Palladium(II)-assisted ortho alkylation of C(sp2)-H bonds in substituted azobenzenes with simple alkyl halides

Article abstract of DOI:10.1080/00958972.2018.1545089

A new and relatively simple synthetic strategy has been described for Pd(II)-catalyzed C-C bond formation via alkylation of ortho C(sp²)-H bonds in substituted azobenzenes possessing (2-phenylamino)phenylazo directing group employing different

Full text of DOI:10.1080/00958972.2018.1545089

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Palladium(II)-assisted ortho alkylation of C(sp2)-H
bond in substituted azobenzenes with simple alkyl
halides
Mainak Mitra, Debojyoti Mukherjee, Ujjwal Mandal & Albert A Shteinman
To cite this article: Mainak Mitra, Debojyoti Mukherjee, Ujjwal Mandal & Albert A Shteinman
(2018): Palladium(II)-assisted ortho alkylation of C(sp2)-H bond in substituted azobenzenes with
simple alkyl halides, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2018.1545089
To link to this article: https://doi.org/10.1080/00958972.2018.1545089
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Palladium(II)-assisted ortho alkylation of C(sp2)-H bond in substituted
azobenzenes with simple alkyl halides
MAINAK MITRA*a,b, DEBOJYOTI MUKHERJEEc, UJJWAL MANDALc and ALBERT A SHTEINMANd
aDepartment of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C.
Mullick Road, Jadavpur, Kolkata-700032, India
bDepartment of Chemistry, Burdwan Raj College, Frazer Avenue, Purba Bardhaman, W.B.-713104, India
cDepartment of Chemistry, University of Burdwan, Golapbag Campus, Purba Bardhaman, W.B.-713104, India
dInstitute of Problems of Chemical Physics, 142432, Chernogolovka, Moscow District, Russian Federation
A new and relatively simple synthetic strategy has been described for Pd(II)-catalyzed C-C bond
formation via alkylation of ortho C(sp2)-H bonds in substituted azobenzenes possessing
(2-phenylamino)phenylazo directing group employing different alkyl iodides. The yields of
various ortho alkylated products are found to be good to excellent (65-85%). A palladocyclic
intermediate complex has been isolated and fully characterized. Based on the experimental
results and the isolation of the palladocyclic intermediate, a catalytic cycle involving a sequential
C-H activation/oxidative addition followed by reductive elimination pathway has been proposed.
Keywords: Palladium; C-C Coupling; Alkylation; Azobenzenes
Graphical abstract
*Corresponding author. Email: mainakmitra274@gmail.com
1

1. Introduction
Developing new methods for selective C-H bond functionalization in complex organic molecules
is a challenging task in synthetic chemistry [1]. Metal-ion promoted C-H bond activation [2] has
evolved as a valuable tool in synthesis of natural products and drugs [3]. Functional groups in
complex organic molecules, as directing groups, can coordinate to a metal-center to enable the
site selection of one particular C-H bond over others. Palladium complexes are among the most
popular catalysts for this purpose because they can readily promote C-H bond activation at both
sp2 and sp3 C-center and usually require mild conditions [4]. Palladium catalyzed C-H alkylation
reactions have emerged as an efficient tool for C-C bond formation [5]. In this regard, Pd(II)-
catalyzed transformations of C(sp2)-H bonds of arenes into C-C/C-N/C-O bonds have been
investigated [6]. Our present research focuses on C-H bond activation in substituted
azobenzenes.
Azobenzenes are important compounds widely used in many fields, such as organic dyes
and pigments, food additives, photoluminophores and photoconductors, liquid crystals, etc. [7].
Organometallic Pd(II) complexes incorporating azo group(s) are active towards Suzuki and Heck
and other coupling reactions [8a-c] and alkene epoxidation [8c]. Synthesis of newly substituted
azobenzenes via directed C-H activation represents an active area of chemical research. Metal-
center promoted functionalization of azobenzenes including halogenations, alkylation, arylation,
acylation, alkoxylation, amination, etc. using azo directing groups has gained attention [9-11].
Su Kim and co-workers have recently described remarkable one-pot syntheses of oxindoles via
selective C-H alkylation of azobenzenes with internal olefins, such as maleimides, maleates and
fumarates, followed by reductive intramolecular cyclization [12]. The formation of an oxindole
scaffold could be a valuable contribution to development of bioactive compounds with medical
applications [13]. However, selective introduction of substituents into unsymmetrical
azobenzenes still represents a formidable challenge [14].
While Pd(II) assisted C-H activation in 2-alkylamino azobenzene is reported [15], there is
no information on the corresponding reactivity of 2-phenylamino-azobenzene. In the present
2

