Cobalt(II) and iron(II) tris(trimethylsilyl)siloxides: synthesis, structure and reactivity

Article abstract of DOI:10.1016/S0022-328X(01)01095-6

A series of cobalt(II) and iron(II) siloxide complexes, [(Me₃Si)₃SiO]₂M(L_n) {M=Co, L_n=none (1), (THF) (3), (THF)₂ (4), (DME) (5), (MeCN)₂ (6), (PhCN)₂ (7), (2,2′-dipyridyl) (8), 4,4′-dipyridyl (9), (Ph₃P)₂ (10); M=Fe, L_n=none (2), (2,2′-dipyridyl) (11) were prepared by the reaction of metal silylamides [(Me₃Si)₂N]₂M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with two [(Me₃Si)₃SiO]₂Co units bonded via the two μ₂-O atoms. The central [Co(μ₂-O)]₂ cycle has a 'butterfly shape' being bent along the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The μ₂-bridging and terminal CoO distances are 1.945(7)-1.963(7) and 1.781(8), 1.793(7) A?, respectively. The Co?Co distance in 1 is relatively short, 2.735(2) A?. However, the high value of magnetic moment (6.0 μ_B) of compound 1 indicates the absence of a direct interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2′-dipyridyl and two terminal OSi(SiMe₃)₃ groups and has a distorted tetrahedral environment. The FeN(1), FeN(2) and FeO(1), FeO(2) distances in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) A?, respectively. Addition of one equivalent of PhCCH to 7 results in the substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC₂)CoOSi(SiMe₃)₃}₂. Subsequent addition of PhC₂H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and 4 in solution.

Full text of DOI:10.1016/S0022-328X(01)01095-6

Journal of Organometallic Chemistry 642 (2002) 20–31
www.elsevier.com/locate/jorganchem
Cobalt(II) and iron(II) tris(trimethylsilyl)siloxides: synthesis,
structure and reactivity
Tatiana A. Chesnokova, Elena V. Zhezlova, Alexander N. Kornev *,
Yana V. Fedotova, Lev N. Zakharov, Georgy K. Fukin, Yurii A. Kursky,
Tatiana G. Mushtina, Georgy A. Domrachev
Razu6ae6 Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinin Street, 603600 Nizhny No6gorod, Russia
Received 6 April 2001; accepted 27 June 2001
Abstract
A series of cobalt(II) and iron(II) siloxide complexes, [(Me3Si)3SiO]2M(Ln) {M=Co, Ln=none (1), (THF) (3), (THF)2 (4),
(DME) (5), (MeCN)2 (6), (PhCN)2 (7), (2,2%-dipyridyl) (8), 4,4%-dipyridyl (9), (Ph3P)2 (10); M=Fe, Ln=none (2), (2,2%-dipyridyl)
(11) were prepared by the reaction of metal silylamides [(Me3Si)2N]2M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal
structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with
two [(Me3Si)3SiO]2Co units bonded via the two m2-O atoms. The central [Co(m2-O)]2 cycle has a ‘butterfly shape’ being bent along
the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The m2-bridging
,
and terminal CoꢀO distances are 1.945(7)–1.963(7) and 1.781(8), 1.793(7) A, respectively. The Co···Co distance in 1 is relatively
,
short, 2.735(2) A. However, the high value of magnetic moment (6.0 mB) of compound 1 indicates the absence of a direct
interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2%-dipyridyl and two
terminal OSi(SiMe3)3 groups and has a distorted tetrahedral environment. The FeꢀN(1), FeꢀN(2) and FeꢀO(1), FeꢀO(2) distances
in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) A, respectively. Addition of one equivalent of PhCꢁCH to 7 results in the
,
substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC2)CoOSi(SiMe3)3}2.
Subsequent addition of PhC2H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient
temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and
4 in solution. © 2002 Published by Elsevier Science B.V.
Keywords: Transition metals; Siloxides; Polysilanes; X-ray diffraction
novel and intriguing class of organometallic com-
pounds. Their stability, synthetic ways and reactivity
depend on various factors such as the redox poten-
tial and oxidation state of the metal atom, reducing
properties of the polysilyl substituent, polarity of the
MꢀO bond, and the enthalpy of rearrangement
SiꢀSiꢀOꢀM“SiꢀOꢀSiꢀM.
As a part of our continuing study of low-coordinate
transition metal siloxides this report describes the
preparation and characterization of the homoleptic
cobalt(II) and iron(II) tris(trimethylsilyl)siloxides,
Lewis-base derivatives of these compounds as well as
their thermal rearrangements and reactivity.
1. Introduction
The chemistry of low-valent transition metal com-
plexes is of great interest in having to do with the
catalytic transformations and activation of small
molecules. Transition metal bulky siloxides occupy a
specific place among other oxy-derivatives, because
they are the models of catalytic centers in the widely
used zeolites. Siloxides containing a system of SiꢀSi
bonds and possessing strong donor properties are a
* Corresponding author. Fax: +7-8312-661497.
E-mail address: akornev@imoc.sinn.ru (A.N. Kornev).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01095-6

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
21
2. Results and discussion
The reactions proceed in hexane for 10 h at ambient
temperature affording crystalline products after solvent
removal. Complexes 3–7, 9, 10 were prepared by the
2.1. Synthesis
treatment of homoleptic 1 with Lewis bases:
L
The homoleptic cobalt(II) and iron(II) tris(trimethyl-
silyl)siloxides were synthesized by silanolysis of the
corresponding bis(trimethylsilyl)amides:
[(Me3Si)3SiO]2M“[(Me3Si)3SiO]2M(Ln)
3–7, 9, 10
M=Co, (Ln)=THF (3), (THF)2 (4), DME (5), MeCN
(6), PhCN (7), 4,4%-dipy (9), (Ph3P)2 (10).
2,2%-Dipyridyl complexes of cobalt (8) and iron (11)
were synthesized by the workup of the corresponding
dipyridyl silylamide complexes with tris(trimethylsilyl)-
silanol:
[(Me3Si)2N]2M + 2(Me3Si)3SiOH
“ [(Me3Si)3SiO]2M + 2(Me3Si)2NH
M=Co (1), Fe (2)
[(Me3Si)2N]2M2ꢀ,2ꢀ%-dꢀiꢀpyꢀrꢀidꢂyl[(Me3Si)2N]2M(2,2%-dipy)
PhH
Table 1
2(Me Si) SiOH
3
3
Crystal data and structure refinement parameters for compounds 1
and 11
ꢀꢀꢀꢀꢀꢀꢀꢂ [(Me3Si)3SiO]2M(2,2%-dipy)+2 (Me3Si)2NH
M=Co (8); Fe (11)
Homoleptic compounds 1 and 2 crystallize well from
hexane solution. Oxygen-donor molecules (THF,
DME) form complexes 3–5 that represent oil (4) or
solids of poor crystallinity, apparently owing to the
considerable lability of their coordination bond with
the metal atom. Indeed, simple pumping of the THF
solution of 4 in vacuo at 20 °C affords violet oil that
corresponds to the complex, containing two THF lig-
ands. Further prolonged pumping of 4 in vacuo for 5 h
affords a green solid 3. IR-spectra of 3 shows new
absorption (SiꢀOꢀCo) at 935 cm−1 instead of 955
cm−1 (4) and still shows absorption at 1020 cm−1, but
of less intensity. Note that the analogous cobalt(II)
triphenylsiloxide, containing one THF molecule,
[Co(OSiPh3)2(THF)]2, has a dimeric structure in the
solid state [1]. Dipyridyl ligands are favorable toward
the separation of complexes 8, 9, and 11 in the crys-
talline form. [(Me3Si)3SiO]2Co moieties form very stable
fine crystalline coordination polymer (9) with 4,4%-
dipyridyl. Its solubility is very poor in comparison with
derivatives of 2,2%-dipyridyl.
1
11
Diffractometer
Siemens P3/PC
C36H108Co2O4Si16
1172.52
Smart
Empirical formula
Formula weight
Temperature (K)
C
28H62FeN2O2Si8
739.37
100(2)
0.71073 A
Monoclinic
P21/n
213(2)
,
Wavelength (A)
0.71073 A
Orthorombic
P212121
Crystal system
Space group
Unit cell dimensions
,
a (A)
14.017(10)
22.73(2)
22.746(11)
90
90
90
7247(8)
4
1.075
0.750
13.2394(4)
24.3198(7)
13.7720(5)
90
93.18(2)
90
4427.5(2)
4
1.109
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (mg m−3
Absorption
)
0.581
coefficient (mm−1
)
F(000)
Crystal size (mm)
2536
0.7×0.5×0.3
Theta range for data 1.27–23.05
collection (°)
1592
0.5×0.5×0.4
1.67–30.99
Index ranges
−15BhB15,
0BkB2,
5−22BlB25
5867
−14BhB18,
−29BkB33,
−16BlB18
35 499
2.2. Structures
Reflections collected
Independent
The structure of complexes 1 and 11 has been deter-
mined by the X-ray diffraction method. (Although the
full X-ray experiment for complex 2 has not been
carried out, it was found that the unit cell parameters
of 1 and 2 are close to each other, i.e. the crystals of 1
and 2 are isostructural). The crystal data and some
details on data collection and refinement for 1 and 11
are given in Table 1.
As expected [2], complex 1 has a dimeric structure
with the two [(Me3Si)3SiO]2Co units bonded via the two
m2-O atoms (Fig. 1). The central [Co(m2-O)]2 cycle has a
‘butterfly shape’ being bent along the bridging oxygen
atoms. The dihedral angle between the Co(1)O(4)Co(2)
and Co(1)O(3)Co(2) planes is 143.1°. A similar angle
between the two average O3Co(1) and O3Co(2) planes is
144.2°. Each Co atom has a slightly distorted planar-
5602
12 691
reflections
Reflections observed 3492
[I\2|(I)]
Data/restraints/
parameters
Absolute structure
parameter
[Rint=0.5382]
[Rint=0.0700]
9842
5602/0/524
12691/0/618
0.38(4)
1.093
–
Goodness-of-fit on
1.022
F2
Final R indices
[I\2|(I)]
R indices (all data)
R1=0.0855,
wR2=0.1681
R1=0.1539,
wR2=0.1995
R1=0.0366,
wR2=0.0927
R1=0.0529,
wR2=0.1035
Largest difference
0.663 and −0.514 1.057 and −0.410
peak and hole
−3
,
(e A
)

