Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose

Article abstract of DOI:10.1016/j.reactfunctpolym.2017.04.010

A novel ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose has been prepared by multi-step synthesis. The complex proved to be robust and efficient heterogeneous catalyst for synthesis of biaryls in Suzuki-Miyaura cross coupling reaction.

Full text of DOI:10.1016/j.reactfunctpolym.2017.04.010

Accepted Manuscript
Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-
heterocyclic carbene-Pd complex anchored on cellulose
Dolly Kale, Gajanan Rashinkar, Arjun Kumbhar, Rajashri
Salunkhe
PII:
S1381-5148(17)30074-3
DOI:
Reference:
doi: 10.1016/j.reactfunctpolym.2017.04.010
REACT 3841
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Reactive and Functional Polymers
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Accepted date:
15 August 2016
22 April 2017
22 April 2017
Please cite this article as: Dolly Kale, Gajanan Rashinkar, Arjun Kumbhar, Rajashri
Salunkhe , Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic
carbene-Pd complex anchored on cellulose. The address for the corresponding author
was captured as affiliation for all authors. Please check if appropriate. React(2017), doi:
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Graphical Abstract
Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic
carbene-Pd complex anchored on cellulose
Dolly Kale, Gajanan Rashinkar, Arjun Kumbhar, Rajashri Salunkhe*
Department of Chemistry, Shivaji University, Kolhapur, 416004, M.S., India
E-mail: rss234@rediffmail.com
∗Corresponding author Tel.: +91 231 260 9169; fax: +91 231 2692333.

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Graphical Abstract
Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic
carbene-Pd complex anchored on cellulose
Dolly Kale, Gajanan Rashinkar, Arjun Kumbhar, Rajashri Salunkhe*
Department of Chemistry, Shivaji University, Kolhapur, 416004, M.S., India
E-mail: rss234@rediffmail.com
∗Corresponding author Tel.: +91 231 260 9169; fax: +91 231 2692333.

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Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic
carbene-Pd complex anchored on cellulose
Dolly Kale, Gajanan Rashinkar, Arjun Kumbhar, Rajashri Salunkhe*
Department of Chemistry, Shivaji University, Kolhapur, 416004, M.S., India
E-mail: rss234@rediffmail.com
∗Corresponding author Tel.: +91 231 260 9169; fax: +91 231 2692333.
Abstract: A novel ferrocene tethered N-heterocyclic carbene-Pd complex anchored on
cellulose has been prepared by multi-step synthesis. The complex proved to be robust and
efficient heterogeneous catalyst for synthesis of biaryls in Suzuki-Miyuara cross coupling
reaction.
Keywords: N-Hetereocyclic carbene, Ferrocene, Cellulose, Suzuki-Miyuara reaction,
Reusability.

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1. Introduction
Transition-metal-catalyzed cross-coupling reactions have opened new avenues for
creating sophisticated organic scaffolds precisely and efficiently with widespread use
across a variety of disciplines [1]. The anticipated manipulation in chemo and stereo
selectivity in these reactions has been pursued with the aid of suitable ligands which play
a crucial role in stabilizing and activating the transition metal ensuing fine-tuning of the
selectivity in the transformation [2]. In recent years, N-Heterocyclic carbenes (NHCs)
have emerged as the most powerful ancillary ligands for cross coupling reactions [3].
NHCs tend to bind more strongly with metals, avoiding the necessity for the use of
excess ligand in catalytic reactions. In addition, they are exceptionally stable toward heat,
air as well as moisture and their steric and electronic properties can be tuned with simple
modular synthetic approaches making them process compatible. However, despite these
intriguing properties, insight into the homogeneous NHC–transition metal catalytic
systems has revealed some basic problems in terms of separation and recycling [4]. This
factor coupled with their ability to induce contamination of the ligand residue in the
products has spurred extensive interest for the development of heterogeneous NHC–
transition metal catalysts [5]. The field of heterogeneous NHCs has witnessed impressive
progress during the past few years [6]. However, there is a still scope to develop novel
heterogeneous NHCs and apply them in cross coupling reactions to realize the goal of
sustainable and environmentally benign catalytic technologies.
The recent quest towards sustainable development has spurred an extensive
interest in the use of natural renewable resources in catalytic technology [7,8]. In this
regard, cellulose which is the most abundant biopolymer derived from natural resources

