Syntheses and coordination chemistry of bis(4-pyridyl)- and mixed (4-pyridyl) (2-pyridyl)-phospholes

Article abstract of DOI:10.1002/hc.20687

The syntheses, spectroscopic characterizations, and X-ray structures of two new N,P,N-ligands 1 and 2 are described. These ligands are based on a central 2,5-substituted phosphole ring and have, respectively, two 4-pyridyl moieties, or one 4-pyridyl moiet

Full text of DOI:10.1002/hc.20687

Heteroatom Chemistry
Volume 22, Number 3/4, 2011
Syntheses and Coordination Chemistry
of Bis(4-pyridyl)- and Mixed (4-Pyridyl)
(2-pyridyl)-phospholes
Christophe Lescop,1 Lo¨ıc Toupet,2 and Re´gis Re´au1
1Sciences Chimiques de Rennes, UMR 6226, CNRS-Universite´ de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
2Institut de Physique, IPR – UMR CNRS 6251, Baˆtiment 11A, Universite´ de Rennes 1,
35042 Rennes Cedex, France
Received 7 October 2010; revised 28 October 2010
the two coordination sites providing unique reac-
ABSTRACT: The syntheses, spectroscopic charac-
terizations, and X-ray structures of two new N,P,N-
ligands 1 and 2 are described. These ligands are based
on a central 2,5-substituted phosphole ring and have,
respectively, two 4-pyridyl moieties, or one 4-pyridyl
moiety and one 2-pyridyl moiety as substituents. The
coordination chemistry of these ligands has been in-
vestigated. A Au(I)-complex 5 bearing ligand 1 as a
P-donor and a Pt(II) complex 6 featuring ligand 2
as a P,N-chelate were obtained. Complex 6 sponta-
neously evolves to complex 7 bearing a 2-phospholene
ring. Spectroscopic characterizations for complexes 5–
7 as well as the X-ray crystal structure of 7 are de-
tivity to their metal complexes. Although different
N-donors (imines, pyridines, quinolines, oxazolines,
pyrazolines, oxazines, etc.) have been used for the
design of P,N-chelates [1], less attention has been
paid to the variation of the P-donors, the great ma-
jority of P,N-ligands bearing diarylphosphino frag-
ments. In this context, phospholes are the most stud-
ied P-heterocycles due to their easy accessibility,
good stability, and versatile chemical behavior [2].
This group 15 heteroles exhibits a limited aromatic
character, owing to the inherent property of the P-
atom (pyramidal geometry, inert s-pair effect) [3],
resulting in a high reactivity of both their dienic-
and heteroatom-moieties. This behavior, which is
very different from that of their N-analogues, makes
phospholes appealing derivatives for many purposes
including coordination chemistry [2]. Indeed, phos-
pholes act as classical terminal two-electron donors
toward a large range of transition metals. Therefore,
a variety of multidentate phosphole-containing lig-
ands, including heteroditopic P,N-donors, have been
reported as illustrated with selected examples de-
picted in Fig. 1 [2,4].
ꢀ
C
scribed. 2011 Wiley Periodicals, Inc. Heteroatom Chem
22:339–347, 2011; View this article online at wileyonlineli-
brary.com. DOI 10.1002/hc.20687
INTRODUCTION
Heteroditopic P,N-chelates have attracted consid-
erable interest in coordination chemistry and ho-
mogeneous catalysis for several decades [1]. The
importance of these mixed donor ligands arises
from the different stereo-electronic properties of
In this field, the coordination behavior of
(2-pyridyl)-substituted phospholes ligands was re-
cently explored in our group with the aim to
obtain complexes with original structures and in-
teresting physical properties. For example, 2-(2-
pyridyl)phosphole-based chromophores A–J (Fig. 2)
display extended π-conjugated systems and can act
Dedicated to Professor Kin-ya Akiba on the occasion of his 75th
birthday.
Correspondence to: Re´gis Re´au; e-mail: regis.reau@
univ-rennes1.fr.
c
ꢀ
2011 Wiley Periodicals, Inc.
339

340 Lescop, Toupet, and Re´au
+
Me Me
Me
Me
Me
Me
Ph
Me
N
OClO3
P
Ph
Ph
Ph
Ph
Pd
P
P
P
P
Ph
Ph
Pd
(CO)4Mn
Mn(CO)4
Me
Me
Ar
N
Et
Et
N
Et
Et
N
P
Pd
S
P
Ar
Ph
N
P
Ph
N
N N
P
Pd
Cl
P
N
N
Cl
Ph
W
Pd
(CO)4
Me
Ar
Cl
Cl
Me
Ph
Ph
FIGURE 1 Selected examples of complexes bearing phosphole-based ligands.
P
P
P
P
N
N
N
N
S
N
N
Ph
Ph
Ph
Cy
B
A
C
D
P
P
P
N
N
N
S
Bu2N
Ph
Ph
Ph
E
H3CO
F
G
P
P
P
N
N
N
Ph
Ph
Ph
H
I
J
FIGURE 2 Selected examples of (2-pyridyl)-substituted phosphole ligands.
as heteroditopic P,N-chelates toward a large range of
transition metals. Because of the different nature of
the donor atoms (a soft P- and a hard N-centers ac-
cording to the Pearson’s classification) [5], they un-
dergo highly stereoselective coordination processes
to d8 square-planar metal ions by virtue of the an-
tisymbiotic rule. Furthermore, these heteroditopic
P,N-ligands exhibit a hemilabile behavior, a dynamic
property which is very important to obtain the ther-
modynamically more stable transition metal com-
plex. The use of these appealing properties allowed
the coordination-driven synthesis of C2-symmetrical
metallic complexes active in nonlinear optics
[6] and chiral metal-bis(azahelicene phosphole)
assemblies [7].
