Preparation of some dinuclear rhodium complexes with the orthometallated ligand [2,6-(PPh2CH2)2C6H3] - and their catalytic activity for polymerization of phenylacetylene

Article abstract of DOI:10.1016/S0022-328X(99)00710-X

Reaction of 1,3-(PPh₂CH₂)₂C₆H₄ (PCHP) with [RhCl(COD)]₂ in isopropanol produced a mixture of dinuclear complexes [RhCl(COD)]₂(μ₂-PCHP), RhH(PCP)(μ-Cl)₂Rh(COD), and [RhHCl(PCP)]₂(μ₂-PCHP). Reaction of RhH(PCP)(μ-Cl)₂Rh(COD) with CCl₄ produced RhCl(PCP)(μ-Cl)₂Rh(COD). The solid-state structure of the latter complex has been characterized by X-ray diffraction. With the exception of [RhHCl(PCP)]₂(μ₂-PCHP), all the dinuclear complexes in THF are catalytically active for the polymerization of phenylacetylene.

Full text of DOI:10.1016/S0022-328X(99)00710-X

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Journal of Organometallic Chemistry 598 (2000) 228–234
Preparation of some dinuclear rhodium complexes with the
orthometallated ligand [2,6-(PPh2CH2)2C6H3]− and their catalytic
activity for polymerization of phenylacetylene
Junzhi Yao a, Wing Tak Wong b, Guochen Jia a,*
a Department of Chemistry, The Hong Kong Uni6ersity of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
b Department of Chemistry, Uni6ersity of Hong Kong, Pokfulam, Hong Kong
Received 6 August 1999; received in revised form 4 November 1999
Abstract
Reaction of 1,3-(PPh2CH2)2C6H4 (PCHP) with [RhCl(COD)]2 in isopropanol produced a mixture of dinuclear complexes
[RhCl(COD)]2(m2-PCHP), RhH(PCP)(m-Cl)2Rh(COD), and [RhHCl(PCP)]2(m2-PCHP). Reaction of RhH(PCP)(m-Cl)2Rh(COD)
with CCl4 produced RhCl(PCP)(m-Cl)2Rh(COD). The solid-state structure of the latter complex has been characterized by X-ray
diffraction. With the exception of [RhHCl(PCP)]2(m2-PCHP), all the dinuclear complexes in THF are catalytically active for the
polymerization of phenylacetylene. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Rhodium; Phosphine; Orthometallation; Polymerization acetylene
1. Introduction
2. Results and discussion
2.1. Preparation of dinuclear complexes
The formation and properties of transition-metal
complexes with [2,6-(PR2CH2)2C6H3]− and related or-
thometallated tridentate ligands have attracted consid-
erable attention. Transition-metal complexes with these
ligands have been reported for rhodium [1–15], iridium
[1,8,9,15–17], ruthenium [18], palladium [1,7,10,12,19–
26], platinum [1,19–21,23–25,27], and nickel [1,12,28].
These complexes are usually prepared from the reac-
tions of 1,3-(PR2CH2)2C6H4 or 1-R%-2,6-(PR2CH2)2-
C6H3 (R%=alkyl, alkoxyl) with low-valent metal com-
plexes. Most often, mononuclear complexes were ob-
tained from these reactions. We have recently prepared
interesting dinuclear complexes containing 2,6-(PPh2-
CH2)2C6H3 (PCP) from the reactions of [RhCl(COD)]2
with 1,3-(PPh2CH2)2C6H4 (PCHP). Some of the dinu-
clear complexes were found to be catalytically active for
polymerization of PhCꢀCH.
