Synthesis of aromatic tetracyclic tin compounds by template and transmetallation reactions: Alkyl vs aryl migration from tin to nitrogen

Article abstract of DOI:10.1016/j.jorganchem.2009.12.025

The syntheses of [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]diphenyltin (1) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]dichloro-phenyl-stannate (2) by template reactions using 3,5-di-tert-butylcatechol, aqueous ammonia and SnPh₂Cl

Full text of DOI:10.1016/j.jorganchem.2009.12.025

Journal of Organometallic Chemistry 695 (2010) 833–840
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of aromatic tetracyclic tin compounds by template and transmetallation
reactions: Alkyl vs aryl migration from tin to nitrogen
Carlos Camacho-Camacho a, Edgar Mijangos b, Maria E. Castillo-Ramos b, Adriana Esparza-Ruiz b,
b,
Aurora Vásquez-Badillo b, Heinrich Nöth c, Angelina Flores-Parra b, , Rosalinda Contreras
*
*
a Departamento de Sistemas Biológicos, Universidad A. Metropolitana, Xochimilco, Calzada del Hueso 1100, Col. Villa Quietud, CP 04960, México DF, Mexico
b Departamento de Química, Cinvestav México, AP 14-740, CP 07000, México DF, Mexico
c Department Chemie, Ludwig-Maximiliams, Universität, Butenandt-Strasse 5-13 (Haus D), D-81377 Munich, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The syntheses of [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]diphenyltin (1) and [bis(3,5-di-tert-
butyl-2-hydroxy-2-phenyl)amine]dichloro-phenyl-stannate (2) by template reactions using 3,5-di-
tert-butylcatechol, aqueous ammonia and SnPh2Cl2 are reported. We also report the syntheses of
compounds 2, [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]trichloro-stannate (4), [bis(3,5-di-tert-
butyl-2-hydroxy-2-phenyl)methylamine]chloro-methyltin (5), and [bis(3,5-di-tert-butyl-2-hydroxy-2-
phenyl)-n-butylamine]n-butyl-chlorotin (6) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]
n-butyl-dichloro-stannate (7), performed by transmetallation reactions of the octahedral zinc coordi-
nation compound Zn[3,5-di-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-1-phenyl)imine]2 (3)
with SnPhCl3 or SnPh2Cl2, SnCl4, SnMe2Cl2, Sn(nBu)2Cl2 and Sn(nBu)Cl3, respectively. The X-ray diffrac-
tion structures of compounds 1, 2, 4 and 6 are reported. The transmetallation reactions with Sn(alk-
yl)2Cl2 afforded pentacoordinated tin compounds, where an alkyl group migrated from tin to
nitrogen, while similar reactions with Sn–Ph compounds did not present any phenyl group migration.
Ó 2010 Elsevier B.V. All rights reserved.
Received 5 November 2009
Received in revised form 29 December 2009
Accepted 31 December 2009
Available online 6 January 2010
Keywords:
Tin aromatic heterocyclic
Hypervalent tin compounds
Transmetallation and template reactions
Alkyl group migration from tin to nitrogen
1. Introduction
aqueous ammonia, oxygen and metallic salts which afforded a ser-
ies of main group coordination compounds derived from bis[4,6-
We are currently working on the chemistry of tin heterocycles
derived from planar and aromatic ligands such as diphenoloxa-
mides [1–3] and diphenolamines [4,5]. The combination of planar
aromatic polycyclic ligands and tin atoms produces suitable mod-
els for biological studies as biocides, due to the potential anticancer
activity of tin compounds [6–11] and to the biocidal activity of
diphenolamine [12]. Interest in these molecules is based on their
polyfunctional nature, high reactivity and unusual electronic and
structural properties. The phenolate ligands increase the Lewis
acidic character of the metallic centers allowing stabilization of
uncommon species, due to their electronegativity, planar frame-
work and rigidity [13–18].
The diphenolamines can be prepared as reported by Frye from
reaction of iodoanisole and copper powder followed by 2-amino-
anisole and cleavage of the resulting dimethyl ether with BBr3
[19]. This apparently simple method can be problematic as the li-
gand is easily oxidised during purification. Therefore, the template
methods for the synthesis of diphenolamine derivatives are better
as was shown by template reactions of 3,5-di-tert-butylcatechol,
di-tert-butylphenol]amine [18].
