Reactions of Tris(dimethylsilyl)methane and polymers containing Si-H groups with various hydroxy compounds under aerobic and mild conditions

Article abstract of DOI:10.1002/hc.20440

Tris(dimethylsilyl)methane, (HMe₂Si)₃-CH, reacts with n-propyl, iso-propyl, n-butyl, s-butyl, iso-butyl, n-pentyl, s-pentyl, n-hexyl alcohol, and phenol in the presence of chloroplatinic acid (H ₂PtCl₆·6H₂O) in air to give products (ROMe₂Si)₃CH (where R is n-propyl, iso-propyl, n-butyl, s-butyl, iso-butyl, n-pentyl, s-pentyl, n-hexyl, phenyl). Similar reactions with benzyl alcohol and acetic acid lead to the unexpected products, (PhCH ₂)₂O and HC(Me₂SiOSiMe₂) ₃CH, respectively. The compound (n-BuOMe₂Si) ₃CSiMe₂H was made from (n-BuOMe₂Si) ₃CH by treatment with lithium diisopropylamide, followed by quenching with HMe₂SiCl. The homopolymer poly{(4-chloromethyl)styrene) and copolymers with styrene (in 1:1 and 1:3 mol ratio) were synthesized by free radical polymerization, and (HMe₂Si)₃C groups were linked to them by nucleophilic substitution reactions between (HMe₂Si) ₃CLi and the chloromethyl groups of the polymer side chains. The resulting functional polymers containing Si-H bonds reacted with various alcohols in the presence of chloroplatinic acid under heterogeneous conditions.

Full text of DOI:10.1002/hc.20440

Heteroatom Chemistry
Volume 19, Number 4, 2008
Reactions of Tris(dimethylsilyl)methane
and Polymers Containing Si–H Groups
with Various Hydroxy Compounds under
Aerobic and Mild Conditions
Kazem D. Safa,1,2 Shahin Tofangdarzadeh,1
and Hossein Heydari Ayenadeh1
1Organosilicon Research Laboratory, Faculty of Chemistry, University of Tabriz, 51664 Tabriz, Iran
2Research Institute for Fundamental Sciences, Tabriz, Iran
Received 2 September 2007; revised 23 December 2007
19:365–376, 2008; Published online in Wiley InterScience
ABSTRACT: Tris(dimethylsilyl)methane, (HMe2Si)3-
(www.interscience.wiley.com). DOI 10.1002/hc.20440
CH, reacts with n-propyl, iso-propyl, n-butyl, s-
butyl, iso-butyl, n-pentyl, s-pentyl, n-hexyl alcohol,
and phenol in the presence of chloroplatinic acid
INTRODUCTION
(H2PtCl6·6H2O) in air to give products (ROMe2Si)3CH
(where R is n-propyl, iso-propyl, n-butyl, s-butyl,
Among the diverse reactions at silicon centers,
iso-butyl, n-pentyl, s-pentyl, n-hexyl, phenyl). Sim-
those involving silicon–oxygen bond formation are
ilar reactions with benzyl alcohol and acetic
particularly important and silyl ethers are among
acid lead to the unexpected products, (PhCH2)2O
the most widely used protecting groups for hydroxyl
and HC(Me2SiOSiMe2)3CH, respectively. The com-
functions in organic synthesis [1]. They also play an
pound (n-BuOMe2Si)3CSiMe2H was made from (n-
important role in inorganic synthesis as precursors
BuOMe2Si)3CH by treatment with lithium diiso-
in the preparation of sol–gels and other condensed
propylamide, followed by quenching with HMe2SiCl.
siloxane materials [2]. Silyl ethers are most com-
The homopolymer poly{(4-chloromethyl)styrene} and
monly prepared from chlorosilanes, by the reaction
copolymers with styrene (in 1:1 and 1:3 mol ratio)
with alcohols or alkoxides, under acidic or basic
were synthesized by free radical polymerization, and
conditions [3].
(HMe2Si)3C groups were linked to them by nucle-
The addition of hydrosilanes to alcohols is, how-
ophilic substitution reactions between (HMe2Si)3CLi
ever, also an attractive route to silyl ethers because
and the chloromethyl groups of the polymer side
the only side product is hydrogen gas (Eq. (1)).
chains. The resulting functional polymers containing
R4–xSiHx + xRꢁOH c−at→alyst R4–xSi(ORꢁ)x + xH2 (1)
Si H bonds reacted with various alcohols in the pres-
ence of chloroplatinic acid under heterogeneous con-
ꢀ
The alcoholysis requires a catalyst because alcohols
are not generally sufficiently nucleophilic to attack
hydrosilanes. Strongly nucleophilic or electrophilic
catalysts can be used [2], and a limited number of
transition metal complexes [4–10]. It has been found
that chloroplatinic acid, even in minute amounts, is
C
ditions. 2008 Wiley Periodicals, Inc. Heteroatom Chem
Correspondence to: Kazem D. Safa; e-mail: dsafa@tabrizu.ac.ir.
Contract grant sponsor: Research Institute for Fundamental
Sciences, Tabriz, Iran.
c
ꢀ
2008 Wiley Periodicals, Inc.
365

366 Safa, Tofangdarzadeh, and Ayenadeh
an extremely potent catalyst, but few examples have
been reported in the literature [11].
General Procedure for the Synthesis of
(ROMe2Si)3CH
The work described in this paper centers on the
preparation of tris(alkoxydimethysilyl)methanes un-
der mild aerobic conditions and a study of their
lithiation. We also report the synthesis of new
polymers containing (HMe2Si)3C functions and the
preparation of homo- and co-polymers by the re-
action of several Si H-containing polymers with
alcohols in the presence of the Pt catalyst.
Four drops of 0.04 M H2PtCl6·6H2O in EtOH were
added to a solution of (HMe2Si)3CH (2 g, 10.6 mmol)
in ROH (50 mL). The mixture was heated under re-
flux for 24 h, during which eight more drops of the
H2PtCl6·6H2O solution were added. The solution was
filtered, the solvent was evaporated from the filtrate,
and the residue was distilled to give (ROMe2Si)3CH.
Analytical and spectroscopic data are given below.
