Novel pentacoordinate silicon compounds bearing [Si-N-C-N-C-N] chelate ring derived from biguanide ligands

Article abstract of DOI:10.1016/j.jorganchem.2003.08.022

The reactions between secondary carbosilanes 1-3 and 1-propylbiguanide/1-phenylbiguanide, H₆bigR proceed via SiH/NH dehydrocoupling and afford 1,4-bis(silyl)-5-propyl/phenylbiguanides with the general formula (R¹R²₂

Full text of DOI:10.1016/j.jorganchem.2003.08.022

Journal of Organometallic Chemistry 687 (2003) 190Á196
/
www.elsevier.com/locate/jorganchem
Novel pentacoordinate silicon compounds bearing [Si-N-C-N-C-N]
chelate ring derived from biguanide ligands
Pooja Kumar, Ravi Shankar *
Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
Received 24 April 2003; received in revised form 4 August 2003; accepted 20 August 2003
Abstract
The reactions between secondary carbosilanes 1Á
dehydrocoupling and afford 1,4-bis(silyl)-5-propyl/phenylbiguanides with the general formula (R1R22SiCH2CH2SiMeH)2×
[R1ꢀPh, R2ꢀMe, Rꢀn Ph (5); R1ꢀMe, R2ꢀPh, RꢀnPr (6), R1ꢀR2ꢀ
Pr (4), Rꢀ Et, RꢀPh (7)]. These compounds represent
/3 and 1-propylbiguanide/1-phenylbiguanide, H6bigR proceed via SiH/NH
/H4bigR,
/
/
/
/
/
/
/
/
/
/
a new family of pentacoordinate silicon derivatives comprising of [Si-N-C-N-C-N] chelate ring and have been characterized by
elemental analysis, FAB mass, IR and multinuclear (1H, 13C and 29Si) NMR spectral studies.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Pentacoordination; Silylbiguanides; SiH/NH dehydrocoupling; Carbosilanes
1. Introduction
studies are of relevance to understand the effect of
pentacoordinate silicon on the electronic attributes and
conformational behavior in these oligomers.
Synthesis and structural studies of neutral pentacoor-
dinate silicon compounds derived from ligands with
strategically placed donor atoms (O, N and S) have
received considerable attention in the past [1]. Major
emphasis has been directed to understand the enhanced
reactivity of these compounds towards nucleophiles and
also their role in the mechanistic interpretation of
nucleophilic substitution reactions at tetracoordinate
silicon centers [1a,1b,1c]. While the majority of such
compounds possess five- and six-membered chelate
rings, a few reports on related hypercoordinate silicon
derivatives containing higher-membered cyclic rings
have also appeared [2]. Reductive coupling of penta-
coordinate chlorosubstituted silicon precursors contain-
ing 8-dimethylamino-1-naphthyl group with magnesium
is known to afford neutral hypercoordinate silicon
We have been interested in the study of SiN bonded
derivatives containing biguanide ligands, hereafter ab-
breviated as H6bigR (Chart 1). Although these ligands
[5] have been extensively used in the coordination
chemistry of transition metals [6], their potential in the
main group chemistry is confined to only a few reported
examples of tetracoordinate boron heterocycles (Chart
1). These have been synthesized by the reactions of
amino boranes/boronic acid with biguanide [7] and are
found to be stable towards hydrolysis. It is generally
believed that the electronic effects arising from p-
delocalized framework of biguanide ligand impart
unusual stability to the metal chelates. It is thus desired
to utilize the chelation property as well as the underlying
electronic attributes of these ligands in the preparation
of novel SiN bonded compounds.
compounds containing Siꢀ/Si bonds [3]. Recently, Ta-
In literature, SiH/NH dehydrocoupling reactions of
naka et al. [4] have reported the synthesis and X-ray
structure of pentacoordinate silicon compounds invol-
ving tri-, tetra- and pentasilane framework. These
diorganosilanes, R2SiH2 (Rꢀalkyl, aryl) with nitrogen
/
bases such as ammonia, amines or hydrazines are
known to proceed efficiently only under transition
metal/Fꢁ ion catalyzed conditions [8,9]. We have
recently reported that biguanide ligands as nitrogen
precursors undergo SiH/NH dehydrocoupling reactions
with methylphenylsilane/diphenylsilane at moderate
* Corresponding author. Tel.: ꢂ
2641-2292.
E-mail address: shankar@netearth.iitd.ac.in (R. Shankar).
