Penta- and heptacoordinated tin(IV) compounds derived from pyridine Schiff bases and 2-pyridine carboxylate: Synthesis and structural characterization

Article abstract of DOI:10.1016/j.jorganchem.2009.04.035

The synthesis of the Sn(IV)-complexed, Schiff base derivatives 1a-1l, prepared in one pot by the reaction of 2-amino-4-R-phenol (R = H, Me, Cl, NO₂), 2-pyridinecarboxaldehyde, 2-picolinic acid and dimethyl-, dibutyl-, and diphenyltin oxides, is

Full text of DOI:10.1016/j.jorganchem.2009.04.035

Journal of Organometallic Chemistry 694 (2009) 2965–2975
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Penta- and heptacoordinated tin(IV) compounds derived from pyridine Schiff
bases and 2-pyridine carboxylate: Synthesis and structural characterization
*
Alejandro Ramírez-Jiménez, Elizabeth Gómez , Simón Hernández
Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México 04510, D.F., Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of the Sn(IV)-complexed, Schiff base derivatives 1a–1l, prepared in one pot by the reaction
of 2-amino-4-R-phenol (R = H, Me, Cl, NO2), 2-pyridinecarboxaldehyde, 2-picolinic acid and dimethyl-,
dibutyl-, and diphenyltin oxides, is described. The complexes were characterized by IR, MS, 1H, 13C,
119Sn NMR. Suitable crystals of 1e and 1h enabled us to use X-ray diffraction to determine their molecular
structures, which exhibited pentagonal–bipyramidal geometries where the butyl groups occupied the
axial positions whereas the nitrogen and the oxygen atoms occupied the equatorial positions. The reac-
tion of the Schiff base 2 with dibutyltin oxide led to the pentacoordinated complex, 2h, through the addi-
tion of methanol to the C@N bond. An unusual reduction–oxidation reaction took place by the reaction of
2-amino-4-nitro-phenol, dibutyltin oxide and 2-pyridinecarboxaldehyde, which produced the corre-
sponding amine, 3h, and the amide, 4h, tin(IV) derivatives. Both structures were established by X-ray
crystallography and exhibited a distorted, bipyramidal trigonal (BPT) geometry.
Received 11 February 2009
Received in revised form 25 April 2009
Accepted 27 April 2009
Available online 5 May 2009
Keywords:
Schiff base
Tin(IV) heptacoordinate
Pentacoordinate
Reduction
Oxidation
119Sn NMR
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
chlorides giving oligomeric structures with distorted TBP geome-
tries [42]. Some organotin complexes derived from picolinic acid
Organotin complexes have been studied in view of their
structural diversity and their possible biological applications. In
this regard, compounds which exhibit anti-microbial [1–5],
anti-inflammatory [7–11], bactericidal [12,13], cardiovascular
[1,5–14,15] biocidal [16], antitubercular [17,18], antifungal [19]
and cytotoxic [20–23] biological activity have been described. Dif-
ferent complexes have been investigated in the search of treat-
ments for diseases such as trypanosomiasis [24] and jaundice [25].
Pyridine ligands, which have been used in the coordination
chemistry of a variety of metals [26–30], occupy a unique position
in the synthesis of biologically active compounds [31]. The chem-
istry of organostannyl carboxylates is one of the more fascinating
fields, and pyridine tin carboxylates are the focus of many studies
due to their different coordination geometries and their structural
diversity, which depends upon the reaction conditions. The 2,6-
pyridine dicarboxylic acid reacts with diorganotin oxide or diorga-
notin diacetate, thereby generating structures with a pentagonal
bipyramidal environment [32–39]. Interestingly, the presence of
alkaline alkoxides favors the formation of complexes with octahe-
dral geometry [40]. The reaction of 2,5-pyridinedicarboxylic acid
with dimethyl, dibutyl or diphenyl tin oxides gives cyclotrimeric
or polymeric seven coordinated tin derivatives [41]. In addition,
the 2,4-, 3,4- and 3,5-pyridine dicarboxylates react with organotin-
possess octahedral or five-coordinated trigonal bipyramidal struc-
tures where the carboxylate acts as a monodentated ligand [43,44].
It has been reported that seven coordinated tin complexes exhibit
higher activity towards some cancer cell lines when the 2,6-pyri-
dine carboxylate moiety is part of the molecule [45]. Other studies
have focused on the structural aspects of the hypervalent species of
the Schiff-based organotin complexes [46–48]. These class of com-
pounds are important due to their biological and catalytic
applications.
On the other hand, few examples of mixed ligands diorganotin
complexes have been described which include the chelate ligands
dithiocarbamate and quinolinates that have been used to prepare
octahedral SnR2LL0 complexes [49], the mixed diorganotin(IV)
complexes containing thiosemicarbazones and acetate or dith-
iophosphinate ligands which have shown antiproliferative activity
towards different cell lines [50–51], the bis (dicyclohexylammoni-
um)oxalate and pyridine-2,6-dicarboxylate that affords to the se-
ven coordinated mixed-chelate diorganotin(IV) compound [52]
and the octahedral mixed-complexes which obtained when two
different Schiff-base ligands are used [53].
Herein, we report on the synthesis and characterization of five
and seven tin coordinated complexes, using mixed ligands (Schiff
bases, aminopyridine, and pyridine carboxylates) with the specific
aim of evaluating the influence of the aromatic substituents on the
schiff base, the stoichiometry, and the reaction conditions upon the
formation of the hypervalent species.
* Corresponding author.
E-mail address: eligom@servidor.unam.mx (E. Gómez).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.04.035

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A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
and 4J(13C–119/117Sn) for butyl groups attached to the tin, which al-
2. Results and discussion
lowed us to corroborate the 13C NMR assignation. The obtained
coupling constants values were similar to those described in the
literature [52].
The complexes 1a–1l were obtained in one step by the reaction
of dimethyl, dibutyl, or diphenyltin oxide, the corresponding 2-R-
aminophenol (R = H, Me, Cl, NO2), 2-pyridinecarboxaldehyde, and
2-pyridinecarboxylic acid and using methanol or benzene as the
solvent. The reaction times were in the range of 15–40 min. The
crystalline complexes 1c and 1d were obtained when the reaction
was carried out in benzene. The 1a–1l complexes were isolated in
yields of 51–99%. The air stable products were characterized by
mass spectrometry, spectroscopic methods (IR, 1H, 13C, and 119Sn
NMR), and X-ray crystallography.
Surprisingly, when the reaction was carried out in one step with
dibutyltin oxide using a toluene/methanol (4:6) mixture as solvent
and 8 h of reflux in absence from 2-pyridinecarboxylic acid, a mix-
ture of complexes, 1h, 2h, and 3h in a ratio of (1:12:1), was ob-
tained. The ratios where determined by the integration of the 1H
NMR spectra using the proton signals of the N@CH, N–CH and N–
CH2, respectively (Scheme 1). The addition of MeOH to the reaction
mixture led to the precipitation of the major compound; the 1H
and 13C NMR data allowed us to characterize the complex, 2h.
Additional evidence supporting the formation of the three com-
plexes could be deduced from 119Sn NMR spectra, where typical
signals of penta- and heptacoordinated tin atoms were detected
(ꢀ83.0 ppm, ꢀ67.9 ppm, and ꢀ441.0 ppm). Although the separa-
tion of the remaining products of the mixture was not possible,
the assignment of the individual signals for the 1h and 3h com-
plexes was accomplished based on the comparison of the mixture’s
NMR spectra with the NMR spectra of the pure 1h and 2h com-
plexes, which allowed us to successfully characterize the 3h com-
plex. The 3h complex showed three different signals, two doublets
and a singlet at 6.64 ppm, 7.68 ppm, and 7.26 ppm corresponding
to H-11, H-12 and H-14, respectively. The protons of the pyridine
ring showed four different signals, and there was a singlet at
4.78 ppm corresponding to the methylene resonance, H-7. Addi-
tional evidence for the formation of 3h was obtained from the sig-
nal at 49.3 ppm in the 13C NMR.
The analysis of the FT-IR spectra of these complexes showed
bands in the region of 1592–1598 cmꢀ1 due to the
m(N@C) stretch-
ing vibrations, and similar shifts to those found for heptacoordinat-
ed tin derivatives [54], which are shifted towards lower wave
number compared to the m(N@C) stretch of the Schiff base ligand,
were observed. Such shifts are a result of the displacement of the
electron density from the nitrogen to the tin atom. Additionally,
the spectra exhibited two different absorption bands in the ranges
of 1641–1659 cmꢀ1 and 1352–1364 cmꢀ1, which correspond to the
m
AS(COOꢀ) and
respectively. Deacon has proposed that
are associated with unidentated coordination [55]. The
m
S(COOꢀ) modes of the coordinated carbonyl group,
D
m
values >200 cmꢀ1
of the
D
m
1a–1l derivatives are in the range of 282–303 cmꢀ1. Following
the results of Deacon, we assume that the pyridinecarboxylate is
coordinated to the metal center in a monodentated mode (Table
1). The 1a–1l complexes also displayed stretching bands in the
range of 417–420 cmꢀ1, which are attributed to the vibration
Interestingly, the reaction of the Schiff base 2 with dibutyltin
oxide using the aforementioned reaction conditions led to the for-
mation of the complex 2h as the unique product in a yield of 94%
(Scheme 1). The 1H NMR spectroscopy exhibited a singlet at
6.37 ppm, corresponding to the proton of the stereogenic carbon,
and an additional singlet for the methyl group was observed at
2.86 ppm. However, there was a signal at 84.0 ppm in the 13C
NMR, which was characteristic of a tertiary carbon. No evidence
of an iminic carbon was observed. This fact supports the possibility
that the C@N center reacted with a molecule of methanol, which
might also explain the presence of both the methoxy and the
methyne signals in the spectrum, additionally, using the Lockhart
equation and the coupling constant J(13C–119Sn) = 560.7 Hz, the
bond angle C–Sn–C 125.9° was calculated. The 119Sn NMR showed
an intense singlet, which was indicative of a pentacoordinated tin
species (d = ꢀ83.0 ppm). The mass spectrometry showed the
molecular ion [Mꢁ+] and a peak corresponding to the loss of the
methoxy group, thereby confirming the addition of methanol to
the iminic carbon. These results suggest that the first step of the
reaction is the formation of the imine followed by the addition of
(MeOH) to the C@N bond (Scheme 2). This last step could be fa-
vored by the presence of tin, which could polarize the C@N bond,
thereby facilitating the nucleophile to react with the iminic carbon.
