Ionic liquid in synthesis: A phase transfer reagent and a redox mediating medium

Article abstract of DOI:10.1002/jccs.201200408

Ionic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to depolymerizeMX₂ (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2′-bipyridine (= bpy) to give the (bpy)MX₂ product. Supersonic irradiation of equiv-molar bpy, PdX ₂, and IL in CHCl₃ produced almost quantitative precipitate of (bpy)PdX₂ in a short time at ambient temperature, where IL is either [BEIm]Br or [BMIm]Br. That is, ILs and sono-techniques assisted greatly on the synthesis of (bpy)PdX₂. For preparation of (bpy)PtX₂, nonetheless, free bpy always remained inmixture even after a long time of supersonic treatment. The system of equiv-molar bpy, PtBr ₂, and IL in CHCl3, produced yellow (bpy)PtBr₂ and orange (bpy)PtBr₄, both being characterized with ¹HNMR and ¹⁹⁵Pt NMR in d₆-Me₂SO as well as with single crystal X-ray diffraction. Overall for PtX₂ reactions with halide anions in highly polar environments attributable to ILs, the redox pathway becomes important in that Pt(II) transforms to Pt(IV) to yield (bpy)PtBr ₂ and (bpy)PtBr₄.

Full text of DOI:10.1002/jccs.201200408

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Ionic Liquid in Synthesis: A Phase Transfer Reagent and a Redox Mediating Medium
Guei-Wei Lin,a,c Yi-Chin Lin,a,c Su-Ching Lin,a Yuh-Sheng Wena and Ling-Kang Liua,b*
aInstitute of Chemistry, Academia Sinica, Nangang, Taipei 115, Taiwan
bDepartment of Chemistry, National Taiwan University, Taipei 106, Taiwan
cDepartment of Chemistry and Biochemistry, National Chung-Cheng University, Minxiong Township, Chiayi County
621, Taiwan
(Received: Jul. 25, 2012; Accepted: Oct. 31, 2012; Published Online: Dec. 17, 2012; DOI: 10.1002/jccs.201200408)
Ionic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to
depolymerize MX2 (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2¢-bipyridine (= bpy) to give
the (bpy)MX2 product. Supersonic irradiation of equiv-molar bpy, PdX2, and IL in CHCl3 produced almost
quantitative precipitate of (bpy)PdX2 in a short time at ambient temperature, where IL is either [BEIm]Br
or [BMIm]Br. That is, ILs and sono-techniques assisted greatly on the synthesis of (bpy)PdX2. For prepa-
ration of (bpy)PtX2, nonetheless, free bpy always remained in mixture even after a long time of supersonic
treatment. The system of equiv-molar bpy, PtBr2, and IL in CHCl3, produced yellow (bpy)PtBr2 and or-
ange (bpy)PtBr4, both being characterized with 1H NMR and 195Pt NMR in d6-Me2SO as well as with sin-
gle crystal X-ray diffraction. Overall for PtX2 reactions with halide anions in highly polar environments
attributable to ILs, the redox pathway becomes important in that Pt(II) transforms to Pt(IV) to yield
(bpy)PtBr2 and (bpy)PtBr4.
Keywords: Inorganic coordination polymer; Ionic liquid; Phase transfer reagent; Sonochemistry;
Disproportionation.
