Synthesis of 5-(dimethylsilyl)pentylalkylferrocene-grafted HTPB (alkylFc-HTPB) via platinum-catalyzed hydrosilylation

Article abstract of DOI:10.1007/s13738-017-1154-5

In this work, at first alkylferrocene derivatives were synthesized according to procedure described in the literature. (5-Chloropentanoyl)ferrocene derivatives were prepared by Friedel–Crafts acylation of ferrocene and alkylferrocene derivatives with 5-ch

Full text of DOI:10.1007/s13738-017-1154-5

J IRAN CHEM SOC
DOI 10.1007/s13738-017-1154-5
ORIGINAL PAPER
Synthesis of 5‑(dimethylsilyl)pentylalkylferrocene‑grafted HTPB
(alkylFc‑HTPB) via platinum‑catalyzed hydrosilylation
1
2
1,2
Reza Teimuri‑mofrad · Kazem D. Safa · Saiedeh Abedinpour
Keshvar Rahimpour
·
1
Received: 22 July 2016 / Accepted: 12 June 2017
©
Iranian Chemical Society 2017
Abstract In this work, at ꢀrst alkylferrocene derivatives
were synthesized according to procedure described in the
literature. (5-Chloropentanoyl)ferrocene derivatives were
prepared by Friedel–Crafts acylation of ferrocene and
alkylferrocene derivatives with 5-chloropentanoyl chloride
composite propellants were investigated. For example, the
viscosity increased with increasing iron content because of
the greater extent of ferrocene grafting in the polymer.
Keywords Ferrocene · Alkylferrocene · Hydrosilylation ·
in dichloromethane, and AlCl was used as catalyst. The
Hydroxyl-terminated polybutadiene (HTPB)
3
corresponding 5-chloropentylferrocene derivatives were
synthesized from reduction of these products by NaBH in
4
diglyme at 0 °C. Finally (5-alkylferrocenylpentyl)dimethyl-
silane was synthesized from reaction of 5-chloropentylfer-
rocene derivatives with magnesium in THF and reaction of
corresponding Grignard reagents with chlorodimethylsi-
Introduction
Ferrocene has been subject of intensive research, attracted
considerable attention because of its fascinating chemistry
where played outstanding role in various ꢀelds of organo-
metallic chemistry in past decades [1]. Therefore, chem-
ists studied more about these compounds and to use them
in different ꢀelds [2, 3]. Usually, ferrocene and its deriva-
tives have favorable properties like stability in 400 °C with-
out noticeable decomposition [4, 5]. Ferrocene-containing
organometallic materials are useful in making nonlinear
optical (NLO) materials and electrochemical sensors [6, 7].
Ferrocene group is one of the most effective electrochemi-
cal signaling units that have stable redox characteristics
[8]. Ferrocene and its derivatives have magnetic properties
[9], excellent thermal and photochemical stability which
protect polymeric systems from photodegradation [10].
In addition, the ferrocene building block has been used in
conductive polymers and dendritic macromolecules [11],
semiconducting [12], liquid crystal [13], chiral ligands for
asymmetric catalysis [14], precursors of ceramics [15],
medicines [16–18], polymeric mediator for applications in
sensor/biosensor [19], resins [20], organic cathode mate-
rials [21], nonlinear optical applications [22] and burning
rate accelerator catalysts in propellants [23]. Compos-
ite propellants have more use in military, automobile and
aerospace [24]. Solid propellants during combustion must
1
13
lane in 82–87% yields. H and C NMR, FT-IR spectros-
copy supported the predicted structure of the product. Nine
samples of alkylferrocene-grafted hydroxyl-terminated
polybutadiene (alkylFc-HTPB) derivatives, containing dif-
ferent percent of iron, were synthesized by hydrosilyla-
tion reaction of [5-(alkylferrocenyl)pentyl]dimethylsilane
with hydroxy-terminated polybutadiene (HTPB), in the
presence of catalytic amount of the hexachloroplatinic
acid (Speier’s catalyst). FT-IR spectroscopy was utilized
to follow the progress of the reaction, by monitoring the
−
1
loss of the Si–H absorption at 2110 cm , and the reac-
tion was completed in 24 h. Some properties of resulting
prepolymer like viscosity, glass transition temperature and
iron percentage as important parameters in production of
*
Reza Teimuri-mofrad
teymouri@tabrizu.ac.ir
1
Organic Synthesis Research Laboratory, Department
of Organic and Biochemistry, Faculty of Chemistry,
University of Tabriz, Tabriz 51664, Iran
2
Organicsilicon Research Laboratory, Department of Organic
and Biochemistry, Faculty of Chemistry, University of Tabriz,
Tabriz 51664, Iran
1
3

J IRAN CHEM SOC
produce large amount of non-toxic gasses and little or no
pollution. Some kind of these products need to have high
combustion rate and will be suitable for using in accelera-
tor units, antiaircraft rockets and as a gas generator for air
bags in safety devices. In the formulation of composite pro-
pellant, prepolymers like hydroxyl-terminated polybutadi-
ene (HTPB) are usually used as a binder and diisocyanate
as a cross-linking agent to form an elastomeric binder,
ammonium perchlorate (AP) as oxidizer and the appropri-
ate burn rate accelerator catalyst [25]. HTPB prepolymer
and its derivatives are used as binder in rocket or missile
solid propellant because of their low-glass transition tem-
perature, good mechanical properties at low temperature,
high speciꢀc impulse and good ballistic resistance. Previ-
ously, Fe O or CuCr O was used as burn rate catalysts
Butacene and Catocene with the same amount of iron
showed that burn rates of the Butacene propellant are
always higher than Catocene propellant; it is because of the
catalytic effect of the ferrocenic moiety. In enhancing burn
rates, the effect of 0.5% Butacene is equal to 1% Catocene.
