Reactions of 1-(3′-Amino)- and 1-(3′-acetamido) propylsilatranes with cobalt(II) chloride and dicobalt octacarbonyl

Article abstract of DOI:10.1023/A:1021686313063

1-(3′-Amino)propylsilatrane (I) and 1-(3′-acetamido) propylsilatrane (II) react with anhydrous cobalt(II) chloride to give dichlorobis[1-(3′-amino)propylsilatrane]cobalt(II) {Co[NH ₂CH₂CH₂CH₂Si(OCH₂CH ₂)₃N]₂Cl₂} (III) and dichlorobis[1-(3′-acetamido)propylsuatrane]cobalt(II) {Co[CH ₃C(O)NHCH₂CH₂CH₂Si(OCH ₂CH₂)₃N]₂Cl₂} (IV). Being unstable, compound IV transforms into an imidic acid derivative. Reactions of silatranes I and II with dicobalt octacarbonyl afford hexakis[1-(3′-aminoamido)propylsilatrane]cobalt(II) bis(tetracarbonylcobaltate) {Co[NH₂CH₂CH ₂CH₂Si(OCH₂CH₂)₃N] _4.8[HC(O)NHCH₂CH₂CH₂Si(OCH ₂CH₂)₃N]_1.2} [Co(CO) ₄]₂ (V) and hexakis[1-(3′-acetamido)propylsilatrane] cobalt(II) bis(tetracarbonylcobaltate) {Co[CH₃C(O)NHCH ₂CH₂CH₂Si(OCH₂CH₂X ₃N]₆) [Co(CO)₄]₂ (VI), respectively. In acetonitrile, tetracarbonylcobaltate anions of compound VI are oxidized with atmospheric oxygen and moisture to cobalt hydroxocarbonate, giving a carbonate gel (VII).

Full text of DOI:10.1023/A:1021686313063

Russian Journal of Coordination Chemistry, Vol. 28, No. 12, 2002, pp. 856–863. Translated from Koordinatsionnaya Khimiya, Vol. 28, No. 12, 2002, pp. 915–922.
Original Russian Text Copyright © 2002 by Semenov, Cherepennikova, Khorshev, Mushtina, Lopatin, Domrachev.
Reactions of 1-(3'-Amino)- and 1-(3'-Acetamido)propylsilatranes
with Cobalt(II) Chloride and Dicobalt Octacarbonyl
V. V. Semenov, N. F. Cherepennikova, S. Ya. Khorshev, T. G. Mushtina,
M. A. Lopatin, and G. A. Domrachev
Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
ul. Tropinina 49, Nizhnii Novgorod, 603950 Russia
Received March 21, 2001
Abstract—1-(3'-Amino)propylsilatrane (I) and 1-(3'-acetamido)propylsilatrane (II) react with anhydrous cobalt(II)
chloride to give dichlorobis[1-(3'-amino)propylsilatrane]cobalt(II) {Co[NH2CH2CH2CH2Si(OCH2CH2)3N]2Cl2}
(III) and dichlorobis[1-(3'-acetamido)propylsilatrane]cobalt(II) {Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]2Cl2}
(IV). Being unstable, compound IV transforms into an imidic acid derivative. Reactions of silatranes I and II
with dicobalt octacarbonyl afford hexakis[1-(3'-aminoamido)propylsilatrane]cobalt(II) bis(tetracarbonylcobal-
tate) {Co[NH2CH2CH2CH2Si(OCH2CH2)3N]4.8[HC(O)NHCH2CH2CH2Si(OCH2CH2)3N]1.2}[Co(CO)4]2 (V)
and
hexakis[1-(3'-acetamido)propylsilatrane]cobalt(II)
bis(tetracarbonylcobaltate)
{Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]6}[Co(CO)4]2 (VI), respectively. In acetonitrile, tetracarbon-
ylcobaltate anions of compound VI are oxidized with atmospheric oxygen and moisture to cobalt hydroxocar-
bonate, giving a carbonate gel (VII).