2. Results and discussion
2.1. General comments
Herein, we report the synthesis of two tetracyclic compounds (1
and 2) by template reactions using 3,5-di-tert-butylcatechol, aque-
ous ammonia and SnPh2Cl2 or SnPhCl3 (Scheme 1). Similar
reactions for alkyl substituents gave the pentacoordinated dimeth-
yltin when the reaction was performed with SnMe2Cl2 and the
hexacoordinated n-butyldichloro tin compound when the reagent
is Sn(nBu)Cl3 [18].
An interesting characteristic of diphenolamine ligands is that
they can be found in different oxidation states depending on the
coordination number and the oxidation state of associated metal
ions, (Scheme 2) [20,21]. As a consequence, their pentacoordinated
tin compounds are paramagnetic where the ligand oxidation state
corresponds to structure d, whereas the hexacoordinated com-
pounds are diamagnetic with the ligand in oxidation state e.
Stegmann and Scheffler reported in 1970 [22] that the reaction
of 2-amino-4,6-di-tert-butyl-phenol with SnPh2Cl2 afforded a para-
* Corresponding authors. Tel.: +55 5061 3720; fax: +55 5061 3389 (A. Flores-Parra).
E-mail address: aflores@cinvestav.mx (A. Flores-Parra).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.12.025

834
C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
R'
R'
5
3
6
.
4
1
R'
R'
R'
O
O
Sn
O
R'
OH
OH
Cl
2
Ph
Ph
Ph2SnCl2
NH4OH,EtOH, O2
PhSnCl3
EtOH, O
Sn
Ph
N
N
Cl
NH4OH,
2
O
R'
R'
R' = t-Bu
R'
R'
2
1
Scheme 1. Template reactions for the synthesis of compounds 1 and 2.
R
N
R
R
N
R
R
N
R
R
N
R
R
O
R
R
.
-
-
-
-
O
O
O
O
R
R
R
R
O
O
R
R
O
O
R
R
+
-
N
O
R
.
-
a
d
e
b
c
Scheme 2. Oxidation states of the bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine [21].
magnetic tetracoordinated tin compound forming an eight mem-
bered heterocycle. In our hands, the template reaction of 3,5-di-
tert-butylcatechol and SnPh2Cl2 in the presence of NH4OH, ethanol
and O2 afforded the paramagnetic compound 1. The X-ray diffrac-
tion analyses of 1 showed a pentacoordinated tin atom in a tetra-
cyclic framework, which could be the actual structure of the
Stegmann and Scheffler compound. A similar reaction with SnPhCl3
gave the hexacoordinated stannane bearing a SnPhCl2 group (2).
The 119Sn NMR spectrum [119Sn d = À426 ppm] gave a characteris-
tic signal for a hexacoordinated compound. The structure was con-
firmed by X-ray diffraction analysis.
We also report the preparation of compounds 2, 4–7 by trans-
metallation reactions using the octahedral zinc coordination com-
pound 3 and SnCl4, SnPhCl3, SnPh2Cl2, SnBu2Cl2, SnMe2Cl2, SnBuCl3
(Scheme 3). The zinc compound 3 was synthesized from a template
reaction using 3,5-di-tert-butylcatechol, ammonium hydroxide
and Zn(OAc)2 in ethanol [23], Scheme 4.
compounds. The NMR spectral data showed two different n-butyl
or methyl groups, which is not consistent with a symmetric struc-
ture where the tin is bound to two alkyl groups. The explanation
for this spectral behavior was found in the solid state structure
of compound 6 which showed a folded tetracyclic structure. The
new structure is derived from the n-butyl group migration from
tin to nitrogen. The product has a tetrahedral coordinated nitrogen
atom instead of the planar sp2 tricoordinated nitrogen found in
compounds 1, 2 and 4. The N ? Sn coordination afforded a penta-
coordinated tin atom bearing in addition to the ligand one alkyl
group and one chlorine atom. The 13C NMR data, characteristic
for a phenolamine and not for a quinone, are explained by the loss
of the planar arrangement of the ligand which inhibits the elec-
tronic delocalization through the nitrogen but not through the
phenolic groups. Based on the analogy of the NMR spectral data
for compounds 5 and 6, we have concluded that compound 5, ob-
tained from SnMe2Cl2, is structurally similar to 6.