Reaction of ligand 1 with [RhCl(COD)]2 (2) in iso-
propanol produced a mixture of dinuclear complexes
[RhCl(COD)]2(m2-PCHP) (3), RhH(PCP)(m-Cl)2Rh-
(COD) (4), and [RhHCl(PCP)]2(m2-PCHP) (5), the
amounts of which depend on the reaction conditions
(see Scheme 1). Reaction of ligand 1 with one equiva-
lent of [RhCl(COD)]2 in isopropanol led to a mixture of
complexes 3 and 4 in a ratio of ca. 1.4:1 along with a
very minor amount of complex 5. Reaction of ligand 1
with 0.55 equivalents of [RhCl(COD)]2 led to a mixture
of complexes 4 and 5 in a ratio of ca. 1:1 along with a
very minor amount of complex 3. There is no evidence
for the production of the coordinatively unsaturated
complex RhHCl(PCP). Interestingly, the related
complex RhHCl[2,6-((t-Bu)2PCH2)2C6H3] has been
prepared from the reaction of 1,3-((t-Bu)2PCH2)2C6H4
with RhCl3·H2O [1] or from the reaction of 1-OMe-
2,6-((t-Bu)2PCH2)2C6H3 with [RhCl(COE)2]2 [10].
The origin of the failure to obtain RhHCl(PCP) in
our case could be the less steric bulkiness of the
PCP ligand and the Lewis-acidity character of the
* Corresponding author. Fax: +852-2358-1594.
E-mail address: chjiag@usthk.ust.hk (G. Jia)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00710-X

J. Yao et al. / Journal of Organometallic Chemistry 598 (2000) 228–234
229
olefinic protons were observed at ca. 2.9 and 5.6 ppm.
1
The H-NMR data for the COD ligand are very similar
to those of related complexes RhCl(COD)(PR3) [29]. In
the 13C-NMR spectrum, the signals due to the CH2
groups of the COD ligand were observed at 28.6 and
32.6 ppm, and those assignable to the olefinic carbons
of the COD ligand were observed at 70.3 and 104.1
ppm. Consistent with the structure, the 31P-NMR spec-
trum showed the PPh2 signal at 26.3 ppm as a doublet.
The NMR and mass spectroscopic data support the
structure of 4. The FAB mass spectrum showed the
expected molecular ion peak at 859. The CH2 signals of
the COD ligand were observed in the regions of 1.35–
1.50 ppm and 2.10–2.30 ppm and the olefinic signals at
1
3.38 and 3.80 ppm in the H-NMR spectrum. In the
13C-NMR spectrum, the COD signals were observed at
30.3 ppm for CH2 and at 77.4 and 77.9 ppm for the
olefinic carbons. The 1H-NMR spectrum showed a
hydride signal at −18.20 ppm as a doublet of triplet.
The structural assignment is further supported by its
reaction with CCl4 to give the analogous complex
RhCl(PCP)(m-Cl)2Rh(COD) (6). The solid-state struc-
ture of compound 6 has been confirmed by an X-ray
diffraction study (see below). The reported complex
closely related to 6 is RhCl(NCN)(m-Cl)2Rh(COD)
(NCN=2,6-(NMe2CH2)2C6H3) [30].
Scheme 1.
rhodium center. In this regard, it is noted that the
six-coordinated complex RhHCl(PPh3)(PCP) has been
prepared from the reaction of ligand
[RhCl(COE)2]2 in the presence of PPh3 [4].
Complexes 3–5 can be readily purified by recrystal-
lization and column chromatography. The presence of
1
with
The structure of complex 5 can be readily assigned
1
based on the 31P- and H-NMR spectroscopic data. In
particular, the 31P-NMR spectrum showed a doublet of
doublet signal for the PCP ligand at 47.4 ppm and a
doublet of triplet signal for the bridging diphosphine
1
the COD ligand in complex 3 is supported by the H-
1
and 13C-NMR spectra. In the H-NMR spectrum, the
1
ligand at 18.8 ppm. The H-NMR spectrum showed a
signals of the CH2 protons of the COD ligand were
observed in the region 1.84–2.47 ppm and those of the
hydride signal at −17.20 (dq, J(RhꢁH)=24 Hz,
J(PH)=15 Hz), indicating that the hydride is cis to the
three phosphorus atoms and that the bridging ligand is
trans to the orthometallated carbon.