Using Butacene in composite propellants solves migration
problem, and on the other hand, the safety characteristics
and ballistic performance of the Butacene propellants are
better than conventional catalysts [31]. Physical properties
of this type of binder, e.g., iron percentage, viscosity, glass
transition temperature and density, have important role in
preparation of composite propellants and their efꢀciency.
Experimental
2
3
2
4
in composite propellants. Based on the literature, HTPB/
AP propellants including ferrocene-type and carborane-
type burn rate catalysts were studied. The results showed
that the ferrocenic catalysts enhance burn rate. This fact
depends on the appropriate oxidizer/fuel ratio in the propel-
lant, the place of the leading reaction of combustion and
the propellant combustion mechanism. Potential sites of the
ferrocenic catalysts improve reactions between the binder
HTPB and oxidizer at the binder/oxidizer interface. They
catalyze the heterogenous reactions between the binder and
the AP in the binder/oxidizer interface or promote pyrolysis
of the binder [26]. Some research centers suggested liquid
ferrocene catalysts (such as Catocene) in place of Fe O or
Solvents and reagents
Chemicals were purchased from Merck, Fluka, Sigma-
Aldrich and Yantai Suny Chem. International Co., Ltd.
Commercial solid reagents were used without further puri-
ꢀcation. Liquid reactants were distilled prior to use. Sol-
vents were dried and distilled prior to use according to the
standard laboratory practices; water was doubly distilled.
THF and diglyme were dried by reꢁuxing under argon over
sodium wire and distilled directly before use. Column chro-
matography was performed on silica gel 60 (Merck, grain
size 0.063–0.2 mm) with n-hexane as eluant. All reactions
were carried out under an atmosphere of argon in oven-
dried glassware with magnetic stirrer.
2
3
CuCr O in these propellants. A binuclear ferrocene deriva-
2
4
tive, for example 2, 2-Bis(ethylferrocenyl)propane (Cato-
cene), is used as burning rate modiꢀers in rocket applica-
tions [27]. But these types of compounds have tendency to
oxidize, evaporation, phase separation by crystallization
and migrate toward to the surface of propellants during
storage [28]. The physical instability of these compounds
in composite propellants is the most important disadvan-
tage of ferrocene derivatives, which cause the irregularity
in its combustion, and furthermore, the adhesion of the
inhibitor to the propellant can be effected. Comparative test
between Catocene and mono-nuclear derivatives like ethyl
or n-butylferrocene showed that the migration rate of Cato-
cene is lower. For solving these problems, ferrocene deriva-
tives covalently grafted into the binder like hydroxyl- or
carboxyl-terminated polybutadiene at its ethylenic unsatu-
rated groups during its synthesis [29]. SNPE inset Buta-
cene as a new burn rate catalyst which ferrocenic units
grafted chemically to the prepolymer. Ferrocene derivatives
grafted directly to the backbone of the prepolymer HTPB
in Butacene. The propellants formulated with this new cat-
alyst have good property of process ability, high energetic
performance, extended range of burning rates, good safety
properties and enhanced behavior in thermal vulnerability
tests [30]. Combustion behavior of propellants containing
Instrumentation
The Bruker FT 400 and 100 MHz spectrometer, respec-
1
13
tively, for H NMR and C NMR was used at room tem-
perature and with CDCl as solvent while chemical shifts
are presented delta values expressed in ppm referenced to
3
CHCl residue at 7.25 and 78 ppm, respectively. The FT-IR
3
spectra were recorded on a Bruker-Tensor 270 spectropho-
tometer as KBr disks or smears between salt plates. The
mass spectra obtained with a GC-Mass Agilent quadrupole
mode 5973 N instrument, operating at 70 eV. Elemental
analyses were carried out with an Elementor Vario EL. III
instrument. Iron analysis was performed by Analytikjene
(novaa 400) atomic absorption spectrophotometer.
General procedure A: synthesis of alkylferrocene (1b–c)
A solution of acid chloride (63 mmol) in 30 mL dry
dichloromethane was added to a suspension of anhy-
drous aluminum chloride (8.41 g, 63 mmol) in 30 mL
dry dichloromethane, and the mixture was stirred at 5 °C
for 1 h under Argon. The solution of aluminum chloride/
1
3

J IRAN CHEM SOC
acid chloride complex was added dropwise over 30 min
to a solution of ferrocene (11.16 g, 60 mmol) in 100 mL
dry dichloromethane at 0 °C. The reaction mixture was
warmed to room temperature and stirred for 16 h. A solu-
A dark orange solution was formed and stirred at 0 °C for
1 h. The mixture was then hydrolyzed with the addition
of 120 mL water while maintaining its temperature at less
than or equal to 5 °C. The mixture was allowed to separate
by settling, and the organic phase was then withdrawn. The
aqueous phase was extracted with 3 times 50 mL of dichlo-
romethane, and then all the organic phases were combined.
