SPS–Ni(II) pincer compounds of the type [Ni(phPS2)(P(C6H4-4-R)3)] Synthesis, characterization and catalytic evaluation in C–S cross-coupling reactions

Article abstract of DOI:10.1016/j.poly.2017.09.026

The synthesis and characterization of a series of SPS–Ni(II) pincer complexes with different para-substituted triphenylphosphines has been performed. The molecular structure of [Ni(phPS₂)(PPh₃)] (1) (phPS₂H₂ = PhP(C₆H₄-2-SH)₂, bis(phenyl-2-thiol)phenylphosphine) was unequivocally determined by single crystal X-ray diffraction analysis. The metal centre exhibited a slightly distorted square planar geometry. The complexes showed a high catalytic activity in the C–S cross-coupling reaction of both alkyl- and aryl-disulfides with iodobenzenes for the production of non-symmetric sulfides. In general, the different para-substituted triphenylphosphine ligands do not affect the catalytic performance of the SPS–Ni(II) complexes. However, activity of the catalyst decreases with the steric hindrance of the different alkyl groups in the disulphide substrates.

Full text of DOI:10.1016/j.poly.2017.09.026

Accepted Manuscript
SPS-Ni(II) Pincer Compounds of the Type [Ni(phPS2)(P(C6H4-4-R)3)] Synthe-
sis, Characterization, Catalytic Evaluation in C-S Cross-Coupling Reactions
Valente Gómez-Benítez, Hugo Valdés, Simón Hernández-Ortega, Juan Manuel
German-Acacio, David Morales-Morales
PII:
S0277-5387(17)30603-4
https://doi.org/10.1016/j.poly.2017.09.026
POLY 12836
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
16 July 2017
11 September 2017
15 September 2017
Please cite this article as: V. Gómez-Benítez, H. Valdés, S. Hernández-Ortega, J. Manuel German-Acacio, D.
Morales-Morales, SPS-Ni(II) Pincer Compounds of the Type [Ni(phPS2)(P(C6H4-4-R)3)] Synthesis,
Characterization, Catalytic Evaluation in C-S Cross-Coupling Reactions, Polyhedron (2017), doi: https://doi.org/
10.1016/j.poly.2017.09.026
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SPS-Ni(II) Pincer Compounds of the Type [Ni(phPS2)(P(C6H4-4-R)3)]
Synthesis, Characterization and Catalytic Evaluation in C-S Cross-
Coupling Reactions.
Valente Gómez-Beníteza*, Hugo Valdésb, Simón Hernández-Ortegab, Juan Manuel
German-Acacioc, David Morales-Moralesb*
aFacultad de Ciencias Químicas, Universidad Autónoma de Chihuahua. Circuito
Universitario S/N. Chihuahua, Chihuahua, C. P. 31125. México. bInstituto de Química,
Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria,
Ciudad de México. C. P. 04510, México. cRed de Apoyo a la Investigación, Instituto
Nacional de Ciencias Médicas y Nutrición SZ-Universidad Nacional Autónoma de
México (CIC-UNAM), Ciudad de México. 14000. México.
Abstract
The synthesis and characterization of a series of SPS-Ni(II) pincer complexes with
different para-substituted triphenylphosphines have been performed. The molecular
structure of [Ni(phPS2)(PPh3)] (1) (phPS2H2 = PhP(C6H4-2-SH)2, bis(phenyl-2-
thiol)phenylphosphine) was unequivocally determined by single crystal X-ray
diffraction analysis. The metal centre exhibited a slightly distorted square planar
geometry. The complexes showed a high catalytic activity in the C-S cross-coupling
reaction of both alky- and aryl-disulfides with iodobenzenes for the production of non-
symmetric sulfides. In general, the different para-substituted triphenylphosphine
ligands do not affect the catalytic performance of the SPS-Ni(II) complexes. However,
activity of the catalyst decreases with the steric hindrance of the different alkyl groups
in the disulphide substrates.
Keywords: SPS-pincer complex, nickel complex, C-S cross-coupling, thioether
synthesis, nickel catalyst, thioetherification reaction.
*E-mail: damor@unam.mx (D. Morales-Morales); valentexal@yahoo.com.mx (V.
Gómez-Benítez)

