Synthesis and reactivity of bis(diphenylphosphino)amine ligands and their application in Suzuki cross-coupling reactions

Article abstract of DOI:10.1016/j.ica.2012.01.057

Two new bis(diphenylphosphino)amines, N,N-bis(diphenylphosphino)benzidine 1 and N,N-bis(diphenylphosphino)-3,3-dimethoxybenzidine 2 were prepared by aminolysis. Their corresponding oxides, sulfides and selenides were readily prepared by reaction with hydrogen peroxide, elemental sulfur or grey selenium, respectively. Symmetric dinuclear palladium and platinum complexes were also isolated from the reaction with [M(cod)Cl₂] (M = Pd or Pt, cod = cycloocta-1,5-diene). All compounds were characterized by IR and NMR spectroscopy and elemental analysis and the structure of [(Ph₂P) ₂N-C₆H₄-C₆H₄-N(PPh ₂)₂] was determined by single crystal X-ray diffraction. The catalytic activity of palladium complexes in Suzuki coupling reactions was also investigated.

Full text of DOI:10.1016/j.ica.2012.01.057

Inorganica Chimica Acta 385 (2012) 164–169
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Inorganica Chimica Acta
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Synthesis and reactivity of bis(diphenylphosphino)amine ligands and their
application in Suzuki cross-coupling reactions
a
a
b
Cezmi Kayan a, , Nermin Biricik , Murat Aydemir , Rosario Scopelliti
⇑
a Department of Chemistry, Dicle University, TR-21280 Diyarbakır, Turkey
b Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 July 2011
Received in revised form 20 December 2011
Accepted 26 January 2012
Available online 1 February 2012
Two new bis(diphenylphosphino)amines, N,N-bis(diphenylphosphino)benzidine 1 and N,N-bis(diphenyl-
phosphino)-3,3-dimethoxybenzidine 2 were prepared by aminolysis. Their corresponding oxides, sulfides
and selenides were readily prepared by reaction with hydrogen peroxide, elemental sulfur or grey sele-
nium, respectively. Symmetric dinuclear palladium and platinum complexes were also isolated from the
reaction with [M(cod)Cl2] (M = Pd or Pt, cod = cycloocta-1,5-diene). All compounds were characterized by
IR and NMR spectroscopy and elemental analysis and the structure of [(Ph2P)2N–C6H4–C6H4–N(PPh2)2]
was determined by single crystal X-ray diffraction. The catalytic activity of palladium complexes in
Suzuki coupling reactions was also investigated.
Keywords:
Bis(phosphino)amine
Palladium complex
X-ray structure
Catalysis
Ó 2012 Elsevier B.V. All rights reserved.
Suzuki reaction
1. Introduction
tools for the preparation of unsymmetrical biaryl and stilbene
compounds [9] and represent essential steps in the synthesis of
Synthesis of new aminophosphines to stabilize transition met-
als in low valent states is considered to be a most challenging task
in view of their potential utility in a variety of metal-mediated or-
ganic transformations [1]. To date, a number of such systems with
a variety of backbone frameworks have been synthesized and their
transition metal chemistry has been explored [2]. Potentially this
ligand family is attractive since their various structural modifica-
tions are accessible via simple P–N bond formation. The effect of
ligand type on structure and reactivity of transition metal com-
plexes is an important topic of research in coordination and orga-
nometallic chemistry [3]. Ligands containing direct phosphorus–
nitrogen bonds are quite attractive as structural modifications
can be introduced via simple P–N bond formation [4] and they
have proved to be versatile ligands, and varying the substituents
on both to P- and N-centers gives rise the changes in the P–N–P an-
gle and to conformation around the P-centers [5]. Small variations
in the ligands can cause significant changes in their coordination
behavior and the structural features of the resulting complexes [6].
Because of their remarkable catalytic potential and their large
versatility, palladium complexes have become the most popular
organometallics used in organic synthesis [7]. In particular, palla-
dium catalyzes most of the carbon–carbon bond formation reac-
tions, such as Heck and Suzuki reactions, [8] which are powerful
many compounds including herbicides [10] and natural products
[11].
