Synthesis and studies of Rh(I) catalysts within and across poly(alkyl aryl ether) dendrimers

Article abstract of DOI:10.1016/j.jorganchem.2010.09.054

In order to study the efficiencies of catalytic moieties within and across dendrimer generations, partially and fully functionalized dendrimers were synthesized. Poly(alkyl aryl ether) dendrimers from zero to three generations, presenting 3 to 24 peripher

Full text of DOI:10.1016/j.jorganchem.2010.09.054

Journal of Organometallic Chemistry 696 (2011) 722e730
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and studies of Rh(I) catalysts within and across poly(alkyl aryl ether)
dendrimers
*
Baskar Natarajan, Narayanaswamy Jayaraman
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
In order to study the efficiencies of catalytic moieties within and across dendrimer generations, partially
and fully functionalized dendrimers were synthesized. Poly(alkyl aryl ether) dendrimers from zero to
three generations, presenting 3 to 24 peripheral functionalities, were utilized to prepare as many as 12
catalysts. The dendrimer peripheries were partially and fully functionalized with triphenylphosphine in
the first instance. A rhodium(I) metal complexation was performed subsequently to afford multivalent
dendritic catalysts, both within and across generations. Upon synthesis, the dendritic catalysts were
tested in the hydrogenation of styrene, in a substrate-to-catalyst ratio of 1:0.001. Turn-over-numbers
were evaluated for each catalyst, from which significant increases in the catalytic activities were iden-
tified for multivalent catalysts than monovalent catalysts, both within and across generations.
Ó 2010 Elsevier B.V. All rights reserved.
Received 14 July 2010
Received in revised form
14 September 2010
Accepted 24 September 2010
Keywords:
Dendrimers
Hydrogenations
Organometallic catalysis
Rhodium
1. Introduction
Specifically, the studies were focused on varying the number of
catalytic sites within each generation and also across the genera-
Interfacing organometallic catalysis with dendrimers was
explored on many occasions, in an effort to assess the effect of
dendritic structural features in organometallic catalysis [1e5]. The
catalytic moieties are incorporated generally at the interior or at
the peripheries of dendritic structures [6e25]. Both positive and
negative effects in catalysis were reported, either due to a
co-operativity or a stabilization assisting the catalysis and steric
hindrances affecting the catalysis. It is accepted generally that
dendritic catalysts function as supported homogeneous catalysts.
In an effort to identify the effect of dendritic scaffolds, we reported
recently multivalent poly(ether imine) dendritic catalysts, wherein
each dendrimer generation was presented with varying number of
catalytic moieties [26]. When organometallic catalysis was per-
formed on the basis of molar equivalents of the catalytic sites,
a considerable increase in the catalytic activities was observed for
dendritic structures presented with more catalytic units than that
presented with lesser units. The beneficial effect of clustering the
catalytic units was presumed to arise from altered kinetic profiles
of association-dissociation of the intermediates involved in the
catalytic cycle. In continuing this effort, we undertook to study
organometallic catalysis mediated by a constitutionally different
poly(alkyl aryl ether) dendrimer-based multivalent catalysts.
tions. Rhodium(I)-mediated catalysis was studied upon synthesis
of a number of monovalent and multivalent catalysts. This report
describes synthesis of these catalysts and an evaluation of their
catalytic profiles.
2. Results and discussion
2.1. Synthesis and characterization of multivalent dendritic
catalysts
Phloroglucinol-based poly(alkyl aryl ether) dendrimers [27]
were chosen for the present study. The first generation den-
drimer of this type can provide 1 to 6 catalytic moieties when the
moieties are presented at its periphery. Second generation and
third generation dendrimers can provide 1 to 12 and 1 to 24 cata-
lytic moieties at their peripheries, respectively. Pre-formed poly
(alkyl aryl ether) dendrimers were synthesized as previously
reported [27]. These dendrimers are constituted with phlor-
oglucinol which formed as the core, branch point functionalities
and n-pentyl group as the linker between the branch points.
Dendrimer generations 0, 1, 2 and 3 presenting 3, 6, 12 and 24
peripheral functionalities, respectively, were chosen for the prep-
aration of multivalent dendritic organometallic catalysts. Whereas
complete functionalization with catalytic moieties involved least
chemical modifications at the peripheries of pre-formed
dendrimers, partial substitution with catalytic moieties required
* Corresponding author. Tel.: þ91 8022932578; fax: þ91 8023600529.
E-mail address: jayaraman@orgchem.iisc.ernet.in (N. Jayaraman).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.09.054

B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
723
protection of defined number peripheral functionalities. Thus,
modification with required number of peripheral hydroxyl groups
formed the initial efforts towards synthesis of multivalent catalysts.
A triphenylphosphine ligand, wherein one of the phenyl groups
emanating from dendrimer peripheries, was chosen for complex-
ation with Rh(I) metal and subsequent catalysis studies. Key
monomer building blocks for elaboration of dendrimer peripheries
with phosphine ligand were derivatives IeVI (Scheme 1). These
were prepared by phenolic O-alkylation with appropriate alkyl
bromides, details of which are provided in the Supporting Infor-
mation. Zero generation dendritic catalysts providing 1e3 catalytic
moieties were prepared by O-alkylations of appropriate monomer
building blocks, followed by a reduction [28,29] of phosphine
oxides to afford phosphines 1, 2 and 3 and their subsequent metal
complexations with Rh(I) (Scheme 1), leading to the formation of
catalysts 4, 5 and 6, respectively. O-Alkylation and subsequent
reduction reactions led to moderate to good yields of phosphine
oxides and phosphines 1e3. On the other hand, metal complexa-
tions, using dimeric Rh(cod)Cl (cod: 1,5-cyclooctadiene) were facile
and the products formed in good yields. Whereas phosphine oxides
and phosphines were colorless oils, the corresponding metal
complexes were yellow gums.
Scheme 2. Reagents and conditions. (i) K2CO3, 18-C-6 (cat.), DMF, 70 ꢁC; (ii) LiAlH4,
CeCl3, THF, 60 ꢁC; (iii) [Rh(cod)Cl]2, CH2Cl2, rt.
A similar strategy was adopted for the synthesis of first gener-
ation catalysts, possessing one, three and six catalytic sites at their
peripheries. Dendrimer VII with partial functionalization of
hydroxyl groups at its peripherey and fully hydroxyl group func-
tionalized dendrimer VIII were secured through deprotections of
the corresponding fully protected dendrimer. Details of synthesis
and characterization are provided in the Supporting Information.
Phosphine-functionalized dendrimers were obtained through O-
alkylations with appropriate phosphine oxide containing deriva-
tives, followed by LiAlH4/CeCl3 mediated reduction to phosphines
7e9 (Scheme 2). Rh(I) complexation with dendritic phosphines was
performed using Rh(cod)Cl dimer in CH2Cl2 and complexes 10e12
were obtained as orange gums or semi-solids. Metal co-ordinations
by phosphines were confirmed by the absence of a resonance at
wꢀ 6.9 ppm, corresponding to metal-free phosphine resonance and
the appearance of a doublet at w29.5 ppm (Jw150 Hz), corre-
sponding to metal co-ordinated phosphine resonance. Elemental
analysis and metal analysis, performed using inductively coupled
plasma-optical emission spectrometer (ICP-OES), further confirmed
the constitutions of 10e12. Synthesis of partially and fully func-
tionalized second and third generation dendrimers were under-
taken by utilizing pre-formed dendrimers.
Schemes 3 and 4 provide synthetic sequences to prepare second
and third generation dendrimers phosphineemetal complexes. In
these instances too, the number of hydroxyl groups at the
peripheries of dendrimers defined the number of phosphines and
catalytic moieties. Three catalysts within each generation was
prepared through O-alkylation, using appropriate phosphine oxide
Scheme 1. Reagents and conditions. (i) K2CO3, 18-C-6 (cat.), DMF, 70 ꢁC; (ii) LiAlH4,
Scheme 3. Reagents and conditions. (i) NaH, DMF, 70 ꢁC; (ii) LiAlH4, CeCl3, THF, 60 ꢁC;
(iii) [Rh(cod)Cl]2, CH2Cl2, rt.
CeCl3, THF, 60 ꢁC; (iii) [Rh(cod)Cl]2, CH2Cl2, rt.

724
B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
phosphine moieties to metal. Metal content stoichiometries in the
complexes were confirmed through atomic absorption analysis.