22
T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
Fig. 1. X-ray structure of 1.
,
(THF)]2 2.916 A. However, the high value of the mag-
trigonal environment. The sums of these angles (358.0
and 357.8° at the Co(1) and Co(2) atoms, respectively)
are close to 360°. At the same time Co(1)ꢀO(3)ꢀCo(2)
and Co(1)ꢀO(4)ꢀCo(2) angles are orthogonal, being
89.4(3) and 88.5(3)°, respectively (Table 2). The
Co(1)ꢀO(3) and Co(2)ꢀO(3) distances (1.945(7) and
netic moment (6.0 mB) testifies against the existence of
the CoꢀCo bond in 1. Both cobalt atoms in 1 seem to
be independent paramagnetic centers. Further, it may
be assumed that d-electrons of both cobalt atoms have
parallel spins. High possibility of ferromagnetic cou-
pling of transition metal atoms in dimers R3SiOꢀM(m-
OSiR3)2MꢀOSiR3 was predicted by the density
functional Hartree–Fock theory in Ref. [3].
,
1.945(8) A) in one m2-bridge are slightly shorter than
the Co(1)ꢀO(4) and Co(2)ꢀO(4) distances (1.963(7) and
,
1.957(7) A) in the other. All bridging CoꢀO distances
In contrast to the homoleptic complexes 1 and 2,
complex 11 (Fig. 2)with an additional coordinated lig-
and has a monomeric structure with the pseudotetrahe-
dral cobalt atom surrounded by a single 2,2%-dipyridyl
molecule and two (Me3Si)3SiO ligands. 2,2%-Dipyridyl
are significantly longer than the terminal CoꢀO dis-
,
,
tances (1.793(7) A and 1.781(8) A for Co(1)ꢀO(1) and
Co(2)ꢀO(2) bonds, respectively).
There are very few X-ray structurally characterized
low-coordinate Co(II) complexes. The bridging CoꢀO
distances found in 1 are very close in the lengths of
similar bonds in {[Co(OCPh3)2]2(n-C6H14)} with a pla-
nar-trigonal environment at the Co atom (1.964–1.982
,
molecule is planar within 0.055 A. The O(1) and O(2)
atoms are below and above the average plane of 2,2%-
dipyridyl molecule. The OꢀFeꢀO angle, 137.14(5)°, is
significantly more than the ideal tetrahedral angle
109.47°. The FeꢀO and FeꢀN distances in 11 are
2.148(1), 2.164(1) and 1.863(1), 1.900(1) A. Selected
bond distances and angles for 11 are given in Table 3.
,
A);
in
{Co[OC(C6H11)3]2·CH3OH·1/2C6H12·THF}
,
(1.951–1.966 A) and slightly more than those in the
,
THF-adduct [Co(OSiPh3)2(THF)]2 with a distorted te-
,
trahedral coordination of the Co atom (1.977–1.991 A)
[1].
The CoꢀOꢀSi angles in the terminal (Me3Si)3SiO
groups in 1 (159.4(5) and 160.9(5)°) are large due to the
non-bonded repulsion and close to those in
[Co(OSiPh3)2(THF)]2 (161.3 and 170.7°).
2.3. IR and electronic spectra
Selected IR spectral data of complexes 1–11 are
given in Table 4. Generally, w(MꢀOꢀSi) stretching fre-
quencies are in the 900–1000 cm−1 range. These bands
disappear when the sample of the complex is main-
tained in open air for several minutes owing to hydrol-
ysis. All compounds contain strong w(SiꢀMe)
,
The Co(1)···Co(2) distance in 1, 2.735(2) A, is notice-
ably shorter than in the above-mentioned compounds
,
[Co(OCPh3)2]2·(n-C6H14) 2.910 A, Co[OC(C6H11)3]2·
,
CH3OH·1/2C6H12·THF 2.904 A, and [Co(OSiPh3)2-