INTRODUCTION
Room temperature ionic liquids (ILs) are composed
fication of the (bpy)PdCl2 with fluorinated pony tails on
bpy allowed convenient recovery and reusage of the Pd cat-
alysts for cross-coupling C-C bond formation reaction.5
fully of charged particles, with each cation immediately
surrounded by anions and each anion by cations, where cat-
ions are organic in nature. Given embedded charges, ILs
have a number of uniquely desirable physical properties.1
In the past decades, research carried out on IL has been ex-
tensive in order to find useful applications with these envi-
Scheme I
o
ronmentally benign solvents that melt below 100 C espe-
cially, exhibiting negligible vapor pressure, high thermal
stability, and tunable polarity. As one of the utilizations IL
is currently investigated as medium for reactions, in many
cases IL simultaneously serving as active catalyst.2,3
In the solid state of PtCl2 for instance, each four-coor-
dinate Pt center is surrounded by four chloride ligands in
square planar geometry. Complementarily, each two-coor-
dinate Cl center is bridging two Pt centers.6 MX2 is com-
monly used as precursors in the preparation of other molec-
ular Pt and Pd compounds.7,8 Most reactions of MCl2 pro-
ceed via treatment with ligands to give molecular deriva-
tives. Such transformations are actually a depolymeriza-
tion process to cleave the M-Cl-M linkages. Not particu-
larly soluble, MCl2 utilization often starts in the first step
with formation of labile but soluble Lewis base adducts,
The goal of this study is the employment of ILs with
chloride anion or bromide anion, as a phase transfer re-
agent, to see to what extent ILs could promote the conver-
sion of bpy (= 2,2¢-bipyridine) and MX2 (M = Pt, Pd; X =
Br, Cl) to (bpy)MX2 in chloroform (Scheme I), taking note
that the inorganic coordination polymers MX2 are insolu-
ble in less polar organic solvents and also insoluble in wa-
ter. Complex (bpy)PtCl2 was reported to show interesting
optical luminescence property, upon varying Pt-Pt dis-
tances in the solid state with respect to temperature.4 Modi-
* Corresponding author. E-mail: liuu@chem.sinica.edu.tw
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Table 1. The bpy consumption vs. time for sonocation of the 5
such as those derived from refluxing in acetonitrile to pro-
duce MCl2(MeCN)2,9 as well as production of isomers of
PtCl2(SMe2)2.10 Alternatively, MCl2 is solubilized in the
form of tetrachloropalladate or platinate dianion, by react-
ing with the appropriate alkali metal chloride in water.11
Less common than MCl2, the commercially available bro-
mide analog MBr2 is also coordination polymer and proc-
eeds with similar chemistry.
mL CDCl3 solution consisting of equal molar PdX2,
bpy, and IL at 250 mmol level
PdX2
IL
Time/min
bpy consumed/%
PdBr2
PdBr2
PdBr2
PdBr2
PdBr2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
none
120
20
30
15
30
120
60
90
120
60
90
60
71
100
76
100
61
82
87
100
66
91
100
[BEIM]Br
[BEIM]Br
[BMIM]Br
[BMIM]Br
none
[BEIM]Cl
[BEIM]Cl
[BEIM]Cl
[BMIM]Cl
[BMIM]Cl
[BMIM]Cl
RESULTS AND DISCUSSION
PdX2 reactions
As a proof of concept, into a 20 mL sample vial was
introduced typically 5.00 mL CDCl3, and 250 mmol each of
bpy, PdBr2, and [BEIm]Br (= 1-butyl, 3-ethyl-imidazolium
bromide) and the vial was subject to ultrasound treatment
at room temperature. IL indeed served as a phase transfer
agent moving PdBr2 “units” from surface of the dark brown
coordination polymer to react with bpy in CDCl3 leading to
the orange (bpy)PdBr2, which upon formation is precipi-
tated out of the CDCl3 solution. The reactant mixture was
supersonically irradiated for 30 min before collection of or-
ange precipitates of (bpy)PdBr2. Full conversion was indi-
cated in 1H NMR spectroscopic monitoring, free bpy signals
being absent at this point.
120
Table 2. The bpy consumption vs time for sonocation of the 5
mL CDCl3 solution consisting of equal molar PtX2, bpy,
and IL at 250 mmol level
PtX2
IL
Time/min
bpy consumed/%
PtBr2
PtBr2
PtBr2
PtBr2
PtBr2
PtCl2
PtCl2
PtCl2
PtCl2
PtCl2
none
480
240
480
240
480
360
240
360
240
360
19
33
34
31
33
28
32
36
49
53
[BEIM]Br
[BEIM]Br
[BMIM]Br
[BMIM]Br
none
[BEIM]Cl
[BEIM]Cl
[BMIM]Cl
[BMIM]Cl
Similar supersonic irradiation experiments were also
performed on possible combinations of bpy, MX2 (M = Pd,
Pt; X = Br, Cl), and ILs in CD(H)Cl3. The coordination
polymer MX2 was halide-matched with ionic liquid
[BEIm]X or [BMIm]X (BMIm = 1-butyl, 3-methyl-imi-
dazolium). In the case when IL is [BEIm]Br, the isolated
yield of (bpy)PdBr2 was 99%; and [BMIm]Br, 92%. For
similar preparation of (bpy)PdCl2, it took 120 min on sono-
cation and the isolated yields were 97% using [BEIm]Cl
and 99% using [BMIm]Cl.