In our previous studies, we have shown that many bis(amino-
phosphine) palladium(II) complexes can be used in Heck and
Suzuki cross-coupling reactions. In the continuation of our interest
in new ligand systems with different spacers to control the
electronic attributes at phosphorus centers and to explore their
coordination chemistry, herein we describe the synthesis and
characterization of two new bis(phosphine)amine ligands and
their reactivity towards chalcogens and with transition metal com-
plexes. The application of the Pd(II) complexes as pre-catalysts in
Suzuki cross-coupling reactions is also described.
2. Experimental
All manipulations were performed under an inert atmosphere
of dry argon. Solvents were dried using the appropriate reagents
and distilled prior to use. The starting materials [M(cod)Cl2]
(M = Pd, Pt; cod = cycloocta-1,5-diene) were prepared according
to literature procedures [12,13]. Other starting materials were ob-
tained from commercial sources and were used as received. NMR
spectra were obtained on a Bruker AV400 spectrometer operating
at the appropriate frequencies using SiMe4 (for 1H and 13C) as
internal and 85% H3PO4 (for 31P) as external references. IR spectra
were recorded on a Mattson 1000 ATI UNICAM FT-IR spectrometer
in the range 4000À400 cmÀ1 in KBr matrices. Elemental analyses
⇑
Corresponding author. Tel.: +90 412 248 8550; fax: +90 412 248 8300.
E-mail address: cezmik@dicle.edu.tr (C. Kayan).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2012.01.057

C. Kayan et al. / Inorganica Chimica Acta 385 (2012) 164–169
165
were carried out using a Fisons EA 1108 CHNS-O instrument. GC
analyses were performed on a HP 6890 N gas chromatograph
equipped with capillary column (5% biphenyl, 95% dimethylsilox-
2.4. Synthesis of (Ph2P(O))2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–
N(P(O)Ph2)2 2a
ane) (30 m  0.32 mm  0.25
l
m). Melting points were deter-
Aqueous hydrogen peroxide (30%, w/w, 0.0462 g, 0.408 mmol)
was added dropwise to a suspension of 2 (0.100 g, 0.102 mmol) in
thf (20 ml) and the mixture was stirred for 2 h at room tempera-
ture. The volume of solvent was reduced under vacuum to ca.
1–2 mL and n-hexane (15 mL) was added to give 2a as a light
grey solid which was collected by suction filtration and dried in
vacuum. Yield: 0.0833 g (78.2%), mp: 233–235 °C. 1H NMR (ppm,
CDCl3): d {7.14-7.56 (m, 30H), 7.75–7.91 (m, 16H)} (Ar), 3.50 (s,
6H, OCH3). 31P-{1H} NMR (ppm, CDCl3): d 29.6 (s). Selected IR
mined in capillary tubes with a Gallenkamp MID 350 BM 2.5
apparatus.
2.1. Synthesis of [(Ph2P)2N–C6H4–C6H4–N(PPh2)2] 1
Chlorodiphenylphosphine (2.395 g, 10.86 mmol) was added
dropwise into a solution of benzidine (0.500 g, 2.71 mmol) and tri-
ethylamine (1.23 g, 12.2 mmol) in dichloromethane (25 mL) at
0 °C, the resulting suspension was stirred for 1 h and then the sol-
vent was removed under reduced pressure. The remaining solid
was consecutively washed with distilled water (25 mL) and diethyl
ether (3 Â 10 mL), and dried in vacuum to produce a white solid.
Yield: 2.17 g (86.8%), mp: 210–211 °C 1H NMR (ppm, CDCl3): d
(m
, cmÀ1): 912 (P–N–P), 1221 (P@O), 1439 (P-Ph), 2852 (OMe).
C62H52N2P4O6: Calc. C, 71.26; H 5.02; N, 2.68. Found: C, 70.89;
H, 4.84; N, 2.51%.
2.5. Synthesis of (Ph2P(S))2N–C6H4–C6H4–N(P(S)Ph2)2 1b
3
3
{6.66 (d, 4H, JHH = 7.9 Hz, H-2), 7.07 (d, 4H, JHH = 7.9 Hz, H-3),
7.29À7.38 (m, 40H)} (Ar). 13C-{1H} NMR (ppm, CDCl3): d 145.30
Compound
1 (0.100 g, 0.109 mmol) and elemental sulfur
1
(0.0139 g, 0.434 mmol) were heated to reflux in thf (25 mL) for
5 h. After allowing the mixture to cool to room temperature the
white solid was collected by suction filtration and dried in vacuum.