The combined organic layer was washed with 100 mL of
brine. After the drying of organic layer on the Na SO ,
tion of NaBH (2.38 g, 63 mmol) in 25 mL diglyme was
4
added dropwise to the purple reaction mixture at −5 °C. An
orange solution was formed and stirred at 0 °C for 1 h. The
mixture was then hydrolyzed with addition of 20 mL water
while maintaining its temperature at less than or equal to
2
4
1
0 °C. The mixture was allowed to separate by settling,
dichloromethane was distilled under atmospheric pressure.
The diglyme was evaporated under reduced pressure. The
residue was puriꢀed by column chromatography on silica
gel with n-hexane as eluant. Speciꢀc details are given for
each compound.
and the organic phase was then withdrawn. The aqueous
phase was extracted with 3 times 30 mL of dichlorometh-
ane, and then all the organic phases are combined. Com-
bined organic layer was washed with 50 mL of brine. After
the drying of organic layer on the Na SO , dichlorometh-
2
4
ane was distilled under atmospheric pressure. The diglyme
and the residual ferrocene which was found to be entrained
by the diglyme were then distilled at reduced pressure
approximately 20 mm Hg and a column head temperature
of 85–95 °C. The alkylferrocene derivatives were distilled
at a more reduced pressure, less than 5 mm Hg.
5‑Chloropentylferrocene (2a)
From 5.58 g ferrocene, 7.23 g of dark orange oil was
1
obtained in 83% yield HNMR (400 MHz, CDCl ): δ 4.10
3
(s, 5H, Cp), 4.05 (d, 4H, Cp), 3.52-3.56 (t, 2H, CH Cl),
2
2.33–2.36 (t, 2H, CH Fc), 1.77–1.81 (m, 2H, CH CH Cl),
2
2
2
1
3
1
.47–1.55 (m, 4H, CpCH CH CH ); C NMR (100 MHz,
2 2 2
Ethylferrocene (1b)
CDCl ): δ 87.42; (CpCH ), 66.83, 67.59, 67.94 (Cp), 43.97
3 2
(
1C, CH Cl), 31.28 (1C, CpCH ), 27.38, 27.54, 27.61 (3C,
2 2
From 4.95 g acetylchloride, 11.43 g of light brown liquid
–CH –); FT-IR (KBr) ν : 3084, 2938, 1648, 1455, 1312,
2
max
1
−1
+
was obtained in 89% yield. HNMR (400 MHz, CDCl ):
1025, 815 and 496 cm ; ESI–MS m/z: 292 (58%[M] ),
3
+
δ 3.99–4.16 (m, 9H, Fc), 2.32–2.37 (q, 2H, FcCH ), 1.16–
290 (100%[M] ). ESI-HRMS calcd for C H ClFe: C,
2
15 19
+
1
.19 (t, 3H, CH ); ESI–MS m/z: 214 (100% [M] ).
61.98; H, 6.59; Fe, 19.21, Found: C, 61.93; H, 6.51; Fe,
3
1
9.14.
Propylferrocene (1c)
5
‑Chloropentylethylferrocene (2b)
From 5.83 g propionylchloride, 11.63 g of light brown
1
liquid was obtained in 85% yield. HNMR (400 MHz,
From 6.42 g ethylferrocene, 7.83 g of dark orange oil was
1
CDCl ): δ 4.05–4.15 (m, 9H, Fc), 2.31–2.35 (t, 2H,
obtained in 82% yield. HNMR (400 MHz, CDCl ): δ 3.98–
3
3
FcCH ), 1.49–1.58 (m, 2H, CH CH ), 0.93–0.96 (t, 3H,
4.12 (m, 8H, Fc), 3.52–3.54 (t, 2H, CH Cl), 2.29–2.35 (m,
2
2
3
2
+
CH ); ESI–MS m/z: 228 (100% [M] ).