1. Introduction
The C-S cross-coupling reaction has represented an important tool in organic
synthesis. This procedure has been successfully employed in the industry for the
synthesis of drugs and herbicides.1 The use of transition metal complexes to promote
this reaction has allowed the development of safer and greener procedures. For example,
Taniguchi has reported the use of copper in the presence of a reducing agent to catalyse
the C-S formation.2,3 In other relevant reports, transition metals such as Co,4 Pd,5-7 Cu8-
10 and Ni11-14 have been used for this purpose.
Pincer complexes have been used as effective catalytic species in several
transformations15-29 that range from C-C couplings to dehydrogenation reactions.
However, the catalytic activity of pincer complexes in the C-S cross-coupling reaction
has only been explored to a certain extent.30-32 In fact, our group has reported some of
the first examples of nickel pincer complexes exhibiting good catalytic activity in this
process.33-36 Hence, we have successfully employed a series of NNN,33,34 SNS35 and
POCOP36 based Ni(II)-pincer compounds. Thus, following our continuous interest in C-
S cross-coupling reactions catalyzed by Ni(II)-pincer complexes, herein we report the
synthesis, characterization and catalytic evaluation in the C-S cross-couplings of a series
-2
of SPS-Ni(II) pincer compounds including the ligand phPS2 .
2. Results and discussion
Synthesis and characterization of the SPS-Ni(II) pincer complexes.
The preparation of the SPS-Ni(II) pincer complexes was carried out by the
stoichiometric reaction of trans-[NiCl2(P(C6H4-4-R)3)2] (R= H (1), Cl (2), F (3), CH3
(4), OCH3 (5), CF3 (6)) with the proligand phPS2H2 in the presence of triethylamine as
base in CH2Cl2 as solvent (Figure 1). In all cases the products were obtained as
2

greenish-brown powders in good yields. The series of SPS-Ni(II) complexes were fully
characterized by NMR spectroscopy, mass spectrometry and elemental analysis.
P
2 Et3N
CH2Cl2
HS
Ni
P
S
S
2 Et3HN+Cl-
PAr3
+
trans-[NiCl (PAr ) ]
+
+
2
3 2
P
R
R
SH
R
R = H(1), Cl(2), F(3), Me(4), OMe(5), CF3(6)
Figure 1. General synthesis of the series of PSP-Ni(II) pincer complexes.
The structure of the six complexes is very similar, thus they share similar
1
spectroscopic properties. Characterization by H and 13C{1H} NMR, is not very
informative and only afford signals due, either to the aromatic protons or carbons due to
-2
the presence of both the phPS2 ligand and the phosphines in the series of complexes.
More valuable structural information is obtained from the 31P{1H} NMR spectra,
showing for all compounds two doublets. One at about 25.5 ppm with a coupling
2
constant of JP-P  278 Hz, corresponding to the para-substituted triarylphosphine
ligands and another assigned to the phPS2-2 pincer ligand at about 86.5 ppm with a 2JP-P
of about 279 Hz. In addition, FAB+ mass spectrums of the complexes were recorded. In
all cases, the samples showed the molecular ion at m/z = 644 (1), 748 (2), 698 (3), 686
(4), 734 (5) and 848 (6), these results being in accordance with the proposed structures.
Elemental analyses were also performed, which values attained fit well with the
expected percentages for the proposed structures. Furthermore, crystals of 1 suitable for
single crystal X-ray diffraction analysis were obtained by slow evaporation of a solution
of 1 in MeOH/CH2Cl2. Crystallographic data are shown in Table 1. Compound 1
3