Molecules
NH2CH2CH2CH2Si(OCH2CH2)3N (I) and 1-(3'-acet- complexes. Earlier [11, 12], we found that CoCl2 and
amido)propylsilatrane Co2(CO)8 react with the functionalized organosilicon
of
1-(3'-amino)propylsilatrane amines afford both tetra- and hexacoordinated Co(II)
CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N (II) contain amine NH2CH2CH2CH2Si(OEt)3 to give tetrahedral
two (I) or three (II) atoms capable of coordination [1, [Co(NH2R)2Cl2] and octahedral [Co(NH2R)6][Co(CO)4]2
2]. It is believed [3–5] that the lone electron pair of the complexes, respectively (R = CH2CH2CH2Si(OEt)3).
silatranyl N atom is directed toward the interior of the These complexes are used as the starting substances for
silatrane cage to form a transannular N–Si bond. As a preparation of gels and films.
result, the basicity of the N atom decreases substan-
tially, while the electron-donating effect of the
−Si(OCH2CH2)3N group increases several times (σI =
−0.56) as compared to that of –Si(OEt)3 group (σI =
−0.13) [6–8]. It can be expected that amino or amido
silatranes will be coordinated by transition metals only
through the NH2CH2– or CH3C(O)NH– fragments.
In this study, we investigated reactions of silatranes
I and II with cobalt(II) chloride and dicobalt octacar-
bonyl Co2(CO)8. With amines, CoCl2 usually forms tet-
racoordinated complexes [Co(NH2R)2Cl2] [9]. Under
similar conditions, Co2(CO)8 undergoes disproportion-
ation [10] (one third of the cobalt atoms is oxidized to
Co(II), while the remaining two thirds give a
[Co(CO)4]– anion):
Oxygen absorption and the low- and high-tempera-
ture oxidation of Co(II) complexes with 3-aminopro-
pyl(triethoxy)silane have been studied in [11–13]. Sila-
tranes are used as ligands and substituents in several
coordination and organometallic compounds [14–20].
The superelectron-donating effect of the silatranyl
group was employed in [21] to construct asymmetric
structures with nonlinear optical properties.
EXPERIMENTAL
3-Aminopropyl(triethoxy)silane (PO “Altaikhim-
prom”, Slavgorod) was preliminarily fractionated in
vacuo on a column (1 × 50 cm) packed with Nichrome
wire spirals and analyzed on a Tsvet-500 gas chromato-
graph (stainless steel column 0.3 × 200 cm, XC-2-1
(5%) on Chromaton-N-AWDMCS as a stationary
phase, katharometer, helium as a carrier gas). Dicobalt
octacarbonyl (GNIIKhTEOS) was of 98% purity
3Co2(CO)8 + 12NH2R
2[Co(NH2R)6][Co(CO)4]2 + 8CO.
The oxidation is accompanied by replacement of (HPLC: Milikhrom-1A, column 2 × 64 mm, Separon-
carbon monoxide by RNH2 groups. In the complex SGX, 5 µm, UV detector, 250 nm, hexane) and was
obtained, the Co2+ cation is surrounded by six amino used as purchased. Acetonitrile was desiccated over a
ligands and neutralized with two tetracarbonylcobaltate 3 Å molecular sieve and distilled over P4O10. Toluene
anions. Thus, the reactions of CoCl2 and Co2(CO)8 with and diethyl ether were purified by distillation over
1070-3284/02/2812-0856$27.00 © 2002 åÄIä “Nauka /Interperiodica”

REACTIONS OF 1-(3'-AMINO)- AND 1-(3'-ACETAMIDO)PROPYLSILATRANES
857
1
1
2
2
4000
3500
3000
2500
2000
1500
1000
500
ν, cm–1
Fig. 1. IR spectra of (1) amino silatrane I and (2) complex III.