360 min, reached free bpy consumption at 53% level (Table
2). The other entries in Table 2 were all at about 1/3 free
bpy consumption and the blank entries much less.
Insoluble in CDCl3, (bpy)PtX2 however has a better
solubility in d6-Me2SO for NMR characterization. Accord-
ingly, organic volatiles were removed under vacuum for the
crude product mixture of (bpy)PtBr2 at 33% free bpy con-
sumption (entry 5, Table 2) were removed under vacuum.
The remaining crude product mixture and d6-Me2SO (0.50
mL) were then transferred to an NMR tube, for 1H NMR
and 195Pt NMR characterization. Figure 1 is the 1H NMR
COSY spectrum of the crude, exhibiting clearly that two
sets of coordinated bpy were present without free bpy (d
7.46, 7.95, 8.39, 8.69). One set of peaks (d 7.85, 8.43, 8.60,
9.77) was later assigned to (bpy)PtBr2 and the other set (d
8.15, 8.57, 8.96, 9.72) to (bpy)PtBr4.
Table 1 is related to the time profile on the synthesis
of (bpy)PdBr2 and (bpy)PdCl2. Sonocation clearly assists
the reaction since reaction mixtures at room temperature
without any sonocation take days/weeks to realize the
products. IL further mediates the reaction. For comparison
on [BEIm]X with [BMIm]X, the difference on reactivity
seems minimal.
PtX2 reactions
Different from preparation of the Pd analogs, similar
procedures on preparation of (bpy)PtX2 did not give quan-
titative (bpy)PtX2, even after sono-irradiations for 360-480
min. The best one was the synthesis of (bpy)PtCl2, in that
the mixture of PtCl2, bpy, [BMIm]Cl, upon irradiation for
A close-up view of the NMR tube holding the above
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Ionic Liquid in Synthesis
crude product mixture in d6-Me2SO is shown in Figure 2.
The yellow crystals at bottom were found to be (bpy)PtBr2
and the orange crystals at top mainly (bpy)PtBr4 (vide in-
fra). These solids indicated that both (bpy)PtBr2 and
(bpy)PtBr4 in d6-Me2SO were saturated. The natural occur-
ring isotope 195Pt has an abundance of 33.8% and a spin I of
1/2. It has a very wide chemical shift range, useful in con-
firmation of the Pt oxidation state in a platinum compound.
In the 195Pt NMR spectrum the yellow (bpy)PtBr2 revealed
its chemical shift at d -2563 (Figure 3A) whereas the or-
ange (bpy)PtBr4 at d -1421 (Figure 3B), both agreeing
nicely with the reported chemical shifts.12 The crude prod-
uct mixture in d6-Me2SO exhibited signals at d -2563 and d
-1421 (Figure 3C). The 1H NMR spectra in Figure 4 were in
nice agreement with the 195Pt NMR spectra.
X-ray molecular structures of (bpy)PtBr2 and
(bpy)PtBr4
Nice quality crystals of (bpy)PtBr2 and (bpy)PtBr4
were obtained after a few recrystallization attempts, and
X-ray structure analysis proceeded with data sets collected
at 100 K. The resultant molecular structures are shown in
Figures 5 and 6 correspondingly. Both structures had al-
ready been reported in the literature at different tempera-
tures, room temperature for the (bpy)PtBr2 structure and
200 K for the (bpy)PtBr4 structure.13,14 No significant dif-
ference in structural parameters was noticed.
The yellow crystals in crude product mixture were
Fig. 1. 1H NMR COSY spectrum of the crude product
mixture in d6-Me2SO, after the ultrasound treat-
ment of equi-molar PtBr2, bpy, and [BEIm]Br
in CHCl3 and the organic solvents were re-
moved at end of the reaction. Two sets of coor-
dinated bpy could be found, one set at (d 7.85,
8.43, 8.60, 9.77) and the other set at (d 8.15,
8.57, 8.96, 9.72). The peaks with much greater
intensity at d 7.82, 9.33 are attributed to the
very high backgrounds of [BEIm]Br.
Fig. 3. 195Pt NMR spectra in d6-Me2SO of (A)
(bpy)PtBr2, (B) (bpy)PtBr4, and (C) crude prod-
uct mixture. The ranges were -1350 - -1550
ppm and -2350 - -2550 ppm.
