Preparation and properties of palladium(II) complexes of 3-oxo-1-(2,4,6-tri-t-butylphenyl)-1,3-diphosphapropenes

Article abstract of DOI:10.1016/j.jorganchem.2005.07.075

Kinetically stabilized 3-oxo-1,3-diphosphapropenes were prepared by oxidation of 1,3-diphosphapropenes with m-CPBA or from reaction of the corresponding phosphaethenyllithium with phosphinic chloride. The 3-oxo-1,3-diphosphapropenes were used as P,O-unsymmetrical bidentate ligands and the catalytic activity of the palladium(II) complexes in some cross-coupling reactions was investigated.

Full text of DOI:10.1016/j.jorganchem.2005.07.075

Journal of Organometallic Chemistry 690 (2005) 4809–4815
www.elsevier.com/locate/jorganchem
Preparation and properties of palladium(II) complexes
of 3-oxo-1-(2,4,6-tri-t-butylphenyl)-1,3-diphosphapropenes
*
*
Katsunori Nishide, Hongze Liang, Shigekazu Ito , Masaaki Yoshifuji
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan
Received 21 April 2005; received in revised form 21 July 2005; accepted 22 July 2005
Available online 31 August 2005
Abstract
Kinetically stabilized 3-oxo-1,3-diphosphapropenes were prepared by oxidation of 1,3-diphosphapropenes with m-CPBA or from
reaction of the corresponding phosphaethenyllithium with phosphinic chloride. The 3-oxo-1,3-diphosphapropenes were used as
P,O-unsymmetrical bidentate ligands and the catalytic activity of the palladium(II) complexes in some cross-coupling reactions
was investigated.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Phosphorus ligand; Phosphaalkene; Palladium complex; X-ray crystallography; Cross-coupling reaction
1. Introduction
group and the PPh2 moiety, which enables the 1,3-di-
phosphapropene to act as a chelating ligand in the
complex formation. Indeed, 1a afforded chelate transi-
tion-metal complexes of tungsten(0), palladium(II) and
platinum(II) [4]. On the other hand, 2-chloro-3,3-di-
phenyl-1-(2,4,6-tri-t-butylphenyl)-1,3-diphosphapropene
[Mes*P@C(Cl)–PPh2: 1a-Cl] afforded neither palladium
nor platinum complex, though it afforded mono-coordi-
nated and chelate tungsten complexes [5], suggesting
that the substituent on the sp2 carbon in 1,3-diphospha-
propenes is important for complexation [6].
The 1,3-diphosphapropene systems can be transfor-
med chemically into other molecular structures. We
recently reported sulfurization of 1a to the correspond-
ing 3-thioxo-1,3-diphosphapropene 2a and utilization
of 2a as a ligand for transition-metal complexes [7].
3-Thioxo-1,3-diphosphapropene consists of the P@C–
P@S skeleton and behaves as a P,S-chelating ligand to
afford the corresponding five-membered transition-
metal complexes. The palladium(II) complexes contain-
ing the ligated 3-thioxo-1,3-diphosphapropene are stable
in air and moisture, and can be used for catalytic
reactions such as the Sonogashira and the Suzuki
cross-coupling reactions [7] (see Chart 1).
Chemistry of low-coordinated phosphorus compounds
has greatly developed in recent years and we have repor-
ted a number of kinetically stabilized phosphaethenes
with a bulky Mes* (2,4,6-tri-t-butylphenyl) group [1,2].
Phosphaethenes with the P@C bond, which exhibits un-
ique properties such as p-electron accepting effect, are
novel and attractive ligands for synthetic catalysts [3].
Indeed, DPCB (=3,4-diphosphinidenecyclobutene) has
afforded several unique catalysts for organic reactions
[3]. We recently reported preparation and coordination
chemistry of kinetically stabilized 2-methyl-3,3-diphe-
nyl-1,3-diphosphapropene 1a [4,5] which was used as
ligands for transition-metal complexes. Compound 1a
contains both a low-coordinated sp2 phosphorus and a
normal sp3 phosphino phosphorus in the molecular
system. Basically, 1a predominantly forms an E-config-
uration to avoid steric congestion between the Mes*
*
Corresponding authors. Tel.: +81 22 795 6560.
E-mail addresses: ito@synchem.chem.tohoku.ac.jp (S. Ito),
yoshifj@mail.tains.tohoku.ac.jp (M. Yoshifuji).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.07.075

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K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
Mes*
Me
C
PPh2
Mes*
Me
C
PR2
Mes*
Me
P C
Mes*
P
P Mes*
X
Mes*
Me
P C
Cl2Pd(MeCN)2
m-CPBA
P
P
1
PR2
PPh2
Cl2Pd
X
O
O
S
5
6
1a
2a
DPCB
Mes*
Scheme 2.