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
23
absorption (1240, 840 cm−1) that has a fixed position.
Complexes 3–5, containing THF or DME ligands show
the w(CꢀO) band at 1020 cm−1 shifted by 60 cm−1
relatively to those specific for the free ligand (1080
cm−1). Poor soluble 4,4%-dipypidyl complex 9 contains
the band 1590 cm−1 shifted by 15 cm−1 relatively to
those specific for the free 4,4%-dipyridyl ligand (1575
cm−1). It should be noted that the analogous changes
in IR spectra were observed for coordinate polymers of
transition metals bearing bridged 4,4%-dipyridyl ligands
[4] in contrast to monomer complexes, RnM(4,4%-dipy)2,
where dipyridyl bands are not shifted and remain of the
same intensity as those that are inherent to the free
base.
The electronic spectral measurements of some cobalt
complexes were made in order to understand their
behavior in solution. Homoleptic complex 1 shows
three d–d absorptions in hexane solution (Table 5).
The lowest energy transition, 685 nm is of the highest
intensity. Bis(THF)-adduct (4) has quite a different
spectrum of low intensity in THF-solution, however,
being dissolved in hexane, the color of the solution
turned greenish-violet and the spectrum became more
similar to homoleptic 1. The solution of mono THF-ad-
duct (3) in hexane has an electronic spectrum identical
to 1. Therefore, this indicates the loss of two THF
molecules according to the following equation:
hexane
Table 2
,
Selected bond lengths (A) and bond angles (°) for 1
Bond lengths
Co(1)ꢀO(1)
Co(1)ꢀO(3)
Co(1)ꢀO(4)
Co(1)···Co(2)
Co(2)ꢀO(2)
Co(2)ꢀO(3)
Co(2)ꢀO(4)
O(1)ꢀSi(1)
1.793(7)
1.945(7)
1.963(7)
2.735(2)
1.781(8)
1.945(8)
1.957(7)
1.644(8)
1.641(8)
1.703(8)
1.686(7)
2.363(6)
2.368(5)
2.375(5)
2.310(7)
2.326(6)
2.399(8)
2.339(7)
2.357(6)
2.404(6)
2.356(6)
2.361(6)
2.391(7)
O(2)ꢀSi(2)
O(3)ꢀSi(3)
O(4)ꢀSi(4)
Si(1)ꢀSi(12)
Si(1)ꢀSi(11)
Si(1)ꢀSi(13)
Si(2)ꢀSi(23)
Si(2)ꢀSi(22)
Si(2)ꢀSi(21)
Si(3)ꢀSi(32)
Si(3)ꢀSi(31)
Si(3)ꢀSi(33)
Si(4)ꢀSi(42)
Si(4)ꢀSi(43)
Si(4)ꢀSi(41)
Bond angles
O(1)ꢀCo(1)ꢀO(3)
O(1)ꢀCo(1)ꢀO(4)
O(3)ꢀCo(1)ꢀO(4)
O(2)ꢀCo(2)ꢀO(3)
O(2)ꢀCo(2)ꢀO(4)
O(3)ꢀCo(2)ꢀO(4)
Si(1)ꢀO(1)ꢀCo(1)
Si(2)ꢀO(2)ꢀCo(2)
Si(3)ꢀO(3)ꢀCo(2)
Si(3)ꢀO(3)ꢀCo(1)
Co(2)ꢀO(3)ꢀCo(1)
Si(4)ꢀO(4)ꢀCo(2)
Si(4)ꢀO(4)ꢀCo(1)
Co(2)ꢀO(4)ꢀCo(1)
O(1)ꢀSi(1)ꢀSi(12)
O(1)ꢀSi(1)ꢀSi(11)
O(1)ꢀSi(1)ꢀSi(13)
Si(12)ꢀSi(1)ꢀSi(11)
Si(12)ꢀSi(1)ꢀSi(13)
Si(11)ꢀSi(1)ꢀSi(13)
O(2)ꢀSi(2)ꢀSi(23)
O(2)ꢀSi(2)ꢀSi(22)
O(2)ꢀSi(2)ꢀSi(21)
Si(23)ꢀSi(2)ꢀSi(22)
Si(23)ꢀSi(2)ꢀSi(21)
Si(22)ꢀSi(2)ꢀSi(21)
O(3)ꢀSi(3)ꢀSi(32)
O(3)ꢀSi(3)ꢀSi(31)
O(3)ꢀSi(3)ꢀSi(33)
Si(32)ꢀSi(3)ꢀSi(31)
Si(32)ꢀSi(3)ꢀSi(33)
Si(31)ꢀSi(3)ꢀSi(33)
O(4)ꢀSi(4)ꢀSi(42)
O(4)ꢀSi(4)ꢀSi(43)
O(4)ꢀSi(4)ꢀSi(41)
Si(42)ꢀSi(4)ꢀSi(43)
Si(42)ꢀSi(4)ꢀSi(41)
Si(43)ꢀSi(4)ꢀSi(41)
137.4(3)
135.5(3)
85.1(3)
134.6(4)
137.9(3)
85.3(3)
159.4(5)
160.9(5)
133.3(4)
137.3(5)
89.4(3)
132.5(4)
127.7(4)
88.5(3)
112.6(3)
110.2(3)
110.6(3)
107.6(2)
105.3(2)
110.3(2)
109.1(4)
110.8(4)
111.7(4)
111.6(4)
105.1(4)
108.2(4)
106.4(4)
111.6(3)
113.6(4)
109.9(3)
109.1(2)
106.2(2)
112.2(3)
107.2(3)
112.5(3)
110.1(2)
108.0(2)
106.7(3)
[(Me3Si)3SiO]2Co(THF)2 -TlHF [(Me3Si)3SiO]2Co(THF)
hexane
l
[(Me3Si)3SiO]2Co
-THF
Moreover, we also observed a concentration-depen-
dent shift of the two bands in the electronic spectrum of
homoleptic complex 1. This may be due to the existence
of equilibrium between the monomeric and dimeric
forms of 1 in solution.
2[(Me3Si)3SiO]2CoU{[(Me3Si)3SiO]2Co}2
In a week’s time, the splitting in the spectra of
compounds 1–3 disappears while the overall intensity is
enhanced. This corresponds to the slow decomposition
of compounds 1–3 in solution. The benzonitrilic com-
plex 7 shows a more intensive highest energy transition
than 1–3. Its stability in hexane solution is approxi-
mately three times higher than those found for com-
pounds 1–3.
Triphenylphosphine ligands possess a more apprecia-
ble stabilization effect; the solutions of complex 10 are
stable for an unlimited period and the crystals possess
optical dichroism.
2.4. Reacti6ity
All complexes are air and moisture sensitive. Hydrol-
ysis of complexes prepared under an inert atmosphere
yields metal(II) hydroxide and tris(trimethylsilyl)silanol.
Homoleptic iron(II) compound is inflammable in open

24
T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
Fig. 2. X-ray structure of 11.
air in the powder state while tris(trimethylsilyl)silanol is
partially oxidized in a period of several weeks [5].
parallel processes (Scheme 1). In the case of the cobalt
complex (1), all the oxygen is consumed for the oxida-
tion of SiꢀSi bonds. Compounds of three-valent cobalt
were not detected during the process of oxidation.
Therefore, cobalt shows a better oxygen activation
effect than iron.
2.4.1. Oxygen acti6ation
We have studied the oxidation of 1 and 2 in various
(O2–complex) ratios. The addition of 0.9 mol O2 per 1
mol of 2 in benzene solution yields the mixture that
gives a set of silanols after hydrolysis (Table 6). Nearly
50% of tris(trimethylsilyl)silanol was recovered. At the
same time, the major product was the twice oxidized
silanol, (Me3SiO)2(Me3Si)SiOH, while it should have
been (Me3SiO)2(Me3Si)SiOH statistically. In our earlier
investigations, we found that one Me3SiO-substituent at
the SiꢀSi bond increases the rate of its electrophylic
oxidation in comparison with the unsubstituted disi-
lane. However, the presence of two Me3SiO-groups at
the same silicon atom causes an opposite effect [6]. The
molar ratio of the products observed coincides well
with this rule. Moreover, it was noticed that the process
of SiꢀSi bond oxidation is accompanied with the oxida-
tion of iron. Therefore, 36% of iron was turned to the
three-valent state. When 1.25 mol of oxygen was added,
all Fe(II) turned to Fe(III), the process of catalytic
oxidation stopped and the following reaction with oxy-
gen proceeded very slowly, over weeks. The tentative
scheme of oxidation may be depicted as a sequence of
2.4.2. Reactions with carbonyl compounds
Iron tris(trimethylsilyl)siloxide reacts readily with
acetone to give (Me3Si)3SiOH, mesityl oxide and
iron(II) oxide. Formation of these products apparently
proceeds via bis-ketolate complexes, according to
Scheme 2 proposed earlier for zinc alkoxide complexes
[7].
2.4.3. Interaction with CO
We found that cobalt tris(trimethylsilyl)siloxides 1
and 3 in toluene solution absorb ca. 2 mol of carbon
monoxide per cobalt atom at ambient conditions to
form a dark brown solution. After concentrating the
solution and cooling at 0 °C dark brown thermally
unstable crystals were formed. The IR spectrum of the
new complex contains strong absorptions at 840 and
1240 cm−1 corresponding to SiꢀMe fragments and a
number of carbonyl bands (2040, 2030, 2000 and 1870
cm−1) that may be assigned to the cobalt carbonyl

