Novel phosphine ligands bearing 3(5)-pyrazolyl and 4-(2-amino)pyrimidinyl groups: Synthesis and coordination chemistry

Article abstract of DOI:10.1016/j.jorganchem.2005.08.032

Novel triphenyl phosphine ligands bearing pyrazole or 2-aminopyrimidine groups in the ortho or meta position of one or three of the phenyl rings were obtained starting from the corresponding acyl derivatives Ph₂P(o- C₆H₄-C

Full text of DOI:10.1016/j.jorganchem.2005.08.032

Journal of Organometallic Chemistry 691 (2006) 291–298
www.elsevier.com/locate/jorganchem
Novel phosphine ligands bearing 3(5)-pyrazolyl and
4-(2-amino)pyrimidinyl groups: Synthesis and coordination chemistry
a
b
b
c
a,
*
Yu Sun , Antje Hienzsch , Jens Grasser , Eberhardt Herdtweck , Werner R. Thiel
a
FB Chemie, Technische Universita¨t Kaiserslautern, Erwin-Schro¨dinger-Strasse, Geb. 54, 67663 Kaiserslautern, Germany
b
Institut fu¨r Chemie, Technische Universita¨t Chemnitz, Straße der Nationen 62, 09111 Chemnitz, Germany
Fakulta¨t fu¨r Chemie, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4, 85747 Garching b. Mu¨nchen, Germany
c
Received 2 June 2005; received in revised form 4 August 2005; accepted 12 August 2005
Available online 20 October 2005
Abstract
Novel triphenyl phosphine ligands bearing pyrazole or 2-aminopyrimidine groups in the ortho or meta position of one or three of the
phenyl rings were obtained starting from the corresponding acyl derivatives Ph2P(o-C6H4-COCH3), Ph2P(m-C6H4-COCH3), or P(m-
C6H4-COCH3)3. Conversion of the acyl groups into 3-dimethylamino-2-propen-1-onyl units was achieved by reaction with HC(O-
Me)2NMe2 which underwent ring closing with hydrazine or guanidine to yield the desired heterocycles. Two palladium complexes were
synthesized using the coordinatively labile precursor (PhCN)2PdCl2, one of them could be characterized by X-ray structure analysis.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Phosphine ligands; Pyrazoles; Pyrimidines; Palladium
1. Introduction
quantified by modern analytical methods such as NMR
or X-ray). Recently, we have reported some phosphine li-
gands bearing additional donor sites in the backbone for
the binding of Lewis acids. It has been proved that this
binding of Lewis acids to phosphine ligands is not only
detectable in terms of spectroscopy features but also rele-
vant for catalysis [1].
In the present paper, we describe a facile and efficient ac-
cess to yet unknown phosphine ligands bearing 3(5)-pyraz-
olyl- or 4-(2-amino)pyrimidinyl groups [2] and derived
complexes with palladium. These ligands may be of poten-
tial interest for catalytic reactions. For example, the mono
functionalized derivatives are structurally closely related to
diphenyl(2-(2-pyridyl)phenyl) phosphine, which has been
used as ligand in different catalytic transformations [3].
Additionally, multiple functionalization of PPh3 with pyr-
azole or pyrimidine groups, which is as simple as mono
functionalization, opens up a new access to water soluble
ligands, due to the basic (pyrazole, pyrimidine) and protic
(pyrazole) properties of the heterocycles or by further
derivatization. Such ligands may also find application in
aqueous-phase organometallic catalysis [4].
Controlled modifications of already known ligand sys-
tems have greatly changed the face of homogeneous catal-
ysis in the last decades. The modifications not only resulted
in improved catalytic performances (i.e. higher conversion
and selectivity), but also enlarge the scope of homogeneous
catalysis. For example, more and more metal-based cata-
lytic organic processes could be realized under aqueous
conditions, or contrarily in non-polar organic solvents,
both of which were not generally considered as suitable
reaction media until a few years ago.
For some time, our group has been interested in the
reinvestigation of phosphine ligands. Our strategy is to
implement new functionalities in this known ligand system,
which may allow to realize some of the principles of metal-
lo-proteins in homogeneous catalysis (i.e. some weak chem-
ical interactions, which are still difficult to be completely
*
Corresponding author. Tel.: +49 631 2052752; fax: +49 631 2054676.
E-mail address: thiel@chemie.uni-kl.de (W.R. Thiel).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.08.032

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Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
2. Results and discussion
product, a yellow oil, was not purified but used directly
for the following C–C coupling reaction.
Pyrazoles or pyrimidines can be obtained by ring closing
condensation of b-diketones with either hydrazine or pre-
cursor compounds bearing a NH@C(R)–NH2 unit. Only
a few arylphosphines with b-diketone side chains have been
described up to now, probably due to synthetic difficulties
[5]. We have been working on the synthesis of arylpyrazoles
and developed a different access to such compounds a few
years ago. Here, 1-aryl-3-dimethylamino-2-propen-1-ones
are used as ‘‘masked’’ aromatic b-ketones, showing an
analogous reactivity in ring closing reactions with hydra-
zine [6]. These compounds can easily be prepared by the
condensation of aromatic acyl derivatives with N,N-
dimethylformamide dimethyl acetale. For the application
of this route in phosphine chemistry, an acetyl group at-
tached to at least one of the phenyl rings of PPh3 is re-
quired. Such compounds have already been reported
several times in the literature [7].
