Synthesis and reactivity of substituted cyclopentadienyl rhodium(I) and (III) complexes

Article abstract of DOI:10.1016/j.jorganchem.2003.11.031

New cyclopentadienyl derivatives of rhodium COD complexes [Cp=C₅H₄COOCH₂CH=CH₂ (1); C₅H₄CH₂CH₂CH= CH₂ (2); C₅H(i-C₃H₇) ₄ (3)] and carbonyl complex [Cp=C₅H (i-C₃H₇)₄ (4)] were synthesized from [RhCl(COD)]₂ and [RhCl(CO) ₂]₂. 1, 2 and 3 oxidized by iodine gave iodine bridged dimers 5, 6 and 7, respectively. Triphenyl phosphine, carbon monoxide and carbon disulfide molecules broke down the iodine bridged structure easily and produced monomer products Cp*RhI₂L [Cp=C₅H₄COOCH₂CH=CH₂, L=CS₂ (8); L=PPh₃ (9). Cp= C₅H(i-C₃H₇)₄, L=CO (10)]. All of these new compounds were characterized by elemental analysis, ¹H NMR, IR, UV-Vis and mass spectroscopy. The crystal structure of 1 was solved in the triclinic space group P1? with one molecule in the unit cell, the dimensions of which are a=7.082(9) ?, b=8.392(3) ?, c=13.889(5) ?, α=101.19(3)°, β=99.06(6)°, γ=105.11(5)°, and V=763(1) ?³. The crystal structure of 3 was solved in the orthorhombic space group Pn21a with four molecules in the unit cell, the dimensions of which are a=9.748(3) ?, b=16.054(5) ?, c=14.816(4)? and V=2319(1) ?³. Least squares refinement leads to values for the conventional R₁ of 0.0251 for 1 and 0.0558 for 3, respectively. Compared to that in 1, a shorter metal-ligand bond length in 3 was observed and this is attributed to the rich electron density on Rh(I) metal center piled up by the C₅H(i-C₃H₇)₄ ligand.

Full text of DOI:10.1016/j.jorganchem.2003.11.031

Journal of Organometallic Chemistry 689 (2004) 823–832
www.elsevier.com/locate/jorganchem
Synthesis and reactivity of substituted cyclopentadienyl
rhodium(I) and (III) complexes
a
Xu You-Feng , Shen Yan , Pang Zhen
a
a,b,
*
a
Department of Chemistry, Fudan University, Shanghai 200433, China
b
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai, China
Received 15 September 2003; accepted 27 November 2003
Abstract
New cyclopentadienyl derivatives of rhodium COD complexes [Cp* ¼ C5H4COOCH2CH@CH2 (1); C5H4CH2CH2CH@CH2
(2); C5H(i-C3H7)4 (3)] and carbonyl complex [Cp* ¼ C5H(i-C3H7)4 (4)] were synthesized from [RhCl(COD)]2 and [RhCl(CO)2]2. 1, 2
and 3 oxidized by iodine gave iodine bridged dimers 5, 6 and 7, respectively. Triphenyl phosphine, carbon monoxide and carbon
disulfide molecules broke down the iodine bridged structure easily and produced monomer products Cp*RhI2L [Cp* ¼ C5H4CO-
OCH2CH@CH2, L ¼ CS2 (8); L ¼ PPh3 (9). Cp* ¼ C5H(i-C3H7)4, L ¼ CO (10)]. All of these new compounds were characterized by
elemental analysis, 1H NMR, IR, UV–Vis and mass spectroscopy. The crystal structure of 1 was solved in the triclinic space group
ꢀ
ꢁ
ꢁ
ꢁ
P1 with one molecule in the unit cell, the dimensions of which are a ¼ 7:082ð9Þ A, b ¼ 8:392ð3Þ A, c ¼ 13:889ð5Þ A, a ¼ 101:19ð3Þ°,
3
ꢁ
b ¼ 99:06ð6Þ°, c ¼ 105:11ð5Þ°, and V ¼ 763ð1Þ A . The crystal structure of 3 was solved in the orthorhombic space group Pn21a with
3
ꢁ
ꢁ
ꢁ
ꢁ
four molecules in the unit cell, the dimensions of which are a ¼ 9:748ð3Þ A, b ¼ 16:054ð5Þ A, c ¼ 14:816ð4ÞA and V ¼ 2319ð1Þ A .
Least squares refinement leads to values for the conventional R1 of 0.0251 for 1 and 0.0558 for 3, respectively. Compared to that in 1,
a shorter metal–ligand bond length in 3 was observed and this is attributed to the rich electron density on Rh(I) metal center piled up
by the C5H(i-C3H7)4 ligand.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Rhodium complexes; Cyclopentadienyl ligands; Hamilabile substituent
1. Introduction
complexes during substitution that is important in cat-
alytic process [3]. Such pendant side chain can tempo-
rarily and reversibly coordinate to a metal, acts as an
intramolecular solvent, thus stabilizes reactive interme-
diates. The electron density of the cyclopentadienyl ring
can be changed by its ring substituent or by introducing
a hetero-atom into the ring structure [4]. Such structural
modifications to the cyclopentadienyl ligand have re-
ceived much attention by numerous research groups.
Our interest is in the study of the influences of the
chemical properties of an organometallic compound by
electronic or stereo modifications to its cyclopentadienyl
ligand [5]. Here we report the synthesis and the reac-
tivity of some rhodium complexes with structural
modifications to their cyclopentadienyl ligand. The
pendant substituents to the cyclopentadienyl ligand
include butenyl, tetraisopropanyl and allyloxycar-
bonyl groups, which varying from electron-donating to
Organometallic compound of the transition metals
with one or more cyclopentadienyl ligands is one of the
most important classes of organometallic complexes.
Over 80% of the known organometallic complexes
contain the cyclopentadienyl ligand or a derivative of it
[1]. The cyclopentadienyl ligand has been modified to
improve the properties of the complex towards its spe-
cific applications. Alkylation on the cyclopentadienyl
ring can improve the solubility of the complexes in or-
ganic solvent [2]. A pendant substituent with an electron
donating functional group to the cyclopentadienyl li-
gand can be designed to change the properties of the
* Corresponding author. Tel: +86-21-65643885; fax: +86-21-
65641740.
E-mail address: zpang@fudan.edu.cn (P. Zhen).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.11.031

824
X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
electron-withdrawing in nature, or may create steric
hindrance around the metal center.
of 40 min. The reaction mixture was continuously stir-
red for another 3 h. The precipitate was separated by
centrifuge and washed with hexane for 3 times, then
dried under vacuum. 0.2484 g of solid as pale pink
powder was obtained, yield 46%.
