Coordination chemistry of ester-functionalized cp ligands: Synthesis and catalytic activity of [Rh{CpCO2(CHPh)2OH}(NBD)] and [Rh{CpCO2(CH2)3MOH}(NBD)]

Article abstract of DOI:10.1016/j.jorganchem.2004.04.010

Two new sodium hydroxyalkoxycarbonylcyclopentadienide salts Na [rac- CpCO₂(CHPh)₂OH] (1) and Na[(2S,3S) -CpCO₂(CHPh)₂OH] (2) were prepared by reaction of NaCp with the five-membered cyclic carbonates cis -4,5-diphenyl-1,3-dioxolan-2-one and (4 S ,5 S )-4, 5-diphenyl-1,3-dioxolan-2-one. The reaction of these salts with [Rh(NBD)Cl]₂ gave [Rh{ rac -CpCO₂ (CHPh)₂OH}(NBD)] (3) and (-)-[Rh{(2 S ,3 S ) -CpCO₂(CHPh)₂OH}(NBD)] (4) whose catalytic activity in the hydroformylation of hex-1-ene and styrene has been investigated and compared with that of the previously reported rhodium complexes [Rh{CpCO₂(CHR)₂OH}(NBD)] (R=H, Me). In addition we also discuss some preliminary results regarding the behavior of these complexes in the hydrogenation of the same substrates. The reactivity of NaCp toward the six-membered cyclic carbonate 1,3-dioxan-2-one has also been studied and it has been found that the reaction leads to two cyclopentadienide anions [CpCO₂(CH₂) ₃OH]^- (5) and [CpCO₂(CH₂) ₃OC(O)O(CH₂)₃OH]^- (6) in amounts strictly dependent on the carbonate/NaCp stoichiometric ratio.

Full text of DOI:10.1016/j.jorganchem.2004.04.010

Journal of Organometallic Chemistry 689 (2004) 2216–2227
www.elsevier.com/locate/jorganchem
Coordination chemistry of ester-functionalized cp ligands:
synthesis and catalytic activity of [Rh{CpCO2(CHPh)2OH}(NBD)]
and [Rh{CpCO2(CH2)3OH}(NBD)]
a,
a
a
b,
*
Luigi Busetto *, M. Cristina Cassani , Rita Mazzoni , Piero Frediani
,
b
Eleonora Rivalta
a
Dipartimento di Chimica Fisica ed Inorganica, Universitꢀa degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
Dipartimento di Chimica Organica, Universitaꢀ degli Studi di Firenze, via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
b
Received 1 March 2004; accepted 7 April 2004
Abstract
Two new sodium hydroxyalkoxycarbonylcyclopentadienide salts Na[rac-CpCO2(CHPh)2OH] (1) and Na[(2S,3S)-
CpCO2(CHPh)2OH] (2) were prepared by reaction of NaCp with the five-membered cyclic carbonates cis-4,5-diphenyl-1,3-
dioxolan-2-one and (4S,5S)-4,5-diphenyl-1,3-dioxolan-2-one. The reaction of these salts with [Rh(NBD)Cl]2 gave
[Rh{rac-CpCO2(CHPh)2OH}(NBD)] (3) and ())-[Rh{(2S,3S)-CpCO2(CHPh)2OH}(NBD)] (4) whose catalytic activity in the
hydroformylation of hex-1-ene and styrene has been investigated and compared with that of the previously reported rhodium
complexes [Rh{CpCO2(CHR)2OH}(NBD)] (R ¼ H, Me). In addition we also discuss some preliminary results regarding the
behavior of these complexes in the hydrogenation of the same substrates. The reactivity of NaCp toward the six-membered
cyclic carbonate 1,3-dioxan-2-one has also been studied and it has been found that the reaction leads to two cyclopenta-
dienide anions [CpCO2(CH2)3OH]ꢀ (5) and [CpCO2(CH2)3OC(O)O(CH2)3OH]ꢀ (6) in amounts strictly dependent on the
carbonate/NaCp stoichiometric ratio.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Carbonyl-derived cyclopentadienyl ligands; Rhodium complexes; Hydroformylation; Hydrogenation
1. Introduction
the homogeneous hydroformylation of hex-1-ene and
styrene [1c,1d].
In the course of our studies concerning the develop-
ment of new ester-functionalized Cp ligands we have
recently disclosed that the reaction of NaCp with ali-
phatic five-membered cyclic carbonates leads, in one
step and high yields, to the formation of a variety of
novel chiral and non-chiral hydroxy-functionalized
alkoxycarbonylcyclopentadienides Na[CpCO2(CHR)2
OH] (R ¼ H, Me) (Scheme 1) [1].
Pursuing an extension of our studies, we now report
the synthesis and catalytic activity of similar rhodium
derivatives containing (i) an aromatic substituent
(R ¼ Ph) on the hydroxyalkoxycarbonyl pendant and
(ii) a longer alkylene side chain (n ¼ 3).
2. Results and discussion
The easy availability of such ligands provided a
valuable route to rhodium complexes of the type [Rh
{CpCO2(CHR)nOH}(L,L)] [R ¼ H, Me; n ¼ 2; L,L ¼
2CO, NBD] which showed to exert catalytic activity in
2.1. Synthesis of Na[CpCO2(CHPh)2OH] and rhodium
complexes
In order to obtain the title ligand we reacted NaCp
with cis-4,5-diphenyl-1,3-dioxolan-2-one, easily avail-
able through transesterification of meso-1,2-diphenyl-
ethane-1,2-diol with diethyl carbonate in the presence of
* Corresponding authors. Tel. +39-051-2093700; fax: +39-051-
2093690.
E-mail address: busetto@ms.fci.unibo.it (L. Busetto).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.04.010

L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
2217
O
OH
O
O
OH
O
O
O
O
+
O
O
O
O
OH
Y = 91%
O
Y = 97%
S
O
S
O
O
O
O
O
O
O
THF,r.t.,30h
OH
OH
S
S
O
O
Y = 93%
Y = 90%
Scheme 1.
sodium methoxyde. Through our procedure the cyclic
carbonate was converted into Na[rac-CpCO2(CHPh)2
OH] (1), a racemic mixture of the 2S,3R-1 and 2R,3S-1
enantiomers. Similarly, from optically active ())(4S,5S)-
(4,5)-diphenyl-1,3-dioxolan-2-one (prepared from ())-
(1S,2S)-1,2-diphenyl-ethane-1,2-diol) the enantiomeri-
cally pure Na[(2S,3S)-CpCO2(CHPh)2OH] (2) was
obtained (Scheme 2). In both cases the yields (ca. 60%)
were lower than that previously found with R ¼ H, Me
(ca. 90%).
Due to the insolubility of the starting carbonates in
diethyl ether the previously described work-up is not
effective and a strict 1:1 ratio between the reagents must
be employed in order to have a carbonate-free product.
However, at least for the rhodium derivatives herein
presented, this is not a crucial problem as the excess of
carbonate can be easily separated by chromatography
once the metal complex is obtained.
The ring opening reactions proceeded without any
racemization at the chiral carbon centers as confirmed
by the nature of their metal complexes described below.
The sodium salts rac-1 and (2S,3S)-2 are air and mois-
ture sensitive light brown solids. Their NMR spectra in
[D5]Pyr showed, as expected, two AA0BB0 pseudotriplets
for the Cp protons H(3,4) and H(2,5) [1H NMR d 7.5–
6.5] and 13C NMR Cp signals in the range d 113–109
[1b,1c]. With regard to the spectral pattern of the b-
hydroxyalkoxycarbonyl group –CO2CH(Ph)CH(Ph)OH
of the pendant side chain, the NMR spectra for rac-1
and (2S,3S)-2 exhibit a single set of signals with very
Ph
O
OH
O
O
O
Na+
Ph
O
Ph
rac-1 , Y = 61%
Ph
similar chemical shifts (see Section 3); however, while in
3
Ph
rac-1 the J
coupling constant between the two
ðCH;CHÞ
Na+
CH protons is 4.4 Hz, it rises to 6.7 Hz in (2S,3S)-2. This
difference reflects a significative variation in the con-
formation and configuration of the side chains con-
taining the two chiral centers that is retained in their
rhodium complexes (see next). In addition, contrary to
what found with analogous systems where the resonance
of the –OH group has never been observed, with the
help of a 1H, 1H-gCOSY correlation experiment, we
located the OH proton resonance in the aromatic region
around 7.40 ppm and found a 3JðCH;OHÞ coupling of ca. 4
Ph
S
O
S
O
O
Ph
O
OH
S
S
O
Na+
Ph
(2S, 3S)-2,Y = 63%
Scheme 2.