This behavior has only been observed for the nitro-derivative,
which suggests that the electron withdrawing effect increases
the electrophilicity and reactivity of the C@N bond, thereby favor-
ing the addition of nucleophiles. Indeed, this rationalization is part
of a key step to a well-known procedure in which the use of orga-
nometallic reagents facilitates the addition of different nucleo-
philes [57–60].
m
(Sn–N).
The monomeric structure of complexes 1a–1l was established
by mass spectrometry, which showed the molecular ions for all
complexes. Fragment ions [MÅ+ꢀR], [M+ꢀPyCOOꢀ], which corre-
spond to the base peak for the complexes 1a–1h, and
[M+ꢀPyCOOꢀ2R] were also detected.
The evidence that newly heptacoordinated, tin heterocyclic ring
species had formed was provided by 119Sn, 1H, and 13C NMR spec-
troscopy. Typical signals for the heptacoordinated tin atoms were
observed in the 119Sn NMR spectra for the 1a–1l complexes as a
consequence of the coordination of the nitrogen atoms to the metal
center, which, in connection with the simultaneous formation of
Sn–O bonds, accounted for the expected geometry.
The C–Sn–C bond angles of 170.5°, for 1a and 1b, 170.3° and
169.8° for 1c and 1d were calculated by using the values of the
119Sn coupling constants 2J(1H–119Sn) = 115.7, 115.7, 115.6, and
115.3 Hz, respectively, whereas, for 1e and 1f the coupling con-
stants J(13C–119Sn) = 1130 Hz and 1128 Hz were used which gave
angles of 175.9° and 175.7°, respectively [56].
For complexes 1e and 1f was also possible to measure the cou-
pling constants J(13C–119/117Sn), J(13C–119/117Sn), J(13C–119/117Sn)
1
2
3
Table 1
FT-IR vibration (cmꢀ1) for complexes 1a–1l.
Compound
m
asCOO–
m
sCOOꢀ
D
m
N (Sn–N)
1a
1b
1c
1d
1e
1f
1g
1h
1i
1645
1651
1659
1649
1642
1641
1644
1648
1660
1656
1658
1649
1364
1359
1356
1352
1360
1359
1358
1354
1359
1345
1359
1352
281
292
303
297
282
282
286
294
312
311
299
297
421
418
419
419
418
417
417
416
421
420
419
420
A different reactivity was also observed for the reaction of
2-amino-4-nitrophenol with 2-pyridinecarboxaldehyde and dibu-
tyltin oxide using benzene as the solvent (Scheme 1). In this case,
the NMR structural analysis indicated that the reaction gives rise to
a mixture of three compounds in a ratio (1:2:1). The addition of
MeOH to the crude reaction resulted in the precipitation of one
compound, whose 1H and 13C NMR spectra exhibited signals
1j
1k
1l

A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
2967
OMe
R
R
7
14
10
13
5
9
Bu
4
N
Bu
N
1h
+
+
12
N
N
Sn
Sn
3
11
O
O
2
Bu
Bu
2h R= NO2
3h R=NO2
Bu2SnO
toluene/MeOH (4:6)
5
7
6
4
3
R
14
11
R1
R
NH2
OH
R
9
N
O
N
13
(R1)2SnO/
N
1
O
+
Sn
O
2-picolinic acid
2
Bu2SnO
toluene/MeOH (4:6)
EtOH
N
N
2h
12
10
MeOH or Benzene
OH
O
21
R1
H
N15
20
2 R=NO2
16
19
17
18
Bu2SnO
Benzene
1a R= H,
R1= CH3
1b R= CH3, R1= CH3
1c R= Cl, R1= CH3
1d R= NO2 R1= CH3
1e R= H,
R1= Bu
O
1f R= CH3, R1= Bu
1g R= Cl, R1= Bu
1h R= NO2 R1= Bu
R
14
7
5
1i R= H,
R1= Ph
Bu
N
Sn
4
1h
3h
+
1j R= CH3, R1= Ph
1k R= Cl, R1= Ph
1l R= NO2 R1= Ph
+
12
N
3
2
11
O
Bu
4h R= NO2
Scheme 1.
H
CH3
O
O
CH3
N
N
N
N
O2N
R
O2N
N
O2N
N
R
-H2O
Sn
Sn
R
O
R2SnO
R
OH
O
O
H
2h R=Bu
Scheme 2. Possible reaction mechanism for the formation of 2h.
characteristic of the complex, 1h. Eventually, the separation of the
remaining products of the reaction was achieved by the addition of
MeOH to the filtered solution, from which the major compound
was crystallized and separated by filtration. The analysis of the
1H NMR spectrum of this new compound, 4h, showed different res-
onances for the aromatic protons, three doublets at 6.81 ppm,
7.95 ppm, and 9.67 ppm, which were assigned to H-11, H-12 and
H-14, respectively, while the pyridine ring exhibited four different
and more complex signals at 7.79 ppm, 8.24 ppm, 8.38 ppm,
8.59 ppm for the H-3, H-4, H-2, and H-5 protons, respectively.
The 13C NMR spectrum showed signal at 162.6 ppm corresponding
to the carbonyl group. The presence of an amide carbonyl was also
plex 3h, which showed the previously described chemical shifts
and the coupling constant 1J(13C–119Sn) = 559.6 Hz which was used
to calculate the C–Sn–C bond angle 125.8°. The 119Sn NMR spectra
of 3h and 4h showed signals at ꢀ67.9 ppm and ꢀ122 ppm, which
corresponded to the 3h complex and 4h complex, respectively, and
are indicative of pentacoordinate geometries. According to the lit-
erature, the unexpected formation of the 3h complex in the ab-
sence from a reducing agent might be taking place through a
Cannizzaro reaction. This type of behavior has been observed for
the reaction of 4-nitrobenzaldehyde with 2-amino-4,6-dimethyl-
pyrimidine [61]. In this respect, the hydride shift of the hemiami-
nal intermediate to another molecule of the aldehyde could explain
the formation of the 4h complex; however, no evidence of the
expected byproduct, 2-pyridinemethanol, was detected, indicating
that the hydride was probably transferred to C@N bond,
which could be polarized by the metal, thereby giving rise to
complex 3h. The nucleophilic attack of the intermediate A on the
detected in the IR spectrum m
(CO) at 1648 cmꢀ1, which corrobo-
rated the formation of the 4h, additionally, the coupling constant
J(13C–119Sn) = 566.4 Hz, allowed us to calculate the C–Sn–C bond
angle 126.2°. Once the compound 4h was separated, the remaining
complex still present in the mother liquor was identified as com-

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A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
N
N
O2N
N
O2N
N
O
R
H
O
Sn
R
H
R
O
Sn
O
O
H
R
N
A
A
R
Sn
R
O
H
N
N
N
O2N
O
O2N
N
H
O
R
N
H
R
Sn R
H
Sn
O
N
N
O
O
R
N
O
O
H
O2N
N
O
Sn
R
O2N
-H2O
R
-H2O
O
R
R
O2N
O2N
R
O2N
N
O
N
O
N
O
N
O
R
N
N
Sn
Sn
R
Sn
R
+
3h
+
O
N
4h
3h
Scheme 3. Possible reaction mechanism for the formation of 1h, 3h and 4h.
1h
2-pyrididinecarboxaldehyde could explain the formation of 1h and
ratio (1:2:1) of 1h, 3h and 4h, respectively (Scheme 3). The reduc-
tion of coordinated Schiff bases has also been described for tung-
sten and aluminum complexes [62,63].
The examination of the molecular structure of the 1e and 1h
complexes revealed that their structural geometry is pentagonal–
bipyramidal (PBP) (see Fig. 1). The equatorial plane is constituted
of two oxygen atoms and three nitrogen atoms, the azomethine
and the nitrogen atoms of the pyridine rings, whereas the axial
positions are occupied by the two butyl groups, which exhibit dis-
order in the two positions and form angles of 169.2(1)° and
170.8(1)° for 1e and 1h complexes, respectively, which are in
agreement with the values for C–Sn–C bond angles performed from
the NMR data solution. The Sn(1)–N(1) bond length of 2.538(2) Å
and the Sn(1)–N(3) bond length of 2.423(2) Å for the 1e complex
are slightly longer than Sn(1)–N(2) bond length of 2.303(2) Å.