Two other remarkable properties of mixed
pyridine–phosphole ligands are notable. The first
one is the original coordination mode of bis(2-
pyridyl)phosphole A (Fig. 2) that acts as a N,P,N-
chelate with a bridging P-atoms to stabilize a vari-
ety of metal dimers [8] such as complexes K and
L (Fig. 3a) [8d,e,9a]. These CuI-dimers are power-
ful “U-shape” molecular clips for the supramolecu-
lar synthesis of π-stacked [2,2]metallacyclophanes
upon reaction with ditopic π-linkers [9]. The sec-
ond one is the stereoselective isomerization of
Heteroatom Chemistry DOI 10.1002/hc

Syntheses and Coordination Chemistry of Bis(4-pyridyl)- and Mixed (4-pyridyl)(2-pyridyl)-Phospholes 341
2+ 2 X-
,
-
2+
,
2 X
a)
P
N
N
P
Ph
N
N
Cu
Cu
Ph
Ph
N
Cu
Cu
L
N
L
P
Ph2P
PPh2
L
L
X- = BF4 , PF6
L = CH3CN
K
L
b)
H
CH2Cl2
Base
Ar :
,
,
Ar
Ar
S
N
P
N
Pd
P
N
R
R
Pd
R :
,
Cl
Cl
Cl
Cl
M
N
FIGURE 3 (a) Chemical structure of “U-shaped” molecular clips K and L, (b) Stereoselective isomerization of 2-
pyridylphospholes into their corresponding 2-pyridyl-2-phospholenes in the coordination sphere of Pd(II) ions.
Pd(II)-coordinated 2-pyridylphosphole ligands into
their corresponding 2-pyridyl-2-phospholene iso-
mers in the presence of an organic base (pyridine,
triethylamine, . . . ; Fig. 3b) [10]. This general trans-
formation, involving a base-catalyzed [1,3]-H migra-
tion, gave access to enantiopure P,N-chelates that
can be used as ligands for asymmetric homogeneous
catalysis [11].
These results prompted us to extend our studies
of mixed pyridine–phosphole ligands to phospholes
substituted by a 4-pyridyl moiety. In this paper,
we describe the synthesis and the coordination
behavior of the new derivatives 1 and 2 (Fig. 4) in
which the phosphole rings are substituted by two
4-pyridyl moieties, or by both a 4-pyridyl and a
2-pyridyl fragments.
P
P
N
N
N
N
Ph
Ph
1
2
FIGURE 4 Chemical structure of (4-pyridyl)phospholes 1
and 2.
zirconacyclopentadienes that were reacted in situ
with dibromophosphine PhPBr2 to give the corre-
sponding phospholes 1 and 2 in moderate yields (1,
30%; 2, 46%) as air-stable yellow powders. These
new phosphole derivatives were characterized by
multinuclear nuclear magnetic resonance (NMR)
spectroscopies and mass spectrometry. Their 31P
NMR spectrum displays a sharp singlet at +14.2 ppm
(1) and +13.6 ppm (2). These chemical shifts are
typical of P-phenyl substituted λ3,σ3 phosphole ring
[13]. The simplicity of the room temperature 1H and
13C NMR spectra of derivative 1 is fully consistent
with a symmetrical structure. For example, the sig-
nal of the NCH protons of the (4-pyridyl) groups
consists in a doublet of doublets at 8.49 ppm, and
only one signal is recorded for the Cβ carbon atoms
RESULTS AND DISCUSSION
Syntheses and Characterizations of Derivatives
1 and 2
Phospholes 1 and 2 were prepared via the “Fagan–
Nugent method” (Scheme 1) [12], a general and
an efficient organometallic route to phosphole moi-
eties. Functionalized 1,7-diynes 3 and 4 were read-
ily obtained via Sonogashira coupling reactions in
good yields (Scheme 1). The intramolecular oxida-
tive coupling of these diynes, possessing a (CH2)4
spacer to obtain the desired 2,5-substitution pat-
tern, with “zirconocene” provides the corresponding
2
(147.4 ppm, d, JP-C = 11.0 Hz). As expected, in the
1H NMR spectrum of mixed derivative 2, two signals
for the NCH protons are observed at 8.57 ppm (H2)
and 8.46 ppm (H6ꢁ) with a relative integration ratio
of 2:1. The unsymmetrical nature of phosphole 2 is
Heteroatom Chemistry DOI 10.1002/hc

342 Lescop, Toupet, and Re´au
(i) Cp2ZrCl2
2,1 eq BuLi
2 eq.
8
7
N
Br,HCl
β
6
4
3
5
N
N
α
P
H
H
N
N
4
(ii) PhPBr2
Ph
2
Pd(PPh3)2Cl2
CuI,HNiPr2
3
3
2
1
Pd(PPh3)2Cl2
CuI,HNiPr2
1 eq.
Br
N
(i) Cp2ZrCl2
2,1 eq BuLi
3
3'
1 eq.
2
N
Br, HCl
4'
5'
P
N
H
N
N
N
Ph
N
(ii) PhPBr2
Pd(PPh3)2Cl2
CuI,
6'
4
HNiPr2
2
SCHEME 1 Syntheses of (4-pyridyl)phospholes 1 and 2.
also proven by the 13C NMR spectrum that displays a
set of signals for each carbon atom of the phosphole
ring and of the fused cyclohexyl ring.