The reaction of compound 3 with SnCl4 in toluene gave in good
yield (65% after purification) the diamagnetic compound 4. The
119Sn NMR resonance (d = À514 ppm) was attributed to a hexaco-
ordinated tin heterocycle bearing a SnCl3 group. The X-ray diffrac-
tion analysis confirmed the structure. Each molecule of zinc
compound reacted with two SnCl4 molecules giving two tin het-
erocycles and one molecule of ZnCl2.
The reaction of one equivalent of compound 3 with two of Sn(n-
Bu)Cl3 after 3 h in refluxing toluene gave compound 7. The 119Sn
spectrum (d 119Sn = À311 ppm) shows that 7 is the main product
(90%) together with a signal for compound 4 (5%). The X-ray dif-
fraction structure of compound 7 is known, however its NMR data
were not previously reported [18].
Some comments are pertinent. As we have previously reported,
the direct template reactions with catechol and alkyltin reagents:
SnMe2Cl2 or Sn(n-Bu)Cl3 afford the respective planar compounds
analogous to 1 and 2, without migration of the alkyl group [18].
However the transmetallation reactions using the zinc compound
favored the migration of alkyl groups from tin to nitrogen in dial-
kyltin halides. The migration was selective for alkyl groups and
does not occur with phenyl groups.
The intermolecular alkyl transference from tin to carbon in the
presence of palladium reagents is known [24] as well as the pref-
erence for the methyl groups transference over phenyl groups
[25–27]. In compounds 5 and 6 the transformation from the hexa-
coordinated to pentacoordinated compounds could be catalyzed by
the zinc compounds present in the reaction medium, Scheme 5.
Zinc mediated intramolecular acyl and imine transfer reactions of
aryliodides are known [28]. The synthesis of compound 2 by the
The reaction of the zinc compound 3 with SnPhCl3 gave com-
pound 2 by elimination of a chlorine atom from tin and formation
of ZnCl2
(
119Sn d = À427 ppm). The reaction of 3 with SnPh2Cl2
could give different compounds: the SnPh2 pentacoordinated com-
pound
1 or the hexacoordinated derivatives bearing groups
SnPhCl2 or SnPh2Cl. The 119Sn NMR resonance (d = À427 ppm)
showed that the product was again compound 2 and that a phenyl
group instead of the chlorine atom was substituted, with ZnPh2
being a probable product. This behavior is explained by the fact
that chlorine atoms better stabilize the hexacoordinated stannate
by withdrawing electron density from it.
The reaction of the zinc compound 3 with SnMe2Cl2 or Sn(n-
Bu)2Cl2 in refluxing toluene, gave unexpectedly diamagnetic com-
pounds (5 and 6, respectively), Scheme 3. The 119Sn resonances (5
d = À65 ppm and 6 d = À186 ppm) indicated pentacoordinated

C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
835
R'
6
R
5
R
4
1
O
R'
R'
2
Sn
Cl
O
N
Cl
3
Sn Cl
N
Cl
O
R´
Me2SnCl2
or
R´
R'
O
SnCl4
toluene
toluene
-1/2 ZnCl2
R´
nBu2SnCl2
-1/2 ZnCl2
R'
4
R'
R = CH δ 119Sn -165
5
6
δ 119Sn -514
3
R'
O
Zn
O
R'
δ 119Sn -186
R = nBu
O
R'
N
1/2
N
O
R'
R'
R'
Ph2SnCl2
or
nBuSnCl3
toluene
-1/2 ZnPh2
or
R'
PhSnCl3
3
-1/2 ZnCl2
-1/2 ZnCl2
toluene
R'
N
R'
O
R'
Cl
O
R'
Cl
Sn
O
nBu
Sn
O
Ph
N
Cl
Cl
R'
R'
7
R'
δ 119Sn -311
2
R'
δ 119Sn -427
Scheme 3. Synthesis of compounds 2, 4–7 by transmetallation reactions of the zinc compound 3.
2.2. X-ray diffraction analyses
R'
N
The X-ray diffraction analyses of compounds 1, 2, 4 and 6 were
performed. Crystallographic data is in Table 1, and selected bond
angles and lengths are in Tables 2–5.