However, the shortest tin-nitrogen bond length for the 1h complex
is Sn(1)–N(3) bond length of 2.436(3) Å. For the 1e and 1h com-
plexes, the 2-pyridinecarboxylate is bonded to the tin atom in a
monodentated manner, as evidenced by the spectral data. The
Sn(1)–O(2) bond lengths of 2.304(2) Å and 2.242 (3) Å are slightly
shorter than those found for the 2,6-pyridine carboxylate dibutyl-
stannate derivatives [45].
Fig. 1 depicts the molecular structure of compound 2h, which
contains two five-membered ring heterocycles. The tin atom has a
pentagonal coordination environment, and the geometry could be
interpreted as distorted trigonal bipyramidal, with the oxygen
and the nitrogen of the pyridine ring occupying the axial positions
and the nitrogen and the carbons of the butyl groups occupying the
equatorial positions. The distortion of the geometry is evident from
the N(1)–Sn–O(1) bond angle of 150.4(3)°; meanwhile, the atoms in
the equatorial plane exhibit bond angles in the range of 115.7(2)–
124.4(2)°. The five-membered rings are not completely planar since
the Sn atom deviates by 0.109(7) Å and 0.086(7) Å from the mean
plane formed by the pyridine and the six-membered rings, respec-
tively. Meanwhile, the C-7 is coplanar to the pyridine and aromatic
rings. The N ? Sn bond length of 2.394(4) Å is slightly longer than
that found for pentacoordinated tin complexes [64], where the pyr-
idine nitrogen forms a coordinative bond, the Sn–N and Sn–O dis-
tances are in the range of 2.062(3) Å and 2.114 (3) Å, respectively.
The unit cell of the 3h complex consists of two chemically equiv-
alent, but crystallographically independent, molecules. Similar to
When 2 equiv. of 2-pyridine carboxaldehyde, 1 equiv. of 2-ami-
no-4-R-phenol R = H, Me, Cl), and the corresponding diorganotin
oxide were used, the reaction led to the selective formation of
the 1e–1g complexes as unique products, where the reaction was
carried out using different solvents, such as toluene/methanol
(4:6), MeOH, and benzene. However, only the heptacoordinate
tin complexes were isolated irrespective of the solvent. In this case,
the pyridinecarboxaldehyde was oxidized to the corresponding
carboxylate, and it was coordinated to the metal center affording
the heptacoordinated tin derivatives (Scheme 4).
Since the 2-amino-4-nitro-phenol showed the most versatile
behavior, we performed the reaction under different conditions.
Firstly, the reaction of 2-amino-4-nitrophenol with 2 equiv. of 2-
pyridinecarboxaldehyde gave two complexes in a ratio of (1:1)
when a mixture of toluene/methanol solvent was used. The analy-
sis of 1H NMR spectrum of the reaction mixture revealed the for-
mation of both pentacoordinated and heptacoordinated tin
complexes, the 1h and 3h complexes, respectively. In this case,
the pyridine carboxaldehyde was oxidized to carboxylate, whereas
for the pentacoordinated tin complexes, the spectroscopic data
indicates that the imine had been reduced to the corresponding
amine. When MeOH was used as solvent, only the complex, 2h,
was obtained. Finally, the same reaction in presence of benzene
gave a mixture of products, 1h, 3h and 4h, as was previously ob-
served when 1 equiv. of aldehyde was used (Scheme 4).
3. X-ray diffraction
The molecular structures for the complexes 1e–1h, 2h, 4h were
established by X-ray diffraction. For the series 1e–1h, the 1e and
1h complexes were selected as representatives for the analysis. De-
tails of the crystal data and a summary of the data collection
parameters for the complexes are given in Table 2. Selected bond
lengths and bond angles are listed in Table 3.

A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
2969
Bu
R
N
N
Sn
O
O
Bu
O
N
1e R= H
1f R= CH3
1g R= Cl
Bu2SnO
toluene/MeOH(4:6) or MeOH
or Benzene
R
NH2
OH
Bu2SnO
Bu2SnO
MetOH
2
+
3h
2h
1h
+
O
toluene/MeOH (4:6)
N
H
Bu2SnO
Benzene
+
+
4h
3h
1h
Scheme 4.
Table 2
Crystallographic data for compounds 1e, 1h, 2h and 4h.
Complex
1e
1h
2h
3h
4h
Formula
C26H31N3O3Snꢁ0.5CH Cl3
1223.82
0.40 ꢂ 0.20 ꢂ 0.08
Red
C27H32Cl2N4O5Sn
682.16
C21H29N3O4Sn
506.16
C20H27N3O3Sn
476.14
C20H25N3O4Sn
490.12
Formula weight (g molꢀ1
Crystal size (mm)
Color
)
0.42 ꢂ 0.26 ꢂ 0.16
0.26 ꢂ 0.15 ꢂ 0.10
0.32 ꢂ 0.12 ꢂ 0.11
0.24 ꢂ 0.16 ꢂ 0.10
Red
Orange
Red
Red
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
C2/c
26.777(2)
12.937 (1)
16.426(1)
90
102.202 (1)
90
5561.6(6)
4
Monoclinic
P21/c
14.517(2)
9.838(1)
20.984(2)
90
91.807(2)
90
2995.1(6)
4
Triclinic
P1
Triclinic
P1
Monoclinic
C2/c
17.158(2)
16.566(2)
16.262(2)
90
113.587(2)
90
4236.3(9)
8
ꢀ
ꢀ
10.501 (1)
10.792(1)
11.501(2)
82.468(2)
81.355(2)
61.566(2)
1130.5(3)
2
11.350(1)
12.165(2)
16.728(2)
70.251(2)
78.666(2)
86.249(2)
2131.5(5)
4
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc. (g/cm3)
1.462
1.513
1.487
1.484
1.537
No. of collected reflections
No. of independent reflections (Rint
No. of observed reflections
No. of parameters
22 352
4901 (0.0498)
4901
399
0.0311
23 732
5256 (0.0439)
5256
358
0.0407
9403
4121 (0.0360)
4121
292
0.0437
7782
7782 (0.0519)
7782
599
0.0437
17 221
3867 (0.0498)
3867
310
0.0513
)
Ra
b
Rw
0.0546
0.1063
0.1023
0.0942
0.1423
GOF
0.850
0.968
1.031
0.876
1.001
a
R = ||Fo| ꢀ |Fc||/|Fo|.
P
P
2
2
1=2
RwðFoÞ ¼ ½ wðF2o ꢀ Fc2Þ = wFo4ꢃ
.
b
complex 2h, the molecular structure of the 3h and 4h complexes
contain two five-membered ring heterocycles. For both complexes,
the geometry around the tin atom is distorted trigonal bipyramidal,
where the amine or amide nitrogen and the butyl groups occupy
the equatorial positions and the pyridinic nitrogen and the oxygen
occupy the axial ones. The butyl group of the 3h complex and the
carbonyl group of 4h exhibit disorder in two positions. The two
Sn–N bonds of the 3h/4h complexes show significant differences,
in which the Sn(1)–N(2) bond length of 2.059(2)/2.086(4) Å is
shorter than Sn(1)–N(1) bond length of 2.319(4)/2.323(5) Å (Table
3) and that found for the bond length of tyrosinylphenylalani-
nate-O,N,N-(2)-dimethyltin(IV), 2.103(7) Å [65]. In this geometry,
the C(14)–Sn(1)–C(18) bond angles of 122.5(2)/116.9(4)° and
O(1)–Sn(1)–N(1) 151.2(1)/150.9(2)° represent a high degree of

2970
A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
Table 3
Bond lengths (Å) and angles (°) for complexes 1e, 1h, 2h, 3h and 4h.