Further, 1H and 31P NMR resonances for phosphine oxides, phos-
phines and the metal complexes were observed to have the
following trend. Aromatic moieties in phosphine oxides showed
resonances in the region of 7.30e7.70 ppm, that in phosphines were
between 7.15 and 7.30 ppm. In the metal complexes, aromatic
moieties were observed between 7.25 and 7.75 ppm. Correspond-
ing 31P NMR values were observed in the region of: phosphine
oxides 29.3e29.4 ppm; phosphines wꢀ 6.9 ppm and metal
complexes w29.5 ppm as a doublet, with a coupling constant of
150 Hz.
2.2. Assessment of catalytic activities
Catalytic activities of multivalent dendritic Rh(I) organometallic
catalysts, 4e6, 10e12, 16e18 and 22e24 were assessed in a case
study involving hydrogenation of styrene, monitored by gas chro-
matography. In assessing catalytic activities, the reactions were
conducted on the basis of per catalytic site, so as to treat multivalent
catalysts with respect to the number of catalytic sites. Dendritic
catalysts having more than one catalytic site were considered in
multiples according to the number of such sites within the den-
drimer. Studies were thus performed with uniform molar equiva-
lent of the metal in each catalytic reaction. After few trial reactions,
the substrate-to-one catalytic moiety mole ratio of 1:0.001 was
chosen, and the studies were performed in 1,4-dioxane, at a H2 (g)
pressure of 10 bar. The formation of ethyl benzene was monitored
at varying time interval. The reactions proceeded generally without
an induction period and a complete conversion to product occurred
at varying durations. Significant differences in the catalytic profiles
were noticed during initial periods of the reaction. Catalytic effi-
ciencies, measured as turn-over-number (TON), are presented in
Fig. 2 for each catalyst during 30 and 60 min reaction durations.
Upon completion of hydrogenation, the catalyst was recovered,
by removing the solvent in vacuo and washing the catalyst with n-
hexane, and re-used in order to assess the efficacy of recovered
Scheme 4. Reagents and conditions. (i) NaH, DMF, 70 ꢁC; (ii) LiAlH4, CeCl3, THF, 60 ꢁC;
(iii) [Rh(cod)Cl]2, CH2Cl2, rt.
monomer building blocks, followed by reduction to phosphines
and metal complexations with Rh(I). Whereas O-alkylation reac-
tion yields were moderate, reduction of phosphine oxide to phos-
phine and the metal complexation were facile and good yields were
obtained. Molecular structures of third generation catalysts 23 and
24 are shown in Fig. 1, whereas molecular structures of remaining
catalysts are presented in the Supporting Information. The metal
complexes and phosphine intermediates were characterized for
their identities and homogeneities by routine physical methods.
Disappearance of 31P resonance at wꢀ 6.9 ppm and the appearance
of a doublet at w29.5 ppm, with phosphorusemetal coupling
constant of w150 Hz, confirmed complete complexation of all
Fig. 1. Molecular structures of third generation catalysts 23 and 24.

B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
725
Fig. 2. Turn-over-number (TON) during (a) 30 min reaction duration and (b) 60 min reaction duration of hydrogenation of styrene.
catalysts. Catalysts 11 and 24 were undertaken for recovery and re-
use studies. A second time use of the catalysts led to hydrogena-
tions, with more than 80% of catalytic efficiencies as judged after
60 min, thereby ascertaining that the catalysts largely retained
their efficacies for reusability. Impediment to recovery and re-use
was encountered when the catalysts were exposed to hydrogena-
tion conditions for several hours, during which period catalysts
precipitated, possibly due to loss of (cod) ligand upon hydrogena-
tion. Stability of catalysts was also assessed by heating catalysts 6
and 24 in 1,4-dioxane at 50 ꢁC for w2 h, followed by characterizing
the complexes by 1H and 31P NMR spectroscopies. Spectral
comparisons showed that catalysts were intact. Further, catalysis
mediated by (Ph3P)Rh(cod)Cl (25) was conducted in the presence of
excess triphenylphosphine, in order to identify whether an alter-
nate mode of metal complexation during the catalytic reaction
might contribute to increased catalytic efficiencies. Presence of
externally added 2 and 4 M equivalents of triphenylphosphine
along with 25 led to marginal decrease in the catalytic activities.
Formation of higher stoichiometric in situ RheP complexes thus
appeared to be unlikely.
topologically well-defined dendritic structures. In such an effort,
initial requirement was to synthesize dendrimers capable to
present varying number of such ligands and metal complexes
within the generation. The present study focused on identifying the
effect of dendritic backbone, when catalysis is mediated by varying
number of catalysts within a given dendrimer generation. Thus,
when comparing monovalent catalysts 4, 10, 16 and 22, each with
one catalytic center across zero, first, second and third generations,
the activities of styrene hydrogenation increased as the generations
advanced. Higher catalytic activities of higher generations
appeared to be in part due the effect of dendrimer backbone. The
origin of higher catalytic effects is unclear. We presume that the
observed effects arise due to several catalytic moieties available
within the same dendritic structure, that alter kinetic associa-
tionedissociation rate constants, as opposed to least number of
catalytic moieties present on the same generation. Comparable
results observed with un-related poly(ether imine) dendrimer
catalysts and their efficacies to mediate CeC bond forming reac-
tions[26] reiterate that activities of individual catalytic moieties are
moderate to significantly higher when the moieties are clustered
on a dendrimer structure.
An analysis of the hydrogenation reaction showed that (i) of the
twelve dendritic catalysts, three in each zero, first, second and
third generations, and also 25, a higher catalytic activity was
observed for higher generations; (ii) within a given generation,
multivalent catalysts mediated the reaction considerably more
effectively than monovalent catalysts; (iii) across generations,
monovalent catalysts 4, 10, 16 and 22 led to considerable increases
in catalytic activities in the increasing order and (iv) among fully
functionalized multivalent catalysts 6, 12, 18 and 24, the increase
in catalytic activities was more significant with higher genera-
tions. When comparing these results, it is important to note that
the reactions are performed on the basis of individual catalytic site
basis. The observations of increased catalytic activities by multi-
valent catalysts are in line with our earlier studies involving poly
(ether imine) dendrimer type, presented with partial and
complete substitution of Pd-based catalytic units at the periph-
eries [26]. Increases in activities of individual catalytic sites were
either significant across the generations, or considerable within
the generations, thereby indicating beneficial effects of clustering
the catalytic sites.
3. Conclusion
Synthesis and evaluation of catalytic activities of Rh(I) catalysts
presented both within and across dendrimer generations was
undertaken. Phloroglucinol-based poly(alkyl aryl ether) den-
drimers, in the generation series 0e3, presenting 3, 6, 12 and 24
peripheral functional groups, were chosen for installation of varying
number of catalytic moieties at their peripheries. Twelve catalysts
with varying number phosphine ligands and Rh(I) complexes with
above dendrimer generations were thus prepared. Upon synthesis,
the catalysts were studied in a hydrogenation reaction with styrene
as the substrate. Acomparison of the catalytic activities, measured as
TON, of each dendritic catalyst showed that moderate to significant
increases in the efficacies of individual catalytic moiety occurred
when the moiety was presented along with several such moieties at
the peripheries of a dendrimer structure, than as isolated moiety
within the same dendrimer structure. The observations verify not
only a role of dendritic backbone, but also an effect of clustering the
catalytic moieties within and across dendrimer generations.
The basis of present study was to identify catalytic effects upon
clustering dendritic ligands and metal complexes in spatially and

726
B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
4. Experimental
70 ꢁC for 24 h and proceeded as described in general procedure to
afford phosphine oxide, as a colorless gum (0.28 g, 82%). TLC: Rf 0.5
4.1. General methods
(PhMe/EtOAc ¼ 25:75). 1H NMR (CDCl3, 300 MHz)
d 1.64 (m, 6 H),
1.83 (m, 12 H), 3.97 (m, 12 H), 6.06 (s, 3 H), 6.93 (m, 8 H), 7.26 (m,
Chemicals were purchased from commercial sources and were
used without further purification. K2CO3 (AR grade) was dried at
120 ꢁC for 24 h before being used. Solvents were dried and distilled
according literature procedures and saturated with Ar. Analytical
TLC was performed on commercial Merck plates coated with silica
gel GF254 (0.25 mm) and I2 was used as staining agent for TLC. Silica
gel (230e400 mesh) was used for column chromatography. The 1H,
13C and 31P NMR spectra were recorded on the following spec-
trometers: Jeol AC 300 FT NMR spectrometer (1H: 300 MHz, 13C:
75.5 MHz), Bruker AMX 400 (1H: 400 MHz, 13C: 100 MHz, 31P:
162 MHz), with TMS or H3PO4 as a reference. The following abbre-
viations are used to explain the multiplicities: s, singlet; d, doublet;
t, triplet; m, multiplet; br, broad; band, several overlapping signals.
Atomic absorption spectroscopic measurements of metal content
were conducted using Thermo iCAB 6500 DUO ICP-OES instrument.
4 H), 7.41e7.69 (m, 12 H); 13C NMR (75.5 MHz, CDCl3)
d 22.7, 28.8,
28.9, 67.5, 67.6, 67.8, 93.8, 114.4, 114.6, 120.5, 128.4 (d, J ¼ 11.3 Hz),
129.4, 131.7, 132.0 (d, J ¼ 9.8 Hz), 132.3, 133.6, 133.9 (d, J ¼ 9.8 Hz),
158.9, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.42; ESI-MS m/z: calcd.
for C51H57O7P [M þ H]þ: 813.3920; found: 813.3945. Anal. calcd. for
C51H57O7P: C,75.35; H,7.07; found C,75.45; H,7.17.