work we report effective and convenient synthetic strategies for making C-C bonds via C(sp2)-H
activation of azobenzene containing a (2-phenylamino)phenylazo bidentate directing group
(figure 1). Bidentate directing groups are more effective in palladium-catalyzed C-H bond
alkylations with alkyl halides than monodentate groups due to their ability to form metal chelates
[16]. Pd(II)-catalyzed formation of C-C bonds using alkyl halide remains a critical task [17]. In
the favorable case of alkyl iodides a large excess of AgOAc is often required to scavenge I- from
PdI [18].
2. Results and discussion
The azobenzene substrates were prepared by condensation of N-(phenyl)-o-phenylenediamine
with corresponding substituted nitrobenzenes (or nitrosobenzenes) at 50-60 C in the presence of
NaOH (scheme 1) following a literature method [19] for synthesis of 2-(phenylazo)aniline.
Scheme 1. Synthesis of azobenzene substrates used in this work for ortho alkylation.
We started our catalytic study with extensive survey of reaction conditions (table 1). Initially we
explored the reaction between NPhAzo (1 equiv, cf. table 1) with excess CH3I (5 equiv) in the
presence of catalytic amounts of PdCl2(CH3CN)2 (10 mol%) in dichloroethane (DCE) at 90 C
for about 12 h. Under such conditions, the reaction afforded about 11% of ortho methylated
product (isolated yield) (entry 1). Addition of 1 equiv. of K2CO3 as a base significantly enhanced
the yield of the ortho methylated product to 63% (isolated yield) under identical reaction
conditions (entries 2-4).
Following this encouraging result we performed optimization for catalytic reaction
conditions using different bases, solvents and temperatures. As shown in table 1, strong base
t
such as BuOK was more effective, bringing about 84% yield (entries 12-15). Temperature
played an important role in the catalysis.
3

The ortho methylation reaction did not proceed at room temperature. Increasing the
temperature resulted in formation of the desired product with best results (in terms of yield)
obtained at 100 C (entries 12 and 17). Nitrogen atmosphere instead of air has no effect on the
catalytic process. We also examined ortho alkylation reactions using different Pd(II) starting
salts (e.g. PdCl2, Pd(OAc)2) and observed similar reactivities. In contrast Pd(0) salt (Pd(dba)2;
dba = ) did not afford any alkylated product under the reaction conditions. This result together
with absence of any influence to reaction of air (dioxygen) and reductants strongly indicates a
Pd(II)/Pd(IV) catalytic cycle over Pd(II)/Pd(0) catalytic cycle as proposed by Sanford and co-
workers [20].
We observed that this reaction does not require AgOAc, perhaps due to strong
coordination ability of bidentate N-phenyl-(2-phenylazo)aniline group. After 12 h of catalysis
side products were observed besides the starting material and minor quantities of dialkylated
substrates. The last one can be prepared using more excess of MeI (more than 10) or starting
from monoalkylated product.
Having established the optimized set of conditions for ortho methylation, we then
explored the same for a series of ligands containing methyl and chloro substituents at the ortho,
meta and para-positions of the phenyl ring bearing an azo moiety. In all cases we observed
formation of ortho methylated products in high yields (67-82%, cf. table 2).
The substrates bearing methyl groups at ortho, meta and para positions exhibited similar
reactivities (entries 1-3, cf. table 2). Substrates having strong electron-donating groups like
methoxy and amine at ortho and para positions also had similar yields of the corresponding
ortho alkylated product (entries 9-11, cf. table 2). Substrates bearing electron-withdrawing
groups like chloro, bromo and nitro at ortho and para positions showed marginal decrease in the
reactivities (entries 4-6 and 12, cf. table 2).
We have also been successful in introducing ethyl and iso-propyl groups into NPhAzo
ligand system by using ethyl iodide and iso-propyl iodide, respectively (entries 6 and 7, cf.
table 2). This reaction also runs well for secondary alkyl iodides.
On the basis of previous papers [16b,c, 17b, 20, 21] and our experimental results, a
plausible mechanism of this palladium-catalyzed alkylation of C(sp2)-H bond in substituted
azobenzenes was proposed as shown in scheme 2.
4