crystallized in a triclinic system with a P1 space group. Figure 2 shows its molecular
structure. The structure reveals the SPS pincer ligand to be coordinated to the nickel
atom and completing the coordination sphere the triarylphosphine ligand. The nickel
center exhibited a slightly distorted square planar geometry. The main distortion of the
square geometry caused by the rigidity of the SPS pincer ligand, as evidenced by both
angles S(1)-Ni(1)-S(2) 165.27(7), P(1)-Ni(1)-P(2) 174.92(6). The Ni-S distances are
slightly different, being the Ni(1)-S(1) 2.1557(15) bond length shorter than Ni(1)-S(2)
2.1881(15) Å, same situation being observed for the Ni(1)-P(1) 2.1330(14) Å and Ni(1)-
P(2) 2.2350(14) bond lengths.
Figure 2. An ORTEP representation of the molecular structure of 1. The ellipsoids are
represented at 50% of probability showing the labelled atoms in the scheme. The
hydrogen atoms have been omitted for clarity. Selected bond lengths (Å): Ni(1)-P(1)
2.1330(14), Ni(1)-S(1) 2.1557(15), Ni(1)-S(2) 2.1881(15), Ni(1)-P(2) 2.2350(14) and
Bond angles (o): P(1)-Ni(1)-S(1) 88.56(6), P(1)-Ni(1)-S(2) 86.19(6), S(1)-Ni(1)-S(2)
165.27(7), P(1)-Ni(1)-P(2) 174.92(6), S(1)-Ni(1)-P(2) 96.37(6), S(2)-Ni(1)-P(2)
89.32(5).
4

Table 1. Structural data and refinement compound [Ni(phPS2)(PPh3)] (1).
Empirical formula
C36H28NiP2S2
645.35
Formula weight
Temperature
298(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Triclinic
P-1
Unit cell dimensions
a = 10.0122(17) Å
b = 10.0851(16) Å
c = 17.472(3) Å
= 91.908(14)°.
= 105.118(13)°.
 = 113.999(12)°.
3
Volume
1536.3(5) Å
2
Z
3
Density (calculated)
Absorption coefficient
F(000)
1.395 Mg/m
-1
0.896 mm
668
3
Crystal size
0.313 x 0.192 x 0.088 mm
2.239 to 25.374°.
Theta range for data collection
Index ranges
-12 ≤ h ≤ 11, -11 ≤ k ≤ 12, -20 ≤ l ≤ 21
25530
Reflections collected
Independent reflections
Completeness to theta = 25.242°
Absorption correction
Max. and min. transmission
Refinement method
Data / restraints / parameters
5623 [R(int) = 0.1252]
99.9 %
Integration
0.9472 and 0.8354
2
Full-matrix least-squares on F
5623 / 0 / 370
2
Goodness-of-fit on F
1.094
Final R indices [I>2sigma(I)]
R indices (all data)
R1 = 0.0637, wR2 = 0.1227
R1 = 0.1092, wR2 = 0.1488
-3
Largest diff. peak and hole
0.449 and -0.512 e.Å
Catalytic Studies.
The SPS-Ni(II) pincer complexes 1-6 were used as catalyst in the arylthiolation
of iodobenzene. The reactions were carried out in DMF at 150ºC, using a catalyst
loading of 0.1 mol%. As a model reaction, the coupling between diphenyl disulfide and
iodobenzene in the presence of Zn as reducing agent was studied (Table 2). In general,
5