/
91-11-2659-1513; fax: ꢂ91-11-
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.08.022

P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á
/
196
191
2. Results and discussion
The carbosilanes R1R22SiCH2CH2SiMeH2 [R1ꢀ
R2ꢀMe (1); R1ꢀMe, R2ꢀPh (2); R1ꢀR2ꢀ
Et (3)]
/
Ph,
/
/
/
/
/
have been synthesized in two steps (Eq. (1)). The initial
step involves hydrosilylation reaction between equimo-
lar quantities of dichloromethylvinylsilane and the
appropriate hydrosilane R1R22SiH in presence of Kar-
stedt’s catalyst. Subsequent reaction of the resulting
chlorocarbosilane with lithium aluminium hydride af-
Chart 1.
temperature in the absence of any external catalyst
[10,11]. In order to understand the role of biguanide
ligands in these uncatalyzed reactions as well as other
factors affecting SiH/NH dehydrocoupling, these studies
have been extended to a few alkylsubstituted secondary
silanes. The carbosilanes R1R22SiCH2CH2SiMeH2 1Á
bearing terminal ꢀSiH2 groups serve as alkyl analogs to
secondary silanes and thus have been chosen as the
precursors owing to their ease of preparation and
handling at elevated temperatures. In the absence of
any external catalyst these carbosilanes react with 1-
propylbiguanide/1-phenylbiguanide by SiH/NH dehy-
drocoupling pathway to afford the corresponding 1,4-
fords the corresponding carbosilane 1Á
/
3, in Â
/
70Á75%
/
yield. The carbosilane 3 is formed exclusively as the b-
isomer, while 1 and 2 are isolated as a mixture of b-
isomer (Â
/
95%) and minor amounts of a-isomer (Â
/5%)
as evident from HPLC data. Predominant formation of
the b-isomer in these compounds is evident from 1H and
13C{1H} DEPT-135 NMR spectra. 29Si-NMR spectrum
/
3
/
of compound 3 reveals two signals at d 8.3 (s, Et3Si) and
1
29.3 (t, SiMeH2, JSiH
ꢁ
/
ꢀ189 Hz) arising from the b-
/
isomer. On the other hand, the presence of a- and b-
isomeric mixture is discernable from 29Si{1H}-NMR
spectra of 1 and 2 (Section 3). The mass spectra (EI)
reveal [Mꢁ
H]ꢂ ion in each case. In addition,
structurally significant ions are observed by the cleavage
/
bis(silyl)-5-propyl/phenylbiguanides 4Á7 (Scheme 1)
/
comprising of novel six-membered [Si-N-C-N-C-N]
chelate ring with pentacoordinate silicon atom. The
results obtained are reported in this communication.
of SiC bonds and the relevant data are given in Section
3.
(1)
Scheme 1.

192
P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á196
/
2.1. Reactions of the carbosilanes 1Á
propylbiguanide/1-phenylbiguanide- synthesis of 1,4-
bis(silyl)-5-propyl/phenylbiguanides, 4Á
/
3 with 1-
cmꢁ1) and dSiH2 (945 cmꢁ1) modes provides a
qualitative evidence for the occurrence of SiH/NH
dehydrocoupling. The absorptions due to nNH mode
/
7
(3350Á
to those observed in the parent biguanide (3370Á
cmꢁ1) and suggests the coordinative association of
imine NH with the silicon atom. The nCꢁN and
/
3120 cmꢁ1) shift to lower frequency as compared
3294
SiH/NH dehydrocoupling reactions between the car-
bosilanes 1Á3 and biguanide ligands in a stoichiometric
/
/
ratio of 2:1 in THF medium are extremely sluggish at
room temperature. As evident from 1H-NMR spectra of
the reaction mixture at different time intervals, concen-
tration of the SiH groups does not show a perceptible
/
nNCN absorptions appear at ca 1625 and 1560, 1426
cmꢁ1 and remain practically unaltered. In the nSiH
region, two medium intensity absorptions are observed
at ca 2100 and 2200 cmꢁ1 which persist in the solution
state (CH2Cl2) as well. These results find an analogy
with those of related silylbiguanides [10] as well as a few
aminosilanes [12] and disilanes [13] reported earlier and
suggest the existence of conformational mixtures. The
change with respect to the parent silane (d 3.64Á3.73).