Heating a 1:2 mixture of the acetyl phosphines 3a,b and
N,N-dimethylformamide dimethyl acetale for 2 h yielded
almost quantitatively the corresponding meta and ortho
substituted 1-aryl-3-dimethylamino-2-propen-1-ones 4a,b
(Scheme 2). Reacting 3c under the same conditions with
6 equivalents of the acetale, led to the trisubstituted deriv-
ative 4c in 60% yield.
Compounds 4a–c are intensively orange–yellow to
orange–red colored, a characteristic feature for these
donor/acceptor substituted olefins [6] The structure of the
a, b-unsaturated ketones can clearly be assigned by means
of NMR spectroscopy (1H NMR: two doublets at ꢁ7.7
3
and ꢁ5.5 ppm with JHH coupling constants of ꢁ12 Hz
for @CHN(CH3)2 and COCH@; 13C NMR: d ꢁ 190 ppm
for C@O, and ꢁ155 and ꢁ95 ppm for @CHN(CH3)2 and
COCH@). Compared to the corresponding acetyl phos-
phines 3a–c, the 31P NMR resonances of 4a–c are slightly
shifted to higher field (d = ꢀ6.36, ꢀ8.76 and ꢀ3.89 ppm
for 4a–c).
(3-Acetylphenyl)diphenyl phosphine (3a) and (2-acetyl-
phenyl)diphenyl phosphine (3b) were obtained in good
yields by a modified published procedure [7b] starting
from (3-bromophenyl)methyl ketone and (2-bromophenyl)-
methyl ketone, respectively (Scheme 1). 3a is a highly
viscous colorless oil exhibiting a 31P NMR resonance at
ꢀ3.84 ppm, while 3b is a lemon yellow solid with a 31P
NMR resonance at ꢀ1.49 ppm.
The color of 3b is not due to impurities, since the com-
pound can be recrystallized without changing its yellow
color. Schiemenz et al. [7b] already reported this color
and the intense deep orange color of the difunctionalized
derivative PhP(o-C6H4-COCH3)2 but gave no explanation
for it. We are at the moment investigating this phenome-
non by means of spectroscopy and quantum chemical
calculations.
Tri(3-acetylphenyl) phosphine (3c), the trisubstituted
analogue of 3a, was synthesized following the same strat-
egy as for 3a,b (Scheme 1), except the fact that after the for-
mation of the Grignard reagent, phosphorus trichloride
was used instead of chlorodiphenyl phosphine. The crude
Scheme 2. (i) HC(OMe)2(NMe2), reflux.
Scheme 1. (i) Ts-OH, HOCH2CH2OH, toluene, reflux; (ii) Mg, thf, ClPPh2; (iii) H2O/thf, Ts-OH, reflux; (iv) Mg, thf, PCl3.

Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
293
3
The ring closure of 4a–c with excess of hydrazine mono-
hydrate was carried out under reflux conditions in EtOH
solution. After removal of the solvent and recrystallization,
the pyrazoles 5a–c were obtained as colorless to light yel-
low solids in yields of 64–94% (Scheme 3). 13C NMR spec-
tra show characteristic chemical shifts at ꢁ150, ꢁ140–135
and ꢁ105 ppm for the carbon atoms C-3pz, C-5pz and
C-4pz. The pyrazolyl rings also exhibit characteristic reso-
at 6.65 ppm with a coupling constant JHH of 2.2 Hz,
which is clearly separated from the aromatic resonances
and typical for 4pz-H of 3-aryl substituted pyrazoles.
Reaction of 4a with an excess of guanidinium carbonate
in EtOH/aqueous KOH at reflux temperature for several
hours, resulted in the formation of a 4-(2-amino)pyrimidi-
nyl ring in the meta position of one of the phenyl rings of
1
the PPh3 unit (Scheme 3). In H NMR spectrum of ligand
1
nances in the H NMR spectra: 5c, e.g. shows a doublet
6a, two doublets at 8.26 and 6.99 ppm with a coupling con-
stant 3JHH of 5.2 Hz originate from the protons at 6pm and
5pm positions. In DMSO-d6, the two protons of the amino
group are found at a chemical shift of 6.68 ppm. The 13C
NMR signals at 164.7, 163.9, 160.1 and 106.7 ppm can
be assigned to the four carbon atoms of the pyrimidine
ring.
The introduction of the 3(5)-pyrazolyl and 4-(2-
amino)pyrimindyl rings only slightly influences the elec-
tronic situation of the phosphorus center. The 31P NMR
resonances of 5a–c and 6a are observed between ꢀ4.44
and ꢀ10.46 ppm, which is almost the same as for com-
pounds 4a–c.
Oxidation at the phosphorous center is performed quan-
titatively by hydrogen peroxide. The phosphine oxide 5a-O
was synthesized exemplary, its solid state structure was
determined by single crystal X-ray structure analysis. 5a-O
crystallizes from ethanol as colorless prisms in the ortho-
rhombic space group P212121 with four molecules in the unit
cell. As expected, hydrogen bonding dominates the solid
state structure: the proton of the N–H function of the pyra-
zole undergoes intermolecular hydrogen bonding to the
˚
phosphine oxide (bond distances [A]: N2–H2 0.89(2),
H2ꢂ ꢂ ꢂO 1.84(2), N2ꢂ ꢂ ꢂO 2.707(2); bond angle [ꢁ]: 164(2)).