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
25
Table 3
fragments and bridged CO-group [8,9]. At the same
time a strong siloxane band (1050 cm−1) arises while
the SiꢀOꢀCo absorption (935 cm−1) disappears. Hy-
drolysis of this complex did not yield tris(trimethylsi-
lyl)silanol. Tentatively we assigned the complex as the
cobalt–carbonyl cluster compound, (Me3Si)2(Me3SiO)-
SiꢀCox(CO)y. Unfortunately, full characterization of
the complex is difficult because of its low stability.
Interestingly, coordinatively saturated bis-THF-adduct,
4, and the other compounds except phosphine complex
10 did not react with carbon monoxide. It is known,
that the reaction of cobalt(I) tris(trimethylsilyl)-
silyltellurolate, Co[TeSi(SiMe3)3](PMe3)3, with carbon
monoxide yields dicarbonyl cobalt(I) complex
Co(CO)2[TeSi(SiMe3)3](PMe3)2 [10]. Carbon monoxide
stabilizes the low valent state of the metal that causes
the rearrangement of the more electronegative
tris(trimethylsilyl)siloxide substituent to form the
cobalt–silyl complex. Note that the rearrangement
products of 1 or 3 did not absorb carbon monoxide.
Triphenylphosphine complex 10 slowly reacts with CO
to form an insoluble yellow powder which shows a wide
absorption in the IR spectrum at 1900–2000 cm−1
corresponding to carbonyl ligands, and the presence of
organosilicon fragments (840, 1240 cm−1) along with
triphenylphosphine ligands (500, 530, 550 cm−1). The
SiꢀOꢀCo absorption is absent and the hydrolysis of this
complex did not yield tris(trimethylsilyl)silanol. Further
characterization was also found to be difficult because
of poor solubility and crystallinity of this compound.
,
Selected bond lengths (A) and bond angles (°) for 11
Bond lengths
Fe(1)ꢀO(1)
Fe(1)ꢀO(2)
Fe(1)ꢀN(1)
Fe(1)ꢀN(2)
O(1)ꢀSi(1)
O(2)ꢀSi(5)
Si(1)ꢀSi(2)
Si(1)ꢀSi(3)
Si(1)ꢀSi(4)
Si(2)ꢀC(23)
Si(2)ꢀC(21)
Si(2)ꢀC(22)
Si(3)ꢀC(31)
Si(3)ꢀC(32)
Si(3)ꢀC(33)
Si(4)ꢀC(42)
Si(4)ꢀC(41)
Si(4)ꢀC(43)
Si(5)ꢀSi(8)
Si(5)ꢀSi(7)
Si(5)ꢀSi(6)
Si(6)ꢀC(62)
Si(6)ꢀC(63)
Si(6)ꢀC(61)
Si(7)ꢀC(73)
Si(7)ꢀC(72)
Si(7)ꢀC(71)
Si(8)ꢀC(83)
Si(8)ꢀC(81)
Si(8)ꢀC(82)
N(1)ꢀC(1)
N(1)ꢀC(5)
N(2)ꢀC(10)
N(2)ꢀC(6)
C(1)ꢀC(2)
C(2)ꢀC(3)
C(3)ꢀC(4)
C(4)ꢀC(5)
C(5)ꢀC(6)
C(6)ꢀC(7)
C(7)ꢀC(8)
C(8)ꢀC(9)
C(9)ꢀC(10)
1.8626(10)
1.8997(10)
2.1477(12)
2.1644(13)
1.6316(11)
1.6453(11)
2.3660(6)
2.3659(6)
2.3794(6)
1.883(2)
1.887(2)
1.890(2)
1.885(2)
1.885(2)
1.889(2)
1.884(2)
1.885(2)
1.895(2)
2.3602(6)
2.3627(6)
2.3825(6)
1.880(2)
1.881(2)
1.881(3)
1.879(2)
1.884(2)
1.894(2)
1.883(2)
1.883(2)
1.891(2)
1.345(2)
1.357(2)
1.345(2)
1.359(2)
1.392(2)
1.390(2)
1.392(2)
1.397(2)
1.489(2)
1.395(2)
1.396(2)
1.385(2)
1.388(2)
2.4.4. Interaction with phenylacetylene
Catalytic amounts of cobalt(II) and iron(II)
tris(trimethylsilyl)siloxides cause exothermic oligomeri-
sation of phenylacetylene in a solution of hydrocar-
bons. The gradual addition of PhCꢁCH to a solution of
complexes 1–7 (0.01 mol%) in toluene or hexane yields
a dark-red gel for 10 min. Cobalt-containing complexes
yield the mixture consisting of 1.3.5-triphenylbenzene
(20%) and insoluble polymer. In the case of iron com-
plex 2 as a catalyst, the amount of 1.3.5-triphenylben-
zene rises up to 90%. We found that the first stage of
oligomerisation is the exchange of one tris(trimethylsi-
lyl)silanol group for ꢀCꢁCPh. Therefore, benzonitrile
complex 7 reacts with 1 mol of phenylacetylene to
afford cobalt(II) siloxyacetylenid 12.
Bond angles
O(1)ꢀFe(1)ꢀO(2)
O(1)ꢀFe(1)ꢀN(1)
O(2)ꢀFe(1)ꢀN(1)
O(1)ꢀFe(1)ꢀN(2)
O(2)ꢀFe(1)ꢀN(2)
N(1)ꢀFe(1)ꢀN(2)
Si(1)ꢀO(1)ꢀFe(1)
Si(5)ꢀO(2)ꢀFe(1)
O(1)ꢀSi(1)ꢀSi(2)
O(1)ꢀSi(1)ꢀSi(3)
O(1)ꢀSi(1)ꢀSi(4)
Si(2)ꢀSi(1)ꢀSi(3)
Si(2)ꢀSi(1)ꢀSi(4)
Si(3)ꢀSi(1)ꢀSi(4)
O(2)ꢀSi(5)ꢀSi(8)
O(2)ꢀSi(5)ꢀSi(7)
O(2)ꢀSi(5)ꢀSi(6)
Si(8)ꢀSi(5)ꢀSi(7)
Si(8)ꢀSi(5)ꢀSi(6)
Si(7)ꢀSi(5)ꢀSi(6)
137.14(5)
105.26(5)
105.76(5)
111.87(5)
103.92(5)
75.77(5)
149.24(7)
138.92(6)
110.74(4)
107.64(4)
115.91(4)
109.81(2)
105.90(2)
106.70(2)
109.60(5)
107.75(4)
115.35(4)
110.42(2)
106.67(2)
107.02(2)
Compound 12 is stable in the solid state; however, it
decomposes for 2 h in solution. Hydrolysis of 12 yields
tris(trimethylsilyl)silanol, phenylacetylene, benzonitrile
and cobalt(II) hydroxide in quantitative yield. Magnetic
measurements show that 12 is diamagnetic. Since low