The proposed structures for derivatives 1 and
2 were confirmed by X-ray diffraction studies. Sin-
gle crystals of 1 and 2 suitable for X-ray analysis
were obtained by slow evaporation of their CH2Cl2
solutions at room temperature (Table 1). Derivative
1 (Fig. 5a) crystallizes in the P21/c space group of
the monoclinic system, and compound 2 (Fig. 5b)
crystallizes in the P-1 space group of the triclinic
system. In both cases, one phosphole molecule is
present in the unit cell. The metric parameters of
the phosphole ring of these (4-pyridyl)-substituted
derivatives (Table 2) are very similar to those
of their corresponding (2-pyridyl) containing com-
pounds A (Fig. 2) [13]. The central phosphole ring
is almost planar, whereas the phosphorus atom’s
TABLE 1 Crystal Data and Structure Refinement for Phospholes 1 and 2 and Complex 7
1
2
7
Molecular formula
CCDC number
Molecular weight
C24H30N2P1
794109
368.40
C24H21N2P1
794106
368.40
C24H21N2P1Pt1Cl2
794107
634.39
˚
A (A)
9.2607(2)
20.2677(5)
9.350(3)
10.397(4)
10.0311(2)
16.1057(3)
˚
B (A)
˚
C (A)
9.9655(3)
90
91.5920(10)
90
1869.73(8)
4
1.309
Monoclinic
P21/c
293(2)
11.050(3)
81.85(2)
65.55(2)
85.26(2)
967.6(6)
2
1.264
Triclinic
P-1
14.0646(2)
90
102.219(1)
90
2220.77(7)
4
1.897
Monoclinic
P21/n
293(2)
α◦◦)
β◦)
γ 0
3
˚
V (A )
Z
ρcalcd (Mg m−3
Crystal system
Space group
T (K)
)
293(2)
˚
Wavelength Mo Kα (A)
0.71069
0.71069
0.71069
Crystal size (mm)
0.32 × 0.30 × 0.30
0.35 × 0.15 × 0.15
0.42 × 0.35 × 0.35
μ (Mo Kα) (cm−1
F(000)
)
0.159
0.153
6.645
776
2.28–27.00
388
1.98–26.96
1224
1.95–27.00
θ limit (◦)
Index ranges hkl
0 ≤ h ≤ 11, 0 ≤ k ≤ 25,
−12 ≤ l ≤ 12
4057
0 ≤ h ≤ 11, −13 ≤ k ≤ 13,
−12 ≤ l ≤ 14
4469
0 ≤ h ≤ 12, 0 ≤ k ≤ 20,
−17 ≤ l ≤ 17
4841
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I )]
R indices (all data)
4057
4057/0/244
1.040
R1 = 0.0520 wR2 = 0.1241
R1 = 0.0801 wR2 = 0.1430
0.550 and −0.343
4204
4204/0/245
0.887
R1 = 0.0662 wR2 = 0.1382
R1 = 0.1663 wR2 = 0.1571
0.328 and −0.215
4841
4841/0/272
1.073
R1 = 0.0345 wR2 = 0.0880
R1 = 0.0433 wR2 = 0.0953
2.175 and −1.705
Largest different peak and
−3
˚
hole (e A
)
Heteroatom Chemistry DOI 10.1002/hc

Syntheses and Coordination Chemistry of Bis(4-pyridyl)- and Mixed (4-pyridyl)(2-pyridyl)-Phospholes 343
◦
˚
TABLE 2 Selected Bonds Lengths (A) and Angles ( ) of the Phosphole Moieties in Phospholes A [13], 1 and 2, and Complex 7
2
7
1
8
P
P C1 P C8
C1 C3
C2 C7
C7 C8
C7 CPy C8 CPy
C1 P C8
A
1
2
7
1.806(6) 1.806(6)
1.799(2) 1.818(2)
1.790(3) 1.799(3)
1.835(5) 1.810(5)
1.365(9)
1.369(3)
1.357(4)
1.525(7)
1.478(9)
1.469(3)
1.472(4)
1.469(7)
1.354(8)
1.367(3)
1.360(4)
1.353(7)
1.466(9) 1.467(8)
1.467(3) 1.470(3)
1.478(4) 1.469(4)
1.497(7) 1.478(7)
90.5(3)
91.29(10)
91.05(16)
93.2(2)
FIGURE 5 View of the X-ray crystal structures of phospholes 1 (a) and 2 (b).
(soft P-atom, hard N-atoms). It was thus interesting
to study its coordination ability, and (tht)AuCl
(tht = tetrahydrothiophene) was selected as Au(I)
precursor with the hope to obtain a selective P-
coordination. Compound 1 was reacted with 1 equiv
of (tht)AuCl and, after workup, the novel complex
5 was isolated as an air-stable hygroscopic light
yellow powder in a 91% yield (Scheme 2). The ele-
mental analysis supports the formation of a (1)AuCl
[thtAuCl]
P
P
N
N
N
N
CH2Cl2, RT
AuCl
Ph
Ph
5
1
SCHEME 2 Synthesis of the complex 5.
1
complex. Its 31P{ H} NMR spectrum displays a
environment is strongly pyramidalized. The torsion
angles between the central phosphole ring and the
2- or 4-pyridyl fragments range from 23.2◦ to 33.2◦.
They are slightly larger than those found in the solid-
state structure of the bis(2-pyridyl)phosphole A (tor-
sion angles, 0.5◦ and 26.1◦) [13]. It is noteworthy
that derivative 1 can be considered as “phosphole-
modified” viologen (N1 C8 C1 N2, 1.9◦).
sharp singlet at +42.1 ppm. This chemical shift is
typical of a terminal coordination of the phosphorus
atom of λ3, σ3 phosphole ligands on a Au(I) center
1
[14]. The room temperature H NMR spectrum of
5 displays one set of signals only, which are very
similar to those of the free ligand 1, indicating a
symmetric structure. These data clearly show that
the Au(I) metal center coordinates exclusively to the
phosphorus atom of ligand 1. Indeed, this chemise-
lective modification opens the route to a variety of
novel derivatives because the terminal N-atoms of
complex 5 are potentially reactive sites for further
functionalizations or coordination polymer for-
mation. Preliminary experiments showed that
Coordination Behavior of Bis(4-pyridyl)
phosphole 1
Derivative 1 potentially possesses two available co-
ordination sites with different electronic properties
Heteroatom Chemistry DOI 10.1002/hc

344 Lescop, Toupet, and Re´au
H
H
[PtCl2(CH3CN)2]
CH2Cl2, RT
RT
P
P
P
N
N
N
N
N
N
Ph
Cl
Pt
Ph
Pt
Ph
Cl
Cl
Cl
6
7
1
SCHEME 3 Synthesis of complexes 6 and 7.
reacting
5
with
([Cu(NO3)2].