2218
L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
Hz. The IR spectra of rac-1 and (2S,3S)-2 in THF show,
in both cases, a m(C@O) broad band around 1640 cmꢀ1
2.2. Reaction of NaCp with 1,3-dioxan-2-one
.
The reactions of rac-1 and (2S,3S)-2 with
[Rh(NBD)Cl]2 in THF at r.t. gave, after chromatogra-
phy on silica gel, the corresponding yellow, air and
moisture stable, complexes [Rh{rac-CpCO2(CHPh)2
OH}(NBD)] (3) and [Rh{(2S,3S)-CpCO2(CHPh)2OH}
(NBD)] (4) (56–58% yields).
The reaction between NaCp and the six-membered
cyclic carbonate 1,3-dioxan-2-one carried out in THF at
room temperature for 24 h, presented some significative
differences compared to what observed for the just de-
scribed five-membered ring case. The most informative
1
feature came from the H NMR spectrum of the reac-
tion mixture in [D5]Pyr which showed the appearance, in
the cyclopentadienyl protons region (d 7.40–6.60), of
two sets of AA0BB0 multiplets whose relative intensities
changed depending on the molar ratio of the reactants.
In addition, the same trend was observed in the regions
around 4 and 2 ppm where the resonances of the alk-
ylene protons were expected. A parallel behavior was
also found in the 13C–{1H} NMR spectra that presented
three –C@O resonances of variable intensities at d 168.8,
168.4 and 155.5 ppm and two sets of signals for the Cp
ring carbons in the range d 113–109 ppm. Finally, the IR
spectrum in THF (range 2300–1500 cmꢀ1) exhibited two
distinct m(C@O) bands: a broad one centered at 1644
cmꢀ1, due to the conjugated C@O and C@C of the Cp
ring p system and a sharp band at 1747 cmꢀ1, attributed
to the presence of a non-conjugated –OC(O)O– group,
with relative intensities depending on the carbonate/
NaCp molar ratio employed.
We tentatively interpreted these findings with the
presence of a mixture of two cyclopentadienide anions:
the expected [CpCO2(CH2)3OH]ꢀ (5) and the unex-
pected [CpCO2(CH2)3OC(O)O(CH2)3OH]ꢀ (6). The
product 5 derives from the intramolecular deprotona-
tion of the likely intermediate A whereas 6 is formed
from a nucleophilic attack of A on a second molecule of
carbonate followed by deprotonation (Scheme 3).
Accordingly, Table 1 contains the products distribu-
tion, as determined by NMR analysis of the crude
product, of the reaction carried out in the same condi-
tions (THF, room temperature, reaction time 24 h) but
with three different carbonate/NaCp ratios. The experi-
ments showed that the higher is the carbonate/NaCp
CO2X
Rh
X =rac-CH(Ph)CH(Ph)OH (3)
X = (2S,3S)-CH(Ph)CH(Ph)OH (4)
The NMR and IR spectral properties of these mate-
rials present features similar to those previously de-
scribed [1b,1c]. We could not obtain suitable crystals for
X-ray diffraction studies; however, the different
3JðCH;CHÞ coupling constants for rac-3 and S,S-4 (5.8 and
7.1 Hz, respectively) are consistent with those of the free
ligands and in agreement with what previously found for
[Rh{rac-CpCO2(CHMe)2OH}(NBD)] (3J
¼ 3:5
ðCH;CHÞ
Hz) and [Rh{(2S,3S)-CpCO2(CHMe)2OH}(NBD)]
(3J
¼ 6:1 Hz) [2]. It is worth mentioning that the
ðCH;CHÞ
X-ray diffraction studies of these latter complexes
showed that the two molecules significant differ in the
conformation and configuration of the –CH(Me)CH-
(Me)OH side chains containing the two chiral centers
with dihedral angles equal to 68.4(3)° and 58.7(3)°,
respectively.
O
1) Intramolecular deprotonation
OH
O
_
Na+
5
O
O
_
THF, r.t.,24 h
O
O
ONa
O
NaCp
+
O
A
O
O
O
O
OH
O
O
O
1)
_
Na+
2) Intramolecular deprotonation
6
Scheme 3.

L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
2219
Table 1
Reaction of NaCp with 1,3-dioxan-2-one: products distribution
cyclic carbonates compared to the five-membered ones
due to a larger ring-strain energy (ca. 2.86 kcal/mol) [3].
The two salts 5 and 6 could not be separated and the
mixtures I, II and III were reacted with [Rh(NBD)Cl]2.
The metathetic reactions in THF at r.t. gave several
moisture and air stable yellow mono- and dinuclear
complexes (Scheme 4), separated by chromatography on
silica gel.
Mixtures 1,3-Dioxan-2-one/
NaCp
5/6 Yields of 5 Yields of 6
(%)
1.7 30
1.2 33
0.6
(%)
I
1.3
1.6
2.2
18
26
12
II
III
7
As it can be seen in Scheme 4 the complex
[Rh{CpCO2(CH2)3OH}(NBD)] (7) is always the major
product but, while with I the yield is 50%, similar to
what usually found for these systems, it drops to 23%
with III where a lower content of 5 is present. The for-
mation of 8 confirmed the presence of 6 in all the anionic
mixtures and the yield increased going from I to III due
to the larger occurrence of 6.
From Scheme 4 can also be observed that only when
the anionic mixture III is employed, the isolation of
small amounts of 9 was observed. The formation of 9
can be explained with the fact that, in the presence of a
larger excess of carbonate, the reaction between NaCp
and 1,3-dioxan-2-one proceeds further to give a product
of the type Na[CpCO2{(CH2)3OC(O)O}2(CH2)3OH],
ratio, the lower the 5/6 ratio becomes and that while the
total yield for I and II is ca. 50%, it drops to just 19% for
III. It must be noted that when a 1:1 carbonate/NaCp
ratio was employed the NMR spectra showed the
presence of unreacted NaCp together with 5 and 6 in a
ratio ca. 2/1 demonstrating that a competitive reaction
involving the carbonate occurs. Finally, non-significant
differences were observed in the products distribution
varying the reaction times.
The formation of type 6 anion, never observed with
five-membered cyclic carbonates, can be explained with
(a) the intramolecular deprotonation of A requires the
formation of a less favored nine-membered ring inter-
mediate and (b), the higher reactivity of the six-membered
O
O
O
OH
O
O
THF, r.t., 3 h
O
OH
O
_
_
+ [Rh(NBD)Cl]2
+
5
6
O
O
O
OH
O
OH
O
O
O
Rh
+
+
Rh
7
8
I,Y= 50 %;
I,Y = 3 %;
II,Y = 8 %;
III,Y = 11 %.
II, Y= 30 %;
III,Y= 23 %.
O
O
O
O
O
OH
O
O
O
Rh
9
I, Y = 0 %;
II, Y = 0 %;
III, Y = 4 %.
O
O
O
O
O
O
O
O
O
O
O
+
Rh
Rh
Rh
Rh
10
11
I,Y = 6 %;
II, Y = 2 %;
III, Y = 5 %.
I,Y = 4 %;
II, Y = 0 %;
III, Y = 0 %.
Scheme 4.