4H, CH Fc), 1.74–1.81 (m, 2H, CH CH Cl), 1.49–1.53
3
2
2
2
1
3
(
m, 4H, CpCH CH CH ), 1.15–1.19 (t, 3H, CH );
C
2
2
2
3
General procedure B: synthesis
NMR (100 MHz, CDCl ): δ 86.14, 88.28 (Cp CH ), 66.58,
3 2
of 5‑chloropentylalkylferrocene (2a–c)
67.13, 67.38, 68.28, (Cp), 43.94 (1C, CH Cl), 31.39, 31.49
2
(
2C, CpCH ), 27.38, 27.54, 27.61 (3C, –CH –), 12.56 (1C,
2
2
A solution of 5-chloropentanoyl chloride (4.6 g, 30 mmol)
in 30 mL of dry dichloromethane was added dropwise at
room temperature to a suspension of anhydrous aluminum
chloride (4.4 g, 33 mmol) in 30 mL of dry dichlorometh-
ane. The mixture was stirred at room temperature for 1 h
under Argon. The homogeneous yellow solution was
added dropwise to a solution of ferrocene or alkylferro-
cene derivatives (30 mmol) in 30 mL dry dichloromethane
at 0 °C. The dark purple solution was then slowly allowed
to warm to room temperature. After 24 h stirring at room
CH ); FT-IR (KBr) ν : 3082, 2935, 1675, 1449, 1309,
3 max
−1
+
1032, 820 and 496 cm ; ESI–MS m/z: 320 (56%[M] ),
+
318 (100%[M] ). ESI-HRMS calcd for C H ClFe: C,
1
7
23
64.06; H, 7.27; Fe, 17.52, Found: C, 63.98; H, 7.23; Fe,
17.49.
5‑Chloropentylpropylferrocene (2c)
From 6.84 g propylferrocene, 8.57 g of dark orange oil
1
was obtained in 86% yield. HNMR (400 MHz, CDCl ):
3
temperature, a solution of NaBH (1.13 g, 30 mmol) in
δ 3.98–4.11 (m, 8H, Fc), 3.51–3.54 (t, 2H, CH Cl), 2.27–
4
2
5
0 mL diglyme was added, while maintaining the tempera-
2.36 (m, 4H, CH Fc), 1.76–1.80 (m, 2H, CH CH Cl),
2
2
2
ture at less than or equal to 0 °C to the reaction mixture.
1.51–1.55 (m, 6H, CH CH , CpCH CH CH ), 0.95–0.97
2
3
2
2
2
1
3

J IRAN CHEM SOC
(
t, 3H, CH3); 13C NMR (100 MHz, CDCl ,): δ 87.13, 86.37
67.13, 67.31, 67.38 (Cp), 31.56, 34.65 (CpCH ), 27.64,
3
2
(
CpCH ), 67.15, 67.34, 68.48, 67.58 (Cp), 43.98 (CH Cl),
27.88, 28.49, 28.64 (–CH –), 25.36 (CH Si(CH ) ),
2
2
2
2
3 2
3
1.29, 31.38, 31.49 (CpCH ), 23.81, 27.52, 27.60, 27.71
13.26 (CH CH ), −3.59 (Si(CH ) ); FT-IR (KBr) ν
:
2
2
3
3 2
max
−
1
(–CH –), 12.59 (1C, CH ); FT-IR (KBr) ν : 3099, 2935,
3089, 2954, 2110, 1635, 1452, 1251, 1032 and 495 cm ;
2
3
max
−
1
+
1
3
675, 1449, 1319, 1039, 820 and 497 cm ; ESI–MS m/z:
ESI–MS m/z: 342 (100%[M] ) ESI-HRMS calcd for
+
+
34 (55%[M] ), 332 (100%[M] ). ESI-HRMS calcd for
C H FeSi: C, 66.65; H, 8.83; Fe, 16.31, Found: C, 66.61;
1
9
30
C H ClFe: C, 64.97; H, 7.57; Fe, 16.78, Found: C, 64.94;
H, 8.78; Fe, 16.28.
1
8
25
H, 7.52; Fe, 16.71.
[
5‑(Propylferrocenyl)pentyl]dimethylsilane (3c)
General procedure C: synthesis of [5‑(alkylferrocenyl)
pentyl]dimethylsilane (3a‑c)
From 8.63 g propylferrocene, 8.05 g of brown oil was
obtained in 87% yield. HNMR (400 MHz, CDCl ,): δ
4
1
1
3
5
mL of solution of 5-chloropentyl alkylferrocene
.05–4.17 (9H, m, Cp, Si–H), 2.33–2.37 (4H, m, CpCH2),
.49–1.53(m, 4H, CpCH CH ), 1.32–1.39 (m, 4H, CH
(26.18 mmol) in dry THF (12 mL) was added to a solution
2
2
of magnesium turning (0.14 g, 6 mmol) and a large iodine
crystal in dry THF under argon atmosphere. This mixture
was stirred at room temperature, after 10 min the remain-
ing 5-chloropentyl alkylferrocene solution was added dur-
ing 5 min. The reaction mixture was reꢁuxed for 24 h. In
continues, the heating bath was removed and the reaction
mixture was cooled to −10 to −15 °C and chlorodimethyl-
silane (0.96 g, 10 mmol) diluted in 10 mL THF was added
dropwise to reaction mixture at this temperature. After
completion of addition, the mixture was reꢁuxed for 3 h.
When reaction was completed as indicated from TLC,
solvent was removed under reduce pressure and [5-(alky-
lferrocenyl)pentyl]dimethylsilane puriꢀed by column
chromatography.