all the complexes exhibited good activity, ranging yields from 85 % for compound 6 to
90 % for complex 3. These minimal differences in yield suggest that the para-
substituted groups in the phosphine are not affecting the catalytic activity of the
complexes and most likely, is leaving the coordination sphere to provide a valuable
coordination site at the nickel center. Based on these observations, we decided to use
complex 1 for continue the catalytic studies.
Table 2. C-S cross coupling using the nickel complexes [Ni(phPS2)(P(C6H4-4-R)3)]a
S
I
S
[Ni(phPS2)(P(C6H4-4-R)3)]
S
+
Zn
Entry
Complex
Conversion (%)*
1
2
3
4
5
6
1
2
3
4
5
6
86
88
90
86
88
85
aReaction conditions: 2.45 mmol of diphenyl disulphide, 4.9 mmol of iodobenzene,
4.5x10-3 mmol of the catalyst, 4.9 mmol of Zn and 3 mL of DMF, 5 h. 150 °C.
*Conversions obtained by GC-MS are based on residual iodobenzene and the average
of two runs.
In order to study the selectivity of complex 1, we evaluated its catalytic activity
towards different para-substituted iodobenzenes (Table 3). In these experiments,
compound 1 only produced the C-S cross-coupling products in good yields, tolerating
functional groups such as ether, ketone, or the less reactive halogen atoms. As expected,
the influence of the electron-withdrawing groups in the iodobenzene increases the
conversion, while the opposite effect is observed when an electron-donating group is
present.
6

Table 3. C-S couplings of para-substituted iodobenzenes catalysed by [Ni(phPS2)(PPh3)] (1)a
S
I
S
S
[Ni(phPS2)(PPh3)2]
+
Zn
Y
Y
Entry
Y
-OMe
-Me
-H
Conversion (%)*
1
2
3
4
5
6
81
89
86
88
96
95
-F
-Br
-COMe
aReaction conditions: 2.45 mmol of diphenyl disulphide, 4.9 mmol of the corresponding
iodobenzene, 4.5x10-3 mmol of catalytic precursor, 4.9 mmol of Zn and 3 mL of DMF, 5
h. 150 °C. *Conversions obtained by GC-MS are based on residual iodobenzene and
are the average of two runs.
We also explored the possibility of performing the C-S couplings of dialkyl
disulfides and iodobenzene. In this case, we employed the same reaction conditions as
those described for the previous catalytic experiments (Table 4). Thus, when the
substrate is dimethyl disulfide the conversion obtained was of 56 %. However, using di-
tert-butyl disulfide as substrate dramatically drops the conversion to only 13 %. In the
case of di-iso-propyl disulfide the conversion was 48 %. These changes in reactivity can
be attributed to steric effects of the different alkyl groups. Thus, the tert-butyl group
displays the higher steric hindrance of the series, and so the lower yields to the
unsymmetrical sulfides (Table 4). Using di-sec-butyl disulfide the conversion increases
(47 %) in comparison with the linear di-n-butyl disulfide (27 %). In this case, probably,
due to higher inductive effects of the di-sec-butyl disulfide the reaction affords a higher
conversion.
Compound 1 represents a good alternative for the catalysis of the C-S cross-
coupling reaction of iodobenzene. For example, the reaction conditions that Taniguchi
7

employed was using 10 mol % of catalyst at 110ºC for 18h. It is noteworthy that
employing compound 1 as catalyst at 150ºC the reaction time decreases to 5 h as well as
the amount of nickel, improving the yields and reaction times.
Table 4. C-S couplings of dialkyl disulphides catalysed by [Ni(phPS2)(PPh3)] (1)a
S
I
R
S
R
[Ni(phPS2)(PPh3)2]
R
S
+
Zn
Entry
1
R
Conversion*(%)
56
S
S
S
2
48
S
S
S
S
3
4
5
13
27
47
S
S
S
aReaction conditions: 2.45 mmol of dialkyl disulphide, 4.9 mmol of the corresponding
iodobenzene, 4.5x10-3 mmol of catalytic precursor, 4.9 mmol of Zn and 3 mL of DMF, 5
h. 150 °C. *Conversions obtained by GC-MS are based on residual iodobenzene and
the average of two runs.
Although at this moment and with the current information a clear mechanistic
route cannot be envisaged, one can surely think in the elimination of the phosphine
ligand to provide a coordination center, and after this, several scenarios can be
conceived, but in order to provide the proper condition to perform and oxidative
addition the nickel center must be reduced by the elemental zinc. Then, either the
disulphide of the iodobenzene can oxidatively add and in the following steps produce
the non-symmetric disulfide, regenerating the active species [Ni(phPS2)] and start the
catalytic cycle all over again. Another possibility, may invoke hemilabile properties of
8