2. Experimental
2.1. General procedures
2.3. K(g5-C5H(i-C3H7)4)
All reactions were carried out by standard Schlenk
techniques under an inert atmosphere of dinitrogen.
Solvents were deoxygenated and dried by standard
methods and distilled under dinitrogen before use [6].
Na(g5-C5H4COOCH2CH@CH2) [7], C5H2(i-C3H7)4,
[RhCl(CO)2]2 and [RhCl(COD)]2 (COD ¼ C8H12) were
prepared according to the literature methods [8]. Ele-
mental analyses were performed on a Rapid CHN-O
240C Analyzer (Heraeus, Germany) at the Shanghai
Institute of Organic Chemistry, Chinese Academy of
Sciences. IR spectra were recorded on a Nicolet AVA-
TAR-360IR spectrophotometer in KBr pellets. 1H
NMR spectra were recorded on a Bruker A VAVCE-
DMX 500 NMR spectrometer and the chemical shifts
are reported in ppm referenced to tetramethylsilane.
UV–Vis spectra were recorded on a HP diode-array
model 8453 spectrometer in CH2Cl2. Mass spectra were
recorded on HP 5989A spectrometer with EI source.
The crystal structure was determined on an ENRAF-
Nonius CAD4 X-ray diffractometer equipped with a
graphite monochromator. Data collection was per-
2.10 g (8.96 mmol) C5H2(i-C3H7)4 was dissolved in 30
ml of THF, the solution was transferred slowly into a
125 ml of Schlenk tube containing 0.333 g (8.52 mmol)
of metallic potassium. The reaction mixture was heated
to reflux overnight. The metallic potassium disappeared
and a lot of white crystals precipitated. The white
crystals were filtered and washed with hexane until the
washings was colorless. The precipitate was dried under
vacuum. 2.33 g of white crystalline of solid was ob-
tained, yield 99%.
2.4. Preparation of (g5-C5H4COOCH2CH@CH2)
Rh(C8H12) (1)
[RhCl(COD)]2 (0.728 g, 1.48 mmol) was dissolved in
30 ml of THF in a 150 ml Schlenk tube under stirring,
and added slowly 25 ml of THF solution containing
Na(g5-C5H4COOCH2CH@CH2) (0.483 g, 2.81 mmol).
The reaction mixture was allowed to stir overnight un-
der room temperature. The solvent was evaporated to
dryness in vacuo and the residue was added 25 ml of
hexane. The yellow turbid hexane solution was filtered
through a pad of Celite. The yellow clear filtrate was
adsorbed by 2 g of alumina and then loaded on an
alumina column. The column was rinsed with a mixed
solvent of hexane and THF in the ratio of 25–1. The
yellow band was collected and the eluent was evapo-
rated in vacuo. 0.41 g of yellow solid was obtained.
Yield: 40%. Anal. Found: C, 56.7: H, 6.10. Calc. for:
C17H21O2Rh (360.25 g/mol): C, 56.7; H, 5.88%. IR (KBr
pallet), mmax/cmꢀ1: 3115 (@CH of C5H4 ring), 2989,
2971, 2933 (–CH aliphatic), 2875, 2827, 1691 (C@O),
1649 (C@C), 1470 (C–C), 1374,1323 (COD), 1272, 1127,
968 (COD), 867 (COD), 804 (COD). UV–Vis kmax/nm
(CH2Cl2): 236 (e/dm3 molꢀ1 1.51 ꢁ 104), 306 (0.41 ꢁ
104). Mass spectrum (EI) m=e: 360 (100, Mþ), 319 (24.2,
C5H4COORhCODþ), 275 (38.5, C5H4RhCODþ), 210
(6.9, C5H4COORhþ), 168 (39.8, C5H5Rhþ). dH
((CD3)2CO): 5.48 (t, 2H, Cp, J ¼ 2.1 Hz), 5.44 (t, 2H,
Cp, J ¼ 2.1 Hz), 6.04 (m, 1H, –CH@), 5.42 (d, 1H,
@CH2 trans, J ¼ 17.4 Hz), 5.23 (d, 1H, @CH2 cis,
J ¼ 10.5 Hz), 4.71 (m, 2H, –OCH2–), 4.03 (br s, 4H,
COD, vinylic), 2.14 (m, 4H, CH2 of COD), 1.92 (m, 4H,
CH2 of COD). The yellow solid product was redis-
solved in hexane and cooled under )28 °C. Yellow
crystals suitable for X-ray crystallographic analysis were
obtained. The crystal data and structure refinement
parameters are given in Tables 1 and 2.
ꢁ
formed with Mo Ka radiation (k ¼ 0:71073 A) using the
x–2h scan technique to a maximum 2h value of 29.77° at
the room temperature. The structure of the crystal was
solved by direct methods and expanded using Fourier
techniques. The non-hydrogen atoms were refined an-
isotropically with full-matrix least-squares. Hydrogen
atoms were not included in refinement. The final
agreement factors are described with R1 and wR2 values
for observed reflections. All calculations were performed
on a PC computer using SHELX-97 (Sheldrick, 1997).
2.2. Li(g5-C5H4CH2CH2CH@CH2)
0.496 g (21.6 mmol) of sodium sand was reacted with
2.6 ml of freshly distilled cyclopentadiene in 15 ml of
THF under ice water bath. When sodium sand disap-
peared, the solvent was evaporated under vacuum. The
white residue was re-dissolved in 35 ml of THF and
cooled to )40 °C. 2.2 ml (21.7 mmol) of 4-bromo-1-
butene was added slowly. After 2 h stirring under )40
°C, the orange yellow solution was filtered through a
pad of Celite. The solvent was removed from the filtrate
by distillation under atmosphere and 0.5145 g of
C5H5CH2CH2CH@CH2 was obtained by distillation
under reduced pressure. The distillate was dissolved in
10 ml of hexane and cooled to )45 °C. 4.28 ml of n-
butyllithium (1.6 M in hexane) was added in the period

X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
825
(sh). Mass spectrum (EI) m=e: 330 (19.1, Mþ), 289 (5.03,
C5H4CH2RhCODþ), 275 (2.81, C5H4RhCODþ), 222
(100, RhCODþ), 182 (38.6, C5H5CH2Rhþ), 168 (8.39,
C5H5Rhþ). dH ((CD3)2CO): 5.15 (br s, 2H, Cp), 4.98 (br
s, 2H, Cp), 5.86ꢂ5.93 (m, 1H, –CH@), 5.04 (d, 1H,
@CH2 trans, J ¼ 17.9 Hz), 4.95 (d, 1H, @CH2 cis,
J ¼ 10.7 Hz), 3.78 (br s, 4H, COD, vinylic), 2.32 (m,
2H,–CH2C2H3–), 2.21 (m, 2H, –CH2C3H5–), 2.18 (m,
4H, CH2 of COD), 1.91 (m, 4H, CH2 of COD).