A solution of above intermediate (0.18 g, 0.22 mmol) in THF
(5 mL) was added to the stirred suspension of CeCl3 (0.16 g,
0.65 mmol) and LAH (0.05 g, 1.29 mmol) in THF (20 mL) and pro-
ceeded as described in general procedure to afford 1, as a colorless
gum (0.17 g, 98%). TLC: Rf 0.6 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3,
300 MHz) d 1.63 (br, 6 H), 1.84 (br, 12 H), 3.94 (m, 12 H), 6.06 (s, 3 H),
6.90 (m, 8 H); 7.24e7.30 (m, 16 H); 13C NMR (75.5 MHz, CDCl3)
d
22.7, 28.9, 67.6, 67.7, 93.7, 114.4, 114.6 (d, J ¼ 7.5 Hz), 120.5, 127.2
(d, J ¼ 9.0 Hz), 128.4 (d, J ¼ 7.5 Hz),129.4,133.4 (d, J ¼ 18.8 Hz), 135.5
(d, J ¼ 22.6 Hz), 137.8 (d, J ¼ 9.8 Hz), 158.9, 159.8, 160.8; 31P NMR
4.2. General procedures. Synthesis of phosphine oxides
(CDCl3, 162 MHz)
d
ꢀ6.88; Anal. calcd. for C51H57O6P: C, 76.86; H,
7.21; found C, 76.57; H, 7.01.
A solution of phenol (1 M equiv.), bromide functionalized
monomer (1.2 M equiv. per hydroxyl group), K2CO3 (1.2 M equiv. per
hydroxyl group) and 18-C-6 (cat.) in DMF was stirred for 24e48 h at
70 ꢁC. Solvents were removed in vacuo, the resulting residue was
dissolved in CH2Cl2, washed with water, dried, concentrated and
purified (SiO2), using PhMe/EtOAc gradient elution, to afford
dendritic phosphine oxide. Alternatively a solution of phenol (1 M
2. A mixture of IV (0.25 g, 0.86 mmol), III (0.96 g, 2.16 mmol),
K2CO3 (0.30 g, 2.16 mmol) and 18-C-6 (cat.) in DMF (20 mL) was
stirred at 70 ꢁC for 24 h and proceeded as described in general
procedure to afford phosphine oxide, as a colorless gum (0.69 g,
79%). TLC: Rf 0.4 (CHCl3/MeOH ¼ 95:5). 1H NMR (CDCl3, 300 MHz)
d
1.65 (m, 6 H), 1.85 (m, 12 H), 4.03 (m, 12 H), 6.06 (s, 3 H), 6.93 (m,
7 H), 7.26 (m, 2 H), 7.41e7.69 (m, 24 H); 13C NMR (75.5 MHz, CDCl3)
22.7, 28.8, 28.9, 67.5, 67.6, 67.8, 93.7, 114.4, 114.5, 120.5, 128.4 (d,
equiv.), bromide functionalized monomer (1.2
M
equiv. per
d
hydroxyl group), NaH (60% in mineral oil, 1.2 M equiv. per hydroxyl
group) in DMF was stirred for 48e72 h at 70 ꢁC. Solvents were
removed in vacuo, the resulting residue was dissolved in CH2Cl2,
washed with water, dried, concentrated and purified (SiO2), using
CHCl3/MeOH gradient elution, to afford dendritic phosphine oxide.
J ¼ 11.3 Hz), 129.4, 131.7, 132.0 (d, J ¼ 9.8 Hz), 132.3, 133.6, 133.9 (d,
J ¼ 9.8 Hz), 158.9, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.39; ESI-
MS m/z: calcd. for C63H66O8P2 [M]þ: 1012.42; found: 1013.5; Anal.
calcd. for C63H66O8P2: C,74.69; H, 6.57; found C, 74.55; H, 6.70.
A solution of above intermediate (0.34 g, 0.33 mmol) in THF
(5 mL) was added to the stirred suspension of CeCl3 (0.5 g,
2.0 mmol) and LAH (0.15 g, excess) in THF (25 mL) and proceeded as
described in general procedure to afford 2, as a colorless gum
(0.32 g, 97%). TLC: Rf 0.7 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3,
4.3. Reduction of phosphine oxides
LiAlH4 (3.0 M equiv. per phosphine oxide) was added to a stirred
suspension of CeCl3 (2.0 M equiv. per phosphine oxide) in THF,
followed by the addition of dendritic phosphine oxide in THF. The
reaction mixture was warmed at 70 ꢁC for 7 h, quenched with
water, filtered, concentrated and purified (SiO2, PhMe/EtOAc) to
afford dendritic phosphine.
300 MHz)
d 1.63 (br, 6 H), 1.84 (br, 12 H), 3.94 (m, 12 H), 6.06 (s, 3 H),
6.89 (m, 7 H), 7.15e7.30 (m, 26 H); 13C NMR(75.5 MHz, CDCl3)
d
22.7, 28.9, 67.6, 67.7, 93.7, 114.4, 114.7 (d, J ¼ 7.5 Hz), 120.5, 127.3
(d, J ¼ 9.0 Hz), 128.4 (d, J ¼ 7.5 Hz), 129.0, 129.4, 133.4 (d,
J ¼ 19.6 Hz), 135.5 (d, J ¼ 21.1 Hz), 137.8 (d, J ¼ 9.8 Hz), 158.9, 159.8,
160.8; 31P NMR (CDCl3, 162 MHz)
d
ꢀ6.91; Anal. calcd. for
4.4. Preparation of dendritic Rh catalysts
C63H66O6P2: C,77.12; H,6.78; found C,77.09; H, 6.66.
3. A mixture of V (0.32 g, 0.56 mmol), VI (0.6 g, 2.0 mmol), K2CO3
(0.31 g, 2.2 mmol) and 18-C-6 (cat.) in DMF (15 mL) was stirred at
70 ꢁC for 24 h and proceeded as described in general procedure to
afford phosphine oxide, as a colorless gum (0.55 g, 82%). TLC: Rf 0.5
A mixture of dendritic phosphine and [Rh(cod)Cl]2 (0.5 M equiv.
per phosphine group) in CH2Cl2 was stirred for 10 min at room
temperature under an Ar atmosphere. The solvents were evapo-
rated in vacuo, washed with hexane and Et2O to afford the desired
dendritic Rh catalyst.
(CHCl3/MeOH ¼ 93:7). 1H NMR (CDCl3, 300 MHz)
d 1.64 (m, 6 H),
1.85 (m,12 H), 3.93 (t, J ¼ 6.3 Hz, 6 H), 4.01 (t, J ¼ 6.3 Hz, 6 H), 6.06 (s,
3 H), 6.95 (d, J ¼ 8.7 Hz, 6 H), 7.27e7.69 (m, 36 H); 13C NMR
4.5. Hydrogenation reactions
(75.5 MHz, CDCl3) d 22.7, 28.8, 28.9, 67.6, 67.8, 93.7, 114.4 (d,
J ¼ 13.6 Hz), 128.4 (d, J ¼ 12.0 Hz), 131.7, 132.0 (d, J ¼ 9.8 Hz), 132.2,
The dendritic catalyst (0.005 mmol of Rh content) and styrene
(5 mmol) in 1,4-dioxane (10 mL) were charged into an autoclave,
flushed twice with H2 (g) and pressurized (10 bar). At defined time
intervals, aliquot of the reaction mixture were withdrawn, filtered
133.6, 133.9
(d, J ¼ 11.3 Hz), 160.8, 161.9; 31P NMR (CDCl3, 162 MHz)
d 29.3; ESI-
MS m/z: calcd. for C75H75O9P3 [M]þ: 1212.46; found: 1213.366.
Anal. calcd. for C75H75O9P3: C,74.24; H, 6.23; found C,74.03; H,6.63.
A solution of above intermediate (0.1 g, 0.08 mmol) in THF
(3 mL) was added to the stirred suspension of CeCl3 (0.1 g,
0.37 mmol) and LAH (0.04 g, excess) in THF (20 mL) and proceeded
as described in general procedure to afford 3, as a colorless gum
(0.32 g, 97%). TLC: Rf 0.7 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3,
(0.45 m) and analyzed by GC. GC parameters: silica capillary column;
N2 carrier gas; column initial temperature, 80 ꢁC; column final
temperature, 200 ꢁC; column temperature rate, 20 ꢁC/min. The TON
was calculated as: mole of product formed/mole of catalyst used.
1. A mixture of I (0.3 g, 1.25 mmol), II (0.2 g, 0.42 mmol), K2CO3
(0.23 g, 1.67 mmol) and 18-C-6 (cat.) in DMF (10 mL) was stirred at
300 MHz) d 1.60 (br, 6 H), 1.84 (br, 12 H), 3.94 (m, 12 H), 6.05 (s, 3 H),

B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
727
6.87 (d, J ¼ 8.4 Hz, 6 H), 7.23e7.30 (m, 36 H); 13C NMR (75.5 MHz,
128.5,133.3 (d, J ¼ 19.0 Hz),135.6 (d, J ¼ 21.2 Hz),136.8,160.6,160.8;
31P NMR (CDCl3, 162 MHz)
77.37; H, 6.76; found C, 77.80; H, 6.46.