metallic sodium and P4O10, respectively. Tetrahydrofu-
Dichlorobis[1-(3'-amino)propylsilatrane]co-
ran (THF) was successively refluxed over NaOH and balt(II) (III). Anhydrous Co(II) chloride (0.60 g,
metallic sodium and then distilled. All manipulations 4.6 mmol) was added to a solution of silatrane I (2.30 g,
with complexes III–VI and VIII were carried out in 9.9 mmol) in 10 ml of CH3CN. The reaction mixture
vacuo or under argon in oxygen-free solvents.
was stirred at 25°C for 2 h until CoCl2 was completely
dissolved. The resulting bright blue solution was con-
centrated in vacuo to dryness; the solid residue was
reprecipitated from a toluene–acetonitrile mixture,
washed with ether, and dried in vacuo to give complex III
as a blue powder. The yield of III was 2.03 g (3.4 mmol,
74%). Its IR spectrum is shown in Fig. 1. Electronic
absorption spectrum (AB) (ν, cm–1): 17400 sh, 16400 sh,
16000 (ε 332 l mol–1 cm–1), 15500 sh.
Reaction of silatrane II with cobalt(II) chloride.
Anhydrous Co(II) chloride (0.35 g, 2.7 mmol) was
added to a solution of silatrane II (1.47 g, 5.4 mmol) in
10 ml of CH3CN. The reaction mixture was homoge-
nized by stirring for 3 h, and the solvent was removed
in vacuo. Attempts to recrystallize the solid blue resi-
due from mixtures of acetonitrile with toluene, ether, or
hexane resulted in the formation of a heavy blue liquid.
The solvents were removed by decanting. Drying the
liquid in vacuo gave complex IV as a blue powder. The
powder became cohesive when stored at room temper-
ature for one to two days and regained its original fria-
bility on washing with hexane. The IR spectrum of IV
is shown in Fig. 2.
1
1-(3'-Amino)propylsilatrane (I). A mixture of
3-aminopropyl(triethoxy)silane (8.84 g, 0.04 mol) and
triethanolamine (5.69 g, 0.04 mol) was heated with
simultaneous removal of the alcohol evolved. The prod-
uct was recrystallized from toluene and then from chlo-
roform. The yield of silatrane I was 4.90 g (0.021 mol,
53%). The IR spectrum of I is shown in Fig. 1. 1H NMR
δ, ppm: 0.360, 0.401, 0.443 (t, 2 H, –CH2Si), 1.245 (s,
2 H, NH2), 1.521 (m, 2 H, –CH2–), 2.589, 2.623, 2.658
(t, 2 H, –CH2N), 2.782, 2.811, 2.840 (t, 6 H, –CH2N),
3.737, 3.766, 3.795 (t, 6 H, –CH2O).
1-(3'-Acetamido)propylsilatrane (II). A solution
of 3-aminopropyl(triethoxy)silane (16.20 g, 0.073 mol)
and triethylamine (7.40 g, 0.073 mol) in 50 ml of ether
was added dropwise to acetyl chloride (5.75 g, 0.073 mol)
in 30 ml of ether while stirring and cooling it with ice
water. The reaction mixture was refluxed with stirring
for 2 h and then filtered. Triethanolamine (10.90 g,
0.073 mol) was added to the filtrate. The alcohol was
removed, and the product was recrystallized from a
chloroform–hexane mixture. The yield of silatrane II
was 9.41 g (0.034 mol, 47%). Its IR spectrum is shown
in Fig. 2. 1H NMR δ, ppm: 0.391, 0.429, 0.469 (t, 2 H,
−CH2Si), 1.532, 1.565, 1.606, 1.643, 1.676 (m, 2 H,
−CH2–), 1.936 (s, CH3), 2.780, 2.809, 2.839 (t, 6 H,
−CH2N), 3.161, 3.194, 3.221, 3.253 (q, 2 H, –CH2N),
3.732, 3.761, 3.790 (t, 6 H, –CH2O), 6.068 (s, 1 H, NH).