(CH3CH2CH2OMe2Si)3CH (1). Yield: 2.34 g,
61.1%, b.p. 110◦C/2 mmHg; IR: 2962 (C H), 1255,
832 (Si C), 1088 (Si O), 1008 (C O) cm−1; 1H NMR
(CDCl3, 400 MHz): δ −0.03 (s, 1H, CH), 0.18 (s, 18H,
EXPERIMENTAL
Materials
3
SiMe2), 0.87 (t, 9H, CH2CH3, JHH = 8 Hz), 1.51 (m,
6H, CH2CH3, 3 JHH = 8 Hz), 3.47 (t, 6H, CH2O, 3 JHH = 8
Hz); 13C NMR (CDCl3, 100.6 MHz): δ 0.1 (SiMe2), 3.1
(CH), 9.5 (CH2CH3), 24.8 (CH2CH3), 63.0 (CH2O); MS
(EI) m/z (%): 349 (100, [M − Me]+), 305 (20), 247
(30), 205 (70), 189 (25). Anal. Calcd for C16H40Si3O3:
C, 52.7; H, 10.9. Found: C, 52.3; H, 10.5.
For the synthesis of (HMe2Si)3CH [12], bromo-
form, THF, and Mg were obtained from Merck
(Germany, Frankfurter Str. 250, 64293 Darmstadt)
and dried by standard methods. HMe2SiCl Aldrich
(Aldrich Chemical Co. P.O. Box 2060. Milwaukee,
WI 53201) was used as received. Alcohols such
as methanol, ethanol, n-propanol, iso- propanol,
n-butanol, s-butanol, iso-butanol, n-pentanol, s-
pentanol, n-hexanol, and phenol (Merck) were dis-
tilled before use. The monomer styrene (Merck)
and 4-chloromethylstyrene (CMS) (Merck; 99%)
were distilled under reduced pressure to remove in-
hibitors. Toluene was stirred over calcium hydride
for 24 h and distilled under dry argon. The initia-
tor α,αꢁ-azobis(isobutyronitrile) (AIBN) (Merck) was
purified by crystallization from methanol.
[(CH3)2CHOMe2Si]3CH (2). Yield 2 g, 52.2%,
b.p. 100◦C/2 mmHg; IR: 2968 (C H), 1252, 837
(Si C), 1128 (Si O), 1021 (C O) cm−1; 1H NMR
(CDCl3): δ −0.11 (s, 1H, CH), 0.19 (s, 18H, SiMe2),
3
1.10 (d, 18H (CH3)2CH, JHH = 8 Hz), 3.95 (m, 3H,
CHO, 3 JHH = 8 Hz); 13C NMR (CDCl3,): δ 0.9 (SiMe2),
10.2 (CH), 24.8 ((CH3)2CH), 63.4 (CHO); MS (EI)
m/z (%): 349 (50, [M − Me]+), 305 (10), 247 (20), 205
(100), 189 (20). Anal. Calcd for C16H40Si3O3: C, 52.7;
H, 10.9. Found: C, 52.5; H, 10.9.
(CH3CH2CH2CH2OMe2Si)3CH (3). Yield: 3.1 g,
72%, b.p. 120◦C/2 mmHg; IR: 2957 (C H), 1251,
851 (Si C), 1092 (Si O), 1012 (C O) cm−1; 1H
NMR (CDCl3): δ −0.04 (s, 1H, CH), 0.17 (s, 18H,
Measurements
Infrared spectra from KBr pellets were recorded
with a 4600 Unicam FTIR spectrophotometer. H
1
3
and 13C NMR spectra were run on a Bruker 400 MHz
spectrometer at room temperature with CDCl3 as
a solvent. The mass spectra were obtained with a
GC-mass Agilent quadrupole mode 5973N instru-
ment operating at 70 eV. Elemental analyses were
carried out with an Elementar, Vario EL III mode
instrument. The molecular weights (Mw and Mn)
were determined using a Waters 501 gel permeation
chromatograph fitted with 102 and 103 nm Waters
styragel columns. THF was used as an elution solvent
at a flow rate of 1 mL/min and polystyrene standards
were employed for calibration. Glass transition tem-
peratures (Tg) were determined by a Shimadzu DSC-
50 instrument with a heating rate of 10 K/min and
5 K/min in air or N2. The Tgs were taken from inflec-
tions in the heat flow plots.
SiMe2), 0.89 (t, 9H, CH3CH2, JHH = 8 Hz), 1.33
3
(m, 6H, CH3CH2CH2, JHH = 4 Hz), 1.46 (m, 6H,
CH3CH2CH2, 3 JHH = 4 Hz), 3.51(t, 6H, CH2O, 3 JHH = 8
Hz); 13C NMR (CDCl3): δ 0.1 (SiMe2), 9.6 (CH), 12.9
(CH3CH2), 18.1 (CH3CH2CH2), 33.8 (CH3CH2CH2),
60.9 (CH2O); MS (EI) m/z (%): 391(100, [M − Me]+),
333 (10), 261 (25), 205 (70), 189 (20). Anal. Calcd for
C19H46Si3O3: C, 56.1; H, 11.3. Found: C, 55.8; H, 11.2.
[(CH3CH2)(CH3)CHOMe2Si]3CH (4). Yield 1.72
g, 40.2%, b.p. 60◦C/2 mmHg; IR: 2971 (C H), 1255,
863 (Si C), 1096 (Si O), 1006 (C O) cm−1; 1H NMR
(CDCl3): δ −0.08 (s, 1H, CH), 0.20 (d, 18H, SiMe2,
3 JHH = 8 Hz), 0.86 (t, 9H, CH3CH2, 3 JHH = 8 Hz), 1.08
(d, 9H, CH3CHO, 3 JHH = 8 Hz), 1.42 (m, 6H, CH3CH2,
3
3 JHH = 8 Hz), 3.69 (m, 3H, CHO, JHH = 4 Hz); 13C
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Tris(dimethylsilyl)methane and Polymers Containing Si H Groups with Various Hydroxy Compounds 367
NMR (CDCl3): δ 1.0, 1.1 (SiMe2), 10.6 (CH), 14.2
24.7 (CH3CH2CH2), 30.7 (CH3(CH2)2CH2), 31.7
(CH3(CH2)3CH2), 61.3 (CH2O); MS (EI) m/z (%):
475(5, [M − Me]+), 391 (35), 375 (8), 291 (10), 205
(100), 189 (38). Anal. Calcd for C25H58Si3O3: C, 61.2;
H, 11.8. Found: C, 61.3; H, 11.7.