the pincer moiety phPS2, behaviour that we have observed previously.37 Efforts aimed
to shed further light into the mechanistic insights of this reactions are currently under
process in our research lab and will be disclosed in due time.
3. Conclusions
We have synthesized a series of nickel complexes with the phosphinothiol
(PhP(C6H4-2-SH)2) pincer type ligand SPS and p-substituted triarylphosphines. The
complexes were fully characterized including the unequivocal determination of the
crystal structure of compound 1. The series of complexes [Ni(phPS2)(P(C6H4-4-R)3)]
were successfully evaluated in the C-S cross-coupling reactions of iodobenzene and
diphenyl disulfide in the presence of zinc as reducing agent, producing good
conversions. The different para-substituted triarylphosphine ligands do not affect the
catalytic behaviour of the complexes. The catalytic reaction conditions tolerate
functional groups such as ketones and ethers. Additionally, some dialkyl disulfides were
also successfully used as substrates in C-S couplings with iodobenzene. The results
obtained showed the yields to be determined by the steric hindrance of the alkyl
substituents exhibiting lower conversion with those with higher steric demand.
4. Experimental Section
All chemical compounds were commercially obtained from Aldrich Chemical
Co. and used as received without further purification. Melting points were recorded on a
1
13
31
Mel-Temp II apparatus and are reported without correction. The H, C{1H}, P{1H}
NMR spectra were recorded on a JEOL GX300 spectrometer. Elemental analyses were
performed in a Thermo Scientific Flash 2000 elemental analyzer, using a Mettler
Toledo XP6 Automated-S Microbalance and sulfanilamide as standard (Thermo
9

Scientific BN 217826, attained values N = 16.40 %, C = 41.91 %, H = 4.65 %, y S =
18.63 %; certified values N = 16.26 %, C = 41.81 %, H = 4.71 %, y S = 18.62 %).
Positive-ion FAB mass spectra were recorded on a JEOL JMS-SX102A mass
spectrometer operated at an accelerating voltage of 10 kV. Samples were desorbed from
a nitrobenzyl alcohol (NOBA) matrix using 3keV xenon atoms. Mass measurements in
FAB+ were performed at a resolution of 3000 using magnetic field scans and the matrix
ions as the reference material or, alternatively, by electric field scans with the sample
peak bracketed by two (polyethylene glycol or cesium iodide) reference ions.
General procedure for the synthesis of pincer complexes [Ni(phPS2)(P(C6H4-4-R)3)].
Complexes 1–6 were synthesized using the same experimental procedure. Thus,
as a representative example, the synthesis of complex [Ni(phPS2)(PPh3)] (1) is
described below.
A solution of phosphino-dithiol [phPS2H2]38 (200 mg, 0.613 mmol) and NEt3
(0.116 mg, 1.227 mmol) in (10 mL) of CH2Cl2 was added to a solution of trans-
[Ni(Cl)2(PPh3)2]39 (0.613 mmol) in CH2Cl2 (10 mL). The solution was stirred for 24 h.
After this time, the solution was filtered and the volume was reduced. The greenish-
brown residue was recrystallized from a mixture of CH2Cl2/MeOH. Yield 277: mg
(70%). M.p. 253-256 °C. 1H NMR (300 MHz, CDCl3) 7.71 – 7.67 (m, 1H), 7.58 – 7.54
(m, 4H), 7.44 – 7.31 (m, 21H), 7.21 – 7.14 (m, 1H), 7.00 – 6.95 (m, 1H); 13C{1H} NMR
(75 MHz, CDCl3) 135.3, 135.2, 134.5, 134.3, 132.2, 131.7, 131.3, 131.2, 130.7, 130.3,
130.1, 129.1, 129.0, 128.6, 128.5, 128.2, 128.1, 128.0, 122.8, 122.7. 31P{1H} NMR (121
2
2
MHz,CDCl3) 86.45 (d, JPP = 267.16 Hz, 1P), 26.26 (d, JPP = 272.39 Hz, 1P). EM-
FAB+: m/z 644 (65) [M]+·, 382 (37) [M-PPh3]+, 262 (53) [M-NiphPS2]+. Elem. Anal.
Calcd. for C36H28P2NiS2: C, 67.00; H, 4.37 Found : C, 66.77; H, 4.31.
10