26
T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
Table 4
IR spectra of Co(II) and Fe(II) tris(trimethylsilyl)siloxides
No.
Compound
w(CoOSi) (cm−1
)
Other bands (cm−1
)
Colour
1
2
3
4
5
6
7
8
[(Me3Si)3SiO]2Co
[(Me3Si)3SiO]2Fe
935
960
935
955
950
940
950
920sh, 950
960, 980sh
960, 980sh
950
1240, 840 (SiꢀMe)
1240, 840 (SiꢀMe), 750, 680, 620
1020 (THF); 1240, 840 (SiꢀMe)
1020 (THF); 1240, 840 (SiꢀMe)
Green
Pale yellow
Green
Violet
Green
[(Me3Si)3SiO]2Co(THF)
[(Me3Si)3SiO]2Co(THF)2
[(Me3Si)3SiO]2Co(DME)
[(Me3Si)3SiO]2Co(MeCN)2
[(Me3Si)3SiO]2Co(PhCN)2
[(Me3Si)3SiO]2Co(2,2%-dipy)
{[(Me3Si)3SiO]2Co(4,4%-dipy)}n
[(Me3Si)3SiO]2Co(Ph3P)2
[(Me3Si)3SiO]2Fe(2,2%-dipy)
1020 (DME); 1240, 840 (SiꢀMe)
2280, 2260 (CN); 1030; 1240, 840 (SiꢀMe)
2240 (CN), 930, 550 (Ar); 1240, 840 (SiꢀMe)
1585, 1430, 760 (2,2%-dipy); 1240, 840 (SiꢀMe)
1590(4,4%-dipy); 1240, 840 (SiꢀMe)
1580, 1240, 850 (SiꢀMe), 550, 520, 500 (Ph3P)
1580, 760 (2,2%-dipy); 1240, 840 (SiꢀMe)
Violet
Dark vinous
Dark brown
Red
Blue–violet
Dark green
9
10
11
Table 5
Electronic spectra of selected compounds
Compound
u (nm), (m) colour of solution
[(Me3Si)3SiO]2Co (1), green crystals
Hexane, 10.0 mmol l−1, 575 (15), 640 (20), 685
(420), green
Hexane, 2.5 mmol l−1 515 (15) 575 (70) 685
(400), green
[(Me3Si)3SiO]2Co(THF) (3), green crystals 515 (30), 580 (45), 690 (350)
[(Me3Si)3SiO]2Co(THF)2 (4), violet oil Hexane, 505 (30), 580 (65), 695 (230), 740 (25),
greenish-violet
Hexane, 2.5 mmol l−1, green
THF, 505 (20), 590 (30), 670 (55), 740 (15),
violet
[(Me3Si)3SiO]2Co(PhCN)2 (7), dark vinous 515 (120), 610 (120), 700 (380), 735 (sh)
Hexane, vinous
crystals
[(Me3Si)3SiO](PhCN)CoꢀCꢁCPh (12), blue 568 (50), 610 (50), 694 (350)
CH2Cl2, green
Hexane, green
crystals
[(Me3Si)3SiO]2Co(Ph3P)2 (12), blue–violet
crystals(10)
510 (30), 590 (120), 700 (130), 740 (20)
Table 6
Hydrolysis of the oxidized complexes 1 and 2
Compound
Absorbed O2, mol/mol 1 or 2
Products, mol/mol 1 or 2 (T=Me3Si)
T2(TO)SiOH
T(TO)2SiOH
T3SiOH
M(OH)3
[(Me3Si)3SiO]2Fe (2)
[(Me3Si)3SiO]2Co (1)
0.90
1.25
1.79
0.26
0.28
0.08
0.68
0.86
1.50
1.06
0.86
0.40
0.36
1.00
1.00
0.81
1.74
0.30
0.52
0.66
1.48
1.04
0
–
–
spin two-valent cobalt has to possess one unpaired
electron, compound 12 should be a dimer to compen-
1
sate the spins. At ambient temperature, the H-NMR
spectrum of 12 revealed a singlet assigned to the
(Me3Si)3SiO-group and a multiplet corresponding to
the C6H5-ring of phenylacetylene and benzonitrile
groups. The subsequent addition of PhCꢁCH to com-
plex 12 causes its decomposition and oligomerisation of
the monomer. Diphenylacetylene does not form a com-
plex with compounds 1–10 perhaps due to steric
hindrances.
Scheme 1.

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
27
Scheme 2.
2.5. Thermal transformations
Complexes 3–7, containing THF, DME, MeCN,
PhCN or 2,2%-dipyridyl ligands, also undergo transfor-
mations in solution. 4,4%-Dipyridyl adduct (9), in con-
trast to the other cobalt tris(trimethylsilyl) siloxides is
stable at 20 °C for an indefinite period of time partly
due to insolubility.
Although compounds 1 and 2 are isostructural, they
differ in their thermal stability significantly. Iron silox-
ides are the most stable. Homoleptic complex 2 decom-
poses at a temperature over 180 °C. The products of its
slow thermolysis in the temperature range of 180–
250 °C are (Me3Si)3SiOH, (Me3Si)3SiOSiMe3 and solid
polyferrosiloxane, soluble in hexane or THF. The pro-
cess is accompanied with hydrogen evolution. Metal
iron was not found in the products of thermolysis.
Hydrolysis of the solid residue in THF solution gave
soluble oligosiloxane of unknown structure and iron(II)
hydroxide; Fe+3 ions were absent. Earlier we had found
that the thermolysis of the ate-complex {(Me3Si)3-
SiOFe[m-OSi(SiMe3)3]2Na(DME)} gave somewhat dif-
ferent products: polyferrisiloxane and oligosilanes
(Me3Si)4Si and (Me3Si)3SiSi(SiMe3)3 [11]. The reason for
thermolysis in a different way in the last case may be
explained by the presence of sodium-silanolate frag-
ments of the basic nature that is usually known
to cause the disproportionation [12]. Interestingly
lithium tris(trimethylsilyl)siloxide, (Me3Si)3SiOLi, gave
(Me3Si)3SiH (!) as the main product in the course of
thermolysis [13].
Cobalt(II) tris(trimethylsilyl)siloxides are significantly
less stable. Homoleptic complex 1 remains unchange-
able in the solid state at 0 °C for a long time. However,
in hydrocarbon solutions at ambient temperature it
undergoes a slow transformation which is accompanied
with the formation of Me3SiOSi(SiMe3)3 and gas evolu-
tion. GLC analysis showed the presence of methane and
hydrogen in the molar ratio of 1:0.13 per mole of 1. The
color of the solution turned dark brown. Acid hydroly-
sis of the liquid gave Me3SiH and oligosilanes contain-
ing hydride function (absorption at 2100, 1050, 1240
and 840 cm−1). Distillation of the residue in vacuo gave
Me3SiOSi(SiMe3)3 (which remains unchangeable in the
course of hydrolysis) and the product, been tentatively
characterized as (Me3Si)3SiꢀOꢀSiH(SiMe3)(OSiMe3) ac-
cording to NMR and IR spectral data. The cobalt–silyl
bonds formed in the course of the transformation of 1,
evidences the presence of the silicon hydrides as main
products of hydrolysis.
On comparing the tendency of the transition metal
tris(trimethylsilyl)siloxides
toward
rearrangement
(SiꢀSiꢀOꢀM“SiꢀOꢀSiꢀM), it should be noted that it
depends on several factors: redox potential of the metal
atom; polarity of the MꢀO bond; reducing properties of
polysilyl substituents; and the enthalpy of oxygen mi-
gration into the SiꢀSi bond. On going from iron to
cobalt and nickel, the rearrangement becomes more
favorable (Table 7) that is confirmed experimentally.
Analogous nickel and palladium derivatives are non-ex-
istent at room temperature. The attempt of synthesizing
them from (Me3Si)3SiONa and metal salt yields a mix-
ture of unidentified products.
Recently Levitsky et al. [15] report a new way of
introducing the metal oxide fragment into polysilane
chains by the heterofunctional condensation of perme-
thyl-a, v-dichlorooligosilanes with cobalt(II) and cop-
per(II) acetates. Apparently, linear polysilyl fragments
such as ꢀ(R2SiꢀSiR2)Oꢀ in oligosilanes possess lesser
reducing properties than the tris(trimethylsilyl)siloxy
one; therefore, metal-oxide oligomers on their base
seems to be more stable.
Interestingly, the tellurium analog of compound 1
does not exist. Attempt in synthesizing it from
cobalt(II) bromide and lithium tris(trimethylsi-
Table 7
Redox potentials of selected metals and enthalpy of oxygen migration
into SiꢀSi bond a
€° (V),
Rearrangement
DH (kcal mol−1
)
M2+“M°
Fe−0.44
Co−0.28
Ni−0.25
Pd+0.91
FeꢀOꢀSiꢀSi“FeꢀSiꢀOꢀSi
CoꢀOꢀSiꢀSi“CoꢀSiꢀOꢀSi −77
NiꢀOꢀSiꢀSi“NiꢀSiꢀOꢀSi
PdꢀOꢀSiꢀSi“PdꢀSiꢀOꢀSi
−72
−88
−107
a Enthalpy of rearrangements were calculated from bond energies
according to Ref. [14].