Chart 1.
the reaction of (Z)-1-chloro-2-(2,4,6-tri-t-butylphenyl)-
2-phosphaethenyllithium and Ph2P(O)Cl in 34% yield,
whereas attempts to obtain 5a-Cl from 1a-Cl by using
m-CPBA resulted in decomposition of the substrate. A
single crystal of 5c was employed for X-ray crystallogra-
phy and Fig. 1 shows an ORTEP drawing of the molec-
ular structure. Selected metric parameters are displayed
in Table 1. The P1–C1–P2–O1 skeleton takes an s-cis
form with the torsion angles of H = 12.3(2)ꢁ, which is
similar to a 3-thioxo-1,3-diphosphapropene [7]. The
P1–C1 distance indicates a P@C double bond [1], and
the P2–O distance is close to the corresponding data
The oxygen atom in phosphine oxides coordinates on
metals. Moreover, a number of biphosphine monoxides
have been developed and utilized as catalysts for organic
reactions [8]. Therefore, combination of phosphaethene
and phosphine oxide is expected to provide novel
ligands that are useful for exploring new catalysts. In this
paper, we report preparation of novel 1,3-diphospha-
propene and 3-oxo-1,3-diphosphapropene derivatives.
Coordination chemistry of P@C–P@O ligands as well
as catalytic activities has also been investigated.
˚
of triphenylphosphine oxide (1.46 A) [11].
2. Results and discussion
3-Oxo-1,3-diphosphapropenes 5a–d afforded the
corresponding dichloropalladium(II) complexes 6a–d
in 75–85% yields [7]. Similarly, 5a-Cl was allowed to re-
act with PdCl2(CH3CN)2 to generate the corresponding
dichloropalladium(II) complex, but it gradually decom-
posed affording unidentified products [12]. The palla-
dium(II) complex 6a was recrystallized from a mixture
of CH2Cl2 and toluene to afford single crystals, one of
which was employed for X-ray crystallography. The
molecular structure of 6a and selected metric parameters
are displayed in Fig. 2 and Table 1, respectively. The
structure around the palladium atom in 6a revealed
a square-planar structure. The Pd–P1–C1–P2–O five-
membered chelate ring is almost planar [H(Pd–P1–C1–
P2) = 0.6(3)ꢁ, H(P1–C1–P2–O) = À13.0(4)ꢁ] , which is
similar to the structure of 7a [7b]. The Pd–Cl1 bond of
Compound 1a was prepared according to our pre-
vious report [4]. Compound 3, prepared from (Z)-
2-bromo-1-(2,4,6-tri-t-butylphenyl)-1-phosphapropene
and butyllithium [9], was allowed to react with phos-
phorus trichloride to give 2-methyl-3,3-dichloro-1,3-
diphosphapropene 4 [dP = 316, 168 (2JPP = 596 Hz)]
almost quantitatively. Air- and moisture-sensitive 4
was characterized only by 31P NMR spectroscopy and
2
E-configuration was identified from a large JPP value.
Steric congestion between the Mes* group and the PCl2
moiety is responsible for the formation of 4 of E-form.
Compound 4 was allowed to react with two equivalents
of organolithium reagent to give the corresponding
1,3-diphophapropene derivatives (1b–d) (Scheme 1). In-
deed, 4 is a promising reagent to prepare various 1,3-
diphosphapropenes. Molecular structure of 1c was
successfully analyzed by X-ray crystallography (30%
of molecules in the crystal were 3-oxo-1,3-diphospha-
propene 5c) [10]. The structure of 1c is similar to that
of 1a-Cl [6].
˚
˚
2.326(1) A is longer than that of Pd–Cl2 [2.257(2) A]
indicating the greater trans influence of the P@C moiety
The 1,3-diphosphapropenes 1a–d were allowed to
react with an equimolar amount of m-chloroperbenzoic
acid (m-CPBA) to give the corresponding 3-oxo-1,3-
diphosphapropenes 5a–d in 70–75% yields (Scheme 2).
No oxidation on the sp2 phosphorus in 1 was observed
under the employed conditions. Alternatively, 2-chloro-
3-oxo-1,3-diphosphapropene 5a-Cl was prepared from
Mes*
Me
C
Mes*
Me
P C
Mes*
Me
C
PCl3
2RLi
P
P
PCl2
PR2
Li
1
3
4
R = p-MeC6H4 (b), p-MeOC6H4(c), n-Bu (d)
Fig. 1. Molecular structure of 5c (40% probability ellipsoids). Hydro-
Scheme 1.
gen atoms are omitted for clarity.

K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
4811
Table 1
Mes*
Cl
Mes*
Me
P C
2+
2BF4
P O
P
O P
P
˚
Selected bond lengths (A) and angles (ꢁ) of 5c and 6a
Complex 5c
–
P C
Pd
PPh2
PPh2
Complex 6a
Cl2Pd
O
S
P = PPh2
P1–C1
P1–CMes
P2–O1
P2–C1
P2–Carom
P2–Carom
C1–C2
Pd–Cl1
Pd–Cl2
Pd–P1
1.673(3)
1.858(3)
1.486(2)
1.814(3)
1.814(3)
1.798(3)
1.507(4)
1.671(6)
1.812(5)
1.513(4)
1.794(5)
1.783(6)
1.784(6)
1.501(8)
2.326(1)
2.257(2)
2.208(1)
2.075(4)
Ã
5a-Cl
7a
Chart 2.