Scheme 2. Plausible reaction mechanism of Pd(II)-catalyzed ortho alkylation.
In the first step of the catalytic cycle, azobenzene coordinates with Pd(II)-salt and subsequent
C-H activation takes place to form palladocycle intermediate A. Then intermediate A undergoes
oxidative addition with RI to generate Pd(IV) species B. In the last step the final alkylated
product is obtained via the reductive elimination from B, followed by regeneration of the Pd(II)
catalyst.
We presume that intermediate A has a structure close to that of palladocyclic complex 1
except the amine N is deprotonated and a solvent molecule is coordinated to Pd(II)-center instead
of chloride. Complex 1 can be prepared from reaction of one equiv of NPhAzo with one equiv of
Pd(II)Cl2(CH3CN)2 in methanol in the presence of Et3N (figure 2, cf. ESI for detailed synthesis)
1
[22]. The complex was characterized by ESI-MS, H NMR spectroscopy and elemental analysis
1
and its molecular structure was confirmed by X-ray crystallography. The H NMR spectrum
(cf. figure S15, ESI) shows that PhNH proton in 1 shifts upfield (δ 9.12) relative to the ligand
NPhAzo (δ 10.07) supporting ligand coordination. This shift (-0.98) is comparable to that of
BzNH proton (-0.8) [19].
Suitable X-ray quality crystals of 1 were obtained by slow diffusion of a CH2Cl2 solution
of the complex into hexane. The crystals are monoclinic and the space group is P21/c. A
perspective view with the atom numbering scheme is given in figure 2. Selected bond distances
5

and angles are collected in table 3. The asymmetric unit of 1 in the crystal lattice contains the
weak bounded dimer of two equivalent molecules just as in the structure of 2-benzylamine
complex of Pd(II) [19]. The molecular structure exhibits a distorted square planar geometry
around palladium, where the anionic ligand NPhAzo binds the metal ion in a tridentate (N,N,C)
fashion via C-H activation and the chloride completes the coordination around Pd(II). The Pd-Cl
and Pd-Nazo distances are within the usual range [8d, 19]. The Pd-C bond length is similar to
other reported orthopalladed azobenzene complexes [8d, 19]. The Pd-Nam bond length is much
longer than the Pd-Nazo distance because of stronger trans-influence of the aryl carbon. The
pendant phenylam rings do not lie on the molecular plane and makes almost a right angle with the
rest.
Although isolation of intermediate A under catalytic reaction conditions was not
successful, the full characterization of 1 under a 1:1 reaction between ligand NPhAzo and Pd(II)-
salt shows C-H activation in the ligand leading to formation of a stable Pd(II)-C bond. This
supports the C-H activation step being the first step of the catalytic cycle. Hence under catalytic
conditions using excess substrates with respect to Pd-salt, the C-H activation can be followed by
oxidative addition of alkyl iodide to form a Pd(IV) species and then subsequent reductive
elimination.
3. Summary and conclusion
We examined activation of sp2 C-H bonds of 2-phenylamino substituted azobenzenes using
bidentate substrates for coordination to palladium complexes. In the presence of Pd(II)
complexes the selective ortho-alkylation of these azobenzene ligands with different alkyl iodides
was observed. A new and relatively simple synthetic strategy has been found for Pd(II)-catalyzed
C-C bond formation in substituted azobenzenes. We believe this method can have application for
syntheses of medically important heterocycles and also for materials chemistry.
4. Experimental
4.1. Materials
Reagents and solvents were of at least 99% purity and used as received. N-Phenyl-1,2-
phenylenediamine was purchased from Sigma Aldrich. PdCl2 was purchased from Arora
Matthey Limited, India. PdCl2(CH3CN)2 was prepared by stirring PdCl2 in CH3CN at room
6