CH CH Si(CH ) ), 0.58–0.60 (m, 2H, CH Si(CH ) ),
2
2
2
3 2
2
3 2
1
3
0
.09–0.93 (t, 3H, CH ), 0.07 (s, 6H, Si(CH ) ); C NMR
3 3 2
(
100 MHz, CDCl ,): δ 86.13, 88.26 (CpCH ), 66.68,
3
2
6
2
1
3
7.15, 67.34, 67.48 (Cp), 31.38, 31.49 (CpCH ), 23.81,
2
7.88, 27.71, 28.49 (–CH –), 25.35 (CH Si(CH ) ),
2
2
3 2
2.59 (CH CH ), -3.57 (Si(CH ) ); FT-IR (KBr) ν :
max
2
3
3 2
−
1
087, 2963, 2110, 1631, 1460, 1252, 1028 and 496 cm ;
+
ESI–MS m/z: 356 (100%[M] ). ESI-HRMS calcd for
C H FeSi: C, 67.40; H, 9.05; Fe, 15.67, Found: C, 67.37;
2
0
32
H, 9.01; Fe, 15.64.
General procedure D: synthesis of alkylFC‑HTPB
4a–i)
(
[
5‑(Ferrocenyl)pentyl]dimethylsilane (3a)
A 25 mL round-bottom ꢁask with magnetic stirrer was
charged with [5-(alkylferrocenyl)pentyl]dimethylsilane,
From 7.55 g ferrocene, 6.69 g of brown oil was obtained
in 82% yield. HNMR (400 MHz, CDCl ,): δ 4.05–4.17
(
(
i(CH ) ), 0.58–0.60 (t, 2H, CH Si(CH ) ), 0.07 (s, 6H,
Si(CH ) ); C NMR (100 MHz, CDCl ,): δ 87.96 (CpCH ),
6
2
0
.2 g of HTPB and 15 mL dry hexane as solvent. 30 mL
1
3
catalyst the hexachloroplatinic acid was added. The FT-IR
spectroscopy was utilized to follow the progress of the
reaction, by monitoring the loss of the Si–H absorption.
The reaction mixture was reꢁuxed at 60 °C until the com-
plete disappearance of Si–H bond in FT-IR spectra. The
reaction mixture was ꢀltered, and the solvent was evapo-
rated under reduced pressure to provide the desired prod-
ucts as a viscose and brown oil.
m, 9H, Cp, Si–H), 2.30–2.34 (m, 2H, CH Cp), 1.49–1.51
2
m, 2H, CpCH CH ), 1.32–1.39 (m, 4H, CH CH CH S
2
2
2
2
2
3
2
2
3 2
1
3
3
2
3
2
6.64, 67.16, 67.48 (Cp) 34.53 (CpCH ), 27.78, 28.34,
2
8.59 (–CH –), 25.34 (CH Si(CH ) ), −3.56 (Si(CH ) );
2
2
3 2
3 2
FT-IR (KBr) ν : 3088, 2960, 2119, 1632, 1454, 1257,
1
max
−1
+
031 and 491 cm ; ESI–MS m/z: 314 (100%[M] ). ESI-
HRMS calcd for C H FeSi: C, 64.96; H, 8.29; Fe, 17.76,
1
7
26
Found: C, 64.92; H, 8.29; Fe 17.71.
Synthesis of Fc‑HTPB with 6.93% iron (4a)
[5‑(Ethylferrocenyl)pentyl]dimethylsilane (3b)
Using the same method as detailed for procedure D with
[
5-(ferrocenyl)pentyl]dimethylsilane 3a (0.1 g) and 0.2 g of
1
From 8.28 g ethylferrocene, 7.28 g of brown oil was
HTPB as described above. HNMR (400 MHz, CDCl ,): δ
3
1
obtained in 82% yield. HNMR (400 MHz, CDCl ): δ
4
4.93–5.41 (m, C = CH, C = CH , HTPB), 4.03–4.09 (m,
3
2
.05–4.17 (m, 9H, Cp, Si–H), 2.30–2.32 (m, 4H, CpCH2),
.49–1.51 (m, 2H, CpCH CH ), 1.32–1.39 (m, 4H, CH
9H, Cp) 2.28–2.32 (m, 2H, CpCH ), 2.03–2.08 (m, CH ,
2
2
1
HTPB), 1.47–1.51 (m, 2H, CpCH CH ), 1.19–1.33 (m, 4H,
2
2
2
2
CH CH Si(CH ) ), 1.04–1.09 (t, 3H, CH ), 0.58–0.60
CH CH CH Si(CH ) ), 0.47–0.50 (t, 4H, CH Si(CH ) ),
2 2 2 3 2 2 3 2
2
2
2
3 2
3
1
3
(
(
m, 2H, CH Si(CH ) ), 0.07 (s, 6H, Si(CH ) ); C NMR
0.05–0.10 (m, 6H, Si(CH ) ); FT-IR (KBr) νmax: 3438,
3 2
2
3 2
3 2
−
1
100 MHz, CDCl ): δ 86.14, 88.28 (CpCH ), 66.58,
3086, 1636 and 1251 cm .