Yield: 0.0788 g (69.2%), mp: 331–333 °C. 1H NMR (ppm, CDCl3): d
(d, C-1, J31PÀ13C = 17.15 Hz), 130.69 (C-4), 127.30 (C-3), 116.27
1
1
(d, C-2, J31PÀ13C = 12.3 Hz), 140.16 (d, J31PÀ13C = 12.2 Hz, i-carbon
2
atoms of phenyls), 131.33 (d, J31PÀ13C = 7.6 Hz, o-carbon atoms
of phenyls), 131.13 (s, p-carbon atoms of phenyls), 128.56 (t,
3J31PÀ13C = 6.1 Hz, m-carbon atoms of phenyls), assignment was
based on the 1H-13C HETCOR spectrum. 31P-{1H} NMR (ppm,
3
{6.82 (d, 4H, JHH = 8.5 Hz), 7.19–7.29 (m, 24H), 7.58 (d, 4H,
3
3JHH = 8.3 Hz), 8.06–8.11 (q, 16H, JHH = 7.0 Hz)} (Ar) 31P-{1H}
NMR (ppm, CDCl3): d 69.1 (s). Selected IR (m
, cmÀ1): 657 (P = S),
CDCl3): d 68.4 (s). Selected IR (m
, cmÀ1): 901 (P–N–P), 1431 (P-
889 (P–N–P), 1447 (P-Ph). C60H48N2P4S4: Calc. C, 68.69; H, 4.61;
N, 2.67. Found: C, 68.35; H, 4.46; N, 2.52%.
Ph). C60H48N2P4: Calc.: C, 78.25; H, 5.25; N, 3.04. Found: C, 77.87;
H, 5.11; N, 2.83%.
2.6. Synthesis of (Ph2P(S))2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–
N(P(S)Ph2)2 2b
2.2. Synthesis of (Ph2P)2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–N(PPh2)2
2
Compound
2 (0.100 g, 0.102 mmol) and elemental sulfur
Chlorodiphenylphosphine (1.806 g, 8.19 mmol) was added
(0.0131 g, 0.409 mmol) were heated to reflux in thf (25 mL) for
5 h. After allowing the mixture to cool to room temperature, the
white solid was collected by suction filtration and dried in vacuum.
Yield: 0.0791 g (69.9%), mp: 281À283 °C. 1H NMR (ppm, CDCl3): d
{7.10–7.23 (m, 14H), 7.36–7.49 (16H), 7.87–8.29 (m, 16H)} (Ar),
3.37 (s, 6H, OCH3). 31P-{1H} NMR (ppm, CDCl3): d 69.1 (s). Selected
dropwise, to
a solution of 3,3-dimethoxybenzidine (0.500 g,
2.05 mmol) and triethylamine (0.900 g, 8.89 mmol) in dichloro-
methane (15 mL) at 0 °C, with vigorous stirring. The mixture was
stirred at 0 °C for 1 h, and then the solvent was removed under re-
duced pressure. Thf (10 mL) was added to form a white precipitate
(triethylammmonium chloride) that was removed by filtration un-
der argon and the solvent was then removed under vacuum. The
brown solid was dried in vacuum. Yield: 1.43 g (71.3%), mp: 195–
197 °C. 1H NMR (ppm, CDCl3): d {6.91–7.99 (m, 46H, Ar), 3.48 (s,
6H, OCH3). 13C-{1H} NMR (ppm, CDCl3): d 148.16 (C-3), 134.50
(C-2), 131.48 (C-6), 128.03 (C-5), 118.38 (C-1), 110.23 (C-4), 54.7
IR (m
, cmÀ1): 650 (P–S), 912 (P–N–P), 1439 (P-Ph), 2838 (OMe).
C62H52N2P4S4: Calc.: C, 67.13; H, 4.73; N, 2.53. Found: C, 66.78;
H, 4.52; N, 2.33%.