Scheme 3. (i) EtOH, N2H4 Æ H2O, reflux; (ii) H2O2, toluene; (iii)
[(NH2)3C]2CO3, EtOH/H2O, KOH, reflux.
This results in the formation of planar zig-zag chains
˚
Fig. 1. PLUTON [9] plot of the solid state structure of 5a-O showing the hydrogen bound chains running parallel to the a-axis. Selected bond lengths [A],
angles [ꢁ] and torsion angles [ꢁ]: P–O 1.494(1), P–C11 1.802(2), P–C21 1.799(2), P–C31 1.801(2), N2–H2 0.89(2), H2ꢂ ꢂ ꢂO 1.84(2), N2ꢂ ꢂ ꢂO 2.707(2); N2–
H2ꢂ ꢂ ꢂO 164(2); C12–C13–C17–N1 16.8(2).

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Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
(Fig. 1) parallel to the a-axis of the unit cell. These chains are
oriented perpendicular to each other, interconnected by
additional (weaker) hydrogen bonds between proton H251
at one of the phenyl rings and the phosphine oxide (bond
low) clearly weakens the N–H bond (5b: 3186, 7b:
3227 cmꢀ1). As expected, the 31P resonances of 7a (25.43)
and 7b (26.96 ppm) are shifted towards lower field com-
pared to the free ligands 5a and 5b.
˚
distances [A]: C25–H251 0.97(2), H251ꢂ ꢂ ꢂO 2.55(2),
Yellow crystals of 7b suitable for X-ray diffraction stud-
ies were obtained from slowly cooling a hot saturated solu-
tion in MeOH (Fig. 2). Fig. 2 shows the structure in the
solid state. 7b crystallizes in the monoclinic space group
P21/n with four molecules in the unit cell, forming dimers
via intermolecular hydrogen bonding between the N–H
proton of one molecule and one of the chloro ligands of a
neighboring complex (N2–H2 0.78(4), H2ꢂ ꢂ ꢂCl2 2.55(4),
N2ꢂ ꢂ ꢂO 3.460(2); bond angle [ꢁ]: 157(2)), leading to a three
dimensional network of hydrogen interactions. The phenyl
rings at the phosphorous center are oriented in the typical
paddle wheel mode. The pyrazole ring is almost coplanar
to the phenyl ring (torsion angle [ꢁ]: 16.8(2)). To our knowl-
edge, this is the first solid state structure showing a hydrogen
bound polymer with a phosphine oxide and a nitrogen con-
taining heterocycle [8].
˚
N2ꢂ ꢂ ꢂCl2 3.219(3) A, N2–H2ꢂ ꢂ ꢂCl2 145(3)ꢁ). Additionally,
Reaction of two equivalents of 5a with (PhCN)2PdCl2
gave complex 7a (Scheme 4). Elemental analysis advised
that in 7a ligand 5a coordinates monodentate via the phos-
phorous atom (comparable to PPh3) to the Pd2+ center.
Due to 31P NMR data, the two phosphine ligands are coor-
dinated in cis-configuration. In contrast to the behavior of
the meta-substituted ligand 5a, its ortho-substituted conge-
ner 5b always reacts in a 1:1 ratio with (PhCN)2PdCl2.
Even with large excesses of 5b only the chelate complex
7b can be isolated (Scheme 4).
an intramolecular hydrogen bond is found (N2–H2
˚
0.78(4), H2ꢂ ꢂ ꢂCl1 2.78(3), N2ꢂ ꢂ ꢂCl1 3.162(3) A, N2–
H2ꢂ ꢂ ꢂCl1 113(3)ꢁ). The dimers are linked by (weak) hydro-
gen bonds between H331 and Cl1 leading to double chains
The different coordination of the ligands 5a and 5b to
1
the PdCl2 moiety is clearly expressed by the H and 31P
NMR data of the resulting complexes 7a and 7b. In the
1H NMR of 7a, the resonance of the N–H proton
(12.97 ppm) is observed at almost the same chemical shift
as in the free ligand 5a (12.92 ppm), while the N–H proton
in 5b (12.94 ppm) is deshielded by the coordination of the
pyrazole ring in 7b (13.23 ppm). The same effect is found
for the proton in the 4-position of the pyrazole ring: 5a,
6.62; 7a, 6.62; 5b, 6.30; 7b, 7.13 ppm. The N–H stretching
frequencies of 5a and 7a are observed at almost the same
energies (3215 and 3218 cmꢀ1), indicating an negligible
influence of the Pd–P coordination on the situation of the
pyrazole ring. However P–Pd–N coordination in 7b and
additional hydrogen bonding (see structure discussion be-
Fig. 2. PLUTON [9] plot of the solid state structure of 7b. Selected bond
lengths [A], angles [ꢁ] and torsion angles [ꢁ]: Pd–Cl1 2.3714(8), Pd–Cl2
˚
2.2897(7), Pd–P 2.2257(8), Pd–N1 2.018(3), N2–H2 0.78(4), H2ꢂ ꢂ ꢂCl2
2.55(4), N2ꢂ ꢂ ꢂCl2 3.219(3), H2ꢂ ꢂ ꢂCl1 2.78(3), N2ꢂ ꢂ ꢂCl1 3.162(3); Cl1–Pd–
Cl2 90.90(3), Cl1–Pd–P 172.28(3), Cl1–Pd–N1 89.49(7), Cl2–Pd–P
95.28(3), Cl2–Pd–N1 176.16(7), P–Pd–N1 84.65(7), N2–H2ꢂ ꢂ ꢂCl2 145(3),
N2–H2ꢂ ꢂ ꢂCl1 113(3); Pd–P–C11–C12 43.1(3), P–C11–C12–C3 0.8(4), N1–
C3–C12–C11 –28.5(5), Pd–N1–C3–C12 –0.5(4), N1–Pd–P–C11 –48.2(1).