3
2
1
3

J IRAN CHEM SOC
Synthesis of Fc‑HTPB with 8.1% iron (4b)
Using the same method as detailed for procedure D with
Synthesis of ethyl Fc‑HTPB with 9.2% iron (4f)
Using the same method as detailed for procedure D with
[
5-(ferrocenyl)pentyl]dimethylsilane 3a (0.35 g) and
[5-(ethylferrocenyl)pentyl]dimethylsilane 3b (0.53 g) and
HTPB (0.2 g) as described above. HNMR (400 MHz,
1
1
HTPB (0.2 g) as described above. HNMR (400 MHz,
CDCl ): δ 4.93–5.41 (m, C = CH, C = CH , HTPB),
CDCl ): δ 4.94–5.58 (m, C = CH, C = CH , HTPB),
3
2
3
2
4
2
1
4
.06–4.10 (m, 9H, Cp), 2.27–2.29 (t, 2H, CpCH ), 2.03–
3.95–4.10 (m, 8H, Cp), 2.26–2.32 (m, 4H, CpCH ), 2.05–
2
2
.07(m, CH , HTPB), 1.47–1.49 (m, 2H, CpCH CH ),
2.10 (m, CH , HTPB), 1.52–1.53 (m, 2H, CpCH CH ),
2
2
2
2
2
2
.25–1.34 (m, 4H, CH CH CH Si(CH ) ), 0.58–0.60 (t,
1.23–1.31(m, 4H, CH CH CH Si(CH ) ), 1.03–1.08 (t,
2 2 2 3 2
3H, CH ), 0.52–0.54 (t, 4H, CH Si(CH ) ), 0.02–0.09
3 2 3 2
2
2
2
3 2
H, CH Si(CH ) ), 0.04–0.07 (m, 6H, Si(CH ) ); FT-IR
2
3 2
3 2
−
1
(
KBr) νmax: 3591, 3078, 1642 and 1251 cm
.
(m, 6H, Si(CH ) ); FT-IR (KBr) νmax: 3445, 3086, 1646
3 2
−
1
and 1250 cm
.
Synthesis of Fc‑HTPB with 10.57% iron (4c)
Synthesis of propyl Fc‑HTPB with 5.9% iron (4g)
Using the same method as detailed for procedure D with
5-(ferrocenyl)pentyl]dimethylsilane 3a (0.48 g) and
HTPB (0.2 g) as described above. HNMR (400 MHz,
[
Using the same method as detailed for procedure D
1
with
[5-(propylferrocenyl)pentyl]dimethylsilane
3c
1
CDCl ): δ 4.81–5.41 (m, C = CH, C = CH , HTPB),
(0.27 g) and HTPB (0.2 g) as described above.; HNMR
3
2
4
2
1
4
.03–4.09 (m, 9H, Cp), 2.28–2.32 (m, 2H, CpCH ), 2.03–
(400 MHz, CDCl ): δ 4.92–5.41 (m, C = CH, C = CH ,
2
3
2
.08 (m, CH , HTPB), 1.47–1.49 (m, 2H, CpCH CH ),
HTPB), 4.02–3.97 (m, 8H, Cp), 2.28–2.30 (m, 4H,
2
2
2
.28–1.31 (m, 4H, CH CH CH Si(CH ) ), 0.46–0.50 (t,
CpCH ), 2.03–2.08 (m, CH , HTPB), 1.43–1.47 (m, 4H,
2
2
2
3 2
2
2
H, CH Si(CH ) ), 0.04–0.13 (m, 6H, Si(CH ) ); FT-IR
CpCH CH ), 1.26–1.37 (m, 4H, CH CH CH Si(CH ) ),
2 2 2 2 2 3 2
0.90–0.96 (m, 3H, CH ), 0.50–0.52 (t, 4H, CH Si(CH ) ),
3 2 3 2
2
3 2
3 2
−
1
(
KBr) νmax: 3445, 3091, 1646 and 1250 cm
.
0
3
.07–0.09 (m, 6H, Si(CH ) ); FT-IR (KBr) νmax: 3434,
3 2
083, 1640 and 1254 cm .
−
1
Synthesis of ethyl Fc‑HTPB with 3.16% iron (4d)
Using the same method as detailed for procedure D with
Synthesis of propyl Fc‑HTPB with 8.2% iron (4h)
[
5-(ethylferrocenyl)pentyl]dimethylsilane 3b (0.1 g) and
1
HTPB (0.2 g) as described above. HNMR (400 MHz,
Using the same method as detailed for procedure D with
CDCl ): δ 4.91–5.41 (m, C = CH, C = CH , HTPB),
[5-(propylferrocenyl)pentyl]dimethylsilane 3c (0.3 g) and
(0.2 g) of HTPB as described above. HNMR (400 MHz,
3
2
1
3
2
1
3
6
1
.96–4.01 (m, 8H, Cp), 2.28–2.30 (m, 4H, CpCH ), 2.03–
2
.07 (m, CH , HTPB), 1.53–1.55 (m, 2H, CpCH CH ),
CDCl ): δ 4.99–5.43 (m, C = CH, C = CH , HTPB),
2
2
2
3
2
.22–1.49 (m, 4H, CH CH CH Si(CH ) ), 1.04–1.08 (t,
3.96–4.04 (m, 8H, Cp), 2.29–2.35 (m, 4H, CpCH ), 2.06–
2
2
2
3 2
2
H, CH ), 0.5–0.54 (t, 4H, CH Si(CH ) ), 0.04–0.07 (m,
2.10 (m, CH , HTPB), 1.48–1.54 (m, 4H, CpCH CH ),
3
2
3 2
2
2
2
H, Si(CH ) ); FT-IR (KBr) νmax: 3435, 3085, 1641and
1.34–1.39 (m, 4H, CH CH CH Si(CH ) ), 0.92–0.96 (t,
2 2 2 3 2
3H, CH ), 0.58–0.60 (t, 4H, CH Si(CH ) ), 0.08–0.15
3 2 3 2
3
2
−
1
249 cm .
