Structural and conformational analysis of neutral dinuclear diorganotin(IV) complexes derived from hexadentate Schiff base ligands

Article abstract of DOI:10.1016/j.jorganchem.2006.09.064

The synthesis of three hexadentate Schiff base ligands has been carried out, which contain two sets of ONO donor atoms. These were reacted with diorganotin(IV) dichloride derivatives (R = Me, nBu, Ph) to prepare seven dinuclear diorganotin(IV) complexes i

Full text of DOI:10.1016/j.jorganchem.2006.09.064

Journal of Organometallic Chemistry 692 (2007) 731–739
www.elsevier.com/locate/jorganchem
Structural and conformational analysis of neutral dinuclear
diorganotin(IV) complexes derived from hexadentate Schiff base ligands
a,
a
a
a
Victor Barba *, Edgar Vega , Rolando Luna , Herbert Ho¨pfl ,
b
c
´
Hiram I. Beltran , Luis S. Zamudio-Rivera
a
Centro de Investigaciones Qu´ımicas, Universidad Auto´noma del Estado de Morelos, Av. Universidad 1001, C.P. 62209 Cuernavaca, Morelos, Mexico
Departamento de Ciencias Naturales, C. N. I., UAM-Cuajimalpa, Av. Pedro A. de los Santos 84, Col. San Miguel Chapultepec, 11850 D.F., Mexico
b
c
Programa de Ingenier´ıa Molecular, Instituto Mexicano del Petro´leo, Eje Central L. Cardenas 152, C.P. 07730 D.F., Mexico
Received 16 August 2006; received in revised form 16 September 2006; accepted 16 September 2006
Available online 12 October 2006
Abstract
The synthesis of three hexadentate Schiff base ligands has been carried out, which contain two sets of ONO donor atoms. These were
reacted with diorganotin(IV) dichloride derivatives (R = Me, nBu, Ph) to prepare seven dinuclear diorganotin(IV) complexes in moder-
ate yields. Aside from IR and NMR (1H, 13C, 119Sn) spectroscopic studies, mass spectrometry and elemental analysis, four tin complexes
were characterized by X-ray diffraction analysis. The spectroscopic analyses showed that in solution the tin atoms have five-coordinate
environments with a distorted trigonal bipyramidal geometry. Each tin atom is coordinated to the nitrogen atom and forms covalent
bonds with two oxygen atoms and two carbon atoms. Due to the presence of a methylene group as bridge between the two ONO che-
lates, the overall molecular structures can have cis or trans conformation, having either mirror or C2-symmetry. While in solution a fast
equilibrium can be supposed, in the solid state different intermediate conformations have been detected. Furthermore, for the dialkyltin
derivatives Snꢀ ꢀ ꢀO intermolecular interactions were found allowing for a dimeric or crinkled polymeric organization, whereas for the
diphenyltin derivatives no such interactions were observed.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Hexadentate Schiff base ligands; Diorganotin(IV) complexes; Structural analysis; Coupling constant
1. Introduction
Most of the diorganotin(IV) complexes resulting from
tridentate Schiff base ligands have been synthesized from
salicylaldehyde derivatives in combination with aliphatic
aminoalcohols [15], aminoacids [16–19] and aminophenols
[20–23]. The importance of diorganotin(IV) complexes
derived from tridentate Schiff base ligands is in part due
to their biocide and toxicological activities [15], as well as
their use as initiators for lactide polymerization [24]. Usu-
ally, tin atoms in complexes derived from ONO tridentate
ligands are penta-coordinate with a trigonal bipyramidal
(TBP) geometry [15–23]. Generally, in this class of com-
pounds the oxygen atoms occupy the axial positions, while
the nitrogen atom and the two additional organic substitu-
ents are in equatorial positions. In tin derivatives with TBP
geometry, the metal center can act as Lewis acid, which
allows to increase its coordination number by addition of
The chemistry of diorganotin(IV) compounds derived
from ligands containing nitrogen and oxygen donor atoms
has attracted much attention in the last few years, a fact
that underlies the increasing number of publications deal-
ing with this class of compounds [1–5]. In particular, diorg-
anotin(IV) complexes using Schiff bases as ligands are
being widely studied (e.g. [6–8]) . The easy accessibility
and structural features made them the target of numerous
biological [9–11] and catalytic [12–14] studies.
*
Corresponding author. Tel./fax: +52 7773297997.
E-mail address: vbarba@ciq.uaem.mx (V. Barba).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.09.064

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V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
molecules having electron donating atoms (e.g. solvent
molecules) [16–21], changing the geometry to distorted
octahedral. For that reason, five-coordinate tin complexes
frequently form Snꢀ ꢀ ꢀO intermolecular bonds in the solid
state, thus giving dimeric aggregates through the formation
of a Sn2O2 four-membered ring [22,23].
As part of our investigation dealing with the study of
diorganotin(IV) species derived from Schiff base ligands,
we report herein the synthesis and structural analysis of
seven new derivatives containing hexadentate Schiff base
ligands. The ligands are derived from 5,50-methylene-
bis(salicylaldehyde) and three different 2-aminophenols,
and contain a double set of ONO donor atoms, thus allow-
ing for the preparation of dinuclear metal complexes.
parative part (Scheme 1) for the organometallic tin deriva-
tives containing aliphatic groups (2a, 2b, 2d and 2f), while
triethyl amine was used in the case of the phenyl tin deriv-
atives (2c, 2e and 2g). Using KOH for the reaction of the
diphenyltin derivative, the formation of either
[Ph2Sn(Cl)OH]2 (3) or [Ph4Sn2O(OMe)Cl]2 (4) was
observed, inhibiting the formation of the desired tin com-
plexes. Compounds 2a–2g are solids with intense colors
(from orange to dark red), which are soluble in polar
organic solvents and are stable under atmospheric condi-
tions. The title compounds were purified by slow precipita-
tion of saturate solutions from methanol allowing the
isolation of pure products in moderate yields (59–91%).
In all seven cases the melting points of the products are
higher than those of the ligands, whereby the highest melt-
ing points correspond to the diphenyltin(IV) derivatives.