1e
1h
2h
4h
3h molecule A
3h molecule B
Bond lengths
Sn(1)– O(1)
Sn(1)– O(2)
Sn(1)– N(1)
Sn(1)– N(2)
Sn(1)– N(3)
Sn(1)–C(14)
Sn(1)– C(18)
Sn(1)– C(19)
Sn(1)– C(20)
Sn(1)– C(23)
Sn(1)– C(24)
N(2)– C(6)
2.177(2)
2.304(2)
2.538(2)
2.383(2)
2.423(2)
2.243(3)
2.242(3)
2.538(3)
2.436(3)
2.382(3)
2.114(3)
2.104(5)
2.108(3)
Sn(2)–O(4)
2.118(3)
2.349(4)
2.062(3)
2.323(5)
2.086(4)
2.319(4)
2.059(2)
Sn(2)–N(4)
Sn(2)–N(5)
2.357(4)
2.053(4)
2.114(5)
2.123(5)
2.120(9)
2.113(9)
2.132(5)
2.125(5)
Sn(2)–C(38)
Sn(2)–C(34)
2.130(5)
2.108(6)
2.119(3)
2.115(3)
1.275(3)
2.128(4)
2.137(4)
1.274(4)
N(2)– C(7)
C(7)–O(2)
C(7)–O(4)
1.413(5)
1.420(5)
1.368(7)
1.178(8)
2h
1.434(5)
N(5)–C(27)
1.444(5)
1e
1h
4h
3h molecule A
3h molecule B
Bond angles
O(1)–Sn(1)–N(2)
O(1)–Sn(1)–N(3)
O(2)–Sn(1)–N(1)
O(2)–Sn(1)–N(3)
N(2)–Sn(1)–N(1)
C(19)–Sn(1)–C(23)
C(19)–Sn(1)–O(1)
C(19)–Sn(1)–N(2)
C(19)–Sn(1)–N(1)
C(19)–Sn(1)–O(2)
C(19)–Sn(1)–N(3)
C(23)–Sn(1)–O(1)
C(23)–Sn(1)–N(2)
C(23)–Sn(1)–N(1)
C(23)–Sn(1)–O(2)
C(23)–Sn(1)–N(3)
71.7(1)
77.4(1)
76.5(1)
68.9(1)
65.9(1)
169.2(1
93.4(1)
90.0(1)
84.0(1)
85.8(1)
96.5(1)
97.2(1)
91.2(1)
86.7(1)
86.7(1)
87.9(1)
O(1)–Sn(1)–N(2)
69.8(1)
78.1(1)
76.2(1)
70.6(1)
65.5(1)
170.8(1)
89.1(2)
86.8(1)
86.7(2)
93.6(2)
93.1(2)
92.1(2)
85.1(1)
86.0(2)
90.1(1)
96.1(2)
O(1)–Sn(1)– N(2)
77.7(1)
96.0(2)
104.2(2)
150.4(1)
72.7(1)
77.7(2)
97.3(3)
104.3(3)
150.9(2)
73.2(2)
77.8(1)
98.9(2)
97.8(2)
151.2(1)
73.4(1)
95.7(2)
95.0(2)
122.5(2)
123.7(3)
116.1(3)
118.6(2)
118.6(2)
111.0(3)
120.2(3)
O(4)–Sn(2)– N(5)
O(4)–Sn(2)– C(34)
O(4)–Sn(2)–C(38)
N(4)–Sn(2)–O(4)
N(5)–Sn(2)–N(4)
C(34)–Sn(2)–N(4)
C(38)–Sn(2)–N(4)
C(38)–Sn(2)–C(34)
C(27)–N(5)–Sn(2)
C(28)–N(5)–Sn(2)
N(5)–Sn(2)–C(38)
N(5)–Sn(2)–C(34)
N(5)–C(27)–C(26)
C(28)–N(5)–C(27)
77.4(1)
102.3(2)
97.0(2)
150.2(2)
72.9(2)
93.5(2)
O(1)–Sn(1)–N(3)
O(2)–Sn(1)–N(1)
O(2)–Sn(1)–N(3)
N(2)–Sn(1)–N(1)
C(20)–Sn(1)–C(24)
C(20)–Sn(1)–O(1)
C(20)–Sn(1)–N(2)
C(20)–Sn(1)–N(1)
C(20)–Sn(1)–O(2)
C(20)–Sn(1)–N(3)
C(24)–Sn(1)–O(1)
C(24)–Sn(1)–N(2)
C(24)–Sn(1)–N(1)
C(24)–Sn(1)–O(2)
C(24)–Sn(1)–N(3)
O(1)–Sn(1)–C(14)
O(1)–Sn(1)–C(18)
N(1)–Sn(1)–O(1)
N(2)–Sn(1)–N(1)
C(14)–Sn(1)–N(1)
C(18)–Sn(1)–N(1)
C(18)–Sn(1)–C(14)
C(7)–N(2)–Sn(1)
C(8)–N(2)–Sn(1)
N(2)–Sn(1)–C(18)
N(2)–Sn(1)–C(14)
N(2)–C(7)–C(6)
90.4(2)
96.7(2)
97.2(3)
91.3(3)
94.3(2)
124.4(2)
125.0(3)
115.7(3)
115.7(2)
119.1(2)
110.0(3)
119.3(3)
116.9(4)
122.1(4)
114.9(3)
120.9(4)
121.4(3)
114.3(5)
122.8(4)
123.0(2)
125.0(3)
124.5(3)
116.7(3)
117.3(2)
117.1(3)
109.9(4)
118.4(4)
C(8)–N(2)–C(7)
N(2)–C(7)–O(4)
N(2)–C(7)–O(2)
115.3(4)
distortion in the molecule. The N(2)–C(7) bond length of 1.434(5) Å
and the N(2)–C(7)–C(6) bond angle of 111.0(3)° corroborate the for-
mation of the reduced complex, 3h.
were refined anisotropically, using full-matrix, least squares tech-
niques. All hydrogen atoms were placed on idealized positions
based on the hybridization with thermal parameters fixed at 1.2
times (for –CH) and 1.5 times (for –CH3) the value of the attached
atom. Structure solutions and refinements were performed using
SHELXTL v 6.10.
4. Conclusions
This contribution reveals that heptacoordinated complexes, 1a–
1l, and pentacoordinated complexes, 2h, 3h, 4h, can be isolated
depending upon the stoichiometry and the reaction conditions.
The electronic effect of the nitro-phenols favors the formation of
products where the original imine bond (C@N) acts as an electro-
philic center for both the reduction and the oxidation reactions,
thereby generating the corresponding amine or amide 3h and 4h
complexes, most probably via a Cannizzaro reaction.
5.1. Complex 1a
To a solution of 0.1143 g (1.048 mmol) de 2-aminophenol in
20 mL of benzene, 0.1 mL (1.048 mmol) of 2-pyridinecarboxalde-
hyde, 0.1732 g (1.051 mmol) of dimethyltin oxide and 0.1290 g
(1.048 mmol) of 2-picolinic acid was added. The reaction mixture
was refluxed for 20 min, then 15 mL of solvent was removed under
reduced pressure giving a precipitate, which was filtered to leave
0.4493 g (91.6% yield) of a dark red solid, m.p. 234–237 °C; IR
5. Experimental
(KBr cmꢀ1): 1645 (s,
421 (w,
Sn–N); 1H NMR (CDCl3, 300 MHz) d: 0.50 (6H, s,
masymCO2), 1364 (s, msymCO2), 1593 (s, mC@N),
m
2-Aminophenol, 2-amino-4-methylphenol, 2-amino-4-chloro-
2J(1H–119/117Sn) = 115.7, 110.7 Hz, Sn-CH3), 6.65 (1H, ddd, J = 8.2,
7.1, 1.1 Hz, H-13), 7.05 (1H, dd, J = 8.4, 1.1 Hz, H-11), 7.31 (1H,
ddd, J = 8.4, 7.1, 1.4 Hz, H-12), 7.56 (1H, dd, J = 8.2, 1.4 Hz, H-14),
7.60 (1H, ddd, J = 7.6, 5.1, 1.0 Hz, H-3), 7.69 (1H, ddd, J = 7.6, 5.3,
1.2 Hz, H-17), 7.74 (1H, d, J = 7.8 Hz, H-5), 8.00 (1H, ddd, J = 7.8,
7.6, 1.5 Hz, H-4), 8.07 (1H, ddd, J = 7.8, 7.6, 1.5 Hz, H-18), 8.52
(1H, d, J = 7.8 Hz, H-19), 8.75 (s, 1H, H-7), 9.77 (1H, d, J = 5.3 Hz,
H-16) 9.88 (1H, d, J = 5.1 Hz, H-2); 13C NMR (CDCl3, 75 MHz) d:
13.8 (Sn-CH3), 115.4 (C-14), 116.5 (C-11), 122.0 (C-13), 125.7 (C-
19), 126.3 (C-17, C-3), 126.4 (C-5), 129.9 (C-9), 133.4 (C-12),
139.0 (C-4), 140.0 (C-18), 142.2 (C-7), 148.0 (C-16), 149.9 (C-6),
151.2 (C-2), 155.6 (C-20), 164.1 (C-10), 166.6 (C-21); 119Sn
NMR (CDCl3, 112 MHz) d: ꢀ428.1; MS (FAB+) [m/z] (%): [(Mꢁ+, 469]
phenol,
2-amino-4-nitrophenol,
2-pyridinecarboxaldehyde,
2-picolinic acid, dimethyl, diphenyl and dibutyltin oxide, were ob-
tained from the Aldrich Chemical Co. The 1H, 13C and 119Sn NMR
spectra were recorded on a JEOL Eclipse +300. Chemical shifts
(ppm) are relative to (CH3)4Si, and coupling constants are quoted
in Hz. Melting points were measured on a Fisher Johns apparatus
and are uncorrected. Mass spectra were obtained with a JEOL
JMS-AX505 HA mass spectrometer. The elemental analysis was ob-
tained on an Exeter Analytical CE-440. The IR spectra were re-
corded on a Bruker Tensor 27. The X-Ray crystallographic studies
were done on a Bruker Smart Apex CCD diffractometer with a
k(Mo
) = 0.71073 Å, graphite monochromator, at T = 293 K. All
Ka
structures were solved by direct methods; all nonhydrogen atoms

A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
2971
1e
1h
2h
3h molecule A
3h molecule B
4h
Fig. 1. Perspective view of molecular structures of complexes 1e, 1h, 2h, 3h and 4h ORTEP (Thermal ellipsoids at 30% of probability level minor component of disordered side
chain drawn using open ellipsoids and broken lines).
(5); [(MꢀMe)+, 454] (20), [(MꢀPyCOO)+, 347] (100), [(MꢀPyCOO
ꢀ2Me)+, 317] (20);HR-MS (FAB+) m/z: 454.0214 (Calcd. for the frag-
ment ion C19H16O3N3Sn), Observed: 454.0200. Anal. Calc. for
C20H19N3O3Sn: C, 51.32; H, 4.09; N, 8.98. Found: C, 51.37; H, 4.17;
N, 9.02%.