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offers most promising class of sustainable and economic feedstock for catalysis. The
characteristic feature of cellulose is its unique linear polysaccharide structure comprising
of ß-D-glucose units linked by 1,4 glycosidic bonds with flipped monomer subunits
imparts rigidity and high tensile strength [9]. An important attribute that explains its
potential for catalytic applications is its tendency to act as support for immobilizing the
active catalytic systems [10]. The hydroxyl groups in the cellulose can be easily
functionalized thereby providing handle for catalyst immobilization. In addition, high
surface area, non-toxicity, stability in common organic solvents, unlimited availability as
a renewable bioresource and excellent biodegradability has made cellulose undoubted
protagonist of the major recent breakthroughs in the field of green supports for synthesis
of heterogeneous catalysts. The interesting properties of cellulose spurred us to
investigate its feasibility in the synthesis of heterogeneous NHC-transition metal
complexes.
In continuation of our previous work related to C-C cross coupling reactions using
cellulose supported reagents [11], we report herein synthesis of ferrocene tethered N-
heterocyclic carbene-Pd complex anchored on cellulose and its catalytic activity in
Suzuki-Miyaura reaction.
2. Experimental section
2.1. General Remarks:
Infrared spectra were recorded on a Perkin-Elmer FTIR spectrometer. Elemental analyses
were performed on EURO EA3000 vectro model. The thermalgravimetric analysis
(TGA) curves were obtained using the instrument TA SDT Q600 in the presence of static
air at a linear heating rate of 10 °C min−1 from 25 °C to 1000 °C. The elemental

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composition of materials was analyzed by an energy-dispersive X-ray spectra (EDS)
attached to the field emission scanning electron microscope (FE-SEM, Model Hitachi S
4800, Japan). GC-MS spectra were recorded by SHIMADZU QP2010.X-ray
photoelectron spectra (XPS) were recorded on a KRATOS AXIC 165 equipped with Mg
Kα
radiation.
1-N-Ferrocenylmethyl
imidazole
and
l-ferrocenyImethyl-3-
methylimidazolium iodide was synthesized following the literature procedure [12, 13].
All chemicals were obtained from Sigma Aldrich or Spectrochem India and used as
received. All reactions were carried out under air atmosphere in dried glasswares.
2.2. Preparation of the Cel/Al2O3 composite (2)
The Cel/Al2O3 composite (2) was prepared following the literature procedure with slight
modification [13]. A mixture of microcrystalline cellulose (15 gm), aluminum chloride
hexahydrate (15 gm) in water (200 ml) was stirred for 12 hours. The mixture was filtered
and the solid was exposed to ammonia gas, washed with water and dried under vacuum at
room temperature. The amount of aluminum was determined by calcining 0.300 g of 2 to
600 °C for 8 h and the residue weighed as Al2O3, which was found to be 3.27 wt %,
corresponding to 0.31 mmol g-1 aluminium.
2.3. Preparation of chloropropyl cellulose (3)
A mixture of 2 (10gms) and (3-chloropropyl)triethoxysilane (9.6 gm, 40 mmol) in
toluene (30 mL) was refluxed for 24 h. The mixture was filtered and the solid was
washed with toluene and dried under vacuum at room temperature. IR (neat, thin film): υ
= 2896, 1427, 1334, 1314, 1204, 1160, 1109, 1056, 1032, 901, 762, 664 cm-1; Loading:
0.21 mmol functional group g-1 of cellulose.
2.4. Preparation of [CelFemImi]Cl (5)