Hexakis[1-(3'-aminoamido)propylsilatrane]co-
balt(II) bis(tetracarbonylcobaltate) (V). Dicobalt
octacarbonyl (0.71 g, 2.1 mmol) was added to a solu-
tion of silatrane I (1.93 g, 8.3 mmol) in 20 ml of tolu-
ene. After 2 h, a gas (37 ml) evolved, and the brown
solution turned crimson-red. The toluene was removed,
and the residue was washed with ether to give com-
pound V as a pink-lilac powder. The yield of V was
1
Compounds I and II were prepared as described in [1, 2].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 12 2002

858
SEMENOV et al.
1
2
4000
3500
3000
2500
2000
1500
1000
500
ν, cm–1
Fig. 2. IR spectra of (1) acetamido silatrane II and (2) the product of its reaction with cobalt(II) chloride.
4000
3500
3000
2500
2000
1500
1000
500
ν, cm–1
Fig. 3. IR spectrum of complex V.
2.08 g (1.1 mmol, 79%). Its IR spectrum is shown in CH3CN was added to CoCl2 (0.16 g, 1.23 mmol) in
Fig. 3. AB (ν, cm–1): 18000 (ε 60 l mol–1 cm–1).
6 ml of CH3CN. The reaction mixture was homoge-
nized by stirring at 25°C for 5 h. The solvent was
removed. Repeated washing of the solid residue with
benzene gave complex VIII (0.35 g, 0.616 mmol) as a
light blue powder. IR (ν, cm–1): 1480 m, 1365 m, 1350
w, 1260 s, 1170 w, 1130 s, 1090 vs, 1055 vs, 1030 vs,
945 s, 910 vs, 880 m, 830 s, 810 m, 790 vs, 750 w, 690
s, 670 vs, 640 w, 580 w, 460 w. For ethoxysilatrane, IR
Hexakis[1-(3'-acetamido)propylsilatrane]co-
balt(II) bis(tetracarbonylcobaltate) (VI) was obtained
in CH3CN using the same procedure. The yield of VI
was 74%. Its IR spectrum is shown in Fig. 4. AB
(ν, cm–1): 19000 (ε 126 l mol–1 cm–1), 17400 (ε 166 l
mol–1 cm–1), 15800 sh.
Xerogel (VII). Complex VI (0.23 g) was dissolved (ν, cm–1): 1480 m, 1360 m, 1270 s, 1170 w, 1150 m,
in 1.5 ml of CH3CN and the solution was kept in an 1120 vs, 1080 vs, 1060 w, 1030 s, 945 vs, 925 vs, 875
open tube for two days. The resulting transparent violet w, 800 vs, 770 vs, 740 s, 725 m, 630 s, 575 m.
gel was dried, and the residue was washed with THF
and dried in vacuo to give xerogel VII (0.10 g) as a
brown powder. Its IR spectrum is shown in Fig. 4.
Elemental analysis data for complexes III–VIII are
presented in table.
IR spectra were recorded on Perkin-Elmer 57 and
1
Reaction of ethoxysilatrane with cobalt(II) chlo- Specord 75IR spectrophotometers (Nujol mulls). H
ride. Ethoxysilatrane (0.49 g, 2.23 mmol) in 5 ml of NMR spectra were recorded on a Bruker-DPX 200
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 12 2002

REACTIONS OF 1-(3'-AMINO)- AND 1-(3'-ACETAMIDO)PROPYLSILATRANES
859
1
1
2
2
4000
3500
3000
2500
2000
1500
1000
500
ν, cm–1
Fig. 4. IR spectra of (1) complex VI and (2) xerogel VII.
spectrometer in CDCl3. Electronic absorption spectra from 3340 and 3270 cm–1 to 3240 and 3150 cm–1, while
were measured on a Specord-M 40 spectrophotometer the deformation vibrations occur at higher frequencies
(10-mm quartz cell) in oxygen-free acetonitrile.
(1600 versus 1575 cm–1). In the 3700–3000 cm–1 range,
the IR spectrum of complex III is identical with the
spectrum of a previously synthesized [11] complex of
CoCl2 with 3-aminopropyl(triethoxy)silane.