8
(2.0 mmol) in triethylamine (8 mL) reacted with phenyl-
acetylene (2.0 mmol) at room temperature in the pre-
sence of 6 (0.050 mmol) and copper(I) iodide (0.050
mmol) for 4 h at room temperature to afford the corre-
sponding diphenylacetylene. Table 2 summarizes the
results of the Sonogashira reactions (Scheme 3(a)). The
catalytic activity of 6 is inferior to that of 7a [7b], sug-
gesting a considerable p-accepting effect of P@C moiety
as well as a smaller electron-donating effect of the P@O
moiety. In Table 2, 6c gave the best result, indicating
that the p-anisyl groups might facilitate the oxidative
addition relatively with other complexes. On the other
hand, the catalytic activity of 6 in the Suzuki reaction
[15] in Scheme 3(b) [conditions: iodobenzene (2.0
mmol), phenylboric acid (2.0 mmol), 6 (0.080 mmol),
potassium carbonate (4.0 mmol), THF (15 mL), reflux
20 h] is moderate (Table 3) and similar to the catalytic
activity of 9 [16]. We are studying to establish other
catalytic reaction systems which are suitable to 3-oxo-
1,3-diphosphapropenes (see Chart 3).
Pd–O
Ã
C1–P1–CMes
P1–C1–P2
P1–C1–C2
P2–C1–C2
O–P2–C1
99.8(1)
115.2(2)
127.5(2)
116.9(2)
112.4(1)
112.5(1)
113.6(1)
107.2(1)
113.0(3)
109.4(3)
128.6(4)
122.0(4)
109.7(2)
110.4(3)
110.5(2)
112.9(3)
93.90(6)
174.98(8)
91.0(1)
90.62(5)
174.6(1)
84.6(1)
112.3(2)
134.7(2)
120.3(2)
O–P2–Carom
O–P2–Carom
C
arom–P2–Carom
Cl1–Pd–Cl2
Cl1–Pd–P1
Cl1–Pd–O
Cl2–Pd–P1
Cl2–Pd–O
P1–Pd–O
Pd–P1–C1
Pd–P1–CMes
Pd–O–P2
Ã
PhC CH / Et3N
a
b
PhC CPh
Ph Ph
6 / CuI / rt / 4 h
Ph
I
PhB(OH)2 / THF
6 / K2CO3 / reflux / 20 h
Scheme 3.
Table 2
Sonogashira reaction (Scheme 3(a))
Catalyst
Yield (%)
6a
6b
6c
6d
35
60
68
39
Fig. 2. Molecular structure of 6a with 30% probability ellipsoids.
Hydrogen atoms and the solvent molecules (dichloromethane) are
omitted for clarity.
than that of the P@O moiety. The P1–C1 distance of 6a
˚
is longer than that in 7a [1.644(9) A] [7b]. The P2–O dis-
˚
Table 3
tance of 6a is comparable to that for 8 [1.509(11) A]
Suzuki reaction (Scheme 3(b))
[13a] or for [Ph2PCH2P(@O)Ph2][Pd(Me)Cl] [1.508(4)
˚
Catalyst
Yield (%)
A] [13b]. The P1–Pd and Pd–O distances of 6a are com-
˚
parable to the corresponding distances of 7a [2.186(3) A]
6a
6b
6c
6d
71
60
57
64
˚
and 8 [2.088(12) A] [13a], respectively (see Chart 2).
To estimate the catalytic activity of 6, we employed
the Sonogashira coupling reaction [14]. Iodobenzene

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K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
1
1
(dd, JPC = 59 Hz, JPC = 30 Hz, P@C), 153.6 (s, o-C
Me
Me
Ph2
P
1
Me
Me
Me
of Mes*), 150.1 (s, p-C of Mes*), 139.4 (dd, JPC = 68
O
3
Hz, JPC = 24 Hz, ipso-C of Mes*), 138.9 (s, p-Tol),
Fe
2
1
Me
PdCl2
134.2 (d, JPC = 19 Hz, o-Tol), 133.7 (dd, JPC = 16
P
3
3
Me
Hz, JPC = 4 Hz, ipso-Tol), 129.5 (d, JPC = 7 Hz,
m-Tol), 122.0 (s, m-C of Mes*), 38.3 (s, o-CMe3), 35.3
Ph2
Me
9
4
(s, p-CMe3), 33.2 (d, JPC = 7 Hz, o-CMe3), 31.8 (s, p-
CMe3), 22.5 (dd, 2JPC = 15 Hz, 2JPC = 11 Hz, P@CMe),
21.8 (s, p-C6H4CH3).
Chart 3.
3. Conclusion
4.3. Preparation of 1c
We have demonstrated the preparation of 3-oxo-1,3-
diphosphapropenes 5a–d which have been used as the
P@C–P@O chelate ligands of palladium(II) complexes
6a–d. The molecular structure of 6a was confirmed by
the X-ray crystallography. The catalytic activities of 6
in some cross-coupling reactions were investigated as a
property of 3-oxo-1,3-diphosphapropene ligands.
Although 6 did not show efficient catalytic activity in
the Sonogashira or Suzuki coupling reactions, the preli-
minary results prompt us to survey unique activity of the
P@C–P@O ligands.
