Hypervalent and binuclear silicon and germanium derivatives from bis-(3,5-di-tert-butyl-2-phenol)-oxamide

Article abstract of DOI:10.1016/j.jorganchem.2007.08.042

The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl₂SiR₂ (Me or Ph) or Cl₂GeR₂ (Me, nBu or Ph) in THF provided binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylgermane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsilane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-phenol)acetamide (7) and Cl₂SiR₂ (R = Me and Ph). Comparison of the ²⁹Si NMR chemical shifts of the penta- (2 and 3) and tetracoordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical positions.

Full text of DOI:10.1016/j.jorganchem.2007.08.042

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5549–5554
www.elsevier.com/locate/jorganchem
Hypervalent and binuclear silicon and germanium derivatives
from bis-(3,5-di-tert-butyl-2-phenol)-oxamide
a
b
c
´
´
´
´
Vıctor M. Jimenez-Perez , Carlos Camacho-Camacho , Angel Ramos-Organillo ,
a
a
a
´
´
Rau´l Ramırez-Trejo , Adrian Pena-Hueso , Rosalinda Contreras ,
˜
a,
*
Angelina Flores-Parra
a
Departamento de Quı´mica, Cinvestav, A.P. 14-740, C.P. 07000, Me´xico, D.F., Mexico
Departamento de Sistemas Biolo´gicos, Universidad Auto´noma Metropolitana, Xochimilco, Calzada del Hueso 1100, Colonia Villa Quietud,
C.P. 04960 Me´xico, D.F., Mexico
b
c
Facultad de Ciencias Quı´micas, Universidad de Colima, A.P. 28400, Coquimatla´n, Colima, Mexico
Received 26 July 2007; received in revised form 21 August 2007; accepted 23 August 2007
Available online 14 September 2007
Abstract
The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl2SiR2 (Me or Ph) or Cl2GeR2 (Me, nBu or Ph) in THF provided
binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-
(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4),
bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenyl-
germane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsi-
lane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-
phenol)acetamide (7) and Cl2SiR2 (R = Me and Ph). Comparison of the 29Si NMR chemical shifts of the penta- (2 and 3) and tetraco-
ordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon
atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central
atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical
positions.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Organosilane; Organogermane; X-ray structures; 29Si NMR; Aromatic hexacycles
1. Introduction
interest and applications in synthesis [4–6]. On the other
hand, oxamides are well known as excellent ligands with
transition metals and have been the subject of several
reviews [7,8]; however less attention has been paid to oxam-
ide coordination compounds with main group elements.
Indeed there are scarce reports of solid state analyses of
these kinds of crystalline structures [9–14]. Additionally,
oxamides have been described as inhibitors of HIV
[15,16] and responsible of hypoglycemic activity [17].
We recently reported the synthesis and characterization
of pentacoordinated tin compounds derived from the sym-
metric bis-(3,5-di-tert-butyl-2-phenol)-oxamide (1) [18,19]
as well as optically active oxamides [20] (Scheme 1).
The group 14 elements show a versatile chemistry due to
their diverse electronegativities and metallic characters and
to their ability to show hypervalent coordination numbers
[1]. Even though pentacoordinated silicon atoms were first
described in the beginning of XIX century by Gay-Lussac
[2] and Davy [3], it is only in the last three decades that sil-
icon and germanium compounds with high coordination
numbers have been widely studied, due to their structural
*
Corresponding author. Tel.: +55 5061 3720; fax: +55 5061 3389.
E-mail address: aflores@cinvestav.mx (A. Flores-Parra).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.042

5550
V.M. Jime´nez-Pe´rez et al. / Journal of Organometallic Chemistry 692 (2007) 5549–5554
tBu
N
butyl-2-phenol)-acetamide (7) to be used as models of tet-
racoordinated silicon compounds.