2.2. Description of the structure of
RhCl(PCP)(v-Cl)2Rh(COD) (6)
The
molecular
structure
of
RhCl(PCP)(m-
Cl)2Rh(COD) in solid state is shown in Fig. 1. The
crystallographic details are given in Table 1 and se-
lected bond distances and angles in Table 2. The com-
plex contains a four-coordinated and a six-coordinated
rhodium center bridged by two chlorides.
The geometry around Rh(1) can be described as a
distorted octahedron. The distortion can be attributed
to the special geometry of the PCP ligand. The
P(1)ꢁRh(1)ꢁC(1) (82.39(1)°), P(2)ꢁRh(1)ꢁC(1) (83.0(3)°)
and P(1)ꢁRh(1)ꢁP(2) (165.2(1)°) angles are close to
those observed in rhodium complexes containing simi-
lar ligands, for example, RhCl(CH3)((P(t-Bu)2CH2)2-
C6H-3,5-Me2) [9], trans-RhCl2(EtOH)((PCy2CH2)2-
C6H3) [5], trans-RhCl2(MeOH)((PCy2CH2)2C6H3) [5],
trans-RhCl2(H2O)((PCy2CH2)2C6H3) [5], and RhCl-
Fig. 1. The molecular structures of RhCl(PCP)(m-Cl)2Rh(COD)·
CH2Cl2. The solvent molecule is omitted for clarity.

230
J. Yao et al. / Journal of Organometallic Chemistry 598 (2000) 228–234
Table 1
distances in the COD ligand and Rh(2)ꢁligand bond
distances are normal compared to those in related
Rh(COD) complexes such as [Rh(COD)]2(m-Cl)2 [32],
[RuRhHCl(COD)(dppm)2]BF4 [33], and Cp2TiRh-
(COD)(m-CH2)(m-Cl) [34].
Crystallographic details for RhCl(PCP)(m-Cl)2Rh(COD)·CH2Cl2
Formula
C41H41Cl5P2Rh2
978.80
Red, block
Triclinic
Formula weight
Color and habit
Crystal system
Lattice type
Primitive
2.3. Reactions with PhCꢀCH
(
Space group
P1 (no. 2)
,
a (A)
11.891(1)
12.950(1)
14.405(1)
72.83(2)
69.72(2)
85.60(2)
1987.2(5)
2
,
b (A)
During the process of studying the reactivity of com-
plexes 3–6 toward terminal acetylenes, it was found
that 3, 4, and 6 are all catalytically active for polymer-
ization of phenylacetylene (Eq. (1)). As indicated by the
1H- and the 13C-NMR spectra, the poly(phenyl-
acetylene) formed from these reactions has a cis–trans-
oidal structure [35,36]. Unfortunately, we have not been
able to detect the intermediates for the polymerization
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc. (g cm−3
F(000)
Radiation (A)
)
1.636
984
Mo–Ka
(u=0.71073)
65–63
,
reactions. The in situ 31P- and H-NMR measurements
1
Scan range (°)