2.5
H2O,
[Cu(CH3CN)4]PF6,
[PdCl2(CH3CN)2],
[AgNO3],
or [AgCF3SO3]) afforded materials that are insoluble
in organic solvents (CH2Cl2, THF, CH3OH, and
acetone), probably due to their polymeric structure.
Coordination Behavior of (4-Pyridyl)(2-pyridyl)
phosphole 2
Ligand
2 was first reacted with 1 equiv of
[PtCl2(CH3CN)2] to form the complex 6 (Scheme 3).
1
The 31P{ H} NMR spectrum of the resulting
crude clear yellow solution displays one signal at
1
+36.6 ppm. This 31P{ H} NMR chemical shift is low
field shifted compared with that of the free ligand 2,
and typical for (2-pyridylphosphole)PtCl2 complexes
in which the organic ligand acts as a 1,4-P,N chelate
[10b]. The coordination of the P-atom is also sup-
ported by the presence of a large 1 JP Pt coupling con-
stant (3694 Hz), and that of the N-atoms of the 2-
pyridyl moiety by the loꢁw field chemical shift of the
1H NMR signal of the H6 proton (δ = 9.86 ppm). Fur-
thermore, the chemical shift of the H2 proton of the
4-pyridyl moiety is almost unchanged (δ = 8.51 ppm)
compared with the free ligand 2 (δ = 8.46 ppm).
These data clearly support the proposed structure
with ligand 2 acting as a P,N-chelate on the Pt(II)
center in complex 6 (Scheme 3).
FIGURE 6 View of the X-ray crystal structure of complex 7.
2-pyridyl moiety is low field shifted (δ = 10.15 ppm),
indicating that a P,N-chelate is still present in deriva-
tive 7. These data reveal a profound modification of
the phosphorus heterocycle structure and fit with a
2-phospholene structure [10]. This proposed struc-
ture was confirmed by X-ray diffraction studies
(Fig. 6). Single crystals of derivative 7 suitable for X-
ray diffraction analysis (Table 1) were obtained from
a slow diffusion of pentane vapors into a CH2Cl2 so-
lution of 7. Complex 7 contains an almost square
planar Pt(II) center linked to two chlorine atoms, a
pyridine, and a 2-phospholene ring. Note that the
pendant 4-pyridyl group of the ligand is not coor-
dinated to any metal center (shortest intermolecular
All attempts to isolate complex 6 in a pure form
failed. Indeed, if this complex is left for a few min-
utes in solution at room temperature, a new signal
1
appears at +40.5 ppm in the 31P{ H} NMR spectrum.
This sharp singlet is associated with a 1 JP Pt coupling
constant of 3815 Hz. After a few hours, the trans-
formation is complete and the resulting light yellow
solution does not evolve anymore. This observation
suggests that the complex 6 undergoes in solution
a spontaneous transformation into a new derivative
7 in which the phosphorus atom is still coordinated
on the Pt(II) center. After evaporation of the solvent,
derivative 7 (Scheme 3) is collected as a yellow pow-
˚
Pt-N(1) distance: 5.679 A). The existence of the phos-
pholene framework is clearly indicated by the tetra-
hedral geometry about the C(1) carbon atom and
˚
˚
the C(1)-C(2) (1.525(7) A) and C(7)–C(8) (1.353(7) A)
bond lengths, which are typical of single and dou-
ble carbon–carbon links, respectively. The two en-
˚
docyclic P C distances (1.810(5) and 1.835(5) A) are
1
characteristic for single bonds. It is also noteworthy
that the C(3) carbon atom has a planar geometry and
der. Its H NMR spectrum shows a broad doublet
at 4.7 ppm (JP H = 8.H Hz, 1H) andꢁ a multiplet at
6.35 ppm (1H). The signal of the H6 proton of the
that the C(2)–C(3) distance (1.324(8) A) is consistent
˚
Heteroatom Chemistry DOI 10.1002/hc

Syntheses and Coordination Chemistry of Bis(4-pyridyl)- and Mixed (4-pyridyl)(2-pyridyl)-Phospholes 345
with a double bond. Clearly, the fused carbocycle is
Synthesis of 1,8-Bis(4-pyridyl)octa-1,7-diyne 3
now a cyclohexene fragment. These solid-state struc-
tural data are in full agreement with the NMR spec-
troscopic data recorded in solution.
Catalytic amounts of [PdCl2(PPh3)2] (0.11 g,
0.15 mmol) and CuI (0.03 g, 0.15 mmol) were
added to a solution of 1,7-octadiyne (400 mg,
3.70 mmol) and 4-bromopyridine, hydrochloride
(1.464 g, 7.4 mmol) in diisopropylamine (70 mL).
The heterogeneous brown mixture was stirred for a
night at 40◦C. All volatiles materials were removed
in vacuo, and the residue was extracted with di-
ethylether (3 × 20 mL). After purification by column
chromatography on silica gel (heptane/ether, 2/1),
the product 3 was obtained as a pale yellow solid
The [1,3]-hydrogen shift leading to 7 (Scheme 3)
creates a new stereogenic center (the C(1)-carbon
atom), and the fact that only one diastereoisomer
out of the two possible is detected by NMR spec-
troscopy reveals a stereoselective process. The solid-
state studies show that the H-atom linked to the
C(1) atom and the P-substituent are in a mutual
cis configuration. This type of stereoselective pro-
cess has already been observed with either Pd(II) or
Pt(II) complexes bearing (2-pyridyl)-phosphole lig-
ands (Fig. 3b) [10]. Note that in the present case
(6 → 7, Scheme 3), it is very probable that the un-
coordinated 4-pyridyl acts as a base to promote the
[1,3]-hydrogen shift.
