(Amidomethyl)dimethylsilanol hydrohalides: Synthesis, NMR and IR studies. Characteristic features of the electronic structure from high-resolution X-ray study and quantum chemical calculation

Article abstract of DOI:10.1016/j.jorganchem.2006.05.047

(C,O)-chelate silanol hydrohalides RC(O)NHCH₂SiMe₂OH · HHal (2a,b and 5b), and their precursors, (C,O)-chelate chlorosilanes RC(O)NHCH₂SiMe₂Cl (6a,b) and disiloxanes [RC(O)NHCH₂SiMe₂]₂O (8a,b) (R = Me (a), Ph (b); Hal = Cl (2), Br (5)), were obtained by several routes. The original scheme of hydrolysis of the above chlorides was discussed in detail. X-ray analysis has shown that the silanol hydrohalogenides PhC(O)NHCH₂SiMe₂OH · HX (2b and 5b) in the crystal exist in the form of cation-anion pairs [PhC(O)NHCH₂SiMe₂(OH₂)]⁺ · X^- (14b · Cl^- and 14b · Br^-) assembled by H-bonds in a 3D framework. The Si atom in the cation has a trigonal bipyramidal configuration with the oxygen atom of the carbonyl group and protonated hydroxyl exo-substituent in axial positions. The endocyclic Si-O bonds are equal with an average of 1.905 A? while the exocyclic Si-O bonds are 1.979 and 2.009 A?, for Hal = Cl and Br, respectively. Quantum chemical calculations have shown that the cation [PhC(O)NHCH₂SiMe₂(OH₂)]⁺ (14b) is stable only in the crystal. Based on a high-resolution X-ray study and a quantum chemical calculation, it was found that the chemical bonding pattern in the OSiO axial fragment of the cation 14b corresponds to a three-centred four electron interaction. The cation 14b should be considered as a silylium cation stabilized by coordinated H₂O molecules rather than a silyloxonium ion.

Full text of DOI:10.1016/j.jorganchem.2006.05.047

Journal of Organometallic Chemistry 691 (2006) 3962–3975
www.elsevier.com/locate/jorganchem
(Amidomethyl)dimethylsilanol hydrohalides: Synthesis, NMR and
IR studies. Characteristic features of the electronic structure from
high-resolution X-ray study and quantum chemical calculation
a,
b
b
Alexander A. Korlyukov *, Sergey A. Pogozhikh , Yuri E. Ovchinnikov ,
a
a
c
Konstantin A. Lyssenko , Mikhail Yu. Antipin , Aleksander G. Shipov ,
c
c
c
Oksana A. Zamyshlyaeva , Evgeniya P. Kramarova , Vadim V. Negrebetsky ,
d
c
Igor P. Yakovlev , Yuri I. Baukov
a
A.N. Nesmeyanov Institute of Organoelement Compounds, X-ray Laboratory, Vavilov St. 28, 119991 Moscow, Russian Federation
b
Novosibirsk State Pedagogical University, Vilyuiskaya St. 28, Novosibirsk 630126, Russian Federation
c
Russian State Medical University, Ostrovityanov St. 1, Moscow 117997, Russian Federation
N.D. Zelinsky Institute of Organic Chemistry, Leninsky Prosp., 47, 119991 Moscow, Russian Federation
d
Received 28 December 2005; received in revised form 22 May 2006; accepted 24 May 2006
Available online 7 June 2006
Abstract
(C,O)-chelate silanol hydrohalides RC(O)NHCH2SiMe2OH Æ HHal (2a,b and 5b), and their precursors, (C,O)-chelate chlorosilanes
RC(O)NHCH2SiMe2Cl (6a,b) and disiloxanes [RC(O)NHCH2SiMe2]2O (8a,b) (R = Me (a), Ph (b); Hal = Cl (2), Br (5)), were obtained
by several routes. The original scheme of hydrolysis of the above chlorides was discussed in detail. X-ray analysis has shown that the
silanol hydrohalogenides PhC(O)NHCH2SiMe2OH Æ HX (2b and 5b) in the crystal exist in the form of cation–anion pairs
[PhC(O)NHCH2SiMe2(OH2)]+ Æ Xꢀ (14b Æ Clꢀ and 14b Æ Brꢀ) assembled by H-bonds in a 3D framework. The Si atom in the cation
has a trigonal bipyramidal configuration with the oxygen atom of the carbonyl group and protonated hydroxyl exo-substituent in axial
˚
˚
positions. The endocyclic Si–O bonds are equal with an average of 1.905 A while the exocyclic Si–O bonds are 1.979 and 2.009 A, for
Hal = Cl and Br, respectively.
Quantum chemical calculations have shown that the cation [PhC(O)NHCH2SiMe2(OH2)]+ (14b) is stable only in the crystal. Based on
a high-resolution X-ray study and a quantum chemical calculation, it was found that the chemical bonding pattern in the OSiO axial
fragment of the cation 14b corresponds to a three-centred four electron interaction. The cation 14b should be considered as a silylium
cation stabilized by coordinated H2O molecules rather than a silyloxonium ion.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Pentacoordinated silicon compounds, synthesis; X-ray diffraction study, intramolecular coordination, intermolecular coordination; Quantum
chemical calculations, distribution of electron density
1. Introduction
characterized by the (C,O)-chelate structure with an intra-
molecular coordinate bond O ! Si [1a,1b]. Much less is
known about the corresponding intermolecular homoasso-
ciates [1b].
Recently, we have reported preliminary data on the syn-
thesis and structure of the first representatives of monosub-
stituted amides of the general type RC(O)NHCH2SiMe2X
(R = Alk, Ar; X = Hal) [2a,2b]. The coordinate interaction
in these compounds can be achieved by the participation of
At present, the N-silylmethyl derivatives of the amides
and related compounds have been relatively well studied
[1a,1b]. Most of them include at least one sufficiently elec-
tronegative substituent group at the silicon atom and are
*
Corresponding author. Tel.: +7 495 1359214; fax: +7 495 1355085.
E-mail address: alex@xrlab.ineos.ac.ru (A.A. Korlyukov).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.047

A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
3963
both the oxygen atom of the amide group and the hydro-
gen atom of the NH group. Thus, such compounds are use-
ful as models for the investigation of the inter- and
intramolecular processes of coordinate bonding. Indeed,
both types of coordinate interaction have been detected
in the crystals of the fluorides RC(O)NHCH2SiMe2F (1a,
R = Me; 1b, R = Ph) [2b].
chemical calculations of the molecular and crystalline
structure, and the electronic structure of the hydrohalides
2b and 5b.
2. Results and discussion
2.1. Synthesis
Preliminary data concerning the formation and oxo-
nium structure of the first representative of another type
of monosubstituted amide derivatives, the hydrochloride
PhC(O)NHCH2SiMe2OH Æ HCl (2b), have been reported
in a short communication [3]. An X-ray investigation
revealed the nature of the pentacoordinate silicon atom
in 2b. Note, that both tetra- and pentacoordinated proton-
ated silanols are of interest as intermediate products in the
hydrolysis of organohalosilanes, of particular theoretical
and practical importance in the chemistry of organosilicon
compounds. At present, similar compounds containing
water molecules as ligands have not been investigated in
detail. Inþ particular,ꢀ the cation–anion complex
½But3SiOH2ꢁ ½Br6CB11H6ꢁ ð3Þ [4a], containing a tetracoor-
dinated silicon as the cation and the non-nucleophilic
brominated closo-carborane anion as well as the pentaco-
ordinated protonated silanol 4 [4b] are rare examples of
such compounds that have been characterized by X-ray
data.
The hydrochloride 2b described in the short communica-
tion [3] was obtained as a result of a lengthy (about 8
months) storage of the N-(dimethylchlorosilylmethy)benz-
amide under conditions which failed to completely exclude
the presence of atmospheric moisture. Accordingly, we con-
sidered that the hydrolysis of the chlorides RC(O)NHCH2-
SiMe2Cl (6) and corresponding bromides was the most
rational route to the hydrohalides of the silanols. However,
the preparation of the individual compounds proved to be
a more complex task. We investigated several approaches
to the chlorides 6 (see previous papers [2b,3,5a,5b]). The
first one is based on the reaction of the amides RC(O)NH2
with dimethyl(chloromethyl)chlorosilane ClCH2SiMe2Cl
in the presence of hexamethyldisilazane, i.e. a one pot
synthesis for the N-chloromethylsilylmethylation of the
non-substituted and monosubstituted amides using the
ClCH2SiMe2Cl–(Me3Si)2NH system (Scheme 1) [5a,5b].
In the case of a twofold excess of the latter the reaction
leads to the N,N-bis(dimethylchlorosilylmethyl)amides
(7), via intermediate formation of the monochlorides 6.
Hydrolysis of the monochlorides 6 by aqueous NaHCO3
proceeds practically quantitatively (see below) with forma-
tion the disiloxane 8 (see Scheme 1, equation (c)). The anal-
ogous hydrolysis of the dichloride 7, as described earlier,
yields products of the intermolecular cyclocondensation,
4-acyl-2,6-disilamorpholines (9) (see Scheme 1, equation
(d)) [5b,6a,6b].
Me
O
Me
N
H
H
O
C
Si
Cl
4
In this paper, the modified technique for the synthesis of
the hydrochloride 2b, and the synthesis of its analogs, the
hydrochloride 2a and hydrobromide 5b, are given. We also
discuss the results of an X-ray investigation and quantum
The dichlorides 7, for example, compound 7a (R = Me)
[5b], can be obtained according to Scheme 1, equations (a)
and (b), in high yield. In contrast, the products of the
a) (Me3Si)2NH,
ClCH2SiMe2Cl
b) (Me3Si)2NH,
O
O
C
O
C
ClCH2SiMe2Cl
R
NH2
R
N
H
CH2SiMe2Cl
R
C
N
CH2SiMe2Cl
– Me3SiCl,
– NH4Cl
– Me3SiCl,
– NH4Cl
CH2SiMe2Cl
6
7
c) H2O,
NaHCO3
d) H2O,
NaHCO3
Me
Me
O
C
O
Si
Si
N
H
CH2SiMe2)2O
(R
R
C
N
O
Me
Me
8
9
R = H, Alk, Ar
Scheme 1.