2.7. Synthesis of (Ph2P(Se))2N–C6H4–C6H4–N(P(Se)Ph2)2 1c
1
(OCH3), 138.93 (d, J31PÀ13C = 21.5 Hz, i-carbon atoms of phenyls),
Compound
1 (0.100 g, 0.109 mmol) and grey selenium
2
131.92 (d, J31PÀ13C = 24.5 Hz, o-carbon atoms of phenyls), 130.57
(0.0343 g, 0.434 mmol) were heated to reflux in thf (25 mL) for
5 h. After allowing the mixture to cool to room temperature the
white solid was collected by suction filtration and dried in vacuum.
Yield: 0.0831 g (61.9%), mp: 271–273 °C. 1H NMR (ppm, CDCl3): d
(s, p-carbon atoms of phenyls), 128.84 (d, 3J31PÀ13C = 7.0 Hz, m-car-
bon atoms of phenyls), assignment was based on the 1H–13C HET-
COR spectrum. 31P-{1H} NMR (ppm, CDCl3): d 68.8 (s). Selected IR
(m
, cmÀ1): 893 (P–N–P), 1439 (P-Ph), 2853 (OMe). C62H52N2P4O2:
3
{6.82 (d, 4H, JHH = 8.3 Hz), 7.21–7.30 (m, 24H), 7.59 (d, 4H,
3JHH = 7.6 Hz), 8.12–8.18 (q, 16H, JHH = 7.4 Hz)} (Ar) 31P-{1H}
Calc.: C, 75.91; H, 5.34; N, 2.86. Found: C, 75.63; H, 5.12; N, 2.86%.
3
NMR (ppm, CDCl3): d 69.7 (s). Selected IR (m
, cmÀ1): 565 (P@Se),
2.3. Synthesis of (Ph2P(O))2N–C6H4–C6H4–N(P(O)Ph2)2 1a
889 (P–N–P), 1439 (P-Ph). C60H48N2P4Se4: Calc.: C, 58.27; H, 3.91;
N, 2.27. Found: C, 57.91; H, 3.68; N, 2.12%.
Aqueous hydrogen peroxide (30%, w/w, 0.0492 g, 0.434 mmol)
was added dropwise to a suspension of 1 (0.100 g, 0.109 mmol)
in thf (20 mL) and the mixture was stirred for 2 h at room temper-
ature. The volume of the solvent was reduced under vacuum to ca.
1–2 mL and n-hexane (25 mL) was added to afford 1a as a white
solid which was collected by suction filtration and dried in vacuum.
Yield: 0.214 g (88.1%), mp: 275–277 °C. 1H NMR (ppm, CDCl3): d
2.8. Synthesis of (Ph2P(Se))2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–
N(P(Se)Ph2)2 2c
Compound
2 (0.100 g, 0.102 mmol) and grey selenium
(0.0322 g, 0.408 mmol) were heated to reflux in thf (25 mL) for
5 h. After allowing the mixture to cool to room temperature the
white solid was collected by suction filtration and dried in vacuum.
Yield: 0.0977 g (73.9%), mp: 343–345 °C. 1H NMR (ppm, CDCl3): d
{7.11–7.50 (m, 16H), 7.92–8.37 (m, 30H)] (Ar), 3.36 (s, 6H, OCH3).
3
{6.91 (d, 4H, JHH = 8.5 Hz), 7.18–7.37 (m, 28H), 7.81–7.86 (m,
16H)} (Ar). 31P-{1H} NMR (ppm, CDCl3): d 24.5 (s). Selected IR (
m,
cmÀ1): 908 (P–N–P), 1216 (P@O), 1447 (P-Ph). C60H48N2P4O4: Calc.:
C, 73.17; H, 4.91; N, 2.84. Found: C, 72.79; H, 4.73; N, 2.66%.
31P-{1H} NMR (ppm, CDCl3): d 67.6 (s). Selected IR ( , cmÀ1): 554
m

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C. Kayan et al. / Inorganica Chimica Acta 385 (2012) 164–169
Table 1
(P@Se), 901 (P–N–P), 1439 (P-Ph), 2838 (OMe). C62H52N2P4Se4:
Crystal data and details of the structure determination for 1.
Calc.: C, 57.42; H, 4.04; N, 2.16. Found: C, 57.09; H, 3.86; N, 2.01%.