Exposure (min)
2qmax (°)
No. of reflections measured
No. of unique reflections measured
for the reactions using 3 and 6 as the catalytic precur-
sors in CD2Cl2 indicate that poly(phenylacetylene) was
formed within minutes, and that the only rhodium-con-
5
51.0
17942
6814
taining species detectable by the H- and 31P-NMR are
1
complexes 3 and 6. When complex 4 was used as the
catalytic precursor, a complicated uncharacteristic mix-
ture of rhodium species, which do not contain the
RhꢁH functional group, were produced along with the
(Rint=0.044)
All
non-hydrogen
atoms
Anomalous dispersion
No. of observed reflections
4746
[I\3.00|(I)]
452
10.50
0.069; 0.131
3.03
0.10
Table 2
No. of variables refined
Reflection/parameter ratio
Residuals: R; Rw
Goodness-of-fit indicator
Maximum shift/error in final cycle
,
Selected bond lengths (A) and angles (°) for RhCl(PCP)(m-Cl)2Rh-
(COD)·CH2Cl2
Bond lengths
Rh(1)ꢁCl(1)
Rh(1)ꢁCl(3)
Rh(1)ꢁP(2)
Rh(2)ꢁCl(1)
Rh(2)ꢁC(33)
Rh(2)ꢁC(37)
C(33)ꢁC(34)
C(34)ꢁC(35)
C(36)ꢁC(37)
C(38)ꢁC(39)
2.555(3)
2.344(3)
2.336(3)
2.412(4)
2.11(2)
2.11(1)
1.49(2)
1.58(3)
1.40(2)
1.49(2)
Rh(1)ꢁCl(2)
Rh(1)ꢁP(1)
Rh(1)ꢁC(1)
Rh(2)ꢁCl(2)
Rh(2)ꢁC(36)
Rh(2)ꢁC(40)
C(33)ꢁC(40)
C(35)ꢁC(36)
C(37)ꢁC(38)
C(39)ꢁC(40)
2.377(3)
2.312(3)
2.03(1)
2.404(3)
2.14(2)
2.15(1)
1.47(2)
1.53(3)
1.52(2)
1.49(2)
Maximum peak in final difference map
1.54
−3
,
(e A
)
−3
,
Minimum peak in final difference map (e A
)
−1.14
(CH3)(PEt3)((PMe2CH2)2C6H-3,5-Me2) [6]. The Rh(1)ꢁ
Cl(3) bond distance at 2.344(3) A is comparable to
those [5] observed in trans-RhCl2(EtOH)((PCy2CH2)2-
,
,
C6H3) (2.354(3), 2.376(3) A), trans-RhCl2(MeOH)-
Bond angles
,
((PCy2CH2)2C6H3) (2.342(3), 2.347(3) A), and trans-
C(1)ꢁRh(1)ꢁP(1)
C(1)ꢁRh(1)ꢁCl(1)
C(1)ꢁRh(1)ꢁCl(3)
P(1)ꢁRh(1)ꢁCl(1)
P(1)ꢁRh(1)ꢁCl(3)
P(2)ꢁRh(1)ꢁCl(2)
Cl(1)ꢁRh(1)ꢁCl(2)
Cl(2)ꢁRh(1)ꢁCl(3) 177.5(1)
Cl(1)ꢁRh(2)ꢁC(33) 157.3(5)
Cl(1)ꢁRh(2)ꢁC(37)
Cl(2)ꢁRh(2)ꢁC(33)
Cl(2)ꢁRh(2)ꢁC(37) 160.4(5)
C(33)ꢁRh(2)ꢁC(36) 82.4(7)
C(33)ꢁRh(2)ꢁC(40) 40.4(7)
C(36)ꢁRh(2)ꢁC(40) 90.6(6)
Rh(1)ꢁCl(1)ꢁRh(2)
C(34)ꢁC(33)ꢁC(40) 123(1)
C(35)ꢁC(36)ꢁC(37) 125(1)
82.39(1) C(1)ꢁRh(1)ꢁP(2)
83.0(3)
90.6(4)
165.2(1)
94.3(1)
101.2(1)
91.7(1)
93.2(1)
87.3(1)
93.2(5)
,
RhCl2(H2O)((PCy2CH2)2C6H3) (2.345(2), 2.371(2) A).