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A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
Table 1
mono-N-dimethylchlorosilylmethylation 6 could not be
isolated from the reaction mixture in acceptable yields even
on varying the reagent ratios. Thus, the reaction of acetam-
ide with an equimolecular amount of ClCH2SiMe2Cl and
the required amount of (Me3Si)2NH in boiling benzene
gives the N-dimethylchlorosilylmethylacetamide (mono-
chloride 6a) in only 23% yield. The reason for such a low
yield was found to be the formation of a significant amount
of the dichloride 7a. In addition, we established that the
bissilylmethylation product 7a could be formed using both
the ClCH2SiMe2Cl–(Me3Si)2NH system and the reaction
of the acetamide with ClCH2SiMe2Cl in the presence of
Et3N, i.e. by the known general methods of preparation
of mono-(C,O)-chelate pentacoordinated chlorosilanes [7].
The ratio of products of mono- and bissilylmethylation
of acetamide depends on the nature and relative amount
of the silylmethylation reagent as shown in Table 1.
The determination of the mole ratio of the chlorides 6a
and 7a was performed by 1H NMR spectroscopy after
hydrolysis of the reaction mixture by aqueous NaHCO3,
which resulted in their almost quantitative conversion into
the acyclic disiloxane 8a (see below) and disilamorpholine
9a (R = Me), respectively.
The ratio of products of mono- and bissilylmethylation of acetamide, 6a
and 7a, depending on the nature and relative amount of the silylmethy-
lation reagent
Reagents
The ratio of
acetamide and
reagents
The ratio of
chlorides
6a and 7a
ClCH2SiMe2Cl–(Me3Si)2NH
ClCH2SiMe2Cl–(Me3Si)2NH
ClCH2SiMe2Cl–Et3N
(Me3Si)2NH, ClCH2SiMe2Cla
a
1:1:0.4
1:1:1
1:1:1
1.74:1
1.08:1
1.94:1
1.28:1
1:0.4:1
Successive addition of reagents to acetamide.
report the reactions of the disiloxanes 8 with electrophilic
reagents such as SOCl2, Me3SiBr and HCl.
The disiloxanes 8a,b were found to react readily with
thionylchloride in benzene leading to the formation of
purer samples of the chlorides 6a,b (equation (2a)) in
higher yields (ꢂ80%) than in previous cases
O
a) SOCl2
RC(O)NHCH2SiMe2Cl
6a,b
(RCNHCH2SiMe2)2O
8a,b
ð2Þ
The second approach to the monochlorides 6 is based on
the use of the general method for the preparation of (C,O)-
chelate Si-substituted N-(silylmethyl)amides and -lactams
[7–9],1 using a transsilylation reaction, i.e. the reaction of
N-TMS-amides RC(O)NHSiMe3 with ClCH2SiMe2Cl
b) H2O
RC(O)NHCH2SiMe2OH•HCl
2a,b
Unlike the reaction of N-(dimethylchlorosilylm-
ethyl)amides 6a,b with aqueous NaHCO3 which gave the
corresponding disiloxanes 8a,b (see Scheme 1, equation
(c)), hydrolysis of the chlorides 6a,b in the absence of an
HCl acceptor gives the hydrochlorides 2a,b which are pre-
viously unknown (equation (2b)).
So, as mentioned earlier [3], when storing the chloride 6b
for long periods under conditions where moisture was not
completely excluded, its conversion into the hydrochloride
2b took place. The same compound was isolated by treat-
ment of the freshly prepared chloride 6b with the appropri-
ate amount of water in boiling acetonitrile in practically
quantitative yield. The interaction of the disiloxane 8a with
thionylchloride in heptane in contact with atmospheric
moisture yielded the extremely unstable hydrochloride 2a.
The transformation of the silanol hydrochlorides 2 into
the disiloxanes 8 proceeds easily as was established when
compound 2b was treated with excess of aqueous
NaHCO3.
R
R
H
O
N
H
ClCH2SiMe2Cl
– Me3SiCl
O
N
Me
Me
ð1Þ
Si
Cl
CH2
SiMe3
6a,b
R = Me (a), Ph (b)
In this case the yield of the monochlorides 6a,b were higher
than those obtained by the reaction shown in Scheme 1,
equation (a). However, the samples of the chlorides 6a,b
isolated from the reaction mixture were rather unstable,
deliquescent powders. Their hydrolysis by aqueous NaH-
CO3 gave quite stable acyclic disiloxanes 8a,b (see Scheme
1, equation (c)). The latter were obtained without isolation
of the intermediate monochlorides by hydrolysis of the
reaction mixture immediately following heating of the N-
TMS-amides with ClCH2SiMe2Cl. Thus, the conversion
of 6 into the disiloxane 8 essentially provides a method
for the identification of the hydrolytically labile chlorides
6 (Scheme 1, equation (a), and reaction (1)).
The reaction of the disiloxane 8b with Me3SiBr when in
contact with atmospheric moisture does not lead to
expected bromide PhC(O)NHCH2SiMe2Br but gives the
product of its subsequent hydrolysis, the hydrobromide 5b
In addition, the disiloxanes 8 are of interest because
their reactions lead to pentacoordinated silicon compounds
Me3SiBr, H2O
containing
a stable intramolecular coordinate bond
[P hC(O)NHCH2SiMe2]2O
PhC(O)NHCH2SiMe2OH•HBr
O ! Si. In particular, their interaction with BF3 Æ Et2O
8b
5b
results in the fluorides 1 mentioned above [2b]. We now
ð3Þ
Treatment of the disiloxane 8b by an HCl solution in ace-
tonitrile (obtained ‘‘in situ’’ from the calculated amounts of
thionylchloride and water) on heating to 90 ꢁC yielded a
1
The multistage nature of these transsilylation reactions is discussed in
detail in the review [1a].