(CH3CH2), 21.9 (CH3CHO), 31.22 (CH3CH2), 68.37
(CHO); MS (EI) m/z (%): 391 (30, [M − Me]+), 333
(20), 261 (18), 205 (100), 189 (17). Anal. Calcd for
C19H46Si3O3: C, 56.1; H, 11.3. Found: C, 55.9; H, 11.3.
[(CH3)2CHCH2OMe2Si]3CH (5). Yield 2.4 g,
56.2%, b.p. 90◦C/2 mmHg; IR (KBr): 2960 (C H),
1253, 865 (Si C), 1086 (Si O), 1016 (C O) cm−1;
1H NMR (CDCl3): δ −0.0 (s, 1H, CH), 0.2 (s, 18H,
(PhOMe2Si)3CH (10). Yield: 2.22 g, 45.3%, m.p.
48–50◦C; IR (cm−1): 3029 (Ar H), 2960 (C H), 1597,
1497 (C C), 1272, 852 (Si C), 1060 (Si O), 1027
(C O); 1H NMR (CDCl3): δ 0.43 (s, 1H, CH), 0.49 (s,
18H, SiMe2), 6.85–6.87 (dd, 6H, m-H), 6.96–6.99 (t,
3H, p-H), 7.23–7.27 (t, 6H, o-H); 13C NMR (CDCl3): δ
0.1 (SiMe2), 9.8 (CH), 118.0 (m-C), 119.3 (p-C), 127.5
(o-C), 153.0 (i-C); MS (EI) m/z (%): 391 (8, [M −
Ph]+), 316 (4), 301 (7), 281 (7), 253 (4), 223 (100),
207 (25), 93 (5). Anal. Calcd for C25H34 Si3O3: C, 64.3;
H, 7.3. Found: C, 63.9; H, 7.1.
3
SiMe2), 0.9 (d, 18H, (CH3)2CH, JHH = 8 Hz), 1.7
(m, 3H, (CH3)2CH, 3 J(H H) = 8 Hz), 3.3 (d, 6H,
CH2O, 3 JHH = 8 Hz), 13C NMR (CDCl3): δ 0.1 (SiMe2),
9.7 (CH), 18.2 ((CH3)2CH), 29.7 ((CH3)2CH), 68.2
(CH2O); MS (EI) m/z (%): 391 (70, [M − Me]+), 333
(20), 261(25), 205 (100), 189 (18). Anal. Calcd for
C19H46Si3O3: C, 56.1; H, 11.3. Found: C, 56.1; H, 11.2.
(CH3CH2CH2CH2CH2OMe2Si)3CH
(6). Yield
Reaction between (HMe2Si)3CH and PhCH2OH
3.31 g, 70%), b.p. 130◦C/2 mmHg; IR: 2953 (C H),
1251, 858 (Si C), 1094 (Si O), 1008 (C O) cm−1;
1H NMR (CDCl3): δ −0.04 (s, 1H, CH), 0.18 (s, 18H,
An attempt to synthesize PhCH2OMe2Si)3CH by the
general procedure unexpectedly gave the product
(PhCH2)2O (9), b.p. 120◦C/2 mmHg; IR: 3031 (Ar H),
2922 (C H), 1645, 1453 (C C), 1093 (C O), 741
3
SiMe2), 0.88 (t, 9H, CH3CH2, JHH = 8 Hz), 1.29 (m,
3
12H, CH3(CH2)2CH2, JHH = 4 Hz), 1.48 (m, 6H,
1
CH3(CH2)2CH2 3 JHH = 4 Hz), 3.51 (t, 6H, CH2O,
3 JHH = 8 Hz); 13C NMR (CDCl3,): δ 0.0 (SiMe2),
9.6 (CH), 13.0 (CH3CH2), 21.5 (CH3CH2), 27.2
(CH3CH2CH2), 31.4 (CH3(CH2)2CH2), 61.2 (CH2O);
MS (EI) m/z (%): 433 (100, [M − Me]+), 361 (15), 275
(18), 205 (60),189 (18). Anal. Calcd for C22H52Si3O3:
C, 58.9; H, 11.6. Found: C, 58.9; H, 11.5.
(Ar H bend.) cm−1; H NMR (CDCl3): δ 4.66 (s, 4H,
CH2O), 7.45–7.47 (10H, Ph); 13C NMR (CDCl3): δ
70.9 (CH2O), 126.3, 126.5, 127.3, 137.1 (Ph); MS (EI)
m/z (%): 107 (20), 92 (100), 77 (19). Anal. Calcd for
C14H14O: C, 84.8; H, 7.1. Found: C, 84.4; H, 6.9.
Attempted Synthesis of (CH3COOMe2Si)3CH
[(CH3CH2CH2)(CH3)CHOMe2Si]3CH (7). Yield:
2.4 g, 50.8%, b.p. 120◦C/2 mmHg; IR: 2963 (C H),
1251, 846 (Si C), 1127 (Si O), 1018(C O) cm−1; 1H
NMR (CDCl3): δ −0.09 (s, 1H, CH), 0.19 (d, 18H,
The reaction between (HMe2Si)3CH and acetic acid
with the general procedure described above gave the
known compound HC(Me2SiOSiMe2)3CH (11), 1.25
g, 56.3%, m.p. 275–276◦C; IR 2952 (C H), 1258, 868
3
1
SiMe2,3 JHH = 8 Hz), 0.87 (t, 9H, CH3CH2, JHH = 8
(Si C), 1051 (Si O Si) cm−1; H NMR (CDCl3): δ
3
Hz), 1.07 (d, 9H, CH3CHO, JHH = 8 Hz), 1.32 (m,
−0.85 (s, 2H, CH) and 0.18 (s, 36H, SiMe2); 13C NMR
(CDCl3): δ 5.2 (SiMe2), 12.3 (CH); MS (EI) m/z (%):
422 (2, M+), 407 (100, [M − Me]+), 391 (5), 319 (8),
303 (10), 188 (7). Anal. Calcd for C14H38 Si6O3: C,
39.7; H, 8.9. Found: C, 39.7; H, 8.9.
