H,
Ha′). 31P{1H} NMR (162 MHz, DMSO-d6, δ): 29.7 (virtual triplet),
6.8 (virtual triplet). 13C{1H} NMR (100 MHz, DMSO-d6, δ): 29.7
(CH3), 29.8 (CH3), 34.7 (C(CH3)), 34.9 (C(CH3)), 114.8 (C1),
118.1 (C9), 119.6 (q, 1JCF = 345.1 Hz, CF3), 125.5 (C4), 126.2 (C6),
126.9 (C3), 128.8 (d, 1JPC = 7 Hz, i′-CPh), 129.2 (m′-CPh), 129.6 (br,
3
18H, CH3), 7.14 (d, JPH= 10.4 Hz, 2H, Ha), 7.59−7.89 (m, 20H,
CHPh), 8.30 (s, H, NCHN), 9.23 (s, 2H, Hb). 31P{1H} NMR (162
1
1
p′-/m-CPh), 130.2 (C7), 130.8 (p-CPh),131.8 (d, JPC = 7 Hz, i-CPh),
MHz, DMSO-d6, δ): 27.2 (s), −143.2 (sept, JPF = 720.9 Hz, PF6).
13C{1H} NMR (100 MHz, DMSO-d6, δ): 29.9 (CH3), 35.3
132.7 (o-/o′-CPh), 135.4 (C10/C11), 142.5 (C2), 145.0 (C8), the
carbene carbon could not be detected. HRMS (ESI) (m/z): [M-
1
(C(CH3)), 110.0 (br s, C5), 118.1 (C1/C9), 122.7 (d, JPC = 65
2O3 SCF3 ]2 +
, 845.2486. Element analysis calcd for
1
3
Hz, C4/C6), 123.5 (d, JPC = 62 Hz, i-CPh), 125.1 (d, JPC = 2 Hz,
C88H84Au2F6N4O6P4S2 (1989.60): C 53.12, H 4.26, N 2.82; found:
C 54.24, H 4.12, N 2.87.
2
3
C10/C11), 130.0 (d, JPC = 10 Hz, C3/C7), 131.0 (d, JPC = 13 Hz,
m-CPh), 134.6 (d, 4JPC = 2 Hz, p-CPh), 134.8 (d, 2JPC = 10 Hz, o-CPh),
146.7 (C2/C8), C5 can not be detected. HRMS (ESI) (m/z): [M-
PF6]+, 1113.1609. Element analysis calcd for C43H43Au2Cl2F6N2P3
(1259.58): C 41.00, H 3.44, N 2.22; found: C 40.58, H 3.24, N 2.13.
Synthesis of Complex 5. Method A. The solution of free carbene
1 (25.0 mg, 0.0385 mmol) and [Au(tht)2](OTf) (40.2 mg, 0.077
mmol) in THF (10 mL) was stirred at room temperature for 2 h and
concentrated to 2−3 mL under reduced pressure; hexane (15 mL)
was added to precipitate complex 5, which was collected as an orange
solid by filtration. Yield: 71.3% (36.7 mg, 0.0137 mmol).
Method B. The solution of complex 4 (25.0 mg, 0.0126 mmol) and
[Au(tht)2](OTf) (13.1 mg, 0.0252 mmol) in THF (15 mL) was
stirred at room temperature for 3 h and concentrated to 2−3 mL
under reduced pressure; hexane (15 mL) was added to precipitate
complex 5, which was collected as an orange solid by filtration. Yield:
51.3% (16.1 mg, 0.006 mmol). Suitable crystals for X-ray analysis
Synthesis of Complex 3. The approximately saturate solution of
[AuCl(SMe2)] (74.8 mg, 0.254 mmol) in CH2Cl2 (6 mL) was slowly
added dropwise to a solution of free carbene 1 (150.0 mg, 0.231
mmol) in hexane (80 mL), and the instantly formed yellow
precipitate was collected by filtration. After recrystallization with
THF at −18 °C, the desired product 3 was collected as a light-yellow
solid by filtration. Yield: 72.3% (147.2 mg, 0.084 mmol). Suitable
crystals for X-ray analysis were obtained by slow diffusion of diethyl
ether into the solution of 3 in DMF. Due to the fluxional process in
1
solution, the proton resonance in the H NMR spectrum can not be
clearly ascribed (see the Supporting Information). 13C{1H} NMR
E
DOI: 10.1021/acs.inorgchem.9b00514
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Inorganic Chemistry
Article
Table 1. Crystallographic Data for Compounds 1−5
1
2
3
4
5
CCDC No.