/
The unreacted silane was obtained in nearly quantitative
yields after 96 h. However, at elevated temperatures
(65Á70 8C, 48 h) these reactions proceed efficiently in
/
the absence of a catalyst to afford the corresponding 1,4-
bis(silyl)-5-propyl/phenylbiguanides with the general
presence of different conformers in 4Á7 is also evident
/
formula (R1R22SiCH2CH2SiMeH)2×
/
H4bigR, [R1ꢀ
Ph (5); R1ꢀMe, R2ꢀ
Et, Rꢀ
/
Ph,
from 13C{1H}-NMR spectra in DEPT-135 mode which
exhibit two signals for each of the methylene carbons as
well as for the SiMe groups linked to the biguanide
R2ꢀ
Rꢀn
/
Me, Rꢀn
Pr (6), R1ꢀ
/
Pr (4), Rꢀ
/
/
/Ph,
/
/
R2ꢀ
/
/
Ph (7)]. The silylbigua-
1
nides, thus isolated are hygroscopic, low melting solids
and tend to decompose thermally above 100 8C. These
compounds are soluble in common organic solvents
such as CHCl3, CH2Cl2, THF and DMSO.
moiety (Section 3). In H-NMR spectra, the resonances
arising
from
the
carbosilyl
functionalities,
R1R22SiCH2CH2SiMeH are broad and devoid of J-
coupling information, while NPr/NPh groups show their
usual spectral characteristics. The integral intensities of
various signals associated with the carbosilyl and NPr/
NPh groups are in conformity with the proposed
All attempts to grow single crystals of 4Á7 were
/
unsuccessful. However, the structural identity of these
compounds has been established by FAB mass, IR and
multinuclear (1H, 13C, 29Si) NMR studies. FAB mass
spectra (3-nitrobenzylalcohol matrix) reveal the mole-
cular ion peak, [M]ꢂ in each case and confirm the
molecular nature of these compounds. The calculated
isotopic distributions for the [M]ꢂ ions are in accord
with the observed pattern. Structurally important frag-
ment ions arise primarily from the cleavage of SiC, SiN
and SiPh bonds. A representative FAB mass spectrum
of 5 is given in Fig. 1 and the relevant data are
summarized in Table 1. In the IR spectra (KBr pellet,
Fig. 2), the absence of absorptions due to nNH2 (3420
structure. In addition to a broad signal at d 3.2Á
due to NH protons, a downfield resonance at d 6.8Á
is attributed to the coordinated Cꢁ
signal due to SiH protons appears at d 4.6Á
/
5.0
/6.9
/
NH groups. The
4.7.
/
However its appearance with the broad NH resonance
makes a large uncertainty in the integrals. 29Si{1H}-
NMR spectrum of each compound in CDCl3 reveals
signals at d ꢁ
/
1.3 (for 4), ꢁ
/
1.3 (for 5), ꢁ4.8 (for 6) and
/
8.2 (for 7) and are assigned to R1R22Si moiety of the
carbosilyl side chain by comparison with 29Si{1H}-
NMR spectra of the corresponding carbosilanes. Two
Fig. 1. FAB mass spectrum of (PhMe2SiCH2CH2SiMeH)2×H4bigPh (5).
/

P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á
/
196
193
Table 1
FAB mass and 29Si-NMR data of the compounds 4Á
/
7
Compound m/z [fragment ion]
d
29Si NMR
R1R22Si C2Si(H)N C2Si(H)N2
4
5
555 [M]ꢂ, 478 [Mꢁ
2PhMe2Si]ꢂ, 197 [Mꢁ
589 [M]ꢂ, 514 [MꢁC6H3]ꢂ, 453 [Mꢁ
353 [MꢁPhMe2SiCH2CH2SiMeꢁ
2Me]ꢂ, 291 [Mꢁ
Phꢁ
NH3]ꢂ, 178 [C8H11N5]ꢂ, 135 [PhMe2Si]ꢂ
623 [M]ꢂ, 469 [Mꢁ2C6H5]ꢂ, 454 [MꢁPh2MeSi]ꢂ, 398 [Mꢁ
Ph2MeSiCH2CH2Si]ꢂ, 229 [Mꢁ2Ph2MeSi]ꢂ, 144 [C5H13N5]ꢂ
549 [M]ꢂ, 520 [MꢁEt]ꢂ, 434 [MꢁEt3Si]ꢂ, 378 [Mꢁ Et3SiCH2CH2Si]ꢂ, 291 [Mꢁ
178 [C8H11N5]ꢂ
/
C6H5]ꢂ, 420 [Mꢁ
2PhMe2SiCH2ꢁ
PhMe2Siꢁ
/
PhMe2Si]ꢂ, 348 [Mꢁ
C3H7ꢁ
NH3]ꢂ, 144 [C5H13N5]ꢂ, 135 [PhMe2Si]ꢂ
H]ꢂ, 367 [Mꢁ
PhMe2SiCH2CH2SiMeHꢁ
2PhMe2SiCH2]ꢂ, 197 [Mꢁ
2PhMe2SiCH2ꢁ
/
PhMe2SiCH2CH2SiMeH]ꢂ, 285 [Mꢁ
/
ꢁ
/
1.3
1.3
ꢁ
/
7.8
7.7
ꢁ
/
85.5
/
/
/
/
/
/
/
/
Me]ꢂ
,
ꢁ/
ꢁ/
ꢁ/
86.5
/
/
/
/
/
/
6
7
/
/
/
Ph2MeSiCH2CH2]ꢂ, 370 [Mꢁ
2Et3SiCH2]ꢂ
/
ꢁ/
4.8
8.3
ꢁ/
7.8
7.5
ꢁ/
85.5
/
/
/
/
/
,
ꢁ/
ꢁ/
86.3
additional resonances are observed at d ꢁ
/
7 to ꢁ
/
8 and
dehydrocoupling phenomena involving biguanide li-
gands. A few significant conclusions which can be
conceived are as follows.