3
12H, CH3(CH2)2, JHH = 4 Hz), 3.74 (m, 3H, CHO,
3 JHH = 4 Hz); 13C NMR CDCl3): δ 0.9, 1.0 (SiMe2),
10.6 (CH), 13.2 (CH3CH2), 17.9 (CH3CHO), 22.5
(CH3CH2), 41.0 (CH3CH2CH2), 66.9 (CHO); MS (EI)
m/z (%): 433 (25, [M − Me]+), 361 (20), 275 (15), 205
(100), 189 (14). Anal. Calcd for C22H52Si3O3: C, 58.9;
H, 11.6. Found: C, 59.0; H, 11.5.
Synthesis of (n-BuOMe2Si)3CSiMe2H (12)
A 50-mL round-bottom flask equipped with a stir-
rer, septum, and gas-inlet needle was charged
with diisopropylamine (0.25 g, 2.5 mmol) and
THF (5 mL). The flask was placed in a water/ice
bath and then n-BuLi (0.93 mL, 2.7 M solution
in hexane) was added dropwise via a syringe to
give a clear yellow solution that was stirred for
an additional 30 min. The lithium diisopropy-
lamide (LDA) solution was transferred into a drop-
ping funnel and added to a 100-mL round-bottom
(CH3CH2CH2CH2CH2CH2OMe2Si)3CH
(8).
Yield 3.2 g, 62.1%), b.p. 100◦C/2 mmHg; IR: 2952
(C H), 1252, 862 (Si C), 1093 (Si O), 1013(C O)
cm−1; 1H NMR (CDCl3): δ −0.0 (s, 1H, CH), 0.2
3
(s, 18H, SiMe2), 0.9 (t, 9H, CH3CH2, JHH = 8 Hz),
3
1.3 (m, 18H, CH3(CH2)3CH2, JHH = 4 Hz), 1.5
3
(m, 6H, CH3(CH2)3CH2, JHH = 8 Hz), 3.5 (t, 6H,
3
CH2O, JHH = 8 Hz); 13C NMR (CDCl3): δ 0.12
(SiMe2), 9.6 (CH), 13.0 (CH3CH2), 21.7 (CH3CH2),
Heteroatom Chemistry DOI 10.1002/hc

368 Safa, Tofangdarzadeh, and Ayenadeh
flask containing tris(butoxydimethylsilyl)methane,
(n-BuOMe2Si)3CH (1.00 g, 2.5 mmol), in THF
(10 mL) under argon at −78◦C during 2 h. Then, the
silane HMe2SiCl (0.24 g, 2.5 mmol) was added drop-
wise via a syringe at −78◦C. A white precipitate of
LiCl formed immediately. The mixture was allowed
to warm up to room temperature during 2 h. Sol-
vent was removed, and the residue was extracted
with pentane (20 mL) to leave a white solid. This
was filtered off, and solvents were removed from the
filtrate to give a yellow oil. An analytically pure col-
orless liquid was obtained by preparative TLC (silica
gel, 1:2 n-hexane: CH2Cl2), (0.55 g, 48.2%). IR: 2961
(C H), 2123 (Si H), 1256, 816 (Si C), 1050 (Si O),
Synthesis and Characterization of
Homopolymer P1 and Copolymers (P2, P3)
The homopolymerization of 4-chloromethylstyrene
to give polymer P1 and copolymerizations of 4-
chloromethylstyrene with styrene to give P2 and P3
were carried out according to the standard proce-
dure described previously [14] (see also Table 3).
Spectroscopic results for P1: IR (KBr, cm−1) 3030
(aromatic C H), 2910–2860 (aliphatic C H), 1590,
1
1480 (aromatic C C); H NMR (CDCl3) δ: 1.4 (2H,
CH2CH), 1.9 (1H, CH2CH), 4.6 (2H, CH2Cl), 7.2–8.4
(4H, Ar H); 13C NMR (CDCl3): δ 40.0 (CH2CH), 41.0
(CH2CH), 48.2 (CH2Cl), 125–145.5 (aromatic). Anal.
Calcd for C9H9Cl (per polymeric unit): C, 70.8; H,
5.9. Found: C, 70.7; H, 5.8.
Spectroscopic results for copolymer P3, IR (KBr,
cm−1): 3030 (aromatic C H), 2900, 2850 (aliphatic
C H), 1600, 1485 (aromatic C C); 1H NMR (CDCl3):
δ 1.4 (2H,CH2CH), 1.8 (1H,CH2CH) 4.6 (2H,CH2Cl),
7.4–8.3 (4H, Ar H); 13C NMR (CDCl3): δ 41.0 (CH2-
CH), 41.5(CH2-CH), 48.0(CH2-Cl), 125–145 (aro-
matic). Anal. Calcd for C17H17Cl (one polymeric
unit): C, 79.5; H, 6.6. Found: C, 79.3; H, 6.5.
1
1010 (C O) cm−1; H NMR (CDCl3): δ 0.23 (s, 18H,
3
SiMe2), 0.24 (d, 6H,SiMe2H, JHH = 4 Hz), 0.89 (t,
9H, CH3CH2, 3 JHH = 8 Hz), 1.34 (m, 6H, CH3CH2CH2,
3 JHH = 4 Hz), 1.47 (m, 6H, CH3CH2CH2, 3 JHH = 4 Hz),
3
3.51 (t, 6H, CH2O, JHH = 8 Hz), 4.68 (m, 1H, SiH);
13C NMR (CDCl3): δ −0.16 (SiMe2H), 0.0 (SiMe2),
4.6 (C), 12.8 (CH3CH2), 18.10 (CH3CH2CH2), 33.82
(CH3CH2CH2), 60.94 (CH2O); MS (EI) m/z (%): 407
(100, [M − Bu]+), 392 (2), 377 (4), 351 (20), 335 (80),
319 (10), 303 (5), 263 (25), 247 (28), 205 (10), 189
(15). Anal. Calcd for C21H52Si4O3:C, 54.3; H, 11.2.
Found: C, 54.2; H, 11.1
Addition of (HMe2Si)3C Groups to Polymer Side
Chains (Polymers P
, P2-SiH, P3-SiH)
1-SiH
Synthesis of (HMe2Si)3CCH2Ph (13)
In a 100-mL two-necked flask equipped with a drop-
ping funnel and a reflux condenser, 0.5 g of polymer
P1 (with 3.3 mmol of chlorine-containing monomer
units) was dissolved in 30 mL THF. A gas inlet was
attached to the top of the dropping funnel, and the
system was maintained under a slight pressure of
argon. A solution of (HMe2Si)3CLi (25 mmol) was
prepared as described above, transferred into the
dropping funnel under argon and added dropwise
with stirring to the solution of P1 at room temper-
ature. The reaction mixture was heated under re-
flux for 6 h, allowed to cool, and poured into an
excess of methanol. The yellow precipitate was dis-
solved in THF (15 mL), and the solution was poured
into 50 mL of cooled methanol. The precipitate was
washed with methanol several times to give white
polymer P1-SiH that was dried under vacuum at room
temperature.