Fig. 2. Close-up view of the NMR tube of crude prod-
uct mixture in d6-Me2SO. The yellow crystals
at bottom were (bpy)PtBr2 and the orange crys-
tals at top (bpy)PtBr4.
Fig. 4. 1H NMR spectra in d6-Me2SO of (A) (bpy)PtBr2,
(B) (bpy)PtBr4, and (C) crude product mixture
with very high signals attributed to [BEIm]Br.
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single component of (bpy)PtBr2 that was collected in 10-
20% yield. The orange crystals however, seemed multiple
components in nature attributable to the presence of very
high background of [BEIm]Br.15 Compound (bpy)PtBr4
could be collected in 20-30% yield.
states II and IV, with Pd(IV) being known much less stable
than Pt(IV). In the current (bpy)PtBr2 plus (bpy)PtBr4 ex-
ample, participation of bromide anions is suggested in con-
version between Pt(II) and Pt(IV) via the inner sphere elec-
tron transfer pathway to take advantage of the presence of
IL with high polarity and supply of bromide anions, similar
in nature to the well known Pt(NH3)2Br2×Pt(NH3)2Br4 that
has chains of alternating Pt(II) and Pt(IV) atoms with bridg-
ing bromide anions.16
The Pd and Pt dyad is characterized by oxidation
The highly polar nature of ILs surely increases the
life time of a charge-separated transition state during the
reaction, thus creating different pathway(s) from that of
similar reactions performed in conventional organic sol-
vents. The present results agreed very much that as media
of reactions, ILs could shift the reaction to follow a more
ionic pathway.
Seddon et al. found that in the Friedel-Crafts acetyla-
tion reaction of naphthalene employing [EMIm][Al2Cl7]
melts as solvent, the thermodynamically not favored 1-iso-
mer became the major product whereas the thermodynami-
cally favored 2-isomer exhibited only a 2% yield.17 Xiao et
al. also reported that the Pd-catalyzed Heck arylation reac-
tion of electron rich olefins and aryl halides in [BMIm]BF4
produced essentially the less common branched products,
not the linear ones.18
Fig. 5. (a) Molecular structure of (bpy)PtBr2. (b) Side
view of one column of (bpy)PtBr2 molecules.
The Pt atom is 3.409 Å away from both neigh-
boring molecular planes.
Thus inside reactant mixture consisting of equiv-mo-
lar MX2, bpy, and IL in CHCl3 solution, IL has a greater af-
finity towards MX2 than CHCl3 does, leading to effective
dissolution of the inorganic coordination polymer and for-
mation of the more soluble MX42- anions in this study. The
bpy ligand or the CHCl3 solvent molecule then enters the
first coordination sphere of metal center. In the case of
PdX2, the expected formation of square planar (bpy)PdX2
proceeds smoothly with quantitative yields. In the case of
PtX2 on the other hand, the redox reaction is more impor-
tant. Pt(II) likely disproportionates to Pt(IV) and Pt(0) with
favoring potential (Table 3),19 as assisted by the stabilizing,
excess halide anions and the highly polar IL environment.
It is not surprising that the neutral products obtained from
the product mixture at the end were both (bpy)PtBr2 and
(bpy)PtBr4 with lower yields. Studies on nature of the IL
mediated product mixture are in progress.
CONCLUSION
Fig. 6. (a) Molecular structure of (bpy)PtBr4. (b) Side
view of (bpy)PtBr4 molecular planes from the
bpy direction. The Pt atom is 3.475 Å away
from both neighboring molecular planes.
As a summary, ILs are useful phase transfer reagents
to depolymerize the inorganic coordination polymer MX2
(M = Pt, Pd; X = Br, Cl). ILs facilitate the quantitative for-
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Ionic Liquid in Synthesis
Table 3. Calculation of standard redox potential for the Pt(II)
disproportionation reaction to produce Pt(IV) and Pt(0)
in the presence of chloride anions
Hz, 2H), 9.13 (d, J = 5.6 Hz, 2H).