Scheme 4.

Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
295
running parallel to the crystallographic c-axis (not shown in
Fig. 2; C33–H331 0.98(5), H331ꢂ ꢂ ꢂCl1 2.81(5), C33ꢂ ꢂ ꢂCl1
red solid in almost quantitative yield. Anal. Calc. for
C23H22NOP: C, 76.86; H, 6.17; N, 3.90. Found: C, 76.30;
H, 6.02; N, 3.79%. IR (KBr, cmꢀ1): 2914m, 1644vs, 1586m,
1574w, 1556m, 1538m, 1477w, 1434s, 1420s, 1353m, 1300w,
1284m, 1264w, 1236m, 1205w, 1118w, 1103w, 1087m,
1066m, 1024w, 995w, 976m, 909m, 766s, 744s, 696vs,
˚
3.579(4) A, C33–H331ꢂ ꢂ ꢂCl1 136(3)ꢁ). Due to the small bite
angle of the chelate system, the phenylene backbone is bent
from the plane defined by Pd, N1 and P. Additionally, this
plane is not coplanar to the plane defined by Pd, Cl1 and
Cl2, probably due to the intermolecular hydrogen bonds.
Only a few palladium complexes with chelating P,N-ligands
wherein the nitrogen donor atom is part of a heterocycle
and Pd, N, and P are included in a six membered ring sys-
tem have been described up to now [10]. However, the
geometry of the coordination site of 7b is generally compa-
rable with the solid state structures of those compounds.
1
650m, 541w, 528m, 509m, 495m, 488m, 430w, 410w. H
NMR (250.1 MHz, 25 ꢁC, CDCl3): d 7.87 (tt, 3JHH = 8.8 Hz,
3
4JHH = 1.9 Hz, 2H, p-H), 7.73 (d, 1H, JHH = 12.3 Hz,
@CHN(CH3)2), 7.42–7.26 (m, 12H, ar-H), 5.56 (d, 1H,
COCH@), 3.07, 2.83 (2 s, 6H, N(CH3)2). 13C{1H} NMR
(62.9 MHz, 25 ꢁC, CDCl3): d 188.6 (C@O), 154.7 (@CHN-
3
1
(CH3)2), 141.0 (d, JPC = 7.2 Hz, C-3), 137.5 (d, JPC
=
1
12.0 Hz, C-1), 137.4 (d, JPC = 10.6 Hz, C-i), 136.4 (d,
2JPC = 16.3 Hz, C-2), 134.2 (d, 2JPC = 19.7 Hz, C-o), 133.4
(d, JPC = 23.0 Hz, C-6), 129.2 (s, C-p), 129.0 (d, JPC
6.7 Hz, C-m), 128.9 (d, JPC = 5.8 Hz, C-5), 128.4 (s, C-4),
92.6 (COCH@), 45.5, 37.6 (N(CH3)2). 31P{1H} NMR
(101.2 MHz, 25 ꢁC, CDCl3): d ꢀ6.36. MS, m/z (%): 359
(88) [M]+.
3. Conclusion
2
3
=
3
A simple and efficient synthesis of novel phosphine li-
gands with 3(5)-pyrazolyl- and 4-(2-amino)pyrimidinyl-side
functions could be presented and their effectiveness in coor-
dination to palladium could be shown. The NH and NH2
functions of the ligands allow to introduce further function-
alities for substrate recognition, chirality transfer as well as
the adoption of the ligands and derived metal complexes to
different reaction media, especially to the aqueous phase.
These investigations are on the way at the moment.
4.2. [2-(3-Dimethylamino-1-oxoprop-2-en-yl)phenyl]di-
phenylphosphine (4b)
Compound 4b was synthesized similarly to 4a as a red–
brown solid in quantitative yield. It crystallizes with half
an equivalent of the solvent. Anal. Calc. for C23H22NOP Æ
(C2H5OH)0.5: C, 75.39; H, 6.54; N, 3.66. Found: C, 76.71;
H, 6.73; N, 3.68%. IR (KBr, cmꢀ1): 3047w, 2905w, 1637vs,
1575vs, 1552s, 1477w, 1430s, 1422s, 1356m, 1292w, 1274m,
1237m, 1200w, 1114w, 1078m, 1034m, 975w, 897m, 813w,
758m, 742m, 694s, 653w, 545w, 505m, 485w. 1H NMR
(400.1 MHz, 25 ꢁC, CDCl3): d 7.66–7.63 (m, 1H, 3-H), 7.38
4. Experimental
General remarks. The synthesis of compounds containing
phosphorus was carried out under an inert gas atmosphere
of argon or nitrogen and with dried solvents. PdCl2(PhCN)2
(Strem 46-0400) was obtained commercially. All other start-
ing materials were obtained from Aldrich and used without
further purification. Elemental analyses were carried out at
the Institute of Chemistry (TU Chemnitz) or the Depart-
ment of Chemistry (TU Kaiserslautern). Infrared spectra
were recorded with a Perkin–Elmer FT-IR 1000 spectrom-
eter. NMR spectra were recorded with a Bruker Avance
400 or 250 spectrometer. The NMR resonances were as-
signed according to Scheme 5.