RESULTS AND DISCUSSION
Reactions of silatranes I, II with cobalt(II) chloride.
The reaction of amino silatrane I with CoCl2 in acetonitrile
yields dichlorobis[1-(3'-amino)propylsilatrane]cobalt(II)
RNH2 Cl
RNH2 Cl
Co
Co
Co
{Co[NH2CH2CH2CH2Si(OCH2CH2)3N]2Cl2}
(III).
RNH2 Cl
(cis-III)
Cl
NH2R
Complex III was precipitated with toluene from the
solution in CH3CN and washed with ether to give a
bright blue powder. The IR spectra of the starting sila-
trane I and complex III are displayed in Fig. 1. It can
be seen that the absorption bands of the hydrocarbon
(trans-III)
R = CH2CH2CH2Si(OCH2CH2)3N
The doublets at 3470 and 3240 cm–1 suggest the for-
radical at the Si atom and those of the silatrane frame- mation of isomers of complex III. The electronic
work [22] remain virtually unchanged (ν 1480, 1360, absorption spectrum of complex III in acetonitrile (Fig.
1270, 1180, 1130, 1100, 1030, 950, 920, 875, 860, 800, 5), which consists of a multiple band with a maximum
760, 725, 625, and 575 cm–1). At the same time, the at 16000 cm–1, is characteristic of diaminodichloro com-
ν(N–H) bands are shifted to the low-frequency range plexes of cobalt(II) [23].
Elemental analysis data for complexes III–VIII
Found/calculated, %
No.
Empirical formula
Yield, %
74
C
H
Cl
Co
Si
III
IV
C18H40Cl2CoN4O6Si2
C22H44Cl2CoN4O8Si2
37.23/36.36 6.38/6.78 11.15/11.93 9.59/9.91
39.30/38.94 6.81/6.54 10.82/10.45 8.54/8.68
9.14/9.45
8.14/8.28
9.09/9.22
8.51/8.23
V
C63.2H120Co3N12O27.2Si6 41.10/41.51 6.25/6.61
9.53/9.67
8.97/8.63
79
74
VI
C74H132Co3N12O32Si6
C78H160Co4N14O37Si7
C16H34Cl2CoN2O8Si2
42.97/43.41 6.67/6.50
39.06/40.41 6.78/6.96
VII
VIII
9.94/10.17 9.08/8.48
34.08/33.81 5.88/6.03 12.60/12.47 10.50/10.37 10.01/9.88
55
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 12 2002

860
SEMENOV et al.
The amido analog of complex III, namely, di- absorption band at 1630 cm–1 of the azomethine group
chlorobis[1-(3'-acetamido)propylsilatrane]cobalt(II)
{Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]2Cl2},
is unstable and undergoes further transformations and
thus cannot be isolated as individual compound using
the reaction of silatrane II with CoCl2 in CH3CN. The
reaction product IV is a coarse blue powder, which is
well soluble in acetonitrile and insoluble in THF. When
stored under argon, the powder coheres due to an oily
film covering its surface. This film can easily be
removed with toluene or hexane, and the powder
regains its friability. At 100°C, the powder rapidly
changes into a dark blue oil; on cooling to room tem-
perature, the substance remains liquid. The IR spectra
of silatrane II and the product of its reaction with CoCl2
are shown in Fig. 2. They are nearly identical in the
1500–400 cm–1 range, which indicates that the silatrane
framework of the ligand is retained in the complex. The
changes are most significant in the 3400–3000 cm–1 (N–
H and O–H stretching vibrations) and 1700–1500 cm–1
ranges (absorption bands of amide I and amide II) [24].
The very intense and broad absorption band at 3600–
3000 cm–1 corresponds to the OH group in the tauto-
meric form of the secondary amideCH3–C(OH)=N–
CH2– (of the imidic acid) [25]. This form is stabilized
–C=N–.