2. Results and discussion
2.1. Synthesis of the diorganotin(IV) complexes
2.2. Spectroscopic analysis
The hexadentate ligands 1a–1c were obtained in moder-
ate yields from the reaction of 5,50-methylenebis(salicylal-
dehyde) [25] with 2-aminophenol (1a), 2-amino-4-
chlorophenol (1b) and 2-amino-4-t-butylphenol (1c). The
dinuclear tin compounds 2a–2g were prepared by reaction
of one equivalent of the ligands 1a–1c with two equivalents
of the corresponding diorganotin(IV) dichloride derivative
(R = Me, nBu, Ph). Potassium hydroxide was used as base
for the deprotonation of the ligand as described in the pre-
The mass spectrometric data of 2a–2g indicate the for-
mation of dinuclear bis-diorganotin(IV) complexes. For
all seven compounds, the molecular ion was detected and
the base peaks correspond to the ion resulting from a frag-
mentation involving one of the organic groups directly
attached to the tin atoms [MꢁR]+.
In the IR spectra of complexes 2a–2g, the broad bands
observed at approximately 3400 cmꢁ1 for the stretching
vibrations of the O–H groups in the free ligands are absent.
For each of these compounds, bands typical for m(C@N)
vibrations were detected in the range of 1615–1617 cmꢁ1
,
which are considerably shifted towards lower frequencies
with respect to the free ligands (1625–1631 cmꢁ1), suggest-
ing the coordination of the azomethine nitrogen to the tin
atom [21].
R'
R'
N
N
1
The H and 13C NMR data suggest that the complexes
OH
OH
have a mirror plane or a C2 axis as symmetry element in
solution, since there are only signals for a half of the molec-
ular entity. As shown in Chart 1 two isomers are possible
indeed, the cis-derivative (hSnL–LSn = 0ꢁ) having mirror
symmetry and the trans (hSnL–LSn = 180ꢁ) derivative having
HO
OH
1
2 R"2SnCl2,
2 KOH or Et3N
EtOH
Δ
1
C2-symmetry. In the H NMR spectra the chemical shifts
R'
O
R'
12
for the hydrogen atoms of the ligands vary only slightly
after complexation with the diorganotin(IV) fragment.
The hydrogen atoms of the azomethine group (HC@N)
13
11
10
7
3
6
14
8
4
2
1
N
N
9
5
O
Sn
R''
Sn
O
O
R
R
R''
R''
R''
2
N
N
N
Sn
Comp
2a
2b
2c
R’
H
H
R’’
Me
Sn
Sn
Sn
N
R
nBu
Ph
R
R
R
R
H
R
2d
2e
2f
Cl
Cl
tBu
tBu
nBu
Ph
nBu
Ph
cis
trans
Chart 1. Schematic representation of the two possible conformations for
the dinuclear tin compounds. In the cis conformation the two diorganotin
moieties are oriented in the same direction (hSnL–LSn = 0ꢁ), while they have
opposite orientation in the trans conformation (hSnL–LSn = 180ꢁ).
2g
Scheme 1. Synthesis of the dinuclear diorganotin(IV) complexes 2a–2g.

V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
733
exhibit single signals in the d = 8.51–8.60 ppm range for
compounds 2a–2g, which are similar for other diorgano-
tin(IV) compounds derived from ligands containing the
ONO set of donor atoms [20–23]. Interestingly, in all cases
it was possible to observe signals resulting from the cou-
pling between the azomethine proton and the tin atoms
(3JSn–H = 54–56 Hz, Table 1), indicating that the Sn–N
coordination bond is present in solution. When comparing
the 13C NMR spectra of the free ligands and the tin com-
plexes belong to the Cs or C2 point group. Fortunately,
compounds 2a, 2b, 2c and 2e could be crystallized by slow
evaporation of concentrate ethanol/methylene chloride
solutions (1:1 ratio), and their structures determined by sin-
gle crystal X-ray diffraction analyses (Fig. 1). The most rel-
evant crystallographic data are summarized in Table 2. For
compound 2c crystals could be also grown from a concen-
trate solution in benzene, so that it was possible to analyze
two isomorphs, one solventless (2c) and the other contain-
ing two benzene molecules in the unit cell (2c0). Both sys-
tems crystallized in the monoclinic space group P21/c and
only small differences in their molecular structures were
observed (Table 3). In the case of compounds 2a and 2e,
coordinating solvent molecules were included in the unit
cell (EtOH for 2a and H2O for 2e), which, however, did
not form part of the tin atom coordination sphere.
In all structures analyzed, each of the two tin atoms has
a coordination number of five, resulting from the bonding
to one nitrogen and two oxygen atoms from the ligand, and
two carbon atoms from the organic tin substituents. The
distortion from the perfect trigonal bipyramidal geometry
is mainly due to the rigidity of the chelate rings and the
large covalent radius of tin(IV) atoms. As observed in sim-
ilar compounds, the oxygen atoms are in axial position; the
nitrogen atom forms a coordination bond with the tin atom
and it is found in equatorial position, as well as the two
organic substituents.
plexes, the most important changes occurred for the CPh
–
O carbon atoms numbered C1 and C9 (Scheme 1), whereby
a downfield chemical shift was observed in agreement with
the formation of covalent Sn–O bonds (Dd ꢂ 10 ppm).
The existence of five-coordinate tin(IV) cores could be
demonstrated by 119Sn NMR spectroscopy, whereby single
signals were observed at d = ꢁ152 ppm for the dimethyltin
derivative 2a, at d = ꢁ192, ꢁ178 and ꢁ188 ppm for the di-
nbutyltin derivatives 2b, 2d and 2f, and at d = ꢁ333, ꢁ329
and ꢁ331 ppm for the diphenyltin complexes 2c, 2e and 2g,
respectively. These shifts are in the range of reported values
for related five-coordinate diorganotin(IV) complexes [20–
23], the highfield chemical shifts for the phenyltin deriva-
tives being a consequence of anisotropic shielding effects
in addition with the pi interactions.
1
The J(119Sn–13C) coupling constants of the diorgano-
tin(IV) compounds are consistent with those generally
observed for five-coordinate tin species (Table 1). The
0
Ca–Sn–Ca angles were estimated with the equations
Interestingly, most of the molecules do not possess ideal
or approximate mirror or C2 symmetry, as it might have
been expected from the spectroscopic data. Only in the case
of compound 2e the molecule is located at a crystallo-
graphic mirror plane. Apparently, the flexibility present
in the –CH2-moiety of the systems allows the complexes
to adopt different orientations when relating the two diorg-
anotin moieties. As a consequence, the angles between the
planes of the two salicylidene rings attached to the bridging
methylene group have values ranging from 34.8ꢁ to 174.5ꢁ
(Fig. 2). Compounds 2b and 2e with torsion angles of 34.8ꢁ
and 76.4ꢁ show a disposition closer to the cis conformation
(mirror-symmetry), whereas for compounds 2a, 2c and 2c0
a disposition closer to the trans conformation (C2-symme-
try) was observed (154.9ꢁ, 174.5ꢁ and 143.2ꢁ, respectively)
(Fig. 2). These different conformations are attributed to
packing effects in the crystalline structure and it may be
reported by Lockhart (R = Me) [26], Holecˆek (R = nBu)
[27] and Beltran (R = Ph) [16] giving values of 131ꢁ for
´
the methyltin derivative 2a [26], 133–139ꢁ for 2b, 2d and
2f (R = nBu), and 124–128ꢁ for 2c, 2e and 2f (R = Ph).