Table 1
Crystal data and structure refinement for (g5-C5H4CO-
OCH2CH@CH2)Rh(COD) (1)
Empirical formula
Formula weight
T (K)
C34H42O4Rh2
720.50
295(2)
ꢁ
k (A)
0.71073
triclinic
Crystal system
Space group
Unit cell dimensions
ꢀ
P1
ꢁ
a (A)
7.082(9)
8.392(3)
ꢁ
b (A)
2.6. Preparation of (g5-C5H(i-C3H7)4)Rh(C8H12) (3)
ꢁ
c (A)
13.889(5)
101.19(3)
99.06(6)
a (°)
b (°)
c (°)
To an orange red solution of [RhCl(COD)]2 (0.20 g,
0.41 mmol) in 30 ml of THF was added slowly a solu-
tion of K(g5-C5H(i-C3H7)4) (0.35 g, 1.3 mmol) in 15 ml
of THF. The reaction mixture was stirred overnight
under room temperature and was then filtered through a
pad of Celite. The orange red clear filtrate was adsorbed
by 2 g of alumina and then loaded on an alumina col-
umn. The column was rinsed with hexane. The yellow
band was collected and the eluant was evaporated in
vacuo. 0.17 g of orange red oil was obtained. Yield:
47%. Anal. Found: C, 67.5: H, 9.70. Calc. for: C25H41Rh
105.11(5)
763(1)
3
ꢁ
V (A )
Z
1
1.569
qcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F ð000Þ
)
1.118
368
Crystal size (mm)
h range for data collection (°)
Index ranges
0.50 ꢁ 0.20 ꢁ 0.10
1.53–25.18
ꢀ8 6 h 6 8, ꢀ10 6 k 6 9,
0 6 l 6 16
2859/2738 (0.0140)
Reflections collected/unique
(Rint
)
(444.51 g/mol): C, 67.6; H, 9.30%. IR (neat), mmax/cmꢀ1
:
Completeness to 2h ¼ 25:18 (%) 99.8
Maximum and minimum
transmission
Refinement method
0.8964 and 0.6048
2960, 2929, 2871 (–CH aliphatic), 1460 (C–C), 1380,
1364, 1321 (COD), 1179, 1100, 964 (COD), 858 (COD),
810 (COD). Mass spectrum (EI) m=e: 444 (100, Mþ),
401 (7.18, C5H(i-C3H7)3RhCODþ), 370 (23.0, C5H(i-
C3H7)2CRhCODþ), 315 (7.73, C5H(i-C3H7)RhCODþ).
dH ((CD3)2CO): 4.99 (s, 1H, ring-CH), 3.73 (br s, 4H,
COD vinylic), 2.73–2.86 (m, 4H, CHMe2), 2.22 (m, 4H,
CH2 of COD), 1.90 (m, 4H, CH2 of COD), 1.33 (d, 6H,
CH3, J ¼ 7.12 Hz), 1.27 (d, 6H, CH3, J ¼ 7.17 Hz), 1.14
(d, 6H, CH3, J ¼ 2.84 Hz), 1.13 (d, 6H, CH3, J ¼ 2.78
Hz). The yellow oil was dissolved in 1 ml of hexane and
cooled under )28 °C. The yellow crystals suitable for X-
ray crystallographic analysis were obtained. The crystal
data and structure refinement parameters are given in
Tables 3 and 4.
full-matrix least-squares on F 2
2738/0/182
1.061
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2rðIÞ]
R indices (all data)
R1 ¼ 0:0251, wR2 ¼ 0:0664
R1 ¼ 0:0370, wR2 ¼ 0:0711
0.0005(9)
Extinction coefficient
Largest diffraction peak and
0.360 and )0.316
ꢀ3
ꢁ
hole (e A
)
2.5. Preparation of (g5-C5H4CH2CH2CH@CH2)Rh
(C8H12) (2)
[RhCl(COD)]2 (0.408 g, 0.83 mmol) was dissolved in
25 ml of THF in a 150 ml Schlenk tube under stirring,
and added slowly 25 ml of THF solution containing
Li(g5-C5H4CH2CH2CH@CH2) (0.248 g, 1.97 mmol).
The reaction mixture was stirred overnight under room
temperature. The reaction mixture was evaporated to
dryness in vacuo and the residue was added 25 ml of
hexane. The yellow turbid hexane solution was filtered
through a pad of Celite. The clear yellow filtrate was
adsorbed by 2 g of alumina and then loaded on a silica
column. The column was rinsed with hexane. The yellow
band was collected and the solvent was evaporated in
vacuo. 0.26 g of yellow oil was obtained. Yield: 47%.
Anal. Found: C, 62.1: H, 7.08. Calc. for: C17H23Rh
2.7. Preparation of (g5-C5H(i-C3H7)4)Rh(CO)2 (4)
To an orange red solution of [RhCl(CO)2]2 (0.324 g,
0.833 mmol) in 25 ml of THF was added slowly a solu-
tion of K(g5-C5H(i-C3H7)4) (0.549 g, 2.01 mmol) in 25
ml of THF. The reaction mixture was stirred overnight
under room temperature. The reaction mixture was fil-
tered through a pad of Celite and the filtrate was ad-
sorbed by 2 g of alumina, loaded on an alumina column.
The column was rinsed with hexane. Two bands of dif-
ferent colors on the column were resulted. The first band
was orange red and the second band was blue. The or-
ange red band was collected. The eluant was evaporated
in vacuo. 0.20 g of nacarat oil was obtained. Yield: 31%.