CDCl3)
d
22.7, 28.9, 67.6, 67.7, 93.8, 114.7 (d, J ¼ 7.5 Hz), 128.4 (d,
d
ꢀ6.94; Anal. calcd. for C97H101O13P: C,
J ¼ 7.5 Hz), 133.4 (d, J ¼ 19.6 Hz), 135.6 (d, J ¼ 21.1 Hz), 137.9 (d,
J ¼ 10.6 Hz), 159.8, 160.8; 31P NMR (CDCl3, 162 MHz)
d
ꢀ6.93; Anal.
8. A mixture of V (0.28 g, 0.49 mmol), IX (1.1 g, 1.95 mmol),
K2CO3 (0.4 g, 2.9 mmol) and 18-C-6 (cat.) in DMF (10 mL) was
stirred at 70 ꢁC for 36 h and proceeded as described in general
procedure to afford phosphine oxide, as a yellow oil (0.73 g, 72%).
calcd. for C75H75O6P3: C,77.30; H,6.49; found C,77.43; H,6.59.
4. A mixture of 1 (0.034 g, 0.043 mmol) and [Rh(cod)Cl]2 (0.010 g,
0.021 mmol) in CH2Cl2 (1 mL) was stirred at room temperature for
10 min and proceeded as described in general procedure to afford 4,
TLC: Rf 0.4 (CHCl3/MeOH ¼ 95:5). 1H NMR (CDCl3, 300 MHz)
d 1.61
as a yellow gum (0.044 g, 98%). 1H NMR (CDCl3, 300 MHz)
d
1.62 (br,
(br, 12 H), 1.81 (br, 24 H), 3.93 (t, J ¼ 6.0 Hz, 18 H), 4.00 (t, J ¼ 6.0 Hz,
6 H), 4.98 (s, 6 H), 6.06e6.15 (m, 12 H), 6.95 (d, J ¼ 8.4 Hz, 6 H),
6 H), 1.83e2.05 (br, 16 H), 2.39 (br, 4 H), 3.13 (s, 2 H), 3.96 (m, 12 H),
5.55 (s, 2 H), 6.06 (s, 3 H), 6.91 (m, 8 H), 7.25e7.76 (m,16 H); 13C NMR
7.30e7.68 (m, 51 H); 13C NMR (75.5 MHz, CDCl3)
d 22.7, 28.8, 28.9,
(75.5 MHz, CDCl3)
d
22.7, 29.0, 33.0, 67.6, 67.8, 70.5 (d, J ¼ 13.6 Hz),
67.7, 67.8, 70.0, 93.7, 94.1, 114.5 (d, J ¼ 12.0 Hz), 127.5, 127.9, 128.4 (d,
J ¼ 12.8 Hz), 128.5, 131.7 (d, J ¼ 3.0 Hz), 132.0 (d, J ¼ 9.8 Hz), 132.4,
133.4, 134.0 (d, J ¼ 11.3 Hz), 136.8, 160.6, 160.8, 162.0; 31P NMR
94.0, 104.9 (m, J ¼ 7.5 Hz), 114.4e114.5 (d, J ¼ 10.8 Hz), 120.5, 128.0
(d, J ¼ 10.5 Hz),129.4, 129.9, 132.0,132.5, 134.5 (d, J ¼ 10.5 Hz),136.9
(d, J ¼ 12.8 Hz), 159.0, 160.7, 160.9; 31P NMR (CDCl3, 162 MHz)
d
29.5
(CDCl3, 162 MHz) d 29.4; MALDI-TOF-MS m/z: calcd. for
(d, JPRh ¼ 150 Hz); Anal. calcd. for C59H69ClO6PRh: C, 67.91; H, 6.66;
C129H135O18P3 [M þ H]þ: 2065.36; found: 2065.487. Anal. calcd. for
Rh, 9.86; found C, 67.70; H, 6.74; Rh, 9.5.
C129H135O18P3: C,74.98; H,6.59; found C,74.63; H, 6.92.
5. A mixture of 2 (0.04 g, 0.04 mmol) and [Rh(cod)Cl]2 (0.02 g,
0.04 mmol) in CH2Cl2 (1 mL) was stirred at room temperature for
10 min and proceeded as described in general procedure to afford 5,
A solution of above intermediate (0.2 g, 0.1 mmol) in THF (5 mL)
was added to the stirred suspension of CeCl3 (0.14 g, 0.57 mmol)
and LAH (0.06 g, excess) in THF (25 mL) and proceeded as described
in general procedure to afford 8, as a colorless gum (0.18 g, 92%).
as a yellow foam (0.057 g, 96%). 1H NMR (CDCl3, 300 MHz)
d 1.63 (br,
6 H), 1.83e2.05 (br, 20 H), 2.42 (br, 8 H), 3.13 (s, 4 H), 3.96 (m, 12 H),
TLC: Rf 0.7 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3, 300 MHz)
d 1.59
5.55 (s, 4 H) 6.06 (s, 3 H), 6.91 (m, 7 H), 7.25e7.95 (m, 26 H); 13C NMR
(br, 12 H), 1.81 (br, 24 H), 3.94 (m, 24 H), 4.98 (s, 6 H), 6.05e6.14 (m,
(75.5 MHz, CDCl3)
d
22.7, 28.9, 33.0, 67.7, 67.8, 70.5 (d, J ¼ 13.6 Hz),
12 H), 6.86 (d, J ¼ 8.4 Hz, 6 H), 7.22e7.41 (m, 51 H); 13C NMR
93.8, 104.9 (m, J ¼ 7.5 Hz), 114.2, 114.3 (d, J ¼ 10.8 Hz), 120.5, 128.0
(75.5 MHz, CDCl3) d 22.7, 29.0, 67.6, 67.7, 70.0, 94.2, 114.7 (d,
(d, J ¼ 10.5 Hz),129.4, 129.9, 132.0,132.5, 134.4 (d, J ¼ 10.5 Hz),136.9
J ¼ 7.6 Hz), 127.5, 127.9, 128.4 (d, J ¼ 7.5 Hz), 128.6, 133.4 (d,
(d, J ¼ 12.8 Hz), 159.1, 160.7, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.5
J ¼ 18.8 Hz), 135.6 (d, J ¼ 21.1 Hz), 136.8, 137.9 (d, J ¼ 10.5 Hz), 159.8,
(d, JPRh ¼ 150 Hz). Anal. calcd. for C79H90Cl2O6P2Rh2: C, 64.36; H,
160.6, 160.8; 31P NMR (CDCl3, 162 MHz)
C129H135O15P3: C,76.76; H, 6.74; found C,76.88; H, 6.73.
d
ꢀ 6.96; Anal. calcd. for
6.15; Rh, 13.8; found C, 64.08; H, 6.17; Rh, 14.4.
6. A mixture of 3 (0.05 g, 0.043 mmol) and [Rh(cod)Cl]2 (0.032 g,
0.064 mmol) in CH2Cl2 (1 mL) was stirred at room temperature for
10 min and proceeded as described in general procedure to afford 6,
9. A mixture of VIII (0.21 g, 0.27 mmol), III (0.86 g, 1.9 mmol),
K2CO3 (0.34 g, 2.4 mmol) and 18-C-6 (cat.) in DMF (25 mL) was
stirred at 70 ꢁC for 48 h and proceeded as described in general
procedure to afford phosphine oxide, as a brown oil (0.55 g, 70%).
as a yellow foam (0.080 g, 98%). 1H NMR (CDCl3, 400 MHz)
d 1.62
(br, 6 H), 1.73e2.05 (m, 24 H), 2.40 (br, 12 H), 3.13 (s, 6 H), 3.93 (t,
J ¼ 6.0 Hz, 6 H), 3.99 (t, J ¼ 6.4 Hz, 6 H), 5.55 (s, 6 H) 6.06 (s, 3 H),
6.91 (d, J ¼ 8.0 Hz, 6 H), 7.18e7.77 (m, 36 H); 13C NMR (100 MHz,
TLC: Rf 0.5 (CHCl3/MeOH ¼ 93:7). 1H NMR (CDCl3, 300 MHz)
d 1.62
(br, 18 H), 1.82 (br, 36 H), 3.92 (t, J ¼ 6.6 Hz, 24 H), 4.00 (t, J ¼ 6.6 Hz,
12 H), 6.05 (s, 12 H), 6.95 (d, J ¼ 8.7 Hz, 12 H), 7.42e7.68 (m, 72 H);
CDCl3)
d
22.7, 28.9, 33.0, 67.7, 70.5 (d, J ¼ 13.7 Hz), 93.8, 104.9 (m,
13C NMR (75.5 MHz, CDCl3)
d 22.7, 28.8, 28.9, 67.7, 67.8, 93.8, 114.5
J ¼ 7.0 Hz), 114.2 (d, J ¼ 10.8 Hz), 128.0 (d, J ¼ 9.8 Hz), 129.9, 131.9,
(d, J ¼ 13.6 Hz), 128.4 (d, J ¼ 12.8 Hz), 131.7, 132.0 (d, J ¼ 9.8 Hz),
132.4, 134.4 (d, J ¼ 11.1 Hz), 136.8 (d, J ¼ 12.9 Hz), 160.6, 160.8; 31P
132.2, 133.5, 133.8 (d, J ¼ 11.3 Hz), 160.8, 161.9; 31P NMR (CDCl3,
NMR (CDCl3, 162 MHz)
d
29.5 (d, JPRh ¼ 149 Hz); Anal. calcd. for
162 MHz) d 29.44; MALDI-TOF-MS m/z: calcd. for C177H186O24P6
C99H111Cl3O6P3Rh3: C, 62.42; H, 5.87; Rh, 16.2; found C, 61.25; H,
6.04; Rh, 17.1.