A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
3965
mixture of chloride 6b and silanol hydrochloride 2b. Re-
crystallization of this mixture from damp acetonitrile
yielded only one substance, the silanol hydrochloride 2b,
in a yield of 94%.
similar interaction in the disiloxanes 8a,b were established
on the basis of the IR and 29Si NMR spectral characteris-
tics of these compounds as described below.
It may be suggested that the first stage in this case is the
formation of the disiloxane [PhC(O)NHCH2SiMe2]2O Æ
2HCl (10b), where both amide oxygen atoms are proton-
ated. This process is analogous to the formation of the
adduct (L5SiMe2)2O Æ 2CCl3COOH (where Ln is a lacta-
momethyl n-membered C,O-coordinating ligand) from
the corresponding disiloxane and CCl3COOH [10a]. Other
evidence for the presence of the intermediate adduct 10b
comes from comparison with the structurally characterized
products of partial hydrolysis of the chloride L5SiMe2Cl,
the dihydrochloride (L5SiMe2)2O Æ 2HCl [10b] and of the
chloride MeC(O)N(Me)CH2SiMe2Cl (6c) and the dihydro-
chloride [MeC(O)N(Me)CH2SiMe2]2O Æ 2HCl (10c), which
will be discussed in a subsequent paper. Heating the dihy-
drochloride 10b leads to rupture of the disiloxane bond
with the formation of hydrochloride 2b.
Thus, the results obtained provide evidence that the pen-
tacoordinated silanol hydrochlorides 2 are primary prod-
ucts of hydrolysis of the pentacoordinated chlorosilanes
in the absence of HCl acceptors and that the dihydrochlo-
rides of the disiloxanes 10 which contain tetracoordinated
silicon atoms are also possibly secondary products
(Scheme 2).
2.2. IR studies
The IR spectra of the chlorides 6a,b in solution show
two absorption bands with frequencies 1635 and
1540 cmꢀ1 for the chloride 6a, as well as two bands with
frequencies 1618 and 1520 cmꢀ1 for the chloride 6b. Taking
into account the 29Si NMR data (see below) we suggest
that these bands relate to coupled stretching vibrations of
the amide fragment N'C'O. As with the related (C,O)-
chelate pentacoordinated chlorosilanes [7b–9], this con-
firms the presence of an intramolecular coordinate bond
O ! Si in 6a,b.
The frequencies of the two strong absorption bands in
the region 1670–1520 cmꢀ1 detected in IR spectra of the
disiloxanes 8a,b are similar to those in the spectra of the
chlorides 6a,b. However, taking into account the 29Si
NMR data which show the absence of an intramolecular
coordinate bond O ! Si in 8a,b (see below) we suggest that
these bands arise from the stretching vibration of the non-
coordinated carbonyl group of the amide fragment (NCO)
(ꢂ1640 cmꢀ1, amide I, mC@O) and the NH-deformation
vibration (ꢂ1530 cmꢀ1, amide II, dNH).
In the IR-spectra of the silanol hydrohalides 2b and 5b,
(KBr disks), characteristic bands for intramolecular coor-
dinate bonds O ! Si and intermolecular H-bonds with
chlorine and bromine atoms were observed (see Section
3). The presence of bands in the region 1700–1500 cmꢀ1
assigned to stretching vibrations which are strongly cou-
pled as a result of delocalization in the N'C'O frag-
ments [7b–9] is evidence for the intramolecular
The final stage of the process resulting in the formation
of disiloxane 8 only requires the presence of suitable HCl
acceptors. The structure of the chlorides 6, disiloxanes 8
and silanol hydrohalides 2 and 5b were confirmed by IR
1
and H, 13C, 29Si NMR spectroscopy, and X-ray crystal-
lography. The presence of the intramolecular coordinate
bond O ! Si in the chlorides 6a,b and the absence of the
R
R
C
C
O
R'
R'
O
N
N
–H2O
Me
Me
Me
2H2O
2
CH2
Si
CH2
Si
O
2
+ H2O
Me
H
Cl
Cl–
H
6
2
Me Me
Me
Me
H
R
O
Si
O
Cl
Si
O
– 2 HCl
2 HCl
O
CH2
CH2
R
N
N
R'
R'
2
2
10
8
R, R’ = H, Alk, Ar
R = Me, R’ = H(a); R = Ph, R’ = H (b); R = Me, R’ = Me (c); R = Me, R’ = CH(Ph)Me(d)
Scheme 2.

3966
A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
coordinate bond O ! Si in these compounds. There were
no adsorptions corresponding to uncoordinated amide
groups indicating stable O ! Si coordination.
compounds 12 and 13 were 40.5 ppm (Si–O+(H)–Si) and
ꢀ23.4 ppm (Si–O–Si), respectively (cf. 67.6 ppm calculated
for the silicon atoms in [(Me3Si)2OH]+TFPBꢀ [11b])
A broad intense absorption in the range 3600–
2600 cmꢀ1 (O–H stretching vibration, perturbed by inter-
molecular H-interactions) was observed in the IR spectra
of the hydrohalides 2b and 5b. In both spectra, a narrow
band for the N–H stretching frequency at 3225 and
3215 cmꢀ1 for the hydrochloride 2b and the hydrobromide
5b, respectively, was observed. These lower N–H frequen-
cies compared to ‘‘free’’ secondary amides (3450–
3400 cmꢀ1) show hydrogen bonding involving the halide
ion.
H
H
tBu3Si
tBu3Si
SitBu3
O
O
H3Si
SiH3
Si
Si
Si
Si
–
TFPB
Si
Si
SitBu3
Si
Si
H3Si
SiH3
11
H3Si
12
O
SiH3
Si
Si
2.3. NMR studies
Si
Si
H3Si
SiH3
In principle, 29Si NMR data is more informative con-
cerning the extent of silicon coordination in the solution
in the compounds discussed. Indeed, resonances detected
in the 29Si NMR spectra of the compounds 6a,b (ꢀ27.4,
ꢀ26.5 (br. s) ppm) and 8a,b (4.5, 4.7 ppm) were found to
be in the range of chemical shifts corresponding to the pen-
tacoordinated state of the silicon atom in chlorides 6a,b
and close to the tetracoordinated state of silicon in the dis-
iloxanes 8a,b [cf. silicon resonances in chlorides 6c
(ꢀ37.6 ppm) and MeC(O)N(CHMePh)CH2SiMe2Cl (6d,
ꢀ38.1 ppm) and disiloxanes 8c,d (3.4 and ꢀ0.1 ppm) [11a].
Due to the limited solubility of the silanol hydrohalides
2a,b and 5b in solvents such as CDCl3 or CD2Cl2, we
have failed to determine NMR spectra under conditions
where there is a low probability of hydrolysis or the for-
13
2.4. X-ray structural studies and analysis of the electron
density distribution of crystals 2b and 5b
2.4.1. The crystal and molecular structure of 2b and 5b
Silanol hydrohalogenides 2b and 5b are isostructural cat-
ion–anion pairs assembled in the crystal into three-dimen-
sional framework via intramolecular H-bonds (Fig. 1).
The Si atom has a trigonal bipyramidal (TBP) configuration
with a deviation from the plane of the equatorial carbon
˚
˚
atoms (DSi) of ꢀ0.02 A and ꢀ0.04 A for 2b and 5b, respec-
tively (the minus sign means a deviation towards the O(1)
atom). The O(1) and O(2) atoms occupy the axial positions
(Fig. 2). The average lengths of the Si(1)–O(1) and Si(1)–
1
mation of higher coordinate complexes. The H and 13C
˚
O(2) bonds are 1.902 and 1.994 A, respectively. The shortest
NMR spectral data (CD3CN) for compounds 2a,b were
consistent with the proposed structures. In particular, in
the 1H NMR spectrum, broadened singlets at 5.21 and
8.09 ppm, respectively, corresponding to the three slowly
exchanging protons of the OH2 and the NH groups were
observed. Note that protons of the OH2 group of the pro-
tonated silanol 3 were observed at 8.04 ppm (CD2Cl2)
[4a].
interatomic Si. . .Cl and Si. . .Br distances are 4.047 and
˚
4.239 A, respectively (Table 2).
Thus, the Si(1)–O(1) bonds in 2b and 5b which are com-
monly described as ‘‘coordinate’’ are significantly shorter
than the Si(1)–O(2) bond. In this respect the hydrohaloge-
nides of the silanols are significantly different from the
majority of hypervalent silicon compounds. Analysis of
the geometry of the silicon atom coordination polyhedra
allowed us to conclude that the water ligand may be
described as a ‘‘good’’ leaving group, such as I, Br and
OTf [13]. In particular, one of the shortest Si–O coordinate
By compþarison, in ꢀ the case of complexes
½But SiðOH2Þꢁ ½Br6CB11H6ꢁ ð3Þ, [Me3Si(OEt2)]+TFPBꢀ
3
(TFPBꢀ = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate),
[Me3Si(MeCN)]+TFPBꢀ, and ½ Pri SiðMeCNÞꢁþ½Br5CB9-
3
H5ꢁꢀ containing the tetracoordinated Si atom, the silicon
resonance was observed at 46.7 ppm (CP–MAS) [4a],
66.9 ppm (CD2Cl2, at ꢀ70 ꢁC), 38.5 ppm (CD2Cl2, at
ꢀ10 ꢁC) and 33.8 ppm (CD2Cl2) [11b], respectively.
˚
bonds (1.753 A) was found in the chelate compound
L6SiMe2OTf with triflate group as the exo-substituent.
This molecule may be considered to be a close cation–
anion pair with a Si(1). . .O(2) interatomic distance of
˚
2.78 A. The ability of the triflate group to act as a ‘‘good’’
In turn, for the protonated tetracoordinated disiloxane
[(tBu3Si)4Si4OH]+TFPBꢀ (11), the structure of which was
confirmed by X-ray crystallography, the chemical shifts
of the (Si–O+(H)–Si) silicon atoms were found to be
44.2 ppm [12]. Thus, the resonance of the silicon atoms
connected to the oxygen atom in 11 is shifted downfield
by approximately 50 ppm compared with that of the corre-
sponding non-protonated species. The chemical shifts of
the silicon atoms calculated by the authors for the model
leaving group is closely related to high extent of delocaliza-
tion of the negative charge due to electron-withdrawing
effect of the fluorine atoms. It should be noted that the
O(2) atom in 2b and 5b has a formal positive charge and
the water ligand may be described as an oxonium fragment.
The latter statement contradicts the results of a topological
analysis of electron density [14]. According to this topolog-
ical analysis, the positive charge in hypervalent silicon