temperature and the resulting yellow precipitate was filtered off and dried. All other reagents and
solvents were purchased from Spectrochem, India and Fisher Scientific. Dichloromethane and
acetonitrile were dried by distillation from CaH2.
4.2. Physical measurements
NMR spectra were obtained using a Bruker Avance 400/500 MHz spectrometer and SiMe4 was
used as the internal standard. A Perkin-Elmer 240C elemental analyzer was used to collect
microanalytical data (C, H, N). High resolution mass spectra were recorded on a Micromass Q-
TOF mass spectrometer (Model No. YA263). Infrared spectra were obtained using a Perkin-
Elmer 783 spectrophotometer.
4.3. Syntheses
4.3.1. Synthesis of NPhAzo. N-Phenyl-ortho-phenylenediamine (1.84 g, 0.01 mol) was mixed
with nitrobenzene (1.23 g, 0.01 mol) in a clean 100 ml beaker and to it, finely divided NaOH
pellets (0.04 g, 0.01 mol) were added. The mixture was gently heated to 70 C with constant
scratching and stirring with a glass rod for about 20 min. The mixture became dark red and
sticky. It was cooled to room temperature and dissolved in minimum volume of CH2Cl2. The
solution was then passed through a silica column using a mixture of hexane:toluene (9:1) as an
eluent. The red band thus separated was collected and the pure ligand was obtained as a red
liquid. Yield: 1.56 g (57%). ESI-MS: 272.0673. 1H NMR (500 MHz, CDCl3) δ (ppm): 10.069 (s,
1H), 7.9065 (d, 1H, J = 7.5 Hz), 7.8525 (d, 2H, J = 7.5 Hz), 7.5 (t, 2H), 7.426 (t, 1H), 7.371 (t,
13
2H), 7.317-7.242 (m, 4H), 7.109 (t, 1H), 6.907 (t, 1H). C NMR (125 MHz, CDCl3) δ (ppm):
152.81, 140.72, 140.46, 137.61, 132.44, 130.35, 129.61, 129.29, 128.73, 123.77, 122.38, 118.44,
114.60.
4.3.2. Syntheses of o-Me/m-Me/p-MeNPhAzo. o-MeNPhAzo, m-MeNPhAzo and
p-MeNPhAzo were prepared following the same procedures as that of NPhAzo except 2-methyl
nitrosobenzene, 3-methyl nitrosobenzene and 4-methyl nitrosobenzene were used instead of
2-nitrobenzene.
7