[M þ Na]þ: 2904.17 Found: 2904.65; Anal. calcd. for C177H186O24P6:
C, 72.32; H, 6.54; found C, 72.14; H, 6.72.
7. A mixture of VII (0.7 g, 0.61 mmol), phosphine monomer III
(0.41 g, 0.92 mmol), K2CO3 (0.17 g, 1.23 mmol) and 18-C-6 (cat.) in
DMF (15 mL) was stirred at 70 ꢁC for 24 h and proceeded as
described in general procedure to afford phosphine oxide, as
a colorless gum (0.69 g, 74%). TLC: Rf 0.5 (PhMe/EtOAc ¼ 50:50). 1H
A solution of above intermediate (0.25 g, 0.086 mmol) in THF
(5 mL) was added to the stirred suspension of CeCl3 (0.19 g,
0.8 mmol) and LAH(0.08 g, excess) in THF (25 mL) and proceeded as
described in general procedure to afford 9, as a colorless gum (0.2 g,
84%). TLC: Rf 0.7 (PhMe/EtOAc ¼ 95:5). 1H NMR (CDCl3, 300 MHz)
NMR (CDCl3, 400 MHz)
d
1.64 (m, 8 H), 1.83 (m, 16 H), 3.91 (t,
d 1.63 (m, 18 H), 1.83 (m, 36 H), 3.93 (m, 36 H), 6.05 (s, 12 H), 6.86 (d,
J ¼ 6.0 Hz,14 H), 3.99 (t, J ¼ 6.0 Hz, 2 H), 4.98 (s,10 H), 6.06e6.23 (m,
J ¼ 7.8 Hz, 12 H), 7.15e7.30 (m, 72 H); 13C NMR (75.5 MHz, CDCl3)
12 H), 6.95 (d, J ¼ 8.7 Hz, 2 H), 7.29e7.67 (m, 37 H); 13C NMR
d
22.7, 29.0, 67.6, 67.7, 93.9, 114.7 (d, J ¼ 8.2 Hz), 128.4 (d, J ¼ 7.5 Hz),
(100 MHz, CDCl3)
d
22.7, 28.9, 67.7, 67.8, 70.0, 93.8, 94.1, 94.5, 114.5
129.0, 133.4 (d, J ¼ 19.6 Hz), 135.6 (d, J ¼ 21.2 Hz), 138.0 (d, J ¼ 11.3
(d, J ¼ 12.9 Hz), 127.5, 127.9, 128.4 (d, J ¼ 11.9 Hz), 128.5, 131.7, 132.0
Hz), 159.9, 160.9; 31P NMR (CDCl3, 162 MHz)
d
ꢀ 6.97; Anal. calcd.
(d, J ¼ 9.8 Hz), 132.4, 133.6, 133.9 (d, J ¼ 11.2 Hz), 136.8, 160.6, 160.8;
for C177H186O18P6: C, 76.27; H, 6.73; found C, 76.52; H, 6.51.
10. A mixture of 7 (0.04 g, 0.026 mmol) and [Rh(cod)Cl]2 dimer
(0.0065 g, 0.013 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 10, as a yellow gum (0.044 g, 97%). 1H NMR
31P NMR (CDCl3, 162 MHz)
d 29.35; MALDI-TOF-MS m/z: calcd. for
C97H101O14P [M þ H]þ: 1522.70; found: 1522.61. Anal. calcd. for
C97H101O14P: C, 76.56; H, 6.69; found C,76.30; H, 6.57.
A solution of above intermediate (0.28 g, 0.18 mmol) in THF
(4 mL) was added to the stirred suspension of CeCl3 (0.1 g,
0.37 mmol) and LAH (0.05 g, excess) in THF (25 mL) and proceeded
as described in general procedure to afford 7, as a colorless gum
(0.23 g, 86%). TLC: Rf 0.65 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3,
(CDCl3, 400 MHz) d 1.62 (br, 8 H), 1.79e2.05 (br, 20 H), 2.40 (br, 4 H),
3.12 (s, 2 H), 3.92 (t, J ¼ 6.1 Hz, 14 H), 3.98 (t, J ¼ 6.1 Hz, 2 H), 4.98 (s,
10 H), 5.55 (s, 2 H), 6.06e6.23 (m, 12 H), 6.90 (d, J ¼ 8.6 Hz, 2 H),
7.29e7.73 (m, 37 H); 13C NMR (100 MHz, CDCl3)
d 22.7, 28.9, 33.0,
400 MHz)
d
1.61 (m, 8 H), 1.82 (m, 16 H), 3.92 (m, 16 H), 4.98 (s,
67.7, 67.8, 70.0, 70.5 (d, J ¼ 13.6 Hz), 93.7, 94.0, 94.4, 104.9 (m,
J ¼ 7.1 Hz), 114.3 (d, J ¼ 10.8 Hz), 127.5, 127.9, 128.3 (d, J ¼ 12.0 Hz),
128.5, 129.9, 132.0, 132.3, 134.4 (d, J ¼ 11.2 Hz), 136.8, 136.9 (d,
10 H), 6.06e6.23 (m, 12 H) 6.87 (d, J ¼ 8.0 Hz, 2 H), 7.22e7.41 (m,
37 H); 13C NMR (100 MHz, CDCl3)
22.7, 28.9, 67.6, 67.7, 70.0, 93.7,
94.0, 94.4, 114.6 (d, J ¼ 8.0 Hz), 127.5, 127.9, 128.4 (d, J ¼ 8.8 Hz),
d
J ¼ 7.8 Hz), 160.6, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.6 (d,

728
B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
JPRh ¼ 149 Hz). Anal. calcd. for C105H113ClO13PRh: C, 71.97; H, 6.50;
Rh, 5.86; Found C, 73.34; H, 6.82; Rh, 5.40.
11. A mixture of 8 (0.056 g, 0.027 mmol) and [Rh(cod)Cl]2
(0.02 g, 0.041 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 11, as a yellow foam (0.073 g, 98%). 1H NMR
A solution of above intermediate (0.25 g, 0.05 mmol) in THF
(6 mL) was added to the stirred suspension of CeCl3 (0.1 g, 0.4 mmol)
and LAH (0.06 g, excess) in THF (25 mL) and proceeded as described
in general procedure to afford 14, as a colorless gum (0.2 g, 82%).
TLC: Rf 0.7 (PhMe/EtOAc ¼ 95:5). 1H NMR (CDCl3, 300 MHz)
d 1.59
(br, 30 H),1.80 (br, 60 H), 3.92 (br, 60 H), 4.98 (s,12 H), 6.05e6.14 (m,
(CDCl3, 400 MHz)
d 1.61 (br, 12 H), 1.79e2.05 (br, 36 H), 2.38 (br,
30 H), 6.86 (d, J ¼ 8.1 Hz, 12 H), 7.25e7.39 (m, 102 H); 13C NMR
12 H), 3.13 (s, 6 H), 3.92 (t, J ¼ 6.0 Hz, 18 H), 3.98 (t, J ¼ 6.0 Hz, 6 H),
(75.5 MHz, CDCl3) d 22.7, 28.8, 28.9, 67.5, 67.6, 70.0, 93.8, 94.1, 114.6
4.99 (s, 6 H), 5.55 (s, 6 H), 6.06e6.15 (m, 12 H), 6.90 (d, J ¼ 8.4 Hz,
(d, J ¼ 8.4 Hz), 127.5, 127.9, 128.3 (d, J ¼ 7.5 Hz), 128.6, 133.4 (d,
6 H), 7.30e7.76 (m, 51 H); 13C NMR (100 MHz, CDCl3)
d 22.7, 28.9,
J ¼ 19.2 Hz), 135.6 (d, J ¼ 21.2 Hz), 136.8, 137.9 (d, J ¼ 10.5 Hz), 159.8,
33.0, 67.6, 67.7, 70.0, 70.5 (d, J ¼ 13.8 Hz), 93.7, 94.1, 104.9 (m,
J ¼ 7.0 Hz), 114.2 (d, J ¼ 10.9 Hz), 127.5, 127.9, 128.0 (d, J ¼ 9.8 Hz),
128.5, 129.9, 131.9, 132.2, 134.4 (d, J ¼ 11.1 Hz), 136.8, 136.9 (d,
160.6, 160.8; 31P NMR (CDCl3, 162 MHz)
C285H306O36P6:C,76.18; H, 6.86; found C, 75.88; H,7.06.
d
ꢀ6.99; Anal. calcd. for
15. A mixture of XI (0.35 g, 0.187 mmol), III (1.25 g, 2.8 mmol),
NaH (0.12 g, 2.8 mmol, 60% in mineral oil) in DMF (15 mL) was
heated at 70 ꢁC for 72 h and proceeded as described in general
procedure to afford phosphine oxide, as a brown oil (0.75 g, 65%).