28
T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
lyl)tellurolate leads to the monovalent cobalt derivative,
(Me3Si)3SiTeCo(Ph3P)3 [10], while the analogous reac-
tion with iron(II) chloride affords the divalent iron
tellurolate, [(Me3Si)3SiTe]2Co(dmpe)2.
bination of direct methods and calculations of Fourier
maps. The positions of the H atoms were calculated
using the general geometrical conditions and the H
atoms were refined in a rigid group model. All calcula-
tions were performed using the SHELXTL-PLUS package
[22]. Selected bond distances and angles in 1 and 11 are
3. Experimental
given in Tables 2 and 3, respectively.
3.1. General considerations
3.3. Synthesis
The solvents were purified following standard meth-
ods [16]. THF and DME were thoroughly dried over
Na/benzophenone; hexane, MeCN, benzene and tolu-
ene over P2O5 and distilled prior to use. The com-
pounds (Me3Si)3SiOH [13,17], [(Me3Si)2N]2Co [18,19],
[(Me3Si)2N]2Fe [18] were prepared according to known
methods. The reagents 2,2%-dipyridyl and 4,4%-dipyridyl
were obtained commercially (Aldrich) and purified by
vacuum sublimation prior to use. All manipulations
were performed with a rigorous exclusion of oxygen
and moisture, in vacuum or under an Ar atmosphere
using standard Schlenk techniques.
3.3.1. [(Me3Si)3SiO]2Co (1)
Tris(trimethylsilyl)silanol (7.37 g, 28.0 mmol) in 15
ml of hexane was added to
[(Me3Si)2N]2Co (5.28 g, 14.0 mmol) in 15 ml of the
same solvent. The mixture was maintained for 5 h at
20 °C. The solvent and hexamethyldisilazane were re-
moved in vacuo to give green crystals that were recrys-
tallized from hexane. Yield: 7.40 g (90%). Anal. Calc.
for C18H54Si8O2Co: C, 36.88; H, 9.28; Co, 10.05.
Found: C, 36.13; H, 9.17; Co, 9.93%. veff=6.0 mB.
a
solution of
3.3.2. [(Me3Si)3SiO]2Fe (2)
Simultaneous spectrophotometric determination of
iron(II) and total iron with 1,10-phenantroline was
provided by the method in Ref. [20]; spectrophotomet-
ric determination of cobalt(II) with 1-nitroso-2-naphtol
was provided by the method in Ref. [21].
IR spectra (Table 4) were recorded on a Perkin–
Elmer 577 spectrometer from 4000 to 200 cm−1 in
Nujol. Electronic spectra (Table 5) were measured on a
Specord M-40 device from 200 to 800 nm.
Tris(trimethylsilyl)silanol (3.27 g, 12.4 mmol) in 15
ml of hexane was added to a solution of [(Me3Si)2N]2Fe
(2.13 g, 6.18 mmol) in 15 ml of the same solvent. The
mixture was heated for 5 h at 70 °C. The green solu-
tion slowly turned light brown. The solvent and hexam-
ethyldisilazane were removed in vacuo to give
pale-yellow crystals that were recrystallized from hex-
ane. Yield: 3.44
g
(95%). Anal. Calc. for
C18H54Si8O2Fe: C, 37.07; H, 9.33; Fe, 9.58. Found: C,
Room-temperature magnetic moments were mea-
sured by the Faraday method.
36.94; H, 9.39; Fe, 9.50%. veff=4.0 mB.
NMR spectra were recorded in CDCl3 or C6D6 solu-
tions using the ‘Bruker DPX-200’ device, with Me4Si as
the internal standard.
Thermal decomposition of compound 1 was carried
out in vacuo (or in an Ar atmosphere) with a heating
rate of 3 °C min−1. The temperature range studied
extended from 20 to 300 °C.
Gas chromatography analysis of organosilicon prod-
ucts were carried out on a Tsvet-500 chromatograph,
equipped with stainless steel columns 0.4 cm×200 cm,
packed with 5% SE-30 on Chromatone N-Super.
Gaseous products (H2, CH4) were analyzed on a
column 0.4 cm×300 cm, packed with zeolite NaX with
a thermoconductivity detector and with helium (Ar for
H2 analysis) as carrier gas.
3.3.3. [(Me3Si)3SiO]2Co(THF)n, n=1 (3), n=2 (4)
Hexane was removed in vacuo from a solution of
homoleptic complex (1) and changed for THF. The
starting green solution immediately turned violet. Fur-
ther removal of THF in vacuo at 20 °C affords a violet
oil showing intensive absorption at 1020 (CꢀO, THF)
and 955 cm−1 (SiꢀOꢀCo) in IR spectra and corre-
sponds to 4 by elemental analysis. Anal. Calc. for
C26H70Si8O4Co: C, 42.75; H, 9.66; Co, 8.07. Found: C,
43.05; H, 9.70; Co, 7.98%.
A sample of 4 was pumped in vacuo at 50 °C for 4
h to give green crystals of 3. The IR spectra of 3 still
show absorption at 1020 cm−1, but of less intensity and
a new absorption (SiꢀOꢀCo) at 935 cm−1. Anal. Calc.
for C22H62Si8O3Co: C, 40.13; H, 9.49; Co, 8.95. Found:
C, 40.08; H, 9.43; Co, 9.07%.
3.2. X-ray diffraction studies
3.3.4. [(Me3Si)3SiO]2Co(DME) (5)
X-Ray data were collected on a Siemens P3/PC (1)
and SMART CCD (11) diffractometers at 213 (1) and
100 K (11). The crystal data and some details on data
collection and refinement for 1 and 11 are given in
Table 1. Both structures were determined using a com-
Hexane was removed in vacuo from a solution of
homoleptic complex (1) and changed for DME. The
green color of the solution gets dark. Further removal
of DME in vacuo at 20 °C affords green crystalline
solid showing absorption at 1020 (CꢀO, DME) and 950