To a THF solution of p-bromoanisole (2.60 mmol)
was added t-butyllithium at À78 ꢁC, and stirred for
0.5 h. The reaction mixture was added to a solution of
4 (ca. 1.30 mmol) in THF at À78 ꢁC. The reaction mix-
ture was allowed to warm to room temperature and stir-
red for 2 h. The solvent was removed in vacuo and the
residual materials were purified by silica-gel column
chromatography (hexane/AcOEt = 19:1) to afford 1c:
356 mg (0.65 mmol) (50% yield). Colorless amorphous
solid; 31P{1H} NMR (162 MHz, CDCl3) d = 284.8 (d,
2
1
2JPP = 214 Hz), 7.8 (d, JPP = 214 Hz); H NMR (400
MHz, CDCl3) d = 7.51–7.47 (m, 4H, arom), 7.43 (s,
2H, arom), 6.96–6.94 (m, 4H, arom), 3.85 (s, 6H,
3
4. Experimental
OCH3), 1.51 (s, 18H, o-tBu), 1.42 (dd, JPH = 14 Hz,
3JPH = 10 Hz, 3H, CH3), 1.37 (s, 9H, p-tBu); 13C{1H}
1
4.1. Preparation of 4
NMR (101 MHz, CDCl3) d = 182.3 (dd, JPC = 61 Hz,
4
1JPC = 29 Hz, P@C), 162.6 (d, JPC = 2 Hz, p-Anis),
To a solution of (Z)-2-bromo-1-(2,4,6-tri-t-butylphe-
nyl)-1-phosphapropene (0.50 g, 1.30 mmol) in THF (20
mL) was added butyllithium (1.30 mmol) at À78 ꢁC. To
the reaction mixture containing 3 was added phospho-
rus trichloride (ca. 2.5 mmol) in Et2O (10 mL) at À78
ꢁC. After being warmed to room temperature, the vola-
tile materials were removed in vacuo and the residue was
extracted with hexane. Removal of the solvent afforded
4: 0.52 g (1.30 mmol, >99% yield).
153.6 (s, o-C of Mes*), 150.1 (s, p-C of Mes*), 139.6
(dd, JPC = 68 Hz, JPC = 20 Hz, ipso-C of Mes*),
1
3
2
1
135.8 (d, JPC = 20 Hz, o-Anis), 128.1 (dd, JPC = 16
3
Hz, JPC = 10 Hz, ipso-Anis), 122.0 (s, m-C of Mes*),
3
114.4 (d, JPC = 8 Hz, o-Anis), 55.6 (s, p-C6H4OCH3),
4
38.4 (s, o-CMe3), 35.3 (s, p-CMe3), 33.1 (d, JPC = 7
Hz, o-CMe3), 32.0 (s, p-CMe3), 22.8 (dd, JPC = 32
Hz, JPC = 17 Hz, P@CMe).
2
2
4.4. Preparation of 1d
4.2. Preparation of 1b
To an Et2O solution of butyllithium (2.60 mmol) was
added a solution of 4 (ca. 1.30 mmol) in THF at À78 ꢁC.
The reaction mixture was allowed to warm to room tem-
perature and stirred for 2 h. The solvent was removed in
vacuo and the residue was purified by silica-gel column
chromatography (hexane/AcOEt = 19:1) to afford 1d:
264 mg (0.59 mmol) (45% yield). Pale yellow oil;
31P{1H} NMR (162 MHz, CDCl3) d = 277.0 (d,
To a THF solution of p-bromotoluene (2.60 mmol)
was added t-butyllithium at À78 ꢁC, and stirred for
0.5 h. The reaction mixture was added to a solution of
4 (ca. 1.30 mmol) in THF at À78 ꢁC. The reaction
mixture was allowed to warm to room temperature
and stirred for 2 h. The solvent was removed in vacuo
and the residual materials were purified by silica-gel col-
umn chromatography (hexane/AcOEt = 19:1) to afford
1b: 294 mg (0.57 mmol) (44% yield). Colorless amor-
phous solid; 31P{1H} NMR (162 MHz, CDCl3) d =
2
2JPP = 214 Hz), À5.4 (d, JPP = 214 Hz); 1H NMR
(400 MHz, CDCl3) d = 7.47 (s, 2H, arom), 7.43 (s, 2H,
arom), 1.55 (s, 18H, o-tBu), 1.35 (s, 9H, p-tBu), 1.75–
1.30 (m, 21H, nBu, Me); 13C{1H} NMR (101 MHz,
2
2
289.0 (d, JPP = 243 Hz), 8.5 (d, JPP = 243 Hz); 1H
NMR (400 MHz, CDCl3) d = 7.53–7.49 (m, 6H, arom),
7.27–7.25 (m, 4H, arom), 2.45 (s, 6H, p-CH3), 1.59 (s,
18H, o-tBu), 1.37 (s, 9H, p-tBu), 1.48–1.43 (m, 3H,
CH3); 13C{1H} NMR (101 MHz, CDCl3) d = 181.3
1
1
CDCl3) d = 183.4 (dd, JPC = 60 Hz, JPC = 32 Hz,
P@C), 153.7 (s, o-C of Mes*), 150.0 (s, p-C of Mes*),
1
3
139.1 (dd, JPC = 68 Hz, JPC = 20 Hz, ipso-C of
Mes*), 122.2 (s, m-C of Mes*), 38.3 (s, o-CMe3), 35.3

K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
4813
4
1
1
(s, p-CMe3), 33.0 (d, JPC = 7 Hz, o-CMe3), 31.8 (s, p-
d = 173.6 (dd, JPC = 77 Hz, JPC = 63 Hz, P@C),
2
4
CMe3), 28.9 (d, JPC = 14 Hz, CH2), 26.4 (dd,
162.6 (d, JPC = 2 Hz, p-Anis), 153.6 (s, o-C of Mes*),
1JPC = 18 Hz, JPC = 14 Hz, CH2), 24.8 (d, JPC = 12
150.7 (s, p-C of Mes*), 136.6 (dd, JPC = 67 Hz,
3
3
1
2
2
3
Hz, CH2), 21.5 (dd, JPC = 15 Hz, JPC = 10 Hz,
P@CMe), 14.1 (s, CH3).