J ¼ 7.9 Hz), 160.7, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.5 (d,
JPRh ¼ 149 Hz). Anal. calcd. for C153H171Cl3O15P3Rh3: C, 66.63; H,
6.25; Rh, 11.14; found C, 66.58; H, 6.06, Rh, 9.60.
12. A mixture of 9 (0.036 g, 0.013 mmol) and [Rh(cod)Cl]2
(0.019 g, 0.04 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 12, as a yellow foam (0.053 g, 96%). 1H NMR
TLC: Rf 0.5 (CHCl3/MeOH ¼ 80:20). 1H NMR (300 MHz, CDCl3)
d 1.61
(br, 42 H), 1.82 (br, 84 H), 3.91 (br, 60 H), 3.98 (t, J ¼ 6.6 Hz, 24 H),
6.05 (s, 30 H), 6.94 (d, J ¼ 8.0 Hz, 24 H), 7.44e7.67 (m, 144 H); 13C
NMR (75.5 MHz, CDCl3)
d 22.7, 28.8, 28.9, 67.6, 67.7, 93.8, 114.4 (d,
(CDCl3, 300 MHz)
d
1.63 (br, 18 H), 1.82e2.08 (br, 60 H), 2.39 (br,
J ¼ 13.6), 128.4 (d, J ¼ 12.0 Hz), 131.7, 132.0 (d, J ¼ 9.7 Hz), 132.3,
24 H), 3.13 (s, 12 H), 3.92 (t, J ¼ 6.0 Hz, 24 H), 4.00 (t, J ¼ 6.0 Hz,
133.5, 133.9 (d, J ¼ 11.3 Hz), 160.8, 162.0; 31P NMR (CDCl3,
12 H), 5.55 (s,12 H) 6.06 (s,12 H), 6.90 (d, J ¼ 8.1 Hz,12 H), 7.35e7.77
162.0 MHz)
d 29.4.
(m, 72 H); 13C NMR (75.5 MHz, CDCl3)
d
22.7, 28.9, 33.0, 67.7, 70.5 (d,
A solution of above intermediate (0.26 g, 0.04 mmol) in THF
(6 mL) was added to the stirred suspension of CeCl3 (0.15 g,
0.6 mmol) and LAH (0.06 g, excess) in THF (25 mL) and proceeded
as described in general procedure to afford 15, as a colorless gum
(0.2 g, 80%). TLC: Rf 0.41 (PhMe/EtOAc ¼ 95:5). 1H NMR (300 MHz,
J ¼ 13.6 Hz), 93.8, 104.9 (m, J ¼ 7.5 Hz), 114.2 (d, J ¼ 10.5 Hz), 128.0
(d, J ¼ 9.8 Hz), 129.9, 131.8, 132.4, 134.4 (d, J ¼ 11.3 Hz), 136.8 (d,
J ¼ 12.8 Hz), 160.7, 160.8; 31P NMR (CDCl3, 162 MHz)
d 29.5 (d,
JPRh ¼ 149 Hz); Anal. calcd. for C225H258Cl6O18P6Rh6: C, 63.34; H,
6.10; Rh, 14.48; found C, 63.69; H, 6.11; Rh, 14.84.
CDCl3) d 1.60 (br, 42 H), 1.80 (br, 84 H), 3.95 (br, 84 H), 6.05 (s, 30 H),
13. A mixture of X (0.65 g, 0.23 mmol), phosphine monomer III
(0.2 g, 0.46 mmol), K2CO3 (0.062 g, 0.46 mmol) and 18-C-6 (cat.) in
DMF (20 mL) was stirred at 70 ꢁC for 36 h and proceeded as
described in general procedure to afford phosphine oxide, as
a colorless gum (0.62 g, 85%). TLC: Rf 0.6 (PhMe/EtOAc ¼ 50:50). 1H
6.94 (d, J ¼ 8.1 Hz, 24 H), 7.15e7.32 (m, 144 H); 13C NMR (75.5 MHz,
CDCl3)
d
22.7, 28.9, 67.6, 67.7, 93.8, 114.6 (d, J ¼ 9.0 Hz), 128.4 (d,
J ¼ 7.5 Hz), 129.0, 133.4 (d, J ¼ 18.1 Hz), 135.5 (d, J ¼ 21.1 Hz), 138.0
(d, J ¼ 10.6 Hz), 159.8, 160.8; 31P NMR (CDCl3, 162.0 MHz)
d
ꢀ 7.0;
Anal. calcd. for C381H408O42P12: C, 75.88; H, 6.82; found: C, 75.84; H,
6.54.
NMR (CDCl3, 400 MHz)
d 1.59 (m, 20 H), 1.80 (m, 40 H), 3.90 (t,
J ¼ 6.0 Hz, 38 H), 3.99 (t, J ¼ 6.0 Hz, 2 H), 4.97 (s, 22 H), 6.05e6.23
16. A mixture of 13 (0.063 g, 0.02 mmol) and [Rh(cod)Cl]2
(0.005 g, 0.01 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 16, as a yellow foam (0.066 g, 97%). 1H NMR
(m, 30 H) 6.87 (d, J ¼ 8.4 Hz, 2 H), 7.22e7.67 (m, 67 H); 13C NMR
(100 MHz, CDCl3)
d 22.7, 28.8, 28.9, 67.7, 67.8, 70.0, 93.8, 94.1, 94.5,
114.5 (d, J ¼ 12.9 Hz), 127.5, 127.9, 128.4 (d, J ¼ 12.1 Hz), 128.5, 131.7,
132.0 (d, J ¼ 9.8 Hz), 132.3, 133.5, 133.9 (d, J ¼ 11.2 Hz), 136.8, 160.6,
(CDCl3, 400 MHz)
d 1.59 (br, 20 H), 1.77e2.05 (br, 44 H), 2.36e2.50
160.9; 31P NMR (CDCl3, 162 MHz)
d
28.9; Anal. calcd. for
(br, 4 H), 3.13 (s, 2 H), 3.90 (t, J ¼ 6.0 Hz, 38 H), 3.98 (t, J ¼ 6.0 Hz,
2 H), 4.97 (s, 22 H), 5.55 (s, 2 H), 6.05e6.22 (m, 30 H), 6.93 (d,
J ¼ 8.4 Hz, 2 H), 7.28e7.67 (m, 67 H); 13C NMR (75.5 MHz, CDCl3)
C205H221O32P:C, 76.28; H, 6.90; found C, 76.47; H, 6.96.
A solution of above intermediate (0.19 g, 0.086 mmol) in THF
(3 mL) was added to the stirred suspension of CeCl3 (0.05 g,
0.18 mmol) and LAH (0.03 g, excess) in THF (20 mL) and proceeded
as described in general procedure to afford 13, as a colorless gum
(0.17 g, 91%). TLC: Rf 0.65 (PhMe/EtOAc ¼ 98:2). 1H NMR (CDCl3,
d
22.7, 29.0, 33.1, 67.7, 67.8, 70.0, 70.5 (d, J ¼ 13.5 Hz), 94.0, 94.4,
94.7, 104.9 (m, J ¼ 6.8 Hz), 114.3 (d, J ¼ 10.5 Hz), 127.5, 127.9, 128.3
(d, J ¼ 12.0 Hz),128.5, 129.9, 131.9, 132.3, 134.4 (d, J ¼ 11.1 Hz), 136.8,
136.9 (d, J ¼ 7.7 Hz), 160.7, 160.9; 31P NMR (CDCl3, 162 MHz)
d 29.6
400 MHz)
d
1.59 (br, 20 H), 1.80 (br, 40 H), 3.92 (br, 40 H), 4.97 (s,
(d, JPRh ¼ 149 Hz). Anal. calcd. for C213H233ClO31PRh: C, 73.97; H,
22 H), 6.05e6.23 (m, 30 H) 6.87 (d, J ¼ 8.1 Hz, 2 H), 7.23e7.41 (m,
6.79; Rh, 2.96; found C, 73.59; H, 6.71; Rh, 2.98.