1
(yield 95%, 0.91 g, 3.55 mmol). NMR H (200 MHz,
CDCl3): δ = 1.80 (m, 4H, C CCH2CH ), 2.50 (m,
2
4H, C CCH ), 7.20 (dd,3 J(H, H) = 4.5 Hz, 5 J(H,
2
H) = 1.7 Hz, 4H, pyridyl H3), 8.50 (dd,3 J (H, H) =
4.5 Hz, 5 J(H, H) = 1.7 Hz, 4H, pyridyl H2). NMR 13C-
{1H}(50 MHz, CDCl3) : δ = 19.5 (s, C CCH2CH2),
27.9 (s, C CCH2), 79.3 (s, C C-4py), 95.5 (s, C C-
4py), 128.8 (s, pyridyl C3), 150.0 (s, pyridyl C2).
CONCLUSION
The syntheses, spectroscopic characterizations, and
X-ray crystal structure study of two new stable
N,P,N-ligands associating a central phosphole ring
and 4-pyridyl termini have been described. The phos-
phorus atom of ligand 1 bearing two (4-pyridyl)
fragments can be coordinated to a Au(I) metal cen-
ter, affording a monometallic complex 5 in which
the nitrogen atoms are free. Ligand 2, having a (2-
pyridyl)phosphole moiety, reacts with Pt(II) metal
centers as a 1,4-chelate. It spontaneously isomer-
izes to a phospholene ring in the Pt(II)-coordination
sphere. These results show that the new ligands 1
and 2 can be used for the synthesis of new coordina-
tion complexes having various structures.
Synthesis of 1-(4-Pyridyl),8-(2ꢁ-pyridyl)
octa-1,7-diyne 4
Catalytic amounts of [PdCl2(PPh3)2] (0.180 g,
0.26 mmol) and CuI (0.050 g, 0.26 mmol) were
added to a solution of 1-(2-pyridyl)octa-1,7-diyne
[10] (1.574 g, 8.59 mmol) and 4-bromopyridine,
hydrochloride (1.674 g, 8.59 mmol) in diisopropy-
lamine (50 mL). The heterogeneous brown mixture
was stirred overnight at 40◦C. All volatile materi-
als were removed in vacuo, and the residue was
extracted with diethylether (3 × 20 mL). After purifi-
cation by column chromatography on silica gel (hep-
tane/ether, 2/1), the product 4 was obtained as a pale
yellow solid (yield 72%, 1.60 g, 6.1 mmol). NMR1H
(200 MHz, CDCl3): δ = 1.60 (m, 4H, C CCH2CH ),
2
2.30 (m, 4H, C CCH ), 6.86 (ddd,3 J (H, H) = 7.7 Hz,
2
EXPERIMENTAL
4 J = 7.7 Hz, J (H, H) = 1.2 Hz,1H, pyridyl H5 ),
3
ꢁ
All experiments were performed under an at-
mosphere of dry argon using standard Schlenk
techniques. Commercially available reagents were
used as received without further purification. Sol-
vents were freshly distilled under argon from
sodium/benzophenone (diethylether) or from phos-
phorus pentoxide (dichloromethane, acetonitrile).
1H, 13C, and 31P NMR spectra were recorded on
Bruker AV300, DPX200, or AV500 spectrometers
7.06 (dd, 3 J (H, H) = 4.4 Hz, 5 J(H, H) = 1.6 Hz, 2H,
pyridyl H3), 7.08 (ddd, 3 J (H, H) = 7.7 Hz, 4 J (H, H) =
1.8 Hz, 5 J (H, H) = 1.2 Hz, 1H, pyridyl H3), 7.29
3
4
(ddd, J (H, H) = 7.7 Hz,3 J (H, H) = 7.7 Hz, J (H,
3
H) = 1.8 Hz, 1H, pyridyl H4), 8.32 (dd, J H, H) =
4.4 Hz, 5 J(H, H) = 1.6 Hz, 2H, pyridyl H2), 8.35
13
ꢁ
(m, 1H, pyridyl H6 ). NMR C-{1H}(50 MHz, CDCl3):
δ = 19.4 (s, C CCH2CH2), 19.5 (s, C CCH2CH2), 27.6
(s, C CCH2), 27.8 (s, C CCH2), 79.1 (s, C C-4py),
81.2 (s, C C-2py), 90.5 (s, C C-2py), 95.6 (s, C C-
(Bruker AXS Inc., Madison, WI). H and 13C NMR
1
ꢁ
chemical shifts were reported in parts per million
(ppm) relative to Me4Si as external standard. 31P
NMR downfield chemical shifts were expressed with
a positive sign, in ppm, relative to external 85%
H3PO4.
4py), 122.7 (s, pyridyl C5 ), 126.1 (s, pyridyl C3), 127.1
ꢁ
(s, pyridyl C3 ),132.4 (s, pyridyl C4),136.4 (s, pyridyl
C4 ), 144.0(s, pyridyl C2 ), 150.0 (s, pyridyl C2), 150.1
ꢁ
ꢁ
ꢁ
(s, pyridyl C6 ). HR-MS (EI): m/z measured 260.1302
[M]+; C18H16N2calculated 260.13135.