A solution of P2 (0.5 g with 1 mmol of chlorine-
containing monomer units) or 0.5 g P3 (with 2 mmol
of chlorine-containing monomer units) in THF
(30 mL) was treated with an excess of (HMe2Si)3CLi
(20 mmol) and heated under reflux for 8 h as de-
scribed above. After workup, white solids P2-SiH or
P3−SiH were collected and dried under vacuum at
room temperature. Spectroscopic results for ho-
mopolymer P1-SiH: IR (KBr, cm−1) 3029 (aromatic
A solution of (HMe2Si)3CLi in THF was pre-
pared from (HMe2Si)3CH and LDA according to
the literature [13]. In a 50-mL two-necked flask
equipped with a condenser, a solution of 10.5
mmol of (HMe2Si)3CLi in THF was prepared from
(HMe2Si)3CH (2.00 g,10.5 mmol) and LDA (6.5 mL,
13 mmol). The red-brown solution was stirred at am-
bient temperature for 6 h under argon. Then, a solu-
tion of 1.32 g benzyl chloride (10.5 mmol) in 15 mL
THF was added dropwise. The mixture was heated
under reflux for 3 h, then allowed to cool and poured
into aqueous NH4Cl. The products were extracted
with ether, and the etheral layer was dried with
anhydrous Na2SO4, filtered and solvent was evap-
orated from the filtrate. The residue was purified by
TLC (silica gel, n-hexane as eluent) to give a clear
gel. IR: 3020 (aromatic C H), 1930 (aliphatic C H),
2120 (Si H), 1590, 1480 (aromatic C C), 1250, 895
1
(C Si) cm−1; H NMR (CDCl3, 400 MHz): δ 0.2 (d,
18H, SiMe2), 3.1 (s, 2H, CH2Ph), 4.2 (sept, 3H, SiH),
7.3–7.4 (m, 5H, ArH); 13C NMR: (CDCl3): δ −3.8
(6C, SiMe), 3.8 ((SiMe2H)3C), 34.9 (CH2-Ph), 125.2–
139.3 (aromatic); MS (EI) m/z (%): 175 (100), [M −
SiMe2H]+), 189 (60), 59 (40), 91 (50, [C6H5CH2]+).
Anal. Calcd for C14 H28Si3: C, 59.9; H, 9.9. Found: C,
60.0; H, 10.0.
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Reactions of Tris(dimethylsilyl)methane and Polymers Containing Si H Groups with Various Hydroxy Compounds 369
C H), 2910–2860 (aliphatic C H), 2115 (Si H),
1590, 1480 (aromatic C C), 1255, 850 (C Si); H
C C), 1090 (Si O), 1000 (C O), 1254, 850 (C Si);
1H NMR (CDCl3): δ 0.18 (18H, Si(CH3)2), 0.92
(9H, CH2CH3,), 1.4–1.9 (3H, CH2-CH), 1.56 (6H,
1
NMR (CDCl3): δ 0.16 (18H, Si(CH3)2), 1.4–1.9 (3H,
CH2CH), 3.1 (2H, CH2Ph), 4.0 (3H, Si H),7.2–8.4
(4H, Ar H); 13C NMR (CDCl3): δ 2.6 (CH3Si), 5
((HMe2Si)3C), 35.0 (CH2-Ph), 40.0 (CH2CH), 41.0
(CH2CH), 125–145.5 (aromatic carbons). Anal. Calcd
for C16H30Si3 (one polymeric unit): C, 62.8; H, 9.8.
Found: C, 62.5; H, 9.8. Elemental analysis for copoly-
mer P3−SiH: Anal. Calcd for C17H21Si3 (one polymeric
unit): C, 67.9; H, 9.0. Found: C, 67.6; H, 8.9.
CH2CH3,), 3.31 (2H, CH Ph), 3.50 (6H, CH2O), 7.2–
2
8.4 (4H, Ar-H); 13C NMR (CDCl3): δ 2.6 (CH3-Si),
7.0 (C(SiMe2OR)3), 10.2 (CH2CH3), 25.83 (CH2CH3),
34.0 (CH2-Ph), 40.0 (CH2CH), 41.0 (CH2CH), 62.99
(CH2O), 125–145.5 (aromatic). Anal. Calcd for
C25H48Si3O3 (one polymeric unit): C, 62.5; H, 10.2.
Found: C, 62.1; H, 10.3.
P1-OBu. IR (KBr, cm−1): 2953 (C H), 1251, 858
(Si C), 1094 (Si O), 1008 (C O), 1254, 850 (C Si);
1H NMR (CDCl3): δ 0.22 (18H, Si(CH3)2), 0.82 (9H,
CH2CH3), 1.4–1.9 (3H, CH2CH, 6H, CH2CH2O), 1.56
General Procedures for Synthesis of Polymers
(P-OR) Containing SiMe2R-Substituted
Side Chains
(6H, CH2CH3), 3.31 (2H, CH Ph), 3.55 (6H, CH2O),
2
7.2–8.4 (4H, Ar-H); 13C NMR (CDCl3): δ 2.2 (SiMe2),
8.5 (CH), 12.00 (CH3CH2), 22.47 (CH3CH2), 28.19
(CH3CH2CH2), 32.39 (CH3(CH2)2CH2), 35.0 (CH2-
Ph), 41.0 (CH2CH), 43.0 (CH2CH), 62.19 (CH2O);
Anal. Calcd for C28H54Si3O3 (one polymeric unit): C,
64.3; H, 10.3. Found: C, 64.5; H, 10.2.
Four drops of 0.04 M H2PtCl6·6H2O in EtOH were
added to a mixture of polymer PSi-H (0.5 g) in ROH
(50 mL).The heterogeneous mixture was heated un-
der reflux for 48 h, during which eight more drops of
the catalyst were added. The color gradually changed
to black, and the progress of the alcoholysis reaction
was monitored by FT-IR spectroscopy. The resulting
polymer was filtered off and washed several times
with cold methanol. It was dissolved in chloroform
(10 mL), the solution was filtered to remove Pt parti-
cles, and the polymer reprecipitated from methanol.