(
m, 6H, Si(CH ) ); FT-IR (KBr) νmax: 3434, 3083, 1640
3 2
−
1
and 1254 cm
.
Synthesis of ethyl Fc‑HTPB with 8.2% iron (4e)
Using the same method as detailed for procedure D with
Synthesis of propyl Fc‑HTPB with 10.27% iron (4i)
[
5-(ethylferrocenyl)pentyl]dimethylsilane 3b (0.25 g) and
1
HTPB (0.2 g) as described above. HNMR (400 MHz,
Using the same method as detailed for procedure D
CDCl ): δ 4.09–5.41 (m, C = CH, C = CH , HTPB),
with
[5-(propylferrocenyl)pentyl]dimethylsilane
3c
3
2
1
3
2
1
2
6
1
.94–4.09 (m, 8H, Cp), 2.26–2.30 (m, 4H, CpCH ), 2.03–
(0.44 g) and HTPB (0.2 g) as described above. HNMR
(400 MHz, CDCl3): δ 4.96–5.41 (m, C = CH, C = CH2,
HTPB), 3.96–4.09 (m, 8H, Cp), 2.24–2.30 (m, 4H,
CpCH2), 2.03–2.08 (m, CH2, HTPB), 1.48–1.97 (m, 4H,
CpCH2CH2), 1.26–1.33 (m, 4H, CH2CH2CH2Si(CH3)2),
0.91–0.94 (t, 3H, CH3), 0.5–0.52 (t, 4H, CH2Si(CH3)2),
2
.07 (m, CH , HTPB), 1.51–1.53 (m, 2H, CpCH CH ),
2
2
2
.25–1.49 (m, 4H, CH CH CH Si(CH ) ), 1.06–1.07 (t,
2
2
2
3 2
H, CH ), 0.5–0.54 (t, 4H, CH Si(CH ) ), 0.03–0.07 (m,
3
2
3 2
H, Si(CH ) ); FT-IR (KBr) νmax: 3445, 3086, 1646 and
3
2
−
1
250 cm
.
1
3

J IRAN CHEM SOC
0
3
.04–0.07 (m, 6H, Si(CH ) ); FT-IR (KBr) νmax: 3435,
085, 1641 and 1149 cm .
Then (5-ferrocenylpentyl)dimethylsilane derivatives
(3a–3c) were synthesized from reaction of 5-chloropen-
tylferrocene derivatives (2a–2c) with magnesium in THF
and reaction of corresponding Grignard reagents with chlo-
rodimethylsilane in 82, 82 and 87% yields, respectively
3
2
−
1
Results and discussion
(
Scheme 1). Data obtained from the mass spectra, FT-IR,
H and C FT-NMR spectra and elemental analyses are
1
13
To the best of our knowledge, there is no report avail-
able for the synthesis of alkylferrocene-grafted hydroxyl-
terminated polybutadiene (alkylFc-HTPB) by ꢀve carbon
chain spacer. In this article, these compounds have been
designed and synthesized through hydrosilylation reaction
of [5-(alkylferrocenyl)pentyl]dimethylsilanes with HTPB
fully consistent with the proposed structures.
The hydrosilylation reaction of (5-ferrocenylpentyl)
dimethylsilane derivatives (3a–3c) with hydroxyl-termi-
nated polybutadiene (HTPB) in the presence of catalytic
amount of the hexachloroplatinic acid was carried out in
hexane at reꢁux temperature (Scheme 2).
prepolymer.
[5-(alkylferrocenyl)pentyl]dimethylsilanes
were synthesized from (5-chloropentyl)alkylferrocene via
a Grignard reaction. Furthermore, some physical properties
of this type of binder, e.g., iron percentage, viscosity, glass
transition temperature and density, were also studied.
Alkylferrocene derivatives, ethylferrocene (1b) and pro-
pylferrocene (1c), were synthesized according to the modi-
FT-IR spectroscopy was utilized to follow the progress
of the reaction, by monitoring the loss of the Si–H absorp-
−1
tion at 2110 cm (Fig. 1), and the reaction was completed
in 24 h.
In the 1H NMR spectra of alkylferrocene-grafted
hydroxy-terminated
polybutadiene
(alkylFc-HTPB),
ꢀ
ed procedure described by Graindorge and co-workers in
exhibited two sharp resonances for the two sets of cyclo-
pentadienyl protons at 4.03 and 4.09 ppm and the proton’s
resonance from (CH ) Si– is visible at about 0.07 ppm. In
8
9 and 85% yields, respectively [32]. (5-chloropentanoyl)
ferrocene derivatives were prepared by Friedel–Crafts
3
2
acylation of ferrocene (1a) or alkylferrocene derivatives
addition, multiple signals at 4.93 and 5.41 ppm revealed for
unsaturated bonds of polymer (Fig. 2).