Heteroatom Chemistry DOI 10.1002/hc

346 Lescop, Toupet, and Re´au
Hortho), 7.29 (dd, 3 J(H, H) = 4.5 Hz, 4 J(H, H) = 1.6 Hz,
2H, pyridyl H3), 7.44 (bd, 3 J(H, H) = 8.0 Hz, 1H,
Synthesis of 1-Phenyl-2,5-di(4-pyridyl)
phosphole 1
3
4
ꢁ
pyridyl H3 ), 7.56 (dd, J(H, H) = 7.9 Hz, J(H, H) =
To a tetrahydrofuran (THF) solution (20 mL)
of Cp2ZrCl2 (874 mg, 3 mmol) and 1,8-bis(4-
pyridyl)octa-1,7-diyne 3 (782 mg, 0.3 mmol), was
added dropwise (ca. 1 min), at −78◦C, a hexane so-
lution of n-BuLi (1.6 M, 3.9 mL, 6 mmol). The solu-
tion was warmed to room temperature, and stirred
over night. To this solution, freshly distilled PhPBr2
(620 μL, 0.3 mmol) was added at −78◦C. The solu-
tion was allowed to warm to room temperature and
stirred for 6 h. The solution was filtered on basic alu-
mina (THF), and the volatile materials were removed
under vacuo. The desired product was washed with
pentane and obtained as a yellow solid (yield 30%,
332 mg, 0.09 mmol). NMR1H (200 MHz, CDCl3): δ =
3
ꢁ
1.8 Hz, 1H, pyridyl H4 ), 8.46 (dd, J(H, H) = 4.6 Hz,
4 J (H, H) = 1.6 Hz, 2H, pyridyl H2), 8.57 (ddd, 3 J (H,
H) = 4.9 Hz, 4 J (H, H) = 1.8 Hz, 5 J(H, H) = 0.9 Hz,
pyridyl H6 ). RMN 13C-{1H} (50 MHz, CDCl3): δ =
ꢁ
23.4 (s, C CCCH2CH2), 23.5 (s, C CCCH2CH2), 28.6
ꢁ
(s, C CCH2), 29.0 (s, C CCH2), 121.2 (s, pyridyl C5 ),
3
ꢁ
123.7 (d, J(P, C) = 8.1 Hz, pyridyl C3 ), 124.1 (d,
3 J(P, C) = 9.0 Hz, pyridyl C3), 128.9 (d, J(P, C) =
2
8.2 Hz, phenyl Cmeta), 129.8 (s, phenyl Cpara), 131.5
1
2
(d, J(P, C) = 11.9 Hz, phenyl Cipso), 133.9 (d, J(P,
ꢁ
C) = 18.6 Hz, phenyl Cortho), 136.4 (s, pyridyl C4 ),
2
145.2 (s, P C C), 145.3 (s, P C C), 147.8 (d, J(P,
2
C) = 10.0 Hz, P C C), 147.3 (d, J (P, C)=11.0 Hz,
ꢁ
P C C), 150.0 (s, pyridyl C6 ), 150.1 (s, pyridyl C2),
1.60–1.90 (m, 4H, C CCH2CH ), 2.55–2.80 (m, 2H,
2
2
31
ꢁ
155.8 (d, J(P, C) = 18.1 Hz, pyridyl C2 ). NMR P-
{1H}(81 MHz, CDCl3): δ = +13.6. HR-MS (EI):
m/z measured 368.1426 [M]+; C24H21N2P calculated
368.14424.
C CCH ), 2.90–3.1 (m, 2H, C CCH2), 7.05–7.12 (m,
2
3
5
5H, HPh), 7.26 (dd, J (H, H) = 4.6 Hz, J(H, H) =
1.6 Hz, 4H, pyridyl H3), 8.49 (dd, 3 J H, H) = 4.6 Hz,
5 J(H, H) = 1.6 Hz, 4H, pyridyl H2). NMR13C-{1H}
(50 MHz, CDCl3): δ = 23.3 (s, C CCCH2CH2), 28.4
(s, C CCH2), 123.3 (d, 2 J(P, C) = 5.6 Hz, pyridyl C3),
124.0 (d, 3 J(P, C) = 9.6 Hz, pyridyl C2), 129.2 (d, 3 J(P,
C) = 8.5 Hz, phenyl Cmeta), 130.3 (s, phenyl Cpara),
133.8 (d, 2 J(P, C) = 19.1 Hz, phenyl Cortho), 143.2
(s, P C C), 144.9 (d, 1 J(P, C) = 19.2 Hz, phenyl
Synthesis of the Derivative 5
To a CH2Cl2 solution (5 mL) of the ligand 2 (0.040 g,
0.11 mmol), a CH2Cl2 solution (5 mL) of (tht)AuCl
(0.035 g, 0.11 mmol) was added at room temper-
ature. After 1 h, the solvent was evaporated. The
residue was washed with pentane, and a yellow
powder of 6 was recovered (yield 91%, 0.060 g,
0.10 mmol). NMR 1H (200 MHz, CDCl3): δ = 1.7–1.9
(m, 4H, C CCH2CH2) 2.6–3.0). (m, 4H, C CCH2),
7.3–7.5 (m, 9H, pyridyl H3, HPh), 8.4–8.6 (bs, 4H,
pyridyl H2). NMR 31P{1H} (81 MHz, CDCl3): δ = 42.1.
elemental analysis (%) calcd for C24H21N2P1Au1Cl1: C
47.98, H 3.52, N 4.66; found: C 47.69, H 3.33, N 4.89.
2
Cipso), 147.4 (d, J(P, C) = 11.0 Hz, P C C), 150.2
(s, pyridyl C2). NMR31P-{1H}(81 MHz, CDCl3): δ =
+14.2. HR-MS (EI): m/z measured 368.1426 [M]+;
C24H21N2P calculated 368.14424.
Synthesis of 1-Phenyl-2,5-(4-pyridyl),8-(2ꢁ-
pyridyl)phosphole 2
To a THF solution (20 mL) of Cp2ZrCl2 (0.85 g,
2.91 mmol) and 1-(4-pyridyl),8-(2ꢁ-pyridyl)octa-1,7-
diyne 4 (0.76 g, 2.91 mmol) was added dropwise
(ca. 1 min), at −78◦C, a hexane solution of n-BuLi
(1.6 M, 3.82 mL, 6.11 mmol). The solution was
warmed to room temperature and stirred overnight.