1
tBu
O
O
R
R
2. Results and discussion
R
R
3
3
H
H
Sn
N
Sn
O
O
The bis-(2-phenol)-oxamide is a planar molecule with
two strong bifurcated N–H hydrogen bonds. It is interest-
ing to note that the C3–H forms a short hydrogen bond
3
O
R
R
O
R
Sn
O
N
H
Sn
O
N
R
Me
˚
with the carbonyl oxygen (2.22 A). Furthermore, the pla-
tBu
nar conformation forces the C3–H proton to approach
the carbonyl group shifting the 1H signal to higher frequen-
cies [21], Fig. 1a. The substituted oxamide molecule bis-
(3,5-di-tert-butyl-2-phenol)-oxamide has a different confor-
mation where the OH group is not on the same side as the
N–H. A view of its solid state structure is shown in Fig. 1b.
The 1H NMR spectra confirm that the same conformation
was found in solution, as was deduced from the C3–H sig-
nal, d = 7.31 ppm. This fact could be explained by this dif-
ferent conformation where the O–H proton can avoid the
steric effect produced by the tert-butyl group [19].
However, in spite of the preferred non-planar structure
of ligand 1, the tin derivatives acquire a planar conforma-
tion in order to form bimetallic fused hexacycles. The
ligand acts as a clamp, due to the high acidity of the OH
and NH protons. The metal atom which takes their place
becomes a very acidic center. This atom has the effect of
imposing a rigid and planar structure on the ligand, which
in turn forces the C@O so close to the metal that it cannot
avoid coordination with it, giving strongly bonded penta-
Ph
tBu
R = Me, nBu and Ph
R = nBu and Ph
Scheme 1. Tin compounds derived from ligand 1 [18,19] and from
(1S,2R)-(ꢀ)-[N-(2-hydroxy-1-methyl-2-phenyl-ethyl)-N0-(2-hydroxy- phe-
nyl)-oxalamide [20]. The distance of the C–H3 proton to the C@O is ꢁ2.2–
˚
2.4 A.
Continuing with this research based on coordination com-
pounds of main group elements, we decided to prepare the
corresponding organosilicon and organogermanium binu-
clear compounds derived from ligand 1, in order to estab-
lish
a comparative study of their structures and
spectroscopic properties with those of the tin compounds,
already reported. It was important to determine if silicon
or germanium atoms could become hypervalent. Further-
more, in order to evaluate the coordination bond in the sil-
icon compounds by 29Si NMR, we have prepared two
tetracoordinated silicon derivatives from N-(3,5-di-tert-
Fig. 1. (a) Solid state structures for bis-(2-phenol)oxamide [21], and (b) bis-(3,5-di-tert-butyl-2-phenol)-oxamide [19].

V.M. Jime´nez-Pe´rez et al. / Journal of Organometallic Chemistry 692 (2007) 5549–5554
5551
coordinated tin atoms [19], (C@O ! Sn coordination bond
Comparison of the IR stretching vibrations of the C@O
groups in 2 (1664 cmꢀ1) and 3 (1666 cmꢀ1) and the free
ligand (1662 cmꢀ1), does not clearly indicate the presence
of an intramolecular coordination of the oxygen towards
the silicon atoms. This may be due to the fact that the free
ligand shows a strong intramolecular coordination of the
N–H proton.
˚
˚
length is 2.22 A, while the covalent bond O–Sn is 2.06 A),
Scheme 1. As a consequence of these findings, we decided
to prepare the corresponding hypervalent silicon and ger-
manium compounds and to explore, if in spite of the fact
that these elements have less metallic character than tin,
the structure of the ligand could force the formation of iso-
structural pentacoordinated compounds, especially in the
case of silicon which has a weaker metallic character.