The two bridging chlorides are bonded to Rh(1) unsym-
173.5(3)
91.6(4)
93.5(1)
87.3(1)
87.4(1)
84.7(1)
C(1)ꢁRh(1)ꢁCl(2)
P(1)ꢁRh(1)ꢁP(2)
P(1)ꢁRh(1)ꢁCl(2)
P(2)ꢁRh(1)ꢁCl(1)
P(2)ꢁRh(1)ꢁCl(3)
Cl(1)ꢁRh(1)ꢁCl(3)
Cl(1)ꢁRh(2)ꢁCl(2)
Cl(1)ꢁRh(2)ꢁC(36)
Cl(1)ꢁRh(2)ꢁC(40) 162.3(4)
Cl(2)ꢁRh(2)ꢁC(36) 161.2(5)
Cl(2)ꢁRh(2)ꢁC(40)
C(33)ꢁRh(2)ꢁC(37) 99.4(7)
C(36)ꢁRh(2)ꢁC(37) 38.4(6)
C(37)ꢁRh(2)ꢁC(40) 81.9(6)
,
metrically with Rh(1)ꢁCl(1)=2.555(3)
A
and
,
Rh(1)ꢁCl(2)=2.377(3) A. The longer Rh(1)ꢁCl(1) bond
is undoubtedly caused by the stronger trans influence of
the orthometallated aryl ligand. For comparison, the
RhꢁCl bonds trans to orthometallated aryl ligands in
RhCl(CH3)((P(t-Bu)2CH2)2C6H-3,5-Me2) [9] and RhCl-
(CH3)((2 - P(t - Bu)2CH2) - 6 - (Et2NCH2)C6H - 3,5 - Me2)
90.4(5)
89.9(5)
4.5(4)
,
[31] were observed at 2.470(4) and 2.4576 (10) A,
respectively.
The overall geometry around Rh(2) is very similar to
that of [Rh(COD)]2(m-Cl)2 except that the Cl(1)ꢁ
Rh(2)ꢁCl(2) angle (87.3(1)°) is slightly larger than that
in [Rh(COD)]2(m-Cl)2 (85°) [32]. The CꢁC and CꢂC
91.2(1)
Rh(1)ꢁCl(2)ꢁRh(2)
C(33)ꢁC(40)ꢁC(39) 125(1)
C(36)ꢁC(37)ꢁC(38) 123(1)
96.0(1)

J. Yao et al. / Journal of Organometallic Chemistry 598 (2000) 228–234
231
polymers as indicated by the 31P- and 1H-NMR
spectroscopy.
In summary, we have prepared several interesting
dinuclear complexes with PCP or PCHP ligands. Binu-
clear complexes with Rh(COD) moiety were found to
be catalytically active for polymerization of phenyl-
acetylene to give stereo regular cis-transoidal
poly(phenylacetylene).
(1)
3. Experimental
It is possible that the active center for the polymer-
ization reaction is the Rh(COD) moiety. In fact, several
Rh(diene) complexes have been reported to be active
catalysts for polymerization of terminal aromatic
acetylenes, for example, [RhCl(diene)]2 (diene=COD,
NBD) [36–38], [Rh(SR)(COD)]2 (R=Ph [39],
C6F5[39,40]), [Rh(diene)(NꢁN)]+ (diene=NBD, COD;
NꢁN=bidentate nitrogen donor ligands) [36],
Rh(SC6F5)(PPh3)(COD) [39], RhCl(L)(COD) (L=neu-
tral nitrogen donors) [36], Rh(COD)BPh4/HSiR3 [41],
Rh(NBD)(B(C6H4-4-R)4) (R=H, C(CH3)3) [42],
TpRh(COD) [43], and Rh(CꢀCPh)(NBD)(PPh3)2 [44].
Like our systems, many of these Rh(diene) complexes
promote the formation of predominantly cis–trans-
oidal poly(phenylacetylene).
In contrast to complexes 3, 4 and 6, which effect
polymerization of phenylacetylene, no reaction was ob-
served when complex 5 was treated with phenyl-
acetylene. The lack of catalytic activity of complex 5 for
polymerization of phenylacetylene is consistent with the
assumption that the active center for polymerization of
phenylacetylene is the Rh(COD) moiety. The lack of
reactivity of complex 5 toward phenylacetylene is prob-
ably not surprising, as it is coordinatively saturated.
Although complexes 3, 4, and 6 are active for poly-
merization of phenylacetylene, these complexes failed to
effect polymerization of alkyl terminal acetylenes such
as t-BuCꢀH and 1-octyne. Others also noted that
aliphatic terminal acetylenes could not be polymerized
with Rh(diene) complexes [39,40]. The reason why our
complexes are inactive for polymerization of alkyl ter-
minal acetylenes is not clear, but it could be due to the
poorer coordination ability of alkyl terminal acetylenes
compared with phenylacetylene.