To this solution, freshly distilled PhPBr2 (0.6 mL,
2.91 mmol) was added at −78◦C. The solution was
allowed to warm to room temperature and stirred
for 6 h. The solution was filtered on basic alumina
(THF), and the volatile materials were removed un-
der vacuo. The desired product was washed with
pentane and obtained as a yellow solid (yield 46%,
0.49 g, 1.33 mmol). NMR1H (200 MHz, CDCl3): δ =
1.72 (m, 4H, C CCH2CH2), 2.80 (m, 3H, C CCH2),
3.40 (m, 1H, C CCH2), 7.01(ddd, 3 J (H, H) = 7.3 Hz,
Synthesis of the Derivative 6
To a CH2Cl2 solution (5 mL) of the ligand 2
(0.040 g, 0.11 mmol), a CH2Cl2 solution (5 mL) of
[PtCl2(CH3CN)2] (0.038 g, 0.11 mmol) was added
at room temperature. After 2 min, the solvent was
evaporated. The residue was washed with pentane,
and a yellow powder of 6 was recovered (yield 85%,
0.059 g, 0.09 mmol). NMR1H (200 MHz, CDCl3): δ =
1.8 (m, 4H, C CCH2CH ), 2.5 (m, 2H, C CCH2CH ),
2
2
2.9 (m, 1H, C CCH ), 3.2 (m, 1H, C CCH2), 7.24
2
(m, 3H, pyridyl H5 , phenyl Hmeta), 7.60 (d, 3 J (H, H)
ꢁ
ꢁ
= 6.6 Hz, 2H, pyridyl H3), 7.66 (m, 4H, pyridyl H3 ,
phenyl Hortho, phenyl Hpara), 8.01 (bt, 3 J (H, H) = 8.0
4
ꢁ
Hz, J (H, H) = 1.0 Hz, 1H, pyridyl H4 ), 8.51 (bd,
4 J (H, H) = 4.9 Hz, J (H, H) = 1.3 Hz, 1H, pyridyl
3 J(H, H) = 6.6 Hz, 2H, pyridyl H2), 9.86 (bd, J (H,
5
3
31
ꢁ
ꢁ
H5 ), 7.06–7.15 (m, 3H, phenyl Hmeta, Hpara), 7.25 (td,
H) = 5.6 Hz, 1H, pyridyl H6 ). NMR P{1H} (81 MHz,
5
3 J (H, H) = 8.0 Hz, J (H, H) = 2.0 Hz, 1H, phenyl
CDCl3): δ = 36.6 (1 JP−Pt = 3694 Hz).
Heteroatom Chemistry DOI 10.1002/hc

Syntheses and Coordination Chemistry of Bis(4-pyridyl)- and Mixed (4-pyridyl)(2-pyridyl)-Phospholes 347
C.; Balavoine, G. G. A. Tetrahedron, 2000, 56, 85;
Synthesis of the Derivative 7
(d) Escalle, A.; Mora, G.; Gagosz, F.; Mezailles, N.; Le
Goff, X. F.; Jean, Y.; Le Floch, P. Inorg Chem 2009,
48, 8415; (e) Thoumazet, C.; Melaimi, M.; Ricard, L.;
Le Floch, P. C. R. Chim 2004, 7, 823; (f) Matano, Y.;
Nakabuchi, T.; Fujishige, S.; Nakano, H.; Imahori,
H. J Am Chem Soc 2008, 130, 990; (g) Matano,
Y.; Miyajima, T.; Ochi, N.; Nakabuchi, T.; Shiro,
M.; Nakao, Y.; Sakaki, S.; Imahori, H. J Am Chem
Soc 2008, 130, 16446; (h) Matano, Y.; Nakashima,
M.; Saito, A.; Imahori, H. Org Lett 2009, 11, 3338;
(i) Burck, S.; Gudat, D.; Nieger, M. Angew Chem, Int
Ed 2007, 46, 2919; (j) Burck, S.; Gudat, D.; Nieger, M
Organometallics 2009, 28, 1447.
To a CH2Cl2 solution (5 mL) of the ligand 2
(0.020 g, 0.055 mmol), a CH2Cl2 solution (5 mL) of
[PtCl2(CH3CN)2] (0.019 g, 0.055 mmol) was added
at room temperature. After 36 h, the solvent was
evaporated. The residue was washed with pentane,
and a yellow powder of 7 was recovered (yield 80%,
1
0.028 g, 0.04 mmol). NMR H (200 MHz, CDCl3): δ
1.9 (m, 4H, C CCH2CH ), 2.9 (m, 2H, C CCH2), 4.66
2
(bd, 2 J(P, H) = 8.4 Hz, C CH), 6.3 (m,1H, PCH),
ꢁ
6.9–8.0 (m, 11H, pyridyl H3 , pyridyl H2, pyridyl H3,
ꢁ
pyridyl H5 , phenyl Hortho, phenyl Hmeta, phenyl Hpara),
[5] (a) Pearson, R. G. Inorg Chem 1973, 12, 712;
(b) Harvey, J. N.; Heslop. K. M.; Orpen, A. G.; Pringle,
P. G. Chem Commun 2003, 278.
[6] Fave, C.; Hissler, M.; Se´ne´chal, K.; Ledoux, I.; Zyss,
J.; Re´au, R. Chem Commun 2002, 1674.
3
ꢁ
8.20 (bt, 1H, J (H, H) = 5.6 Hz, pyridyl H4 ), 10.15 (d,
J(H, H) = 7 Hz, pyridyl H6 ). NMR 31P{1H}(81 MHz,
3
ꢁ
CDCl3): δ = 40.5 (1 JP-Pt = 3815 Hz); elemental anal-
ysis (%) calcd for C24H21N2P1Pt1Cl2: C 45.44, H 3.34,
N 4.42; found: C 45.69, H 3.12, N 4.09.
[7] (a) Graule, S.; Rudolph, M.; Vanthuyne, N.;
Autschbach, J.; Roussel, C.; Crassous, J.; Re´au, R.
J Am Chem Soc 2009, 131, 3183; (b) Graule, S.;
Rudolph, M.; Shen, W.; Lescop, C.; Williams. J. A.
G.; Autschbach, J.; Crassous, J.; Re´au, R. Chem Eur J
2010, 16, 5976; (c) Shen, W.; Graule, S.; Crassous, J.;
Lescop, C.; Gornitzka, H.; Re´au, R. Chem Commun
2008, 850.