151.2 (C-2), 149.9 (C-20), 162.1 (C-10); 119Sn NMR (CDCl3,
112 MHz) d: ꢀ426.2; MS (FAB+) [m/z] (%): [MÅ+, 483] (2); [(MꢀMe)+,
468] (5), [(MꢀPyCOO)+, 361] (40), [(MꢀPyCOOꢀ2Me)+, 331] (10);
HR-MS (FAB+) m/z: 468.0370 (Calcd. for the fragment ion
C20H18O3N3Sn), Observed 468.0376. Anal. Calc. for C21H21N3O3Sn:
C, 52.32; H, 4.39; N, 8.72. Found: C, 51.03; H, 4.57; N, 8.49%.
5.2. Complex 1b
5.3. Complex 1c
Following the procedure described for complex 1a, complex 1b
was prepared from 0.1289 g (1.048 mmol) of 2-amino-4-methyl-
phenol, 0.1 mL (1.048 mmol) of 2-pyridinecarboxaldehyde,
0.1727 g (1.048 mmol) dimethyltin oxide, and 0.1291 g (1.048
mmol) of 2-picolinic acid in 30 mL of methanol. The reaction mix-
ture was refluxed for 20 min, giving 0.4875 g (96.5% yield) of dark
Following the procedure described for complex 1a, complex 1c
was prepared following from 0.1505 g (1.048 mmol) of 2-amino-4-
chlorophenol, 0.1 mL (1.048 mmol) of 2-pyridinecarboxaldehyde,
0.1728 g (1.049 mmol) dimethyltin oxide and 0.1290 g (1.048
mmol) of 2-picolinic acid in 30 mL of benzene. The reaction mixture
was refluxed for 40 min, yielding 0.2673 g (50.8% yield)
of dark red crystals, m.p. 246–250 °C; IR (KBr cmꢀ1): 1651
red solid, m.p. 236–239 °C; IR (KBr cmꢀ1): 1659 (s,
(s, symCO2), 1596 (s, C@N), 419 (w,
Sn–N); 1H NMR (CDCl3,
masymCO2), 1356
m
m
m
300 MHz) d: 0.49 (6H, s, 2J(1H–119/117Sn) = 115.7, 110.8 Hz, Sn-
CH3), 2.32 (1H, s, CH3), 6.97 (1H, d, J = 8.5 Hz, H-11), 7.15 (1H, dd,
J = 8.5, 2.1 Hz, H-12), 7.36 (1H, d, J = 2.1 Hz, H-14), 7.58 (1H, ddd,
J = 7.6, 5.2, 1.0 Hz, H-3) 7.69 (1H, ddd, J = 7.6, 5.4, 1.2 Hz, H-17),
7.72 (1H, d, J = 7.4 Hz, H-5), 7.99 (1H, ddd, J = 7.6, 7.4, 1.6 Hz, H-
4), 8.07 (1H, ddd, J = 7.7, 7.6, 1.6 Hz, H-18), 8.52 (1H, d, J = 7.7 Hz,
H-19), 8.72 (1H, s, H-7), 9.76 (1H, d, J = 5.4 Hz, H-16), 9.87 (1H, d,
J = 5.2 Hz, H-2); 13C NMR (CDCl3, 75 MHz) d: 13.8 (Sn-CH3), 20.8
(Ar-CH3), 116.1 (C-14), 121.7 (C-11), 124.7 (C-13), 125.7 (C-19),
126.4 (C-17), 126.2 (C-3), 125.7(C-5), 129.3 (C-9), 134.9 (C-12),
139.0 (C-4), 139.9 (C-18), 141.6 (C-7), 148.0 (C-16), 148.1 (C-6),
(s, masymCO2), 1359 (s, msymCO2), 1594 (s, mC@N), 418 (w, mSn–N);
1H NMR (CDCl3, 300 MHz) d: 0.49 (6H, s, 2J(1H–119/117Sn) = 115.6,
110.5 Hz, Sn-CH3), 6.98 (1H, d, J = 8.9 Hz, H-11), 7.24 (1H, dd,
J = 8.9, 2.6 Hz, H-12), 7.54 (1H, d, J = 2.6 Hz, H-14), 7.63 (1H, ddd,
J = 7.6, 5.1, 1.1 Hz, H-3), 7.71 (1H, ddd, J = 7.6, 5.4, 1.4 Hz, H-17),
7.77 (1H, d, J = 7.7 Hz, H-5), 8.03 (1H, ddd, J = 7.7, 7.6, 1.7 Hz, H-4),
8.09 (1H, ddd, J = 7.7, 7.6, 1.5 Hz, H-18), 8.53 (1H, d, J = 7.7 Hz, H-
19), 8.71 (1H, s, H-7), 9.72 (1H, d, J = 5.4 Hz, H-16), 9.88 (1H, d,
J = 5.1 Hz, H-2); 13C NMR (CDCl3, 75 MHz) d: 13.8 ((1J(13C–119/
117Sn) = 1190, 1130 Hz, Sn-CH3), 116.3 (C-14), 123.0 (C-11), 120.0
(C-13), 125.7 (C-19), 126.7 (C-3,C-17), 126.5 (C-5), 130.2 (C-9),

2972
A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
132.2 (C-12), 139.2 (C-4), 140.2 (C-18), 143.0 (C-7), 147.9 (C-16),
148.1 (C-6), 149.7 (C-20), 151.3 (C-2), 162.7 (C-10), 166.5 (C-21);
119Sn NMR (CDCl3, 112 MHz) d: ꢀ425.7; MS (FAB+) [m/z] (%): [MÅ+,
503] (5); [(MꢀMe)+, 488] (20), [(MꢀPyCOO)+, 381] (100); HR-MS
(FAB+) m/z: 487.9824 (Calcd. for the fragment ion C20H18O3N3Sn),
Observed 487.9821. Anal. Calc. for C20H18N3O3ClSn: C, 47.80; H,
3.61; N, 8.36. Found: C, 48.23; H, 3.74; N, 8.30%.
496.0694. Anal. Calc. for C20H18N4O5Sn: C, 56.55; H, 5.55; N, 7.61.
Found: C, 57.56; H, 5.98; N, 7.37%.
5.6. Complex 1f
Following the procedure described for complex 1a, complex 1f
was prepared from 0.1 mL (1.048 mmol) of 2-pyridinecarboxalde-
hyde, 0.1290 g (1.048 mmol) of 2-amino-4-methylphenol, 0.2609 g
(1.048 mmol) of dibutyltin oxide and 0.1290 g (1.048 mmol) of
2-picolinic acid in 25 mL of methanol. This yielded 0.4701 g (79.3%
yield) of a dark red solid, m.p. 224–227 °C; IR (KBr cmꢀ1): 1644 (s,
5.4. Complex 1d
Following the procedure described for complex 1a, complex 1d
was prepared from 0.1618 g (1.048 mmol) of 2-amino-4-nitrophe-
nol, 0.1 mL (1.048 mmol) of 2-pyridinecarboxaldehyde, 0.1730 g
(1.050 mmol) dimethyltin oxide and 0.1290 g (1.048 mmol) of 2-
picolinic acid. The reaction mixture was refluxed for 40 min giving
0.3718 g (69% yield) of orange crystals, m.p. 267–270 °C; IR (KBr
m
asymCO2), 1358 (s, msymCO2), 1597 (s, mC@N), 416 (w, m
Sn–N); 1H
NMR (300 MHz, CDCl3) d: 0.49 (6H, t, J = 7.02 Hz, Sn(CH2)3CH3),
0.79–1.15 (12H, m, Sn-(CH2)3CH3), 2.30 (3H, s, Ar-CH3), 6.97 (1H, d,
J = 8.5 Hz, H-11), 7.14 (1H, dd, J = 8.5, 1.8 Hz, H-12), 7.36 (1H, d,
J = 1.8 Hz, H-14), 7.57 (1H, ddd, J = 7.6, 5.1, 1.0 Hz, H-3), 7.68 (1H,
ddd, J = 7.5, 5.4, 1.2 Hz, H-17), 7.72 (1H, d, J = 7.7 Hz, H-5), 7.99
(1H, ddd, J = 7.7, 7.6, 1.7 Hz, H-4), 8.06 (1H, ddd, J = 7.6, 7.5, 1.7 Hz,
H-18), 8.52 (1H, d, J = 7.6 Hz, H-19), 8.76 (1H, s, H-7), 9.73 (1H, d,
J = 5.4 Hz, H-16), 9.83 (1H, d, J = 5.1 Hz, H-2); 13C NMR (75 MHz,
CDCl3), d: 13.5 (4J(13C–119Sn) = 12.7 Hz, Cd), 20.8 (Ar-CH3), 26.3
cmꢀ1): 1649 (s,
419 (w,
m
asymCO2), 1351 (s,
msymCO2), 1592 (s, mC@N),
m
Sn–N); 1H NMR (CDCl3, 300 MHz) d: 0.52 (6H, s, 2J
(1H–119/117Sn) = 115.30, 110.35 Hz, Sn-CH3), 7.00 (1H, d, J = 9.4 Hz,
H-11), 7.71 (1H, ddd, J = 7.7, 5.1, 1.2 Hz, H-3), 7.75 (1H, ddd, J = 7.6,
5.4, 1.4 Hz, H-17), 7.94 (1H, d, J = 7.6 Hz, H-5), 8.12 (1H, ddd,
J = 7.7, 7.6, 1.7 Hz, H-4), 8.13 (1H, ddd, J = 7.7, 7.6, 1.7 Hz, H-18),
8.22 (1H, dd, J = 9.4, 2.8 Hz, H-12), 8.55 (1H, d, J = 7.7 Hz, H-19),
8.62 (1H, d, J = 2.8 Hz, H-14), 9.01 (1H, s, H-7), 9.70 (1H, d,
J = 5.4 Hz, H-16), 9.92 (1H, d, J = 5.1 Hz, H-2); 13C NMR (CD2Cl2,
75 MHz) d: 13.8 (Sn-CH3), 114.3 (C-11), 121.3 (C-12), 125.9 (C-5),
127.1 (C-3), 127.8 (C-17), 128.1 (C-19), 128.4 (C-14), 129.6 (C-9),
136.1 (C-13), 140.0 (C-4), 140.7 (C-18), 146.9 (C-7), 147.6 (C-6),
147.9 (C-16), 149.7 (C-20), 151.2 (C-2), 166.0 (C-10), 170.0 (C-21);
119Sn NMR (CDCl3, 112 MHz) d: ꢀ427.9; MS (FAB+) [m/z]
(%): [(M+1)+, 515] (5); [(MꢀMe)+, 499] (15), [(MꢀPyCOO)+, 392]
(60); [(MꢀPyCOOꢀ2Me)+, 362] (10); HR-MS (FAB+) m/z: 499.0064
(Calcd. for the fragment ion C20H18O3N3Sn), Observed 499.0064.