R'
R'
O
R'
R'
OH
OH
O
R'
Zn(OAc)2,
NH4OH, H2O, O2
EtOH
Zn
N
Compound 1 crystallized from CH2Cl2/methanol and its structure
was obtained by X-ray diffraction analysis. There are two molecules
in the asymmetric unit (1a and 1b). The tin atoms have distorted tbp
geometries, Fig. 1. The oxygen atoms are at the apical positions. The
symmetry in the bond lengths of the heterobicycle shows that it is a
delocalized system. The O–Sn bond lengths are shorter 2.084(3) and
2.098(3) Å than that of N–Sn 2.145(4) and 2.161(4) Å, which is the
coordination bond. For the two molecules 1a and 1b the phenyl
groups are oriented, in such a way, that four intramolecular hydro-
gen bonds are formed between the ortho C–H protons and the oxy-
gen atoms (within distances of 2.57–2.88 Å), (Fig. 2).
The solid state structure of compound 2 showed that the tin
atom is hexacoordinated with a distorted octahedral geometry
due to the tension of the planar ligand. The O–Sn–O angle is
149.57(9)°, Fig. 3. The phenyl group is anti to the nitrogen atom
(N–Sn–C angle is 179.7(2)°) and is lying in the same plane as the
tin and the two chlorine atoms. The halides are in anti position
[Cl–Sn–Cl angle is 164.09(7)°], and slightly oriented towards the
nitrogen atom indicating a slight interaction ClÁ Á ÁN. It is also note-
worthy that the two C–H in ortho position to the nitrogen have a
shorter distance (1.8 Å) than the sum of the van der Waals radii
(2.4 Å). These interactions have been reported for peptide struc-
tures [29].
O
R'
R'
O
R'
R' = t-Bu
3
R'
Scheme 4. Synthesis of compound 3 by template reactions [23].
R'
R
R
O
R'
R'
Sn
Cl
O
N
R
Sn
Cl
N
O
R
R´
R'
R´
O
R´
R = CH3 or nBu
R' = t-Bu
R'
Scheme 5. Possible hexacoordinated tin compound intermediate in the synthesis of
compounds 5 and 6.
zinc transmetallation reaction with SnPh3Cl, indicates also that
elimination of a phenyl group is preferred over that of a chlorine
atom giving ZnPh2.
The syntheses of compounds 2 and 7 indicate also that electron
withdrawing groups such as chlorine and phenyl groups are neces-
sary for stabilization of hexacoordinated tin atoms.
The ortho C–H groups of the phenyl group form hydrogen bonds
with the chlorine (2.71 and 2.74 Å). The bond lengths around the
tin atom [Sn–O 2.112(2), Sn–C 2.117(7); Sn–N 2.268(5) and Sn–
Cl 2.450(2) and 2.453(2) Å] indicate the coordination bond charac-
ter of the Sn–N bond.

836
C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
Table 1
Crystal data for compounds 1, 2, 4 and 6.
1
2
4
6
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C40H50N1O2Sn1
695.53
193
0.71073
Monoclinic
P21/c
24.3068(3)
14.6458(2)
20.9481(3)
90
C34H45Cl2N1O2Sn1
689.33
193
0.71073
Monoclinic
Cm
11.333(2)
15.879(3)
9.4530(19)
90
C28H40Cl3N1O2Sn1
647.68
193
0.71073
Monoclinic
P21/n
10.833(3)
28.016(8)
11.235(3)
90
C36H58Cl1N1O2Sn1
691
193
0.71073
Monoclinic
P21/c
12.6895(9)
20.5584(15)
15.1216(10)
90
b (Å)
c (Å)
a
(°)
b (°)
100.5067(3)
90
7332.33 (17)
8
1.26
0.73
96.67(3)
90
1689.5(6)
2
1.355