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A mixture of 3 (5.0 g) and 1-N-ferrocenylmethyl imidazole 4 (2.66 g, 10 mmol) in DMF
(25 mL) was heated at 80 °C in an oil bath. After 48 h, the solid was filtered, washed
with DMF (3x50 mL), MeOH (3x50 mL), CH2Cl2 (3x50 mL) and dried under vacuum at
room temperature to afford of [CelFemImi]Cl (5). IR (neat, thin film): υ = 3261, 2958,
2897, 1640, 1535, 1427, 1368, 1338, 1315, 1286, 1242, 1161, 1110, 1057, 1032, 892,
706, 665 cm-1; Loading: 0.21 mmol functional group g-1of cellulose.
2.5. Preparation of CelFemImiNHC@Pd complex (6)
[CelFemImi]Cl (5) (2.00 g) was added in a solution of Pd(OAc)2 (0.336 g, 1.5 mmol) in
THF (15 mL). The resulting mixture was heated at reflux for 24 h and cooled to room
temperature. Afterwards, the solid was filtered and washed with THF (3x20 mL) and
dried under vacuum at room temperature for 48 h to afford CelFemImiNHC@Pd
complex (6). IR (neat, thin film): υ = 3254, 2982, 1494, 1390, 1303, 1215, 1138, 1086,
1042, 935, 848, 681, cm-1; 13C CP-MAS NMR (500 MHz.): δ 171 (s, 1C, -N-CH-CH-
N=), 130 (s, 1C, -N-CH-CH-N=), 126 (s, 1C, -N-CH-CH-N=), 112 (bs, C-1 [from
cellulose matrix]), 90 (bs, C-4 [from cellulose matrix]), 71-77 (m, C-2,3,5 [from cellulose
matrix]), 68 (bs, C-6 [from cellulose matrix]), 71 (s, C, Cp ring from Ferrocene), 79 (s, C,
Cp ring from Ferrocene), 49 (s, 1C, =N-CH2-CH2-), 28 (s, 1C, =N-CH2-CH2-), 8.0 (s, 1C,
-CH2-Si); Loading: 0.016 mmol of Pd g-1 of cellulose.
2.6 General Procedure for the Suzuki Miyaura Coupling Reaction
An oven-dried Schlenk flask, equipped with a magnetic stir bar was charged with aryl
halide (1.0 mmol), arylboronic acid (1.2 mmol), Cs2CO3 (2 mmol), CelFemImiNHC@Pd
complex (6) (50 mg, 1 mol %) and 5 mL of solvent. The reaction mixture was stirred at
ambient temperature in an open air. After completion of the reaction as monitored by

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TLC, the catalyst was filtered and washed with ethanol (3 X 5 mL). The filtrate was
concentrated in vacuo to leave the crude products which were analyzed by GCMS.
2.7
Preparation
of
bis[1-ferrocenylmethyl-3-methyl-imidazoline-2-ylidene]-
diiodopalladium(II) (11)
A mixture of 10 (0.204 mg, 0.5 mmol) and Pd(II) acetate 108 mg (112 mg, 0.5 mmol)
Pd(II) acetate was refluxed in THF (15 mL) for one hour. Afterwards, THF was removed
in vacuo and the solid residue was washed with ether (3 X 5 mL). The crude product was
dissolved in dichloromethane and crystallized by addition of hexane, yielding 174 mg of
bis[1-ferrocenylmethyl-3-methyl-imidazoline-2-ylidene]-diiodopalladium(II) (11). IR
(neat, thin film): υ = 3120, 2928, 2857, 1626, 1545, 1431, 1331, 852, 750, 493 cm-1;1H
NMR (300 MHz, CDCl3): δ 7.92, 7.73, 7.33, 7.28 (4 H, Imidazole), 5.37 (s, 2H, Fc-CH2),
4.85 (s, 2H, Fc-CH2), 4.85 (m, 2H, Cp substituted), 4.47 (m, 2H, Cp substituted), 4.28 (s,
10H, Cp unsubstituted), 4.10 (m, 2H, Cp substituted), 4.05 (m, 2H, Cp substituted), 4.05
(m, 2H, Cp substituted), 3.87 (s, 3H, CH3), 3.84 (s, 3H, CH3); 13CNMR (75Hz, CDCl3): δ
173.8, 145.8, 144.3, 142.6, 69.75, 69.42, 69.32. 69.16, 52.38, 35.7.
2.8 Preparation of CelMeImiNHC@Pd complex (11)
CelMeImiNHC@Pd complex (11) was prepared using the same procedure described for
the synthesis of 6 except that 1-methyl imidazole was used instead of 1-N-
ferrocenylmethyl imidazole 4. IR (neat, thin film): υ = 2927, 2854, 1674, 1570, 1450,
1378, 1249, 1131, 1049, 861, 791 cm-1; Loading: 0.035 mmol of Pd g-1 of cellulose.
3. Results and discussion
The synthesis of ferrocene tethered N-heterocyclic carbene-Pd complex anchored
on cellulose is shown in Scheme 1. In an initial step, aluminum oxide was highly