Anal. Calc. for C20H18N4O5Sn: C, 46.82; H, 3.54; N, 10.92. Found: C,
46.63; H, 3.74; N, 10.60%.
(3J(13C–119Sn) = 183.5 Hz, C ), 27.8 (2J(13C–119Sn) = 46.2 Hz, Cb),
c
32.5 (1J(13C–119/117Sn) = 1128, 1080 Hz, C ), 116.1 (C-14), 121.6
a
(C-11), 124.3 (C-13), 125.6 (C-19), 125.9 (C-5), 126.0 (C-3), 126.2
(C-17), 129.9 (C-9), 134.7 (C-12), 138.9 (C-4), 139.8 (C-18), 141.6
(C-7), 148.3 (C-16), 148.6 (C-6), 150.4 (C-20), 151.4 (C-2), 162.3
(C-10), 167.0 (C-21); 119Sn NMR (112 MHz, CDCl3) d: ꢀ441.3; MS
(FAB+) [m/z] (%): [MÅ+, 567] (3); [(MꢀBu)+, 510] (75), [(MꢀPyCOO)+,
445] (100), [(MꢀPyCOO-2Bu)+, 331] (95); HR-MS (FAB+) m/z:
510.0840 (Calcd. for the fragment ion C23H24N3O3Sn), Observed
510.0851. Anal. Calc. for C27H33N3O3Sn: C, 57.27; H, 5.87; N, 7.42.
Found: C, 57.01; H, 5.88; N, 7.31%.
5.7. Complex 1g
5.5. Complex 1e
For complex 1g 0.2609 g (1.048 mmol) of dibutyltin oxide was
added to a solution of 0.1 mL (1.048 mmol) 2-pyridinecarboxalde-
hyde and 0.1501 g (1.046 mmol) of 2-amino-4-chlorophenol in
20 mL methanol. After 5 min, the solution turned dark red, and
0.1290 g (1.048 mmol) of 2-picolinic acid was added. The reaction
mixture was refluxed for 20 min after which time the solvent was
removed under vacuum. The solution was filtered, affording
0.4310 g (70.2% yield) of a dark red solid, m.p. = 217–220 °C; IR
Following the procedure described for complex 1a, complex 1e
was prepared from 0.1144 g (1.048 mmol) of 2-aminophenol,
0.1 mL (1.048 mmol) of 2-pyridinecarboxaldehyde, 0.2609 g
(1.048 mmol) dibutyltin oxide and 0.1290 g (1.048 mmol) of 2-
picolinic acid. The reaction mixture was refluxed for 40 min, then
80% of the solvent was evaporated under vacuum. The resulting pre-
cipitate was filtered thereby giving 0.4541 g (78.5% yield) of a dark
red solid, m.p. 218–221 °C; IR (KBr cmꢀ1): 1642 (s,
masymCO2), 1360
(KBr cmꢀ1): 1641 (s,
417 (w,
Sn–N); 1H NMR (300 MHz, CDCl3) d: 0.50 (6H, t, J = 7.0 Hz,
masymCO2), 1359 (s, msymCO2), 1594 (s, mC@N),
(s, symCO2), 1594 (s, C@N), 416 (w,
m
m
m
Sn–N); 1H NMR (300 MHz,
m
CDCl3) d: 0.47 (6H, t, J = 6.85 Hz, Sn(CH2)3CH3), 0.80–1.16 (12H, m,
Sn-(CH2)3CH3), 6.63 (1H, ddd, J = 8.1, 7.0, 1.0 Hz, H-13), 7.05 (1H,
dd, J = 8.4, 1.0 Hz, H-11), 7.31 (1H, t, J = ddd, 8.4, 7.0, 1.3 Hz, H-12),
7.56 (1H, dd, J = 8.1, 1.3 Hz, H-14), 7.57 (1H, ddd, J = 7.7, 5.2, 1.0 Hz,
H-3), 7.69 (1H, ddd, J = 7.6, 5.6, 1.2 Hz, H-17), 7.75 (1H, d,
J = 7.7 Hz, H-5), 8.00 (1H, ddd, J = 7.7, 7.7, 1.4 Hz, H-4), 8.07 (1H,
ddd, J = 7.6, 7.6, 1.5 Hz, H-18), 8.51 (1H, d, J = 7.6 Hz, H-19), 8.80
(1H, s, H-7), 9.74 (1H, d, J = 5.6 Hz, H-16), 9.84 (1H, d, J = 5.2 Hz, H-
2); 13C NMR (75 MHz, CDCl3), d: 13.5 (4J(13C–119Sn) = 13.9 Hz, Cd),
Sn-(CH2)3CH3), 0.80–1.15 (12H, m, Sn-(CH2)3CH3), 6.98 (1H, d,
J = 8.9 Hz, H-11), 7.23 (1H, dd, J = 8.9, 2.5 Hz, H-12), 7.53 (1H, d,
J = 2.5 Hz, H-14), 7.62 (1H, ddd, J = 7.6, 5.0, 1.0 Hz, H-3), 7.70 (1H,
ddd, J = 7.5, 5.4, 1.2 Hz, H-17), 7.76 (1H, d, J = 7.7 Hz, H-5), 8.03
(1H, ddd, J = 7.7, 7.6, 1.7 Hz, H-4), 8.09 (1H, ddd, J = 7.6, 7.5,
1.7 Hz, H-18), 8.53 (1H, d, J = 7.6 Hz, H-19), 8.74 (1H, s, H-7), 9.68
(1H, d, J = 5.4 Hz, H-16), 9.86 (1H, d, J = 5.1 Hz, H-2); 13C NMR
(75 MHz, CDCl3), d: 13.5 (Cd), 26.2 (C ), 27.8 (Cb), 32.6 (C ),
c
a
116.1(C-14), 119.7 (C-13), 122.9 (C-11), 125.8 (C-19), 126.4
(C-17), 126.5 (C-3), 126.6 (C-5), 130.7 (C-9), 133.1 (C-12), 139.1
(C-4), 140.1 (C-18), 143.2 (C-7), 148.1 (C-16), 148.3 (C-6), 150.2
(C-20), 151.5 (C-2), 157.2 (C-10), 163.4 (C-21), 119Sn NMR
(112 MHz, CDCl3) d: ꢀ441.4; MS (FAB+) [m/z] (%): [MÅ+, 587] (2);
[(MꢀBu)+, 530] (50), [(MꢀPyCOO)+, 465] (100), [(Mꢀ
PyCOOꢀ2Bu)+, 351] (55); HR-MS (FAB+) m/z: 530.0293 (Calcd. for
the fragment ion C22H21N3O3ClSn), Observed 530.0298. Anal. Calc.
for C26H30N3O3ClSn: C, 53.23; H, 5.15; N, 7.16. Found: C, 53.90; H,
5.24; N, 7.11%.