ꢁ
/
85 to ꢁ87 in the spectrum of each compound. Based
/
on DEPT-135 29Si{1H}-NMR spectra, the former value
is assigned to tetracoordinate silicon associated with
C2Si(H)N while the latter is assigned to pentacoordinate
C2Si(H)N2 moieties. These results are consistent with
those of related tetra- and pentacoordinate silicon
derivatives reported in literature [14]. The UV spectra
(i) In contrast to the earlier reports [8,9], the reactions
of secondary organosilanes R1R2SiH2 (R1ꢀ
/
Ph, R2ꢀ
/
Ph, Me) [10] or carbosilanes 1Á3 with biguanide ligands
/
proceed at moderate temperature under uncatalyzed
conditions. It is thus implicated that strong chelating
ability of biguanide ligand is the driving force for
activation of SiH bonds in the precursor silanes via
hypercoordinate silicon intermediate. This proposition
is consistent with the literature report on SiH/NH
dehydrocoupling reactions in presence of strong nucleo-
philes [9]. (ii) Presence of pentacoordinate silicon atom
of compounds 4Á
the biguanide functionality at 235Á
From the foregoing studies, it is apparent that
molecular compounds 4Á7 bearing [Si-N-C-N-C-N]
/7 reveal an absorption characteristic of
/240 nm.
/
chelate ring are accessible by adopting a straightforward
synthetic protocol which involves SiH/NH dehydrocou-
pling between the carbosilanes 1Á
/
3 and biguanide
in compounds 4Á7 is a unique feature not observed in
/
ligands. A comparative assessment of these studies
with those reported earlier [10] is significant in qualita-
tive interpretation of the factors which govern SiH/NH
their oligomeric analogs reported earlier [10]. In litera-
ture, a number of crystallographically authenticated
examples of metalÁbiguanide chelates are known to
/
Fig. 2. IR spectrum (KBr pellet) of (PhMe2SiCH2CH2SiMeH)2×H4bigPr (4).
/

194
P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á196
/
possess planar structure [6c,6e,6f]. By analogy, it thus
appears that the silicon atom in the vicinity of CꢁNH
group in compounds 4Á7 lies in the plane of biguanide
ligand thereby favoring pentacoordination while any
deviation from such planarity disfavors N0Si interac-
tion as observed in the oligomeric silylbiguanides. (iii)
Subtle difference in the rate of SiH/NH dehydrocou-
pling reactions has been observed depending upon the
nature of substituents (alkyl or aryl) on silicon. Forma-
3.2. Synthesis of the carbosilanes 1Á
/
3
/
/
3.2.1. Preparation of 1
To a stirred solution of dichloromethylvinylsilane
(14.1 g, 13.0 ml, 0.10 mol) containing catalytic amount
of Karstedt’s catalyst (10ꢁ7 mol of Pt/mol of silane),
dimethylphenylsilane (13.6 g, 15.3 ml, 0.10 mol) was
added dropwise. Induction period was observed after a
few milliliters of the silane was added. After the
complete addition, the reaction mixture was heated at
70 8C for 7 h. The crude mixture was fractionally
/
tion of monomeric compounds 4Á7 derived from the
/
carbosilanes may be attributed to slow rate of SiH/NH
dehydrocoupling in comparison to that of aryl substi-
tuted secondary silanes which afford oligomers.
distilled (b.p. 95Á97 8C/5 mmHg, yield 85%). The
/
resulting chlorocarbosilane (23.5 g, 0.08 mole) in Et2O
was added dropwise to a dispersion of LiAlH4 (3.5g,
0.09 mol) in ether at 0 8C. The contents were gently
3. Experimental
refluxed for 4Á5 h and hydrolyzed with 1N HCl. Ether
/
layer was extracted and dried over anhydrous Na2SO4.