4
(td, 3JHH = 7.5 Hz, JHH = 1.2 Hz, 1H, 5-H or 4-H), 7.31–
7.27 (m, 12H, ar-H, @CHN(CH3)2), 7.07–7.04 (m, 1H, 6-
H), 5.42 (d, 3JHH = 12.5 Hz, 1H, COCH@), 2.96, 2.71 (2 s,
6H, N(CH3)2). 13C{1H} NMR (100.6 MHz, 25 ꢁC, CDCl3):
d
192.0 (C@O), 155.0 (@CHN(CH3)2), 148.1 (d,
1
2JPC = 27.0 Hz, C-2), 139.3 (d, JPC = 12.1 Hz, C-i), 136.5
2
(d, JPC = 19.5 Hz, C-6), 135.0 (s, C-1), 134.2 (d,
2JPC = 19.8 Hz, C-o), 129.6 (s, C-5), 128.7 (s, C-4), 128.6
3
4.1. [3-(3-Dimethylamino-1-oxoprop-2-en-yl)phenyl]diphe-
nylphosphine (4a)
(d, JPC = 6.7 Hz, C-m), 128.5 (s, C-p), 127.9 (d,
3JPC = 5.4 Hz, C-3), 97.1 (COCH@), 45.2, 37.3 (N(CH3)2).
31P{1H} NMR (162.0 MHz, 25 ꢁC, CDCl3): d ꢀ8.76. MS,
m/z (%): 359 (95) [M]+.
A mixture of 9.9 g (32.6 mmol) of 3a and 7.7 g
(64.7 mmol) of N,N-dimethylformamide dimethyl acetale
was refluxed for 2 h. After evaporation under high vacuum,
the residue was crystallized from EtOH to give an orange–
4.3. Tri[3-(3-dimethylamino-1-oxoprop-2-en-yl)phenyl]
phosphine (4c)
According to the procedure given above for 4a and 4b,
4c was prepared and crystallized from MeOH as a deep or-
ange–yellow microcrystalline solid with one equivalent of
the solvent in 60% yield. Anal. Calc. for C33H36N3O3P Æ
(CH3OH): C, 69.73; H, 6.88; N, 7.17. Found: C, 69.87;
H, 6.77; N, 7.04%. IR (KBr, cmꢀ1): 2909w, 2803w,
1718w, 1642vs, 1587s, 1575s, 1551vs, 1434s, 1420s, 1355s,
1306w, 1285m, 1267m, 1238s, 1204w, 1096m, 1065m,
Scheme 5. Numbering of the phosphines.

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Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
2
979w, 909m, 764m, 726w, 689w, 653w, 587w, 553w, 534w,
(d, JPC = 18.8 Hz, C-2), 134.8 (s, C-1), 134.2 (d,
477w. 1H NMR (400.1 MHz, 25 ꢁC, CDCl3): d 7.91, 7.85 (2
2JPC = 19.9 Hz, C-o), 132.1 (d, JPC = 9.2 Hz, C-6), 130.5
2
3
3
3
d, 6H, JHH = 7.5 Hz, JHH = 8.5 Hz, 4-H, 6-H), 7.79 (d,
(d, JPC = 4.8 Hz, C-5), 129.7 (s, C-4), 129.4 (d,
3
3H, JHH = 12.2 Hz, @CHN(CH3)2), 7.44–7.35 (m, 6H,
3JPC = 6.5 Hz, C-m), 129.4 (s, C-p), 128.5 (s, C-3), 106.5
(C-4pz). 31P{1H} NMR (162.0 MHz, 25 ꢁC, DMSO-d6): d
ꢀ10.46. ESI MS, m/z (%): 345.1184 (10) [M + O + H]+,
329.1217 (100) [M + H]+.
2-H, 5-H), 5.55 (d, 3H, COCH@), 3.12, 2.85 (2 s, 18H,
N(CH3)2). 13C{1H} NMR (100.6 MHz, 25 ꢁC, CDCl3): d
188.2 (C@O), 155.0 (@CHN(CH3)2), 141.0 (d,
1
3JPC = 7.4 Hz, C-3), 137.1 (d, JPC = 12.0 Hz, C-1), 136.4
2
2
(d, JPC = 17.6 Hz, C-6), 133.3 (d, JPC = 23.1 Hz, C-2),
4.6. Tri[3-(3-pyrazolyl)phenyl]phosphine (5c)
3
129.0 (d, JPC = 6.5 Hz, C-5), 128.6 (s, C-4), 92.7
(COCH@), 45.4, 37.8 (N(CH3)2). 31P{1H} NMR
(162.0 MHz, 25 ꢁC, CDCl3): d ꢀ3.89. ESI MS, m/z (%):
570.2133 (18) [M + O + H]+, 527.1793 (100) [M + H]+.