26.3 (3J(13C–119Sn) = 182.3 Hz, C ), 27.8 (2J(13C–119/117Sn) = 60.0,
c
45.0 Hz, Cb), 32.6 (1J(13C–119/117Sn) = 1130, 1080 Hz, C ), 115.1 (C-
a
14), 116.3 (C-11), 121.9 (C-13), 125.7 (C-19), 126.1 (C-17), 126.2
(C-3), 126.3 (C-5), 130.5 (C-9), 133.3 (C-12), 139.0 (C-4), 139.9 (C-
18), 142.3 (C-7), 148.2 (C-16), 148.5 (C-6), 150.4 (C-20), 151.4 (C-
2), 162.9 (C-10), 167.0 (C-21); 119Sn NMR (112 MHz, CDCl3) d:
ꢀ443.6; MS (FAB+) [m/z] (%): [MÅ+, 553] (2); [(MꢀBu)+, 496] (53),
[(MꢀPyCOO)+, 431] (100), [(MꢀPyCOOꢀ2Bu)+, 317] (55); HR-MS
(FAB+) m/z: 496.0683 (Calcd. for C22H22N3O3Sn), Observed

A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
2973
5.8. Complex 1h
7.09 (6H, m, H-m, H-p), 7.18 (1H, d, J = 1.7 Hz, H-14), 7.19 (1H, d,
J = 8.4 Hz, H-11), 7.24 (1H, dd, J = 8.4, 1.7 Hz, H-12), 7.42 (1H, d,
J = 7.6 Hz, H-5), 7.53 (1H, ddd, J = 7.6, 5.4, 1.4 Hz, H-3), 7.58–7.63
(5H, m, H-17, H-o), 7.83 (1H, ddd, J = 7.6, 7.6, 1.7 Hz, H-4), 7.86
(1H, ddd, J = 7.7, 7.7, 1.7 Hz, H-18), 8.29 (1H, d, J = 7.7 Hz, H-19),
8.39 (1H, s, H-7), 9.84 (1H, d, J = 4.7 Hz, H-16), 10.27 (1H, d,
J = 5.4 Hz, H-2); 13C NMR (75 MHz, CDCl3), d: 20.8 (Ar-CH3), 116.4
(C-14), 120.7 (C-11), 125.2 (C-13), 125.4 (C-19), 126.1 (C-3),
126.6 (C-5), 127.0 (C-17), 128.0 (C-m, C-p), 130.2 (C-9), 134.4 (C-
p), 135.0 (C-12), 139.0 (C-4), 139.9 (C-18), 141.9 (C-7), 147.6 (C-
ipso), 148.2 (C-16), 149.1 (C-20), 151.4 (C-2), 151.9 (C-6), 162.6
(C-10), 166.0 (C-21), 119Sn NMR (112 MHz, CDCl3) d: ꢀ582.7; MS
(FAB+) [m/z] (%): [MÅ+, 607], (2), [(MꢀPh)+, 530] (1), [(MꢀPyCOO)+,
485] (15), [(MꢀPyCOOꢀ2Ph)+, 331] (3); HR-MS (FAB+) m/z:
485.0676; (Calcd. for the fragment ion C25H21ON2Sn), Observed
485.0686. Anal. Calc. for C31H25N3O3Sn: C, 61.42; H, 4.16; N, 6.93.
Found: C, 61.23; H, 4.23; N, 6.88%.
Following the procedure described for complex 1g, complex 1h
was prepared from 0.1 mL (1.048 mmol) of 2-pyridinecarboxalde-
hyde, 0.1615 g (1.048 mmol) of 2-amino-4-nitrophenol, 0.2609 g
(1.048 mmol) of dibutyltin oxide, and 0.1290 g (1.048 mmol) of
2-picolinic acid thereby giving 0.5247 g (83.7% yield) of a brown-
orange solid, m.p. = 211–216 °C; IR (KBr cmꢀ1): 1648 (s, masym
CO2), 1354 (s, msymCO2), 1593 (s, mC@N), 416 (w, m
Sn–N); 1H NMR
(300 MHz, CDCl3) d: 0.50 (6H, t, J = 7.3 Hz, Sn-(CH2)3CH3), 0.77–
1.17 (12H, m, Sn-(CH2)3CH3), 7.01 (1H, d, J = 9.4 Hz, H-11), 7.68
(1H, ddd, J = 7.6, 5.3, 1.1 Hz, H-3), 7.75 (1H, ddd, J = 7.6, 5.4,
1.2 Hz, H-17), 7.91 (1H, d, J = 7.6 Hz, H-5), 8.12 (1H, ddd, J = 7.6,
7.6, 1.7 Hz, H-4), 8.14 (1H, ddd, J = 7.7, 7.6, 1.7 Hz, H-18), 8.22
(1H, dd, J = 9.4, 2.5 Hz, H-12), 8.55 (1H, d, J = 7.7 Hz, H-19), 8.65
(1H, d, J = 2.5 Hz, H-14), 9.00 (1H, s, H-7), 9.65 (1H, d, J = 4.5 Hz,
H-16), 9.87 (1H, d, J = 5.0 Hz, H-2); 13C NMR (75 MHz, CDCl3), d:
13.4 (Cd), 26.2 (C ), 27.8 (Cb), 32.9 (C ), 113.8 (C-11), 121.3
c
a
(C-12), 125.9 (C-19), 126.7 (C-5), 127.3 (C-3), 127.5 (C-17), 128.4
(C-14), 129.7 (C-9), 135.8 (C-13), 139.6 (C-4), 139.6 (C-18), 146.2
(C-7), 147.7 (C-6), 147.9 (C-16), 149.9 (C-20), 151.7 (C-2), 166.7
(C-10), 170.4 (C-21), 119Sn NMR (112 MHz, CDCl3) d: ꢀ441.1; MS
(FAB+) [m/z] (%): [MÅ+, 598] (2); [(MꢀPyCOO)+, 476] (100),
[(MꢀPyCOOꢀ2Bu)+, 362] (35), [(MꢀPyCOOꢀNO2)+, 430] (10);
HR-MS (FAB+) m/z: 476.0996 (Calcd. for the fragment ion
C20H26N3O3Sn), Observed 476.0996. Anal. Calc. for C26H30N4O5Sn:
C, 52.29; H, 5.06; N, 9.38. Found: C, 51.78; H, 5.11; N, 9.10%.
5.11. Complex 1k
Following the procedure described for 1i, complex 1k was
formed from 0.1 mL of 2-pyridinecarboxaldehyde, 0.1509 g
(1.051 mmol) of 2-amino-4-chlorophenol, 0.3031 g diphenyltin
oxide and 0.1291 g (1.048 mmol) 2-picolinic acid, which was re-
fluxed for 20 min and which lead to 0.5445 g (83% yield) of a red
solid, m.p. 280–285 °C; IR (KBr cmꢀ1): 1659 (s,
(s, symCO2), 1594 (s, C@N), 419 (w,
m
asymCO2), 1359
m
m
m
Sn–N); 1H NMR (300 MHz,
CDCl3) d: 6.91–7.11 (6H, m, H-m, H-p), 7.23 (1H, d, J = 9.4 Hz, H-
11), 7.35 (1H, dd, J = 9.4, 2.5 Hz, H-12), 7.36 (1H, s, H-14), 7.50
(1H, d, J = 7.6 Hz, H-5), 7.54–7.52 (5H, m, H-3, H-o), 7.67 (1H,
ddd, J = 7.5, 5.2, 1.1, H-17), 7.89 (2H, ddd, J = 7.7, 7.5, 1.1 Hz, H-4,
H-18), 8.33 (1H, d, J = 7.7 Hz, H-19), 8.38 (s, 1H, H-7), 9.82 (1H, d,
J = 5.2 Hz, H-16), 10.29 (1H, d, J = 5.2 Hz, H-2); 13C NMR (75 MHz,
CD2Cl2), d: 116.7 (C-14), 120.6 (C-13), 122.4 (C-11), 125.6 (C-19),
127.1 (C-3), 127.3 (C-17), 128.2 (C-5), 128.4 (C-m, p), 131.3 (C-9),
133.5 (C-12), 134.3 (C-o), 139.8 (C-4), 140.5 (C-18), 144.5 (C-7),
147.3 (C-ipso), 148.3 (C-16), 149.5 (C-6), 151.8 (C-20), 151.9 (C-
2), 163.3 (C-10), 166.2 (C-21); 119Sn NMR (112 MHz, CDCl3) d:
ꢀ580.6; MS(FAB+) [m/z] (%): [MÅ+, 627] (5); [(MꢀPh)+, 550] (5),
[(MꢀPyCOO)+, 505] (20), [(MꢀPyCOOꢀ2Ph)+, 351] (5); HR-MS
(FAB+) m/z: 549.9980 (Calcd. for the fragment ion C24H17O3N3ClSn),
Observed 549.9989. Anal. Calc. for C30H22N3O3ClSn: C, 57.50; H,
3.54; N, 6.71. Found: C, 56.30; H, 3.60; N, 6.32%.
5.9. Complex 1i
0.3030 g (1.049 mmol) diphenyltin oxide and 0.1290 g
(1.048 mmol) of 2-picolinic acid in 30 mL benzene was added to
a solution of 0.1 mL (1.048 mmol) of 2-pyridinecarboxaldehyde,
0.1144 g (1.048 mmol) of 2-aminophenol. The combined solution
was refluxed for 40 min. After evaporating 20 mL of solvent to vac-
uum, a precipitate formed which was then filtered to give 0.6175 g
(99.5%) of a dark red solid, m.p. 295 °C; IR (KBr cmꢀ1): 1657 (s,
m
asymCO2), 1343 (s, msymCO2), 1594 (s, mC@N), 421 (w, m
Sn–N); 1H
NMR (300 MHz, CDCl3) d: 6.67 (1H, ddd, J = 8.6, 7.0, 1.4 Hz, H-
13), 6.97–7.02 (6H, m, H-m, H-p), 7.28 (1H, dd, J = 9.1, 1.4 Hz, H-
11), 7.39–7.44 (2H, m, H-12, H-14), 7.51 (1H, d, J = 8.1 Hz, H-5),
7.56 (1H, ddd, J = 7.4, 5.5, 1.3 Hz, H-3), 7.60–7.63 (4H, m, H-o),
7.64 (1H, ddd, J = 7.6, 5.2, 1.2 Hz, H-17), 7.89 (2H, ddd, J = 7.8, 7.6,
1.5 Hz, H-4, H-18), 8.33 (1H, d, J = 7.8. Hz, H-19), 8.49 (1H, s, H-
7), 9.87 (1H, d, J = 5.2. Hz, H-16), 10.31 (1H, d, J = 5.5 Hz, H-2);
13C NMR (75 MHz, CDCl3), d: 115.9 (C-14), 116.5 (C-11), 121.1 (C-
13), 125.5 (C-19), 126.4 (C-17), 126.6 (C-3), 127.2 (C-5), 128.0 (C-
p), 128.1 (C-m), 133.6 (C-12), 134.3 (2J(13C–119Sn) = 66.9 Hz, C-o),
139.1 (C-4), 139.9 (C-18), 142.5 (C-7), 148.1 (C-16), 148.3 (C-6),
151.6 (C-2); 119Sn NMR (112 MHz, CDCl3) d: ꢀ583.8; MS (FAB+)
[m/z] (%): [MÅ+, 593] (5); [(MꢀPh)+, 516] (10), [(MꢀPyCOO)+, 471]
(40), [(MꢀPyCOOꢀPh)+, 394] (20), [(MꢀPyCOOꢀ2Ph)+, 317] (10);
HR-MS (FAB+) m/z: 516.0370; (Calcd. for the fragment ion
C24H18N3O3Sn), Observed 516.0372. Anal. Calc. for C30H23N3O3Sn:
C, 60.84; H, 3.91; N, 7.10. Found: C, 58.81; H, 4.34; N, 6.61%.