Thereafter the solvent was removed and the contents
3.1. General comments
were distilled to yield 1 as a colorless liquid. (b.p. 130Á
135 8C, yield 75%). HPLC (hexane): b-isomer (95%), a-
isomer (5%). EI mass: 208 [Mꢁ
H]ꢂ, 193 [MꢁCH3]ꢂ,
179 [Mꢁ
CH3-CH2]ꢂ, 135 [PhMe2Si]ꢂ. 1H-NMR
(CDCl3): d 7.60Á7.35 (m, SiPh), 3.72Á3.68 (m, SiH),
0.72Á0.70, 0.60Á0.58 (m, SiCH2CH2, b), 0.24 (s,
PhMe2Si, b), 0.11 (t, JHH
(d, 3JHH
7.4 Hz, CHCH3, a), 0.33Á
/
All operations were carried out using standard
Schlenk line techniques under dry nitrogen atmosphere.
Solvents were freshly distilled under inert atmosphere
over sodium benzophenone (tetrahydrofuran, Et2O) or
phosphorous pentoxide (CH2Cl2, hexane) before use.
Dichloromethylvinylsilane (Aldrich) was distilled over
magnesium prior to use. Karstedt’s catalyst (plati-
num(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane com-
/
/
/
/
/
/
/
3
ꢀ
/
4.0 Hz, SiMeH2, b), 1.00
ꢀ
/
/
0.29 (m, SiCH, a),
0.22 (s, PhMe2Si, a), 0.02 (t, 3JHH
ꢀ4.0 Hz, SiMeH2, a).
/
plex),
dimethylphenylsilane,
diphenylmethylsilane,
13C{1H} DEPT-135 NMR (CDCl3): d 134.4 (o-SiPh),
129.7 (p-SiPh), 128.6 (m-SiPh), 9.4, 7.3 (SiCH2CH2, b),
Et3SiH and lithium aluminium hydride (Aldrich) were
used as procured. Infrared spectra were routinely
obtained as thin films or KBr pellets on a Nicolet FT-
IR 460 (Prote´ge´) spectrometer. The UV spectra were
ꢁ
/
0.7 (PhMe2Si, b), ꢁ
2.4 (SiCH, a), 0.2 (PhMe2Si, a), ꢁ
29Si{1H}-NMR (CDCl3): d ꢁ
1.0 (PhMe2Si, b), ꢁ
/
2.5 (SiMeH2, b), 11.6 (CCH3, a),
2.0 (SiMeH2, a).
28.5
/
/
/
obtained in THF solution on a PerkinÁ
/Elmer (Lambada
(SiMeH2, b), 0.1 (PhMe2Si, a), ꢁ29.4 (SiMeH2, a). IR
/
Bio 20) spectrophotometer. H-, 13C-, and 29Si- NMR
spectra were obtained in Me2SO-d6, acetone-d6 or
CDCl3 on a Bruker Spectrospin DPX 300MHz instru-
ment. Chemical shifts are quoted relative to Me4Si.
13C{1H}- and 29Si{1H}-NMR spectra in DEPT mode
were obtained using standard pulse sequence with a J
modulation time 3.7 ms and 5 s delay time. EI (70 eV)
mass spectra were carried out on VG analytical (Model
70-s) mass spectrometer. The FAB mass spectra in 3-
nitrobenzyl alcohol (NBA) matrix were recorded at
room temperature on a JEOL SX 102/DA-6000 Mass
Spectrometer/Data System using Argon/Xenon (6 kV,
10 mA) as the FAB gas. The accelerating voltage was 10
(cmꢁ1): n(SiH) 2126, d(SiH2) 946, n(SiPh) 1114,
n(SiMe) 1256. Anal. Calc. for C11H20Si2: C, 63.46, H,
9.61. Found: C, 63.17, H, 9.52%.
1
3.2.2. Preparation of 2
The reaction between diphenylmethylsilane (19.8 g,
20.0 ml, 0.1 mol) and dichloromethylvinylsilane (14.1 g,
13.0 ml, 0.1 mol) was carried out in a manner similar to
that described for 1. The chlorocarbosilane thus ob-
tained (b.p. 140Á
with LiAlH4 (3.4 g, 0.09 mol) to afford the carbosilane 2
as a colorless liquid (b.p. 90Á93 8C/5 mmHg, yield 70%).