[Ni(phPS2){P(C6H4-4-Cl)3}] (2).
1
Yield: 303 mg (66 %). M.p. 240-242 °C. H NMR (300 MHz, CDCl3) 7.65 – 7.31 (m,
24H), 7.11 – 6.99 (m, 1H); 13C NMR (75 MHz, CDCl3) 135.6, 135.4, 132.4, 130.7,
130.6, 130.5, 130.4, 129.3, 129.2, 129.1, 129.0, 128.8, 123.0, 122.9; 31P{1H} NMR (121
2
2
MHz, CDCl3) 87.13 (d, JPP = 277.63 Hz, 1P), 25.49 (d, JPP = 282.87 Hz, 1P). EM-
FAB+: m/z 748 (52) [M]+·, 382 (100) [M-P(C6H4-4-Cl)3]+, 366 (23) [M- NiphPS2]+.
Elem. Anal. Calcd. for C36H25Cl3P2NiS2: C, 57.75; H, 3.37. Found: C, 57.71; H, 3.35.
[Ni(phPS2){P(C6H4-4-F)3}] (3).
Yield: 292 mg (68 %). M.p. 242 °C. 1H NMR (300 MHz, CDCl3) 7.65 – 7.49 (m, 6H) ,
7.45 – 7.20 (m, 13H), 7.11 – 7.00 (m, 6H); 13C{1H} NMR (75 MHz, CDCl3) 136.6,
136.5, 136.4, 136.3, 132.4, 130.8, 130.6, 130.5 , 129.3, 129.1, 129.0, 123.0, 122.9,
31
2
116.1, 115.9, 115.8, 115.6; P{1H} NMR (121 MHz, CDCl3) 86.83 (d, JPP = 267.16
Hz, 1P), 24.67 (d, 2JPP = 282.87 Hz, 1P). EM-FAB+: m/z 698 (100) [M]+·, 382 (94) [M-
P(C6H4-4-F)3]+, 316 (68) [MNiphPS2]+. Elem. Anal. Calcd. for C36H25F3P2NiS2: C,
61.83; H, 3.60. Found: C, 61.79; H, 3.57.
[Ni(phPS2){P(C6H4-4-Me)3}] (4).
Yield: 308 mg (73 %). M.p. 221 °C. 1H NMR (300 MHz, CDCl3) 7.56 – 7.25 (m, 12H),
7.21 – 7.09 (m, 12H), 7.00 – 7.95 (m, 1H), 2.36 (s, 9H); 13C{1H} NMR (75 MHz,
CDCl3) 140.9, 134.3, 134.1, 132.1, 131.7, 131.4, 131.2, 130.3 (br s), 130.1, 129.4,
129.2, 129.1, 128.9, 122.7, 122.6, 21.5; 31P{1H} NMR (121 MHz, CDCl3) 86.19 (d, 2JPP
2
= 277.63 Hz, 1P), 22.08 (d, JPP = 277.63 Hz, 1P). EM-FAB+: m/z 686 (28) [M]+·, 382
(17) [M-P(C6H4-4-Me)3]+, 304 (37) [M-NiphPS2]+. Elem. Anal. Calcd. for
C39H34P2NiS2: C, 68.14; H, 4.99; Found %: C, 67.78; H, 4.89.
11