They agree well with the proposed coordination geometry.
As observed in previous reports, an increase of the bond
angles from 120–125ꢁ to more than 130ꢁ, as it occurs in
the cases of 2a, 2b, 2d and 2f, indicates the possibility to
have an increment in the coordination sphere of the tin
atoms, a characteristic that has been denoted by the X-
ray diffraction study for complexes 2a and 2b.
2.3. Solid state structure analysis
From the NMR spectroscopic analyses carried out in
solution it was not clear, whether the dinuclear tin com-
Table 1
Selected 1H, 13C and 119Sn NMR spectroscopic data and comparison between calculated and experimental C–Sn–C bond angles for compounds 2a–2g
1H (H-7) (ppm)
13C (C-7) (ppm)
119Sn (ppm)
3J(119Sn–1H7) (Hz)
1J(119Sn–13Ca) (Hz)
h CSnC (ꢁ)Calcd
h CSnC (ꢁ)Found
a
b
Entry
2a
2b
2c
2d
2e
2f
2g
a
8.54
8.58
8.60
8.56
8.51
8.59
8.60
161.7
161.9
161.2
162.1
161.8
160.8
160.6
ꢁ152
ꢁ192
ꢁ333
ꢁ178
ꢁ329
ꢁ188
ꢁ331
50
44
58
44
52
48
56
625
650
1020
588
1070
610
955
131.12
139.74
126.93
133.53
128.87
135.73
124.54
130.6(6)/129.3(7)
143.1(5)/118.0(7)
121.0(3)/128.7(3)c
119.5(4)
Calculated using the equations reported in Ref. [26] (2a), [27] (2b, 2d and 2f) and [16] (2c, 2e and 2g).
From X-ray data.
Values taken from the data collection of 2c.
b
c

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V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
Fig. 1. Molecular structures for complexes 2a, 2b, 2c and 2e.
Table 2
Crystallographic data for compounds 2a–2c and 2e
Identification code
2a
2b
2c
2c0
2e
Empirical formula
Formula weight
C
778.02
31H30N2O4Sn2 Æ C2H5OH
C43H54N2O4Sn2
900.26
C51H38N2O4Sn2
980.21
C51H38N2O4Sn2 Æ 2C6H6
1136.43
C51H36Cl2N2O4Sn2 Æ 4H2O
1121.16
(g molꢁ1
)
Crystal size (mm3)
Crystal system
0.20 · 0.14 · 0.10
Monoclinic
P21/n
0.20 · 0.12 · 0.10
Triclinic
0.20 · 0.20 · 0.16
Monoclinic
P21/c
0.30 · 0.20 · 0.16
Monoclinic
P21/c
0.22 · 0.18 · 0.12
Monoclinic
P2/c
ꢀ
Space group
Unit cell dimensions
P1
˚
a (A)
12.696(3)
15.595(3)
17.125(3)
90
108.435(4)
90
3216.5(11)
4
1.607
10.8083(12)
14.791(2)
15.4376(18)
64.342(3)
74.681(2)
68.857(2)
2057.6(4)
2
17.066(3)
26.523(5)
9.6710(19)
90
96.83(3)
90
4346.4(15)
4
1.498
19.860(4)
13.853(3)
19.915(4)
90
109.394(3)
90
5168.2(17)
4
1.461
8.9824(10)
13.0474(15)
21.631(3)
90
91.874(2)
90
2533.7(5)
2
1.470
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Dcalc (g/cm3)
l (mmꢁ1
1.453
1.256
)
1.595
1.196
1.017
1.144
Collected refl.
24608
9052
17526
48879
20291
Independent refl.
4210 (0.1120)
5605 (0.0458)
5898 (0.0414)
9089 (0.0416)
3539 (0.0602)
(Rint
)
Parameters
R1 [I > 2r(I)]
wR2 (all data)
GOF
370
465
533
641
294
0.0837
0.1991
1.093
0.0738
0.1837
1.012
0.0571
0.1496
1.063
0.0361
0.0903
1.025
0.0715
0.1998
1.175
supposed that in solution there is a fast dynamic equilib-
rium between them.
Selected bond distances and angles are summarized in
Table 3. Considerable variations could be only found for
some bond angles that are affected by the different organic
substituents attached to the tin atoms. For example, the
axial oxygen substituents have O–Sn–O bond angles rang-
ing from 154.5(5)ꢁ for the dimethyltin derivative 2a to
161.6(3)ꢁ for the diphenyltin derivative 2c. Interesting vari-
ations are also observed for the C–Sn–C angles: if phenyl
groups are attached to the tin atom, then the angle is close
to 120ꢁ, whereas with aliphatic moieties the angles tend to

V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
735
Table 3
0
˚
Selected bond distances (A) and angles (ꢁ) for compounds 2a, 2b, 2c, 2c and 2e
2a (R = Me)
2b (R = nBu)
2c (R = Ph)
2c0 (R = Ph)
2ea (R = Ph)
b
˚
Bond distances (A)
Sn1–N1/Sn2–N2
Sn1–O1/Sn2–O3
Sn1–O2/Sn2– O4
Sn1–Ca/Sn2 –Ca00
Sn1–Ca0/Sn2–Ca000
N1–C7/N2 –C21
2.166(11)/2.192(12)
2.110(9)/2.125(10)
2.136(11)/2.100(11)
2.105(15)/2.092(14)
2.115(14)/2.130(15)
1.287(15)/1.325(17)
2.212(8)/2.236(9)
2.164(7)/2.074(9)
2.132(7)/2.080(9)
2.125(11)/2.06(2)
2.113(12)/2.149(12)
1.295(12)/1.292(13)
2.188(5)/2.178(5)
2.085(5)/2.077(5)
2.065(5)/2.084(6)
2.113(8)/2.102(8)
2.128(7)/2.108(8)
1.295(7)/1.277(7)
2.189(2)/2.175(2)
2.067(2)/2.083(2)
2.076(2)/2.088(2)
2.104(4)/2.110(3)
2.113(3)/2.113(3)
1.306(4)/1.301(4)
2.191(7)
2.079(6)
2.094(6)
2.094(10)
2.114(10)
2.293(10)
Bond angles (ꢁ)
O1–Sn1–N1/O3–Sn2–N2
O1–Sn1–O2/O3–Sn2–O4
O1–Sn1–Ca/O3–Sn2–Ca00
O1–Sn1–Ca0/O3–Sn2–Ca000
O2–Sn1–N1/O4–Sn2–N2
O2–Sn1–Ca/O4–Sn2–Ca00
O2–Sn1–Ca0/O4–Sn2–Ca000
N1–Sn1–Ca/N2–Sn2–Ca00
N1–Sn1–Ca0/N2–Sn2–Ca000
Ca–Sn1–Ca0/C00–Sn2–Ca000
a
81.8(4)/ 81.6(4)
156.0(4)/154.5(5)
97.4(6)/96.9(5)
91.7(5)/89.8(5)
75.1(4)/76.4(5)
96.6(6)/100.8(6)
93.9(5)/93.1(6)
110.5(6)/104.0(6)
118.9(5)/126.7(5)
130.6(6)/129.3(7)
81.3(3)/82.0(3)
156.7(3)/149.8(4)
93.2(4)/99.7(8)
90.6(4)/89.1(5)
75.4(3)/75.9(4)
94.6(4)/106.1(8)