5.12. Complex 1l
Following the procedure described for 1i, complex 1l
was formed from 0.1 mL of pyridinecarboxaldehyde, 0.1614 g
(1.047 mmol) of 2-amino-4-nitrophenol, 0.3031 g (1.049 mmol)
of diphenyltin oxide and 0.1289 g (1.048 mmol) of 2-picolinic acid,
refluxed 20 min to give 0.6069 g (90.9% yield) of an orange solid,
m.p. 290 °C (dec); IR (KBr cmꢀ1): 1648 (s,
CO2), 1592 (s, C@N), 420 (w,
m
asymCO2), 1362 (s, msym-
m
m
Sn–N); 1H NMR (300 MHz, CDCl3) d:
6.95–7.09 (6H, m, H-m, H-p), 7.50 (4H, dd, J = 7.7, 1.8 Hz, H-o), 7.29
(1H, d, J = 9.5 Hz, H-11), 7.63 (1H, ddd, J = 7.5, 5.4, 1.4 Hz, H-3), 7.71
(1H, d, J = 7.4 Hz, H-5), 7.78 (1H, ddd, J = 7.7, 5.1, 1.2 Hz, H-17), 7.97
(1H, ddd, J = 7.5, 7.4, 1.65 Hz, H-4), 8.03 (1H, ddd, J = 7.7, 7.7,
1.7 Hz, H-18), 8.34 (1H, dd, J = 9.5, 2.8 Hz, H-12), 8.37 (1H, d,
J = 7.7. Hz, H-19), 8.48 (1H, d, J = 2.8 Hz, H-14), 8.72 (s, 1H, H-7),
9.79 (1H, d, J = 5.1 Hz, H-16), 10.32 (1H, d, J = 5.4 Hz, H-2); 13C
NMR (75 MHz, CD2Cl2), d: 114.1 (C-11), 120.9 (C-12), 125.8 (C-5),
127.3 (C-3), 128.1 (C-17), 128.6 (2J(13C–119Sn) 119.42 Hz, C-m),
128.7 (C-p), 128.7 (C-14), 128.9 (C-19), 130.2 (C-9), 134.0 (C-o),
137.0 (C-13), 140.2 (C-4), 140.8 (C-18), 147.1 (C-ipso), 147.4 (C-
7), 148.1 (C-16), 149.3 (C-6), 151.1 (C-20), 152.0 (C-2), 166.1 (C-
10), 170.0 (C-21); 119Sn NMR (112 MHz, CD2Cl2) d: ꢀ580.5; MS
5.10. Complex 1j
Following the procedure described for complex 1i, complex 1j
was formed from 0.1 mL (1.048 mmol) of 2-pyridinecarboxalde-
hyde, 0.1290 g (1.048 mmol) of 2-amino-4-methylphenol,
0.3031 g (1.049 mmol) diphenyltin oxide and 0.1289 g
(1.048 mmol) of 2-picolinic acid, thereby producing 0.6030 g
(94.9%) of a dark red solid, m.p. 250 °C (dec); IR (KBr cmꢀ1):
1657 (s, masym CO2), 1345 (s,
msymCO2), 1598 (s, mC@N), 420 (w,
m
Sn–N); 1H NMR (300 MHz, CDCl3) d: 2.30 (3H, s, Ar-CH3), 6.90–

2974
A. Ramírez-Jiménez et al. / Journal of Organometallic Chemistry 694 (2009) 2965–2975
(FAB+) [m/z] (%): [MÅ+, 638] (4), [(MꢀPh)+, 561] (10), [(MꢀPyCOO)+,
516] (50), [(MꢀPyCOOꢀ2Ph)+, 362] (5); HR-MS (FAB+) m/z:
561.0221 (Calcd. for the fragment ion C24H17O5N4Sn), Observed
561.0236. Anal. Calc. for C30H22N4O5Sn: C, 55.55; H, 3.48; N, 8.79.
Found: C, 55.70; H, 3.67; N, 8.52%.
1.15–1.62 (12H, m, Sn-(CH2)3CH3), 6.81 (1H, d, J = 8.9, H-11), 7.79
(1H, ddd, J = 7.7, 5.5, 1.2 Hz, H-3), 7.96 (1H, dd, J = 8.9, 2.8 Hz, H-
12), 8.25 (1H, ddd, J = 7.8, 7.7, 1.2 Hz, H-4), 8.38 (1H, d, J = 5.4 Hz,
H-2), 8.62 (1H, d, J = 7.8 Hz, H-5), 9.70 (1H, d, J = 2.8 Hz, H-14);
13C NMR (75 MHz, CDCl3) d: 13.5 (Cd), 20.6 (1J(13C–119/117Sn) =
566.4, 538.8 Hz, (C ), 26.5 (Cb), 27.1 (C ), 116.0 (C-14), 121.8 (C-
a
c
5.13. Complex 2h
12), 114.8 (C-11), 124.9 (C-5), 127.6 (C-3), 132.2 (C-9), 137.5 (C-
13), 142.3 (C-4), 143.6 (C-2) 149.7 (C-6), 161.8 (C-10), 162.6 (C-
7); 119Sn NMR (112 MHz, CDCl3) d: ꢀ122.3; MS (EI): [Mꢁ+, 491]
(100), [(MꢀBu)+, 434] (10), [Mꢀ2Bu)+, 377] (50). Anal. Calc. for
C20H25N3O4Sn: C, 49.01; H, 5.14; N, 8.57. Found: C, 49.51; H,
5.40; N, 8.63%.
For complex 2h 0.2609 g (1.048 mmol) of the dibutyltin oxide
was added to a solution of 0.2547 g (1.048 mmol) of the Schiff base
2 in 30 mL of toluene/methanol (4:6) mixture. The reaction mix-
ture was refluxed for 8 h, then the solvent was evaporated under
reduced pressure, thereby giving 0.4864 g (94.5% yield), of an or-
ange solid which was crystallized from methanol; m.p. 122 °C, IR
(KBr cmꢀ1): 3071, 3036, 2950, 2928, 2859, 395, 419, 467, 532,
575, 649, 671; 1H NMR (300 MHz, CDCl3) d: 0.76 (3H, t, J = 7.3 Hz,
Sn-(CH2)3CH3), 0.88 (3H, t, J = 7.3 Hz, Sn-(CH2)3CH3), 1.14–1.71
(12H, m, Sn-(CH2)3CH3), 2.86 (3H, s, –O–CH3), 6.37 (1H, s, H-7),
6.69 (1H, d, J = 8.7 Hz, H-11), 7.65 (1H, ddd, J = 7.6, 5.4, 1.1 Hz,
H-3), 7.74 (1H, dd, J = 8.7, 2.8 Hz, H-12), 7.89 (1H, d, J = 2.8 Hz, H-
14), 7.97 (1H, d, J = 7.8, H-5), 8.17 (1H, ddd, J = 7.8, 7.6, 1.5 Hz, H-
4), 8.35 (1H, d, J = 5.4 Hz, H-2); 13C NMR (75 MHz, CDCl3) d: 13.5
6. Supplementary material
CCDC 719552, 719553, 719554, 719555, 719556, 719557,
719558 and 719559 contain the supplementary crystallographic
data for 1h, 1c, 1e, 3h, 2h, 1f, 1g and 4h. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
(Cd), 13.6 (Cd), 19.9, 20.7 (1J(13C–119/117Sn) = 559.6, 535.4 C ),
a
26.4, 26.8 (Cb) 27.2 27.5 (C ), 84.0 (C-7), 47.7 (–O–CH3), 112.5
c
Authors thank the financial support from DGAPA (IN203908)
and thank Rocío Patiño, Eréndira García, Javier Pérez and Luis
Velasco for the IR, elemental analysis, and mass spectrometry tech-
nical support.
(C-14), 117.1 (C-12), 106.3 (C-11), 125.4 (C-5), 125.7 (C-3), 138.2
(C-9), 139.4 (C-13), 141.4 (C-4), 143.9 (C-2), 157.1 (C-6), 162.0
(C-10); 119Sn NMR 112 MHz, (CDCl3) d: ꢀ83.0; MS(ESI): [Mꢁ+] 507
(1), [(M+Na)+, 530], (5), [(MꢀMeO)+, 476] (100). Anal. Calc. for
C21H29N3O4Sn: C, 49.83; H, 5.77; N, 8.30. Found: C, 50.00; H,
5.78; N, 8.37%.
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