[Ni(phPS2){P(C6H4-4-OMe)3}] (5).
1
Yield: 293 mg (65 %). M.p. 218-220 °C. H NMR (300 MHz, CDCl3) 7.54 – 7.32 (m,
22H), 7.21 – 7.11 (m, 1H), 6.92 – 6.89 (m, 2H), 3.80 (s, 9H). 13C{1H} NMR (75 MHz,
CDCl3) 161.4, 135.9, 135.7, 132.1, 131.7, 131.3, 131.2, 130.4, 130.1, 129.1, 128.9,
2
122.7, 122.6, 114.2, 114.0, 55.3. 31P{1H} NMR (121 MHz, CDCl3) 86.00 (d, JPP
=
2
282.87 Hz, 1P), 22.08 (d, JPP = 277.63 Hz, 1P). EM-FAB+: m/z 734 (32) [M]+·, 382
(19) [M-P(C6H4-4-OMe)3]+, 352 (46) [M-NiphPS2]+. Elem. Anal. Calcd. for
C39H34O3P2NiS2: C, 63.69; H, 4.66. Found: C, 63.41; H, 4.61.
[Ni(phPS2){P(C6H4-4-CF3)3}] (6).
1
Yield: 359 mg (69 %). M.p. 230 °C. H NMR (300 MHz, CDCl3) 7.82 – 7.77 (m, 1H),
13
7.70 – 7.50 (m, 11) 7.42 – 7.29 (m, 12), 7.06 – 7.01 (m, 1H); C{1H} NMR (75 MHz,
CDCl3) 134.5, 134.3, 132.6, 130.8, 130.7, 130.6, 130.5, 129.4, 129.2, 129.0, 125.9,
31
2
125.8, 125.7, 125.6, 123.29, 123.2; P{1H} NMR (121 MHz, CDCl3) 86.78 (d, JPP =
403 Hz, 1P), 23.12 (d, 2JPP =403 Hz, 1P). EM-FAB+: m/z 848 (37) [M]+·, 466 (15) [M-
NiphPS2]+, 382 (100) [M-P(C6H4-4-CF3)3]+. Elem. Anal. Calcd. for C39H25F9P2NiS2: C,
55.15; H, 2.97. Found: C, 54.95; H, 2.78.
Alkyl- and Arylthiolation of Iodobenzenes.
Under an atmosphere of nitrogen, a solution of 4.9 mmol of halobenzene, 2.45
mmol of the corresponding alkyl- or aryldisulfide, 0.0045 mmol of the corresponding
catalyst and 202 mg (0.924 mmol) of diethylene glycol di-n-butylether (internal
standard) in 3.0 mL of DMF, was introduced into a Schlenk tube containing a magnetic
stir bar and charged with 4.9 mmol of zinc dust. The tube was sealed and fully
o
immersed in a 150 C silicon oil bath. After 5 h, the reaction mixture was cooled to
12

room temperature and the organic phase analyzed by gas chromatography (GC-MS)
(Quantitative analyses were performed on an Agilent 6890N GC with a 30.0 m DB-
1MS capillary column coupled to an Agilent 5973 Inert Mass Selective detector).
Data collection and refinement for compound [Ni(phPS2)(PPh3)] (1)
The crystals of compound 1 were mounted on a glass fiber at room temperature,
then placed on a Bruker SMART APEX CCD-based X-ray diffractometer system
equipped with a Mo-target X-ray tube (λ = 0.71073Å). The detector was placed at a
distance of 5.0 cm from the crystals, showing a negligible decay. The frames were
integrated with the Bruker SAINT software package using a narrow-frame integration
algorithm. Systematic absences and intensity statistics were used in space group
determination. The structure was solved using direct methods using SHELXS-2014/7
program.39 Absorption correction was applied using SADABS program or face indexed-
numerical method. Anisotropic structure refinements were achieved using full matrix,
least-squares technique on all non-hydrogen atoms. All hydrogen atoms were placed in
idealized positions, based on hybridization, with isotropic thermal parameters fixed at
1.2 times the value of the attached atom. Structure refinements were performed using
SHELXL-2014/7.40
Supplementary information
Supplementary data for compound (1) have been deposited at the Cambridge
Crystallographic Data Centre. Copies of this information are available free of charge on
request from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax:
+44-1223-336033;
e-mail
deposit@ccdc.cam.ac.uk
or
www:
http://www.ccdc.cam.ac.uk) quoting the deposition numbers CCDC 1562756.
13