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
29
cm−1 (SiꢀOꢀCo) in IR spectra and corresponds to 5 by
elemental analysis. Anal. Calc. for C22H64Si8O4Co: C,
39.06; H, 9.54; Co, 8.71. Found: C, 39.11; H, 9.60; Co,
8.65%.
let. The mixture was maintained for 2 h. Toluene was
removed in vacuo and replaced with hexane. Slow
cooling to 0 °C overnight gave dark blue–violet crys-
tals. Yield: 1.88
g
(81%). Anal. Calc. for
C54H84Si8O2P2Co: C, 58.38; H, 7.62; Co, 5.31. Found:
3.3.5. [(Me3Si)3SiO]2Co(MeCN)2 (6)
C, 58.48; H, 7.81; Co, 5.28%. veff=5.1 mB.
[(Me3Si)3SiO]2Co(MeCN)2 (6) was prepared similar
to 5 using 1 and MeCN. Pink plate crystals were
obtained. Anal. Calc. for C22H60Si8O2N2Co: C, 39.53;
H, 9.05; Co, 8.82. Found: C, 39.60; H, 9.11; Co, 8.91%.
3.3.10. [(Me3Si)3SiO]2Fe(2,2%-dipy) (11)
A mixture of 2,2%-dipyridyl (0.95 g, 6.1 mmol) and
[(Me3Si)2N]2Fe (2.30 g, 6.10 mmol) in 15 ml of benzene
was maintained at r.t. for 3 h. The solvent was removed
in vacuo to give green crystals that were recrystallized
from n-hexane. Yield of 3.2 g (93%) of [(Me3Si)2N]2-
Fe(2,2%-dipy). Anal. Calc. for C22H44Si4N4Fe: C, 49.56;
H, 8.32; Fe, 10.48. Found: C, 49.94; H, 8.26; Fe, 9.90%.
IR (cm−1): 1250 (s), 1240 (sh), 840 (vs), 750 (m), 680
(m), 620 (w) (SiMe); 1175 (w), 1020 (w), 990 (m), 970
(m) (NSi2), 1580 (m), 760 (m) (2,2%-dipy).
3.3.6. [(Me3Si)3SiO]2Co(PhCN)2 (7)
Benzonitrile (0.20 g, 2 mmol) was added to a solution
of [(Me3Si)3SiO]2Co (0.58 g, 1 mmol) in 10 ml of
toluene. Green color of the solution turned vinous. The
mixture was maintained for 3 h at 20 °C and the
solvent was removed in vacuo. Further crystallization
from cold toluene affords dark vinous crystals. Yield:
0.75 g (96%). Anal. Calc. for C32H64Si8O2N2Co: C,
48.50; H, 8.14; Co, 7.44. Found: C, 48.12; H, 8.21; Co
7.30%.
Tris(trimethylsilyl)silanol (2.23 g, 8.46 mmol) in 10
ml of benzene was added to
a
solution of
[(Me3Si)2N]2Fe·2,2%-bipy (2.25 g, 4.23 mmol) in 15 ml of
the same solvent. The mixture was maintained for 24 h
at 20 °C. The green solution slowly turned dark green–
brown. Benzene was removed in vacuo and the solid
residue recrystallized from toluene affords greenish-
brown crystals. Yield: 2.99 g (96%). Anal. Calc. for
C28H62Si8O2N2Fe: C, 45.49; H, 8.45; Fe, 7.55. Found:
C, 43.94; H, 9.56; Fe, 8.11%.
3.3.7. [(Me3Si)3SiO]2Co(2,2%-dipy) (8)
A mixture of 2,2%-dipyridyl (0.58 g, 3.7 mmol) and of
[(Me3Si)2N]2Co (1.40 g, 3.7 mmol) in 10 ml of benzene
was stirred at room temperature (r.t.) for 3 h. The
solvent was removed in vacuo to give brown crystals
that were recrystallized from n-hexane. Yield: 1.80 g
(91%) of [(Me3Si)2N]2Co(2,2%-dipy). Anal. Calc. For
C22H44Si4N4Co: C, 49.31; H, 8.28; Co, 11.00. Found: C,
49.44; H, 8.23; Co, 10.95%. IR (cm−1): 1240 (s), 840
(vs), 750 (m), 675 (m), (SiMe); 975 (m) (NSi2), 1580
(m), 760 (m) (2,2%-dipy).
Tris(trimethylsilyl)silanol (2.50 g, 9.5 mmol) in 10 ml
of benzene was added to a solution of [(Me3Si)2N]2Fe-
(2,2%-bipy) (3.53 g, 4.75 mmol) in 15 ml of the same
solvent. The mixture was maintained for 24 h at 20 °C.
Solvent was removed in vacuo. Dark brown crystals of
the product were obtained from cold toluene. Yield of
2.75 g (92%) of 8. Anal. Calc. for C28H62Si8O2N2Co: C,
45.29; H, 8.42; Co, 7.94. Found: C, 45.38; H, 8.50; Co
7.88%. veff=3.5 mB.
3.4. Reacti6ity
3.4.1. Reaction of 2 with oxygen and subsequent
hydrolysis
The calculated volume of dry oxygen was slowly
bubbled through a benzene solution of 1 or 2 at 17 °C.
The solvent was removed in vacuo and changed for
THF. Twofold excess of water was added. The mixture
was stirred for 20 min, filtered and then concentrated.
Quantitative GLC analysis of the resulting solution
showed the presence of three silanols, (Me3Si)3SiOH,
Me3SiO(Me3Si)2SiOH, (Me3SiO)2(Me3Si)SiOH which
were characterized as described earlier [11]. The precip-
itate was washed with THF and water, and then dis-
solved in dilute HCl for subsequent simultaneous
spectrophotometric determination of iron(II) and total
iron (Table 6). The precipitate of iron hydroxides did
not contain the organic impurities according to the IR
spectrum and elemental analysis.
3.3.8. {[(Me3Si)3SiO]2Co(4,4%-dipy)}n (9)
4,4%-Dipyridyl (0.18g, 1.14 mmol) in 5 ml of THF was
added to a solution of [(Me3Si)3SiO]2Co (0.83 g, 1.14
mmol) in 15 ml of the same solvent. Red fine crystalline
precipitate was formed immediately. It was washed
with THF and dried in vacuo. Yield: 0.68 g (97%).
Anal. Calc. for C28H62Si4O2N2Co: C, 45.30; H, 8.42.
Found: C, 44.99; H, 8.39%. veff=5.4 mB.
3.4.2. Interaction of 2 with acetone
An excess of dry acetone was added to a solid
compound 2. After initial dissolution, the slow precipi-
tation of FeO began. The mixture was maintained for
24 h and then filtered. The filtrate contained mesityl
oxide and tris(trimethylsilyl)silanol in quantitative yield
3.3.9. [(Me3Si)3SiO]2Co(Ph3P)2 (10)
Triphenylphosphine (1.10 g, 4.0 mmol) was added to
a solution of homoleptic 1 (1.22 g, 2.0 mmol) in 20 ml
of toluene. The green solution turned dark green–vio-

30
T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
according to GLC analysis. The FeO precipitate did
not contain HO-groups according to the IR spectrum.
Iron content was found to be 76.03% (Calc. 77.73%).
ml of toluene was maintained at 40 °C for 8 h. Green
color of the solution slowly turned dark brown. The
volume of gaseous products (0 °C) was found to be 75
ml. GLC analysis showed the presence of methane and
hydrogen in the molar ratio of 1:0.13 per mole of 1.
Toluene was removed in vacuo. IR spectra of the
residue showed the absence of (CoꢀOꢀSi) bond. Hy-
drolysis of the residue in THF solution with 10% HCl
(5 ml) gave hydrogen and Me3SiH according GLC
analysis and IR spectrum (w(SiH)=2135 cm−1 (gas
phase) or 2118 cm−1 in solution [24]; 840, 1250 cm−1
(SiMe)).
Organic layer after THF removal contained oil which
was distilled in vacuo to give 0.3 g of crystalline
(Me3Si)3SiOSiMe3 (subl. at ꢀ80 °C/0.01 mmHg [13]),
1H-NMR (300 K, C6D6, l ppm): 0.14 (s, 27H,
(Me3Si)3Si), 0.02 (s, 9H, OSiMe3) and 0.6 g of viscous
oil (b.p. 105 °C/0.01 mmHg), which was tentatively
characterized as (Me3Si)3SiꢀOꢀSiH(SiMe3)(OSiMe3).
1H-NMR (C6D6, 200 MHz, 300 K, l ppm): 0.32 (s,
27H, (Me3Si)3), 0.35 (s, 9H, Si(SiMe3)), 0.18 (s, 9H,
OSiMe3), 5.00 (s, 1H, SiH). 13C-NMR (C6D6, 50 MHz,
300 K, l ppm): −0.36 (s, OSiMe3), −0.08 (s,
(Me3Si)3), 0.21 (s, Si(SiMe3). 29Si-NMR (C6D6, 40
MHz, 300 K, l ppm): 7.5 (OSiMe3), −9.5 (Si(SiMe3),
−10.0 ((Me3Si)3), −16.3 (SiH), −16.6 ((Me3Si)3SiO).
IR (cm−1): w(SiH) 2110 m, w(SiMe) 1240s, 840vs, 675s,
620m, w(SiOSi) 1050 m.
3.4.3. Interaction of 1 with CO
The ampoule containing 0.59 g (1 mmol) of 1 in 5 ml
of toluene was attached to a mercury burette with
carbon monoxide and maintained for 24 h at 20 °C.
The green color of the solution slowly turned dark
brown. The overall volume of the consumed gas was 40
ml. Nearly all the solvent part was removed under
reduced pressure; the liquid residue was maintained at
0 °C for 1 h affording a small amount of unstable dark
brown crystals. IR (cm−1): (2040 (s), 2030 (s), 2000 (s),
1870 (m), 1240 (s), 1050 (s), 840 (vs).
3.4.4. Interaction of 7 with PhCꢁCH. Synthesis of
(Me3Si)3SiOCoꢀCꢁCPh(PhCN) (12)
Phenylacetylene (0.10 g, 1 mmol) in 5 ml of hexane
was added to a solution of [(Me3Si)3SiO]2Co(PhCN)2
(7) (0.54 g, 1 mmol) in 8 ml of hexane. The resulting
solution was maintained for 3 h at 20 °C. For this
period of time a blue fine crystalline precipitate was
formed. The supernatant was decanted, and the remain-
ing blue crystals were washed with cold toluene and
dried in vacuo. Yield: 0.51 g (95%). Anal. Calc. for
Si4C24H37ONCo: C, 54.71; H, 7.08; Co, 11.19. Found:
C, 54.55; H, 7.12; Co 11.23%. IR (cm−1): w(SiMe) 1235
(vs), 840 (vs); w(CꢁN) 2222 (m); w(C6H5) 1580 (m), 1560
(sh); w( SiC3) 780 (m), 755 (m), 745 (m) 680 (s), 620 (w);
3.5.2. Thermal decomposition of iron(II)
tris(trimethylsilyl)siloxide (2)
1
550 (m), 500 (s), 435 (m). H-NMR (l ppm): 7.2–7.5
(m, 10 H), 0.15 (27 H). Hydrolysis of 12 yields
tris(trimethylsilyl)silanol, phenylacetylene, benzonitrile
in the molar ratio (1:1:1) according to the quantitative
GLC analysis and cobalt(II) hydroxide that did not
contain the organic impurities according to the IR
spectrum and elemental analysis. Cobalt content was
found to be 62.14% (Calc. 63.40%).
Thermal decomposition was carried out in vacuo
(0.01 mmHg) with a heating rate of 3 °C min−1. The
temperature range studied extended to 250 °C. Volatile
products of thermolysis were collected at 180–250 °C
to be (Me3Si)3SiOH and (Me3Si)3SiOSiMe3 in the molar
ratio 0.15:0.10 per mole of 2 according GLC. The
hydrogen evolution being slow at 200 °C rises signifi-
cantly above 220 °C. The solid residue with IR absorp-
tion at w(SiMe) 1240 (m), 840 (s), w(SiꢀOꢀSi) 1050 (vs),
w(SiOFe) 950 (w) was dissolved in THF and hydrolyzed
to form a green precipitate of Fe(OH)2 (Fe2+ content
58.66%, Calc. 62.15%) and soluble oligosiloxane. Filtra-
tion followed by the solvent removal gave viscous oil
3.4.5. Oligomerisation of phenylacetylene with
[(Me3Si)3SiO]2Fe (2)
Phenylacetylene (5 g, 0.049 mol) was gradually added
for 5 min to a 15 ml of 0.01 M solution of 2 in toluene
with vigorous stirring. A dark red gel was centrifuged,
the centrifugate was pumped in vacuo, and the residue
was recrystallized from glacial AcOH and sublimated in
vacuo to form pure 1,3,5-triphenylbenzene. Yield: 4.5 g
(90%). M.p. 170 °C (lit. data 170 °C [23]). Anal. Calc.
for C24H18: C, 93.84; H, 6.16%. Found: C, 93.80; H,
6.13%.
1
showing broad H-NMR signals at 0.2–0.3 ppm and
IR absorption at w(SiMe) 3400 (w), 1240 (m), 840 (s),
w(SiꢀOꢀSi) 1050 (vs). Hydrochloric solution of the pre-
cipitate also gave also negative test with K4[Fe(CN)6)]
showing the absence of Fe+3 ions in the products of
thermolysis.
3.5. Thermal decomposition
4. Supplementary material
3.5.1. Thermal decomposition of cobalt(II)
tris(trimethylsilyl)siloxide (1)
A solution of 1.77g (3 mmol) of homoleptic (1) in 10
Crystallographic data for structural analysis have
been deposited with the Cambridge Crystallographic