Anal. Found: C, 58.7: H, 8.04. Calc. for: C19H29O2Rh
(330.28 g/mol): C, 61.8; H, 7.02%. IR (neat), mmax/cmꢀ1
:
3076, 2985, 2927, 2872 (–CH aliphatic), 1641 (C@C),
1472 (C–C), 1447 (COD), 1358, 1323 (COD), 1298,
1152, 960 (COD), 8137 (COD), 790 (COD). UV–Vis
k
max/nm (CH2Cl2): 242 (e/dm3 molꢀ1 1.30 ꢁ 104), 280
(392.35 g/mol): C, 58.2; H, 7.45%. IR (neat), mmax/cmꢀ1
:

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X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
Table 2
5
ꢁ
Selected bond lengths (A) and angles (°) for (g -C5H4COOCH2CH@CH2)Rh(COD) (1)
Rh(1)–C(1)
Rh(1)–C(2)
Rh(1)–C(3)
Rh(1)–C(4)
Rh(1)–C(5)
Rh(1)–C(10)
Rh(1)–C(11)
Rh(1)–C(14)
Rh(1)–C(15)
C(1)–C(2)
2.221(3)
2.294(4)
2.301(4)
2.231(3)
2.255(3)
2.114(4)
2.127(3)
2.128(3)
2.114(4)
1.409(5)
1.427(5)
1.390(6)
1.419(6)
1.417(5)
C(5)–C(6)
C(6)–O(1)
1.455(5)
1.197(5)
1.330(4)
1.447(5)
1.35(1)
C(6)–O(2)
O(2)–C(7)
C(7)–C(8)
C(8)–C(9)
0.98(1)
C(10)–C(11)
C(10)–C(17)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–C(17)
1.393(6)
1.533(7)
1.501(6)
1.467(6)
1.506(5)
1.378(6)
1.495(7)
1.445(8)
C(1)–C(5)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(10)–Rh(1)–C(1)
C(15)–Rh(1)–C(4)
C(15)–Rh(1)–C(5)
C(10)–Rh(1)–C(5)
C(11)–Rh(1)–C(2)
C(14)–Rh(1)–C(3)
C(3)–C(2)–C(1)
C(2)–C(3)–C(4)
C(5)–C(4)–C(3)
C(4)–C(5)–C(1)
C(4)–C(5)–C(6)
C(1)–C(5)–C(6)
O(1)–C(6)–O(2)
101.1(2)
O(1)–C(6)–C(5)
O(2)–C(6)–C(5)
124.8(4)
100.5(2)
112.6(2)
114.2(2)
103.3(2)
105.9(2)
108.3(3)
108.1(3)
108.6(3)
106.2(3)
124.6(3)
129.0(3)
123.4(4)
111.7(3)
116.4(4)
112.1(6)
143(2)
C(6)–O(2)–C(7)
C(8)–C(7)–O(2)
C(9)–C(8)–C(7)
C(11)–C(10)–C(17)
C(10)–C(11)–C(12)
C(13)–C(12)–C(11)
C(12)–C(13)–C(14)
C(15)–C(14)–C(13)
C(14)–C(15)–C(16)
C(17)–C(16)–C(15)
C(16)–C(17)–C(10)
122.4(4)
124.5(4)
115.4(3)
114.9(3)
123.8(4)
125.0(4)
115.7(4)
115.1(4)
2964, 2931, 2871 (–CH aliphatic), 2025 (C@O), 1960
(C@O), 1463 (C–C), 1380, 1365, 1312, 1182 and 1099.
Mass spectrum (EI) m=e: 392 (14.8, Mþ), 364 (20.4,
C5H(i-C3H7)4RhCOþ), 336 (100, C5H(i-C3H7)4Rhþ).
dH ((CD3)2CO): 5.05 (s, 1H, ring-CH), 2.87–3.01 (m, 4H,
CHMe2), 1.19 (d, 12H, CH3, J ¼ 7.2 Hz), 1.13 (d, 12H,
CH3, J ¼ 6.8 Hz). The eluant was changed to ether to
rinse the second blue band. The eluant was evaporated to
give blue oil, which was very air sensitive. The IR spec-
nm (CH2Cl2): 229 (e/dm3 molꢀ1 4.2 ꢁ 104), 254
(4.03 ꢁ 104), 315 (1.73 ꢁ 104), 510 (0.8 ꢁ 104). Mass
spectrum (EI) m=e: 757 (3.770, M–2Iþ), 493 (1.72,
C5H4COOCH2CH2RhI2þ), 367 (7.36, C5H4CO-
OCH2CH3RhIþ), 338 (10.69, C5H4COORhIþ), 168
(30.41, C5H5Rhþ). dH (CDCl3): 6.07 (m, 4H, ring-CH),
5.71 (m, 4H, ring-CH), 6.00 (m, 2H, –CH@), 5.42 (d,
2H, @CH2 trans, J ¼ 17.2 Hz), 5.31 (d, 2H, @CH2 cis,
J ¼ 10.4 Hz), 4.83 (d, 4H, –OCH2–, J ¼ 5.83).
trum of it showed a very strong absorption at 1730 cmꢀ1
,
which is a characteristic band for metal-bridged carbonyl
stretching frequency. Thus the blue oil was assigned to
[C5H(i-C3H7)4Rh-l-(CO)2-RhC5H(i-C3H7)4] dimer [9].
2.9. Preparation of [(g5-C5H(i-C3H7)4)RhI2]2 (6)
To a solution of (g5-C5H(i-C3H7)4)Rh(C8H12) (0.10 g,
0.22 mmol) in 15 ml of ether was added slowly a solution
of iodine (0.063 g, 0.25 mmol) in ether. Red purple pre-
cipitate occurred immediately. The reaction mixture was
continuously stirred for another 2 h. The precipitate was
filtered and washed with 3 ꢁ 5 ml of ether and dried in
vacuo. 0.113 g of red purple solid was obtained. Yield:
85%. Anal. Found: C, 34.2: H, 4.70. Calc. for:
C34H58Rh2I4 (1180.3 g/mol): C, 34.6; H, 4.95%. IR (KBr
pallet), mmax/cmꢀ1: 2958, 2928, 2871 (–CH aliphatic), 1462,
1384, 1366, 1172, 1101, 963, 868. UV–Vis kmax/nm
(CH2Cl2): 229 (e/dm3 molꢀ1 5.17 ꢁ 104), 274 (4.6 ꢁ 104),
336 (2.02 ꢁ 104), 574 (0.81 ꢁ 104). Mass spectrum (EI)
m=e: 1053 (20.9, M–Iþ), 926 (2.27, M–2Iþ), 590 (11.41, M/
2þ), 463 (100, M/2–Iþ). dH (CDCl3): 5.50 (s, 2H, HC5R4),
3.03 (br, 4H, CHMe2), 2.91 (br, 4H, CHMe2), 1.56 (m,
12H, CH3), 1.47 (m, 24H, CH3), 1.27 (m, 12H, CH3).