[8] (a) Sauthier, M.; Le Guennic, B.; Deborde, V.; Toupet,
L.; Halet, J-F.; Re´au, R. Angew Chem, Int Ed 2001,
40, 228; (b) Sauthier, M.; Leca, F.; Toupet, L.;
Re´au, R. Organometallics 2002, 21, 1591; (c) Leca,
F.; Sauthier, M.; Deborde, V.; Toupet, L.; Re´au, R.
Chem Eur J 2003, 9, 3785; (d) Leca, F.; Lescop, C.;
Rodriguez-Sanz, E.; Costuas, K.; Halet, J-F.; Re´au, R.
Angew Chem, Int Ed 2005, 44, 4362; (e) Nohra, B.;
Rodriguez-Sanz, E.; Lescop, C.; Re´au, R.; Chem Eur J
2008, 14, 3391; (f) Welsch, S.; Nohra, B.; Peresypkina,
E. V.; Lescop, C.; Scheer, M.; Re´au, R. Chem Eur J
2009, 15, 4685; (g) Welsch, S.; Lescop, C.; Re´au, R.;
Scheer, M. Inorg Chem 2009, 47, 2994.
REFERENCES
[1] (a) Braunstein, P.; Naud, F. Angew Chem, Int Ed Engl
2001, 40, 680; (b) Helmchem, G.; Pfaltz, A. Acc Chem
Res 2000, 33, 336; (c) Drury, W. J., III; Zimmermann,
N.; Keenan, M.; Hayashi, M.; Kaiser, S.; Goddard,
R.; Pfaltz, A. Angew Chem, Int Ed Engl 2004, 43, 70;
(d) Chelucci, G.; Orru, G.; Pinna, G. A. Tetra-
hedron 2003, 59, 9471; (e) Espinet, P.; Soulan-
tica, K. Coord Chem Rev 1999, 193–195,
499; (f) Braunstein, P.; Knorr, M.; Stern,
C. Coord Chem Rev 1998, 178–180, 9039;
(g) Bianchini, C.; Meli, A. Coord Chem Rev 2002,
225, 35; (g) Guiry, P. J.; Saunders, C. P. Adv Synth
Catal 2004, 346, 497; (h) Carrasco, A. C.; Pidko, E.
A.; Masdeu-Bulto, A. M.; Lutz, M.; Spek, A. L.; Vogt,
D.; Mu¨ller, C. New J Chem 2010, 34, 1547.
[9] (a) Nohra, B.; Graule, S.; Lescop, C.; Re´au, R. J Am
Chem Soc 2006, 128, 3520; (b) Yao, Y.; Shen; W.;
Nohra, B.; Lescop, C.; Re´au, R. Chem Eur J 2010, 16,
7143.
[10] (a) Leca, F.; Sauthier, M.; le Guennic, B.; Lescop,
C.; Toupet, L.; Halet, J-F.; Re´au, R. Chem Commun
2003, 1774; (b) Leca, F.; Lescop, C.; Toupet, L.; Re´au,
R. Organometallics 2004, 23, 6191; (c) Nyula´szi, L.;
Hollo´czki, O.; Lescop, C.; Hissler, M.; Re´au, R. Org
Biomol Chem 2006, 4, 996.
[11] Leca, F.; Fernandez, F.; Muller, G.; Lescop, C.; Re´au,
R.; Gomez, M. Eur J Inorg Chem 2009, 5583.
[12] (a) Fagan, P. J.; Nugent, W. A. J Am Chem Soc 1988,
110, 2310; (b) Fagan, P. J.; Nugent, W. A.; Calabrese,
J. C. J Am Chem Soc 1994, 116, 1880.
[2] (a) Mathey, F. Phosphorus-Carbon Heterocyclic
Chemistry: The Rise of a New Domain; Elsevier Sci-
ence: Oxford, UK, 2001; (b) Dillon, K.; Mathey, F.;
Nixon, J. F. Phosphorus: The Carbon Copy; Wiley:
Chichester, UK, 1998; (c) Nyulaszi, L. Chem Rev
2001, 101, 1229; (d) Mathey, F. Angew Chem, Int Ed
2003, 42, 1578; (e) Baumgartner, T.; Re´au, R. Chem
Rev 2006, 106, 4681; (f) Re´au, R., Dyer, P. In Com-
prehensive Heterocyclic Chemistry III’; Katritzky, A.
R.; Ramsden, C. A.; Scriven, E. F. V.; Taylor, R. J. K.
(Eds.); Elsevier: Oxford, UK, 2008; Vol.3, pp. 1029–
1148.
[3] Regitz M.; Scherer O. J. Multiple Bonds and Low Co-
ordination in Phosphorus Chemistry; Georg Thieme:
Stuttgart, Germany, 1990.
[13] (a) Le Vilain, D.; Hay, C.; Deborde, V.; Toupet,
L.; Re´au, R. Chem Commun 1999, 345; (b) Hay,
C.; Hissler, M.; Fischmeister, C.; Rault-Berthelot, J.;
Toupet, L.; Nyulaszi, L.; Re´au, R. Chem Eur J 2001,
7, 4222.
[14] Attar, S.; Bearden, W. H.; Allcock, N. W.; Alyea, E. C.;
Nelson, J. H. Inorg Chem 1990, 29, 425.
[4] (a) Lescop, C.; Hissler, M. Tomorrow’s Chemistry
Today, Concepts in Nanoscience, Organic Materials
and Environmental Chemistry, Pignatoro, B. (Ed.);
Wiley-VCH: Weinheim, Germany, 2008; pp. 295–319;
(b) Ogasawara, M.; Ito, A., Yoshida, K.; Hayashi,
T. Organometallics 2006, 25, 2715; (c) Tissot, O.;
Hydrio, J.; Gouygou, M.; Dallemer, F.; Daran, J.
Heteroatom Chemistry DOI 10.1002/hc