3JPC = 18 Hz, ipso-C of Mes*), 134.2 (d, JPC = 11 Hz,
1
m-Anis), 123.9 (d, JPC = 110 Hz, ipso-Anis), 122.3 (s,
m-C of Mes*), 114.1 (d, JPC = 13 Hz, o-Anis), 55.6 (s,
2
4.5. Oxidation of 1 with m-CPBA
p-C6H4OCH3), 38.2 (s, o-CMe3), 35.3 (s, p-CMe3), 33.1
4
(d, JPC = 5 Hz, o-CMe3), 31.7 (s, p-CMe3), 20.8 (dd,
2
A solution of 1a (0.550 g, 1.13 mmol) and m-CPBA
(1.13 mmol) in CH2Cl2 (20 mL) was stirred at room tem-
perature for 2 h. The solvent was removed in vacuo and
the residual solid was purified by silica-gel column chro-
matography (hexane/AcOEt = 1:1) to afford 5a; 0.43 g
(0.85 mmol) (75% yield). Compound 5a: Colorless crys-
tals, mp 168–169 ꢁC; 31P{1H} NMR (162 MHz, CDCl3)
2JPC = 14 Hz, JPC = 5 Hz, P@CMe); IR (KBr)
m = 1176 (P@O) cmÀ1. Compound 5d (70% yield): Col-
orless crystals, mp 120–121 ꢁC; 31P{1H} NMR (162
2
MHz, CDCl3) d = 309.8 (d, JPP = 92 Hz), 47.0 (d,
1
2JPP = 92 Hz); H NMR (400 MHz, CDCl3) d = 7.33
(s, 2H, arom), 1.37 (s, 18H, o-tBu), 1.83–1.30 (m, 21H,
nBu, Me), 1.23 (s, 9H, p-tBu); 13C{1H} NMR (101
MHz, CDCl3) d = 172.1 (pt, (1JPC + 1JPC)/2 = 64 Hz,
P@C), 153.7 (s, o-C of Mes*), 150.9 (s, p-C of Mes*),
2
2
d = 320.9 (d, JPP = 115 Hz), 33.0 (d, JPP = 115 Hz);
1H NMR (400 MHz, CDCl3) d = 7.86–7.81 (m, 4H,
arom), 7.48–7.43 (m, 6H, arom), 7.40 (s, 2H, Mes*),
1.50–1.47 (m, 3H, CH3), 1.47 (s, 18H, o-tBu), 1.29 (s,
9H, p-tBu); 13C{1H} NMR (101 MHz, CDCl3)
1
3
135.8 (dd, JPC = 66 Hz, JPC = 15 Hz, ipso-C of
Mes*), 122.3 (s, m-C of Mes*), 38.2 (s, o-CMe3), 35.3
4
(s, p-CMe3), 33.0 (d, JPC = 11 Hz, o-CMe3), 31.6 (s,
1
1
1
3
d = 172.1 (dd, JPC = 76 Hz, JPC = 64 Hz, P@C),
153.8 (s, o-C of Mes*), 151.0 (s, p-C of Mes*), 136.3
p-CMe3), 29.3 (dd, JPC = 67 Hz, JPC = 7 Hz, CH2),
2
3
24.6 (d, JPC = 15 Hz, CH2), 24.2 (d, JPC = 3 Hz,
1
3
2
2
(dd, JPC = 66 Hz, JPC = 18 Hz, ipso-C of Mes*),
CH2), 20.6 (dd, JPC = 15 Hz, JPC = 5 Hz, P@CMe),
1
3
132.5 (dd, JPC = 102 Hz, JPC = 4 Hz, ipso-Ph), 132.5
(d, JPC = 9 Hz, m-Ph), 132.2 (d, JPC = 2 Hz, p-Ph),
128.7 (d, JPC = 12 Hz, o-Ph), 122.5 (s, m-C of Mes*),
14.0 (s, CH3); IR (KBr) m = 1170 (P@O) cmÀ1
4.6. Preparation of 5a-Cl
.
3
4
2
4
38.2 (s, o-CMe3), 35.3 (s, p-CMe3), 33.2 (d, JPC = 7
Hz o-CMe3), 31.7 (s, p-CMe3), 22.9 (dd, JPC = 14 Hz,
2
To a solution of 2,2-dichloro-1-(2,4,6-tri-t-butylphe-
nyl)-1-phosphaethene (0.500 g, 1.43 mmol) in THF (20
mL) was added butyllithium (1.58 mmol) at À100 ꢁC.
After being stirred for 10 min, diphenylphosphinic chlo-
ride (1.60 mmol) was added to the reaction mixture. The
reaction mixture was stirred for 1 h at À100 ꢁC and was
allowed to warm to room temperature. The solvent was
removed in vacuo and silica-gel column chromatogra-
phy (hexane/AcOEt 2:1) gave 5a-Cl (0.257 g, 34% yield).