2.8. Preparation of [(g5-C5H4COOCH2CH@CH2)
RhI2]2 (5)
To
a
solution of (g5-C5H4COOCH2CH@CH2)
Rh(C8H12) (0.205 g, 0.569 mmol) in 15 ml of ether was
added slowly a solution of iodine (0.159 g, 0.626 mmol)
in 5 ml of ether. Red purple precipitate appeared im-
mediately. The reaction mixture was continuously stir-
red for another 2 h. The precipitate was filtered, washed
with 3 ꢁ 5 ml of ether and dried in vacuo. 0.26 g of red
purple solid was obtained. Yield: 90%. Anal. Found: C,
20.8: H, 2.04. Calc. for: C18H18O4Rh2I4 (1011.77 g/mol):
C, 21.4; H, 1.79%. IR (KBr pallet), mmax/cmꢀ1: 3086,
3065, 2971 (–CH aliphatic), 1723 (C@O), 1649 (C@C),
1460 (C–C), 1396, 1368, 1270, and 1152. UV–Vis mmax
/

X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
827
2.11. Preparation of (g5-C5H4COOCH2CH@CH2)
RhI2CS2 (8)
Table 3
Crystal data and structure refinement for (g5-C5H(i-C3H7)4)Rh(COD)
(3)
deep red solution of [(g5-C5H4CO-
Empirical formula
Formula weight
T (K)
C25H41Rh
444.49
293(2)
To
a
OCH2CH@CH2)RhI2]2 (0.0791 g, 0.078 mmol) in 8 ml
of methylene chloride was added slowly 0.020 ml (0.33
mmol) of CS2 under stirring. The reaction mixture was
stirred overnight under ambient temperature. The vol-
ume of the reaction mixture was reduced to about 1 ml
under vacuum and the resulting solution was loaded on
a silica column, rinsed with a mixed solvent of THF and
hexane in 1.25–1 ratios. The deep red band was collected
and the solvent was evaporated in vacuo. 0.055 g of
black purple solid was obtained. Yield: 60%. Anal.
Found: C, 20.8: H, 1.70. Calc. for: C10H9S2O2RhI2
ꢁ
k (A)
0.71073
orthorhombic
Pn21a
Crystal system
Space group
Unit cell dimensions
ꢁ
a (A)
9.748(3)
16.054(5)
ꢁ
b (A)
ꢁ
c (A)
14.816(4)
90
a (°)
b (°)
c (°)
90
90
3
ꢁ
V (A )
2319(1)
4
1.273
Z
(582.01 g/mol): C, 20.6; H, 1.56%. IR (KBr pallet), mmax
/
qcalc (Mg/m3)
cmꢀ1: 3088, 3067, 2975 (–CH aliphatic), 1724 (C@O),
1649 (C@C), 1460 (C–C), 1393, 1369, 1274, 1156, 1026
(C@S). UV–Vis kmax/nm (CH2Cl2): 229 (e/dm3 molꢀ1
0.95 ꢁ 104), 254 (0.94 ꢁ 104), 313 (0.37 ꢁ 104). dH
(CDCl3): 6.08 (m, 2H, ring-CH), 6.01 (m, 1H–CH@),
5.71 (m, 2H, ring-CH), 5.42 (d, 1H, @CH2 trans,
J ¼ 16.5 Hz), 5.31 (d, 1H, @CH2 cis, J ¼ 11.0 Hz), 4.82
(d, 2H, –OCH2–, J ¼ 5.56 Hz).
Absorption coefficient (mmꢀ1
F ð000Þ
)
0.742
368
Crystal size (mm)
h range for data collection (°)
Index ranges
0.40 ꢁ 0.20 ꢁ 0.20
1.87–29.77
ꢀ5 6 h 6 12, ꢀ18 6 k 6 19,
ꢀ20 6 l 6 20
11 838/5275 (0.0466)
Reflections collected/unique
(Rint
)
Completeness to 2h ¼ 29:77 (%) 81.0
Refinement method
Data/restraints/parameters
Goodness-of-fit on F 2
full-matrix least-squares on F 2
5275/0/243
1.056
2.12. Preparation of (g5-C5H4COOCH2CH@CH2)
RhI2PPh3 (9)
Final R indices [I > 2rðIÞ]
R1 ¼ 0:0558, wR2 ¼ 0:1174
R1 ¼ 0:0898, wR2 ¼ 0:1328
0.41(12)
R indices (all data)
deep red solution of [(g5-C5H4CO-
Absolute structure parameter
Largest diffraction peak and
To
a
1.100 and )0.334
OCH2CH@CH2)RhI2]2 (0.10 g, 0.099 mmol) in 15 ml of
methylene chloride was added slowly a solution of PPh3
(0.049 g, 0.19 mmol) in methylene chloride. The reaction
mixture was stirred overnight under ambient tempera-
ture and was then evaporated to dryness. The solid res-
idue was washed with hexane for several times and was
then recrystallized in the mixed solution of THF and
hexane to give 0.055 g of red purple solid. Yield: 36%.
Anal. Found: C, 41.9: H, 3.01. Calc. for: C27H24O2RhPI2
ꢀ3
ꢁ
hole (e A
)
2.10. Preparation of [(g5-C5H4CH2CH2CH@CH2)
RhI2]2 (7)
To
a
solution of (g5-C5H4CH2CH2CH@CH2)
Rh(C8H12) (0.10 g, 0.30 mmol) in 15 ml of ether was
added slowly a solution of iodine (0.078 g, 0.31 mmol) in
ether. Black purple precipitate occurred immediately.
The reaction mixture was continuously stirred for an-
other 2 h. The precipitate was filtered and washed with
3 ꢁ 5 ml of ether and dried in vacuo. 0.115 g of red
purple solid was obtained. Yield: 80%. Anal. Found: C,
22.7: H, 2.47. Calc. for: C18H22Rh2I4 (951.8 g/mol): C,
22.7; H, 2.33%. IR (KBr pallet), mmax/cmꢀ1: 3088, 3070
(–CH aliphatic), 2985, 1640 (C@C), 1470 (C–C), 1393,
1107, 915. UV–Vis kmax/nm (CH2Cl2): 230 (e/dm3 molꢀ1
5.66 ꢁ 104), 345 (1.02 ꢁ 104), 488 (0.91 ꢁ 104). Mass
spectrum (EI) m=e: 476 (18.33, M/2þ), 349 (83.94, M/2–
Iþ), 230 (14.25, RhIþ), 222 (17.42, M/2-2Iþ), 181 (17.42,
C5H4CH2Rhþ). dH (CDCl3): 5.78 (m, 2H, –CH@), 5.49
(m, 4H, ring-CH), 5.46 (m, 4H, ring-CH), 5.07 (d, 2H,
@CH2 cis, J ¼ 11.6 Hz), 5.06 (d, 2H, @CH2 trans,
J ¼ 17.2 Hz), 2.66 (m, 4H, –CH2C2H3), 2.37 (m, 4H, –
CH2C3H5).