Following the same method as for 5a and 5b, 5c was ob-
tained as a light yellow crystalline solid in the yield of 83%,
which crystallizes with one equiv. of water. Anal. Calc. for
C27H21N6P Æ (H2O): C, 67.78; H, 4.84; N, 17.56. Found: C,
67.83; H, 5.37; N, 17.81%. IR (KBr, cmꢀ1): 3170s, 3055w,
2966m, 2921m, 1594m, 1572w, 1533w, 1454m, 1398m,
1349m, 1293w, 1172w, 1095m, 1081w, 1047m, 996w,
963w, 931m, 795s, 764s, 694s, 662w, 612w, 580w, 516w,
4.4. [3-(3-Pyrazolyl)phenyl]diphenylphosphine (5a)
3.5 g (9.7 mmol) of 4a and 2.5 g (50.0 mmol) of hydra-
zine monohydrate were refluxed in EtOH for 3 h. After
cooling to r.t., the solvent was removed in vacuum. The
remaining yellow oil was crystallized from MeOH to give
a light yellow crystalline solid. Yield: 3.0 g, 94%. Anal. Calc.
for C21H17N2P: C, 76.82; H, 5.22; N, 8.53. Found: C, 75.77;
H, 5.27; N, 8.39%. IR (KBr, cmꢀ1): 3215m, 1596w, 1582w,
1524w, 1476m, 1449m, 1432s, 1398m, 1326w, 1305w,
1178m, 1130w, 1096m, 1081m, 1051m, 1026m, 996m,
952m, 923w, 896w, 842w, 808m, 777s, 742s, 693s, 658m,
600w, 575w, 562m, 542m, 519m, 490s, 467w, 454w, 431w,
1
503w, 475w. H NMR (400.1 MHz, 25 ꢁC, DMSO-d6): d
12.94 (br, 3H, N–H), 7.88-7.80 (m, 6H, ar-H), 7.71 (d,
3
3H, JHH = 2.4 Hz, 5pz-H), 7.51–7.44 (m, 3H, ar-H), 7.23–
7.18 (m, 3H, ar-H), 6.65 (d, 3H, 4pz-H). C{1H} NMR
(100.6 MHz, 25 ꢁC, DMSO-d6): d 148.7 (C-3pz), 138.0 (d,
1JPC = 12.0 Hz, C-1), 134.2 (d, JPC = 6.5 Hz, C-3), 133.0
3
2
2
(d, JPC = 16.6 Hz, C-6), 130.9 (d, JPC = 24.0 Hz, C-2),
3
130.0 (d, JPC = 6.5 Hz, C-5), 126.8 (s, C-4), 102.8 (C-4pz),
C-5pz not observed. 31P{1H} NMR (162.0 MHz, 25 ꢁC,
DMSO-d6): d ꢀ4.44. ESI MS, m/z (%): 477.1405 (43)
[M + O + H]+, 461.1491 (100) [M + H]+.
1
416w. H NMR (400.1 MHz, 25 ꢁC, DMSO-d6): d 12.92
(br, 1H, N–H), 7.82–7.26 (m, 14H, ar-H, 5pz-H), 7.12 (t,
3
3
1H, JHH = 7.2 Hz, 5-H), 6.62 (d, 1H, JHH = 1.5 Hz, 4pz-
H). 13C{1H} NMR (100.6 MHz, 25 ꢁC, DMSO-d6): d
150.3 (C-3pz), 138.0 (C-5pz), 137.5 (d, JPC = 11.3 Hz, C-i),
4.7. [3-(4-(2-Amino)pyrimidinyl)phenyl]diphenylphosphine
(6a)
1
2
3
134.2 (d, JPC = 19.5 Hz, C-o), 132.9 (d, JPC = 1.8 Hz, C-
2
1
3), 132.9 (d, JPC = 17.3 Hz, C-6), 132.4 (d, JPC = 9.6 Hz,
C-1), 130.8 (d, 2JPC = 22.6 Hz, C-2), 130.0 (d,
3JPC = 6.5 Hz, C-5), 130.0 (s, C-p), 129.6 (d, 3JPC = 6.9 Hz,
C-m), 126.8 (s, C-4), 102.8 (C-4pz). 31P{1H} NMR
(162.0 MHz, 25 ꢁC, DMSO-d6): d-5.30. ESI MS, m/z (%):
345.1157 (53) [M + O + H]+, 329.1224 (100) [M + H]+.
2.9 g (8.1 mmol) of 4a and 1.5 g (8.5 mmol) of guanidi-
nium carbonate were suspended in 20 mL of EtOH. After
the addition of 0.95 g of KOH in 4 mL of H2O, the mixture
was heated to reflux for 2 h. After the removal of the solvent
in vacuum, the residue was dissolved in diluted HCl, and fol-
lowed by neutralization with 25% of ammonia. A light yel-
low solid was precipitated during the neutralization, which
was further washed with small amounts of EtOH and ether.