Spectroscopic results for homopolymers are as
follows:
Spectroscopic data for copolymers P2-OR and
P3-OR were similar to those for the homopolymer.
RESULTS AND DISCUSSION
The metals of groups 8–10 and some of their salts
are known to catalyze the cleavage of the silicon-
hydrogen bond by a wide variety of nucleophilic
reagents. The most widely studied nucleophiles have
been alcohols and carboxylic acids [15]. This general
class of reaction constitutes a convenient method for
the preparation of substances containing the silicon-
oxygen bonds in high yields.
P1-OMe. IR (KBr, cm−1): 3029 (aromatic C H),
2910–2860 (aliphatic C H) 1590, 1480 (aromatic
C C), 1094 (Si O), 1008 (C O), 1255, 850 (C-Si); 1H
NMR (CDCl3): δ 0.18 (18H, Si(CH3)2), 1.4–1.9 (3H,
CH2CH), 3.1 (2H, CH2Ph), 3.60 (s, 3H, OMe), 7.2–
8.4 (4H, Ar-H); 13C NMR (CDCl3,): δ 2.6 (CH3Si), 7.0
(C(SiMe2OR)3), 34.0 (CH2Ph), 40.0 (CH2CH), 41.0
(CH2CH), 56.2 (OMe), 125–145.5 (aromatic). Anal.
Calcd for C19H36Si3O3 (one polymeric unit): C, 57.5;
H, 9.09. Found: C, 57.2; H, 9.1.
Transition metal catalyzed activation of silanes
can occur by oxidative addition Eq. (2) or by forma-
tion of a σ complex (Eq. (3)).
P1-OEt. IR (KBr, cm−1): 3029 (aromatic C H),
2910–2860 (aliphatic C H) 1590, 1480 (aromatic
C C), 1092 (Si O), 1005 (C O), 1255, 850 (C Si);
1H NMR (CDCl3): δ 0.18 (18H, Si(CH3)2), 1.4–1.9
(3H, CH2-CH), 1.32 (t, 9H, CH2CH3,), 3.1 (2H,
CH Ph), 3.57 (6H, CH2O), 7.2–8.4 (4H, Ar-H); 13C
2
NMR (CDCl3): δ 2.6 (6C, CH3-Si), 7.0 (C(SiMe2OR)3),
14.0 (CH2CH3), 34.0 (CH2Ph), 41.0 (CH2CH), 44.0
(CH2CH), 60.2 (CH2O), 125–145.5 (aromatic). Anal.
Calcd for C22H42Si3O3 (one polymeric unit): C, 60.2;
H, 9.5. Found: C, 60.5; H, 9.8.
Oxidative addition appears to be implicated in
the catalysis of alkene hydrosilylation, because the
key step is the insertion of the unsaturated sub-
strate into an M H or M Si bond. Silane alcoholysis
(eq. 1) is thought to be catalyzed most efficiently by
formation of an intermediate σ-complex. The metal
is believed to polarize the Si H bond and so favors
nucleophilic attack by ROH (Scheme 1) [16].
P1-OPr. IR (KBr, cm−1): 3018 (aromatic C H),
2920–2860 (aliphatic C H), 1592, 1482 (aromatic
Heteroatom Chemistry DOI 10.1002/hc

370 Safa, Tofangdarzadeh, and Ayenadeh
SCHEME 1 Proposed mechanism for the alcoholysis reaction of (HMe2Si)3CH.
Synthesis of (ROMe2Si)3CH
The compound (HMe2Si)3CH was made from the
reaction between HMe2SiCl and CHBr3 in the
presence of Mg in THF. Monofunctional alcohols
SCHEME 2 Alcoholysis reaction of (HMe2Si)3CH with var-
ious alcohols.
(n-propyl, iso-propyl, n-butyl, s-butyl, iso-butyl, n-
pentyl, s-pentyl, and n-hexyl) were treated with
(HMe2Si)3CH in the presence of H2PtCl6·6H2O as a
catalyst in air under mild conditions. The related
tris(alkoxydimethylsilyl)methanes were produced in
good yields (Table 1). The progress of the reaction
was monitored by IR spectroscopy until the Si H
absorbance in the IR spectrum had disappeared
(Scheme 2). The reaction is assumed to proceed
through reduction of the Pt(IV) catalyst to colloidal
Pt(0), as metallic particles can be observed at the
end. These reactions occurred in air. In contrast,
most reported alcoholysis reactions promoted by
transition metal catalysts have been carried out un-
der inert atmospheres such as argon or nitrogen.
Reactions of (HMe2Si)3CH with primary alcohols
gave higher yields than analogous reactions with sec-
ondary alcohols, probably because of the increase in
steric hindrance (see Table 1). No reaction was ob-
served with the tertiary alcohol ButOH (entry 12).
Similarly, (PhOMe2Si)3CH was obtained from the
reaction of phenol with (HMe2Si)3CH in the pres-
ence of the Pt-catalyst. In the case of benzyl alcohol,
the spectroscopic results show that treatment with
(HMe2Si)3CH gave dibenzyl ether instead of the ex-
pected (PhCH2OMe2Si)3CH.
The reaction between acetic acid and
(HMe2Si)3CH in the presence of chloroplatinic
acid as catalyst gave (Me2SiOSiMe2)3CH. This
compound was made previously by Eaborn and
coworkers by a different method, but we have
obtained it in high yield and in a one-pot process.
Lithiation of (ROMe2Si)3CH (R = Me, n-Bu)
Organometallic compounds containing (MeOMe2-
Si)2(Me3Si)C and (MeOMe2Si)3C ligands have
been reported previously. We describe the lithi-
ation of (ROMe2Si)3CH, and a new organosil-
icon compound containing the (BuOMe2Si)3C-
ligand. Eaborn and coworkers [17] have previ-
ously shown that treatment of (Me3Si)3CCl with
ICl followed by MeOH-Et3N gave (MeOMe2Si)3CCl.