(768.17 g/mol): C, 42.2; H, 3.15%. IR (KBr pallet), mmax
/
cmꢀ1: 3085, 3056, 2970 (–CH aliphatic), 1718 (C@O),
1655 (C@C), 1580 (Ph), 1480 (C–C), 1433, 1399, 1278,
1150, 1092. UV–Vis kmax/nm (CH2Cl2): 230 (e/dm3
molꢀ1 5.79 ꢁ 104), 300 (1.98 ꢁ 104), 444 (0.49 ꢁ 104). dH
(CDCl3): 7.6 (br, 15H, PPh3), 6.05 (m, 2H, ring-CH),
6.01 (m, 1H–CH@), 5.69 (m, 2H, ring-CH), 5.46 (d, 1H,
@CH2 trans, J ¼ 16.1 Hz), 5.33 (d, 1H, @CH2 cis,
J ¼ 10.8 Hz), 4.85 (d, 2H, –OCH2–, J ¼ 5.7 Hz).
2.13. Preparation of (g5-C5H(C3H7)4)RhI2CO (10)
A 100 ml Schlenk tube with [(g5-C5H(C3H7)4)RhI2]2
(0.10 g, 0.085 mmol) in it was evacuated, flushed with
N2 and then filled with 1 atm of carbon monoxide. 20 ml
of THF was injected into the Schlenk tube. The reaction
mixture was stirred overnight under ambient tempera-
ture. The solvent was removed in vacuo and the residue

828
X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
Table 4
5
ꢁ
Bond lengths (A) and angles (°) for (g -C5H(i-C3H7)4)Rh(COD) (3)
Rh(1)–C(1)
Rh(1)–C(2)
Rh(1)–C(3)
Rh(1)–C(4)
Rh(1)–C(5)
Rh(1)–C(18)
Rh(1)–C(19)
Rh(1)–C(22)
Rh(1)–C(23)
C(1)–C(2)
2.308(5)
2.110(11)
2.308(10)
2.208(12)
2.317(9)
2.159(9)
1.977(12)
2.172(9)
2.048(11)
1.344(15)
1.411(12)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
1.498(19)
1.343(8)
1.521(18)
1.23(2)
C(18)–C(25)
C(18)–C(19)
C(19)–C(20)
C(20)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(24)–C(25)
1.55(2)
1.43(2)
1.520(19)
1.353(17)
1.57(3)
1.43(2)
1.69(3)
C(1)–C(5)
C(19)–Rh(1)–C(18)
C(23)–Rh(1)–C(18)
C(19)–Rh(1)–C(22)
C(23)–Rh(1)–C(22)
C(1)–C(2)–C(3)
C(1)–C(2)–C(6)
C(3)–C(2)–C(6)
C(4)–C(3)–C(9)
C(4)–C(3)–C(2)
C(9)–C(3)–C(2)
C(3)–C(4)–C(5)
C(3)–C(4)–C(12)
C(5)–C(4)–C(12)
C(15)–C(5)–C(1)
C(15)–C(5)–C(4)
C(1)–C(5)–C(4)
43.7(7)
73.5(8)
75.8(6)
43.5(7)
120.5(9)
111(1)
125(1)
129(1)
98 (1)
C(2)–C(6)–C(8)
C(2)–C(6)–C(7)
113(1)
112(1)
124(1)
112(1)
112(1)
117(1)
112(1)
120(1)
115(1)
124(1)
114(1)
109.4(9)
120(1)
121(1)
111(1)
105(1)
C(11)–C(9)–C(3)
C(3)–C(9)–C(10)
C(14)–C(12)–C(4)
C(13)–C(12)–C(4)
C(5)–C(15)–C(17)
C(5)–C(15)–C(16)
C(25)–C(18)–C(19)
C(20)–C(19)–C(18)
C(19)–C(20)–C(21)
C(22)–C(21)–C(20)
C(21)–C(22)–C(23)
C(24)–C(23)–C(22)
C(23)–C(24)–C(25)
C(18)–C(25)–C(24)
133(1)
111(1)
113(1)
133.4(9)
118(1)
133(1)
108.7(8)
was recrystallized in a mixed solvent of THF and hexane
to give 0.042 g of black purple solid. Yield: 40%. Anal.
Found: C, 34.6: H, 4.50. Calc. for: C18H29ORhI2 (618.14
the functionally substituted cyclopentadienyl metal
complexes [12]. The halogenated cyclopentadienyl metal
complexes are useful reaction precursors for halogen–
lithium exchange reaction, which could be further
transferred to the desired metal complexes. In our ex-
periments, the functionalized cyclopentadienyl salts
were the desired reaction precursor. During the syn-
thetic procedure, the electronic property of the sub-
stituent displayed great impact to the reaction. The
influence of the substituent to the reaction is depicted by
Scheme 1.
g/mol): C, 35.0; H, 4.73%. IR (KBr pallet), mmax/cmꢀ1
:
2964, 2922, 2869 (–CH aliphatic), 2050 (CO), 1467 (C–
C), 1368, 1261 and 1103. dH (CDCl3): 5.48 (s, 1H,
HC5(i-propanyl)4), 3.01 (br, 2H, CHMe2), 2.84 (br, 2H,
CHMe2), 1.56 (m, 6H, CH3), 1.48 (m, 12H, CH3), 1.28
(m, 6H, CH3).
Scheme 1 illustrates that the major side-reaction is
dimerization. In order to reduce the influence from side-
reaction, faster functionization k1 and deprotonation k3
are both appreciated. Faster k1 and k3 can reduce the
reaction time take by the dimerization before and after
3. Results and discussion
The way to synthesis a functionally substituted cy-
clopentadienyl metal complex is versatile. Usually a
functionalized cyclopentadienyl salt is prepared as the
reaction precursor. This salt reacts with a metal chloride
can lead to the aimed products. Direct modification of
the cyclopentadienide with formyl-, acetyl- or meth-
oxycarbonyl substituent was reported [10]. These func-
tionalized cyclopentadienyl ligand were convenient
precursors for the functionally substituted half-sand-
wich cobalt complexes. The synthetic method could be
easily extended to other metals like Rh, Ir, Mn, Tc, Re,
Cr, Mo, W or Ti. Direct functionalization with the cy-
clopentadienyl metal carbonyl complexes through Fri-
edel–Crafts reaction was also reported [11]. Indirect
modification through halogenation of the cyclopenta-
dienide was reported as another way to the synthesis of
Scheme 1.

X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
829
deprotonation. The x-butenyl is an electron-donating
substituent. x-Butenyl cyclopentadiene dimerizes easily
even under the temperature of )40 °C. The dimerization
began as soon as the substituted cyclopentadiene was
formed. Choosing 4-bromide-1-butene instead of 4-
chloride-1-butene was favored the functionalization re-
action k1 owing to the activity of bromide. Compared to
its bromide analogue, chloride usually gave poorer yield
only because of its relatively inertness, which required
longer time to finish the functionalization, therefore
more dimerized side products resulted. The deprotona-
tion of the functionalized cyclopentadiene was also
competed by its dimerization. Metallic sodium is a clean
deprotonation reagent, but its reaction rate is too slow.