1
o-MeNPhAzo. Yield: 1.7 g (59%). ESI-MS: 286.1535. H NMR (500 MHz, CDCl3) δ (ppm):
10.464 (s, 1H), 7.958 (d, 1H, J = 8 Hz), 7.715 (d, 1H, J = 7.2 Hz), 7.418-7.232 (m, 9H), 7.104 (t,
1H), 6.931 (t, 1H), 2.673 (s, 3H). 13C NMR (125 MHz, CDCl3) δ (ppm): 150.93, 140.84, 139.62,
138.05, 136.64, 132.12, 131.31, 130.75, 130.26, 129.61, 126.84, 123.73, 122.33, 118.39, 115.42,
114.41, 18.36.
1
m-MeNPhAzo. Yield: 1.55 g (54%). ESI-MS: 286.0597. H NMR (500 MHz, CDCl3) δ (ppm):
10.106 (s, 1H), 7.9 (d, 1H, J = 8 Hz), 7.665 (s, 2H), 7.388-7.241 (m, 8H), 7.115 (t, 1H), 6.91 (t,
1H), 2.457 (s, 3H). 13C NMR (100 MHz, CDCl3) δ (ppm): 152.19, 140.39, 139.18, 137.64,
132.29, 131.16, 129.60, 128.79, 123.74, 122.71, 122.42, 119.77, 118.42, 114.58, 21.54.
1
p-MeNPhAzo. Yield: 1.89 g (66%). ESI-MS: 286.1081. H NMR (400 MHz, CDCl3) δ (ppm):
9.961 (s, 1H), 7.874 (d, 1H, J = 8 Hz), 7.75 (d, 1H, J = 8.4 Hz), 7.378-7.216 (m, 9H), 7.09 (t,
13
1H), 6.89 (t, 1H), 2.242 (s, 3H). C NMR (100 MHz, CDCl3) δ (ppm): 150.90, 140.90, 140.87,
140.42, 137.70, 132.08, 129.94, 129.58, 128.11, 123.59, 122.35, 122.22, 118.47, 114.60, 21.
4.3.3. Synthesis of [PdII(L)Cl] (1). One equivalent of NPhAzo (L) (1.36 mg, 0.5 mmol) was
dissolved in CH3OH in a 50 ml round bottom flask. To it, one equivalent of [PdCl2(CH3CN)2]
(1.3 mg, 0.5 mmol) was added under stirring at room temperature followed by addition of 2-3
drops of triethylamine. The color of the reaction mixture immediately changed from orange red
to purple. The reaction was stirred for about 30 min and the solvent was evaporated. The crude
solid thus obtained was dissolved in minimum amount of CH2Cl2 and isolated as crystalline 1 by
slow evaporation of the CH2Cl2 solution. Yield: 1.31 mg (63%). ESI-MS (m/z): exp. 377.7693;
calc. 378.0234 ([Pd(L)]+]. Elemental analysis: calc. (%): C, 52.2; H, 3.41; N, 10.14. Found (%):
C, 54.01; H, 3.29; N, 10.03. 1H NMR (400 MHz, CDCl3) δ (ppm): 9.12 (s, 1H), 7.654 (d, 1H, J =
3.6 Hz), 7.444 (t, 2H), 7.345-7.281 (m, 3H), 7.222-7.185 (m, 3H), 7.11 (t, 1H), 7.025 (t, 1H),
6.838 (d, 1H, J = 7.2 Hz), 6.636 (t, 1H). FTIR (υ, cm-1; KBr): 3472 (br, NH), 1587 (s, C=C),
1479 (s, C=N), 1308 (m, N=N).
8

4.4. X-ray crystallography of 1
Suitable X-ray quality crystals of 1 were obtained by slow diffusion of a CH2Cl2 solution of the
complex into hexane. All data were collected on a Bruker SMART APEX-II diffractometer
equipped with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å), and were corrected
for Lorentz polarization effects. Data for 1: a total of 10954 reflections were collected, of which
1744 were unique (Rint = 0.050), satisfying the I > 2σ(I) criterion, and were used in subsequent
analysis. The structure was solved by employing the SHELXS-97 program package50 and were
refined by full-matrix least-squares based on F2 (SHELXL-97).51 All hydrogens were added in
calculated positions. Selected crystallographic data for 1 are listed in table 4.
4.5. General reaction conditions for catalytic ortho methylation
In a 50 ml round bottom flask, NPhAzo (0.18 gm, 1 mmol), methyl iodide (0.21 gm, 5 mmol),
Pd-salt (10 mol% of the ligand) and appropriate base (1.5 equiv. to the ligand) were taken
together and 25 ml dichloroethane (DCE) was added. The reaction mixture was refluxed under
air for 12 h and then cooled to room temperature. The solvent was evaporated under reduced
pressure and the residue was dissolved in 5 ml CH2Cl2. The CH2Cl2 solution was subjected to a
preparative TLC (silica) plate using a mixture of hexane:toluene (9:1) as an eluent. The product
was separated, isolated and analyzed by ESI-MS, 1H and 13C NMR.
Supplementary data
Supplementary data includes ESI-MS, 1H and 13C-NMR spectra of NPhAzo and all the catalytic
1
products; ESI-MS, H NMR and FTIR spectra of 1. Supplementary data for the structural
analysis have been deposited with the Cambridge Crystallographic Center, CCDC No. 1578352
for 1.
Acknowledgements
This work has been funded by the Science and Engineering Research Board (SERB) of India via
project no. YSS/2015/000304/CS (Start-up research grant for young scientist to MM). The
authors acknowledge the Indian Association for the Cultivation of Science for instrumental
facilities and infrastructures.
9