1
2.9. Synthesis of [PdCl2{(Ph2P)2N–C6H4–C6H4–N(PPh2)2PdCl2}] 1d
Chemical formula
Formula weight
Crystal system
Space group
a (Å)
C
72H60N2P4
1077.10
monoclinic
P21/c
8.7561(9)
16.4593(16)
19.728(2)
90
100.113(11)
90
2799.0(5)
4
1.278
1132
0.182
140(2)
0.71073
22586
5685
[Pd(cod)Cl2] (0.0619 g, 0.217 mmol) and
1
(0.100 g,
0.109 mmol) were dissolved in thf (25 mL) and stirred for 1 h at
room temperature. The volume of the solvent was reduced to ca.
1–2 mL by evaporation under reduced pressure and diethyl ether
(15 mL) was added to afford 1d as a light yellow solid which was
collected by suction filtration and dried in vacuum. Yield: 0.107 g
(77.3%), mp: >300 °C (dec.). 1H NMR (ppm, CDCl3): d {6.53 (d, 4H,
3JHH = 8.5 Hz), 7.27–7.38 (m, 14H), 7.64–7.87 (m, 30H)} (Ar). 31P-
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
{1H} NMR (ppm, CDCl3): d 34.9 (s). Selected IR ( , cmÀ1): 893 (P–
m
N–P), 1440 (P-Ph). C60H48N2P4Pd2Cl4: Calc. C, 56.50; H, 3.79; N,
2.20. Found: C, 56.13; H, 3.61; N, 2.04%.
Dcalc (g cmÀ3
F(000)
)
l
(mmÀ1
)
T (K)
k (Å)
2.10. Synthesis of [PdCl2{(Ph2P)2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–
N(PPh2)2}PdCl2] 2d
Measured reflections
Unique reflections
Unique reflections
2949
[I > 2
r(I)]
[Pd(cod)Cl2] (0.0581 g, 0.204 mmol) and
2
(0.100 g,
Data/parameters
5685/352
0.0606
0.1310
0.906
0.102 mmol) were dissolved in thf (15 mL) and stirred for 1 h at
room temperature. The volume of the solvent was reduced to ca.
1–2 mL by evaporation under reduced pressure and diethyl ether
(15 mL) was added to afford 2d as a yellow solid which was col-
lected by suction filtration and dried in vacuum. Yield: 0.0893 g
(65.6%), mp: 262À264 °C. 1H NMR (ppm, CDCl3): d 6.90À7.82 (m,
46H, Ar); 3.87 (s, 6H, OCH3). 31P-{1H} NMR (ppm, CDCl3): d 41.4
Ra [I > 2
r(I)]
wR2a (all data)
Goodness-of-fit (GOF)b
P
P
P
|F0|, wR2 = { [w(F0 À Fc2)2]/ [w(F02)2]}1/2
.
a
2
R = ||F0| À |Fc||/
R
b
2
GOF = {
R
[w(Fo À Fc2)2]/(n À p)}1/2 where n is the number of data and p is the
number of parameters refined.
(s). Selected IR (
62H52N2P4O2Pd2Cl4: Calc.: C, 55.76; H, 3.92; N, 2.10. Found: C,
m
, cmÀ1): 892 (P–N–P), 1438 (P-Ph), 2857 (OMe).
and the mixture was heated to 80 °C for 1.5 h. The progress of the
reaction was monitored by GC. Upon completion, the mixture was
cooled, the product extracted with ethyl acetate/hexane (1:5), fil-
tered through silica gel with copious washing, concentrated and
purified by flash chromatography on silica gel. The purity of the
compounds was determined by NMR and GC, and yields are based
on arylbromide.
C
55.49; H, 3.75; N, 1.96%.
2.11. Synthesis of [PtCl2{(Ph2P)2N–C6H4–C6H4–N(PPh2)2}PtCl2] 1e
[Pt(cod)Cl2] (0.0812 g, 0.217 mmol) and 1 (0.100 g, 0.109 mmol)
were dissolved in dry thf (25 mL) and stirred for 1 h. The volume of
the solvent was reduced to ca. 1–2 mL by evaporation under re-
duced pressure and diethyl ether (15 mL) was added to afford 1e
as a white solid which was collected by suction filtration and dried
in vacuum. Yield: 0.114 g (72.2%), mp: >300 °C (dec.). 1H NMR
2.14. X-ray diffraction structure analysis
Single crystals of 1 suitable for X-ray diffraction analysis were
obtained by recrystallization in benzene. The solid state structure
of this compound was established by single crystal X-ray
diffraction and the details of the structure determination are given
in Table 1.