0.943
117.596(4)
90
3021.9(14)
4
1.423
1.14
102.2720(10)
90
3854.7(5)
4
1.191
0.76
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
l
(mmÀ1
)
Absorption correction
Tmaximum, Tminimum
F(0 0 0)
None
0.75, 0.83
712
None
0.71, 0.85
1456
0.75, 0.88
2904
0.67, 0.92
1328
Crystal size (mm)
Crystal color
2h Range (°)
0.25 Â 0.22 Â 0.2
0.3 Â 0.3 Â 0.2
0.35 Â 0.35 Â 0.07
Dark violet
2.9 to 59.0
À15 6 h 6 15,
À38 6 k 6 38,
À15 6 l 6 15,
5489
0.49 Â 0.45 Â 0.22
Black
Violet
Violet
3.3 to 50.5
À32 6 h 6 24,
À18 6 k 6 18,
À26 6 l 6 26,
43 025
4.4 to 54.8
À14 6 h 6 14,
À20 6 k 6 20,
À11 6 l 6 11,
12 008
3.2 to 57.7
À15 6 h 6 16,
À26 6 k 6 26,
À20 6 l 6 13,
22 560
7074
> 3.0 r(I) 3595
0.035
Index ranges
Reflection collected
Independent reflections
Reflections for F0
Rint
13 643
3629
5489
>2.0
r(I) 8558
> 3.0
r
(I) 1882
> 2.0
0.0
r(I) 3849
0.054
0.034
Completeness to h (°)
Goodness-of-Fit (GOF) on F2
Final R1
25.24, 86.5%
1.07
0.046 (I > 2.0
0.039
26.62, 99.5%
1.08
0.021 (I > 3.0
0.026
25.07, 84.9%
1.01
0.039 (I > 2.0
0.045
25.10, 86.4%
1.02
0.058 (I > 3.0
r)
r)
r)
r)
Final wR2
0.076
Table 2
Table 4
Selected bond lengths (Å) for compounds 1 and 6.
Selected bond lengths (Å) for compounds 2 and 4.
R'
R'
R'
C4
S n
O1
R
R'
R'
1
O1
S n
O2
O
R'
4
O
R'
R'
Cl
C4
C3
Cl
C l
O2
N
N
Sn
Y
N
Cl
Sn
Y
N
Cl
5
R´
R'
R´
O
R'
3
O
R´
R'
R'
1a
1b
6
R'
2
4
Bond lengths
Sn–O1
Sn–N
Sn–O2
Sn–Cl(C3)
Sn–C4
2.098(3)
2.145(4)
2.096(3)
2.132(6)
2.122(5)
2.084(3)
2.161(4)
2.086(3)
2.130(6)
2.127(5)
1.990(6)
2.323(6)
1.998(5)
2.381(2)
2.13(1)
Bond lengths
Sn–O1
Sn–N
Sn–O3
Sn–Cl4
Sn–Cl5
Sn–Y
2.112(2)
2.268(5)
2.112(2)
2.450(2)
2.453(2)
2.117(7)
2.096(3)
2.198(5)
2.110(3)
2.375(2)
2.369(2)
2.331(2)
Table 3
Selected bond angles (°) for compounds 1 and 6.
The structure of compound 4 is similar to that of 2, Fig. 4. The
tin atom is hexacoordinated, the ligand is not completely planar.
The O–Sn–O angle is 149.9(2)°. The three chlorine atoms and the
nitrogen atom are in the same plane. The chlorine atom anti to
the nitrogen has the shortest bond length [2.331(2) Å], the others
are 2.375(2) and 2.369(2) Å. The molecule has intermolecular
interactions produced by C–HÁ Á ÁCl hydrogen bonds, (Fig. 5).
The X-ray diffraction analysis of compound 6 showed that the
diphenolamine is folded, with one n-butyl group at the nitrogen,
and the other at the tin atom, (Fig. 6). The N–Bu and the Sn–Bu
bonds are in gauche conformation, in order to minimise their
repulsion. The dihedral angle C18–Sn–N–C30 is 26.3°. The tin atom
1a
1b
6
Bond angles
O1–Sn–N
76.6(1)
152.3(1)
99.4(2)
94.4(2)
76.7(1)
110.6(2)
127.5(2)
96.7(2)
96.0(2)
121.9(2)
76.6(1)
151.4(1)
98.7(2)
93.4(2)
76.5(1)
106.5(2)
129.5(2)
98.1(2)
96.1(2)
124.0(2)
78.0(2)
116.7(2)
91.1(2)
114.1(4)
77.9(2)
156.6(2)
102.6(3)
89.0(2)
O1–Sn–O2
O1–Sn–Cl(C3)
O1–Sn–C4
N–Sn–O2
N–Sn–Cl(C3)
N2–Sn–C4
O3–Sn–Cl(C3)
O3–Sn–C4
C4–Sn–Cl(C3)
127.9(4)
100.7(3)

C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
837
Table 5
Selected bond angles (°) for compounds 2 and 4.