Hence, compound IV is a Co complex with an N-sil-
atranylacetimidic acid {Co[RN=C(OH)(CH3)]2Cl2},
where R = N(CH2CH2O)3SiCH2CH2CH2. In a liquid
obtained by heating complex IV, the silatrane frame-
work is destroyed (IR data). An attempt to synthesize
an amido analog of compound III in THF failed. The
reaction of CoCl2 with silatrane II occurred very slowly
because of their low solubility in this solvent.
Reactions of silatranes I and II with dicobalt octacar-
bonyl.Amines and acid amides react with Co2(CO)8 [10] to
give hexakis[amino(amido)]cobalt(II) bis(tetracarbonylco-
baltates) {Co(NH2R)6 – x[HC(O)NHR]x}[Co(CO)4]2. In the
case of primary amines, the evolved carbon monoxide
is usually inserted in part into the N–H bond to form a
formamide derivative, which is also coordinated by a
Co2+ cation. Thus, the resulting compound contains
both amino and amido ligands. The reaction of silatrane
I with Co2(CO)8 in toluene is accompanied by vigorous
gas evolution and affords hexakis[1-(3'-aminoamido)pro-
pylsilatrane]cobalt(II)
bis(tetracarbonylcobaltate)
{Co[NH2CH2CH2CH2Si(OCH2CH2)3N]4.8[HC(O)NHCH2
CH2CH2Si(OCH2CH2)3N]1.2}[Co(CO)4]2 (V) as a pink-
lilac powder in 79% yield. The volume of the gas
evolved suggests that about 30% of carbon monoxide is
combined with the amino groups; as a result, the Co2+
coordination sphere includes both amino and form-
CH N C CH
CH N C CH
2
3
2
3
H O
OH
by coordination of the acetamido group of silatrane II
to the cobalt atom. The bands at 1660 cm–1 (amide I)
and 1545 cm–1 (amide II) coalesce into a broader amido silatranyl ligands.
Siat
NH
2+
2+
Siat
NH
2
NH
O
NH
NH
2
2
2
2
O
O
O
O
–
–
Co
2[Co(CO) ]
4
Co
O
2[Co(CO) ]
4
NH
O
NH
Siat
NH
Siat
(V)
(VI)
Siat = Si(OCH2CH2)3N
The IR spectrum of compound V (Fig. 3) shows a set of the doublet at 1555 and 1545 cm–1 was assigned to the
N–H deformation vibrations in the amido (amide II)
and amino silatranes coordinated by the Co2+ cation. In
the visible AB spectrum (Fig. 5), complex V absorbs at
18000 cm–1, which is characteristic of hexacoordinated
octahedral amino complexes of cobalt(II) (4T1g(P)–4T1g
transition) [23].
absorption bands characteristic of a silatrane frame-
work in the 1300–500 cm–1 range. An intense band at
1870 cm–1 and a band at 2000 cm–1 were assigned to the
[Co(CO)4]– anion. A set of ill-resolved absorption
bands in the 3500–3100 cm–1 range (ν(N–H)) corre-
sponds to the Co(NH2CH2–) and Co[HC(O)NH–CH2–]
fragments. The formation of formamido ligands is con-
In the reaction of silatrane II with dicobalt octa-
firmed by the absorption bands at 1625 cm–1 (amide I); carbonyl in CH3CN, a stoichiometric amount of car-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 12 2002

REACTIONS OF 1-(3'-AMINO)- AND 1-(3'-ACETAMIDO)PROPYLSILATRANES
861
bon monoxide was evolved (eight moles per three
D
moles of Co2(CO)8). Hexakis[1-(3'-acetamido)pro-
pylsilatrane]cobalt(II) bis(tetracarbonylcobaltate)
{Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]6}[Co
(CO)4]2 (VI) was obtained as a brown powder in 74%
yield. The powder is soluble in CH3CN and THF and
insoluble in toluene or ether. The IR spectrum of com-
plex VI (Fig. 4) contains a set of absorption bands cor-
responding to the silatrane fragment (1270, 1180, 1135,
1080, 1050, 1030, 950, 925, 880, 800, 760, 725, and
625 cm–1), the tetracarbonylcobaltate anion (2000 and
1870 cm–1), the N–H stretching (3500–3100 cm–1) and
deformation (1550 cm–1, amide II) vibrations, and the
C=O group (1620 cm–1, amide II). The bands due to the
N–H stretching vibrations and the band of amide I are
most sensitive to complexation (Fig. 2). In the IR spec-
trum of complex VI, these bands are broadened and
shifted to the lower wavenumbers. Their broadening,
especially pronounced for the ν(N–H) bands, is proba-
bly due to hydrogen bonding. Complexation between
acid amides and transition metals is known to primarily
involve the acid C=O group [26]. This explains why the
band due to amide I is shifted, while the position of the
band due to amide II remains virtually unchanged. The
electronic absorption spectrum of complex VI exhibits
an absorption band of complicated structure with a cen-
ter at 18000 cm–1 (Fig. 5). The shape of the band and
the positions of its maxima are typical of octahedral
hexaamidocobalt(II) cations [23].