formula
1894301
C43H42N2P2
1894302
C43H43Au2Cl2F6N2O6P3·
4(CH3)2NCHO
1894303
C86H84Au2Cl2N4P4·
2(CH3)2NCHO
1894304
1894305
C88H84Au2F6N4O6P4S2·(CH3)2NCHO· C90H84Au4F12N4O12P4S4·
CH3CH2OCH2CH3
2209.83
4(CH3)2NCHO
2964.90
formula
weight
648.72
1551.92
1908.47
crystal system
space group
orthorhombic monoclinic
monoclinic
P21/n
monoclinic
P21/c
triclinic
P-1
Pbca
C2/c
temperature
(K)
123
173
123
123
123
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
14.093(2)
16.545(2)
30.850(5)
90
90
90
7193.3(18)
8
1.198
0.153
2752
22.392(5)
16.519(4)
16.628(4)
90
98.342(3)
90
6086(2)
4
1.694
14.259(11)
31.08 (2)
20.805(16)
90
99.714(13)
90
9088(12)
4
1.395
15.779(12)
25.547(19)
24.151(19)
90
97.082 (15)
90
9662(13)
4
1.519
15.762(2)
15.767(2)
23.977(4)
82.204(2)
78.435(2)
85.067(2)
5773.2(15)
2
dcalcd (g cm−3
)
1.620
5.270
2744
μ (mm−1
F000
)
5.049
3064
3.402
3840
3.213
4456
no. reflns
no. unique
reflns
32784
6331
15774
6215
54785
22722
58187
24011
30206
22790
Rint
0.0829
0.0274
0.0351
0.1005
1.087
0.0311
0.0384
0.0930
1.019
0.0240
0.0341
0.0921
1.016
0.0287
0.0612
0.1975
1.033
R1 [I > 2σ(I)] 0.0429
wR2 (all data)
GOF
0.1005
0.957
were obtained by slow diffusion of diethyl ether into the solution of 5
in dimethylformamide. H NMR (400 MHz, DMSO-d6, δ): 1.12 (s,
from The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
1
36H, CH3), 6.65 (s, 4H, Hb), 6.91−8.21(m, 40H, CHPh), 9.06 (d, 3JPH
= 22.0 Hz, 4H, Ha). 31P{1H} NMR (162 MHz, DMSO-d6, δ): 36.3
(s). 13C{1H} NMR (100 MHz, DMSO-d6, δ): 29.7 (CH3),
34.7(C(CH3)), 118.2 (C1/C9), 119.1 (C4/C6), 122.4 (C10/C11),
125.9 (C3/C7), 129.5 (i-CPh), 130.2 (m-CPh), 132.0 (p-CPh), 133.2 (o-
CPh), 143.4 (C2/C8), the carbene carbon and carbons of triflates
could not be detected. HRMS (ESI) (m/z): [M-4O3SCF3]4+,
521.1086. Element analysis calcd for C90H84Au4F12N4O12P4S4
(2681.66): C 40.31, H 3.16, N 2.09; found: C 39.87, H 3.32, N 1.77.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.9b00514.
NMR spectra, crystallographic data (PDF)
Accession Codes
CCDC 1894301−1894305 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
■
X-ray Diffraction Studies. Crystals suitable for the X-ray
structural determination were mounted on a Bruker SMART APEXII
CCD diffractometer and irradiated with graphite monochromated Mo
Kα radiation (λ = 0.71073 Å) for data collection. The data were
processed using the APEX3 program suite and be seen in Table 1. All
structures were solved using an intrinsic phasing method with the
SHELXT program (ver. 2014/4−2014/5).43 Refinement on F2 was
carried out using full-matrix least-squares with the SHELXL44 and
expanded using Fourier techniques. All non-hydrogen atoms, except
those of disordered solvents, were refined using anisotropic thermal
parameters. Hydrogen atoms were assigned to idealized geometric
positions and included in structure factor calculations. The SHELX
was interfaced with SHELXLE GUI for most of refinement steps.45
The pictures of molecules were prepared using Pov-Ray 3.6.46
Crystallographic data (CCDC 1894301−1894305) can be obtained
Corresponding Authors
*E-mail: rshang@hiroshima-u.ac.jp.
*E-mail: yyama@sci.hiroshima-u.ac.jp.
ORCID
Rong Shang: 0000-0002-5446-5909
Yohei Adachi: 0000-0001-8311-5046
Joji Ohshita: 0000-0002-5401-514X
Funding
This work was supported by Grants-in-Aid for Scientific
Research on Priority Areas (24109002, Stimuli-responsive
Chemical Species) and for Science Research B (26288017)
from the Ministry of Education, Culture, Sports, Science, and
Technology, Japan.
F
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Notes
The authors declare no competing financial interest.
(17) Kuhnel, E.; Shishkov, I. V.; Rominger, F.; Oeser, T.; Hofmann,
̈
ACKNOWLEDGMENTS
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8000−8011.
■
The authors would like to thank Prof. M. Abe for his
permission and help to use his group spectrofluorometer.
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