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12

Figure 1. Ligand system (azobenzene substrates) used in this work for ortho alkylation.
13

Figure 2. Molecular structure of 1 (thermal ellipsoids are drawn with 30% probability ellipsoids);
H4 attached to amine N4 is shown; all other hydrogens have been omitted for clarity.
14

Table 1. Optimization of reaction conditionsa for Pd(II)-catalyzed ortho alkylation of NPhAzo by
using CH3I (PA = 2-phenylamino).
Entry
Catalyst (mol%)
Solvent
Base (equiv)
Temp. (ºC) Yieldb (%)
1.
2.
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (10)
PdCl2(CH3CN)2 (15)
PdCl2(CH3CN)2 (5)
PdCl2 (10)
DCE
DCE
none
90
90
11
63
63
58
66
47
47
71
77
n.r.c
28
84
82
82
82
77
86
62
79
83
n.r.
K2CO3 (1.5)
K2CO3 (2)
3.
DCE
90
4.
DCE
K2CO3 (1)
90
5.
DCE
NaOH (1.5)
(C2H5)3N(1.5)
PhCOOK(1.5)
NaOCH3 (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
tBuOK (1.5)
90
6.
DCE
90
7.
DCE
90
8.
DCE
90
9.
DCE
90
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
DCE
25
DCE
50
DCE
100
110
110
100
100
100
100
110
110
110
DCE
Toluene
Toluene
1,4-dioxane
DCE
DCE
DCE
Pd(OAc)2 (10)
DCE
21.
Pd(dba)2 (10)
DCE
a
Reaction conditions: NPhAzo (1.0 equiv), CH3I (5 equiv), Pd catalyst (5-15 mol %), base
(0-2 equiv), solvent (25 mL), under air, time 10-12 h. bIsolated yield. cn.r. = no reaction.
15

Table 2. Substrate scope.
Product
Entry
1
Substrate
Yield
76%
2
3
80%
77%
4
67%
5
6
71%
71%
85%
80%
77%
76%
76%
65%
7
8
9
10
11
12
16

Table 3. Selected bond distances (Å) and angles () for 1.
Pd(1)-Cl(1)
2.309(1)
1.945(3)
1.975(5)
2.212(5)
1.261(6)
178.4(1)
99.3(1)
Pd(1)-N(2)
Pd(1)-C(1)
Pd(1)-N(3)
N(1)-N(2)
Cl(1)-Pd(1)-N(2)
Cl(1)-Pd(1)-C(2)
Cl(1)-Pd(1)-N(4)
N(2)-Pd(1)-C(2)
N(2)-Pd(1)-N(4)
C(2)-Pd(1)-C(4)
Pd(1)-N(2)-N(1)
Pd(1)-N(2)-C(5)
100.2(1)
79.1(2)
81.4(2)
160.5(2)
122.4(3)
117.4(3)
17

Table 4. Crystallographic data table for 1.
Empirical formula
Formula weight
Temperature
C36H28N6Cl2Pd2
828.41
150(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Monoclinic
P21/c
Unit cell dimensions
a = 10.815(2) Å
b = 26.258(5) Å
c = 12.434(2) Å
α = 90
β = 108.618(5)
γ = 90
Volume
3346.2(10) Å3
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.630 Mg m-3
1.270 mm-1
1648.0
Crystal size
0.18 × 0.16 × 0.14 mm3
Theta range for data collection
Index ranges
2.31 to 22.57
-13<=h<=13, -32<=k<=32, -13<=l<=15
Reflections collected
Independent reflections
Completeness
42480
7048
99.6% (to theta = 25.937)
Absorption correction
Refinement method
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I>2sigma(I)]
R indices (all data)
Largest diff. peak and hole
Empirical
Full-matrix least-squares on F2
6512 / 0 / 415
0.904
R1 = 0.0401, wR2 = 0.1126
R1 = 0.072, wR2 = 0.1410
0.484 and -0.607 e.Å-3
18