2220
L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
deriving from a successive nucleophilic attack of the
intermediate C5H5CO2(CH2)3OC(O)O(CH2)3Oꢀ (anal-
ogous to A) on a third molecule of carbonate.
Finally, the dimeric products 10 and 11 are deriving
from transesterification reactions catalyzed by the li-
gands similar to what already reported and described for
[Rh{CpCO2(CH2)2OH}(L,L)] [1b].
All the above compounds 7–11 have been fully char-
acterized by standard analytical/spectroscopic tech-
1
niques. The H and 13C NMR spectra in CDCl3 of all
the complexes depicted in Scheme 4 showed the expected
resonances for the C5H4– and NBD moieties which are
strictly comparable with those of the previously reported
[Rh{CpCO2(CH2)2OH}(NBD)] [1b].
All complexes showed in the IR spectra a strong
m(C@O) band at 1712 cmꢀ1 for the Cp-linked ester
group and a corresponding signal at d 165 in the 13C
NMR spectra; in addition, complexes 8, 9, and 11 also
showed a strong band at 1749 cmꢀ1 and a parallel signal
at d 155.0, attributed to the –OC(O)O– group. The ESI-
MS spectra showed the molecular ion peak [M]þ for all
the five complexes.
2.3. Catalytic activity
We have previously reported that the hydroformyla-
tion of olefins, in the presence of rhodium catalysts
containing a b-hydroxyalkoxycarbonylcyclopentadienyl
ligand, is affected by the nature of the substituents
present on the lateral chain [1c,1d]. The new Rh(I)
complexes 3, 4 and 7, herein synthesized, were tested in
order to collect new evidences on the relation between
the steric hindrance of the lateral chain and the catalytic
activity of the corresponding rhodium complexes. The
results are compared with those previously reported
for [Rh{CpCO2(CHR)2OH}(NBD)] [R ¼ H (12), Me
(rac-13, S,S-14)]. The reaction conditions and the hyd-
roformylation results are reported in Tables 2–4. In
addition we also report some preliminary results
regarding the behavior of these complexes in the hy-
drogenation of the same substrates.
2.3.1. Hydroformylation of hex-1-ene
Complexes rac-3 and S,S-4 are catalytically active in
the hydroformylation and isomerization of hex-1-ene
although the rates of these reactions are lower than
those reported for rac-13 and S,S-14 having two methyl
groups on the lateral chain therefore confirming that in
the hydroformylation of hex-1-ene the presence of sub-
stituents on the side chain has a negative impact on the
catalytic performances of the complexes. The data are
summarized in Table 2, while in Table 3 are reported
details regarding the yields of aldehydes and isomerized
olefins.
Complex rac-3 did not show any catalytic activity at
60 or 80 °C for 4 h (entry 1 and 2), however at 80 °C an

Table 3
Hydroformylation of hex-1-ene in the presence of [Rh(CpX)(NBD)] catalystsa
Entry Catalyst
code
T
Time (h) Hexane
(yield %)
Hex-1-ene
(yield %)
cis-Hex-2-ene
(yield %)
trans-Hex-2-ene
(yield %)
cis-Hex-3-ene trans-Hex-3-ene Heptanal 2-Methylhexanal
(yield %) (yield %)
2-Ethylpentanal
(yield %)
(°C)
(yield %)
(yield %)
3
4
3
3
80
80c
60c
80
60
60
24
4
0.5
0.6
1.1
0.5
0
0.9
1.4
10.7
20.5
3.5
17.7
29.6
8.6
1.6
1.9
0.8
1.6
0.1
0.7
6.8
7.0
0.1
6.6
3.0
3.1
33.8
25.2
15.8
32.3
25.4
47.9
28.1
13.7
7.1
0
0
5
3
4
62.9
0.7
6
4
24
4
5.9
7.6
17.0
22.2
14.5
35.4
11.1
22.4
0
0
0
10
11b
7
12
30.6
1.2
4
0.5
9.7
a Reaction conditions: catalyst 20 lmol, hex-1-ene 2 mmol, THF 25 ml, p(CO) 15 bar, p(H2) 15 bar.
b See [1c,1d].
c The catalyst was pre-activated: a THF solution was heated up to 80 °C for 24 h, under a CO/H2 ¼ 1:1 at 30 bar, then cooled to r.t. and the gases vented out. The substrate was introduced by
suction into the vessel.
Table 4
Hydroformylation of styrene of [Rh(CpX)(NBD)] catalystsa
Entry
Catalyst
code
X
T (°C)
Time (h)
Conversion
(yield %)
2-Phenylpropanal
(yield %)
3-Phenylpropanal
(yield %)
Ethylbenzene Regioselectivity
(yield %)
(2-phenylpropanal/total
aldeydes) (yield %)
12b
13
12
7
CO2(CH2)2OH
CO2(CH2)3OH
80
80
60
80
60
60
80
80
80
80
4
4
53.1
51.6
11.2
64.0
6.7
30.0
26.5
10.1
47.0
6.7
23.1
25.1
1.1
0
56.4
51.4
90.0
67.1
100
0
14
15
3
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
(S,S)-CO2(CHPh)2OH
(S,S)-CO2(CHPh)2OH
(S,S)-CO2(CHPh)2OH
(S,S)-CO2(CHPh)2OH
rac-CO2(CHMe)2OH
(S,S)-CO2(CHMe)2OH
4
0
3
4
21.0
0
0
16
17
4
4
0
4
24
4
10.1
42.1
99.9
51.5
30.0
10.1
21.4
50.7
26.4
23.5
0
0
100
18
4
20.5
48.1
25.1
6.5
0.2
1.1
0
51.1
51.3
51.1
78.4
19
4
24
4
20b
21b
13
14
4
0
a Reaction conditions: catalyst 20 lmol, styrene 2 mmol, THF 25 ml, p(CO) 15 bar, p(H2) 15 bar.
b See [1c,1d].

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L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
almost complete conversion (99.1%) of hex-1-ene has
been reached after 24 h, with an aldehyde yield of 61.8%
(entry 3). This behavior suggested that an activation of
the catalyst at 80 °C is necessary before starting a cata-
lytic cycle. This hypothesis was supported by a test where
the catalyst rac-3 was pre-activated at 80 °C for 24 h
under CO/H2 (1/1, 30 bar). The solution was then cooled
down to room temperature, the gases vented and hex-1-
ene (substrate/catalyst ¼ 100/1) added. The autoclave
was re-pressurized with 30 bar of CO/H2 (1/1) and heated
up to 80 °C (entry 4) for 4 h obtaining an almost com-
plete conversion of hex-1-ene and a slightly higher regi-
oselectivity. In these latter conditions, however, the
yields of aldehydes and isomerized olefins were very
different from those obtained in the reaction performed
at 80 °C for 24 h (entry 3). If the hydroformylation, after
the same pre-activation procedure, is carried out at 60 °C
for 4 h, a 37.1% conversion was obtained (entry 5). These
data confirmed our hypothesis on the required pre-acti-
vation of the catalyst and they also showed that different
rhodium active species must be present either using or
not the pre-activated catalyst. Furthermore, the pre-ac-
tivated catalysts were more active in the isomerization
than in the hydroformylation. The regioselectivity of the
reaction performed without catalyst pre-activation is
lower than that obtained with the pre-activated one. The
catalytic activity of rac-3 in the hydroformylation and
isomerization of hex-1-ene was similar to that shown by
S,S-4: the conversion [99.1% (entry 3) and 99.3% (entry
6), respectively] and yield of aldehydes [61.8% and
67.7%, respectively] are almost the same. These results
are significantly different from those previously reported
for the racemic and chiral rhodium complexes rac-13 and
S,S-14, having two methyl groups on the lateral chain
(entry 7, 8 and 9), indicating a different steric influence of
the phenyl groups with respect to the methyl ones.
The hydroformylation of hex-1-ene is also affected by
the length of the lateral chain on the cyclopentadienyl
ligand: the presence of three methylene groups on the
side arm of 7 decreases its catalytic activity with respect
to 12. In fact the correlation of the data obtained with
the catalysts 7 and 12 showed that the olefins conversion
drops from 98.8 (12, entry 11) to 69.4% (7, entry 10). The
reduction of the catalytic activity is mainly reflected in
the hydroformylation. In fact, the yield of aldehydes
goes down from 70.2% to 36.5%, while the regioselec-
tivity remains almost unchanged. On the contrary, the
isomerization slightly increases from 28.1% to 32.9%.
The complex 7 showed a slightly lower activity in the
isomerization of hex-1-ene than in the hydroformyla-
tion. In these conditions, the hydrogenation of the
starting olefin is almost absent.
with respect to the results obtained with the aliphatic
substrate just described (Table 4). The most remarkable
difference concerned the reaction temperature.
Complexes rac-3 and S,S-4 hydroformylated styrene
after 4 h at 60 °C with low conversions but very high (3,
entry 14) or complete (4, entry 16) regioselectivities to-
ward 2-phenylpropanal. With regard to S,S-4, entry 17
shows that when the reaction time was raised up to 24 h,
a low increase of the conversion was obtained (10.1 %),
while the regioselectivity remained unchanged. How-
ever, in both cases (entry 16 and 17), the enantiomeric
excess of 2-phenylpropanal was not higher than 3%.
With the same complex at 80 °C for 4 h, the conversion
of styrene has been increased up to 42.1% (entry 18) and
it was almost complete (99.9%, entry 19) after 24 h,
however in both cases the regioselectivity (51%) is re-
markably lower than that found at 60 °C.
Moreover with respect to the influence of the sub-
stituents on the side chain, the results obtained running
the reaction for 4 h, at 80 °C showed that in the presence
of two Ph groups the catalytic activity of the rhodium
complexes is higher than that of the analogous systems
with two Me groups (rac-3 vs. 13, entries 15 and 20; S,S-
4 vs. 14, entries 18 and 21). Conversely at this temper-
ature the regioselectivity is slightly affected by the steric
hindrance of the lateral chain and remained in the range
51–79%.
The length of the lateral chain of the cyclopentadienyl
ligand did not affect the catalytic activity of these rho-
dium complexes in the hydroformylation of styrene:
complex 7 showed an almost identical catalytic activity
(entry 13) to that shown by 12 (entry 12) with a 51.6%
conversion.
2.3.3. Catalytic activity in the hydrogenation: preliminary
results
The rhodium cyclopentadienyl catalysts described so
far did not hydrogenate alkenes in the hydroformylation
conditions nevertheless, with the aim of testing their
catalytic activity in the absence of CO, we have per-
formed the hydrogenation of hex-1-ene and styrene. In
this paper we report some preliminary results regarding
the catalytic activity of 12, 3, (respectively bearing
R ¼ H, Ph on the side chain) in comparison with the
unsubstituted [Rh(Cp)(NBD)] (15). The reaction con-
ditions and the hydrogenation results are reported in
Tables 5 and 6.
As usually found for rhodium complexes [4], com-
pounds 3 and 12 resulted to be more active in the hy-
drogenation than in the hydroformylation of hex-1-ene
and styrene. Working at 20 °C under 15 bar of H2 for 4
h in the presence of 12 (for hex-1-ene and styrene) and 3
(for hex-1-ene only) an almost complete conversion was
reached, while in the hydroformylation higher temper-
atures (>60 °C) or longer times were required to obtain
these results. Nevertheless the hydrogenation reaction
2.3.2. Hydroformylation of styrene
The catalytic activity of these catalysts in the hydro-
formylation of styrene showed significant differences