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3967
Fig. 1. Three-dimensional framework in crystal of 2b constructed via H-bonds cations 14b and Clꢀ anions. Hydrogen with exception of H(200), H(20) and
H(1N) atoms are omitted for clarity. The parameters of H-bonds are presented in Table 2.
not allow us to discuss the nature of this group. So, the nat-
ure of water group in the cation [PhC(O)NHCH2Si-
Me2(OH2)]+ (14b) in the structures of 2b and 5b is still
an open question.
With the exception of 2b and 5b there are only a few
examples of compounds where the silicon atom is
bonded to a water moiety [4a,4b,15]. All of these com-
pounds are characterized by a significant elongation of
the Si–O(H2) bond in comparison with its standard
˚
value for tetracoordinated silicon (1.64 A [16]). For
example, in the tris(t-butyl)silyloxonium cation of com-
plex 3 in which the silicon atom is tetracoordinated,
˚
the Si–O bond is 1.779 A [4a]. In salts of pentafluoro-
aquasilicon or tetrafluorodiaquasilicon with protonated
azacrown-ethers the Si–O bonds are much longer than
Fig. 2. The molecular structure of 2b. Atoms are presented as thermal
ellipsoids at 50% probability. Hydrogen with exception of H(200), H(20)
and H(1N) atoms are omitted for clarity.
˚
in the previous case (1.84–1.85 and 1.917 A [15], respec-
Table 2
tively). Inspection of the Cambridge structural database
(CSD [17]) has shown that the influence of the water
group as a ligand is very similar to that of OR2 moieties
(R = Me, Et [18]).
˚
Important bond lengths (A) and angles (ꢁ) in the experimental crystal
structures 2b and 5b
2b
5b
Si(1)–O(1)
Si(1)–O(2)
Si(1)–C(1)
Si(1)–C(2)
1.906(1)
1.979(1)
1.902(1)
1.863(1)
1.858(1)
0.87(2)
3.061(1)
3.014(1)
3.141(1)
4.047(1)
1.898(4)
2.009(4)
1.903(5)
1.859(5)
1.855(5)
0.85
3.254(4)
3.186(4)
3.284(4)
4.239(1)
It should be noted that the oxygen atom of an OEt2
group in ½Me3SiðOEt2ÞꢁþBðC6F5Þꢀ [19] has an almost pla-
4
nar configuration while in the pentacoordinated silicon
species ClSiH3OMe2 [18a] and ½NðCH2CH2OÞ3-
SiðOMe2ÞꢁþBF4ꢀ [18b], the OMe2 groups are pyramidal.
Possibly, the water moiety is also planar in the case of tetr-
acoordination at the Si atom [4a] and it is more likely to be
pyramidal when the Si atom is pentacoordinate (as in 4
[4b]). The O(2) atom in the structures 2b and 5b adopts a
pyramidal configuration. However, due to the problems
related to localization of hydrogen atoms it is difficult to
prove this statement.
Si(1)–C(3)
O(2)–H (averaged)
Hal(1)a. . .O(2)
Hal(1). . .O(2)b
Hal(1). . .N(1)c
Hal(1). . .Si(1)
O(1)–Si(1)–O(2)
169.17(2)
169.0(2)
a
Hal = Cl (2b), Hal = Br (5b).
b
Atoms are generated by symmetry operations: 1 ꢀ x, 1/2 + y, 1/2 ꢀ z.
Atoms are generated by symmetry operations: x, 1 + y, z.
c
The only structure which is similar to 2b and 5b which
can be found in the CSD [17] is the hydrochloride monohy-
drate 4 [4b]. The Si(1)–O(1) bond in 4 (1.960 A) is some-
compounds is mainly localized at the silicon atom. The
absence of information about the exact electron structure
of the organosilicon compounds with a water ligand does
˚
what longer than those in 2b (while the Si(1)–O(2) is

3968
A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
˚
˚
slightly shorter (1.911 A)). The value of DSi is 0.04 A in 4
order to investigate the chemical bonding pattern in the
axial fragment O(1)Si(1)O(2) in 2b and 5b as described
later.
˚
˚
vs. ꢀ0.02 A and ꢀ0.04 A for 2b and 5b, respectively.
Such a difference may be explained both by the different
type of five-membered chelate cycle and crystal packing
effects. Undoubtedly, crystal packing will affect the geome-
try of the silicon atom coordination centre. The hydrogen
atoms in 2b, 5b and 4 participate in the rather strong H-
bonds with halogen atoms (Table 2) so that the organosil-
icon cations [PhC(O)NHCH2SiMe2(OH2)]+ (14b) and in 4
form a three-dimensional network in the crystal. The O(2)
atom is not involved in any H-bonding and participates
only in weak van der Waals interactions. The quality of
the collected X-ray data in the case of 2b (high resolution
and collection at low temperature) allows us to locate the
position of H(20) and H(200) atoms with high accuracy.
Even in the presence of heavy bromine atom (5b) the
H(20) and H(200) atoms are localized with sufficient accu-
racy. According to CSD [17] the H2O molecules do not
forms contacts with Clꢀ for which H. . .Cl and O. . .Cl dis-
2.4.2. The stability of the [PhC(O)NHCH2SiMe2(OH2)]+
cation (14b) in the crystal and isolated state
We carried out quantum chemical calculations of crys-
tals 2b and 5b as well as on isolated cation–anion pairs
14b Æ Halꢀ (Hal = Cl, Br) using density functional theory
(DFT) with CPMD [21] code (exchange-correlation func-
tional PBE [22], plane wave basis set). The energies of the
isolated cation–anion pairs 14b Æ Halꢀ (Hal = Cl, Br) and
isolated cation 14b were also calculated using the PRIRODA
program [23] (PBE functional, cc-pVTZ basis set). For
details see the respective Section 3.
The calculated Si(1)–O(1) and Si(1)–O(2) bond lengths
(Table 3) in the crystals 2b and 5b agree with the experi-
mental values. Differences are observed in the case of 2b
where the calculated Si(1)–O(2) bond length is elongated
˚
˚
tances shorter than 1.8 and 2.9 A, respectively. We found
by 0.06 A compared to the experimental value. In 5b the
in CSD [17] approximately 500 structures where H. . .Cl
and O. . .Cl distances fall in ranges 2.0 ‚ 2.2 and
deviations between the experimental and calculated bond
lengths do not exceed 0.02 A.
˚
˚
2.9 ‚ 3.1 A. The H-bonding in structure of 2b (averaged
The calculated interatomic O(N). . .Br and H. . .Br dis-
tances in structure 5b reproduce the experimental data by
˚
distances H. . .Cl and O. . .Cl are equal 2.18 and 3.04 A) is
˚
typical for crystals of organic and organoelement com-
pounds. Thus, one may conclude the absence of proton
transfer between Clꢀ and H2O moiety in crystal of 2b.
The same conclusion holds for the structure of 5b (H. . .Br
better than 0.05 A. The calculated O. . .Cl distances are
˚
up to 0.2 A shorter than the experimental values (Tables
2 and 3). This overestimation of the strength of the H-
bonds may have an effect on the effective charge of the
O(2) atom that may result in the above-mentioned elonga-
tion of the Si(1)–O(2) bond.
˚
and O. . .Br distances are 2.38 and 3.22 A, on average). The
CSD search reveals 137 structures where H. . .Br and
˚
O. . .Br distances vary in ranges of 2.1 ‚ 2.4 and 3.0 ‚ 3.3 A.
The calculated structures of the isolated cation–anion
pairs 14b Æ Halꢀ (Hal = Br, Cl) differ considerably from
the experimental crystal structures. The H. . .Cl and H. . .Br
distances in 14b Æ Halꢀ are shortened by up to 1.37 and
It is noteworthy that the silicon atom can be coordi-
nated with other electron pair donors, such as nitriles
[20]. The silicon atom in these compounds has a tetrahedral
configuration where the bond between the silicon atom and
the nitrogen atom of the nitrile group is longer than a stan-
˚
1.56 A, which essentially means the elimination of the
H-atom from the coordinated water molecule. Such a
transformation leads to a change of geometry of the axial
fragment O(1)Si(1)O(2), i.e. the Si(1)–O(2) bond is short-
˚
dard Si–N bond [16], up to 0.15 A.
Unfortunately, our structural studies can give one only
limited information about the nature of chemical bond-
ing in the cation 14b. So, we carried out quantum chem-
ical calculations and high-resolution X-ray studies in
˚
ened by 0.2 A while the Si(1)–O(1) bond is elongated by
˚
up to 0.3 A in comparison with the corresponding values
in the crystal. The opposite distribution of bond lengths
Table 3
Calculated structural parameters of 2b and 5b
A
B
C
2b
5b
2b
5b
Si(1)–O(1)
Si(1)–O(2)
Si(1)–C(1)
Si(1)–C(2)
1.886
2.045
1.909
1.870
1.876
0.980
1.056
2.865
1.895
2.006
1.918
1.867
1.884
1.006
1.006
3.219
2.379/2.397
1.774/1.755
1.935/1.927
1.881/1.870
1.889/1.880
0.971/0.974
1.558/1.598
2.928/2.955
177.3/176.2
2.319/2.257
1.794/1.789
1.937/1.930
1.881/1.872
1.880/1.881
0.973/0.975
1.464/1.432
3.020/3.000
170.7/176.1
1.838
2.487
1.925
1.873
1.874
0.973
0.973
Si(1)–C(3)
O(2)–H(20)
O(2)–H(200)
Hal(1). . .O(2)
O(1)–Si(1)–O(2)
171.7
171.3
165.8
A, crystal; B, cation–anion pairs 14b Æ Halꢀ (Hal = Cl, Br) (CPMD/PRIRODA calculated values); C, isolated cation [PhC(O)NHCH2SiMe2(OH2)]+ (16b).