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dispersed on the cellulose (1) with a good degree of adhesion to form Cel-Al2O3
composite (2) following literature procedure [14]. The inherent ability of surface Al-OH
groups of 2 to form stable Al-O-Si bonds with Si-OR groups of (3-
chloropropyl)triethoxysilane allowed facile synthesis of chloropropyl cellulose (3) with a
high degree of organofunctionalization. 1-N-Ferrocenylmethyl imidazole (4) was then
covalently anchored in the cellulose matrix with the help of tethered chloropropyl group
by quaternization reaction to yield heterogeneous azolium salt, [CelFemImi]Cl (5) that
served as precursor for the synthesis of desired NHC-Pd complex. Finally, the
complexation of (5) with Pd(OAc)2 in THF resulted in the formation of desired ferrocene
tethered N-heterocyclic carbene-Pd complex anchored on cellulose acronymed as
CelFemImiNHC@Pd complex (6).
The reactions involved synthesis of CelFemImiNHC@Pd complex (6) were
monitored by using FTIR spectroscopy. The appearance of peaks in the FT IR spectrum
at 1640 and 1535 cm−1 (the C=N and C=C stretching vibrations of imidazolium ring),
3261 cm−1 and 2958 cm−1 (C–H stretching vibrations of the imidazolium ring) confirmed
the formation of 5. The formation of 6 was inferred from a characteristic v(NCN) band in
the FTIR spectrum at 1494 cm−1. In addition, cross‐polarization magic angle spinning
(CP‐MAS) 13CNMR spectrum displayed characteristic peak at δ 171 ascribed to the
carbenic carbon confirming the formation of 6.
The degree of organofunctionalization during quaternization was measured by
elemental analysis. The results revealed loading of 0.32 mmol g−1 of ferrocenyl
imidazolium units g−1 of cellulose in [CelFemImi]Cl. The Pd content in 6 was quantified
using energy dispersive spectroscopy (EDS) and was found to be 0.016 mmol g−1.

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The FESEM analysis (Fig.1) was undertaken to study the morphology of the
CelFemImiNHC@Pd complex (6). Fibrous morphology was observed with diameters in
the range of several hundreds of nanometers up to a few micrometers. The FESEM
images also revealed the uniform dispersion of Pd species on the surface of cellulose.
The X-ray photoelectron (XPS) spectroscopy was used to investigate the
elemental coordination state of Pd species in CelFemImiNHC@Pd complex (6). The XPS
spectrum of Pd 3d core level region displayed peaks of binding energy at 345.2 (Pd 3d3/2)
and 339.6 eV (3d5/2). These values corroborate the existence of palladium (II) in 6.
Thermogravimetric (TGA) analysis was carried out to investigate the thermal
behavior of CelFemImiNHC@Pd complex (6). The TGA curve showed three
characteristic decomposition stages (Fig. 2). The initial weight loss of 4.94 % below 100
oC is attributed to the evaporation of physisorbed water. The second weight loss of ~53 %
o
in the range 100-333 C is ascribed to the mutual loss of ferrocenyl unit and surface-
bound organic scaffolds from crystalline cellulose. The third weight loss of ~21 % from
o
333 to 458 C is due to decomposition of cellulose in oxidizing atmosphere. The large
residual weight is due to formation of metallic oxides.
Nitrogen adsorption-desorption isotherms were recorded to evaluate the textural
properties of CelFemImiNHC@Pd complex (6). A typical irreversible-type IV adsorption
isotherm with H1 hysteresis loop was observed. The 6 showed BET surface area of 14
m2/g which was significantly smaller as compared to pristine cellulose with BET surface
area of 20 m2/g indicating occupation of the free porous arrangement due to grafting of
organic moieties on the surface of cellulose.