Microanalyses were performed by M-H-W Laborato-
1
ries (Phoenix, AZ, USA). H-, 13C{1H}- and 31P{1H}-
NMR spectra were collected on a Bruker ARX-300
spectrometer (300 MHz). 1H- and 13C{1H}-NMR
chemical shifts are relative to TMS, and 31P{1H}-NMR
chemical shifts relative to 85% H3PO4. The 31P{1H}-
NMR data are collected in Table 3. Molecular weights
of polymers were measured on a Shimadzu LC-4A
GPC spectrometer using THF as the eluent. All manip-
ulations were carried out at room temperature under
nitrogen atmosphere using standard Schlenk tech-
niques, unless otherwise stated. Solvents were distilled
under nitrogen from sodium–benzophenone (hexane,
diethyl ether, THF, benzene) or calcium hydride
(dichloromethane, CHCl3). The compounds [RhCl-
(COD)]2 [45], and 1,3-(PPh2CH2)2C6H4 (PCHP) [19]
were prepared according to literature methods. All
other reagents were used as purchased from Aldrich or
Strem, USA.
3.1. Preparation of [RhCl(COD)]2(v2-PCHP) (3) and
RhH(PCP)(v-Cl)2Rh(COD) (4)
A mixture of 1,3-(PPh2CH2)2C6H4 (2.37 g, 5.0 mmol)
and [RhCl(COD)]2 (2.71 g, 5.5 mmol) in 150 ml of
degassed isopropanol was refluxed for 24 h to give a
brown precipitate. The solid was recrystallized with a
mixed solvent of CH2Cl2 (50 ml) and ether (150 ml).
The soluble portion was treated with hexane (200 ml) to
give a yellow–brownish precipitate, which was collected
by filtration, washed with hexane and dried to give 2.4
g of complex 3 (yield, 43%). The CH2Cl2–ether-insolu-
ble portion was redissolved in CH2Cl2 and the resulting
solution was passed through a silica gel column. The
CH2Cl2 of the eluent was removed under vacuum to
give a yellow solid of complex 4 (1.53 g, 32% yield).
Table 3
31P{1H}-NMR data for the new dinuclear complexes a
Complex
l(PCP)
l(PCHP)
2J(PP) (Hz)
1
Characterization data for 3: H-NMR (CD2Cl2, 300.13
(1J(RhꢁP)) (Hz) (1J(RhꢁP)) (Hz)
MHz): l 1.84–2.47 (m, 16 H, CH2 (COD)), 2.96–2.80
(m, 4 H, CHꢂ (COD)), 3.99 (d, J(PH)=11.6 Hz, 4 H,
CH2 (PCHP)), 5.55 (br, 4 H, CHꢂ (COD)), 7.33–8.10
(m, 24 H, Ph). 13C-NMR (CD2Cl2, 75.5 MHz): l 28.6
(s, CH2 (COD)), 32.6 (s, CH2 (COD)), 34.2 (d, J(PC)=
22.6 Hz, CH2 (PCHP)), 70.3 (d, J(RhꢁC)=13.8 Hz,
CHꢂ (COD)), 104.1 (dd, J(PꢁC)=7.1, J(RhꢁC)=12.3
Hz, CHꢂ (COD)), 127.7–135.4 (m, aromatic signals).
3
4
5
6
26.3 (152.3)
44.8 (116.9)
47.4 (111.2)
33.5 (98.0)
18.8 (82.8)
24.5
a The spectra were obtained in CD2Cl2 on a Bruker NMR spec-
trometer operating at 121.5 MHz. Chemical shifts are in ppm with
respect to 85% H3PO4 (l0.0).