PtX2 reactions
In a similar way, 250 mmol PtBr2 (89.0 mg) was put into a
20 mL sample viral, followed by an aliquot of 5.00 mL stock solu-
tion to introduce 250 mmol bpy and 250 mmol [BEIm]Br. The re-
actant mixture was supersonically irradiated and monitored by
the 1H NMR spectroscopic methods regularly during overall 480
min. The conversion was estimated to be 34% from 1H NMR of
crude product mixture. After standing for full precipitation, the
liquid layer of product mixture was decanted. The precipitates
were dried under vacuum for 3 h before being washed with cold
acetone. The acetone washings (10 mL * 3-4) were combined and
volume rotary reduced to about 3 mL. Slow evaporation produced
yellow crystalline materials of (bpy)PtBr2 in 10-20% yields. 1H
NMR (400 MHz, d6-DMSO) d 7.85 (vt, J = 6.8 Hz, 2H), 8.43 (vt, J
= 8.4 Hz, 2H), 8.60 (d, J = 7.6 Hz, 2H), 9.77 (d, J = 5.6 Hz, 2H);
195Pt NMR (107 MHz, d6-DMSO) d -2563. The precipitates after
being washed by cold acetone were layered using DMSO/ether,
DMSO/EtOAc, or DMSO/CH2Cl2 to produce yellow crystals and
orange crystals. The orange crystals were collected, combined,
and recrystallized from CH2Cl2 to give (bpy)PtBr4, in 20-30%
yields. 1H NMR (400 MHz, d6-DMSO) d 8.15 (vt, J = 6.8 Hz, 2H),
Half reduction reaction
Eo /V
PtCl6 + 2e- ® PtCl4 + 2Cl-
+0.726
+0.758
2-
2-
PtCl4 + 2e- ® Pt(s) + 4Cl-
2-
Full redox reaction
2 PtCl4 ® PtCl6 + 2Cl- + Pt(s)
+0.032
2-
2-
mation of (bpy)PdX2 from PdX2 in a CHCl3 solution. With
high polarity and abundant halide anions ILs facilitate the
disproportionation of Pt(II) in the case of PtX2 to give both
(bpy)PtX2 and (bpy)PtX4 as products.
EXPERIMENTAL SECTION
General
Starting chemicals, organic solvents, and reagents used
were from commercial sources, e.g. Aldrich, Merck, Waco, etc.,
1
and were used directly without further purification. H NMR
spectra were recorded using 400 MHz or 500 MHz machines,
with chemical shifts in d units, downfield positive, and referenced
to the residual peak of deuterated solvents (CDCl3 d 7.24, d6-
DMSO d 2.50). The ILs, i.e., [BEIm]Br, [BEIm]Cl, [BMIm]Br,
and [BMIm]Cl were prepared according to literature procedure
with local modification.20 A Leo ultrasonic steri-cleaner (46 kHz)
was employed for sonocation reactions.
8.58 (vt, J = 7.8 Hz, 2H), 8.97 (d, J = 8.0 Hz, 2H), 9.72 (d, 3JH-H
6.0 Hz, 2H; d, 3JPt-H = 28 Hz); 195Pt NMR (107 MHz, d6-DMSO) d
=
-1421.