67 H); 13C NMR (100 MHz, CDCl3)
d
22.7, 28.9, 67.7, 70.0, 93.7, 94.0,
17. A mixture of 14 (0.034 g, 0.0076 mmol) and [Rh(cod)Cl]2
(0.011 g, 0.023 mmol) in CH2Cl2 (1 mL) was stirred at room temper-
ature for 10 min and proceeded as described in general procedure to
afford 17, as a yellow foam (0.043 g, 96%). 1H NMR (CDCl3, 300 MHz)
94.4, 114.6 (d, J ¼ 8.0 Hz), 127.5, 127.9, 128.4 (d, J ¼ 8.1 Hz), 128.5,
133.3 (d, J ¼ 18.9 Hz), 135.5 (d, J ¼ 21.2 Hz), 136.8, 160.6, 160.8; 31P
NMR (CDCl3, 162 MHz)
76.66; H, 6.94; found C, 76.65; H, 6.89.
d
ꢀ 6.9; Anal. calcd. for C205H221O31P: C,
d1.63 (br, 30H),1.84e2.05(br, 84 H), 2.39 (br, 24 H), 3.13 (s,12 H), 3.97
14. A mixture of VIII (0.19 g, 0.24 mmol), XII (1.3 g, 1.75 mmol),
NaH (0.1 g, 2.4 mmol, 60% in mineral oil) in DMF (10 mL) was stirred
at 70 ꢁC for 48 h and proceeded as described in general procedure to
afford phosphine oxide, as a brown oil (0.77 g, 69%). TLC: Rf 0.4
(br, 60 H), 4.99 (s, 12 H), 5.54 (s, 12 H) 6.05e6.16 (m, 30 H), 6.91 (d,
J ¼ 8.4 Hz, 12 H), 7.33e7.77 (m, 102 H); 13C NMR (75.5 MHz, CDCl3)
d
22.7, 28.9, 33.0, 67.7, 67.8, 70.0, 70.5 (d, J ¼ 13.6 Hz), 93.8, 94.3,104.9
(m, J ¼ 6.8 Hz),114.3 (d, J ¼ 11.2 Hz),127.5, 127.9,128.0 (d, J ¼ 9.8 Hz),
(CHCl3/MeOH ¼ 9:1). 1H NMR (CDCl3, 400 MHz)
d 1.62 (br, 30 H),
128.5, 130.0, 132.0, 132.5, 134.4 (d, J ¼ 11.1 Hz), 136.8, 136.9 (d,
1.84 (br, 60 H), 3.90 (t, J ¼ 6.0 Hz, 48 H), 4.00 (t, J ¼ 6.0 Hz,12 H), 4.99
J ¼ 7.9 Hz), 160.7, 160.9; 31P NMR (CDCl3, 162 MHz)
d 29.5 (d,
(s,12 H), 6.05e6.24 (m, 30 H), 6.95 (d, J ¼ 8.4 Hz,12 H), 7.31e7.68 (m,
JPRh ¼ 149 Hz). Anal. calcd. for C333H378Cl6O36P6Rh6: C, 66.97; H, 6.38;
102 H); 13C NMR (100 MHz, CDCl3)
d 22.7, 28.8, 28.9, 67.7, 67.8, 70.0,
Rh, 10.34; found C, 67.11; H, 6.14; Rh, 9.80.
93.7, 94.1, 114.5 (d, J ¼ 13.0 Hz), 127.5, 127.9, 128.4 (d, J ¼ 12.2 Hz),
18. A mixture of 15 (0.047 g, 0.0077 mmol) and [Rh(cod)Cl]2
(0.023 g, 0.047 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
128.5, 131.7, 132.0 (d, J ¼ 9.7 Hz), 132.4, 133.4, 133.8 (d, J ¼ 11.2 Hz),
136.7, 160.6, 160.8, 162.0; 31P NMR (CDCl3, 162 MHz)
d 29.34.

B. Natarajan, N. Jayaraman / Journal of Organometallic Chemistry 696 (2011) 722e730
729
procedure to afford 18, as a yellow foam (0.067 g, 97%). 1H NMR
(CDCl3, 300 MHz) 1.62 (br, 42 H), 1.82e2.05 (br, 132 H), 2.38 (br,
TLC: Rf 0.4 (CHCl3/MeOH ¼ 80:20). 1H NMR (300 MHz, CDCl3)
d
1.60
d
(br, 90 H), 1.81 (br, 180 H), 3.91 (br, 180 H), 6.05 (s, 66 H), 6.93 (d,
48 H), 3.13 (s, 24 H), 3.97 (m, 84 H), 5.54 (s, 24 H) 6.05 (s, 30 H), 6.90
J ¼ 8.4 Hz, 48 H), 7.43e7.67 (m, 288 H); 13C NMR (75.5 MHz, CDCl3)
(d, J ¼ 8.4 Hz, 24 H), 7.36e7.77 (m, 144 H); 13C NMR (75.5 MHz,
d
22.7, 28.9, 29.6, 67.7, 67.8, 93.7, 114.5 (d, J ¼ 12.0 Hz), 128.4 (d,
CDCl3)
d
22.7, 28.9, 33.0, 67.7, 67.8, 70.5 (d, J ¼ 13.6 Hz), 93.8, 104.9
J ¼ 12.0 Hz), 131.7, 132.0 (d, J ¼ 9.8 Hz), 132.3, 133.4, 133.9 (d,
(m, J ¼ 7.1 Hz),114.2 (d, J ¼ 11.2 Hz),128.0 (d, J ¼ 9.8 Hz),130.0,131.8,
J ¼ 11.2 Hz), 160.8, 162.0; 31P NMR (CDCl3, 162.0 MHz)
d 29.2. Anal.
132.4, 134.4 (d, J ¼ 11.3 Hz), 136.8 (d, J ¼ 13.6 Hz), 160.7, 160.8; 31P
calcd. for C789H852O114P24: C, 73.45; H, 6.66; found: C, 73.23; H, 7.11.
A solution of above intermediate (0.215 g, 0.016 mmol) in THF
(3 mL) DMF (0.1 mL) was added to the stirred suspension of CeCl3
(0.2 g, 0.83 mmol) and LAH (0.1 g, excess) in THF (25 mL) and
proceeded as described in general procedure to afford 21, as
a brown gum (0.17 g, 81%). TLC: Rf 0.30 (PhMe/EtOAc ¼ 90:10). 1H
NMR (CDCl3, 162 MHz)
d
29.5 (d, JPRh ¼ 149 Hz); Anal. calcd. for
C477H552Cl12O42P12Rh12: C, 63.73; H, 6.19; Rh, 13.72; found C, 64.21;
H, 6.33; Rh, 12.48.
19. A mixture of XIII (0.19 g, 0.03 mmol), phosphine monomer
III (0.027 g, 0.06 mmol) and NaH (0.003 g, 60% in mineral oil,
0.06 mmol) in DMF (15 mL) was stirred at 70 ꢁC for 24 h and pro-
ceeded as described in general procedure to afford phosphine
oxide, as a colorless gum (0.16 g, 80%). TLC: Rf 0.6 (PhMe/
NMR (300 MHz, CDCl3)
180 H), 6.05 (s, 66 H), 6.85 (d, J ¼ 8.4 Hz, 48 H), 7.15e7.38 (br,
288 H); 13C NMR (100 MHz, CDCl3)
22.7, 28.9, 67.6, 67.7, 93.8, 114.7
d 1.60 (br, 90 H), 1.82 (br, 180 H), 3.94 (br,
d
EtOAc ¼ 60:40). 1H NMR (CDCl3, 400 MHz)
d
1.60 (br, 44 H), 1.79 (br,
(d, J ¼ 8.0 Hz), 128.2, 128.4 (d, J ¼ 7.5 Hz), 129.0, 133.4 (d,
88 H), 3.90 (t, J ¼ 6.0 Hz, 86 H), 4.00 (t, J ¼ 6.0 Hz, 2 H), 4.97 (s, 46 H),
6.05e6.22 (m, 66 H), 6.94 (d, J ¼ 8.4 Hz, 2 H), 7.16e7.44 (m, 127 H);
J ¼ 19.0 Hz), 135.5 (d, J ¼ 21.3 Hz), 137.7 (d, J ¼ 10.2 Hz), 159.9, 160.9;
31P NMR (CDCl3, 162.0 MHz)
d - 6.9. Anal. calcd. for C789H852O90P24:
13C NMR (100 MHz, CDCl3)
d
22.7, 28.9, 29.0, 67.7, 67.8, 70.0, 93.8,
C, 75.7; H, 6.86; found: C, 75.29; H, 6.52.
94.5, 127.5, 127.9, 128.4 (d, J ¼ 12.1 Hz), 128.5, 132.0 (d, J ¼ 9.8 Hz),
22. A mixture of 19 (0.1 g, 0.015 mmol) and [Rh(cod)Cl]2
(0.0037 g, 0.0075 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 22, as a yellow gum (0.102 g, 98%). 1H NMR
132.3, 133.5, 133.9,136.8, 160.6, 160.8; 31P NMR (CDCl3, 162 MHz)
d
29.9; Anal. calcd. for C421H461O68P:C, 76.15; H, 7.00; found C,76.30;
H, 6.77.