96.2(4)/92.3(4)
108.2(4)/106.6(6)
108.6(5)/135.4(4)
143.1(5)/118.0(7)
82.61(19)/84.65(18)
159.7(2)/161.6(3)
91.6(3)/92.3(3)
96.3(3)/93.1(3)
77.2(2)/77.1(2)
96.4(3)/96.3(3)
95.5(3)/96.7(3)
118.3(2)/116.5(2)
120.7(2)/114.9(2)
121.0(3)/128.7(3)
83.51(9)/82.96(8)
83.2(3)
158.6(3)
96.8(4)
90.5(3)
76.8(3)
98.4(4)
95.0(3)
114.9(3)
125.6(3)
119.5(4)
160.25(9)/159.79(9)
95.45(14)/93.17(11)
91.99(12)/92.94(11)
77.29(9)/76.86(9)
96.72(14)/95.86(11)
94.45(12)/95.82(11)
114.70(11)/113.60(10)
122.62(10)/118.93(10)
122.67(12)/127.47(11)
Only one value is described due to the mirror symmetry of the molecule.
a and a00 = carbon atoms located at the endo position; a0 and a000 = carbon atoms located at the exo position.
b
Fig. 2. Overall conformation of the molecular structures of 2a, 2b, 2c and 2e,showing the angles between the planes of the two salicylidene moieties (hSnL–
LSn = 34.8–174.5ꢁ) attached to the bridging methylene group.
be larger. In the case of the dimethyltin derivative (com-
pound 2a), the C–Sn–C bond angles have values of
129.3(7)ꢁ and 130.6(6)ꢁ, allowing for the interaction with
neighboring molecules through Snꢀ ꢀ ꢀO intermolecular
interactions to form a 1D crinkled polymeric chain
(Fig. 3). The four-membered Sn2O2 rings within the coordi-
nation polymer are not symmetric, since one Snꢀ ꢀ ꢀO inter-
action is formed with the oxygen atom of the five-
formed to the oxygen corresponding to the six-membered
heterocycle (3.81 A). As it can be noticed, the latter interac-
˚
tion is significantly weaker and slightly longer than the sum
˚
of the van der Waals radii (3.69 A). Due to the Snꢀ ꢀ ꢀO
intermolecular interactions the tin atoms adopt a distorted
octahedral geometry in the solid state, which is not
observed in solution. It is important to remark that in all
Schiff base–tin complexes reported so far, the Snꢀ ꢀ ꢀO inter-
actions occur between the oxygen atoms forming part of
˚
membered chelate ring (3.36 A), whereas the other one is

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V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
Fig. 3. Snꢀ ꢀ ꢀO interactions give rise to a crinkled 1D polymeric structure for 2a, and a dimeric compound in the case of 2b.
the five-membered heterocycles, so that this is the first case,
in which Snꢀ ꢀ ꢀO interactions occur with the oxygen atoms
involved in a six-membered heterocycle. In the case of com-
pound 2b, the C–Sn–C bond angles have values of
143.1(5)ꢁ and 118.0(7)ꢁ for the two chelate rings present
in the complex. The larger angle allows for the formation
at room temperature. The central part of the molecular
structure of compound 3 [28] consists of a four-membered
heterocycle with the composition (Sn(OH))2 (Fig. 4), in
which the hydroxyl groups bridge the two tin atoms. The
Sn–O distance of 2.170(16)ꢁ is analogous to that found in
a related compound containing quinoline in the unit cell
[29]. In the molecular structure of compound 4 [30] three
four-membered Sn2O2 rings are present, of which the cen-
tral ring is formed by bridging oxygen atoms, while the lat-
eral rings involved also bridging methoxy groups (Fig. 4).
The bond distances and angles are in accordance with those
previously reported for an analogous compound, which
contains OH instead of OMe fragments [31].
˚
of a Snꢀ ꢀ ꢀO intermolecular interaction (2.96 A), giving
place to a dimeric organization (Fig. 3). The smaller angle
at the opposite side of the molecule (118.0(7)ꢁ) inhibits such
an interaction, so that the polymeric organization observed
in the case of 2a is avoided. In the case of the diphenyltin
derivatives 2c and 2e, Snꢀ ꢀ ꢀO intermolecular interactions
were not observed.
As mentioned above, compounds [Ph2Sn(Cl)OH]2 (3)
and [Ph4Sn2O(OMe)Cl]2 (4) resulted from the hydrolysis
of Ph2SnCl2 when the reactions were carried out in the
presence of KOH. Suitable crystals for the X-ray analysis
were isolated after leaving the reaction mixture over night
3. Conclusions
Schiff base ligands having a two-fold ONO donor sys-
tem can give rise to dinuclear tin complexes, in which the
diorganotin chelates are connected by a methylene group.
In solution, the tin atoms have a five-coordinate coordina-
tion geometry, which is retained in the solid state for the
diphenyltin derivatives, while the dimethyl and dibutyl
derivatives can change their geometry to distorted octahe-
dral owing to the presence of Snꢀ ꢀ ꢀO intermolecular inter-
actions. Two molecular conformations are possible, which
involve either a cis- or a trans-orientation of the diorgano-
tin groups. Since in the solid state different intermedium
states have been observed that approximate to one or the
other isomer, it can be supposed that in solution a fast
dynamic equilibrium is present.