Colorless crystals, mp 163–164 ꢁC; 31P{1H} NMR (162
2JPC = 6 Hz, P@CMe); IR (KBr) m = 1178 (P@O)
cmÀ1; HR-ESI-MS found: m/z 527.2603; calcd for
C32H42OP2 Æ Na (M+ + Na): 527.2603. Compounds
5b-d were prepared in a similar manner. Compound 5b
(70% yield): Colorless solid, mp 164–165 ꢁC; 31P{1H}
2
NMR (162 MHz, CDCl3) d = 318.2 (d, JPP = 116
2
Hz), 33.2 (d, JPP = 116 Hz); 1H NMR (400 MHz,
CDCl3) d = 7.74–7.69 (m, 4H, arom), 7.40 (s, 2H,
arom), 7.25–7.23 (m, 4H, arom), 2.34 (s, 6H, p-CH3),
1.49–1.43 (m, 3H, CH3), 1.43 (s, 18H, o-tBu), 1.29 (s,
9H, p-tBu); 13C{1H} NMR (101 MHz, CDCl3)
2
MHz, CDCl3) d = 319.7 (d, JPP = 80 Hz), 30.0 (d,
1
2JPP = 80 Hz); H NMR (400 MHz, CDCl3) d = 7.87–
1
1
d = 172.9 (dd, JPC = 76 Hz, JPC = 64 Hz, P@C),
153.8 (s, o-C of Mes*), 150.9 (s, p-C of Mes*), 142.3
7.84 (m, 4H, arom), 7.55–7.53 (m, 2H, arom), 7.48–
7.46 (m, 4H, arom), 7.42 (s, 2H, arom), 1.43 (s, 18H,
o-tBu), 1.32 (s, 9H, p-tBu); 13C{1H} NMR (101 MHz,
CDCl3) d = 158.7 (pt, (1JPC + 1JPC)/2 = 83 Hz, P@C),
153.9 (s, o-C of Mes*), 151.7 (s, p-C of Mes*), 133.5
4
1
(d, JPC = 3 Hz, p-Tol), 136.6 (dd, JPC = 67 Hz,
3JPC = 18 Hz, ipso-C of Mes*), 132.6 (d, JPC = 10 Hz,
3
1
3
m-Tol), 129.4 (dd, JPC = 105 Hz, JPC = 3 Hz, ipso-
2
1
3
Tol), 129.4 (d, JPC = 12 Hz, o-Tol), 122.4 (s, m-C of
(dd, JPC = 61 Hz, JPC = 11 Hz, ipso-C of Mes*),
132.7 (s, o-Ph), 132.64 (s, p-Ph), 132.61 (s, m-Ph),
Mes*), 38.2 (s, o-CMe3), 35.3 (s, p-CMe3), 33.1 (d,
4JPC = 7 Hz o-CMe3), 31.7 (s, p-CMe3), 22.0 (s, p-
1
3
131.1 (dd, JPC = 107 Hz, JPC = 2 Hz, ipso-Ph), 122.8
(s, m-C of Mes*), 38.2 (s, o-CMe3), 35.4 (s, p-CMe3),
2
2
C6H4CH3), 20.9 (dd, JPC = 14 Hz, JPC = 5 Hz,
P@CMe); IR (KBr) m = 1184 (P@O) cmÀ1. Compound
5c (75% yield): Colorless solid, mp 140–142 ꢁC;
31P{1H} NMR (162 MHz, CDCl3) d = 316.8 (d,
4
33.3 (d, JPC = 7 Hz o-CMe3), 31.7 (s, p-CMe3); IR
(KBr) m = 1190 cmÀ1 (P@O).
2
2JPP = 116 Hz), 32.6 (d, JPP = 116 Hz); 1H NMR
4.7. Preparation of 6
(400 MHz, CDCl3) d = 7.70–7.66 (m, 4H, arom), 7.33
(s, 2H, arom), 6.90–6.88 (m, 4H, arom), 3.70 (s, 6H, p-
OCH3), 1.42–1.31 (m, 3H, CH3), 1.37 (s, 18H, o-tBu),
1.23 (s, 9H, p-tBu); 13C{1H} NMR (101 MHz, CDCl3)
A solution of 5a (200 mg, 0.397 mmol) and
PdCl2(CH3CN)2 (0.397 mmol) in dichloromethane (30
mL) was stirred at room temperature for 0.5 h. Hexane

4814
K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
(10 mL) was added to the reaction mixture and the pre-
cipitates were collected by filtration. Purification by sil-
ica-gel column chromatography (hexane/AcOEt = 1:2)
afforded 6a: 230 mg (0.337 mmol) (85%). Yellowish-
brown solid (CH2Cl2/toluene), mp 144–145 ꢁC;
31P{1H} NMR (162 MHz, CDCl3) d = 255.1 (d,
cmÀ1. Complex 6d (75% yield): Yellowish-brown amor-
phous solid; 31P{1H} NMR (162 MHz, CDCl3)
2
2
1
d = 249.0 (d, JPP = 50 Hz), 90.0 (d, JPP = 50 Hz); H
3
NMR (400 MHz, CDCl3) d = 7.49 (d, 2H, JPH = 3
Hz, arom), 1.63 (s, 18H, o-tBu), 1.45 (dd, JPH = 30
3
3