A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
3969
in the axial fragment O(1)Si(1)O(2) is observed in the iso-
lated cation 14b. The Si(1)–O(2) is very long (2.49 A) so
analysis of q(r) and the lattice energy calculation allow us
to provide a good description of the chemical bonding pat-
tern in 2b and 5b.
˚
one may assume that a coordinated water molecule can
be easily eliminated from the silicon coordination sphere.
To confirm our assumption we calculated the energies of
decomposition of the cation–anion pairs 14b Æ Halꢀ into
the silanol PhC(O)NHCH2SiMe2OH (15b) and HHal, as
well as the energy of decomposition of the cation 14b into
2.4.3. Chemical bonding in cation 14b
Qualitative analysis of the chemical bonding of 2b and
5b on the basis of the deformation electron density
(DED) has demonstrated the presence of two maxima in
PhCðOÞNHCH2SiMeþ (16b) and H2O. The calculated val-
the q(r) (0.4 e A ) localized at 0.45 A from the oxygen
atoms along the OSiO line. The maximum in the q(r) cor-
responds to the lone pair of the O(2) atom which is local-
ized at the vertex of the imaginary tetrahedra constructed
from the Si(1)–O(2), O(2)–H(20) and O(2)–H(200) bonds,
while the maximum corresponding to the lone pair of the
O(1) atom is localized along the line C(1)O(1). The distri-
bution of DED in region of O(2)–H(200). . .Cl(1) intermolec-
ular bond supports the conclusion about absence of proton
transfer between Clꢀ and H2O moiety (Fig. 3).
ꢀ3
˚
˚
2
ues are 6.43 and 7.74 kcal/mol for the cation–anion pairs
14b Æ Halꢀ (Hal = Cl, Br) and 7.99 kcal/mol for cation
14b, respectively. Thus, the quantum chemical calculations
allowed us to conclude that cation 14b is only stable in the
crystalline state.
The calculations of the lattice energies are useful to esti-
mate the effect of crystal packing on the geometry of the
cation 14b. The lattice energy was determined as the differ-
ence between the energy of the full crystal and the energy of
the formula unit (obtained separately by a single point
energy calculation, its geometry extracted from the unit
cell) multiplied by the number of formula units. The values
of the lattice energy are 24.75 and 20.43 kcal/mol for 2b
and 5b, respectively. However, the difference between the
energy of the full crystal and the energy corresponding to
the optimized ionic pairs 14b Æ Halꢀ multiplied by number
of formula units was 9.92 and 7.12 kcal/mol, respectively.
The discrepancies between the two sets of lattice energies
may reflect the strengthening of the H. . .Hal bonds by up
to 13–14 kcal/mol in the crystalline state compared to the
isolated state.
However, the values of the lattice energy may be only
used as a rough guide to show the influence of the crystal
packing on the structure of cation 14b. The contribution
of each of the intermolecular interactions in the crystal
and the energy of the coordinative O ! Si bonds can be
estimated from a topological analysis of the experimental
and calculated electron density distribution functions
(q(r)). The comparison of the results from the topological
It should be noted that the observed distribution of
DED is similar to that observed in the acetylhydrazine
derivative 17 [24]. On the basis of an experimental study
of q(r) we showed that the chemical bonding pattern in
the axial fragment OSiO of the above compound corre-
sponds to a similar (3c–4e) bond. Based on the similar
distribution of DED functions one may propose the
presence of a three centre one electron bond in 2b and
5b
Me
Me
CF3
C
N
N
F
Ph
C
F
O
N
Si
O
O
N
CH3
CH3
CH3
CH2 Si
C
Ph
CH3
N
Me
N
Cl
Me
17
18
Fig. 3. Multipole static DED maps for the compounds 2b in O(1)–Si(1)–C(1) (left) and O(2)–Cl(1)–H(200) planes (right). Isolines are drawn through
0.1 e Aꢀ3, negative contours are dashed.
˚

3970
A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
Table 4
Topological characteristics of the electron density distribution in cation [PhC(O)NHCH2SiMe2(OH2)]+ (16b)
Experiment
CPMD/ABINIT calculation
q(r)
$2q(r)
E(r)
q(r)
$2q(r)
E(r)
2b
2b
2b
2b
5b
2b
5b
2b
5b
Si(1)–O(1)
Si(1)–O(2)
Si(1)–C(1)
Si(1)–C(2)
Si(1)–C(3)
0.55
0.42
0.89
0.89
0.89
3.86
3.43
ꢀ2.85
ꢀ2.11
ꢀ0.88
ꢀ0.20
ꢀ0.11
ꢀ0.73
ꢀ0.73
ꢀ0.69
0.43
0.40
0.84
0.89
0.89
0.56
0.43
0.82
0.87
0.89
3.25
2.32
0.46
2.05
1.45
6.95
3.25
1.22
1.27
1.74
ꢀ0.11
ꢀ0.07
ꢀ0.75
ꢀ0.74
ꢀ0.70
ꢀ0.12
ꢀ0.06
ꢀ0.74
ꢀ0.74
ꢀ0.70
A more detailed description of the chemical bonding
was obtained by a topological analysis of the electron den-
sity distribution functions in terms of Bader’s ‘‘Atom in
molecules’’ (AIM) theory2 [25]. The usage of this approach
allowed us to investigate the chemical bonding pattern in
silatranes and monochelate compounds which contain the
pentacoordinated silicon atom [26]. The CPs (3, ꢀ1) are
located at all chemical bonds including Si(1)–O(1) and
Si(1)–O(2). Also the CP (3,ꢀ1) corresponding to the
O(N)-H. . .Hal bonds have also been found (Table 4). The
character sets of the CPs satisfied the Poincarre–Hopf
equation [25].
Si(1)–O(2) bond dissociation in the isolated cation 14b is
7.99 kcal/mol. So, we may conclude that the Si(1)–O(2)
bond in 2b and 5b is approximately 12 kcal/mol stronger
than in the isolated cation 14b.
Based on the proposal that the overall bond order of the
axial Si(1)–O(1) and Si(1)–O(2) bonds is constant one may
propose that in the isolated cation 14b the Si(1)–O(1) bond
is approximately 12 kcal/mol stronger than in the crystal.
The estimation of the Si(1)–O(1) and Si(1)–O(2) bond
strengths according to AIM theory is in agreement with
that based on the density matrix diagonalization procedure
[27].
The C–C, N–C and O–C bonds are characterized by
negative values of the Laplacian of the electron density
($2q(r)) and negative values of the local energy density
(Ee(r)) in CP (3, ꢀ1). These bonds may be described as
shared interactions in terms of AIM theory. On the con-
trary, at the CP (3, ꢀ1) of the Si(1)–O(1) and Si(1)–O(2)
bonds, positive values of the $2q(r) are observed. The val-
ues of the Ee(r) for these bonds still have a negative sign
and the magnitudes of the q(r) at CP’s (3, ꢀ1) are large.
Thus, according to the AIM theory [25] the axial Si(1)–
O(1) and Si(1)–O(2) bonds in 2b and 5b are classified as
an intermediate type of interatomic interactions.
The advantage of using the AIM theory is the possibility
of estimating the strength of the Si(1)–O(1) and Si(1)–O(2)
bonds based on the correlation between the potential
energy density in CP (3, ꢀ1) and the energy of the inter-
atomic interaction. The estimated values are 19.2 and
21.84 kcal/mol for the Si(1)–O(2) bonds in the 2b and 5b,
respectively. A similar calculation for the Si(1)–O(1) bonds
in 2b and 5b gave us values of 37.66 and 35.81 kcal/mol
which significantly exceed the magnitudes of the Si(1)–
O(2) bond. It should be noted that the energy of the
Important information about the chemical bonding in
the axial fragment O(1)Si(1)O(2) may be obtained from
analysis of the AIM charges on the Si and O atoms. A pre-
vious computational study [14b] of the classic species with
3c–4e bonds such as H3ꢀ, FHFꢀ, ClHClꢀ showed that the
charges of the terminal atoms are noticeably lower com-
pared to diatomic molecules (HCl, HF). On the contrary,
the positive charge of the central atom is increased com-
pared to HCl and HF. In turn, in the SiFꢀ5 anion and the
molecule PF5 where the central atom has an ideal TBP con-
figuration the charges of the Si and P atoms have large
positive values (3.85 and 3.56 e). The corresponding value
for the hexacoordinated Si atom in 18 (3.23 e) [14a] is only
slightly lower than that in SiFꢀ5 .
In 2b the charge on the Si atom (1.84 e) is significantly
decreased while the charges of the O(1) and O(2) atoms
are increased in comparison with other compounds con-
taining a hexacoordinated Si atom [14a]. Analysis of the
AIM charges verifies the formation of 3c–4e bonds in 2b
and 5b. The magnitude of the negative charge of the O(2)
atom (ꢀ1.14 e) is slightly increased compared with that
of the O(1) atom (ꢀ1.06 e). So, the description of the
O(2) atom as an oxonium ion is only a formal description
since the main positive charge is localized at the Si(1)
atom.
2
According to this theory the existence of interatomic interaction
indicated by presence of critical point (CP) (3, ꢀ1); that is, a saddle point
in electron density distribution function between two atoms. For analysis
of type and energy of interatomic interactions the values of three
parameters in CP (3, ꢀ1) are important: the q(r), the Laplacian of q(r)
($2q(r)) and the local energy density Ee(r). Two latter characteristics show
the contribution of kinetic and potential energy in interatomic interaction.
If contribution of potential energy in CP (3, ꢀ1) dominates over kinetic
one ($2q(r) and Ee(r) < 0) than interatomic interaction corresponds to
covalent bond (shared interaction). In case when contribution of kinetic
energy dominates over potential one ($2q(r) and Ee(r) > 0) the interatomic
interaction have pronounced ionic character.
H
H
H
H
Si
O
Si
O
Thus, the cation 14b containing a pentacoordinate sili-
con atom in the crystals 2b and 5b should be considered
as a silylium cation stabilized by a coordinated H2O mole-
cule rather than as a silyloxonium ion.