This compound was treated with n-BuLi at
−78◦C to give (MeOMe2Si)3CLi, which reacted
TABLE 1 Product Yields from Pt-Catalyzed Reactions of Various Hydroxy Compounds with (HMe2Si)3CH
Entry
Hydroxy Compounds
CH3CH2CH2OH
Products
Yield (%)
1
2
3
4
5
6
7
8
(CH3CH2CH2OMe2Si)3CH (1)
[(CH3)2CHOMe2Si]3CH (2)
61.1
52.2
72.6
40.2
56.2
70.1
50.8
62.1
–
(CH3)2CHOH
CH3CH2CH2CH2OH
(CH3CH2)(CH3)CHOH
(CH3)2CHCH2OH
CH3CH2CH2CH2CH2OH
(CH3CH2CH2)(CH3)CHOH
CH3CH2CH2CH2CH2CH2OH
PhCH2OH
PhOH
CH3COOH
(CH3)3COH
(CH3CH2CH2CH2OMe2Si)3CH (3)
[(CH3CH2)(CH3)CHOMe2Si]3CH (4)
[(CH3)2CHCH2OMe2Si]3CH (5)
(CH3CH2CH2CH2CH2OMe2Si)3CH (6)
[(CH3CH2CH2)(CH3)CHOMe2Si]3CH (7)
(CH3CH2CH2CH2CH2CH2OMe2Si)3CH (8)
PhCH2OCH2Ph (9)
9
10
11
12
(PhOMe2Si)3CH (10)
45.3
56.3
–
HC(Me2SiOSiMe2)3CH (11)
No Product obtained
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Tris(dimethylsilyl)methane and Polymers Containing Si H Groups with Various Hydroxy Compounds 371
ity, and constitutes an important research field in its
own right [19–22].
Preparation of CMS Homopolymer and Copoly-
mes with Styrene by Free Radical Polymerization.
The monomer of 4-CMS was homopolymerized and
copolymerized with styrene at 70◦C with AIBN as
SCHEME 3 Synthetic pathway leading to the new com-
radical initiator. The reaction conditions are shown
in Table 2. The composition of P2 and P3 was de-
termined by use of 1H NMR spectroscopy. The mole
fractions of CMS and styrene were calculated from
the ratio of the areas of the peaks at 4.6 ppm corre-
sponding to two protons of the chloromethyl group
in CMS to the total area between 7.4 and 8.3 ppm,
attributed to four aromatic protons of CMS and five
aromatic protons of styrene. Gel permeation chro-
matography (GPC) with THF as solvent was used to
determine the number and weight-average molecu-
lar weights of the homopolymer (P1) and copolymers
(P2, P3). The results are listed in Tables 2 and 3.
pounds (ROMe2Si)3CSiMe2H.
with HMe2SiCl to give (MeOMe2Si)3CSiMe2H. In
view of the previous observation that lithiation of
(MeOMe2Si)2(Me3Si)CH with MeLi was not repro-
ducible as MeLi attacked Si OMe as well as C H
bonds [18], we turned to LDA as an alternative meta-
lating agent. The reaction between (MeOMe2Si)3CH
and LDA proceeded smoothly at −78◦C and, after
addition of HMe2SiCl, gave (MeOMe2Si)3CSiMe2H.
To throw light on the effect of the alkyl group on
lithiation, we chose to study (n-BuOMe2Si)3CH be-
cause the alkoxy-substituted derivative is obtained
in the highest yield. The final product was (n-
BuOMe2Si)3CSiMe2H (Scheme 3) (see also Fig. 1).
Attachment of Bulky (HMe2Si)3C Groups
via Nucleophilic Substitution. The reaction of
(HMe2Si)3CH with 1 equivalent of LDA in THF
resulted in quantitative formation of (HMe2Si)3-
CLi·2THF.
A few coupling reactions between
Preparation of New Polymers Containing Si H
Group in Side Chains
(HMe2Si)3CLi and chlorosilanes have been reported
but, as far as we are aware, there has hitherto been
no reference in the literature to the reaction between
(HMe2Si)3CLi and benzyl chloride. We carried out
this reaction to examine the possibility of attach-
ing (HMe2Si)3C groups to polymer side chains.
The model compound (HMe2Si)3CCH2Ph was
The attachment of organosilyl groups to macro-
molecules chain leads to important modifications
in polymer properties such as gas permeability
and permselectivity parameters, mechanical, ther-
mal, surface properties, and photochemical reactiv-
FIGURE 1 1H NMR spectra: (a) (n-BuOMe2Si)3CH and (b) (n-BuOMe2Si)3CSiMe2H in CDCl3 without tetramethylsilane.
Heteroatom Chemistry DOI 10.1002/hc

372 Safa, Tofangdarzadeh, and Ayenadeh
TABLE 2 Conditions of Preparation of Homopolymer and Copolymers at 70 1◦C
Sample No. Monomer 1 Monomer 2 Amount of 1 (mmol) Amount of 2 (mmol)
Solvent
Time (h) Nonsolvent
P1
P2
P3
CMS
CMS
CMS
–
20
10
20
–
30
20
–
12
30
30
MeOH
MeOH
MeOH
Styrene
Styrene
Toluene
Toluene
TABLE 3 Compositions and Molecular Weights of P1, P2, and P3
Sample
mol% CMS
mol% Styrene
Mw× 103
Mn× 103
Mw/Mn
Tg (◦C)
P1
P2
P3
100
25
52
–
75
48
20.4
30.4
31.5
12.3
18.9
19.3
1.65
1.60
1.63
103
93
98
2115 cm−1 and the appearance of Si CH3 bonds with
isolated as
a clear gel in fairly good yield
1
absorption at 1255 and 830 cm−1. In the H NMR
(Scheme 4a). Therefore, a mixture of homopoly-
mer P1 (0.5 g) was treated with optimized amount
of (HMe2Si)3CLi (25 mmol) in THF (Scheme 4b).
The replacement of chlorine atoms by (HMe2Si)3C
groups was easily followed by the appearance of
the Si H absorption at 2110–2130 cm−1. A FTIR
spectrum of the obtained polymer P1-SiH exhibits the
following characteristics: The appearance of Si H
bonds is associated with the strong absorption at
spectrum (Fig. 2b) of the homoplymer P1-SiH, the ab-
sorption at 4.6 ppm, assigned to the methylene pro-
tons of benzyl chloride, disappeared completely and
a new signal appeared at 3.1 ppm due to methylene
protons adjacent to the (HMe2Si)3C groups. A new
18-proton signal from (HMe2Si)3C appeared at 0.16
ppm. The peaks at 4.0 ppm are assigned to the Si H
resonance. Other assignments for P4 are the same as
SCHEME 4 Synthetic routes for preparation of (a) model compound, (b) substitution of (HMe2Si)3C groups in P1, and
(c) substitution of (HMe2Si)3C groups at copolymers P2 and P3.