Hz, JPH = 15 Hz, 3H, CH3), 2.05–1.40 (m, 18H, nBu),
2JPP = 62 Hz), 65.0 (d, JPP = 62 Hz); H NMR (400
MHz, CDCl3) d = 7.79–7.75 (m, 6H, arom), 7.62–7.60
(m, 4H, arom), 7.55–7.54 (m, 2H, arom), 1.70 (s, 18H,
o-tBu), 1.32 (s, 9H, p-tBu), 1.37–1.30 (m, 3H, CH3);
13C{1H} NMR (101 MHz, CDCl3) d = 156.6 (d,
2JPC = 3 Hz, o-C of Mes*), 156.1 (s, p-C of Mes*),
1.20 (s, 9H, p-tBu); 13C{1H} NMR (101 MHz, CDCl3)
2
1
1
1
d = 157.1 (dd, JPC = 64 Hz, JPC = 29 Hz, P@C),
156.5 (d, JPC = 3 Hz, o-C of Mes*), 155.9 (s, p-C of
Mes*), 124.8 (d, JPC = 9 Hz, m-C of Mes*), 116.9
(brd, JPC = 7 Hz, ipso-C of Mes*), 39.5 (s, o-CMe3),
3
2
1
35.7 (s, p-CMe3), 34.8 (s, o-CMe3), 31.3 (s, p-CMe3),
1
1
1
3
153.7 (dd, JPC = 78 Hz, JPC = 28 Hz, P@C), 134.8
27.9 (dd, JPC = 65 Hz, JPC = 6 Hz, CH2), 24.2 (d,
3
3
3
(d, JPC = 2 Hz, m-C of Mes*), 132.4 (d, JPC = 11
2JPC = 15 Hz, CH2), 23.6 (d, JPC = 5 Hz, CH2), 19.6
2
2
2
Hz, m-Ph), 130.0 (d, JPC = 13 Hz, o-Ph), 125.9 (d,
(dd, JPC = 16 Hz, JPC = 7 Hz, P@CMe), 14.1 (s,
1JPC = 8 Hz, ipso-Ph), 124.9 (d, JPC = 9 Hz, p-Ph),
CH3); IR (KBr) m = 1122 (P@O) cmÀ1
4.8. X-ray crystallography for 5c
.
4
1
116.7 (d, JPC = 10 Hz, ipso-C of Mes*), 39.6 (s, o-
CMe3), 35.8 (s, p-CMe3), 34.7 (s, o-CMe3), 31.3 (s, p-
2
2
CMe3), 19.7 (dd, JPC = 15 Hz, JPC = 6 Hz, P@CMe).
IR (KBr) m = 1120 (P@O) cmÀ1; HR-ESI-MS found:
m/z 645.1431; calcd for C32H42ClOP2Pd (M+–Cl):
645.1429. Complexes 6b-d were prepared in a similar
manner. Complex 6b (84% yield): Yellowish-brown so-
lid, mp 163–164 ꢁC; 31P{1H} NMR (162 MHz, CDCl3)
C34H46O3P2, M = 564.68, crystal dimensions: 0.20 ·
0.20 · 0.10 mm3, monoclinic, space group P21/c (No.
˚
˚
14), a = 16.3881(6) A, b = 10.2144(3) A, c = 19.9335(6)
3
˚
˚
A, b = 108.0622(7)ꢁ, V = 3172.3(2) A , Z = 4, T = 133
K, 2hmax = 55.0ꢁ, q = 1.182 g cmÀ1, l(Mo Ka) = 0.168
mmÀ1, F000 = 1216, 25165 measured reflections, 7108
unique reflections (Rint = 0.044), R1 = 0.057 (I > 2.0r(I)),
Rw = 0.132 (all data) (CCDC-269267).
2
2
d = 250.7 (d, JPP = 62 Hz), 65.4 (d, JPP = 62 Hz);1H
NMR (400 MHz, CDCl3) d = 7.55–7.50 (m, 4H, arom),
7.42 (s, 2H, Mes*), 7.29 (brs, 4H, arom), 2.31 (s, 6H, p-
3
CH3), 1.52 (s, 18H, o-tBu), 1.31 (dd, JPH = 29 Hz,
3JPH = 15 Hz, 3H, CH3), 1.19 (s, 9H, p-tBu); 13C{1H}
NMR (101 MHz, CDCl3) d = 156.5 (s, o-C of Mes*),
4.9. X-ray crystallography for 6a
1
155.9 (s, p-C of Mes*), 155.4 (dd, JPC = 77 Hz,
C32H42Cl2OP2Pd Æ CH2Cl2, M = 766.87, crystal dimen-
sions: 0.25 · 0.20 · 0.20 mm3, monoclinic, space group
1JPC = 29 Hz, P@C), 145.7 (s, m-C of Mes*), 132.3 (d,
2
3JPC = 11 Hz, m-Tol), 130.3 (d, JPC = 13 Hz, o-Tol),
P21 (No. 4), a = 8.8009(3) A, b = 16.1300(6) A, c =
˚
˚
3
4
1
˚
˚
124.8 (d, JPC = 9 Hz, p-Tol), 122.0 (dd, JPC = 110
13.2923(5) A, b = 103.307(2)ꢁ, V = 1936.3(3) A , Z =
2, T = 223 K, 2hmax = 55.0ꢁ, q = 1.387 g cmÀ1, l(Mo
Ka) = 0.907 mmÀ1, F000 = 788, 14672 measured reflec-
tions, 4303 unique reflections (Rint = 0.040), R1 = 0.042
(I > 2.0r(I)), Rw = 0.052 (all data) (CCDC-249371).