232
J. Yao et al. / Journal of Organometallic Chemistry 598 (2000) 228–234
Anal. Calc. for C48H52Cl2P2Rh: C, 59.58; H, 5.42; Cl,
7.34. Found: C, 59.73; H, 5.22; Cl, 7.19%. Characteri-
zation data for 4: H-NMR (CD2Cl2, 300.13 MHz): l
CHꢂ (COD)), 4.06 (m, 4 H, CH2 (PCP)), 4.15 (m, 2 H,
CHꢂ (COD)), 6.99–8.18 (m, aromatic signals). 13C-
NMR (CD2Cl2, 75.5 MHz): l 30.0 (s, CH2 (COD)),
30.4 (s, CH2 (COD)), 37.3 (t, J(PC)=15.2 Hz, CH2
(PCP)), 77.7 (d, J(RhꢁC)=13.7 Hz, CHꢂ (COD)), 77.9
(d, J(RhꢁC)=14.0 Hz, CHꢂ (COD)), 123.4–145.5 (m,
aromatic signals). Anal Calc. for C40H39Cl3P2Rh2: C,
53.75; H, 4.40; Cl, 11.90. Found: C, 54.00; H, 4.68; Cl,
11.70%.
1
−18.20 (dt, J(RhꢁH)=30.0, J(PH)=12.0 Hz, 1 H,
RhꢁH), 1.35–1.50 (m, 4 H, CH2 (COD)), 2.10–2.30 (m,
4 H, CH2 (COD)), 3.38 (br, 2 H, CHꢂ (COD)), 3.63 (dt,
J(HH)=16.0, J(PH)=4.7 Hz, 2 H, CH2 (PCP)), 3.80
(br, 2 H, CHꢂ (COD)), 4.13 (dt, J(HH)=16.0,
J(PH)=3.9 Hz, 2 H, CH2 (PCP)), 6.82–8.09 (m, aro-
matic signals). 13C-NMR (CD2Cl2, 75.5 MHz): l 30.3
(s, CH2 (COD)), 40.9 (t, J(PC)=15.2 Hz, CH2 (PCP)),
77.4 (d, J(RhꢁC)=14.1 Hz, CHꢂ (COD)), 77.9 (d,
J(RhꢁC)=14.2 Hz, CHꢂ (COD)), 167.7 (dd,
J(RhꢁC)=25.1, J(PꢁC)=125.6 Hz, ipso-PCP), 122.4–
145.4 (m, aromatic signals). Anal. Calc. for:
C40H40Cl2P2Rh2: C, 55.90; H, 4.69; Cl, 8.25. Found: C,
56.06; H, 4.55; Cl, 8.41%.
3.4. Polymerization of phenylacetylene
In a typical reaction, a mixture of phenylacetylene
(7.0 ml, 64 mmol) and 0.015 mmol of the Rh catalyst in
THF (20 ml) was stirred at room temperature for 5 h.
Then 60 ml of MeOH was added to the THF solution
to give a yellow precipitate. The solid was collected by
filtration, washed with MeOH and hexane and dried
under vacuum. A second batch of polymer could be
obtained when the volume of the filtrate was reduced.
The molecular weight of the polymers is around 50 000
as determined by GPC. In the case of RhCl(PCP)(m-
Cl)2Rh(COD), addition of acetonitrile to the reaction
mixture accelerated the polymerization rate signifi-
3.2. Preparation of RhH(PCP)(v-Cl)2Rh(COD) (4) and
[RhHCl(PCP)]2(v-PCHP) (5)
A mixture of 1,3-(PPh2CH2)2C6H4 (1.04 g, 2.2 mmol)
and [RhCl(COD)]2 (0.49 g, 1.0 mmol) in 60 ml of
degassed isopropanol was refluxed for 24 h to give a
brown precipitate. The solid was redissolved in CH2Cl2
and the resulting solution was loaded on a silica gel
column. Complex 4 was obtained (0.36 g, 42% yield)
with CH2Cl2 as the eluent. Complex 5 was obtained
(0.78 g, 46% yield) with acetone as the eluent. Charac-
1
cantly. H-NMR (CDCl3, 300.13 MHz): l 5.91 (br s, 1
H, ꢂCH), 6.70 (br, 2 H, o-Ph), 7.00 (br, 3 H, m, p-Ph).
13C-NMR (CDCl3, 75.5 MHz): l 126.6 (s, p-Ph), 127.4
(s, o- or m-Ph), 127.7 (s, o- or m-Ph), 131.7 (s, ꢂCH),
139.2 (s, ipso-Ph), 142.8 (s, ꢂCPh). The NMR data
match those reported in the literature [35,36].