Treatment of quinone 1 with Cl2SiR2 (R = Me or Ph) or
2.1. NMR studies
n
Cl2GeR2 (R = Me, Bu or Ph) in THF and NEt3 at low
An important probe for the coordination to silicon or
germanium in solution, is the shift to higher frequencies
of the 1H NMR signals for H-3 [2 (8.12), 3 (8.22), 4
(8.32), 5 (8.24), 6 (8.52 ppm)], with respect to the signal
in ligand 1 (7.31 ppm). This shift could be due to the prox-
imity of the carbonyl group to H3, when the molecules 2–6
adopt a planar conformation. This intramolecular interac-
tion is confirmed in the solid state of 3 and 6 by X-ray dif-
fraction, which showed a short distance C3–Hꢂ ꢂ ꢂO@C
temperature resulted in the pentacoordinated silicon and
germanium binuclear derivatives in good yield (Scheme
2), Both compounds are isostructural with the tin com-
pounds previously reported [19].
Under the same conditions, the reaction of the phenola-
mide 7 with Cl2SiR2 (R = Me or Ph) afforded the tetraco-
ordinated organosilicon compounds 8 and 9 (Scheme 3).
The silicon derivatives 2, 3, 8 and 9 are unstable in the
presence of air and moisture whereas the germanium com-
pounds 4–6 are very stable. All compounds were character-
ized by NMR in solution and the molecular structures of 3
and 6 were determined in the solid state by X-ray
crystallography.
˚
˚
(2.45 A in 3 and 2.30 A in 6).
The 29Si NMR spectra of the organosilicon compounds
2 and 3 shows a singlet at d 29Si = ꢀ21.6 and ꢀ60.9 ppm,
respectively, which correspond to pentacoordinated silicon
atoms [22]. The 29Si chemical shift difference between 2 and
3 is due to the electronic properties of the Si–Me and Si–Ph
groups. In order to confirm the pentacoordinated structure
of the silicon compounds 2 and 3; model compounds with-
out the carbonyl group were prepared. The synthesis of tet-
racoordinated organosilicon compounds was carried out as
described in Scheme 3. The 29Si spectra of compounds 8
and 9 exhibit resonances (at ꢀ10.1 and ꢀ11. 8 ppm, respec-
tively) which correspond to tetracoordinated silicon atoms.
Comparison of 29Si data of compounds 2, 3, 8 and 9,
clearly indicates the pentacoordination of 2 and 3, and con-
firms the same molecular structures in solution and in solid
state (vide infra).
The mass analyses show the molecular ions of com-
pounds 2 [M+] 608, 3 [M+] 856, 4 [M+] 698, 5 [M+] 867,
and 6 [M+] 946. In all cases, the first loss observed corre-
sponds to the organyl groups bonded to the central atom,
indicating that the hexacyclic framework is very stable.
tBu
tBu
6
5
1
4
tBu
OH
O
tBu
O
2
3
R
R
H
NH
2 Cl2MR2, THF
-78ο C, 4 Et3N
N
7
M
O
O
O
- 4 Et3N+HCl
R
R
2.2. X-ray diffraction analyses
M
N
HN
H
Structures of compounds 3 and 6 are similar. Com-
pound 3 is shown in Fig. 2. Both compounds have two sil-
icon or two germanium atoms in hexacyclic planar arrays.
Based on the bond angles analyses, it is deduced that the
central atoms present a tbp geometry with a distortion
due to rings tension. One nitrogen and two carbon atoms
are in equatorial positions and two oxygen atoms are in
apical positions (Fig. 1). Selected bonds and angles are pre-
sented in Table 1 and compared with data of the analogue
tin compound [19].
HO
tBu
O
tBu
tBu
1
tBu
M = Si; 2 R = Me, 3 R = Ph
M = Ge; 4 R = Me, 5 R = nBu, 6 R = Ph
Scheme 2. Heterobinuclear compounds derived from oxamides.
tBu
tBu
6
5
The five bond lengths around the central atom are
slightly longer than covalent bonds indicating delocalized
structures with some anionic character at the silicon or ger-
manium atom and a delocalized positive charge in the
ligand. N1–C1 and C1–O1 bonds of the oxamide group
have double bond character, whereas the central C1–C1
bond lengths correspond to single bonds. It is quite inter-
esting that N–C@O angles are wide (127.8–132.5°), Table
Cl2SiR2, THF
-78ο C, 2 Et3N
1
4
tBu
O
tBu
OH
2
3
R
Si
- 2 Et3N+HCl
H
N
7
NH
Me
R
O
O
Me
7
8 R = Me, 9 R = Ph
Scheme 3. Synthesis of tetracoordinated silicon compounds.