4. Experimental
Fig. 4. Molecular structures for compounds [Ph2Sn(Cl)OH]2 (3) and
˚
[Ph4Sn2O(OMe)Cl]2 (4). Selected bond distances (A) and angles (ꢁ) for 3:
4.1. Materials and methods
Sn1–O1 2.0170(16), Sn1–Cl1 2.4748(6), Sn1–C1 2.114(2), Sn1– C7
2.120(2), O1–Sn1–Cl1 115.32(8), C1–Sn1–C7 129.27(9), O1–Sn2–O10
70.62(7). 4: Sn1–O1 2.175(5), Sn1–O2 2.031(4), Sn2–O1 2.196(5), Sn2–
O2 2.014(4), Sn2–Cl1 2.466(2), Sn1–O1–Sn2 101.62(19), Sn1–O2–Sn2
113.8(2), C13–Sn2–C19 124.6(3), O2–Sn2–Cl1 85.50(13), O1–Sn1–O2
72.26(17), O1–Sn2–O2 72.13(17).
All reagents and solvents used were obtained from com-
mercial suppliers and used without further purification.
The 1H, 13C and 119Sn NMR spectra were recorded at
room temperature using a Varian Gemini 200 spectropho-

V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
737
tometer. As standard references TMS (internal, 1H,
d = 0.00 ppm, 13C, d = 0.00 ppm) and SnMe4 (external,
119Sn, d = 0.0 ppm) were used as standard references. 2D
COSY and HMQC experiments have been carried out for
the unambiguous assignment of the 1H and 13C NMR
spectra. Infrared spectra have been recorded on a Bruker
Vector 22 FT-IR spectrophotometer. Mass spectra were
obtained on a Jeol JMS 700 equipment. Elemental analyses
were carried out on a Perkin Elmer Series II 2400 instru-
39.7 (C-14) ppm. Anal. Calc. for C27H22N2O4: C, 73.95;
H, 5.05; N, 6.38. Found: C, 73.76; H, 4.98; N, 6.23%.
4.3.1.2. Ligand 1b. Ligand 1b was prepared from 1.00 g
(3.9 mmol) of 5,50-methylenebis(salicylaldehyde) and
1.121 g (7.8 mmol) of 2-amino-4-chlorophenol. An orange
solid was obtained in
M.p. = 242–245 ꢁC. IR (KBr) m: 3429, 2370, 1625 (C@N),
1579, 1491, 1360, 1276, 1229, 1149, 920, 816 cmꢁ1 1H
a yield of 71 % (1.41 g).
.
ment. Melting points were determined with a Buchi B-
¨
540 digital apparatus.
NMR (200 MHz, DMSO-d6) d: 10.12 (2H, s, OH) 8.91
(2H, s, H-7), 7.46 (2H, d, J = 2.4 Hz, H-3), 7.29 (2H, dd,
J = 8.2, 2.4 Hz, H-5), 7.26 (2H, d, J = 2.2 Hz, H-13),
7.15 (2H, dd, J = 8.2. 2.2 Hz, H-11), 6.95 (2H, d,
J = 8.2 Hz, H-6), 6.91 (2H, d, J = 8.2 Hz, H-10), 3.95
(2H, s, H-14) ppm. 13C NMR (50 MHz, DMSO-d6) d:
162.6 (C-7), 158.8 (C-1), 149.9 (C-9), 136.2 (C-8), 133.6
(C-5), 131.9 (C-3), 131.6 (C-4), 127.1 (C-11), 122.9 (C-
12), 119.1 (C-2), 117.6 (C-6), 117.3 (C-13), 116.4 (C-10),
39.9 (C-14) ppm. Anal. Calc. for C27H20N2O4Cl2: C,
63.91; H, 3.97; N, 5.52. Found: C, 63.57; H, 3.82; N, 5.32%.
4.2. X-ray crystallography
X-ray diffraction studies were performed on a Bruker-
APEX diffractometer equipped with a CCD area detector,
˚
graphite
MoKa-radiation (k = 0.71073 A), and
a
monochromator. Frames were collected at T = 293 K. The
measured intensities were reduced to F2 and corrected for
absorption with SADABS (SAINT-NT) [32]. Corrections were
made for Lorentz and polarization effects. Structure solu-
tion, refinement and data output were carried out with the
SHELXTL-NT program package [33]. All non-hydrogen atoms
were refined anisotropically except for 2a, wherein the etha-
nol solvent molecule was refined only isotropically. Hydro-
gen atoms were placed in geometrically calculated
positions using a riding model. High R values are observed
in some cases due to solvent molecule disorder.
4.3.1.3. Ligand 1c. Ligand 1c was prepared from 1.00 g
(3.9 mmol) of 5,50-methylenebis(salicylaldehyde) and
1.29 g (7.8 mmol) of 2-amino-4-t-butylphenol. An orange
solid was obtained in a yield of 74% (1.6 g). M.p. = 248–
251 ꢁC. IR (KBr) m: 3448, 2959, 2373, 1627 (C@N), 1516,
1494, 1363, 1278, 1243, 1148, 817 cmꢁ1
.
1H NMR
(200 MHz, DMSO-d6) d: 9.54 (2H, s, OH), 8.93 (2H, s,
H-7), 7.48 (2H, d, J = 2.0 Hz, H-3), 7.33 (2H, d,
J = 2.2 Hz, H-13), 7.27 (2H, dd, J = 8.4, 2.0 Hz, H-5),
7.12 (2H, dd, J = 8.0, 2.2 Hz, H-11), 6.88 (2H, d,
J = 8.4 Hz, H-6), 6.86 (2H, d, J = 8.0 Hz, H-10), 3.86
(2H, s, H-14) ppm. 13C NMR (50 MHz, DMSO-d6) d:
161.8 (C-7), 159.6 (C-1), 149.2 (C-9), 142.6 (C-12), 134.7
(C-8), 133.7 (C-5), 132.5 (C-3), 132.1 (C-4), 125.9 (C-11),
119.9 (C-2), 117.3 (C-6), 117.0 (C-10), 116.5 (C-13), 39.6
(C-14) ppm. Anal. Calc. for C35H38N2O4: C, 76.33; H,
6.95; N, 5.08. Found: C, 76.17; H, 6.85; N, 4.97%.
4.3. Syntheses
4.3.1. General procedure for the preparation of the
hexadentate ligands 1a–1c
A mixture of one equivalent of 5,50-methylenebis(salicyl-
aldehyde) and two equivalents of the corresponding o-ami-
nophenol was dissolved in ethanol. The solution was
refluxed for 60 min using a Dean-Stark trap to remove
the water formed during the reaction and part of the sol-
vent. The solution was evaporated to dryness to give com-
pounds 1a–1c as orange solids, which were used for the
subsequent reaction without further purification.