A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
3971
Table 5
3. Experimental
Crystallographic parameters for the compounds 2b and 5b
2b 5b
C10H16ClNO2Si C10H16BrNO2Si
IR spectra were recorded in tablets pressed with KBr
(1 mg/200 mg KBr), in suspensions of compounds in a
liquid paraffin on CaF2 laminas, in organic solvents in
KBr cells, and in a film between KBr laminas for liquid sub-
stances using Specord IR-75, M80, and M82 instruments.
The 1H, 13C, and 29Si NMR spectra of solutions in
CDCl3 and (CD3)2C(O) were measured on Varian XL-400
spectrometer operating at 400.0, 100.6 and 79.5 MHz,
respectively, with Me4Si as the internal standard.
X-ray diffraction measurements for 2b and 5b were car-
ried out with a Syntex P21 four-circle diffractometer. Struc-
tures were solved by direct methods and non-hydrogen
atoms were refined in full-matrix anisotropic approxima-
tion. The hydrogen atoms were located from differential
Fourier synthesis of the electron density and refined iso-
tropically (the exception is 5b in which H atoms refined
using rigid body model). All calculations were carried out
using the SHELXTL 5.1 program package [28]. Details of
crystallographic data and experimental condition are pre-
sented in Table 5.
Molecular formula
Formula weight
Temperature (K)
245.78
173(2)
290.24
173(2)
˚
a (A)
9.9334(4)
6.9815(3)
18.0828(7)
90
104.780(1)
90
1212.55(9)
P21/c, 4
90
10.037(5)
7.050(3)
18.579(8)
90
103.84(4)
90
1276.5(10)
P21/c, 4
52
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Space group, Z
2hmax (ꢁ)
Scan type
H/2H
H/2H
Reflections collected
Number of independent
46,226
9479 (0.072)
2578
2433 (0.044)
reflections (Rint
)
Number of reflections with I > 2r(I) 7299
2172
Parameters
200
3.93
None
138
33.0
Linear absorbtion (cmꢀ1
Absorbtion correction
Tmin/Tmax
)
W-scan
0.848/0.848
0.958
0.0612
0.1278
Goodness-of-fit
R1 [I > 2r(I)]
wR2 (all reflections)
0.991
0.036
0.106
The analytical form of the experimental electron density
was obtained by a multipole refinement of 2b based on the
Hansen–Coppens [29] formalism using the XD program
package [30]. C–H, N–H and O–H bonds were normalized
˚
PRIRODA [23] program have been applied for the quan-
tum chemistry calculations of isolated ionic pairs
14b Æ Halꢀ (Hal = Cl, Br) and cation 14b using cc-pVTZ
basis set. All calculated structures are in the local minima
of their respective potential energy surfaces that have been
proved by vibrational analysis. The values of dissociation
energies include zero-point corrections.
at 1.07, 1.00 and 0.96 A according to neutron diffraction
data [16]. The level of the multipole expansion was hexadeca-
pole for the Si, O, N, Cl atoms and dipole for hydrogens. In
the case of C(1) and C(2) atoms for the refinement of values
of multipole expansion population coefficients of the local
symmetry m were used. The scattering factor of the hydrogen
atoms was calculated from the contracted radial density
functions (j = 1.2). The ratio of the number of reflections
to the number of refined parameters was more than 20.
The quantum chemical calculations of the crystal struc-
tures 2b and 5b and the isolated ionic pairs 14b Æ Halꢀ
(Hal = Cl, Br) have been carried out in terms of density
functional theory (exchange-correlation functional PBE
[22]) utilising CPMD code [21]. Vanderbilt’s ultrasoft
pseudopotentials [31] have been applied to account for core
electrons while valence electrons were approximated by
plane-wave expansion with 25 Ry cutoff. The experimental
structures of 2b and 5b were taken as starting points in
geometry optimization procedure while cell parameters
were fixed at the experimental values. The isolated ionic
pairs 14b Æ Halꢀ (Hal = Cl, Br) were calculated in cubic cell
Syntheses of the initial N-trimethylsilylacetamide and N-
trimethylsilylbenzamide were reported earlier [34].
3.1. (O ! Si)-chelate
N-(dimethylchlorosilylmethyl)acetamide (6a)
(a) ClCH2SiMe2Cl (28.6 g, 0.2 mol) was added dropwise
to
a solution of acetamide (11.8 g, 0.2 mol) and
(Me3Si)2NH (12.9 g, 0.08 mol) in 100 ml of C6H6. The
reaction mixture was refluxed for 1 h, the precipitate was
filtered out, and the solvent was removed in vacuo. Double
fractionation of the residue yielded 7.45 g (23%) of chloride
6a, b.p. 156–158 ꢁC (8 mm Hg), m.p. 87–90 ꢁC (benzene)
(cf. [2a]). IR spectrum (C6H6, m, cmꢀ1): 1635, 1540
1
˚
(NCO). H NMR (CDCl3, d, ppm): 0.56 (6H, s, Me2Si);
with side length 15 A.
2.16 (3H, br. s, CH3); 2.79 (2H, br. s, NCH2). 13C NMR
(CDCl3, d, ppm): 23.06 (Me); 0.99 (SiMe2); 33.50 (CH2);
175.43 (C@O). 29Si NMR (CDCl3, d, ppm): ꢀ27.4 s. Anal.
Found (%): C, 36.92; H, 6.96. C5H12NOSiCl. Calc. (%): C,
36.22; H, 7.30.
Topological analysis of electron density of hydrohalides
2b and 5b have been carried out using ABINIT program suite
[32] for the crystal structures optimized by the CPMD
code. Electron density function of core electron was pre-
computed whereas valence part of electron density function
was described by plane-wave with 100 Ry cutoff using PBE
exchange-correlation functional. The energy of Si–O bonds
was estimated according to formalism by Espinosa Mollins
and Lecomte [33].
(b) Thionyl chloride (1.79 g, 15 mmol) was added drop-
wise to a solution of disiloxane 8a (2.2 g, 7.96 mmol) in
benzene (5 ml). The reaction mixture was distilled to yield
2.0 g (76%) of chloride 6a, b.p. 161–163 ꢁC (10 mm Hg).