(1b–1c) with 5-chloropentanoyl chloride in dichlorometh-
ane in the presence of AlCl as catalyst, and the corre-
sponding 5-chloropentylferrocene derivatives (2a–2c) were
We investigated some properties like viscosity, glass
transition temperature and iron percentage of the synthe-
sized 5-(dimethylsilyl)pentylalkylferrocene-grafted HTPB
(alkylFc-HTPB) derivatives. These properties have impor-
tant role in production of composite propellants. The iron
3
synthesized from reduction of these products by NaBH in
4
diglyme at 0 °C in 83, 82 and 89% total yields, respectively
(Scheme 1).
Scheme 1 Synthesis of (5-ferrocenylpentyl)dimethylsilane derivatives (3a–3c)
1
3

J IRAN CHEM SOC
Scheme 2 Synthesis of Fc-HTPB derivatives
Fig. 1 Comparing the FT-IR
spectra of a) (5-ferrocenylpen-
tyl)dimethylsilane (3a) b)
Fc-HTPB (4a)
content, viscosity and glass transition temperature of the
different alkylFc-HTPBs are given in Table 1.
feature for these compounds, because the low viscosity
improves processability of prepolymer in the manufacture
of composite solid propellant.
Atomic absorption spectrophotometer analysis revealed
that the concentration levels of iron in the alkylFc-HTPBs
were in the range of 3.16–10.57 wt%. It was clear that the
grafting of (5-ferrocenylpentyl)dimethylsilane derivative
increased as the iron content of the samples increased. This
clearly conꢀrmed the presence of ferrocene with respect
to the amount of grafting. The viscosity increased with
increasing iron content because of the greater extent of
ferrocene grafting in the polymer. But on the other hand,
with increasing the length of alkyl branch on the ferrocene
ring, viscosity was decrease in compounds with the same
iron percentage. Decreasing in viscosity is an outstanding
The glass transition temperatures of the alkylFc-HTPBs
derivatives, Fc-HTPB (4b), ethyl Fc-HTPB (4e) and pro-
pyl Fc-HTPB (4h) containing 8.1–8.2 wt% iron, were
−62.3, −68.4 and −71.5 °C, respectively. Concerning the
thermal properties of these alkylferrocene-grafted copoly-
mers reveals that glass transition temperature increase with
increasing the iron percentage. Increasing in iron percent-
age means that the grafting of ferrocene units on the poly-
mer was increased. On the other hand, when the number
of carbon in the substituted groups is increasing, the glass
transition temperatures are clearly started to decrease. This
1
3

J IRAN CHEM SOC
Fig. 2 NMR spectra of a HTPB
b Fc-HTPB (4a)
Table 1 Viscosity, glass
transition temperature and iron
percentage data for HTPB and
Fc-HTPB derivatives
Entry Number Sample
Iron content (%) Viscosity (Pa s) Glass transition temperature (°C)
1
2
3
4
5
6
7
8
9
1
4
HTPB
0.0
6.93
8.1
3.4
−73.2
−67.2
−62.3
−56.3
−70.8
−68.4
−64.3
−72.4
−71.5
−70.1
4a
Fc-HTPB
4.71
5.12
5.68
3.92
4.48
5.13
3.62
4.26
4.98
4b
4c
4d
4e
4f
Fc-HTPB
Fc-HTPB
10.57
3.16
8.2
Ethyl Fc-HTPB
Ethyl Fc-HTPB
Ethyl Fc-HTPB
9.2
4g
4h
4i
Propyl Fc-HTPB 5.9
Propyl Fc-HTPB 8.2
Propyl Fc-HTPB 10.27
0
1
3

J IRAN CHEM SOC
feature provides the necessary conditions for the use of
product in the low temperatures.
8. Y.C.J. Lim-, J.M. Cunningham, J.J. Davis, D.P. Beer, Chem.
Commun. 51, 14640 (2015)
9
.
P.W. Cyr, M. Tzolov, I. Manners, E.H. Sargent, Macromol.
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Conclusion
In summary, we have developed an efꢀcient and convenient
method for synthesis of organo-silicon ferrocene grafted
with HTPB (alkylFc-HTPB) from readily available starting
materials. The reaction proceeds including Friedel–Crafts
acylation of alkyl ferrocene, reduction of carbonyl group
and ꢀnally the synthesis of organo-silicon ferrocene, via
reaction of Grignard reagent with chlorodimethylsilane.
The alkylFc-HTPBs were synthesized by hydrosilyla-
tion reaction of [5-(alkylferrocenyl)pentyl]dimethylsilane
derivatives with HTPB in the presence of hexachlorop-
latinic acid catalyst. We investigated some properties like
viscosity, glass transition temperature, iron percentage
and density that are needed in the production of composite
propellants.
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