4.3.2. General procedure for the preparation of the
diorganotin(IV) complexes 2a–2g
To a solution of one equivalent of the ligand (1a–1c) in
20 ml of methanol, two equivalents of the base were added
(KOH in case of compounds 2a, 2b, 2d and 2f, and NEt3
for 2c, 2e and 2g). After 15 min of stirring, two equivalents
of the dialkyltin dichloride (2a, 2b, 2d and 2f) or diphenyl-
tin dichloride (2c, 2e and 2g) were added. The reaction mix-
ture was refluxed for 6 h using a Dean-Stark trap to remove
the water formed during the reaction and/or part of the sol-
vent. The solution was evaporated to dryness to give com-
pounds 2a–2g as orange-red dark solids. The title
compounds were purified by slow precipitation of saturate
solutions from methanol allowing the isolation of pure
products in moderate to good yields (59–91%).
4.3.1.1. Ligand 1a. Ligand 1a was prepared from 1.00 g
(3.9 mmol) of 5,50-methylenebis(salicylaldehyde) and
0.852 g (7.8 mmol) of 2-aminophenol. An orange solid
was obtained in a yield of 83% (1.42 g). M.p. = 227–
230 ꢁC. IR (KBr) m: 3405, 3048, 2896, 2557, 1631 (C@N),
1590, 1526, 1492, 1458, 1369, 1304, 1273, 1244, 1138,
1
823, 797, 746 cmꢁ1. H NMR (200 MHz, CDCl3) d: 9.73
(2H, s, OH) 8.92 (2H, s, H-7), 7.46 (2H, s, H-3), 7.34
(2H, d, J = 7.8 Hz, H-5), 7.26 (2H, d, J = 7.8 Hz, H-6),
7.11 (2H, t, J = 8.0 Hz, H-12), 6.95 (2H, d, J = 8.0 Hz,
H-13), 6.90 (2H, d, J = 8.0 Hz, H-10), 6.86 (2H, t,
J = 8.0 Hz, H-11), 3.90 (2H, s, H-14) ppm. 13C NMR
(50 MHz, CDCl3) d: 161.0 (C-7), 158.6 (C-1), 150.7 (C-9),
132.9 (C-5), 131.5 (C-3), 131.2 (C-4,8), 127.6 (C-11),
119.3 (C-2), 119.0 (C-6, 12), 116.5 (C-10), 116.1 (C-13),
4.3.2.1. Complex 2a. Compound 2a was obtained from
0.30 g (0.68 mmol) of ligand 1a and 0.30 g (1.36 mmol) of

738
V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
dichlorodimethyltin. A red dark solid was obtained in a
yield of 78% (0.39 g). M.p. = 238–241 ꢁC. IR (KBr) m:
2919, 1616 (C@N), 1590, 1534, 1473, 1381, 1305, 1214,
1157, 743 cmꢁ1. EI MS, m/z (%): 734 ([M+1], 64), 732
C51H38N2O4Sn2: C, 62.48; H, 3.90; N, 2.85. Found: C,
61.85; H, 3.93; N, 2.72%.
4.3.2.4. Complex 2d. Compound 2d was obtained from
0.10 g (0.20 mmol) of ligand 1b and 0.12 g (0.40 mmol) of
dichlorodibutyltin. A red dark solid was obtained in a yield
of 68% (0.13 g). M.p. = 257–260 ꢁC. IR (KBr) m: 2954,
2921, 1617 (C@N), 1585, 1531, 1472, 1414, 1378, 1299,
819 cmꢁ1. EI MS, m/z (%). 970 ([M+1], 61), 968 (M+,
1
(M+, 65), 717 ([MꢁMe]+, 100), 702 ([M–2Me]+, 43). H
3
NMR (200 MHz, CDCl3) d: 8.54 (2H, s, JSn–H = 25 Hz,
H-7), 7.25 (2H, d, J = 8.2 Hz, H-5), 7.16 (2H, d,
J = 7.8 Hz, H-13), 7.09 (2H, t, J = 7.8 Hz, H-12), 6.74
(2H, d, J = 8.2 Hz, H-6), 6.67 (2H, d, J = 7.8 Hz, H-10),
6.61 (2H, t, J = 7.8 Hz, H-11), 6.95 (2H, s, H-3), 3.75
(2H, s, H-14), 0.89 (2H, s, Me) ppm. 13C NMR (50 MHz,
CDCl3) d: 168.0 (C-1), 161.8 (C-7), 159.0 (C-9), 138.0 (C-
5), 137.8 (C-3), 134.4 (C-8), 130.4 (C-4, 11), 122.9 (C-12),
118.7 (C-6), 118.0 (C-2), 116.8 (C-10), 114.9 (C-13), 39.0
(C-14), 22.3 (Me) ppm. 119Sn NMR (75 MHz, CDCl3) d:
ꢁ152 ppm. Anal. Calc. for C31H30N2O4Sn2: C, 50.86; H,
4.13; N, 3.82. Found: C, 50.76; H, 3.98; N, 3.70%.
1
65), 912 ([M–Bu]+, 100). H NMR (200 MHz, CDCl3)d:
3
8.56 (2H, s, JSn–H = 22 Hz, H-7), 7.29 (2H, dd, J = 7.4,
2.2 Hz, H-5), 7.26 (2H, d, J = 2.0 Hz, H-13), 7.12 (2H,
td, J = 8.7 Hz, 2.0 Hz, H-11), 7.04 (2H, d, J = 2.2 Hz, H-
3), 6.78 (2H, d, J = 7.4 Hz, H-6), 6.77 (2H, d, J = 8.7 Hz,
H-10), 3.84 (2H, s, H-14), 1.58-1.65 (8H, m, H-b), 1.45-
1.52 (8H, m, H-a), 1.30 (8H, sex, J = 7.2 Hz, H-c), 0.86
(12H, t, J = 7.2 Hz, H-d) ppm. 13C NMR (50 MHz,
CDCl3) d: 168.9 (C-1), 162.2 (C-7), 158.2 (C-9), 138.6 (C-
3, 5), 132.4 (C-8), 129.9 (C-11), 129.5 (C-4), 121.0 (C-12),
119.6 (C-10), 117.5 (C-2, 6), 115.1 (C-13), 39.5 (C-14),
27.4 (C-b), 26.9 (C-c), 22.4 (C-a), 13.8 (C-d) ppm. 119Sn
NMR (75 MHz, CDCl3) d: ꢁ178 ppm. Anal. Calc. for
C43H52N2O4Cl2Sn2: C, 53.28; H, 5.40; N, 2.89. Found: C,
53.62; H, 5.14; N, 2.98%.