L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
2223
Table 5
Hydrogenation of hex-1-ene in the presence of [Rh(CpX)(NBD)] catalystsa
Entry
Catalyst code
X
T (°C)
p(H2) (bar)
Hexane (conversion %)
22
23
24
25
26
27
12
3
CO2(CH2)2OH
20
20
20
40
60
20
15
1
97.6
0
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
H
3
15
15
15
15
99.0
3
100
100
97.1
3
15
a Reaction conditions: catalyst 20 lmol, hex-1-ene 2 mmol, THF 25 ml, time 4 h.
Table 6
Hydrogenation of styrene in the presence of [Rh(CpX)(NBD)] complexesa
Entry
Catalyst code
X
T (°C)
p(H2) (bar)
Ethylbenzene (conversion %)
28
29
30
31
32
33
34
35
36
37
12
12
12
12
3
CO2(CH2)2OH
CO2(CH2)2OH
20
20
40
20
20
30
40
60
20
20
15
5
100
0
CO2(CH2)2OH
CO2(CH2)2OH
1
5b
0.2
4.0
2.5
7.7
100
100
6.4
8.1
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
rac-CO2(CHPh)2OH
rac-CO2(CHMe)2OH
H
15
15
15
15
15
15
3
3
3
13
15
a Reaction conditions: catalyst 20 lmol, styrene 2 mmol, THF 25 ml, time 4 h.
b The catalyst 12 was pre-activated: a THF solution was heated up to 20 °C for 4 h under/H2 ¼ 20 bar, then the gases was vented out. The substrate
was introduced by suction into the vessel.
required hydrogen under pressure to take place: more
than 5 bar of hydrogen are necessary (3, entry 23; 12,
entry 29).
8.1% conversion (entry 37). On the other hand, an in-
crease of the steric encumbrance on the lateral chain
reduces the catalytic activity as shown by the data re-
ported in Table 6 for the complexes 12 (conversion
100%, entry 28), rac-13 (conversion 6.4%, entry 36), and
rac-3 (conversion 2.5%, entry 32). An analogous be-
havior was observed in the hydroformylation of olefins
catalyzed by the same complexes [1c,1d]. In particular,
the presence of two phenyl groups on the lateral chain of
the cyclopentadienyl ligand strongly decreases the cat-
alytic activity of the corresponding rhodium complex
and a reaction temperature of 40 °C is required to reach
a complete conversion after 4 h.
The observation that in the course of the hydro-
formylation reaction a very low hydrogenation of the
substrate takes place, allow us to draw the conclusion
that the presence of CO strongly inhibits the formation
of a rhodium hydride complex and consequently the
hydrogenating activity of these catalysts.
In order to shed light on the real nature and structure
of the active catalytic species, high pressure NMR and
IR studies in hydroformylation (CO/H2 ¼ 1/1, 30 bar)
and hydrogenation (H2, 15 bar) conditions are under
investigation. Preliminary results obtained using the
rhodium complexes [Rh{CpCO2CH2CH2OH}(L,L)]
(L,L ¼ 2CO, NBD) showed that the integrity of the
starting Cp–Rh moiety is maintained throughout the
In our opinion, the relatively high pressure of hy-
drogen required is necessary to maintain the active
catalyst. To confirm this hypothesis a solution of 12 was
stirred under 15 bar of hydrogen for 4 h at 20 °C. The
hydrogen was then vented, styrene was added and the
solution stirred again under 5 bar of hydrogen for 4 h at
20 °C: a 4% conversion was observed (entry 31). We can
consequently assume that a hydrogen pressure higher
than 5 bar is required to perform the catalytic cycle. This
behavior was confirmed by the fact that running the
same reaction with 12 at higher temperature (40 °C)
under a 1 bar of hydrogen only a 0.2% conversion was
obtained (entry 30).
Contrary to what observed in the hydroformylation,
the presence of different groups on the lateral chain of
the cyclopentadienyl ligand did not affect the hydroge-
nation of hex-1-ene. Furthermore, we observed that also
the unsubstituted rhodium cyclopentadienyl complex 15
gave a 97.1% conversion (entry 27).
The presence of a lateral chain on the cyclopenta-
dienyl ligand did affect the catalytic activity of the rho-
dium complexes in the hydrogenation of styrene. While
12 showed a complete conversion at 20 °C and 15 bar of
H2 (entry 28), 15 showed, in the same conditions only