2
4
Bond angles
O1–Sn–N
O1–Sn–O3
O1–Sn–Cl4
O1–Sn–Cl5
O1–Sn–Y
N–Sn–O3
N–Sn–Cl4
N–Sn–Cl5
N–Sn–Y
O3–Sn–Cl4
O3–Sn–Cl5
O3–Sn–Y
Cl4–Sn–Cl5
Cl4–Sn–Y
Cl5–Sn–Y
74.84(6)
149.57(9)
89.19(7)
86.67(7)
105.1(1)
74.84(6)
81.9(1)
82.2(1)
179.7(2)
89.2(7)
75.2(1)
149.9(2)
87.75(9)
90.09(9)
104.9(1)
75.0(1)
88.0(1)
87.7(1)
179.3(1)
87.0(1)
92.87(9)
105.0(1)
175.50(7)
92.77(6)
91.60(6)
86.67(7)
105.15(6)
164.09(7)
98.4(2)
97.5(2)
Fig. 3. X-ray diffraction analysis of compound 2, the distance between the two C–H
ortho to the nitrogen is shown together with intramolecular C–HÁ Á ÁCl and C–HÁ Á ÁO
bonds.
Fig. 1. X-ray diffraction structures of compound 1. Two molecules (1a, 1b) were
found in the asymmetric unit. The hydrogen atoms are not shown for clarity.
Fig. 4. X-ray diffraction analysis of compound 4. The C–HÁ Á ÁO distances are 2.36
and 2.44 Å.
lengths of Sn–O [1.998(5) and 1.990(6) Å], Sn–C [2.13(1) Å] and
Sn–Cl [2.381(2) Å] are characteristic of strong covalent bonds.
The N–Sn [2.323(6) Å] bond length indicates a coordination bond.
The phenylene rings are completely aromatic.
Fig. 2. Hydrogen bonds between ortho C–H of the Sn–Ph groups and the oxygen
atoms for compound 1 are shown. The distances vary from 2.57 to 2.88 Å.
Some features are general for compounds 1–2, 4–7. Two C–H
from the tert-butyl groups form two intramolecular hydrogen
bonds with each oxygen atom (within distances 2.27–2.45 Å) as
is shown for compounds 2 (Fig. 3) and 4 (Fig. 4).
In all compounds, the two phenylene rings are not exactly
coplanar. The dihedral angles between the phenylene rings and
is pentacoordinated and has a distorted tbp geometry. The chlorine
and nitrogen atoms are in apical positions as is deduced from the
N–Sn–Cl angle 156.6(2)° whereas, two oxygen atoms and the n-bu-
tyl group are equatorial. The O–Sn–O angle is 116.7(2)°. The bond

838
C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
the C–HÁ Á ÁH–C distance for compounds 1, 2, 4 and 6 are in Table 6.
In all cases, the C–HÁ Á ÁH–C distances are shorter than the van der
Waals radii (2.4 Å).
The analysis of bond lengths in the hexacoordinated com-
pounds 2 and 4 shows a symmetric pattern which indicates a res-
onance system (coordination bond M covalent bond) for the ligand
acting as a phenolate iminoquinone, structure c in Scheme 2. The
two resonance contributors of compounds 2 and 4 are shown in
Scheme 6 [30].
3. Summary
The syntheses of pentacoordinated and hexacoordinated tin
compounds derived from bis[4,6-di-tert-butylphenol]amine are re-
ported. Transmetallation reactions using a zinc coordination com-
pound are compared with synthesis using template reactions.
Migrations of alkyl groups from tin to nitrogen were observed.
119Sn NMR data and the solid state structures of some of the com-
pounds are reported.
4. Experimental
Fig. 5. Intermolecular interactions in compound 4.
4.1. General comments
All solvents were freshly distilled before use according to estab-
lished procedures. The tin reagents are commercial. Melting points
were measured on a Mel-Temp II apparatus and are uncorrected.