4.3.2.2. Complex 2b. Compound 2b was obtained from
0.26 g (0.60 mmol) of ligand 1a and 0.36 g (1.20 mmol) of
dichlorodibutyltin. A red dark solid was obtained in a yield
of 59 % (0.32 g). M.p. = 242–245 ꢁC. IR (KBr) m: 2954,
2920, 2853, 1616 (C@N), 1588, 1532, 1473, 1380, 1306,
1212, 1155, 833, 741 cmꢁ1. EI MS, m/z (%): 902 ([M+1],
82), 900 (M+, 84), 843 ([MꢁBu]+, 100), 786 ([Mꢁ2Bu]+,
1
3
35). H NMR (200 MHz, CDCl3) d: 8.58 (2H, t, JSn–H
= 22 Hz, H-7), 7.29 (2H, d, J = 8.1 Hz, H-5), 7.20 (2H,
d, J = 8.0 Hz, H-13), 7.15 (2H, t, J = 8.0 Hz, H-12), 7.01
(2H, d, J = 2.2 Hz, H-3), 6.82 (2H, d, J = 8.1 Hz, H-6),
6.74 (2H, d, J = 8.0 Hz, H-10), 6.65 (2H, t, J = 8.0 Hz,
H-11), 3.81 (2H, s, H-14), 1.56–1.64 (8H, m, CH2-b),
1.40–1.50 (8H, m, CH2-a), 1.31 (8H, sex, J = 7.3 Hz,
CH2-c), 0.83 (12H, t, J = 7.3 Hz, CH2-d) ppm. 13C NMR
(50 MHz, CDCl3) d: 168.2 (C-1), 161.4 (C-7), 159.5 (C-9),
137.8 (C3, 5), 134.3 (C-8), 130.4 (C-4, C-11), 122.8 (C-
12), 118.6 (C-6), 117.6 (C-2), 116.4 (C-10) 114.8 (C-13),
39.7 (C-14), 27.4 (C-b), 27.0 (C-c), 22.4 (C-a), 14.0 (C-d)
ppm. 119Sn NMR (75 MHz, CDCl3)d: ꢁ192 ppm. Anal.
Calc. for C43H54N2O4Sn2: C, 57.36; H, 6.04; N, 3.11.
Found: C, 56.96; H, 5.88; N, 3.20%.
4.3.2.5. Complex 2e. Compound 2e was obtained from
0.10 g (0.20 mmol) of ligand 1b and 0.14 g (0.40 mmol) of
dichlorodiphenyltin. An orange solid was obtained with
yield of 48% (0.10 g). M.p. = 295–298 ꢁC. IR (KBr) m:
2946, 1617 (C@N), 1590, 1534, 1473, 1377, 1296, 825,
732 cmꢁ1. FAB MS, m/z (%): 1050 ([M+1], 54), 1048
(M+, 60), 974 ([MꢁPh]+, 100). 1H NMR (200 MHz,
3
CDCl3) d: 8.51 (2H, s, JSn–H = 27 Hz, H-7), 7.82–7.92
(8H, m, H-o), 7.32–7.42 (12H, m, H-m, p), 6.96–7.30
(12H, m, H-3, 5, 6, 10, 11, 13), 3.81 (2H, s, H-14) ppm.
13C NMR (50 MHz, CDCl3) d: 168.4 (C-1), 161.8 (C-7),
157.4 (C-9), 139.4 (C-5), 138.6 (C-3, C-i), 136.5 (C-o),
131.7 (C-8), 130.5 (C-11), 129.9 (C-p), 129.8 (C-4), 128.7
(C-m) 121.5 (C-12), 119.9 (C-10), 117.5 (C-2, 6), 114.9
(C-13), 39.6 (C-14) ppm. 119Sn NMR (75 MHz, CDCl3)
d: ꢁ329 ppm. Anal. Calc. for C51H36N2O4Cl2Sn2: C,
58.38; H, 3.45; N, 2.67. Found: C, 57.99; H, 3.43; N, 2.73%.
4.3.2.3. Complex 2c. Compound 2c was obtained from
0.19 g (0.436 mmol) of ligand 1a and 0.30 g (0.87 mmol)
of dichlorodiphenyltin. An orange solid was obtained in
a yield of 91% (0.39 g). M.p. = 285–287 ꢁC. IR (KBr) m:
3050, 1615 (C@N), 1590, 1535, 1473, 1379, 1305, 1157,
835, 735 cmꢁ1. FAB MS, m/z (%): 982 ([M+2, 70), 980
(M+, 75), 903 ([MꢁPh]+, 100). 1H NMR (200 MHz,
4.3.2.6. Complex 2f. Compound 2f was obtained from
0.10 g (0.18 mmol) of ligand 1c and 0.11 g (0.36 mmol) of
dichlorodibutyltin. A red dark solid was obtained in a yield
of 80 % (0.16 g). Mp = 288–291 ꢁC. IR (KBr) m: 2923,
2861, 1616 (C@N), 1589, 1532, 1492, 1465, 1375, 1279,
1168, 827 cmꢁ1. FAB MS, m/z (%): 1014 ([M+1], 92),
3
CDCl3)d: 8.60 (2H, s, JSn–H, = 29 Hz, H-7), 7.84 (8H,
1
dd, J = 7.3,1.8 Hz, H-o), 6.90–7.20 (18H, m, H-3, 5, 6,
10, 12, 13, m, p), 6.66 (2H, td, J = 8.4, 2.2 Hz, H-11),
3.82 (2H, s, H-14) ppm. 13C NMR (50 MHz, CDCl3)d:
168.2 (C-1), 161.2 (C-7), 156.5 (C-9), 139.7 (C-5, C-i),
138.1 (C-3), 136.5 (C-o), 134.5 (C-8), 130.3 (C-11, C-p),
128.7 (C-m), 128.1 (C-4), 123.1(C-12), 119.0 (C-6), 117.3
(C-2), 116.9 (C-10), 114.7 (C-13), 39.7 (C-14) ppm. 119Sn
NMR (75 MHz, CDCl3) d: ꢁ333 ppm. Anal. Calc for
1012 (M+, 98), 956 ([MꢁBu]+, 100). H NMR (200 MHz,
3
CDCl3) d: 8.59 (2H, s, JSn–H = 24 Hz, H-7), 7.15–7.25
(6H, m, H-5, H-11, H-13), 7.08 (2H, s, H-3), 6.78 (2H, d,
J = 8.4 Hz, H-6), 6.74 (2H, d, J = 8.4 Hz, H-10), 3.83
(2H, s, H-14), 1.60–1.70 (8H, m, H-b), 1.40–1.50 (8H, m,
H-a),1.32 (18H, m, t-Bu), 1.27 (8H, sex, J = 7.4 Hz, H-c),
0.83 (12H, t, J = 7.4 Hz, H-d) ppm. 13C NMR (50 MHz,
CDCl3) d: 167.9 (C-1), 160.8 (C-7), 157.1 (C-9), 139.7 (C-

V. Barba et al. / Journal of Organometallic Chemistry 692 (2007) 731–739
739
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5), 137.6 (C-3), 134.2 (C-12), 130.6 (C-8), 129.2 (C-4), 127.5
(C-11), 122.7 (C-10), 117.9 (C-6), 117.7 (C-2), 111.2 (C-13),
39.8 (C-14), 34.7 (C(Me)3), 32.0 (C(Me)3), 27.4 (C-b), 27.0
(C-c), 22.4 (C-a), 14.0 (C-d) ppm. 119Sn NMR (75 MHz,
CDCl3) d: ꢁ188 ppm. Anal. Calc. for C51H70N2O4Sn2: C,
60.49; H, 6.96; N, 2.76. Found: C, 60.72; H, 5.74; N, 2.42%.