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The screening for the catalytic efficiency of CelFemImiNHC@Pd complex (6)
was carried out on model reaction involving Suzuki-Miyaura cross coupling between
phenyl boronic acid (7a) and iodobenzene (8a). The influence of parameters such as
solvents, base and catalyst loading was investigated. The conversion was readily
established by monitoring the composition of the reaction mixture by Thin Layer
Chromatography followed by gas chromatography–mass spectrometry (GC-MS) analysis.
The initial experiments were carried out by reaction equimolar quantities of 7a and 8a (1
mmol each) in presence of 6 (50 mg, 0.008 mol%) in ethanol at ambient temperature.
Various bases such as Na2CO3, Cs2CO3, KOtBu, K3PO4, KOH and NaOH were screened.
To our delight, Cs2CO3 afforded the desired product in 87% yield, whereas the other
bases resulted in much lower yields (Table 1, entries 1-6). An array of solvents including
ethanol, THF, acetonitrile, DMF, toluene and water was examined. The studies revealed
ethanol as the best solvent for the present transformation (Table 1, entries 7-11). The
effect of catalyst loading was investigated with varying amount of catalyst. A maximum
yield of 87 % was obtained with 50 mg of 6 (0.008 mol%). Decreasing the amount of the
catalyst resulted in low yield of the product even after prolonged reaction time (Table 1,
entry 12). Increase in quantity of catalyst did not have any significant effect on the yield
and reaction time of product (Table 1, entries 13,14).
After the optimization of reaction conditions, the scope and generality of the
reaction was ascertained by performing Suzuki-Miyaura cross coupling reactions
between phenyl boronic acid and structurally diverse aryl halides (Scheme 1). The results
are summarized in Table 2. Gratifyingly, aryl iodides and aryl bromides with diverse
structural and electronic nature underwent smooth cross-coupling process yielding

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corresponding biaryls with the TON in the range of 9125–11125 and TOF in the range of
151–556 min−1 (Table 2, entries 1-9). In general, the electronic nature of the substituents
attached to the aromatic ring had a slight influence on the yield of the products. Aryl
halides with electron withdrawing groups displayed greater reactivity furnishing cross
coupling products in higher yields than those with electron donating groups. In order to
extend the scope of the methodology, we attempted reaction between phenyl boronic acid
and less reactive aryl chlorides (Table 2, entries 10-13). We were delighted to note that
various aryl chlorides could serve as a substrate in this reaction, albeit giving the
corresponding biaryls in a slightly lower yields (TON: 6250–7000; TOF 34–77 min−1).
The lower TON and TOF values in Suzuki-Miyaura reactions of aryl chlorides can be
attributed their reluctance towards oxidative addition to Pd. To further widen the
applicability of the protocol, we have carried out Suzuki Miyaura cross coupling
reactions of various phenyl boronic acids (Table 2, entries 14-19). The phenyl boronic
acids with electron withdrawing as well as electron donating functionalities reacted
efficiently with aryl iodides and bromides provided higher yields of anticipated biaryls in
shorter reaction time.
To demonstrate that the developed protocol is also suitable for scale-up chemistry,
CelFemImiNHC@Pdcomplex (6) assisted gram scale synthesis of 9a was carried out
with 82 % yield from 7a (20 mmol) and 8a (20 mmol) under optimized reaction
conditions.
The catalytic activity of CelFemImiNHC@Pd complex (6) was compared with its
corresponding homogeneous analogue, bis[1-ferrocenylmethyl-3-methyl-imidazoline-2-
ylidene]-diiodopalladium(II) (11) in which cellulose is replaced by methyl group