5552
V.M. Jime´nez-Pe´rez et al. / Journal of Organometallic Chemistry 692 (2007) 5549–5554
gave selectively bimetallic hexacyclic symmetric heterocy-
cles bearing pentacoordinated silicon or germanium com-
pounds. The silicon atoms are strongly coordinated by
the carbonyl group, in solution, as was deduced from the
29Si NMR, and in solid state, as was determined by X-
ray diffraction. It was confirmed that the structure of ligand
1 allows a strong coordination to silicon atoms, compara-
ble to that of germanium and tin atoms.
4. Experimental
4.1. General comments
All manipulations were carried out in a vacuum line.
THF was dried by distillation from sodium–benzophenone.
NEt3 was dried by distillation from KOH and then from
CaH2. The organosilicon and organogermanium com-
pounds were purchased from Aldrich and used without fur-
ther purification. The bis-(3,5-di-tert-butyl-2-phenol)-
oxamide was prepared according to the literature [19].
The melting points were obtained on a Mel-Temp II appa-
ratus and are uncorrected. IR spectra were recorded on an
FT-IR 1600 Perkin–Elmer spectrophotometer using KBr
pellets in the 4000–400 cmꢀ1 range. Mass spectra in the
EI mode were recorded at 20 eV on a Hewlett–Packard
HP 5989 spectrometer. Fast atom bombardment mass
spectrometry (FAB+) was performed on a Jeol SX102A
instrument of inverted geometry, in a matrix of 3-nitroben-
zyl alcohol and in the 0–2200 m/z range. Elemental analy-
ses were performed on Eager 300 equipment. NMR spectra
Fig. 2. Single crystal X-ray diffraction of compound 3. Hydrogen bonds
are omitted for clarity.
1. As expected, the central atom bond lengths increase in
the order Si < Ge < Sn, and the less distorted bpt geometry
is that of the silicon, due to a longer N–Si bond and the
smaller size of the silicon atom.
Compound 3 shows, in the unit cell, three CHCl3 mole-
cules. One of them is disordered over two positions. Com-
pound 6 shows two molecules in the unit cell with one
disordered molecule of THF.
3. Summary
Reactions of bis-(3,5-di-tert-butyl-2-phenol)-oxamide
(1) with diorganyldichlorosilicon and germanium reagents
Table 1
Selected bond lengths and angles for 3, 6 and their tin analogue [19]
tBu
tBu
O
R
N1
N
H
M
R
C1
O
O1
C1
O
O1
R
R
M
N
N1
O
tBu
tBu
Bonds
Sn19
Ge
Si
Angles
M–O1
M–O3
M–N
M–C
M–C
C2–N1
C1–N1
C1–C1
O1–C1
2.22(1)
2.07(1)
2.15(1)
2.12(1)
2.14(1)
1.41(1)
1.30(1)
1.52(2)
1.28(1)
2.204(3)
1.864(3)
1.937(4)
1.936(5)
1.937(5)
1.427(5)
1.311(5)
1.511(5)
1.257(5)
2.026(5)
1.739(5)
1.852(5)
1.869(8)
1.856(6)
1.410(9)
1.301(9)
1.489(9)
1.273(8)
O1–Si–O3
166.9(2)
161.84(12)
151.4(3)
119.3(3)
120.3(2)
129.7(4)
132.5(6)
129.3(4)
127.8(4)
O1–Ge–O3
O1–Sn–O3
C–Si–C
C–Ge–C
C–Sn–C
(Si) N1–C1–O1
(Ge) N1–C1–O1
(Sn) N1–C1–O1

V.M. Jime´nez-Pe´rez et al. / Journal of Organometallic Chemistry 692 (2007) 5549–5554
5553
were obtained on a Jeol GSX-270, Jeol Eclipse 400 MHz
and Bruker Advance 300 MHz.