2224
L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
experiments. However so far we did not succeed in
determining the nature of the rhodium species formed
during the catalytic cycle.
the composition of the residual hexenes. A GC-MS
Shimadzu QP 5050 instrument was used to verify the
identity of the products obtained. A 150 ml Parr auto-
clave was employed for the catalytic tests. Elemental
analyses were performed on a ThermoQuest Flash 1112
Series EA Instrument.
3. Conclusions
The reagents ())(1S,2S)-1,2-diphenyl-1,2-ethanediol
[5], cis-4,5-diphenyl-1,3-dioxolan-2-one [6], ())(4S,5S)-
4,5-diphenyl-1,3-dioxolan-2-one [6], and 1,3-dioxan-2-
one [7] were prepared according to the literature pro-
cedures; meso-1,2-diphenyl-ethane-1,2-diol (Aldrich),
[Rh(NBD)Cl]2 (Strem) were used as purchased. The
complexes 12 [1b,8], rac-13, S,S-14 [1c] were prepared as
previously described. Petroleum ether (Etp) refers to a
fraction having b.p. 60–80 °C. The THF (RPE C. Erba)
used in the catalytic experiments was dried by refluxing
over Na/K under nitrogen atmosphere, distilled
(b.p. 65 °C) and stored under nitrogen. Hex-1-ene (Al-
drich), eluted through an Al2O3 column and distilled,
had b.p. 64 °C. Styrene (Aldrich), distilled prior to use,
had b.p. 145 °C. Silica gel was heated at about 200 °C
while a slow stream of a dry nitrogen was passed
through it [9]. Melting points were taken in sealed cap-
illaries and were uncorrected.
In the first part of this paper we have presented an
extension of our previously described procedure to ob-
tain chiral and non-chiral hydroxy-functionalized alk-
oxycarbonylcyclopentadienides Na[CpCO2(CHR)2OH]
and synthesized the novel ligands 1 and 2. We have also
demonstrated that the above procedure applied to six-
membered cyclic carbonates such as 1,3-dioxan-2-one
leads to the unselective formation of a mixture of at least
two anionic cyclopentadienide systems in a ratio strictly
dependent on the carbonate/NaCp stoichiometric ratio.
In the second part we have examined the catalytic
activity in the hydroformylation of hex-1-ene and sty-
rene of the novel rhodium complexes 3, 4, and 7 and
compared with that of previously reported analogous
complexes [Rh{CpCO2(CHR)2OH}(NBD)] (R ¼ H,
Me). The present studies have confirmed that the cata-
lytic activity of these complexes is strongly affected by
the nature of the substituents present on the lateral
chain. Finally, preliminary results showed that the same
effect is present in the hydrogenation of styrene.
4.1.1. PreparationofNa[rac-C5H4CO2(CHPh)2OH](1)
To a solution of NaCp (0.56 g, 6.36 mmol) in THF
(25 ml) solid meso-4,5-diphenyl-1,3-dioxolan-2-one was
added (1.53 g, 6.38 mmol) at room temperature. The
mixture was stirred for 24 h, the volatiles were removed
under vacuum and the residue kept under vacuum at
60 °C for 2 h. The resulting solid was washed with Et2O
4. Experimental
4.1. Materials and procedures for the syntheses
1
to give 1.29 g of 1 (61%) as a beige solid. H NMR
All reactions with organometallic reagents or sub-
strates were carried out under argon or nitrogen using
standard Schlenk techniques. Solvents were dried and
distilled under nitrogen prior to use. The prepared de-
rivatives were characterized by elemental analysis and
spectroscopic methods. The IR spectra were recorded
with a FT-IR spectrometer Perkin–Elmer Spectrum
2000 or with a Perkin–Elmer mod. 1760-X instrument.
The NMR spectra were recorded using Varian Gemini
XL 300 (1H, 300.1; 13C, 75.5 MHz), Varian Mercury-
Plus VX 400 (1H, 399.9; 13C, 100.6 MHz), Varian Inova
600 (1H, 599.7, 13C, 150.8 MHz) instruments. The
spectra were referenced internally to residual solvent
resonances, and were recorded at 298 K for character-
ization purposes. EI-MS spectra were taken using a VG
7070E mass spectrometer. ESI-MS analyses were per-
formed by direct injection of methanol solutions of the
metal complexes using a WATERS ZQ 4000 mass
spectrometer. A GC Shimadzu GC-14A, equipped with
a flame ionization detector (FID), and integrator Shi-
madzu C-R4A was used to evaluate the hydroformyla-
tion products, while a GC Perkin–Elmer mod. 8320,
equipped with a FID detector, was employed to analyze
gCOSY (599.7 MHz, [D5]Pyr): d ¼ 7:74–7:55 (m, Ph),
3
7.46 (AA0BB0, JH;H ¼ 2:9 Hz, 2H; Cp), 7.39 (d,
3JCH;OH ¼ 4:2 Hz, 1H; OH); 7.36-7.10 (m, Ph), 6.70 (d,
3JCH;CH ¼ 4:4 Hz, 1H; CO2CH), 6.65 (AA0BB0,
3
3JH;H ¼ 2:9 Hz, 2H; Cp), 5.50 (dd, JH;H ¼ 4:4 Hz,
3JCH;OH ¼ 4:2 Hz, 1H; CHOH), 13C–{1H} gHSQC
NMR (150.8 MHz, [D5]Pyr): d ¼ 167:8 (C@O), 143.0
(ipso-C; Ph), 141.1 (ipso-C; Ph), 128.4, 128.2, 127.8,
127.7, 127.2, 127.0 (Ph), 113.3 (CH; Cp), 111.5 (CH;
Cp), 109.7 (ipso-C; Cp), 77.7 (CHOH), 77.2 (CO2CH).
IR (THF, cmꢀ1) m(C@O) 1673 (bs), 1619 (bs). Anal.
Calc. for C20H17NaO3: C, 73.2; H, 5.22. Found: C, 73.6;
H, 5.00%.
4.1.2. Preparation of Na[(2S,3S)-C5H4CO2(CHPh)2-
OH] (2)
To a solution of NaCp (0.61 g, 6.93 mmol) in THF
(25 ml), solid 4S, 5S-diphenyl-1,3-dioxolan-2-one (1.67
g, 6.96 mmol) was added at room temperature. The
mixture was stirred at room temperature for 24 h, the
solvent removed under vacuum and the residue kept
under vacuum at 60 °C for 2 h. The resulting solid was
washed with Et2O and 2 (1.45 g, 63%) was obtained as a