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(Scheme 3). The synthetic route for the preparation of 11 involved quaternization of 4
with methyl iodide to form l-ferrocenylmethyl-3-methylimidazolium iodide (10) followed
by in situ deprotonation with acetate as base and complexation with Pd(OAc)2. The
activity of 11 was evaluated for model reaction between 7a and 8a under optimized
reaction conditions. The results revealed that reaction time and yield for the formation of
corresponding biphenyl (94 % yield in 30 min with 5 mol% of catalyst) was better for 11
than 6. However, 11 could not be recycled and reused thereby confirming superior nature
of 6 to the homologues analogue.
A
reasonable explanation for the notable catalytic activity of
CelFemImiNHC@Pd complex (6) is attributed to the tethered ferrocenyl group which can
be justified by considering the general catalytic cycle for Suzuki-Miyaura cross coupling
involving oxidative addition of aryl halide to NHC-Pd complex followed by the
transmetalation of the boronate substrate to finally generate biaryls via reductive
elimination. It is now well established that electron rich NHC-metal complexes undergo
faster oxidative addition which is the key step in Suzuki-Miyaura cross coupling reaction
[14]. One of the reliable approach to design electron rich catalytic systems for cross
coupling reactions is to tether an organometallic moiety like ferrocene at wingtip position
in the ligand framework. In the present case, by virtue of its relatively steric bulk owing
to unique cylindrical shape and powerful electron donor capacity, ferrocene causes
substantial electron donation from the carbene to the metal centre rendering electron rich
CelFemImiNHC@Pd complex (6) that undergoes faster oxidative addition to produce
biaryls in high yields within short reaction time. To experimentally ascertain the role of
ferrocene, the catalyst structurally resembling to CelFemImiNHC@Pd complex (6) but

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without ferrocenyl group acronymed as CelMeImiNHC@Pd complex (12) was
synthesized. The efficiency of cross coupling between 7a and 8a under optimized
reaction conditions in the presence of 12 was low as the corresponding biphenyl was
obtained in 78 % yield within 3 hours clearing reflecting the significant role of ferrocene
in catalytic cycle.
The heterogeneity of the CelFemImiNHC@Pd complex (6) was comprehended by
multiple experimental methods. Initially, the hot filtration test for model reaction was
performed under standard reaction conditions. After completion of 50 % of reaction
(GC), 6 was separated from the reaction using a hot frit and the Suzuki reaction in the
filtrate was monitored. There was no further conversion in the catalyst-free solution
phase after prolonged reaction time (3h). The leaching of Pd into reaction mixture was
analyzed by ICP-OES analysis. For this purpose, the reaction mixture was filtered and
filtrate was evaporated to dryness. The residue was dissolved in HNO3 and subjected to
ICP-OES analysis. The analysis revealed that Pd concentration in the reaction solution
was less than detection limit (< 50ppb). These experimental results undoubtedly
demonstrated that there was no Pd leaching during the reaction and the catalyst is indeed
heterogeneous in nature.
The recyclability and reusability of CelFemImiNHC@Pd complex (6) was
evaluated by performing model reaction under optimized reaction conditions. After the
completion of reaction, the catalyst was isolated from reaction by simple filtration. The
recovered catalyst was washed with copious amount of ethanol and dried under vacuo at
room temperature and used for next run. The amounts of reactants were recalculated on