1.0
2.0
0.8
0.6
0.4
0.2
1.6
1.2
3
1
2
0.8
0.4
26
24
22
20
18
16 14
12
ν × 10–3, cm–1
Fig. 5. Electronic absorption spectra of complexes III, V,
and VI in acetonitrile (c = (1) 2.47 × 10 , (2) 2.15 × 10
and (3) 1.6 × 10 mol/l, respectively).
–3
–3
,
When stored in an open tube, a brown 0.075 M solu-
tion of complex VI in CH3CN turned violet, becoming
significantly thicker after 20 h. Two days later, it
changed into a transparent violet gel, which was dried
in vacuo and washed with THF to give a small amount
of xerogel VII as a light brown powder. Earlier [13],
similar processes were observed for cobaltates
–3
nor by accumulation of disiloxane ones. Thus, the binder
of the gel is cobalt hydroxocarbonate CoCO3 · xCoO ·
yH2O [27]. When a solvent is removed, such an unsta-
ble binder is destroyed to give a fine powder. According
to the elemental analysis data, the composition of xero-
gel VII can be formulated as [CoCO3 · 2CoO · 2H2O] ·
[CoB6](OH)2 · B (B = silatrane II).
[CoB6][Co(CO)4]2
(B
=
Py,
DMF,
or
NH2CH2CH2CH2Si(OEt)3). Gels were found to have a
carbonate structure since the tetracarbonylcobaltate
anions oxidize with atmospheric oxygen to cobalt
hydroxocarbonate. Most of the hexaamino- or hexa-
amidocobalt cations [CoB6]2+ are retained in the result-
ing gels. According to the IR data (Fig. 4), xerogel VII
is composed of cobalt hydroxocarbonate, hexakis(ace-
tamidosilatranyl)cobalt(II) cations, and free silatrane
II. Complete oxidation of the tetracarbonylcobaltate
anions is evident from the absence of corresponding
absorption bands at 1870 and 2000 cm–1. The carbonate
fragment gives two intense broad bands at 3600–3100
and 1600–1350 cm–1. A set of peaks in the 1300–
600 cm–1 range is characteristic of a silatrane frame-
work. Three sharp absorption bands at 3300, 1660, and
1545 cm–1 rising above broader carbonate bands indi-
cate the presence of free silatrane II. A portion of the
acetamidosilatranylcobalt(II) complexes is retained;
they absorb at 1620 and 1550 cm–1. The shapes and
intensities of absorption bands in the 1100–1000 cm–1
range remain unchanged; therefore, gelation is accom-
A highly diluted (0.0016 mol/l) solution of complex
VI in acetonitrile formed no gel in air because of a too
low concentration of the binder. When aerated, the ini-
tial light brown solution turned violet and then (within
10 to 15 min) became turbid. The suspension was
allowed to settle; the electronic absorption spectrum of
the resulting solution, recorded one hour after the aera-
tion, shows a more intense and differently shaped band
in the 21000–15000 cm–1 range. Such effects are usu-
ally attributed to oxygen absorption and to the presence
of a metal–ligand charge transfer band, which is more
intense than d–d transitions in a Co2+ cation [28]. Under
similar conditions, complex V forms no gel even on
prolonged storage in air. Oxygen absorption turns the
solution deep brown and intensifies the band at
18000 cm–1. Apparently, the differences in the behavior
of compounds V and VI can be explained by the stabil-
panied neither by destruction of the silatrane fragments ity of their complexes with molecular oxygen and by its
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 12 2002

862
SEMENOV et al.