3
(ppm, CDCl3): d {6.53 (d, 4H, JHH = 8.5 Hz), 7.27–7.38 (m, 14H),
7.64–7.87 (m, 30H)} (Ar). 31P-{1H} NMR (ppm, CDCl3): d 20.5 (s,
1JPt–P: 3421.0 Hz). Selected IR ( , cmÀ1): 906 (P–N–P), 1439 (P-
m
Ph). C60H48N2P4Pt2Cl4: Calc.: C, 49.60; H, 3.33; N, 1.93. Found: C,
49.24; H, 3.17; N, 1.75%.
Data collection was performed at low temperature using Mo K
a
radiation. An Oxford Diffraction Sapphire/KM4 CCD, having a kap-
pa geometry goniometer, was employed to measure the diffraction
data of 1. Data reduction was carried out by means of Crysalis PRO
[14] and then corrected for absorption [15]. Solution and refine-
ment were calculated by SHELX [16]. Structure was refined using
full-matrix least-squares on F2 with all non hydrogen atoms aniso-
tropically defined. Hydrogen atoms were placed in calculated posi-
2.12. Synthesis of [PtCl2{(Ph2P)2N–C6H3–(o-OCH3)–C6H3–(o-OCH3)–
N(PPh2)2}PtCl2] 2e
[Pd(cod)Cl2] (0.0762 g, 0.204 mmol) and
2
(0.100 g,
0.102 mmol) were dissolved in thf (15 mL) and stirred for 1 h at
room temperature. The volume of the solvent was reduced to ca.
1–2 mL by evaporation under reduced pressure and diethyl ether
(15 mL) was added to afford 2e as a white solid which was col-
lected by suction filtration and dried in vacuum. Yield: 0.118 g
(76.5%), mp: 195–198 °C. 1H NMR (ppm, CDCl3): d 7.13–7.90 (m,
tions and then refined as isotropic with free coordinates and Uiso
.
3. Results and discussion
46H, Ar), 3.91 (s, 6H, OCH3). 31P-{1H} NMR (ppm, CDCl3): d 19.5
The bis(phosphino)amine ligands N,N-bis(diphenylphos-
1
(s, JPt–P: 3110.2 Hz). Selected IR (
m
, cmÀ1): 925 (P–N–P), 1438
phino)benzidine
thoxybenzidine
1
2
and N,N-bis(diphenylphosphino)-3,3-dime-
were prepared via aminolysis between
(P-Ph), 2852 (OMe). C62H52N2P4O2Pt2Cl4: Calc.: C, 49.22; H, 3.46;
N, 1.85. Found: C, 48.85; H, 3.31; N, 1.72%.
benzidine or 3,3-dimethoxybenzidine with two equivalents of
Ph2PCl in the presence of Et3N (Scheme 1) [17]]. The reactions were
monitored by 31P-{1H} NMR spectroscopy which indicated that the
reactions had reached completion within 1 h. Compound 1 is an
air-stable solid and therefore the Et3NHCl by-product could be re-
moved easily by washing with distilled water, whereas 2 is unsta-
ble and was purified by extraction into dry thf.
2.13. General procedure for the Suzuki coupling reaction
The palladium complexes (1d or 2d) (0.01 mmol, 1%), arylbro-
mide (1.0 mmol), phenylboronic acid (1.5 mmol), Cs2CO3
(2.0 mmol) and 1,4-dioxane (3 mL) were placed into a Schlenk tube

C. Kayan et al. / Inorganica Chimica Acta 385 (2012) 164–169
167
Scheme 1. Synthesis of 1 and 2 and their chalcogen (O, S and Se) derivatives.