HPLC (hexane): b-isomer (96%), a-isomer (4%). EI
mass: 269 [Mꢁ
H]ꢂ, 255 [MꢁCH3]ꢂ, 241 [Mꢁ
CH3ꢁ
CH2]ꢂ, 197 [Ph2MeSi]ꢂ, 192 [MꢁC6H6]ꢂ.
1H-NMR (CDCl3): d 7.50Á
7.30 (m, SiPh), 3.68Á3.64
(m, SiH), 1.04Á1.00, 0.63Á0.61 (m, SiCH2CH2, b), 0.50
(s, Ph2MeSi, b), 0.07 (t, 3JHH
3.9 Hz, SiMeH2, b), 0.99
(d, 3JHH
7.5 Hz, CHCH3, a), 0.22Á0.18 (m, SiCH, a),
/
145 8C/5 mmHg, 0.09 mol) was treated
/
kV. C, H and N analyses were carried out on a PerkinÁ
/
/
/
/
Elmer 240-C rapid elemental analyzer. The HPLC data
were obtained on Waters 1525 Binary HPLC fitted with
Waters 2487 dual wavelength absorbance detector and a
C-18 column. Hexane was used as the mobile phase. 1-
Propylbiguanide and 1-phenylbiguanide were prepared
following the methods known in literature [15,16] and
were recrystallized from CH2Cl2 prior to use. In accord
with the IUPAC nomenclature [17], the numbering
scheme for these ligands is as shown in Chart 1.
/
/
/
/
/
/
ꢀ
/
ꢀ
/
/
0.54 (s, Ph2MeSi, a), 0.02 (t, 3JHH
ꢀ4.0 Hz, SiMeH2, a).
/
13C{1H} DEPT-135 NMR (CDCl3): d 134.8 (o-SiPh),
129.4 (p-SiPh), 128.8 (m-SiPh), 10.6, 7.6 (SiCH2CH2,
b), ꢁ
/
1.0 (Ph2MeSi, b), ꢁ2.3 (SiMeH2, b), 11.3 (CCH3,
/

P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á
/
196
195
a), 2.2 (SiCH, a), 1.2 (Ph2MeSi, a), ꢁ
/
2.2 (SiMeH2, a).
28.8
29.5 (SiMeH2, a).
3.3.2. Synthesis of (PhMe2SiCH2CH2SiMeH)2×
/
29Si{1H}-NMR (CDCl3): d ꢁ
/
4.9 (Ph2MeSi, b), ꢁ
/
H4bigPh (5)
(SiMeH2, b), ꢁ
/
4.0 (Ph2MeSi, a), ꢁ
/
The reaction between 1-phenylbiguanide (0.26 g, 1.5
mmol) and PhMe2SiCH2CH2SiMeH2 (1) (0.61 g, 2.9
mmol) was performed in a similar manner as described
for 4. After the usual workup the compound 5 was
IR (cmꢁ1): n(SiH) 2125, d(SiH2) 945, n(SiPh) 1113,
n(SiMe) 1256. Anal. Calc. for C16H22Si2: C, 71.11, H,
8.15. Found: C, 70.94, H, 8.02%.
obtained as a white solid (yield: 0.8 g, 90%, m.p. 68Á
70 8C). 1H-NMR (Me2SO-d6): d 7.61Á
7.30 (SiPh, 10H),
7.20Á6.82 (m, NPh, 5H), 6.94Á6.90 (CꢁNH, 1H), 4.80Á
3.64 (br, NHꢂSiH, 5H), 0.65Á0.61, 0.47Á0.43
(SiCH2CH2, 8H), 0.21Á0.19 (PhMe2Si, 12H), ꢁ0.08
to ꢁ
0.06 (SiMeH, 6H). 13C-NMR (Me2SO-d6): d
159.4, 159.2 (C ꢁN), 136.4 (i-SiPh), 133.4 (o-SiPh),
/
/
3.2.3. Preparation of 3
/
/
/
/
The reaction between Et3SiH (14.0 g, 19.0 ml, 0.12
mol) and dichloromethylvinylsilane (16.9 g, 16.0 ml,
0.12 mol) was carried out following the procedure
described for 1. The resulting chlorocarbosilane was
/
/
/
/
/
/
/
distilled (b.p. 95Á
with LiAlH4 (4.26 g, 0.11 mol) in Et2O. The carbosilane
3 was obtained as a colorless liquid (b.p. 60Á65 8C/5
mmHg, yield 75%). EI mass: 187 [Mꢁ
H]ꢂ, 173 [Mꢁ
CH3]ꢂ, 159 [MꢁEt]ꢂ, 115 [Et3Si]ꢂ. 1H-NMR
(CDCl3): 3.73Á3.69 (m, SiH), 0.52Á
SiCH2CH2), 0.95 (t, JHH
3JHH
(CDCl3): d 7.1 (CH3ꢀ
/
100 8C/5 mmHg, 0.10 mol) and treated
129.8 (p-SiPh), 127.5 (m-SiPh), 149.9 (i-NPh), 128.3
(m-NPh), 123.9 (p-NPh), 120.6 (o-NPh), 9.8, 9.5, 5.7,
/
5.5 (SiCH2CH2),
ꢁ
/
2.3,
ꢁ
/
2.5 (SiMeH),
ꢁ4.5
/
(PhMe2Si). IR (KBr pellet, cmꢁ1): 3348, 3150 (nNH),
2198, 2099 (nSiH), 1625 (nCN), 1559, 1426 (nNCN),
1257 (nSiMe), 1113 (nSiPh). Anal. Calc. for
C30H47N5Si4: C, 61.12, H, 7.98, N, 11.88, Si, 19.01.