The 1H, 13C, and 119Sn NMR spectra were recorded with JEOL
GXS-270 (1H 270 MHz) or JEOL Eclipse (1H 400 MHz) and Bruker
(1H 300 MHz) instruments. 1H and 13C (ppm) are referenced to
TMS and 119Sn to SnMe4. Assignments were performed by 2D
NMR experiments. High resolution mass spectra were obtained
by LC/MSD TOF on an Agilent Technologies instrument with APCI
as ionization source. Elemental analyses were performed in an Ea-
ger 300 analyzer.
X-ray diffraction studies of single crystals were determined on a
Bruker SMART instrument with an area detector using graphite-
monochromated Mo Ka radiation at 193 K. Intensities were mea-
sured using hemisphere scans. All structures were solved using di-
rect methods, using Shelxl-97 [31] and the refinement (based on F2
of all data) was performed by full-matrix least-squares techniques
with Crystals 12.84 [32]. All non-hydrogen atoms were refined
anisotropically and all hydrogen atoms were located in the differ-
ence map and allowed to ride on their respective atoms.
Fig. 6. Solid state of compound 6, the tin geometry is a distorted tbp.
Table 6
Phenhylene rings dihedral angles and ortho C–HÁ Á ÁH–C distances.
4.2. Syntheses
Compounds Phenylene rings dihedral angle
ortho C–HÁ Á ÁH–C distances
4.2.1. Zn[3,5-di-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-
1-phenyl)imine]2 (3)
(°)
(Å)
1a
1b
2
4
6
14.8
9.5
13.0
27.8
56.3
1.96
1.89
1.80
1.98
2.30
Compound 3 was prepared according to reported method [23].
3,5-Di-tert-butylcatechol (5.34 g, 24 mmol) was dissolved in
150 mL of ethanol and added to a solution of Zn(Ac)2Á2H2O
(1.15 g, 6.1 mmol) in 25 mL of water and 20 mL of NH4OH. The
reaction mixture was air bubbled and stirred for 24 h. Compound
3 is a dark green powder (4.1 g, 75%).
4.2.2. [Bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]diphenyltin
(1)
R'
R'
To a solution of 3,5-di-tert-butylcatechol (1.11 g, 5 mmol) in
15 mL of ethanol at 0 °C, conc. aqueous ammonia (3 mL) was added
followed by SnPh3Cl (964 mg, 2.5 mmol) in 10 mL of ethanol. After
2 h at 0 °C, the reaction was set aside for 48 h at room temperature.
The reaction mixture was filtered and washed with water and eth-
anol and vacuum dried. The solid was extracted with CH2Cl2. The
solvent was evaporated under vacuum and the violet crystalline
product was recrystallized from CH2Cl2 : ethanol (820 mg, 47%).
Mp 161–163 °C. Anal. Calc. for C40H50NO2Sn: C, 69.08; H, 7.25; N,
2.01. Found: C, 68.74; H, 7.14; N, 2.13.
O
R'
R'
O
R'
Cl
Cl
Sn
O
Y
N
Sn
Y
N
Cl
Cl
O
R'
R'
R'
Scheme 6. Resonance contributors in compounds 2 (Y@Ph) and 4 (Y@Cl).

C. Camacho-Camacho et al. / Journal of Organometallic Chemistry 695 (2010) 833–840
839
4.2.3. [Bis(3,5-di-tert-butyl-2-hydroxy-2-
phenyl)amine]dichlorophenylstannate (2)
tBu quartet: 34.6 and 29.6, tBu CH3: 35.5 and 31.7, Sn–nBu: 29.8,
28.0, 20.4, 13.9 N–nBu 60.0, 31.7, 24.7, 13.6. Mass – TOF found
726.2856 calc. for C36H58NO2SnCl2 726.2867. Anal. calc. for
C36H59ClO2NSn: C, 62.48; H, 8.59; N, 2.02. Found: C, 62.50; H,
8.39; N, 1.96.
4.2.3.1. Method A. To a solution of 3,5-di-tert-butylcatechol (1.11 g,
5 mmol) in 15 mL of ethanol at 0 °C of conc. aqueous ammonia
(3 mL) was added followed by SnPhCl3 (755 mg, 2.5 mmol) in
10 mL of ethanol. After 2 h at 0 °C, the reaction was continued at
room temperature for 48 h. The reaction mixture was filtered
and the solid washed with water and ethanol and dried. The solid
was dissolved in CH2Cl2 and filtered. The solution was evaporated
under vacuum. Dark green crystals were obtained that were
recrystallized from CH2Cl2 : ethanol (360 mg, 21%).