Fig. 1. ORTEP plot of 1 showing the labeling scheme (solvent is omitted for clarity). Main bond lengths [Å] and angles [°]: P1–N1 = 1.738(3); P2–N1 = 1.725(3); N1–
C13 = 1.439(4); C16–C16A = 1.489(6); C13–N1–P2 = 122.9(2); C13–N1–P1 = 122.7(2); P2–N1–P1 = 114.0(1). Letter A indicates the following symmetry transformation: Àx,
Ày, Àz.
The31P-{1H}NMRspectraof1and2containsingletsatd(P)68.4 ppm
andd(P)68.8,respectively,similartothosefoundforcloselyrelatedsys-
tems[18–21].Solutionsof1and2inCDCl3,preparedunderanaerobic
conditions, are unstable and decompose slowly to give the

168
C. Kayan et al. / Inorganica Chimica Acta 385 (2012) 164–169
Table 2
The Suzuki coupling reactions of aryl bromides with phenylboronic acid.
1d and 2d (1 %)
R
B(OH)2
Br
R
Cs2CO3 (2 equiv.)
Entry
1
R
Cat
Product
Conv. (%)
Yield (%)
TOF (%)
4-CH3C(O)-
1d
2d
99
95
98
93
67
62
C(O)CH3
C(O)H
H
2
3
4
5
4-CH(O)-
1d
2d
95
97
90
96
60
64
4-H
1d
2d
88
81
87
78
58
52
4-CH3O-
4-CH3-
1d
2d
64
65
61
63
41
42
OCH3
CH3
1d
2d
74
75
71
73
47
49
Conditions: 1.0 mmol of p-R-C6H4Br aryl bromide, 1.5 mmol of phenylboronic acid, 2.0 mmol Cs2CO3, 0.01 mmol (1%) catalyst, dioxane (3.0 mL). Purity of compounds was
assessed by NMR and yields are based on the arylbromide. All reactions were monitored by GC; 80 °C, 1.5 h. TOF = (mol product/mol cat) Â hÀ1. The GC-yield was obtained
using diethyleneglycol-di-n-butylether as an internal standard.
correspondingoxideand[P(O)Ph2PPh2],thelatterindicatedbysignals
atd34.60(d)ppmanddÀ24.30(d)ppm,(1J(P–P) = 226 Hz).The1HNMR
spectraof1and2exhibitnoNHresonanceinaccordwithcompleteN–H
substitution. Characteristic J(31P–13C) coupling constants of the car-
bons of the phenyls rings are observed in the 13C NMR spectra, which
are consistent with the literature values for related compounds
[5,22]].Otherpertinentspectroscopicandanalyticaldataareprovided
intheSection2.
Single crystals of 1 were obtained by slow evaporation from
benzene at room temperature. The solid state structure of 1 is
shown in Fig. 1 and its geometric parameters are given in the cap-
tion, and general crystallographic data are shown in Table 2. Com-
pound 1 crystallizes in space group P21/c with four molecules in
the unit cell, the molecule itself shows a perfect Ci symmetry, hav-
ing a center of inversion at the midpoint of the C–C single bond of
the biphenyl moiety. The nitrogen atom shows a planar geometry
[sum of angles = 359.6(2)°] with a P–N–P angle of 114.0(1)° due to
the steric hindrance of the PPh2 groups. The C–N distance
[1.439(4) Å] is slightly smaller than those found for PhN(PPh2)2
[23], presumably due to the electronic effect of the biphenyl moi-
ety. The biphenyl moiety is tilted by 98.3° compared to the plane
made by P1, N1 and P2. This almost perpendicular orientation re-
duces the very high steric congestion within the molecule.
Reaction of 1 and 2 with aqueous H2O2, elemental sulfur or sele-
nium powder in thf affords the corresponding oxides (1a and 2a),
sulfides (1b and 2b) and selenides (1c and 2c), which were charac-
terized by analytical and spectroscopic methods. The 31P NMR
spectra of the oxides contain singlet resonances at 24.5 and
29.6 ppm for 1a and 2a, respectively. Similarly, singlet resonances
are observed for 1b and 2b at 69.1 ppm and for 1c and 2c at 69.7
and 67.6 ppm, respectively. The 31P NMR resonances of these
chalcogenes are within the anticipated ranges [3,19,22a] and in
the case of the selenides 1JP–Se satellites of ca. 800 Hz are observed
that are characteristic of phosphine selenide systems.