Found: C, 61.10, H, 7.92, N, 11.80, Si, 18.52%.
/
/
/
d
/
/
0.48 (m,
Et), 0.12 (t,
3
ꢀ
/
7.6 Hz, CH3 ꢀ
/
ꢀ
4.0 Hz, SiMeH2). 13C{1H} DEPT-135 NMR
/
/
Et), 7.0, 2.5 (SiCH2CH2), 0.6
(SiMeH2). 29Si-NMR (CDCl3): d 8.3 (Et3Si), ꢁ
/
26.2,
3.3.3. Synthesis of (Ph2MeSiCH2CH2SiMeH)2×
/
1
32.5 (SiMeH2, JSiH
ꢁ
/
29.3, ꢁ
/
ꢀ
/
189 Hz). IR (cmꢁ1):
H4bigPr (6)
n(SiH) 2124, d(SiH2) 946, n(SiMe) 1257. Anal. Calc. for
C9H24Si2: C, 57.45, H, 12.77. Found: C, 57.36, H,
12.64%.
The reaction between 1-propylbiguanide (0.30 g, 2.1
mmol) and Ph2MeSiCH2CH2SiMeH2 (2) (1.13 g, 4.2
mmol) was performed by following the procedure as
described for 4. The compound 6 was obtained as a
white solid (yield: 1.2 g, 95%, m.p. 70Á
(Me2SO-d6): d 7.51Á7.20 (SiPh, 20H), 6.90Á
NH, 1H), 6.22Á4.20 (br, NHꢂSiH, 5H), 2.96 (t,
3JHH
7.6 Hz, NCH2, 2H), 1.48Á1.46 (m, NCH2CH2,
2H), 0.90 (br, CH3 ꢀPrꢂSiCH2, 7H), 0.50Á0.46
(SiCH2CH2ꢂPh2MeSi, 10H), ꢁ0.09 to ꢁ0.07 (Si-
MeH, 6H). 13C{1H}-NMR (Me2SO-d6): d 162.2, 162.1
(C ꢁN), 136.4 (i-SiPh), 134.2 (o-SiPh), 129.4 (p-SiPh),
128.2 (m-SiPh), 41.5 (NCH2), 22.2 (NCH2CH2), 10.3
(CH3ꢀPr), 10.5, 9.8, 6.4, 6.2 (SiCH2CH2), ꢁ2.4, ꢁ2.5
(SiMeH), ꢁ
1.6 (Ph2MeSi). IR (KBr pellet, cmꢁ1):
/
72 8C). 1H-NMR
6.86 (Cꢁ
3.3. Synthesis of 1,4-bis(silyl)-5-propylbiguanides, 4-7
/
/
/
/
/
3.3.1. Synthesis of (PhMe2SiCH2CH2SiMeH)2×
H4bigPr (4)
To a clear solution of 1-propylbiguanide (0.32 g, 2.2
mmol) in dry THF (15 ml) was added PhMe2-
SiCH2CH2SiMeH2 (1) (0.93 g, 4.5 mmol) with the help
of a hypodermic syringe. The contents were heated at
/
ꢀ
/
/
/
/
/
/
/
/
/
65Á
/
70 8C for Â/48 h. The solvent was stripped off under
/
/
/
vacuum resulting in a sticky mass. Repeated washings
with hexane afford a white solid which was filtered and
/
3330, 3154 (nNH), 2190, 2099 (nSiH), 1625 (nCN),
1560, 1427 (nNCN), 1256 (nSiMe), 1110 (nSiPh). Anal.