Yield: 2.4 g, 83%. Anal. Calc. for C22H18N3P Æ (C2H5-
OH)0.25: C, 73.66; H, 5.36; N, 11.43. Found: C, 74.08; H,
5.42; N, 11.07%. IR (KBr, cmꢀ1): 3496m, 3396w, 3274m,
3134m, 1624s, 1569s, 1549s, 1465s, 1433s, 1340m, 1281m,
1274m, 1218m, 1126w, 1093m, 1026w, 997w, 920w,
817m, 791m, 745s, 696m, 630m, 541w, 518m, 495m, 461w,
4.5. [2-(3-Pyrazolyl)phenyl]diphenylphosphine (5b)
Compound 5b was prepared following the same proce-
dure as for 5a as a colorless crystalline solid. Yield: 2.0 g,
64%. Anal. Calc. for C21H17N2P: C, 76.82; H, 5.22; N,
8.53. Found: C, 76.44; H, 5.18; N, 8.53%. IR (KBr,
cmꢀ1): 3186s, 3050w, 1583w, 1524m, 1490m, 1477m,
1456m, 1433s, 1417m, 1354m, 1306w, 1291w, 1173m,
1122m, 1080m, 1055m, 1036m, 1025m, 998w, 974w,
948m, 928w, 871w, 847w, 806m, 756s, 747s, 695s, 610m,
1
432w, 418w. H NMR (250.1 MHz, 25 ꢁC, DMSO-d6): d
3
8.26 (d, 1H, JHH = 5.2 Hz, 6pm-H), 8.14–8.02 (m, 2H, ar-
H), 7.53–7.17 (m, 12H, ar-H), 6.99 (d, 1H, 5pm-H), 6.68
(br, 2H, NH2). 13C{1H} NMR (62.9 MHz, 25 ꢁC, DMSO-
d6): d 164.7 (C-2pm), 163.9 (C-4pm), 160.1 (C-6pm), 138.2 (d,
1
532w, 516m, 499m, 486m, 464w, 438w, 418w. H NMR
(400.1 MHz, 25 ꢁC, DMSO-d6): d 12.94 (br, 1H, N–H),
3
3
7.66-7.62 (m, 2H, 3-H, 5pz-H), 7.44 (t, JHH = 7.4 Hz,
2JPC = 18.2 Hz, C-6), 138.2 (d, JPC = 2.8 Hz, C-3), 137.2
1
1
1H, 4-H), 7.36–7.34 (m, 6H, m, p-H), 7.27 (t, 1H, 5-H),
7.19–7.15 (m, 4H, o-H), 6.92–6.90 (m, 1H, 6-H), 6.30 (br,
1H, 4pz-H).13C{1H} NMR (100.6 MHz, 25 ꢁC, DMSO-
d6): d 150.8 (C-3pz), 140.2 (C-5pz), 138.8 (br, C-i), 135.9
(d, JPC = 11.2 Hz, C-i), 135.6 (d, JPC = 11.7 Hz, C-1),
2
2
134.2 (d, JPC = 19.6 Hz, C-o), 132.7 (d, JPC = 28.7 Hz,
C-2), 130.1 (d, 3JPC = 4.3 Hz, C-5), 130.0 (s, C-p), 129.7 (d,
3JPC = 6.8 Hz, C-m), 128.3 (s, C-4), 106.7 (C-5pm). 31P{1H}

Y. Sun et al. / Journal of Organometallic Chemistry 691 (2006) 291–298
297
NMR (101.2 MHz, 25 ꢁC, DMSO-d6): d ꢀ7.60. ESI MS, m/z
1157w, 1132m, 1101s, 1078m, 1057w, 1026w, 999w, 972w,
922w, 879w, 844w, 784m, 764s, 752m, 744m, 732m,
714m, 694s, 678w, 656w, 617w, 598m, 546s, 527m, 518s,
506s, 470m, 452w, 435m. 1H NMR (400.1 MHz, 25 ꢁC,
DMSO-d6): d 13.23 (br, 1H, N–H), 8.15–8.12 (m, 1H, 3-
(%): 372.1231 (15) [M + O + H]+, 356.1297 (100) [M + H]+.
4.8. cis-Dichlorobis{[3-(3-pyrazolyl)phenyl]diphenylphos-
phine} palladium(II) (7a) and Dichloro{[2-(3-
pyrazolyl)phenyl] diphenylphosphine} palladium(II) (7b)
3
H), 7.99 (br, 1H, 5pz-H), 7.82 (t, JHH = 7.4 Hz, 1H, 4-
H), 7.65–7.45 (m, 11H, ar-H), 7.13 (br, 1H, 4pz-H), 6.99–
6.95 (m, 1H, 6-H). 31P{1H} NMR (162.0 MHz, 25 ꢁC,
DMSO-d6): d 26.96.
250 mg (0.65 mmol) of di(benzonitrile)dichloropalla-
dium(II) were added to solutions of compound 5a
(427 mg, 1.30 mmol) or 5b (214 mg, 0.65 mmol) in 20 mL
of toluene. The mixtures were refluxed for 4 h. The prod-
ucts, which precipitated as yellow microcrystalline solids
were slightly contaminated with traces of elemental palla-
dium. Thus, they were recrystallized from hot saturated
MeOH solutions.