Acknowledgments
We would like to thank Chem. Eng. Luis Velasco Ibarra, Dr. Francisco Javier
Pérez Flores, Q. Eréndira García Ríos, M.Sc. Lucia del Carmen Márquez Alonso, M.Sc.
Lucero Ríos Ruiz, M.Sc. Alejandra Núñez Pineda (CCIQS), Q. María de la Paz Orta
Pérez and Q. Roció Patiño-Maya for technical assistance. H. V. would like to thank
Programa de Estancias Posdoctorales en México CONACYT-SENER-Hidrocarburos
2015-2016 (Oficio: COIC/CSGC/1244/16) and Programa de Becas Posdoctorales-
DGAPA-UNAM for postdoctoral scholarships (Oficio: CJIC/CTIC/1060/2017). The
financial support of this research by PAPIIT (grant No. IN213214) is gratefully
acknowledged.
14

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18

Highlights
A series new SPS-Ni(II) pincer complexes were synthesized
The SPS-Ni(II) pincer complexes efficiently catalyse C-S couplings of disulfides
and iodobenzene.
The performance of the catalysts strongly depends on the steric demand of the
substituent at the disulphide.
19

Graphical Abstract-Pictogram
SPS-Ni(II) Pincer Compounds of the Type [Ni(phPS2)(P(C6H4-4-R)3)]
Synthesis, Characterization and Catalytic Evaluation in C-S Cross-
Coupling Reactions.
Valente Gómez-Beníteza*, Hugo Valdésb, Simón Hernández-Ortegab, Juan Manuel
German-Acacioc, David Morales-Moralesb*
aFacultad de Ciencias Químicas, Universidad Autónoma de Chihuahua. Circuito
Universitario S/N. Chihuahua, Chihuahua, C. P. 31125. México. bInstituto de Química,
Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria,
Ciudad de México. C. P. 04510, México. cRed de Apoyo a la Investigación, Instituto
Nacional de Ciencias Médicas y Nutrición SZ-Universidad Nacional Autónoma de
México (CIC-UNAM), Ciudad de México. 14000. México.
S
I
R
S
R
[Ni(phPS2)(PPh3)2]
R
S
+
Zn
Y
Y
20

Graphical Abstract-Synopsis
SPS-Ni(II) Pincer Compounds of the Type [Ni(phPS2)(P(C6H4-4-R)3)]
Synthesis, Characterization and Catalytic Evaluation in C-S Cross-
Coupling Reactions.
Valente Gómez-Beníteza*, Hugo Valdésb, Simón Hernández-Ortegab, Juan Manuel
German-Acacioc, David Morales-Moralesb*
aFacultad de Ciencias Químicas, Universidad Autónoma de Chihuahua. Circuito
Universitario S/N. Chihuahua, Chihuahua, C. P. 31125. México. bInstituto de Química,
Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria,
Ciudad de México. C. P. 04510, México. cRed de Apoyo a la Investigación, Instituto
Nacional de Ciencias Médicas y Nutrición SZ-Universidad Nacional Autónoma de
México (CIC-UNAM), Ciudad de México. 14000. México.
Abstract
-
A series of SPS-Ni(II) pincer complexes of the type [Ni(phPS2)(P(C6H4-4-R)3)] (phPS2
2
= (PhP(C6H4-2-S)2)-2; R= H (1), Cl (2), F (3), CH3 (4), OCH3 (5), CF3 (6)) have been
synthesized and fully characterized including the unequivocal determination of the
molecular structure of [Ni(phPS2)(PPh3)] (1) by single crystal X-ray diffraction
techniques. The complexes exhibited high catalytic activity in C-S couplings of both
alky- and aryl-disulfides with iodobenzenes for the production of non-symmetric
sulfides.
21