4.2.7. [Bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]n-butyl-
dichlorostannate (7)
A solution of compound 3 (300 mg, 0.33 mmol) and SnCl3nBu
(0.11 mL, 0.66 mmol) in 15 ml of toluene was refluxed for 3 h
and the solvent was evaporated under vacuum. A violet solid
was obtained (260 mg, 59%). The 119Sn spectrum of the reaction
product showed a main signal for compound 7 (d = À311 90%),
and 5% of compound 4. The -TOF mass spectrum showed a main
peak at 704.1866, calc 704.1851 for C32H49NO2SnCl3 which corre-
sponds to compound 7 plus a chlorine atom. Mp 130–137 °C.
NMR (CDCl3, ppm), 1H d = H3 7.37, H5 7.27, tBu: 1.44, 1.32, nBu
3.55, 2.37, 1.26 0.87. 13C d = C1 174.1, C2 132.5, C3 116.9, C4
141.7, C5 138.6, C6 149.7, tBu quater 35.6, 34.8, tBu CH3 31.7,
29.7, nBu 29.4, 28.2, 20.3 13.9.
4.2.3.2. Method B. A solution of compound 3 (300 mg, 0.33 mmol)
and SnPh2Cl2 (227 mg, 0.66 mmol) or SnPhCl3 (254 mg, 0.66 mmol)
in 10 mL of toluene was heated at 100 °C. After 3 h, the solvent was
evaporated under vacuum. The solid was washed with water and
the main product extracted with CH2Cl2. The solvent was evapo-
rated and the crystalline product was recrystallized from [1:1]
CH2Cl2:hexane (340 mg, 75%).
Mp 216–218 °C. NMR (CDCl3, ppm), 119Sn d = À427, 1H d = H3
7.56, H5 7.50, tBu: 1.39, 1.33, Ph: Ho and Hp 8.20, Hm 7.67. 13C
d = C1 174.3, C2 135.0 [83 Hz], C3 116.2 [49.5 Hz], C4 145.2
[26 Hz], C5 138.9, C6 149.8, tBu quater 35.8, 35.5, tBu CH3 30.0,
29.2, Ph: Ci 144.5, Co 133.8 [86 Hz], Cm 128.8 [138 Hz], Cp 130.4
[28 Hz]. Mass – TOF found 689.1858 calculated for C34H45NO2SnCl2
689.1849. Anal. calc. for C34H45Cl2NO2Sn: C, 59.24; H, 6.58; N, 2.03.
Found: C, 59.43; H, 6.82; N, 1.96.
Acknowledgments
Financial support from Cinvestav and Conacyt-Mexico is
acknowledged. The authors are grateful to J. Guthrie for valuable
comments and discussions.
Appendix A. Supplementary material
4.2.4. [Bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]trichloro-
stannate (4)
CCDC 711032, 711033. 711034 and 711035 contain the supple-
mentary crystallographic data for compounds 1, 2, 5 and 3 respec-
tively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2009.12.025.
Compound 3 (0.3 g, 0.33 mmol) and SnCl4 (0.1 mL, 0.45 mmol)
in 10 mL of toluene were heated at 90 °C. After 3 h, the solvent
was evaporated under vacuum. The solid product was washed with
water and the main product extracted with CH2Cl2. The solvent
was evaporated in vacuum and the product recrystallized from
[1:1] CH2Cl2:hexane (200 mg, 65%). Mp 222–224 C. NMR (CDCl3,
ppm), 119Sn d = À514, 1H d = H3 7.65, H5 7.44, H9 1.45, H10 1.34.
13C d = C1 174.1, C2 133.1, C3 115.4, C4 145.4, C5 140.4, C6
151.1, tBu quater 35.9, 35.6, tBu CH3 29.6, 29.2. Mass – TOF found
647.1138, calc for C28H40NO2SnCl3 647.1147. Anal. Calc. for
C28H40NO2SnCl3: C, 51.93; H, 6.23; N, 2.16. Found: C, 51.62; H,
5.92; N, 2.44.
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