4.2.4. Bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-(di-
n-butylgermane) (5)
Compound 5 is an orange solid (330 mg, 95%), dec at
1
4.2. Syntheses
350 °C. NMR (CDCl3), H: d 0.80 (t, CH3-d, n-Bu2Ge,
12H), 1.42–1.72 [m, CH2-a,b,c, n-Bu2Ge, 8 H], 1.27 (s, t-
4
4.2.1. Bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-
(dimethylsilane) (2)
Bu-4, 18 H), 1.38 (s, t-Bu-6, 18H), 7.06 [d, H5, J(H,H)
2.2 Hz, 2H], 8.25 [d, H3, J(H,H) 2.2 Hz, 2H]. 13C: 13.8
4
General procedure for compounds 2–6 and 8–9.
To a solution of 0.1 g (0.2 mmol) of oxamide 1 in THF
(15 mL) at 0 °C was added dropwise via syringe NEt3
(0.1 mL, 0.083 mmol). After 1 h SiMe2Cl2 (0.05 mL,
2 mmol) was added dropwise at ꢀ78 °C. The reaction mix-
ture was warmed to rt and stirred for 18 h. The solvent was
evaporated in vacuum and the residue washed twice with
cold THF (5 mL) to yield an orange solid of 2 (112 mg,
(CH3-d, n-Bu2Ge), 22.6 [CH2-a, n-Bu2Ge), 25.7 [CH2-c,
n-Bu2Ge], 26.2 [CH2-b, n-Bu2Ge], 29.44 [(CH3) t-Bu–C6],
31.9 [(CH3) t-Bu–C4], 34.7 (t-Bu–C6), 35.1 (t-Bu–C4),
113.8 (C3), 121.3 (C5), 128.0 (C2), 135.1 (C6), 138.8 (C4),
151.4 (C1), 158.7 (C7). EM (FAB+): 867 m/z. IR (KBr) m
(cmꢀ1): 1631 (C@O), 1477, 1422, 1359, 1263. Anal. Calc.
for C46H76N2O4Ge2: C, 63.78; H, 8.84; N, 3.23. Found:
C, 63.45; H, 8.95; N, 2.89%.
1
92%). Mp: 284–286 °C. NMR (CDCl3): H d 0.62 (CH3,
Me2Si), 1.37 (s, t-Bu-4, 18 H), 1.42 (s, t-Bu-6, 18H), 7.18
4.2.5. Bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-
(diphenylgermane) (6)
4
4
[d, H5, J(H,H) 2.2 Hz, 2H], 8.12 [d, H3, J(H,H) 2.2 Hz,
2H]. 13C: d 2.28 (CH3, Me2Si), 29.3 [(CH3) t-Bu–C6],
31.8 [(CH3) t-Bu–C4, 34.8 (t-Bu–C6)], 35.6 (t-Bu–C4),
112.6 (C3), 121.7 (C5), 127.9 (C2), 134.8 (C6), 140.5 (C4),
148.6 (C1), 157.6 (C7). 29Si: d ꢀ21.6 ppm. MS (EI, 20 eV)
m/z: [M+] 608. IR (KBr) m (cmꢀ1): 1664 (C@O), 1483,
1433, 1361, 1261. Anal. Calc. for C34H52N2O4Si2 THF:
C, 67.06; H, 8.61; N, 4.60. Found: C, 67.41; H, 8.33; N,
4.14%.