The preparation of (bpy)PtCl2 and (bpy)PtCl4 was similar
with yields also in 10-20% and 20-30%, respectively. For
(bpy)PtCl2, 1H NMR (400 MHz, d6-DMSO) d 7.85 (vt, J = 6.8 Hz,
2H), 8.42 (vt, J = 7.0 Hz, 2H), 8.59 (d, J = 8.0 Hz, 2H), 9.50 (d, J =
5.2 Hz, 2H); 195Pt NMR (107 MHz, d6-DMSO) d -2328. For
(bpy)PtCl4, 1H NMR (400 MHz, d6-DMSO) d 8.16 (vt, J = 6.8 Hz,
2H), 8.60 (vt, J = 8.4 Hz, 2H), 8.97 (d, J = 7.6 Hz, 2H), 9.51 (d, J =
5.6 Hz, 2H); 195Pt NMR (107 MHz, d6-DMSO) d -316.
PdX2 reactions
For preparation of (bpy)MX2, a 50 mL CHCl3 stock solu-
tion was prepared to contain 2.50 mmol bpy (390 mg) and 2.50
mmol IL of choice so that the 50.0 mM IL stock solution could
easily and quantitatively be transferred in a volumetric way to a
sample viral for reaction. As a typical example accordingly, 250
mmol PdBr2 (66.6 mg) was put into a 20 mL sample viral, fol-
lowed by an aliquot of 5.00 mL stock solution to introduce 250
mmol bpy and 250 mmol [BEIm]Br. The reactant mixture was su-
personically irradiated for 30 min. After standing for full precipi-
tation, the liquid layer of product mixture was decanted. The pre-
cipitates were washed with CHCl3 (10 mL * 3) and then dried un-
der vacuum for 3 h to result in orange solids of (bpy)PdBr2, (yield
Single crystal X-ray structure analysis
X-ray crystallographic data for (bpy)PtBr2 and (bpy)PtBr4
were collected with a Bruker-AXS SMART CCD diffractometer
at 100 K using graphite monochromated Mo Ka radiation. The
crystals were coated with mineral oil, attached to a glass fiber, and
quickly transferred under the cold nitrogen stream of the dif-
fractometer. The Bruker manufacture softwares were employed
for data collection, integration, and absorption corrections. The
structures were solved by direct methods and subsequently com-
pleted by Fourier recycling and refined by the full-matrix least-
squares refinements based on F2 with all observed reflections. All
non-hydrogen atoms were refined anisotropically. The hydrogen
atoms were idealized. Crystal data and refinement details were
summarized in Table 4. The cif files were deposited as supporting
1
99%, 105 mg). In the case using [BMIm]Br, 92% (97 mg). H
NMR (400 MHz, d6-DMSO) d 7.81 (vt, J = 6.6 Hz, 2H), 8.36 (vt, J
= 7.8 Hz, 2H), 8.60 (d, J = 8.0 Hz, 2H), 9.39 (d, J = 5.6 Hz, 2H).
Similar procedures were also used for preparation of
(bpy)PdCl2, taking 120 min on sonocation. The precipitates were
washed with cold CH2Cl2, and the yields 97% (using [BEIm]Cl)
1
and 99% (using [BMIm]Cl). H NMR (400 MHz, d6-DMSO) d
7.81 (vt, J = 6.4 Hz, 2H), 8.36 (vt, J = 8.4 Hz, 2H), 8.58 (d, J = 8.0
J. Chin. Chem. Soc. 2013, 60, 281-287
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Lin et al.
Table 4. Crystal data and refinement details of (bpy)PtBr2 and (bpy)PtBr4
(bpy)PtBr2
(bpy)PtBr4
CCDC 893404
C10H8Br4N2Pt
670.87
100.0(1) K
0.71073 Å
Monoclinic
Pn
Identification code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
CCDC 893405
C10H8Br2N2Pt
511.09
100.0(1) K
0.71073 Å
Monoclinic
C 2/c
Unit cell dimensions
a 17.0738(12) Å
b 9.3425(5) Å
c 7.3823(4) Å
a 90°
8.2966(3) Å
6.8692(2) Å
12.5057(4) Å
90°
b 112.526(8)°
g 90°
103.014(2)°
90°
Volume
Z
1087.72(11) Å3
4
694.41(4) Å3
2
Density (calculated)
Absorption coefficient
F(000)
Crystal size
q range for data collection
Index ranges
3.121 Mg.m-3
20.211 mm-1
920
3.209 Mg.m-3
21.589 mm-1
600
0.08 ´ 0.04 ´ 0.04 mm3
3.52 - 29.45°
-22 £ h £ 22,
-11 £ k £ 11,
-10 £ l £ 10
5022
0.24 ´ 0.2 ´ 0.18 mm3
2.69 - 26.37°
-10 £ h £ 10,
-8 £ k £ 6,
-15 £ l £ 15
13345
Reflections collected
Independent reflections
Completeness to q = 25.00°
Absorption correction
1344 [R(int) = 0.0358]
99.8 %
2778 [R(int) = 0.0317]
100.0%
Semi-empirical from equivalents
Max. and min. transmission
Refinement method
1 and 0.26887
0.9704 and 0.6526
Full-matrix least-squares on F2
Data / restraints / parameters
Goodness-of-fit on F
1344 / 0 / 70
1.070
2778 / 2 / 154
1.084
2
Final R indices [I > 2s(I)]
R indices (all data)
Extinction coefficient
Largest diff. peak and hole
R1 0.0207, wR2 0.0369
R1 0.0230, wR2 0.0376
0.00094(6)
R1 0.0196, wR2 0.0455
R1 0.0200, wR2 0.0457
0.022(10)
1.163 and -1.017 e.Å-3
2.272 and -0.774 e.Å-3
vents: Progress and Prospects; ACS Symp. Ser., 856; ACS:
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ACKNOWLEDGMENT
The authors thank Academia Sinica, Institute of
Chemistry, for financial supports.
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