We chose sodium ethoxide as the deprotonation reagent,
the yield was less than 30%. With the more reactive
n-butyllithium as the deprotonation reagent, the yield
was increased to 46%. Proper reaction concentration
was also desired. If the concentration of the sub-
strate was too low, it needed longer time to finish the
synthetic reaction, and more dimerization resulted.
However, higher reaction concentration would increase
the rate of dimerization and was also disadvantageous.
A proper reaction concentration for the substrate was
found about 0.3 M, which was balanced by k2 and k3.
Allyl chloroformate has an active acyl chloride and an
electron-withdrawing group of allyloxycarbonyl. With
allyl chloroformate as the functionalization reagent, k1
was increased and the time for dimerization was decre-
aded. The yield of allyloxycarbonyl cyclopentadienide
was 85% even though sodium ethoxide was used as the
deprotonation reagent. This result supported the fact
that the electron-withdrawing substituent disfavored the
dimerization. A general atom-economizing method for
the synthesis of hydroxyalkoxycarbonylcyclopentadie-
nide was reported recently by Busetto and Albano [13].
High yields of over 90% were achieved through the re-
action of the easily obtained sodium cyclopentadienide
and cyclic carbornates with a mechanism in which the
deprotonation of the 1-substituted cyclopentadiene in-
termediate occurs intramolecularly. This synthesis
method avoid the transesterification type reaction be-
tween two alkoxycarbonylcyclopentadiene molecules
[14], although the dimmers derived from a transesteri-
fication type reaction between two molecules of the
corresponding mononuclear complexes was also found
during the synthesis of the metal complexes.
Scheme 2.
as THF, diethyl ether and dichloromethane, or in non-
polar solvent as benzene and hexane. The analytically
pure products were obtained through column chroma-
tography. The COD complexes of 1, 2 and 3 were yel-
low, a typical color for Rh(I) compound; while 4 was
nacarat, which is the typical color for Rh(I) carbonyl
compound. The IR spectrum of 1 showed typical skel-
etal vibrations of cyclopentadienyl ring at 3084, 2933,
1470, 1374, 1272, 1127 cmꢀ1 and typical COD skeletal
vibrations at 2875, 2827, 1323, 968, 867 and 804 cmꢀ1
.
Vibrational frequency of a free terminal alkene group
m(C@C) is found at 1649 cmꢀ1. Frequency of m(C@O) is
found at 1692 cmꢀ1, apparently red shifted comparing
to the ordinary ester m(C@O) value that is around 1750–
1735 cmꢀ1, indicating a conjugating effect to the cyco-
pentadienyl ring system. The yield of the carbonyl
compound 4 was lower than that of the COD com-
plexes. During the separation of 4 on alumina column, a
blue band was found and was collected to give blue oil.
It was very air-sensitive and did not obtain analytically
pure substance. It showed a very strong absorption at
The reactions with the substituted cyclopentadienide
as the starting material leading to the metal complexes
are presented in Scheme 2. Rh(I) complexes were pre-
pared through the reactions of substituted cyclopenta-
dienide and rhodium chloride dimer [RhCl(COD)]2 or
[RhCl(CO)2]2 in THF solution, thus the corresponding
half-sandwich type complexes of 1, 2, 3 and 4 were ob-
tained in moderate yields. These complexes have pretty
good solubility in organic solvent, either in polar solvent

830
X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
1730 cmꢀ1 in IR spectrum, which was considered the
vibrational frequency of a bridged metal carbonyl group
[9]. So the most possibility about the composition of the
blue oil should be a carbonyl bridged dimer product
[Cp4iRh(CO)]2.
The conjugation system between the ring and the
oxycarbonyl group in the substituent is confirmed by the
crystal structure of 1 (see Fig. 1). In the crystal structure
of 1, the average metal–ring carbon distance is found
the coordinated carbon atoms of the double bonds in
the COD ring are also not the same. The bond lengths of
ꢁ
Rh(1)–C(10) and Rh(1)–C(15) [both are 2.114(4) A] are
comparatively shorter than that of Rh(1)–C(11)
ꢁ
ꢁ
[2.127(3) A] and Rh(1)–C(14) [2.128(3) A]. Opposite to
the shorter rhodium–carbon bonds with COD are the
longer rhodium–carbon bonds with Cp, and longer
rhodium–carbon bonds with COD are opposite to the
shorter rhodium–carbon bonds with Cp. The phenom-
ena may be due to the trans effect. The bond lengths of
C(10)–C(11) and C(14)–C(15) are 1.393(6) and 1.378(6)
ꢁ
2.260 A. Among the five metal–ring carbon bonds,
Rh(1)–C(2) and Rh(1)–C(3) have longer bond length
ꢁ
[2.294(4) and 2.301(4) A], while Rh(1)–C(1) and Rh(1)–
ꢁ
A, respectively, showing the normal characteristic of the
ꢁ
C(4) have shorter bond length [2.221(3) and 2.231(3) A].
ꢁ
The length of Rh(1)–C(5) [2.255(3) A] is in between.
Thus the cyclopentadienyl ring is found in a slightly
puckered form. The C–C bond lengths in the cyclo-
ꢁ
pentadienyl ring are in the range of 1.390(6)–1.427(5) A.
Among them, C(2)–C(3) band was located furthest from
the ring substituent and has the shortest bond length
ꢁ
[1.390(6) A], showing more double bond character than
other C–C bonds. The strong electron-withdrawing
substituent of allyloxycarbonyl group is attached to
C(5), resulting in a relatively electronic deficient situa-
tion on it. A longer metal–carbon bond length of
Rh(1)–C(5) was found compared to its neighboring
metal–carbon bond length of Rh(1)–C(1) and Rh(1)–
C(4). The oxycarbonyl group is found coplanar with the
cyclopentadienyl ring and forms a large p conjugating
system. Similar bonding character was also found in the
crystal structure of (g5-C5H4COOCH3)Co(COD) [15],
(g5-C5H4COOCH2C6H5)Co(PPh3)I2 [5c] and the re-
cently reported b-hydroxyalkoxycarbonylcyclopentadie-
nyl rhodium complexes [13], respectively. In these
complexes, the shortest metal–carbon bond was also
found linking to the strong electron-withdrawing sub-
stituent. In 1, the distances between rhodium atom and
coordinated double bond [16].