1
terization data for 5: H-NMR (CD2Cl2, 300.13 MHz):
l −17.20 (dq, J(RhꢁH)=24 Hz, J(PH)=15 Hz, 1 H,
RhꢁH), 2.55 (d, J(PH)=3.8 Hz, 4 H, CH2 (m-PCHP)),
3.81 (dt, J(HH)=11.0, J(PH)=4.4 Hz, 4 H, CH2
(PCP)), 4.47 (dbr, J(HH)=11.0 Hz, 4 H, CH2 (m-
PCHP)), 4.90 (br, 1 H, 2-C6H4 (m-PCHP)), 5.53 (d,
J(HH)=5.9 Hz, 2 H, 4,6-C6H4 (m-PCHP)), 5.95 (t,
J(HH)=5.9 Hz, 1 H, 5-C6H4 (m-PCHP)), 6.75–7.74
(m, other aromatic signals). 13C-NMR (CD2Cl2, 75.5
MHz): l 30.9 (d, J(PC)=11.5 Hz, CH2 (PCHP)), 47.0
(m, CH2P), 166.6 (dd, J(PꢁC)=100.4, J(RhꢁC)=25.1
Hz, ipso-PCP), 121.6–144.8 (m, other aromatic sig-
nals). Anal. Calc. for: C96H84Cl2P6Rh2: C, 67.82; H,
4.98; Cl, 4.17. Found: C, 67.60; H, 5.23; Cl, 4.57%.
3.5. Crystallographic analysis for
RhCl(PCP)(v-Cl)2Rh(COD)·CH2Cl2
Suitable crystals for X-ray diffraction study were
grown by slow diffusion of ether to a saturated solu-
tion of RhCl(PCP)(m-Cl)2Rh(COD) in CH2Cl2. One
molecule of CH2Cl2 was co-crystallized with the
rhodium compound. A red block crystal of RhCl(PCP)-
(m-Cl)2Rh(COD)·CH2Cl2, having approximate dimen-
sions of 0.18×0.28×0.28 mm3, was mounted in a
glass capillary and used for X-ray structure determina-
tion. Intensity data were collected at ambient tempera-
ture on a MAR research image plate scanner, using
,
3.3. Preparation of RhCl(PCP)(v-Cl)2Rh(COD) (6)
Mo–Ka radiation (u=0.71073 A) with a graphite-crys-
tal monochromator in the incident beam. 65–3° frames
with an exposure time of 5 min per frame were used.
The diffraction intensities were corrected for Lorentz
and polarization effects. An approximation to absorp-
tion corrections by inter-image scaling was also applied.
A total of 6814 reflections are unique and 4746 of these
are considered, observed with I\3|(I). The structure
was solved by direct methods (SIR 88) [46] and
expanded using difference Fourier techniques. Some
non-hydrogen atoms were refined anisotropically, while
the rest were refined isotropically [47]. Hydrogen
A sample of RhH(PCP)(m-Cl)2Rh(COD) (0.50 g, 0.58
mmol) in a mixed solvent of CHCl3 (30 ml) and CCl4
(20 ml) was stirred at room temperature for 3 days. The
solvents were then removed under vacuum. The result-
ing residue was redissolved in a minimum amount of
CH2Cl2 and the solution was passed through a silica gel
column with C6H6 as the eluent. Removal of the solvent
produced 0.44 g of complex 6 (yield, 85%). H-NMR
(CD2Cl2, 300.13 MHz): l 1.28–1.57 (m, 4 H, CH2
(COD)), 2.02–2.36 (m, 4 H, CH2 (COD)), 3.03 (m, 2 H,
1

J. Yao et al. / Journal of Organometallic Chemistry 598 (2000) 228–234
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Crystallographic data for the structural analysis
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this information may be obtained free of charge from
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Acknowledgements
We acknowledge the financial support from the
Hong Kong Research Grant Council and the Croucher
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