Compound 6 is an orange microcrystalline solid
(340 mg, 89.5%). It was recrystallized in CHCl3/C6H6
1
(2:8). Mp: 316 °C. NMR (CDCl3), H: d 1.43 (s, t-Bu-4,
4
18 H), 1.64 (s, t-Bu-6, 18H), 7.33 [d, H5, J(H,H) 6.9 Hz,
4
2H], 8.68 [d, H3, J(H,H) 6.9 Hz, 2H], 7.40 (m, m,p-H,
Ph2Ge, 12H), 7.90 (d, o-H, Ph2Ge, 8H). 13C d 29.9
[(CH3) t-Bu–C6], 31.9 [(CH3) t-Bu–C4], 35.0 (t-Bu–C6),
35.8 (t-Bu–C4), 115.9 (C3), 122.8 (C5), 128.3 (C2), 137.4
(C6), 138.5 (C4), 153.0 (C1), 158.1 (C7), 138.0 C-i, Ph2Ge),
136.4 (C-o, Ph2Ge), 128.6 (C-m, Ph2Ge), 130.9 (C-p,
Ph2Ge). MS (FAB+) [M+] 945 m/z. IR (KBr) m (cmꢀ1):
1633 (C@O), 1478, 1426, 1360, 1255. Anal. Calc. for
C54H60N2O4Ge2: C, 59.92; H, 5.79; N, 2.44. Found: C,
60.14; H, 5.83; N, 2.47%.
4.2.2. Bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-
(diphenylsilane) (3)
Compound 3 is an orange solid (320 mg, 95%). Mp: 296–
298 °C. NMR CDCl3 1H, d 1.42 (s, t-Bu-4, 18H), 1.50 (s, t-
4
Bu-6, 18H), 7.29 [d, H5, J(H,H) 2.2 Hz, 2H], 8.21 [d, H3,
4J(H,H) 2.2 Hz, 2H], 7.32 [m, m,p-H, Ph2Si, 12H], 8.00 [d,
3
o-H, Ph2Si, J(H,Sn) 69 Hz, 8H]. 13C: d 29.8 [(CH3) t-Bu–
4.2.6. N-(3,5-di-tert-Butyl-2-phenol)acetamide (7)
C6], 31.7 [(CH3) t-Bu–C4], 31.3 (t-Bu–C6), 34.8 [(C) t-Bu–
C4], 113.0 (C3), 122.9 (C5), 127.1 (C2), 134.0 (C6), 141.6
(C4), 149.1 (C1), 157.6 (C7), 134.9 (C-i, Ph2Si), 136.4 (C-o,
Ph2Si), 128.6 (C-m, Ph2Si), 130.9 (C-p, Ph2Si). 29Si: d
ꢀ60.9 ppm. MS (EI, 20 eV): [M+] 856 m/z. IR (KBr) m
(cmꢀ1): 1666 (C@O), 1480, 1434, 1387, 1303, 1262. Anal.
Calc. for C54H60N2O4Si2 CHCl3: C, 67.06; H, 6.29; N,
2.86. Found: C, 67.14; H, 6.15; N, 2.69%.
A solution of 4,6-di-tert-butyl-2-aminophenol (2.0 g,
9.1 mmol) in acetic anhydride (25 mL) and in water
(20 mL) was refluxed for 30 min, then the precipitate was
filtered and washed with cold water. A white solid was
obtained (2.3 g, 94%). Mp: 143–145 °C. NMR (CDCl3),
1H: d 2.22 (t, CH3, H-8, 3H), 1.23 (s, t-Bu-4, 9 H), 1.38
4
(s, t-Bu-6, 9H), 6.78 [d, H5, J(H,H) = 2.1 Hz, 1H], 7.12
4
[d, H3, J(H,H) = 2.1 Hz, 1H)], 7.28 (s, –OH, 1H), 8.41
(bs, –NH, 1H). 13C: d 23.67 (C8), 29.8 (t-Bu–C4), 31.7 (t-
Bu–C6), 34.4 (t-Bu–C4), 35.6 (t-Bu–C6), 117.8 (C3),
122.4 (C5), 142.6 (C2), 140.2 (C6), 126.0 (C4), 146.5 (C1),
4.2.3. Bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-
(dimethylgermane) (4)
1
1
Compound 4 is an orange microcrystalline solid
170.9 (C7). 15N: d ꢀ245 ppm, J(15N, H) = 91 Hz. MS;
(EI, 20 eV) m/z [M+] 263. IR (KBr) m (cmꢀ1) O–H 3330,
N–H 3275, C@O 1628, 1420, 1359, 1314, 1235, 951.