7a. Yield: 385 mg, 71%. Anal. Calc. for C42H34N4Cl2-
P2Pd Æ (CH3OH): C, 59.63; H, 4.42; N, 6.47. Found: C,
59.51; H, 4.29; N, 6.41%. IR (KBr, cmꢀ1): 3218m, 3135w,
3051w, 1530w, 1481m, 1464w, 1450w, 1435s, 1390m,
1352w, 1334w, 1313w, 1282w, 1179m, 1158w, 1124w,
1095s, 1083w, 1046m, 1028w, 997w, 960w, 904w, 808m,
789m, 770w, 747m, 708m, 690s, 660w, 612w, 565m, 512s,
506s, 488m, 458w, 448w, 432w. 1H NMR (400.1 MHz,
25 ꢁC, DMSO-d6): d 12.97 (br, 2H, N–H), 8.23–7.80 (m,
6H, ar-H, 5pz-H), 7.68–7.23 (m, 24H, ar-H), 6.62 (br, 2H,
4pz-H). 31P{1H} NMR (162.0 MHz, 25 ꢁC, DMSO-d6): d
25.43.
4.9. X-ray crystal structure determination of compounds
5a-O and 7b (data in parentheses)
Crystal data and details of the structure determination
are presented in Table 1. Suitable single crystals for the X-
ray diffraction studies were grown as mentioned above. A
clear colorless prism (7b: yellow plate) was stored under per-
fluorinated ether, transferred in a Lindemann capillary,
fixed, and sealed. Preliminary examination and data collec-
tion were carried out on an area detecting system (NONIUS,
MACH3, j-CCD) at the window of a rotating anode (NON-
IUS, FR951) and graphite monochromated Mo Ka radia-
˚
tion (k = 0.71073 A). The unit cell parameters were obtained
by full-matrix least-squares refinement of 1839 (7b: 3751)
reflections. Data collection were performed at 123 (7b:
123) K (OXFORD CRYOSYSTEMS) within a h-range of
2.29ꢁ < h < 25.34ꢁ (7b: 1.92ꢁ < h < 25.35ꢁ). Measured each
with nine data sets in rotation scan modus with Du/
Dx = 1.0ꢁ (7b: 1.5ꢁ). A total number of 40,474 (7b: 46,996)
intensities were integrated. Raw data were corrected for
Lorentz polarization and, arising from the scaling proce-
dure, for latent decay and absorption effects. After merging
7b. Yield: 240 mg, 73%. Anal. Calc. for C21H17N2PCl2-
Pd: C, 49.88; H, 3.39; N, 5.54. Found: C, 49.70; H, 3.54;
N, 5.38%. IR (KBr, cmꢀ1): 3227s, 1586w, 1567w,
1526w, 1496w, 1480m, 1463m, 1434s, 1424m, 1377m,
1332w, 1302w, 1284w, 1261w, 1195m, 1184m, 1172w,
Table 1
Summary of the crystal data and details of data collection and refinement for compounds 5a-O and 7b
5a-O
7b
Empirical formula
Formula mass
Crystal system
Space group
C
344.34
21H17N2OP
C21H17Cl2N2PPd
505.66
Monoclinic
P21/n (no. 14) [14]
9.1883(1)
21.2540(2)
10.3636(1)
101.1593(5)
1985.62(3)
4
Orthorhombic
P212121 (no. 19) [14]
10.6486(1)
11.4396(1)
14.2171(1)
90
1731.87(3)
4
1.321
˚
a (A)
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
qcalc. (g cmꢀ3
)
1.691
1.293
123
l (mmꢀ1
T (K)
)
0.169
123
F (000)
720
1008
Crystal size (mm)
h-range (ꢁ)
Index ranges
0.33 · 0.36 · 0.71
2.3/25.3
h: 12/k: 13/l: 17
40,474
0.05 · 0.20 · 0.28
1.9/25.4
h: 11/k: 25/l: 12
3635
Reflections collected
Independent reflections (I0 > 2r(I0)/all data/Rint
Data/restraints/parameters
R1 (I0 > 2r(I0)/all data)
wR2 (I0 > 2r(I0)/all data)
)
3002/3163/0.038
3163/0/294
0.0265/0.0291
0.0664/0.0681
1.04
3295/3635/0.049
3635/0/312
0.0281/0.0330
0.0657/0.0677
1.06
Goodness-of-fiꢀt3
˚
Dqmax/min (e A
)
ꢀ0.27/0.14
ꢀ0.38/2.43

298
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with the SHELXL-97 weighting scheme and stopped at shift/
err<0.001 (7b: 0.001). 5a-O: The final residual electron density
maps showed no remarkable features. 7b: The high positive
residual electron density is probably caused by a deficient
absorption correction procedure. Neutral atom scattering
factors for all atoms and anomalous dispersion corrections
for the non-hydrogen atoms have been taken from Interna-
tional Tables for Crystallography. All calculations were per-
formed on an Intel Pentium II PC, with the STRUX-V
system, including the programs PLATON [11] SIR92 [12],
and SHELXL-97 [13]. 5a-O: The correct enantiomer is proved
by Flackꢀs Parameter e = ꢀ0.00(8). Crystallographic data
(excluding structure factors) for the structures reported in
this paper have been deposited with the Cambridge Crystal-
lographic Data Center as supplementary publication no.
CCDC-284453 (5a-O) and CCDC-284454 (7b). Copies of
the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
(+44)1223 336 033; e-mail: deposit@ccdc.cam.ac.uk).
(p) F.Y. Kwong, C.W. Lai, Y. Tian, K.S. Chan, Tetrahedron Lett.
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The authors thank the Deutsche Forschungsgemeins-
chaft (SPP 1118) for financial support of this work.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2005.08.032.
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