L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
2225
beige solid. 1H NMR gCOSY (599.7 MHz, [D5]Pyr):
¼ 7.51 (AA0BB0, 3JH;H ¼ 2:9 Hz, 2H; Cp), 7.49–7.46 (m,
Ph, OH overlapped peaks), 7.27–7.05 (m, Ph), 6.70 (d,
3JH;H ¼ 6:7 Hz, 1H; CO2CH), 6.68 (AA0BB0,
5.53 (m, 1H; Cp), 5.40 (m, 1H; Cp), 5.37 (m, 1H; Cp),
5.00 (dd, 3JH;H ¼ 7:1 Hz, 3JCH;OH ¼ 3:0 Hz 1H; CHOH),
3.32 (m, 2H, H1;4; NBD), 3.26 (m, 4H, H2;3;5;6; NBD),
2.83 (d, 3JCH;OH ¼ 3:3 Hz, 1H; OH), 0.96 (t, 3JH;H ¼ 1:5
Hz, 2H, H7; NBD); 13C–{1H} NMR gHSQC (100.6
MHz, CDCl3): d ¼ 165:0 (C@O), 139.1 (ipso-C; Ph),
137.2 (ipso-C; Ph), 128.0, 127.9, 127.8, 127.2, 127.1 (Ph),
91.6 (d, JC;Rh ¼ 4:9 Hz, ipso-C; Cp), 88.6 (d, JC;Rh ¼ 3:2
Hz, CH; Cp), 88.5 (d, JC;Rh ¼ 4:1 Hz, CH; Cp), 86.1 (d,
JC;Rh ¼ 4:0 Hz, CH; Cp), 86.0 (d, JC;Rh ¼ 4:0 Hz, CH;
Cp), 85.9 (d, JC;Rh ¼ 4:0 Hz, CH; Cp), 79.5 (CO2CH),
77.2 (CHOH), 57.5 (d, JC;Rh ¼ 7:2 Hz, C7; NBD), 46.7
(d, JC;Rh ¼ 2:4 Hz, C1;4; NBD), 32.8 (d, JC;Rh ¼ 10:6 Hz,
@CH; NBD), 32.6 (d, JC;Rh ¼ 10:6 Hz, @CH; NBD). IR
(THF, cmꢀ1): m(C@O) 1704 (s). Anal. Calc. for
C27H25O3Rh: C, 64.8; H, 5.03. Found: C, 64.7; H,
5.04%. ESI-MS [M + Na]þ ¼ 523 m=z; m.p. ¼ 150–151 °C.
3
3JH;H ¼ 2:9 Hz, 2H; Cp), 5.48 (dd, JCH;CH ¼ 6:7 Hz,
3JCH;OH ¼ 4:1 Hz, 1H; CH OH); 13C–{1H} NMR
gHSQC (150.8 MHz, [D5]Pyr): d ¼ 168:9 (C@O), 143.0
(ipso-C; Ph), 140.7 (ipso-C; Ph), 128.4, 128.3, 127.8,
127.7, 127.3, 127.1 (Ph), 113.5 (CH; Cp), 111.7 (CH;
Cp), 109.6 (ipso-C; Cp), 77.7 (CHOH), 77.6 (CO2CH).
IR (THF, cmꢀ1) m(C@O) 1673 (bs), 1619 (bs). Anal.
Calc. for C20H17NaO3: C, 73.2; H, 5.22. Found: C, 73.5;
H, 5.23%.
4.1.3. Preparation of [Rh(NBD){rac-CpCO2(CHPh)2-
OH}] (3)
To a solution of 1 (1.13 g, 3.44 mmol) in THF (30 ml),
solid [Rh(NBD)Cl]2 (0.65 g, 1.41 mmol) was added. The
solution was stirred for 3 h at room temperature. The
solvent was removed under vacuum and CH2Cl2 was
added. The yellow suspension was first filtered on a celite
pad and then chromatographed on silica gel. Eluting with
Et2O/Etp 1:1 a yellow fraction 0.79 g (56%) was collected
4.1.5. Reactions of NaCp with 1,3-dioxan-2-one
Synthesis of I. To a solution of NaCp (2.00 g, 19.0
mmol) in THF (25 ml), solid 1,3-dioxan-2-one (2.49 g,
24.4 mmol) was added and the reaction mixture stirred
at room temperature for 24 h. The suspension was fil-
tered on a celite pad and the solvent removed under
vacuum. After keeping the solid under vacuum at 60 °C
for 2 h, the residue was washed with Et2O to give 2.05 g
of an inseparable mixture of 5 (30%) and 6 (18%) (de-
termined by NMR analysis of the crude product) ob-
1
and identified as the product 3. H NMR (399.9 MHz,
CDCl3): d ¼ 7:34–7:25 (m, 10H; Ph), 6.00 (d, 3JH;H ¼ 5:8
Hz, 1H; CO2CH Ph), 5.44 (m, 1H; Cp), 5.38 (m, 1H; Cp),
5.29 (m, 1H; Cp), 5.27 (m, 1H; Cp), 5.00 (dd, 3JH;H ¼ 5:8
3
Hz, JCH;OH ¼ 3:7 Hz, 1H; CHOH), 3.18 (m, 2H, H1;4
;
1
NBD), 3.14 (m, 4H, H2;3;5;6
;
NBD), 2.26 (d,
tained as a beige solid. For 5: H NMR (300.1 MHz,
3
3JCH;OH ¼ 3:7 Hz, 1H; OH), 0.98 (t, JCH;CH ¼ 1:5 Hz,
2H, H7; NBD); 13C–{1H} NMR gHSQC (100.6 MHz,
CDCl3): d ¼ 164:9 (C@O), 139.7 (ipso-C; Ph), 137.2
(ipso-C; Ph), 128.2, 128.0, 127.9, 127.4, 127.2 (Ph), 91.7
(d, JC;Rh ¼ 3:8 Hz, ipso-C; Cp), 88.4 (d, JC;Rh ¼ 3:4 Hz,
CH; Cp), 86.1 (d, JC;Rh ¼ 4:0 Hz, CH; Cp), 86.0 (d,
JC;Rh ¼ 4:0 Hz, CH; Cp), 78.4 (CO2CH), 76.7 (CHOH),
57.5 (d, JC;Rh ¼ 6:8 Hz, C7; NBD), 46.7 (d, JC;Rh ¼ 2:9
Hz, C1;4; NBD), 32.7 (d, JC;Rh ¼ 8:0 Hz, @CH; NBD),
[D5]Pyr): d ¼ 7:40 (AA0BB0, JH;H ¼ 3:0 Hz, 2H; Cp),
3
3
6.64 (AA0BB0, JH;H ¼ 3:0 Hz, 2H, Cp), 4.56 (t,
3
3JH;H ¼ 6:0 Hz, 2H; CO2CH2), 3.93 (t, JH;H ¼ 5:5 Hz,
2H; CH2OH), 2.03 (m, 2H, CH2CH2CH2); 13C–{1H}
NMR (75.5 MHz, [D5]Pyr): d ¼ 168:8 (C@O), 112.9
(CH; Cp); 111.2 (CH; Cp), 109.6 (ipso-C; Cp), 65.6
(CO2CH2), 58.5 (CH2OH), 29.5 (CH2). IR (THF, cmꢀ1
)
m ¼ 1644 (s) (C@O). For 6: 1H NMR (300.1 MHz,
3
[D5]Pyr): d ¼ 7:36 (AA0BB0, JH;H ¼ 3:0 Hz, 2H; Cp),
32.5 (d, JC;Rh ¼ 8:0 Hz, @CH; NBD). IR (THF, cmꢀ1
)
6.60 (AA0BB0, JH;H ¼ 3:0 Hz, 2H; Cp), 4.56 (t,
3
3
m(C@O) 1713 (s). Anal. Calc. for C27H25O3Rh: C, 64.8;
H, 5.03. Found: C, 64.8; H, 5.05%. ESI-MS
[M + Na]þ ¼ 523 m=z; m.p. ¼ 164–166 °C.
3JH;H ¼ 6:0 Hz, 2H; CO2CH2,), 4.35 (t, JH;H ¼ 6:3 Hz,
3
2H; CH2OC(O)O), 4.32 (t, JH;H ¼ 6:3 Hz, 2H;
3
OC(O)OCH2), 3.93 (t, JH;H ¼ 5:5 Hz, 2H; CH2OH),
2.03 (m, 4H; CH2CH2CH2); 13C–{1H} NMR (75.5
MHz, [D5]Pyr): d ¼ 168:4 (C@O), 155.5 (OC(O)O),
112.7 (CH; Cp), 111.2 (CH; Cp), 109.4 (ipso-C; Cp), 65.6
(CO2CH2), 59.1 (CH2OC(O)O), 59.0 (OC(O)OCH2),
4.1.4. Preparation of ())-[Rh(NBD){(2S,3S)CpCO2-
(CHPh)2OH}] (4)
To a solution of 2 (0.62 g, 1.89 mmol) in THF (30
ml), solid [Rh(NBD)Cl]2 (0.36 g, 0.78 mmol) was added.
The solution was stirred for 3 h at room temperature.
The solvent was removed under vacuum and CH2Cl2
was added. The yellow suspension was first filtered on a
celite pad and then chromatographed on silica gel.
Eluting with Et2O/Etp ¼ 1/1 a yellow fraction was col-
lected and identified as the product 8 (yellow solid, 0.45
58.5 (CH2OH), 34.3 (CH2), 29.5 (CH2). IR (THF, cmꢀ1
)
m ¼ 1748 (s) (OC(O)O), 1644 (s) (C@O).
Synthesis of II. To a solution of NaCp (1.13 g, 10.7
mmol) in THF (25 ml), solid 1,3-dioxan-2-one (1.74 g,
17.1 mmol) was added and the reaction mixture stirred
at room temperature for 24 h. The suspension was fil-
tered on a celite pad and the solvent removed under
vacuum. After keeping the solid under vacuum at 60 °C
for 2 h, the residue was washed with Et2O to give 1.48 g
of an inseparable mixture of 5 (33%) and 6 (26%)
19:0
g, 58%). ½aꢁD ¼ ꢀ17:6 (c ¼ 0:63, CHCl3). 1H NMR
(399.9 MHz, CDCl3): d ¼ 7:26–7:18 (m, 10H; Ph), 5.98
3
(d, JH;H ¼ 7:1 Hz, 1H; CO2CHPh), 5.58 (m, 1H; Cp),