3972
A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
(c) Chloro(chloromethyl)dimethylsilane (17.04 g, 0.12
layer was removed and the aqueous layer was extracted by
CHCl3 (20 ml). The volatiles from combined organic layers
were removed in vacuo. H NMR spectra of the residue
indicated the presence of disilamorpholine 9a and disilox-
ane 8a in 1:0.87 ratio.
mol) was added dropwise to a solution of N-trimethylsily-
lacetamide (13.1 g, 0.10 mol) in n-xylene (50 ml). The reac-
tion mixture was heated for 0.5 h at 110 ꢁC and the solvent
was removed in vacuo. The residue was distilled to yield
6.25 g (66%) of chloride 6a, b.p. 163–170 ꢁC (12 mm Hg).
(d) The mixture of N-trimethylsilylacetamide (24 g,
0.18 mol) and ClCH2SiMe2Cl (28.6 g, 0.2 mol) was heated
to remove Me3SiCl (18.5 g, 94%, b.p. 58–59 ꢁC). Distilla-
tion of the residue yielded 20.1 g (67%) of chloride 6a,
b.p. 164–167 ꢁC (10 mm Hg).
1
3.5. Reaction of acetamide with (Me3Si)2NH and
ClCH2SiMe2Cl with the subsequent hydrolysis of the
reaction mixture
The mixture of acetamide (30 g, 0.5 mol), (Me3Si)2NH
(16.1 g, 0.1 mol) and catalytic amount of Me3SiCl was
refluxed for 1.5 h. The remaining (Me3Si)2NH was
removed in vacuo, and ClCH2SiMe2Cl (71 g, 0.5 mol)
was added to the residue. The reaction mixture was
refluxed to remove Me3SiCl (71%, b.p. 58–90 ꢁC). The res-
idue was cooled down, dissolved in CHCl3 (150 ml) and
stirred with a solution of NaHCO3 (45 g) in water
(200 ml). The organic layer was removed and the aqueous
layer was extracted by CHCl3 (150 ml). The volatiles from
combined organic layers were removed in vacuo. Disil-
amorpholine 9a (28.6 g, 0.13 mol), b.p. 124–127 ꢁC
(10 mm Hg), m.p. 36–40 ꢁC [6a] and disiloxane 8a
(22.9 g, 83 mmol), b.p. 230–234 ꢁC (10 mm Hg), nD20
1.4680 (ratio 1:0.64) were obtained by distillation of the
residue. IR spectrum (CHCl3, m/cmꢀ1): 1640 (amide I,
3.2. Reaction of acetamide with (Me3Si)2NH and
ClCH2SiMe2Cl (1:1:1) with subsequent hydrolysis of the
reaction mixture
ClCH2SiMe2Cl (5.68 g, 40 mmol) was added dropwise
a solution of acetamide (2.36 g, 40 mmol) and
to
(Me3Si)2NH (6.5 g, 40 mmol) in benzene (50 ml) and
refluxed for 1 h. The reaction mixture was cooled down,
the precipitate was filtered out, and the solvent was
removed in vacuo. CHCl3 (30 ml) was added to the residue
after solvent removing. The residue was treated with
CHCl3 (30 ml) and a solution of NaHCO3 (1.67 g) in water
(20 ml). The organic layer was removed and the aqueous
layer was extracted by CHCl3 (20 ml). The volatiles from
combined organic layers were removed in vacuo. 1H
NMR spectra of the residue indicated the presence of dis-
ilamorpholine 9a and disiloxane 8a in 1:0.54 ratio.
m
C@O), 1520 (amide II, dNH).
3.6. (O ! Si)-chelate N-
(dimethylchlorosilylmethyl)benzamide (6b)
3.3. Reaction of acetamide with ClCH2SiMe2Cl and Et3N
(1:1:1) with subsequent hydrolysis of the reaction mixture
(a) Thionyl chloride (1.64 g, 14 mmol) was added drop-
wise to a solution of disiloxane 8b in benzene (10 ml). The
residue was filtered to yield 1.9 g (84%) of chloride 7b, m.p.
92–95 ꢁC (C6H6). IR spectrum (dioxane), m/cmꢀ1: 1618,
ClCH2SiMe2Cl (5.68 g, 40 mmol) was added dropwise
to a solution of acetamide (2.36 g, 40 mmol) and Et3N
(4.05 g, 40 mmol) in benzene (50 ml). The reaction mixture
was refluxed for 1 h, then cooled down and filtered. The
volatiles from the filtrate were removed in vacuo. The res-
idue was treated with CHCl3 (30 ml) and a solution of
NaHCO3 (1.67 g) in water (20 ml). The organic layer was
removed and the aqueous layer was extracted by CHCl3
(20 ml). The volatiles from combined organic layers were
1
1520 (NCO). H NMR [(CD3)2C(O), d, ppm J/Hz]: 0.51
(6H, br. s, SiMe2); 2.87 (2H, br. s, CH2); 7.96 (d,
3
3
3JHH = 7.3), 7.63 (t, JHH = 7.3), 7.50 (t, JHH = 7.3), 5H,
C6H5; 6.7 (1H, br. s, NH). 13C NMR [(CD3)2C(O), d,
ppm]: 34.44 (CH2), 129.66 (C-ortho), 128.46 (C-meta),
129.52 (C-para), 133.38 (C-ipsi), C6H5. The NMR signals
of SiMe2 and C@O groups at room temperature were not
observed due to broadening. 29Si NMR [(CD3)2C(O), d,
ppm]: ꢀ26.5 (br. s). Anal. Found (%): C, 52.48; H, 6.50; N,
5.89. C10H14ClNOSi. Calc. (%): C, 52.73; H, 6.20; N,
6.15.
1
removed in vacuo. H NMR spectra of the residue indi-
cated the presence of disilamorpholine 9a and disiloxane
8a in 1:0.97 ratio.
3.4. Reaction of acetamide with (Me3Si)2NH and
ClCH2SiMe2Cl (1:0.4:1) with subsequent hydrolysis of the
reaction mixture
(b) A mixture of N-trimethylsilylbenzamide (5.0 g,
0.026 mol) and ClCH2SiMe2Cl (3.65 g, 0.02 mol) was
refluxed to remove Me3SiCl (2.4 g, 85%, b.p. 57–59 ꢁC).
The residue was treated with hexane (15 ml) to produce
5.2 g (88%) of chloride 7b, m.p. 90–93 ꢁC (hexane).
ClCH2SiMe2Cl (5.68 g, 40 mmol) was added dropwise
to
a solution of acetamide (2.36 g, 40 mmol) and
(Me3Si)2NH (2.6 g, 16 mmol) in benzene (50 ml). The reac-
tion mixture was refluxed for 1 h, then cooled down and fil-
tered. The volatiles from the filtrate were removed in
vacuo. The residue was treated with CHCl3 (30 ml) and a
solution of NaHCO3 (1.67 g) in water (20 ml). The organic
3.7. 1,1,3,3-Tetramethyl-1,3-bis(acetamidomethyl)-1,3-
disiloxane (8a)
(a) A solution of chloride 6a (9.8 g, 0.059 mol) in CHCl3
(25 ml) was stirred with solution of NaHCO3 (5 g) in water