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4.3.2.7. Complex 2g. Compound 2g was obtained from
0.10 g (0.18 mmol) of ligand 1c and 0.12 g (0.36 mmol) of
dichlorodiphenyltin. An orange solid was obtained in a
yield of 63% (0.14 g). M.p. = 293–296 ꢁC. IR (KBr) m:
2957, 2372, 1616 (C@N), 1536, 1494, 1468, 1374, 1289,
1164, 829, 730 cmꢁ1. FAB MS, m/z (%): 1094 ([M+1],
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14), 1092 (M+, 15), 1016 ([MꢁPh]+, 100). H (200 MHz,
3
CDCl3) d: 8.60 (2H, s, JSn–H = 28 Hz, H-7), 7.90–7.92
(8H, m, H-o), 7.22–7.38 (16H, m, H-5, 13, m, p), 7.02
(2H, d, J = 9.0, H-6), 6.98–7.10 (6H, m, H-3, 10, 11),
3.83 (2H, s, H-14), 1.30 (18H, s, t-Bu) ppm. 13C NMR
(50 MHz, CDCl3) d: 167.8 (C-1), 160.6 (C-7), 156.5 (C-9),
139.8 (C-i), 139.7 (C-5), 137.8 (C-3), 136.6 (C-o), 134.5
(C-12), 130.2 (C-p), 130.0 (C-8), 129.6 (C-4), 128.6 (C-m),
127.8 (C-11), 123.1 (C-10), 118.4 (C-6), 117.7 (C-2), 111.1
(C-13), 39.8 (C-14), 34.7 (C-15), 31.9 (C-16) ppm. 119Sn
NMR (75 MHz, CDCl3) d: ꢁ331 ppm. Anal. Calc. for
C59H54N2O4Sn2: C, 64.86; H, 4.98; N, 2.56. Found: C,
65.19; H, 5.01; N, 2.57%.
´
´
´
´
´
Farfan, Chem. Eur. J. 9 (2003) 2291.
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Willem, V. Gramlich, S. Mitra, J. Organomet. Chem. 590 (1999) 88.
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2480.
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allics 17 (1998) 3058.
Acknowledgements
The authors thank PROMEP and IMP for financial
support.
[20] J.M. Rivera, H. Reyes, A. Cortes, R. Santillan, P.G. Lacroix, C.
´
Lepetit, K. Nakatani, N. Farfan, Chem. Mater. 18 (2006) 1174.
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Troyanov, Inorg. Chim. Acta 325 (2001) 103.
Appendix A. Supplementary material
´
´
[22] N. Farfan, T. Mancilla, R. Santillan, A. Gutierrez, L.S. Zamudio-
´
Rivera, H.I. Beltran, J. Organomet. Chem. 689 (2004) 3481.
CCDC 607131, 607132, 607133, 607134, 607135, 616312
and 616313 contain the supplementary crystallographic
data for 2a, 2b, 2c, 2c0, 2e, 3 and 4. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2006.09.064.
´
´
[23] H. Reyes, C. Garcıa, N. Farfan, R. Santillan, P.G. Lacroix, C.
Lepetit, K. Nakatani, J. Organomet. Chem. 689 (2004) 2303.
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Dale, J. Am. Chem. Soc. 126 (2004) 13598.
[25] S. Marvel, N. Tarko¨y, J. Am. Chem. Soc. 79 (1957) 939.
[26] T.P. Lockhart, W.F. Manders, J. Am. Chem. Soc. 109 (1987) 7015.
[27] J. Holecˇek, A. Lycˇka, Inorg. Chim. Acta 118 (1986) L15.
[28] Crystal data for 3: Triclinic, a = 8.2267(6), b = 9.9035(7),
˚
c = 10.1551(7)
A,
a = 68.9280(10),
b = 77.5380(10),
3
˚
c = 87.8340(10)ꢁ, space group P ꢁ 1, V = 753.13(9) A , T = 293 K,
Z = 1, l(Mo Ka) = 0.71073 mmꢁ1, 7841 reflections measured, 2945
unique (Rint = 0.0232), R1 [I > 2rI] = 0.0216, wR2 (all data) = 0.0506.
[29] J.R. Anacona, C. Rivas, G.D. Delgado, J. Coord. Chem. 56 (2003)
245.
References
[30] Crystal data for 4: Monoclinic, a = 11.4507(9), b = 21.0612(17),
˚
c = 10.3973(8) A, b =
106.2770(10), space group P21ꢁ/c1,
3
˚
V = 2407.0(3) A , T = 293 K, Z = 4, l(Mo Ka) = 0.71073 mm
,
´
[1] R. Luna-Garcıa, B.M. Damian-Murillo, V. Barba, H. Ho¨pfl, H.I.
22770 reflections measured, 4249 unique (Rint = 0.0716), R1
[I > 2rI] = 0.0458, wR2 (all data) = 0.1129.
Beltran, L.S. Zamudio, Chem. Commun. (2005) 5527.
´
[2] R. Garcıa-Zarracino, H. Ho¨pfl, Angew. Chem. Int. Ed. 43 (2004)
[31] J.F. Vollano, R.O. Day, R.R. Holmes, Organometallics 3 (1984) 745.
[32] Bruker Analytical X-ray Systems, SAINT-NT Version 6.04, 2001.
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1507.
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Martins, M. Biesemans, R. Willem, Organometallics 17 (1998) 4259.