2226
L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
(determined by NMR analysis of the crude product) as a
beige solid.
The major product [Rh{C5H4CO2(CH2)3OH} (NBD)]
(7) was obtained eluting with Et2O. Yellow crystals (0.158
g, 50%) have been obtained by evaporation of Et2O. 1H
NMR (300.1 MHz, CDCl3): d ¼ 5:47 (AA0BB0X,
Synthesis of III. To a solution of NaCp (0.62 g, 5.97
mmol) in THF (25 ml), solid 1,3-dioxan-2-one (1.34 g,
13.1 mmol) was added and the reaction mixture stirred at
room temperature for 24 h. The suspension was filtered
on a celite pad and the solvent removed under vacuum.
After keeping the solid under vacuum at 60 °C for 2 h,
the residue was washed with Et2O to give 0.29 g of an
inseparable mixture of 5 (7%) and 6 (12%) (determined
by NMR analysis of the crude product) as a beige solid.
Rhodium(I) derivatives . By reacting the three mix-
tures I, II, or III with [Rh(NBD)Cl]2 several mono- and
dinuclear yellow complexes were obtained in yields de-
pending on the starting mixtures employed.
3
3JH;H ¼ 2:1 Hz, JH;Rh ¼ 0:6 Hz, 2H; Cp), 5.34
3
3
(AA0BB0X, JH;H ¼ 2:1 Hz, JH;Rh ¼ 0:9 Hz, 2H; Cp),
4.37 (t, 3JH;H ¼ 6:0 Hz, 2H; CO2CH2), 3.75 (m, 2H; CH 2-
3
OH), 3.32 (m, 6H, CH; NBD), 2.66 (t, JH;H ¼ 6:0 Hz,
1H; OH), 1.92 (m, 2H; CH2), 0.97 (t, 3JH;H ¼ 1:4 Hz, 2H,
CH2; NBD); 13C–{1H} NMR (75.5 MHz, CDCl3):
d ¼ 166:8 (C@O), 91.5 [d, JC;Rh ¼ 4:9 Hz, ipso-C; Cp],
88.5 (d, JC;Rh ¼ 3:6 Hz, CH; Cp), 85.9 (d, JC;Rh ¼ 4:9 Hz;
CH; Cp), 60.6 (CpCO2CH2), 59.0 (CH2OH), 57.4 (d,
JC;Rh ¼ 7:3 Hz, C7; NBD), 46.7 (d, JC;Rh ¼ 2:5 Hz, C1;4
;
NBD), 32.6 (d, JC;Rh ¼ 10:8 Hz, C2;3;5;6; NBD), 32.2 (s,
CH2). IR (THF, cmꢀ1): m ¼ 1711 (s) (C@O). EI-MS (70
eV): m=z (%): 362 (100) [M]þ, 303 (47) [M-
CH2CH2CH2OH]þ, 259 (68) [M-CO2(CH2)3OH]þ, 194
(47) [Rh(C7H7)]þ, 168 (67) ([Rh(C5H5)]þ, 103 (18) [Rh]þ.
Anal. Calc. (%) for C16H19O3Rh: C, 53.0; H, 5.29. Found:
C, 53.0; H, 5.28%; m.p. ¼ 62 °C.
(a) To a solution of 0.28 g of I in THF (25 ml), solid
[Rh(NBD)Cl]2 (0.20 g, 0.43 mmol) was added. The so-
lution was stirred for 3 h at room temperature. The
solvent was removed under vacuum and CH2Cl2 was
added. The suspension was first filtered on a celite pad
and then chromatographed on silica gel. Eluting with a
mixture of Et2O/Etp (1:1) a first fraction (0.012 g, 0.019
mmol, 4%) was collected as a yellow solid and identified
as [Rh2{l-(CpCO2(CH2)3CO2Cp)}(NBD)2] (10). 1H
NMR (300.1 MHz, CDCl3): d ¼ 5:54 (AA0BB0,
3JH;H ¼ 2:4 Hz, 4H; Cp), 5.36 (AA0BB0, 3JH;H ¼ 2:4 Hz,
4H; Cp), 4.39 (t, 3JH;H ¼ 6:3 Hz, 4H; CO2CH2), 3.34 (m,
Finally by further elution with Et2O, a fourth yellow
oily fraction was collected and identified as
[Rh{C5H4CO2(CH2)3OC(O)O(CH2)3OH}(NBD)] (8)
1
(0.013 g, 3%). H NMR gCOSY (599.7 MHz, CDCl3):
3
d ¼ 5:49 (AA0BB0, JH;H ¼ 2:1 Hz, 2H; Cp), 5.34
(AA0BB0, 3JH;H ¼ 2:1 Hz, 2H; Cp), 4.31 (m, 6H; CpCO2-
CH2CH2CH2OC(O)O, OC(O)OCH2CH2CH2OH), 3.74
(m, 2H; CH2OH), 3.32 (m, 6H, CH; NBD), 2.09 (m, 2H,
CpCO2CH2CH2CH2OC(O)O), 1.93 (m, 3H, OC(O)-
OCH2CH2CH2OH, OH overlapping resonances), 0.98
3
12H; NBD), 2.13 (quintet, JH;H ¼ 6:3 Hz, 2H; CH2),
3
0.99 (t, JH;H ¼ 1:4 Hz, 4H; NBD); 13C–{1H} NMR
(75.5 MHz, CDCl3): d ¼ 166.1 (C@O), 91.5 (ipso-C;
Cp), 88.3 (d, JC;Rh ¼ 3:4 Hz; Cp), 86.0 (d, JC;Rh ¼ 4:0
Hz; Cp), 60.4 (CO2CH2), 57.5 (d, JC;Rh ¼ 6:8 Hz, C7;
NBD), 46.8 (d, JC;Rh ¼ 2:3 Hz, C1;4; NBD), 32.4 (d,
JC;Rh ¼ 10:2 Hz, C2;3;5;6; NBD), 28.6 (s, CH2CH2CH2).
IR (THF, cmꢀ1): m ¼ 1712 (s) (C@O); ESI-MS
[M + Na]þ ¼ 671 m=z. Anal. Calc. for C29H30O4Rh2: C,
53.7; H, 4.66. Found: C, 53.6; H, 4.68%; m.p. ¼ 126 °C.
Further eluting with the same solvent mixture a sec-
ond yellow fraction (0.021 g, 6%) was collected and a
yellow crystalline solid identified as [Rh2l-(CpCO2-
(CH2)3OC(O)O(CH2)3O2CCp)}(NBD)2] (11). 1H NMR
3
(t, JH;H ¼ 1:4 Hz, 2H; CH2, NBD); 13C–{1H} NMR
(150.8 MHz, CDCl3, gHSQC): d ¼ 166.0 (C@O), 155.4
(OC(O)O), 91.7 (d, JC;Rh ¼ 4:8 Hz, ipso-C; Cp), 88.3 (d,
JC;Rh ¼ 3:7 Hz, CH; Cp), 86.0 (d, JC;Rh ¼ 3:7 Hz; CH;
Cp), 64.9, 64.8 (OC(O)OC H2), 60.0 (C5H4CO2CH2),
59.0 (CH2OH), 57.5 (d, JC;Rh ¼ 7:0 Hz, C7; NBD), 46.7
(d, JC;Rh ¼ 2:4 Hz, C1;4; NBD), 32.5 (d, JC;Rh ¼ 10:2 Hz,
C2;3;5;6; NBD), 31.6 (s, CH2CH2CH2OH), 28.4 (s,
CH2CH2CH2OC(O)O). IR (THF, cmꢀ1): m ¼ 1748 (s)
(OC(O)O), 1712 (s) (C@O); ESI-MS [M + Na]þ ¼ 487
m=z. Anal. Calc. for C20H25O6Rh: C, 51.7; H, 5.43.
Found: C, 51.8; H, 5.44%.
(b) To a solution of 0.20 g of II in THF (25 ml), solid
[Rh(NBD)Cl]2 (0.160 g, 0.35 mmol) was added. Using
the same work up described in (a), the following com-
plexes were obtained (in elution order): [Rh2{l-
(CpCO2(CH2)3OC(O)O(CH2)3O2CCp)}(NBD)2] (11)
(0.011 g, 2%), [Rh{CpCO2(CH2)3OH}(NBD)] (7) (0.077
g, 30%) [Rh{CpCO2(CH2)3OC(O)O(CH2)3OH(NBD)]
(8) (0.024 g, 8%).
3
(300.1 MHz, CDCl3): d ¼ 5:50 (AA0BB0X, JH;H ¼ 2:1
3
Hz, JH;Rh ¼ 0:6 Hz, 4H; Cp), 5.35 (AA0BB0X,
3
3JH;H ¼ 2:1 Hz, JH;Rh ¼ 0:9 Hz, 4H; Cp), 4.31 (m, 8H;
CO2CH2, OC(O)OCH2), 3.33 (m, 12H; NBD), 2.08 (m,
4H; CH2), 0.99 (t, 3JH;H ¼ 1:4 Hz, 4H; NBD); 13C–{1H}
NMR (75.5 MHz, CDCl3): d ¼ 165:9 (C@O), 155.0
(OC(O)O), 91.5 (ipso-C; Cp), 88.3 (d, JC;Rh ¼ 3:7 Hz,
CH; Cp), 86.0 (d, JC;Rh ¼ 3:7 Hz, CH; Cp), 64.7
(OC(O)OCH2), 60.1 (CO2CH2), 57.5 (d, JC;Rh ¼ 6:1 Hz,
C7; NBD), 46.7 (d, JC;Rh ¼ 2:4 Hz, C1;4; NBD), 32.4 (d,
JC;Rh ¼ 10:9 Hz, C2;3;5;6; NBD), 28.4 (s, CH2CH2CH2).
IR (THF, cmꢀ1): m ¼ 1749 (s) (OC(O)O), 1712 (s)
(C@O); ESI-MS [M + Na]þ ¼ 773 m=z. Anal. Calc. for
C33H36O7Rh2: C, 52.8; H, 4.80. Found: C, 53.0; H,
4.82%; m.p. ¼ 80 °C.
(c) To a solution of 0.28 g of III in THF (25 ml), solid
[Rh(NBD)Cl]2 (0.190 g, 0.41 mmol) was added. Using
the same work up described for (a) the following com-
plexes were obtained (in elution order): [Rh2
{l-(CpCO2(CH2)3OC(O)O(CH2)3O2CCp)}(NBD)2] (11)