ready transfer from a Co2+ cation to a tetracarbonylco-
baltate anion.
3. Voronkov, M.G. and D’yakov, V.M., Silatrany (Sila-
tranes), Novosibirsk: Nauka, 1978.
4. Voronkov, M.G., Dyakov, V.M., and Kirpichenko, S.V.,
Silatranes I and II form complexes with CoCl2 and
Co2(CO)8 only through the –NH2 and –NHC(O)CH3
groups, whereas n-donor centers of the silatranyl frag-
ment (oxygen and nitrogen atoms) take no part in coor-
dination (IR data). In the 1300–500 cm–1 range corre-
sponding to the vibrations of the silatrane cage, the
starting organosilicon compound and the resulting
complex have the same set of bands. At the same time,
it is known [3] that complexation between silatranes X–
Si(OCH2CH2)3N (X = C2H5, C2H5O, or C6H5) and
AlBr3 (1 : 1 complexes) or TiCl4 (1 : 1 and 1 : 2 com-
plexes) involves O–M bonding. In connection with this,
it was interesting to study a CoCl2–silatrane system for
amino- and amido-free silatranes. The reaction of
Co(II) chloride with ethoxysilatrane (X = C2H5O) in
acetonitrile gave a solid sky-blue precipitate (VIII).
The precipitate was not divided into the starting compo-
nents by washing it repeatedly with toluene, (unlike
CoCl2, ethoxysilatrane is soluble in toluene). The IR
spectra of complex VIII and ethoxysilatrane signifi-
cantly differ in the range of the silatrane Si–O–C vibra-
tions (1150–1080 and 800–630 cm–1), which can be due
to Co–O coordination bonding. According to the ele-
mental analysis data, compound VIII is
{Co[C2H5OSi(OCH2CH2)3N]2Cl2}. Thus, CoCl2 can
form complexes with nonfunctionalized silatrane; how-
ever, if the Si atom bears an amino- or amido-contain-
ing substituent, only these functions are involved in
coordination. Compound VIII is very sensitive to atmo-
spheric moisture. The IR spectrum of partially air-hydro-
lyzed product contains a set of absorption bands corre-
sponding to –SiOH (broad band at 3400–3100 cm–1),
N−H (3320 and 3160 cm–1), and ≡NH+Cl– (2750–
2500 cm–1).
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Hypervalent Compounds, Akiba, K., Ed., Chichester:
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Organometallics, 1990, vol. 9, no. 6, p. 1976.
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ACKNOWLEDGMENTS
19. Oh, A.-S., Chung, Y.K., and Kim, S., Organometallics,
This work was supported by the INTAS (grant no.
97-1785), the Russian Foundation for Basic Research
(project nos. 99-03-32911, 00-15-97439, and 00-02-
81206 Bel. 2000), and the Russian Academy of Sci-
ences (Comprehensive Programs “Nanomaterialy i
supramolekulyarnye sistemy” and “Fundamental’nye
issledovaniya khimicheskikh svyazei i stroenie metal-
loorganicheskikh i koordinatsionnykh soedinenii”).
Analyses were carried out at the analytical center of the
Institute of Organometallic Chemistry of the Russian
Academy of Sciences with financial support from the
RFBR (project no. 96-03-40-042).
1992, vol. 11, no. 3, p. 1394.
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