T.A. Chesnoko6a et al. / Journal of Organometallic Chemistry 642 (2002) 20–31
31
[5] Conversion of tris(trimethylsilyl)silanol was found to be ꢀ30%
after staying in open air for a month. At least five products was
observed according GLC analysis, while oxidation with perox-
ibenzoic acid gives only two intermediates and one final product,
(Me3SiO)3SiOH [11]. Apparently, oxidation with oxygen involves
free radical processes.
[6] V.V. Semenov, E.Yu. Ladilina, T.A. Chesnokova, A.N. Kornev,
M.A. Lopatin, A.N. Egorochkin, Organomet. Chem. USSR 5
(1992) 368.
Data Centre, CCDC no. 159595 for compound 11 and
the refcode FOVLAD for compound 1. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
[7] A. Vioux, Chem. Mater. 9 (1997) 2292.
Acknowledgements
[8] O. Vohler, Chem. Ber. 91 (1958) 1161.
[9] K.M. Abraham, G. Urry, Inorg. Chem. 12 (1973) 2850.
[10] D.E. Gindelberger, J. Arnold, Inorg. Chem. 32 (1993) 5813.
[11] A.N. Kornev, T.A. Chesnokova, V.V. Semenov, E.V. Zhezlova,
L.N. Zakharov, L.G. Klapshina, G.A. Domrachev, V.S.
Rusakov, J. Organometal. Chem. 547 (1997) 113.
[12] S.K. Mehrotra, H. Kawa, J.R. Baran Jr., M.M. Ludvig, R.J.
Lagow, J. Am. Chem. Soc. 112 (1990) 9003.
[13] A.N. Kornev, T.A. Chesnokova, V.V. Semenov, Yu.A. Kurskii,
Russ. Chem. Bull. 44 (1995) 1107.
[14] V.I. Vedeneev, L.V. Gurvich, V.N. Kondrat’yev, V.A.
Medvedev, Ye.L. Frankevich, Bond Energies, Ionization Poten-
tials and Electron Affinities, St. Martin’s Press, New York, 1966.
[15] M.M. Levitsky, B.G. Zavin, A.I. Chernyavsky, V.V. Erokhin,
Russ. Chem. Bull. 9 (1999) 1811.
We are grateful to the International Center for Ad-
vanced Studies in Nizhny Novgorod (grant 99-3-04)
and Russian Fonds of Basic Researches (grants 00-15-
97439 and 00-15-97359, scientific schools; 00-03-42004,
Regional Center of investigations) for financial support
of this work. We are also grateful to the X-Ray Struc-
tural Centre of Central and Technical Chemistry Divi-
sion of Russian Academy of Sciences for their kind
permission to use the single crystal diffractometer.
[16] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, Pergamon Press, Oxford, 1980.
[17] B.H. Boo, H.K. Kang, S.K. Kang, S.S. Lee, J. Organomet.
Chem. 436 (1992) 1.
[18] R.A. Andersen, K. Faegri, J.C. Green, A. Haaland, M.F. Lap-
pert, W.-P. Leung, K. Rypdal, Inorg. Chem. 27 (1988) 1782.
[19] H. Burger, U. Wannagat, Monatsh. Chem. 94 (1963) 1007.
[20] A.E. Harvey, J.A. Smart, E.S. Amis, Anal. Chem. 127 (1955) 26.
[21] G. Graue, S. Eckhard, W. Gradtke, Angew. Chem. 71 (1959) 28.
[22] G.M. Sheldrick, Structure Determination Software Program
Package (PC version), Siemens Analytical X-ray Instruments,
Inc., Madison, WI, 1989.
References
[1] G.A. Sigel, R.A. Bartlett, D. Decker, M.M. Olmstead, P.P.
Power, Inorg. Chem. 26 (1987) 1773.
[2] While tris(trimethylsilyl)silyl group seems quite bulky, its steric
parameter Es (effective size) is approximately equal or slightly
more than those found for tert-butyl group. See: J. Frey, E.
Schottland, Z. Rappoport, D. Bravo-Zhivotovskii, M. Nakash,
M. Botoshansky, M. Kaftory, Y. Apeloig, J. Chem. Soc. Perkin
Trans. 2 12 (1994) 2555.
[3] E. Ruiz, S. Alvarez, P. Alemany, J. Chem. Soc. Chem. Commun.
(1998) 2767.
[4] M. Hanack, S. Deder, A. Lange, Coord. Chem. Rev. 83 (1988)
115.
[23] R.D. Rose, F.S. Statham, J. Chem. Soc. (1950) 69.
[24] G. Kessler, H. Kriegsmann, Z. Anorg. Allg. Chem. 342 (1966)
53.