L. Busetto et al. / Journal of Organometallic Chemistry 689 (2004) 2216–2227
2227
(0.014 g, 5%) [Rh{CpCO2(CH2)3OH(NBD)] (7) (0.069
g, 23%), [Rh{CpCO2(CH2)3OC(O)O(CH2)3OH}(NBD)]
(8) (0.042 g, 11 %). By further elution with Et2O a fifth
yellow oily fraction was collected and the product
identified as the complex [Rh{CpCO2[(CH2)3OC-
used to analyze the residual hexenes: the column was
kept at 130 °C for 32 min, heated with a rate of 30 °C/
min up to 200 °C and kept at this temperature for 16
min. A 2 m FFAP packed column (‘Free Fatty Acids
Phase’ supported on Chromosorb G AW-DMCS 5%)
was used to analyze the styrene hydroformylation and
hydrogenation products; the column was kept at 40 °C
for 15 min, then heated with a rate of 5 °C/min up to 140
°C and kept at this temperature for 40 min.
1
(O)O]2(CH2)3OH}(NBD)] (9) (0.026 g, 4%). H NMR
gCOSY (599.7 MHz, CDCl3): d ¼ 5:50 (AA0BB0,
3
3JH;H ¼ 2:1 Hz, 2H; Cp), 5.35 (AA0BB0X, JH;H ¼ 2:1
3
Hz, JH;Rh ¼ 0:9 Hz, 2H; Cp), 4.30 (m, 6H; CpCO2
CH2CH2CH2OC(O)O, OC(O)OCH2CH2CH2 OH),
4.25 (m, 4H; OC(O)OCH2CH2CH2OC(O)O), 3.74 (m,
2H; CH2OH), 3.33 (m, 6H; CH, NBD), 2.09 (m, 2H,
CpCO2CH2CH2CH2OC(O)O), 2.03 (m, 2H; OC(O)-
OCH2CH2CH2OC(O)O), 1.92 (m, 2H; OC(O)-
Acknowledgements
The authors wish to thank the Universities of Bolo-
gna and Firenze and the Ministero della Industria,
3
OCH2CH2CH2OH), 1.84 (t, JH;H ¼ 6:0 Hz, 1H; OH),
3
0.99 (t, JH;H ¼ 1:3 Hz, 2H; CH2, NBD); 13C–{1H}
ꢀ
Universita e Ricerca (MIUR), Programmi di Ricerca
NMR gHSQC (150.8 MHz, CDCl3): d ¼ 166:0 (C@O),
155.4 (OC(O)O), 155.0 (OC(O)O), 91.6 (d, JC;Rh ¼ 4:6
Hz, ipso-C; Cp), 88.3 (d, JC;Rh ¼ 4:0 Hz, CH; Cp), 86.0
(d, JC;Rh ¼ 4:0 Hz; CH; Cp), 65.0, 64.8, 64.3, 64.2
(OC(O)OCH2), 60.1 (C5H4CO2CH2), 58.9 (CH2OH),
57.5 (d, JC;Rh ¼ 6:8 Hz, C7; NBD), 46.7 (d, JC;Rh ¼ 2:3
Hz, C1;4; NBD), 32.5 (d, JC;Rh ¼ 10:2 Hz, C2;3;5;6; NBD),
31.6 (CH2CH2CH2OH), 28.3, 28.0 (CH2C H2CH2). IR
(THF, cmꢀ1): m ¼ 1750 (s) (OC(O)O), 1711 (s) (C@O);
ESI-MS [M + Na]þ ¼ 589 m=z. Anal. (%) for C24H31
O9Rh Calc.: C, 50.9; H, 5.52. Found: C, 51.0; H, 5.50.
Scientifica di Notevole Interesse Nazionale, Cofinanzia-
mento MIUR 2003-04, for financial support.
References
[1] (a) L. Busetto, M.C. Cassani, R. Mazzoni, IT Appl. BO2001A
ꢀ
000308, 17/05/2001, Universita degli Studi di Bologna; Eur. Pat.
Appl. 02010935.1, 16/05/2002
(b) L. Busetto, M.C. Cassani, V.G. Albano, P. Sabatino, Organo-
metallics 21 (2002) 1849;
(c) L. Busetto, M.C. Cassani, R. Mazzoni, V.G. Albano, P.
Sabatino, P. Frediani, E. Rivalta, Organometallics 21 (2002)
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4.2. Catalysis
(d) L. Busetto, M.C. Cassani, R. Mazzoni, P. Frediani, E. Rivalta,
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The catalytic reactions were carried out in a 150 ml
stainless steel Parr autoclave stirred with a self-sealing
packing gland and electrically thermostated (ꢂ1 °C). A
solution of 0.02 mmol of the selected rhodium complex
and 2 mmol of substrate in 25 ml of THF was prepared
in a Schlenk tube and transferred into the autoclave by
suction. The autoclave was pressurized at room tem-
perature with the gases at the required pressure. The
reaction mixture was stirred and heated at the prefixed
temperature for the established time. After cooling the
autoclave to r.t., the gases were vented and the solution
collected. The reaction products were analyzed by GC.
GC-MS spectra were collected to confirm the nature of
the products obtained. A PPG column (‘Polypropylene
Glycol’ supported on Chromosorb W LB-550 X) was
used to analyze the hex-1-ene hydroformylation and
hydrogenation products. The oven was kept at 35 °C for
5 min, then heated at a rate of 5 °C/min up to 50 °C and
kept at this temperature for 2 min, then heated up to 100
°C, with a rate of 1 °C/min and kept at this temperature
for 60 min. A Chrompack capillary column Al2O3/
Na2SO4 PLOT (length: 50 m, diameter: 0.45 mm) was
[2] In the previous paper [1c] the resonances for the CO2CH(Me)
protons were reported as multiplets and no coupling costants were
given. The spectra collected with a Varian Inova 600 (now
available) show a more detailed spin system.
[3] H. Tomita, F. Sanda, T. Endo, J. Polym. Sci. A 39 (2001) 162, and
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Tetrahedron 49 (1993) 10511.
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[8] The yield previously reported [1b] as 43% has been increased up to
56% using a 2.4/1 reagents ratio between Na[CpCO2(CH2)2OH]
and [Rh(NBD)Cl]2 in THF at r.t. for 3 h.
[9] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, second ed., Pergamon Press, New York,
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