A solution of above intermediate (0.32 g, 0.048 mmol) in THF
(CDCl3, 400 MHz)
d 1.59 (m, 44 H), 1.78e2.05 (m, 90 H), 2.40 (br,
(5 mL) was added to the stirred suspension of CeCl3 (0.024 g,
0.1 mmol) and LAH (0.02 g, excess) in THF (20 mL) and proceeded as
described in general procedure to afford 19, as a colorless gum
(0.28 g, 86%). TLC: Rf 0.65 (PhMe/EtOAc ¼ 96:4). 1H NMR (CDCl3,
4 H), 3.13 (s, 2 H), 3.92 (br, 88 H), 4.98 (s, 46 H), 5.55 (s, 2 H),
6.05e6.23 (m, 66 H), 6.90 (d, J ¼ 8.6 Hz, 2 H), 7.24e7.67 (m, 127 H);
13C NMR (100 MHz, CDCl3)
d 22.7, 28.9, 67.7, 67.8, 70.0, 93.7, 94.5,
127.5, 127.9, 128.0, 128.5, 130.0, 134.4 (d, J ¼ 11.1 Hz), 136.8, 160.6,
400 MHz)
d
1.59 (br, 44 H), 1.80 (br, 88 H), 3.92 (br, 88 H), 4.97 (s,
160.8; 31P NMR (CDCl3, 162 MHz)
calcd. for C422H467ClO67PRh: C, 74.75; H, 6.94; Rh, 1.52. Found C,
73.94; H, 6.95; Rh, 1.57.
d
29.5 (d, JPRh ¼ 150 Hz). Anal.
46 H), 6.05e6.23 (m, 66 H) 6.86 (d, J ¼ 8.4 Hz, 2 H), 7.22e7.40 (m,
127 H); 13C NMR (100 MHz, CDCl3)
d
22.7, 28.8, 67.6, 67.7, 70.0, 93.7,
94.0, 94.4, 114.6 (d, J ¼ 8.0 Hz) 127.5, 127.9, 128.2, 128.4 (d,
23. A mixture of 20 (0.03 g, 0.0032 mmol) and [Rh(cod)Cl]2
(0.0094 g, 0.019 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 23, as a yellow foam (0.038 g, 96%). 1H NMR
J ¼ 7.0 Hz), 128.5, 133.3 (d, J ¼ 18.9 Hz), 135.5 (d, J ¼ 21.7 Hz), 136.8,
160.5, 160.8; 31P NMR (CDCl3, 162 MHz)
d
ꢀ6.94; Anal. calcd. for
C421H461O67P:C, 76.33; H, 7.01; found C, 76.16; H, 6.89.
20. A mixture of XI (0.11 g, 0.06 mmol), XII (0.65 g, 0.88 mmol),
K2CO3 (0.14 g, 1.0 mmol) and 18-C-6 (cat.) in DMF (20 mL) was
stirred at 70 ꢁC for 72 h and proceeded as described in general
procedure to afford phosphine oxide, as a brown oil (0.41 g, 72%).
(CDCl3, 400 MHz) d 1.62 (br, 66 H), 1.83e2.05 (br, 180 H), 2.39 (br,
48 H), 3.13 (s, 24 H), 3.98 (br, 132 H), 4.99 (s, 24 H), 5.55 (s, 24 H)
6.06e6.17 (m, 66 H), 6.92 (d, J ¼ 8.6 Hz, 24 H), 7.34e7.78 (m, 204 H);
13C NMR (100 MHz, CDCl3)
d 22.7, 28.9, 33.0, 67.7, 67.8, 70.0, 70.5 (d,
TLC: Rf 0.4 (CHCl3/MeOH ¼ 9:1). 1H NMR (CDCl3, 400 MHz)
d
1.61
J ¼ 13.7 Hz), 93.8, 94.3, 104.9 (m, J ¼ 7.1 Hz), 114.2 (d, J ¼ 11.2 Hz),
127.5, 127.9, 128.0 (d, J ¼ 9.8 Hz), 128.5, 129.9, 131.9, 132.2, 134.4 (d,
J ¼ 11.2 Hz), 136.7, 136.8 (d, J ¼ 8.1 Hz), 160.7, 160.9; 31P NMR (CDCl3,
(br, 66 H), 1.82 (br, 132 H), 3.90 (t, J ¼ 6.0 Hz, 108 H), 4.00 (t,
J ¼ 6.0 Hz, 24 H), 4.99 (s, 24 H), 6.01e6.14 (m, 66 H), 6.95 (d,
J ¼ 8.6 Hz, 24 H), 7.31e7.68 (m, 204 H); 13C NMR (100 MHz, CDCl3)
162 MHz)
d
29.5 (d, JPRh ¼ 149 Hz). Anal. calcd. for C693H792Cl12O78
d
22.7, 28.8, 28.9, 67.7, 67.8, 70.0, 93.8, 94.2, 114.6 (d, J ¼ 13.0 Hz),
P12Rh12: C, 67.12; H, 6.44; Rh, 9.96; found C, 67.04; H, 6.26; Rh, 10.2.
24. A mixture of 21 (0.05 g, 0.004 mmol) and [Rh(cod)Cl]2
(0.024 g, 0.048 mmol) in CH2Cl2 (1 mL) was stirred at room
temperature for 10 min and proceeded as described in general
procedure to afford 24, as a yellow foam (0.072 g, 97%). 1H NMR
127.5, 127.9, 128.4 (d, J ¼ 12.8 Hz), 128.5, 131.7, 132.0 (d, J ¼ 9.8 Hz),
132.4,133.5, 134.0 (d, J ¼ 11.3 Hz),136.8, 160.6, 160.8, 161.9; 31P NMR
(CDCl3, 162 MHz)
d 29.34; Anal. calcd. for C597H648O90P12:C,74.42;
H,6.78; found C,74.26; H, 6.52.
A solution of above intermediate (0.16 g, 0.016 mmol) in THF
(5 mL) was added to the stirred suspension of CeCl3 (0.1 g,
0.4 mmol) and LAH (0.024 g, excess) in THF (20 mL) and proceeded
as described in general procedure to afford 20, as a colorless gum
(0.14 g, 89%). TLC: Rf 0.6 (PhMe/EtOAc ¼ 95:5). 1H NMR (CDCl3,
(CDCl3, 400 MHz) d 1.62 (br, 90 H), 1.73e2.05 (br, 276 H), 2.38 (br,
96 H), 3.12 (s, 48 H), 3.97 (br, 180 H), 5.54 (s, 48 H) 6.05 (s, 66 H),
6.90 (d, J ¼ 8.4 Hz, 48 H), 7.29e7.76 (m, 288 H); 13C NMR (100 MHz,
CDCl3)
d
22.7, 28.8, 28.9, 33.0, 67.7, 67.8, 70.5 (d, J ¼ 13.5 Hz), 93.8,
104.9 (m, J ¼ 6.8 Hz), 114.2 (d, J ¼ 11.0 Hz), 128.0 (d, J ¼ 9.8 Hz),
400 MHz)
d 1.60 (br, 66 H), 1.81 (br, 132 H), 3.92 (br, 132 H), 4.99 (s,
130.0, 131.9, 132.3, 134.4 (d, J ¼ 11.0 Hz), 136.8 (d, J ¼ 13.1 Hz), 160.7,
24 H), 6.06e6.15 (m, 66 H), 6.86 (d, J ¼ 8.4 Hz, 24 H), 7.25e7.39 (m,
160.8; 31P NMR (CDCl3, 162 MHz)
d
29.5 (d, JPRh ¼ 150 Hz). Anal.
204 H); 13C NMR (100 MHz, CDCl3)
d
22.7, 28.9, 67.5, 67.6, 70.0, 93.8,
calcd. for C981H1140Cl24O90P24Rh24: C, 63.91; H, 6.23; Rh, 13.40;
found C, 64.07; H, 6.41; Rh, 13.70.
94.1, 114.5 (d, J ¼ 8.4 Hz), 127.5, 127.9, 128.4 (d, J ¼ 7.5 Hz), 128.6,
133.4 (d, J ¼ 18.8 Hz), 135.6 (d, J ¼ 21.1 Hz), 136.8, 137.9 (d,
J ¼ 10.5 Hz), 159.8, 160.6, 160.8; 31P NMR (CDCl3, 162 MHz)
ꢀ 6.99;
d
Anal. calcd. for C597H648O78P12: C, 75.93; H, 6.92; found C, 75.46; H,
6.67.
Acknowledgements
21. A mixture of XIV (0.21 g, 0.05 mmol), III (0.62 g, 1.4 mmol),
NaH (0.071 g, 60% in mineral oil, 1.8 mmol) in DMF (30 mL) was
heated at 90 ꢁC for 72 h and proceeded as described in general
procedure to afford phosphine oxide, as a brown oil (0.48 g, 74%).
Financial support of the work from Department of Science and
Technology, New Delhi, is gratefully acknowledged. Council of
Scientific and Industrial Research, New Delhi, is acknowledged for
a research fellowship BN.

730
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