Bis(phoshino)amines tend to react spontaneous with H2O2 at
room temperature, whereas reaction with elemental sulfur or
Scheme 2. Reaction of [M(cod)Cl2] (M = Pd or Pt; cod = cycloocta-1,5-diene) with 1 and 2 to give the corresponding metal complexes.

C. Kayan et al. / Inorganica Chimica Acta 385 (2012) 164–169
(b) P.W.N.M. Van Leeuwen, Organometallics 16 (1997) 3027;
169
selenium require elevated temperatures, especially for phosphorus
compounds with bulky phenyl-substituent groups [24]. The
selenium compounds decompose, to deposit elemental selenium,
upon exposure to air [22a], and therefore must be handled under
an inert atmosphere.
(d) H. Bricout, J.F. Carpentier, A. Mortreuz, Tetrahedron Lett. 37 (1996) 6105;
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Reaction of 1 and 2 with [M(cod)Cl2] (M = Pd or Pt; cod = cyclo-
octa-1,5-diene) in CH2Cl2 affords the palladium complexes (1d and
2d) and the platinum complexes (1e and 2e) in good yield (Scheme
2). The 31P{1H} NMR spectra of the complexes contain singlet res-
onances at 34.9 and 41.4 ppm for 1d and 2d and at 19.5 and
20.5 ppm for 1e and 2e, respectively. The spectra of the platinum
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1
complexes also exhibit JP–Pt couplings of 3200–3400 Hz, consis-
tent with the expected cis-geometry [25]]. The 31P NMR chemical
shifts of the complexes are in keeping with structurally related
compounds [3,19,20].
_
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The palladium complexes 1d and 2d were evaluated as pre-
catalysts in the Suzuki reaction of selected aryl bromides with
phenylboronic acid initially under similar conditions to those
reported elsewhere [26]. Following optimization of the reaction,
a catalyst loading of 0.01 mmol was employed together with
Cs2CO3 as the base in dioxane at 80 °C. Control experiments
showed that in the absence of the catalyst no reaction took place.
In the presence of 0.01 mmol of 1d or 2d, however, p-bromoaceto-
phenone, p-bromobenzaldehyde, p-bromobenzene, p-bromotolu-
ene and p-bromoanisole react cleanly with phenylboronic acid to
give appropriate the cross-coupling products in high yield (Table
2). As expected, the yields of the coupling product in reactions of
aryl bromides with electron-withdrawing substituents are higher
than those with an electron-releasing substituent. It is worth not-
ing that ligand 2 is unstable (see above), but once coordinated to
the palladium(II) center, appears to be stable and robust.
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5. Conclusions
In conclusion, two new bis(diphenylphosphino)amines and their
oxides, sulfides and selenides have been prepared. In addition, the
coordination behaviour of ligands 1 and 2 towards palladium(II)
and platinum(II) were described. We also demonstrated the appli-
cation of palladium complexes of these bis(phosphino)amine li-
gands as pre-catalyst in the Suzuki coupling and Heck reactions of
aryl halides. Because of the strength of the Pt–C bonds, Pt(II)-
bis(phosphino)amine 1e and 2e system exhibited no catalytic activ-
ity. Only the palladium complexes were found to show catalytic
activity in both the Suzuki coupling reactions of aryl bromides. In
both cases, the catalytic activities of complexes 1d and 2d were
found to be higher in reactions of aryl bromides with electron-with-
drawing substituent than those with electron-releasing substitu-
ent. The procedure is quite simple and efficient towards various
aryl bromides and does not require an induction period.
(b) F. Durap, N. Biricik, B. Gumgum, S. Özkar, W.H. Ang, Z. Fei, R. Scopelliti,
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Polyhedron 26 (2007) 3373.
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Acknowledgement
(b) A.M.Z. Slawin, J.D. Woollins, Q. Zhang, J. Chem. Soc., Dalton Trans. (2001)
621.
Financial support from Dicle University Research Fund (Project
number: DUBAP-06-FF-07) is gratefully acknowledged.
_
[26] I. Özdemir, S. Yasßar, S. Demir, B. Çetinkaya, Heteroatom Chem. 16 (7) (2005)
557.
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