A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
3973
(30 ml). The organic layer was removed and the water layer
was extracted by CHCl3 (20 ml). Distillation of combined
organic layers produced 7.65 g (84%) of disiloxane 8a,
b.p. 228–230 ꢁC (7 mm Hg), n2D0 1.4680. IR spectrum
(CHCl3), m/cmꢀ1: 1640 (amide I, mC@O), 1520 (amide II,
the water layer was extracted by CHCl3 (3 ml). The solvent
from combined organic extracts was removed in vacuo and
benzene (2 ml) was added to the residue. The crystals
formed were isolated to yield disiloxane 8b (0.26 g. 93%),
m.p. 120.5–121 ꢁC (benzene).
d
NH). 1H NMR (CDCl3, d, ppm, J/Hz): 1.98 (6H, s,
2Me); 0.08 (6H, s, 2SiMe2); 2.65 (4H, 2CH2); 6.9 (2H, br.
s, 2NH). 13C NMR (CDCl3, d, ppm): 22.56 (Me); 0.71
(SiMe2); 31.00 (CH2); 170.63 (C@O). 29Si NMR (CDCl3,
d, ppm): 4.47 s. Anal. Found (%): C, 43.18; H, 8.84; N,
9.98. C10H24N2O3Si2. Calc. (%): C, 43.44; H, 8.75; N,
10.13.
(b) A mixture of N-trimethylsilylacetamide (33.6 g,
0.25 mol) and ClCH2SiMe2Cl (35.5 g, 0.25 mol) was
refluxed to remove of Me3SiCl (21.75 g, 76%, b.p. 57–
59 ꢁC). The residue was dissolved in CHCl3 (150 ml) and
stirred for 1 h with a solution of NaHCO3 (22.5 g) in water
(150 ml). The organic layer was removed and the aqueous
layer was extracted by CHCl3 (100 ml). Disiloxane 8a
(5.0 g, 43%) was obtained by distillation of combined
organic extracts; b.p. 234–236 ꢁC (7 mm Hg), n2D0 1.4680.
3.9. (O ! Si)-chelate dimethyl(acetamidomethyl)silanole
hydrochloride (2a)
Thionyl chloride (2.6 g, 22 mmol) was added to a solu-
tion of disiloxane 9a (3.05 g, 11 mmol) in heptane
(20 ml). On the next day hydrochloride 2a (3.25 g, 80%)
was isolated by filtration; m.p. 92–96 ꢁC (heptane). 1H
NMR (d, ppm, CD3CN): 0.24 (6H, s, SiMe2); 2.26 (3H,
s, Me); 2.85 (2H, s, CH2); 5.21 (3H, br. s, OH2, NH). 13C
NMR (CD3CN, d, ppm): 20.03 (Me); ꢀ2.62 (SiMe2);
34.45 (CH2); 175.18 (C@O). 29Si NMR (CDCl3, d, ppm):
4.70 s. Anal. Found (%): C, 32.68; H, 7.49; N, 7.57.
C5H14ClNO2Si. Calc. (%): C, 32.68; H, 7.68; N, 7.62.
Hydrochloride 2a is highly hydroscopic which makes it
impossible to obtain an informative IR spectrum. The
spectrum appears significantly distorted due to the pres-
ence of absorptions of water at various frequencies.
3.8. 1,1,3,3-Tetramethyl-1,3-bis(benzamidomethyl)-1,3-
disiloxane (8b)
3.10. (O ! Si)-chelate dimethyl(benzamidomethyl)silanole
(2b) hydrochloride
(a) Suspension of chloride 6b (5.2 g, 23 mmol) in CHCl3
(20 ml) was treated with a solution of NaHCO3 (2 g) in
water (25 ml). The organic layer was removed and the
water layer was extracted by CHCl3 (25 ml). The solvent
from combined organic extracts was removed in vacuo
and the C6H6 (15 ml) was added to the residue. On the
next day crystals of disiloxane 8b (2.65 g, 58%), m.p.
119–121 ꢁC (benzene) were formed. IR spectrum (tablet
(a) N-(dimethylchlorosilylmethyl)benzamide 6b (0.45 g)
was exposed to air for 8 months. Compound 2b (0.39 g,
80%), m.p. 124–127 ꢁC (CH3CN) was obtained by re-crys-
tallization from CH3CN. IR spectrum (CaF2, vaseline oil),
1
m/cmꢀ1: 1612, 1521 (NCO), 1581 (Ph). H NMR (CD3CN,
d, ppm): 0.44 (6H, s, SiMe2); 2.91 (2H, s, CH2); 7.88 (d,
3
3
with KBr), m/cmꢀ1: 3350, 3310 (mNH), 1635 (amide I,
3JHH = 7.3), 7.65 (t, JHH = 7.3), 7.57 (t, JHH = 7.3), 5H,
C6H5; 8.09 (3H, br. s, OH2, NH). Anal. Found (%): C,
48.59; H, 6.33; N, 5.36. C10H16ClNO2Si. Calc. (%): C,
48.87; H, 6.56; N, 5.70. A single crystal of 6b for X-ray dif-
fraction study was obtained from CH3CN.
1
m
C@O), 1545 (amide II, dNH). H NMR (CDCl3, d, ppm,
J/Hz): 0.16 (6H, br. s, 2SiMe2); 2.87 (4H, s, 2CH2); 7.78
3
3
3
(d, JHH = 7.7), 7.32 (t, JHH = 7.7), 7.42 (t, JHH = 7.7),
10H, 2C6H5; 7.15 (br. s, 2 NH). 13C NMR (CDCl3, d,
ppm): ꢀ0.32 (SiMe2); 31.93 (CH2); 128.37 (C-ortho),
127.38 (C-meta), 126.99 (C-para), 134.79 (C-ipso), C6H5;
167.89 (C@O). 29Si NMR (CDCl3, d, ppm): 4.70 s. Anal.
Found (%): C, 60.24; H, 6.94; N, 7.00. C20H28N2O3Si2.
Calc. (%): C, 59.96; H, 7.04; N, 6.99.
(b) Chloride 6b (0.5 g, 2.2 mmol) was added to a mixture
CH3CN (5 ml) and water (18 mg, 1.1 mmol). The reaction
mixture was refluxed for several hours. The crystals formed
were isolated by filtration to produce hydrochloride 2b
(0.5 g, 93%), m.p. 124–125 ꢁC (Me3CN). Anal. Found
(%): C, 48.97; H, 6.63; N, 5.64. C10H16ClNO2Si. Calc.
(%): C, 48.87; H, 6.56; N, 5.70.
(c) Disiloxane 8b (1.0 g, 2.5 mmol) was added to a solu-
tion of CH3CN (22 ml) and thionyl chloride (0.6 g,
5.0 mmol) in water (0.09 g, 5.0 mmol). The reaction mix-
ture was heated to 90 ꢁC. The crystals formed were filtered
and dried in vacuo. Two types of crystals were obtained:
chloride 6b (m.p. 92–94 ꢁC) and hydrochloride 2b (124–
125 ꢁC). The latter was isolated from the mixture by re-
crystallization from CH3CN, yield 1.15 g (94%), m.p.
124–125 ꢁC (Me3CN). IR spectrum (tablet with KBr), m/
cmꢀ1: 1615 (s), 1520 (s) (NCO). Anal. Found (%): C,
48.87; H, 6.63; N, 5.65. C10H16ClNO2Si. Calc. (%): C,
48.87; H, 6.56; N, 5.70.
(b) A mixture of N-trimethylsilylbenzamide (10.1 g,
0.05 mol) and ClCH2SiMe2Cl (7.4 g, 0.05 mol) was
refluxed to remove Me3SiCl (5.22 g, 91%, b.p. 57–59 ꢁC),
then CHCl3 (50 ml) was added and the reaction mixture
was stirred with solution of NaHCO3 (4.5 g) in water
(30 ml). The organic layer was removed and the water layer
was extracted by CHCl3 (20 ml). The solvent from com-
bined organic layers was removed in vacuo. Benzene
(20 ml) was added to the residue, and the crystals formed
were isolated to yield disiloxane 8b (7.55 g, 75%), m.p.
119–121 ꢁC (benzene).
(c) A mixture of hydrochloride 2b (0.35 g, 1.4 mmol)
and CHCl3 (5 ml) was treated with a solution of NaHCO3
(0.12 g) in water (3 ml). The organic layer was removed and

3974
A.A. Korlyukov et al. / Journal of Organometallic Chemistry 691 (2006) 3962–3975
(b) A.G. Shipov, E.P. Kramarova, E.A. Mamaeva, O.A. Zam-
yshlyaeva, Vad.V. Negrebetsky, Yu.E. Ovchinnikov, S.A. Pogoz-
hikh, A.R. Bassindale, P.G. Taylor, J. Organomet. Chem. 620
(2001) 139.
3.11. (O ! Si)-chelate dimethyl(benzamidomethyl)silanol
hydrobromide (5b)
Me3SiBr (0.92 g, 6.0 mmol) was added dropwise to a
suspension of disiloxane 8b (1.2 g, 3 mmol) in benzene
(5 ml). The reaction mixture was stirred for 1 h. The resi-
due formed (1.55 g) was filtered and exposed to the air
for 11 months. Hydrobromine 5b (1.05 g, 60%) was
obtained by re-crystallization from CH3CN, m.p. 123–
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125 ꢁC (CH3CN). IR spectrum (tablet with KBr), m/cmꢀ1
1612 (s), 1520 (s) (NCO). Anal. Found (%): C, 41.13; H,
5.47; N, 4.68. C10H16BrNO2Si. Calc. (%): C, 41.38; H,
5.56; N, 4.83.
Single crystals for X-ray diffraction study were obtained
from CH3CN.
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Acknowledgements
The work was supported by RFBR (Grant Nos. 02-03-
335, 03-03-32214, 04-03-32557, 04-03-32371, 05-03-32964),
INTAS-RFBR (Grant 95-0070) and INTAS (Grant 03-51-
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Appendix A. Supplementary data
CCDC (refcodes 293721 and 293722) contain supple-
mentary crystallographic data for this paper. These data
can be obtained free of charge at www.ccdc.acm.ac.uk/
retrieving.html or from the Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge, CB2 1EZ,
UK (fax: +44 1223 336 033), e-mail: deposit@ccdc.cam.
ac.uk. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/
j.jorganchem.2006.05.047.
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