1H NMR spectrum of 1 in (CD3)2CO shows one set
of multiplet at 6.04 ppm and two sets of doublets at
5.42 and 5.23 ppm for the allyl protons, similar to the
values found in its cobalt(I) analogue (g5-C5H4CO-
OCH2CH@CH2)Co(CO)2 [7]. However, the split of the
two sets of the pseudo triplet for Cp ring protons at 5.48
and 5.44 ppm is only 0.04 ppm in 1, smaller than the
value of 0.15 ppm found in its cobalt(I) carbonyl ana-
logue. In (g5-C5H4COOCH3)Co(COD), the corre-
sponding value is found 0.70 ppm. On the contrary, the
split of the ring protons in 2 is 0.17 ppm, although the
substituent of x-butenyl in 2 is electron-donating in
nature. The electron-withdrawing substituent –COR to
the Cp ring causes a split of the chemical shift of the ring
protons about 0.60 ppm for cymantrene derivatives and
about 0.15 ppm for cobalt(I) carbonyl analogues were
reported [14]. In the case of electron-donating sub-
stituent as –CH2CH2CO2R and –CH2CO2R to the Cp
ring of cymantrene derivatives, the corresponding values
were found only 0.02 and 0.15 ppm, respectively. The
small split of the chemical shift of the ring protons is
considered a hint that the Rh(I) atom in 1 is an more
electron-rich metal center compared with Co(I) and
Mn(I) complexes mentioned above.
Usually an electron-rich metal compound like Rh(I)
complex is air sensitive, but 3 is air stable. Even the
carbonyl compound 4 can stay in air for a reasonable
long period of time. The probable explanation on this
may be drawn from the crystal structure of 3 (see Fig. 2).
The average metal and Cp ring-carbon distance in 3 is
ꢁ
2.250 A. And the average metal and COD-carbon dis-
ꢁ
tance is 2.089 A. Both of them are shorter than the
corresponding values found in 1. It is considered that
part of the electron density on the mental center of 1 is
dispersed into its p system, therefore leads a weaker
bonding ability of the metal with its circumambient li-
gands. On the contrary, the four isopropanyl groups in
C5H(i-C3H7)4 ligand are electron-donating. The mental
center of 3 is more electron-rich than 1. The shorter
metal–carbon bond distances reflect the stronger bond-
ing ability of the metal with its circumambient ligands.
In spite of such an electron-rich metal center, the four
steric bulky isopropanyl groups are arrayed parallel to
Fig. 1. Molecular structure of (g5-C5H4COOCH2CH@CH2)Rh(COD)
(1). Ellipsoids are drawn at 50% probability level.

X. You-Feng et al. / Journal of Organometallic Chemistry 689 (2004) 823–832
831
their dimer structures. Hadjiliadis reported that the 2-
(dimethylamino)ethyl cyclopentadienyl Rh(I) COD
compound or carbonyl compound gave chelated ha-
logenide monomer after treated with iodine or chlorine.
However, after the nitrogen atom in the side chain was
protonated, the amino group lost its donating ability.
The addition of the halogen to the 2-(dimethyla-
mino)ethyl cyclopentadienyl Rh(I) COD compound
resulted in the iodine or chlorine bridged dimer product
then [17]. The alkene group in the side chain of 5 and 7
has very weak donating ability. It cannot compete with
halogen atom. The formation of the iodine bridged
dimer of 5 and 7 will not be affected by their chelatable
substituent.
When stronger electron donating molecule existed,
the iodine bridged dimer structure was destroyed. Thus
5 treated with triphenyl phosphine or carbon monoxide
resulted the corresponding monomer 9 or 10. Carbon
disulfide could also break down the iodine bridged
structure. About two equivalent of carbon disulfide was
added to the solution of 5 in CH2Cl2, one of the coor-
dination site on the Rh(III) was occupied by CS2 and
resulted the CS2 substituted product of monomer 8. The
IR spectrum of 8 shows a medium strong stretching
frequency at 1026 cmꢀ1, which is the characteristic
frequency for the m(C@S) of a p bonded CS2 molecule
[18].
Fig. 2. Molecular structure of (g5-C5H(i-C3H7)4)Rh(COD) (3).
Ellipsoids are drawn at 50% probability level.
each other and perpendicularly to the Cp ring, therefore
they enwrapped the metal atom and protect it from
being oxidized when exposed to air.
The addition of a solution of iodine in ether to the
solutions of COD complexes of 1, 2 and 3 in ether
resulted in the loss of COD ligand and yielded the io-
dine bridged dimer products of 5, 6 and 7, respectively,
in high yields. The IR spectrum of 5 showed typical
skeletal vibrations of cyclopentadienyl ring at 3067,
1460, 1275, 1157 and 1026 cmꢀ1, very similar to its
parent compound 1. However, the frequency of
m(C@O) and m(C-H of Cp ring) are now 1724 and 2962
cmꢀ1, respectively, considerable blue shifted compared
to the values of 1691 and 2933 cmꢀ1, respectively,
found in its parent compound 1, reflecting the elec-
tronic effect from a less electron-rich metal center of
Rh(III) in 5 compare to Rh(I) in 1. Frequency of
m(C@C) at 1649 cmꢀ1 is unchanged, indicating the ex-
istence of an untouched free terminal alkene group. The
IR spectrum of 7 shows typical skeletal vibrations of
cyclopentadienyl ring at 3088, 3070, 1470, 1393, 1107
and 1031 cmꢀ1, similar to its parent compound 2. Vi-
brational frequency of a free terminal alkene group of
m(C@C) at 1640 cmꢀ1 is also found unchanged in its IR
4. Supplementary data
Crystallographic data have been deposited with the
CCDC (12 Union Road, Cambridge, CB2 1EZ, UK)
and are available on request quoting the deposition
numbers 196053 for (g5-C5H4COOCH2CH@CH2)
Rh(COD) (1) and 196052 for (g5-C5H(i-C3H7)4)Rh
(COD) (3), respectively.
Acknowledgements
Project 29771008 was supported by the National
Natural Science Foundation of China.
1
spectrum. In the H NMR spectrum, the chemical shift
of the ring protons of 5 (a derivative from 1) in CDCl3
are at 6.07 and 5.71 ppm, respectively, giving a split of
0.36 ppm. The corresponding chemical shifts of 7 (a
derivative from 2) are 5.49 and 5.46, with a split of only
0.03 ppm. These situations match the cases found in the
substituted cyclopentadienyl Co(I) and Mn(I) com-
plexes reported in the literatures mentioned above.
Although 5, 6 and 7 did not give molecular ion peaks
for their dimer structures in mass spectra, the peaks of
the molecular fragments of these complexes supported
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