3
1
Hz, JPC = 7 Hz, ipso-Tol), 116.7 (d, JPC = 8 Hz,
ipso-C of Mes*), 39.5 (s, o-CMe3), 35.7 (s, p-CMe3),
34.6 (s, o-CMe3), 31.3 (s, p-CMe3), 22.3 (s, p-
2
2
C6H4CH3), 19.9 (dd, JPC = 15 Hz, JPC = 6 Hz,
P@CMe); IR (KBr) m = 1119 (P@O) cmÀ1. Complex
6c (82% yield): Yellowish-brown solid, mp 175–177 ꢁC;
31P{1H} NMR (162 MHz, CDCl3) d = 249.0 (d,
4.10. Sonogashira coupling reaction
2JPP = 64 Hz), 64.8 (d, JPP = 64 Hz); H NMR (400
MHz, CDCl3) d = 7.64–7.59 (m, 4H, arom), 7.47 (d,
3JPH = 4 Hz, 2H, Mes*), 7.04–7.01 (m, 4H, arom),
3.83 (s, 6H, p-OCH3), 1.59 (s, 18H, o-tBu), 1.38 (dd,
A solution of iodobenzene (2.0 mmol), phenylacety-
lene (2.0 mmol), catalyst (6, 0.050 mmol), and copper(I)
iodide (0.050 mmol) in triethylamine (8 mL) was stirred
for 4 h at room temperature. The volatile materials were
removed in vacuo and the residue was extracted with
hexane. Silica-gel column chromatography (hexane) of
the hexane extracts afforded diphenylacetylene.
2
1
3JPH = 30 Hz, JPH = 14 Hz, 3H, CH3), 1.25 (s, 9H, p-
3
tBu); 13C{1H} NMR (101 MHz, CDCl3) d = 164.6 (d,
4JPC = 3 Hz, p-Anis), 156.6 (d, JPC = 3 Hz, m-C of
3
1
Mes*), 155.9 (s, p-C of Mes*), 155.5 (dd, JPC = 76
Hz, JPC = 3 Hz, P@C), 134.5 (d, JPC = 12 Hz, m-
1
3
4.11. Suzuki coupling reaction
2
Anis), 124.8 (d, JPC = 9 Hz, o-C of Mes*), 116.8 (d,
1JPC = 3 Hz, ipso-C of Mes*), 116.7 (d, JPC = 8 Hz,
A solution of iodobenzene (2.0 mmol), phenylboric
acid (2.0 mmol), catalyst (6, 0.080 mmol), and potas-
sium carbonate (4.0 mmol) in THF (15 mL) was refluxed
for 20 h. After being cooled to room temperature, the
reaction mixture was concentrated in vacuo. The residue
1
2
ipso-Anis), 115.6 (d, JPC = 14 Hz, o-Anis), 55.2 (s, p-
C6H4OCH3), 39.5 (s, o-CMe3), 35.7 (s, p-CMe3), 34.6
2
(s, o-CMe3), 31.3 (s, p-CMe3), 19.9 (dd, JPC = 15 Hz,
2JPC = 6 Hz, P@CMe); IR (KBr) m = 1119 (P@O)

K. Nishide et al. / Journal of Organometallic Chemistry 690 (2005) 4809–4815
4815
(c) H. Liang, S. Ito, M. Yoshifuji, Org. Biomol. Chem. 1 (2003)
3054;
(d) S. Ito, H. Liang, M. Yoshifuji, J. Organomet. Chem. 690
(2005) 2531.
was extracted with hexane and purified by silica-gel col-
umn chromatography (hexane) to afford biphenyl.
[8] V.V. Grushin, Chem. Rev. 104 (2004) 1629.
[9] (a) S. Ito, S. Kimura, M. Yoshifuji, Chem. Lett. (2002) 708;
(b) S. Ito, S. Kimura, M. Yoshifuji, Bull. Chem. Soc. Jpn. 76
(2003) 405.
[10] The oxidized product 5c seemed to have been formed during the
recrystallization. Crystal data: C34H46O2.3P2, M = 553.48, crystal
dimensions: 0.20 · 0.20 · 0.15 mm3, monoclinic, space group
Acknowledgments
This work was supported in part by Grants-in-Aid
for Scientific Research (Nos. 13303039 and 14044012)
from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan. H. Liang is grateful to
the Japan Society for the Promotion of Science for the
Postdoctoral Fellowships for Foreign Researchers.
˚
˚
P21/c (No. 14), a = 16.4465(6) A, b = 10.1438(3) A, c = 19.8486(6)
3
˚
˚
A, b = 107.7497(8)ꢁ, V = 3153.7(2) A , Z = 4, T = 153 K, 2hmax
=
55.0ꢁ, q = 1.166 g cmÀ1, l(Mo Ka) = 0.167 mmÀ1, F000 = 1193,
23096 measured reflections, 6975 unique reflections (Rint = 0.061),
R1 = 0.061 (I > 2.0r(I)), Rw = 0.148 (all data) (CCDC-268951).
Both compounds 1c and 5c were observed in ca. 2:1 ratio in 31P
NMR spectrum after attempted recrystallization of 1c.
[11] J.A. Thomas, T.A. Hamor, Acta Crystallogr., Sect. C 49 (1993)
355.
References
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[12] The observed complex [dP = 257.7, 57.8 (2JPP = 71 Hz)] gradually
decomposed affording an unidentified complex [dP = 47.3, 29.6
(2JPP = 5 Hz)].
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