Calc. for C37H53N5Si4: C, 71.27, H, 8.51, N, 11.24, Si,
17.98. Found: C, 71.02, H, 8.23, N, 11.03, Si, 17.58%.
dried under vacuum (yield: 1.1 g, 95%, m.p. 63Á
1H-NMR (Me2SO-d6): d 7.62Á
7.31 (SiPh, 10H), 6.89Á
6.87 (CꢁNH, 1H), 4.82Á3.20 (br, NHꢂSiH, 5H), 2.90
(t, JHH 7.4 Hz, NCH2, 2H), 1.40Á1.36 (m,
NCH2CH2, 2H), 0.83 (t, JHH Pr, 3H),
7.4 Hz, CH3 ꢀ
0.64Á0.60, 0.40Á0.36 (SiCH2CH2, 8H), 0.17Á0.15
(PhMe2Si, 12H), 0.03Á
0.01 (SiMeH, 6H). 13C{1H}-
NMR (CDCl3): d 162.4, 162.2 (C ꢁN), 136.2 (i-SiPh),
/
65 8C).
/
/
/
/
/
3
ꢀ
/
/
3
ꢀ
/
/
3.3.4. Synthesis of (Et3SiCH2CH2SiMeH)2×
/H4bigPh
/
/
/
(7)
/
The synthesis of compound 7 was achieved by the
reaction of 1-phenylbiguanide (0.35 g, 2.0 mmol) with
Et3SiCH2CH2SiMeH2 (3) (0.75 g, 4.0 mmol). The
/
132.3 (o-SiPh), 127.6 (p-SiPh), 126.5 (m-SiPh), 41.3
(NCH2), 22.1 (NCH2CH2), 10.5 (CH3-Pr), 10.1, 9.7,
reaction conditions employed are similar to those
1
5.5, 5.3 (SiCH2CH2), ꢁ
/
2.4, ꢁ
/
2.5 (SiMeH), ꢁ
/
4.5
described for 4 (yield: 1.0 g, 95%, m.p. 58Á
NMR (Me2SO-d6): d 7.22Á
6.94 (CꢁNH, 1H), 6.21Á4.20 (br, NHꢂ
0.86Á0.82 (CH3 ꢀEt, 9H), 0.45Á0.41 (SiCH2, 20H),
0.03Á
0.01 (SiMeH, 6H). 13C{1H}-NMR (dmso-d6): d
159.0, 158.3 (CꢁN), 149.8 (i-NPh), 128.9 (m-NPh),
/
60 8C). H-
(PhMe2Si). IR (KBr pellet, cmꢁ1): 3340, 3160 (nNH),
2206, 2099 (nSiH), 1625 (nCN), 1560, 1426 (nNCN),
1257 (nSiMe), 1113 (nSiPh). Anal. Calc. for
C27H49N5Si4: C, 58.38, H, 8.83, N, 12.61, Si, 20.18.
Found: C, 58.20, H, 8.64, N, 12.43, Si, 19.98%.
/
6.80 (m, NPh, 5H), 6.97Á
/
/
/
/SiH, 5H),
/
/
/
/
/

196
P. Kumar, R. Shankar / Journal of Organometallic Chemistry 687 (2003) 190Á196
/
[4] (a) I. El-Sayed, Y. Hatanaka, C. Muguruma, S. Shimada, M.
Tanaka, N. Koga, M. Mikami, J. Am. Chem. Soc. 121 (1999)
5095;
122.8 (p-NPh), 120.1 (o-NPh), 7.1 (CH3ꢀ
/
Et), 2.5, 2.7
(SiCH2), 0.6 (SiMeH). IR (KBr pellet, cmꢁ1): 3343,
3120 (nNH), 2203, 2099 (nSiH), 1620 (nCN), 1560, 1427
(nNCN), 1257 (nSiMe). Anal. Calc. for C26H55N5Si4: C,
56.83, H, 10.02, N, 12.23, Si, 20.12. Found: C, 56.64, H,
9.86, N, 11.98, Si, 20.04%.
(b) I. El-Sayed, Y. Hatanaka, S. Onozawa, M. Tanaka, J. Am.
Chem. Soc. 123 (2001) 3597.
[5] (a) D. Karipides, W.C. Fernelius, Inorg. Synth. 7 (1963) 56;
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Acknowledgements
(c) M.L. Simms, J.L. Atwood, D.A. Zatko, J. Chem. Soc. Chem.
Commun. (1973) 46;
The authors are grateful to DST (India) for financial
support and U.G.C. (India) for S.R.F. to P.K.
(d) A. Marchi, L. Marvelli, M. Cattabriga, R. Rossi, M. Neves, V.
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