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Tris(dimethylsilyl)methane and Polymers Containing Si H Groups with Various Hydroxy Compounds 373
FIGURE 2 1H NMR spectra: (a) P1 and (b) P1-SiH in CDCl3 without tetramethylsilane. The Si H (δ 4.0 ppm), which are well
defined in the P1-SiH
.
those observed for the homopolymer P1. In the 13C
NMR spectrum of P1-SiH, the peak at 46 ppm corre-
sponding to the methylene carbon of benzyl chlo-
ride is replaced by a new signal at 35 ppm, corre-
sponding to the methylene carbon adjacent to the
(HMe2Si)3C subsitutent. In addition, the peaks at 5
and 2.6 ppm are the resonance peaks, respectively, of
the central carbon and the six methyl carbon atoms
of the (HMe2Si)3C group. All spectroscopic results
indicate that coupling reactions with an excess of
(HMe2Si)3CLi (25 mmol) were successful and com-
plete, i.e. that all the chlorine atoms in homopoly-
mer P1 were replaced by (HMe2Si)3C groups. The
complete replacement of the chlorine atoms was also
confirmed by comparison of elemental analyses of
homopolymer P1 with homopolymer P1-SiH. Treat-
ment of 0.5 g of polymers P2 and P3 with an excess of
(HMe2Si)3CLi in THF solution led to complete sub-
stitution of chlorine atoms by (HMe2Si)3C groups
to give new copolymers (P2-SiH and P3-SiH) (Scheme
4c). The appearance of peaks attributed to Si H vi-
brations in IR spectra and the concomitant disap-
1
pearance of peaks at 4.6 and 46 ppm in H and 13C
NMR spectra, respectively, clearly indicated that the
coupling reactions (as with P1) were successful and
complete (see also Figs. 3a and 3b). The result was
confirmed by elemental analysis.
Glass transition temperatures (Tg) of the new
polymers were determined by DSC analysis. As
shown in Fig. 4, the curves showed that incorpora-
tion of (HMe2Si)3C into polymer side chain increases
the rigidity. The glass transition temperature of the
homopolymer P1-SiH was found to be 197◦C (Fig. 4a),
which is 94◦C higher than that (105◦C) found for ho-
mopolymer P1. Tgs of P2 and P3 are 93 and 98◦C,
respectively, whereas those of P2-SiH and P3-SiH are
150◦C and 177◦C (Figs. 4b and 4c). The bulkiness
of the (HMe2Si)3C substituent effectively restricts
the free volume of the macromolecules. In addition,
with increasing CMS mole fraction in the copolymer,
bulky groups are incorporated in higher yields and,
therefore, the free volumes of the macromolecules
Heteroatom Chemistry DOI 10.1002/hc

374 Safa, Tofangdarzadeh, and Ayenadeh
FIGURE 3 1H NMR spectra: (a) P3 and (b) P2-SiH (c) P2-OMe in CDCl3 without tetramethylsilane. The Si H (δ 4.0 ppm),
which are well defined in the P2-SiH
.
further decreased. The higher Tg value of homopoly-
mer P1-SiH is ascribed to the high (HMe2Si)3C con-
tent of P1. For the same reason the Tg of the poly-
mer, P3-SiH (177◦C) is higher than that of P2-SiH
(150◦C).
copolymers containing such polymeric units have
been reported [11], but to our knowledge there are
no references in the literature to alcoholyses of
groups attached to polystyrene side chains. Alkoxy
groups were attached to polymer side chains under
the same conditions as those used for monomeric
compounds, but the reactions were heterogeneous
since the polymers were insoluble in alcohols. The
spectroscopic results indicated that under optimal
conditions replacement of H by OR at the silicon
center was complete. This was proven by complete
Alcoholyses of the Side Chains of Polymers
P1-OMe, P1-OEt, P1-OPr , and P1-OBu
Alcoholysis reactions of polymeric silicon com-
pounds such as polysiloxanes and polysilanes or
TABLE 4 Compositions and molecular weights of P1, P2, and P3
Sample
Mn × 103
Mw × 103
Mw/Mn
Tg(◦C)
P1-SiH
P2-SiH
P3-SiH
P1-OMe
P1-OEt
P1-OPr
P1-OBu
12.1
17.9
18.3
12.1
12.1
12.1
12.0
19.2
30.0
30.5
19.2
19.1
19.1
19.0
1.58
1.67
1.66
1.58
1.57
1.57
1.58
197
177
150
199
205
220
250
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Tris(dimethylsilyl)methane and Polymers Containing Si H Groups with Various Hydroxy Compounds 375
FIGURE 4 DSC curves of polymers: (a) P2-SiH (b) P3-SiH, (c) P1-SiH and (d) P1-OBu at 10◦C/min in air.
coholysis of hydrosilanes in air.
A
series of
tris(alkoxydimethysilyl)methanes are obtained in
near quantitative yields from the catalytic reaction
of (HMe2Si)3CH with monofunctional alcohols. Pri-
mary alcohols gave higher yields than secondary,
and no reaction took place with t-butanol. Reac-
tions with benzyl alcohol and acetic acid led to un-
expected products. The compound (BuOSiMe2)3CH
(3) was metalated with LDA at low temperatures.
(HMe2Si)3C groups have been attached to polymer
side chains, and alcoholyses have been effected un-
der the same conditions as those for monomeric
compounds. DSC showed that introduction of bulky
groups into the side chains of polymers gave big in-
creases in the glass transition temperatures of the
polymers.
SCHEME 5 Preparation of silyl ether on the side chain of
polymer.
disappearance of Si H peak at 2115 cm−1 and the
concomitant disappearance of signals correspond-
1
ing to Si H at 4.0 ppm in the H NMR spectra of
ACKNOWLEDGMENTS
the polymers (Scheme 5). The results were verified
by elemental analysis. As shown in Table 4, the
Tg of the polymer increased with alkyl groups of
increasing bulk. For the same reason, the Tg of the
polymer P1-OBu (250◦C) was higher than that of P1-OPr
(220◦C) or P1-OEt (205◦C).
We thank Dr. J. D. Smith for helpful comments.
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Heteroatom Chemistry DOI 10.1002/hc

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