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the basis of recovered catalyst. The catalyst displayed almost consistent activity with
marginal decrease in yield up to five consecutive catalytic cycles (Fig. 3).
The mechanical stability of CelFemImiNHC@Pd complex (6) was confirmed
from its post catalytic FTIR analysis. The appearance of bands at 1530, 1642, 2970 and
3256 cm-1 in the FTIR spectrum of spent catalyst confirmed the intactness of organic
functional groups in the 6. Further, the quantification of Pd from spent catalyst was
found to be 0.014 mmol/g which is close to that of fresh catalyst confirming the
robustness of 6.
A comparison of CelFemImiNHC@Pd complex (6) with some of the NHC-Pd
complexes reported to catalyze Suzuki-Miyaura cross coupling reaction is presented in
Table 3. The analysis reveals better performance of 6 in terms of reaction time and
catalyst loading as compared to many of the reported catalytic systems.
In conclusion, we have synthesized a novel ferrocene tethered NHC-Pd complex
anchored on cellulose support that constitutes a unique arrangement encompassing
tethered ferrocenyl group which allows straightforward control of steric properties and
natural feedstock based backbone consisting of cellulose to achieve the goal of
sustainability. The complex has been characterized on the basis of FTIR, solid state
13CNMR, EDX and XPS spectroscopy as well as by SEM and TGA analysis. The
complex has been successfully used in the synthesis of biaryls using Suzuki-Miyaura
cross coupling reaction between phenyl boronic acids and aryl halides. A good catalytic
efficiency along with high yields of products, easy separation, large scale synthesis, high
TON and TOF and facile recyclability are the notable features of the reported procedure.

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Acknowledgement
We gratefully acknowledge Indian Institute of Sciences (IISc), Bangalore and
Sophisticated Analytical Instrumental Facility, Indian Institute of Technology, Madras
(IITM) for providing spectral facilities.
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Scheme 1. Synthesis of CelFemImiNHC@Pd complex (6)

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CelFemImiNHC@Pd complex
OH
OH
+ X
B
Cs2CO3, Ethanol, RT
R1
R1
R2
R2
Scheme 2. CelFemImiNHC@Pd complex catalyzed Suzuki-Miyaura cross coupling reaction

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Me
N
Pd I
N
N
+
Me
N
N
Fe
I
Pd(OAc)2
THF
MeI
Fe
Me
N
4
MeOH
Fe
11
10
Scheme 3. Synthesis of bis[1-ferrocenylmethyl-3-methyl-imidazoline-2-ylidene]-
diiodopalladium(II) (11)

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Fig. 1. Field emission scanning electron microscopy (FESEM) images of
CelFemImiNHC@Pd complex (6)

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Fig. 2. Thermogravimetric analysis (TGA) curve of CelFemImiNHC@Pd complex (6)

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Fig. 3. Reusability of CelFemImiNHC@Pd complex (6) in Suzuki-Miyaura cross
coupling reaction

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Table 1
Optimization of the reaction conditions
CelFemImiNHC@Pd complex
Base, Solvent, RT
OH
I
+
B
OH
7a
8a
9a
Entry
Solvent
Base
Yielda
(%)
Time
(min)
30
TON
TOF
(min-1)
362
1
2
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
THF
87
10875
9250
9875
10125
6500
7250
10625
10250
9750
8750
-
Cs2CO3
Na2CO3
KOtBu
K3PO4
74
79
81
52
58
85
82
78
70
NR
51
89
90
45
50
40
60
60
40
60
45
60
120
100
25
25
205
197
253
108
120
265
170
216
145
-
3
4
5
KOH
6
NaOH
7
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
8
CH3CN
DMF
9
10
11
12b
13c
14d
Toluene
Water
Ethanol
Ethanol
Ethanol
6375
11125
11250
63
445
450
a Isolated yields after chromatography.
b Reaction with 25 mg of CelFemImiNHC@Pd complex.
cReaction with 100 mg of CelFemImiNHC@Pd complex.
d Reaction with 200 mg of CelFemImiNHC@Pd complex.

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Table 2
CelFemImiNHC@Pd complex assisted Suzuki Miyaura cross coupling coupling of
phenyl boronic acid with aryl halides
Entry
Aryl halide
Product
Yielda Time
TON
TOF
(%)
87
(min)
30
(min-1)
(8)
(9)
I
10875
10500
10625
362
262
303
1
2
3
H2N
I
H2N
84
85
40
35
MeO
O2N
I
MeO
I
O2N
89
20
11125
556
4
Br
78
79
80
73
55
50
50
45
9750
9875
10000
9125
243
151
200
201
5
6
7
8
Me
OHC
Br
Br
Me
OHC
H3COC
Br
H3COC
MeO
Br
78
54
50
9750
6750
195
61
MeO
9
Cl
110
10