1
(135 mg, 97%). Mp: 390 °C. NMR (CDCl3), H: d 0.99
(CH3, Me2Ge), 1.36 (s, t-Bu-4, 18 H), 1.44 (s, t-Bu-6,
18H), 7.16 [d, H5, 4J(H,H) 2.3 Hz, 2H], 8.42 [d, H3,
4J(H,H) 2.3 Hz, 2H]. 13C: d 5.85 (CH3, Me2Ge), 29.3
[(CH3) t-Bu–C6], 31.9 [(CH3) t-Bu–C4], 34.7 (t-Bu–C6),
35.1, (t-Bu–C4], 113.7 (C3), 121.5 (C5), 127.6 (C2), 135.2
(C6), 139.0 (C4), 151.0 (C1), 158.5 (C7). MS (EI, 20 eV,
DIP): [M+] 698 m/z. IR (KBr) m (cmꢀ1): 1634 (C@O),
1478, 1424, 1360, 1260. Anal. Calc. for C34H52N2O4Ge2:
C, 58.51; H, 7.51; N, 4.01. Found: C, 58.94; H, 7.69; N,
3.95%.
4.2.7. N-Acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-
bis-(dimethylsilane) (8)
Compound 8 is an orange microcrystalline solid
(105 mg, 90%). Mp: 226–228 °C. NMR (CDCl3), 1H: d
0.15 (CH3, Me2Si), 1.27 (s, t-Bu-4, 18 H), 1.44 (s, t-Bu-6,
18H), 2.19 [s, Me–C(O)–], 6.82 [d, H5, 4J(H,H) 2.2 Hz,
4
2H], 7.23 [d, H3, J(H,H) 2.2 Hz, 2H]. 13C: d 0.52 (CH3,
Me2Si), 29.9 (t-Bu–C6), 31.6 (t-Bu–C4), 34.4 (t-Bu–C6),

5554
V.M. Jime´nez-Pe´rez et al. / Journal of Organometallic Chemistry 692 (2007) 5549–5554
35.6 (t-Bu–C4), 117.9 (C3), 122.2 (C5), 126.2 (C2), 140.0
(C6), 142.4 (C4), 146.1 (C1), 171.1 (C7). 29Si: d ꢀ10.1 ppm.
Appendix A. Supplementary material
CCDC 654612 and 654611 contains the supplementary
crystallographic data for 3 and 6. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2007.08.042.
4.2.8. N-Acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-
bis-(diphenylsilane) (9)
Compound 9 is an orange microcrystalline solid
(270 mg, 82%). Mp: 268–269 °C. NMR (CDCl3), 1H: d
1.97 [s, MeC(O)–, 3H], 1.42 (s, t-Bu-4, 18 H), 1.50 (s, t-
Bu-6, 18H), 7.29 [d, H5, 4J(H,H) 2.2 Hz, 2H], 8.21 [d,
H3, 4J(H,H) 2.2 Hz, 2H], 7.32 (m, m,p-H, Ph2Si, 12H),
8.00 (d, o-H, Ph2Si, 8H). 13C: d 23.27 (CH3CO), 29.8 (t-
Bu–C6), 31.7 (t-Bu–C4), 31.3 (t-Bu–C6), 34.8 (t-Bu–C4),
113.0 (C3), 122.9 (C5), 127.1 (C2), 134.0 (C6), 141.6 (C4),
149.1 (C1), 157.6 (C7), 134.9 (C-i, Ph2Si), 136.4 (C-o,
Ph2Si), 128.6 (C-m, Ph2Si, 130.9 (C-p, Ph2Si). 29Si: d
ꢀ11.8 ppm.
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˚
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Acknowledgement
Financial support from Conacyt-Mexico and Cinvestav
is acknowledged as well as Conacyt-Mexico scholarships
for V.M.J.-P, A.R.-O, R.R.-T and A.P.-H, and J. Guthrie
for valuable discussions.
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